Second International Conference on Smart Materials and Nanotechnology in Engineering

Front Matter: Volume 7493

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This PDF file contains the front matter associated with SPIE Proceedings Volume 7493, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Design and construction of pre-stressed piezoelectric unimorph for trailing edge flap actuation

Lae-Hyong Kang, Jong-Won Lee, Jae-Hung Han

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This paper presents a trailing edge flap actuation mechanism using a novel pre-stressed piezoelectric unimorph, PUMPS (Piezoelectric Unimorph with Mechanically Pre-stressed Substrate). Experimental evaluation of actuation performance such as force-displacement characteristics of PUMPS actuators showed that the performance of PUMPS satisfied the requirements for trailing edge flap actuation. Subsequently, flap actuation mechanisms were designed and constructed with several slot types in the flaps, and stacked PUMPS actuators were applied to the flap actuation mechanisms. Experimental study of the test wing models with four flaps was accomplished, and the flap angle was achieved up to ±5.5° within 15Hz under maximum applicable voltage.

Finite element modeling of beam bimorph piezoelectric power harvesters including visco-elasticity

S. D. Yu, S. He, W. Li

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This paper presents a finite element procedure for modeling beam bimorph piezoelectric power harvesters including viscoelasticity. A three node beam finite element is employed to model the longitudinal and flexural response of the piezoelectric structure carrying an offset proof mass. Within a beam finite element, the proposed element permits a quintic polynomial shape function for lateral deformations and a quadratic polynomial shape function for the longitudinal deformation. The dynamic equations of the electromechanical system are established using the Lagrange equations method and solved for harmonic base motions. A series of experiments were carried out to quantify the visco-elasticity constant of a piezoelectric structure and validate the simulation results. Excellent agreement was observed between the measurement and simulation data for a range of operating parameter.

Fabrication and computer simulation of nanoparticle/rubber composite elastomer with precious piezoresistance response

Qingwen Zhu, Long Ba, Chengxi Zhou, et al.

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A new conductive rubber composite was fabricated by mixing the ruthenium oxide nanoparticles with silicone rubber. The ruthenium oxide nanoparticles were synthesized by oxidation of metallic ruthenium nanoparticles, which were made using a polyol method. The size of the ruthenium oxide can be tuned by changing the annealing duration in inert atmosphere. It was found that the composite filled with ruthenium oxide of the less size presents more stable piezoresistance recurrence. Based on the random resistor network model and transfer matrix approach, a numerical calculation of the tunneling bonds resistor lattice was conducted to simulate the percolation and piezoresistance behavior of the composite. The simulation shows that the particle size and distribution have strong influences on both the percolative conductivity and the piezoresistance sensitivity.

Axisymmetrical analysis of functionally graded circular piezoelectric plate by graded element using MATLAB

B. L. Shao, R. Q. Xu

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Circular piezoelectric bimorph has been successfully used in numerous types of microdevices, such as actuators for flowcontrol applications, transducers for acoustic applications, and in locomotion of robotic systems, energy harvesting and active structural health monitoring applications. Recently, the concept of the functionally graded material (FGM) is introduced to improve properties and increase lifetime by selectively grading the elastic, piezoelectric, and/or dielectric properties along the thickness of a piezoceramic. However, even for the simple case of homogeneous circular piezoelectric geometry, analytical treatments are severely limited. This study established an axisymmetric and isoparametric graded element to model the functionally graded circular piezoelectric plates. All the material properties including elastic coefficients, piezoelectric coefficients, dielectric parameters and mass density are graded in the element and interpolated using the shape functions, which is also used to render the displacements and electric potential distribution in the element. Both static and dynamic cases can be considered in this element. MATLAB is used to implement the whole FEM code and gives some numerical examples to demonstrate the presented method.

Piezoelectric paper speaker using a regenerated cellulose film

Joo-Hyung Kim, Gyu-Young Yun, Jung-Hwan Kim, et al.

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Acoustic performance of regenerated cellulose electroactive paper (EAPap) as a thin flexible film speaker was investigated. The enhancement of piezoelectric properties was obtained by a simple mechanical stretching process. As a prototype of flexible paper speaker, the sound pressure level (SPL) of cellulose EAPap film was evaluated as a function of distance, speaker size and geometry. It was revealed that the higher acoustic output from a small rectangular shape in low frequency range, while circular one seems to be better than that of all rectangular type speakers in audible frequencies.

Exact analysis of longitudinal vibration of a nonuniform piezoelectric rod

W. Q. Chen, C. L. Zhang

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Piezoelectric rods are frequently used as transformer, known as Rosen transformer. This paper shows that the equations of motion governing the free longitudinal vibration of a nonuniform piezoelectric rod, for two special variations of crosssectional area, can be reduced to those that can be solved analytically by using suitable variable substitutions. Exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for the nonuniform rod are derived. Numerical examples are given to show the effect of geometric non-uniformity on the dynamic characteristics of the rod.

Self-assembly thin films of poly (acrylic acid)-titanium oxide

Xuefeng Li, Shaoxian Peng

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A poly (acrylic acid)-titanium oxide (PAA-TiO2) was successfully prepared and verified by particle size distribution analyzer and transmission electron microscopy. The fabrication of self-assembly films from diazoresin and PAA-TiO₂ was confirmed by UV-vis measurement. Thickness of the films was regularly increased with the layer-by-layer selfassembly process. Furthermore, the ionic bonds in the polymer films converted to covalent bonds under UV irradiation, with the decomposition of diazoresin group. Finally, the surface morphology of the films was investigated by atomic force microscopy (AFM). Results indicate TiO₂ were uniformly dispersed in thin films by the self-assembly process.

Mechanical characterization of zinc oxide thin films on glass substrates by nanoindentation

Yichong Cheng, Zhan-Sheng Guo

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Microstructures and mechanical properties of zinc oxide (ZnO) thin films deposited onto glass substrates by rf magnetron sputtering were studied. Surface morphologies and crystalline structural characteristics were examined using atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. Mechanical properties were measured by nanoindentation. The crystalline structures of ZnO thin films were well ordered with high c-axis (002) orientations. The surface morphologies of ZnO thin films were smooth and grains grew and distributed uniformly. A single pop-in in the load-displacement curve was clearly observed at a specific depth (7-10nm) of the thin film. The hardness and Young's modulus of ZnO thin films were ranged from 8.2 to 10.4GPa and 105 to 120GPa, respectively.

Microwave irradiation of lead zirconate titanate thin films

Z. J. Wang, M. W. Zhu

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The effect of microwave irradiation process on crystallization of Pb(Zr_xTi_1-x)O₃ (PZT) films was investigated. The PZT thin films were coated on Pt/Ti/SiO₂/Si substrates by a sol-gel method and then crystallized by single-mode 2.45 GHz microwave irradiation in the magnetic field at 500°C for 30 min and 650°C for 60 s, respectively. The crystalline phases, microstructures and electrical properties of the PZT films are investigated. X-ray diffraction analysis indicated that both the films heated by microwave irradiation at 500°C for 30 min and those at 650°C for 60 s were crystallized well into the perovskite phase. However, the PZT films crystallized at 500°C for 30 min had a (100)-preferred orientation while the PZT films crystallized at 650°C for 60 s had a (111)-preferred orientation. The average values of remanent polarization, coercive field, dielectric constant and loss of the PZT films crystallized at 500°C for 30 min are approximately 21 μC/cm², 90 kV/cm, 510 and 0.07 respectively, whereas the PZT films crystallized at 650°C for 60 s are approximately 27 μC/cm², 82 kV/cm, 900 and 0.05 respectively. The difference between the electrical properties of the PZT films crystallized by deferent process can be related to the microstructure effect.

Effect of Polyaniline additions on structural and gas sensing behaviour of metal oxides thin films

Mohammad Hafizuddin Hj. Jumali, Izura Izzuddin, Norhashimah Ramli, et al.

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The structural and gas sensing behaviour of metal oxides namely TiO₂ and ZnO thin films were investigated. In this paper, commercial Polyaniline (PANi) powder were added into two different metal oxides sol gel solutions with PANi : metal oxides weight ratios of 1wt.%, 2wt.% and 3wt.%. The thin films were fabricated using spin coating technique. Structural investigation using XRD presented that all films exhibited amorphous structure. Typical films surface morphology consists of agglomerated round shaped particles with the particles size varies between 57nm to 200nm. Addition of PANi formed network chains between the particles. Ethanol vapor detection test conducted at room temperature showed that both TiO₂ and ZnO based films were capable to sense the vapor. The optimum ratio in sensing ethanol vapour for both PANi-TiO₂ and PANi-ZnO films was 3:1. However, other issues such as reliability, selectability and repeatability remain as the major problems.

Corrosion monitoring of reinforcing steel in RC beam by an intelligent corrosion sensor

Guofu Qiao, Yi Hong, Jinping Ou

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Health degradation by corrosion of steel in civil engineering is a persistent problem. Structural health monitoring techniques can lead to improve estimates of structural safety and serviceability effectively. The corrosion sensor and the monitoring method have been explored and applied in RC beam's corrosion monitoring. A novel five-electrode corrosion sensor has been developed to provide the platform for corrosion monitoring of the steel bar in concrete beam by electrochemical method. Half-cell potential of the RC beam has been measured to identify the corrosion statues of the steel bar qualitatively. Galvanostatic step method has been used to excite the steel-concrete system and the transient response of the system has been obtained. The data of the transient response has been analyzed by segmented method. Some important electrochemical parameters have been extracted by this method. The results show it is effectively to analyze the data of the transient response by segmented method.

Point-by-point scanning piezoelectric phased array for detecting damage for SHM

Xingang Li, Zhenqing Wang

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The aim of the present work is to develop a system of smart devices that could be permanently attached on the surface of the structure for monitoring cracks in most aerospace structures in isolated environments. It is shown that temporal and spatial focusing can be achieved through synthetic time-reversal array method for a linear phase array of sensors and actuators. Numerical simulation verifies the convergence of piezoelectric phased array. Near-field and far-field radiation pattern are also investigated to get the ultrasound field convergence plot. The scanning precision can be adjusted by changing the size of the focus patch. A Piezoelectric phased array system performs a point-by-point scanning in which focusing allows the inspection of large areas. Damage to the structure can be inferred if there is a significant change in the transient response of the structure using the analysis of the amplitude of the received signal. The location of this damaged area can be determined using the analysis of the time it reaches the transducer. By the method of synthesis of received signal time delay from multiple sensors, we can considerably enhance the signal strength, thus reducing the negative effects of noises to solve the tough problem of processing the echo signal. The results suggest accuracy better than 1 mm in finding the location of crack tips.

Distributed fiber-optic sensing system with OFDR and its applications to structural health monitoring

H. Murayama, K. Kageyama, K. Uzawa, et al.

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In the field of fiber-optic sensing technology, distributed sensors that return a value of the measurand as a function of linear position along an optical fiber are regarded as a promising sensor which can be applied to structural health monitoring (SHM). We have developed a distributed strain sensing technique using long gauge fiber Bragg grating (FBG) based on optical frequency domain reflectometry (OFDR). FBGs functioning as mirrors with wavelengthselective reflectivity have been used as strain or temperature sensors. OFDR is a technique designed to measure backreflections from optical fiber networks and components. In our system, we use a longer gauge FBG whose length is ordinarily more than 100 mm and we can measure strain at an arbitrary position along the FBG. Therefore, we can obtain continuous strain data along the FBG. Furthermore, since the spatial resolution in strain measurements is less than 1 mm, it enables us to measure the strain distribution of stress concentrated area, such as welded and bonded joints, precisely. In this paper, we describe the principle of the distributed sensing technique based on OFDR and the applications to strain monitoring of a bonded joint and a wing box structure.

Strain monitoring of composite pressure vessel with thin metal liner using fiber Bragg grating

Jun-qing Zhao, Rong-guo Wang, Xiao-dong He, et al.

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Composite pressure vessel with thin metal liner has the advantage of both composite and metal. Due to the difference of elastic strain limits of composite and metal, there is problem of the compatibility of deformation. Nine fiber Bragg gratings were bonded to the surface of longitudinal and hoop directions of pressure vessel to monitor the strain status during 4.5MPa service pressure condition. The measured strain by the Bragg sensor is perfectly linear with the applied force. However, the hoop strain decreased as loading process and increased as unloading process, it is also negative value on middle part of the dome. The phenomena had been discussed in this investigation. As a smart structure Bragg sensor can detect the real strain state of composite pressure vessel and is suitable for damage monitoring in service. Analyzing result shows the pressure vessel can work safely with the applied hydrostatic pressure.

Application of cement-based piezoelectric composites in acoustic emission detection for concrete

Lei Qin, Yaping Peng, Hongwei Ren, et al.

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1-3 cement-based piezoelectric composites that have good compatibility with concrete material have been developed for health monitoring of concrete structures. Transducers made of this type of composites have been especially designed to meet the requirement of being embedded into concrete materials. In the property calibration, the transducers show broadband frequency response which is the basic requirement of acoustic emission (AE) transducers. The frequency response of the transducers made of 1-3 cement-based composites and piezoelectric ceramic are compared. Plain concrete beams with embedded 1-3 cement-based piezoelectric transducers are prepared and tested. During loading, AE events are recorded. The accumulated AE event number is analyzed with the loading history. The damage evolution of concrete beam could be monitored using the system including embedded transducers and software to record and analyze the data.

A new type of intelligent wireless sensing network for health monitoring of large-size structures

Ying Lei, Ch. Liu, D. T. Wu, et al.

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In recent years, some innovative wireless sensing systems have been proposed. However, more exploration and research on wireless sensing systems are required before wireless systems can substitute for the traditional wire-based systems. In this paper, a new type of intelligent wireless sensing network is proposed for the heath monitoring of large-size structures. Hardware design of the new wireless sensing units is first studied. The wireless sensing unit mainly consists of functional modules of: sensing interface, signal conditioning, signal digitization, computational core, wireless communication and battery management. Then, software architecture of the unit is introduced. The sensing network has a two-level cluster-tree architecture with Zigbee communication protocol. Important issues such as power saving and fault tolerance are considered in the designs of the new wireless sensing units and sensing network. Each cluster head in the network is characterized by its computational capabilities that can be used to implement the computational methodologies of structural health monitoring; making the wireless sensing units and sensing network have "intelligent" characteristics. Primary tests on the measurement data collected by the wireless system are performed. The distributed computational capacity of the intelligent sensing network is also demonstrated. It is shown that the new type of intelligent wireless sensing network provides an efficient tool for structural health monitoring of large-size structures.

FRP debonding monitoring using OTDR techniques

Shuang Hou, C. S. Steve Cai, Jinping Ou

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Debonding failure has been reported as the dominant failure mode for FRP strengthening in flexure. This paper explores a novel debonding monitoring method for FRP strengthened structures by means of OTDR-based fiber optic technology. Interface slip as a key factor in debonding failures will be measured through sensing optic fibers, which is instrumented in the interface between FRP and concrete in the direction perpendicular to the FRP filaments. Slip in the interface will induce power losses in the optic fiber signals at the intersection point of the FRP strip and the sensing optic fiber and the signal change will be detected through OTDR device. The FRP double shear tests and three-point bending tests were conducted to verify the effectiveness of the proposed monitoring method. It is found that the early bebonding can be detected before it causes the interface failure. The sensing optic fiber shows signal changes in the slip value at about 36~156 micrometer which is beyond sensing capacity of the conventional sensors. The tests results show that the proposed method is feasible in slip measurement with high sensitivity, and would be cost effective because of the low price of sensors used, which shows its potential of large-scale applications in civil infrastructures, especially for bridges.

Stress analysis of shape memory alloy composites

Yulong Wang, Limin Zhou, Zhenqing Wang, et al.

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Shape memory alloys (SMAs), when in the form of wires or short fibers, can be embedded into a host material to form SMA-composite for satisfying a wide variety of engineering requirements. Due to the weak interface strength between the SMA wire and the matrix, the interface debonding often happens when the SMA composites act by external force or actuation temperature or combination of them. It is, therefore, very important to understand the stress transfers between the SMA fibers and matrix and the distributions of internal stresses in the SMA composite in order to improve its properties. In this paper, a theoretical model incorporated with Brinson's constitutive law of SMA for the prediction of internal stresses has been successfully developed. The assumed stress functions which satisfy equilibrium equations in the fiber and matrix respectively and the principle of minimum complementary energy are utilized to analyze the internal stress distributions during fiber pull-out and/or thermal loading processes. The complete axisymmetric states of stresses in the SMA fiber and matrix have been developed. A finite element analysis has been also conducted to compare with the theoretical results.

Scaling analysis for hardness of shape memory alloys in sharp conical indentation

G. Z. Kang, Q. H. Kan, W. Yan

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Based on the dimensional analysis approach and finite element calculations, several scaling relationships in the indentation of super-elastic shape memory alloys with sharp conical indenter were obtained. These scaling relationships illustrate the dependence of the indentation response and the hardness on the material properties of shape memory alloys, such as the phase transformation and plastic deformation. In the finite element calculation, a newly developed constitutive model of super-elastic shape memory alloy including the plasticity of induced martensite phase was employed. It is shown that the yield stress and strain-hardening parameter of induced-martensite plays an important role in the indentation response besides the phase transition properties. Additionally, the general relationships between the indentation hardness and the phase transformation stress, maximum transformation strain, martensite yield stress, and strain-hardening parameter of shape memory alloys were obtained. The results show that the indentation hardness of shape memory alloys is not proportional to the phase transformation stress and martensite yield stress, and cannot be used directly to measure the phase transformation stress and yield stress of super-elastic shape memory alloys.

TWSME improvement by thermal cycling at zero stress in NiTi shape memory alloys

C. Urbina, S. De la Flor, F. Ferrando

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This paper describes an experimental study of the influence of thermal cycling at zero stress and the associated R-phase on two different training procedures for developing the two-way shape memory effect (TWSME) in shape memory alloys (SMAs). Two different sets of NiTi wire are used in the study: one set has been heat treated to ensure a transformation path with no R-phase, whereas the other set has had the same heat treatment which is then followed by repeated thermal cycling at zero stress to develop the R-phase. The study analyzes how both thermal cycling and the Rphase affect the transformation temperatures and the SMA hardness. Subsequently, two different TWSME trainings, thermal cycling under constant load and isothermal tensile deformation, are performed on each sample set. The study then analyzes the training procedures, the training parameters, the recoverable two-way strain and the transformation temperatures. The results show that after 30 thermal cycles, the SMA develops the R-phase and becomes harder. To obtain a substantial εtw together with a minimum plastic strain, the results suggest that the NiTi wire should be thermally cycled at zero stress prior to training until the R-phase is developed and trained by thermal cycling under constant load.

Thermoelectric module driving flexible shape memory alloy actuator

Baiqing Sun, Chao Zhang, Fengxiang Wang, et al.

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In this paper, a flexible Shape Memory Alloy (SMA) actuator based on Thermoelectric Module is presented. The proposed actuator is consist of a pre-shaped SMA wire at several located positions, and a two couples of Thermoelectric Modules (TEM), and some temperature sensors. This actuator is adopted the TEM as the driven mechanism, and it can drive the pre-shape SMA directly. Using this driven mode can directly control pre-location of the SMA actuator. Therefore the control flexibility of the actuator is greatly increased. This paper analyze of the differences and advantages between the TEM actuator and the traditional SMA actuators, and introduced the operational mechanism, structure and driven approach. The experimental results indicate that the actuator can make reciprocating motion smoothly and softly.

Constraint super-elastic SMA based experimental study of self-monitoring and repairing of concrete beam crack

Sheng-kui Di, Sheng-wei Ji, Wei-pan Hua, et al.

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Taking advantages of the characteristics of super-elasticity and restoring forces while the shape memory alloy(SMA) wire (4.0mm in diamerer) was excited, concrete modal beams was established, and Ni-Ti SMA wire with different prestretching length and different quantity under martensitic state were embedded into the concrete tensile zone before the concrete casted under environmental temperature. The relationship between the resistance rate of SMA and the cracks width of beams was studied under loaded process, and the variety regulation of the cracks width of beam was reply while excited by electrifying. The impact of slip and bond between the concrete and SMA was taken into account (to prevent the slip of the SMA by embedding the anchors into both ends of the beam), while the process was simulated considering the influence of additional resistance coming from the anchor. The result agreed with the experiment well. It is shown that: the crack closed almost completely and the deformation recovered suddenly after the SMA was excited by electrifying; The drive effect can be improved by adding the quantity of SMA; If the cracks width of beam were less than 1.5mm, Clearly a linear relationship was between the rate of change alloy resistance and the rate of crack width of the concrete beam. The residual deformation of rebar played a very negative role in the recovering of the residual deformation.

Electro-activity of electro-spun IPMC and cast IPMC

Danyu Liu, Guifen Gong, Yujun Zhang

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The cast and electro-spun membranes of EVOH-g-nSPEG were prepared by solution cast method and electro-spun method respectively. The cast membrane Ionomer/Metal composites (IPMC) and electro-spun membrane IPMC were prepared by penetration-reduction process. The micro-morphology of these two IPMCs was studied by scanning electron microscope (SEM). The surface resistance (R_S) and critical response voltage (U_R) of IPMC electrode were tested and calculated by four electrode structure method and intercept method. And the bending stress of IPMC was tested by electro-deformation experiment. The results indicated that the surface of cast membrane IPMC had better smoothness and compactness than that of electro-spun one. The electro-spun membrane possessed compact surface and loose internal structure. The U_R for electro-spun membrane IPMC was lower than that of cast one. And the U_R for both IPMCs increased with the R_S increasing when tested with the same membrane structure and metal electrode. The cast membrane IPMC had higher bending stress with the maximum value being 4.75MPa while being only 0.66MPa for electro-spun membranes.

A nonlinear scalable model for designing ionic polymer-metal composite actuator systems

A. J. McDaid, K. C. Aw, E. Hämmerle, et al.

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This paper proposes a conclusive scalable model for Ionic Polymer Metal Composites (IPMC) actuators and their interactions with mechanical systems and external loads. This dynamic, nonlinear model accurately predicts the displacement and force actuation in air for a large range of input voltages. The model addresses all the requirements of a useful design tool for IPMC actuators and is intended for robotic and bio-mimetic (artificial muscle) applications which operate at low frequencies. The response of the IPMC is modeled in three stages, (i) a nonlinear equivalent electrical circuit to predict the current drawn, (ii) an electro-mechanical coupling term, representing the conversion of ion flux to a stress generated in the polymer membrane and (iii) a mechanical beam model which includes an electrically induced torque for the polymer. Mechanical outputs are in the rotational coordinate system, 'tip angle' and 'torque output', to give more practical results for the design and simulation of mechanisms. Model parameters are obtained using the dynamic time response and results are presented demonstrating excellent correspondence between the model and experimental results. This newly developed model is a large step forward, aiding in the progression of IPMCs towards wide acceptance as replacements to traditional actuators.

Sub-percolative composites for dielectric elastomer actuators

H. Stoyanov, M. Kollosche, D. McCarthy, et al.

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Dielectric elastomer actuators (DEA) based on Maxwell-stress induced deformation are considered for many potential applications where high actuation strain and energy are required. However, the high electric field and voltage required to drive them limits some of the applications. The high driving field could be lowered by developing composite materials with high-electromechanical response. In this study, a sub-percolative approach for increasing the electromechanical response has been investigated. Composites with conductive carbon black (CB) particles introduced into a soft rubber matrix poly-(styrene-co-ethylene-co-butylene-co-styrene) (SEBS) were prepared by a drop-casting method. The resulting composites were characterized by dielectric spectroscopy, tensile tests, and for electric breakdown strength. The results showed a substantial increase of the relative permittivity at low volume percentages, thereby preserving the mechanical properties of the base soft polymer material. Young's modulus was found to increase with content of CB, however, due to the low volume percentages used, the composites still retain relatively low stiffness, as it is required to achieve high actuation strain. A serious drawback of the approach is the large decrease of the composite electric breakdown strength, due to the local enhancement in the electric field, such that breakdown events will occur at a lower macroscopic electric field.

Fullerene reinforced ionic polymer transducer

J. H. Jung, T. H. Cheng, I. K. Oh

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Novel fullerene reinforced nano-composite transducers based on nafion were developed inorder to improve the ionic polymer metal composite transducer. The fullerene reinforced nano-composite membranes were fabricated by recasting method with 0.1 and 0.5 weight percentage of a Fullerenes. Stress-Strain tests showed tremendous increase in stiffness and modulus of the nano-composite membranes even at these minute concentrations of Fullerenes. Ionic exchange capacity analysis and proton conductivity test were performed to calculate the electrical property of the composite films. Water uptake was measured to understand the liquid adsorbing characteristics of the membranes. Also, tip displacement of the nano-composite membrane transducer was investigated under AC excitations with various magnitudes and frequencies. Furthermore, the generated energy was measured from external sinusoidal physical input vibration with several displacements and frequencies by using a mechanical shaker. As a result, the fullerene reinforced nanocomposite membrane based on nafion shows higher stiffness and Young's modulus than that of pure nafion membrane. Also, the nano-composite membrane had better water uptake and proton conductivity than the pure membrane. Fullerene reinforced nano-composite membrane transducer actuates to a much larger deformations than pure nafion membrane transducer. The developed membrane transducer dissipates more energy from the physical input vibration than that of unfilled(or virgin) Nafion membrane transducer.

Electromechanical stability domain of dielectric elastomer film actuators

Shouhua Sun, Liwu Liu, Zhen Zhang, et al.

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The dielectric elastomer film will encounter electrical breaking-down frequently in its working state due to the coupling effect of electric field and mechanical force field. Referring to the electromechanical coupling system stability theory of dielectric elastomer proposed by Suo and Zhao, the electromechanical stability analysis of dielectric elastomer has been investigated. The free energy function of dielectric elastomer can be represented by the principle of superposition based on Suo's theory. Unstable domain of electromechanical coupling system of Neo-Hookean type silicone was analyzed by R. Díaz-Calleja et al. In the current work, the elastic strain energy function with two material constants was used to analyze the stable domain of electromechanical coupling system of Mooney-Rivlin type silicone, and the results seem to support R. Díaz-Calleja's theory. These results provide useful guidelines for the design and fabrication of actuators based on dielectric elastomer.

Effect of precipitations on the damping capacity of Fe-13Cr-2.5Mo alloy

Xiaofeng Hu, Xiuyan Li, Bo Zhang, et al.

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The influence of precipitations on the damping capacity of Fe-13Cr-2.5Mo (mass %) based alloys has been investigated in this paper. The damping behaviors were examined by dynamic mechanical analyzer (DMA) at temperature t = 35 °C, vibrate frequency f = 1 Hz and strain amplitude ε of 10^-6 and 10-3. Field-emission scanning electron microscope (FESEM) with X-ray energy dispersive spectrometer (EDS) was used to observe microstructure and determine the composition of precipitations. The results show that damping capacity of Fe-13Cr-2.5Mo based alloys is more strongly correlated with intragranular precipitation than with grain boundary (GB) precipitation. Fe-Cr-Mo alloy annealed at 1100 °C for 1 h followed by furnace cooling (FC) with relatively fewer intergranular precipitations, exhibits higher damping behavior. With the increase of annealing temperature, the amount of intragranular precipitations increases while damping capacity of Fe-Cr-Mo alloy decreases. Addition of 1.0% Ti obviously inhibits precipitation of GB precipitations, but promotes the intragranular precipitations in the alloy distinctly, so the damping capacity of Fe-Cr-Mo- 1Ti is slightly lower than that of Fe-Cr-Mo alloy. Addition of 1.0% Nb can significantly decrease damping capacity of Fe-Cr-Mo-1Nb at low strain amplitude. But at higher strain amplitude, damping capacity increases more rapidly and Fe- Cr-Mo-1Nb possesses the highest damping capacity. This result reveals that larger amount of precipitations in Fe-Cr-Mo based alloys can interact with dislocations and generate an amplitude-dependent dislocation damping Q^-1_dis at high strain amplitude.

Study of the response time of MR dampers

Xinchun Guan, Pengfei Guo, Jinping Ou

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Response time is an important parameter which determines the applied fields and practical vibration reduction effects of magnetorheological (MR) dampers. However, up to now, only a few papers discuss the test and analysis of response times. In this paper, the response time of a large-scale MR damper at different velocities and currents was firstly tested. Then, the transient magnetic field excited by the time-variant excitation current was simulated by finite element method (FEM). Based on the variation of the shear yield stress of magnetorheological fluids in the gap between the cylinder and the piston, the response time of the MR damper was investigated. Influences of eddy current and excitation current response time on the damper's response were also explored. Results show that by utilizing finite elements method, the calculated average effective shear yield strength can be used to predict the response time of a MR damper. Electromagnetic response is the predominant factor influencing the response time of a MR damper, and reducing eddy currents is the key to accelerate the response of a MR damper. Moreover, influence of eddy currents is much larger under stepping down excitation currents than stepping up currents, and with a same magnitude of step, no matter when the current increases or decreases, the smaller the initial current, the greater the eddy current affects a damper's response and the longer the response time of damping force is. A fast response excitation current may induce large eddy currents which reduce the response of the damper instead.

Hierarchical fuzzy identification of MR damper

Hao Wang, Haiyan Hu

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Magneto-rheological (MR) dampers, recently, have found many successful applications in civil engineering and numerous area of mechanical engineering. When an MR damper is to be used for vibration suppression, an inevitable problem is to determine the input voltage so as to gain the desired restoring force determined from the control law. This is the so-called inverse problem of MR dampers and is always an obstacle in the application of MR dampers to vibration control. It is extremely difficult to get the inverse model of MR damper because MR dampers are highly nonlinear and hysteretic. When identifying the inverse model of MR damper with simple fuzzy system, there maybe exists curse of dimensionality of fuzzy system. Therefore, it will take much more time, and even the inverse model may not be identifiable. The paper presents two-layer hierarchical fuzzy system, that is, two-layer hierarchical ANFIS to deal with the curse of dimensionality of the fuzzy identification of MR damper and to identify the inverse model of MR damper. Data used for training the model are generated from numerical simulation of nonlinear differential equations. The numerical simulation proves that the proposed hierarchical fuzzy system can model the inverse model of MR damper much more quickly than simple fuzzy system without any reduction of identification precision. Such hierarchical ANFIS shows the higher priority for the complicated system, and can also be used in system identification and system control for the complicated system.

Electromagnetic multi-mode shunt damper for flexible beams based on current flowing circuit

T. H. Cheng, X. L. Wang, I. K. Oh

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In this paper, the multiple current flowing electromagnetic shunt damper was newly employed for the semi-active vibration suppression of the flexible structures. The electromagnetic shunt damper consists of a coil and a permanent magnet. The ends of the coil were connected to the multimode current flowing electromagnetic shunt circuit for vibration reduction of the cantilever beam employing energy dispersion method. The system was electro-magneto-mechanically coupled between the electrical circuit and mechanical vibrating cantilever beam with a electromagnetic transducer. The circuits were designed for first two mode control of the cantilever. The vibration and damping characteristics of the flexible beams with the electromagnetic shunt damper were investigated by tuning the circuit parameters. The effect of the magnetic intensity on the shunt damping was studied with the variation of the gap between the aluminum beam and the permanent magnet. The resistances of the shunt circuit were used to investigate vibration damping effect of cantilever. The theoretical prediction of frequency response of the beam under multiple mode electromagnetic shunt damping method has a good agreement with experimental results. Present results show that the magnet shunt damper can be successfully applied to reduce the vibration of the flexible structures.

Design method of spring accumulator of single-ended MR dampers

Xinchun Guan, Yonghu Huang, Shaohua Hu, et al.

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Compared to the double-ended magnetorheological (MR) dampers, single-ended MR dampers are more suitable in limited-space required fields for their larger strokes. An accumulator is needed for a single-ended MR damper to balance the volume changes as the piston pulled out and back into the cylinder. Since an accumulator has a great influence on the damper's performances, this influence should be taken into account in the damper's designing procedure. In this paper, damping force formula is deduced for the single-ended MR damper with spring accumulator. Then both the method of determination main parameters of regular spring accumulator and its inherent drawbacks are presented. Finally, by utilizing the pseudoelastic character of shape memory alloy (SMA), a SMA spring accumulator is proposed and its design method is given as well.

