Electron beam Moeller polarimeter at Hall A, TJNAF
Author(s):
Jean-Ping Chen;
Eugene A. Chudakov;
Daniel S. Dale;
Ashot Gasparian;
Alexander V. Glamazdin;
Victor G. Gorbenko;
Leonid G. Levchuk;
Sirish K. Nanda;
Roman I. Pomatsalyuk;
Arun Saha;
Pavel V. Sorokin
Show Abstract
As a part of the spin-physics program at the Jefferson Laboratory (TJNAF), a Moller polarimeter has been developed to measure the polarization of electron beam of energies between 0.8 and 6.0 GeV. A unique design of this polarimeter was developed using a set of three quadrupole magnets that provide an angular selection of the Moller electron pairs, a dipole magnet for their energy analysis, an a rotatable target system. The test procedure and commissioning of the polarimeter are presented. The results of beam polarization measurements in long-term physical experiments, the correlation for the three-beam accelerator mode and other effects are discussed.
Electron spin polarimeters based on the exchange asymmetry in ferromagnetic layers
Author(s):
Nicolas Rougemaille;
C. Cacho;
Henri-Jean Drouhin;
G. Lampel;
Y. Lassailly;
Jacques Peretti;
A. Schuhl
Show Abstract
We determine the polarization vector of a spin-polarized electron beam emerging from a ferromagnet and we study the particular case of two uncoupled ferromagnetic layers with in-plane magnetizations in a perpendicular configuration. We show that the transmitted intensity depends on the three components of the primary polarization and we propose to use such a structure as a convenient spin detector for low- energy electrons.
CPT invariance examination in quantum electrodynamics bound systems and production of a muonium or antimuonium in the scattering of electrons or positrons on nuclei
Author(s):
Enver A. Choban;
Georgi A. Kazakov
Show Abstract
In the present work the possibility of CPT invariance examination of the bound states in quantum electrodynamics (QED) is considered. For this purpose, we calculated the cross section for the processes e- + Z yields Z + M0 + (mu) - and e+ + Z yields Z + M0 + (mu) +. The differential cross section via the invariant mass of (M0, (mu) -)- system and the total cross section of the above processes in the framework of QED are obtained. Also, we considered the registration method of muonium and antimuonium due to the oscillation of basic and exited states on the decay curves. The admixture of the exited muonium to the final state is determined.
New superlattices for spin-polarized electron sources
Author(s):
Yuri A. Mamaev;
Arsen V. Subashiev;
Yuri B. Bolkhovityanov;
Aleksandr I. Toropov;
Askhat K. Bakharov;
Mikhail A. Revenko;
Alexander M. Gilinskii;
Yuri P. Yashin;
Anton N. Ambrajei;
Alexander V. Rochansky
Show Abstract
We report the results on polarized electron emission from a new strained InGaAlAs/AlGaAs superlattices with an enlarged band gap, modulation doping and an optimized last GaAs layer. The yield and polarization measurements show that this structure delivers more than 0.1% quantum yield at the maximum of the polarization spectrum, the maximum polarization degree being equal to 80% at room temperature. These values present a 10-fold improvement in the quantum yield over that of the previously designed InAlGaAs-AlGaAs superlattices at the same vacuum conditions.
Improved strained GaAsP photocathodes
Author(s):
Yuri A. Mamaev;
Arsen V. Subashiev;
Yuri P. Yashin;
Anton N. Ambrajei;
Alexander V. Rochansky
Show Abstract
The parameters of spin-polarized electron photocathode based on strained layer GaAs0.95P0.05/GaAs0.7P0.3 structure have been improved on the base of X-ray, Raman and polarized photoluminescence studies of such structure. The polarization maximum value 86% in conjunction with Y equals 0.16% makes such cathodes one of the best no matter where.
Charge limitation effects in emission from semiconductor photocathodes at inhomogeneous excitation
Author(s):
Boris I. Reznikov;
Arsen V. Subashiev
Show Abstract
Photoemission from a semiconductor with negative electron affinity surface is investigated theoretically for the case of local excitation regime and Gaussian distribution of the light intensity over a sample surface. While the maximum emission current is an exponential function of the negative electron affinity value, the inhomogeneous intensity distribution results in smoothed dependence of the emission current on the light intensity in the region of maximum current. The relaxation processes to the stationary emission and the cathode restoring time are found to be less sensitive to light non-homogeneity due to photovoltage level over the surface.
Weak localization of electrons by quasi-elastic scattering
Author(s):
Victor V. Dubov;
Vadim V. Korablev
Show Abstract
New type of weak localization of electrons scattered quasielastically from disordered media is studied. This type of weak localization leads to modification of the angular spectra of electrons scattered quasielastically. The results obtained can be applied to the detail study of the effects of weak localization at small energy transfer and for determination of the parameters of near crystal surface region.
