Inter-temporal inventory competition and the effects of capacity constraints

This paper addresses an intertemporal inventory competition between a supplier (a provider, manufacturer) and a retailer engaged in a supply chain. The paper's focus is on the effect of capacity constraints on both parties when demands are seasonal. The paper provides a comparative study of two solution approaches, one is based on supply chain competition and the other is based on system wide optimization. Our results demonstrate that with dynamic inventory competition, the retailer reduces inventory costs by reducing the response period to higher demands while increasing the supply requests compared to the system-wide optimal approach. As a result, the supplier's inventory costs increase. An example illustrating these particular facets of the problem and its application is presented and discussed in light of the supplier and the retailer coordinating policies.     

采购限制下的电子采购策略库存水平分析

库存是影响供应链成本性能的主要因素之一,有效地减少库存可以降低整个供应链的成本性能,因此库存管理是优化供应链运作、提高竞争优势的重要手段。论文针对库存管理中的(s,S)策略,建立了库存水平变化的模型,分别分析了无采购条件限制和有采购条件限制下的库存水平的变化,并分别给出了期望值和方差。     

Impact of RFID information-sharing strategies on a decentralized supply chain with reverse logistics operations

The integration of environmental practices in a supply chain has been study for the past few decades. However, most of the work relies on centralized decisions made by one player. Few papers address the complex dynamics of environmental decentralized supply chains and how these dynamics can affect environmental and economic outcomes. To study this problem, we consider a supply chain with a manufacturer and two different suppliers: a recycled-material and a raw-material supplier. The players make individual inventory decisions to satisfy demand and reduce cost. Further, this supply chain encompasses stochastic elements such as in demands, returns, and collection leadtimes. These decentralized decisions and random factors can cause underperforming results; therefore, new inventory models and technologies are needed to help companies increase coordination within these systems. We model the implementation of Radio Frequency Identification (RFID) in the supply chain to determine if real-time inventory monitoring and information sharing can help the system attain higher environmental benefits (more returns) and higher economic benefits (less cost). We study two scenarios through a simulation-based analysis: No RFID and RFID. Numerical studies show that environmental benefits are significantly increased with the attainment of more returns. However, although economic benefits are realized, they are less significant than the environmental benefits. Further regression and sensitivity analyses on the cost performance measures reveal that economic benefits depend on several drivers inside the system. We present managerial insights that illustrate what configurations within this complex system can lead to the achieving of environmental as well as economic benefits.     

Modeling defaults of companies in multi-stage supply chain networks

The interest in supply chain networks and their analysis as complex systems is rapidly growing. The physical approach to the topic draws on the concept of heterogenous interacting agents. The interaction among agents is considered as a repeated process of orders and production. The dynamics of production in the supply chain network which we observe is nonlinear due to the random failures in processes of orders and production. We introduce an agent-based model of a supply chain network which represents in more detail the real economic environment in which firms operate. We focus on the influence of local processes on the global economic behavior of the system and study how the proposed modifications change the general properties of the model. We observe collective bankruptcies of firms, which lead to self-emerging network structures. Our results give insight into the dynamics of default processes in supply chain networks, which have important implications both for risk managers and policy makers. Based on the simulations we show that agent-based modeling is a powerful tool for optimization of supply chain networks.     

Supplier selection-order allocation: A two-stage multiple criteria dynamic programming approach

This paper proposes a two-stage multiple criteria dynamic programming approach for two of the most critical tasks in supply chain management, namely, supplier selection and order allocation. In the first stage, to address multiple decision criteria in supplier ranking, the analytic hierarchy process (AHP) is employed. In the second stage, supplier ranks are fed into an order allocation model that aims at maximizing a utility function for the firm as well as minimizing the total supply chain costs, subject to constraints on demand, capacity, and inventory levels. A dynamic programming approach is crafted to solve the proposed bi-objective model.     

Inventory control in a two-echelon dual-channel supply chain with setup of production and delivery

This paper considers a two-echelon dual-channel supply chain model with setup of production and delivery and develops a new inventory control policy for the supply chain. Previously, a two-echelon supply chain model without setup of production and delivery is considered and a one-for-one inventory control policy is applied to the supply chain. In the inventory control policy, production is stopped when the warehouse inventory reaches the upper limit and is started again immediately after the inventory drops below the limit. Moreover, delivery to the retailer is stopped when the store inventory reaches the upper limit and is started again immediately after the inventory drops below the limit. The total cost that consists of inventory holding costs and lost sales cost is considered, and setup costs are not considered in the total cost. Once setup costs are introduced, the one-for-one inventory control policy is no longer appropriate. Then, this paper develops a new control policy for the two-echelon dual-channel supply chain with setup of production and delivery. As performance measure, the total cost that consists of inventory holding costs, lost sales cost, and production and delivery setup costs is considered, and the total cost calculated on the basis of Markov analysis demonstrates the effectiveness of the proposed control policy.     

