(Q,r)库存中的提前期压缩问题研究

本文在提出了新的具有分段可微特征的提前期压缩成本函数的基础上,构建了一个两阶段(Q,r)库存模型。并在一定服务水平约束条件下,进一步利用成本函数分段可微的特性结合数学分析的理论将原问题分解为一个无约束问题和一个等式约束问题。理论分析及算例表明,可以通过合理的确定模型中的订货量Q、订货点r、提前期加速因子τ等参数值使得在服务水平得到一定提高的同时成本也得到优化。     

中国省际资本使用效率测算:1981～2005

采用永续盘存法和最新的数据测算中国31个省份1980年~2005年的建筑和设备资本存量,而后结合各省的GDP数据测得中国各省份1981年~2005年的资本边际产出比。从计算结果看,东部省份资本积累已经相对饱和且在2001年前后开始出现资本边际产出递减的情况;中部省份资本存量水平适中;西部省份资本积累还不足,应继续加大资本投入。     

“批对批”策略下关于供应商管理库存机制的一个探讨

本文考虑了一个由单供应商和单采购商构成的两级供应链系统,在供应商采取"批对批"策略下,引入VMI后将对供应链系统以及各渠道成员利益带来的影响.我们发现,渠道权力配置对VMI作为供应链企业间合作机制的有效性存在重要影响.在采购商占主导地位的渠道中,当系统参数满足一定条件时,引入VMI后可以同时降低供应商和采购商总成本,从而VMI可以成为供应商和采购商之间的有效合作机制.但在供应商占主导地位的渠道中,引入VMI必将增加供应商的总成本,此时VMI不是供应商和采购商之间的有效合作机制.     

Joint Initial Stocking and Transshipment—Asymptotics and Bounds

A common problem faced by many firms in their supply chains can be abstracted as follows. Periodically, or at the beginning of some selling season, the firm needs to distribute finished goods to a set of stocking locations, which, in turn, supply customer demands. Over the selling season, if and when there is a supply‐demand mismatch somewhere, a re‐distribution or transshipment will be needed. Hence, there are two decisions involved: the one‐time stocking decision at the beginning of the season and the supply/transshipment decision throughout the season. Applying a stochastic dynamic programming formulation to a two‐location model with compound Poisson demand processes, we identify the optimal supply/transshipment policy and show that the optimal initial stocking quantities can be obtained via maximizing a concave function whereas the contribution of transshipment is of order square‐root‐of T. Hence, in the context of high‐volume, fast‐moving products, the initial stocking quantity decision is a much more important contributor to the overall profit. The bounds also lead to a heuristic policy, which exhibits excellent performance in our numerical study; and we further prove both the bounds and the heuristic policy are asymptotically optimal when T approaches infinity. Extension to multiple locations is also discussed.     

Safety Stock,Excess Capacity or Diversification: Trade‐Offs under Supply and Demand Uncertainty

Firms mitigate uncertainty in demand and supply by carrying safety stock, planning for excess capacity and diversifying supply sources. In this study, we provide a framework to jointly optimize these three levers in a periodic review infinite horizon setting, and in particular we examine how one can reduce inventory and capacity investments through proper diversification strategies. Observing that a modified base‐stock inventory policy is optimal, we find that the capacity‐diversification problem is well behaved and characterize the optimal mix of safety stock, excess capacity and extra number of supply sources. We find that higher supply uncertainty results in higher safety stock, more excess capacity, and higher diversification. But safety stock and diversification are non‐monotonic in demand uncertainty. Our results can be extended to situations in which suppliers are heterogeneous, and can be used to develop effective heuristics.     

农民专业合作社存货质押融资运作模式分析

解决融资问题是保障农民专业合作社可持续发展的重要问题之一。把农民专业合作社生产加工或闲置的存货作为质押物向银行融资是解决其融资困境的有效途径。本文在分析农民专业合作社开展存货质押融资业务的现实条件基础上,并结合其拥有存货特性和质押融资业务特征,提出了银行直接质押模式和专业担保公司担保模式、供应链核心企业担保模式及农民专业合作社联合担保三种担保模式,并进行对比分析的基础提出有政府扶持和第四方物流参与的优化模式,以期为缓解农民专业合作社融资困境提供决策借鉴。     

一个基于数量折扣的变质商品定价和库存模型

建立了一个变质率为指数分布基于数量折扣的变质商品定价和库存模型，模型考虑资本的时间价值性，给出了模型解的算法．计算结果表明，资本的时间价值性和商品的变质特性对最优决策者有重要影响．     

Managing Production and Distribution for Supply Chains in the Processed Food Industry

We develop and evaluate a modeling approach for making periodic review production and distribution decisions for a supply chain in the processed food industry. The supply chain faces several factors, including multiple products, multiple warehouses, production constraints, high transportation costs, and limited storage at the production facility. This problem is motivated by the supply chain structure at Amy's Kitchen, one of the leading producers of natural and organic foods in the United States. We develop an enhanced myopic two‐stage approach for this problem. The first stage determines the production plan and uses a heuristic, and the second stage determines the warehouse allocation plan and uses a non‐linear optimization model. This two‐stage approach is repeated every period and incorporates look‐ahead features to improve its performance in future periods. We validate our model using actual data from one factory at Amy's Kitchen and compare the performance of our model to that of the actual operation. We find that our model significantly reduces both inventory levels and stockouts relative to those of the actual operation. In addition, we identify a lower bound on the total costs for all feasible solutions to the problem and measure the effectiveness of our model against this lower bound. We perform sensitivity analysis on some key parameters and assumptions of our modeling approach.     

RFID‐Enabled Visibility and Retail Inventory Record Inaccuracy: Experiments in the Field

Accurate inventory records are key to effective store execution, affecting forecasting, ordering, and replenishment. Prior empirical research, however, shows that retailer inventory records are inherently inaccurate. Radio Frequency Identification (RFID) enables visibility into the movement of inventories in the supply chain. Using two different field experiments, the current research investigates the effectiveness of this visibility in reducing retail store inventory record inaccuracy (IRI). Study 1 used an interrupted time‐series design and involved daily physical counts of all products in one category in 13 stores (8 treatments and 5 controls) of a major global retailer over 23 weeks. Results indicate a significant decrease in IRI of approximately 26% due to RFID‐enabled visibility. Using an untreated control group design with pre‐test and post‐test, Study 2 expands the number of categories to five and the number of stores to 62 (31 treatment and 31 control stores). Results show that the effectiveness of RFID in reducing IRI varies by category (ranging from no statistically significant improvement to 81%). Results also suggest that RFID ameliorates the effects of known determinants of IRI and provide the key insight that the technology is most effective for product categories characterized by these determinants.     

Optimal Planning Quantities for Product Transition

The replacement of an existing product with a new one presents many challenges. In particular, uncertainties in a new product introduction often lead to extreme cases of demand and supply mismatches. This paper addresses inventory planning decisions for product upgrades when there is no replenishment opportunity during the transition period. We allow product substitution: when a company runs out of the old product, a customer may be offered the new product as a substitute. We show that the optimal substitution decision is a time‐varying threshold policy and establish the optimal planning policy. Further, we determine the optimal delay in a new product introduction, given the initial inventory of the old product.