岩土工程中极限分析数值模拟的研究进展

评述极限分析数值模拟在岩土工程中的发展和应用情况。介绍应用有限元和极限原理相结合的刚塑性有限元法及常用的线性规划法和非线性规划法等优化方法，并与条分法及弹塑性有限元进行比较。     

应用于MICs／MMICs中高次模式提取的混合FDTD-SVD方法综述

针对微波集成电路／单片微波集成电路中不连续性的导波结构,系统地综述了一种提取高次模的方法。该方法基于时域有限差分（FDTD）法的麦克斯韦方程求解技术,结合频域奇异值分解分析方法而实现。对基于系统的传输模态分析,该方法用于研究微波集成电路／单片微波集成电路中的不连续性,可确定系统的模式散射参数（S-参数）。文中所有结构宽波段的分析结果表明,这种方法计算准确、高效。     

Computational model of asperity contact for the prediction of UHMWPE mechanical and wear behaviour in total hip joint replacements

The effect of sliding friction on the size of yielding region in the ultra high molecular weight polyethylene asperity in contact with metal was investigated. The main objective of this work was to gain an understanding of wear particle generation mechanism from the two-dimensional finite element model. To assess the influence of the parameters of interest, different friction coefficients and loading conditions were used in the numerical simulations. Results from the finite element analysis show that the increase of the yielding region is strongly influenced by the friction coefficient and the rise in the tangential force, which is related to the generation of wear particles. Finite element wear particle generation model, based on strain discontinuities, was therefore proposed. The results obtained in this study can lead to the development of an accurate finite element particle generation model that would be of use in the assessment of an artificial implant performance and their development.     

岩体随机不连续面产状数据划分方法研究

动态聚类算法从本质上讲是单目标组合优化算法,一般需要事先给定目标分类数和初始聚类中心,且初始聚类中心的选择对数据划分结果影响较大。为了解决该问题,提出将产状数据的划分问题转化为多目标优化问题,并采用小生境Pareto遗传算法进行求解。针对聚类问题的特殊性,采用基于链表的编码方案,并建议相应的遗传操作算子;通过引入小生境技术和Pareto支配集理论,仅通过一次求解可由Pareto支配集给出对应于不同目标组数的最优分组结果,而且不用事先给定目标组数以及初始聚类中心。最后,将算法应用于三峡船闸高边坡岩体实测不连续面产状数据的划分,得到较为符合实际的优势结构面分组。     

一种基于结构面密度的岩体结构均质区划分方法

根据结构面发育的主要特点以及工程实际需要，合理选择划分岩体结构均质区的岩体参数是必要的。在某些特殊情况下，选择结构面密度作为划分均质区的依据更为合适。为此，提出了一种基于结构面密度的岩体结构均质区划分方法，即密度分区方法，并通过对西南某大型水电站工程侧裂结构面的密度分区，证明了该方法的可行性。该方法简单、直观、易于操作，有很强的推广实用价值。     

三维块体不连续变形分析理论简析

详细论述了三维不连续变形分析理论建立的全过程，并就ＤＤＡ实施过程的几个关键问题进行讨论，给出相应的公式。     

Free and Forced Vibrations of a Segmented Bar by a Meshless Local Petrov–Galerkin (MLPG) Formulation

We use the meshless local Bubnov–Galerkin (MLPG6) formulation to analyze free and forced vibrations of a segmented bar. Three different techniques are employed to satisfy the continuity of the axial stress at the interface between two materials: Lagrange multipliers, jump functions, and modified moving least square basis functions with discontinuous derivatives. The essential boundary conditions are satisfied in all cases by the method of Lagrange multipliers. The related mixed semidiscrete formulations are shown to be stable, and optimal in the sense that the ellipticity and the inf-sup (Babuška-Brezzi) conditions are satisfied. Numerical results obtained for a bimaterial bar are compared with those from the analytical, and the finite element methods. The monotonic convergence of first two natural frequencies, first three mode shapes, and a static solution in the L ², and H ¹ norms is shown. The relative error in the numerical solution for a transient problem is also very small.     

Depth Discontinuities by Pixel-to-Pixel Stereo

An algorithm to detect depth discontinuities from a stereo pair of images is presented. The algorithm matches individual pixels in corresponding scanline pairs, while allowing occluded pixels to remain unmatched, then propagates the information between scanlines by means of a fast postprocessor. The algorithm handles large untextured regions, uses a measure of pixel dissimilarity that is insensitive to image sampling, and prunes bad search nodes to increase the speed of dynamic programming. The computation is relatively fast, taking about 600 nanoseconds per pixel per disparity on a personal computer. Approximate disparity maps and precise depth discontinuities (along both horizontal and vertical boundaries) are shown for several stereo image pairs containing textured, untextured, fronto-parallel, and slanted objects in indoor and outdoor scenes.