Bounding the scaling window of random constraint satisfaction problems

The model \(k\)-CSP is a random CSP model with moderately growing arity \(k\) of constraints. By incorporating certain linear structure, \(k\)-CSP is revised to a random linear CSP, named \(k\)-hyper-\({\mathbb F}\)-linear CSP. It had been shown theoretically that the two models exhibit exact satisfiability phase transitions when the constraint density \(r\) is varied accordingly. In this paper, we use finite-size scaling analysis to characterize the threshold behaviors of the two models with finite problem size \(n\). A series of experimental studies are carried out to illustrate the scaling window of the model \(k\)-CSP.     

A random walk model of skin permeation.

A new mathematical model for permeability of chemicals in aqueous vehicle through skin is presented. The rationale for this model is to represent diffusion by its fundamental molecular mechanism, i.e., random thermal motion. Diffusion is modeled as a two-dimensional random walk through the biphasic (lipid and corneocyte) stratum corneum (SC). This approach permits calculations of diffusion phenomena in a morphologically realistic SC structure. Two concepts are key in the application of the model to the prediction of steady-state skin permeability coefficients: "effective diffusivity" and "effective path length," meaning the diffusivity and thickness of a homogeneous membrane having identical permeation properties as the stratum corneum. Algebraic expressions for these two variables are developed as functions of the molecular weight and octanol-water partition coefficient of the diffusing substance. Combining these with expressions for membrane-vehicle partition coefficient and permeability of the aqueous epidermis enables the calculation of steady-state skin permeability coefficients. The resulting four-parameter algebraic model was regressed against the "Flynn data base" with excellent results (R2 = 0.84: SE = 0.0076; F = 154; N = 94). The model provides insight into the contributions of stratum corneum diffusivity and effective path lengths to overall skin permeability and may prove useful in the prediction of non-steady-state diffusion phenomena.     

具有最大总加权满意度的单机调度问题的dynasearch算法

研究了总加权满意程度最大化的单机调度问题.对最优解的性质进行分析和证明,提出该类问题的统治规则.提出该问题新的基于dynasearch 邻域的迭代局域搜索算法(ILS).算法主要特点:1)dynasearch 是基于多摄动的思想,即一次可以做多个相互独立的交换(或插入);2)用动态规划获得最优dynasearch移动;3)ILS采用随机kick 策略对局部最优解进行摄动,然后继续迭代.实现了该问题的两种dynaearch算法;把两种dynasearch算法与统治规则相结合;在进行kick时引入误差限制.实验表明:嵌入统治规则的算法优于没有统治规则的算法;基于dynasearch交换的ILS 优于基于dynasearch插入的ILS;dynaearch算法要优于以交换为邻域的多初始点改进算法.     

A column generation heuristic for dynamic capacitated lot sizing with random demand under a fill rate constraint

This paper deals with the dynamic multi-item capacitated lot-sizing problem under random period demands (SCLSP). Unfilled demands are backordered and a fill rate constraint is in effect. It is assumed that, according to the static-uncertainty strategy of Bookbinder and Tan [1], all decisions concerning the time and the production quantities are made in advance for the entire planning horizon regardless of the realization of the demands. The problem is approximated with the set partitioning model and a heuristic solution procedure that combines column generation and the recently developed _ABCβ${\mathit{ABC}}_{\beta }$ heuristic is proposed.     

Local search algorithms for multiple-depot vehicle routing and for multiple traveling salesman problems with proved performance guarantees

We consider two related problems: the multiple-depot vehicle routing problem (MDVRP) and the Multiple traveling salesman problem (mTSP). In both of them, given is the complete graph on n vertices \(G = (V,E)\) with nonnegative edge lengths that form a metric on V. Also given is a positive integer k. In typical applications, V represents locations of customers and k represents the number of available vehicles. In MDVPR, we are also given a set of k depots \(\{O_1,\ldots ,O_k\} \subseteq V\) , and the goal is to find a minimum-length cycle cover of G of size k, that is, a collection of k (possibly empty) cycles such that each \(v \in V\) is in exactly one cycle, and each cycle in the cover contains exactly one depot. In mTSP, no depots are given, so the goal is to find (any) minimum-length cycle cover of G of size k. We present local search algorithms for both problems, and we prove that their approximation ratio is 2.     

