一种考虑动态时间窗的满载问题模型及算法

针对时间约束在满载问题中的复杂性,建立了一个考虑装载时间和次序的具有动态时间窗的满载车辆调度模型,并给出了一个基于动态构造原理的启发式算法。该模型和算法改进了以往满载问题中对时间窗的考虑,使得求解更具有实际派车意义,并且该算法通过参数调整,经过少量迭代即可快速求得最小化总成本的满意解。     

基于改进差分进化算法的VRP-SDPTW研究

整合前向物流和逆向物流,提出带时间窗的同时送货和取货的车辆路径问题(VRP-SDPTW)的混合整数规划数学模型.首次提出改进的差分进化算法(IDE)求解该问题,算法对不可行解设计惩罚机制,当基因值超过规定的范围时,设计基于整数序规范的辅助算子解决变异问题,设计一种随进化代数自动更新的交叉率.数值实验表明,改进的差分进化算法能有效地求解VRP-SDPTW.     

有时间窗车辆路径问题的模型及其改进模拟退火算法研究

论文在对有时间窗车辆路径问题进行描述的基础上,建立了该问题的基于直观描述的数学模型.论文还根据有时间窗车辆路径问题的特点构造了求解该问题的改进模拟退火算法,并进行了实验计算.计算结果表明,用本文设计的改进模拟退火算法求解有时间窗车辆路径问题,不仅可以取得很好的计算结果,而且算法的计算效率较高,收敛速度较快,计算结果也较稳定.     

考虑三维装箱约束的车辆路径问题研究

针对实际物流配送问题的特点,建立考虑三维装箱约束的车辆路径问题模型,提出求解该问题的引导式局部搜索算法。采用改进的模糊遗传算法求解车辆路径问题,提出一种新的模糊逻辑控制器,并采用引导式局部搜索算法求解三维装箱问题。通过计算标准算例检验算法性能,试验结果表明引导式局部搜索算法能够在较短时间内得到质量较高的近似最优解。     

时间依赖型多配送中心带时间窗的开放式车辆路径问题研究

本文研究了时间依赖型多配送中心带时间窗的开放式车辆路径问题,基于道路通行情况,建立车辆行驶速度时间函数;考虑车辆载重、里程限制与客户点服务时间窗的约束,建立混合整数规划模型,目标函数为最小化车辆总成本,具体包括车辆行驶时间成本和车辆固定发车成本;提出了一种二维编码方式的混合遗传算法,针对混合遗传算法设计了多分区段单点交叉策略、动态插入算子及局部搜索策略;最后,基于Solomon VRPTW基准数据集生成27个测试算例,使用混合遗传算法进行求解。数值实验结果表明,考虑道路通行情况,选择合理的出发时间,避免拥堵时段进行配送服务,能明显减少车辆的总行驶时间,且验证了混合遗传算法能够获得问题的满意解。     

多车场带时间窗车辆路径问题的变邻域搜索算法

多车场带时间窗车辆路径问题是车辆路径问题集合中的一个极为复杂、且仍未得到较好解决的问题。针对这一问题,建立了它的整数规划数学模型,提出了一种改进型变邻域搜索算法。该算法在初始解的构造阶段采用聚类方法完成客户的分配,运用混合算子进行局部搜索,通过后优化过程增强寻优效果,引入模拟退火模型对新解的接受进行控制。最后,在Cordeau提出的标准用例上对改进型变邻域算法进行了实验,实验结果更新了大部分目前该问题的最优解,并在算法的稳定性和求解时间上体现出一定优势。实验表明,该算法是一种求解多车场带时间窗车辆路径问题的有效方法。     

基于多目标优化的模糊需求VRPTW动态管理

针对具有模糊顾客需求的带时间窗车辆路径问题,建立了最小化车辆行驶距离和最小化配送服务延迟时间的多目标模糊机会约束规划模型,提出了管理车辆服务模糊需求的动态优化策略,设计了嵌入模糊模拟的改进非支配排序混合遗传算法来求解模型。通过Solo-mon标准算例的仿真实验,不仅讨论了决策者主观偏好值对决策目标的影响,而且与传统车辆调度方法进行了对比分析,验证了该动态管理策略的有效性。     

基于模糊聚类与车辆协作策略的随机车辆路径问题

以多辆车协作的随机车辆路径问题为研究对象,设计了通用的随机车辆路径问题机会约束模型,提出了大规模随机车辆路径问题的车辆协作策略,并基于该策略与模型设计了求解天规模随机车辆路径问题的混合启发式算法,计算实验结果说明了该算法与策略的有效性与实用性.     

