多货栈及变质情形下两种可替代物品的经济订货批量模型

研究了多货栈及变质情形下两种可替代物品的经济订货批量问题.在计划期内,若某一种易变质物品发生缺货,则可以被另一种易变质物品以一定的替代率代替补充,不同物品有不同的变质率,且要决定租用货栈的数量.以库存系统的总费用最小为目标函数,分别对货栈容量无限与有限的情形建立模型,证明了最优策略存在的唯一性,并分别给出了求解最优订购策略的算法,最后通过一个算例验证了算法的最优性.     

一类变质性物品在考虑信用期时的补货策略

随着人们物质生活的不断丰富,库存控制系统所处的环境变得既复杂又多变,光靠规模化的经营已经不能满足顾客的需要,经典的EOQ模型的订购批量解也与实际的最优值之间具有很大的差距.由次,本文修改了EOQ模型中的一些假设,在考虑信用期的情况下,研究了需求率为常数、物品存贮寿命为两参数维布尔分布的单一变质性物品在有限计划期内的补货策略,证明了最优补货策略的存在性及惟一性,同时给出了求解最优补货策略的算例,得到了应用更为广泛的结论.     

上升线性需求条件下考虑资金时间价值的变质性物品生产库存模型

变质性物品生产库存系统的研究具有重要实际意义.本文研究了变质性物品生产库存系统在上升趋势线性需求条件下,考虑资金的时间价值,在有限计划时间水平内,如何确定最优生产周期,各周期最优生产率,以及最优库存安排策略.通过本文的研究,得到了一些有用的结论.     

带有两货栈及时变需求的变质性物品的最优EOQ模型

本文针对一般的时变需求与两个货栈，建立了变质性物品的最优确定性ＥＯＱ模型，提供了用来寻求最优补充策略的方法，并步线性需求出示了两个数值例子。     

带有两货栈及时变需求的变质性物品的最优EOQ模型(英)

本文针对一般的时变需求与两个货栈（自己货栈和租用货栈），建立了变质性物品的最优确定性EOQ模型，提供了用来寻求最优补充策略的方法，并就线性需求出示了两个数值例子．     

库存系统中的时滞变质物品的EOQ模型

本文考虑时段性变质物品的库存问题 .给出了一订货就交货 ,不允许缺货的时滞变质物品的库存模型与最优库存策略 ,并证明了该模型不是那物品自始至终有变质性质的 EOQ模型的简单叠加 .     

通货膨胀对带有时变需求的变质性物品库存补充策略的影响

本文在考虑通货膨胀的情形下，建立了带有时变需求的变质性物品在有限计划期内的库存补充模型，提供了最优补充次数、最优补充周期长度以及各次补充的最优补充量的一种简单而有效的逼近方法，并用数学例子说明了该方法的实现过程．     

延期支付条件下允许缺货的变质物品库存模型

在延期支付条件下,建立了缺货量部分拖后的变质物品库存模型,证明了最优解的存在性与唯一性,并给出确定最优订购策略的算法步骤,最后用数值例子验证了模型与算法的有效性.     

考虑时值及通货膨胀率的多阶段变质性物品最优库存模型

本文考虑了时值及通货膨胀率下，部分短缺量拖后的变质性物品最优订购问题。在假定变质率为常数和短缺期间损失率与实际缺货量成正比的前提下，给出了寻找最优订购策略的算法，并且证明了在该策略下费用函数取得最小值。最后给出数字实例以说明本模型及求解过程。     

一类最优EOQ模型的进一步扩展

对一类经济批量订购模型作如下进一步扩展:第一,允许短缺,短缺量部分拖后供给,且短缺期间损失率与实际缺货量成正比;第二,订购费用是可变的,且线性依赖于订购量.在此假定下,研究了有限计划时间水平及常数变质率下,部分短缺量拖后的变质性物品多阶段库存问题,给出了寻找最优订购策略的算法,证明了所给最优策略的存在唯一性及在该策略下费用函数取得最小值.最后给出应用实例.     

An algorithm for repairable item inventory system with depot spares and general repair time distribution

We consider the problem of determining the initial spare inventory level for a multi-echelon repairable item inventory system. We extend the previous results to the system, which has an inventory at the central depot as well as at bases and with a general repair time distribution. We propose an algorithm which finds spare inventory level to minimize the total expected cost and simultaneously to satisfy a specified minimum service rate. Extensive computational experiments show that the algorithm is accurate and efficient.     

Assessing the impact of inventory inaccuracies within a Newsvendor framework

This paper examines a Newsvendor framework in which a wholesaler who sells products to retailers is subject to inaccuracies in inventory data. The wholesaler’s decision regarding the management of his warehouse inventory is based on inventory data recorded in the information system. We assume that the wholesaler uses barcode labels and scanners in order to gather information concerning the available inventory in the warehouse. Because of errors arising during the manual barcode scanning process, the information on the available inventory level can deviate from the physical quantity and can result in an additional cost. This paper quantifies the economic impact of having uncertainty on the inventory level. We first analyze the case of a wholesaler that is not aware of inventory errors or chooses to ignore them in order to evaluate the efficiency loss due to errors compared with an error free situation. We then assess the effect of various actions enabling to tackle the inventory inaccuracy issue with a particular focus on actions such as the deployment of a new data capture technology.     

