地震力对高架桥梁上轨道车辆的动态分析与安全性研究

The stability and derailment behavior analysis of railway vehicle system has been discussed by many papers in the past. In stability, give first place to consider hunting behavior of vehicle, therefore most of papers was only consider lateral and yaw motion, but vertical motion is the important factor in derailment behavior, and it will be quite effect in stability. We will probe the running stability and derailment behavior of railway vehicle moving on the viaduct in this paper. In this paper, we use Nadal’s formula to get the derailment quotient. In this paper, the railway vehicle is considered to be three subsystems, carbody, bogie and wheelset. There are secondary suspension systems between carbody and bogies, and primary suspension systems connecting bogies and wheelsets. A vehicle with vertical, lateral, roll, and yaw directions motion is considered to derive the mathematical equations. A vehicle with three-dimensional model has 16 degrees of freedom is used to develop the equations of train motion. In this study, results show that the track shift force and derailment factor increase with an increase of ground acceleration. But for the track shift force and derailment factor, the effects of track irregularities and train speed are very small. Key words: earthquake, railway vehicle, viaduct, derailment factor.

月球机器人仿真中一种消除轮地交互误差的方法

利用虚拟现实技术虚拟出月球机器人在月面上的作业环境和作业过程,是提高机器人作业的安全系数和工作效率的一条有效途径。在3D重建得到的虚拟月面环境中,如果采用通常的单纯基于运动学(或者动力学)模型的仿真方法,对机器人的作业和运动进行虚拟,那么机器人与地形交互的过程中容易产生接触偏差。而且,随着仿真时间的推进,这种接触偏差会逐渐积累并不断增大,进而严重影响仿真测试的精度和效果。为了消除月球机器人仿真中的轮地交互误差,在分析误差来源的基础上,提出了基于运动学优化的解决方法。最后利用实际的虚拟现实仿真系统,验证了所提出方法的有效性。

被动柔顺式月面巡视探测器轮-地交互及运动控制研究

月面巡视探测器（简称月球车）是一类在月面环境下执行巡视探测、科学考察及样品采样等任务的空间机器人，是我国月球探测二期工程中执行月面探测任务的关键载体。月球车行走能力事关我国探月二期工程的成败，开展在复杂地形下移动能力和地形通过能力的研究，是目前移动机器人研究中的前沿课题，是月面巡视任务的关键技术之一。本论文的选题具有重要的理论意义和应用价值。 月面环境的特殊性使月球车进行长距离、大范围的巡视任务面临一系列问题，包括地形对月球车移动性的影响、移动能力、地形通过能力、地形适应能力、安全性等。本文以月球车保持复杂地形下的高移动能力和地形通过能力为研究目标，以一种典型的被动柔顺式月球车为对象，从月球车与环境地形具有整体不可分离性的角度，将机器人与环境地形看成是相互作用的整体，深入研究了轮-地交互关系、软硬地形上的轮-地接触模型、环境地形给月球车带来的影响、软硬地形上的月球车建模、参数估计及运动控制等问题。根据对月球车移动性能影响程度之不同，本文从硬质地形与松软地形两个方面来考察环境地形的物理属性和轮-地交互关系。在硬质地形上，主要考虑地形平坦与不平坦对机器人移动的影响及其控制，六个驱动轮的速度协调控制，车轮打滑（前滑、侧滑、转向滑移）对机器人的建模、分析及控制的影响。在松软地形上，主要考虑轮-地接触关系，土壤特性对移动的影响及其控制。在大量阅读国内外文献并归纳总结的基础上，重点开展了如下几方面的研究： （1）在硬质不平坦地形下，引入轮-地几何接触角概念以反映地形不平坦时轮-地接触点在轮缘上位置的变化，去掉了通常采用的车轮纯滚动假设，考虑车轮滑移（包括侧滑、侧滑以及转向滑移），并结合月球车被动柔顺式移动机构的特点，提出了一种基于速度闭链的运动学建模方法，进行了基于整车模型的月球车速度协调控制研究。该运动学建模方法基于轮心处的速度投影建立整体运动学模型，物理概念清晰、便于实时运动学正反解计算。 （2）针对运动学模型中轮-地几何接触角难以直接测量的问题，提出了两种在线估计方法：误差计算法和卡尔曼滤波估计法。这两种方法均基于月球车整体运动学模型，只需要车轮内部传感器的测量信息，就能在线估计轮-地几何接触角。 （3）由于车轮滑移的影响，采用航位推算方法进行月球车状态估计以及里程计计算存在较大误差。本文提出了基于整体运动学模型的车体运动状态估计方法，并在月球车样机上对车体速度估计、航向角估计、里程计实时计算等方法进行了大量实验研究，验证了算法的有效性。 （4）针对松软地形上刚性轮与地形的交互建模问题，提出了一种基于Guass-Legendre数值积分和Newton-Raphson数值解法的地形参数实时估计方法。以月壤参数的变化范围为参考空间，通过数值仿真将不同地形参数对轮-地接触力的影响进行比较，进而选取对轮-地接触力有较大影响的地形参数进行在线估计，仿真和实验结果均表明估计算法是有效的。 （5）松软地形上常规的速度控制效果差，本文开展了月球车准静力学建模及牵引力控制算法研究，提出了两种牵引力控制算法。对月球车准静力学模型进行简化，提出了一种基于目标优化、考虑车体姿态变化的牵引力控制算法。利用上一章在线估计出的地形参数，对车轮滑移率进行最优估计，提出了一种基于最优滑移率的牵引力控制算法，并进行了仿真验证。

