Assessing the benefits of remanufacturing option under one-way substitution and capacity constraint

In this article, we investigate the profitability of remanufacturing option when the manufactured and remanufactured products are segmented to different markets and the production capacity is finite. It is assumed that remanufactured products can be substituted by the manufactured ones. A single period profit model under substitution is constructed to investigate the system conditions under which remanufacturing is profitable. We present analytical findings and computational results to show profitability of remanufacturing option under substitution policy subject to a capacity constraint of the joint manufacturing/remanufactruing facility

Value of supplier's capacity information in a two-echelon supply chain

In traditional supply chain models it is generally assumed that full information is available to all parties involved. Although this seems reasonable, there are cases where chain members are independent agents and possess different levels of information. In this study, we analyze a two-echelon, single supplier-multiple retailers supply chain in a single-period setting where the capacity of the supplier is limited. Embedding the lack of information about the capacity of the supplier in the model, we aim to analyze the reaction of the retailers, compare it with the full-information case, and assess the value of information and the effects of information asymmetry using game theoretic analysis. In our numerical studies, we conclude that the value of information is highly dependent on the capacity conditions and estimates of the retailers, and having information is not necessarily beneficial to the retailers

Near-optimal modified base stock policies for the capacitated inventory problem with stochastic demand and fixed cost

In this study, we investigate a single-item, periodic-review inventory problem where the production capacity is limited and unmet demand is backordered. We assume that customer demand in each period is a stationary, discrete random variable. Linear holding and backorder cost are charged per unit at the end of a period. In addition to the variable cost charged per unit ordered, a positive fixed ordering cost is incurred with each order given. The optimization criterion is the minimization of the expected cost per period over a planning horizon. We investigate the infinite horizon problem by modeling the problem as a discrete-time Markov chain. We propose a heuristic for the problem based on a particular solution of this stationary model, and conduct a computational study on a set of instances, providing insight on the performance of the heuristic. © 2014 World Scientific Publishing Co

Selecting transfer station locations for large solid waste systems

In a city with a population over 6 000 000, solid waste collection activities require a lot of attention. The resources used for collection and transport, trucks and labor, can be utilized more effectively if waste is transported to the disposal area via transfer stations. The location of transfer stations becomes especially important when the daily average of solid waste to be transferred is around 6 000 tons and disposal areas are at least 30 kilometres away from the metropolitan. A general mathematical programming approach with four stages is proposed to determine the locations of transfer stations. Certain modifications are required for the case considered, all resulting in a model which identifies the trade-off between costs of carrying the waste by different transportation modes. The identification of the trade-off requires the estimation of relative cost values rather than individual costs. On the basis of the results obtained, economic feasibility of different alternatives can be evaluated upon the availability of cost information. The application of the model to İstanbul is summarized together with the details of analysis

Contracting under uncertain capacity: a generalisation

International audienceIn this paper, we develop a two-stage supply chain model consisting of a supplier with uncertain capacity and a retailer facing an uncertain demand. We consider that the payment of the retailer to the supplier has two steps: a prepayment based on the quantity ordered by the retailer and a final payment based on the quantity actually delivered by the supplier. We first consider the centralised version of this model and determine the optimal policy analytically. We investigate the effects of the prepayment and capacity restriction. We then consider a decentralised version and characterise optimal decisions of both the supplier and the retailer in the framework of Stackelberg equilibrium. We analyse the efficiency loss of the described decentralised system compared to the centralised system. We discuss different contracting alternatives and propose a generalised contract structure that enables coordination of the decentralised system to achieve the performance of the centralised one

Optimal inventory policies under imperfect advance demand information Optimal Inventory Policies under Imperfect Advance Demand Information

Abstract: We consider an inventory control problem where it is possible to collect some imperfect information on future demand. We refer to such information as imperfect Advance Demand Information (ADI), which may occur in different forms of applications. A simple example is a company that uses sales representatives to market its products, in which case the collection of sales representatives' information as to the number of customers interested in a product can generate an indication about the future sales of that product, hence it constitutes imperfect ADI. Other applications include internet retailing, Vendor Managed Inventory (VMI) applications and Collaborative Planning, Forecasting, and Replenishment (CPFR) environments. We develop a model that incorporates imperfect ADI with ordering decisions. Under our system settings, we show that the optimal policy is of order-up-to type, where the order level is a function of imperfect ADI. We also provide some characterizations of the optimal solution. We develop an expression for the expected cost benefits of imperfect ADI for the myopic problem. Our analytical and empirical findings reveal the conditions under which imperfect ADI is more valuable

Kapalı çevrimli bir otomatik sistemde işletme ve depolama uygulama problemleri ve önerileri

TÜBİTAK MİSAG Proje01.01.1995Otomatik tezgahların, hatasız, hızlı ve programlanabilir nitelikte olmaları nedeniyle çalışmaları esnasındaki fiziksel özelliklerinin özenle incelenmesini gerekir. Bu işletme özelliklerinin anlaşılmasının bir yolu da küçük ölçekli modellerinin kurulup deneysel ortamlarda çalıştınlmalandır. Bu raporda, yükleme amaçlı bir robot kolu da bulunan küçültülmüş ölçekte bir otomatik imalat hücresinde ürün-oranlama probleminin incelenme metodolojisi ve sonuçlan anlatılmaktadır. Fiziki sistem Orta Doğu Teknik Üniversitesi Endüstri Mühendisliği Bölümü Otomatik İmalat Modelleme Laboratuvannda yeralmakta ve yedi modülden oluşmaktadır. İmalat süreci, parçalan temsil eden ağaç ve plastik bloklann akışı ile benzetilmiştir. İki tür ürününün kanşık imalatında değişik ürün oranlamalan kullamlarak bir dizi fiziksel benzetim (simulasyon) deneyi yapılmıştır. Deneylerden derlenen veriler bir matematiksel optimizasyon modelinin parametreleri olarak kullamlarak iki ayn yaklaşımın (matematiksel modelleme/fıziki benzetim) birbiriyle ilişkileri araştınlmış ve karşılaştırmasına girişilmiştir. Değişik ürün oranlamalannın belirli üstün yanlan olabileceği görülmüştür. Ancak, bir safhanın bütün ürünler için darboğaz oluşturduğu hallerde bu üstünlükler belirgin olmaktan çıkmaktadır