Scheduling a maintenance activity and due-window assignment based on common flow allowance

We study a due-window assignment problem on a single machine. The job-dependent due-windows are obtained by the common flow allowance criterion. The scheduler has the option to perform a maintenance activity which is rate modifying, i.e., improves the processing times of the following jobs. We consider a number of versions of this setting: (i) The maintenance requires a constant time, (ii) The maintenance duration is an increasing function of its starting time (linear deterioration), and (iii) The maintenance duration is position-dependent (general deterioration). We study the standard setting of regular job processing times, and investigate also the extension to position-dependent processing times. The set of potential optimal positions for the maintenance activity is fully characterized. Consequently, the problems based on all the combinations of these settings are shown to be solved in polynomial time.     

汶川地震灾区绿色旅游发展研究

绿色旅游是旅游业发展过程中在外生因素诱导下的内生的动态创新。根据绿色旅游的内涵,汶川地震灾区绿色旅游系统主要包括绿色旅游供给、绿色旅游中介以及绿色旅游需求3个子系统。绿色旅游资源与环境的恢复和保护性利用以及绿色旅游市场的恢复和开拓,是当前地震灾区绿色旅游业发展的所要解决的核心问题。而解决这些问题的基本路径就是旅游产品开发、旅游制度安排和旅游市场运作的创新。     

如何激发高职学生的学习动力

高职学生学习动力不足已经成为高职院校发展过程中的一大障碍。本文主要从分析高职学生学习动力不足这一问题入手,并针对此问题,提出提高高职学生学习动力的对策。     

政府科技管理信息公开若干问题的思考

政府科技管理信息作为政府信息的重要组成部分,在科技兴国和可持续发展的今天显得越发重要,因此有必要加强其信息公开力度。但目前条件下政府科技管理信息公开在公开内容、公开依据、公开救济制度等方面还存在着诸多问题,就此提出健全政府科技管理信息公开法规体系、完善政府科技管理信息公开内容制度等针对性建议,以期有利于指导我国政府科技管理信息公开实践。     

A note on finite sample breakdown points of projection based multivariate location and scatter statistics

In this note, general results of finite sample breakdown point are obtained for two classes of projection based location and scatter statistics: the Stahel-Donoho statistics and the Maronna-Yohai statistics. It is shown that these projection based location and scatter statistics can achieve the maximum breakdown point of affine equivariant multivariate location and scatter statistics. General relationships between the finite sample breakdown point of these statistics and the uniform finite sample breakdown point of the sample median and a modified sample median absolute deviation are formally established. Received: May 1999     

Multivariate L1 mean

The center of a univariate data set {x ₁,…,x _n} can be defined as the point μ that minimizes the norm of the vector of distances y′=(|x ₁−μ|,…,|x _n−μ|). As the median and the mean are the minimizers of respectively the L ₁- and the L ₂-norm of y, they are two alternatives to describe the center of a univariate data set. The center μ of a multivariate data set {x ₁,…,x _n} can also be defined as minimizer of the norm of a vector of distances. In multivariate situations however, there are several kinds of distances. In this note, we consider the vector of L ₁-distances y′₁=(∥x ₁- μ∥₁,…,∥x _n- μ∥₁) and the vector of L ₂-distances y′₂=(∥x ₁- μ∥₂,…,∥x _n-μ∥₂). We define the L ₁-median and the L ₁-mean as the minimizers of respectively the L ₁- and the L ₂-norm of y ₁; and then the L ₂-median and the L ₂-mean as the minimizers of respectively the L ₁- and the L ₂-norm of y ₂. In doing so, we obtain four alternatives to describe the center of a multivariate data set. While three of them have been already investigated in the statistical literature, the L ₁-mean appears to be a new concept. Received January 1999     

新时期高校教育工作——高校思想政治教育专业的教学创新探析

加强高校思想政治教育专业的思政教育,有着极其重要的理论意义和实践意义。我们要采取各项切实有效的措施,加强高校思政教育的广度和深度。在实践中,我们既要正确处理好教育目标与教育者之间的关系;又要正确处理好教育目标与教育对象之间的关系;还要正确处理好教育目标与教育内容和教育方法之间的关系。     

WHY DO LARGE FIRMS TEND TO INTEGRATE VERTICALLY?

We provide a theoretical framework to discuss the relation between firm size and vertical structures. The framework is based on a Hotelling model with three downstream and three upstream firms. We show that vertical integration enhances the degree of product differentiation and show the strategic complementarity of product positioning. We also show that the downstream firm that has the largest market share is more likely to integrate vertically. Enhancing the degree of product differentiation is more beneficial for the large firm than for the rest of the downstream firms because the large firm supplies a large amount of product.     

水利工程施工存在的问题及建议

文章全面分析了水利工程施工中存在的问题,并针对问题提出相应措施及建议。     

基于运输负荷和稳定性的废弃物回收服务选址评价

废弃物回收中介在绿色经济和循环经济的落实和推进中,起着重要的促进作用,而回收服务选址问题则是研究废弃服务中介运行机制和实践模式的基础。以两点间最短距离的矩阵算法为基础,结合废弃物的运输负荷、运输稳定性,构建了工业区废弃物回收服务选址评价模型,并将该模型应用到某石化工业区渣油回收服务选址的案例中。结果表明,运输稳定度对服务选址的影响较大,并可将更多的衡量指标纳入评价模型中。