域上两类矩阵保逆的诱导映射

令F是一个域,S_n(F)是F上所有n×n上对称矩阵的集合.用T_n(F)记F上所有n阶上三角阵的集合.首先分别给出诱导映射和保逆性的定义.然后改进了关于复对称阵保逆的主要相关结果及其证明,得到了S_n(F)保逆诱导映射的一般形式,最后借助于类序列技术和初等方法刻画了T_n(F)保逆诱导映射.它推广和改进了带有附加条件(f_(ij)(x)=0x=0)的相关结果.     

双对称矩阵的一类反问题

给定矩阵X和B,得到了矩阵方程X^TAX=B有双对称解的充分必要条件及有解时解的一般表达式．用SE表示此矩阵方程的解集合,证明了SE中存在唯一的矩阵^↑A,使得^↑A与给定矩阵A^*的差的Frbenius范数最小,并且给出了矩阵^↑A的表达式。     

闭凸集约束下线性矩阵方程求解的松弛交替投影算法

研究线性矩阵方程AXB=C在闭凸集合R约束下的数值迭代解法.所考虑的闭凸集合R为(1)有界矩阵集合,(2)Q-正定矩阵集合和(3)矩阵不等式解集合.构造松弛交替投影算法求解上述问题,并用算子理论证明了由该算法生成的序列具有弱收敛性.给出了矩阵方程AXB=C求对称非负解和对称半正定解的数值算例,大量数值实验验证了该算法的可行性和高效性,并说明该算法与交替投影算法和谱投影梯度算法比较在迭代效率上的明显优势.     

矩阵方程A~TXA=D的双对称最小二乘解

１．引 言 本文用 Ｒｎ×ｍ表示全体 ｎ×ｍ实矩阵集合，用 ＳＲｎ×ｎ（ＳＲ０ｎ×ｎ）表示全体 ｎ× ｎ实对称（实对称半正定）矩阵集合，ＯＲｎ×ｎ表示全体 ｎ× ｎ实正交矩阵集合，ＢＳＲｎ×ｎ表示全体ｎ×ｎ双对称实矩阵集合．这里，一个实对称矩阵Ａ＝（ａｉｊ）ｎ×ｎ被称为双对称矩阵，如果对所有的 　　　　　　　 　　　　　　　　　　　　　　　用Ａ×Ｂ表示矩阵 Ａ与 Ｂ的Ｈａｄａｍａｒｄ乘积，Ｉｋ表示 ｋ× ｋ阶单位矩阵，Ｏ表示零矩阵，Ｓｋ＝（ｅｋ，…，ｅ２，ｅ１）∈ Ｒｋ×ｋ，其中ｅｉ表示Ｉｋ的第ｉ列． 矩阵方程…     

间隔序列与拟对称映射

本文研究了欧式空间上拟对称映射的不变量问题,利用定义集合间隔序列的方法,获得了一个新的d-维拟对称映射的不变量,深化了Lipschitz不变量研究中类似的结果.     

基于关系代数的软集合理论研究与应用

基于关系代数理论中的部分思想,定义了软集合理论中的差运算、选择运算和投影运算.探讨了关系代数和软集合的关系,运用关系代数的选择、投影、并、差等运算实现了软集合参数约简算法,并用SQL语言实现了算法.最后将算法运用到房屋置业选择问题中进行验证.结果表明,软集合方法能以一种更简单直接的形式为决策问题提供有效的参考依据.     

一类矩阵方程的对称次反对称解及其最佳逼近

利用矩阵的广义奇异值分解 ,得到了矩阵方程 ATXA =B有对称次反对称解的充分必要条件及其通解的表达式 ,并且给出了在矩阵方程的解集合中与给定矩阵的最佳逼近解的表达式 .     

线性约束下Hermite-广义反Hamilton矩阵的最佳逼近问题

本文利用对称向量与反对称向量的特征性质,给出了约束矩阵集合非空的充分必要条件及矩阵的一般表达式.运用空间分解理论和闭凸集上的逼近理论,得到了任一n阶复矩阵在约束矩阵集合中的惟一最佳逼近解.     

数学集合在计算机中的应用

以数学的集合概念和并、交、差运算方法为理论依据,给出了数学集合在关系数据库、创建复杂实体的应用,提出了对数学集合运算进行拓展和附加的条件,并阐明了解决实际问题的需要.     

S_n的换位子群

在一个群中，两个换位子的乘积并不一定是换位子，通常对于一个给定的群，它的换位子群不能由它的一切换位子所作成的集合而构成，只能是由这个集合生成的子群。一个换位子群的所有元素在什么时候都是换位子，对于这个问题似乎没有什么很好的判定法则或研究结果。本文证明了在ｎ次对称群Ｓｎ中，它的换位子群的元素都是换位子，即在Ｓｎ中，两个换位子的乘积仍然是一个换位子。     

THE LOWER DENSITIES OF SYMMETRIC PERFECT SETS

In this paper, we give the exact lower density of Hausdorff measure of a class of symmetric perfect sets.     