Model-based simulation of the responses of ultrananocrystalline diamond and nano structures

Luming Shen, Zhen Chen

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Owing to their outstanding mechanical, tribological, electronic transport, chemical and biocompatibility properties, the ultrananocrystalline diamond (UNCD) films grown by the microwave plasma chemical vapor deposition method under hydrogen-poor conditions have become the subject of intense research interests over the past decade. Based on the available computational capabilities and experimental data, a combined kinetic Monte Carlo (KMC) and molecular dynamics (MD) procedure has been developed for large-scale atomistic simulation of the responses of polycrystalline UNCD films under various loading conditions. The mechanical responses of resulting UNCD film have been investigated by applying displacement-controlled loading in the MD simulation box. Recently, a systematic study is being performed to understand the combined effects of grain size, loading rate, temperature, imperfection, loading path and history on the material strengths and failure patterns of both pure and nitrogen-doped UNCD films. Furthermore, recent MD simulation results of the notch size effect on the failure mechanism of nano-scale hierarchical structures consisting of one-dimensional members arranged in parallel will also be discussed to better design MEMS devices.

Preparation, modification, morphology tailor and application of conjugated conductive polymer in chemical sensors

Xingfa Ma, Mingjun Gao, Huizhong Xu, et al.

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Polyaniline nanotube was prepared with aid of lactic acid assembly. A chemical prototype sensor was constructed based on nanotube-structured polyaniline and two typical structured chemical sensors, one is an interdigital electrodes on flexible polymer substrate, the other is a highly sensitive quartz resonators. The gas-sensing behavior of the two typical sensors to some organic vapors operating at room temperature was investigated. Results showed rapid response, and good reversibility of these two typical sensors. The response time is 10-20 s, the reversible time is about 100 s. This study provides a simple approach for preparation of materials needed for a chemical sensor to selected organic volatiles with rapid response or organic flexible nanoelectronic devices.

Decentralised information management in facility management using radio frequency identification technology

Zixiang Cong, Farhan Manzoor, Hang Yin, et al.

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Facility Management (FM) is a critical component of the operational phase of a building's life cycle, which includes management of building systems and its services. A large quantity of data is collected from maintaining a building through FM. One question that arises is how can this data be distributed between different systems? A solution to this problem is important for facility managers and maintenance staff. This paper discusses the merits of Radio Frequency Identification (RFID) technology and its potential use in applications within the FM sector. The paper also reports a prototypical demonstrator implementation of an RFID based information management system for FM-scenarios. The prototype was deployed and tested in an office room at University College Cork (UCC), Ireland. The applicability of RFID for Decentralised Information Management (DIM) was applied and specific results for demonstration outputs were achieved.

Use of optically transparent lead lanthanum zirconate titanate as actuators and sensors

Quantian Luo, Liyong Tong

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The photo-induced strain in transparent lead lanthanum zirconate titanate (PLZT) materials is due to a process of superposition of photovoltaic and converse piezoelectric effects. The photovoltaic effect in PLZT materials is observed only in the direction of spontaneous polarization of ferroelectric materials. In this paper, electrical and mechanical performance of PLZT ceramics polarized in 0-1 or 0-3 direction are investigated, and PLZT actuators and sensors with the 0-3 polarization are studied. For multilayer PLZT actuators, presented also are the formulas for the calculation of energy release rates due to debonding.

Ultrasonic damage detection of concrete structures by using pulse-echo sensor arrays and SAFT

Li-hua Shi, Zhi-xue Shao, Zhe Shao

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In ultrasonic nondestructive testing (NDT) of concrete structures, the synthetic aperture focusing technique (SAFT) can improve the resolution of target and therefore gives a better image display of the B-scan data. In traditional B-scan of concrete structures the ultrasonic transducers are usually moved manually to detect the whole structure, the detection speed and the consistency in different test points are greatly affected. A PZT sensor array is designed in this paper to perform B-scan on large concrete structures more efficiently. The excitation of the sensor array and the data processing techniques for the array data are discussed. A signal processing approach is proposed to improve the consistency between different test channels in the array. Experiments on real structures show the embedded objects can be located accurately by using the array sensor and SAFT method.

Guided wave propagation based damage detection in welded rectangular tubular structures

Xi Lu, M. Y. Lu, L. M. Zhou, et al.

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Guided wave based methods have shown great potential to practical use and have been the object of many researches for structural health monitoring (SHM). In this paper, a welded steel structure with rectangular section, which is almost 1:1 scale model for a bogie frame segment of train, is investigated by using both finite element method (FEM) and experimental analysis for the purpose of damage detection. Finite element models are established to simulate the propagation behavior of guided waves in the structure. An active actuator/sensor network is employed to generate guided waves propagating in the structures and collect response signals. Excitations at selected frequency are used to minimize the effect of the intrinsic multi-mode phenomenon of guided waves on the consequent signal interpretation. Modern signal processing approaches, such as continuous wavelet transform (CWT) and Hilbert transform (HT), are applied to all collected signals. An algorithm based on the concept of damage presence probability (DPP) is proposed for estimation of damage location. The results indicate that the recommended guided wave propagation based approach is reasonable for damage detection in such kind of structures.

A comparison of interrogation schemes for impact event monitoring using fiber Bragg gratings

C. S. Shin, B. L. Chen

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Fiber Bragg gratings (FBGs) are capable of acquiring transient impact signals and are suitable for impact event monitoring and impact position locating. Previous application of this technique showed that the accuracy and the range within which the impact position can be located is limited. A detailed analysis concluded that the major cause of the above limitations was due to poor equipment resolution and angular insensitivity of the FBG. In order to minimize the number of FBGs deployed yet still maintains reasonable prediction accuracy and locating range, the sensitivity of the interrogation system has to be optimized. To identify a better technique to serve the above purpose, four different interrogating schemes have been compared in the current work. The configurations with an ASE light source modified by a commercial edge filter or an FBG are the least sensitive but remained stable under all impact conditions. In the other two configurations which comprise a ring laser scheme, the one with the sensing FBG being part of the laser ring is extremely sensitive and is capable of detecting the impact of a 70g projectile from a height of 0.1mm at a distance of 60cm. However, with increasing impact severity, the system may become unstable. The configuration where the sensing FBG is not part of the laser ring gives a good compromise between sensitivity and stability. Based on the above results, the implications on the sensitivities and limitations of the different configurations when used for impact event monitoring on large structures will be discussed.

Dielectric properties of carbon nanotube/silicone elastomer composites

Zhen Zhang, Shouhua Sun, Liwu Liu, et al.

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Dielectric elastomers have received a great deal of attention recently for effectively transforming electrical energy to mechanical work. Their large strains and conformability make them enticing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In order to maximize actuator performance, the dielectric elastomer actuators should have a high dielectric constant and high dielectric breakdown strength. Here we have investigated the increase in permittivity of a commercial silicone elastomer by the addition of carbon nanotube. The percolation threshold of the composites is obtained to be low. Experimental results suggest that for the case of conductive filler particle-elastomer matrix interaction, actuation strain increases with increasing carbon nanotube content.

Hysteresis in dielectric electroactive polymers

B. Lassen, M. Jaffari, C. Melvad, et al.

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In this paper experimental results indicating the presents of hysteresis in the acrylic tape VHB 4910 produced by 3M are presented. It is shown that there are large stress relaxation times associated with this material making it difficult to separate viscoelastic effects and hysteresis. Additionally, a set of Preisach hysteresis models is presented and it is shown that these models fit the experimental results well. The simplest model having only 5 fitting parameters is suggested as the best model as the parameters can be uniquely determined, this not being the case for the other models.

Optimal design of link systems using successive zooming genetic algorithm

Young-Doo Kwon, Chang-hyun Sohn, Soon-Bum Kwon, et al.

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Link-systems have been around for a long time and are still used to control motion in diverse applications such as automobiles, robots and industrial machinery. This study presents a procedure involving the use of a genetic algorithm for the optimal design of single four-bar link systems and a double four-bar link system used in diesel engine. We adopted the Successive Zooming Genetic Algorithm (SZGA), which has one of the most rapid convergence rates among global search algorithms. The results are verified by experiment and the Recurdyn dynamic motion analysis package. During the optimal design of single four-bar link systems, we found in the case of identical input/output (IO) angles that the initial and final configurations show certain symmetry. For the double link system, we introduced weighting factors for the multi-objective functions, which minimize the difference between output angles, providing balanced engine performance, as well as the difference between final output angle and the desired magnitudes of final output angle. We adopted a graphical method to select a proper ratio between the weighting factors.

The application of conductive polymer nano emulsion in printing ink

Luhai Li, Linxin Mo, Fang Yi, et al.

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In order to achieve the acquirement of flexible displayer, such as e-paper and touch screen, and to reduce the cost of conductive printing ink, the application of conductive polymer in printing ink is studied, and conductive flexible layer is acquired. The effect of N, N-dimethylformamide, glycerol, deionizer water, and pH value on the performance of water-based nano conductive polymer ink is studied by the second doping of conductive polymer nano suspension. The effect of various polymers on the conductivity of printing ink is researched by adding various polymer resins. At last, printing performance of the conductive polymer ink is tested by some printing methods, such as screen, and offset printing. Conductive printing layer which can be compared with the traditional conductive ink in the conductivity is acquired and the conductive layer is waterproof.

Development of novel low shrinkage dental nanocomposite

Yi Sun, Xiaorong Wu, Yanju Liu, et al.

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It has been the focus to develop low shrinkage dental composite resins in recent ten years. A major difficulty in developing low shrinkage dental materials is their deficiency in mechanical properties to clinical use. This paper reviews the present investigations of low shrinkage dental composite resins and attempts to develop a novel system with multifunctional POSS incorporated. In this paper, it is especially interesting to evaluate the influences of shrinkage with different weight percentage of POSS (0~15wt%) incorporated in dental composite resins. Their double bond conversions are evaluated and their microstructures are characterized with Fourier-transform infra-red spectroscopy and X-ray diffraction. Their mechanical properties are also presented in this paper. The results show that the shrinkage of nanocomposites with POSS can be reduced effectively from 3.53% to 2.18%. The mechanical properties of this novel system, such as strength, hardness and toughness, are also enhanced greatly. Especially with 2wt%POSS incorporated, the best integrative improved effects are revealed. The mechanism of shrinkage is discussed.

Magnetic field activation of SMP networks containing micro nickel (Ni) powder

Dawei Zhang, Yanju Liu, Jinsong Leng

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In this paper shape memory effect of shape memory composite in magnetic field was studied. The shape memory composite was filled by nickel powder, and the nickel powder was treated by silane coupling agent. The Tg of shape memory composite was measured by dynamic mechanical analyzer. The surface element of treated nickel powder was analysized with FT-IR. Furthermore, the dispersion of nickel powder in polymer was observed by SEM. The results indicated that the shape of composite filled by untreated nickel powder did not change in the magnetic field, while the composite filled by treated nickel powder was drawn in the magnetic field. The tensile stretch was decrease with the increase of nickel powder content in the shape memory composite. The addition of silane coupling agent onto nickel powder surface was helpful for the dispersion of nickel in polymer.

Membrane wrinkling patterns and control with SMA and SMPC actuators

Mingyu Lu, Yunliang Li, Huifeng Tan, et al.

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Wrinkling is a main factor affecting the performance of the membrane structures and is always considered to be a failure as it can cause dramatic decrease of shape accuracy. The study of membrane wrinkling control has the analytical and experimental meanings. In this paper, a feasible membrane shape control method is presented. An expression of wrinkle wavelength using stress extremum principle is established based on the tension field theory and the Von Karman large deflection formula which verifies the generation and evolution reason of membrane wrinkles. The control mechanism for membrane wrinkles is developed using shape memory alloy (SMA) and shape memory polymer composite (SMPC) actuators which are attached to the boundaries of the membrane for producing contraction/expansion forces to adjust the shape of the membrane. The whole control process is monitored by photogrammetric technique. Numerical simulations are also conducted using ANSYS finite element software with the nonlinear post-buckling analytical method. Both the experimental and numerical results show that the amplitudes of wrinkles are effectively controlled by SMA and SMPC actuators. The method introduced in this paper provides the foundation for shape control of the membrane wrinkling and is important to the future work on vibration control of space membrane structures.

Smart goggles based on all-plastic electrochromic devices

Chao Ma, Chunye Xu

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A novel smart goggle with tunable light transmittance was designed, fabricated and characterized in this research. The developed smart goggle lens was all-plastic based electrochromic (EC) device. The working EC material was a layer of thin film conducting polymer: poly (3,4-(2,2-dimethylpropylenedioxy)thiophene) (PProDOT-Me₂), while the counter material of the device was a layer of thin film inorganic oxide: vanadium oxide-titanium oxide (V₂O₅-TiO₂) composite, which serves as an ion storage layer. A transparent electrolyte as the ion transport layer was sandwiched between the working and counter parts of the device. The whole device was sealed with an UV cured flexible film sealant. The smart goggle exhibited tunable light transmittance in visible light wavelength (380-800nm), with a maximum contrast ratio at 580nm. Meanwhile, other unique properties include fast switching speed, low driving voltage, memory function (no power needed after switching, bi-stable), great durability, high flexibility, light weight, and inexpensiveness.

The theoretical model and application of the double-N SMA bundles cooperating with rubber bearing

Guangping Zou, Jie Lu, Zhiqiang Shen

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A novel isolation seismic bearing model named the double-N SMA-rubber bearing was proposed and designed in this paper. The basic design idea was to add SMA wire bundles closed around the rubber bearing to improve the whole mechanical properties of the isolation seismic bearing. The corresponding theories equations and the working mechanism of this new isolation device were deduced. The application of this isolation model which was employed in the model shaking table test of a 1000m³ storage tank was presented. Different test working conditions and seismic excitations were given to analyze the structure response of the storage tank and the presented bearing properties. The presented bearing model was used in the first working condition. The displacement and acceleration responses of vertical tank model were obtained. Only the rubber bearing without SMA bundles was applied in another working condition. Meanwhile the structure response results were gained and contrasted with the former results. The experimental results show the presented isolation seismic model is effective in absorbing energy and can be used in the isolation seismic design of the vertical storage tanks.

Experimental thermo-stress analysis for a bending shape control of composite beams embedded with SMA wires

Gang Zhou, Peter Lloyd

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An experimental study has been conducted to design and fabricate smart composite beams embedded with prestrained nitinol wire actuators. The fabrication process developed allowed both quasi-isotropic E-glass/epoxy and carbon/epoxy hosts to be eccentrically embedded with 10 parallel prestrained wires with a purpose-made alignment device and cured successfully in an autoclave. Smart composite beams of three different lengths were made for each type of host. Both single-cycle and multi-cycle thermomechanical bending actuations of these beams in the cantilever set-up were characterised experimentally by applying various levels of electric current to the nitinol wires. The performance characteristics showed that the present fabrication process was repeatable and reliable. While the end deflections of up to 41 mm were easily achieved from smart E-glass/epoxy beams, the limited end deflections were observed from the smart carbon/epoxy beams due primarily to our inability to insulate the nitinol wires. Moreover, it seemed necessary to overheat the prestrained wires to much higher temperatures beyond the complete reverse transformation in order to generate recovery stress.

Highway bridge unseating and reduction analysis using SMA restrainers under earthquake excitations

Anxin Guo, Qingjie Zhao, Hui Li

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During the past several strong earthquakes, most of the highway bridge suffered from unseating and pounding damage due to large displacement between the adjacent frames. One traditional approach for mitigating the unseating of the highway bridge is to use restrainers made of steel cables and rods. However, the elastic design demands of the restrainers will induce large additional forces on the structural components of the bridges. The aim of the study is to investigate the effects of the strong ground motions on the unseating and pounding damages of the base-isolated highway bridges, and the performance of the shape memory alloy (SMA) restrainers for the unseating reduction of the highway bridge. An analytical model of the highway bridge with SMA restrainers and pounding effects is established, and the performance of the SMA restrainer for eliminating the bridge unseating and pounding of the highway bridge is also analyzed. Numerical simulation results indicate that the pounding strongly increase the structural responses and the SMA restrainer can be effectively used to mitigate the bridge unseating and pounding damage when subjected to the strong ground motions.

Strain properties analysis and wireless collection system of PVDF for structural local health monitoring of civil engineering structures

Yan Yu, Yang Wang, Weijie Dong, et al.

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For large civil engineering structures and base establishments, for example, bridges, super-high buildings, long-span space structures, offshore platforms and pipe systems of water & gas supply, their lives are up to a few decades or centuries. Damaged by environmental loads, fatigue effects, corrosion effects and material aging, these structures experience inevitably such side effects as damage accumulation, resistance reduction and even accidents. The traditional civil structure is a kind of passive one, whose performance and status are unpredictable to a great extent, but the informatics' introduction breaks a new path to obtain the status of the structure, thus it is an important research direction to evaluate and improve reliability of civil structures by the use of monitoring and health diagnosis technique, and this also assures the security of service for civil engineering structures. Smart material structure, originated from the aerospace sector, has been a research hotspot in civil engineering, medicine, shipping, and so on. For structural health monitoring of civil engineering, the research about high-performance sensing unit of smart material structure is very important, and this will possibly push further the development and application of monitoring and health diagnosis techniques. At present, piezoelectric materials are one of the most widely used sensing materials among the research of smart material structures. As one of the piezoelectric materials, PVDF(Polyvinylidene Fluoride)film is widely considered for the advantages of low cost, good mechanical ability, high sensibility, the ability of being easily placed and resistance of corrosion. However, only a few studies exit about building a mature monitoring system using PVDF. In this paper, for the sake of using PVDF for sensing unit for structural local monitoring of civil engineering, the strain sensing properties of PVDF are studied in detail. Firstly, the operating mechanism of PVDF is analyzed. Secondly, wireless collection system of PVDF is integrated with PVDF film, charge amplifier, wireless transceiver and the corresponding software. Then, with strain gauge as a reference, experiments have also been done to study the quasi-static and dynamic strain response of PVDF, such as sensitivity, linearity and frequency responding, etc. The experimental results show that PVDF is sensitive to the impact response of civil engineering structures, and can provide local monitoring in different frequency response cooperating with a strain gauge. The developed wireless collection system has the characteristics of no lines, saving cost and installation time, and thus further pushes the practical application of PVDF for civil engineering structures.

Health monitoring of reinforced concrete structures based on PZT admittance signal

Dansheng Wang, Hongping Zhu, Danyan Shen, et al.

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Reinforced concrete (RC) structure is one of most familiar engineering structure styles in the civil engineering community, which often suffer crack damage during their service life because of some factors such as overloading, excessive use, and bad environmental conditions. Thus early detection of crack damage is of special concern for RC structures. Piezoelectric materials have direct and converse piezoelectric effects and can serve as actuators or sensors. A health monitoring method based on PZT admittance signals is addressed in this paper, which use the electromechanical coupling property of piezoelectric materials. An experimental study on health monitoring of a RC beam is implemented based on the PZT admittance signals. In this experiment, the electrical admittances of distributed PZT sheets are measured when the host beams are suffering from variable loads. From the obtained PZT admittance curves one can find that the presence of incipient crack can be captured and the cracking load of the RC beam can also generally determined. By the experimental study it is concluded that the health monitoring technique is quite effective and sensitive for RC structures, which indicates its favorable application foreground in civil engineering field.

Simulation of fiber Bragg grating sensor for rebar corrosion

Jiang Geng, Jin Wu, Xinming Zhao

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It is world widely concerned in the durability of reinforced concrete structures. Corrosion of rebar is one of the most important factors which can affect the durability of the concrete structures, and may result in damage to the structures in the form of expansion, cracking and eventually spalling of the cover concrete. In addition, the structural damage may be due to loss of bond between reinforcement and concrete and reduction of reinforcement cross-sectional area, and finally it may cause structure failure. With the advantages of linear reaction, small volume, high anti-erosion capability and automatic signal transmission, the smart sensors made of fiber bragg grating (FBG) to monitor strain, stress, temperature and local crack have got wide application in buildings, bridges and tunnels. FBG can be adhered to the surface of the structure, and also can be embedded into the inner of the structures when the project is being under construction to realize the real-time health monitoring. Based on volume expansion, the fiber bragg grating sensor for rebar corrosion is designed. The corrosion status of the structure can be obtained from the information provided by sensors. With the aid of the finite element software ANSYS, the simulation of the corrosion sensor was carried in this paper. The relationship between corrosion ratio and the shift of wavelength was established. According to the results of the simulation, there were differences between simulated results and measured results. The reason of the differences was also studied in this paper.

Prediction of impact damage on stitched sandwich composite panels

Xitao Zheng, Linhu Gou, Xiaoxia Zheng, et al.

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Based on the analysis of experiments, the damage of composite stitched foam-core sandwich structure under low-velocity impact has been studied in this paper. A numerical simulation is performed to predict the effects of stitching on the low-velocity impact response of stitched sandwich composite panels. The results of numerical simulation show that the damage areas of upper face sheet are greater than the lower one for both unstitched and stitched sandwich, however, the main patterns of damage are different. For the unstitched structure, the upper face sheet's damage is the main pattern of damage, whereas the crushing damage is the stitched one's main damage. The finite element results have corresponded well with the experimental results, which prove the correctness of the finite element model. The results indicate that stitching does not increase the load at which delamination begins to propagate, but greatly reduces the extent of delamination growth at the end of the impact event. Then, the damage areas' change has been taken into consideration as some factors change, those various factors include the impact energy, the thickness of upper panel, the thickness of foam core and the stitched density (stitched row spacing×needle spacing, suture thickness). And also it presents some related theoretical analysis.

Online debonding detection in honeycomb sandwich structures using multi-frequency guided waves

F. Song, G. L. Huang, G. K. Hu

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Due to the complex nature of sandwich structures, development of the online structural health monitoring system to detect damages in honeycomb sandwich panels inherently imposes many challenges. In this study, the leaky guided wave propagation in the honeycomb sandwich structures generated by piezoelectric wafer actuators/sensors is first simulated numerically based on the finite element method (FEM). In the numerical model, the real geometry of the honeycomb core is considered. To accurately detect debonding in the honeycomb sandwich structures, signal processing based on continuous wavelet transform is adopted to filter out the unwanted noise in the leaky Lamb wave signals collected from the experimental testing. A correlation analysis between the benchmark signals at the normal condition and those recorded at the debonded condition is then performed to determine the differential features due to the presence of debonding. Finally, the image of the debonding is formed by using a probability analysis. Specifically, fusing images acquired from multi-frequency leaky Lamb waves are obtained to enhance the quality of the final image of the structure. The location and size of the debonding in the honeycomb sandwich structures are estimated quantitatively.

Preparation of single crystal of TiNi alloy and its shape memory performance

Chonghe Li, Ziming Guo, Ming Zhu, et al.

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The unidirectional solidification equipment based on Bridgman method with high temperature gradient was designed, and the single crystal of Ti-50.0at%Ni alloy was successfully fabricated by this equipment as well as a selective growing zigzag-shaped crystallizer and a steady growth container that were made of electro graphite. The microstructure of single crystal sample was studied by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS); the orientation of single crystal was measured by X-ray technology; the phase transformation points were determined by Differential Scanning Calorimetry (DSC). It is resulted that, the single crystal of TiNi shape memory alloy (SMA) can be prepared with a set of suitable process parameters; the microstructure of the single crystal obtained in this study is dendritic, there is Ti₂Ni intermetallic between the dendrites, the angle between the orientation of single crystal and [111] plane is about 15 degree; the shape memory performances are improved obviously and the maximum recoverable strain reaches 10%.

A method of calculating residual stresses through elastic modulus measured by nanoindentation

Yanshen Wang, Yuxian Gai, Shiliang Qu D.D.S., et al.

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Nanoindentation is a good method for characterizing residual stresses with large gradient that distributed in a very confined area. In our previous research, a formula was brought out to characterize residual stresses from elastic modulus measured in nanoindentation experiments. In this paper, aluminum alloy bulks were used as samples to validate the formula. The bulks were machined to be mirror surface on one side through ultra-precision diamond turning. Two samples were compressed and stretched by load instruments respectively. Nanomechanical properties such as elastic modulus in the areas on the mirror surface of the compressed and stretched samples were both measured by a commercial nanomechanical test system (TriboIndenter, Hysitron Inc.). Using the formula, then, the mean values of residual stresses on the mirror surface were calculated through the acquired experiment data. After that, the two stressed samples were tested by a commercial XRD instrument (X'Pert, Philips Inc.). Comparing the residual stresses that obtained through nanoindentation and XRD methods, their difference was no more than 10.5%, which showed that the formula is suitable for characterizing residual stresses in materials even it has high plasticity. Thus, the formula was validated.

Snap-through dynamics of bi-stable IPMC actuator considering beam configuration

Jin-Han Jeon, Tai-Hong Cheng, Joong-Woo Park, et al.

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The snap-through dynamics of the bi-stable IPMC actuators were investigated to generate much larger displacements and periodical stable locomotion based on jumping phenomena according to boundary conditions. First, in the clamped-free BC, two curved cantilever IPMC actuators with a constant curvature and initial tip deflections of 8mm and 16mm were fabricated from flat IPMCs through thermal treatment under hot water simultaneously to reduce the residual stresses. A flat and two curved IPMC actuators were tested to evaluate the effect of initial shape in terms of step responses, harmonic responses and frequency response function tests under small and large deformation. The snap-through phenomena for the curved IPMC actuators unlike the flat IPMC actuator were observed with much larger tip displacements, low power consumption and periodical jumps of the instant velocity. Second, in case of all-clamped BC, the large and bistable responses were observed under DC and AC excitation through the end-shortening effect. These tests were conducted with various end-shortenings of 0.25, 0.5, and 1.0 mm. The jumping phenomena of IPMC actuator was remarkably observed at their conditions, respectively. Present results show that the initial curved deflection and endshortening of the IPMC actuator strongly affects the large deformation at respective boundary conditions due to the snapthrough phenomena.

Active vibration control of a composite wing model using PZT sensors/actuators and virtex: 4 FPGAs

Shashikala Prakash, D. V. Venkatasubramanyam, Bharath Krishnan, et al.

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The reduction of vibration in Aircraft/Aerospace structures as well as helicopter fuselage is becoming increasingly important. A traditional approach to vibration control uses passive techniques which are relatively large, costly and ineffective at low frequencies. Active Vibration Control (AVC), apart from having benefits in size, weight, volume and cost, efficiently attenuates low frequency vibration. Hitherto this was being achieved using high speed Digital Signal Processors (DSPs). But the throughput requirements of general purpose DSPs have increased very much and the Field Programmable Gate Arrays (FPGAs) have emerged as an alternative. The silicon resources of an FPGA lead to staggering performance gains i.e. they are 100 times faster than DSPs. In the present paper Active Vibration Control of a Composite Research Wing Model is investigated using Piezo electric patches as sensors and PZT bimorph actuators collocated on the bottom surface as secondary actuators. Attempt has been made to realize the State - of - the - Art Active Vibration Controller using the Xilinx System Generator on VIRTEX - 4 FPGA. The control has been achieved by implementing the Filtered-X Least Mean Square (FXLMS) based adaptive filter on the FPGA. Single channel real time control has been successfully implemented & tested on the composite research wing model.

Nanometer functional materials from explosives

Xinghua Xie, Jing Zhu, Huisheng Zhou, et al.

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The growth of Li_1+xMn₂O₄ via detonation reaction was investigated with respect to the presence of energetic precursors, such as the metallic nitrates and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Li1+xMn2O4 with 1~2μm spherical morphology and more uniform secondary particles, but with smaller primary particles of diameters from 20 to 60 nm and a variety of morphologies were found. The oxides produced by this cheap method affirmed the validity of detonation synthesis of nano-size powders.

In-situ synthesis and thermal-electrical properties of CP2- polyimide/pristine and amine-functionalized carbon nanofiber composites

David H. Wang, J. David Jacobs, Aaron Trionfi, et al.

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Vapor-grown carbon nanofibers (VGCNF) functionalized with amine-containing pendants, viz.H2N-VGCNF, reacted with 2,2-bis(phthalic anhydride)-1,1,1,3,3,3-hexafluoroisopropane, which was the dianhydride monomer used in in-situ polymerization with 1,3-bis(3-aminophenoxy)benzene to afford a series of CP2-polyimide nanocomposite films (FCNFCP2), containing 0.18-9.19 wt % of H2N-VGCNF (corresponding to 0.10-5.0 wt % of pristine VGCNF), via conventional poly(amic acid) precursor method. For comparison, another series of in situ nanocomposites containing pristine VGCNF (0.10-5.0 wt %) was also prepared similarly. While H2N-VGCNFs enabled direct formation of CP2 grafts on the nanofibers, pristine VGCNFs would result in a relatively weak interface between nanofibers and the CP2 matrix. Conducting-tip atomic force microscopy (C-AFM) showed that the electrical transport was solely through the nanofiber networks in the PCNF-CP2. In general, low-frequency ac impedance measurements followed well the percolation bond model with low percolation threshold; 0.24 and 0.68 vol % for PCNF-CP2 and FCNF-CP2, respectively. However, the design of interface is determined to be crucial for controlling the electrical behavior in four substantial ways: (i) magnitude of limiting conductivity, (ii) linearity of I-V response, (iii) magnitude and direction of temperature-dependent resistivity, and (iv) reproducibility of the absolute value of resistivity with thermal cycling. These observations are consistent with a direct CNF-CNF contact limiting transport in the PCNF-CP2 system, where the CP2 grafts on FCNF form a dielectric layer between individual CNFs, limiting transport within the FCNF-CP2 system. Furthermore, the CP2 grafts on the FCNF surface reduce local polymer dewetting at the nanofiber surfaces when the temperatures exceed the CP2 glass transition, and stabilize the structure of the percolation network and associated conductivity. The general behavior of these interfacial extremes (pristine and fully functionalized CNFs) set important bounds on the design of interface modification for CNFs when the intended use is for electrical performance at elevated temperatures or under extreme current loads. The influence of processing conditions resulting in the spread of measured conductivity by several orders of magnitude for films containing the same type and same amount of CNFs is also reported.

Study on interface behavior of 3D composites reinforced with chemically connected CNTs using molecular dynamics

Lin Yang, Xiaodong He, Liyong Tong

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In this study, we used several molecular dynamic models to simulate the pull-out process of a carbon nanotube (CNT) that is assumed to be chemically connected to a carbon fiber, and to calculate the CNTs' geometry variation, displacement, energy and stress during this process. In the simulation, the CNTs' elongation and necking phenomena have been noted prior to the movement of the CNT's end embedded in resin. The simulation yields a CNT's plastic constitutive model in the pull-out process. The fracture resistance capability of a chemically connected CNT is then discussed. In the simulation of shearing, the prediction of the CNTs' capability of shear resistance has been conducted. Finally, by comparing the experiment result with the simulation, we predict the amido link break before the CNT pull-out in the shearing test.

A numerical study on the effect of sweep angle on flapping-wing flight using fluid-structure interaction analysis

Dae-Kwan Kim, Jun-Seong Lee, Jae-Hung Han

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The sweep-back effect of a flexible flapping wing is investigated through fluid-structure interaction analysis. The aeroelastic analysis is carried out by using an efficient fluid-structure interaction analysis tool, which is based on the modified strip theory and the flexible multibody dynamics. To investigate the sweep-back effect, the aeroelastic analysis is performed on various sweep-back wing models defined by sweep-chord ratio and sweep-span ratio, and then the sweep-back effect on the aerodynamic performance is discussed. The aeroelastic results of the sweep-back wing analysis clearly confirm that the sweep-back angle can help a flexible flapping wing to generate greater twisting motion, resulting in the aerodynamic improvement of thrust and input power for all flapping-axis angle regimes. The propulsive efficiency can also be increased by the sweep-back effect. The sweep angle of a flapping wing should be considered as an important design feature for artificial flexible flapping wings.

Structural shape monitoring using strain sensing for morphing structures

W. C. Gao, K. Yang, W. Liu

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This paper describe a structural shape monitoring methodology based on modal transformation and strain sensing for morphing structures. There are four important components to this problem: constructing the displacement-strain relationship, modal identification, strain measurement and signal processing. These issues are addressed in this paper and a simple laboratory experiment was carried out, which shows there are still many challenges inherent in the problems.

Enhancing space satellite performance by integrating smart sensors and actuators for sensing and shape morphing

H. Baier, L. Datashvili, S. Rapp

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Satellite mechanical performance is to be further enhanced e.g. by active launch vibration attenuation, and even more so by in-orbit micro-vibration and shape control and possibly also significant shape morphing. This puts stringent requirements on the actuators and their materials, such as high resolution of possibly large strokes, or a very broad operational temperature range going down to -150°C or even lower. The discussion also shows the need to consider the host material and structure together with the actuator as a highly interacting system. This holds to a considerable extent also for integrated fiber optic sensors used for strain and temperature monitoring.

Magnetorheological smart nanocomposites and their viscoelastic behavior

Rui Li, Lizhi Sun

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Magnetorheological elastomers (MREs) are smart materials whose mechanical behavior can be tailored by external magnetic fields, showing promises for wide use in on-demand stiffness control applications. However, conventional MREs have comparatively inferior mechanical properties due to matrix materials. Meanwhile carbon nanotubes (CNTs) have proved to be excellent reinforcing fillers with increased stiffness, strain at failure, and damping performance for nanocomposites. In this project, synthesis and dynamic mechanical analysis are conducted for silicone-rubber-based magnetorheological nanocomposites embedded with multi-walled carbon nanotubes.