Optimality of Base-Stock and (s, S) Policies for Inventory Problems with Information Delays

Information delays exist when the most recent inventory information available to the inventory manager (IM) is dated; namely, the IM observes only the inventory level of an earlier period. We introduce information delays into the standard multiperiod stochastic inventory problem with backorders. We consider two types of information delays: (i) a constant delay and (ii) a random delay. We define an appropriate reference inventory position, which is a sufficient statistics for finding the optimal order quantity. We show that the optimal ordering policy is of base-stock type with respect to the reference inventory position and is of (s, S) type if there is also a fixed cost of ordering.All authors were supported in part by NSF Grant DMS-0509278.     

Comparing improvement strategies for inventory inaccuracy in a two-echelon supply chain

Classical inventory theory often assumes no discrepancies between recorded inventory and actual inventory. However, inventory records are usually inaccurate due to many reasons in practice. For example, inventory shrinkage refers to the difference between booked inventory that a company should have as a result of its sales, purchasing, and manufacturing processes and actual inventory that it has on hand. This paper concerns the impact of inventory shrinkage to a supply chain and investigates different strategies to deal with inventory shrinkage. We consider a single-period two-echelon supply chain consisting of a Stackelberg manufacturer and a retailer whose inventory is subject to shrinkage errors. Our analysis is based on a single-period newsvendor model and considers the following cases of order decisions: (a) the retailer ignores the inventory errors; (b) the retailer estimates the errors; (c) the retailer shares the inventory error information with the manufacturer; and (d) RFID technology is used to reduce or eliminate the errors. The first case is the base strategy and a common practice for many supply chains, the other two represent certain non-technological strategies of the retailer when dealing with inventory inaccuracy, and the last one represents a technology improvement strategy by the manufacturer to reduce or eliminate inventory shrinkage errors. We compare these improvement strategies and derive critical tag price for RFID implementation as a technological remedy for the inventory inaccuracy problem. Conditions for the profitability of RFID adoption are discussed.     

A queuing approach for inventory planning with batch ordering in multi-echelon supply chains

This paper presents stylized models for conducting performance analysis of the manufacturing supply chain network (SCN) in a stochastic setting for batch ordering. We use queueing models to capture the behavior of SCN. The analysis is clubbed with an inventory optimization model, which can be used for designing inventory policies . In the first case, we model one manufacturer with one warehouse, which supplies to various retailers. We determine the optimal inventory level at the warehouse that minimizes total expected cost of carrying inventory, back order cost associated with serving orders in the backlog queue, and ordering cost. In the second model we impose service level constraint in terms of fill rate (probability an order is filled from stock at warehouse), assuming that customers do not balk from the system. We present several numerical examples to illustrate the model and to illustrate its various features. In the third case, we extend the model to a three-echelon inventory model which explicitly considers the logistics process.     

A periodic review inventory system with two supply modes

We describe a periodic review inventory system in which there are two modes of resupply, namely a regular mode and an emergency mode. Orders placed through the emergency channel have a shorter supply lead time but are subject to higher ordering costs compared to orders placed through the regular channel. We analyze this problem within the framework of an order-up-to-R inventory control policy. At each epoch, the inventory manager must decide which of the two supply modes to use and then order enough units to raise the inventory position to a level R. We show that given any non-negative order-up-to level, either only the regular supply mode is used, or there exists an indifference inventory level such that if the inventory position at the review epoch is below the indifference inventory level, the emergency supply mode is used. We also develop procedures for solving for the two policy parameters, i.e., the order-up-to level and the indifference inventory level.     

Analyzing the effect of the inventory policy on order and inventory variability with linear control theory

In this paper we apply linear control theory to study the effect of various inventory policies on order and inventory variability, which are key drivers of supply chain performance. In particular, we study a two-echelon supply chain with a stationary demand pattern under the influence of three inventory policies: an inventory-on-hand policy that bases orders on the visible inventory at an installation, an installation-stock policy that bases orders on the inventory position (on-hand plus on-order inventory) at an installation, and an echelon-stock policy that bases orders on the inventory position at that installation and all downstream installations. We prove analytically that the inventory-on-hand policy is unstable in practical settings, confirming analytically what has been observed in experimental settings and in practice. We also prove that the installation-stock and echelon-stock policies are stable and analyze their effect on order and inventory fluctuation. Specifically, we show the general superiority of the echelon-stock in our setting and demonstrate analytically the effect of forecasting parameters on order and inventory fluctuations, confirming the results in other research.     

Inventory Positioning in Multiple Product Supply Chains

In this paper we address the problem of inventory positioning, i.e., the determination of the supply chain node where inventory should be held, to minimize holding costs given a pre-specified order fill rate. A single-echelon inventory system with multiple products models the problem. The value of inventory is assumed to be an increasing function of the amount of processing performed at upstream nodes, while achieved fill-rates are dependent on the distance or time between the inventory storage and customer locations. We propose a novel analytical approach to solve the problem for the case of normally distributed demand that is based on iterative calculations of inventory holding costs at the various potential inventory locations.     

Dynamic inventory and pricing policy in a capacitated stochastic inventory system with fixed ordering cost

We study a dynamic inventory and pricing optimization problem in a periodic review inventory system with setup cost and finite ordering capacity in each period. We show that the optimal inventory control is characterized by an (s,s^′,p) policy in four regions of the starting inventory level.     

在中心仓库有损失销售的二级分布库存管理模型的研究

通过对一个中心仓库和N个零售商的二级分布库存系统进行分析,采用基本(S-1,S)库存策略,综合运用了排队法和M ETR IC近似法,提出了一种在中心仓库有损失销售的二级库存管理模型,该模型描述在中心仓库缺货情况下,多数零售商不等待延期付货,而直接与供应商订货,导致中心仓库就会因损失销售而产生机会成本.该模型可达到二级分布库存系统的总成本最小.