基于遗传算法的随机需求IRP问题研究

本文利用遗传算法求解了一种随机需求条件下的IRP问题的数学模型,并以配送系统为例,获得了路径安排和库存策略的优化目标解。计算结果表明模型的求解可以改善优化计算结果。     

遗传算法在VMI多周期随机需求补货策略中的应用分析

供应商管理库存(VMI)正在被越来越多的企业所采用,它优化了企业的供应链体系,使企业的效益及效率不断得到提高。在VMI库存管理模式以及采用第三方物流服务下,供应商将同时面对库存决策与运输协调的问题。在由一个供应商、一个仓库、多个零售商组成的供应链系统中,对于多周期随机需求下的补货策略问题,提出了整数规划模型,并用遗传算法来求解,实验表明,遗传算法能在较短的时间内解决大规模问题,且获得效果很好的满意解。     

随机需求下带时间窗IRP问题的遗传算法研究

研究随机需求条件下带时间窗的IRP问题的数学模型,并借助遗传算法来求解这一模型。以某物流公司配送系统为例,获得了路径安排和库存策略的优化目标解。实验结果表明这不仅能明显减少迭代次数,而且可以改善优化计算结果。     

考虑多种返修品补充销售品库存的订货策略

考虑厂商对多种产品以某种形式回收,进行简单返修重新补充到销售品库存情况下的库存策略,将传统一种产品的订购策略扩展到多种产品的订购策略,对需求确定、回收率确定的多品种库存控制策略进行了改进,加入库存容量限制这一条件,使其更加符合实际。在此基础上,对两种订货策略,即单一周期订货策略和分周期联合订货策略进行了推导,进行了算例求解,对结果进行了比较分析。     

含逆向物流的电子产品生产企业库存控制研究

库存控制是逆向物流的重要研究内容。而电子产品由于其自身的特性,更容易产生逆向物流,因此研究含逆向物流的电子产品生产企业的库存控制方法和策略是非常有意义的。本文结合电子产品的特点,在假定回流产品经处理后仍可原价卖出的前提下,建立了确定需求下的单生产周期、多再制造周期的含逆向物流的电子产品生产企业的库存控制模型,并通过求解模型得出最优再制造周期及最优生产批量,最后分析了不同回流率和不同价值衰减率对最优再制造周期及最优生产批量的影响。     

供应链运输与库存整合优化技术应用分析

文章指出,运输与库存是物流配送过程中的两个关键环节,这两个环节的整合优化是供应链管理研究的前沿课题.运输与库存的整合优化是指,在满足给定的产品需求及运输限定条件下,同时寻求最优的库存与运输配送策略,使供应链系统运输与库存的总费用达到最小的最优化技术或方法.运输与库存整合优化应着重解决四个问题:一是确定最优库存水平;二是确定补货频率及补货时刻;三是确定所需车辆数量及配送区域;四是确定运输线路.进而实现对运输与库存问题的联合统筹决策,最低化运输与库存总成本.文章提出,尽管目前运输与库存整合优化问题研究还面临许多困难(如抽象出具有特定应用背景的实际问题并运用恰当的数学优化模型进行全面而准确的描述,然后用可行算法求解等),但随着先进库存管理模式在我国的广泛应用及市场供应链竞争的不断加剧,对运输调度与库存决策整合优化技术进行研究将变得越来越迫切,其广泛应用也将成为必然趋势.     

