Planning personnel retraining: column generation heuristics

Retraining of staff is a compulsory managerial function in many organisations and often requires planning for a large number of employees. The large scale of this problem and various restrictions on the resultant assignment to classes make this planning challenging. The paper presents a complexity analysis of this problem together with linear and nonlinear mathematical programming formulations. Three different column generation based optimisation procedures and a large neighbourhood search procedure, incorporating column generation, are compared by means of computational experiments. The experiments used data typical to large electricity distributors.     

A lower bound for the adaptive two-echelon capacitated vehicle routing problem

Adaptive two-echelon capacitated vehicle routing problem (A2E-CVRP) proposed in this paper is a variant of the classical 2E-CVRP. Comparing to 2E-CVRP, A2E-CVRP has multiple depots and allows the vehicles to serve customers directly from the depots. Hence, it has more efficient solution and adapt to real-world environment. This paper gives a mathematical formulation for A2E-CVRP and derives a lower bound for it. The lower bound is used for deriving an upper bound subsequently, which is also an approximate solution of A2E-CVRP. Computational results on benchmark instances show that the A2E-CVRP outperforms the classical 2E-CVRP in the costs of routes.     

企业集团内部管理体制的生成与演进分析--以湖南华菱集团"二元分层经营"体制为例

华菱集团"二元分层经营"体制是由参与人关联博弈产生的"内生性规则",它的多条反馈路径构成了复杂的互动机制,使"二元分层经营"体制具有自我维系或自组织倾向,路径依赖和创新是其演进特征.     

Sequence Independent Lifting in Mixed Integer Programming

We investigate lifting, i.e., the process of taking a valid inequality for a polyhedron and extending it to a valid inequality in a higher dimensional space. Lifting is usually applied sequentially, that is, variables in a set are lifted one after the other. This may be computationally unattractive since it involves the solution of an optimization problem to compute a lifting coefficient for each variable. To relieve this computational burden, we study sequence independent lifting, which only involves the solution of one optimization problem. We show that if a certain lifting function is superadditive, then the lifting coefficients are independent of the lifting sequence. We introduce the idea of valid superadditive lifting functions to obtain good aproximations to maximum lifting. We apply these results to strengthen Balas' lifting theorem for cover inequalities and to produce lifted flow cover inequalities for a single node flow problem.     

The web proxy location problem in general tree of rings networks

The Web proxy location problem in general networks is an NP-hard problem. In this paper, we study the problem in networks showing a general tree of rings topology. We improve the results of the tree case in literature and get an exact algorithm with time complexity O(nhk), where n is the number of nodes in the tree, h is the height of the tree (the server is in the root of the tree), and k is the number of web proxies to be placed in the net. For the case of networks with a general tree of rings topology we present an exact algorithm with O(kn ²) time complexity.This research has been supported by NSF of China (No. 10371028) and the Educational Department grant of Zhejiang Province (No. 20030622).     

信息环境、年报披露时间选择与下年盈余管理

年报披露时间是否有助于投资者合理估计下年盈余管理程度,不同信息环境对这种估计又有什么影响?本文利用2004-2006年间的3451家公司样本对此进行了检验.结果表明:年报披露时间与下年盈余管理负相关,年报披露时间能向市场传递有效的未来信号;在标准审计意见和有较高质量经营现金流量支持的信息环境下,年报披露时间选择对下年盈余管理的信号作用更强.这些结论对理解公司年报披露时间安排有一定积极意义.     

财务弹性与企业投资的关系研究

基于现金持有量的视角,在采用中位数法、拟合值法、三分位数法等三种方法对财务弹性作出界定的基础上,考察了财务弹性与企业投资之间的关系。结果表明,通过持续持有足够现金而保持财务弹性的企业,其投资水平会显著提高。并对企业持续持有较多现金是否是因为面临融资约束或公司治理不佳所致作出了检验,实证结果进一步支持持续储备较多现金是企业秉持财务弹性策略的结果。研究结果意味着财务弹性也是影响我国企业投融资决策的一个重要因素。     

The Role of Emotions in Risk Communication

We present two experiments investigating the role of emotions concerning technological and natural hazards. In the first experiment, technological hazards aroused stronger emotions, and were considered to be riskier than natural hazards. No differences were found between the texts versus audio presentations. However, the presence of pictures aroused stronger emotions and increased the perceived risk. Emotions play a mediating role between hazard types and perceived risk, as well as between pictures and perceived risk. The second experiment adopted real‐world materials from webpages and TV. Emotions again play a mediating role between pictorial information and risk perception. Moreover, specific emotions were found to be associated with different types of action tendencies. For example, loss‐based emotions (e.g., fear, regret) tend to lead to prevention strategies, whereas ethical emotions (e.g., anger) lead to aggressive behavior. We also find that loss‐based emotions in the technical hazard scenario trigger more coping strategies (from prevention to retaliation) than in the natural hazard scenario.     

威布尔分布场合步加试验和步降试验的效率比较分析

 本文通过大量的Monte-Carlo模拟,在四个不同的准则下就威布尔分布比较了步进应力加速寿命试验和步降应力加速寿命试验的效率,认为步降应力加速寿命试验很值得推广,尤其是针对耗损型产品。     

Smoothing spline Gaussian regression: more scalable computation via efficient approximation

Summary.  Smoothing splines via the penalized least squares method provide versatile and effective nonparametric models for regression with Gaussian responses. The computation of smoothing splines is generally of the order O ( n ³), n being the sample size, which severely limits its practical applicability. We study more scalable computation of smoothing spline regression via certain low dimensional approximations that are asymptotically as efficient. A simple algorithm is presented and the Bayes model that is associated with the approximations is derived, with the latter guiding the porting of Bayesian confidence intervals. The practical choice of the dimension of the approximating space is determined through simulation studies, and empirical comparisons of the approximations with the exact solution are presented. Also evaluated is a simple modification of the generalized cross-validation method for smoothing parameter selection, which to a large extent fixes the occasional undersmoothing problem that is suffered by generalized cross-validation.