关于解大型稀疏线性代数方程组一种算法的误差分析

本文利用J.H.Wilkinson“向后分析”误差理论证明了Ⅰ中算法的稳定性,并给出近似解残量的估计式。 Ⅰ 算法 给定线性代数方程组 Ax=b,(1.1)其中A是大型稀疏对称正定矩阵。为了有效地求解它,所用算法必须是稳定的,且在计算过程中要求充分利用和保持A的稀疏性,以节省存储量,并使计算时间短,解的     

关于矩阵方程X+A*X-αA+B*X-βB=I的正定解

本文研究了矩阵方程X+A*X-αA+B*X-βB=I在α,β∈(0,1]时的正定解.利用单调有界极限存在准则,构造三种迭代算法,获得了方程的正定解,拓宽了此类方程的求解方法.数值算例说明算法的可行性.     

一种改进的隐式Euler切线法

对于Hessian矩阵正定的情形,在求解二次函数模型信赖域子问题的隐式分段折线算法的基础上,提出一种求解信赖域子问题的改进的隐式Euler切线法,并分析该路径的性质.数值实验表明新算法是有效可行的,且较原算法具有迭代次数少、计算时间短等优点.     

对称双正型线性互补问题的多重网格迭代解收敛性理论

多重网格法是七十年代产生并获得迅速发展的快速送代法.八十年代初,此方法开始应用于变分不等式的求解,其中包括一类互补问题,近十年来大量的数值实验证实,算法是成功的,而算法的收敛性理论也正在逐步建立,当A正定对称时的多重网格收敛性可见[3]和[7];[4]讨论了A半正定时的情况·本文考虑A为更广的一类矩阵:对称双正阵(见定义1.1),建立互补问题:     

对称双正型线性互补问题的多重网格迭代解收敛性理论

多重网格法是七十年代产生并获得迅速发展的快速送代法.八十年代初,此方法开始应用于变分不等式的求解,其中包括一类互补问题,近十年来大量的数值实验证实,算法是成功的,而算法的收敛性理论也正在逐步建立,当A正定对称时的多重网格收敛性可见[3]和[7];[4]讨论了A半正定时的情况·本文考虑A为更广的一类矩阵:对称双正阵(见定义1.1),建立互补问题:     

求解正定二次规划的一个全局收敛的滤子内点算法

现有的大多数分类问题都能转化成一个正定二次规划问题的求解.通过引入滤子方法,并结合求解非线性规划的原始对偶内点法,给出求解正定二次规划的滤子内点算法.该算法避免了使用效益函数时选取罚因子的困难,在较弱的假设条件下,算法具有全局收敛性.     

解变分不等式的一种二次投影迭代算法

本文研究了一类新的求解伪单调变分不等式的二次投影迭代算法.利用Armijo型线性搜寻程序,建立了一类新的超平面,他们严格分离当前迭代点与变分不等式的解集.运用超平面的这种分离性质,在较弱的条件下证明了该算法生成的无穷序列是全局收敛的.数值实验证明该算法是有效的.     

一种求解二次函数模型信赖域子问题的分段切线算法

在Hessian矩阵正定的前提下,建立一种最优曲线的微分方程模型.针对此微分方程模型,提出一种求解二次函数模型信赖域子问题的分段切线算法,并分析和证明分段切线路径的合理性.数值结果表明新算法是有效且可行的.     

一个求解广义圆锥互补问题的无导数光滑算法

本文研究了一个求解广义圆锥互补问题的无导数光滑算法.利用光滑函数将广义圆锥互补问题等价转化成一个光滑方程组,然后再利用牛顿法求解此方程组.该算法采用了一种新的非单调无导数线搜索技术,并且在适当条件下具有全局和局部二次收敛性质.数值实验结果表明算法是非常有效的.     

矩阵方程X+A~*X~(-n)A=P的Hermite正定解及其扰动分析

考虑非线性矩阵方程X A~*X~(-n)A=P,其中A是m阶非奇异复矩阵,P是m阶Hermite正定矩阵.本文利用不动点理论讨论了该方程Hermite正定解的存在性及包含区间,给出了极大解的性质及求极大,极小解的迭代算法.研究了极大解的扰动问题,利用微分等方法获得了两个新的一阶扰动界,并给出数值例子对所得结果进行了比较说明.     

