A Comparison between Basic Cyclic Scheduling and Variable Cyclic Scheduling in a Two‐stage Hybrid Flow Shop

In this paper the impacts of two types of repetitive scheduling systems on the makespan in a two‐stage hybrid flow shop, which consists of one machine in the first stage and multiple process lines in the second stage, are compared. First, we analyzed, through a simulation, how the makespan is affected by the setup frequency and sequencing rules for products under two types of scheduling systems: One is repetitive scheduling with only one batch per product family per scheduling cycle (basic cyclic scheduling system). The other is repetitive cyclic scheduling with various batches per product family per scheduling cycle (variable cyclic scheduling system). Second, we compared which scheduling system is superior under various manufacturing situations. The following points were noted. (1) The superior scheduling system can be shown by a two‐dimensional diagram of the setup frequency and the imbalance in workload for processing among process lines in the second stage. (2) Variable cyclic scheduling is superior in comparison with basic cyclic scheduling when there is a large imbalance in the workload to be processed among process lines in the second stage, or the workload in the second stage is larger than that in the first stage. The result of this research provides guidelines for selecting which scheduling system should be adopted.     

基于风险的考虑成本和允许等待的车辆运输调度问题研究

本文同时考虑了成本约束和允许等待情形,研究了最小化风险的车辆运输调度问题,其中运输风险是随时间不同而变化的,即研究在时间依赖网络中基于风险的有约束的运输路径选择问题,以及在选定路径的顶点上决定的出发和等待时间的综合问题。建立了相应的混合整数规划模型,设计了相应的算法,并分析了算法复杂性,最后通过算例验证了该算法的有效性和可行性。     

Influence of Distribution of Animals between Dose Groups on Estimated Benchmark Dose and Animal Welfare for Continuous Effects

The benchmark dose (BMD) approach is increasingly used as a preferred approach for dose–effect analysis, but standard experimental designs are generally not optimized for BMD analysis. The aim of this study was to evaluate how the use of unequally sized dose groups affects the quality of BMD estimates in toxicity testing, with special consideration of the total burden of animal distress. We generated continuous dose–effect data by Monte Carlo simulation using two dose–effect curves based on endpoints with different shape parameters. Eighty‐five designs, each with four dose groups of unequal size, were examined in scenarios ranging from low‐ to high‐dose placements and with a total number of animals set to 40, 80, or 200. For each simulation, a BMD value was estimated and compared with the “true” BMD. In general, redistribution of animals from higher to lower dose groups resulted in an improved precision of the calculated BMD value as long as dose placements were high enough to detect a significant trend in the dose–effect data with sufficient power. The improved BMD precision and the associated reduction of the number of animals exposed to the highest dose, where chemically induced distress is most likely to occur, are favorable for the reduction and refinement principles. The result thereby strengthen BMD‐aligned design of experiments as a means for more accurate hazard characterization along with animal welfare improvements.     

有核网络型集群中知识共享深度与知识型企业的创新资源投入关系研究

针对我国由国内小企业对大企业(国外跨国公司)的依附关系而形成的有核网络型集群.建立集群中知识溢出、知识共享所形成的不同深度组织知识和企业的私有知识对产出的影响分析模型,通过仿真计算,研究了不同知识共享深度及私有知识产出弹性对企业知识共享行为和创新资源投入的影响.研究表明,对大企业而言.只有当公共知识产出弹性超过一定阈值时,才会进行主动知识共享,且该阈值随着知识共享深度的增加而增大:且当公共知识产出弹性超过该阈值时,大企业创新投入将随公共知识产出弹性的增加而显著增加;但此时公共知识产出弹性的增加反而会抑制小企业的创新投入.相关研究结论对促进集群持续发展提供了有益的启示.