Energy harvesting: a key to wireless sensor nodes

Matthew Bryant, Ephrahim Garcia

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Energy harvesting has enabled new operational concepts in the growing field of wireless sensing. A novel energy harvesting device driven by aeroelastic flutter vibrations has been developed and could be used to complement existing environmental energy harvesters such as solar cells in wireless sensing applications. An analytical model of the mechanical, electromechanical, and aerodynamic systems suitable for designing aeroelastic energy harvesters for various flow applications are derived and presented. Wind tunnel testing was performed with a prototype energy harvester to characterize the power output and flutter frequency response of the device over its entire range of operating wind speeds. Finally, two wing geometries, a flat plate and a NACA 0012 airfoil were tested and compared.

Investigation of luminescence property in seawater on long-life afterglow fluorescent coatings modified by nano-TiO2

Yu-hong Qi, Zhan-ping Zhang, Hui Gao

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For developing new marine non-toxic antifouling coating, it was investigated the luminescence property in seawater on long-life afterglow fluorescent coatings modified by nano-TiO₂. The influences of the content and crystalline microstructure of fluorescent powder, different binder resins of coating were studied on the luminescence characteristic of the coating. The results showed that fluorescent coatings modified by nano-TiO₂ represent the good luminescence characteristic in seawater. With the increase of the content of fluorescent and nano-TiO₂ powders in coating, the luminescence property of coating increases. As light afterglow time increases, the illuminance of both fluorescent powder and luminous coating decays exponentially. Compared with long-life afterglow fluorescent coatings not modified by nano-TiO₂, the afterglow illuminance of the coatings modified by nano-TiO₂ was remarkably improved. The luminescence property in seawater of the coating based on fluorocarbon resin is much more than that of the coating based on acrylate resin.

Studies on molecular recognition of thymidines with molecularly imprinted polymers

Zhen-He Chen, Ai-Qin Luo, Li-Quan Sun

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Molecularly imprinted polymers (MIPs) with excellent molecular recognition ability have been used in chemical sensors, chromatographic separation and biochemical analyses. Thymidine is an important part of DNA for biomolecular recognition and the intermediate of many medicines. The polymers imprinted with the template of thymidine and 5'-Otosylthymidine have been prepared, using a non-proton solvent, acetonitrile as the porogen. Direct imprinting with thymidine could not form strong molecular interaction sites in this system. Relative MIPs were obtained by bulk polymerization and their adsorption capacities were investigated. The adsorption capacities of MIP (P₂) and nonimprinted polymer (P₂₀) for thymidine are 0.120 mg•g^-1and 0.103 mg•g^-1, respectively. The imprinting factor is 1.17. As 5'-O-tosylthymidine is more soluble than thymidine moiety in acetonitrile and give rise to more sites of molecular recognition. The results demonstrated that the imprinted polymers were able to bind and recognize thymidine moderately in acetonitrile. MIPs imprinted with 5'-O-tosylthymidine like nature enzymes displayed some recognition ability to its analogues. The insoluble derivatives in the non-proton solvent can be an effective template to prepare efficient imprinting recognition sites.

Nonlinear differential equation approach for the two-way shape memory effects of one-dimensional shape memory alloy structures

Linxiang Wang, Changquan Zhou, Changshui Feng

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In the current paper, a macroscopic differential model is constructed for the modeling of two-way shape memory effects in one-dimensional shape memory alloy (SMA) structures. The model is based on the phenomenological theory of thermoelastic phase transformations in SMAs. Hysteresis loops in both mechanical and thermal fields are treated as macroscopic illustrations of martensite transformations and martensite variant re-orientations. A non-convex free energy function is constructed such that each of its local equilibriums can be used to characterize one of the phases involved in the transformations. System states (strain) can be transformed upon external loadings (mechanical or thermal) from one stable equilibrium to another, thus the dynamics of phase transformations can be modeled by investigating the system state transformations. Governing equations for the transformation dynamics are formulated by employing the Lagrange's equation, and are expressed as nonlinear differential equations. Numerical examples of thermal and mechanical hysteresis loops associated with the transformations caused by thermal and mechanical loadings are presented. Two way shape memory effects and pseudo-elastic effects are successfully modeled.

Frequency response analysis of fatigue behaviour in NiTi shape memory alloys

T. Lilaudomwit, P. Passaranon, P. Lekhakul, et al.

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This paper investigates the relationship between the functional fatigue level and the frequency response behaviour of NiTi Shape Memory Alloys. The specimens, which are SMAs with 0.7-millimeter diameter, were subjected to a constant stress under different number of thermal cycles, leading to different fatigue levels. The fatigue SMAs were tested in open-loop experiments with step inputs and sinusoidal inputs, and their frequency responses were evaluated as the magnitude and phase of the wires' displacement, with respect to the input voltage signal. The results of the experimental study showed that the dc gains of the specimens, subjected to ranges of stresses from 76 to 204 MPa, decreased as the fatigue levels of SMAs increased. Also, the differences between frequency responses of fatigue wires and those of healthy wire were noticeable over the frequency range up to the bandwidth of the wire, especially when the wires were loaded with lower stresses.

A hybrid elements model of stress-strain hysteresis in shape memory alloys

Yongzhong Huo

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Shape memory alloys (SMAs) show strong hysteresis in stress-strain-temperature relations. The hysteretic behavior is mainly caused by the thermodynamic irreversibility during the thermoelastic martensitic transformation. The various types of stress-strain hysteresis observed for SMAs at different temperatures have been attributed to the martensitic reorientation (MR) and the stress-induced martensitic transformation (SIMT) processes occurred under loading. Based on such observations, a model is proposed to consist of two types of elements: MR elements and SIMT elements. The MR elements show only martensitic reorientation and the SIMT elements can behavior only according to the stressinduced martensitic transformation. A SMA sample is a proper combination, determined by two temperature dependent distribution functions, of these two types of elements in series, i.e. the stresses on the elements are identical and the strains sum up. Experiments are designed to determine the distribution functions and numerical simulations are performed to show the capability of the model in reproducing the stress-strain hysteresis of SMAs in the whole temperature range of applications

Wrinkling deformation control of inflatable boom by shape memory alloy

Zhenhui Tian, Zheng Guo, Huifeng Tan, et al.

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The space inflatable structures have received increasing attention in recent years. Inflatable boom is the fundamental structural part to help space inflatable structures maintain the expected configuration. In this paper, the methodology to control local wrinkle growth and the deformation configuration of the inflatable boom structure with Shape Memory Alloy (SMA) wires actuator is developed. The experimental equipment has been established to investigate the growth of wrinkling and the control abilities of SMA actuator, wavelength and amplitude parameters of the wrinkling deformation have been measured by non-contact deformation test system. To understand the behavior of an inflatable boom due to wrinkling, the boom structure is numerically modeled using the ANSYS FE program with the equivalent nodal force method. The recovery force generated by the SMA wires could remove wrinkling and restore the deformation of the inflatable boom. The results from the experiment and numerical analysis show that SMA wires can eliminate the wrinkling deformation of inflatable boom effectively.

Vibration characteristics of Ni-Ti pseudo-elastic wire inter-weaved fabric composites

Lei Xu, Rui Wang, Qiuhong Yang, et al.

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This paper presents a study on the vibration characteristics of Ni-Ti wire inter-weaved glass fabric/epoxy composites. The Ni-Ti pseudo-elastic wires were used as warp yarns and embedded in the fabric preforms with various weaving methods. Dynamic Mechanical Analyzer (DMA) and vibration test technique were used to reveal the dynamical behaviors of specimens in different frequencies of vibration. The storage modulus E', the loss tanδ, the natural frequency f and damping ratio η were examined. The energy dissipation behaviors of the Ni-Ti pseudo-elastic wire, the geometry of textile fabric was also studied. The effect of weaving method on the vibration behavior in Shape Memory Alloy (SMA) based textile composites was considered. The results showed that: (I) the energy dissipation capacity of the wire could be significantly improved by increasing the tensile strain and speed, but slightly affected by loading frequency; (II) the woven of few Ni-Ti warps caused the increase of the storage modulus and the change of the loss tanδ. In the buckling vibration, the damping effects of Ni-Ti pseudo-elastic wires vary with the woven structures. The compact woven structure with proper Ni-Ti warp architectures would receive a small amplitude and good damping.

Research about tensile sensitive characteristics of carbon fibre reinforced concrete and security self-diagnosis system of beam

Longnan Huang, Xinbo Wang, Dongxing Zhang

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Based on real-time diagnosis of health status of reinforced concrete beam, intellectual supervisory layer of carbon fiber reinforced concrete (CFRC) was set up at the bottom of girder structure. The intrinsic law of tensile sensitive characteristic of CFRC was studied and the electrical property collection and the stress transformation system of structure intellectual layer were established. It depends on the premise that carbon fibers are conductive, and that a stable relationship between electric resistivity and stress field exists. The security self-diagnosis of girder structure was fulfilled through online real-time monitoring and evaluation on electrical signal of intelligence layer of reinforced concrete beam.

Experiment and simulation on responses of polymer induced by laser irradiation

Haiming Huang, Xiaoliang Xu

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With the development of microelectromechanical system (MEMS) technology, the limitations of machining technology for silicon-based materials become more and more distinct. With its abilities on sub-micron structure machining, the pulsed laser micro-fabrication technology has an extensive application prospect in MEMS and many other materials. The thermal interaction process of polymer under laser irradiation is very complex, regularities on polymer target under laser irradiation between displacement and laser energy density can only be obtained through experiments. Based on finite element method (FEM), simulations have been performed and compared with experiment results. Relations among pulsed laser intensity, actuation duration and thermal shock loads were obtained from the comparison, and a formula for calculating the maximum ablation pressure of a carbon fiber epoxy resin polymer composites was proposed. This study provides theoretical basis to the pulsed laser micro-fabrication technology's application in the fields of MEMS.

Compressive properties of AM50 and AZ91D alloys using split Hopkinson pressure bar

I. R. Ahmad, D. Wei Shu

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Magnesium alloys have been increasingly used in the automobile, communication and aerospace industries due to their low density, high specific strength and good castability. Higher speed in vehicles, development in weaponry and high speed metal working all are characterized with high rates of loading. In current study, two magnesium alloys AZ91D and AM50 have been investigated at strain rates in the range between 300 s^-1 and 1250 s^-1. For AZ91D, the stress is first increased and than decreased with strain rate between 335/ s^-1 and 1175 s^-1. For AM50, a monotonic increase in the stress is observed with increasing strain rate from 438/ s^-1 to 1238 s^-1. The stress is much higher at higher strain rates than what is at quasi-static strain rate for both alloys. For nearly same strain rate, higher stresses are observed for AZ91D than AM50, although this difference is less at higher strain rates. The strain rate sensitivity of AZ91D first increased with increasing strain rate and than decreased. In case of AM50, the strain rate sensitivity has an overall increasing trend.

Properties of 1-3-2 connectivity piezoelectric ceramic/polymer composite

Shuangshuang Liao, Shifeng Huang, Dongyu Xu, et al.

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Epoxy resin and lead zirconate titanate (P-41) ceramic were respectively used as matrix and functional component to fabricate 1-3 and 1-3-2 connectivity piezoelectric ceramic-polymer composites by dice and filling method. The interface bonding condition between matrix and piezoelectric functional phase was investigated by using SEM. Piezoelectric properties, dielectric properties, electromechanical properties and acoustic impedance of the 1-3 and 1-3-2 connectivity piezoelectric composites were studied. The results show that the interface bonding of the two-phase materials is compact, comparing with the P-41 ceramic, the thickness electromechanical coupling coefficient K_t of both kinds of the composites is almost two times larger than that of P-41 ceramic, while the value of mechanical quality factor Q_m and dielectric loss tanδ are smaller, acoustic impedance Z and relative dielectric constant ε_r are almost half of P-41 ceramic. The value of d₃₃, g₃₃, K_t, Q_m, Z, ε_r, and tanδ of 1-3-2 connectivity piezoelectric composite are close to those of 1-3 connectivity piezoelectric composite, which show that the 1-3-2 connectivity piezoelectric composite can instead of 1-3 connectivity piezoelectric composite in special application field.

Transient torsional responses of finite piezoelectric hollow cylinder

H. M. Wang

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An exact elastodynamic solution is obtained for torsional vibration of a finite piezoelectric hollow cylinder subjected to dynamic shearing stress and time dependent electric potential at the internal surface. The cylinder is traction free at the two ends and is fixed at the external surface. The piezoelectric material belongs to 622 crystal class. In axial direction, the trigonometric series expansion technique is introduced to guarantee the solution satisfies the end conditions. Then the governing equations for new variables about the radial coordinate r and the time variable t are derived. By means of the normal mode expansion method, the solution for torsional vibration is finally obtained. Numerical investigations are presented and the dynamic behaviors of the finite piezoelectric hollow cylinder are analyzed.

The analysis of film acoustic wave resonators with the consideration of film piezoelectric properties

Ji Wang, Jiansong Liu, Jianke Du, et al.

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The vibration frequency analysis of film bulk acoustic resonators (FBAR) is based on the assumption of layered infinite plates vibrating at a working mode, which can be the thickness-extension or thickness-shear depending on the choice of the mode. A transcendental equation is used to determine the vibration frequency with given materials and plate thicknesses. Similar to the analysis and design of quartz crystal resonators of thickness-shear type, frequency equations and displacements in films can be used for the calculation of resonator properties which are important for improvement and modeling. By expanding the formulation to include the piezoelectric effect, we shall also be able to obtain the electrical field as a vital addition to mechanical solutions. Of course, the piezoelectric effect will also be included in the solutions of frequency and displacements. The solutions can be used to calculate the electrical circuit parameters of a resonator. We study vibrations of layered FBAR structures for both thickness-extension and thickness-shear modes and the solutions also include the electrical field under an alternating voltage. With these equations, solutions, and further formulations on the electrical circuit properties of FBAR, we can establish a systematic procedure for the analysis and design, thus completing the currently empirical methodology in resonator development. These one-dimensional formulation based on the infinite plate assumption can be further improved through the consideration of finite plates and numerical solutions based on the commonly used finite element analysis. These studies will be the basis for the formulation and calculation of electrical circuit parameters that are highly demanded as FBAR technology is expanding quickly to other applications. The accurate analysis and resonator property extension will contribute to the sophistication of FBAR technology with improved design procedure and performance.

A study on preparation and mechanical properties of UHMWPE/nylon composite covered yarn

Wei-Hua Yao, Jen-Taut Yeh, Wen-Li Chou, et al.

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The study is describing Nylon yarn, though with low weight (specific weight 1.14), good elongation and high strength (4.5~9.5 g/d). Through the combination of irregular section long staple fiber to reach the core yarn, spun from Nylon fiber and long filament fiber, not only has the advantages of Nylon product but also has it can be used for making army-bag which can enhance the abrasion resistance, low weight and coving yarn that has doubled yarn effect from yarn surface consisting of Nylon fiber and long filament fiber. We used a Hamel's Elasto Twister (hollow-spindle machine) to prepare the yarn samples for our study. During spinning, the spindle speed was kept the same, while yarn through put speed was varied to obtain different wrap twists (700, 800, 900, 1000 T/M). The wrapping yarn is Nylon yarn with different count (40, 70D) and core yarn is ultra-high molecular weight polyethylene (UHMWPE) filament with 375 deniers, respectively. The results revealed the covered yarn have good physical properties and will be good performance in army-bag and army uniform. Keywords: Nylon, abrasion resistance, UHMWPE, physical properties

Thermal shock of silicon-based materials under multi-pulsed intense laser radiation

Haiming Huang, Xiaoliang Xu

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The silicon-based materials are widely used in MEMS. In this article, the thermal shock property of silicon-based materials under the multi-pulsed laser irradiation is studied and theoretical deduction under a relative numerical case is performed. Based on the non-Fourier conduction and the thermo-elastic theories, theoretical expressions between temperature and thermal stress of a silicon-based material under the multi-pulse heat flow are deduced; regularities among inner surplus temperature, time and depth in a silicon-based target and corresponding boundary are studied; further more, curves of inner thermal stress in cases of different relation time are obtained by using the finite difference method. As results indicated, under the multi-pulsed laser irradiation, the temperature curves present a delayed character in different section away from the boundary, which are closely connected with the relaxation time. In the non-Fourier theoretical solution, the front of the stress wave is very steep and presents an obvious thermal shock property. The conclusion may be helpful to the micro-fabrication technology in the fields of MEMS.

Degradation of thermal barrier coated superalloy component during service

Han-Sang Lee, Doo-Soo Kim, Jine-sung Jung, et al.

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The time dependent degradation of first-stage blades for gas turbine was investigated. First, Two used blades were prepared from the operating facilities, and their operating hours were 25,000 and 52,000 hrs, respectively. Microstructural comparison of coating surfaces showed that exposure to the environment increased thickness of TGO (Thermally Grown Oxide) and β depletion region, and then debonding and spallation of TBC (Thermal Barrier Coating) occurred finally. In the case of substrate, Ni-based superalloy, the shape and size of γ' were changed with increasing operating time. Especially, in the leading and trailing edges of blades, the size of γ' was bigger and the shape was more elliptic than other region. It can be thought that the leading and trailing edges of blades can be the starting point of degradation in first-stage blades. Second, TBC failed blade used for 22,000 hrs was prepared and compared with other two blades. Large interfacial cracks were formed between top and bond coat, and TGO was not uniform and continuous. The chemical composition analysis on bond coat showed that low chromium content is responsible for the formation not only of Al oxide but also of Co, Cr, Ni oxides.

Fabrication of organic solar cells based on a blend of poly (3-octylthiophene-2, 5-diyl) and fullerene derivative using inkjet printing technique

Ashkan Shafiee, Muhamad Mat Salleh, Muhammad Yahaya

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This paper reports the fabrication of organic solar cells using inkjet printing technique. The devices consist of an active layer sandwiched between ITO bottom electrode and aluminum as top electrode. The active layer is made of a blend of a fullerene derivative [6,6]-phenyl C61-butyric acid 3-ethylthiophene ester as acceptor and poly (3-octylthiophene-2, 5- diyl) (P3OT) as the donor. The ink of active layer was prepared with variation of donor and acceptor ratio 1:1 and 2:1by weight. The active layers were inkjet printed on ITO substrates layer by layer with variations of one, two and four layers. The performances of the devices were studied by observing the current-voltage characteristics of the device in dark and under illumination of 75 W/m² light. Most of the devices showed rectifier property in the dark and able to generate electrical current under illumination. The photovoltaic performance of the devices was found depending on the thickness and the donor- acceptor ratio of the active layers.

Mechanical behaviour of advanced composite laminates embedded with carbon nanotubes: review

Guanyan Xie, Gang Zhou, Xujin Bao

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Embedding carbon nanotubes (CNTs) in load-bearing composite laminate hosts and thereby turning them into nanolaminates is a rapidly emerging field and has tremendous potential in enhancing mechanical performance of host laminates. This state-of-the-art review intends to provide physical insight into the understanding of enhancing mechanisms of processed and controlled CNTs in nano-laminates. It focuses on four aspects: (1) physical characteristics of CNTs including CNT length, diameter and weight percentage; (2) processing and control techniques of CNTs in fabrication of nano-laminates including distribution, dispersion and orientation controls of CNTs; (3) mechanical properties along with their testing methods including tension, in-plane compression, interlaminar shear (ILS), flexure, mode I and mode II fracture toughness as well as compression-after-impact (CAI); and (4) post-mortem microscopic corroborative evidence after mechanical testing. As this review indicates, selective and uniform production of CNTs with specific dimensions and physical properties has yet to be achieved on a consistent basis. There is little control over CNT orientations in most fabrication processes of nano-laminates except for some cases associated with chemical vapour deposition (CVD). There are only two reports on the in-plane compression and there is none on in-plane shear. For reinforcement-dominated mechanical properties such as tension and flexure, there is little enhancement as reported. However, substantial enhancement in in-plane compression strength was reported. For matrix-dominated mechanical properties such as ILS strength and mode-I and mode-II fracture toughness, significant enhancement, albeit with substantially varying degrees, has been reported. In the meanwhile, the lack of consistent characterisation in those properties was also noticeable. Post-mortem microscopic corroborative evidence was very limited.

Ductility of high strength concrete containing nano-particles

C. Lan, H. Li, Y. Ju

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The ductility of high strength concrete containing nano-TiO₂ were experimentally studied and compared with that of plain concrete and concrete containing silica fume by stress-strain relationship. The results showed that the ductility of high strength concrete containing nano-TiO₂ were better than that of plain concrete and concrete containing silica fume, which demonstrated that it is an available and effective way to improve ductility of high strength concrete by means of mixing nanophase materials into concrete. The origin of nano-particles improving ductility of high strengthen concrete was also preliminary interpreted.

Multifunctional properties of multi-wall carbon nanotubes/cyanate-ester nanocomposites and CFRPs

A. Baltopoulos, E. Fiamegkou, A. Vavouliotis, et al.

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The incorporation of multi-wall carbon nanotubes at weight fractions of 0.5% wt. and 1% wt. in a PRIMASET cyanate ester system (PT-30) was examined. The thermo-mechanical and electrical properties of the developed nanopolymers were investigated and were compared with the neat matrix properties. A preparation method was developed for the incorporation of the fillers in the resin system. The phenomenon of re-agglomeration of nanotubes took place in the first stages of curing schedule but nevertheless according to the SEM images a good dispersion was generally achieved. DSC, DMA, TGA and thermal conductivity tests were performed for the thermal characterization. For the electrical characterization, AC and DC measurements took place. No significant change in the glass transition temperature (Tg), thermal conductivity and mass loss values was observed in comparison with the neat resin systems. However, in both cases the improvement of electrical conductivity was about nine orders of magnitude, indicating that percolation had been achieved. The elastic modulus in bending was examined and a slight increase was observed in direct comparison with the neat resin. Finally, the developed doped nanopolymer was used as matrix for the CFRPs manufacturing. A full manufacturing protocol was developed in order to overcome the challenging issues concerning the cyanate esters' handling and manufacturing processes. Moreover AC and DC measurements were performed along with thermal conductivity measurements and TMA. The produced modified composites were tested for short beam strength.

Adaptive materials and aerostructures: revolutionizing uninhabited aerospace systems

Ron Barrett

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This paper is intended to introduce the international adaptive aerostructures community to the tremendous opportunities these structures can bring to uninhabited aerospace systems. The paper starts with an overview of the most critical classes of adaptive aerostructures for uninhabited aerial vehicles (UAVs) and the materials which are used to drive them. The paper describes several classes of UAVs that take advantage of the various kinds of these technologies. Adaptive aerostructures are shown to be integrated into hovering, high speed, low speed and ultra-high performance UAVs. These ultra-high performance UAVs are shown to significantly benefit from newly invented Post-Buckled Precompressed (PBP) piezoelectric actuators. These UAVs are capable of hovering for extended periods of time as a helicopter in gusty, windy, dusty environments, then pop up, converting and dashing out like a missile at several hundred km/hr. The paper shows photos of ultra-high performance UAV launches from armored vehicles, a battle-damage assessment exercise and a live fire sequence with 40mm munitions. The paper concludes with a description of the Visual Signature Suppression (VSS) system which was employed on a 2m UAV operating at several hundred meters above ground level. The VSS system was shown to reduce the visual cross section to below 1.8cm² which is the threshold for human aircraft observation. Accordingly, the VSS equipped aircraft is said to "disappear" in mid flight.

Variable camber wing based on pneumatic artificial muscles

Weilong Yin, Libo Liu, Yijin Chen, et al.

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As a novel bionic actuator, pneumatic artificial muscle has high power to weight ratio. In this paper, a variable camber wing with the pneumatic artificial muscle is developed. Firstly, the experimental setup to measure the static output force of pneumatic artificial muscle is designed. The relationship between the static output force and the air pressure is investigated. Experimental result shows the static output force of pneumatic artificial muscle decreases nonlinearly with increasing contraction ratio. Secondly, the finite element model of the variable camber wing is developed. Numerical results show that the tip displacement of the trailing-edge increases linearly with increasing external load and limited with the maximum static output force of pneumatic artificial muscles. Finally, the variable camber wing model is manufactured to validate the variable camber concept. Experimental result shows that the wing camber increases with increasing air pressure and that it compare very well with the FEM result.

Novel deployable morphing wing based on SMP composite

Kai Yu, Shouhua Sun, Liwu Liu, et al.

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In this paper, a novel kind of deployable morphing wing base on shape memory polymer (SMP) composite is designed and tested. While the deployment of the morphing wing still relies on the mechanisms to ensure the recovery force and the stability performance, the deploying process tends to be more steady and accurate by the application of SMP composite, which overcomes the inherent drawbacks of the traditional one, such as harmful impact to the flight balance, less accuracy during the deployment and complex mechanical masses. On the other hand, SMP composite is also designed as the wing's filler. During its shape recovery process, SMP composite stuffed in the wing helps to form an aerofoil for the wing and withstand the aerodynamic loads, leading to the compressed aerofoil recovering its original shape. To demonstrate the feasibility and the controllability of the designed deployable morphing wing, primary tests are also conducted, including the deploying speed of the morphing wing and SMP filler as the main testing aspects. Finally, Wing's deformation under the air loads is also analyzed by using the finite element method to validate the flight stability.

A rotary joint sensor using ionic polymer metallic composite

A. van den Hurk, X. J. Chew, K. C. Aw, et al.

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Ionic Polymer Metallic Composite (IPMC) is a smart material that can be used to make sensors for various applications. This paper investigates the use of IPMC for sensing the motion of a rotary joint. In this research, the relationship between the motion of a rotary joint and the IPMC sensor's voltage output was investigated and modeled. The relationships defining the sensor's response were developed into a routine which was used to calculate the bending angle and bending speed of a joint, based on the voltage response of an IPMC sensor. Experimental verification of the model produced results for measuring bending angles with an accuracy of within 3% across most of the range of angles. The accuracy of the measured bending speed was found to be related to the joint motion; with errors ranging from 0.4% at a slow bending speeds ( ≤150°s^-1) up to an error of ~8% at fast bending speeds ( ≥ 200°s^-1). Additional variables such as bending direction and starting position were also investigated to determine their effects on the sensor's response. It is concluded that the methods developed in this study provide a more complete description of the relationship between IPMC sensor voltage and joint motion than has previously been documented.

Functional materials for lithium-ion battery

Huisheng Zhou, Jing Zhu, Xinghua Xie

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Nanoproducts spherical spinel lithium manganese oxide (LiMnO) with about 20nm in diameter was synthesized by explosive method. The growth of lithium manganate via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Lithium manganate with spherical morphology and more uniform secondary particles, with smaller primary particles of diameters from 10 to 30 nm and a variety of morphologies were found. Lithium manganate with a fine spherical morphology different from that of the normal spinel is formed after detonation wave treatment due to the very high quenching rate. It might also provide a cheap large-scale synthesis method. Explosive detonation is strongly nonequilibrium processes, generating a short duration of high pressure and high temperature. Free metal atoms are first released with the decomposition of explosives, and then theses metal and oxygen atoms are rearranged, coagulated and finally crystallized into lithium manganate during the expansion of detonation process.

Integrated piezoceramic transducers for imaging damage in composite laminates

C. T. Ng, M. Veidt, N. Rajic

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This paper presents a two-phase imaging methodology to characterise damage in composite laminates utilising Lamb waves generated by integrated piezoceramic transducers. The proposed methodology uses the transducers to sequentially scan the composite laminates before and after the presence of damage by transmitting and receiving Lamb wave pulses. In phase one the damage localisation image is reconstructed by analysing the cross-correlation of the wavelet extracted information from scatter signals with the excitation pulse for each transducer pair. A potential damage area is then reconstructed by superimposing the image observed from each actuator and sensor signal path. In phase two Lamb wave diffraction tomography is used to reconstruct an image quantifying size and shape of the damage based on the same set of measurement data and identified damage location in phase one. The two-phase imaging approach together with the modified diffraction tomography reconstruction algorithm enables a significant reduction of the required number of transducers without the need to know the damage location in advance. Numerical and experimental results are presented to demonstrate the efficiency, accuracy and sensitivity of the proposed methodology.

Effect of cement-polymer ratio on 1-3 piezoelectric composites

Lili Guo, Dongyu Xu, Shifeng Huang

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A 1-3 type piezoelectric composite was fabricated by cut-filling technique. The effects of cement-polymer ratio on piezoelectric and dielectric properties of the composites were analyzed. The results show that piezoelectric strain factor d₃₃ and piezoelectric voltage factor g₃₃ exhibit the trend of decrease initially and then increase with increasing cement-polymer ratio. With the increase of cement-polymer ratio, the dielectric factor ε_r and dielectric loss tanδ of the composites increase initially and then decrease. Comparing with pure piezoelectric ceramic, the mechanical quality factor Q_m decreases obviously. Acoustic impedance Z is about 9 M raly, which is matching with concrete.

An investigation of magnetic and fluorescent core-shell CdTe/Fe3O4 nano-composites

Juan Yang, Ji mei Zhang, Shi chao Xu, et al.

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The magnetic nanoparticles with luminescent properties make the marker and separation work further convenient in the biological fields, such as bio-imaging, bio-labeling, bio-medicine, bio-treatment, etc. In the current research, a multifunctional nanoparticles with a magnetic Fe₃O₄ core and a CdTe quantum dots (QDs) shell of was prepared via self-assembling method and characterized via transmission electron microscopy (TEM), ultraviolet spectrum (UV), and fluorescence spectrum (FS). Magnetic Fe₃O₄ nanoparticles were firstly prepared by chemical precipitation method with sodium hydroxide as precipitant at 50°C, well dispersed Fe₃O₄ nanoparticles in size of 10 nm were observed via TEM and were use as core. The synthesized CdTe QDs were surface modified with 2-mercaptopropionic acid and the magnetic core-shell CdTe/Fe₃O₄ nanoparticles were constructed by the formation of electrovalent bond between -NH₃+ and -COO-. The prepared core-shell CdTe/Fe₃O₄ nanoparticles can be simply separated or precipitated from the reactant solution. The factors influencing the properties of nanoparticles were investigated, including mol ratio of Fe₃O₄:CdTe, refluxing time, reacting temperature, and pH value etc. The results indicated the core-shell CdTe/Fe₃O₄ nanoparticles with excellent magnetic and fluorescent properties can be achieved when the mol ratio of Fe₃O₄:CdTe is 1:3, and pH was set at 6.0, refluxed for 0.5h at 30 °C. 15nm of average size of the CdTe/Fe₃O₄ nanoparticles was confirmed with TEM. The red shift of maximum emission wavelength from 530 nm to 570 nm and maximum absorbance wavelength from 530 nm to 535 nm were determined via FS and UV, respectively, these data inferred the formation of CdTe shells. The core-shell magnetic and fluorescent CdTe/Fe₃O₄ nano-composites will be an useful tools in biological, genetics, and bio-pharmic applications.

Scanning electron microscopy and atomic force microscopy of Coscinodiscus granii frustules treated by the liquid phase deposition

Kazuo Umemura, Yanfeng Gao, Tetsuya Nishikawa, et al.

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The surface structures of Coscinodiscus granii frustules were investigated before and after liquid phase deposition (LPD) treatment. Scanning electron microscopy (SEM) images showed that the outer surface of the frustules was rapidly covered with a TiO₂ layer within 6 h although the inner surface was not fully covered under the same condition. Comparison between the un-coated samples and the samples coated with metal prior to SEM observation provided valuable results to facilitate the understanding of the differences between the surface properties of the inner and outer frustule structures. Additionally, useful topographical information about the inner frustule surfaces was obtained by AFM imaging. The results of this investigation provide fundamental information about the process of LPD treatment onto frustule surfaces.

Optical properties of subwavelength wiregrid polarizer designed for GaN-based LED

Guiju Zhang, Bing Cao, Qin Han, et al.

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A theoretical simulation is presented on the optical transmission and polarized extinction ratio through subwavelength wiregrid polarizer for GaN-based LED. The micro-polarizers are specially designed based on rigorous coupled wave analysis method for operation wavelengths of blue light (470nm) and green light (520nm) with metal wiregrid on the GaN substrate. The TM transmittance and the extinction ratio of TM and TE transmittances are influenced by period, thickness and duty cycle of the metal wiregrid. Aluminum and silver metal film grating under subwavelength is separately used for optimization design to improve the optical properties at the visible wavelengths. Simulation results show that, as the thickness of the metal grating decreases, the coupled light shifts the TM transmittance peak to shorter wavelength. As the same time, the extinction ratio remains a high value. TM transmittance coefficients separately greater than 95% and 97% with extinction ratio greater than 33dB are achieved for GaN-based aluminum grating and silver grating at the wavelength 470nm. And TM coefficients are greater than 92% and 96% with extinction ratios greater than 33dB, respectively at the wavelength 520nm. The thicknesses and periods of the metal grating are with sizes about 300nm, which are under subwavelength structures. The numerical results are useful for designing and fabricating novel photonic nanostructure polarized optical devices.

