共查询到20条相似文献,搜索用时 31 毫秒
1.
通过求解差分方程,推导了纳米晶体线的晶格动力学格林函数,分析了其晶格振动,并推导了声子数表象中的原子位移及晶格振动哈密顿公式.研究结果表明,纳米晶体线的晶格振动能带分裂为一系列的子带,格波只能沿纳米晶体线的纵向传播,沿纳米晶体线的横截面只存在驻波. 相似文献
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The results of studying the magnetomechanical effects in classical superconductors are analyzed. The energy losses are determined,
and a number of macroscopic parameters are calculated using a developed model. The studies of superconductors by the method
of rotation of a body suspended without contact are described. The results obtained are analyzed, and the values of some parameters
are determined. 相似文献
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S.T. CHOI 《Journal of sound and vibration》2003,259(3):525-539
Free-vibration characteristics of cantilever non-circular curved panels are analyzed by using the differential quadrature method (DQM) in this paper. The equations of motion of a curved panel are based on the Love's hypothesis and are expressed in an orthogonal curvilinear co-ordinate system. By applying the differential quadrature formulation and the proposed modified relationships for specified boundary conditions, the free-vibration equations of motion of the curved panel are transformed to a set of algebraic equations. Natural frequencies of a cantilever flat plate and a circular curved panel are obtained for verifying the applicability of the present approach. Good convergent trend and accuracy are observed. Effects of shallowness, thickness and aspect ratios on the natural frequencies of a cantilever curved panel are also investigated. Furthermore, natural frequencies of parabolic curved panels are obtained. In all cases studied, the efficiency and convenience of the DQM are illustrated. 相似文献
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B. Dreßler K. Graichen G. Brwolff L. Jehring G. Seifert 《Journal of magnetism and magnetic materials》1993,120(1-3):319-322
Steady-state and dynamic flying of a self-acting magnetic disk slider over a hard disk are considered. Some tasks for computations are formulated and the possibilities of developed numerical codes are illustrated. Numerical results of dynamic flying over a disk surface with an obstacle are in agreement with experimental data. 相似文献
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N. N. Komissarova 《Acoustical Physics》2000,46(3):302-309
Computational algorithms and some computed data are presented for the total sound field in a waveguide whose depth arbitrarily depends on two horizontal coordinates. The sound speed is supposed to be constant, and the bottom slopes are considered as small. The algorithm involves three steps. First, horizontal rays, i.e., horizontal projections of the real rays multiply bottom-and surface-reflected, are calculated. Second, the horizontal rays are set up to a point. Third, the real rays are set up to a point. The computational accuracy is analyzed for a homogeneous wedge lying on a halfspace. Calculations are carried out for a coastal region of the ocean. 相似文献
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I. V. Chermyaninov V. G. Chernyak 《Journal of Experimental and Theoretical Physics》2013,117(1):11-20
The cross transport processes that occur in a single-component gas in a capillary and are caused by resonance laser radiation and pressure and temperature gradients are studied. An expression for entropy production is derived using a system of kinetic Boltzmann equations in a linear approximation. The kinetic coefficients that determine the transport processes are shown to satisfy the Onsager reciprocal relations at any Knudsen numbers and any character of the elastic interaction of gas particles with the capillary surface. The light-induced baro- and thermoeffects that take place in a closed heat-insulated system in the field of resonance laser radiation are considered. Analytical expressions are obtained for the Onsager coefficients in an almost free-molecular regime. The light-induced pressure and temperature gradients that appear in a closed heat-insulated capillary under typical experimental conditions are numerically estimated. 相似文献
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Z. Z. Alisultanov 《Journal of Experimental and Theoretical Physics》2014,119(2):300-310
Some problems of the thermodynamics of electrons in a doped graphene bilayer are considered. Analytical expressions are derived for chemical potential and specific heat in the limiting cases of low and high temperatures. The Seebeck and Thomson coefficients are estimated. Landau levels are studied using a semi-classical approach. An expression for thermodynamic potential is obtained and the de Haas-van Alphen oscillations are studied. The oscillations of magnetic entropy and electron temperature in a magnetic field, i.e., the oscillating magnetocaloric effect, are investigated. For all parameters, the cases of graphene bilayer and monolayer are compared. 相似文献
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A review of commonly used analytical and empirical formulae for predicting sound diffracted by a thin screen 总被引:2,自引:0,他引:2
This paper reviews some useful analytical and empirical formulae that are used for the calculation of sound diffracted by a barrier. A brief historic overview of the study of spherical waves diffracted by a rigid half plane is presented also. The physical principles of sound diffraction by a thin plane are explained. The mathematical expressions are cast in a convenient form for ease of numerical implementation. Accurate analytical solutions are expressed in terms of standard mathematical functions that can be computed readily. Among the approximate solutions quoted, quite a few empirical formulations are adequate for most engineering purposes. The information presented in this paper should also be helpful for those who are interested in the study of sound diffracted by a barrier in a room or in a long industrial space. 相似文献
14.
