极小子群对有限群结构的影响

设Ｇ是一个有限群．Ｇ的极小子群如何影响群的结构是一个人们感兴趣的问题．在本文中,我们用极小子群的ｃ－正规的条件刻划群Ｇ的结构．我们推广了一些已知的结果．     

多个相异性矩阵的数据分析

本文给出了分析多个相异性矩阵的三种方法.首先找到了一种图表示,使我们对所有相异性矩阵有一个总体的了解;其次定义了一个新的相异性矩阵,它可以看作是对所有原始相异性矩阵的一个折衷处理;最后提出了一种MIMU方法.在文中我们还对由上述方法得到的坐标图进行了比较.     

统计模拟在几何概率问题中应用的注解

设D为R²上的一个紧集, X 为D上的一个随机覆盖过程的统计量. 由于问题复杂, X的均 值、方差、分布函数均没有解析表达式. 统计模拟可以帮助我们找到它们的近似解. 为了在D上做统 计模拟, 需要D的代表点. 产生代表点的不同方法, 会影响统计模拟的结果. 若D不是一个矩形, 如 何选择合适的代表点至关重要. 文献中研究了一个在单位圆上的随机覆盖问题, 提出在单位圆上产生 代表点的四种方法, 并对这四种方法给予评估. 本文考虑两个随机圆的随机覆盖问题, 给出覆盖面积 的理论公式, 使比较四种产生代表点的方法有一个基准. 我们的研究结果和文献中的结论一致, 并发现 其中两种方法使覆盖面积均值的估计有偏, 且有较大的方差, 这是一个新的结果. 本文进一步指出覆 盖面积的分布可由 β 分布来拟合.     

特殊化思想与数学解题

数学问题面广量大、深浅莫测、变化无穷.虽然我们在平时的教学中都很注重于题型的归纳和方法的总结,试图将一些解题规律教给学生.然而,在一个个具体问题面前,不少学生又难以找到解决问题的方法,究其根源,是我们在教学中重视了从特殊性中概括出普     

覆盖粗糙集属性约简的新算法

覆盖广义粗糙集是Pawlak粗糙集的重要推广,其属性约简是粗糙集理论中最重要的问题之一.Tsang等基于一种生成覆盖设计了覆盖信息系统属性约简算法,但并未明确指出其适用的覆盖粗糙集类型.在本文中,我们首先指出Tsang的属性约简算法适用的覆盖粗糙集是第五,第六和第七类.其次,我们通过建立覆盖与自反且传递的二元关系之间的等价关系,提出了一种时间复杂度更低的属性约简算法,并证明了本文中的属性约简方法就是Wang等所提出的一般二元关系属性约简的特例.本文不仅提出了属性约简的简化算法,还首次建立起覆盖属性约简与二元关系属性约简之间的联系,具有理论和实际的双重意义.     

求有限集合覆盖的构造方法

在近似算法领域,集合覆盖问题是研究的比较早和比较透彻的问题之一.文中解决与经典SCP不同的另一问题,针对有限集合覆盖的构造,提出一种构造有限集合上的集合覆盖的算法,并且给出了该算法的完备性证明.该算法简单有效,是一种用于构造集合覆盖的规范方法.     

有限覆盖定理的教学研究与实践

介绍有限覆盖定理的教学方法,强调如何将无穷问题转化为有限问题的思想方法在一些理论问题中的应用.     

《数学分析》中无限转化为有限的技巧

《数学分析》中我们会遇到许多无限问题,由于无限集不一定有最大值与最小值,而有限集一定有最大值与最小值.因此,《数学分析》中需要把无限问题转化为有限问题.文中主要描述了两个重要的无限化有限的方法.一种是通过把闭区间等分的方法,另一种是利用有限覆盖定理的方法,把无限化为有限,使得问题迎刃而解.     

基于置信分布的多个对数正态总体的公共均值的置信区间的构建（英文）

在实际应用中需要拟合正的偏态数据时,对数正态分布是通常的选择.当通过多重比较确定了多个对数正态分布总体的均值相同时,如何能够利用更多的信息,同时使用这些对数正态分布总体的信息来构建公共均值的置信区间成为了众多学者颇为关注的问题.本篇文章提出了一种新的基于置信分布的方法来构建多个对数正态总体公共均值的置信区间,该方法通过对相关量的样本方差进行加权来提高效率.进而对文中提出的基于置信分布的置信区间的构建方法进行了蒙特卡洛模拟研究,模拟结果表明,我们提出的构建方法可以得到很好的覆盖概率和较短的区间宽度.文章的最后用三个实际数据来验证了文中所提出方法的表现.     

统计模拟中的数论方法

受现实生活的一个案例形成的随机覆盖问题之启发,我们在本文中讨论并比较了统计模拟中的几种方法,包括ELP网、NT网与其他网．我们给出的一些结果对统计模拟是有用的．     

喷灌模型

针对农业生产中的喷灌 ,本文详细研究了喷头的排布问题 .根据分析和计算 ,得到如下结论 :当喷头采用正方形排布 ,且喷头间距是喷水半径 (即射程 )的 1 .0 62 79倍时有最均匀的喷灌效果 ,喷灌均匀系数为0 .982 5 1 2 3 .本模型具有较好的实用价值 .     

