The performance of standard and hybrid em algorithms for ml estimates of the normal mixture model with censoring

Many studies have been made of the performance of standard algorithms used to estimate the parameters of a mixture density, where data arise from two or more underlying populations. While these studies examine uncensored data, many mixture processes are right-censored. Therefore, this paper addresses the accuracy and efficiency of standard and hybrid algorithms under different degrees of right-censored data. While a common belief is that the EM algorithm is slow and inaccurate, we find that the EM generally exhibits excellent efficiency and accuracy. While extreme right censoring causes the EM to frequently fail to converge, a hybrid-EM algorithm is found to be superior at all levels of right-censoring.s     

Empirical power comparisons of two mrpp rank tests

Simulated powers of the MRPP two-sample rank test statistic ?₁- are compared with the powers of the MRPP test statistic ?₂(the two-sided Wilcoxon-Mann-Whitney test) for large samples from several underlying populations. Powers are obtained using two approximate distributions of ?₁ involving three and four moments

respectively, The use of the fourth moment indicates that an approximation to the null distribution of ? based on four moments can perform better     

Probability and statisitics in the service of computer science: illustrations using the assignment problem

Recent work on the assignment problem is surveyed with the aim of illustrating the contribution that stochastic thinking can make to problems of interest to computer scientists. The assignment problem is thus examined in connection with the analysis of greedy algorithms, marriage lemmas, linear programming with random costs, randomization based matching, stochastic programming, and statistical mechanics. (The survey is based on the invited presentation given during the “Statistics Days at FSU” in March 1990.)     

优化算法在手征媒质中的应用研究

由于手征媒质的手征参数可调性,使它成为一种新型的吸波材料,在减缩目标雷达散射截面方面有巨大的应用前景.文中运用传输线法分析了金属衬底上涂敷手征媒质的反射特性,计算了手征参数对手征媒质反射特性的影响;然后基于非均匀有理B样条建模,采用物理光学法比较了目标涂敷常规吸波材料与手征媒质时的雷达散射截面,结果说明了手征媒质减小反射电磁波的效果更好;最后运用粒子群算法和模拟退火算法在给定的范围内优化手征参数,并计算了在此参数下目标的散射截面.     

从二句体、四句体到八句体——绝句与律诗之关系新探

中国古典诗歌以二句为最小构成要素、四句为基本单位构成篇章的传统由来已久。"截句说"不符合绝句形成和发展的事实,反之,八句体律诗应当是绝句倍翻而成,才是一个合理的思路。     

和韵而似原唱——苏轼《水龙吟》（次韵章质夫杨花词）的艺术成就

苏轼《水龙吟（》似花还似非花）,为和章质夫杨花词所作,其艺术造诣却远远高于原作。王国维认为,苏词不似和作,反似原唱。仔细权衡,苏词的突出特点在于：一是咏物拟人,不即不离;二是抒情言志,幽怨缠绵;三是章法句法,淋漓曲折;四是措辞用典,夺胎换骨。体现了苏轼高超的艺术才华和苏词幽深的艺术境界。     

Optimal lineups in Twenty20 cricket

ABSTRACT

This paper considers the determination of optimal team lineups in Twenty20 cricket where a lineup consists of three components: team selection, batting order and bowling order. Via match simulation, we estimate the expected runs scored minus the expected runs allowed for a given lineup. The lineup is then optimized over a vast combinatorial space via simulated annealing. We observe that the composition of an optimal Twenty20 lineup sometimes results in non-traditional roles for players. As a by-product of the methodology, we obtain an ‘all-star’ lineup selected from international Twenty20 cricketers.     

A Simulated Annealing Approach to Communication Network Design

This paper explores the use of the meta-heuristic search algorithm Simulated Annealing for solving a minimum cost network synthesis problem. This problem is a common one in the design of telecommunication networks. The formulation we use models a number of practical problems with hop-limit, degree and capacity constraints. Emphasis is placed on a new approach that uses a knapsack polytope to select amongst a number of pre-computed traffic routes in order to synthesise the network. The advantage of this approach is that a subset of the best routes can be used instead of the whole set, thereby making the process of designing large networks practicable. Using simulated annealing, we solve moderately large networks (up to 30 nodes) efficiently.     

CONSTRUCTION OF RESOLVABLE ROW-COLUMN DESIGNS USING SIMULATED ANNEALING

The paper describes an algorithm which constructs optimal or near optimal resolvable row-column designs. Its performance is assessed against available tables of two-replicate designs.     

解布局问题的模拟退火算法

本文以简化模型为例,给出了用模拟退火算法解布局问题的一般形式、基本步骤以及罚函数的使用方法,所给算法在选用适当的数据结构后即可求解复杂的布局问题,有很强的适应性和灵活性.