Experimental studies of variable selection strategies based on constraint weights

Variable ordering heuristics that sample information before or during search in order to inform subsequent decisions have shown better performance and greater robustness than standard heuristics. One such strategy, the “weighted degree heuristic,” is based on weighting constraints according to their involvement in failure during search. A more recent approach uses “random probing” with restarting to gain information less subject to sampling bias. To date, these approaches have not been carefully analysed experimentally. In the present work, several important findings are presented, including a better delineation of the class of events that is sampled, an analysis of the importance of informed choices at the beginning of search, and a demonstration that random probing identifies sources of global contention effectively even when these are not clearly demarcated. These experiments show how empirical analysis can clarify subtle issues in the analysis of heuristic procedures for difficult search problems.     

Sharp thresholds for constraint satisfaction problems and homomorphisms

We determine under which conditions certain natural models of random constraint satisfaction problems have sharp thresholds of satisfiability. These models include graph and hypergraph homomorphism, the (d,k,t)‐model, and binary constraint satisfaction problems with domain size three. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008     

The scaling window of the 2‐SAT transition

We consider the random 2‐satisfiability (2‐SAT) problem, in which each instance is a formula that is the conjunction of m clauses of the form x∨y, chosen uniformly at random from among all 2‐clauses on n Boolean variables and their negations. As m and n tend to infinity in the ratio m/n→α, the problem is known to have a phase transition at α_c=1, below which the probability that the formula is satisfiable tends to one and above which it tends to zero. We determine the finite‐size scaling about this transition, namely the scaling of the maximal window W(n, δ)=(α_?(n,δ), α₊(n,δ)) such that the probability of satisfiability is greater than 1?δ for α<α_? and is less than δ for α>α₊. We show that W(n,δ)=(1?Θ(n^?1/3), 1+Θ(n^?1/3)), where the constants implicit in Θ depend on δ. We also determine the rates at which the probability of satisfiability approaches one and zero at the boundaries of the window. Namely, for m=(1+ε)n, where ε may depend on n as long as |ε| is sufficiently small and |ε|n^1/3 is sufficiently large, we show that the probability of satisfiability decays like exp(?Θ(nε³)) above the window, and goes to one like 1?Θ(n^?1|ε|^?3 below the window. We prove these results by defining an order parameter for the transition and establishing its scaling behavior in n both inside and outside the window. Using this order parameter, we prove that the 2‐SAT phase transition is continuous with an order parameter critical exponent of 1. We also determine the values of two other critical exponents, showing that the exponents of 2‐SAT are identical to those of the random graph. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 18: 201–256 2001     

Busy Periods of Poisson Arrival Queues with Loss

We consider two queues with loss, one is the finite dam with Poisson arrivals and the other is the M/G/1 queue with impatient customers. We use the method of Kolmogorov's backward differential equation and construct a type of renewal equation to obtain the Laplace transform of busy(or wet) period in both queues. As a consequence, we provide the explicit forms of expected busy periods.     

The Versatility of MMAP[K] and the MMAP[K]/G[K]/1 Queue

This paper studies a single server queueing system with multiple types of customers. The first part of the paper discusses some modeling issues associated with the Markov arrival processes with marked arrivals (MMAP[K], where K is an integer representing the number of types of customers). The usefulness of MMAP[K] in modeling point processes is shown by a number of interesting examples. The second part of the paper studies a single server queueing system with an MMAP[K] as its input process. The busy period, virtual waiting time, and actual waiting times are studied. The focus is on the actual waiting times of individual types of customers. Explicit formulas are obtained for the Laplace–Stieltjes transforms of these actual waiting times.     

中小型民营科技企业员工满意度研究——基于宁波星箭航空航天机械厂的实证分析

随着经济的增长和科技的进步，中小型民营科技企业获得了快速的发展．与此同时，企业内部员工的满意度却呈下降的趋势，人才流动率居高不下．2007年通过对宁波星箭航空航天机械厂的调查，对中小型民营科技企业员工满意度进行了实证分析．结果表明：薪酬激励机制、职业生涯规划、管理层的领导方法、企业文化等因素对员工满意度的影响比较显著．     

Minesweeper on graphs

Minesweeper is a popular single player game. It has been shown that the Minesweeper consistency problem is NP-complete and the Minesweeper counting problem is #P-complete. In this paper, we present efficient algorithms for solving these problems for Minesweeper graphs with bounded treewidth. Our algorithms turn out to be much better than those based directly on dynamic programming. The algorithms mostly use of algebraic operations on multivariate polynomials, so that one may use existing software to implement them easily.     

供应链环境下客户满意度评价的未确知均值聚类模型

未确知均值聚类结合未确知理论和聚类理论构造未确知测度作为集合隶属度来表示样本与各类间的隶属关系.从产品合格、柔性、可靠性等几方面对影响供应链客户满意度的因素进行分析,构建供应链环境下的客户满意度评价指标体系.在此基础上,应用未确知均值聚类理论对供应链环境下的客户满意度进行综合评价,得出聚类结果,找出各类类中心,并给出样本属于各类的隶属度,较好的解决了对供应链环境下客户满意度的分类问题,最后以实例来论证该方法的可行性和有效性.     

基于Vague集的第三方物流客户满意度评价方法研究

首先分析了已有研究中对第三方物流客户满意的评价指标体系,接着将Vague集评价思想引入到该领域中,借助偏差函数确定各个指标的权重,通过正负理想解的定义,确定待评价对象与正负理想解之间的距离,最后借助指标函数的定义得到了各个方案的评价值.研究成果对物流企业改善服务,提高市场竞争力具有一定的促进作用.     

品牌资产在营销活动对顾客忠诚影响中的作用研究

在如今竞争越来越激烈的市场上,品牌资产越来越被学者与实业者所重视.同时,顾客忠诚作为企业获利的根本要素,也是关注的焦点.目前,企业开展营销活动是获取顾客忠诚的重要手段之一,但品牌资产在这一过程中所可能起到的作用的研究仍然较为缺乏.通过构建理论模型与实践调研对这一问题进行了实证研究,结果表明品牌资产的强度影响着营销活动对顾客忠诚的影响.最后在实证结论的基础上提出了相关管理启示.