曲率分析方法在曲面求交中的应用

在曲面求交的跟踪过程中，主要存在两个问题，即确定跟踪方向和计算跟踪步长。本文给出用曲率分析精确计算跟踪方向，并估计跟踪步长的方法。用曲率分析法能够处理相切这种奇异情况。本文最后给出三个实例验证。     

正交各向异性平面问题边界元一边境元素法研究

在文献中，本文作者研究了正交向向异性平面问题边界元素法的有关基本理论和计算公工,基上述工作的基础上，本文进一步研究各向异性颊问题边界邻域的应力分析，当采用边界元素法分析应力时，由于边界积分的奇异性，边界领域应力的计算结果往往存在一定误差，为解决此问题，本文提出一处基于修正余能原理的所谓边境元素，包括四节点边境元素，八节点边境元素和三节点边境元素等，在边界元素法求解的基础上，进一步利用本文述边境元素法，得到了非常满意的计算结果。     

计算形函数有限条在剪力墙分析中的应用

本文采用一种新的有限条－计算形函数有限条，对大开洞及分段变截面的剪力墙进行了分析，计算形函数有限条采用一组计算静力模态作为位移函数，与以往有限条件不同，这种有限条的未知参数正是结线结点的实际位移，而且在某些指定点上可以保持Ｃ０连续，因而易于处理截面突变问题，本文计算结果与高精度有限元法进行比较，证明了本法的计算精度较高，使用非常方便。     

刃边法计算在轨卫星图像MTF的仿真分析

调制传递函数（MTF）较之仅凭借某一个数字量（分辨率、清晰度等）来对成像系统进行质量评价更具有权威性。刃边法适合卫星在轨的特性，易于实现，无需人工对在轨遥感器输入激励信号。本文在实现刃边法计算图像MTF的算法的基础上，通过仿真，分析了像移、刃边角度、噪声对MTF计算结果的影响，并对算法精度进行了检验。仿真结果表明，本文的计算在轨卫星图像MTF的方法具有较高的精度，并且能较好地抵抗噪声。     

一般区域n重积分优化Simpson数值算法

本文给出一般区域ｎ重积分优化Ｓｉｍｐｓｏｎ数值积分法，它在迭代计算过程中避免了重复计算，加速达到近似值精度，并给出了误差估计式。     

地基承载力可靠度指标不同计算方法的比较

本文分别采用改进的JC法、随机投点法以及改进的搜索适应重要抽样法来计算地基承载力可靠度指标，并在计算过程中考虑了土性指标的自相关性和互相关性，将这三种计算方法进行了比较，结果表明，重要抽样法具有更大的优越性。     

变截面压杆稳定计算的有限单元法

本文在文「１」建立的三维退化梁单元的基础上，考虑几何非线性，推导出计算任竭尽为截面压杆稳定问题的有限元无式。计算结果表明，本文公式正确，力学概念清晰明了，计算效率较高，该单元三维梁、板、块单元的连接非常方便，很适合于工程结构的总体分析。     

后张法箱梁预应力筋伸长值计算公式研究

本文介绍了后张法对铁路箱梁预应力钢绞线钢束张拉伸长值计算公式的推导过程，并结合实际情况，提出了在计算理论伸长值时的问题，使计算人员的在具体的计算中有理论依据。最后，总结出适用于现场施工的伸长值的计算方法。     

曲线上较大桥台布置形式的探讨

随着曲线计算理论的日益完善，施工技术的不断提高，曲梁将逐步应用在曲线桥上。桥上线路为曲线，但梁仍为筒支直线梁的曲线桥布景方式目前应用仍最为普遍。本文着重对较大桥台在曲线桥上各种布置形式进行计算分析，并就各布置形式的精度进行探讨，以便于日后施工时参考。     

用Galerkin边界元子域法进行裂纹扩展分析

本文采用完全对称的Ｇａｌｅｒｋｉｎ边界元子域法，粘性裂纹模型计算了边裂纺，内裂纹的扩展过程，计算结果表明了该方法在裂纹扩展分析中的优势，本文还指出该方法迹适用于多种材料组成的结构，并给出了算例。     

基于机器视觉的图像形状特征提取方法研究进展

基于机器视觉的图像形状特征提取应用的常见方法有阈值处理法、基于轮廓的形状特征提取法和基于区域的形状特征提取法3种。阈值处理法是常见的图像分割提取方法,具备操作简单、速度快等优势,但对于需精确提取图像形状和目标图像形状较为复杂的工况不适用;基于轮廓的形状特征提取方法,处理速度较快,但当处理复杂目标图像形状时,容易出现较大的偏差或错误;基于区域的形状特征提取方法,在提取形状特征时更加容易实现,且在处理复杂图像时更加准确,但需要的内部存储空间较大。由此可知,目前形状特征提取方法的应用局限性较大,而发展图像特征提取方法意义重大。     

高分子田菁胶化学结构式修饰方法综述

田菁胶是从田菁种子胚乳中提取的一种天然多糖类高分子有机物。天然的化学结构反映出的理化性质限制了其应用和推广。化学结构式的修饰改进是扩大其应用的有效手段。修饰改进后的田菁胶无毒、无污染,在石油开采、煤开采、纺织、印刷、造纸和食品等领域得到了广泛应用。文中对羧甲基法、羟乙基法、羟丙基法、交联法、羟烷基-羧甲基法、羧甲基-羟烷基法、阳离子法、酶解法、氧化法和两性法等田菁胶化学结构式的主要修饰改进方法进行了详述。总结了修饰改进技术注意事项,并对前景进行了展望。     