Design of sustainable supply chains under the emission trading scheme

Increase in environmental concerns together with legislations are forcing industries to take a fresh look at the impact of their supply chain operations on the environment. This paper introduces a mixed-integer linear programming based framework for sustainable supply chain design that considers life cycle assessment (LCA) principles in addition to the traditional material balance constraints at each node in the supply chain. Indeed, the framework distinguishes between solid and liquid wastes, as well as gaseous emissions due to various production processes and transportation systems. The framework is used to evaluate the tradeoffs between economic and environmental objectives under various cost and operating strategies in the aluminum industry. The results suggest that current legislation and Emission Trading Schemes (ETS) must be strengthened and harmonized at the global level in order to drive a meaningful environmental strategy. Moreover, the model demonstrates that efficient carbon management strategies will help decision makers to achieve sustainability objectives in a cost-effective manner.     

基于连锁零售企业退货管理的供应链协调机制研究

在对连锁零售企业退货物流网络结构进行分析的基础上,建立了与价格相关的随机需求下存在顾客退货和允许库存结转的单一供应商、单一连锁零售企业、单一产品的供应链模型。根据供应链一体化模式下得到的相关决策变量的一阶条件,论证基于回馈和惩罚的批发价格契约能够实现供应链的协调。研究表明,在给定回馈和惩罚因子的前提下,供应商可以通过调整目标订购数量来实现供应链整体利润的任意分配,并且当目标订购数量和回馈惩罚因子满足一定条件时,供应链的协调才是有效的,从而为连锁零售企业的退货物流管理提供了重要的理论依据。     

A holistic network model for supply chain analysis

Supply chain researchers are experiencing a conceptual and analytical paradox. They are asked to move beyond dyadic analyses and investigate larger network effects with only a limited analytical toolkit. This research proposes the use of bilinear mixed-modeling to holistically analyze supply chain phenomena. Through this approach, researchers are able to account for multiple supply chain relationships, higher-order dependencies among member firms, and simultaneously evaluate covariates from buyer and seller perspectives. The model is validated through the lens of a pervasive supply chain problem commonly referred to as the bullwhip effect. A sample of firms from the US apparel industry in 2004 is analyzed and then the findings are confirmed using data from 2005. In addition to validating the model through the presence of the bullwhip effect, the bilinear model illuminates variables such as advertising, price deals, inventory turnover, and inventory backlogs that exacerbate or diminish inventory differences between firms in a supply chain. The results extend research on supply networks and supply efficiency to a more holistic level and show that higher-order dependencies are important drivers of supply chain phenomena.     

On the replenishment policy when the market demand information is lagged

We consider a situation where the most up-to-date information on the market demand and the inventory levels is not available to a replenishment decision maker in a single echelon of a supply chain. The objective of the decision maker is to minimise the sum of the inventory and the production costs. An intuitively attractive strategy under this setting might be to reduce the information time lag as much as possible by utilising information technologies such as RFID. We call this strategy the Time lag Elimination Strategy (TES). However, this course of action requires investment in information systems and will incur a running cost. We propose an alternative strategy that has similar economic consequences as the TES strategy, but it does not require new information systems. We call this strategy the Controlling Dynamics Strategy (CDS). The benefit coming from CDS is quantified and is compared to that from TES. We also quantify the benefits gained from the combined use of these two strategies. A new ordering policy is introduced that is easy to implement without any forecasting systems and can reduce the production cost significantly.     

A review of the extensions of a modified EOQ model for imperfect quality items

Imperfect items in the raw material and production stages of a supply chain directly impact the coordination of the product flow within a supply chain. In response to this concern, production and inventory lot sizing models, which incorporate imperfect items into their formulation have become an important and growing area of research. The contribution of Salameh and Jaber (2000) is one of the fundamental models on lot sizing when procured items are of imperfect quality. Over the past decade, there has been a noticeable amount of interest in the EOQ model for imperfect items that was set forth in Salameh and Jaber (2000). Several researchers have published adaptations and extensions of this original model that address supply chain coordination, quality improvement and yield management, and the impact of human error on production and inventory systems. In this paper, we summarize the current body of research that has extended the Salameh and Jaber (2000) EOQ model for imperfect items. Some possible future research directions are identified at the end of the paper.     