Investigation and detection on corrosion of concrete structure in marine environment

Dandan Zhang, Jin Wu, Junqi Gao

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Due to the effect of marine environment, the corrosion of steel reinforcement in concrete structure is a very serious issue, so the field detection of steel reinforcement corrosion is very important. The Lianyun Harbor, a famous sea harbor in China with more than one hundred year history, was chosen to do the case study of the field detection. The corrosion ratio of the sampled steel reinforcement was obtained according to the field investigation in Lianyun Harbor and the experiment done in the laboratory. The chloride concentration in the concrete of different position and the sampled concrete at different depths in the splash zone was also measured in the laboratory. Moreover, the corrosive parameter of concrete structure was obtained by statistical analysis. The test results indicate that the reinforcement corrosion was very serious. The corrosion ratio of the sampled steel reinforcement and the concentration of chloride in concrete samples were both very high, which showed that Berth 14# in Lianyun Harbor was deteriorated badly. The chloride content at splash zone of Berth 57# and Berth 58# were also very high, which indicated that the chloride penetration for reinforcement concrete structures was very serious. The bearing capacity and the reliability of members could be calculated based on experiment data. The bearing capacity and the reliability of members decreased obviously and the members were needed to be maintained and strengthened in time.

Guided-wave-based detections of weld and crack in steel plates

Mingyu Lu, Xi Lu, Limin Zhou, et al.

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The guided-wave-based damage detection techniques using structurally integrated Lead-zirconate-titanate (PZT) patches for structural health monitoring (SHM) have been developed for many years. However, the method is still in its formative years and one of the main challenges is the application in real-word complicated structures. It's very important to widely study the techniques in the structures with simple geometries which can be used to construct more complicated structures for practical applications. In this paper, different steel plates of the same dimensions were used for detecting a 2mm-gap through-crack in welded zone and studying the effects of different impurities such as water, alcohol, epoxy and mud in the crack on wave propagations. Advanced signal processing and pattern recognition techniques such as the wavelet transform (WT) especially continuous wavelet transform (CWT) and Hilbert transform (HT) were used to enhance the efficiency of damage detections in the steel plates. Some simulation results were obtained to validate of experimental results. The results from both the experiments and simulations show the validity of the proposed method and the effects of different factors on the damage detection of the steel plates.

Effect of different cross-section types on mechanical properties and electromagnetic properties of carbon fibers reinforced plastics

Xin Liu, Sai Wang, Yonggang Yang, et al.

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To study the effect of different cross-section types on properties of carbon fibers, the microstructures of triangleshape carbon fibers and circle-shape carbon fibers were investigated by scanning electron microscope, X-Ray Photoelectron Spectroscopy and X-ray diffraction. The mechanical properties and electromagnetic properties of carbon fibers reinforced plastics were also studied. Results show that their microstructures and tensile-strength were similar, while the imaginary part of complex dielectric constant and loss tangent of the triangle-shape carbon fiber reinforced plastics are higher than those of the circle-shape carbon fiber reinforced plastics. The triangle-shape carbon fiber reinforced plastics have both the function of load bearing and the electromagnetic energy absorbing capability, and the composites will become promising radar absorbing structure material.

Effective thermo-mechanical properties and shape memory effect of CNT/SMP composites

Qingsheng Yang, Xia Liu, Fangfang Leng

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Shape memory polymer (SMP) has been applied in many fields as intelligent sensors and actuators. In order to improve the mechanical properties and recovery force of SMP, the addition of minor amounts of carbon nanotubes (CNT) into SMP has attracted wide attention. A micromechanical model and thermo-mechanical properties of CNT/SMP composites were studied in this paper. The thermo-mechanical constitutive relation of intellectual composites with isotropic and transversely isotropic CNT was obtained. Moreover, the shape memory effect of CNT/SMP composites and the effect of temperature and the volume fraction of CNT were discussed. The work shows that CNT/SMP composites exhibit excellent macroscopic thermo-mechanical properties and shape memory effect, while both of them can be affected remarkably by temperature and the microstructure parameters.

A preliminary study on anti-irradiation performance of epoxy shape memory polymer

Xuelian Wu, Yanju Liu, Jinsong Leng

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As a new class of smart material, shape memory polymer (SMP) receives more and more attention. In this paper, in addition to the fabrication of a new type of epoxy SMP, the thermo-mechanical properties of the polymer with/without gamma irradiation were investigated and compared systematically. The radiation source is Co-60 and the total dosage of radiation is 1×10⁴Gy. Changes of network structures of the polymer were investigated by Fourier Transform Infrared (FTIR) spectroscopy. The influence of gamma irradiation on thermo and mechanical properties of the polymer were investigated by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and tensile test, respectively. Furthermore, shape recovery behaviors of the polymer before/after the irradiation were compared too. Results show that the epoxy SMP possesses good chemical stability, glass transition temperature (T_g) determined by DSC decreased by 7°C after the irradiation. The gamma radiation has a slight influence on storage modulus, loss modulus and tan delta, respectively. No considerable change was found both in tensile strength and elongation at break after the gamma radiation. Finally, the shape recovery ratio of the polymer is near 100% with and without the gamma irradiation. Based on the above results, it can be demonstrated that the epoxy SMP prepared in the study possesses not only good thermo-mechanical properties but unique anti irradiation performance. The epoxy SMP shows potential for application of aerospace fields.

Analysis of impact-sliding wear property of aluminum bronze against titanium alloy and 2Cr13 steel

Yongqiang Wei, Liqin Wang

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Impact-sliding wear of aluminum bronze against titanium alloy and 2Cr13 steel have been conducted using impactsliding wear test rig which was developed independently. Some non-destructive examinations have been performed on worn specimens, using weighing, 2D and 3D profilometry, scanning electron microscopy and EDS technology. Using laser scanning confocal microscope (LSCM), it has been found that the surface of aluminum bronze which wears against titanium alloy is much coarser than the surface which wears against 2Cr13 steel. Results of wear volume show clearly that although the hardness of titanium alloy has greater value than aluminum bronze, the wear volume of titanium alloy has much greater value compared with aluminum bronze. It has been found that there is remarkable material transferring from titanium alloy to aluminum bronze and little material transfer from aluminum bronze to titanium alloy. For the impact-sliding wear between aluminum bronze against 2Cr13 steel, the hardness of aluminum bronze has greater value than 2Cr13 steel, the wear volume of aluminum bronze has much greater value compared with 2Cr13 steel, whose wear volume can be ignored. Using EDS technology, it has been found that there is material transferring from aluminum bronze to 2Cr13 steel and material transferring from 2Cr13 steel to aluminum bronze can be ignored. Through the SEM pictures of worn surfaces and worn debris, flaking, particles and micro-cracks can be found on the worn surfaces. The wear mechanism of aluminum bronze against titanium alloy and 2Cr13 steel is delamination wear.

One kind of fiber Bragg grating displacement sensor using micro-elastic spring

Xuefeng Zhao, Gangbing Song, Michael Fernandez, et al.

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A kind of fiber Bragg grating displacement sensor using micro-elastic spring is proposed and studied in this paper. A type of micro-elastic spring was used as a displacement-wavelength conversion component. According to the sensor package design established, one micro FBG displacement sensor with outer diameter of 1.3mm was constructed. Tests were designed and conducted to study the displacement and temperature sensitivity of the sensor. Results show that there are good linear relationships between wavelength and displacement, as well as between wavelength and temperature. The displacement coefficient and temperature coefficient are 10.97pm/mm, and 21.38pm/°C, respectively. To obtain smaller displacement resolution of the sensor, one kind of sensitivity inhenced FBG displacement sensor is proposed and studied, the displacement coefficient is 110pm/mm.

A novel fiber Bragg grating sensor interrogator based on time division multiplexing technique

Yongbo Dai, Zhichun Zhang, Jinsong Leng, et al.

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A novel fiber Bragg grating (FBG) sensor system for Structure Health Monitoring (SHM) is proposed in this paper. The proposed sensor technique is based on time division multiplexing (TDM). This technique utilizes semiconductor optical amplifier (SOA) as a gain medium and switch. The SOA is driven by a pulse generator which switch on the SOA at different periods, as a switch to select the reflected pulses from a particular sensor. The FBG sensors have identical center wavelengths and can be deployed along the same fiber. This technique relieves the spectral bandwidth issue and permits the interrogation of up to 100 FBGs along a fiber. The sensor system has a fast signal process and control unit, which have a typical scan frequency in 50 Hz and self-adaptive measurement for simple sensor array installation.

Furfural resin-based bio-nanocomposites reinforced by reactive nanocrystalline cellulose

C. Wang, S. Sun, G. Zhao, et al.

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The work presented herein has been focused on reinforcing the furfural resins (FA) by reactive-modified nanocrystalline cellulose (NCC) in an attempt to create a bio-nanocomposite completely based on natural resources. FA prepolymers were synthesized with an acid catalyst, and NCC was rendered reactive via the grafting of maleic anhydride (MAH). The resulting NCC and nanocomposites were characterized using TEM, SEM and FT-IR. It was found that NCC appeared to be spherical in shape with diameters under 100 nm. FT-IR confirmed that there were hydrogen and esterification bonding between MAH and NCC or FA prepolymer. After solidified with paratoluenesulfonic acid, NCC-reinforced FA resin composites showed granular cross-section while FA resin with layered structures. Mechanical property tests indicated that NCC-reinforced FA resin composites possessed the improved tensile and flexural strengths, in comparison with FA resin.

Artificial immune system based approach to fault diagnosis for wireless sensor networks

Yongjun Chen, Shenfang Yuan

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Fault diagnosis has been recognized as one of the key issues in wireless sensor networks. Considering distribution feature of sensor node, however, the fault happened in wireless sensor networks is usually random and unpredictable. The conventional diagnosis approaches become increasingly difficult to deal with. As a result, the application is limited seriously. To solve the problem, a new approach based on artificial immune system for fault diagnosis is proposed. The normal and abnormal character patterns generated by a network simulator for wireless sensor networks, respectively, are regarded as the self and antigen of artificial immune system. According to a real-valued negative selection algorithm, the detectors are generated to improve the covering ability of non-self space. Taking detector as antibody, an immunity calculation is executed by the distribution zones of antibody and evolution learning mechanism of artificial immune system. The type of antigen is decided based on the clustering distribution of cloned and matured antibody. The example shows that the approach has better accuracy and the capability of self-adaptive for the fault diagnosis in wireless sensor networks.

Modal macro-strain vector based damage detection methodology with long-gauge FBG sensors

Bin Xu, Chongwu W. Liu, Sami F. Masri

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Advances in optic fiber sensing technology provide easy and reliable way for the vibration-based strain measurement of engineering structures. As a typical optic fiber sensing techniques with high accuracy and resolution, long-gauge Fiber Bragg Grating (FBG) sensors have been widely employed in health monitoring of civil engineering structures. Therefore, the development of macro strain-based identification methods is crucial for damage detection and structural condition evaluation. In the previous study by the authors, a damage detection algorithm for a beam structure with the direct use of vibration-based macro-strain measurement time history with neural networks had been proposed and validated with experimental measurements. In this paper, a damage locating and quantifying method was proposed using modal macrostrain vectors (MMSVs) which can be extracted from vibration induced macro-strain response measurement time series from long-gage FBG sensors. The performance of the proposed methodology for damage detection of a beam with different damage scenario was studied with numerical simulation firstly. Then, dynamic tests on a simply-supported steel beam with different damage scenarios were carried out and macro-strain measurements were employed to detect the damage severity. Results show that the proposed MMSV based structural identification and damage detection methodology can locate and identify the structural damage severity with acceptable accuracy.

Surrounding rock mass stability monitoring of underground caverns in a geomechanical model test using FBG sensors

Yong Li, Weishen Zhu, Wenhua Zheng, et al.

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Fiber Bragg Gratings (FBG) sensor is widely accepted as a structural stability device for all kinds of geomaterials by either embedding into or bonding onto the structures. The physical model in geotechnical engineering, which can accurately simulate the construction processes and the effects on the stability of underground caverns on basis of satisfying the similarity principles, is an actual physical entity. Due to a large number of restrained factors, a series of experiments are difficult to be carried out, in particular for how to obtain physical parameters during the experiments. Using the geo-mechanical model test of underground caverns in Shuangjiangkou Hydropower Station as a research object, the FBG sensors were mainly focused on and adopted to figure out the problem how to achieve the small displacements in the large-scale model test. The final experimental results show that the FBG sensor has higher measuring accuracy than other conventional sensors like strain gages and mini-extensometers. The experimental results agree well with the numerical simulation results. In the process of building the model, it's successful to embed the FBG sensors in the physical model through making a reserved pore and adding some special glue. In conclusion, FBG sensors can effectively measure the small displacement of monitoring points in the whole process of the geomechanical model test. The experimental results reveal the deformation and failure characteristics of the surrounding rock mass and make some guidance for the in-situ engineering construction.

Application of fiber Bragg grating sensor for rebar corrosion

Jiang Geng, Jin Wu, Xinming Zhao

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Corrosion of rebar is one of the most important factors which can affect the durability of concrete structure, so in the service of these structures, measuring the degree of corrosion, and then evaluating the reliability of these structures are very important. The most significant characteristic of the rebar corrosion is its volume expansion. By the principle and characteristics of fiber bragg grating (FBG), a sensor for rebar corrosion is designed. In this paper, based upon laboratory studies, the fiber bragg grating sensor is applied in No.58 Berth of Lianyungang Port. According to the filed condition, a proper embedding scheme is proposed. Considering the optimal sensor placement, the monitoring points are determined and five sensor groups were applied in the structure. Based on the results of the calibration experiment, the relationship between corrosion ratio and the change of wavelength is established. So the corrosion status of the structure can be obtained by measuring wavelength. The study shows that the FBG sensor was feasible to monitor the status of rebar in concrete structures.

A new diagnostic method of bolt loosening detection for thermal protection systems

Weihua Xie, Songhe Meng, Jiecai Han, et al.

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Research and development efforts are underway to provide structural health monitoring systems to ensure the integrity of thermal protection system (TPS). An improved analytical method was proposed to assess the fastener integrity of a bolted structure in this paper. A new unsymmetrical washer was designed and fabricated, taking full advantage of piezoelectric ceramics (PZT) to play both roles as actuators and sensors, and using energy as the only extracted feature to identify abnormality. This diagnostic method is not restricted by the materials of the bracket, panel and base structure of the TPS whose condition is under inspection. A series of experiments on a metallic honeycomb sandwich panel were completed to demonstrate the capability of detecting bolt loosening on the TPS structure. Studies showed that this method can be used not only to identify the location of loosened bolts rapidly, but also to estimate the torque level of loosening bolts. Since that energy is the only extracted feature used to detect bolt loosening in this method, the diagnostic process become very simple and swift without sacrificing the accuracy of the results.

Full-field measurement of dynamic stress by mechanoluminescence sensing film

Chenshu Li, Chao-Nan Xu, Yusuke Imai, et al.

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Full-field measurement of dynamic stress has been realized by coating the surface of the test object metal with a upgrade mechanoluminescence sensing film of SrAl₂O₄:Eu (SAOE). Mechanoluminescent materials are attractive smart materials that can emit light induced by mechanical deformation. The ML sensing film of SAOE has been developed to make possible to visualize dynamic stress. Consequently this visualization technique has been become a promising experimental technique to investigate full-field stress analysis. In this paper we report the applications of the SAO ML sensing film for full-field stress analysis in aluminum alloy 5052 samples. Using the SAOE ML sensing film, the stress concentration produced by a circular hole was observed with the naked eyes in real time and the two-dimensional stress distribution was quantitatively measured; the complex and dynamic Portevin-Le Chatelier (PLC) effect, known as instability during plastic deformation, has been visualized, and the propagating characteristics of PLC bands were precisely investigated.

Modeling thermo-mechanical behaviors of reinforced shape memory polymer under cyclic loads

Bo Zhou, Xin Lan, Yanju Liu, et al.

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Dynamic mechanical analysis(DMA) tests are conducted on styrene-based fiber reinforced shape memory polymer (SMP) to investigate its glass transition behaviors. Results show the properties of stiffness, damping and energy dissipation of the reinforced SMP are obviously better than that of the pure SMP during the process of glass transition. Static threepoint bending tests are performed on the reinforced SMP to determine its stiffness and strength. Results show the reinforcement in the reinforced SMP improve the material properties of stiffness and strength at the room temperature. Cyclic three-point bending tests are operated to study the material training effect of the reinforced SMP. A training evolutional equation is established to describe the material training effect of the reinforced SMP. Numerical results show the training evolutional equation is able to predict the material training effect of the reinforced SMP effectively.

Wrinkling atop shape memory polymer with patterned surface

W. M. Huang, Y. Zhao, L. Sun, et al.

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We have previously demonstrated that various types of patterns at different scales can be easily realized atop shape memory polymers (SMPs) through a procedure in three steps, namely, indentation, polishing and heating (IPH). On the other hand, by coating a thin metallic layer (e.g., a few nanometers thick of gold) atop SMPs with or without prestraining, different types of wrinkles could be generated. In this paper, we investigate the wrinkling patterns formed on the top of SMPs with a patterned surface, i.e., wrinkling atop a surface with a protrusion pattern. As the wrinkles are resulted simultaneously by two phenomena upon heating, namely the shape recovery of the SMP substrate and buckling of the elastic metallic layer, the wrinkle pattern varies from one location to another depending on the exact local strain. Utilizing this technique, we are able to simultaneously produce a surface with complicate surface patterns at both micro and millimeter levels. Such surfaces could significantly enhance many surface properties, e.g., bonding, adhesion and friction etc.

Synthesis and characterization of shape-memory polyurethane films with blood compatibility

Cunxia Liang, Li Li, Chun Mao, et al.

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Shape memory polyurethane with different hard and soft segment based on aromatic diisocyanate (MDI) and polytetrahydrofuran (PTHF) or Polyethylene glycol (PEG) were synthesized by the prepolymer method. Glass transition temperature was tested by DSC. XRD results showed that the series of shape memory polyurethane has no crystallinity. And the shape memory behavior was also discussed. The results showed that the shape memory polyurethane made up of TMP-PTHF(1000)-MDI (2:1:5) performs better. It can recover 80% of original shape within one more second in the range of 37-45°C. SMPU films with PTHF as soft segment have good blood compatibility.

Nonparametric dynamic modeling of a non-linear frame structure with MR dampers

B. Xu, Z. G. Huang, S. F. Masri

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Identification of nonlinear dynamic systems using vibration measurements is crucial for efficient and reliable damage detection in structural health monitoring and control system design. Because of the complexity of control devices, it is usually difficult to model the nonlinear control devices with enough accuracy in a parametric form. In this study, a multi-storey steel-frame model structure equipped with magneto-rheological (MR) dampers, which were employed to introduce nonlinear phenomena to the model structure, was modeled with a neural network in a nonparametric way. Corresponding to the availability of dynamic response measurements, two different network models were proposed to predict the vibration response of the nonlinear model structure. Raw dynamic response measurements of the model structure under a certain impulse excitation was employed to train the two neural network models and the generality of the trained neural network models were validated in the form of forecasting the raw test dynamic response measurements of the model structure under other impulse excitation conditions. Results show that two neural network models provide a reliable way for the modeling of nonlinear dynamic structures and present a useful way for the control system design of engineering structures equipped with nonlinear control devices.

Effect of nano BaCO3 on pyrolytic reaction of phenol-formaldehyde resin

Xu Zhang, Qing-zhi Ma, Zhong-feng Zhang, et al.

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Phenol-formaldehyde resin is used as the most adhesive to produce waterproof plant-based composite. However, this product contains phenol and formaldehyde which can be easily released to pollute air and water. Based on the single-factor method, the effect of nano BaCO3 on situabtion of pyrolytic reaction of PF resin was studied by Py-GC/MS. There were components including carbon dioxide, D,.alpha.-tocopherol, 1,3-bis(trimethylsilyl) benzene, phenol from PF resin in 590(see manuscript) He gas. However, the 17 compounds including phenol, 2-methyl-, phenol, carbon dioxide, p-xylene, toluene, phenol, 2-ethyl-, phenol, 2,3-dimethyl-, benzene, 1,2,3-trimethyl-, etc were identified by Py-GC/MS after PF/BaCO3 composite was pyrolyzed in 590(see manuscript) He gas, and phenol and phenol derivants were found in the compounds. The result showed that nano BaCO3 could effectively delay the pyrolysis of PF resin.

Reliability assessment of long span bridges based on structural health monitoring: application to Yonghe Bridge

Shunlong Li, Hui Li, Jinping Ou, et al.

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This paper presents the reliability estimation studies based on structural health monitoring data for long span cable stayed bridges. The data collected by structural health monitoring system can be used to update the assumptions or probability models of random load effects, which would give potential for accurate reliability estimation. The reliability analysis is based on the estimated distribution for Dead, Live, Wind and Temperature Load effects. For the components with FBG strain sensors, the Dead, Live and unit Temperature Load effects can be determined by the strain measurements. For components without FBG strain sensors, the Dead and unit Temperature Load and Wind Load effects of the bridge can be evaluated by the finite element model, updated and calibrated by monitoring data. By applying measured truck loads and axle spacing data from weight in motion (WIM) system to the calibrated finite element model, the Live Load effects of components without FBG sensors can be generated. The stochastic process of Live Load effects can be described approximately by a Filtered Poisson Process and the extreme value distribution of Live Load effects can be calculated by Filtered Poisson Process theory. Then first order reliability method (FORM) is employed to estimate the reliability index of main components of the bridge (i.e. stiffening girder).

Improving the damping ability by the addition of Nano SiO2 to the concrete materials

Dujian Zou, Tiejun Liu, Jun Teng

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Damping in structures is commonly provided by viscoelastic nonstructural materials. Due to the large volume of structural materials in a structure, the contribution of a structural material to damping can be substantial. In this paper, the experimental investigation on damping ability of concrete materials and its members with Nana SiO₂ was carried out by the method of 3-point bending beam damping measurement and cantilever beam free vibration respectively. The microstructure of concrete mix with Nano SiO₂ was observed by XRD and SEM, then damping mechanism was discussed. The experimental results show that the damping reinforced effect achieved best with the 4% mixture ratio of Nana SiO₂, but the optimal adulteration quantity of Nano SiO₂ was 3% of cement weight by the comprehensive consideration of cost, workability, strength and dynamic properties. Nano materials as a mixture increase interfaces, and the non-uniform stress distribution under external force improves frictional damping energy consumption ability of concrete. The experimental results on the damping ratio and the loss tangent of the concrete materials with Nano materials are consistent.

Investigation on anti-corrosion property of nano-TiO2 fluoro-carbon coatings

Yu-hong Qi, Zhan-ping Zhang, Li-li Wang, et al.

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To meet the need of long-term anticorrosive protection of steel, a heavy-duty anticorrosive coating systems was developed with Fluorocarbon top paint which was modified by nano-TiO₂. The corrosive characteristics of low carbon steel coated with the system were investigated in seawater by the exposition tests and Electrochemical Impedance Spectroscopy (EIS). The results show that the protective system with fluorocarbon top coating modified by nano-TiO₂ has much better endurance than the reference system with fluorocarbon top coating not modified by nano-TiO₂. There isn't any rusting and blistering on the surface of former coating, the coating system remains in "GOOD" condition. But some rusting and blistering were found on the surface of reference coating. EIS results indicated that the impedance of the nano-coating system decreases much less than that of the reference one. The nano-coating system is hopeful to meet the need of new coatings standard and to provide a target useful coating life of 15 years for ship's ballast.

Effects of nanoparticles on hygrothermal property of epoxy resin composites

Xinying Lv, Rongguo Wang, Wenbo Liu

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Polymer composites are widely used in aerospace field, especially carbon fiber reinforced epoxy resin composites, because of the outstanding performance, became the most popular polymer matrix composites. However, the hygrothermal property of epoxy resin, as the matrix of the structure composite, is crucial to the whole composites. In this paper, the main focus is to modify the epoxy resin with nano-SiO₂ and nano-TiO₂ to enhance the hygrothermal property. Ultrasonic dispersion technology was used to prepare the nano-TiO₂ and nano-SiO₂ epoxy resin composites. The two kinds of composites were disposed in the climatic chamber for constant conditions. The effect of nano-particles on the hygrothermal property of epoxy resin composites were investigated by dynamic mechanics analysis (DMA) and mechanical properties testing. SEM images were taken to characterize the decentralization of the nano-particles in the composites. It is shown that nano-particles can be dispersed uniformly in the epoxy resin by ultrasonic dispersion. Thermo-analysis and mechanical testing results were presented that the epoxy nanocomposites has the excellent hygrothermal property under the same aging condition. Accordingly, the modified epoxy resin matrix can be used to prepare carbon fiber reinforced composites with remarkable hygrothermal property.

Oscillatory shear rheology of chiral liquid crystal polymers

Zhenlu Cui, Qi Wang, Jianbing Su

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We employ a hydrodynamic theory for chiral liquid crystal polymers (CLCPs) to investigate the linear viscoelastic response of CLCPs to small amplitude oscillatory permeation shear flow, when the helix is oriented along the velocity direction and the orientation distortion retain the original planar structure. To predict the linear viscoelasticity, we model the system with Stokes hydrodynamic equations with viscous and nematic as well as cholesteric stresses coupled with orientational dynamics driven by the flow. The key findings are the following: in low frequency limit, both the loss modulus (G") and storage modulus (Gⁱ) exhibit a classical frequency ω dependence (G" ∝ ω, Gⁱ ∝ ω² ) but their magnitudes are of order O(q/Er^1/2 ), where 2π/q defines the pitch of the chiral liquid crystal and Er is the Ericksen number. In high frequency limit, Gi = O(q² /Er) is independent of ω while Gⁱ = O(1)ω is independent of q and Er.

Performance evaluation of 6WD military vehicle featured by MR suspension system considering lumped parameter model of MR damper

Sung Hoon Ha, Qouc-Hung Nguyen, Seung-Bok Choi, et al.

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This paper proposes applies MR fluid based suspension system to military vehicle for vibration control. The suspension system consists of gas spring and MR damper. In order to model of MR damper, a quasi-static modeling of the damper is conducted on the basis of Bingham model of MR fluid after describing the configuration and operating principle of the MR damper. And then the lumped parameter models of MR fluid flows in the damper are established and integrated to whole damper system by taking into account for dynamic motions of annular duct and gas chamber. Subsequently, a military vehicle of 6WD is adopted for the integration of the MR suspension system and its nonlinear dynamic model is established by considering vertical, pitch and roll motion. Then, a sky-hook controller associated with semi-active actuating condition is designed to reduce the imposed vibration. In order to demonstrate the effectiveness of the MR suspension system, computer simulation is undertaken showing vibration control performance such as roll angle and pitch angle. This is vibration control evaluated under bump and random road profiles.

The study on leakage reappearance test of high pressure hose for power steering system

Gi-Chun Lee, Hyoung-Eui Kim, Jong-Won Park, et al.

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Generally, a leakage in a high pressure hose assembly can be determined if hydraulic fluid falls down through fitting which is swaged with a rubber hose. This study tried to visualize leakage, which is considered a failure occurring often in the hydraulic system. In the case of methods which verify leakage paths in the power steering hydraulic system equipped with a high pressure hose assembly, three types of leakage paths, which could be seen by cutting the swaging part, were generally found. However, it was difficult to find out leakage paths by using power steering oil. In this study, four methods, including the thermal burn image method, the hole drilling method of fitting metal, the white paint infiltration method, and the fluorescent infiltration method, were tried to introduce. The thermal burn image method failed to find out the leakage path between the fitting part and the rubber part. The hole drilling method is the way to check a leakage path on the fitting part, which doesn't need to cut a hose assembly. This method succeeds to visualize the leakage path partially but it could not check a sequential path of leakage, either, because it needs to drill more closely. The white paint infiltration method also could find the leakage path partially by using white paint mixed with thinner, which was pressurized by hand pump, instead of power steering oil. This method could check the leakage path by cutting the swaging part. The fluorescent infiltration method could verify the leakage path with naked eyes simply by holding the cutting swaging part closely to the ray of light. Reappearance test methods in the high pressure hose assembly, which include a hole drilling, a white paint infiltration, and a fluorescent infiltration method, can be applied to find the failure mode and to approve the test before the mass production of the high pressure hose.

Position control of ionic polymer metal composite actuator based on neuro-fuzzy system

Truong-Thinh Nguyen, Young-Soo Yang, Il-Kwon Oh

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This paper describes the application of Neuro-Fuzzy techniques for controlling an IPMC cantilever configuration under water to improve tracking ability for an IPMC actuator. The controller was designed using an Adaptive Neuro-Fuzzy Controller (ANFC). The measured input data based including the tip-displacements and electrical signals have been recorded for generating the training in the ANFC. These data were used for training the ANFC to adjust the membership functions in the fuzzy control algorithm. The comparison between actual and reference values obtained from the ANFC gave satisfactory results, which showed that Adaptive Neuro-Fuzzy algorithm is reliable in controlling IPMC actuator. In addition, experimental results show that the ANFC performed better than the pure fuzzy controller (PFC). Present results show that the current adaptive neuro-fuzzy controller can be successfully applied to the real-time control of the ionic polymer metal composite actuator for which the performance degrades under long-term actuation.

Solid biopolymer electrolytes came from renewable biopolymer

Ning Wang, Xingxiang Zhang, Zhijun Qiao, et al.

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Solid polymer electrolytes (SPEs) have attracted many attentions as solid state ionic conductors, because of their advantages such as high energy density, electrochemical stability, and easy processing. SPEs obtained from starch have attracted many attentions in recent years because of its abundant, renewable, low price, biodegradable and biocompatible. In addition, the efficient utilization of biodegradable polymers came from renewable sources is becoming increasingly important due to diminishing resources of fossil fuels as well as white pollution caused by undegradable plastics based on petroleum. So N, N-dimethylacetamide (DMAc) with certain concentration ranges of lithium chloride (LiCl) is used as plasticizers of cornstarch. Li⁺ can complexes with the carbonyl atoms of DMAc molecules to produce a macro-cation and leave the Cl^- free to hydrogen bond with the hydroxyl or carbonyl of starch. This competitive hydrogen bond formation serves to disrupt the intra- and intermolecular hydrogen bonding existed in starch. Therefore, melt extrusion process conditions are used to prepare conductive thermoplastic starch (TPS). The improvements of LiCl concentration increase the water absorption and conductance of TPS. The conductance of TPS containing 0.14 mol LiCl achieve to 10^-0.5 S cm^-1 with 18 wt% water content.

Delamination detection in CFRP laminates using FOD sensor

Fucai Li, Kazuro Kageyama, Hideaki Murayama, et al.

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In this paper, carbon fiber reinforced plastic (CFRP) laminates (pristine and delaminated) are addressed for the purpose of damage assessment. Recently developed Doppler effect-based fiber optic (FOD) sensor was bonded on surface of each CFRP laminate to acquire piezoceramic-disc-excited guided waves propagating in the specimen. Characteristics of the captured guided wave signals were extracted by taking advantage of two well-developed signal processing algorithms, namely, linear-phase finite impulse response filter and Hilbert transform, so as to investigate the influence of the delaminations to the guided wave propagation. When guided waves are incident on discontinuities, mode conversion may occur as a result of satisfying the boundary conditions along the discontinuities. Both the dispersive characteristics of multi-mode guided waves and features of the guided-wave-generated fundamental shear horizontal (SH0) wave were applied for damage evaluation and multiple-damage detection. The results demonstrate that the FOD sensor is effective in multiple delamination detection for CFRP laminates because of its omnidirectional property in ultrasonic detection.

Development and implementation of a remote real-time monitoring system for cable force of Tianjin Yonghe cable-stayed bridge

Hongwei Li, Hui Li, Guohui Liu, et al.

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Bridge cables are used as critical structural components for cable-stayed bridges. It is essential to identify and monitoring the cable force of cable-stayed bridges in real time and continuously. In this paper, the design of a remote real-time cable force monitoring system including both hardware and software components are realized and the specifications of the system are also presented. The system was implemented in the Tianjin Yonghe cable-stayed bridge located in Tianjin, China, to remotely monitor the cable fore of the bridge and provide the condition assessment of the cables to the users via Internet. Experiences with this system demonstrate how effective low cost system provides a tremendous cost savings in terms of travel time, maintenance, and repair costs. This paper will also discuss the monitoring system and provides a preliminary analysis based on the data acquired from this system.