Quenched large deviation principle for words in a letter sequence

When we cut an i.i.d. sequence of letters into words according to an independent renewal process, we obtain an i.i.d. sequence of words. In the annealed large deviation principle (LDP) for the empirical process of words, the rate function is the specific relative entropy of the observed law of words w.r.t. the reference law of words. In the present paper we consider the quenched LDP, i.e., we condition on a typical letter sequence. We focus on the case where the renewal process has an algebraic tail. The rate function turns out to be a sum of two terms, one being the annealed rate function, the other being proportional to the specific relative entropy of the observed law of letters w.r.t. the reference law of letters, with the former being obtained by concatenating the words and randomising the location of the origin. The proportionality constant equals the tail exponent of the renewal process. Earlier work by Birkner considered the case where the renewal process has an exponential tail, in which case the rate function turns out to be the first term on the set where the second term vanishes and to be infinite elsewhere. In a companion paper the annealed and the quenched LDP are applied to the collision local time of transient random walks, and the existence of an intermediate phase for a class of interacting stochastic systems is established.     

Testing for causality in the Richardson arms race model

This paper shows that the Hsiao test can be used to test the causal implication of the Richardson model demonstrating arms race between U.S. and the U.S.S.R. in the presence of China. The impact of Strategic Arms Limitation Talks (SALT I) upon the arms race of the U.S. and the U.S.S.R. is also examined. Two conclusions can be drawn from this study: First, it was found that it was the growth in the U.S.S.R. armament that ‘Granger caused’ the growth in U.S. arms spending over the period from 1952 to 1981. Second, there seems little evidence that SALT I has had any impact upon the armaments of either the U.S. or the U.S.S.R..     

网络外部性条件下差异化双边平台买者参与问题

双边平台存在的基础是参与的用户,因此用户的分配是双边市场上各利益主体最关心的问题。为研究用户分配问题,本文在具有差异性的竞争双边市场上,建立了两阶段的双边平台竞争模型。第一阶段使用Rubinstein讨价还价模型对卖者的参与人数进行分配,利用讨价还价顺序描述卖者进入的先后顺序;第二阶段分别在平台利润最大化和社会福利最大化两种情况下,刻画买者对平台的规模偏好,并求均衡的市场份额。通过此模型分析竞争性平台差异化的情况下,网络外部性系数对平台均衡市场份额以及市场利益相关者利得的影响。研究表明:在考虑平台利润最大化的情况下,买者参与人数受卖者规模与网络外部性系数的影响,平台规模并非越大越好;在考虑社会福利最大化的情况下,买者的网络外部性系数与买者参与人数不相关,但与总社会福利正相关。     

Numerical Simulation of Crack Growth

In recent years the X-FEM based on the partition of unity method and the strong discontinuity approach (SDA) have shown to be powerful tools to model crack growth. Both methods model the crack surface by introducing additional d.o.f.. In the X-FEM the nodes in the mesh around a crack are globally enhanced with new d.o.f. while in in the SDA the new d.o.f. are commonly introduced as internal ones. Thus the jump displacement fields are constant across elements. Therefore the d.o.f. can be condensed on element level which results in jumps in the displacement field at element edges. In this contribution the strong discontinuity approach is used approximating the displacement jump linearly across the crack length similar as e.g. in [3]. New additional nodes of the cracked elements that lie on the element edges are introduced but are not considered as internal nodes but remain global. Thus crack path continuity is automatically given. These global d.o.f. approximate the discontinuous part of the displacement field. The sum of the aforementioned part and the continuous displacement field represent the total displacement field including a possible jump. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

天然心瓣关闭机理研究

本文在二维模型假定的基础上,从一个新的角度,通过理论分析和实验研究,解决了心脏瓣膜在射血加速相的部分关闭机理以及旋涡在瓣关闭中的作用这两个心瓣关闭机理研究中长期以来一直悬而未决的问题,并指出了窦(或瓣叶后空腔)对有效瓣膜关闭的决定性作用.此外,本文还研究了瓣长、频率等对瓣运动的影响.估计本文的研究对人工心瓣的研制有一定参考作用.     

