A DC programming heuristic applied to the logistics network design problem

This paper proposes a new heuristic method for the logistics network design and planning problem based on linear relaxation and DC (difference of convex functions) programming. We consider a multi-period, multi-echelon, multi-commodity and multi-product problem defined as a large scale mixed integer linear programming (MILP) model. The method is experimented on data sets of various size. The numerical results validate the efficiency of the heuristic for instances with up to several dozens facilities, 18 products and 270 retailers.     

Reducing the mean supply delay of spare parts using lateral transshipments policies

Lateral transshipment has been studied lately as a promising policy for increasing the performances of multi-echelon spare parts inventory system. By lateral transshipment spare parts can be moved from one location with excess inventory to another location, at the same echelon, in shortage, with the aim of reducing supply delays of spare parts. This paper will examine the relative effectiveness of two lateral shipments approaches in reducing the mean supply delay (MSD) of a non-repairable item, with respect to a classical policy of no lateral shipments. A simulation model of a two echelon supply network has been implemented and an experiment has been performed by varying different parameters of the supply network, such as the number of warehouses (locations at the lower echelon), the supply lead time from the central depot, the spare parts demand uncertainty, and the size variability of the warehouses. Results show appreciable reductions of MSD when lateral shipments are allowed with respect to the classical policy, in almost every network configuration.     

Integrated inventory model for deteriorating items under a multi-echelon supply chain environment

As the industrial environment becomes more competitive, supply chain management has become essential. The objective of this research is to develop a multi-echelon inventory model for a deteriorating item and to derive an optimal joint total cost from an integrated perspective among the supplier, the producer, and the buyer. A computer code is developed to derive the optimal solution. A numerical example is given to illustrate the model. This paper shows that the integrated approach strategy results in the lowest joint total cost as compared with the independent decision approaches.     

Strategic safety stock placement in supply chain design with due-date based demand

We present a strategic safety stock placement model in supply chain design for assembly-type product with due-date based demand, where demand data are based on dates when company has to ship to customers rather than order receiving dates. We formulate multi-echelon stock placement by guaranteed-service model with demand propagation equations through backward explosion, where demand can be either stationary or nonstationary. The stock placement model is incorporated into network design problem and its optimization procedure is provided. We show effectiveness of the optimization procedure and other significant features of the model through numerical examples of a machinery product supply chain.     

Simulation-based optimisation of multi-echelon inventory systems

Multi-location inventory models are one of the most widely investigated fields in mathematical inventory theory, but the analytically tractable models suffer from various restrictive assumptions. To overcome these restrictions simulation can be used. However, simulation is not an optimisation approach. Therefore, we propose the simulation optimisation approach where a simulator is combined with an appropriate optimisation tool.In the present paper, we show that simulation optimisation successfully can be applied to define optimal policies in very general multi-echelon inventory systems. A numerical example shows the usability of our approach.     

The market-oriented dynamic product recovery model in the just-in-time framework

A market-oriented deterministic dynamic product recovery problem and its multi-echelon model formulation are discussed in this paper. For this general non-linear alternate deterministic dynamic product recovery model a dynamic programming solution procedure is developed. Furthermore, the subcases of the Just-in-time situation with regard to the suppliers as well as customers are considered, for which the two-stage problem is transformed to easily solvable one-stage models. It will be seen that the regarded recovery problem in this formulation is just a special multi-echelon problem with two alternative production options.     

Picture this: Managed change and resistance in business network settings

This paper discusses change management in networks. The literature on business networks tends to downplay the role of managerial initiative in network change. The change management literature addresses such initiative, but with its single-firm perspective it overlooks the interdependence of network actors. In exploring the void between these two streams of literature, we deploy the concept of network pictures to discuss managed change in network settings. We analyze a change project from the furniture industry and address the consequences of attempting to manage change activities in a network context characterized by limited managerial authority over these activities. Our analysis suggests that change efforts unfold as a negotiated process during which the change project is re-negotiated to fit the multiple actor constituencies. The degree of overlap in the co-existing network pictures of the involved actors is found to be decisive for the possibility of successfully implementing network change.     

An efficient hybrid genetic algorithm for the multi-product multi-period inventory routing problem

The inventory routing problem (IRP) addressed in this study is a many-to-one distribution network consisting of an assembly plant and many distinct suppliers where each supplies a distinct product. We consider a finite horizon, multi-periods, multi-suppliers and multi-products where a fleet of capacitated homogeneous vehicles, housed at a depot, transport products from the suppliers to meet the demand specified by the assembly plant in each period. The demand for each product is deterministic and time varying. A mathematical formulation of the problem is given and CPLEX 9.1 is run for a finite amount of time to obtain lower and upper bounds. A hybrid genetic algorithm, which is based on the allocation first route second strategy and which considers both the inventory and the transportation costs, is proposed. In addition to a new set of crossover and mutation operators, we also introduce two new chromosome representations. Several medium and small sized problems are also constructed and added to the existing data sets to show the effectiveness of the proposed approach.     

