نوع مقاله : پژوهشی
دانشکدهی مهندسی صنایع، دانشگاه آزاد اسلامی واحد تهران جنوب
عنوان مقاله [English]
Appropriate management of the inventory control system of perishable items plays an important role in organizations' total cost due to short life cycle and perishability of the items. An inventory control system includes the allocation of orders to suppliers, identification of inventory replenishment quantities, and coordination of joint orders. This paper proposes mathematical models in the multi-supplier joint replenishment problem of perishable items with partial backorder by considering direct and indirect grouping approaches. In the case of direct grouping approach, the inventory items are categorized into permanent groups and all the items in a group are ordered at the same
time, while in the indirect grouping approach, each item is ordered in an integer multiple of a base cycle time. Therefore, in the indirect grouping
approach, the groups are formed temporarily in each cycle with the items that have a common replenishment cycle. In order to simplify the exponential elements of the equations, Taylor's expansion is used to achieve a polynomial approximation for the model. The closed-form solution of the model is presented in a special case in which there is a single supplier and the unsatisfied demand is fully backordered. In this regard, the ratio of time with positive inventory level at each replenishment cycle is equal to the ratio of unit backorder cost to the summation of perishability rate, unit holding cost, and unit backorder costs. The two approaches are analyzed through solving a numerical example in GAMS software. Based on the results, at small values of major ordering cost, the indirect grouping strategy is relatively more preferable. However, at larger values, the two strategies are almost similar. Based on the sensitivity analysis of numerical example, it was found that increasing the rate of perishability caused the system to increase the shortage level and hence, the total sales decreased. In addition, increasing the main
ordering cost increases the replenishment cycle and the total purchasing quantity, but does not have a significant effect on the proportion of time with a positive inventory.