基于滑转率的六轮纵列式月球车驱动控制研究

基于车轮滑转率和车轮地面力学,研究了月球车在松软月面行驶时的车轮过度下陷问题.将月球车车轮下陷和车轮—土壤作用力表达为车轮滑转率的函数,结合车辆地面力学理论并考虑纵列式车轮多通过性土壤参数的修正,建立了月球车的动力学模型.判断车轮是否发生过度下陷的标准为土壤所提供给驱动轮的土壤推力能否克服土壤对车轮的阻力.利用建立的动力学模型,计算出能够保证车轮不会过度下陷的期望滑转率.考虑到月球车动力学系统的非线性和不确定性,设计了以车轮滑转率为状态变量的滑模驱动控制器.仿真结果表明,采用该控制器可以较快地跟踪期望滑转率,避免车轮的过度滑转下陷,保证月球车能够在软质路面上正常行驶.

Experimental Investigations on Interaction of Two Drops by Thermocapillary-Buoyancy Migration

Experiments were performed, in a terrestrial environment, to study the migration and interaction of two drops with different diameters in matrix liquid under temperature gradient field. Pure soybean oil and silicon oil were used as matrix liquid and the drop liquid, respectively. The information on the motions of two drops was recorded by CCD camera system in the experiments to analyze the trajectories and velocities of the drops. Our experiments showed that, upon two drops approaching each other, the influence of the larger drop on the motion of the smaller one became significant. Meanwhile the smaller drop had a little influence on the larger one all the time. The oscillation of migration velocities of both drops was observed as they were approaching. For a short period the smaller drop even moved backward when it became side by side with the larger one during the migration. Although our experimental results on the behavior of two drops are basically consistent with the theoretical predictions, there are also apparent differences. 2006 Elsevier Ltd. All rights reserved. Keywords: Thermocapillary migration; Drop; Interaction; Oscillation 1. Introduction A bubble or drop will move when placed in another fluid with temperature gradient. This motion happens as a consequence of the variation of interfacial tension with temperature. Such a phenomenon is already known as Marangoni migration problem. With the development of microgravity science, bubble dynamics and droplet dynamics became a hot point problem of research because this investigation is very important for basic research as well as for applications in reduced gravity environment, such as space material science, chemical engineering and so on. Young et al. first investigated the thermocapillary migration of

Measuring Receptor/Ligand Interaction at the Single-Bond Level: Experimental and Interpretative Issues

There is increased interest in measuring kinetic rates, lifetimes, and rupture forces of single receptor/ligand bonds. Valuable insights have been obtained from previous experiments attempting such measurements. However, it remains difficult to know with sufficient certainty that single bonds were indeed measured. Using exemplifying data, evidence supporting single-bond observation is examined and caveats in the experimental design and data interpretation are identified. Critical issues preventing definitive proof and disproof of single-bond observation include complex binding schemes, multimeric interactions, clustering, and heterogeneous surfaces. It is concluded that no single criterion is sufficient to ensure that single bonds are actually observed. However, a cumulative body of evidence may provide reasonable confidence. 0 2002 Biomedical Engineering Society.

