Consignment and vendor managed inventory in single-vendor multiple buyers supply chains

In this paper we model a consignment (CS) and vendor-managed inventory (VMI) policy for a single vendor and multiple buyers supply chain with known demand. We study three vendor–buyers partnerships: (i) the vendor and the buyers act independently, (ii) the vendor enters in a vendor-managed inventory consignment (VMI&CS) partnership with the buyers and (iii) the vendor and the buyer belong to a vertically integrated firm where a single decision maker decides about the ordering policies. We use relationships (i) and (ii) to study the benefits of the VMI&CS agreement. We provide analytical and numerical results. We find that such an agreement is more beneficial when the vendor has a flexible capacity. It is also more attractive to buyers when they have significant order costs and the vendor's setup cost is not large. Finally we find that under VMI&CS the vendor will tend to make more frequent shipments with smaller lots.     

供应链管理中VMI系统的研究

通过分析VMI和RMI在概念原理上的本质差异,讨论了VMI在管理思想、决策方式、预测体系、补货模式、延迟策略方面的优越性和先进性。在此基础上,详细描述了VMI工作流程中的八个关键环节,并结合实际指出实施VMI的步骤和注意事项,最后总结了VMI在实践中给供应商、零售商以及供应链整体带来的收益和竞争优势。     

Vendor managed inventory with consignment stock for supply chain with stock- and price-dependent demand

This paper presents a single vendor–single buyer coordinated model. The vendor produces a single deteriorating item and transfers it to the buyer in equal shipments. The model is based on vendor managed inventory with consignment stock (VMI-CS) agreement in which the vendor uses the buyer’s warehouse. The buyer stocks items both on his shelf and in his warehouse. The demand is assumed to be linearly sensitive to inventory level and selling price. The objective is to determine variables that maximise the total profit. An exact solution procedure is proposed to find the optimal solution. Numerical results show that supply chain members will benefit from the advantages of economies of scale in coordinated model with VMI-CS policy.     

供应链上游段VMI模式的共赢条件

选取上游层面VMI模式各参与者为研究对象.考虑实施上游层面VMI模式后,订货(配送)主动权的转移导致订货(配送)策略的不同,以及制造商对各零部件需求速率的不同导致其对各零部件的订货周期也不一致的情况.通过建立数学模型,对实施上游层面VMI模式前后各企业的经济效益进行比较,探讨实施VMI且制造商销售价格不变时,各供应商是否存在合理的销售价格涨幅区间,该区间的价格既能弥补供应商因管理制造商零部件库存多消耗的成本,也能使各制造商和供应商的经济效益都有所提高,实现共赢,为各企业更加长久的合作提供理论依据.     

供应商管理库存的价格效应研究

通过建立数学模型,论证了VMI在供应链中收益的非负性;在此基础上还给出了供求均衡价格与订货成本比、库存成本比的函数关系,该公式说明当订货成本比与库存成本比相差比较大时,VMI可以有效降低均衡价格,否则均衡价格将会上升。     

Multi-period hedging and coordination in a prefabricated construction supply chain

In this paper, a multi-period buffer space hedging coordination between a building contractor (BC) and a logistics provider (LP) is investigated. In order to facilitate the application of the construction lead-time hedging (CLTH) strategy, adopted by the BC, extra buffer space needs to be reserved at LP’s intermediate warehouse for contingency usage. This strategy is defined as ‘buffer space hedging (BSH)’ and it increases the pressure of LP on involving extra storage and maintenance cost. Two coordination mechanisms are adopted for solving this BSH problem. One scheme is by introducing a cost-sharing term. A Nash game model is studied to find the individual optimal decisions. Another scheme is a cooperative game model with proper side-payments. We show that adjusting the BSH amount for each review period benefits the supply chain. Both coordination mechanisms enable a win–win outcome. Especially, if system resources are sufficient, the cooperative game outperforms the Nash game. Numerical experiments further demonstrate that the benefit of the proposed model is more significant under the case with lower unit enlarging/rearrangement cost, higher tardiness penalty and unpredictable and uncontrollable construction process-determined assembled and installed prefabs.     