Effect of surface and bulk electrons on the surface potential formation
Author(s):
Vadim V. Korablev;
Victor V. Dubov
Show Abstract
A study is carried out for the scattering of low-energy electrons near crystal surface due to electron-electron interaction. It is shown the necessity to introduce into the electrons surface scattering considered the influence of the surface-state electron band. The method in question can be used for detailed description electron-scattering measurements and to obtain information regarding the surface carrier density, effective mass, and conductivity. The realized investigation and calculations are useful in construction and producing of modern high technology, primarily nanotechnology devices.
Spontaneous spin polarization in 1D electron gas
Author(s):
Ivan A. Shelykh;
Nikolai T. Bagraev;
Vadim K. Ivanov;
Leonid E. Klyachkin
Show Abstract
The results of theoretical analysis of quasi one-dimensional electron gas within the Hartree-Fock approximation are presented. Ground state energies of completely polarized and non-polarized states are calculated at T equals 0. A formation of spontaneously spin-polarized state at low linear concentration of electrons and its transformation into non- polarized state as concentration grows are discussed.
Feshbach resonances in Si-, Ge-, and Sn- negative ion photodetachment
Author(s):
Vadim K. Ivanov;
Galina Yu. Kashenock;
Constantin V. Lapkin
Show Abstract
A new improved study of resonance features has been made in the photodetachment process from such strong correlated system as negative ions with np3 half-filled shells. The photodetachment cross sections from two outer shells of Si-, Ge- and Sn- negative ions have been calculated with account of many electron correlations. The formation and autodetachment of the quasi-bound 'nsnp4' states revealed themselves as a very sensitive interference structure in the cross section.
Numerical integration of quantum hydrodynamic equations involving self-consistent electric field and isothermal pressure for one-dimensional stationary electron motion
Author(s):
Andrey L. Sanin;
Konstantin V. Khodosevich;
Nikolay A. Krylov
Show Abstract
Quantum hydrodynamic equations jointly with the Maxwell divergent equation for an electric field were applied to investigate the one-dimensional stationary isothermal motion of electron fluid. This model system of equations allows study the spatial oscillations (or structures) of the hydrodynamic variables when the electron isothermal pressure is taken into account. We investigated the different regimes of the motion corresponding the weak spatial oscillations about the equilibrium homogeneous state and intensive oscillations. The intensive oscillations were generated at the determined boundary electric fields and the threshold quantities of coordinates. Impulses of the quantum potential had different heights and very large values. In these cases the chaotic oscillations take place. The typical patterns of spatial oscillations, the Fourier-spectra are represented in this paper.
Nernst-Ettingshausen effect in the hopping condition range: experiment and theory for Pb1-xSnxTe doped with In
Author(s):
Sergei A. Nemov;
Yuri I. Ravich
Show Abstract
In this contribution we report on Nernst-Ettingshausen effect, electrical conductivity, thermoelectric power, and Hall effect in the temperature range from 77 to 400 K for solid solution (Pb0.78Sn0.22)Te with In dopant impurity. Nernst-Ettingshausen coefficient Q exhibits properties unusual for IV-VI materials. It has positive sign and decreases rapidly with an increasing temperature. A theoretical model, taking into account hopping conductivity along strongly localized electronic states of In impurity is suggested. The model gives a good agreement with experimental data.
Light emission from erbium- doped nanostructures embedded in silicon microcavities
Author(s):
Nikolai T. Bagraev;
Alexei D. Bouravleuv;
Wolfgang Gehlhoff;
Leonid E. Klyachkin;
Anna M. Malyarenko;
Margarita M. Mezdrogina;
Vladimir V. Romanov;
Alexander P. Skvortsov
Show Abstract
We present the findings of high efficient light absorption in self-assembled quantum wells (SQW) embedded in silicon microcavities that exhibit a distributed feedback identified by the FIR transmission spectra. The photo and electroluminescence from SQW is found to be enhanced in the range of the Rabi splitting. The intraband hole transitions are shown to give rise to a fast energy transfer into the d- shell transitions of the center incorporated into the microcavity which is caused by strong sp-d mixing in built- in electric field and revealed by the intracenter emission. Besides, high efficient Er3+-related 4I13/2 $ARLR 4I15/2 absorption and emission a re observed from self-assembled quantum wells (SQW) embedded in silicon microcavities. The microcavities of this art are prepared by the short-time diffusion of boron into the Si(100) wafer doped with erbium. The intraband electron transitions accompanied by tunneling through strongly coupled SQW series are found to excite the 4I13/2 yields 4I15/2Er3+-intracenter emission that is enhanced in the range of the Rabi splitting revealed by the transmission spectra.