Nanocomposite materials based on sulfonated polyarylenethioethersulfone and sulfonated polybenzimidazole for proton exchange membrane fuel cell applications

Zongwu Bai, Narayanan Venkat, Shane B. Juhl, et al.

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Fabrication of novel nanocomposite membranes comprising a fully sulfonated polyarylenethioether sulfone (SPTES) and sulfonated poly(p-phenylene benzobisimidazole)(SPBI) and the evaluation of the membrane properties are described. The nanocomposite membrane was obtained via a solvent cast process in a mixture of DMAc and methanol as solvents. The nanocomposite membrane proton conductivity, as measured by four probe impedance spectroscopy, was found to increase with increase in the SPTES content in the nanocomposite. The highest proton conductivity obtained was ~80mS/cm at 65ºC and 85 % relative humidity for the SPTES/SPBI 70/30 nanocomposite membrane which was considerably less than the 300 mS/cm for the pure SPTES membrane, but it was found that the swelling of the nanocomposite membranes was reduced due to the reduced water uptake of the nanocomposite membrane relative to SPTES. The morphology of the SPTES/SPBI nanocomposite membranes was examined by a combination of techniques, such as X-ray diffraction and scanning electron microscopy, to confirm the dispersion of SPBI in the nanocomposite. The membrane electrode assembly performance of the nanocomposite membranes was preliminary studied for H2/O2 fuel cells applications.

Ionic polymer metal composite actuators employing irradiation-crosslinked sulfonated poly(styrene-ran-ethylene) as ion-exchange membranes

Xuanlun Wang, Tai-Hong Cheng, Liang Xu, et al.

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Ionic polymer metal composites (IPMC) are soft polymeric smart materials having large displacement at low voltage in moist environments or water. This type of actuators consists of an ionic membrane and noble metal electrodes plated on both surfaces. The ion-exchange membrane, Nafion, remains as the benchmark for a majority of research and development in IPMC technology. In this research, we employed sulfonated poly(styrene-ran-ethylene) (SPSE) that is crosslinked by UV irradiation as a novel ionic membrane. The crosslinking reaction between polymer matrix and crosslinking agent was proved by FTIR analysis. The sulfonic acid groups were stable during the UV irradiation crosslinking process. Water uptake, ion exchange capacity, and sulfonation degree are characterized for both pure SPSE and crosslinked SPSE membrane. The bending responses of SPSE actuators under both direct current (DC) and alternating current (AC) excitations were investigated. The voltage-current behaviors of the actuators under AC excitations are also measured. Results showed the crosslinked SPSE actuators have better electromechanical performance than that of pure SPSE actuator with regard to tip displacement.

Electro-mechanical analysis of a dielectric elastomer membrane undergoing large deformation

Tianhu He, Cheng Chen, Leilei Cui

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In the family of smart material transducers, muscle-like transducers, i.e., dielectric elastomer transducers, have attracted much interest in recent years due to their many fascinating attributes such as large strain, fast response, high efficiency, simple, potentially low cost and light. The essential part of dielectric elastomer transducers is a dielectric membrane sandwiched between two compliant electrodes. Subject to a voltage, the dielectric membrane reduces its thickness and expands its area, converting electrical energy into mechanical energy. Due to large deformation, nonlinear equations of state, and diverse modes of failure, modeling the electro-mechanical response for dielectric elastomer transducers has been challenging. In this paper, the electro-mechanical behavior of a dielectric membrane deformed by the application of voltage and weight into an out-f-plane, axisymmetric shape is investigated. Ogden model is adopted to formulate the state equations by combining kinematics and thermodynamics. A set of ordinary differential equations characterizing the large out-of-plane deformation of the dielectric membrane are derived, and shooting method is applied to solving the equations numerically. The obtained results show that the field in the membrane is very inhomogeneous, which leads to most part of the membrane functioning inefficiently. This can be used to optimize the design of electromechanical transducers for specific applications.

Analysis of electromechanical stability on dielectric elastomer actuators under large deformations condition

Liwu Liu, Shouhua Sun D.D.S., Kai Yu, et al.

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Dielectric elastomers (DE) are one of the important electroactive polymers used as actuators in adaptive structures due to their outstanding abilities to generate very large deformations while subjected to an external electric filed. In this paper, Mooney-Rivlin elastic strain energy function with two material constants is applied to analyze the electromechanical stability performance of DE. This elastic strain energy couplied with the electric energy incorporating linear permittivity is the main item to construct the free energy of the system. Particular numerical results are also processing for further understanding of DE's typical stability performance. The proposed model offers great help in guiding the design and fabrication of actuators featuring DE.

Isotropical conductive adhesives filled with silver nanowires

Y. Tao, Y. P. Xia, G. Q. Zhang, et al.

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In this study, a solution-phase method was demonstrated to generate silver (Ag) nanowires with diameters in the range of 30~50nm and lengths of up to ~50μm, which was proceed by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). Fundamental material characterizations including X-ray diffraction transmission electro microscopy (TEM) and scanning electro microscopy (SEM) were conducted on these Ag nanowires. A novel kind of isotropical conductive adhesives (ICA) was prepared by using these Ag nanowires as conductive filler. Electrical property including bulk resistivity and mechanical property including shear strength were investigated and compared with that of conventional ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles. The average diameter of these Ag particles is about 1μm and 100 nm respectively. The results shown that ICA filled Ag nanowires exhibited higher conductivity, higher shear strength and low percolation threshold value than traditional ICA. Possible conductive mechanism was discussed based on theory calculation.

Preparation of calcium and titanium precipitation particles and its high electrorheological activity

Kaihua Wu, Yuchuan Cheng, Zhenyang Song, et al.

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A type of calcium and titanium precipitation (CTP) material was synthesized by means of a simple co-precipitation method. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and field emission scanning electron microscopy (FESEM) measurements were utilized to characterize the component, structure, and morphology of the CTP nanoparticles. The obtained particles were nano-scale and rod-like. The electrorheological (ER) measurement showed that the yield stress of the ER fluids reach about 146 KPa at a DC electric field of 5 KV/mm when the weight fraction is 67 wt%. It is substantially enhanced in comparison with the as-reported CTP ER fluids prepared by oxalate route. Furthermore, the ER fluids are very stable, environmentally friendly and attractive for large-scale utilization.

The effect of silicon carbide nanoparticles on the multifunctionality of epoxy polymers and CFRPs

P. Karapappas, A. Baltopoulos, A. Vavouliotis, et al.

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In this work the effect of silicon carbide nanoparticles (n-SiC) into an epoxy matrix was investigated. High shear mixing techniques combined with sonication methods were used to homogeneously disperse the Silicon Carbide nanoparticles (Nano-SiC) in bisphenol-A epoxy resin at 1% weight fraction. SEM and AFM were used to evaluate the achieved dispersion in the nanopolymer. Mechanical, thermal and dynamic tests were performed to evaluate the nanopolymer and directly compared with the neat resin. On polymer level the produced materials showed improvement in the mechanical properties reaching up to 25% and 30% in Young's modulus and failure stress respectively. The nanopolymer exhibited a more brittle behavior through the decrease of the maximum strain at fracture. The thermal properties of the nanocomposite were highly affected leading to an enhancement of the thermal conductivity and thermal effusivity of the material. Meanwhile the glass transition temperature increased up to 28% as measured through DMA tests. The aforementioned material was used as the matrix material in order to produce carbon fibre reinforced panel. The improved properties of the nanopolymer have enhanced the fracture properties of the composite material as the dispersed nanospheres can work as arrestors/deflectors of the propagating cracks through the composite.

Evolution of surface structure of bilayer oleic acid-coated Fe3O4 nanoparticles during ethanol washing

Huabei Peng, Kun Yang, Yuhua Wen

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The excess amount of oleic acid must be added to synthesize the bilayer oleic acid-coated Fe3O4 nanoparticles by onestep method. To know the evolution of surface structure during removing the residual oleic acid by ethanol washing, the surface structure of bilayer oleic acid-coated Fe₃O₄ nanoparticles synthesized by one-step method was studied using TEM, FTIR and TGA with washing times. The results showed that after five times washing, the bilayer oleic acid-coated structure still remained; after twenty times washing, the bilayer oleic acid-coated structure evolved into the single layer one.

Design and test of a micro-displacement actuator based on giant magnetostrictive material

Liang Shao, Dehua Yang, Bintang Yang, et al.

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To meet the performance requirements of co-focusing and co-phasing of segmented mirror active optics (SMAO) in modern astronomical telescope, micro-displacement actuators with nanometer resolution and millimeter stroke are necessary. The design and test of a micro-displacement actuator based on giant magnetostrictive material is present in this paper. The actuator's main components, such as giant magnetostrictive drive core, displacement pantograph mechanism and output guide mechanism, are discussed in detailed. The giant magnetostrictive drive mechanism generally may offer nanometer resolution and micron stroke. A displacement/stroke pantograph mechanism is designed with absolutely sealed flexible hydraulic structure (ASFHS) to enlarge the stroke. In addition, a secondary giant magnetostrictive drive mechanism is integrated to serve final resolution of final displacement output. In view of flexure exhibiting excellent mechanical properties free of friction, clearance and lubrication, a flexure guide mechanism with the capacity of excellent lateral load is designed to fulfill linear displacement output steadily. The sub-systems like the giant magnetostrictive drive core and displacement pantograph mechanism have been tested before integration of the whole actuator. The final test of the actuator is carried out with dual frequency laser interferometer at lab. Besides, to meet technical requirements of future extremely large telescope, further development issues mainly related to application practice of the actuator is discussed at the end.

A biosensing of Toxoplasma gondii DNA with CdTe/Fe3O4 dual functional quantum dot as reporter group

Chu Liang, Shichao Xu, Juan Yang, et al.

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Toxoplasma gondii is an intestinal coccidium that parasitizes members of the cat family as definitive hosts and has a wide range of intermediate hosts. Infection is common in many warm-blooded animals, including humans, the early detection of Toxoplasma gondii was concerned in recent years. In the current research, we presented a fast, specific, and sensitive sensing probe to detect Toxoplasma gondii DNA based on mechanism of fluorescence energy transfer (FRET), and a magnetic-fluorescent CdTe/Fe3O4 core-shell quantum dots (mQDs) was utilized as energy donor, and a commercial quencher (BHQ-2) was used as energy acceptor, respectively. The CdTe/Fe₃O₄ mQDs were prepared by layer-by-layer (LBL) process at ambient temperature. The sensing probe was fabricated through labeling a stem-loop Toxoplasma gondii DNA oligonucleotide with mQDs at the 5' end and BHQ-2 at 3' end, respectively, and the resulting sensing probe can be simply isolated and purified from the reactant with a common magnet. Properties of mQDs and sensing probe were determined by transmission electron microscopy (TEM) and fluorescence spectrum (FS). The TEM data demonstrated that the size of mQDs was ~20nm. the FS data indicated fluorescence intensity (FI) was doubled after the complete complimentary target Toxoplasma gondii DNA was introduced comparing with the FI before addition of target Toxoplasma gondii DNA. Moreover, only weak FI change was observed when the target DNA with one-mismatch base pair was added, this result revealed the sensing probe has high sensitivity and specificity. The current sensing probe will has great potential applications in the life science and related research.

A novel nano-gripper compliant mechanism with parallel movement of gripping arms

Mahmoud M. K. Helal, Lining Sun, Liguo Chen

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Research and development of and on micro and nano sized objects and systems have received considerable interest the last few decades and have accelerated the last decade during the advent of nanotechnology. Compliant mechanisms (CMs) have made an enormous contribution in the design process of various fields such as for adaptive structures, handheld tools, components in transportations, electronics, and surgical tools. Topology optimization has proven to be a powerful method for the conceptual design of structures and mechanisms. Topology optimization is the technique that finds the optimal layout of the structure within a specified design domain. This paper presents a nano-gripper, which can realize a parallel movement of the gripping arms with possibility for simultaneous positioning of the gripped object. The topology optimization is applied for designing two-dimensional nano-gripper compliant mechanism with parallel movement of gripping arms. As objective function, the traditional mean compliance design problem is considered, where the objective is to find the material distribution that minimizes the mean compliance for a certain volume constraint. The optimization algorithm is implemented in ANSYS by using the ANSYS Parametric Design Language (APDL). The final optimal topology configuration of nano-gripper with parallel movement of gripping arms is shown and discussed.

An analytical model for nanomechanical behavior of microcantilever-DNA chip

Zou-Qing Tan, Jing-Jing Li, Neng-Hui Zhang

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The paper is devoted to formulating an analytical relation between various biomolecular interactions during the process of label-free DNA-detection and changes in surface stress, which is widely accepted as the origin of nanomechanical motion of a microcantilever-DNA chip. First, considering electrostatic interactions between neighboring strands, hydration forces between DNA molecules and hydrogen bonding networks in water, conformational entropy of DNA chains, and mechanical energy of non-biolayers, the energy potential of a DNA chip and its first-order approximate expression are formulated. Second, the analytical expression for surface stress of a DNA chip is given by the minimum principle of energy. Third, the effects of grafting density and salt concentration on surface stress are investigated. Numerical results show that surface stress is a strong function of grafting density, which is in agreement with Stachowiak's experimental results. And, comparison of first-order and two-order predictions for surface stress is discussed.

Analysis of elastic wave in carbon nanotubes using continuum mechanics and molecular dynamic simulations

Yan-Gao Hu, K. M. Liew, Q. Wang

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This paper presents a review of elastic waves in carbon nanotubes (CNTs) studied through continuum mechanics and molecular dynamics (MD) simulations. The nonlocal continuum models play an important role in studying wave propagation in CNTs. The applicability of the nonlocal continuum models based on the MD simulation results is summarized.

Multi-walled carbon nanotubes under protons beam irradiation

Ahmad Ishaq, A. R. Sobia, Long Yan, et al.

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We report effects of 70-keV protons irradiation on structure of multi-walled carbon nanotubes (MWCNTs) in a wide range of irradiation doses and temperatures. It is found that graphite phase of MWCNTs structure can be transformed to amorphous phase in a highly controlled fashion at the temperature of 650K. Moreover, at the temperature of 800K, experiments have demonstrated that proton irradiation can create molecular junctions between parallel MWCNTs. The structural stability of MWCNTs at 950K is also discussed.

Modeling the shape memory effect of shape memory polymer

Bo Zhou, Yanju Liu, Jin-Song Leng

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Dynamic mechanical analysis (DMA) tests are conducted on the styrene-based shape memory polymer (SMP) to investigate its state transition behaviors. Tensile tests at various constant temperatures are carried out to reveal the stressstrain- temperature relationship of the styrene-based SMP. A new mechanical constitutive equation is developed to describe the stress-strain-temperature relationship of the styrene-based SMP. Numerical calculations illustrate the proposed theory well describes the thermo-mechanical cycle of shape memory of styrene-based SMP, such as deformation at high temperature, shape fixity, unloading at low temperature and shape recovery.

Fabrication and properties of shape-memory polymer coated with conductive nanofiber paper

Haibao Lu, Yanju Liu, Jan Gou, et al.

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A unique concept of shape-memory polymer (SMP) nanocomposites making up of carbon nanofiber paper was explored. The essential element of this method was to design and fabricate nanopaper with well-controlled and optimized network structure of carbon nanofibers. In this study, carbon nanofiber paper was prepared under ultrasonicated processing and vapor press method, while the dispersion of nanofiber was treated by BYK-191 dispersant. The morphologies of carbon nanofibers within the paper were characterized with scanning electron microscopy (SEM). In addition, the thermomechanical properties of SMP coated with carbon nanofiber paper were measured by the dynamic mechanical thermal analysis (DMTA). It was found that the glass transition temperature and thermomechanical properties of nanocomposites were strongly determined by the dispersion of polymer in conductive paper. Subsequently, the electrical conductivity of conductive paper and nanocomposites were measured, respectively. And experimental results revealed that the conductive properties of nanocoposites were significantly improved by carbon nanopaper, resulting in actuation driven by electrical resistive heating.

Collinear electrodes on the surface of electrostrictive materials

Quan Jiang, Cun-Fa Gao

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Field singularities of collinear electrodes on the surface of a half-infinite electrostrictive solid are studied in terms of the complex variable method. Firstly, the general solutions for the potential functions of electric fields and stresses are derived for the case of collinear electrodes based on analytical continuation method, and then explicit results are given for the cases of single electrode. Numerical calculations are also made to discuss the effects of applied electric loading on the field singularities near the electrode. It is found that even at the low level of applied electric loading, considerable high stresses will be induced around the electrodes, especially at the tip of electrode.

Evaluation of vibration control performance of smart hull structure featuring piezoelectric composite actuators

Jung Woo Sohn, Oh-Cheol Kwon, Seung-Bok Choi

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In the present paper, modal characteristics and vibration control performance of smart hull structure are experimentally investigated and compared between in the air and underwater conditions. End-capped hull structure is manufactured and Macro Fiber Composite (MFC) actuators are attached on the inside surface of the structure. Natural frequency and mode shapes are experimentally investigated for each in the air and underwater conditions. For the verification of modal test results, finite element analysis is conducted and numerical results are compared with modal test results. Optimal controller is designed and then implemented for vibration control of smart hull structure. Structural vibration control performances are evaluated in the air and underwater conditions and presented both in frequency and time domains.

The free vibrations of layered thin film plates and applications in resonator analysis

Ji Wang, Jiansong Liu, Jianke Du, et al.

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Thin film acoustic wave resonators are typical layered structures consisting of piezoelectric and metal films serving as essential elements of resonance and excitation. Such a layered structure can be analyzed for the proper selection of the thicknesses of thin films based on the vibration frequency and resonator property. In recent studies on thin film acoustic wave resonators, especially the film bulk acoustic wave resonators (FBAR) and solidly mounted resonators (SMR) types, extensive fabrication and characterization efforts have been contributing to the development of many novel products and processing technology. The recently renewed global interests on the FBAR technology also expect the design of resonators can be done through sophisticated analysis with wave propagation and circuit theories. These requirements have motivated our studies on the vibrations of layered piezoelectric structures for applications in the FBAR resonator analysis and design. Based on the justified assumption that the microstructure of FBAR can also be treated as infinite plates, the vibration frequencies of the thickness-extension and thickness-shear types are calculated from layered models with perfectly bonded interfaces. The calculated frequencies are in good agreement with experimental data. We now extend the analysis to SMR structures, which have much more bonded layers of piezoelectric and metal films under the same assumption of infinite plates and perfect interfaces. The vibration solutions are given in terms of frequency and displacements. These results can be used for the proper determination of the film thicknesses and selection of materials based on the resonator frequency which can be calculated from mechanical vibrations.

Microencapsulation of self-healing agents with melamine-urea-formaldehyde by the Shirasu Porous Glass (SPG) emulsification technique

Xing Liu, Jong Keun Lee, Michael R. Kessler

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Norbornene-based healing agent candidates, ENB (5-ethylidene-2-norbornene) and ENB with a custom crosslinker, were prepared into a uniform microsphere utilizing a Shirasu Porous Glass (SPG) emulsification technique, and microencapsulated by in-situ polymerization of melamine-urea-formaldehyde (MUF). Resulting microcapsules were observed under optical and scanning electron microscopy for their morphology, outer and inner surface, and shell thickness. Particle size analysis showed more uniform size distribution with a mean diameter of 40 μm, compared to a conventional method using a mechanical impeller. The thermal and mechanical properties of the microcapsules were also examined considering fabrication of self-healing composites.

Study of the thermal property of copper oxide nanowires

C. F. Dee, Y. Y. Wong, K. P. Lim, et al.

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As a high potential candidate for field-emission emitters, gas sensors, high-critical temperature superconductors, copper oxide NWs have been intensively studied in the synthesized methods, electrical properties and chemical properties. However, there are not many literatures report on the thermal property of them. It is important for one to understand the thermal behavior in order to justify the failure limit of the material especially in nanoscale. In this paper, copper oxide NWs synthesized through direct heating in atmospheric ambient were rapidly annealed in nitrogen ambient at different temperature to check the critical thermal failure point where the free standing copper oxide NWs start to collapse. It was found that copper oxide NWs with diameters around 100 nm started to collapse after 30 minutes of annealing in the nitrogen ambient at 300°C due to the thermal shock incurred by rapid annealing. Increase in temperature will cause the NWs with bigger diameters start to fail. NWs in same diameter range will be able to withstand the temperature up to several hours if no thermal shock is induced. This was happening even when the wires were heated in a higher temperature of 600°C. This result is important for copper oxide NWs when they are incorporated into the other heat sensitive device. The results are important for justifying the failure behavior for devices based on copper oxide NWs.

Insertion of intelligent hydrogel into silicone resin for thermal control applications

Hua Wei, Dengteng Ge, Zeng Fan, et al.

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As a kind of intelligent temperature-sensitive polymer, the poly (N-isopropylacrylamide) (PNIPA) hydrogel has lower critical solution temperature (LCST) of 33°C. PNIPA could change from transparency to opacification due to its phase separation. In this work, silicone coatings were doped with PNIPA particles, which were obtained by rotary cutting after N-isopropylacrylamide cross link reaction between N-isopropylacrylamide and N, N-methylenebisacrylamide in the aqueous solution below 20°C. The morphology and optical properties were characterized by SEM, FTIR and UV-Vis-NIR, respectively. The results show that combination of silicone resin and PNIPA particles enhances the diffuse reflection and operability in applications. It proves that the reversible thermal chronic property of PNIPA is useful for intelligent thermal control application.

Thermal stress reduction of bilayered systems by means of linearly graded interlayer

Binglian Wang, Yizeng Li, Yongzhong Huo

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The technique of introducing graded interlayers has been used extensively to mitigate residual thermal stresses in joining dissimilar materials. The case-to-case numerical methods have often been used to discuss the effectiveness of the graded interlayers, because it is always a mathematical difficulty in analytical analysis. In this work, thermal stress reduction of bilayered systems with linearly graded interlayer is considered with analytical approaches. It has been found that the maximal stress in the system will always be lowered with a thick enough interlayer. However, if the interlayer thickness is restricted, a critical range of the elastic modulus and layer thicknesses of the original bilayered system can be identified only in which the maximal stress can be reduced. An even smaller range is found within which the maximal stress always decreases with the increase of the interlayer thickness.

Hybrid finite element formulation for electrostrictive materials: static and buckling analysis of beam

Jerome R, Ganesan N

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A nonlinear electromechanical coupled static finite element formulation for electrostrictive materials is proposed. This formulation includes the quadratic dependence of strain with polarization, valid at a constant temperature and excludes hysteresis. The present formulation uses linear finite element analysis for stress and strain evaluation along with the numerical solution of the nonlinear constitutive equation using Newton - Raphson technique only within each electrostrictive elements and hence this formulation is named as hybrid finite element formulation. Polarization is an explicit independent variable in this formulation and the nonlinear equations at each electrostrictive elements are solved for this variable. Since the nonlinear constitutive equation is a function of polarization and tends to infinity for certain values of polarization, the Newton - Raphson technique is specially modified in order to guarantee the convergence of the solution. A simple technique for obtaining the initial guess of the solution for Newton - Raphson technique is also proposed which gives faster convergence of the solution. Since the polarization is an explicit independent variable in the present formulation, the assumption, made in most of the finite element formulations [15, 16, 17, 18], that polarization is approximately equal to electric displacement has been relaxed. The developed static finite element formulation has been extended to solve buckling problems of electrostrictive beams. Analytical solutions have been developed for static and buckling analysis of electrostrictive beams. The developed finite element formulation results are compared with that of the analytical solution results and it has been found that the results are in very good agreement. The proposed finite element formulation is computationally very efficient than any other available nonlinear finite element formulation for electrostrictive materials. The proposed finite element formulation proves its very high computational efficiency especially in case of buckling analyses as well as in case of electrostrictive patches embedded in large structures.

Investigation of thermal distortion and control of spacecraft based on shape memory materials

Hongwei Sun, Xingwen Du, Huifeng Tan

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Gossamer space structures are relatively large, flimsy, and lightweight. As a result, they are more easily affected or distortion by space thermal environments compared to other space structures. This study examines the structural integrity of a Five-Meter Ka-Band Inflatable/Self-Rigidizable Reflect Antenna under space thermal environments. To maintain the required accuracy of the reflector under orbital temperature changes, the Gossamer space structures will utilize an active control system, consisting of boundary control actuators and an electrostatic figure control system with a real time closed loop feedback. An experimental system is established to verify the control mechanism with photogrammetric measurement technique and Bragg fiber grating (FBG) sensor technique. The shape control experiments are finished by measuring and analyzing small amplitude distortion of Five-Meter Ka-Band Inflatable/Self-Rigidizable Reflect Antenna based on the active components made of shape memory alloy (SMA) and shape memory polymer composite (SMPC) material. Then, simulations are finished by NASTRAN finite element software with active effect which is considered to be deformation applied on the analytical model. The amplitude of distortion is obtained by the simulations. Both the experimental and numerical solution show that the amplitude of accuracy are developed which proves the feasibility of shape control using shape memory materials and this investigation explores the feasibility of utilizing an active cable based control system of shape memory materials to reduce global distortion due to thermal loading. It is found that through proper assemble of cable lengths and attachment points, significant thermal distortion reduction is achieved. Specifically, radial distortion due to on-orbit thermal loading .

Effect of structure on the optical properties of Ni-Mn-Ga alloy: experimental and theoretical investigation

Z. Y. Gao, C. Liu, C. L. Tan, et al.

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Ni-Mn-Ga alloys possess thermoelastic martensitic transformation and ferromagnetic transition. Despite the giant magnetic-field-induced strain and stress-induced martensitic transformation developed in Ni-Mn-Ga alloys, however, little information is obtained about optical properties of Ni-Mn-Ga alloys as candidate materials in digital information storage. In this study, the optical reflectivity of Ni-Mn-Ga alloys in martensite and austenite phases has been investigated. The results reveal that the maximum reflectivity difference between the martensite and austenite phases is about 24%, indicating the promising application in phase-transition information storage. The calculated DOS shows that the effect of martensitic transformation on optical properties is attributed to the change of Ni 3d partial DOS between the austenite and martensite phases.

Study on the bifurcation and chaos of giant magnetostrictive actuators

Hai-quan Zeng, Wen-wang Li

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Nonlinearity between exciting current and output displacement spoils giant magnetostrictive actuators'(GMA) performance. Chaotic and Quasi-periodic motions are important aspects of nonlinear character for GMA. To explore the erratic behaviors of GMA, a nonlinear dynamic model was established. The bifurcation diagrams, phase portrait, Poincaré mapping diagrams, amplitude spectrum, Lyapunov exponent, etc. which demonstrate dynamical characteristics of the system were obtained by numerical integration. Analysis indicates: Nonlinearity of response could be improved by increasing of damping coefficient. Chaos would appear when stiffness of the system is relatively low. At frequencies below 20Hz, exciting current also brings chaos. When exciting current frequency approaches natural frequency of the system, beat vibration will occur.

Electromagnetic design of magneto-rheological mount and its open-loop semi-active control

Ling Zheng, Yinong Li, Zhaoxue Deng

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Magneto-Rheological mount is a new type of semi-active and intelligent vibration isolator. It can adjust damping to reduce unwanted vibration from engine by supplying required input currents. The performance of Magneto-Rheological (MR) mount is much better than the conventional rubber mount or hydraulic mount due to its controllability and flexibility. In this paper, a novel MR engine mount with the flow mode-type for a sedan is devised, manufactured and characterized. Some important parameters are optimized to meet the requirements of MR mount by using Electromagnetic design methodology.. Electromagnetic finite element analysis verifies the effectiveness of the magnetic circuit design. The dynamic performances of MR engine mount in frequency domain are investigated experimentally. The results show that the dynamic stiffness and phase lag of MR engine mount can change continuously. They are frequency-dependent. In additional, a open-loop control strategy based on engine rotational speed measurement is proposed and the control system is performed in hardware and software. The experimental and theoretical results identified the effectiveness of such a semi-active vibration isolation system.

Fabrication, characterization and in-vitro cytotoxicity of magnetic nanocomposite polymeric film for multi-functional medical application

Lingyun Zhao, Xiaoyu Xu, Xiaowen Wang, et al.

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Cancer comprehensive treatment has been fully acknowledged as it can provide an effective multimodality approach for fighting cancers. In this study, various innovative technologies for cancer treatment including cancer nanotechnology, chemotherapy by sustainable release, as well as magnetic induction hyperthermia (MIH) have been integrated for the purpose of cancer comprehensive treatment. Briefly, such kind of treatment can be realized by applying of the tailored magnetic nanoparticles (MNPs) composite polymeric film. Fe₃O₄ MNPs acting as the agent for MIH, and anti-cancer drug docetaxel as chemotherapeutic agent were incorporated within the biodegradable polymeric film. Physiochemical characterizations on MNPs and the film have been systematically carried out by various instrumental analyses. Our results demonstrated that the film has been successfully fabricated by the solvent cast method. Hyperthermia could be induced by stimulating the nanocomposite film under an alternative magnetic field (AMF). The incorporation of MNPs, as well as hyperthermia would facilitate the drug release from the polymeric film. The in-vitro cytotoxicity results indicated the bi-modal cancer treatment approach for combined MIH and chemotherapy is more effective than the mono-modal treatment by docetaxel treatment. The magnetic nanocomposite film can realize cancer comprehensive treatment thus has great potential in clinical application.

Polymer functionalization with manganites

V. Sandu, S. Popa, I. Ivan, et al.

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We investigated the transport properties of a series of composites made of La_2/3Sr_1/3MnO₃ and different copolymers. The temperature dependence of the electrical resistance of the samples is strongly dependent on the nature of the polymers. We found four types of temperature dependences of the electrical resistance: i) simple current dependence of resistivity for poly(methyl-methacrylate-co-styrene) copolymers, ii) single peaked characteristics for poly(acryl amide-co-vinyl acetate), iii) multipeaked dependence found in poly(methyl-methacrylate-co-butadiene) and star type polysiloxane-gstyrene, and iv) current independent characteristics visible in the samples made with linear polysiloxane-based composites.

Fabrication and characterization of nanoclay modified PMR type polyimide composites reinforced with 3D woven basalt fabric

Jianfei Xie, Yiping Qiu

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Nanoclay modified PMR type polyimide composites were prepared from 3D orthogonal woven basalt fiber performs and nanoclay modified polyimide matrix resin, which derived from methylene dianiline (MDA), dimethyl ester of 3,3',4,4'- oxydiphthalic acid (ODPE), monomethyl ester of cis-5-norbornene-endo-2,3-dicarboxylic acid (NE) and nanoclay. The Na+-montmorillonite was organically treated using a 1:1 molar ratio mixture of dodecylamine (C12) and MDA. The rheological properties of neat B-stage PMR polyimide and 2% clay modified B-stage PMR polyimide were investigated. Based on the results obtained from the rheological tests, a two step compression molding process can be established for the composites. In the first step, the 3D fabric preforms were impregnated with polyimide resin in a vacuum oven and heated up for degassing the volatiles and by-products. In the second step, composites were compressed. The internal structure of the composites was observed by a microscope. Incorporation of 2% clay showed an improvement in the T_g and stiffness of the PMR polyimide. The resulting composites exhibited high thermal stability and good mechanical properties.

Structure evolution and phase development of NKN-BNT piezoelectric ceramics

Huiqing Fan, Laijun Liu

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Na_0.5K_0.5NbO₃ (NKN) and Bi_0.5Na_0.5TiO₃ (BNT) are the most potential candidates of lead-base piezoelectric materials. The microstructure and phase transition behavior as well as dielectric and piezoelectric properties of NKN-BNT solid solution fabricated by mechanical alloying method were investigated. Nanopowder (~35 nm) could be obtained after calcining at a relative low temperature. A coexistence region of tetragonal and orthorhombic was found in pure NKN, and the region shifted to low temperature ranges with the introduction of impurities or the second phase. The crystal structure and microstructure of NKN-BNT solid solution changed dramatically with the increaseing of BNT, and all phase transition temperatures deduced. The coexistence region shifted to room temperature while the amount of BNT is at 6 mol %. The morphotropic phase boundary (MPB) as well as the polymorphism behavior (PPB) of NKN-BNT solid solution is discussed in detail.

