Hong-Fwu Yu

Evaluating the service requirements of dedicated container terminals: a revised IPA model with fuzzy AHP

The purpose of this article is to evaluate the service requirements of dedicated container terminals (DCTs). In this article, the service attributes (SAs) of DCTs were first discussed. A fuzzy analytic hierarchy process model was then constructed to measure the users’ perceived importance and dissatisfaction for each of the SAs. Based on these two measurements, a revised importance-performance analysis model was proposed to identify the SAs that should be improved. To validate the model, the dedicated container terminal of Evergreen Marine Corp. (EMC DCT) at Kaohsiung Port and its users were empirically investigated. With respect to the empirical results, managerial implications of the findings in improving service quality for the EMC DCT are discussed.

An EOQ model with imperfective quality items under an announced price increase

The economic ordering quantity (EOQ) model has been widely applied to inventory management. However, some assumptions in the model are unrealistic in practice. One of the assumptions is that all produced units are of good quality. This article deals with an EOQ model for products with imperfect quality under an announced price increase, where the defectives are screened out by a 100% inspection process, and which can be sold as a single batch at the end of the inspection process. The optimal ordering policies associated with three kinds of effective times of the price increase are obtained. A numerical example is then provided to illustrate the proposed model. Besides, based on the numerical example, the effects of some important parameters on the optimal order quantity and the corresponding saving in cost are also investigated.

EOQ model where a portion of the defectives can be used as perfect quality

The main purpose of this article is to investigate an economic order quantity model for products with imperfect quality, where the defective items are screened out by a 100% inspection process and then can be sold in a single batch by the end of the inspection process. However, differing from the previous studies on the topic, we assume, in this article, that a portion of the defectives (called the acceptable defective part) can be utilised as perfect quality and that the utilisation of the acceptable defective part will reduce the consumption of the remaining perfect quality items after the defectives are sold. In practice, there are a number of goods (e.g. clothes, sporting shoes, purses, porcelain dishes, fruits, vegetables, etc.) with such characteristic. First, we construct the model in terms of annual profit and find the optimal order quantity with a constant defective percentage. Next, we determine the optimal order quantity for the case that the defective percentage follows a uniform distribution by maximising the expected annual profit. For both cases, two properties of the optimal order quantity and the corresponding annual profit are also given. Finally, two numerical examples are provided to illustrate the proposed models.

The integrated policy with immediate return for defective items

The economic production quantity (EPQ) and the economic order quantity (EOQ) models have been widely used in inventory management for vendors and retailers, respectively. However, an optimal solution for the EPQ or the EOQ model is only based on either vendors’ or buyers’ viewpoint. That is, such an optimal solution is usually beneficial to one of the vendors and buyers, but detrimental to the others. Hence, to establish a long-term cooperative relationship between the vendor and buyer, an integrated inventory model is needed. The purpose of this paper is to investigate a single-vendor single-retailer production-inventory model for products with imperfect quality. It is assumed that a 100% inspection process is conducted to screen out the defectives contained in the received lot and the defectives screened out during the 100% inspection process will be returned to the vendor immediately. By maximizing the expected annual integrated total profit, the optimal number of shipments in a cycle and the optimal size of each shipment are determined. A numerical example is provided to illustrate the proposed model and demonstrate the superiority of the proposed model to a general single supplier-single buyer system not considering lot-splitting shipments.

AN OPTIMAL POLICY FOR CSP-1 WITH INSPECTION ERRORS AND RETURN COST

ABSTRACT The purpose of this paper is to determine the optimal policy of CSP-1 with inspection errors and return cost. Specifically, for given Type I and Type II errors, the optimal clearance number and sampling frequency are determined by minimizing the long run average unit cost including the inspection cost, the rejection cost, the opportunity cost, and the return cost. Overall, the analytical results indicate that depending on seven parameters (Type I error, Type II error, the unit inspection cost, the unit opportunity cost, the rejection cost, the unit return cost, and the process defective fraction), there are two main optimal inspection policies for CSP-1: No inspection and a 100% inspection. Moreover, an interesting result is that the optimal clearance number is independent of the inspection frequency which is the fraction of the units to be inspected during the partial inspection stage.

