热处理温度对流量计振动管性能的影响

采用真空熔炼的方法制备了铁镍金属振动管,采用XRD对振动管的晶体结构及热处理温度等对振动管晶体结构的影响进行了分析;用阿基米德密度测量方法对金属管的密度进行了测量,用显微硬度计测量了振动管的维氏硬度;采用共振的方法测量了振动管的振动频率及热处理温度对振动频率的影响。结果表明,随着热处理温度的增加,振动管的显微硬度增加、振动管的振动频率也相应增加。     

空化诱发的轴流泵振动特性实验研究

运用LMS多通道振动噪声测试与动力学分析系统,对轴流模型泵最优工况流量下不同空化程度时的振动加速度进行了动态多点测量和分析,获得了振动加速度的特征频率以及低频、高频振动水平随汽蚀余量的变化规律。实验结果表明:轴频、叶频以及其高次谐波是泵振动的主要激励频率;空化诱发的振动主要为高频振动;随汽蚀余量的降低,低频振动和高频振动均呈现先上升后下降的趋势;高频振动比低频振动更易被阻尼力削弱,高频振动水平上升的拐点和空化引起泵能量性能下降的临界点相一致。     

振动合成器

振动合成器是为了演示振动的合成而设计的教学仪器。一个质点参加两种振动时,它的振动将为这两种振动的合振动,它的振动位移将等于两种分振动的位移的矢量和。振动合成器     

弹簧振子振动的探讨

对于弹簧振子的振动,通常只讨论其纵向振动,横向振动由于其恢复力与位移不成正比,不是简谐振动,并且难以求得其振动规律的解析解.通过数值计算的方法可以得到在玩具弹簧和小振动条件下,横向振动的规律.     

巴西果效应分离过程的计算颗粒力学模拟研究

采用离散单元模型对巴西果问题进行了模拟研究,采用本数学模型可以准确地预测出垂直机械振动导致的不同大小颗粒的分离现象.分析了影响振动床内颗粒分层的因素,讨论了振动频率、振动幅度等参数对分层的影响,发现振动频率和振动幅度会对分离效果造成较大的影响.当振动频率或振动幅度较小时,颗粒整体分离效果都较差,但分离的稳定性较好,当振动频率或振动幅度较大时,整体分离效果仍然较差,同时分离的稳定性也较差,振动分离过程中存在一个频率和振幅适中的最优操作点. 关键词： 分层 振动 模式形成 离散单元方法     

一维单原子链中杂质引起的局域振动模

讨论了一维单原子链中杂质引起的晶格局域振动模和局域振动图像,分析了杂质质量和杂质近邻力常数对振动模的影响,通过数值求解晶格振动运动方程组．给出了局域振动模关于杂质质量和杂质近邻力常数分布的相图;分析了含杂质晶格振动模频率相对于完整晶格振动模频率的变化。     

35 kV油浸式配电变压器噪声与振动测试

配电变压器振动与噪声问题日益凸出,研究配电变压器振动与噪声特性对其振动与噪声控制具有重要意义。该文以一台35 k V/800 k VA油浸式配电变压器为研究对象,对不同激励电压作用下配电变压器铁心振动、油箱振动以及噪声进行测试。测试结果表明:配电变压器铁心、油箱振动与噪声具有相似频谱特征,均表现出以100 Hz、200 Hz为主要峰值的频谱特征;随着激励电压增加,变压器振动及噪声水平明显增大;变压器油箱振动值大于铁心,侧面振动水平较高,油箱正面和顶面振动水平略低。测试结果准确地反映配电变压器铁心与油箱的振动与噪声特性,对于其噪声振动控制具有参考价值。     

重复频率脉冲大气放电中氮气的振动温度

氮气分子的振动自由度在大气放电低温等离子体中会被高度激发。从振动能级的简谐振子模型和Boltzmann分布近似出发,研究重复频率脉冲放电中振动温度的变化行为。结果表明,决定重频条件下振动温度的主要过程是电子碰撞振动激发和振动-平动弛豫,而在振动能级高度激发的情形下其与氧原子的化学反应也会产生影响。对于振动激发过程,通过跃迁反比相似率推导出的特征弛豫时间与动理学模型符合较好。在振动-平动弛豫中占主导贡献的为干燥大气中的氧原子或潮湿大气中的水分子。当氧原子数密度为1014 cm-3时,若初始振动温度在5000 K,在化学反应过程中振动能量的特征弛豫时间在0.1~1 s量级。     

结构振动声强法研究及应用

振动声强技术通过绘制功率流矢量图和流线图来分析结构噪声源及能量传播路径,可以清晰体现振动声能的分布和传播。对振动和噪声控制具有重要的理论意义和应用前景。本文总结了振动声强试验和理论计算技术的发展,并推导了受迫振动板中声强分量与振动能量的数学关系;最后对振动声强法在复杂结构振动功率流控制和结构损伤识别中的应用进行了展望。     

重复频率脉冲大气放电中氮气的振动温度

氮气分子的振动自由度在大气放电低温等离子体中会被高度激发。从振动能级的简谐振子模型和Boltzmann分布近似出发,研究重复频率脉冲放电中振动温度的变化行为。结果表明,决定重频条件下振动温度的主要过程是电子碰撞振动激发和振动-平动弛豫,而在振动能级高度激发的情形下其与氧原子的化学反应也会产生影响。对于振动激发过程,通过跃迁反比相似率推导出的特征弛豫时间与动理学模型符合较好。在振动-平动弛豫中占主导贡献的为干燥大气中的氧原子或潮湿大气中的水分子。当氧原子数密度为1014 cm-3时,若初始振动温度在5000 K,在化学反应过程中振动能量的特征弛豫时间在0.1~1 s量级。     

Cyclic Heating-Annealing and Boltzmann Distribution of Free Energies in a Spin-Glass System

Ergodicity of a spin-glass is broken at low temperatures; the system is trapped in one of many ergodic configurational domains. Transitions between different ergodic domains are achievable through a heating-annealing procedure. If this experiment is repeated infinite times, all ergodic configurational domains will be visited with frequences that decreasing exponentially with their free energies. The mean free energy density of a spin-glass system on a random graph is calculated based on this free energy Boltzmann distribution in the present work, by means of the cavity approach.     

