无穷凹角区域各向异性问题的自然边界元法

本文研究无穷凹角区域上一类各向异性问题的自然边界元法.利用自然边界归化原理,获得该问题的Poisson积分公式和自然积分方程,给出了自然积分方程的数值方法,以及逼近解的收敛性和误差估计,最后给出了数值例子,以示方法的可行性和有效性.     

凹角区域双曲外问题的精确人工边界条件

研究一类凹角区域双曲型外问题的数值方法.先用Newmark方法对时间进行离散化,在每个时间步求解一个椭圆外问题.然后引入人工边界,并获得精确的人工边界条件.给出半离散化问题的变分问题,证明了变分问题的适定性,并给出了误差估计.最后给出数值例子,以示该方法的可行性与有效性.     

无穷凹角区域各向异性问题的自然边界元与有限元耦合法

本文研究无穷凹角区域上一类各向异性问题的自然边界元与有限元耦合法.利用自然边界归化原理,获得圆弧或椭圆弧人工边界上的自然积分方程,给出了耦合的变分形式及其数值方法,以及逼近解的收敛性和误差估计,最后给出了数值例子,以示方法的可行性和有效性.     

无界区域Stokes 问题非重叠型区域分解算法及其收敛性

本文研究无界区域Stokes方程外问题的利用有限元法和自然边界归化的非蕈叠型区域分解算法,此方法对无界区域Stokes问题非常有效.给出连续和离散情形的D-N算法及其收敛性分析,得到算法收敛的充要条件及充分条件,并得到最优的松弛因子和压缩因子,最后给出数值算例予以验证.     

空间半无界区域的非重叠区域分解算法

主要研究了空间一种半无界凹球区域上的区域分解算法.在三维空间自然边界规划的基础上,以三维Dirichlet外边值问题为例,进行的D-N交替算法.并提出了该算法与Richardson迭代法的等价性,并分析其收敛性及其收敛速度与网格参数h无关.同时给出了松弛因子的取值范围.     

Stokes问题的非协调区域分解法

1 引言 区域分解法是近年来新崛起的偏微分方程的数值解法.由于区域分解法比通常的数值解法有其独特的优点,再加上并行机的迅速发展,故国内外大批数值分析学家竞相投入这一研究行列.现在这方面的研究工作已有许多[1,2,8,9,10,12,13,15,16,18,19,20],并且在实际计算方面也开始理论化,系统化.但到目前为止,对非协调元的非重迭型区域分解法的研究还甚少,尤其是用来解决Stokes问题.对此,我们提出本文,目的在于利用在实际计算中经常采用的一类非协调元(C-R元),配合区域分解法这一新思想来处理Stokes问题,并得到了所给定算法的几何收敛性结果. 对Stokes问题连续情形下的区域分解算法的讨论已在文[8]中有所涉及,这里不再叙述.本文主要讨论Stokes问题非协调离散情形下的区域分解算法.     

区域信号配时模型的非平衡交通分配算法

本文研究了区域信号配时问题.采用遗传算法和非平衡交通分配的拟Frank-Wolfe算法来求解,通过实例对算法进行验证并与已有的算法结果进行了比较,结果表明算法是有效的,适合求解这类问题.     

具单调收敛性的区域分解法

1 引言 区域分解法和多重网格法都被认为是求解椭圆边值问题的快速算法.这两类算法也先 后应用于变分不等式的求解并获得了较为成功的数值尝试,收敛性理论也相继建 立.但是和用于方程问题不同,建立相应的h无关收敛性理论甚至更初步的收敛率分析遇到 一定的困难.九十年代初,Kornhuber针对变分不等式第一边值问题及摩擦问题进一步 讨论了多重网格法的收敛性质并在其离散问题非退化情形证明了渐近几何收敛速度,但仍 未见到有关h无关收敛性.区域分解法起步稍晚,但自八十年代末Lions给出了Schwarz交 替法的变分解释以来发展很快.Kuznetsov等人于九十年代初证明了乘性 Schwarz和加性Schwarz算法用于求解单边障碍问题时单调收敛于解.在同样条件下, [13]得到了误差估计式并利用无约束情形的有关结果得到了h无关收敛性.但是,在前述 的各种区域分解法中,子问题的求解都是精确的,因此在子域上费时较多而且在数值上也往 往只能得到子问题的近似解.这样自然产生这样一个想法:能否在子问题上和多重网格法 一样用近似解代替?本文即是针对此问题,从加性Schwarz算法入手,不仅证明算法收敛,而     

单障碍问题区域分解法的单调收敛性与收敛速度估计

本文我们考虑一类典型的椭圆型算子的障碍问题的区域分解算法,分析算法的单调收敛性并给出相应的收敛速度估计.障碍问题有着重要的物理背景（参见[3,9]）.近些年来,有关障碍问题的区域分解法方面的研究已经有一些成果.关于线性算子情形,读者可参看[1,2,5,7,8,10,12,13,14,15,17]等文献,而对于非线性算子情形,读者可参看[4,6,16,18].在这些文献中,已经有部分涉及到算法的收敛速度估计.例如,文[15,16]给出了有限元区域分解算法的迭代误差的渐近最大模估计,文[13]给出了求解具M-阵的有限维互补问题     

椭圆外区域各向异性问题基于人工边界条件的Schwarz交替算法

研究一类二维各向异性外问题的重叠型区域分解.基于自然边界归化,对各向异性外问题提出了一种Schwarz交替算法,并给出其离散形式,分析了算法的收敛性.给出数值试验以示算法的可行性与有效性.     

