新鲜产品跨季销售中的动态库存管理策略研究

新鲜产品在跨季销售过程中不可避免地发生变质，给分销商带来较大的风险。本文基于一个两阶段决策模型来帮助分销商动态管理库存，在考虑产品质量随机变化的情形下更好地匹配供给与需求。具体来说，在采摘季节确定采购的总数量；在销售季节结合产品新鲜度的演变以及剩余库存水平的变化动态地决策每周期的销售量，以实现期望利润的最大化。我们采用动态规划模型分析销售期的库存管理决策，刻画了利润函数和最优决策的结构性质，并考察了库存量、新鲜度水平和价格等参数对最优库存决策的影响。数值实验结果表明，当产品变质风险大、需求不确定性低时，动态库存管理策略相比静态策略的利润改进效果更为显著。     

Profitability of Service‐Level‐Based Price Differentiation with Inventory Rationing

In this paper, we study the profitability of service‐level‐based price differentiation (SLBPD) in an inventory‐rationing context. SLBPD implies that a company offers several combinations of prices and guaranteed service levels, from which customers self‐select; different customers choose different offerings because they incur different shortage costs if an order is not fulfilled immediately. We develop an analytical model for SLBPD and explore if and when such a service differentiation strategy yields higher profits than a single undifferentiated offering. The results of our analyses suggest that SLBPD is profitable only if a company faces pricing restrictions, e.g., because of competitive pressure or regulatory restrictions. We develop necessary and sufficient conditions under which a specific and relevant form of SLBPD (called “service‐level‐based upselling”) is profitable, and provide an algorithm to compute the optimal parameters of such a policy. Based on this algorithm we carry out numerical analyses that allow us to characterize the profit increment of service‐level‐based upselling. We derive managerial insights into the attractiveness of SLBPD and explain how our basic analytical framework can be extended to account for more complex practical features.     

Looking Upstream: Optimal Policies for a Class of Capacitated Multi‐Stage Inventory Systems

We consider a multi‐stage inventory system with stochastic demand and processing capacity constraints at each stage, for both finite‐horizon and infinite‐horizon, discounted‐cost settings. For a class of such systems characterized by having the smallest capacity at the most downstream stage and system utilization above a certain threshold, we identify the structure of the optimal policy, which represents a novel variation of the order‐up‐to policy. We find the explicit functional form of the optimal order‐up‐to levels, and show that they depend (only) on upstream echelon inventories. We establish that, above the threshold utilization, this optimal policy achieves the decomposition of the multidimensional objective cost function for the system into a sum of single‐dimensional convex functions. This decomposition eliminates the curse of dimensionality and allows us to numerically solve the problem. We provide a fast algorithm to determine a (tight) upper bound on this threshold utilization for capacity‐constrained inventory problems with an arbitrary number of stages. We make use of this algorithm to quantify upper bounds on the threshold utilization for three‐, four‐, and five‐stage capacitated systems over a range of model parameters, and discuss insights that emerge.     

Storage constrained vendor managed inventory models with unequal shipment frequencies

We consider a supply chain where a vendor manages its multiple retailers' stocks under a vendor managed inventory (VMI) contract that specifies upper stock limits at the retailers' premises and overstock costs for exceeding those limits. We formulate a mixed integer nonlinear program that minimizes total supply chain costs and allows unequal shipment frequencies to the retailers. We develop an algorithm to solve its relaxed version which provides a lower bound cost solution. We propose a cost efficient heuristic procedure to generate delivery schedules to the retailers. We conduct a sensitivity analysis to provide insights on the performance of the proposed heuristic. Results show that our heuristic finds optimal or near optimal solutions, and it proposes substantial savings compared to the total supply-chain cost in the cases where there is no VMI and where there is VMI but with equal shipment frequencies to retailers.     

MRO inventory reduction—challenges and management: a case study of the Tennessee Valley Authority

Emphasis on maintenance, repair, and operations inventory (or MRO inventory) can lead to improved inventory control, reduced operational costs, enhanced productivity, and increased cost accounting accuracy. To review the benefits of MRO inventory reduction, as well as highlight the management challenges associated with the process, a case study of the Tennessee Valley Authority (TVA) is presented. TVA is a not-for-profit electric power generation entity. TVA standardised inventory policies and procedures. Their comprehensive five-year plan included employee training, changes in organisational structure and strategy, reduced MRO inventories and the establishment of new growth drivers. Net inventory reductions of $47 million were realised. Suggestions for future MRO inventory reductions as well as replication of the management involvement and improvement process in other organisations are included.     

