压电发电悬臂梁的非线性动力学建模及响应分析

以单晶悬臂梁压电发电装置为研究对象,在考虑压电材料非线性的情况下,利用广义Hamilton原理、Rayleigh-Ritz法、Euler-Bernoulli梁理论及压电元件恒定电场假设建立了悬臂梁压电发电装置的分布式机电耦合模型,通过数值计算分析谐振频率附近解的特性与系统参数及初始条件的关系,揭示了压电材料非线性、外激励参数对系统响应的影响规律,并通过实验验证了解析解的正确性.结果表明,压电材料的非线性特性会导致近似解的共振峰向左偏移,呈现软特性的非线性特征;当激励频率变化时,系统响应存在多解、跳跃等现象,主共振解的真正实现与初始条件的选取有关.     

Nonextensive lattice gauge theories: Algorithms and methods

High-energy phenomena presenting strong dynamical correlations, long-range interactions and microscopic memory effects are well described by nonextensive versions of the canonical Boltzmann–Gibbs statistical mechanics. After a brief theoretical review, we introduce a class of generalized heat-bath algorithms that enable Monte Carlo lattice simulations of gauge fields on the nonextensive statistical ensemble of Tsallis. The algorithmic performance is evaluated as a function of the Tsallis parameter q$q$ in equilibrium and nonequilibrium setups. Then, we revisit short-time dynamic techniques, which in contrast to usual simulations in equilibrium present negligible finite-size effects and no critical slowing down. As an application, we investigate the short-time critical behaviour of the nonextensive hot Yang–Mills theory at q$q$-values obtained from heavy-ion collision experiments. Our results imply that, when the equivalence of statistical ensembles is obeyed, the long-standing universality arguments relating gauge theories and spin systems hold also for the nonextensive framework.     

Vapor-liquid equilibrium and volumetric properties calculations for solutions in the supercritical carbon dioxide

The calculations of gas solubilities in supercritical solvents require equations of state remaining accurate in the critical range, which are difficult to obtain with classical models. In this work, the Helmholtz energy of a mixture is considered as the sum of the Helmholtz energies of pure components taken at a constant packing fraction and of a residual term which may have the form of a RedlichKister, Van Laar, NRTL, UNIQUAC, or UNIFAC function. Thus it is possible to assign to a given component an equation of state whose form is different from that of the others. This model has been applied to binary systems containing supercritical carbon dioxide. The results are improved with respect to those obtained with the classical model for vapor-liquid equilibria and for volumetric properties.     

Isochoric specific heat of sulfur hexafluoride at the critical point: Laboratory results and outline of a spacelab experiment for the d1-mission in 1985

The specific heat at constant volume c_v shows a weak singularity at the critical point. Renormalization group techniques have been applied, predicting a universal critical behavior which has to be experimentally confirmed for different systems. In this paper an experiment is presented to measure the specific heat of SF₆ along the critical isochore (_c=0.737 g·cm^–3), applying a continuous heating method. The results cover a temperature span of –1.5×10^–2< <1.70×10^–2 [=(T–T _c)/T _c] and were strongly affected by gravity effects that emerge in the sample of 1-mm hydrostatic height near the critical point. Using regression analysis, data were fitted with functions of the form c _v/R=A × ¦¦^– + B for the one-phase state and c _v/R=A × ¦¦^– + B for the twophase state. Within their error bounds the critical values (==0.098, A/A=1.83) represent the measurements for the temperature span 3.5×10^{–5< ¦¦<2.0×10 –3}, in good agreement with theoretical predictions. In order to exclude density profiles in the specimen, which are unavoidable in terrestrial experiments due to the high compressibility of fluids at the critical point and the gravity force, a space-qualified scanning ratio calorimeter has been constructed, which will permit long-term c_v measurements under microgravity (-g) conditions. The experiment will be part of the German Spacelab mission in October 1985. The significant features of the apparatus are briefly sketched.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Simulation of atmospheric phenomena

This paper presents a physically based simulation of atmospheric phenomena. It takes into account the physics of non-homogeneous media in which the index of refraction varies continuously, creating curved light paths. As opposed to previous research on this area, we solve the physically based differential equation that describes the trajectory of light. We develop an accurate expression of the index of refraction in the atmosphere as a function of wavelength, based on real measured data. We also describe our atmosphere profile manager, which lets us mimic the initial conditions of real-world scenes for our simulations. The method is validated both visually (by comparing the images with the real pictures) and numerically (with the extensive literature from other areas of research such as optics or meteorology). The phenomena simulated include the inferior and superior mirages, the Fata Morgana, the Novaya–Zemlya, the Viking's end of the world, the distortions caused by heat waves and the green flash.     

The effect of the trapping of dust grains on the sheath structure and the charging in a plasma

A model of the trapping of dust grains is shown in a plasma for the first time. The multiple sheath potential, the space charge density and the multiple electric field associated with our model are simulated. Our result explains the confinement of the dust grains observed in the experiment.     

多层弯曲磁芯微执行器的吸合现象

从多层弯曲磁芯微执行器的模型及原理出发,应用静磁执行器的吸合方程,分别用磁动势控制模型和磁通控制模型对多层弯曲磁芯微执行器的吸合现象进行了理论分析．计算及仿真结果表明：多层弯曲磁芯微执行器存在临界吸合角度,磁动势控制模型的临界吸合角度约为其最大旋转角度的44％;磁通控制模型的临界吸合角度约为其最大旋转角度的72．35％．磁动势控制实验结果与理论计算值误差约为8％．     

Thermodynamic properties of methane in the critical region

An equation of state is presented for the thermodynamic properties of methane in the vicinity of the critical point. It incorporates the scaled asymptotic critical behavior predicted theoretically and supplements a global analytic equation of state for methane recently developed by Setzmann and Wagner.     

A new psychophysical method: Method of transposition or equal-appearing relations.

"In many experiments dealing with perceptual phenomena, investigators try to find a stimulus which appears equal to a standard stimulus. It often happens, however, that the procedure involved in finding the equivalent stimulus alters the stimulus pattern so that the measurement is not made on the original stimulus pattern. To avoid this difficulty, a new psychophysical method, which is named the method of transposition or the method of equal-appearing relations, was proposed. The major advantage of this method over the traditional ones is that it leaves the original stimulus pattern intact." (PsycINFO Database Record (c) 2010 APA, all rights reserved)