有模糊时间窗的车辆调度组合干扰管理研究

研究带有模糊时间窗的车辆调度组合干扰管理模型及其混合遗传算法.采用时间窗模糊化处理方法,定义客户满意度函数,根据干扰管理思想对车辆调度中组合性干扰事件进行分析,从配送路径、配送成本和客户满意度三个方面进行干扰辨识与度量,建立基于模糊时间窗的车辆调度组合干扰管理模型;构造模型求解的混合遗传算法,将最佳客户插入规则与遗传算法结合,同时在算法中嵌入模糊优化程序以处理问题的模糊特征;进行数值实验,实验结果验证了模型与算法的有效性.     

草畜平衡约束下带时间窗的放牧路径规划研究

草地资源的自然特征决定了草场载畜量的有限性，一年内只有在特定的时间窗适合放牧，承受不了长期、持续地放牧。不合理的放牧路径规划不仅会导致牲畜采食时间与草场生长周期错配，还会导致草场出现超载、欠载及退化等一系列负面问题。本文在考虑草畜平衡的基础上，提出放牧时间惩罚函数，构建了线性时间窗和指数型时间窗放牧路径规划模型，并设计了改进的遗传算法对模型进行求解。最后以青海省海晏县的牧户为例对模型进行了验证。结果表明，带指数型时间窗的算法能够更快地逼近最优解，且综合考虑三种成本比只考虑单一成本为目标得到的放牧路径总成本更低。改进的遗传算法缩短了求解时间并提高了求解稳定性。本文构建的带时间窗路径规划模型充分考虑了草场的自然属性，优化了牧户放牧路径，提高了牧户对草地资源利用的科学性。     

An enhanced loading model for the probabilistic workload control under workload imbalance

Load-oriented manufacturing control (LOMC), a well known probabilistic approach to workload control, is based on limiting and smoothing workload using one static parameter for each workcentre, called load limit (LL). The value of this parameter is set by the shop managers based on the planned lead time at each workcentre. In this paper the use of LL is shown to be inappropriate for the smoothing of workloads when the workload is not sufficiently balanced. We propose to enhance the LOMC model by introducing two sets of parameters:

(i) limiting parameters (LPs), that are statical parameters of the workcentres, set by the shop managers. LPs are used to limit the workload released to the shop;

(ii) smoothing parameters (SPs), that are dynamical parameters of the workcentres, computed as a function of their real workload. SPs are used to smooth the jobs workload over downstream workcentres.

A simulation model was used to compare the enhanced model, based on two parameters sets, with the traditional LOMC model, based on a single parameter set. The simulation runs were earned out with different conditions of due-date assignments, dispatching rules and production mix. The statistical analysis performed on experimental results confirmed that the enhanced model achieves significantly better due dates under unbalanced workload conditions.     

A comparative study of some priority dispatching rules under different shop loads

Priority dispatching rules and shop load affect job-shop performance. This paper evaluates ten different priority dispatching rules with respect to six different performance criteria under light, medium and heavy shop loads. Simulation was used as a tool to determine the rankings of the dispatching rules for a given shop load and performance criteria. A comparative study was conducted to investigate the performance of these rules. Two rules, ‘shortest processing time” and ‘least work remaining’, performed well under criteria related to the processing time. It was found that the rules that perform well in average and r.m.s. tardiness perform poorly under percentage-of-jobs-late criterion. The experimental results are conveyed with critical comments on the performance of the dispatching rules under different loading conditions of the shop.     

The weighted link ring loading problem

In the weighted link ring loading problem, we are given an n-node undirected ring network. Each of its links is associated with a weight. Traffic demands are given for each pair of nodes in the ring. The load of a link is the sum of the flows routed through the link, and the weighted load of a link is the product of its weight and the smallest integer not less than its load. The objective of the problem is to find a routing scheme such that the maximum weighted load on the ring is minimized. In this paper we consider three variants: (i) demands may be split into two parts, and then each part is sent in a different direction; (ii) demands are allowed to be split into two parts but restricted to be integrally split; (iii) each demand must be entirely routed in either of the two directions, clockwise or counterclockwise. We first prove that the first variant is polynomially solvable. We then present a pseudo-polynomial time algorithm for the second one. Finally, for the third one, whose NP-hardness can be drawn from the result in the literature, we derive a polynomial-time approximation scheme (PTAS).     