Cyclic Heating-Annealing and Boltzmann Distribution of Free Energies in a Spin-Glass System

Ergodicity of a spin-glass is broken at low temperatures; the system is trapped in one of many ergodic configurational domains. Transitions between different ergodic domains are achievable through a heating-annealing procedure. If this experiment is repeated infinite times, all ergodic configurational domains will be visited with frequences that decreasing exponentially with their free energies. The mean free energy density of a spin-glass system on a random graph is calculated based on this free energy Boltzmann distribution in the present work, by means of the cavity approach.     

Spreading of a drop on a contaminated substrate

Most wetting or spreading problems are treated with surface and interfacial free energies taken as constants for the system in question. We consider here the case where a two-dimensional drop (ribbon) is deposited on a solid substrate bearing a very fine layer of a contaminant which modifies the effective drop/solid interfacial free energy. As the contaminant diffuses into the drop, the interfacial free energy, and thus the capillary balance, evolve. This has strange effects on wetting behaviour, including causing a wetting `overshoot'. Possible applications are briefly discussed.     

Free energy change of a dislocation due to a Cottrell atmosphere

The free energy reduction of a dislocation due to a Cottrell atmosphere of solutes is computed using a continuum model. We show that the free energy change is composed of near-core and far-field components. The far-field component can be computed analytically using the linearized theory of solid solutions. Near the core the linearized theory is inaccurate, and the near-core component must be computed numerically. The influence of interactions between solutes in neighbouring lattice sites is also examined using the continuum model. We show that this model is able to reproduce atomistic calculations of the nickel–hydrogen system, predicting hydride formation on dislocations. The formation of these hydrides leads to dramatic reductions in the free energy. Finally, the influence of the free energy change on a dislocation’s line tension is examined by computing the equilibrium shape of a dislocation shear loop and the activation stress for a Frank–Read source using discrete dislocation dynamics.     

四能级系统的极化拍频

利用双光子与双光子过程间的干涉研究了四能级系统的超快调制光谱学（ＵＭＳ）,同时论证了用四能级系统的超快调制光谱学测量能级差可以达到消除多普勒增宽的可能性。     

The anisotropy of free path in a vibro-fluidized granular gas

The free path of a vibro-fluidized two-dimensional(2D) inelastic granular gas confined in a rectangular box is investigated by 2D event-driven molecular simulation. By tracking particles in the simulation, we analyze the local free path.The probability distribution of the free path shows a high tail deviating from the exponential prediction. The anisotropy of the free path is found when we separate the free path to x and y components. The probability distribution of y component is exponential, while x component has a high tail. The probability distribution of angle between the relative velocity and the unit vector joined two particle centers deviates from the distribution of two random vectors, indicating the existence of the dynamic heterogeneities in our system. We explain these results by resorting to the kinetic theory with two-peak velocity distribution. The kinetic theory agrees well with the simulation result.     

Free energy in a Markovian model of a lattice spin system

A Markov process which may be thought of as a classical lattice spin system is considered. States of the system are probability measures on the configuration space, and we study the evolution of the free energy of these states with time. It is proved that for all initial states the free energy is nonincreasing and that it strictly decreases from any initial state which is shift invariant but not an equilibrium state. Finally we show that the state of the system converges weakly to the set of Gibbsian Distributions for the given interaction, and that all shift invariant equilibrium states are Gibbsian Distributions.This work was done while the author was a postdoctoral fellow in the Adolph C. and Mary Sprague Miller Institute for Basic Research in Science.     

Photoelectron ionization spectra in a system interacting with a neighbor atom

We study long-time photoelectron ionization spectra of a system interacting with a neighbor two-level atom under the influence of a laser field. The system has at least a ground state and a continuum of states that are free with respect to one electron. In a weak light field, a Fano resonance is revealed. Also we consider an atomic autoionization level of the system, which leads to two Fano resonances under the influence of a weak field.     

Gauge supersymmetric Ising model on a cubic lattice near the critical point in the free field representation

The nature of the set of free fields that represent the system at the critical point has been revealed by studying the correlation functions of the degrees of freedom of the gauge supersymmetric Ising model on the cubic lattice. The same set of free fields represents the continuous supersymmetric Abelian gauge theory. Thus, the name of the lattice system is appropriate. Comparison with the two-dimensional Ising model is given.     

Statistical mechanics of a nonequilibrium steady-state classical particle system driven by a constant external force

A classical particle system coupled with a thermostat driven by an external constant force reaches its steady state when the ensemble-averaged drift velocity does not vary with time. In this work, the statistical mechanics of such a system is derived solely based on the equiprobability and ergodicity principles, free from any conclusions drawn on equilibrium statistical mechanics or local equilibrium hypothesis. The momentum space distribution is determined by a random walk argument, and the position space distribution is determined by employing the equiprobability and ergodicity principles. The expressions for energy, entropy, free energy, and pressures are then deduced, and the relation among external force, drift velocity, and temperature is also established. Moreover, the relaxation towards its equilibrium is found to be an exponentially decaying process obeying the minimum entropy production theorem.