Approximation algorithms for hard variants of the stable marriage and hospitals/residents problems

When ties and incomplete preference lists are permitted in the Stable Marriage and Hospitals/Residents problems, stable matchings can have different sizes. The problem of finding a maximum cardinality stable matching in this context is known to be NP-hard, even under very severe restrictions on the number, size and position of ties. In this paper, we describe polynomial-time 5/3-approximation algorithms for variants of these problems in which ties are on one side only and at the end of the preference lists. The particular variant is motivated by important applications in large scale centralised matching schemes. A preliminary version of this paper appeared in the Proceedings of COCOON 2007, LNCS, vol. 4598, pp. 548–558. This work was supported by EPSRC grant EP/E011993/1.     

Single-machine online scheduling of jobs with non-delayed processing constraint

Journal of Combinatorial Optimization - This paper introduces a new environment of online scheduling in which jobs are scheduled under the non-delayed processing (NDP) constraint, where NDP means...     

Computational complexity of algorithms for MRP and JIT production planning problems in enterprise resource planning systems

An enterprise resource planning system (ERP) is the information backbone of many manufacturing companies. At the core of ERP is a conventional material requirements planning (MRP) production planning system or a variation of MRP when just-in-time (JIT) principles are used in manufacturing. MRP and JIT both organize production planning into a hierarchy of long-, medium- and short-range problems. In all there are eight different problems. Some are common to MRP and JIT, others are specialized for a particular system. This paper analyses the computational requirements of these problems. This is important for ERP because it plans for large numbers of products (e.g. 50 000 products at 3M Company and 44 000 products at States Industries in Oregon) at large numbers of locations (e.g. 82 locations in 21 countries for Visteon Automotive Systems of Michigan and 19 locations at Boeing). We show that adequate algorithms exist for some problems, but better algorithms are needed for other problems if ERP is to provide useful production plans.     

Hamiltonicity of hypercubes with a constraint of required and faulty edges

Let R and F be two disjoint edge sets in an n-dimensional hypercube Q _n . We give two constructing methods to build a Hamiltonian cycle or path that includes all the edges of R but excludes all of F. Besides, considering every vertex of Q _n incident to at most n−2 edges of F, we show that a Hamiltonian cycle exists if (A) |R|+2|F|≤2n−3 when |R|≥2, or (B) |R|+2|F|≤4n−9 when |R|≤1. Both bounds are tight. The analogous property for Hamiltonian paths is also given. Dedicated to Professor Frank K. Hwang on the occasion of his 65th birthday. Lih-Hsing Hsu’s research project is partially supported by NSC 95-2221-E-233-002. Shu-Chung Liu’s research project is partially supported by NSC 90-2115-M-163-003 and 95-2115-M-163-002. Yeong-Nan Yeh’s research project is partially supported by NSC 95-2115-M-001-009.     

Estimation of distribution algorithms using Gaussian Bayesian networks to solve industrial optimization problems constrained by environment variables

Many real-world optimization problems involve two different subsets of variables: decision variables, and those variables which are not present in the cost function but constrain the solutions, and thus, must be considered during optimization. Thus, dependencies between and within both subsets of variables must be considered. In this paper, an estimation of distribution algorithm (EDA) is implemented to solve this type of complex optimization problems. A Gaussian Bayesian network is used to build an abstraction model of the search space in each iteration to identify patterns among the variables. As the algorithm is initialized from data, we introduce a new hyper-parameter to control the influence of the initial data in the decisions made during the EDA execution. The results show that our algorithm improves the cost function more than the expert knowledge does.

     

Effects of role variables on job satisfaction

This study examines the effects of role variables on job satisfaction among physician and non-physician executives in hospital settings. Positive relationships were found for both groups between role variables and job satisfaction. The results indicate that role variables have a significant effect on stress, job satisfaction, and organizational commitment in the physician executive and the non-physician health care executive. On a theoretical level, this research allowed for an extended test of role theory, specifically as it applies to the management of health care. The implications of these findings for role theory and the physician executive are discussed. Since this study is of an exploratory nature, it offers new insights into the field of health care management, and the physician's role as the executive.     

Employee demographics and job training satisfaction: the relationship between dimensions of diversity and satisfaction with job training

Human resource development professionals serve many diverse populations of learners in the workplace. They do so with limited resources which leads to a dilemma: How to most effectively and efficiently meet the needs of all learners in the workplace, given the different job duties, backgrounds, skills and abilities of each learner. This empirical study examines job training satisfaction among customer and technical service employees in nine different organizations in the US and Canada. The study concluded that there were no differences in job training satisfaction when examined with dimensions of diversity such as age groups, gender and race/ethnicity. There were differences in job training satisfaction, however, when examined with job type, job status, and job tenure.     