Experimental observation of Bose condensation in high-temperature superconductors
Author(s):
Nikita P. Seregin;
Pavel P. Seregin;
Farit S. Nasredinov;
Hazem M. Ali;
Vladimir P. Volkov
Show Abstract
Emission Mossbauer spectroscopy on 67Cu (67Zn) and 67Ga (67Zn) isotopes was used to show that for the superconductors Nd1.85Ce0.15CuO4, La1.85Sr0.15CuO4, and Tl2Ba2Ca2CuO8 in the temperature range T > Tc the temperature dependence of the center of gravity S of the Mossbauer spectrum is determined by the Second-order Doppler shift, while in the range T < Tc the Bose condensation of Cooper pairs influences the value of S (here Tc is the superconducting transition temperature). The spatial non- uniformity produced in the electron density by a Bose condensate of Cooper pairs was observed for La1.85Sr0.15CuO4.
Magnetic properties and luminescence of Yb-related centers in InP
Author(s):
Nikolai T. Bagraev;
Vladimir V. Romanov
Show Abstract
We present the first findings of the magnetic susceptibility measurements that identify the spin polarons formed by the exchange interaction of the Yb-related centers through the shallow donor electrons in InP:Yb. The spin polarons are found to be localized on the clusters that consist of the Yb-related centers because of inhomogeneous distribution of dopants during the crystal growth. The influence of the internal magnetic fields created by spin polarons on the photoluminescence assigned to the internal 4f-4f transitions 2F5/2 yields 2F7/2 of Yb3+ (4fd3) ions is also discussed. Zeeman measurements that are in a good agreement with the photoluminescence spectroscopy data further support the model suggested for spin polarons.
Search for new long-wavelength phosphors
Author(s):
Alexander S. Potapov;
Sergei S. Mikhrin;
Alexander N. Mishin;
Piotr A. Rodnyi
Show Abstract
At present there is a great interest in phosphors producing high light yield in long wavelength region (550 - 1050 nm). They have a lot of application in different fields of physics such as laser physics, medical physics and tomography, semiconductor physics and others. The main reason of that is the emission spectra of these materials match well to sensitivity of silicon photodiodes. In this paper we present the spectral and decay time characteristics of some long-wavelength phosphors (such as AIIBVI, Al2O3:Ti, some molybdates, Gd2O2S and Y2O2S doped with Tb, and some others). The process of energy transfer to emission centers are considered. In most cases, types of the centers responsible for radiative transitions were determined.
Influence of native defects on formation absorption spectra of InP[Fe] crystals
Author(s):
Vladimir P. Saveliev;
Mikhail A. Pogarsky;
Vladimir V. Romanov;
Alexander E. Vasiliev;
Sergei A. Starovoitov
Show Abstract
Optical absorption measurements have been carried out on semi-insulating and n-type InP:Fe, InP:Sn. The optical absorption spectra of InP:Fe contain several broad structure-free bands due to charge conduction between Fe ions and band states. However, in the case of InP high doped with Sn, the same absorption band with threshold at 0.64 eV was detected. It is usually attributed to the excitation of electrons from the ground state of one electron trap Fe2+ to the (Gamma) -point conduction band minimum. The spectral photo-ionization cross-section approximation is made on the basis of a phenomenological model for an admixture center with an attracting (delta) -potential in the vicinity of the admixture and Coulomb potential at large distances. A weak electron-phonon interaction is taken into account. High quality of approximation was found. The analysis of the absorption spectra and ionization energies allows to expect that absorption zone with the threshold 0.64 eV occurs due to deep ionized acceptors that are charged indium vacancies.
Computer simulation of copper precipitation in alpha-Fe under neutron irradiation
Author(s):
Evgeni E. Zhurkin;
Olga Ya. Khrushcheva;
Yaroslav A. Berdnikov
Show Abstract
In this contribution we report on our studies of the behavior of copper as one of the typical substitutional impurities in rector vessel steels under neutron irradiation using methods of computer simulation in atomic scale. The properties of alpha-iron with small amount of copper impurity were studied with Metropolis Monte-Carlo method applied for canonical ensemble at constant pressure. For exclusion of boundary effects we considered simulation boxes with periodic boundary conditions. Initial distribution of copper substitutional impurity was chosen uniformly all over the box volume. It was shown, that at both reactor and room temperatures copper has a tendency to form precipitates in pure iron. If we introduce in the simulation box radiation defects, formed by PKA cascades, copper atoms also tend to precipitate, forming stable complexes with vacancy clusters. After introducing an edge dislocation in the simulation box (Burgers vector is 1/2 <100>) the segregation of copper into the area of a dislocation core is observed.
Dynamics of eutectic microstructure during phase nucleation and phase termination: phase-field model computer simulations
Author(s):
Dmitri I. Popov
Show Abstract
Computer simulation using two-dimensional phase-field method was performed in order to observe the evolution of the composition field and the microstructure of lamellar eutectics caused by change in freezing rate. Phase nucleation, phase termination, and migration of the 3- phase junction were studied to elucidate the role of each in micro structure changes. These phenomena are complex due to the interplay between interface kinetics, the composition field, and the phase fraction. When the freezing rate is increased, the supersaturation in front of lamellae increases, causing formation of depressions, followed by nucleation, instability, and motion of the 3-phase junction. Eventually the microstructure becomes stable. With a decrease in freezing rate, instability develops that changes the local growth direction and provokes changes in lamellar width followed by elimination of some lamellae. The time scales for phase nucleation and phase termination were also estimated assuming the overwhelming importance of lateral diffusion. The model explains the time scale-lamellar microstructure parameter dependence provided that the growth rate increases with a constant acceleration, and the volume fraction does not change during an increase in the freezing rate until nucleation occurs.
