Scheduling policies for a repair shop problem

In this paper, we analyze a repair shop serving several fleets of machines that fail from time to time. To reduce downtime costs, a continuous-review spare machine inventory is kept for each fleet. A spare machine, if available on stock, is installed instantaneously in place of a broken machine. When a repaired machine is returned from the repair shop, it is placed in inventory for future use if the fleet has the required number of machines operating. Since the repair shop is shared by different fleets, choosing which type of broken machine to repair is crucial to minimize downtime and holding costs. The optimal policy of this problem is difficult to characterize, and, therefore, is only formulated as a Markov Decision Process to numerically compute the optimal cost and base-stock level for each spare machine inventory. As an alternative, we propose the dynamic Myopic(R) policy, which is easy to implement, yielding costs very close to the optimal. Most of the time it outperforms the static first-come-first-served, and preemptive-resume priority policies. Additionally, via our numerical study, we demonstrate that repair shop pooling is better than reserving a repair shop for each fleet

A Bi-objective Optimization for Vendor Managed Inventory Model

Vendor managed inventory is a continuous replenishment program that is designed to provide major cost saving benefits for both vendors and retailers. Previous research on this area mainly included single objective optimization models where the objective is to minimize the total supply chain costs or to maximize the total supply chain benefits. This paper presents a bi-objective mathematical model for single-manufacture multi-retailer with multi-product in order to maximize their benefits. It is assumed that demand is a decreasing and convex function of the retail price. In this paper, common replenishment cycle is considered for the manufacturer and its retailers. Then, the proposed model converts to the single-objective optimization problem using a weighted sum method. A genetic algorithm (GA) is applied to solve it and response surface methodology is employed to tune the GA parameters. Finally, several numerical examples are investigated to demonstrate the applicability of the proposed model and solution approach

Demand chain management: relationships between external antecedents, web-based integration and service innovation performances

This paper presents an investigation of the relationships between the factors that drive the adoption of integrated, web-based demand chain management (DCM), as well as the relationship between web-based DCM integration and service innovation performance. Data was collected from 256 companies in the health care industry. The results show that collaborative structure (e.g. competitive pressure, trust, information sharing and environmental uncertainty) and technological structure (e.g. security) have a positive and significant influence on an organization׳s decision to adopt web-based DCM integration. However, collaborative structure has the greatest influence by far on an organization׳s adoption of web-based DCM integration. The findings also show strong evidence that web-based DCM integration improves service innovation performance. We also found that web-based DCM implementation has a greater impact on service innovation performance than in organizations that only implement web-based supply or demand integration strategies. This research has important implications for organizations interested in improving their service innovation performance, as well as improving web-based DCM integration. For example, to improve the success of web-based DCM adoption, organizations should focus on improving their collaborative structure with suppliers and customers first, before considering their technological structure. Security is also a key issue that needs to be addressed by organizations to ensure the successful adoption of web-based DCM

VMI-type Supply Chains: a Brief Review

The primary purpose of this paper is to highlight for the research community and practitioners the various aspects of using VMI-type supply chains in today’s business environment as well as a number of directions for future studies. In this regard, fifty articles published in major international journals, beginning in 1995, which contribute to the VMI-type supply chains are reviewed via a systematic review methodology. Our findings show there is an incremental growth in employing of VMI strategies in logistic and supply chains. This paper characterizes the design aspects required to configure and establish a VMI-type supply chain in the industry including demand pattern, number of products, contract type between two parties, and profit sharing scheme. Moreover, the current gaps on the current state of VMI-type supply chain in literature are highlighted in last section of this paper that may motivate future studies

Gestion de la cadena de suministro para las Pymes exportadoras del cluster textil confeccion en Antioquia

Resumen: El presente trabajo de investigación estudia la gestión de la cadena de suministro para las pymes exportadoras del clúster textil confección en Antioquia, tema motivado por la participación del sector en el PIB del país y los indicadores de empleabilidad que reportan las empresas objeto de este estudio. La metodología utilizada fue cuantitativa con un enfoque analítico, método de muestreo y el tipo de muestra estratificada, definiendo el diseño de la muestra con los principios del muestreo estratificado en poblaciones finitas. La estratificación se realizó considerando las pymes exportadoras directas y las pymes proveedoras de ellas. Finalmente se concluye con los hallazgos encontrados después de aplicar el instrumento definido para el trabajo de campo, estableciendo brechas y proponiendo algunos sistemas de medición que pueden aportar a la gestión de la cadena de suministro para estas empresas, contribuyendo así a mejorar su productividad y competitividad.Abstract: The present research studies the management of the supply chain for exporting SMEs i n the textile garment cluster in Antioquia, motivated by the sector's share in GDP of the country and employability indicators reported by firms aim of this study subject. The methodology used was a quantitative analytical approach, sampling method and typ e of stratified simple, defining the sample design with the principles of stratified sampling in finite populations. Stratification was performed considering the direct export SMEs SMEs and the providers of them. Finally we conclude with the findings after applying the tool set for field work, establishing gaps and proposing some measurement systems that can contribute to the management of the supply chain for these enterprises, thus contributing to improve productivity and competitiveness.Maestrí