Combined interior‐point method and semismooth Newton method for frictionless contact problems

In the present paper, a solution scheme is proposed for frictionless contact problems of linear elastic bodies, which are discretized using the finite element method with lower order elements. An approach combining the interior‐point method and the semismooth Newton method is proposed. In this method, an initial active set for the semismooth Newton method is obtained from the approximate optimal solution by the interior‐point method. The simplest node‐to‐node contact model is considered in the present paper, that is, pairs of matching nodes exist on the contact surfaces. However, the discussions can be easily extended to a node‐to‐segment or segment‐to‐segment contact model. In order to evaluate the proposed method, a number of illustrative examples of the frictionless contact problem are shown. The proposed combined method is compared with the interior‐point method and the semismooth Newton method. Two numerical examples that are difficult to solve using the semismooth Newton method are solved effectively using the proposed combined method. It is shown that the proposed method converges within far fewer iterations than the semismooth Newton methods or the interior‐point method. Copyright © 2009 John Wiley & Sons, Ltd.     

基于有限元与边界元耦合法的波浪力分析

利用有限元与边界元耦合法对三维无界区域中直立圆柱所受的波浪力进行进行计算,把整个求解区域分成内域或外域两部分,在内域采用有限元法,对外域采用边界元法,数值计算的结果与理论解吻合良好,表明该方法有效。     

Differential quadrature Trefftz method for Poisson-type problems on irregular domains

In this paper differential quadrature Trefftz method (DQTM), a new meshless method based on coupling the dual reciprocity method (DRM) with the differential quadrature method (DQM) and the Trefftz method, is used to analyze Poisson-type interior and exterior problems. In this method, the DRM is used to construct equivalent equations to the original differential equation. Then the DQM is employed to approximate the particular solutions, while Trefftz method leads to a boundary-only formulation for homogeneous solution. As a result, an inherently meshless, integration-free, boundary-only DQ Trefftz collocation technique is developed for solving Poisson-type problems. Due to the flexibility in choosing points on boundaries, the new method also works well on irregular domains. Numerical results show that the present method works efficiently with quite few points on both uniform and irregular domains.     

The traction boundary contour method for linear elasticity

This paper presents a further development of the boundary contour method. The boundary contour method is extended to cover the traction boundary integral equation. A traction boundary contour method is proposed for linear elastostatics. The formulation of traction boundary contour method is regular for points except the ends of the boundary element and corners. The present approach only requires line integrals for three‐dimensional problems and function evaluations at the ends of boundary elements for two‐dimensional cases. The implementation of the traction boundary contour method with quadratic boundary elements is presented for two‐dimensional problems. Numerical results are given for some two‐dimensional examples, and these are compared with analytical solutions. This method is shown to give excellent results for illustrative examples. Copyright © 1999 John Wiley & Sons, Ltd.     

试样制备对差式扫描法测定聚丙烯管材料熔融温度的影响

通过切粒法和压片法对聚丙烯管材料进行制样,采用差式扫描法进行熔融温度的测定,根据测得的数据分析不同制备方法对熔融温度的影响。结果表明：切粒法制备试样测得的熔融温度偏高,压片法制备试样测定熔融温度的重复性较好。     

超疏水表面制备方法的比较

超疏水性是一种特殊的润湿性,它是指水滴与表面的静态接触角大于150°或者滑动角小于10°,其最初来源于"荷叶效应".本文对近几年关于超疏水理论和自然界中超疏水现象研究进行介绍,并对超疏水表面的制备方法及其应用进行综述.分别总结了基于模板法、涂覆法、刻蚀法的超疏水表面制备方案的优缺点及其改进措施,重点阐述超疏水表面在金属...     

A bridging transition technique for the combination of meshfree method with finite element method in 2D solids and structures

For certain continuum problems, it is desirable and beneficial to combine two different methods together in order to exploit their advantages while evading their disadvantages. In this paper, a bridging transition algorithm is developed for the combination of the meshfree method (MM) with the finite element method (FEM). In this coupled method, the MM is used in the sub-domain where the MM is required to obtain high accuracy, and the FEM is employed in other sub-domains where FEM is required to improve the computational efficiency. The MM domain and the FEM domain are connected by a transition (bridging) region. A modified variational formulation and the Lagrange multiplier method are used to ensure the compatibility of displacements and their gradients. To improve the computational efficiency and reduce the meshing cost in the transition region, regularly distributed transition particles, which are independent of either the meshfree nodes or the FE nodes, can be inserted into the transition region. The newly developed coupled method is applied to the stress analysis of 2D solids and structures in order to investigate its’ performance and study parameters. Numerical results show that the present coupled method is convergent, accurate and stable. The coupled method has a promising potential for practical applications, because it can take advantages of both the MM and FEM when overcome their shortcomings.     

裂缝孔隙介质中驱动问题的特征交替方向有限元方法及分析

本文考虑裂缝孔隙介质中驱动问题的数值方法及理论分析。我们分别对压力方程采用混合元方法,对裂缝系统上的浓度方程采用特征线交替方向有限元方法,对岩块系统上的浓度方程采用交替方向有限元方法,证明了交替方向有限元格式具有最优L~2-模和H~1-模误差估计。