A Thesis Submitted For Degree Of Master Of Science

Recently, with the internationalization of the global economy, competition among enterprises appears more and more intensive, which forces the enterprises to meet the demand of customers with lower cost and quicker response. Competition among the enterprises now is mainly featured as efficient logistics management competition whose cost takes a large percentage in the operation fee. Storage cost is one of the most important parts of the logistics cost. Therefore, efficient inventory control has great significance for reducing logistics cost and promoting the enterprises core competitiveness. In practice, we often found the supplier would offer his retailers/customers a delay period, which means the retailers/customers, should not pay for the items immediately when the items are received from supplier. The retailers/customers could sell the goods and accumulate revenue and earn interest within the trade credit period, which may stimulate retailers and customers' demand. So, in the retail inventory model, it is very worth doing that delay in payments offered by supplier to be considered.For researching the retail's inventory systematically, it is divided into two kinds by the logistics field: two-stage inventory system and three- stage inventory system. If considering only the relations between one supplier and one retailer, it is called two-stage inventory system. When considering the relations among one supplier, one retailer and one customer, it is called three-stage inventory system.In real life, for too many hypothetical conditions, the existing retail's inventory model have rather narrow wide field of application. So, it is necessary to consider some great influences, which affect the decision-making of inventory control, such as deterioration of physical goods, decreasing function of waiting time, varying demand. Of course, When the more real conditions we consider, the wider range of application, the more difficult we seek answer of the model.The main content of this thesis is how to build efficient models of two-stage inventory system and three-stage inventory system. First, it give a brief introduce on the current researches of inventory system, focusing on the presentation of the retail's inventory systems with permissible delay in payments which is researched in this thesis. Then, according to the current researches, the models of two-stage inventory system and three-stage inventory system are perfected respectively, through considering delay in payments, deterioration of physical goods, decreasing function of waiting time, varying demand. Finally, the solving programs are designed by Matlab 6.5.The example results illustrate that four factors mentioned above have a great influence on inventory decision, which show some regularity...