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地磁导航系统中等值线的提取及应用 总被引:1,自引:0,他引:1
地磁导航系统采用等值线最近点迭代算法达到最终匹配定位的目的,等值线最近点迭代算法是在等值线的基础上实现的,因此,等值线的提取是实现地磁导航的“必经之路”。文中介绍了常用的两种等值线提取方法,即线性插值方法和等值线延伸寻找最近点法,其中前者的计算量大,实时匹配效果差,而后者能在地磁匹配过程中快速提取匹配需要的等值线。此外,文中还给出了地磁等值线图层在基于电子海图显示信息系统的地磁导航系统中的生成和添加方法。 相似文献
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对图像进行滤波或称平滑是干涉条纹图像处理中的一项重要工作。一幅未经处理的原始图像或多或少存在着不同程度的噪声干扰,特别是散斑和Insar干涉条纹图,信噪比很低,难以处理。本文针对光测力学中光学干涉方法得到的条纹图,提出了一种新的滤波方法条纹等值线窗口滤波,并对这种滤波方法进行了研究讨论,提出了几种确定等值线窗口的不同方法。这种滤波方法根据干涉条纹图不同断面上灰度分布的不同特点,选择沿条纹走向的条纹等值线窗口进行滤波,在最大消除条纹图噪声的同时,也能保证对条纹损伤最小。摄像测量技术正在迅速发展和得到广泛应用,在国防试验和航天飞行任务中发挥着不可替代的作用。本文也介绍了作者近年来在该领域所做的应用研究,包括在火箭、导弹发射试验,冲击、碰撞等过程中的动态目标运动测量;针对航天航空和力学工程领域的视频图像实时分析;飞行器三维运动测量;基于投影条纹的物体三维形貌精密测量方法研究;以及对接航天器位置和姿态的实时测量。在这些应用中都实现了高精度测量。 相似文献
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作为一个基础统计量,时空关联函数在湍流问题的研究中有着广泛的应用,是研究湍流噪声、湍流中物质扩散和大涡模拟亚格子模型等问题的重要参考.本文通过建立三维多孔结构壁面剪切湍流模型,采用含Darcy-Brinkman-Forchheimer作用力项的格子Boltzmann方程对无穷大多孔介质平行板之间壁湍流进行了数值模拟,进而研究其速度脉动时空关联函数的统计特性.一方面,根据计算得到的流场数据,对比分析了常规槽道湍流与多孔介质壁面槽道湍流的时间关联函数.另一方面,计算并讨论了不同孔隙率和渗透率的多孔介质壁面对速度脉动时空关联性的影响.通过研究表明:多孔结构壁面剪切湍流的时空关联函数等值线与椭圆理论相符;在研究参数范围内,多孔介质壁面的速度时空关联系数随着孔隙率增大而增大,随着渗透率增大而减小.同时发现在槽道壁面的近壁区、过渡区、对数律区和中心区等不同位置处,速度时空关联呈现较大差异性:越远离壁面位置(对数律区和中心区),其时空关联函数所呈现的关联等值线椭圆越细长,高值相关等值线越集中.多孔介质主要改变速度时空关联椭圆图像的椭圆率,说明多孔介质壁面主要影响湍流横扫速度. 相似文献
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Level Set追踪等温非牛顿熔全前沿界面 总被引:1,自引:0,他引:1
应用Level Set方法追踪薄壁型腔内Hele-Shaw熔体流动前沿界面,采用5阶加权本质无振荡格式耦合中心差分格式实现了充填阶段的动态模拟.准确追踪到了不同时刻熔体前沿界面,并得到了对应的压力等值线分布,数值结果表明Level Set方法是准确追踪注塑成型熔体前沿界面的一种行之有效的方法. 相似文献
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利用全场灰度处理云纹数字图象的新方法 总被引:3,自引:0,他引:3
本文介绍并提出了一系列利用全场灰度进行云纹数字图象处理的新方法.由于充分利用了全场每个象素点的灰度信息,所以用这些方法可以得到传统方法难以得到的多种结果,例如条纹倍增、各种应变场图象的建立、应变等值线的提取等等。这些方法大大扩大了云纹法测量的使用范围。 相似文献
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本文提出了一种绘制受载结构等应力图的有效而简单的方法,这种方法是在开发PRSA-1专用有限元程序中逐渐改进和完善的,它能根据有限元的计算结果连续地在结构内搜索等应力点,也采用了适当的方法构造出一些等应力点。借助于AUTOCAD绘图软件包,结构的等应力图可以在计算机屏幕上自动生成,也可以用绘图仪绘出以便永久保留。 相似文献
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A. N. Galybin 《Journal of Elasticity》2011,102(1):15-30
This paper presents unconventional formulations of boundary problems of plane elasticity formulated in terms of orientations
of tractions and displacements on a closed contour separating internal and external domains as the boundary conditions. These
are combined with the conditions of continuity of tractions or displacements across the boundary. Therefore the magnitudes
of neither tractions nor displacements are assumed on the contour. Four boundary value problems for both external and internal
domains are investigated by analyzing the solvability of the corresponding singular integral equations. It is shown that all
considered problems can have non-unique solutions expressed as linear combinations of particular solutions and, hence, contain
free arbitrary parameters, the number of which is finite and determined by the contour orientations of tractions and/or displacements 相似文献
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采用常数边界元对船舶与流体界面进行离散,求解船舶兴波势及船舶兴波阻力。这种方法可避免在船舶与流体自由面交线上安置节点,因而避免了这些节点建立补充方程。因为满足自由面条件的Havelock源函数的源点和场点不能同时在自由面上,使得自由面上的节点无法用Havelock源函数的建立方程。如对自由面交线上的节点建立补充方程,则要对线性自由面条件中包含的未知势函数的二阶导数用差分形式表达,引入较大误差。 相似文献