带杠杆效应的无穷纯跳跃Levy过程期权定价

讨论了带有实时交通信息的动态网络车辆路径派送问题。问题包含重复性拥堵和非重复性拥堵两种情形。用重复性拥堵下的交通信息以安排初始路径,通过采用遗传算法求解时变车辆调度问题。车辆在行驶过程中需要根据接收到的实时交通信息调整路线。提出在关键点更新路线的机制,并采用Dynasearch算法求解一类特殊的旅行商问题调整路线。通过对SiouxFalls网络进行数值模拟分析,结果表明新策略能在较短时间内改进其他策略,且随着网络动态性增加其优越性更加明显。     

基于不变权重次约束的综合评价模型

大部分综合评价研究只解决了评价结果的排序问题,无法具体给出哪些因素才是影响具体评价对象特定评价结果的关键因素.次约束综合评价模型开拓了萃取影响评价对象关键因素的思路,但现有次约束研究的不足也很明显,将1个指标数据替换为最差值0,即去掉了这个指标的贡献后的评价得分反而可能会高于该指标得分不为0时的得分,这就是"完整指标体系"的评价得分反而小于"一个或几个指标对得分的贡献被去掉后"的评价得分的不合理现象.文章的创新与特色一是通过保持有n个指标的完整指标体系与n-1个指标的指标体系前后两次评价中指标的权重不变,来改进现有的次约束模型变权重的做法,改正"完整指标体系"的评价得分反而小于"一个或几个指标对得分的贡献被去掉后"的评价得分这种不合理现象.二是通过改进评价标准,在评价不同对象并萃取其优势和劣势因素时,将1个指标得分变为0前、后评价得分的排序是否变化的标准,改进为比较评价得分变化量大小的标准,避免了因前、后两次评价得分排序的序关系不变而导致的无法萃取优势或劣势因素的弊端.三是通过比较将1个指标得分变为0前、后两次评价得分变化量的大小,萃取出影响副省级城市经济社会发展的关键因素、优势和劣势因素.     

Approximation guarantees for parallelized maximization of monotone non-submodular function with a cardinality constraint

Journal of Combinatorial Optimization - Emerging applications in machine learning have imposed the problem of monotone non-submodular maximization subject to a cardinality constraint. Meanwhile,...     

顾客满意度不确定性对服务质量评价的影响

在以顾客为中心的时代,企业服务质量的评价直接依赖于顾客满意度的高低,而顾客满意度的评价结果往往是基于某种评价等级的一个分布.论文研究顾客满意度评价的不确定性对服务质量总体评价的影响,结果表明在服务质量的评价中存在着一种“反射现象”,即当服务质量总体水平处于满意的状态下,管理者追求的是保持和稳定,展现出对不确定性的厌恶;而当服务质量总体水平处于不满意的状态时,管理者力图改变和进步,展现出对不确定性的偏爱,而且,顾客满意度评价的负面结果要比同等程度的正面结果对服务质量总体评价的影响要大.这些现象在两项实证研究中获得了中高层管理人员的确认.作者进一步建立了一个在顾客满意度有不确定性情况下服务质量评价的模型.     

消费者预算约束对推荐奖励策略的影响研究

在社会化商务研究中,大多数研究考虑消费者的购买意愿对企业决策的影响,很少有文献探讨消费者的资金不足时对企业开展在线营销活动效果的影响.本文讨论了当消费者消费预算有约束情况下,在线企业采用推荐奖励策略对营销效果的影响.首先建立了销售企业、已有顾客、已有顾客的朋友(潜在顾客)三者之间的博弈模型,其中假设朋友的预算是私有信息,企业和已有顾客不知道该信息.通过对博弈模型的求解,发现当朋友存在预算约束时,企业采用高价格、高奖励的推荐奖励策略并不总是有效;当潜在顾客(朋友)对产品的购买意愿处于中间状态时,只有其预算偏高时,企业采取推荐奖励策略才能获得更高的利润.此外,在基本推荐奖励策略的基础上,拓展企业提供融资策略以及考虑朋友对推荐奖励反感程度的情况.研究发现,融资成本较高时,融资和奖励之间存在相互替代效果,但融资成本较低时,与融资效果与消费者的购买意愿程度相关;当潜在消费者对推荐策略存在反感时,企业仍存在一定的赢利空间.研究结果对在线企业开展推荐奖励策略的实践具有参考价值.     

制造企业绿色采购实践对绩效影响的实证研究

绿色采购是企业开展环境管理实践的重要一环,它的有效实施对企业的环境绩效和经济绩效具有重要的影响.根据对275家企业的调研,采用因子分析法,并借助统计分析软件SPSS,识别出中国制造企业绿色采购实践和企业绩效评价的主因子.在此基础上,根据对主因子间的相关分析和回归分析结果进行了结合我国实际的分析讨论,最后指出了进一步研究的方向.