The maximum loading and the optimum number of vehicles in a double-loop of an interbay material handling system

In this paper, the loading analysis of an automated double-loop interbay material handling system (AMHS) in a wafer fabrication was analysed, considering the effects of the vehicle numbers in the inner and outer loops. Discrete-event simulation models were developed in e-M Plant to study this AMHS system with a zone control scheme to avoid any vehicle collision. The layout of an interbay system is a combination configuration in which the hallway contains double loops and the vehicles have double capacity. The combination of the shortest distance with nearest vehicle (SD–NV) and the first-encounter-first-served (FEFS) dispatching rule was used in this study. The maximum loading of this interbay system can be determined by the simulation approach. We also found that the number of vehicles in the inner and outer loops can significantly affect the interbay performance. Furthermore, the optimum combination of the vehicle numbers in the inner and outer loops can be obtained by response surface methodology.     

“行/列约束法”在外贸进出口货柜运输业务上的应用

外贸日常进出口业务活动中,我们经常遇到如何利用物质资源条件,求取并实现最理想目标的问题。本文研究了货柜运输业务上三维装箱问题,给出了一个基于管理数学中“行约法 /列约法”的摆放方法。通过和外贸进出口业务常规计算方法比较,降低了创汇成本,增加了经济效益。同时和其它方法比较发展,我们的方法在实际货柜装箱操作上,方便实用。     

一种基于闭排队网络的集装箱码头设备配置优化模型

将集装箱码头龙门吊装卸工艺抽象为闭排队网络模型,采用估算均值法计算了顾客到达和服务时间分布为一般情况的闭排队网络系统性能指标.仿真结果表明,闭排队网络模型计算结果可以为集装箱码头设备配置提供一定的决策支持.     

Criteria for selecting a production control philosophy

Logistic objectives constitute a compromise between having short leadtimes and a low volume of work in progress on the one hand and a high resource loading and due date obligation on the other. Miscellaneous production planning approaches offered today provide different combinations of logistic objectives for satisfying a manufacturing strategy. To combine the strength of the various approaches into a unified system, a new approach based on a dynamic and distributed production planning methodology is proposed. To customize the approach, various analyses and specifications have to be made and for that reason some important characteristics and criteria for analysing production control philosophies will be given.     

The social construction of the meaning of acute stressors: a qualitative study of the personal accounts of police officers using a stress counselling service

The police profession is one in which acute stressors are encountered more frequently than in other occupations. Using the personal accounts of 35 police officers attending an in-house stress counselling clinic, the aim of the present study was to provide a qualitative examination of how the institutional context of policing influenced the ways in which acute stressors signified to individual police officers experiencing felt distress. Using the framework of Rational Emotive Behaviour Therapy as an analytical tool, it is argued that beliefs contributing to the experience of felt distress are related to the way in which policing as both an identity and an activity is constructed through the police organizational culture. Not only do these constructions influence the ways in which officers perceive themselves and their environments, but they also operate at the collective level to 'normalize' some emotional responses and to 'pathologize' others which, it is argued, could impact upon the outcomes of interventions such as stress counselling.     

The moderating role of social support in Karasek's job strain model

This paper examines whether social support is a boundary-determining criterion in the job strain model of Karasek (1979). The particular focus is the extent to which different sources of social support, work overload and task control influence job satisfaction, depersonalization and supervisor assessments of work performance. Hypotheses are tested using prospective survey data from 80 clerical staff in a university setting. Results revealed 3-way interactions among levels of support (supervisor, co-worker, non-work), perceived task control and work overload on levels of work performance and employee adjustment (self-report). After controlling for levels of negative affect in all analyses, there was evidence that high levels of supervisor support mitigated against the negative effects of high strain jobs on levels of job satisfaction and reduced reported levels of depersonalization. Moreover, high levels of non-work support and co-worker support also mitigated against the negative effects of high strain jobs on levels of work performance. The results are discussed in terms of the importance of social support networks both at, and beyond, the work context.     

Job insecurity, coping resources and personality dispositions in occupational strain

This paper presents research on the relationships between the work-related stressor of perceived job insecurity and various indicators of occupational strain, taking into account employees' personality dispositions (trait negative and positive affectivity) and coping resources. Respondents were 222 Australian public servants surveyed during organizational restructuring that involved downsizing and threat to job certainty. The research was formulated within an adaptation of Osipow, Doty, and Spokane's (1985) framework of stress-strain-coping that included the possible direct as well as moderating effects of personality dispositions in reporting occupational strain (Parkes, 1990). Findings from hierarchical regression analyses indicate consistent significant independent effects of personality dispositions, coping resources and perceived job insecurity on various indicators of strain. There was also support for the moderating roles of negative affectivity and self-care in the relation between perceived job insecurity and physical strain. Implications for the role of dispositional factors, especially negative affectivity, and the utility of various coping resources in accounting for occupational strain in times of threatened job security are discussed.