Monte Carlo simulations of hydrocarbon oligomeric chains: carbon skeleton cross-sectional areas
Author(s):
Alexander L. Rabinovich;
Pauli O. Ripatti
Show Abstract
Monte Carlo (MC) computer simulations of hydrocarbon chain molecules were carried out; variations of all torsion angles of the chains were considered to be continuous from 0 to 360 deg in contrast to the rotational isomeric scheme. The MC method is applied to an investigation of different molecule properties such as carbon skeleton cross sectional areas and their temperature coefficients at temperatures 278 - 298 K; more than 200 unperturbed linear hydrocarbon chains CH3- (CH2)x-(CHequalsCH-CH2)y- (CH2)z-CH3 of 14 - 22 carbons with 1 - 6 methylene-interrupted cis- double bonds were studied. The molecule-fixed coordinate system with the axes along principal axes of inertia of each molecule conformation was used. A close relationship between these characteristics and the structure of the molecules was elucidated.
Molecular dynamics study of monolayers consisting of polyunsaturated diacylglycerolipids
Author(s):
Vasilii V. Kornilov;
Alexander L. Rabinovich;
Nikolay K. Balabaev
Show Abstract
Investigation of six different monolayers of diacylglycerolipid molecules have been carried out using molecular dynamics technique. The molecules of five monolayers contained from one to six cis double bonds in one of the hydrocarbon chains and one monolayer consisted of saturated lipid molecules. The area per molecule and the temperature of thermostat were corresponding to a fluid phase. The time of each computation was 1000 ps. Results of the simulations are compared with available experimental data and with other recent simulations of similar systems.
Comparative investigation of lipid membrane systems
Author(s):
Alexander L. Rabinovich;
Pauli O. Ripatti;
Nikolay K. Balabaev;
Frans A. M. Leermakers
Show Abstract
Molecular dynamics (MC) simulations of bilayers consisted of (1) phosphatidylcholines (PC) and (2) diacylglycerolipids (DG), and lattice-based molecular-level self-consistent field (SCF) calculations of the model lipid bilayers were carried out. Lipid molecules with acyl chains of 18:0/18:0, 18:0/18:1(omega) 9cis, 18:0/18:2(omega) 6cis, 18:0/18:3(omega) 3cis, 18:0/20:4(omega) 6cis, 18:0/22:6(omega) 3cis were investigated. The C-H and C-C bond order parameter (-SCH, SCC) profiles of the hydrocarbon tails, the bond orientation distribution functions, the root-mean-square values of the positional fluctuations of the lipid chain carbons were calculated. The theoretical results are compared with the available experimental data. The main qualitatively characteristic features of the properties of bilayer with lipid chains of a given chemical structure show up in both the MD and in the SCF results. The key physical properties of lipid bilayers that are composed of unsaturated lipids are discussed from a theoretical perspective.
Self-organization of protein with helical domains
Author(s):
Zakhar M. Frenkel;
Alexander I. Melker
Show Abstract
In this contribution, we report on a study of the self- organization of isolated polypeptides. The process is computer simulated by the method of molecular dynamics. We observed that the helical structures have a very impotent role in the protein self-organization. We have found conditions under which such structures to be stable. The process and result of self-organization under these conditions were sharply different from others, unable to maintain the helical structures. The structures obtained have a strong resemblance to the native conformations of the corresponding real proteins in a case of proteins composed by helical domains.
Nucleation of SiC on Si and their relationship to nano-dot formation: I. Experimental investigations
Author(s):
F. Scharmann;
Joerg Pezoldt
Show Abstract
Using in situ reflection high energy electron diffraction (RHEED), ex situ atomic force microscopy (AFM) and transmission electron microscopy (TEM) the nucleation behavior of silicon carbide on silicon during the interaction of elemental carbon with silicon surfaces was investigated. The critical island sizes and the growth mechanisms leading to nano-dot formation were determined.
Nucleation of SiC on Si and their relationship to nano-dot formation: II. Theoretical investigation
Author(s):
Kirill L. Safonov;
Dmitri V. Kulikov;
Yuri V. Trushin;
Joerg Pezoldt
Show Abstract
The processes of SiC clusters growth on Si(111) surface has been investigated theoretically. The SiC cluster formation and growth on Si surface stimulated by deposition of elemental carbon onto Si(111) with molecular beams have been studied by applying the kinetic equations (co-called rate equations) method. The simulated cluster size distribution function obtained within this method appeared to be in reasonable agreement with the experimental data. Obtained cluster capture rates agree with KMC investigations.