The instability of a vortex subjected to a stationary dipolar or tripolar constraint is studied experimentally by using a rotating deformable cylinder on which two or three rollers are applied. As the Reynolds number and the aspect ratio of the cylinder are varied, different modes of instability are observed and their wavelength and frequency are compared to theoretical predictions. Secondary instability and cyclic breakup are also evidenced in the elliptic geometry. 相似文献
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I. Sakai 《Optical and Quantum Electronics》1986,18(4):279-289
Three basic configurations, namely, (i) parallel with a common reference, (ii) parallel with separate references and (iii) series, are studied for a multiplexed system of optical-fibre sensors. With a frequency-modulated laser source, each sensor of a different predetermined path imbalance results in a different beat frequency at the detector and signals are multiplexed in the frequency domain. The cross-term problem arising from undesired interference associated with more than one sensor is described. A series configuration has more cross terms than a parallel configuration if there are four sensors or more and, consequently, suffers more signal power reduction if there are seven sensors or more. Several schemes are presented, which ensures the separation of cross terms from desired signals. In a parallel system with a common reference, signals and cross terms are allocated in the lower and in the higher region, respectively, or to every other line in the frequency domain. In a parallel system with separate references, sensors are made incoherent to each other to produce no cross terms. In a series system, more elaborate schemes are necessary. The estimated maximum number of sensors indicates that a parallel configuration should be used if there are 10 sensors or more to be multiplexed. 相似文献
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Propagation properties of a decentered general astigmatic partially coherent beam (i.e., decentered twisted anisotropic Gaussian Schell-model beam) in a turbulent atmosphere are investigated. Analytical formulas for the cross-spectral density and decentered parameter of a decentered astigmatic partially coherent beam propagating in a turbulent atmosphere are derived. Irradiance properties of a decentered astigmatic partially coherent beam in a turbulent atmosphere are studied graphically, and are found to be quite different from its properties in free space. 相似文献
18.
《中国光学快报(英文版)》2015,(8)
The inclusions in conventionally grown KD2PO4(DKDP) crystals are investigated. The inclusions are captured by a light-scattering technique. The sizes are determined by an optical microscope and a transmission electron microscope(TEM), and the compositions are analyzed by time of flight secondary ion mass spectrometry(TOF-SIMS) and an energy dispersive spectrometer(EDS). Two kinds of inclusions are observed in the DKDP crystals: a submicron-scale inclusion and a micron-scale inclusion. The typical submicron-scale inclusions contain growth solution, and their sizes range from tens to hundreds of nanometers, whereas the micron-scale inclusions contain growth solution and the metal element Na, and the sizes are tens of microns. The possible formation mechanisms of the inclusions are discussed, and the influence of the inclusions on laser-induced damage behaviors are analyzed and discussed. 相似文献
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Properties of planar Nb/α-Si/Nb Josephson junctions with various degrees of doping of the α-Si layer
A. L. Gudkov M. Yu. Kupriyanov A. N. Samus’ 《Journal of Experimental and Theoretical Physics》2012,114(5):818-829
The properties of Nb/??-Si/Nb planar Josephson junctions with various degrees of doping of the amorphous silicon layer are experimentally studied. Tungsten is used as a doping impurity. The properties of the Josephson junctions are shown to change substantially when the degree of doping of the ??-Si layer changes: a current transport mechanism and the shape of the current-voltage characteristic of the junctions change. Josephson junctions with SNS-type conduction are formed in the case of a fully degenerate ??-Si layer. The properties of such junctions are described by a classical resistive model. Josephson junctions with a resonance mechanism of current transport through impurity centers are formed at a lower degree of doping of the ??-Si layer. The high-frequency properties of such junctions are shown to change. The experimental results demonstrate that these junctions are close to SINIS-type Josephson junctions. 相似文献