| Abstract: | 延遲付款在實際商場交易行為中非常普遍，供應商經常以提供延遲付款的優惠吸引更多將延遲付款視為一種降價優惠的零售商。提供延遲付款對供應商而言，可吸引更多的零售商購買，並且也可降低同行之間削價競爭之惡性循環；對零售商而言，不僅減少資金的機會成本，在延遲付款期間，零售商還可利用銷售貨品的收入賺得利息。另外，生活中，常見貨品產生退化的現象。例如新鮮蔬果、醫療藥品、電子元件及汽油、酒精、香水等揮發性液體等，都可能會因為時間、溫度或環境等因素，產生變質、損壞或揮發等現象而使得庫存數量減少。所以，在探討此類貨品的存貨問題時，若不考慮退化的現象，將會做出不正確的決定而造成重大的損失。再者，關於允許延遲付款的存貨問題中，利息支付與利息賺得的計算是很重要的議題。過去探討延遲付款之存貨相關文獻大都假設支付利息的利率、賺得利息的利率及貨品退化率皆為固定常數。然而，在實際生活中，有很多因素會造成這三個參數產生不確定的情況。所以，我們考量以模糊數來處理此問題。
本論文探討允許延遲付款下零售商之存貨問題並進一步討論有限補貨率、貨品產生退化的現象、利率及貨品退化率不確定等議題且提供在不同問題下零售商的最適訂購策略。第一章說明研究動機與目的及相關文獻探討。第二章探討供應商提供零售商延遲付款優惠之存貨問題並考慮有限補貨率及兩種付款方法。第三章討論允許延遲付款及有限補貨率下零售商對退化性貨品之最適訂購策略。第四章進一步將利率及貨品退化率模糊化並建立允許延遲付款和訂購量有關的退化性貨品之模糊存貨系統。本論文建立兩個定理和兩個演算法，協助零售商在不同的存貨問題中決定最適訂購策略。同時，亦探討模型中參數值的變動對最適解的影響。最後，在第五章裡將上述各章所得的結論做一總結，並說明未來的研究方向。
A common phenomenon in the real market is that a supplier usually permits the retailer a delay of a fixed time period to settle the total amount owed to him. The permissible delay in payments produces benefits to the supplier. For example, it will attract some customers who consider it to be a type of price reduction and does not provoke competitors to reduce their prices and thus introduce lasting price reductions. Permissible delay in payments also provides advantages to the retailer due to the fact that the retailer can earn interest on the accumulated revenue received, and delay the payment up to the last moment of the permissible period allowed by the supplier. In addition, the deterioration of physical goods is common in daily life. For examples, the decay, damage or evaporation may occur during the normal storage period of items like fresh vegetables and fruit, pharmaceuticals, electronic component, gasoline, alcohol or perfumes. Consequently, the loss must be taken into account while developing the inventory models for such goods. Furthermore, the interest income and interest payments are important issues in the inventory problem associated with permissible delay in payments. Most studies related to permissible delay in payments assume that the interest rate is both fixed and predetermined. However, in the real market, many factors such as financial policy, monetary policy and inflation, may affect the interest rate. Moreover, within the environment of merchandise storage, some distinctive factors arise which ultimately affect the quality of products such as temperature, humidity, and storage equipment. Thus, the rate of interest charges, the rate of interest earned, and the deterioration rate in a real inventory problem may be fuzzy.
This thesis discusses the retailer’s inventory problems under some common phenomena including permissible delay in payments, finite replenishment rate, the deterioration of physical goods, fuzzy interest rate and fuzzy deterioration rate. Chapter 1 covers the motivation and objectives of this thesis. In this chapter, literature review about related research papers is also included. In Chapter 2, we establish an inventory model with a finite replenishment rate and permissible delay in payments under two different payment methods. Chapter 3 develops the deteriorating inventory model with a finite replenishment rate under permissible delay in payments. In Chapter 4, we discuss the problem that the rate of interest charges, the rate of interest earned, and the deterioration rate may be fuzzy and construct a fuzzy inventory system with deteriorating items under supplier credits linked to ordering quantity. In this dissertation, we develop two theorems and two algorithms to find the optimal ordering policy and provide numerical examples to illustrate the solution procedure. Also, sensitivity analysis is conducted for the parameters of the models. Finally, chapter 5 provides the conclusions of this thesis and some future research topics. |