Computational study of the influence of oxygen vacancies on the polarization in irradiated and annealed PLZT ceramics
Author(s):
Dmitry A. Lesnyh;
Dmitri V. Kulikov;
Yuri V. Trushin;
Roland Bittner;
Karl Humer;
Harald W. Weber;
Andris R. Sternberg
Show Abstract
A physical model for the oxygen defect evolution in PLZT ceramics under neutron irradiation and annealing is proposed. The influence of the defect system on the polarization of these materials has been investigated. The influence of the La content on the material structure and the oxygen defects has been taken into account. Satisfactory agreement between the theoretically estimated oxygen defect concentration after irradiation and annealing and the experimentally determined polarization has been obtained.
Computer simulation and SIMS profiling of Zn implantation in A3B5 semiconductors
Author(s):
Boris J. Ber;
A. P. Kovarsy;
Alexander A. Schmidt;
Yuri V. Trushin;
Evgeni E. Zhurkin;
Fedor A. Krusenstern
Show Abstract
The method for the determination of the impurity displacement threshold energy in semiconductor heterostructures is further developed. New experimental samples for this method are proposed. Important parameters for the samples are defined. Also, simulation of the sputtering of wide impurity depth profiles is carried out. Improved values for the penetration lengths of Zn atoms with different impact energies in GaAs were found.
Irradiation of silicon with relativistic electron beams by Monte Carlo many-body interaction model of radiation damage
Author(s):
Zurab B. Basheleishvili;
Alexander I. Melker;
Sergei N. Romanov
Show Abstract
In this contribution the Monte Carlo method is used to compute the distributions of vacancies with depth in silicon irradiated by relativistic electron beams. The model of N- body interactions in a collision cascade that advances in isotropic continuum was incorporated into the Monte Carlo scheme of successive collisions to obtain depth distributions of vacancies, interstitial atoms, and vacancy clusters produced by 1 - 10 MeV electrons in silicon. The model developed permits to obtain the statistically averaged space distributions of defects and thermal spikes. Besides the model explains the yield of clusters during sputtering. Defects formed by (delta) -electrons and primary knock-in atoms are also taken into account.
Many-body interactions incorporated into a binary collision model of radiation damage in solids
Author(s):
Alexander I. Melker;
Sergei N. Romanov
Show Abstract
In this contribution we consider the model of N-body interactions in a collision cascade that advances in isotropic continuum. The model developed includes as a special case the well-known binary collision models and takes into account formation of athermal vacancy clusters and thermal spikes. It permits to obtain the statistically averaged space distributions of defect and thermal spikes. Besides the model explains the yield of clusters during sputtering. The model can be incorporated into any Monte Carlo scheme of individual collisions to obtain depth distributions of vacancies, interstitial atoms, and vacancy clusters produced by energetic particles.
Phase-shifting digital holography with compensation of aberrations
Author(s):
Sergio De Nicola;
Pietro Ferraro;
Andrea Finizio;
Simonetta Grilli;
Riccardo Meucci
Show Abstract
Off-axis holograms recorded with a CCD camera are numerically reconstructed in amplitude by calculating through the Fresnel-Kirchhoff integral. A phase-shifting Mach-Zehnder interferometer is used for recording four- quadrature phase-shifted off-axis holograms. The basic principle of this technique and its experimental verification are described. We show that the application of this algorithm allows for the suppression of the zero order of diffraction and of the twin image and that the contrast of the reconstructed images can be further enhanced by digital compensation of the aberrations introduced by the holographic recording system.
Portable holographic camera for manufacturing high-quality volume reflection holograms
Author(s):
Sergey N. Gulyaev
Show Abstract
The portable holographic camera for manufacturing high- quality volume reflection holograms reconstructed optically by white light has been designed. The holographic setup comprises a low-power He-Ne laser. The design of the holographic camera is the development of the holographic sandbox technique. High-silica sand is used for mechanical and temperature stabilization. A rigid mounting of an object and photographic plate is not provided for the construction of the holographic camera. This makes possible the high rate of photographic plates changing. The processing arrangement is designed for manufacturing several tens of high-quality reflection holograms in one operating cycle. The portable holographic camera has been used very successfully for making holograms of museum objects.
Fluctuational self-defocusing and maximal brightness of laser pulses
Author(s):
Nikolay E. Galich
Show Abstract
It is shown that the negative nonlinearity of the refractive index leads to the selection of the optimal self-defocusing scales and the optimal (nonlinear) coherence radius of laser radiation pulses. This ensures the minimal beam divergence and creates a granular fluctuating structure of the radiation with the maximum radiation brightness. The results are compared with the available experimental data for laser radiation pulses in liquids and gases.
Numerical model for second-harmonic generation by a laser pulse with nonlinearly rotating polarization
Author(s):
Alexander V. Kir'yanov
Show Abstract
The design of the frequency converter is proposed which exploits laser pulses with changed state of polarization. The use of such pulses as a fundamental wave source of an extra-cavity doubling crystal is shown to result in the large conversion efficiency and to monitor the shape of the generated harmonic pulse. Our study demonstrates the converter to be capable of pulse shortening due to the temporal variation of the direction of polarization of the pulse at the fundamental wavelength which occurs in the same device.