VMI下需求受库存和努力水平影响的供应链协调

针对一个实施VM I(供应商管理库存)的两级供应链,市场需求受供应商和零售商双重努力影响的问题,建立了基于协作关系的库存和努力水平决策模型。通过分析得出在分散决策下供应商选择的库存水平和零售商选择的努力水平均低于集中决策下的最优水平,供应链效率也较低。设计了一个成本分摊契约协调供应链。结果表明,该契约能将供应商和零售商紧密地联系在一起,且通过供应商和零售商的共同努力能获得比分散式决策下更大的利润。     

Coordination of pricing,inventory, and production reliability decisions in deteriorating product supply chains

In this article, we study a two-level supply chain model for deteriorating items, in which the supplier’s production system is unreliable and the retailer’s demand is price-sensitive. The supplier’s production line may randomly shift from the in-control state to the out-of-control state. When the production line is in the out-of-control state, a proportion of the produced products will have bad quality. To mitigate the out-of-control risks, the supplier can improve the production line reliability by investing in high-quality machines, highly skilled workers, or advanced maintenance technologies. We start with the study of pricing and inventory problems concerning endogenous reliability in the integrated and decentralised scenario. To better illustrate the proposed models, two applicable algorithms are designed to determine the optimal production reliability, ordering quantity, and prices. Then, a cooperative reliability investment and revenue-sharing contract is proposed to coordinate the supply chain. Numerical examples and sensitivity analysis of the equilibrium strategies and coordinating results on key system parameters (e.g. deterioration rate, production rate, etc.) are given to verify the effectiveness of the contract, and meanwhile get some managerial insights.     

Joint pricing and inventory strategies in a supply chain subject to inventory inaccuracy

This paper focuses on pricing strategies, inventory policies for a supply chain when Radio Frequency Identification (RFID) technology is adopted to cope with inventory inaccuracy. The supply chain consists of one supplier and one retailer, in which the RFID tag price is shared between the supplier and the retailer. We present and compare the performance differences between a wholesale price contract and a consignment contract when the retailer is the Stackelberg leader and the supplier is the follower. Based on the optimal pricing and inventory decisions, an interesting observation of contract selection is that there are two critical values of inventory available rate such that when the inventory availability is less than the lower value, both the supplier and the retailer prefer a consignment contract; when the inventory availability is greater than the upper value, a wholesale price contract is their best choice; when the inventory availability is between the two values, the supplier prefers a wholesale price contract and the retailer prefers a consignment contract. Additionally, there exist threshold values of RFID tag price and sharing rate to determine the contract preference for the retailer. Furthermore, the profits of both the supplier and the retailer are independent of the RFID tag price sharing rate in a wholesale price contract, and the supplier has the incentive to invest in RFID tag cost in a consignment contract.     

Innovative vendor-managed inventory strategy exploiting interconnected logistics services in the Physical Internet

Traditional supply chain networks are often designed in the interests of a company. Once the network has been defined, the storage and distribution of goods are usually fixed and restricted within the network. This is assumed to be an inherent limit of current inventory control research. Instead of specialised hierarchical storage networks, this paper proposes an innovative vendor-managed inventory strategy exploiting the Physical Internet (PI), which is an open, universal, interconnected logistics system. In such a system, facilities and means of transport are shared and can be allocated according to demands of users. As a result, the PI allows users to stock anywhere in the network and also provides open multisourcing options for orders with on-demand warehousing services within the PI. Inventory decisions can be made dynamically by each player to minimise networkwide inventory levels. A non-linear, simulation-based optimisation model was developed for the vendors’ inventory decision-making when confronted with stochastic demands. A metaheuristic using simulated annealing was applied to solve the problem, and then, the optimised inventory decisions were validated using simulation. The results suggest that the proposed PI inventory model can reduce the total logistics cost while maintaining a comparable or better level of end customers’ services.     

基于提前期的多周期通用件库存模型

在单一周期库存模型的基础上,建立了多周期的通用件库存模型,对无通用件和有通用件的库存模型进行了比较研究,在模型中重点考虑提前期对通用件库存系统的影响,并以风神汽车有限公司有关数据进行了数据分析,揭示出基于提前期的单一周期模型中得出的结论并不能直接套用到多周期模型中,也就是说采用通用件并不总是能够降低库存水平和成本的,这个结论纠正了理论界认为单一周期库存模型的结论普遍适用的观点;研究基于提前期的通用件库存库存模型也是对通用件库存模型没有考虑提前期影响的一个扩展研究。     

