任意曲线边界条件下缓变水深水域波浪传播的数值模拟

缓坡方程被广泛地应用于描述波浪的传播变形计算,目前一般采用矩形网格求解.将计算域剖分为任意四边形网格,以格林公式为基础,在变量沿单元边界线性变化的假定下,对双曲型的波能守恒方程、波数矢无旋性方程进行离散,同时通过等参单元变换推求节点偏导数值以离散椭圆型光程函数方程,从而建立了任意曲线边界条件下缓变水深水域波浪传播的数值模拟模型.将模型应用于平行直线型等深线地形,并将计算域剖分为不规则四边形网格,对不同入射角、底坡、波高等多种组合情况比较了数值解与解析解,结果表明两者一致.应用于复杂边界的实例,数值模拟结果与物模实验值基本吻合.     

Some properties of unstable slip on rough surfaces

In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the acoustic noise level, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred.     

基于节点计算的自适应数值积分及其程序实现

数值积分是基于节点计算的数值分析方法的关键技术之一。针对完全无网格法的计算要求，提出了一种能自动适应任意计算域上各种节点分布方式的数值积分算法。该算法能随计算点的位置不同，自动确定积分域及积分域内的求积点，计算出数值积分结果，给出了临空边坡滑移体和圆孔方板2个实例。结果表明，按文中算法编制的程序具有良好的边界再生能力和较高的计算精度，可作为基于节点数值分析方法的一个程序模块，用于实际计算。底层算法思想，使得程序可方便地转换为其他计算语言。     

非规则边界相变温度场奇异摄动解

研究了季节冻土地区集(输)油管线基础土体在冬季冻结期间的相变温度场的奇异摄动解法，通过共形映射将非规则区域进行规则化，导出映射后坐标系中非线性、非稳定热传导方程和相变界面热通量连续性方程；采用奇异摄动方法和变分原理对映射坐标系中的热传导问题进行近似分析计算，获得集(输)油管线基础土体在冬季冻结过程中的非线性温度场近似解。     

Experimental verification of torsional response control of asymmetric buildings using MR dampers

This paper proposes a semiactive control system to reduce the coupled lateral and torsional motions in asymmetric buildings subjected to horizontal seismic excitations. Magnetorheological (MR) dampers are applied as semiactive control devices and the control input determination is based on a clipped‐optimal control algorithm which uses absolute acceleration feedback. The performance of this method is studied experimentally using a 2‐story building model with an asymmetric stiffness distribution. An automated system identification methodology is implemented to develop a control‐oriented model which has the natural frequencies observed in the experimental system. The parameters for the MR damper model are identified using experimental data to develop an integrated model of the structure and MR dampers. To demonstrate the performance of this control system on the experimental structure, a shake table is used to reproduce an El Centro 1940 N–S earthquake as well as a random white noise excitation. The responses for the proposed control system are compared to those of passive control cases in which a constant voltage is applied to the MR damper. Copyright © 2003 John Wiley & Sons, Ltd.     

软件工程中并发测试的研究与实践

随着计算机技术和Internet的发展，相对于以前的单机版的应用软件，目前已有众多的网络版应用软件犹如雨后春笋，不断的涌现出来，这对传统的测试方法和理论提出了新的挑战。这里重点介绍了基于Internet网络版应用程序的并发测试方法研究与技巧，提供了一些实践经验，总结了在并发测试时应该注意的一些实际问题。     

大型彩色地貌晕渲图的自动生成技术研究

阐述了计算机地貌晕渲的基本原理 ,提出了一个实现地貌晕渲图自动绘制的方案。实践证明 ,该方法能快速、自动地生成大幅面的、满足印刷出版要求和用作专题地理信息系统基础底图的彩色地貌晕渲图 ,适合大规模彩色地貌晕渲图生产     

数字高程模型的生产及更新

数字高程模型(DEM)是基础测绘的重要产品之一，结合测绘生产实际情况，阐述了数字高程模型生产的主要技术环节，并提出了利用已有DEM进行数据更新的方法。     

蒙特卡罗法在势流计算中的应用研究

针对水动力学实际问题多存在复杂几何边界的状况,提出了用不规则游动网格求解偏微分方程的蒙特卡罗法,建立了相应的随机游动模型。选择具有复杂自由面的堰闸流动问题作为算例,验证了新方法的正确性。与有限元法相比,蒙特卡罗法解势流等线性问题时更灵活,可以根据需要,单独计算流动区域内任意一点的未知物理量,且所用计算容量较少。