Modeling an all-fiber low-threshold erbium laser passively Q-switched witha Co2+:ZnSe crystal
Author(s):
Alexander V. Kir'yanov
Show Abstract
Numerical modeling of a cw-pumped all-solid-state fiber erbium laser passively Q-switched with a Co2+:ZnSe crystal is proceeded for the first time to our knowledge. Features of the laser dynamics are investigated from a super-luminescence regime via passive Q-switching mode to cw operation. The basical parameters of the passive Q-switching mode - giant pulses' repetition rate, duration, energy, and peak power - are calculated numerically depending on the laser pump power. Results of the modeling are shown to be in a quite-well agreement with the experimental realization of the laser.
Vibrosensor of new generation
Author(s):
Baghrat V. Melkoumian
Show Abstract
We create vibrosensor of new generation based on linear baghrometer. The same vibrosensor is available for precise measurement of amplitude, frequency and phase of vibration in wide range. Full consent of the proposed theory with experimental results is provided. Semiconductor laser based vibrosensor is presented.
X-ray stress analysis of oxidized Zr-based alloys
Author(s):
Galina Gosmanova;
Ivo Kraus;
Nikolaj Ganev
Show Abstract
The results of X-ray diffraction analysis of macroscopic stresses in oxide layers and substrate of zirconium alloys are presented in this contribution. Stresses were studied on the tubular specimens of three types of alloys:Zr1Nb, low tin Zircaloy-4 and Zr-Nb-Sn alloy (ZIRLO) which were simultaneously exposed for various time in four environments: 360 degree(s)C water, 360 degree(s)C water with 70 ppm Li as LiOH, steam at 400 degree(s)C and steam at 450 degree(s)C. The courses of compressive stresses (sigma) vs. oxide thickness are quantitatively different for two types of alloys in all of environments used. The courses for ZIRLO seem to be less dependent on corrosion conditions. In the range of the large oxide thicknesses (> 10 micrometers ) two cases were observed: (1) the value of stress falls down to zero, (2) the values stay on some levels which differ for different alloys and environments. Only tensile residual stresses were indicated within substrate of all samples investigated. Microstructure characteristics (crystallite size and lattice strains) were evaluated for oxide layers and the metal underlying.
Computer simulation of line profile and data processing in diffraction experiments
Author(s):
Tatiana Gurova;
Joel R. Teodosio;
Joaquim T. Assis;
Vladimir I. Monin;
Yuri F. Titovets
Show Abstract
Data processing of a line profile is one of the most important procedures in a diffraction experiment. The main problem is connected with the presence of K(alpha 1) and K(alpha 2) wave components in X-ray radiation that produces the principal errors while determining the angular position or width of a diffraction line. By using computer methods in data processing, it is possible to realize effectively the Rachinger method of separation of K(alpha 1) and K(alpha 2) components. In this paper, computer simulation of diffraction profiles was used to analyze the possibilities of the Rachinger method. A separation criterion based on searching true principal parameters, namely the distance and intensity interrelation between K(alpha 1) and K(alpha 2) components, was proposed. The separation method is incorporated into the data processing for a portable diffractometer developed by authors from Polytechnical Institute (UERJ).The data processing includes control of an experimental procedure for the case of macro and microstress measurements.
Design and simulation of microelectromechanical transducer using uncoupled finite element models
Author(s):
Ilya Valerievich Avdeev;
Michael R. Lovell;
Dipo Onipede
Show Abstract
Due to the increased complexity demands and precision requirements of microelectromechanical systems (MEMS), there is a need for reliable and accurate simulation methods to model physical behavior involved. In particular, the design of improved MEMS transducers can be facilitated by simulating the interaction between the electrostatic and structural domains associated with these devices. In this work, several computational mechanics issues involving electrostatic and structural coupling for MEMS are presented and discussed, including the trade-off between cost and accuracy. Several uncoupled finite element (FE) models are presented and simulated to optimize the design and fabrication of a combdrive based electrostatic microactuator. The benefits and limitations of these uncoupled FE models are then discussed. The asymmetric structural response of the combdrive actuator is further analyzed and a simplified closed-form analytical model is presented for a basis of comparison for the FE results. Based on differences between FE and analytically calculated values, the contribution of fringing electrostatic fields to the mechanical forces produced in the combdrive are discussed.