A study of the key factors contributing to the bullwhip effect in the supply chain of the retail industry

The purpose of this study is to explore the bullwhip effect in the supply chain of the retail industry. Based on the analysis of key factors, the importance of the factors influencing the bullwhip effect in the supply chain, as well as the causal relationships between the factors, was evaluated. Through the questionnaire survey of the fuzzy Delphi method, the experts’ opinions about the influential key factors that produce the bullwhip effect in the supply chain were acquired using quantitative analysis and the screening procedures. The interpretive structural modeling and decision-making trial and evaluation laboratory were adopted to analyze the effects of the factors and the causal hierarchical relationship, thus providing supply chain managers with a more effective analysis of finding the reasons that contribute to the generation of the bullwhip effect.

An EOQ model with immediate return for imperfect items under an announced price increase

The main purpose of this article is to investigate an economic ordering quantity model with imperfect quality under an announced price increase. It is assumed that a 100% inspection process is conducted to screen out the defectives contained in the received lot, and the defectives thus screened out will be returned to the vendor immediately. In practice, the mechanism of returning defectives to the vendor immediately may result from the increasingly exerted power of retailers, the need of satisfying strict quality requirement of customers, or the limitation of the storage space of retailers. Besides, the mechanism of immediate return usually indicates a promise of the vendor to his/her customers and is used to highlight the vendors confidence in his/her products. The optimal ordering policies associated with three kinds of effective times of the price increase are obtained. A numerical example is then provided to illustrate the proposed model. The results indicate that the optimal special ordering quantity and the corresponding saving cost for an increase in price are both increasing with the increment of the price. For any price increase, both of the optimal special ordering quantity and the corresponding saving cost are negatively related to the remnant stock level at the time that the price increase is effective.

An EOQ model for items with acceptable defective part and shortages

This paper investigates an EOQ model for items with imperfect quality and shortages backordered. It is assumed that the defective items of each lot are screened out by a 100% inspection process and then can be sold in a single batch by the end of the inspection process and that a portion of the defectives (called the acceptable defective part) can be utilized as perfect quality and hence affect the consumption of the remaining perfect quality items after the defectives are sold. By maximizing the expected profit per unit time, the optimal order quantity and the maximum backorder level are determined for the defective percentage being random. Besides, two properties of the optimal order quantity, the maximum backorder level, and the corresponding profit per unit time, are also given. Finally, a numerical example is provided to illustrate the proposed model.

A mixed inspection policy for CSP-2 and precise inspection under inspection errors and return cost

This article deals with a mixed policy between precise inspection and continuous sampling plan-2 (CSP-2) with inspection errors (Types I and II) and return cost. The optimal mixed inspection policy is determined by using the criterion of maximizing the unit net profit. Specifically, with respect to non-repairable and repairable products, the following decision variables are determined such that the unit net profit is maximal: (1) the optimal sampling plan for CSP-2 and (2) the optimal proportions for which precise inspection should be performed for the non-inspected items in the procedure of CSP-2, the non-defective items, and the defective items identified by CSP-2. Overall, the analytical results indicate that, depending on the nine parameters (the process defective fraction, Type I error, Type II error, the selling price of an item, the unit repair cost, the unit return cost, the unit opportunity cost, the unit inspection cost, and the unit cost of precise inspection), both non-repairable and repairable products have two main optimal inspection policies for CSP-2: “do not inspect” and “do 100% inspection”; also, for the non-inspected items, the non-defective items, and the defective items identified in CSP-2, there are two main proportions on which precise inspection should be performed: 100% and 0%. A numerical example is provided to illustrate the proposed method. Besides, a comparison with CSP-2 is also made to evaluate the effectiveness of the proposed model.

An integrated inventory model with immediate return for defective items under unequal-sized shipments

Abstract The purpose of this paper is to investigate a single-vendor single-retailer production-inventory model with immediate return for imperfect items under an unequal-sized policy. It is assumed that the batch quantity will be received by the retailer in n shipments. The first shipment is of small size followed by (n−1) equal-sized shipments of size just equal to the first shipment size times the ratio of the production rate to the demand rate. Moreover, it is assumed that a 100% inspection process is conducted to screen out the defectives contained in the received lot and the defectives screened out during the 100% inspection process will be returned to the vendor immediately. First, the expected annual integrated total profit is constructed. Next, by maximizing the expected annual integrated total profit, the optimal number of shipments in a cycle and the optimal sizes of the shipments in a cycle are determined. Finally, a numerical example is provided to illustrate the proposed model and demonstrate the usefulness of the proposed model when compared with the integrated model under equal-sized policy.