Vendor managed inventory adoption in Malaysia construction industry

The growth of the Malaysian construction industry is burdened by conditions in which 'time overruns' in projects still exist. The quest to overcome construction delays motivates the industry to improve its performance by learning from the other industries. Supply chain management is an important aspect of performance in construction projects recognised by literatures in recent years. The distinctive characteristic of supply chain management in construction does compare to other industries to motivate the need to collaborate horizontally and vertically within the construction industry. Vendor- managed inventory (VMI), famous for eliminating additional costs that may result from the excessive supply and stock-in-hand inventory as practised in other industries, may potentially be adopted and implemented in the construction industry. Therefore, conditions in which VMI is suitable to be adopted, barriers to the effort to adopt VMI and the readiness of the contractors to adopt VMI were evaluated in this study. The results of the survey using 97 ClDB grade G7 registered contractors in Malaysia, show that suppliers' market competition, supplier-buyer cooperation, and demand uncertainty positively influence the intention of contractors to adopt VMI. However, notwithstanding that G7 contractors are large contractors in Malaysia, perceived lack of trust and mutual misunderstanding between supply chain partners are considered top among the many barriers to adopt VMI despite evidence that respondents of the study indicate moderate to high readiness to adopt the recommendations of the study. The study contributes to literature on VMI in the area of the construction industry which has not been explored comprehensively

Optimising Supply Chain Performance via Information Sharing and Coordinated Management

Supply chain management has attracted much attention in the last decade. There has been a noticeable shift from a traditional individual organisation-based management to an integrated management across the supply chain network since the end of the last century. The shift contributes to better decision making in the supply chain context, as it is necessary for a company to cooperate with other supply chain members by utilising relevant information such as inventory, demand and resource capacity. In other words, information sharing and coordinated management are essential mechanisms to improve supply chain performance. Supply chains may differ significantly in terms of industry sectors, geographic locations, and firm sizes. This study was based on case studies from small and medium sized manufacturing supply chains in People Republic of China. The study was motivated by the following facts. Firstly, small and medium enterprises have made a big contribution to China’s economic growth. Several studies revealed that most of the Chinese manufacturing enterprises became aware of the importance of supply chain management, but compared to western firms, the supply chain management level of Chinese firms had been lagging behind. Research on supply chain management and performance optimisation in Chinese small and medium sized enterprises (SMEs) was very scarce. Secondly, there had been plenty of studies in the literature that focused on two or three level supply chains whilst considering a number of uncertain factors (e.g. customer demand) or a single supply chain performance indicator (e.g. cost). However, the research on multiple stage supply chain systems with multiple uncertainties and multiple objectives based on real industrial cases had been spared and deserved more attention. One reason was due to the lack of reliable industrial data that required an enormous effort to collect the primary data and there was a serious concern about data confidentiality from the industry aspect. This study employed two SME manufacturing companies as case studies. The first one was in the Aluminium industry and another was in the Chemical industry. The aim was to better understand the characteristics of the supply chains in Chinese SMEs through performing in-depth case studies, and built models and tools to evaluate different strategies for improving their supply chain performance. The main contributions of this study included the following aspects. Firstly, this study generalised a supply chain model including a domestic supply chain part and an international supply chain part based on deep case studies with the emphasis on identifying key characteristics in the case supply chains, such as uncertainties, constraints and cost elements in association with flows and activities in the domestic supply chain and the international supply chain. Secondly, two important SCM issues, i.e. the integrated raw material procurement and finished goods production planning, and the international sales planning, were identified. Thirdly, mathematical models were formulated to represent the supply chain model taking into account multiple uncertainties. Fourthly, several operational strategies utilising the concepts of just-in-time, safety-stock/capacity, Kanban, and vendor managed inventory, were evaluated and compared with the case company's original strategy in various scenarios through simulation methods, which enabled quantification of the impact of information sharing on supply chain performance. Fifthly, a single objective genetic algorithm was developed to optimise the integrated raw material ordering and finished goods production decisions under (s, S) policy (a dynamic inventory control policy), which enabled the impact of coordinated management on supply chain performance to be quantified. Finally, a multiple objectives genetic algorithm considering both total supply chain cost and customer service level was developed to optimise the integrated raw material ordering and finished goods production with the international sales plan decisions under (s, S) policy in various scenarios. This also enabled the quantification of the impact of coordinated management on supply chain performances

