Analysis theory of random energy of train derailment in wind

Based on the analysis theory of random energy of train derailment, an analysis theory of random energy of train derailment in wind is suggested. Two methods are proposed -the time domain method and the frequency domain method of analysis theory of random energy of train derailment in wind. The curves of σ pw -v under various wind speeds are obtained through the computation. The original curve of σ p -v is expanded, which turns the analysis theory of random energy of train derailment into the all-weather theory. Train derailment condition has been established under wind action. The first and second criterions of train derailment have been proposed in light of wind action. The analysis of train derailment cases at home or abroad is made, in- cluding the first analysis of Xinjiang train derailment case encountered 13-level of gale, which explained the inevitability of train derailment. The analysis theory of random energy of train derailment in wind shows its validity and accuracy. The input energy σ pw of the transverse vibration of train-track(bridge)-wind system is linked to train speed. With the establishment of the analysis theory of random energy of train derailment in wind, It is likely to initiate an all-weather speed limit map for a train or any high-speed train.     

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以碰撞为能量交换机制,按局部热力学平衡近似处理低气压等离子体,并考虑辉光放电二极之间的电位分布,得到了电子密度与气体压力的关系和电子温度与电场强度的关系。提出了一种利用压强、电压和电流就获得电子温度和密度的诊断方法。用Langmuir探针方法验证了获得的结果。     

弹簧地基上大直径单桩海上风机的一阶自振频率

自振频率是海上风机前期动力设计的主要难点之一,计算精度要求极高,而桩-土相互作用对自振频率影响显著。目前,针对桩-土相互作用普遍采用弹簧地基简化模型,为对比分析不同弹簧地基简化模型的准确性和精度,本文采用回传射线矩阵法,建立固定端、单弹簧、双弹簧和三弹簧这4种地基简化模型,基于Bernoulli-Euler梁理论和Timoshenko梁理论,求解风机系统的自振频率,并与风机基频实测值作对比,进一步分析三弹簧简化地基模型中地基旋转刚度、地基耦合刚度和地基水平刚度对风机系统基频的影响。研究结果表明,桩-土相互作用不可忽略,三弹簧地基简化模型计算风机系统基频精度最高;地基刚度对风机系统基频的敏感性次序为,地基耦合刚度>地基旋转刚度>地基水平刚度;当地基旋转(水平)刚度较小时,地基耦合刚度与地基旋转(水平)刚度的耦合效应对风机系统的基频影响较大;地基耦合刚度与地基旋转刚度的耦合效应对风机系统基频的影响程度大于地基耦合刚度与地基水平刚度的耦合效应。     

Strong regularizing effect of a gradient term in the heat equation with the Hardy potential

We deal with the following parabolic problem,

     

两相同部件并联部分可修复系统的可靠性分析

用C_0半群理论,研究了一类两相同部件并联部分可修复系统解的存在惟一性及指数稳定性,并从本征向量的角度讨论了此系统的一些主要可靠性指标,给出了瞬态可用度的数值模拟.     

跳过程的μ-不变测度-含单瞬时态情形

μ-不变测度是随机过程中一类重要的测度.首先,本文得到了含有单瞬时态的q-过程存在性定理,并进-步说明了在一些特殊情况下可以只对q-对加条件,定理仍成立.然后,对给了含单瞬时态q-对的μ-不变测度,何时存在q-过程P(t),使得π是P(t)的μ-不变测度的问题进行了讨论研究,并给出了一个充分条件.     

第14届亚洲物理奥林匹克竞赛实验试题与中国队学生实验能力分析

介绍了第14届亚洲物理奥林匹克竞赛实验试题,并针对参赛学生在竞赛中的失分情况分析了竞赛评分规则,指出了实验数据处理方法中的重点和存在的问题。     

风速测量实验的设计与探究

基于电磁理论和空气动力学的相关知识,利用磁铁、金属棒和DISLAB传感器等器件设计并制作了风速测量系统,可准确地测量2-11级范围内的风速值.该装置还可作为演示电磁感应现象的设计型实验内容,实验过程中可加深学生对电磁感应现象的理解,并提高学生对matlab软件的应用能力.     

Brownian motion at short time scales

Brownian motion has played important roles in many different fields of science since its origin was first explained by Albert Einstein in 1905. Einstein's theory of Brownian motion, however, is only applicable at long time scales. At short time scales, Brownian motion of a suspended particle is not completely random, due to the inertia of the particle and the surrounding fluid. Moreover, the thermal force exerted on a particle suspended in a liquid is not a white noise, but is colored. Recent experimental developments in optical trapping and detection have made this new regime of Brownian motion accessible. This review summarizes related theories and recent experiments on Brownian motion at short time scales, with a focus on the measurement of the instantaneous velocity of a Brownian particle in a gas and the observation of the transition from ballistic to diffusive Brownian motion in a liquid.     

High-pressure spectroscopic studies of free and self-trapped excitons in alkali halides at low temperatures

Abstract

A brief survey of our studies of free and self-trapped excitons (FE and STE) in alkali halide crystals under hydrostatic pressure up to 12.5 kbar at 4.2–140 K is presented. Main attention is paid to the following effects observed: (1) the strong coupling of three energy levels of FE in CsI revealing itself as an exciton analog of pressure-scanned Fermi resonance; (2) emergence of a new emission band of STE in CsI under pressure; (3) a large pressure shift of the thermal quenching curve for STE emission in NaCl.