A robustness study of a multi-echelon inventory model via simulation

This paper examines the robustness of a standard model of multi-echelon inventory systems, specifically the models discussed in Axsäter (Oper. Res. 48(5) (2000) 686). A simulation model was developed to explore the model's ability to predict system performance for a two-echelon one-warehouse, multiple retailer system using (R,Q) inventory policies under conditions that violate the model's fundamental modeling assumptions. In particular, the impact of non-stationary demand on this stationary demand inventory model was examined. The model performs well at the low demand and large retailer order batch size situations, but our testing of the model indicated that care must be taken when applying this model to situations that violate its fundamental assumption. These results should help practitioners to better understand the assumptions of these models and to determine when or when not to apply these models in practice.     

German inventory to sales ratios 1971-2005—An empirical analysis of business practice

The purpose of this study is to test empirically for the first time the general hypothesis that inventory to sales ratios have decreased over time in the German economy. Although inventory reduction has been a prevalent topic in the production and operations management literature, there is a lack of empirically confirmed answers to questions. They are as follows: Have inventories in German firms decreased overall during the past decades? What sectors of German industry are leading (lagging behind) inventory reduction? Has inventory reduction developed differently for raw materials, work-in-process, or finished goods? In which periods was marginal inventory reduction greatest? To the best of our knowledge, this empirical study is the first to broadly investigate inventory development from the 1970s until the present for a major European economy, Germany, and will provide the first answers to the research questions stated above using aggregate industry-level data provided by the Deutsche Bundesbank. We show that inventory levels decreased overall in many sectors of German industry. This reduction was mainly marked for raw materials and finished goods, particularly for the second-half of the time frame investigated.     

供应链管理模式下服装类产品的库存策略

库存管理是众多企业面临的一个重大问题,它对企业的生存及发展有着重要的影响。服装类产品由于生命周期短的特殊性,导致其库存管理的难度较大。通过分析服装类产品的特点、库存所处的位置、库存存在的影响及产生原因,提出建立以整个供应链为整体的库存管理策略,通过行业信息一体化、产业集群、供应商管理库存和共同配送,深入挖掘供应链的潜在能量,增强企业的竞争力。     

A framework for the analysis of global, regional and local business networks

In this article we are dealing with the global, regional and local questions of the business. We raise the following question: is there a relation between network management (networking) and the spatial type of the network. We make a cross analysis of networking and spatial types of the network. The paper builds on the model of networking (Ford et al., 2002; Ford et al., 2003; Håkansson et al., 2009), the network paradoxes (Håkansson and Ford, 2002) and the model of 6 Cs (Ritter & Ford, 2006). We emphasize the strategic importance of the interpretation of network pictures. In order to answer the research question we create a theoretical conceptual frame called the Spatial Networking Matrix. We use the method of explorative expert interview in order to introduce some experiences of company leaders and managers concerning networking and spatiality. We conclude that after further development, the Spatial Networking Matrix can help to analyze networking and spatial types of networks at once, deepen the understanding of the real business world and through all of these, be a useful tool for business practice.     

A tabu search heuristic for redesigning a multi-echelon supply chain network over a planning horizon

This paper addresses the problem of redesigning a supply chain network with multiple echelons and commodities. The problem belongs to a comprehensive class of network redesign problems previously introduced in the literature. Redesign decisions comprise the relocation of existing facilities to new sites under an available budget over a finite time horizon, the supply of commodities by upstream facilities, the inventory levels at storage facilities, and the flow of commodities through the network. The problem is modeled as a large-scale mixed-integer linear program. Feasible solutions are obtained by using a tabu search procedure that explores the space of the facility location variables. The latter prescribe the time periods in which changes in the network configuration occur. They are triggered by the setup of new facilities, which operate with capacity transferred from the existing facilities, and by closing the latter upon their entire relocation. As the problem is highly constrained, infeasible solutions with excess budget are allowed during the course of the search process. However, such solutions are penalized for their infeasibility. Computational experiments on realistically sized randomly generated instances indicate that this strategic oscillation scheme used in conjunction with tabu search performs very well.     

Rise of strategic nets — New modes of value creation

This paper focuses on the type and management of intentionally created business networks called nets. Nets are extensively being used to achieve a variety of benefits over those of a single firm or market transaction. We propose that the effective management of different types of business net is dependent on their underlying value creation logic. Based on this notion a value creation framework of three generic net types - ‘current business nets’, ‘business renewal nets’, and ‘emerging new business nets’ - is suggested. We argue that they pose widely different conditions and requirements for net management. The management mechanisms of these basic net types are then identified and discussed. We contend that the proposed contingency framework captures the complexity and variety of the expanding strategic business nets in a more valid way than the extant classifications of network organizations. The paper contributes to the emerging theory of network management.     