A Longitudinal Study of the Effects of Social Support on the Psychological Adjustment of Divorced Mothers

Social support has been frequently hypothesized as a significant moderating influence on the adverse consequences of marital disruption. This exploratory longitudinal study examined the impact of social support on the psychological adjustment of divorced mothers. Divorced mothers provided social network information and psychological adjustment profiles at two months and six months following divorce. Results indicate that there were major changes in the structural and interactional characteristics of the participants' social networks over time. Some types of social support were related to well-being and several structural and interactional characteristics of the social network were related to adjustment.     

Inventory routing problems in a context of vendor-managed inventory system with consignment stock and transshipment

The inventory routing problem involves the integration and the coordination of two components of the logistics value chain: the inventory management and the vehicle routing decisions. In fact, the aim is to jointly decide on the distribution tour, from a distribution centre to a set of locations, and on the inventory policy for each location. Although many research investigations show great interest in policies such as transshipment or dynamic routings on the distribution system performances, these approaches are often criticised in practice as being too restrictive. In this article, we consider the inventory routing framework in a supplier integration context, i.e. a vendor-managed inventory with a consignment stock policy. Under such framework, we show that the transshipment brings more benefits than the classical context. In particular, we consider the case of static routings and we numerically show that transshipment permits to better optimise the distribution tours and to improve the global performance of the supply network.     

统一授信模式下存货组合与循环质押融资决策

存货质押融资已成为当前中小企业获得融资的重要手段.存货组合与循环质押是近几年存货质押融资业务实践中出现的新模式,尚未引起学者的足够重视.基于此,文章致力于探讨存货组合与循环质押融资的决策问题.首先制定存货组合质押与循环置换的规则,然后根据规则分别建立相应的线性规划函数,并通过算例进行数值分析,演示存货组合与循环质押融资决策过程,为广大融资企业开展存货质押融资业务提供借鉴.     

Sizing Inventory When Lead Time and Demand are Correlated

Determining appropriate inventory levels has been a subject of interest for both researchers and practitioners. Standard practice is to treat lead time demand as a random sum of random numbers and rely on established probability theory to calculate both reorder point and safety stock levels. A key assumption in these calculations, however, is that lead time and demand are not correlated. In this paper, we first explore situations where this assumption is untrue and then develop equations to determine the reorder point and the safety stock when lead time and demand are correlated. More specifically, we (1) derive formulas for the average and variance of the demand in a lead time, which can then be used to calculate the reorder point and the safety stock, (2) apply these formulas to two distributions for which there is a closed‐form solution: normal and Poisson, and (3) examine the effect of correlation on safety stock requirements under the normal distribution.     

A Depository Institution's Optimal Currency Supply Network Under the Fed's New Guidelines: Operating Policies,Logistics, and Impact

The overuse of its currency processing operations by depository institutions (DIs) has motivated the Federal Reserve (Fed) to propose new currency recirculation guidelines. The Fed believes that DIs should play a more active role in recirculating fit (i.e., usable) currency so that the societal cost of providing currency to the public is minimized. The Fed characterizes the overuse by the extent of cross shipping, a practice in which the same DI deposits and withdraws currency of the same denomination within five business days in the same geographic region. The Fed's proposal encourages DIs to fit sort and reuse deposited currency through two components: a custodial inventory program and a recirculation fee that would be charged on withdrawals of cross‐shipped currency. Given the geographical network of the various branches of a DI, the extent of its participation in the proposed programs depends on a variety of factors: the nature of demand and supply of currency, number and locations of the processing centers, and the resulting fit‐sorting, holding, and transportation costs. The interrelated nature of these decisions motivates the need for an integrated model that captures the flow of currency in the entire network of the DI. Based on our work with Brink's Inc., a leading secure‐logistics provider, we develop a mixed‐integer linear programming (MILP) model to provide managers of DIs with a decision‐making tool under the Fed's new guidelines. Broadly, we analyze the following questions: (i) Over all typical practical realizations of the demand for currency that a DI may face, and over all reasonable cost implications, is there a menu of “good” operating policies? (ii) What is the monetary impact of fit‐sorting and custodial inventories on a DI? and (iii) To what extent will the Fed's new guidelines address its main goal, namely, a reduction in the practice of cross shipping by encouraging DIs to recirculate currency?