Computer simulation of transformation of pulse pressure by the mechanical concentrator in technological devices such as an electromagnetic hammer
Author(s):
Alexander V. Mamutov;
Viatcheslav S. Mamutov
Show Abstract
In technological devices such as an electromagnetic hammer, a mobile part in form of a mechanical concentrator transforms impulse pressure of an electromagnetic field to an effort of stamping. The two-dimensional wave transformation of impulse pressure in an elastic concentrator with boundary conditions, conforming magnetic- pulse stamping by polyurethane, was reviewed. The implicit finite-difference algorithm of a numerical solution was designed and program was implemented. For the description of transformation of impulse pressure in the concentrator, a complex of dimensionless parameters was offered On the basis of mathematical experiment, the transformation efficiency of pulse pressure by a mobile part was determined.
Model for the bit-rock interaction analysis
Author(s):
Vladimir A. Palmov;
Yury M. Vetyukov
Show Abstract
In this report a model for drilling response of the so- called drag bits (or PDC bits) is presented. Forces acting on a single cutter are supposed to be known. Discrete and continuous cutters distribution over the bit surface are considered. Both lead to similar relations between the bit kinematics characteristics and the force factors acting on it. While the bit penetration rate into the rock is small, the force and the torque are shown to depend linearly on the ratio between the bit transitional and rotational velocities (the depth of cut per revolution). Particular cases of the bit shape are compared.
Finite element vibration analysis of tibia fixed by Ilizarov apparatus
Author(s):
Leonid B. Maslov;
Alexey L. Severin
Show Abstract
Dynamic simulation of the biomechanical system consisting of the human tibia bone and external holding structure as the Ilisarov apparatus is considered. The finite element method implemented as the program code MechanicsFE3D_VEO on the basis of 20-nodal isoparametric elements is utilized. The numerical vibration analysis has allowed defining both the lowest resonance frequencies and forms of oscillations and amplitude-frequency characteristics of the system in the various points on the surface of the bone and holder. The obtained results can be used as theoretical fundament to developing resonance methods for physiological state diagnostics of the regenerating osseous tissue in fracture zone.
Radial displacements of granular medium surface due to a constant load
Author(s):
Alexander N. Nezlobin;
Oleg I. Zayats
Show Abstract
The dynamic of radial displacements of the surface bounding a half space filled by Kandaurov medium caused by axisymmetric loading is under investigation. The results are obtained for a medium possessing finite values of the sound velocity and of the coefficient of internal friction in Voigt's model.
Surface wave propagation in a granular medium
Author(s):
Alexander N. Nezlobin;
Oleg I. Zayats
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In this contribution we solve the classic Lamb's wave problem for a granular medium. The surface displacements of a granular half-space resulting from a harmonic point force are the subject of investigation. We have found analytical solutions in several cases: (1) quasi-elastic wave in the medium free of internal friction, (2) anelastic wave in case of the infinite sound velocity, (3) anelastic longitudinal wave in case of the finite sound velocity.
Deformation mechanisms in modified polystyrene studied by high-voltage electron microscopy
Author(s):
Elena M. Ivan'kova;
Rameshwar Adhikari;
Goerg H. Michler
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Correlation between morphology and deformation behavior of general purpose polystyrene (GPPS) modified by blending with poly(styrene-b-butadiene-b-styrene) (SBS) star block copolymer based on the results from high voltage electron microscope (HVEM) is reported. It is shown that increasing volume fraction of rubber in the blends leads to enhanced ability of the samples to attain greater elongations at break indicating much more ductile behavior as compared with pure GPPS.
Model of plastic deformation of austenitic titanium-nickel
Author(s):
Andrew D. Bregan;
Alexandre E. Volkov
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The ways of the account of the plastic deformation of titanium-nickel mono- and polycrystals are considered. It is shown that a good description of the dependence of the yield limit on the orientation of the tension axis of a single crystal specimen can be achieved with the help of a condition of plastic slip, which takes into account the dependence of the flow stress on the stress tensor component acting on the shear plane in the direction perpendicular to the slip direction. For the calculation of polycrystal deformation the satisfactory conformity with an experiment can be received with the use of a model based on the classical Schmid law assuming the isotropy of the plastic slip on a shear plane.
Development of residual stresses in shape memory alloys under thermomechanical cycle loadings
Author(s):
Teodor M. Breczko;
Krzysztof Kus
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In this paper the experimental measurement results of the residual stresses in shape memory alloys (SMA's) are discussed. The experimental data are based on the investigation of the changes in root-mean-square (RMS) micro-strains and size of coherent blocks. The study was performed on the samples of Ni50,6Ti49,4 alloy that were subjected to cyclic thermo-mechanical loading. To induce reversible martensite transformations in the material, the external loading was used with subsequent data recording using x-ray method. The results of experimental measurements of the RMS micro-strains and coherent block sizes in austenite phase are presented. Based on the experimental data the computer simulation results are presented. Experimental and theoretical results have shown that the changes of structural parameters can be helpful for evaluate of functional characteristics of NiTi alloys.
Plastic deformation model incorporating coordination of grains in a polycrystalline aggregate
Author(s):
Natalia Yu. Ermakova;
A. A. Zisman;
Nikolai Yu. Zolotorevskii
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A new model is proposed accounting for spatial coordination of grains in a polycrystalline aggregate. The model bridges a gap between ordinary simplified approach to the simulation of polycrystal deformation and complicated FEM analysis. The model provides better prediction of cold rolling texture of f.c.c. metals than widely used Taylor model.