Modeling and optimization of salinization of irrigated soil

Considered in the paper is a filtering model with concentrated sources, which can be used in problems of sprinkler, furrow, etc. irrigation. The problem of optimal control of a parabolic system is investigated, in which control effects enter in both the coefficients of the model under investigation and the right-hand side, which can be an element of a negative Hilbert space. The problem posed is regularized, and an explicit form of the gradient of a quality criterion is obtained. Bibliography: 5 titles. Translated fromObchyslyuval' na ta Prykladna Matematyka, No. 80, 1996, pp. 3–11.     

CONTROLLING GROUNDWATER QUALITY WITH ENDOGENOUS REGULATORY INSTRUMENTS

ABSTRACT. This research presents a competitive dynamic model that endogenously evaluates the economics of regulatory tax-policy options. This model is then applied to an irrigated corn production area west of Kearney, Nebraska, where the average groundwater contamination level from nitrates is reported to be 8.7 parts per million (ppm). Results indicate that no regulatory policies are necessary for maintaining potable groundwater quality with either a surge-flow irrigation system or a sprinkler irrigation system. In areas where conventional furrow irrigation technology is being used, higher net economic benefits result from the adoption of a variable-tax on nitrogen fertilizer use, followed by a constant-unit tax and a pollution tax.     

Discriminantal Arrangements, Fiber Polytopes and Formality

Manin and Schechtman defined the discriminantal arrangement of a generic hyperplane arrangement as a generalization of the braid arrangement. This paper shows their construction is dual to the fiber zonotope construction of Billera and Sturmfels, and thus makes sense even when the base arrangement is not generic. The hyperplanes, face lattices and intersection lattices of discriminantal arrangements are studied. The discriminantal arrangement over a generic arrangement is shown to be formal (and in some cases 3–formal), though it is in general not free. An example of a free discriminantal arrangement over a generic arrangement is given.     

Reducibility of hyperplane arrangements

Certain problems on reducibility of central hyperplane arrangements are settled. Firstly, a necessary and sufficient condition on reducibility is obtained. More precisely, it is proved that the number of irreducible components of a central hyperplane arrangement equals the dimension of the space consisting of the logarithmic derivations of the arrangement with degree zero or one. Secondly, it is proved that the decomposition of an arrangement into a direct sum of its irreducible components is unique up to an isomorphism of the ambient space. Thirdly, an effective algorithm for determining the number of irreducible components and decomposing an arrangement into a direct sum of its irreducible components is offered. This algorithm can decide whether an arrangement is reducible, and if it is the case, what the defining equations of irreducible components are.     

Some properties of the throughput function of closed networks of queues

The throughput function of a closed network of queues is shown to be Schur concave and arrangement increasing. As a consequence of these properties, loading and server-assignment policies can be compared based on the majorization and the arrangement orderings. Implications of the results are discussed.     

The diffeomorphic types of the complements of arrangements in CP~3Ⅱ

For any arrangement of hyperplanes in CP~3,we introduce the soul of this arrangement. The soul,which is a pseudo-complex,is determined by the combinatorics of the arrangement of hyper- planes.In this paper,we give a sufficient combinatoric condition for two arrangements of hyperplanes to be diffeomorphic to each other.In particular we have found sufficient conditions on combinatorics for the arrangement of hyperplanes whose moduli space is connected.This generalizes our previous result on hyperplane point arrangements in CP~3.     

Grid Orientations, (d,d + 2)-Polytopes, and Arrangements of Pseudolines

We investigate the combinatorial structure of linear programs on simple d-polytopes with d + 2 facets. These can be encoded by admissible grid orientations. Admissible grid orientations are also obtained through orientation properties of a planar point configuration or by the dual line arrangement. The point configuration and the polytope corresponding to the same grid are related through an extended Gale transform. The class of admissible grid orientations is shown to contain nonrealizable examples, i.e., there are admissible grid orientations which cannot be obtained from a polytope or a point configuration. It is shown, however, that every admissible grid orientation is induced by an arrangement of pseudolines. This later result is used to prove several nontrivial facts about admissible grid orientations.     

Linear arrangement problems on recursively partitioned graphs

We analyze the complexity of the restrictions of linear arrangement problems that are obtained if the legal permutations of the nodes are restricted to those that can be obtained by orderings of a binary tree structuring the nodes of the graph, the so-called p-tree. These versions of the linear arrangement problems occur in several places in current circuit layout systems. There the p-tree is the result of a recursive partitioning process of the graph. We show that the MINCUT LINEAR ARRANGEMENT problem and the OPTIMAL LINEAR ARRANGEMENT problem can be solved in polynomial time, if the p-tree is balanced. All other versions of the linear arrangement problems we analyzed are NP-complete.     

The diffeomorphic types of the complements of arrangements in ??3 II

For any arrangement of hyperplanes in ℂℙ³, we introduce the soul of this arrangement. The soul, which is a pseudo-complex, is determined by the combinatorics of the arrangement of hyperplanes. In this paper, we give a sufficient combinatoric condition for two arrangements of hyperplanes to be diffeomorphic to each other. In particular we have found sufficient conditions on combinatorics for the arrangement of hyperplanes whose moduli space is connected. This generalizes our previous result on hyperplane point arrangements in ℂℙ³. This work was partially supported by NSA grant and NSF grant