The Convergence of the Spectral Scheme for Solving Two-Dimensional Vorticity Equations

Much work has been done for the spectral scheme of the P.D.E. The author proposed a technique to prove the strict error estimation of the spectral scheme for the K.D.V.-Burgers equation. In this paper, the technique is generalized to two-dimensional vorticity equations. Under some conditions, the error estimation implies the convergence. The more smooth the solution of the vorticity equations, the more accurate the approximate solution.     

Problem of an elastic half-plane with a crack emerging orthogonally at the boundary

The problem of the half-plane, in which a finite crack emerges orthogonally at the boundary, is studied. On the edges of the crack a self-balancing load is applied. A detailed investigation is carried out for an integral equation with respect to the unknown derivative of the displacement jump, to which the problem can be reduced. The exact solution of the integral equation is constructed with the aid of the Mellin transform and the Riemann boundary value problem for the halfplane. The asymptotic behavior of the solution at both ends of the crack is elucidated. First the asymptotic behavior of the solution at the point of emergence of the crack is obtained and the dependence of this asymptotic behavior on the type of the load is established. For a special form of the load one obtains a simple expression of the stress intensity coefficient. In the case of a general load, the asymptotic behavior is used for the construction of an effective approximate solution on the basis of the method of orthogonal polynomials. As a result, the problem reduces to an infinite algebraic system, solvable by the reduction method.Translated from Dinamicheskie Sistemy, No. 4, pp. 45–51, 1985.     

On a lower and upper bound for the curvature of ellipses with more than two foci

Let a set of points in the Euclidean plane be given. We are going to investigate the levels of the function measuring the sum of distances from the elements of the pointset which are called foci. Levels with only one focus are circles. In case of two different points as foci they are ellipses in the usual sense. If the set of the foci consists of more than two points then we have the so-called polyellipses. In this paper we investigate them from the viewpoint of differential geometry. We give a lower and upper bound for the curvature involving explicit constants. They depend on the number of the foci, the rate of the level and the global minimum of the function measuring the sum of the distances. The minimizer will be characterized by a theorem due to E. Weiszfeld together with a new proof. Explicit examples will also be given. As an application we present a new proof for a theorem due to P. Erd?s and I. Vincze. The result states that the approximation of a regular triangle by circumscribed polyellipses has an absolute error in the sense that there is no way to exceed it even if the number of the foci are arbitrary large.     

Derivation of the particle dynamics from kinetic equations

The microscopic solutions of the Boltzmann-Enskog equation discovered by Bogolyubov are considered. The fact that the time-irreversible kinetic equation has time-reversible microscopic solutions is rather surprising. We analyze this paradox and show that the reversibility or irreversibility property of the Boltzmann-Enskog equation depends on the considered class of solutions. If the considered solutions have the form of sums of delta-functions, then the equation is reversible. If the considered solutions belong to the class of continuously differentiable functions, then the equation is irreversible. Also, the so called approximate microscopic solutions are constructed. These solutions are continuous and they are reversible on bounded time intervals. This analysis suggests a way to reconcile the time-irreversible kinetic equations with the timereversible particle dynamics. Usually one tries to derive the kinetic equations from the particle dynamics. On the contrary, we postulate the Boltzmann-Enskog equation or another kinetic equation and treat their microscopic solutions as the particle dynamics. So, instead of the derivation of the kinetic equations from the microdynamics we suggest a kind of derivation of the microdynamics from the kinetic equations.     

Nonstationary boundary problem for model kinetic equations at critical parameters

Nonstationary solutions of the model kinetic equation at critical values of the motion of the wall (the boundary of the half-space occupied by gas) are studied. The characteristic equation is obtained by separating the variables. The eigenfunctions and the eigenvalue spectrum are found in the distribution space. A solution to the equation is expandable over the eigenfunction basis. The Rayleigh problem is considered as an application. The distribution function is continuous in the plane of the wall-motion parameters, including the closed curve of critical parameter values. Translated from Teoreticheskaya i Matematicheskaya Fizika. Vol. 116. No. 2, pp. 305–320. August. 1998.