Low-angle boundary structures in nanoparticles embedded into elastically isotropic matrixes
Author(s):
Eugene B. Baturin;
Anna L. Kolesnikova;
Ilya A. Ovid'ko
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The model for misoriented nano- and micro-crystalline inclusions in composite materials is proposed. Low-angle misorientation boundaries of inclusions are modeled by the arrays of rectangular dislocation loops. The energy of these boundaries for individual nanocrystallite and the cluster of nanocrystallites is determined in dependence of grain boundary misorientation.
Statistical analysis in MRSM approach of computing and experimental results for integrated circuit technology
Author(s):
Alexander A. Kouleshoff;
Wieslaw B. Kuzmicz;
Viktor S. Malyshev;
Vladislav V. Nelayev;
Viktor R. Stempitsky
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With increasing integrated circuit packing density, manufacturing processes are becoming more and more complex and tolerances of process parameters more critical for production yield and product reliability, and thus the economic viability of the integrated circuit (IC) manufacturing. Therefore statistical many-factorial IC technology design and optimization becomes more and more important. Modified Response Surface Methodology (MRSM) had been proposed for the approximation of computer simulation results and natural experiments. Here we present next step and results for the one important problem in statistical analysis of integrated circuit technology when we have a set of incorrect experimental data. Input data-base for the analysis was obtained by means of natural experimental results provided in the real conditions of integrated circuit manufacturing. Detailed inspection for adequacy criterions of statistical results was performed and illustrated duly.
Software united cycle for simulation of static operation modes of power plants
Author(s):
Sergei N. Romanov;
Anatoly G. Kutakhov;
Konstantin S. Romanov
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In this contribution we report how to optimize the structure and composition of a heat-and-power object. This object is represented as a graph, the elements of equipment correspond to its nodes, flows of working media to its arcs. The mathematical model of each node is based on the equations of material and heat balance. The thermodynamic state of the working media is described by the conventional equations acknowledged all over the world. The system of non-linear equations, which describes the object, is supplemented by assignment of several parameters determining the operation mode.
Stereo visualization of model of gas dynamic process in combustion chamber of jet engine
Author(s):
Vladimir M. Degtyarev;
Michael N. Gusev
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In this report we describe stereo visualization of a model of gas dynamic process in the combustion chamber of a jet engine. We use the geometry of the second range surfaces for building of a stereo image of the combustion chamber under construction and the geometry of point in space (each elementary volume equals to voxel) for building of a stereo image of combustion process. Program (Visual C++ 6.0) draws images fore each eye and provides their viewing on a monitor so that using of stereo glasses gives the sense of volume. Moreover, due to the effect of transparency we have the opportunity to see not only out side, but also inner lays of the model that makes possible to observe the development of the process in the whole volume immediately. The investigated parameters such as density, temperature and pressure can be depicted. We plan to use asynchronous parallel super computer for acceleration of visualization process.
Multiresolution mesh representation for biomechanical agents
Author(s):
Pavel N. Grachev;
Sergey Yu. Belyaev;
Victor A. Sholukha
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The paper is dedicated to computer graphics problems that appear when visualizing virtual biomechanical agents in real time rendering. Visualization speed and quality directly depend on the LOD (level of detail) of an agent model. We discuss the problem of dynamic changes in geometric model LOD in real time. An algorithm is suggested that allows us to save computer resources significantly along with dynamic mesh representation and to speed up the model rendering in real time mode.
General approach to boat simulation in virtual reality systems
Author(s):
Vladislav Y. Aranov;
Sergey Yu. Belyaev
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The paper is dedicated to real time simulation of sport boats, particularly a kayak and high-speed skimming boat, for training goals. This training is issue of the day, since kayaking and riding a high-speed skimming boat are both extreme sports. Participating in such types of competitions puts sportsmen into danger, particularly due to rapids, waterfalls, different water streams, and other obstacles. In order to make the simulation realistic, it is necessary to calculate data for at least 30 frames per second. These calculations may take not more than 5% CPU time, because very time-consuming 3D rendering process takes the rest - 95% CPU time. This paper describes an approach for creating minimal boat simulator models that satisfy the mentioned requirements. Besides, this approach can be used for other watercraft models of this kind.
Numerical solution of kinematic equations in problems of rigid body dynamics for applications in computer graphics
Author(s):
Sergey Yu. Belyaev;
Boris S. Grigoriev;
Denis B. Smirnov
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The article is devoted to the solution of kinematic equations that are used for modeling the motion of mechanical objects in virtual reality systems. The components of a quaternion are taken as kinematic parameters. The numerical methods that conserve the quaternion norm are constructed starting from the finite rotation formula. To compare different methods the problem of regular precession of an axisymmetric rigid body (the exact solution of which is known) is considered.