随机型逆向物流的库存模型研究

在现代企业的物流管理中库存控制环节举足轻重,从专业从事物流运输的第一、二、三方物流企业到生产制造企业如何控制库存成本以求最高的利润也受到了越来越多的管理者的重视。本文针对新产品再生数量不确定和市场需求不确定的情况对这种具有不确定性的库存控制研究,通过建立随机型逆向物流中的单周期逆向物流的库存控制模型,为企业提供最优订货量的策略。     

ATO系统库存决策模型研究

如今ATO成为越来越重要的生产方式,但如何协调降低库存成本和快速响应客户需求之间的矛盾是ATO系统亟需解决的问题。文章针对以上矛盾研究了多供应商对单装配商ATO系统中的库存策略问题;运用建模的方法分析了装配商和供应商如何根据自身利益最大化原则决定并调整库存,并讨论了订货提前期较长使得需求不确定性较大时的库存策略。     

Possion分布需求下的多项目订购模型

考虑由一个供应商,一个分销中心和一个零售商组成的供应链系统。假设零售商的需求是随机的,且服从Possion分布。分销中心采取周期订货,定量订货的策略,引入订购范围来进行决策,并结合运输条件的限制,建立一种Possion分布需求下的多项目订购模型,考虑库存成本和运输成本,并对总成本进行最小优化,得出最优订购策略。并用一个算例证实了模型的有效性。     

基于固定分割的库存路径问题最优策略

针对由单个供应商和多个零售商组成的两级供应链分配系统,研究了一体化的库存路径问题.为了节省整个供应链的费用,重新设计了对零售商的区域分割算法.在此基础上,确定了出零售商订货周期与供应商订货周期的大小关系,通过引入周期比例向量,设计了一个全新的整数倍时间策略,给出了详细的理论分析,证明该策略是最优的整数倍时间策略.数字实验结果表明,该策略比其他策略具有明显优越性.     

A Model of Supplier Responses to Just-In-Time Delivery Requirements

When buyers provide incentives for suppliers to deliver just-in-time, suppliers can respond by choosing to hold additional inventory, reducing the variance of flow time to facilitate just-in-time production, or both. A model characterizing the supplier's optimal response to incentives for JIT delivery is presented. The model shows a situation where the optimal action of the supplier is to hold more inventory. When incentives for on-time delivery are increased, the supplier responds by decreasing the variance of flow time and by increasing the lead time allowance. However, the lead time allowance increases more quickly than the variance is reduced, resulting. in a net increase in the amount of inventory that must be held by the supplier. The result is that inventory is pushed upstream. This paper does not suggest that inventory is always pushed upstream in JIT purchasing. Rather, it provides a counter-example to those who presume that holding more inventory is always a non-optimal response to buyer's requests for JIT delivery.     

Do volatility determinants vary across futures contracts? Insights from a smoothed Bayesian estimator

We apply a new Bayesian approach to multiple‐contract futures data. It allows the volatility of futures prices to depend upon physical inventories and the contract's time to delivery—and it allows those parametric effects to vary over time. We investigate price movements for lumber contracts over a 13‐year period and find a time‐varying negative relationship between lumber inventories and lumber futures price volatility. The Bayesian approach leads to different conclusions regarding the size of the inventory effect than does the standard method of parametric restrictions across contracts. The inventory effect is smaller for the most recent contracts when the inventory levels are larger. In contrast, the Bayesian approach does not lead to substantively different conclusions about the time‐to‐delivery effect than do traditional classical methods. © 2009 Wiley Periodicals, Inc. Jrl Fut Mark 30:257–277, 2010     

When Are Deliveries Profitable?

The paper aims to optimize the final part of a firm’s value chain with regard to attended last-mile deliveries. It is assumed that to be profitable, e-commerce businesses need to maximize the overall value of fulfilled orders (rather than their number), while also limiting costs of delivery. To do so, it is essential to decide which delivery requests to accept and which time windows to offer to which consumers. This is especially relevant for attended deliveries, as delivery fees usually cannot fully compensate costs of delivery given tight delivery time windows. The literature review shows that existing order acceptance techniques often ignore either the order value or the expected costs of delivery. The paper presents an iterative solution approach: after calculating an approximate transport capacity based on forecasted expected delivery requests and a cost-minimizing routing, actual delivery requests are accepted or rejected aiming to maximize the overall value of orders given the computed transport capacity. With the final set of accepted requests, the routing solution is updated to minimize costs of delivery. The presented solution approach combines well-known methods from revenue management and time-dependent vehicle routing. In a computational study for a German metropolitan area, the potential and the limits of value-based demand fulfillment as well as its sensitivity regarding forecast accuracy and demand composition are investigated.     