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There are many challenges in the numerical simulation of liquid sloshing in horizontal cylinders and spherical containers using the finite element method of arbitrary Lagrangian–Eulerian (ALE) formulation: tracking the motion of the free surface with the contact points, defining the mesh velocity on the curved wall boundary and updating the computational mesh. In order to keep the contact points slipping along the curved side wall, the shape vector in each time advancement is defined to modify the kinematical boundary conditions on the free surface. A special function is introduced to automatically smooth the nodal velocities on the curved wall boundary based on the liquid nodal velocities. The elliptic partial differential equation with Dirichlet boundary conditions can directly rezone the inner nodal velocities in more than a single freedom. The incremental fractional step method is introduced to solve the finite element liquid equations. The numerical results that stemmed from the algorithm show good agreement with experimental phenomena, which demonstrates that the ALE method provides an efficient computing scheme in moving curved wall boundaries. This method can be extended to 3D cases by improving the technique to compute the shape vector. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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《International Journal of Solids and Structures》2001,38(1):161-178
Two related topics are addressed in this article. The first part of the article proves that, for a certain admissible class of problems in linear elasticity, the hypersingular boundary contour method (HBCM) can be collocated at all boundary points on the surface of a three-dimensional (3-D) body, including those on boundary contours, edges and corners, because the HBCM-shape-functions satisfy, a priori, all the smoothness requirements for collocation at these points. In contrast, the hypersingular boundary element method needs, in general, relaxation of some of these smoothness requirements for its shape functions, even for collocation at regular points that lie on the boundaries of boundary elements.A hypersingular residual, obtained from the standard and hypersingular boundary integral equations (HBIEs), has been recently proposed as a local error estimator for a boundary element, for the boundary integral equation. The second part in the present article is concerned with a definition of an analogous local error estimator for the boundary contour method, for 3-D linear elasticity. This error estimator is then used to drive an h-adaptive meshing procedure. Numerical results are presented to demonstrate adaptive meshing for selected example problems. 相似文献
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Continuity of the derivatives of the main variable is an important feature to obtain an accurate representation of moving boundaries with discrete numerical methods, since the value and direction of the velocity are normally used to relocate the nodal points in a time-marching scheme. A recently developed formulation of the boundary element method using cubic B-splines provides up to C2 continuity between adjacent elements. This formulation is applied in this work to saltwater intrusion problems in confined, leaky and unconfined aquifers. 相似文献
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A. A. Kovalenko 《Fluid Dynamics》1995,30(4):555-562
A method of solving the boundary layer equations is developed taking into account the strong interaction between the boundary layer and the outer hypersonic inviscid flow. The method is aimed at solving problems whose salient feature is the possible upstream propagation of disturbances over distances comparable with the body length. The procedure for fitting a self-consistent contour of the effective body using an artificially formulated boundary value problem for an ordinary second-order differential equation, which lies at the basis of the method, is considered in detail. The method is applied to the problem of flow around a flat plate with roughness in the form of an embankment or a trench; the calculated results are presented.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 81–89, July–August, 1995. 相似文献