Critical Ratio Scheduling: Dynamic Due-Date Procedures under Demand Uncertainty

This paper is concerned with the problem of maintaining order due dates in job shops that manufacture products to replenish a finished goods inventory controlled by an order point system. Two different strategies for maintaining order due dates—static and dynamic due date procedures—are analyzed using both shop and inventory system performance measures. This study examines the influence of the degree of predictability of the final product demand pattern on the performance of the static and dynamic procedures. The demand pattern for individual products is characterized by a long-run demand rate, a period-to-period serial correlation coefficient of demand, and a coefficient of demand variation. The results indicate that the dynamic due-date procedure does not provide a significant improvement in the performance of the production system in comparison with the static procedure - even when the predictability of the demand during the replenishment lead time is improved.     

Optimal Design of Multiserver Queueing Systems with Different Waiting Costs for Time in Queue and Time in Service

The optimal number of servers and service rate are characterized for multiserver systems in which waiting times in service and in queue have different costs. It is shown that the optimal choice of the service rate and the number of servers depends on the ratio of the in-service waiting cost coefficient to the in-queue waiting cost coefficient. For M/M/c systems, a single server is optimal if the cost-coefficient ratio exceeds a threshold value of one-half. For GI/M/c and M/G/c systems, the threshold ratio increases as the variation of the interarrival or service time increases.     

有限等待流水车间调度邻域搜索算法

针对工序间等待时间受限,目标函数为最大完工时间最短的流水车间调度问题,提出了一种动态变邻域搜索算法。算法采用工件对比较算法和贪婪插入规则,构建了初始调度;通过嵌入3-opt,2-opt实现动态变邻域搜索;并在迭代过程中加入动态禁忌策略。     

等待时间受限的并行批处理调度问题研究

研究了任务等待时间受限的并行批处理调度问题,建立它的约束规划模型,设计调度任务的“小s大S”规则,该调度规则最重要的参数为临界队长参数和考虑受限时间的紧急时间参数.基于该规则进行模拟实验,用RSM响应面方法进行参数优化,将模拟结果同约束规划模型(CP方法)在CPLEX环境下求得的解进行比较,分析“小s大S”规则的性能和效果.     

考虑降低碳排放的废钢铁再制造等待时间受限生产调度研究

针对工件等待时间受限的废钢铁再制造生产调度问题,在碳排放约束下构建了等待时间受限的废钢铁再制造生产调度模型,并设计遗传算法进行了求解.最后结合算例,比较分析了碳排放对生产调度的影响,并得出:废钢铁再制造过程产生的碳排放量与设备空转时间呈显著的正相关关系;工件等待时间受限作为约束其主要作用在于避免重调度,对于减少makespan和碳排放量影响不大.     

An Approximate Formula for Waiting Time in Single Server Queues

This note reports the development of a new approximation formula for the mean wait in queue of a single-server queue. Use of the formula requires knowledge of only the first two (2) moments of the interarrival and service time distributions. Comparison of the proposed approximation to existing techniques is included.     

An Active Queue Management Algorithm： CRED

By applying the method of average and variance, a new queue management algorithm named the Classified-Random Early Detection （CRED） algorithm is presented which can identify the media streaming, TCP traffic and other UDP traffic at the edge routers. The algorithm discriminates the slow start and the congestion control phase of the TCP traffic and combines the TCP congestion control with the IP congestion control to alleviate the congestion effectively. Simulation shows that CRED can not only make the media streaming obtain the resources needed but also protect the TCP traffic transmitted effectively and reliably.     

改进遗传算法求解多时间约束的柔性作业车间调度问题

将加工时间、调整时间和移动时间分别作为独立时间因素考虑到柔性作业车间调度模型中,建立以最大完工时间最小、总调整时间最小、总移动时间最小为目标的考虑多时间约束的柔性作业车间调度模型,并提出改进的遗传算法求解该模型。通过测试标准数据集,并对比其他文献算法,验证了改进的遗传算法的可行性和有效性。     

Maintenance Scheduling with Delay-time Modelling: An Overview

Effective maintenance is a key for infrastructures′ high operational reliability. The integration of corrective repairs and schedule-based failure preventions has been a mainstream of modern maintenance, and an associated policy-making technique, delay-time modelling, is overviewedin this paper for optimising the maintenance cost-efficiency in different practical scenarios, including imperfect, opportunistic and nested maintenance. A few typical examples of its applications in minimising maintenance operating expenses are discussed in this paper and their results are explained to better demonstrate the benefits of the technique. This work aims to prepare for the future applications of the delay-time modelling in railway maintenance policy making.     