Impact du partage d'informations et du vendor managed inventory sur la performance des chaines logistiques

Le développement des technologies de l information et de la communication que connait notre siècle a grandement facilité les pratiques d échanges d informations au sein des chaînes logistiques. Ces pratiques ont pu ainsi évoluer vers de nouvelles formes de collaborations entre entreprises, telles que le Partage d Informations (PI) et le Vendor Managed Inventory (VMI). Le VMI est un mécanisme de coordination dans lequel le fournisseur a la responsabilité de la gestion des stocks de son client. Ce mécanisme repose sur plusieurs principes parmi lesquels un partage d informations très développé entre les parties qui s y engagent. Le PI et le VMI sont adoptés par les entreprises pour permettre une augmentation des profits et une réduction des coûts. Toutefois, leurs résultats sont mitigés et nécessitent encore un approfondissement de leur compréhension. La contribution de cette thèse se situe dans l analyse des impacts de ces mécanismes sur des chaînes logistiques où tous les maillons sont des entreprises de production dont les efficacités peuvent être différentes. Pour ce faire, plusieurs scénarios ont été étudiés sur des chaînes logistiques constituées de trois échelons, chaque échelon peut appartenir à quatre classes d efficacité. Ces chaînes peuvent répondre à deux types de demande du marché final ; une demande stable ou une demande variable. De plus, plusieurs mécanismes de coordination sont étudiés : les mécanismes de gestion standard, de partage d informations entre deux échelons, de partage d informations entre trois échelons, de VMI entre deux échelons, puis de VMI étendu aux trois échelons. L outil utilisé pour mener ces expérimentations est le logiciel de simulation à évènements discrets Arena. L interprétation des résultats a montré que le mécanisme de coordination avec partage d informations n a pas eu d amélioration très significative sur les résultats. En effet, puisque les entreprises ont des capacités de production finies, la disponibilité de l information n a pas permis d obtenir des résultats différents. Le VMI, de son côté, a pu réaliser des réductions des stocks et des coûts de la chaîne logistique. Ces réductions ont été plus importantes chez les chaînes logistiques dont les maillons sont de faibles efficacités. Chez ces dernières, ce sont les deux parties concernées par le VMI (le fournisseur et le donneur d ordres) qui ont tiré des avantages du VMI. Chez les chaînes logistiques constituées de maillons de haute efficacité, le VMI a permis une réduction des coûts moins importante, car ces chaînes logistiques sont déjà de performance élevée. Pour celles ci, c est le client qui a tiré profit du VMI, alors que le fournisseur VMI a subi une augmentation des coûts suite à l augmentation de la fréquence de transport qu a impliqué ce mécanisme.The advent of new information and communication technology has greatly facilitated the information exchange practices within supply chains. These practices recently evolved into new forms of collaborations between companies such as Information Sharing (IS) and Vendor Managed Inventory (VMI). The VMI is a coordination mechanism where the supplier is responsible for the inventory management of his customer. This mechanism is based on several principles, including developed information sharing between involved parties. The use of IS and VMI allow companies to increase profits and reduce costs. However, the results about the benefits from their use remain not clear. This motivates the need for new assessments and a better understanding of their effects. This thesis main contribution lies in the analysis and comprehension of IS and VMI s impacts on supply chains. Especially, we address the issue of supply chains where tiers are production companies with different effectiveness levels. The examined scenario is based on a three tiers supply chain where each tier can belong to four effectiveness classes. The supply chain can respond to two types of end market demands: stable demands or fluctuant demands. In addition, several coordination mechanisms are studied: (i) standard management mechanism, (ii) information sharing between two enterprises, (iii) information sharing between three enterprises, (iv) VMI and (v) Extended VMI to all the three enterprises. The tool used to conduct these experiments is the discrete event simulation software Arena . The interpretation of the results showed that the IS coordination mechanism has not very significant improvement. Indeed, as companies have finite capacity, the availability of information did not yield better results. Whereas, the VMI could achieve reductions in both inventory and supply chain costs. In addition, VMI improved profits of the two parties, the vendor and the customer. Finally, the advantages of VMI appear to be stronger when the overall supply chain is less effective.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF