مدل موجودی یکپارچه زنجیره تامین با ارزش فعلی و هزینه توفنده وابسته به چند جمله ای می باشد

Due to today’s highly competitive environment, both reducing lead time and the associated inventory cost are critically important issues in supply chain. And, the consideration of time value effect is lacked in most previous researches. However, the effect of inflation is too critical to ignore. Therefore, we develop an integrated inventory model with crashing cost which was determined by the length of lead time is polynomial to recover the real inventory problems. The objective of this research is to minimize present value of the joint expected total cost over infinite time horizon. Then, we provide a solution algorithm to determine the optimal order quantity, the length of lead time and the number of lots which are delivered from the vendor to the buyer in the solution procedure. Numerical example is provided here to illustrate the solution procedure.

Two of the most important time-based advantages are quickly satisfying the customer demands and reducing total cost effectively. The vendor and the buyer find their own optimal economic-lot-size, respectively, in traditional inventory management systems. As a result, the traditional inventory management system may not result in an optimal policy for whole supply chain. Therefore, an integrated inventory approach may help to determine the optimal order quantity and shipment policy. Wikner [1] indicated that crashing cannot be classified as a lead-time reduction as a long-term strategic time compression program. However, small lot size, postponement and various customized items are often applied as a JIT strategy to confront the fierce competition. The short life cycle is observably common in current situation, and we suppose that will be a basic assumption in this research [1]. We consider that the type of crashing is appropriately applied with agile systems in most short-term management decisions. The market nowadays is fiercely competitive; the length of lead time directly affects the customer service level, inventory investment in safety stock, and the competitive abilities of a business. Hence, the objective of this research is to find out an optimal inventory strategy that can minimize the present value of the joint expected total cost over infinite time horizon.

In this article, we incorporate the view of time value in a production/inventory situation into an integrated inventory model with variable lead time which assumed dependent crashing cost is polynomial. This proposed model is not considered in the previous research. Considering the effect of time value is too critical to ignore, the present value of integrated inventory joint expected total cost function has been derived herein. Eventually, although it is not easy to say that this model can reduce more inventory cost than other models in this article, there is a general recommendation that this model which is considered with time value can always improve the real situations. Most importantly, we will expand our further researches in many other considerable elements: reworking of imperfect items, permissible delay in payments strategy between the vendor and the buyer, and apply fuzzy theory into the proposed models in our research. Also, we will make every endeavor to cooperate with real cases to acquire more perusable and actual data that can illustrate real numerical examples in our future works.