The flaw-detected coating and its applications in R&M of aircrafts

Feng Hu, Mabao Liu, Zhigang Lü

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A monitoring method called ICM (Intelligent Coating Monitoring), which is based mainly on the intelligent coating sensors, has the capability to monitor crack initiation and growth in fatigue test coupons has been suggested in this study. The intelligent coating sensor is normally consisted of three layers: driving layer, sensing layer and protective layer where necessary. Fatigue tests with ICM for various materials demonstrate the capability to detect cracks with l<300μm, corresponding to the increment of the sensing layer's resistance at the level of 0.05Ω. Also, ICM resistance measurements correlate with crack length, permitting crack length monitoring. Numerous applications are under evaluation for ICM in difficult-to-access locations on commercial and military aircrafts. The motivation for the permanently flaw-detected coating monitoring is either (i) to replace an existing inspection that requires substantial disassembly and surface preparation (e.g. inside the fuel tank of an aircraft), or (ii) to take advantage of early detection and apply less invasive life-extension repairs, as well as reduce interruption of service when flaws are detected. Implementation of ICM is expected to improve fleet management practices and modify damage tolerance assumptions.

Ultra thin fiber laser accelerometer for structure vibration detection

Wentao Zhang, Xuecheng Li, Faxiang Zhang, et al.

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Accelerometers are often used in structural health monitoring, smart structures, and aircraft damage detection. In this paper, an ultra thin fiber laser accelerometer (FLA) for structure vibration detection based on a flat diaphragm is presented. This accelerometer uses an flat diaphragm to transfer the acceleration-induced displacement of the mass to the axial elongation of the fiber laser. The flat diaphragm is clamped by the sensor shell to reduce the transverse sensitivity. The interrogation of the fiber laser accelerometer is achieved by using phase generated carrier (PGC) demodulation. A piezo-electric fiber stretcher in one of the unbalanced Mach-Zehnder interferometer (MZI) arms in the demodulator induces a phase-shift carrier signal on the sensor output signals that enables passive recovery of dynamic phase-shift information. This set-up uses a commercially available Dense Wavelength Division Multiplexer (DWDM) as a wavelength filter at the output of the MZI to interrogate multiple sensors. Both theoretical and experimental investigations are presented in this paper. The result shows that the proposed accelerometer has a high sensitivity and a flat frequency response. Owing to the greater deformation of the diaphragm with a mass at its center, ultra thin dimensions have been achieved.

Design of lath-shaped tool in defective nanostructure removal from digital touch-panel surfaces

P. S. Pa

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An effective economic viability that uses micro electroremoval as a reclaim system was developed to remove the defective ITO nanostructure coatings from the optical PET surfaces of digital paper. The low yield of ITO thin film deposition is an important factor in semiconductor production. By establishing the reclaim process using the ultra-precise removal of the nanostructure coatings, the optoelectronic semiconductor industry can effectively reclaim defective products, minimizing both production costs and pollution. In the current experiment, a large lath-shaped cathode with a small gap-width between the cathode and the workpiece takes less time for the same amount of ITO removal. A small end radius of the cathode combines with enough electric power to drive fast machining. Pulsed direct current can improve the effect of dreg discharge, and it is advantageous to associate the workpiece with the fast feed rate. However, this improvement can increase the current rating. A high rotational speed of the electrodes, a higher temperature, or a large flow rate of the electrolyte corresponds to a higher removal rate for the ITO nanostructure. The micro electroremoval requires only a short period of time to remove the ITO thin film coatings easily and cleanly.

Feasibility investigation of self-healing cementitious composite using oil core/silica gel shell passive smart microcapsules

Zhengxian Yang, John Hollar, Xiaodong He, et al.

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This paper presents our work in the concept exploration of a new family of self-healing materials that hold promise for "crack-free" cementitious composites. This innovative system features the design of passive smart microcapsules with oil core and silica gel shell, prepared through an interfacial self-assembly process and sol-gel reaction. Methylmethacrylate monomer and triethylborane were chosen as the healing agent and the catalyst, and were microencapsulated respectively. The microcapsules were dispersed in fresh cement mortar along with carbon microfibers. For the hardened mortar, self-healing can be triggered by crack propagation through the microcapsules, which then releases the healing agent and the catalyst into the microcracks. Polymerization of the healing agent is initiated by contact with the catalyst, bonding the crack faces. Surface analytical tools such as optical microscope and field emission scanning electron microscope were used to examine the localized morphology and encapsulation of the passive smart microcapsules. The self-healing effect was evaluated using gas permeability and electrochemical impedance measurements.

Marine biofouling on the fluorocarbon coatings comprising PTFE powders

Zhan-ping Zhang, Yu-hong Qi, Hong Liu, et al.

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Fluorocarbon coatings were developed with respectively 10%, 20% and 30% PTFE powder to prevent marine biofouling. Influence of content of PTFE on microstructures and roughness of coatings was investigated using SEM and roughometer. It was studied that the effects of coating roughness on settlement of benthic diatom and Ectocarpus by using biological microscope, stereo microscope, image processing and spectrophotometer. Results indicated that the surface roughness of coatings decreases and the quantity of benthic diatom and Ectocarpus reduces attaching onto the coating with the increase of content of PTFE in paint studied. Benthic diatoms attached much more on horizontal specimen than on vertical one; they prefer to settle onto the coatings that there are lots of micro-cracks in it. These results are helpful for developing new non-toxic antifouling paints.

Heat treatment of piezoelectric Pb(ZrTi)O3 ceramic fibers prepared with continuous spinning

Z. X. Xiong, J. Pan, H. Xue, et al.

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Ceramic of Pb(ZrTi)O₃ is one kind of typical smart materials, with excellent ferroelectric and piezoelectric properties. In this paper, a novel heat treatment was applied for the ceramic fibers prepared via sol-gel route with continuous spinning. Aided with microwave energy, dense ceramic fibers are obtained after treated at around 900°C for 1h, in which the diameters of the fibers are between 5μm and 30μm. The samples were also characterized with thermal analysis, FTIR spectroscopy and X-ray diffraction. By using of a scanning electron microscope, SEM, it was observed that a dense microstructure of the fiber was reached.

Thermoset shape-memory polymer nanocomposite filled with nanocarbon powders

Xin Lan, Yanju Liu, Jinsong Leng

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A system of a thermoset styrene-based shape-memory polymer (SMP) filled with nanocarbon powders is investigated in this paper. The thermomechanical properties are characterized by thermal gravity analysis, differential scanning calorimetery and dynamic mechanical analysis. In addition, the distribution of CB is investigated by scanning electron microscope. To realize the electroactive stimuli of SMP, the electrical conductivity of SMP filled with various amounts of CB is characterized. The percolation threshold of electrically conductive SMP filled with CB is about 3.8 % (volume fraction of CB), which is much lower than many other electrically conductive polymers. When applying a voltage of 30V, the shape recovery process of SMP/CB (10 vol%) can be realized in about 100s.

Cured shape prediction of the bistable hybrid composite laminate

Fu-hong Dai, Bo-ming Zhang, Shan-yi Du

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A bistable unsymmetric hybrid composite laminate with quite high stiffness and large shape change is presented. Rayleigh-Ritz method is used to predict the cured shape and the predited results agree well with the experimentals. The critical loads switching between different shapes are tested. It shows that the critical load for hybrid composite laminates increases greatly (up to 10 times) compared with the pure fiber reinforced polymer matrix composite laminates. The influence of different geometric and material properites on the bistable shape is discussed. It reveals that the present hybrid bistable laminate is more designable and miscellaneous.

Effectively tunable dispersion compensation based on chirped fiber Bragg gratings using electroactive polymer

Yongbo Dai, Zhichun Zhang, Liwu Liu, et al.

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A systematic method of tunable dispersion compensation based on chirped fiber Bragg gratings (CFBGs) using electroactive polymer (EAP) as drive device will be proposed. The EAP offer attractive properties of energy transduction from the electrical to the mechanical form for actuator with high active stresses (up to order of 1MPa), low response times, high reliability, high stability and low costs. The special tune device is consisted of a straight beam and two EAP actuators, the CFBG is surface-mounted on one side of the beam. The midpoint of the grating is consistent with the center of the beam. When the EAP is imposed on voltage, the specially designed mechanical device can control the chirping ratio along the fiber gratings and consequently the group delay. The group delay can be linearly controllable since the device induce the linear strain gradient with the input voltage. The dispersion value can be effectively controlled in corresponding to the input voltage. The resonant wavelength shift of CFBG is less than 0.05 nm over the dispersion tuning range.

Upconversion emission of Er3+/Yb3+-codoped silicate glass micro-particle under high excitation intensity

Jiyou Wang, Nanzheng Li, Lipu Wang, et al.

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The silicate glass micro-particles of co-doped with Er³⁺ and Yb³⁺ were prepared by a combustion process and characterized from the spectroscopic point of view, with the aim of investigating the effect and mechanisms of upconversion emissions. The upconversion emissions at 522nm and 547nm have been obtained by exciting the silicate glass micro-particle [about 30μm in diameter] under 976nm diode laser excitation. The excitation intensity was up to about 1800W/cm². It was observed that the intensity ratio of the 522-nm emission to the 547-nm emission (I_522nm/I_547nm) in silicate glass increased when increasing the excitation intensity. I_522nm became larger than I_547nm when the excitation intensity was above 300W/cm². It is proposed that the phenomenon resulted from the rise of the temperature of the sample measured.

Experimental study on the output characteristics of piezoelectric micro-displacement actuator

Tongpeng Han, Guoping Li, Jie Shen

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In this paper, the characteristics and the applications of piezoelectric micro-displacement actuator are introduced, and the actuation principle of the actuator is elaborated. Necessary experimental researches on the WTYD0808042 type piezoelectric micro-displacement actuator have been made with self-designed output characteristics test system. The displacement of actuator together with static and dynamic output characteristics of force have been tested respectively under the conditions of free output of displacement, free output of force, and output of force-displacement coupling of the actuator have also been tested. Based on the tests, the output displacement and force of actuator show the very good linearity with the drive voltage in the 50V-160V area, a satisfied static response characteristic was obtained. Moreover, it can be concluded that the actuator with the ideal characteristics of the transient output in displacement and force within dynamic curve output coincidence good precision. The researches provide the reference for the actuator's application in the turning vibration control system and the noncircular turning system.

Investigation on modeling and controability of a magnetorheological gun recoil damper

Hongsheng Hu, Juan Wang, Jiong Wang, et al.

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Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.

Preparation and microwave absorption property of the core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere as nuclear

Ru-Xin Che, Ying-Juan Ni

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The core-nanoshell composite absorbers with magnetic fly-ash hollow cenosphere as nuclear were prepared by a solid-state reaction method. The results of X-ray diffraction analysis (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and vector network analyzer (VNA) analysis indicated that the hollow cenosphere is dielectric loss; the exchange-coupling interaction happens between ferrite of hollow cenosphere and nanocrystalline magnetic material coating. The exchange-coupling interaction enhance magnetic loss of composite absorbers. They have a perfect electromagnetic parameters at high and low microwave frequency. In the frequency between 2 GHz and 18 GHz, The reflectivity is lower than 10dB in low-frequency, and it is consistent with requirements of the microwave absorbing material at the low-

Study on magneto-mechanical coupling model for giant magnetostrictive actuator

Guoping Li, Tongpeng Han, Luwei Wang

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Based on analysis of the motion law of giant magnetostrictive material magnetic domain under magnetic field, a hysteresis model based on magnetization for giant magnetostrictive actuator is established. The model incorporates operating conditions of the actuator and fully considers nonlinear and hysteresis characteristics of the material. It includes two sub-models: magnetostriction and magnetization. The relationship between the strain λ and the magnetization M is illustrated in the magnetostriction model. The magnetization model describes the relationships amongst the effective field H_eff , the anhysteretic magnetization M_an , the reversible magnetization M_rev , the irreversible magnetization M_irr and the total magnetization M . The full set of parameters was estimated through a least square fit with experimental data. The model is proved to be able to accurate describe the relation between the input current I and the output strain λ by analyzing the experimental result.

An ionic polymer-metal composite actuator based on PSMI-incorporated PVDF with chemical stability and performance durability

Jun Lu, Sang-Gyun Kim, Sunwoo Lee, et al.

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To develop artificial muscles with improved performance, a novel ionic polymer-metal composite (IPMC) actuator was developed by employing the newly-synthesized ionic networking film of poly (styrene-alt-maleimide) (PSMI)- incorporated poly (vinylidene fluoride) (PVDF). Scanning electron microscope and transmission electron microscopy revealed that much smaller and more uniform nano-sized platinum particles were formed on the surfaces of the film as well as within its polymer matrix after the electroless-plating process. Fourier transform infrared results suggested that no hydrolysis occurred for the as-prepared film actuator before and after the exposure to the elevated PH solutions at 25°C for 48h. The new actuator showed much larger tip displacement than that of a Nafion-based counterpart under the applied electrical stimulus, and overcame the back relaxation of the traditional IPMC actuator under the constant voltage. The current actuator was operated over 6.5h at high-frequency sinusoidal excitation, and its tip displacement was still comparable to that of the referenced Nafion actuator when the test was terminated. The excellent electromechanical performance is due to the inherent large ionic-exchange capacity and the unique hydrophilic nano-channels of the ionic networking film. Furthermore, the working principle of the developed IPMC actuator is thought to be based on a combination of piezoelectricity and ionic transport. The film of PSMI-incorporated PVDF has some advantages over the most widely-used Nafion-based one by diversifying niche applications in biomimetic motion, and the present study is believed to open a new avenue for the design and fabrication of the electro-active polymer film with unique functional properties.

External characteristics detection and analysis of magnetically controlled shape memory alloy

Yongzhi Cai, Chengwu Lin

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In this paper, an experimental equipment is presented for researching external characteristics of magnetically controlled shape memory alloy (MSMA). Then the external characteristics of the material are measured accordingly and studied. Finally, The vibration detection was done based on dynamic inverse characteristics of MSMA. The results show that MSMA will induce martensitic transformation under magnetic field, temperature and stress. Due to the advantages of large dynamics behavior, high retractility and reversible characteristics, MSMA is of a bright future of application in self-sensing actuator (SSA) field.

Bioelectrochemical activity of an electroactive macromolecular weight coenzyme derivative

Pu Liu, Haitao Zheng, Pingping Nie, et al.

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As coenzyme utilized by more than hundreds of dehydrogenases, the efficient immobilization and regeneration of nicotinamide adenine dinucleotide (NAD+) are of great importance and have practical applications in industrial, analytical and biomedical field. In this paper, an electroactive macromolecular weight coenzyme derivative (PEI-DHBNAD) was prepared by attaching both NAD+ and 3,4-dihydroxybenzaldehyde (3,4-DHB) to a water-soluble polyelectrolyte, poly(ethylenimine) (PEI). The functional polymer exhibited both electrochemical properties of catechol unites and coenzymatic activity of NAD moieties. The macromolecular NAD analogue showed a substantial degree of efficiency relative to free NAD+ with alcohol dehydrogenase (ADH) and glucose-6-phophate dehydrogenase (G6PDH), and a litter higher Michaelis-Menton constant (Km) was obtained for the coenzyme derivative than free NAD+. The bioelectrochemical properties of PEI-DHB-NAD were investigated by using G6PDH as the model enzyme, and both of them were retained on electrode surface by ultrafiltration membrane. The modified electrode showed typical response to substrate without the addition of free coenzyme, which indicated that PEI-DHB-NAD can carry out the electron transfer between electrode and NAD-dependent dehydrogenase. The utilization of polymer-based PEI-DHB-NAD is convenient for the immobilization of both electron mediator and coenzyme, and offers a practical approach for the construction of reagentless biosensors.

Beam vibration control using electro-active paper sensor

Jungyun Kim, Heung Soo Kim, Ho Cheol Lee, et al.

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In this paper, the possibility of EAPap as a piezoelectric sensor was investigated by the vibration control of the cantilevered beam. The EAPap sample was attached at the root of the cantilevered beam and used as a vibration sensor. The piezoceramic patch was also attached at the root of the beam and played as an actuator. The voltage output of EAPap showed same trend of that measured by the piezoceramic patch. The frequency bandwidth and quality factor of EAPap were similar to those of piezoceramic patch, which results EAPap has similar sensing capability of piezoceramic patch. To find the application of EAPap sensor, beam vibration control was performed. EAPap sensor output was considered as a position error of the cantilevered beam system and a simple PID controller was designed to suppress the vibration of the beam. The EAPap sensor output provided clear time response of the beam. The controlled system showed good vibration control performance of the beam. The results provided that EAPap has great potential as a piezoelectric vibration sensor.

Preparation and electroactive performance of IPMC

Guifen Gong, Yudong Huang, Danyu Liu, et al.

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EVOH-based comb ionic polymer (EVOH-g-nSPEG) was prepared by the sulfonation reaction of poly(ethylene-co-vinyl alcohol) (EVOH) and 1,3-sulfonic acid propiolactone. The EVOH-g-nSPEG composites with different counter ions and metal (IPMC-M) were prepared through the method of solution casting and penetration-reduction method (chemical deposition), respectively. The micro-morphology of IPMC-Na was determined by scanning electron microscope (SEM). The maximum tip displacement was determined by electrode deformation testing equipment, and the relationship between input voltage and electrochemical activity was evaluated by cyclic voltammetry. The results showed that the smoothness and compactness of IPMC surface electrode were improved when using secondary penetration-reduction technology. The tip displacement of IPMC-M(H, Li, Na, K) increased with the input voltage increasing and reached to its maximum value when the input voltage being 4.2~4.4 V. The relationship of the tip response time was T_Li>T_Na>T_K>T_H under the same input voltage. The tip response time of IPMC containing the same counter ion decreased with the input voltage increased.

High birefringence photonic crystal fiber design

Feifei Shi, Meicheng Li, Yu Zhao, et al.

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A novel high birefringence photonic crystal fiber (PCF) was proposed, which consists of hexagonal inner ring and octagonal outer ring. A full vector finite element was applied to investigate the mode birefringence and chromatic dispersion. It has been demonstrated from the calculated results that high birefringence to the order of 0.001 can be achieved and ultra-flattened dispersion of -0.8~+0.2 ps/(km•nm) is obtained in 1.5 to 1.65μm wavelength range.

Preparation and characterization of high contrast electrophoretic display suspension containing charged black-and-white nanoparticles

Xiao-Nan Yao, Jian-Ping Wang, Xing-Xiang Zhang, et al.

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In this study, TiO2 nanoparticles with sizes ranging from 300- 400nm were modified by two-step dispersion polymerization using poly (styrene-co-divinylbenzene)-methyl methacrylate [P (St-co-DVB)-MMA] as shell. And core, carbon black (CB) nanoparticles with size ranging from 30-50nm and polymer shell poly (methacrylic acid) [PMAA] were prepared by grafting polymerization, too. Modified nanoparticles were characterized on structure, mean particle size and size distribution, morphology with FT-IR, TEM, and image analyzer. Furthermore, modified TiO₂ as negatively charged electrophoretic particles and CB nanoparticles as cationically charged electrophoretic particles were homodispersed in tetrachloroethylene (TCE) to make the electrophoretic display suspension with Span-80 as dispersant and OLOA 1200 as charge control agent. The zeta potential and mobility of white (TiO2) and black (CB) charged particles were measured to be -61.4 mV, 9.50×10-6 cm² /V s and 12.8 mV, 1.98×10-6 cm² /V s by using an electrophoresis test device, respectively. Final, the electric response behaviors of the electrophoretic display suspension were studied under electrostatic field. The black-and-white particles moved quickly and reversibly inside ITO electrodes while the electric field alternated.

Research on the optical fiber's photosensitivity influenced by the doping process

Feng Tu, Jie Luo, Jiangtao Guo, et al.

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Based on the plasma chemical vapor deposition (PCVD) process, the Ge/F (Germanium/Fluorine) and Ge/B (Germanium/Boron) co-doped photosensitive fiber was developed. Through analyze the fiber's photosensitivity, study the fiber's photosensitivity influenced by the doping process. The fiber's data indicate that the high F doped (5 mol%) Ge/F photosensitive fiber's grating has the 80% reflectivity, much lower than the low F doped (1 mol%) Ge/F photosensitive fiber's 94% reflectivity. Then the Boron doped would increase the fibre's photosensitivity distinctly just when the dope concentration reach about 5 mol%. Present the experimental study of the influence of doping on fiber photosensitivity. Through measuring the attenuation spectra and comparing the reflectivities of the fabricated fiber Bragg gratings (FBGs), the photosensitivity of GeF and GeB co-doped fibers are investigated.

Non direction high-frequency underwater transducer

G. Wang, L. Qin, L. K. Wang

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A non direction high-frequency acoustic transducer had been designed and prepared with PZT-5 type piezoelectric ceramic ring. When the piezoelectric ceramic ring vibrates on its thickness mode, the resonant frequency is higher than that of other modes. The affiliations of the resonant frequency and the size of the piezoelectric ceramic ring transducer are obtained by finite element analysis. The resonant frequency of the transducer increases when the thickness of the piezoelectric ceramic ring decreases. The resonant frequency of the transducer increases slowly when the height of the piezoelectric ceramic ring decreases. The inner diameter of piezoelectric ceramic ring has nothing to do with its thickness resonant frequency. The actual sample is produced for verifying the accuracy of the simulation results. The affiliation of the resonant frequency and the size of actual transducer is the same as the simulation results. So we have produced a high-frequency acoustic transducer whose resonant frequency is 290 kHz and the maximum transmit voltage response of the product is 143dB. Compare the products and the traditional cylindrical transducers, the products haven't only a good non direction circle directional, but it also has a high resonant frequency (290 kHz).

A comparative study on vibration analysis of beams treated with active constrained layer damping using different assumed modes methods

Miao Wang, Guang Meng, JinQuan Xu

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Recently, active constrained layer damping (ACLD) has been widely used in vibration control and noise reduction. A typical ACLD structure usually consists of three layers: the piezoelectric constraining layer, the viscoelastic damping layer, and the host structure. In present study, the assumed modes method (AMM) is used for vibration modeling of ACLD beams based on the Mead-Markus's sandwich theory. However, two cases called "case A" and "case B" arise from the different choice of modes. The former chooses modes for three displacements including the axial displacement of the active constraining layer, the axial displacement of the host beam, and the flexural displacement of the whole structure, while the later selects modes for the axial and flexural displacements of the host beam. Detailed comparisons are made on natural frequencies and modal loss factors with the results in the reference. It seems that for the same number of modes, case A and B have similar precision on the 1st natural frequency and modal loss factor, yet case B requires considerably less CPU time.

Study on damping property of epoxy-matrix with PbZr0.47Ti0.53O3 piezoelectric film effect

Yan Qin, Wei Mao, Zhixiong Huang, et al.

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A new type of rigid piezo-damping epoxy-matrix composites containing piezoelectric lead zirconate titanate thin films was prepared. The PbZr_0.47Ti_0.53O₃ thin films were fabricated on the Pt/Ti/SiO2/Si substrates by sol-gel method. The crystal structure of the films was characterized. The thin films showed a perovskite phase by changing annealing temperature. The produced film and the substrates have been joined into epoxy resin as constrained layer, and then the damping property of composites has been study. Through improving the annealing process when proparing film, the optimum filming technology which can improve the damping property of composites has obtained. The film was hated up to 700°C with 10°C/min and holding time for 30min, then cooling with furnace. By this way, The dielectric constant and the dissipation factor of the PbZr_0.47Ti_0.53O₃ thin films were about 480 and 0.027 at 1MHz, respectively.The peak of the damping tanδ has reached 0.923. The results show that when the Pb(Zr_0.53Ti_0.47)O₃ thin films annealed at 700°C, the damping loss factor of the composites has reached the maximum.

Study on a new semi-active vibration isolation system

Kexiang Wei, Guang Meng, Hong You, et al.

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Magnetorheological (MR) elastomers are a new class of magnetorheological materials. They are interesting candidates for active-passive hybrid vibration control of structural because they have both advantages of magnetorheological materials and elastomer materials. In this paper, a squeeze mode MR elastomers isolator is designed. A new activepassive hybrid vibration isolation system using the designed MR elastomers isolator is developed. The performance of the system is experimentally evaluated. Results demonstrate that the MR elastomers isolator has good vibration isolation effect and controllable property.

In-situ formation of gold nanoparticles on self-assembly monolayer modified silicon substrate

Lei Qi, Chunxiao Chen, Shantang Liu

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We demonstrate an effective route for the in-situ chemical synthesis of gold nanoparticles on monolayer modified silicon substrate. The formation of gold nanoparticles is based on the ability of the amino groups of the monolayer to bind AuCl₄ ^- ions, followed by the reduction of AuCl₄ ^- to Au⁰ with NaBH4. The particles size can be controlled by the concentration of HAuCl₄ during the deposition-reduction process. By repeating the ion binding and reducing cycle, large amount of gold nanoparticles can be generated on the monolayer. UV visible spectroscopy and scanning electron microscope (SEM) confirm that the well-dispersed gold nanoparticles are formed on the substrate. From Atomic Force Microscope (AFM) images, we find the particles with characteristic of 3-35nm are generated on the monolayer. Therefore, this facile procedure can give a new choice to the formation of gold nanoparticles on the self-assembly monolayer modified silicon substrate.

Sensing performance of magnetic shape memory alloy actuator with self-sensing

Baiqing Sun, Yu Ding, Jun Lu, et al.

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As further studies of active materials, possibilities of developing the self-sensing actuator using the active material are enhanced increasingly. In this paper, for developing self-sensing actuators based on Magnetic shape memory alloy (MSMA), the sensing properties of MSMA actuator are studied. A testing set is developed to measure and analyze relationships among the impact stress, deformation, temperature and magnetization of the MSMA actuator. The experimental results show that the induced voltage is linear with impact stress and movement, and it is feasible to develop MSMA actuator with self-sensing.

DNA biosensors based on layer-by-layer self-assembled multilayer films of carbon nanotubes and gold nanoparticles

Yiyun Xiao, Zhao Dai, Jimei Zhang, et al.

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A novel DNA biosensor based on layer-by-layer self-assembled multi-walled carbon nanotubes (MWNTs) and gold nano-particles (GNPs) was presented in this paper, in which the probe HS-ssDNA oligonucleotides, MWNTs and GNPs were all covalently immobilized by chemical Au-Sulphide bonding. Firstly, the super short MWNTs were prepared and modified with thio groups which could be self-assembled onto the surface of Au elcetrode by Au-sulphide bonding, then the GNPs were chemically adhered to the surfaces of MWNTs by forming Au-sulphide bonding again, at last the selfassamble of probe DNA oligonucleotides were also covalently immobilized via Au-sulphide bonding between thio groups at the ends of the DNA oligonucleotides and GNPs. Hybridization between the probe HS-ssDNA oligonucleotides and target DNA oligonucleotides was confirmed by the changes in the voltammetric peak of an anionic intercalator, anthraquinone-2,6-disulfonic acid (AQDS) as a hybridization indicator. The cyclic voltammetric and differential pulse voltammetry responses demonstrated that the DNA biosensors based on Layer-by-layer self-assembled multilayer films of MWNTs and NGPs offer a higher hybridization efficiency and selectivity compared to those based on only random MWNTs or GNPs.

Effects of self-healing microcapsules on bending performance in composite brake pads

Li Zhang, Xiu-ping Dong, Hui Wang

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For the purpose of reducing self-weight, friction noise and cost, improving shock absorption, enhancing corrosion and wear resistance, brake pads made of composite materials with self-healing function are prepared to substitute metal ones by designing ingredients and applying optimized production technology. As self-healing capsules are chosen, new method with technology of self-healing microcapsules, dicyclpentadiene (DCPD) microcapsules coated with poly (urea-formaldehyde), is put forward in this paper. In the crack's extending process, the stress is concentrated at the crack end, where the microcapsule is designed to be located. When the stress goes through the microcapsules and causes them to break, the self-healing liquid runs out to fill the crack by the capillary and it will poly-react with catalyst in the composite. As a result, the crack is healed. In this paper, polymer matrix composite brake pads with 6 prescriptions are prepared and studied. Three-point bending tests are carried out according to standards in GB/T 3356-1999 and the elastic constants of these polymer matrix composites are obtained by experiments. In accordance with the law of the continuous fiber composite, elastic constants of the short-fiber composite can be calculated by proportions of each ingredient. Results show that the theoretical expected results and the experimental values are consistent. 0.3-1.2 % mass proportion of microcapsules has little effects on the composite's bending intensity and modulus of elasticity. These studies also show that self-healing microcapsules used in composite brake pads is feasible.

Research on piezoelectricity materials films of MEMS surface acoustic wave gas sensor

Chengjun Qiu, Dan Bu, Hongmei Liu, et al.

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The structure of SAW gas sensor based on the PZT film is provided, which includes mainly the PZT piezoelectric thick film, interdigital transducers and gas sensing films. The PZT piezoelectric thick film is fabricated on the structure of Au/Cr/SiO2/Si multilayer films. The fabrication technology of PZT film is also discussed which is compatible with the MEMS fabrication technology. The measurement results show that the remanent polarization and the coercive field of PZT thick films are up to 60μC/cm2 and 23kV/cm at 25V, respectively, and the results demonstrate that the siliconbased PZT thick films possess well property which suitable for SAW device for farther application.

Bio-molecules detection sensor using silicon nanowire

Pan K. Kim, Seong J. Cho, Jungwoo Sung, et al.

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To detect a signal change in nano scale, Schottky barrier - silicon nanowire field effect transistor (SB-SiNWFET) for detecting a bio-molecule was fabricated by combining E-beam lithography and conventional MEMS technique. Detection of few bio-molecules is enabled by realizing the gold nanodots on silicon nanowire (SiNW). By performing pH test and carbohydrate binding measurement, we conclude that our sensor can detect very small quantity of biomolecules.

Adhesion strength of norbornene-based self-healing agents to an amine-cured epoxy

Guang Chun Huang, Jong Keun Lee, Michael R. Kessler, et al.

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Self-healing is triggered by crack propagation through embedded microcapsules in an epoxy matrix, which then release the liquid healing agent into the crack plane. Subsequent exposure of the healing agent to the chemical catalyst initiates ring-opening metathesis polymerization (ROMP) and bonding of the crack faces. In order to improve self-healing functionality, it is necessary to enhance adhesion of polymerized healing agent within the crack to the matrix resin. In this study, shear bond strength between different norbornene-based healing agents and an amine-cured epoxy resin was evaluated using the single lap shear test method (ASTM D3163, modified). The healing agents tested include endodicyclopentadiene (endo-DCPD), 5-ethylidene-2-norbornene (ENB) and DCPD/ENB blends. 5-Norbornene-2-methanol (NBM) was used as an adhesion promoter, containing hydroxyl groups to form hydrogen bonds with the amine-cured epoxy. A custom synthesized norbornene-based crosslinking agent was also added to improve adhesion for ENB by increasing the crosslinking density of the adhesive after ROMP. The healing agents were polymerized with varying loadings of the 1st generation Grubbs' catalyst at different reaction times and temperatures.

Molecular mechanics simulation on the deformation behaviors and the mechanical properties of nano composite of polyethylene and POSS

Enlai Hu, Yi Sun, Fanlin Zeng

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The influence of polyhedral oligomeric silsesquioxane (POSS) on nano-hybrid materials has caused widespread attentions. In the current work, we investigate the deformation behaviors and the mechanical properties of the two kinds of polymers, polyethylene (PE) and PE copolymerized with vinyl-POSS (POSS-PE) by using molecular mechanics simulations. First, the nano scale atomistic models of the PE and POSS-PE incorporated with 25 wt% vinyl-POSS are built. With the aids of the COMPASS force field, the mechanical behaviors of the two kinds of polymers under different tensile strains are then simulated and the stress-strain curves are obtained. From the curve, the stresses and strains of PE keep approximately linear before the yield point. The corresponding tensile modulus is in good agreement with the experimental data. In addition, the simulation results show that the localized necking deformation appears during the yield process. It is believed that the slippage between the adjacent molecule chains is the chief source of such localized deformation. However, the necking phenomenon is not found in POSS-PE nano-composite. It seems that the POSS cages prevent the macromolecule chains from wide-spread slipping. The deformation is restrained locally around POSS monomers, thus leading to the formation of micro voids. We finally analyze the mechanical properties of the two kinds of polymers. The elastic modulus and tensile strength of POSS-PE have been remarkably improved. This work is significant to understand the reinforcement mechanism of POSS and provides important referential message to the applications of POSS.

Preparation, microstructure characterization and dielectric properties of relaxor ferroelectric thick films

Huiqing Fan, Jin Chen

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The phase structure and the microstructure of pyrochlor-free (1-x)PMN-xPT (x=0.2~0.4) relaxor ferroelectric thick films prepared by an electrophoretic deposition on Pt substrate were investigate by XRD and SEM. The dielectric permittivity maximum ε_m (at 1 kHz) were in the range of 18000~26500. Relaxor-like behavior was clearly demonstrated in PMN-PT thick-films. Deviation from Curie-Weiss behavior and temperature evolution of the local order parameter were found in the films. The degree of relaxation obtained from the modified Curie-Weiss law strongly suggests the relaxor behavior.

