Ürün ikamesi olan bir üretim ve yeniden üretim sistemi için envanter analizi

We consider the inventory control problem for an infinite-horizon stochastic hybrid manufacturing /remanufacturing system with product substitution under stochastic demand and returns. Remanufactured and manufactured products are considered as two different products, having different costs and selling prices as well as separate demand streams. Remanufactured products have a higher stock out risk than manufactured products because the remanufacturing capacity is mainly dependent on the amount of returns available for remanufacture. One way to cope with the stock-out issue for remanufactured products is to use a downward substitution strategy, which allows a manufactured product (i.e. higher value item) to be substituted for a remanufactured product (i.e. lower value item) in case the latter runs out of stock. We formulate this problem as Markov Decision Process in order to determine the optimal manufacturing and remanufacturing decisions under product substitution, and through numerical experimentation, we investigate the effects of stochastic demand/return distributions on the profitability of the substitution strategy. The optimal policy determined by MDP has a complicated structure which is very hard to be represented using a few control parameters. We propose several simple-structured intuitive heuristic policies that are easy to implement in practice. Then, we develop several heuristic search methodologies to determine the parameter values for these policies. We evaluate the performance of these techniques with respect to the solution quality as well as computational time.