基于GMRES(m)法的双连通区域数值保角变换的计算法

本文研究了基于模拟电荷法的双连通区域的数值保角变换问题.利用限制Krylov子空间最大维数的算法–GMRES(m)算法,求解基于模拟电荷法的双连通区域数值保角变换中的约束方程,获得了模拟电荷和变换半径,构造了近似保角变换函数.数值实验表明了本文算法的有效性.     

基于LSQR法的外部数值保角逆变换计算法

本文提出了基于模拟电荷法的外部数值保角逆变换计算法.利用LSQR (Least Square QR-factorization)方法来求解基于模拟电荷法的外部数值保角逆变换中的约束方程,得到了电荷量和逆变换半径,进而构造了近似保角逆变换函数.数值实验证明本文提出的算法是有效的.     

多连通区域到狭缝圆环域的共形映射计算法

基于模拟电荷法,研究了将具有高连通度的有界区域映射到带有对数螺旋狭缝单位圆环域的共形映射计算法.提出利用BiCR(bi-conjugate residual)算法求解由Dirichlet边界条件建立的约束方程组,得到模拟电荷,进而构造出高精度的近似共形映射函数.数值实验验证了该文算法的有效性,并成功将该共形映射计算法应用到绕流仿真模拟中,模拟了有界高连通度区域内螺旋点涡的绕流.     

带任意裂纹的一维六方准晶弹性半平面第一基本问题

研究了周期平面内含任意裂纹的一维六方准晶的弹性半平面第一基本问题.首先借助保角变换将半平面第一基本问题转化为单位圆内带任意裂纹的第一基本问题;再利用复变函数方法将求有界域内的弹性平衡问题转化为奇异积分方程的求解,并证明方程是唯一可解的.该问题的求解为研究工程断裂问题提供了理论方法.     

用多复变量应力函数计算任意多连通弹性平面问题

本文应用弹性力学的复变函数理论,用多保角变换的方法,导出了任意多连通无限大弹性板的多复变量应力函数表达式。在边界上进行复Fourier级数展开,用待定系数法确定应力函数的未知系数,从而计算弹性板的应力场,以含有任意多个任意位置椭圆孔的无限板为例,编制了相应的多工况运行的FORTRAN77标准化程序,进行了考题和算例分析,给出了级数的收敛状况和孔边周向应力的分布图,结果表明本方法对处理多连通无限大弹性平面问题行之有效。     

非均匀双周期裂纹场的反平面问题

本文从虎克定律与平衡方程出发,利用复变函数映象的理论.将裂纹发生的矩形区域保角变换到ζ平面的上半平面去.再根据H.И.穆斯黑里什维利[1]的理论,对非均匀双周期裂纹场的反平面问题,我们求得闭合解,并推出了应力强度因子.     

基于拟态物理学的约束多目标共轭梯度混合算法

在拟态物理学优化算法APO的基础上,将一种基于序值的无约束多目标算法RMOAPO的思想引入到约束多目标优化领域中.提出一种基于拟态物理学的约束多目标共轭梯度混合算法CGRMOAPA.算法采取外点罚函数法作为约束问题处理技术,并借鉴聚集函数法的思想,将约束多目标优化问题转化为单目标无约束优化问题,最终利用共轭梯度法进行求解.通过与CRMOAPO、MOGA、NSGA-II的实验对比,表明了算法CGRMOAPA具有较好的分布性能,也为约束多目标优化问题的求解提供了一种新的思路.     

单位圆到任意曲线保角变换的近似计算方法

本文讨论了将单位圆内部映射成由任意曲线(包括任意曲线割缝)边界围成的单连通域内部或外部的保角变换问题.以多边形逼近单连通域的边界,采用Schwartz-Christoffel积分建立单位圆与该多边形的映射函数.给出了确定Schwartz-Christoffel积分中未知参数的数值计算方法.     

计及边缘效应的平行板电容器单位长度电容的计算

将保角变换法与格林函数法相结合,研究计及边缘效应的平行板电容器的电场,得到其电势和场强分布,利用软件MATLAB对场分布进行数值模拟,给出其单位长度电容量的计算公式,并与忽略边缘效应的电容量的计算公式进行比较,得到两计算公式产生的相对误差随其宽与板间距之比变化的函数关系.     

线性规划Karmarkar算法的一种改进算法及其数值检验

本文给出求解线性规划问题的一种改进的Karmarkar算法IKA.本算法通过施行仿射变换,将已给定的一个可行内点,变成另一空间可行域中所有分量为1的点e,然后从e出发,沿梯度方向进行一维搜索,使问题的目标函数单调下降,并收敛于最优值,因而不需假定目标函数最优值为已知.几个有数百个约束方程和变量的实际算例表明本算法比Karmarkar算法有效.     