供应链上游段集中控制型 VMI & TPL模式利益分配机制

以基本的“收益共享契约”为基础,以集中控制型VMI＆TPL模式为对象,研究供应链上游段各成员企业的协调。由于基本的收益共享契约不能对供应链进行有效协调,提出了基于风险共担的收益共享契约,但是该契约不能实现供应链各成员的期望收益的帕累托最优。为了改进这一缺陷,建立了基于不对称的Nash协商的风险共担型的收益共享契约模型。分析表明：该模型不仅克服了不能实现供应链各成员的期望收益达到帕累托最优的缺点,还可以实现各参与企业的期望收益的帕累托最优。     

基于供应链技术的铜盘管季节性库存问题研究

总结铜盘管市场特点,详细分析季节性库存过程中存在的库存产品积压风险、库存产品质量风险、铜价波动风险以及资金短缺风险,提出利用供应链库存管理技术、延迟化策略、套期保值、融通仓等现代供应链管理理论来降低季节性库存所面临的各种风险。     

基于价格折扣机制的VMI系统

由于一般的VMI策略不一定能保证供应链整体的最优化,主要研究如何在VMI策略中配合合理的价格折扣机制,从而VMI策略能使供应链整体得到最优化,并使供应商和零售商的利润在VMI策略下比在传统的RMI策略下得到Pareto改进.探讨了在一般的VMI策略下零售商的订货量可能大于或小于供应链整体最优时的订货量,研究了基于价格折扣机制的VMI策略如何使零售商的订货量等于供应链整体最优时的订货量,并给出了价格折扣的表达式和取值范围.     

供应链库存管理中缺货补偿问题的研究

在供应链库存管理中,往往都是由客户承担缺货所带来的各种损失。针对这种情况,本文提出供应商在缺货时应向客户提供一定比例的补偿,以维持与客户的合作关系,实现双赢的目的,并利用非线性规划的原理,建立了供应商的缺货补偿模型,最后给出了订货量的最优解,并以实例验证了所给模型和算法的有效性。     

基于随机需求的两级多期供应链网络规划模型

本文以三级供应链网络为例,研究了具有随机因素的,两级多期决策的供应链网络优化问题.优化的具体内容包括两个方面:供应链节点的选址和相应配送系统的设计.文章首先在现有研究成果的基础上,将模型设计拓展到多期决策领域.接下来,针对因素的随机性问题,应用了蒙特卡罗方法对随机因素进行了模拟和采样.最后,模型的目标函数不仅考虑了最小成本,同时还考虑了顾客满意度.对多目标模型的处理采用了e条件限制法.用这种方法的得到的供应链网络优化结果是一系列帕累托最优解,它使得决策者可以按照自己的偏好做出最后选择.     

Warehouse location and two-echelon inventory management with concave operating cost

In this paper, we study a location–inventory network design problem which jointly optimises the warehouse location, the warehouse–retailer assignments, the warehouse–retailer echelon inventory replenishment and the safety stock-level decisions over an infinite planning horizon. The consideration of the facility operating cost, the safety stock cost and the two-echelon inventory cost results in an MIP model with several nonlinear terms. Due to the complex trade-offs among the various costs and multiple nonlinear terms in the model, traditional solution approaches no longer work for this problem. We outline a polymatroid cutting-plane approach based on the submodular property of the cost terms to address this problem. Computational results demonstrate that the cutting-plane method based on polymatroid inequalities can efficiently solve randomly generated instances with moderate sizes.     

基于供需一体化协同控制的供应链库存模型

根据供需一体化协同库存控制策略，构建了一个一体化库存模型。在模型里，假定提前期需求是随机的且服从正态分布，允许在提前期内发生缺货，并产生缺货成本；假定提前期是可控的，能够通过增加成本缩短提前期。该模型通过同时计算最优订货量、再订货点、提前期以及运送批次．使供需一体化库存总成本最小。实例分析证明该模型能够达到节约成本的目的。     

关于VMI下供求双方的利润变化的研究

针对传统库存管理系统存在的牛鞭效应,分析了一种新的库存管理方法:供应商管理库存(VMI).通过定量的方法证明了在VMI下供求双方的库存成本及其利润变化的情况.结果表明:在实施VMI的情况下,购买商的利润总是能够提高,而供应商短期内利润会下降,若长期实施VMI其利润在很大程度上也能够提高.通过实例验证了该结论的正确性.