A proof of the basic measure extension theorem of Carathéodory

In this note a direct elementary proof of Carathéodory's measure extension theorem is presented. It is based on an approximation argument for outer measures where elements of the -algebra are approached by elements of the underlying algebra of sets with respect to the symmetric difference. Received: 3 April 2000 / Accepted: 20 September 2000     

Fuzzy implication operators for difference operations for fuzzy sets and cardinality-based measures of comparison

In this paper, we determine by means of fuzzy implication operators, two classes of difference operations for fuzzy sets and two classes of symmetric difference operations for fuzzy sets which preserve properties of the classical difference operation for crisp sets and the classical symmetric difference operation for crisp sets respectively. The obtained operations allow us to construct as in [B. De Baets, H. De Meyer, Transitivity-preserving fuzzification schemes for cardinality-based similarity measures, European Journal of Operational Research 160 (2005) 726–740], cardinality-based similarity measures which are reflexive, symmetric and transitive fuzzy relations and, to propose two classes of distances (metrics) which are fuzzy versions of the well-known distance of cardinality of the symmetric difference of crisp sets.     

On the existence of difference sets in groups of order 96

The correspondence between a (96,20,4) symmetric design having regular automorphism group and a difference set with the same parameters has been used to obtain difference sets in groups of order 96. Starting from eight such symmetric designs constructed by the tactical decomposition method, 55 inequivalent (96,20,4) difference sets are distinguished. Thereby the existence of difference sets in 22 nonabelian groups of order 96 is proved.     

直觉模糊集的距离测度

直觉模糊集的距离测度是两个直觉模糊集差异性大小的度量,许多学者围绕其公理化定义和具体表达公式做了大量的工作,并且被广泛应用在多属性决策、模式识别等许多方面。基于直觉模糊集距离测度的公理化定义,本文对一些学者提出的距离测度公式进行了探讨,并给出了几种一般化构造形式。     

Upper integral and its geometric meaning

The Hahn definition of the integral is recalled, the requirement of measurability of the integrand omitted. Both the upper and lower integrals comply with this definition and so does any measurable function between them. The outer product measure of the hypograph of a nonnegative bounded nonmeasurable function is equal to the upper integral which is equal to one of the Fan integrals. The outer measure of the graph of a bounded nonmeasurable function is equal to the difference between the upper and lower integrals. A norm for not necessarily measurable functions is defined with the upper integral. The linear space with this norm is complete. The convergence in this space implies the convergence in outer measure. The distance as an outer measure of the symmetric difference of two sets gives us a complete metric space of classes of subsets.      

An Isoperimetric Result for the Gaussian Measure and Unconditional Sets

The paper studies an isoperimetric problem for the Gaussianmeasure and coordinatewise symmetric sets. The notion of boundarymeasure corresponding to the uniform enlargement is considered,and it is proved that symmetric strips or their complementshave minimal boundary measure.     

An arithmetic of complete permutations with constraints, I: an exposition of the general theory

We develop an arithmetic of complete permutations of symmetric, integral bases; this arithmetic is comparable to that of perfect systems of difference sets with which there are several interrelations. Super-position of permutations provides the addition of this arithmetic. Addition if facilitated by complete permutations with a certain “splitting” property, allowing them to be pulled apart and reassembled. The split permutations also provide a singular direct product for complete permutations in conjunction with the multiplication (direct product) of the arithmetic which itself derives from that for perfect systems of difference sets.

We pay special attention to complete permutations satisfying constraints both fixed and variable; this is equivalent to embedding partial complete permutations in complete permutations. In the sequel, using this arithmetic, we investigate the spectra of certain constraints with respect to central integral bases which are of interest for the purpose of giving further constructions either of complete permutations with constraints or of irregular, extremel perfect systems of difference sets.     

On the converse of singer's theorem

A construction is given in which the nonzero elements of a planar difference set give rise to a totally symmetric quasi-group. Examples are provided which suggest that the quasi-group is essentially the additive group of the field. The evidence supports the conjecture that the converse of Singer's theorem holds. The Multiplier Theorem is used to characterize when the totally symmetric quasi-groups are totally symmetric loops. The results extend to Abelian group difference sets (λ = 1).     

On Uncountable Unions and Intersections of Measurable Sets

We consider several natural situations where the union or intersection of an uncountable family of measurable (in various senses) sets with a good additional structure is again measurable or may fail to be measurable. We primarily deal with Lebesgue measurable sets and sets with the Baire property. In particular, uncountable unions of sets homeomorphic to a closed Euclidean simplex are considered in detail, and it is shown that the Lebesgue measure and the Baire property differ essentially in this aspect. Another difference between measure and category is illustrated in the case of some uncountable intersections of sets of full measure (comeager sets, respectively). We also discuss a topological form of the Vitali covering theorem, in connection with the Baire property of uncountable unions of certain sets.