The Interaction Between Shock Waves and Foam in a Shock Tube

An experimental study and a numerical simulation were conducted to investigate the mechanical and thermodynamic processes involved in the interaction between shock waves and low density foam. The experiment was done in a stainless shock tube (80mm in inner diameter, 10mm in wall thickness and 5360mm in length). The velocities of the incident and reflected compression waves in the foam were measured by using piezo-ceramic pressure sensors. The end-wall peak pressure behind the reflected wave in the foam was measured by using a crystal piezoelectric sensor. It is suggested that the high end-wall pressure may be caused by a rapid contact between the foam and the end-wall surface. Both open-cell and closed-cell foams with different length and density were tested. Through comparing the numerical and experimental end-wall pressure, the permeability coefficients a and 0 are quantitatively determined.

Analytical Interaction of the Acoustic Wave and Turbulent Flame

A modified resonance model of a weakly turbulent flame in a high-frequency acoustic wave is derived analytically. Under the mechanism of Darrieus-Landau instability, the amplitude of flame wrinkles, which is as functions of the expansion coefficient and the perturbation wave number, increases greatly independent of the 'stationary' turbulence. The high perturbation wave number makes the resonance easier to be triggered but weakened with respect to the extra acoustic wave. In a closed burning chamber with the acoustic wave induced by the flame itself, the high perturbation wave number is to restrain the resonance for a realistic flame.

Grain Refinement at the Nanoscale Via Mechanical Twinning and Dislocation Interaction in a Nickel-Based Alloy

A nanostructured surface layer was formed on an Inconel 600 plate by subjecting it to surface mechanical attrition treatment at room temperature. Transmission electron microscopy and high-resolution transmission electron microscopy of the treated surface layer were carried out to reveal the underlying grain refinement mechanism. Experimental observations showed that the strain-induced nanocrystallization in the current sample occurred via formation of mechanical microtwins and subsequent interaction of the microtwins with dislocations in the surface layer. The development of high-density dislocation arrays inside the twin-matrix lamellae provides precursors for grain boundaries that subdivide the nanometer-thick lamellae into equiaxed, nanometer-sized grains with random orientations.

Numerical simulation of standing solitons and their interaction

Standing soliton was studied by numerical simulation of ifs governing equation, a cubic Schrodiger equation with a complex conjugate term, which was derived by Miles and was accepted. The value of linear damping in Miles equation was studied. Calculations showed that linear damping effects strongly on the formation of a standing soliton and Laedke and Spatschek stable condition is only a necessary condition, but not a sufficient one. The interaction of two standing solitons was simulated. Simulations showed that the interaction pattern depends on system parameters. Calculations for the different initial condition and its development indicated that a stable standing soliton can be fanned only for proper initial disturbance, otherwise the disturbance will disappear or develop into several solitons.

Analysis of super compact finite difference method and application to simulation of vortex-shock interaction

Turbulence and aeroacoustic noise high-order accurate schemes are required, and preferred, for solving complex flow fields with multi-scale structures. In this paper a super compact finite difference method (SCFDM) is presented, the accuracy is analysed and the method is compared with a sixth-order traditional and compact finite difference approximation. The comparison shows that the sixth-order accurate super compact method has higher resolving efficiency. The sixth-order super compact method, with a three-stage Runge-Kutta method for approximation of the compressible Navier-Stokes equations, is used to solve the complex flow structures induced by vortex-shock interactions. The basic nature of the near-field sound generated by interaction is studied.

Influence of Electrostatic Interaction on Fibrinogen Adsorption on Gold Studied by Imaging Ellipsometry Combined with Electrochemical Methods

Imaging ellipsometry was combined with electrochemical methods for studying electrostatic interactions of protein and solid surfaces. The potential of zero charge for gold-coated silicon wafer/solution interfaces wad determined by AC impedance method. The potential of the gold-coated silicon wafer was controlled at the potential of zero charge, and the adsorption of fibrinogen on the potential-controlled and non-controlled surfaces was measured in real time at the same time by imaging ellipsometry The effect of electrostatic interaction was studied by comparing the difference between the potential of controlled adsorption and the Potential of noncontrolled adsorption. It was shown that the rate of fibrinogen adsorption on the potentiostatic surface was faster than that on the nonpotentiostatic surface. The electrostatic influence on fibrinogen adsorption on the gold-coated silicon wafer was weak, so the hydrophobic interaction should be the major affinity.

Fluid-Solid Interaction in Particle-Laden Flows

Liu Qingquan, Singh V.P