Business cycle stylized facts and inventory behaviour: New evidence for the Euro area

The purpose of this paper is for the first time to use Business Tendency Survey data, first, to identify new facts that are useful for the interpretation of the decline in the volatility of real activity in the Euro area, and, second, to test the inventory management hypothesis as an explanation for the Great Moderation in Europe. We present stylized facts from the Business Tendency data on series for inventories, current production, current orders, and expected production for the Euro area, emphasizing the decline in the volatility of the series. Further, we investigate whether the decline in inventory volatility can be attributed to an endogenous change in the persistence of shocks to the accumulation dynamics of inventories or to an exogenous change in the shocks hitting the inventory optimisation process. Our results at Euro level generally indicate that there is no evidence of a break in the inventory accumulation process. On the contrary, the impact of exogenous shocks on inventory volatility appears to be steadily declining over time, beginning from the mid-1980s.     

An inventory reservation problem with nesting and fill rate-based performance measures

In many inventory settings companies wish to provide customer-differentiated service levels. These may, for example, be motivated by differences in the perceived customer lifetime value or by specific contractual agreements. One approach to provide differentiated service levels is to reserve some portion of the available inventory exclusively for specific customer classes. Existing approaches to inventory reservation are typically based on the assumption that a company can assign a customer specific revenue or penalty cost to any order or unit of demand filled or unfulfilled. In practice, however, it is usually extremely difficult to accurately estimate (especially long term) monetary implications of meeting or not meeting customer demand and corresponding service level requirements. The research presented in this paper addresses the problem of setting appropriate inventory reservations for different customer classes based on fill rate-based performance measures. We model a single period inventory reservation problem with two customer classes and nesting. We develop exact expressions for two conflicting performance measures: (1) the expected fill rate of high priority customers and (2) the expected loss in the system fill rate induced by inventory reservation. With these expressions a decision maker can analyze the tradeoff between the loss in overall system performance and the higher expected fill rates for prioritized customers. We provide analytical insights into the effects of nesting and the impact of relevant problem parameters on these two performance measures. The analytical insights are illustrated and highlighted through a set of numerical examples. Although we limit our analysis to a single period inventory reservation problem, we expect that our results can be utilized in a wide range of problem settings in which a decision maker has to ration a perishable resource among different classes of customers.     

提高库存设备完好率的方法

运用六西格玛管理方法,设立六西格玛管理绿带项目一“提高库存设备完好率”这一课题;运用DMAIC逐步改进的方法,解决设备管理过程中出现的维修质量问题。对设备整修、整修验收、存放整个设备管理过程进行细致分析,最终提高库存设备完好率。通过对影响库存设备完好率的各种因素及影响程度,进行充分的分析、论证,最终确定影响设备完好率的关键因素X,对关键X影响问题Y（设备完好率）的贡献率进行计算,并提出改进措施。详细介绍了运用六西格玛管理方法中几种分析工具解决绿带问题的全过程,并对主要影响因素的X贡献率进行计算,针对影响库存完好率的关键因素,提出了最终解决问题的方案。     

Strategic capability architecture: The role of network capability

A firm's network capability refers to its ability to build, handle and exploit relationships. These capabilities are interwoven in a complex configuration with the other capabilities and competencies of the firm and in practice, are very difficult to separate from them. Rather than assuming that firms inherently possess network capability, our aim is to discover if the shared managerial logic of top management teams confirms its presence. In order to understand how managers perceive, process and interpret network capability, we guided the management teams of five industrial suppliers through a novel five-step process of introducing, identifying, critically screening, challenging and verifying the capabilities of the firm. The paper introduces a framework for strategic capability architecture and investigates how network capability emerges from among the configuration of other capabilities in industrial firms. We found that network capabilities are central to the formation of customer capabilities. Network capabilities also play an important role as assets contributing to the formation of other capability sets. Furthermore, we found that the networking capabilities act in unison with other capabilities through three different strategic logics termed partnering, value streaming, and horizontal allying.     

Key network management

Despite the rapid growth of business network research, effective approaches for systematic network management are still in their infancy. This article introduces a systematic approach for managing networks—key network management (KNM). This emerges by expanding the ideas of key account management (KAM) into the network context. A key network refers to a set of actors mobilized by the focal company to realize an opportunity. An opportunity is anything that potentially represents or results in value to the company. A company may manage several key networks. The KNM approach includes three basic elements: (1) identifying a key network, (2) strategies for managing actors of the key network, and (3) developing and applying operational level methods for managing actors within the key network. The KNM approach is not only focused on using networks to fulfill existing needs, but also on discovering new opportunities and establishing and managing networks to realize these opportunities. This article provides a framework for the implementation of KNM approach.