On the domain dependence of the inf-sup and related constants via conformal mapping

In this paper we investigate the domain dependence of the inf-sup stability constant in the family of two-dimensional simply connected domains using its connection to the optimal constant figuring in Friedrichs? inequality for conjugate harmonic functions and the conformal mapping of the domain. A lower estimation of the inf-sup constant is also given in terms of the conformal mapping provided the boundary of the domain is smooth enough. We illustrate the results with several examples.     

Conjugate function method for numerical conformal mappings

We present a method for numerical computation of conformal mappings from simply or doubly connected domains onto so-called canonical domains, which in our case are rectangles or annuli. The method is based on conjugate harmonic functions and properties of quadrilaterals. Several numerical examples are given.     

Doubly Connected Minimal Surfaces and Extremal Harmonic Mappings

The concept of a conformal deformation has two natural extensions: quasiconformal and harmonic mappings. Both classes do not preserve the conformal type of the domain, however they cannot change it in an arbitrary way. Doubly connected domains are where one first observes nontrivial conformal invariants. Herbert Gr?tzsch and Johannes C.C.?Nitsche addressed this issue for quasiconformal and harmonic mappings, respectively. Combining these concepts we obtain sharp estimates for quasiconformal harmonic mappings between doubly connected domains. We then apply our results to the Cauchy problem for minimal surfaces, also known as the Bj?rling problem. Specifically, we obtain a sharp estimate of the modulus of a doubly connected minimal surface that evolves from its inner boundary with a given initial slope.     

On 2D structured mesh generation by using mappings

A grid generation problem in two‐dimensional domains is considered by using a quasi‐conformal mapping of the parametric domain with a given square mesh onto the physical domain where the grid is required. To this end, a harmonic mapping is first applied, which, by the Radó theorem, is a diffeomorphism subject to some known conditions. However, the discrete harmonic mapping may produce folded meshes on a nonconvex domain with a strongly bent boundary. We demonstrate that it is caused by the truncation error. With the aim of controlling grid node location, an additional mapping is used. The Dirichlet problem for the universal elliptic partial differential equations is solved to construct the mapping. This allows to produce unfolded grids with a prescribed cell shape. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 1072–1091, 2011     

Quasiconformal harmonic mappings between \fancyscriptC1,m{{\fancyscript{C}}^{1,\mu}} Euclidean surfaces

The conformal deformations are contained in two classes of mappings quasiconformal and harmonic mappings. In this paper we consider the intersection of these classes. We show that, every K quasiconformal harmonic mapping between surfaces with boundary is a Lipschitz mapping. This extends some recent results of several authors where the same problem has been considered for plane domains. As an application it is given an explicit Lipschitz constant of normalized isothermal coordinates of a disk-type minimal surface in terms of boundary curve only. It seems that this kind of estimates are new for conformal mappings of the unit disk onto a Jordan domain as well.     

用于解析函数复分析的共轭边界元法

由2个共轭的实调和函数构建1个复解析函数,其复分析在应用数学和力学领域具有重要的作用.提出了一个加权残数方程组,证明了该方程组为2个共轭函数的域内控制方程、边界条件和边界上Cauchy Riemann(柯西-黎曼)条件的近似解,等效为复解析函数的逼近方程.在离散空间中,由该加权残数方程分别推导出2个位势问题的直接边界积分方程和1个表示Cauchy-Riemann条件的有限差分方程,随后解决了弱奇异线性方程组的求解难题,并提出用Cauchy积分公式求内点值的方法,从而建立了一种用于复分析的常单元共轭边界元法.最后,用3个算例证明了所提出方法适用于域内或域外的幂函数、指数函数或对数函数形式的解析函数,而且其误差与2维位势问题是同等量级的.     

Conformal mapping of long quadrilaterals and thick doubly connected domains

In this paper we investigate theoretically an approximation technique for avoiding the crowding phenomenon in numerical conformal mapping. The method applies to conformal maps from rectangles to “long quadrilaterals,” i.e., Jordan domains bounded by two parallel straight lines and two Jordan arcs, where the two arcs are far apart. We require that these maps take the four corners of the rectangle to the four corners of the quadrilateral. Our main theorem tackles a conformal mapping problem for doubly connected domains, and we derive from this our results for quadrilaterals. As a corollary, we extend the “domain decomposition” mapping technique of Papamichael and Stylianopoulos. Similar results hold for the inverse maps, from quadrilaterals to rectangles.     

Conformal Contractions and Lower Bounds on the Density of Harmonic Measure

We give a concrete sufficient condition for a simply-connected domain to be the image of the unit disk under a nonexpansive conformal map. This class of domains is also characterized by having sufficiently dense harmonic measure. The relation with the harmonic measure provides a natural higher-dimensional analogue of this problem, which is also addressed.