Some greedyt-intersecting families of finite sequences

Letn, s ₁,s ₂, ... ands _n be positive integers. Assume is an integer for eachi}. For , , and , denotes _p (a)={j|1jn,a _j p}, , and . is called anI _t ^p -intersecting family if, for any a,b ,a _i b _i =min(a _i ,b _i )p for at leastt i's. is called a greedyI _t ^P -intersecting family if is anI _t ^p -intersecting family andW _p (A)W _p (B+A ^c ) for anyAS _p ( ) and any with |B|=t–1.In this paper, we obtain a sharp upper bound of | | for greedyI _t ^p -intersecting families in for the case 2ps _i (1in) ands ₁>s ₂>...>s _n .This project is partially supported by the National Natural Science Foundation of China (No.19401008) and by Postdoctoral Science Foundation of China.     

信息系统决策的极小子集方法

定义范畴矩阵,进而基于范畴矩阵,将信息系统决策的三种基本决策转化为极小子集问题.     

非紧超凸度量空间中的一个新的极大元定理及其对抽象经济的应用(英文)

在非紧超凸度量空间中建立了一个新的极大元定理.作为应用,获得了连续选择及其不动点定理和一个Browder-Fan不动点定理.最后,新建了非紧超凸度量空间中的定性对策和抽象经济的平衡点存在定理.     

A Branch and Bound algorithm for the minimax regret spanning arborescence

The paper considers the problem of finding a spanning arborescence on a directed network whose arc costs are partially known. It is assumed that each arc cost can take on values from a known interval defining a possible economic scenario. In this context, the problem of finding the spanning arborescence which better approaches to that of minimum overall cost under each possible scenario is studied. The minimax regret criterion is proposed in order to obtain such a robust solution of the problem. As it is shown, the bounds on the optimal value of the minimax regret optimization problem obtained in a previous paper, can be used here in a Branch and Bound algorithm in order to give an optimal solution. The computational behavior of the algorithm is tested through numerical experiments. This research has been supported by the Spanish Ministry of Education and Science and FEDER Grant No. MTM2006-04393 and by the European Alfa Project, “Engineering System for Preparing and Making Decisions Under Multiple Criteria”, II-0321-FA.     

Fixed point theorems for multi-valued contractions in complete metric spaces

In this paper the concept of a contraction for multi-valued mappings in a metric space is introduced and the existence theorems for fixed points of such contractions in a complete metric space are proved. Presented results generalize and improve the recent results of Y. Feng, S. Liu [Y. Feng, S. Liu, Fixed point theorems for multi-valued contractive mappings and multi-valued Caristi type mappings, J. Math. Anal. Appl. 317 (2006) 103-112], D. Klim, D. Wardowski [D. Klim, D. Wardowski, Fixed point theorems for set-valued contractions in complete metric spaces, J. Math. Anal. Appl. 334 (2007) 132-139] and several others. The method used in the proofs of our results is new and is simpler than methods used in the corresponding papers. Two examples are given to show that our results are genuine generalization of the results of Feng and Liu and Klim and Wardowski.     

Involutory decomposition of a group and twisted subsets with few involutions

A subset K of some group C is called twisted if 1 ∈ K and x, y ∈ K implies that xy ^?1 x belongs to K. We use the concept of twisted subset to investigate and generalize the concept of involutory decomposition of a group. A group is said to admit involutory decomposition if it contains some involution such that the group is the product of the centralizer of the involution and the set of elements inverted by the involution. We study the twisted subsets with at most one involution. We prove that if a twisted subset has no involutions at all then it generates a subgroup of odd order.     

激光雨滴谱仪光学设计与分析

用来描述降水粒子数浓度随粒子尺度变化函数的雨滴谱,是降水最基本的微物理特征量,利用雨滴谱信息可以更清楚地认识自然降水的发展演变过程。从雨滴在矩形光束中的相对位置出发,理论分析了不同尺寸条件下矩形光束透射强度随粒径的变化,结果显示矩形光束的透过率与雨滴尺寸具有很好的线性关系;数值模拟了不同粒径、不同降落速度下雨滴在矩形光束中的渡越时间。并指出利用测量的雨滴粒子大小和下落时间就可获得降水类型(毛毛雨、普雨、降雪、降霰、冰雹以及混合型降水)、降水强度、降水量和粒子波谱(在体积波谱上的粒子分布)等信息。     

结构随机动力非线性反应的整体灵敏度分析

以随机参数或参数子集对目标函数总方差的相对贡献作为该参数或参数子集的整体随机灵敏度度量,定义了一类整体随机灵敏度指标。结合结构非线性随机反应分析的密度演化方法,给出了计算整体随机灵敏度指标的基本算法。该灵敏度指标物理意义明确、计算实施方便。以滞回结构非线性反应分析为例,考察了以位移反应和滞回耗能为目标函数的不同随机参数(子集)的灵敏度指标。分析表明,不同随机参数(子集)对不同目标函数的灵敏度差异甚大,并且随机参数可能对结构反应的总方差产生负贡献。     

A polynomial time approximation scheme for the two-source minimum routing cost spanning trees

Let G be an undirected graph with nonnegative edge lengths. Given two vertices as sources and all vertices as destinations, we investigated the problem how to construct a spanning tree of G such that the sum of distances from sources to destinations is minimum. In the paper, we show the NP-hardness of the problem and present a polynomial time approximation scheme. For any >0, the approximation scheme finds a (1+)-approximation solution in O(n^1/+1) time. We also generalize the approximation algorithm to the weighted case for distances that form a metric space.     

Nilpotency of the derived subgroup of a finite tangled group

We study finite groups whose every subset containing the identity and closed with respect to the operation x ○ y = xy ^?1 x is a subgroup. We prove that the derived subgroup of such a group is nilpotent, which implies that the derived length of such a group is at most three.