共查询到20条相似文献,搜索用时 27 毫秒
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Molecular-dynamics was used to investigate the structural changes occurring in a three-dimensional solid when the solid is
transferred from an amorphous into a crystalline state. Crystal cells of a new type — pentadecahedrons with five square lateral
faces and ten regular triangular faces at the vertices of a cell — were found for the first time in a computer experiment.
It is shown that a bistructure consisting of crystal cells of different types, including cells with five-fold symmetry axes,
are stable in the solid.
Fiz. Tverd. Tela (St. Petersburg) 40, 1919–1924 (October 1998) 相似文献
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V. M. Korovin 《Technical Physics》2012,57(10):1353-1363
An asymptotic analysis of the equations and boundary conditions of fluid dynamics is performed, and a nonlinear model is constructed for the onset of the development of Rosensweig instability in a thin horizontal ferrofluid layer at rest covered with a thin layer of a lighter nonmagnetic liquid. The surface of a nonmagnetized slab is the lower boundary of the ferrofluid, and the interface with a gas is the upper boundary of the nonmagnetic liquid. The pressure in the gas is constant. The instability being considered arises upon the application of a rather strong uniform vertical magnetic field. The proposed model involves five dimensionless parameters. The critical magnetization of the initial ferrofluid layer with a flat upper boundary and the threshold wave number are found. The effect of the governing parameters on the instability region and on the wavelength of the fastest growing mode is studied in the linear formulation of the problem. 相似文献
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V.A. Naletova V.A. TurkovD.A. Pelevina A.V. RozinK. Zimmermann J. PoppI. Zeidis 《Journal of magnetism and magnetic materials》2012,324(6):1253-1257
The deformation of the free surface of a magnetic fluid containing a cylinder made of a magnetizable material subjected to a uniform applied magnetic field is analyzed. The statics and dynamics of a magnetic fluid free surface is studied theoretically and experimentally. A discontinuous (jump-like) change of the surface shape is shown to occur when the applied magnetic field gradually increases or decreases. If the applied magnetic field increases and then decreases, a hysteresis of the shape is observed. 相似文献
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Inferring the value of a property of a large stochastic system is a difficult task when the number of samples is insufficient to reliably estimate the probability distribution. The Bayesian estimator of the property of interest requires the knowledge of the prior distribution, and in many situations, it is not clear which prior should be used. Several estimators have been developed so far in which the proposed prior us individually tailored for each property of interest; such is the case, for example, for the entropy, the amount of mutual information, or the correlation between pairs of variables. In this paper, we propose a general framework to select priors that is valid for arbitrary properties. We first demonstrate that only certain aspects of the prior distribution actually affect the inference process. We then expand the sought prior as a linear combination of a one-dimensional family of indexed priors, each of which is obtained through a maximum entropy approach with constrained mean values of the property under study. In many cases of interest, only one or very few components of the expansion turn out to contribute to the Bayesian estimator, so it is often valid to only keep a single component. The relevant component is selected by the data, so no handcrafted priors are required. We test the performance of this approximation with a few paradigmatic examples and show that it performs well in comparison to the ad-hoc methods previously proposed in the literature. Our method highlights the connection between Bayesian inference and equilibrium statistical mechanics, since the most relevant component of the expansion can be argued to be that with the right temperature. 相似文献
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Pierre Lemerle Philippe Boulanger Richard Poirot Jean Pierre Galmiche Bernard Simon 《Journal of sound and vibration》2006,298(3):638-650
A design study based on a modelling approach was used to optimise the characteristics of a new concept of suspension for training sulkies. The numerical model of sulky including the suspension and, in a second stage, a mechanical model of driver, allowed the definition of technical specifications. They were used to manufacture a prototype of suspension mounted on a current production model of sulky. The prototype of suspension was then tested in the lab and in a racecourse in real conditions of use.The resulting vibration exposure was assessed from vibration measurements. It was slightly lower than the limit value enacted in the European Vibration directive (1.15 m s2), but drastically reduced in comparison with the exposure measured on the original sulky (2.56 m s2). The prototype and moreover the design procedure is currently in a transfer process towards sulky manufacturers. 相似文献
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This paper reports on an experimental technique to determine a response function of a thermocouple using a short acoustic pulse wave. A pulse of 10 ms is generated in a tube filled with 1 bar helium gas. The temperature is measured using the thermocouple. The reference temperature is deduced from the measured pressure on the basis of a laminar oscillating flow theory. The response function of the thermocouple is obtained as a function of frequency below 50 Hz through a comparison between the measured and reference temperatures. 相似文献
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V. I. Bukreev 《Doklady Physics》2002,47(12):880-882
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V. P. Glashchenko 《Technical Physics》2014,59(5):754-761
The conditions under which the nonuniform compensating field of the reflector of the mass-reflectron can be generated with an acceptable accuracy at the symmetry axis of the reflector and extrapolated to the radial neighborhood of the axial line are determined. The plots that illustrate the distribution of the calculated nonuniform field of the reflector, the possibilities for implementation, and errors of focusing with respect to time of flight in the radial neighborhood are presented. Analytical expressions for the calculation of the time of flight of ions in the reflector in which the field distribution is described using a power series and analytical expressions for the calculation of the field distribution in the reflector in which the time of flight is determined using a power series are derived. A method for the analytical calculation of the compensating nonuniform field of the reflector based on the given dependence of the time of flight in the absence of such a field is proposed using a solution to the Abel integral equation. The solution to this equation yields analytical expressions for the calculation of the compensating field of the reflector in mass-reflectrons that contain the zero-field drift space and regions of acceleration (deceleration) of ions with a uniform field. 相似文献
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A. N. Elsukov 《Russian Physics Journal》1965,8(4):39-42
A rigorous solution is given for modes of TMnmo type. The complex resonant frequency n is expressed via a transcendental characteristic equation. Some particular cases are discussed.Read at the Third All-Union Conference on Ferrites, Leningrad, 23 October 1963. 相似文献
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The free in-plane vibrations of circular rings with wheel-plates as generalised elastic foundations are studied using analytical methods and numerical simulations. The three-parameter Winkler elastic layer is proposed as a mathematical model of the foundation. The effects of rotary inertia and shear deformation are included in the analytical model of the system. The motion equations of systems are derived on the basis of the thin ring theory and Timoshenko?s theory. The separation of variables method is used to find general solutions to the free vibrations. Elaborated analytical models are used to determine the natural frequencies and the natural mode shapes of vibrations of an arbitrarily chosen set of simplified models of aviation gears and railway wheels. The eigenvalue problem is formulated and solved by using a finite element representation for each simplified model. The results for these models are discussed and compared. The proposed solutions are verified by experimental investigation. It is important to note that the solutions proposed here could be useful to engineers dealing with the dynamics of aviation gears, railway wheels and other circular ring systems. 相似文献
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On the basis of computer simulation of propagation of femtosecond light pulses in terms of the one-dimensional nonstationary nonlinear Maxwell equations with a saturable restoring force, the possibility of formation of a sequence of subpulses with different carrier frequencies is shown. The formation of frequency-modulated pulses with an asymmetric distribution of spectral components with respect to the center of a local line is demonstrated. Appearance of such pulses indicates that a hysteretic dependence of the frequency of the corresponding local line on the amplitude of an external signal can be realized. 相似文献