模糊随机环境下考虑碳限额和碳交易机制的库存配送问题研究

本文以高端物流服务集成商与库存配送服务商为研究对象，以集成商的供应链网络成本最小、服务商的运营成本最小且准时制供应为目标，深入研究考虑碳限额、碳交易机制以及残次品处理的多供应商选择多产品多阶段库存配送问题，构建了基于动态规划的双层库存配送模型。利用双层全局--局部--邻域粒子群算法 (Bi-GLNPSO) 设计了模型求解方案，并通过算例验证了模型和算法的有效性和合理性。探讨了碳限额和碳交易机制对总成本和库存配送决策的影响。     

供应链管理环境下的库存控制研究

研究供应链管理环境下企业库存控制方法,对于节约供应链成本、提高供应链整体效率有重要意义。本文从分析供应链管理环境下库存控制在实践中所出现的各种问题入手,阐述了供应链环境下库存控制的新特点,有针对性地提出解决问题的策略和方法。     

On delineating supply chain cash flow under collectionrisk

The credit terms for accounts receivable (AR) offered by sellers to buyers not only create a time lag between supply chain physical flow and cash flow, but also increase the collection risk contributed by late collection and default. Previous studies describing the relationship between the two major supply chain flows did not consider the collection risk, which poses a serious challenge to companies with limited cash resources when seeking growth opportunities in sales. This study first delineates the relationship between the two flows during a growth period without imposing any constraints. A stochastic optimization model is then developed to observe the managerial implications of cash flow risk under tight cash constraints.     

库存控制之供应链多目标视角下的应用研究——以工业润滑油供应链为例

供应链环境下库存控制的研究已经成为趋势,区别于常规的单目标库存控制的研究,本文以工业润滑油供应链为依托,提出了在供应链背景下考虑供应链库存成本最小化和客户平均需求满足率最大化为目标的库存控制研究思路,构建了多目标库存控制模型。最后将所建的供应链视角下多目标库存控制决策模型进行实证分析,为目标供应链上的企业做出生产、销售等决策提供依据。     

基于 DEA 方法的企业绿色供应链运营效率评价研究

绿色供应链在传统供应链的基础上兼顾了经济与环境效益，是社会可持续发展的重要推动力。对绿色供应链运营效率进行评价有助于企业了解自身的不足，从而对企业绿色供应链管理做出反馈，促进企业绿色供应链运营的良好发展。本文通过文献梳理与总结，构建了企业绿色供应链运营效率评价的投入、产出指标，在此基础上，利用 DEA 方法并通过算例进行实证研究，以期为改善企业绿色供应链运营效率、促进企业更好地实施经济效益与环境效益“双赢”的绿色供应链管理模式提出更加有益的建议。     

An integrated production–distribution model for the dynamic location and allocation problem with safety stock optimization

The design and management of a multi-stage production–distribution system is one of the most critical problems in logistics and in facility management. Companies need to be able to evaluate and design different configurations for their logistic networks as quickly as possible. This means coordinating the entire supply chain effectively in order to minimize costs and simultaneously optimize facilities location, the allocation of customer demand to production/distribution centers, the inbound and outbound transportation activities, the product flows between production and/or warehousing facilities, the reverse logistics activities, etc.Full optimization of supply chain is achieved by integrating strategic, tactical, and operational decision-making in terms of the design, management, and control of activities. The cost-based and mixed-integer programming model presented in this study has been developed to support management in making the following decisions: the number of facilities (e.g. warehousing systems, distribution centers), the choice of their locations and the assignment of customer demand to them, and also incorporate tactical decisions regarding inventory control, production rates, and service-level determination in a stochastic environment. This paper presents an original model for the dynamic location–allocation problem with control of customer service level and safety stock optimization. An experimental analysis identifies the most critical factors affecting the logistics cost, and to finish, an industrial application is illustrated demonstrating the effectiveness of the proposed optimization approach.     

低碳经济下考虑满意度的冷链路径优化

为了在降低冷链物流配送成本的同时,保证顾客满意度和碳排放成本达到企业的要求。充分考虑客户软时间窗约束、行驶距离、生鲜变质等多重影响因素,构建考虑顾客满意度的低碳冷链物流路径优化模型,结合固定成本、碳排放成本、损坏成本、冷藏成本、运输成本以及时间窗成本,采用遗传算法进行求解,并应用实例加以验证。结果表明,相对于不考虑满意度的路径优化,以总成本为目标的冷链物流路径优化,能够平均减少23 km的运输距离和降低2.72%的配送总成本;同时结果也更优于以低碳为目标的求解。模型在提高顾客满意度的同时,实现了降低配送总成本以及减少物流活动中碳排放的目标。因此,研究为物流运输企业提高服务质量和经济效益提供了有效的技术路线,结果可为冷链物流行业的服务能力提升以及低碳转型发展提供启示,为物流行业的可持续发展研究提供理论参考。     

The role of ERP tools in supply chain information sharing,cooperation, and cost optimization

The transaction based integrated Enterprise Resource Planning (ERP) software provides different tools that can support supply chain integration but at the same time it has several features that obstructs the integration with business partners. We concentrate on the inventory management aspects of supply chain coordination reviewing the recent quantitative modeling and organizational results available in literature. We summarize the results of a detailed numerical and sensitivity analysis based on our previously published models for supply chain cooperation and joint optimal ordering and shipment policies for the buyer and supplier. These results can be used in enterprise software to measure the potential monetary value of policy coordination, to promote cooperation, and minimize the total supply chain system cost. Our further goal is to combine quantitative tools with organizational and management factors, and to integrate them in a multi-level framework of policy coordination.