The Influence of Quality Inspections on the Optimal Safety Stock Level

Due to yields of less than 50% during the production of curved glass for the displays on their new cell phone series, Samsung has to deal with higher than expected production costs of several million dollars. Where there is random yield, production costs as well as holding costs can be reduced by introducing quality inspections, in which defective items are discarded before further production. To achieve the greatest cost savings, it is important to determine the optimal number and positions of these inspections across the production process which, due to several influencing parameters, is not simple. We show how the positions of inspection within a production process influence the safety stock level that is required to buffer against uncertainties due to demand and yield randomness. Our approach is the first one, combining decisions about the number and positions of inspections with inventory control strategies in a warehouse. We achieve a maximum safety stock reduction of more than 30% in our examples, which can be even larger depending on the parameter setting. For a company like Intel, reporting inventories for finished goods of nearly 1.5 billion dollars in the 2014 annual report, this allows for significant savings.     

民营中小企业人力资源问题原因解析

中国民营中小企业的人力资源问题,既有外部原因,也有内部原因。外部原因包括：计划经济的影响、对民营经济认识上的偏颇、人才市场发育不完善、缺乏良好的社会信用体系。内部原因包括：管理方面的“家长制”决策、信息不畅、“人治”以及组织机构混乱;激励方面的保障不够、重罚轻赏、忽视再培训;企业化方面的“圈子化”、“强人化”;领导方面的家族式领导和“领袖”式领导风格。     

需求信息可部分观察时供应链中的信息汇聚效应

考虑由一个供应商和两个零售商组成的二级供应链,供应链中的上下游企业共享需求信息.假设产品的需求分布未知且需求信息只可部分观察,企业按贝叶斯法则更新自己的先验.由于需求信息在供应商处汇聚,供应商与零售商占有的信息量不同,这就可能扭曲供应商对市场需求的认识,造成供应商认为市场过度膨胀或萎缩,我们把这种现象称为信息汇聚效应.本文将给出信息汇聚效应的定义,并给出在两周期供应链中发生信息汇聚效应的充分条件,进而推出发生信息汇聚效应概率的下界.数值算例表明,在一定情况下,在供应链中发生信息汇聚的概率会很可观.     

A Continuous‐Review Inventory Model with Disruptions at Both Supplier and Retailer

We consider a continuous‐review inventory problem for a retailer who faces random disruptions both internally and externally (from its supplier). We formulate the expected inventory cost at this retailer and analyze the properties of the cost function. In particular, we show that the cost function is quasi‐convex and therefore can be efficiently optimized to numerically find the optimal order size from the retailer to the supplier. Computational experiments provide additional insight into the problem. In addition, we introduce an effective approximation of the cost function. Our approximation can be solved in closed form, which is useful when the model is embedded into more complicated supply chain design or management models.     

Lifetime Buy Decisions with Multiple Obsolete Parts

Life‐cycle mismatch occurs when the life cycles of parts end before the life cycles of the products in which those parts are used. Lifetime buys are one tactic for mitigating the effect of part obsolescence, where a quantity of parts is purchased for the remaining life of a product. We extend prior work that determines optimal lifetime buy quantities for one product with one obsolete part by providing an analytic solution and two simple heuristic policies for the optimal lifetime buy quantities when many parts become obsolete over a product's life cycle. We determine which of our two heuristics is most accurate for different product life cycles, which yields a metaheuristic with increased accuracy. That analysis also reveals critical perspectives in making lifetime buy decisions with nonstationary life‐cycle demand patterns.     

联合促销下双渠道VMI供应链的竞争与协调

本文在双渠道VMI供应链中,假设制造商和零售商分别处于领导者和追随者的地位,考虑了制造商通过联合促销协调供应链上下游的策略以及双渠道需求之间的搭便车效应,以此为背景建立了制造商和零售商之间的Stackelberg博弈模型,并通过拉格朗日乘数法求解出了制造商的最优发货策略和零售商的最优定价与促销策略。研究发现制造商开辟网上渠道直销产品后,零售商缺货时间比例增大。进一步研究发现,制造商承担促销成本的比例,双渠道之间的搭便车效应对供应链成员的决策和利润有显著影响。另外,双渠道的需求越不稳定,则制造商开辟网上销售渠道后获利越高,同时零售商的利润越低。最后,通过算例验证了模型的有效性并对模型中主要参数进行了灵敏度分析。     

基于RFID技术的供应链投资决策及协调策略研究

本文以单制造商和单零售商组成的两级供应链为研究对象,基于链上成员是否投资RFID技术,考虑四种情景:供应链成员均不投资RFID,仅零售商投资RFID,仅生产商投资RFID及供应链成员共同投资RFID。采用Newsvendor模型建立四种情景时链上成员的收益模型,得出Stackelberg均衡解和供应链成员的最优期望收益,探讨了RFID技术投资对各情景时链上成员收益的影响,得到了供应链成员共同投资RFID时的协调策略。研究表明:当RFID标签成本和零售商库存不准确率在相应的阈值内,零售商或制造商单独投资RFID技术均能提升自身收益,同时对链上其他成员的收益存在"正外部性";此外,收益共享契约能够有效地协调链上成员共同投资RFID技术后的供应链,并且该协调思想丰富并拓展了供应链投资RFID技术的协调研究。     

考虑消费者效用与保鲜的生鲜农产品EOQ模型

针对生鲜农产品新鲜度随时间减小的特点,构造受生鲜农产品新鲜度和零售价格影响的消费者时变效用函数,分析了消费者在不同时刻够买生鲜农产品的效用和数量的变化,并基于此建立了消费者偏好影响需求的生鲜农产品EOQ模型;以提高消费者效用为目的,分析了两种不同保鲜情形下零售商的最优订货决策和最优保鲜投入。研究发现,零售商的最优保鲜投入并不能使消费者效用最大化,满足消费者对生鲜农产品新鲜度的要求必须依靠政府的宏观调控。     

一种考虑原材料库存成本的变质物品EPQ模型

在库存管理研究中,单独实现产成品或原材料库存成本最小,往往无法获得整个库存系统的最优控制策略.本文提出了一种同时考虑产成品和原材料库存成本的变质物品EPQ集成模型.运用迭代寻优法得到模型最优解,得出计划期内最优原材料订购次数,原材料订购周期内的最优生产次数和最优服务水平,并对主要参数进行了灵敏度分析,为生产制造企业的库存管理提供了决策依据.     

产能和需求不确定情形下ATO系统最优库存和生产决策研究

通过将产成品的最终组装环节延迟到观察到实际需求以后进行,按订单组装(Assemble-to-Order,ATO)策略能够有效避免按库存生产(Make-to-Stock)策略下因为生产过剩而带来的损失和风险。然而,在未来产能有限的情形下,生产商必须提前组装部分产成品,以最大化自身收益。本文考虑一个未来需求和组装产能同时具有不确定性的单周期ATO系统:在观察到实际需求以前,生产商必须准备好所有的零部件库存,并组装适量的产成品;观察到实际需求和实际可用组装能力以后,则根据需要进一步追加产成品产量,以尽可能满足客户需求,从而最大化自身利益。通过构建一个两阶段规划模型,我们研究了生产商的最优零部件库存和最优生产决策;并进一步考察了生产商可以通过紧急外包来获取额外组装产能时的最优决策。研究结果为随机环境下生产商合理采购零部件库存和合理安排生产提供了有益的管理启示。