Minimal Overrings of an Integrally Closed Domain

Abstract

The main purpose of this paper is to characterize minimal overrings of an integrally closed domain R. We show that there exists a strong relationship between minimal overrings and the notion of ideal transforms. In particular, we prove that if T(M) = S(M) for each maximal ideal M, then there is a bijective correspondence between the set of invertible maximal ideals of R and the set of minimal overrings of R. This study enables us to produce several interesting applications concerning semi-local, Dedekind, Prüferian and Krull domains. Moreover, we investigate the spectrum of a minimal overring in comparison with the spectrum of R, and we determine whether the polynomial ring R[X ₁, X ₂,…, X _n ] has a minimal overring.     

极值复特征的值域

本文考虑单位圆Ｕ＝｛Ｚ｜｜Ｚ｜＜１｝到自身上的极值拟共形映照复特征的值域。在复特征值域的适当限制下，得到一个判别极值复特征的充要条件。作为特殊情形，改进了Ｑｒｔｅｌ和Ｓｍｉｔｈ＾［１］的结果。     

Valuation and Pseudovaluation Subrings of an Integral Domain

Let R, S be two rings. We say that R is a valuation subring of S (R is a VD in S, for short) if R is a proper subring of S and whenever x ∈ S, we have x ∈ R or x ^?1 ∈ R. We denote by Nu(R) the set of all nonunit elements of a ring R. We say that R is a pseudovaluation subring of S (R is a PV in S, for short) if R is a proper subring of S and x ^?1 a ∈ R, for each x ∈ S?R, a ∈ Nu(R). This article deals with the study of valuation subrings and pseudovaluation subrings of a ring; interactions between the two notions are also given. Let R be a PV in S; the Krull dimension of the polynomial ring on n indetrminates over R is also computed.     

整环上保持矩阵等价的映射

矩阵论是代数学的重要分支,而矩阵保持问题是矩阵论中的重要问题.交换环上的矩阵保持问题,主要研究保持交换环上矩阵的某种性质或关系的映射.在整环上的矩阵空间里,给出了映射保持矩阵等价的一个充分必要条件.     

Weil Representation and Metaplectic Groups over an Integral Domain

Given F a locally compact, nondiscrete, non-archimedean field of characteristic ≠ 2 and R an integral domain such that a non-trivial smooth character χ: F → R ^× exists, we construct the (reduced) metaplectic group attached to χ and R. We show that it is in the expected cases a double cover of the symplectic group over F. Finally, we define a faithful infinite dimensional R-representation of the metaplectic group analogue to the Weil representation in the complex case.     

角域内代数体函数的唯一性定理

Let W (z) and M(z) be v-valued and k-valued algebroidal functions respectively,(θ) be a b-cluster line of order ∞ (or ρ(r)) of W (z) (or M(z)).It is shown that W (z) ≡ M(z) provided E(a j ,W (z)) = E(a j ,M(z)) (j = 1,...,2v + 2k + 1) holds in the angular domain Ω(θ- δ,θ + δ),where b,a j (j = 1,...,2v + 2k + 1) are complex constants.The same results are obtained for the case that (θ) is a Borel direction of order ∞ (or ρ(r)) of W (z) (or M(z)).     

Mixed Problem for an Ultraparabolic Equation in Unbounded Domain

We investigate a mixed problem for a nonlinear ultraparabolic equation in a certain domain Q unbounded in the space variables. This equation degenerates on a part of the lateral surface on which boundary conditions are given. We establish conditions for the existence and uniqueness of a solution of the mixed problem for the ultraparabolic equation; these conditions do not depend on the behavior of the solution at infinity. The problem is investigated in generalized Lebesgue spaces.     

角域内亚纯函数的唯一性定理

该文研究了复平面上的亚纯函数在角域内分担两个集合的唯一性,将仪洪勋和林伟川最近得到的复平面上的亚纯函数在全平面上分担两个集合的唯一性定理中的在全平面上分担两个集合的条件改成在角域内分担两个集合,得到了几个唯一性定理.     

Computational Solutions of Matrix Problems Over an Integral Domain

Recent methods for handling matrix problems over an integraldomain are investigated from a unifying point of view. Emphasizedare symbolic matrix inversion and numerically exact methodsfor solving Ax = b. New proofs are given for the theory of themultistep method. A proof for the existence and an algorithmfor the exact solution of Tx = b, where T is a finite Toeplitzmatrix, is given. This algorithm reduces the number of requiredsingle precision multiplications by a factor of order n overthe corresponding Gaussian elimination method. The use of residuearithmetic is enhanced by a new termination process. The matrixinversion problem with elements in the ring of polynomials isreduced to operations over a Galois field. It is shown thatinterpolation methods are equivalent to congruence methods withlinear modulus and that the Chinese remainder theorem over GF(x-p_k)is the Lagrange interpolation formula. With regard to the numerical problem of exact matrix inversion,the One- and Two-step Elimination methods are critically comparedwith the methods using modular or residue arithmetic. Formulasfor estimating maximum requirements for storage and timing ofthe salient parts of the algorithms are developed. The resultsof a series of recent tests, using existing codes, standardmatrices and matrices with random elements are reported andsummarized in tabular form. The paper concludes that the two-stepelimination method be used for the inversion problem of numericmatrices, and in particular when a black-box approach to thematrix inversion problem is attempted such as in commercialtime sharing systems. It is recommended that the inversion problemof matrices with elements over the polynomial ring be reducedto the numeric inversion problem with subsequent interpolation.An extensive Reference list is added.