Large deformation analysis of a dielectric elastomer membrane-spring system

Tianhu He, Leilei Cui, Cheng Chen

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Due to the capability of large strain, dielectric elastomers are promising for applications as transducers in cameras, robots, valves, pumps, energy harvesters and so on. The dielectric elastomer transducers are based on the deformation of a soft polymer membrane contracting in thickness and expanding in area, which is induced by the application of a voltage across the two compliant electrodes coated on both sides of the membrane. This paper focuses on the large deformation analysis of a dielectric elastomer membrane-spring system. The system is constructed from attaching a disk in the middle of a circular dielectric membrane and then connecting the disk with a spring. This configuration can be potentially used as a key part in valves. The basic governing equations describing the large out-of-plane deformations are formulated, and the obtained equations are solved numerically. The relations related to the displacement of the disk, the spring force, the applied voltage, and the parameters of spring including stiffness and initial length are illustrated. The results show the anticipated displacement of the disk can be controlled by adjusting the parameters of spring and the applied voltage individually or simultaneously, and the parameters of the spring, that is, stiffness and initial length, play an important role in the performance of the membrane-spring system.

Effect of humidity on indentation crack growth in lead-free ferroelectric ceramics

H. J. Zhang, J. X. Li, W. Y. Chu, et al.

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The effect of humidity on growth of unloaded indentation crack in KNN free-lead ferroelectric ceramics has been investigated. The results showed that crack growth of unloaded indentation in lead-free ferroelectric ceramics could occur in humid air of 70% and 90%RH without electric field and mechanical stresses, but did not in air with RH≤30%. The growth of indentation crack could occur in dry air when the field was larger than the threshold field E_th(y)=0.01E_C (normal to the poling direction) or E_th(z)=0.05E_C (parallel to the poling direction) and the larger the field, the shorter the incubation time. The increment of crack growth in humid air under sustained field, Δc, was composed of three parts, i.e., Δc=Δc₁ + Δc₂ + Δc₁₂, where Δc₁ was the increment in humid air without field, Δc₂ that in dry air under sustained field and Δc₁₂ that induced by combined effect of electric field and humidity because of humidity promoting domain switching. Crack growth of unloaded indentation could occur during hydrogen charging and the threshold stress intensity factor of hydrogen-induced delayed cracking, KIH, as well as the fracture toughness of hydrogenated ceramics, KIC(H), decreased with increasing hydrogen concentration.

A study of the optimum configuration of injection molded plastic gear by modification of gear tooth

Dae-Suep Lee, Young-Doo Kwon, Jin-Uk Doc, et al.

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In this study, the gear system is optimized by modifying the tooth configuration of the plastic gears. Plastic gear is widely used as a machine element in industries of electric and electronic parts, automotive parts etc. Unlike the steel gear, the plastic gear has low load- transmission, durability and reliability. On the other hand, it is light-weight, low-noise, operable without a lubricant, shock absorptive, and anti-corrosive. The gear characteristics are calculated and analyzed by Hexagon and FEM (Finite Element Method) tools, and the characteristics of the standard gear and the addendum modified gear of the steel gear and the plastic gear are compared. When torque is applied to these gear systems, the system using the addendum modified gear can realize soft contact between gears. So, the noise of the addendum modified gear system was less than that of the common normal gear system. However, this is not applicable to any material, such as steel which is governed by DIN (Deuteshe Industrie Norm) recommendation. This study adopted the narrow tip tooth plastic gear, and proposed the optimum addendum modified gear with respect to stress, noise and contact ratio. To calculate and analyze the simulation of gear matching, we used commercial tools like CATIA, Auto-CAD, MARC for simulation and Hexagon for calculation.

Plane magneto-electro-elastic moduli of fiber composites with interphase

R. Guinovart-Díaz, R. Rodríguez-Ramos, J. Bravo-Castillero, et al.

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In the present paper, closed analytical expressions and universal relations for the effective coefficients are given. Matrix and inclusions materials belong to symmetry class 6mm. It is remarkable that the analytical formulae derived for all effective properties have a simple form. The computational implementation is easy. Besides its theoretical importance, they can be used for checking the implementation of experimental, numerical and analytical models.

Active structural acoustic control by using structural volume velocity sensing

Guoyong Jin, Hongtian Zhang, Wanyou Li

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This paper presents a new volume velocity sensor and its application in active structural acoustic control system. Utilizing the charge output equation of the PVDF piezoelectric film and orthogonal property of trigonometric function, a design strategy for a PVDF sensor detecting the volume velocity induced by a vibrating 2D structure is presented. The designed sensor is made of shaped strips of PVDF film. The experimental implementation of the new sensor in an active structural acoustic control system is then presented. The experimental results obtained validate this new type of volume velocity sensor, and significant attenuation of the radiated sound field is obtained.

Study on the microwave absorbing properties of nano-carbon black/SiC/epoxy resin composites

Youpeng Wu, Xiangxuan Liu, Youjie Zhou, et al.

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Epoxy (EP) was filled with nano-carbon black(CB) and micron SiC. The effects of CB and SiC fraction on the absorbing properties of the EP composites were studied. The structure and morphology of the samples were characterized by scanning electron microscopy (SEM). The spectroanalysis indicates that the absorbent particles are dispersed uniformly in the coating. At 8 ~ 18GHz, for composite coating with 1.05mm thickness, the absorbing bandwidth less than -5dB is 7.7GHz and less than -8dB is 4.6GHz, and the most reflection loss can reach -19.27dB. With the increase thickness of the coating, the absorbing peak value moves to the lower frequency. The bandwidth and the wave absorbing peak values increase along with the increasing of the content of CB filling fraction. And the absorbing mechanism of the composite was also discussed.

Synthesis and photochromic property of nanosized amino acid polyoxometalate compounds

Dehui Sun, Jilin Zhang, Huijuan Ren, et al.

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A series of novel nanosized amino acid-polyoxometalate compounds were successfully synthesized using a low temperature solid-state chemical reaction method. Their compositions, structures, morphologies, photochromic properties were characterized by ICP-AES/MS, TG/DTA, FTIR, XRD, SEM and UV-Vis diffuse reflectance spectra (DRS), respectively. The elemental analysis results showed that the compounds ((HThr)7PMo12O42•4H2O, (HTyr)7PMo12O42·5H2O, (HSer)7PMo12O42•5H2O and (HGlu)7PMo12O42•4H2O) were obtained. The analyses of the TG/DTA, XRD and FTIR confirmed that the four compounds are new phases different from the corresponding reactants and they are composed of the polyoxometalate anions and the corresponding protonated amino acids, respectively. Observation of the SEM revealed that the particle shape (e.g. (HThr)7PMo12O42·4H2O nanoplates, (HTyr)7PMo12O42•5H2O nanorods, (HSer)7PMo12O42•5H2O and (HGlu)7PMo12O42•4H2O nanoparticles) depended strongly on the structures of amino acids. This implied that the amino acids can play a structural template agent role in synthesis of the Silverton-type polyoxometalate compounds. After irradiated with ultraviolet light, these samples all exhibited photochromism. Their photochromic mechanism may be explained based on Yamase's photochromic model. These photochromic compounds could be applied to the field of photosensitive materials.

Investigation on the performance of multi-quantum barriers in InGaN/GaN multi-quantum well light-emitting diodes

Yeu-Jent Hu, Jiunn-Chyi Lee, Ya-Fen Wu

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We introduce a structure of multi-quantum barriers (MQBs) into the multi-quantum well (MQW) heterostructures to improve the performance in light-emitting diodes. The InGaN/GaN MQW LEDs with and without MQBs were prepared by metal-organic vapor phase epitaxy system. The electroluminescence measurements were carried out over a temperature range from 20 to 300 K and an injection current level from 10 to 100 mA. According to the experimental results of the InGaN/GaN MQW LEDs, we observe the enhancement of carrier confinement in the active layer and the inhibited carrier leakage over the barrier to the p-GaN regions for the sample with MQBs, which we attribute to the increase of effective barrier heights due to the quantum interference of the electrons within MQBs. In addition, the variations of electroluminescence external quantum efficiency as a function of injection current at various temperatures are also obtained for the samples. It is observed that the sample possessing MQBs exhibit less sensitive temperature dependence and indeed improve the radiative efficiency.

Ag/WO3-codoped TiO2 nanoparticles: relation between structure, sorption, and photocatalytic activity

Jing Y. Xu, Chen Wen, Li M. Jia, et al.

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Nanostructured Ag/WO₃-TiO₂ particles responding to sunlight were synthesized by dissolving silver nitrate, sodium tungstate and tetrabutyl titanate precursors in a suitable solvent. The obtained powders were characterized by a series of analytical methods including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Zeta potential measurements and UV-vis diffuse reflectance spectra (UV-vis DRS) to demonstrate their physicochemical properties. The as-prepared Ag/WO₃-TiO₂ samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under sunlight irradiations. Both silver (Ag) and tungsten (W) species were well dispersed over TiO₂ surface with less than 6.0 mol % Ag and 3.0 mol % W to Ti element and contributed to a formation of crystalline WO₃. XRD analysis particularly demonstrates the existence of mixed-phase TiO₂ materials, to which the improvement in photocatalytic activity is attributed. Besides, the light absorption of doped samples is prominent red shifted relative to the pure TiO₂ due to the synergetic effect among the components of Ag, WO₃ and TiO₂ in the codoped-TiO₂. The particle size of the Ag/WO₃-TiO₂ powders was found to be a decrease which is accompanied with the increase of the surface area. The excellent stability and dispersity of the Ag/WO₃-TiO₂ powders in aqueous solution could be attributed to the enhanced Zeta potential. On the other hand, the adsorption performances of different samples were tested in the removal of two dyes from aqueous solution(congo red and methylene blue). The first-order adsorption equilibrium constants were determined and the results obtained were fitted by Langmuir monolayer formation. Thus, the Langmuir adsorption isotherm parameters were estimated from the experimental data.

Improving the aging properties of silicone-acrylate copolymers nanocomposites for encapsulation of outdoor exposed stone substrates

Yuan Liao, Shuhua Qi, Qiaomei Fu, et al.

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In the preservation of cultural heritage items, the use of polymeric materials for the consolidation and protection of artifacts with historical and artistic value is widely accepted. In the case of stone conservation, application of polymeric materials is a settled technique used to minimize the rate of stone decay and to strengthen stone deteriorated by processes of weathering, effects of atmospheric pollution or inappropriate interventions. In recent years a new class of composite material is offered by polymeric nanocomposites systems, based on organic polymers and inorganic nano-particles [1, 2]. These systems show a great interfacial area per volume between nano-particles and polymer, with higher properties compared to the unmodified resin. Nanocomposite systems based on silicone-acrylate copolymers and different amounts of the modified nano-silicon dioxide (nano-SiO2) (1, 2 and 4 wt %) were tested as protective and encapsulating agents for the outdoor exposed stone substrates. Conservation and encapsulation efficiency of these treatments was evaluated through physical investigations (resistance to ultra violet, freeze-thaw aging resistance and accelerated ageing resistance to artificial climate). The results have evidenced that the nano-scale dispersion of low amounts of the modified nano-SiO2 into the polymeric matrix enhances the encapsulating and protective action of the outdoor exposed stone substrates. In fact, the outdoor exposed stone substrates treated with the nanocomposite systems exhibits a more marked reduction in resistance to ultra violet, freeze-thaw aging resistance and accelerated ageing resistance to artificial climate with respect to stone treated with the neat silicone-acrylate copolymers and B72 polymer, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA).

Enhancement of retention and antifouling capability for PVDF UF membrane modified by nano-TiO2 sol

Li M. Jia, Chen Wen, Jing Y. Xu, et al.

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Novel PVDF/TiO₂ hybrid membranes were prepared by phase inversion process from a PVDF/DMAc/PVP/tetrabutyltitanate/water system. The membrane characteristics such as morphology, thermal properties, porosity, water contact angle, tensile strength and separability were investigated by a series of analytical methods including atomic force microscope (AFM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and zeta potential measurements. The performances and surface properties of hybrid and PVDF membranes were tested by the removal of bovine serum albumin (BSA) from aqueous solution, evaluated by using two dyes with different charge (congo red and methylene blue). Based on the experimental results, TiO2 nanoparticles of a quantum size (~8 nm or less) in anatase crystal structure were obtained from the controlled hydrolysis of tetrabutyltitanate. Besides, TiO₂ sol was introduced into polymer molecule for the hybrid membrane with less than 12 vol % TiO₂ sol to PVDF and contributed to a smooth surface and more apertures due to both the interaction and compatibility between polymer and TiO2 sol, to which the improvement in hydrophilicity, thermal stability, mechanical strength and antifouling ability is attributed. The observed rejections were optimized for PVDF/TiO₂ hybrid membrane with respect to PVDF membrane. In particular, the pure water permeation flux was increased from126.6 to166.7 L/m2•h for hybrid membrane with a relative flux of 80 % compared to 50 % of relative flux observed for PVDF membrane.

Design and fabrication of a microfluidic chip driven by dielectric elastomers

Bo Li, Hualing Chen, Jiuhui Wu, et al.

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This paper presents a valveless microfluidic chip driven by dielectric elastomers (DEs). First, the planar DE actuator is designed and the diaphragm actuating performances were characterized. Then the micro chip, containing a pump chamber and a pair of nozzle/diffuser, is fabricated on SU-8 under exposure to UV-light with a mask. The diaphragm and the SU-8 is sealed and finally covered by a PMMA. The pumping and flow rate is tested and measured under high AC supply, and a maxim flow rate of 21.2μl is achieved under 3500V, 8Hz sine wave.

Electrochemical properties of multilayer film assembled by layer-by-layer adsorption of redox polymer

Tao Sun, Haitao Zheng, Shiyang Liu, et al.

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A redox polymer, poly(ethylenimine)ferrocene (PEI-Fc) was prepared by attaching electroactive ferrocene groups to the backbone of a water soluble, biocompatible polyelectrolyte, poly(ethylenimine), and multilayer film composed of polystyrenesulfonate sodium (PSS) and PEI-Fc was prepared by alternate layer-by-layer (LBL) self-assembly adsorption technique based on the electrostatic force between the opposite charges carried by these two polymers. UV-Vis spectra was used to monitor the LBL process, and the thickness and immobilization amount of each layer were characterized by quartz crystal microbalance (QCM), which showed the formation of nano-scale multilayer structure and linear mass increase dependent on the alternate adsorption cycles. The electrochemical properties of the PEI-Fc/PSS multilayer film modified gold electrode were investigated by cyclic voltammetry. It was observed clearly that the electrochemical properties of this multilayer film were strongly dependent on the layer number and the ferrocene content in PEI-Fc. The electrochemical kinetic was analyzed based on a general model for surface process, and the experimental data fitted well with that evaluated from the above model. This redox polymer showed potential for the construction of reagentless biosensor.

Structure and property of nano-SiO2-PMMA/Wood composite

Yongfeng Li, Yixing Liu, Fenghu Wang, et al.

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A new wood-based composite, nano-SiO₂-PMMA/Wood, with high mechanical properties including modulus of rupture (MOR), compression strength and hardness, and multifunctional properties involving decay resistance, dimensional stability and thermal stability, was prepared by impregnating a vinyl monomer, methyl methacrylate (MMA), and AIBN as an initiator, and a few modified nano-SiO₂ particles with unsaturated double bonds (C=C) into the cellular structure of wood material; and further initiating them for in situ copolymerization through a catalyst-heat process. Its structure was characterized with SEM, FTIR and XRD. And the performance of the composite was also determined. The analysis results with SEM, FTIR and XRD show that MMA fully polymerized in the porous structure of wood by its double bond, and the resultant polymer chemically bonded to wood cell walls, which mainly existed in an amorphous form. The nano- SiO₂ particles dispersed uniformly in the polymer filling in the porous structure of wood, which might chemically bond to the polymer, as evidenced by SEM-EDAX and FTIR, respectively. The XRD pattern shows that after adding nano- SiO2 particles into the monomers, a slightly higher peak appears at 2θ=39.5° in nano-SiO₂-PMMA/Wood compared with that of PMMA/Wood and untreated wood, which indicates that the adding of nano-SiO₂ slightly improves the degree of order of PMMA in wood. The testing results of comprehensive performances indicate that after adding polymeric monomers and nano-SiO₂ particles into the wood porous structure, the mechanical properties, dimensional stability, decay resistance and thermal stability of wood were remarkably improved, which could endow it with a wide application in the fields of architecture and traffic.

The micro mechanical environment on the comb capacitive micro-machined gyroscope

Hai-peng Liu, Shi-qiao Gao, Shaohua Niu, et al.

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With the in-depth researches on MEMS sensors, a lot of mechanical problems are encountered inevitably. Especially for the comb capacitive micro-machined gyroscope, a typical MEMS inertia sensor, the speciality of its structure and micro size determines the characteristics of the mechanical environment. With the reduction of structural size, the ratio of surface force and body force has increased clearly. Comparing with the roles of body force, the roles of surface force in MEMS sensors become more and more important. The micro forces, such as electrostatic force, Van de Waals force, capillary force and air-damping force were analyzed, and the action extent of these micro forces were obtained.

Highly red luminescence properties from ternary ZnCdTe quantum dots

Norhayati Abu Bakar, Akrajas Ali Umar, Muhamad Mat Salleh, et al.

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This paper reports the synthesis of ternary ZnCdTe quantum dots (QD) system with highly luminescent in the red region. The ternary QD system was prepared by quick injection of trioctylphosphine telluride (TOPTe) into a reactor that contains a hot mixed cadmium and zinc precursors, trioctylphosphine oxide and oleic acid at temperature of as low as 300°C. After the injection of TOPTe, the reaction was left undisturbed for a period of time to facilitate the growth of QDs and then quenched the reaction at a certain period of time. Photoluminescence analysis found that the ZnCdTe QDs exhibited highly luminescent properties with the quantum yield was calculated as high as ca. 60%. The emission wavelength was found to be in the range of 640 to 675 nm. It was also found that the QDs showed a relatively narrow spectral width, namely ca. 28 nm, reflecting a narrow quantum dots size distribution. Owing to their interesting photoluminescence properties, the ternary ZnCdTe QDs should find an extensive used in light-emitting diode, solar cell, laser and biolabelling.

A new digital silicon MEMS gyroscope

L. F. Wu, Zh. Peng, Wei Zhang, et al.

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This paper presents a new, digital silicon MEMS gyroscope, which consists of micro-sensor, signal processing circuit and micro-processor (MSC1214). The gyroscope structure allows it to achieve rolling rate, yaw angular rate and pitch angular rate of rotating carrier. That is, it can detect the attitude of a rotating carrier. The key techniques of MEMS gyroscope, including sensing construct, sensing principle, signal processing circuit design and test results are presented. The test results show that the non-linearity of the gyroscope is less than 0.5% and sensitivity of the gyroscope is 0.01°/s at atmospheric pressure, measuring range of yaw (or pitch) angular rate and rolling rate of rotating carrier is from -500 ° /s to +500 °/s and 0 Hz to 40 Hz, respectively.

Preparation of magnetic fluorescent hollow nanoparticles with multi-layer

Xiuxue Sun, Jimei Zhang, Zhao Dai, et al.

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A kind of novel magnetic fluorescent hollow nanoparticles with multi-layer shells by layer-by-layer self-assembly process was presented in this paper. Non-crosslinking poly(acrylic acid) (PAA) nanoparticles as core with 250 nm in diameters were prepared by distillation-precipitation polymerization in acetonitrile with 2, 2'-Azobisisobutyronitrile (AIBN) as initiator and without any stabilizer and crosslinker. Then 4-vinylpyridine (4-VPy) as monomer was selfassembled on the surface of PAA nanoparticles because of hydrogen-bonding effect between the surface carboxyl of PAA nanoparticles and pyridine of 4-VPy. The 4-VPy as first shell layer were crosslinked by ethylene glycol dimethacrylate (EGDMA) by seeds distillation-precipitation polymerization in acetonitrile. The core/shell structure of this kind of nanoparticles was investigated by FT-IR and TEM. We can find that the products had an absorption peak at 1641 cm^-1 from the FT-IR, which showed that the vinyl groups had been connected in the polyAA microspheres. After that, the non-crosslinking PAA core was removed under a solution of sodium hydroxide in ethanol-water. On the other hand, CdTe quantum dots (QDs) with about 3 nm in diameters as shell were prepared in aqueous solution with 3- mercaptopropionic acid (MPA) as stabilizer and 1, 6-hexylenediamime modified Fe3O4 nanoparticles with about 11 nm in diameters as core were synthesized in water respectively. Because of the hydrogen-bonding between the surface carboxyl of MPA on CdTe QDs and the amino on Fe3O4 nanoparticles, the core/shell magnetic-fluorescent nanoparticles were obtained. Then, the magnetic-fluorescent nanoparticles as second shell layer were self-assembled on the hollow 4VPy nanoparticles.

Optical properties of ZnO nanowires grown by thermal evaporation

Zhi Zhao, Yue Lin, Jian Zuo, et al.

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The mass production of wurtzite-type structure ZnO nanowires were synthesized by a simple and rapid method based on the thermal evaporation of metal zinc pellets without the use of noble metal catalyst. The PL spectrum at room temperature shows a strong near band gap emission (NBE) peak and a weak deep-level emission (DL) peak, which implies its good crystallinity and high optical quality. The DL and NBE emission are considered to originate from the singly ionized oxygen vacancy and the overlap of free exciton and free-to-band emission respectively by electron paramagnetic resonance (EPR) spectroscopy and low temperature photoluminescence. The coupling parameters of exciton-acoustic phonon and of exciton-longitudinal-optical phonon were determined as 63.44 μeV/K and 898 meV, and 251 K for Einstein temperature according to the temperature dependence of free exciton emission spectra.

Microwave hydrothermal synthesis and characterizations of NiS nano-needle

Bo Bai, Xuemei Hou, Pengpeng Wang, et al.

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NiS with needle-like nanostructure was successfully prepared via a facile and rapid microwave-hydrothermal method. The as-prepared products were characterized by XRD, XRF, TEM, BET, Raman spectroscopy and TGA-DTA, respectively. The experimental results showed that NiS was needle-like, and the product possessed a uniform size with the diameter in a range of 20 nm to 35 nm and the length of about 100-200 nm. The structure belonged to α-NiS crystal phase. The specific area exceeded 45.0m²/g. Moreover, the possible growth mechanisms were discussed. It was proposed that with the presence of surfactant of polyethylene glycol-400, the formative micelle in aqueous solution had acted as templates for the formation of these kinds of α-NiS crystal with the typical morphologies due to the orientated aggregation effect. Comparing with the conventional hydrothermal method, microwave hydrothermal technique could not only accelerate the reaction but also make the formed NiS precursors well crystallized.

Preparation and photocatalysis properties of La-doped nano-NiO novel photocatalyst

Peng Liu, Zhiyuan Yang, Pan Ran

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The novel photocatalyst, La-doped Nano-NiO, was prepared by sol-gel with nickel nitrate hexahydrate and lanthanum salt, characterized by means of XRD. The photocatalytic activities of prepared La-NiO photocatalysts were evaluated by degradation of Direct Bordeaux (DB) solution as model compound under irradiation of UV and daylight lamp. The results show that Pure and La-doped NiO are a cubic perovskite structure with space group Fm-3m (225). The grain size of NiO powder decreases whereas the crystal plane spacing of NiO increases with the doping contents of La in NiO increasing. The degradation rates of two kinds of La-doped NiO after UV irradiation for 180min are 98.5% and 65.2%, under daylight, reaches 66.3% and 71.9% respectively. Using six times, the degradation rates under UV are still 49.5% and 47.7%. Meanwhile, the catalyst surface reaction rate constants (K_r) have greatly improved comparing with Pure NiO. The XRD analysis shows that a small amounts of perovskite-like structure of La_xNiO_y exists in composite structure of La-NiO, which contributes to the increase of photo-catalytic activities.

Preparation of nano-TiO2 powder by polyacrylamide gel method

Xiaowei Fan, Xiaoping Liang, Guanqun Guo, et al.

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Polyacrylamide gel method is a new successful technique for preparing nanometer metallic oxide materials, such as α-Al₂O₃, ZnO and ZrO₂. TiO₂ made by this method, however, has not been reported. In this study, the nano-TiO₂ powder was prepared using the novel method with TiCl3 as raw materials, and with acrylamide and N,N'-methylenediacrylamide as crosslinking agent. The TG showed that the optimization sintering process is that: the polyacrylamide gel was dried at 110°C for 2 hour to obtain the xerogel, and then the grinded xerogel was sintered up to 450°C, meanwhile, kept at 250°C, 410°C and 450°C for 1 hour, respectively, to gain TiO₂ particles. The grain size of TiO₂ particles is smaller than 25 nm. And those particles are spherical approximately and have good distribution because of the hindering effect of space grid structure. Adding SO₄ ^2- in the polyacrylamide gel process can maintain the content of anatase-TiO₂ phase at higher sintering temperature. This may be explained that the SO₄ ^2- can form coordination compound with Ti⁴⁺. And the coordination compound is prone to generate anatase-TiO2 with the burning out of SO₄ ^2- , in which structure the adjacent two TiO₆ hexahedrons share only one oxygen atom.

Protein absorption and fouling on poly(acrylic acid)-graft-polypropylene microfiltration membrane

Yanjun Liu, Huiying Ma, Chunying Lv, et al.

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A series of pH-sensitive poly (acrylic acid)-graft-polypropylene hollow fiber microfiltration membranes were prepared by UV-photo-irradiation. Bovine serum albumin (BSA) was chosen as the model protein to investigate its absorption and fouling behaviors on membranes. The results showed that the hydrophilicity of grafted membrane was improved by poly(acrylic acid) chains with parts of membrane pores blocked. The grafted membranes were markedly pH-dependent on the water permeability as pH was altered from 1 to 11. The zeta potential of grafted membranes calculated by streaming potential was negative in most pH range. Electrostatic interaction energy calculated by DLVO theory showed the electric interaction force between grafted membrane and BSA was attractive. With the rise of grafting degree, the electric attractive force between grafted membrane and BSA increased as pH=3 and decreased as pH=8, while it kept basically unchanged as pH=4.7. As a result, most serious fouling was observed as pH=4.7. Grafted membranes had a lower BSA absorption and better antifouling behavior as pH=8, while the opposite result was revealed as pH=3. In conclusion, the absorption and fouling behavior of BSA on membranes was pH-dependent due to the pH-dependence of membrane charge, and the conformation of BSA and grafting chains.

Development of polymer electrolytes based resistive switch

Shouming Wu, Tohru Tsuruoka, Kazuya Terabe, et al.

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The construction of an organic-electronic resistive switch based on polymer electrolytes is the basis to study the interfacial and bulk transport as well as the interaction between ions and electrons/holes at the nanoscale level. Moreover, it could also be potentially applied in novel nanoelectrochemical devices for sensors, fuel cells and batteries, and therefore has attracted much attention in recent years. In this work, we fabricated resistive switching devices with silver-ion-conductive polymer electrolytes. The devices showed bipolar switching behaviors in the current-voltage characteristics for different silver ion concentrations ranging from 1 to 4 wt%. A high resistance up to 1 GΩ in the OFF state and a low resistance with less than tens of kΩ in the ON state can be achieved. We believe that the observed switching results from formation and annihilation of Ag metal filaments inside the polymer film by solid electrochemical reaction. Sequential operations, such as write-read-erase-read, were also demonstrated.

Isothermal physical aging of thin PMMA films near the glass transition temperature

J.-E. Nam, J.-K. Lee, C.-S. Oh

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The isothermal physical aging and the glass transition temperature (T_g) in PMMA thin films were investigated by means of differential scanning calorimetry (DSC). Freestanding thin film was obtained by spin coating onto a silicon wafer substrate and then releasing the coated film using a water floating technique for different molecular weights (MW = 120,000, 350,000, 996,000 g/mole) and film thicknesses (40~667 nm). The thin films were stacked in a DSC pan and isothermally aged for different aging times (t_a = 1 and 12 h) and aging temperatures (T_a =105, 110 and 115 oC) below but near T_g. Enthalpy relaxation (▵H_Relax) due to the isothermal physical aging vs. ▵T_a (T_g - T_a, driving force of aging) data showed that the enthalpy value increased with increasing ▵T_a, reached maximum, and then decreased as ▵T_a increases further. As film thickness decreases, ▵H_Relax was rapidly reduced for samples below ~100 nm of film thickness near T_g (e.g., T_a =110 and 115 °C), indicating the suppression of physical aging. About 7~10 oC depression in T_g was observed for thinner films (~40 nm), compared to thicker films (~660 nm) in this study.

Nitrogen dioxide sensing properties and mechanism of nickel phthalocyanine film

Cheng-jun Qiu, Yan-wei Dou, Wei Qu, et al.

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Nickel phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based nickel phthalocyanine film gas sensor for NO₂ detection is fabricated by MEMS technology. The results show that the current of nickel phthalocyanine film increase obviously from 3×10^-2μA to 1.08μA as the NO₂ concentration increases from 0 ppm to 160 ppm. However, the sensitivity of NiPc thin film gas sensor nearly keeps a constant of 0.94 (average) between 10 ppm and 120 ppm with increasing NO₂ concentration. The best working temperature of the gas sensor is 50°C for NO₂ gas concentrations of 10 ppm, which is much lower than that of general metal oxide gas sensor.

Quantitative analyses of extrudate swell for polymer nanocomposites

Kejian Wang, Chongxiao Sun

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The quantitative theory of extrudate swell for nanocomposite and pure polymer is significant either for optimum processing or for understanding their viscoelasticity. Based on Song's die swell theory for entangled polymers, one extrudate swell correlation with material properties and capillary parameters was developed for polymer melt and their nanocomposites when compensating reservoir entry effect. It was the first to find that the composite swell ratio can be the matrix swell ratio multiplied by the concentration shift factor. The factor is the functions of the shear field, filler content, filler internal structure and the surface state as well as the matrix properties. The quantitative model was well fitful for the five kinds of nanoomposites.

Investigation of the oxygen depletion properties of low density polyethylene resins filled with thermally stable oxygen scavengers

Jen-taut Yeh, Li Cui, Yan-bin Sun, et al.

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The thermal stability, oxygen depletion and tensile properties of low density polyethylene (LDPE) resins filled with ascorbic acid (Vc), sodium ascorbate (SA), iron (Fe) and modified iron (MFe) oxygen scavengers were systematically investigated. Thermogravimetric analysis (TGA) results clearly suggest that the thermal stability of SA powder and L95(SA)5 specimen is significantly better than that of Vc powder and L95(Vc)5 specimen, respectively. The oxygen depletion efficiency of L95(SA)5 is significantly better than that of L95(Vc)5, L95(Fe)5 and L95(MFe)5 specimens, although the virgin SA powders exhibit worse oxygen depletion efficiency than Vc, Fe or MFe powders before melt blending. Moreover, at a fixed weight ratio of Vc (or SA) to MFe of the oxygen scavenger compounds, the oxygen depletion efficiency of L95[SAx(MFe)y]5 series specimens is always significantly better than that of L95[Vcx(MFe)y]5 series specimens. In fact, at weight ratios of Vc/MFe and SA/MFe higher than 3/7 and 5/5, respectively, the residual oxygen concentration values present in the airtight flask of L95[Vcx(MFe)y]5 and L95[SAx(MFe)y]5 series samples at any time are even lower than those of the L95(Vc)5 and L95(SA)5 specimens, respectively. Further tensile experiments show that the tensile properties of the L95[SAx(MFe)y]5 series samples are always higher than those of the corresponding L95[Vcx(MFe)y]5 series samples with the same loadings of oxygen scavenger compounds, respectively. In order to understand these interesting thermal stability, oxygen depletion and tensile properties of these LDPE oxygen-scavenging plastics, scanning electron microscope and energy dispersive X-rays analysis of the compositions on the surfaces of L95[SAx(MFe)y]5 and L95[Vcx(MFe)y]5 series samples were performed. Possible reasons accounting for these interesting properties of these LDPE oxygen-scavenging plastics are proposed.

Calculation of hysteresis losses for Terfenol-D ultrasonic transducer

Jianbin Zeng, Haiquan Zeng, Baodong Bai, et al.

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Thermal is one of critical factors effecting the application of Terfenol-D ultrasonic magnetostrictive transducer. Hysteresis losses are the main source for heating the it. A new method of hysteresis losses calculation, which based on Jiles-Atherton hysteresis model and electro-magnetic field finite element analysis, is proposed in this paper. The hysteresis losses obtained by this method can be used as thermal sources in electro-thermal finite element analysis of Terfenol-D ultrasonic transducer.