延期支付条件下零售商最优支付策略

在延期支付条件下考虑价格折扣的库存模型基础上,进一步考虑通货膨胀对库存系统的影响。通过对一些中小零售商支付情况进行调研分析,建立了货到付款和延期支付两种支付方式下的库存模型,由模型的最优解来确定零售商最优的支付时间。通过算例分析验证了结论,为零售商做出最优支付时间策略提供理论依据。     

运输库存集成优化问题研究

物流配送系统中的运输和库存环节,分别解决供给者与需求者空间和时间的分离,是物流系统创造"空间价值"和"时间价值"的主要功能因素;同时也是物流系统中最重要的两个环节,占物流成本支出的绝大部分,因此对运输库存环节进行集成优化研究具有重要意义。本文以物流配送系统运输库存集成优化问题为研究对象,对运输库存集成优化问题的定义、分类、常用算法等进行了研究,得到了有益的结论。     

一种动态交通导航的寻优模型研究与仿真

针对目前的车辆路径算法不能满足动态导航的要求,提出了一种用于动态交通导航的优中手优模型。该模型定义了出行时间、路径风险性和路径适宜度等三大指标,并以三大指标的目标函数作为适应度因子,通过遗传算法寻找最优路径。仿真实验表明,诙模型能够根据不同的指标提供多种最优出行方案,并动态计算最优路径,满足车辆动态导航的要求。     

The Role of Schedule Mismatch in Ending Inventory Decisions in the Presence of Price Cuts

In the high‐tech sector, component suppliers are often able to offer preannounced price cuts (price markdowns) to manufacturers due to technological innovation that allows them to produce the existing components at lower costs. In this context, manufacturers (buyers) are primarily concerned with their existing inventory carried beyond the price cuts in order to lower inventory costs. In this research, we develop a newsvendor‐based decision model for this problem based on our experience in industry and a focal case study environment. Specifically, we consider the issue of delivery and demand uncertainties, and the interplay of the buying firm's operating hours and the transportation carrier's delivery hours, which combine to influence inventory costs and order fulfillment. We illustrate the results with numerical examples and sensitivity analyses, using a real world data set. We found that stockout cost plays a critical role in the ending inventory decisions. Lowering stockout cost will benefit buyers from lower risk of obsolescence costs.     

The role of e-tailer inventory policy on e-tailer pricing and profitability

This study explores the impact of the e-tailer's inventory policy on its pricing strategy and profitability via a two-period model. Specifically, we identify two inventory policies: zero inventory and positive inventory. The findings show that the zero-inventory e-tailer charges lower prices than the positive-inventory one, but the price differential decreases over time if the market expands rapidly. The findings also show that the zero-inventory policy is preferred under a moderately positive relationship between reservation price and impatience for delivery, whereas the positive-inventory policy is preferred when these two variables are independent of each other. Furthermore, the results show that a more rapid expansion of market is a favorable condition for the zero-inventory e-tailer. The authors also discuss the implications of the inventory policy for an e-tailer's performance.     

基于IEEE802.11 DCF的链路预先修复AODV路由协议

基于无线自组织网络中普遍使用的底层通信协议IEEE802.11 DCF,针对广泛应用于无线自组织网络中的路由协议(AODV),提出了一种链路预先修复算法。该算法首先推算了DCF协议中的不稳定传输范围,然后通过MAC层与路由层的跨层协作,在下一跳节点移动在不稳定传输范围时就事先采取相应的路由修复措施。相对于AODV中采用节点周期性地发送HELLO消息来监测邻居节点变化的方法,该算法更为高效及时。仿真结果表明,该算法能够有效的减小端到端时延,保障了投递率。