A formulation for electrostatic‐mechanical contact and its numerical solution

The progress in advanced technology fields requires more and more sophisticated formulations to consider contact problems properly. This paper is devoted to the development of a new constitutive model for electrostatic‐mechanical contacts, based on a micro–macro approach to describe the contact behaviour. The electric‐mechanical contact constitutive law is obtained considering the real microscopic shape of the contacting surfaces, the microscopic behaviour of force transmission and current flow. Some thermo‐mechanical macroscopic models based on microscopic characterizations have already been developed to compute the normal and tangential contact stiffness and the thermal contact resistance. On the basis of such macroscopic models, a similar model, suitable for the electric‐mechanical field, is developed. With reference to the thermal constriction resistance the electric contact resistance is studied, assuming a flux tube around each contacting asperity, and choosing a suitable geometry for its narrowing at the contact zone. The contact element geometry is based on well known theoretical and experimental micro‐mechanical laws, suitably adapted for the FEM formulation. The macroscopic stiffness matrix is calculated on the basis of the microscopic laws and it is continuously updated as a function of the changes in the mechanical and electric significant parameters. A consistent linearization of the set of equations is developed to improve the computational speed, within the framework of implicit methods. Copyright © 2005 John Wiley & Sons, Ltd.     

三维定常/非定常Stokes方程的维数分裂算法

本文针对三维柱形区域提出了定常/非定常Stokes方程基于一致分裂格式的维数分裂算法(DSA).文章推导了三维定常/非定常Stokes方程维数分裂方法的数值迭代格式.新算法的优势在于一系列的二维问题能够并行执行,而且数值计算中避免了三维网格的生成.大量的数值结果表明新算法既能获得最优收敛阶,而且能获得比采用四面体元求解更精确的逼近解.最后,通过采用并行求解新算法能够得到比较好的加速比和并行效率.     

深部煤体煤的坚固性系数快速测定原理及其应用

通过对不同坚固性系数煤层的煤屑加载破坏试验的数据分析和总结,提出了一套新的坚固性系数快速测定原理和方法,经对比试验,表明新测试方法可行,满足测试要求,而且简单、快速.在此基础上研制了便携式快速测定装备,为推广新的突出预测综合指标提供了保证.     

基于ADINA软基上地震动输入方法研究及其应用

针对传统的刚性边界模型不能真实反映结构与地基的相互作用且对结构的动力响应影响较大的问题,研究了ADINA中实现软基上等效一致黏弹性人工边界及在该边界上波动输入的方法和技术,将其应用于某软基上泵站的三维结构—地基—水体有限元模型,在地震荷载下对结构进行动力分析,并与传统无质量地基模型结果进行对比,发现考虑地基辐射阻尼能有效降低泵站的动力响应,表明本文方法可行、有效。     

A LIMITING PROPERTY OF SAMPLE AUTOCOVARIANCES OF PERIODICALLY CORRELATED PROCESSES WITH APPLICATION TO PERIOD DETERMINATION

Abstract. It is shown that the sample autocovariance of a periodically correlated process converges to a limit which reveals the same periodicity as the process. A theorem is proved relating to the rate of almost sure convergence, which is uniform in the lag up to some orders of observation length. Based on the limiting property, a strongly consistent estimate of hidden period is proposed.     

The role of experience in judging children's photographs.

3 groups of Ss—undergraduates, parents, professional psychologists—ranked photographs of 10 children on intelligence, sociability, activity, sensitivity, and mental health. In comparison with a child psychologist who had observed the children over a 2-year period, Ss, as groups, made consistent judgments of intelligence, sociability, and health; but, as individuals, their judgments were of low validity. Judgments of children's photographs are not related to practical experience or to professional training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

灰色软测量在球磨机料位检测中的应用

1引言目前我国电厂锅炉制粉系统相当一部分配备了低速钢球磨煤机,采用中间仓储式结构,但该系统绝大部分未能达到经济工况运行,原因之一是磨内负荷难以直接测量[1]。因此,解决磨内负荷的测量问题不论对于其控制还是经济运行和监测均具有十分重要的意义。近年来,对球磨机筒内负荷     

水电站过渡过程程序可视化设计的思路及实现

针对水电站过渡过程计算和水电站引水发电系统布置的实际情况，利用面向对象方法，实现对水电站引水发电系统的图形化模拟，实现自动建立实体间的拓扑关系，以及实现数据图形的无缝连接。     

一种新的互耦条件下宽带信号DOA估计算法

基于一致聚焦和Khatri-Rao子空间的思想,提出了一种新的互耦条件下宽带信号DOA 估计算法。首先,通过在阵列两端设置辅助阵元来补偿各个频率处的互耦效应;接着,对补偿后的协方差矩阵进行一致聚焦操作,并重排成一个高维矩阵;最后,通过搜索Khatri鄄Rao 子空间谱估计出宽带信号的DOA。算法适用于互耦未知的场合,对宽带信号频率谱是否平坦没有要求,且在互耦自由度较小时能够分辨多于阵元数的宽带信号。计算机仿真结果证明了算法的有效性。     

基于模糊判断矩阵的两阶段群决策方法

针对多属性群决策问题,提出一种两阶段决策分析方法。通过分析积型模糊一致性判断矩阵和模糊判断矩阵的排序向量之间的偏差,建立并求解一个规划模型,得到专家模糊判断矩阵的排序向量。由最小化专家模糊判断矩阵的排序向量与专家群组排序向量的偏差,再次建立并求解一个规划模型,得到反映专家群组偏好的排序向量,从而得出基于模糊判断矩阵的两阶段群决策方法。通过2个算例说明了该方法的可行性与有效性。