Optical behavior of Pr3+-doped barium titanate-calcium titanate material prepared by sol-gel method

Xiaoyan Wang, Yanxue Tang, Xiyun He, et al.

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Photoluminescence performances of Pr-doped alkaline-earth titanates (Ba,Ca)TiO3 (with rich barium) prepared by a solgel technique are investigated at room temperature. A relatively strong red luminescence is observed in (Ba0.80Ca0.20)TiO3 material when Pr-BaTiO3 material does not exhibit obvious red luminescence. The phenomenon is discussed with respect to the substitute of Ca and the two-photon luminescence effect. The red luminescence is enhanced by a fast thermal treatment. The wavelength range of luminescence near red and infrared light is broadened by the same process as well. These behaviors are ascribed to the randomization of distribution of Ca and Ba at A site in ABO3 perovskite structure. The experimental results provide not only a possible way to develop new materials with pastel visual impression, but also a potential technique to modify photoluminescence properties that can be controlled by external fields because the microscopic structure of BaTiO3, such as electric domains, can be changed by electric field, temperature, and so on.

Microstructure-property correlation for the tunneling-percolation conduction in metal-insulator nanocomposites

Liu-Juan Zhu, Wen-Zhong Cai, Shan-Tung Tu

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A theoretical model is proposed for the tunneling-percolation (TP) conduction in the metal-insulator nanocomposites based on the equivalent-particle concept. To establish a clear microstructure-property correlation, many-particle statistics is adopted firstly for the microstructure characterization in this TP model, and then incorporated hierarchically into effective-medium theory and classical percolation (CP) theory for the local and global TP conduction, respectively. The availability of this TP model is confirmed by experimental data. Results also show that the conventional CP model, regardless of universal or nonuniversal exponents, fails to account for the whole transition process from the electrically tunneling conduction to geometrically percolating conduction in the nanocomposites. Furthermore, the effect of metal particle size on the tunneling conduction thresholds is investigated with an experimental verification. The dominant role of interparticle tunneling conductance on the nanocomposite conductivity is explored, which exactly clarifies the main cause to failure of CP model--significant nonlinearity of percolation exponent.

Electrorheological properties of TiO2/ZnC2O4 nanocomposites

Fenghua Liu, Gaojie Xu, Jinghua Wu, et al.

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TiO₂/ZnC₂O₄ nanocomposites were synthesized by means of co-precipitation method. The XRD, SEM, FTIR and DTA/TG were used to determine the structure of the nanocomposites. The electrorheological (ER) activity of the suspension of TiO₂/ZnC₂O₄ dispersed in silicone oil was investigated under a dc electric field. An excellent ER effect was found. Under 5 kV/mm external electric field, the yield stress of the TiO₂/ZnC₂O₄ suspension can reach up to 90 kPa, and the leaking electric current density is lower than 20 μA/cm². The yield stresses exhibit a near linear dependence on applied electric field unlike the conventional fluids. The results demonstrate that the polar molecules such as hydroxyl groups and oxalate groups adsorbed on the particles play a decisive role in determining the characteristics of the ER fluids.

Fatigue crack growth properties of the base metal and weld metal of a 9% Ni steel for LNG storage tank

Young-Kyun Kim, Kyu-Taek Shim, Jae-Hoon Kim

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Newly developed heavy thick plates of 9% Ni steel for large capacity of LNG tank were fabricated to conduct a fatigue crack growth test. The weld metal specimens were also fabricated by taking the same weld procedures which are applied to actual LNG storage tank inner shell. The effect of changes in load ratio, R, and test temperature on the fatigue crack growth rate has been investigated. Separate fatigue crack growth experiments were performed at load ratio of 0.1 and 0.5 at -162°C and compared to the behavior at room temperature. The fatigue crack growth rates of weld metal were nearly the same as those of the base metal irrespective of load ratio change at room temperature. A decrease in temperature decreased the fatigue crack growth rates of base metal but in the case of weld metal only small scatters appeared in the fatigue crack growth rate compared with those of base metals. The fatigue crack growth rates were dominated by residual stress due to welding processes rather than temperature effects.

Synthesis of shape memory polyurethane using bulk polymerization

Ziming Yang, Qiongling Jiang, Guanru He, et al.

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In this paper, a series of shape memory polyurethanes (SMPUs) containing polycaprolactone diol (PCL4000), 1,4-butanediol (BDO), and 4,4'-diphenylmethane diisocyanate (MDI) were synthesized using bulk polymerization. Their thermal properties, thermomechanical properties were analyzed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), and the shape memory effect was also investigated. Moreover, one kind of shape memory polyurethane fiber was spinned by melting method from these prepared SMPUs and its shape memory properties were also investigated. The results showed that synthesis of shape memory polyurethane using bulk polymerization can effectively enhance the properties of polyurethanes, save cost and improve efficiency compared with solution polymerization.

Analyze the vibration mode of 1-3-2 piezoelectric composite

L. Qin, L. K. Wang, G. Wang, et al.

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Based on finite element analysis method, harmonic analyses with infinite and finite boundary conditions have been performed to investigation the vibration mode of 1-3-2 piezoelectric composite. This method has been checked by the experimental data of 1-3-2 PZT5A/Polymer-618 piezoelectric composites. The admittance curves of samples have been calculated under different boundary conditions. The calculation shows that finite element analysis with infinite boundary condition can be used to simulate the thickness mode, and the error is less than 1.5%. But it is incapable of simulation the interferential vibration mode accrued near to the thickness vibration frequency. To avoid non-considering of periodicity and boundary condition in conventional FEA method, limited elements have been used in FEA model to simulate periodicity and boundary condition. Finite element analysis with finite boundary condition is a substitute way to simulate the high order of lamb mode. The 8th order of lamb mode and the thickness mode have been simulated under finite boundary. It shows a good match between the simulation results and the test results by using laser scanning vibrometer while element number equals to 64 or the width/thickness of model is larger than 2.

Circumferential SH waves in functionally graded piezoelectric hollow cylinders

Jiangong Yu, Tonglong Xue, Xiaoming Zhang

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Based on linear three-dimensional piezoelasticity, the Legendre polynomial approach is used for determining the characteristics of circumferential SH waves in transversely isotropic hollow cylinders composed of functionally graded piezoelectric materials (FGPM) with axial polarization and open circuit. Circumferential SH wave dispersion curves, displacement and electric potential distributions in FGPM hollow cylinders under different gradient fields and different ratios of radius to thickness are calculated. The effect of piezoelectricity on dispersion curves and displacement distributions is shown. The influence of the ratio of radius to thickness on the circumferential SH wave characteristics is discussed. Piezoelectricity can change the extent of the dispersion of the circumferential SH waves in FGPM hollow cylinders. The changing extent is influenced obviously by the ratios of radius to thickness. The ratio also has a significantly influence on the electric potential distribution.

Prewarning of the China National Aquatics Center using Johnson transformation based statistical process control

Deyi Zhang, Yuequan Bao, Hui Li, et al.

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Structural health monitoring (SHM) is regarded as an effective technique for structural damage diagnosis, safety and integrity assessment and service life evaluation. SHM techniques based on vibration modal parameters are ineffective for space structure health maintenance and the statistical process control (SPC) technique is a simple and effective tool to monitor the operational process of structures. Therefore, employing strain measurements from optical fiber Bragg grating (OFBG) sensors, the Johnson transformation based SPC is proposed to monitor structural health state and some unexpected excitements on line in this paper. The large and complicated space structure-the China National Aquatics Center is employed as an example to verify the proposed method in both numerical and experimental aspects. It is found that the Johnson transformation can effectively improve the quality of SPC for SHM process, and it can clearly and effectively monitor structural health state and detect the unexpected external load happened in structures.

A novel nanosilica-reinforced waterborne UV-curable material

Tong Zhang, Wenjian Wu, Yuping Mu

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A novel multifunctional UV-curable waterborne polyurethane-acrylate(WPUA) was synthesized with isophorone diisocyanate(IPDI), polycaprolactone diols(PCL), dimethylol propionic acid(DMPA) and pentaerythritol triacrylate (PETA). The chain structure of the WPUA was identified by ¹H NMR spectrum. After that, the nanosilica modified with KH570 was dispersed in WPUA, and the effects were studied with dispersion and cast films. It was found that the viscosity of the hybrid emulsion was increased, and the water resistance, abrasion resistance and mechanical properties were improved with the addition and increasing amount of silica, to provide the WPUA/SiO₂ hybrid materials with excellent performance and more expansive prospects.

Damage identification method based on fractal dimension and Shannon entropy

Yong Huang, Hui Li, Yongchao Yang

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Fractal geometry has been widely used to describe irregular phenomena such as damage in the structure as a new mathematical tool. However, most of structural damage identification methods based on fractal theory have the drawback of being sensitive to noise which restricts their practical application. A new high noise robustness damage identification method based on fractal dimension and Shannon entropy is presented in this paper. The damage index was deduced from the Katz's fractal dimensions of certain sampling points with arithmetic of Shannon entropy. The selection of the number of sampling points for calculating the proposed damage index is also studied in this paper and it can be regarded as a trade-off between the peak value generated by the damage and the stability of the curve of the proposed damage index. As a validation, the proposed method is applied to detect damage in simply supported beams by numerical and experimental study. The successful detection of the damage in the beam demonstrates that the method is capable of estimating the location of the damage. And tests with measurement noise in simulated and the laboratory tested beams demonstrate the strong robustness of the method under the influence of noise with appropriate number of sampling interval for calculating the proposed damage index.

Investigation of fiber Bragg grating optic acceleration sensor

Dianheng Huo, Jun Chang, Xiaohui Liu, et al.

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A high sensitive fiber Bragg grating (FBG) acceleration sensor is investigated; the sensor is interrogated by narrow line-width DFB laser, the output wavelength of the DFB laser is locked to -3dB of FBG reflectivity spectrum by auto-scan and scout method using single-chip-micyoco (SCM) in order to get high sensitivity. Experiments to test the sensor system's frequency character and linearity have been done, the results show the sensitivity can reach 0.1mg (g=9.8m/s²). The system will have practical usage in the future, such as detecting micro-seismic vibration signal during mine exploration.

Optimal design of dampers within seismic structures

Wenjie Ren, Hui Qian, Wali Song, et al.

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An improved multi-objective genetic algorithm for structural passive control system optimization is proposed. Based on the two-branch tournament genetic algorithm, the selection operator is constructed by evaluating individuals according to their dominance in one run. For a constrained problem, the dominance-based penalty function method is advanced, containing information on an individual's status (feasible or infeasible), position in a search space, and distance from a Pareto optimal set. The proposed approach is used for the optimal designs of a six-storey building with shape memory alloy dampers subjected to earthquake. The number and position of dampers are chosen as the design variables. The number of dampers and peak relative inter-storey drift are considered as the objective functions. Numerical results generate a set of non-dominated solutions.

The application of carbon fiber resistancein monitoring of curing

X. Y. Sun, B. M. Zhang, Yang Zong

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Thermal residual stress in resin matrix composite due to the different coefficient of thermal expansion (CTE). The CTE of carbon fiber is lower than resin matrix. Based on mechanics, rising temperature will induce tensile stress, cooling down will induce compress in fiber. There exists expanding and shrinkage during curing process of epoxy. In single fiber composite system, they play different roles, present with tensile and compress stress on fiber. This paper deals with the relationship of the carbon fiber resistance with strain and temperature. The effect of expanding and shrinkage on residual stress is got by the fiber resistant measurement. Resistance variety curve of the experiment shows the chemical process during resin solidification. The shear stress between fiber and matrix existing during temperature load can also measured by the same method. The carbon fiber's resistant can be used as sensor to monitor and control the curing process. This is a simple and effective method to research the curing process.

Wireless energy transmission through a sealed wall using the acoustic-electric interaction of piezoelectric ceramics

Hongping Hu, Huan Xue, Yuantai Hu, et al.

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We propose a system to transmit and store electric energy by using transmitting element, a chargeable battery, and a rectifier together with a dc-dc converter to connect the two components as an integrated system. The transmitting element is modeled by two piezoelectric transducers. One is as the driving transducer for generating acoustic wave; the other is as the receiving transducer for converting the acoustic energy into electric energy. A dc-dc converter employed in the storage circuit is to match the optimal output voltage of the receiving transducer with the battery voltage for efficient charging. A synchronized switch harvesting on inductor (SSHI) in parallel with the receiving transducer is introduced to artificially extend the closed circuit interval of the rectifier. This analysis extends a previous one by considering that influence of wall thickness which always exists in the application. The characteristics of the energy-transmitting element are studied. Performance of the energy-transmitting element is optimized by synthetic adjusting parameters of the element, and carefully choosing input frequency of electric source.

Calculation of dynamic stress intensity factor of an interfacial crack under moving impacting loading

Jin Cheng, Baoke Guo, Li Zhang

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Multi-layered structures and composite materials have been used broadly and many defects between interfaces are inevitably in them. Among of the defects, the crack plays an important role for the damage of the structures. In practices, surfaces of interfacial cracks often produce complicated impact each other under external loadings. These additional loadings due to the impacting have great effects to the damage of the structures containing cracks. In this study, dynamic stress intensity factors of an interfacial crack between two homogeneous isotropic half infinite mediums are calculated. Other external loadings are neglected and the only load due to closures or frictions of the crack surfaces is assumed to be a pair of anti-plane moving impacting loading with constant velocity. Fourier and Laplace transforms are employed to simplify general wave equation into ordinary differential equation. Consider the zero initial condition and radiation conditions in far-fields, the solution in double transform domains is obtained. The Cauchy singular integral equation of dislocation density function (DDF) is then derived through Fourier integral inversion. By expanding DDF into Jacobi polynomials with a weight function, the DDF in Laplace transform domain is obtained numerically, and dynamic stress intensity factors of crack tips are expressed using the DDF. To determine the dynamic stress intensity factors in time domain, the Guy Miller method for Laplace inversion is used. Finally, a simple example is analyzed and the dynamic stress intensity factors are displayed graphically.

Frequency shift of piezoelectric microcantilever humidity sensors

Fei Wang

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Recent researches on dynamic behavior of micro cantilevers indicate that the flexural resonance frequencies of piezoelectric microcantilever sensors (PEMS) could be influenced by air in which it immersed as a result of viscous damping effect, which reduces the accuracy of the PEMS. A detailed theoretical analysis of the frequency response of a PEM immersed in air and excited by an arbitrary driving force is presented in this paper, in which the couple stress theory (Cosserat theory) is introduced to the dynamic deflection function of a PEM to explain the size effect. Numerical results have shown a good agreement with the experiments. Methods for prediction of dynamic characteristics of long beam-like micro components could be easily derived based on the presented theory, which is of value to users and designers of micro-electro-mechanical systems (MEMS).

Experimental investigation of steel structure with recentering shape memory alloy damper

Hui Qian, Wenjie Ren, Hongnan Li, et al.

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Superelastic shape memory alloys (SMAs) are a class of materials that have the ability to undergo large deformations while reverting back to their original shape through removal of stress. The unique material can be utilized as key components for seismic energy dissipation in earthquake engineering. In this paper, an innovative recentering SMAsbased damper (RSMAD) is introduced. Cyclic tensile-compressive tests on the damper with various pre-strain under different loading frequency and displacement amplitude are conducted. To assess the effectiveness of the damper in reducing dynamic response of structures subjected to strong seismic excitations, an extensive experimental program and main results of shaking table tests performed on reduced-scale steel frame model with and without RSMAD are presented. In the shaking table tests, several representative seismic signals as well as white noise motion are utilized as input energy. The comparisons of dynamic behaviors, i.e. storey displacements, interstorey drifts and storey accelerations, of structural model with and without RSMAD under seismic loading are conducted. The results show that RSMAD is effective in suppressing the dynamic response of building structures subjected to strong earthquakes by dissipating a large portion of energy through their hysteretic loops.

Health monitoring of a continuous rigid frame bridge based on PZT impedance and strain measurements

Junbing Zhang, Hongping Zhu, Dansheng Wang, et al.

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Critical civil infrastructures such as bridges, dams, and pipelines present a major investment and their safety and security affect the life of citizens and national economic development. So it is very important for engineers and researchers to monitor their integrity while in operation and throughout. In recent years, the piezoelectric-ceramic (PZT) patches, which serve both as impedance sensors and actuators, have been increasingly used for structural health monitoring. This paper presents an impedance-based method, which utilizes the electro-mechanical coupling property of PZT sensors. There are a lot of advantages of this method, such as not based on any physical models, sensitive to tiny damage for its high frequency characteristics. An engineering application of this method for health monitoring of a continuous rigid frame bridge is implemented in this study. Some PZT active sensors are embedded into critical sections of the continuous rigid-frame box beam. The electrical admittances of these distributed PZT sensors are measured when the bridge is constructing or suffering from operational loads. For comparison, strain gauges are arranged in adjacent regions of these PZT sensors to obtain the strains of concrete around them at the same time. Based on the admittance sigatures obtained form PZT sensors and the strain measurements of concrete around them, the health status of the bridge is monitored and evaluated successfully.

Experimental research on stable fretting wear of stainless steel wires in transformable component

Xiu-ping Dong, Guo-quan Liu, Li Zhang, et al.

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Cool-drawn 1Cr18Ni9 stainless steel wires of φ 0.1~0.5 mm can be woven and punched to prepare transformable component which has loose, reticulate structures. When it is uploaded with vibrating force, the displacement will cause intense frictions between wires' surfaces which will dissipate abundant energy and thus it can serve as dampers like natural rubbers. Since such new type of material has double characteristics of both rubbers and metals, it is commonly called "Metal Rubber". There is certain amount of contact point/surface on wires in the transformable component and the displacements between wires are at micron levels. Experiments showed that wear course of 'fretting cell' could be plotted as four phases: polish, adherence, forming of the third bed and stabilization. The stabilization phase, in which the friction coefficients are comparatively stable, dominates the whole course. Based on data of Metal Rubber vibration fatigue experiment, φ 0.3 mm cool-drawn 1Cr18Ni9 stainless steel wires' dry fretting experiments at 10 N load are made on SRV high temperature wear tester, friction coefficients are collected and fret traces are studied by laser scanning confocal microscope (LSCM). Results indicate that wire's stabilization wear phase is the circulation process of grindings' forming, concentrating to blocks of φ 20 μm, busting and discharging. Deformation induced martensite transit in wire's cool drawing has significant effects on grinding blocks' bursting performances.

Design and vibration control of vehicle engine mount activated by MR fluid and piezoelectric actuator

D. Y. Lee, Y. K. Park, S. B. Choi, et al.

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An engine is one of the most dominant noise and vibration sources in vehicle systems. Therefore, in order to resolve noise and vibration problems due to engine, various types of engine mounts have been proposed. This work presents a new type of active engine mount system featuring a magneto-rheological (MR) fluid and a piezostack actuator. As a first step, six degrees-of freedom dynamic model of an in-line four-cylinder engine which has three points mounting system is derived by considering the dynamic behaviors of MR mount and piezostack mount. In the configuration of engine mount system, two MR mounts are installed for vibration control of roll mode motion whose energy is very high in low frequency range, while one piezostack mount is installed for vibration control of bounce and pitch mode motion whose energy is relatively high in high frequency range. As a second step, linear quadratic regulator (LQR) controller is synthesized to actively control the imposed vibration. In order to demonstrate the effectiveness of the proposed active engine mount, vibration control performances are evaluated under various engine operating speeds (wide frequency range).

Preparation of Ca2Si5N8:Eu2+,Tm3+ phosphor by calcium hydride and its afterglow properties

Bingfu Lei, Ken-ichi Machida, Takashi Horikawa, et al.

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Reddish-orange emitting long-lasting phosphorescence phosphor Ca₂Si₅N₈:Eu²⁺,Tm³⁺ has been prepared by solid-state reaction method using cheaper CaH₂ as calcium source. Upon UV light excitation, Ca₂Si₅N₈:Eu²⁺,Tm³⁺ phosphor gave a broad band emission peaking at ca. 600 nm. Furthermore, after irradiation by the UV or visible light (in the range of 250-400 nm) for 3 min, the same colored intense afterglow based on the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ion was observed on the phosphor codoped with 0.5 at% of Eu²⁺ and Tm³⁺ ions, and its afterglow can be seen with the naked eye in the dark clearly for more than 1 h after removal of the excitation source. The afterglow decay curve contained fast decay and slow decay components. The substitution of Mg²⁺ to Ca²⁺ ions or addition of excessive Ca²⁺ ions into the phosphor matrix to modify the defect environment were effective to improve the afterglow properties.

Preparation and properties of PBO/SWNT composite fibers

Feng Wang, Hong Lin, Lei Zhao, et al.

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Single-walled carbon nanotubes / poly(p-phenylene benzobisoxazole) (PBO/SWNT) composite fibers were prepared by in situ polymerization and dry-jet wet spinning. PBO/SWNT composite fibers were characterized by Raman spectroscopy, scanning electron microscope, TG-DTG analyses and so on. Furthermore, the thermal resistance and tensile strength of SWNT and PBO/SWNT were characterized. The results showed that SWNT contained many carboxyl and hydroxyl groups after acid treatment. The thermal resistance of the PBO/SWNT fibers was higher than PBO and the tensile strength was also improved by 20-50%.

Molecular dynamics simulations research on the effects of POSS on mechanical properties of polyethylene

Jun Li, Yi Sun, Fanlin Zeng

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The influence of the polyhedral oligomeric silsesquioxane (POSS) as pendant groups on polymer backbone has been drawn the attentions of the science field. In this paper, we investigate the mechanical properties of two kinds of polymers, polyethylene (PE) and PE-POSS, to elaborate the reinforcement mechanism by using molecular dynamics simulations. First, the atomistic models of PE and PE-POSS are built. Then the elastic constants are calculated via the stress and strain fluctuation method after the initial structure optimization. All the simulations are carried out at the temperature range 200-500K and 1 atmosphere under NPT ensemble (constant particle number, pressure and temperature). The volume-temperature (V-T) curves show that the melt temperatures of PE and PE-POSS are almost the same. It indicates that the POSS units have no effect on the melt temperature. However, below the melted temperature, the mechanical properties are reinforced by POSS units obviously. Based on the analysis of the potential energy, it is concluded that the variation of the carbon-carbon bond energy and the Coulomb energy introduced by the POSS units is the chief source to explain the enhancement of the mechanical properties of PE-POSS.

Characteristic of TiNi(Cu) shape memory thin film based on micropump

Huijun Zhang, Chengjun Qiu

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Shape memory thin films offer a unique combination of novel properties and have the potential to become a primary actuating mechanism for micropumps. In this study, a micropump driven by TiNiCu shape memory thin film is designed and fabricated. The micropump is composed of a TiNiCu/Si bimorph driving membrane, a pump chamber and two inlet and outlet check valves. The property of TiNiCu films and driving capacity of TiNiCu/Si bimorph driving membrane are investigated. By using the recoverable force of TiNiCu thin film and biasing force of silicon membrane, the actuation diaphragm realizes reciprocating motion effectively. Experimental results show that the film surface appears a smooth and featureless morphology without any cracks, and the hysteresis width ΔT of TiNiCu film is about 2-3°C, the micropump driving by TiNiCu film has good performance, such as high pumping yield, high working frequency, stable driving capacity, and long fatigue life time.

A three-phase confocal elliptical cylinder model for predicting the thermal conductivity of composites

Fuli Chen, Chiping Jiang

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A three-phase confocal elliptical cylinder model accounting for variations in fiber section shapes and randomness in distribution and orientation is developed for predicting the thermal conductivity of fiber reinforced composites. The representative volume element consisting of a fiber and a matrix elliptical ring is embedded in an infinite homogenous composite. Using the conformal mapping technique and the Laurent series expansions approach, an analytical solution for the thermal conductivities of composites is obtained. A comparison with other micromechanics methods such as the dilute, self-consistent and Mori-Tanaka models shows that the present method provides convergent and reasonable results for a full range of variations in fiber section shapes, for a complete spectrum of the fiber volume fraction. Numerical results are presented to discuss the dependence of the effective conductivities of composites on the fiber conductivity and aspect radio. The present solutions are helpful to analysis and design of such composites.

Stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy

Chengxin Lin, Linlin Liu, Deping Sun, et al.

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The paper presents the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy, namely the alloy causes positive/reverse ε martensitic transformation and accompanied by deformation in order to adapt the variation of the outside macroscopical stress and deformation. From XRD analysis, it is found that the stress-induced γ↔ε martensitic transformation and its reverse transformation would occur in Fe-Mn-Si shape memory alloy under the tension-compression stress and also validated the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy. In cycles of tension and compression deformation, the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloy can increase fatigue life of the alloy by reducing stress concentration, restraining plastics gliding deformation and delaying the formation and growing of microcracks. The fatigue fracture in Fe-Mn-Si alloy shows quasi-cleavage brittle rupture type.

A novel valveless micropump

S. M. Yuan, L. T. Yan, Q. Liu

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A new valveless micropump for controlling micro-flow rate was designed and fabricated using simple fabrication technology. The working principle of valveless micropump was analyzed based on Computational Fluid Dynamics (CFD) program ANSYS/Flotran. The construction of the valveless micropump using piezoelectric actuator as the servo actuator was proposed. In order to make full use of the kinetic energy, two inclusive chambers are actuated by one and the same PZT. The vibration modals and natural frequencies were obtained by means of FEM (Finite Element Method).Two most important parameters that affect flow rate of the micropump were examined, the input voltage and frequency. The experimental results indicate that the flow rates is linear to the driving voltage, the highest flow rate of 180μl/min is obtained when the pump is driven by a voltage of 225Vpp at a resonant frequency of 34 KHz. The flow rate of the micropump has a highly non-linear dependence on the frequency. The maximum flow rate is 110μl/min with an applied voltage of 125Vpp when the frequency is around the resonant frequency of 34 KHz, in good agreement with theory.

Three-dimension finite element analysis on coupling effect of piezoelectric ceramics in concrete slabs under the concentrated load

Chen Qu

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The piezoelectric ceramic has been one of structures extensively applied. Due to the complexity in its boundary condition and its stress state, the relevant researches on these carried out in traditional experimental ways have shown inefficiency and limitations. In view of this, the paper studies the piezoelectric ceramic's boundary condition and its stress state by setting up the three dimension finite models of piezoelectric ceramics in concrete slabs. The computer simulations are conducted. In the simulation, varied concentrated loads are applied and different buried depths of piezoelectric ceramics are considered. The block elements are adopted to simulate the concrete slabs, while the plane elements are used for the piezoelectric ceramics. Firstly, the stress distribution of the concrete slabs and that of the piezoelectric ceramics in slabs are derived from the computer nonlinear solver. Then piezoelectric properties of the piezoelectric ceramics in the stress field are simulated. And the equivalent circuit parameters of the piezoelectric ceramics under the varied concentrated loads are obtained. The results of the analysis show that three dimension finite element analysis is a convenient and reliable tool for studies on the coupling effect of piezoelectric ceramics in concrete slabs. The study offers references for the further three dimension finite element analysis on concrete structure stress monitoring with the use of piezoelectric ceramics in concrete slabs.

A nondestructive study on porosity content and fiber orientation in CFRP composite laminates using ultrasonic technique method

Je-Woong Park, Kwang-Hee Im, David K. Hsu, et al.

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It is found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites. The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head-to-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of composites by processing micrograph images of the laminate. The image processing method developed utilizes a free software package to process micrograph images of the test sample. The results from the image processing method are compared with existing data. Beam profile was characterized in unidirectional CFRP(Carbon fiber reinforced plastics) with using pitch-catch Rayleigh probes and the one-sided and two-sided pitch-catch techniques were utilized to produce C-scan images with the aid of the automatic scanner.

Photo-damage resistant and phase matching properties of double-doped In:Zn:LiNbO3 crystals

Yiran Nie, Rui Wang, Lijuan Min, et al.

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In:Zn:LiNbO₃ crystals have been grown by Czochralski technique. The infrared transmission spectra of the samples showed that the OH- absorption peak of In(3mol.%):Zn(3mol.%):LiNbO₃ located at about 3508cm^-1, while those of In(1mol.%):Zn(3mol.%):LiNbO₃ and In(2mol.%):Zn(3mol.%): LiNbO₃ located at about 3485cm^-1. The photo-damage resistant ability of the crystals was measured with the directly facula-distort observing method. The results showed that, when doped In³⁺ and Zn²⁺ concentration reached their threshold concentration, the photo-damage resistant ability of In(3mol.%):Zn(3mol.%):LiNbO₃ was two orders of magnitude higher than that of pure LiNbO₃. Second harmonic generation (SHG) experimental results showed that the phase matching temperature of In(3mol.%):Zn(3mol.%):LiNbO₃ was almost at room temperature, and their SHG efficiency was higher than that of Zn(7mol.%):LiNbO₃ and pure LiNbO₃.

Residual stress evaluation and fatigue life prediction in the welded joint by x-ray diffraction

Keun Bong Yoo, Kwon Tae Hwang, Jung Chel Chang, et al.

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In the fossil power plant, the reliability of the components which consist of the many welded parts depends on the quality of welding. The residual stress is occurred by the heat flux of high temperature during weld process. This decreases the mechanical properties as the strength of fatigue and fracture. The residual stress of the welded part in the recently constructed power plants has been the cause of a variety of accidents. The objective of this study is measurement of the residual stress and the full width at half maximum intensity (FWHM) by X-ray diffraction method and to estimate the feasibility of this application for fatigue life assessment of the high-temperature pipeline. The materials used for the study is P92 steel for the use of high temperature pipe on super critical condition. The test results were analyzed by the distributed characteristics of residual stresses and FWHM in x-ray diffraction intensity curve. Also, X-ray diffraction tests using specimens simulated low cycle fatigue damage were performed in order to analyze fatigue properties when fatigue damage conditions become various stages. As a result of X-ray diffraction tests for specimens simulated fatigue damages, we conformed that the ratio of the FWHM due to fatigue damage has linear relationship with fatigue life ratio algebraically. From this relationship, it was suggested that direct expectation of the life consumption rate was feasible.

Self-assembly of polystyrene nanoparticles induced by ice templating

Jia Yan, Zhanjun Wu, Li Tan

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An investigation was performed to develop a facile route, named as ice templating, for large scale of three-dimensional assembling of polystyrene nanoparticles. The organic nanoparticles were assembled into a macroscopic subject with sophisticated three-dimensional microstructure, induced by growing ice crystals in freezing process of particle suspension. By controlling freezing direction, freezing rate, and particle concentration in suspension, various interesting microstructures were prepared, including three-dimensional connected porous lamellas, bundles of ribbons, and fibers with uniform diameter (~1.5μm), high aspect ratio, and same orientation. Freezing direction is the key factor to control the assembling direction of particles, while, freezing rate and particle concentration are important parameters which affect morphology and size of microstructures. On the other hand, the route of ice templating has many advantages, including environmental friendly, low cost, high output and universality. Other materials, such as metal and semiconductor nanoparticles, could also be used in our platform for preparation of smart materials and structures. It is anticipated that by this simple approach, various functional nanoparticles would be efficiently assembled into macroscopic subject with sophisticated microstructures which offer synergistic, optimized properties of individual zerodimensional elements, and hence, the derived composite materials or structures could implement desired functions with better performance.

Synthesis, surface modification and ethanol sensing properties of Sb-doped SnO2

Jiarui Huang, Kun Yu, Anna A. Zhukova, et al.

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Sb-doped SnO₂ whiskers were prepared by thermal evaporation of mixture of SnO and Sb₂O₃ powders. And then the surface of the whisker was modified with the Au nanoparticles (Au NPs) by in situ reduction method. FE-SEM observations reveal that the synthesized products consist of a large number of whiskers. The Au NPs were homogeneously distributed on the surface of the whisker. The ethanol sensitive characteristics of single SnO₂ whiskerbased sensors have been investigated. These sensors show good sensitivity, rapid response and recovery. The response and recovery time of the sensor is about 38-45 s and 125-150 s, respectively. It is found that the working temperature of the sensor decreases after the surface of Sb-doped whiskers modified with Au NPs. Compared to the unmodified Sbdoped SnO₂ whisker, Au NPs modified Sb-doped SnO₂ whisker exhibits greatly improvement of sensitivity which could be explained by the catalytic action of Au NPs. These results indicate that the Au NPs modifying the surface of SnO₂ whiskers is important for improving its sensitivity and lowering the working temperature. This is the first step towards fundamental understanding of single-crystalline tin oxide whiskers for sensor applications, which could lead to integration in real devices.

Second International Conference on Smart Materials and Nanotechnology in Engineering

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