Heuristics for solving a capacitated multiple allocation hub location problem with application in German wagonload traffic

In this paper, we present a capacitated multiple allocation hub location problem, which arose from a network design problem in German wagonload traffic. We develop heuristic solution approaches based on local improvements. We solve the problem with the heuristics and CPLEX on test data sets provided by our partner Deutsche Bahn AG. The computational results are presented and compared.     

A dynamic pricing approach for returned products in integrated forward/reverse logistics network design

During the last decade, the stringent pressures from environmental and social requirements have spurred an interest in designing a reverse logistics network. In this paper, we address the problem of designing and planning a multi-echelon, multi-period, multi-commodity and capacitated integrated forward/reverse logistics network. Returned products are categorized with respect to their quality levels, and a different acquisition price is offered for each return type. Furthermore, the reservation incentive of customers, the expected price of customers for one unit of used product described by uniform distribution, is applied to model the customers’ return willingness. Due to the fact that the remaining worthwhile value in the used products is the corporation’s key motivation for buying them from customers, a dynamic pricing approach is developed to determine the acquisition price for these products and based on it determine the percentage of returned products collected from customer zones. The used products’ acquisition prices at each time period are determined based on the customers’ return willingness by each collection center.     

Heuristic algorithms for a vehicle routing problem with simultaneous delivery and pickup and time windows in home health care

This paper addresses a vehicle scheduling problem encountered in home health care logistics. It concerns the delivery of drugs and medical devices from the home care company’s pharmacy to patients’ homes, delivery of special drugs from a hospital to patients, pickup of bio samples and unused drugs and medical devices from patients. The problem can be considered as a special vehicle routing problem with simultaneous delivery and pickup and time windows, with four types of demands: delivery from depot to patient, delivery from a hospital to patient, pickup from a patient to depot and pickup from a patient to a medical lab. Each patient is visited by one vehicle and each vehicle visits each node at most once. Patients are associated with time windows and vehicles with capacity. Two mixed-integer programming models are proposed. We then propose a Genetic Algorithm (GA) and a Tabu Search (TS) method. The GA is based on a permutation chromosome, a split procedure and local search. The TS is based on route assignment attributes of patients, an augmented cost function, route re-optimization, and attribute-based aspiration levels. These approaches are tested on test instances derived from existing VRPTW benchmarks.     

汽配件颜色喷涂顺序问题的TSP转化与建模

汽配件颜色喷涂顺序问题通常以生产线上相邻汽配件颜色切换次数少为最优目标,以进一步降低生产成本.该类问题具有所有汽配件都必须喷涂一次且只喷涂一次的特点,为此提出了TSP转化与建模的方法.将待喷涂汽配件定义为TSP顶点,任意两个待喷涂汽配件的颜色切换定义为顶点的距离,仿照TSP问题构建0-1规划模型;类似于顶点距离,将某些汽配件的颜色或类别不相邻要求定义为0-1矩阵,巧妙地构造了喷涂生产的约束条件.该建模方法简单快速,通用性高,适用于具有类似特点的各类生产实践问题.     

面向装配节点平衡的产品生产物流协调优化研究

在由多个并行零件生产线和装配线组成的产品生产物流中, 各生产线的瓶颈工序制约了装配节点及其整个生产物流的平衡. 为此, 基于约束理论和JIT(Just In Time)思想, 提出主、次瓶颈的概念及其判别方法和主瓶颈拉动次瓶颈、瓶颈前后拉动生产与平行顺序移动生产相结合的生产策略, 研究了基于负荷率的瓶颈工序负荷控制方法和主瓶颈触发次瓶颈拉式生产的时间控制方法, 使瓶颈工序利用率最大化, 各个零件到达装配节点的同步性得到改善. 算例的SIMIO仿真结果表明, 装配节点的在制品存量大幅度减少, 利用率提高.     

考虑完全拆分的拣选分批与拣选路径集成优化模型

在电商海量订单背景下,在线订单拣选作业难度加大,因此设计了基于订单完全拆分的拣选分批与拣选路径综合优化模型解决此问题.模型共分两阶段.第一阶段,基于种子算法,设计考虑订单完成度、等待时间与拣选路径的拣选分批模型;第二阶段以拣选单流为单队列,设计多拣选员并行服务的拣选系统.行走策略为基于返回型和遍历型的综合策略,拣选路径优化模型采用模拟退火算法求解.算例分析表明,与传统的不拆分拣选分批模型相比,构建的综合优化模型能够显著提高拣选系统效率.拣选员为4人时,模型能够使总服务时间减少58.79%,订单完成率提高10.09%.     

洗衣机节水技术研究及其力学原理

利用全自动洗衣机高速脱水时产生的向心力,将衣物上的水沿脱水桶壁向下排出,由此设计了节水型洗衣机,并对这种洗衣机进行了力学原理分析,给出了关键结构参数,以及关键部件——排水阀的设计．新型洗衣机结构简单,洗涤容量进一步扩大,减少了水和洗涤剂的用量,有利于环境保护．     

Impacts of neutral shadowing force on dust particle dynamics in cryogenic plasma

Recently, it was shown that the neutral shadowing force can have a strong impact on the structural properties of the charged dust particles in cryogenic dusty plasmas. Therefore, in this work, we have investigated the impact of the neutral shadowing force on the dynamical properties by means of molecular dynamics simulations. By computing the velocity auto‐correlation function of particles and their spectrum, we found that the neutral shadowing force has a strong impact on the dust particle dynamics if the mean free path of neutrals exceeds the mean inter‐dust particle distance.     

平面三维显示技术的研究现状

平面三维显示技术是近年来最新出现的虚拟现实显示技术,其最大的特点是观察者无需使用任何辅助附加设备,直接用肉眼就可看到屏幕上显示的三维图像。为推进三维显示技术的发展,进一步研究了视差立体成像原理,并据此介绍几种平面三维显示方法及其工作原理,包括障栅立体显示、微柱透镜阵列立体显示、偏振片立体显示和基于微柱透镜立体显示原理的多视点系统,阐述并分析了系统的优缺点。以日本三洋公司的四视角立体显示装置、南京大学的多视点三维显示系统和NEC液晶科技的HDDP三维显示系统为例,描述了国内外该项技术近期的研究现状,分析了存在的技术难点,展望了该应用领域的发展前景。     

改进的生成树遗传算法及其在物流配送成本优化中的应用

针对物流配送成本优化问题的特点,建立了数学模型,并对基本的生成树遗传算法进行了改进,同时详细阐述了改进的生成树编码的遗传算法在物流配送成本优化问题中的运用等关键技术.最后根据此算法设计了一个物流配送优化系统,解决了一个物流配送成本优化问题,效果良好.此系统对于中小型物流公司设计最优物流策略和降低物流成本有着很大的应用前景.