Ou Tang

Multi-product economic lot scheduling problem with separate production lines for manufacturing and remanufacturing

We study the economic lot scheduling problem with two production sources, manufacturing and remanufacturing, for which operations are performed on separate, dedicated lines. We develop an exact algorithm for finding the optimal common-cycle-time policy. The algorithm combines a search for the optimal cycle time with a mixed integer programming (MIP) formulation of the problem given a fixed cycle time. Using case study data from an auto part producer, we perform a sensitivity study on the effects of key problem parameters such as demand rates and return fractions. Furthermore, by comparing to results in Tang and Teunter [Tang, O., Teunter, R.H., 2006. Economic lot scheduling problem with returns. Production and Operations Management] for the situation where all operations are performed on the same line, we analyze the cost benefits of using dedicated lines.

Planning and replanning the master production schedule under demand uncertainty

The Master Production Schedule (MPS) is essential in maintaining customer service levels and stabilising production planning in a Material Requirements Planning (MRP) environment. Traditionally, an ...

An Overview of Input-Output Analysis Applied to Production-Inventory Systems

Input-Output Analysis, together with the Laplace transform, have been applied to multi-level, multi-period production-inventory systems in a number of papers. This article gives a historical overview of the areas involved in these studies. It is shown that the input and output matrices as well as the Leontief inverse can be generalised to include timing properties for the inputs by means of the Laplace transform. The consequent advantages are exemplified in different production models, treating, for instance, capacity requirements and safety stock problems. The main literature in this field concerns assembly systems, but the approach is easily applicable to process industries with a divergent material flow or when feedback is essential.

Cost performance and bullwhip effect in a hybrid manufacturing and remanufacturing system with different control policies

In recent years, remanufacturing has emerged as an important research area. This requires developing methods and models in order to aid companies in systematically evaluating current as well as projected remanufacturing systems. This paper addresses the inventory control problem in a hybrid inventory system with manufacturing and remanufacturing options. In this study, by changing the definition of inventory position of the serviceable stock, we introduce a shift PULL inventory control policy, which is compared with PULL, DUAL, and Separate PULL control policies studied previously in the literature. Besides evaluating the economic consequences with different control policies, we also study system dynamic behaviour such as the bullwhip effect, in order to understand the advantages and disadvantages of different policies. After the experiments, we propose several management guidelines for such a hybrid inventory system. The major findings are: (1) separate PULL and DUAL can be good alternatives when the manufacturing lead time is significantly longer than the remanufacturing lead time; (2) shifted PULL exhibits a good performance when the two lead times differ slightly. Owing to the complexity in solving the optimization problem, a simulation approach is used.

The impact of information transparency on the dynamic behaviour of a hybrid manufacturing/remanufacturing system

A combined manufacturing/remanufacturing system is modelled and its dynamic behaviour is investigated using a control engineering approach. The model is an extension of the automated pipeline, inventory and order based production control system (APIOBPCS), which is well understood from a dynamic perspective. It is assumed that the remanufacturing process is based on a PUSH policy. Utilising different levels of information transparency from the remanufacturing process, three system types are developed and compared. Mathematical and simulation analyses of the system types were undertaken and their robustness to remanufacturing process uncertainties were tested. Our analysis indicates that the greater the degree of information transparency, the greater the robustness of the hybrid system.

The detailed coordination problem in a two-level assembly system with stochastic lead times

In this paper, we study the detailed coordination problem in a two-level assembly system with stochastic lead times for lower-level items and constant and deterministic demand for the finished item ...

Dynamic pricing and ordering decision for the perishable food of the supermarket using RFID technology

Purpose – The purpose of this paper is to study how supermarkets can maximize profits of selling perishable food through price adjustment based on real‐time product quality and values.Design/methodology/approach – The value of the perishable food can be traced based on an automatic product identification technology radio frequency identification (RFID). With the support of the RFID, an optimization model can be developed to enable product tracking.Findings – The analysis of the model shows promising benefits of applying a dynamic pricing policy and obtains the optimal ordering decision in respects of deterministic and stochastic demand function with RFID.Research limitations/implications – Although technological approaches for tracking products have attracted increasing attentions in both research and practice, little research have proved the profit using RFID by mathematics, the result of this paper can prove the benefit by using RFID.Practical implication – The result of this paper can tell the supermar...

A structural framework for closed‐loop supply chains

Purpose – The concept of the customer order decoupling point (CODP) has been used in manydifferent contexts as an important structural concept for the traditional forward supply chain. TheCODP is rarely explicitly applied in reverse supply chain management and the purpose of this paper isto show that the CODP can be an important corner stone of a framework for analysis of the closed-loopsupply chain containing both forward and reverse material flows.Design/methodology/approach – Conceptual similarities are identified using analogies betweenforward and reverse supply chains. First, the concepts are discussed in their original context offorward flows and thereafter the concepts are applied on reverse flows. Finally, a holistic closed-loopmodel is established.Findings – The conventional CODP framework for forward flow supply chains can be extended tocover also reverse material flows and therefore providing a foundation for a more comprehensivediscussion of closed-loop supply chains useful in both education, research, and industrial applications.Using the suggested extended framework it is possible to identify nine fundamental supply chainconfigurations.Practical implications – Differentiating between demand driven and forecast driven activitiesplays a critical role in practical supply chain management and this paper highlights that this approachalso can be applied to closed-loop supply chains and therefore extending the reach of the toolboxpreviously developed for the forward supply chain.Originality/value – The concept CODP has not previously been comprehensively treated for theclosed-loop supply chain and this paper provides a foundation for establishing a strategic structuralframework for discussing issues such as lean vs agile and balancing efficiency and responsiveness in amore comprehensive context involving also reverse material flows.

Economic evaluation of disassembly processes in remanufacturing systems

A model to deal with the disassembly processes in remanufacturing systems is presented with focus being on evaluating their economic consequences. More specifically, the model assists decisions such as to which degree and for the sake of which components should the returned items be disassembled. Consequently, using the economic values of recoverable items, the inventory holding costs of these items are obtained. This information is further used to determine the inventory control policy. To access such economic values, the above average cost approach is compared with the net present value method. The latter is often considered a more ‘correct’ way in remanufacturing systems from the viewpoint of inventory control. The results from the economic evaluation model are intended to aid companies in systematically evaluating current as well as projected remanufacturing systems.

Multi-product economic lot scheduling problem with manufacturing and remanufacturing using a basic period policy

In this research we study the multi-product Economic Lot Scheduling Problem (ELSP) with manufacturing and remanufacturing opportunities. Manufacturing and remanufacturing operations are performed on the same production line. Both manufactured and remanufactured products have the same quality thus they fulfil the same demand stream. Tang and Teunter (2006) firstly studied this type of Economic Lot Scheduling Problem with Returns (ELSPR) and presented a complex algorithm for the optimal solution. More recently Teunter, Tang, and Kaparis (2009) proposed several heuristics to deal with the same problem using more computational efficient approaches. However, both studies have limited the attention to the common cycle policy with the assumption that a single (re)manufacturing lot is used for each item in each cycle. Relaxing the constraint of common cycle time and a single (re)manufacturing lot for each item in each cycle, we propose a simple, easy to implement algorithm, based on Segerstedt (1999), to solve the model using a basic period policy. Several numerical examples show the applicability of the algorithm and the cost savings.