Interpretation of Dispatching Policies on Queue Behavior via Simulation and Time Series Analysis

The behavior of uniformly sampled queues simulated under different dispatching policies are modeled and interpreted using time series techniques. Queue behavior is shown to be adequately described by a first order autoregressive AR(1) model if the job selection discipline does not depend on operation processing time. In those cases where processing time was used in job selection, a second order autoregressive AR(2) model is adequate to characterize the queues. Queue behavior under different selection disciplines is then interpreted via the models as a convolution of the specific selection policy on the basic first come, first served (FCFS) queue. This analysis also demonstrates the inability of linear differential equations to describe queue fluctuation in systems where processing time based selection rules are employed.     

带准备时间的作业车间分批调度算法

研究了带有准备时间的作业车间分批排序问题,通过模拟计算将3种算法进行了对比分析.结果表明,遗传退火两阶段算法不受等分批限制,产生的各子批大小可以不同,这使得解空间更大,因而得到满意解的可能性大大增加.     

多项目关键链进度优化算法分析

针对多项目进度优化问题,综合应用关键链和社会认知优化算法,保证了多项目计划在不确定环境下的稳定运行。文章首先在保证进度工期最短的前提下,进行了多项目的排序,进而确定对后续项目的影响。通过实例应用于多项目进度管理中,为工程决策与管理者全面而准确地进行多项目管理、掌握项目进度、保证项目如期完工,以及对后续项目进行合理地预测提供了依据。并讨论了应用关键链方法进一步研究的方向。     

不同时段下驾驶员复杂反应实验研究

采用心理测试软件在6个不同时段对5名驾驶员进行复杂反应实验,结合实验前后的主观疲劳,综合评估不同时段及实验过程对驾驶员心理疲劳的影响。分析表明,不同时段下驾驶员的复杂反应数据具有显著性差异,10：00最好,18：00次之,6：00、14：00和22：00较差,2：00最差,与主观疲劳基本符合;实验前后表现对比也具有显著性差异,在2：00变化最大。结果说明,驾驶员的心理疲劳程度受时段的影响较大,对安全驾驶具有参考意义。     

Time Horizon: Implications for Aggregate Scheduling Effectivness1

This performance of intuitive aggregate scheduling is compared with the scheduling performance of a mathematical model. A controlled experiment was designed to illustrate one scheduling problem characteristic which accounts for the superiority of model decisions over intuitive decisions. This relative superiority increases as the time-horizon complexity increases. The horizon complexity is a manifestation of the cost structure of the decision setting.     

属性相关的关键链计划缓冲设置方法

考虑链中包含的工序数大小、工序执行时间不确定程度和开工柔性程度三个与具体项目相关的属性,研究关键链项目计划缓冲设置.以项目计划周期和完工保证率为评价目标,通过仿真实验方法评价属性对项目计划的影响.根据仿真实验结果分析.提出缓冲设置的改进方法.算例表明与切粘法和根方差法相比改进方法可显著改善项目计划性能.     

Scheduling Algorithms for the Unbalanced Production Line: An Analysis and Comparison

This paper presents an analysis and comparison of scheduling algorithms for the unbalanced production line. A new heuristic algorithm is presented accompanied by an index for classifying the configuration of a production line. A factorial experiment was conducted in order to determine those factors which were significant with respect to the performance measure under consideration, the average cost of holding in-process inventory. Additional analyses were then performed on the line factors and scheduling algorithms with appropriate conclusions drawn. The best performing algorithm was then compared to the performance of Single Period integer programming over a multiple time frame. The heuristic algorithm was found to yield better average performance than the integer programming solution, although the differences were not statistically significant. Recommendations concerning the implementation of the heuristic algorithm are provided.     

An Analysis of Scheduling Policies In Multiechelon Production Systems

Results of a simulation study of the economics of frequency of rescheduling Material Requirements Planning (MRP) systems are presented for a single-product, two-stage system in which demand is uncertain. The results indicate that for systems with moderate demand uncertainty, frequent rescheduling to maintain customer service may be uneconomical when compared with the alternative of more stable schedules in conjunction with safety stock. This result arises primarily because the cost of “emergency” production setups which occur when rescheduling is frequent exceeds the cost of safety stock required to “protect” stable schedules.     

On a Two Facility Scheduling Problem with Sequence Dependent Processing Time

This paper is concerned with a problem involving two processing facilities where it is assumed that the two facilities are to process operations of a particular project or job. Some of the operations can only be performed by one of the facilities, some by the other, and the remaining operations, by either facility. Further, it is assumed that the processing times for all operations are sequence dependent as well as processor dependent. An algorithm is proposed which obtains minimum or near minimum completion time of all operations. Suitable computational experience is provided.