| 摘要: | 傳統的存貨模式通常假設物品可以永久保存以滿足未來的需求，以及企業擁有單一且無容量限制的倉庫。實際上，大多數的物品於正常的儲存過程中，會有退化的現象發生，例如生鮮食品的腐敗、酒精的揮發和藥物的變質，致使存貨水準因需求而減少外，也因為退化而降低。因此，在決定這類物品的最適存貨策略時，退化現象所造成的額外損失就不可被忽視。另一方面，當企業訂購大量的物品時，受限於自有倉庫的容量，可能需要外租倉庫以存放額外的數量。
本研究在存貨系統中考慮允許缺貨的情況下，建構三個不同的退化性物品存貨模式。第二章在物品退化率隨時間變動的情況下提出一個需求與售價有關的存貨模式。此存貨系統允許發生缺貨，並假設欠撥率為等候下一次補貨的時間長度之函數，而且以指數的方式遞減。第三章則延續第二章對退化率和需求率的一般化假設，另外考慮貨幣的時間價值，利用現金流量法建立一個允許完全欠撥的存貨模式，決定最適的售價和訂購週期，使得總利潤的淨現值為最大。 第二章和第三章均假設自有倉庫的容量不受限制，第四章則將自有倉庫的容量限制納入存貨模式中，並假設與等候時間有關的欠撥率。當訂購數量超過自有倉庫容量時，可向外租借倉庫儲存超額的數量。以上所建立的存貨模式，均被證明最適解不僅存在而且唯一，並於相關章節之後以數值範例來說明其求解過程。第五章為結論，並對本文各章所建構的存貨模式作一總結，同時提出未來的研究方向。
The general assumptions in classical inventory models are that items can be stored indefinitely to meet future demand and the business owns a single warehouse without
capacity limitation. In practice, it is well known that certain products such as medicine, volatile liquids, blood bank, food stuff and many others, decrease under deterioration (vaporization, damage, spoilage, dryness and so on) during their normal storage period. As a result, while determining the optimal inventory policy of that type of products, the loss due to deterioration can not be neglected. On the other hand, while a large stock is
to be held, due to the limited capacity of the own warehouse, one extra warehouse may be required.
In this thesis, three deterministic inventory models for deteriorating items have been formulated with backorders considerations. In Chapter 2, a deterministic inventory model for deteriorating items with price-dependent demand is developed. The demand and deterioration rates are continuous and differentiable functions of price and time, respectively. In particular, we allow for shortages and the unsatisfied demand is partially backlogged at a negative exponential rate with the waiting time. Following the assumptions about deterioration and demand rates, in Chapter 3, an infinite time horizon inventory model with time-value of money is discussed. In addition, we allow for shortages and completely backlogged. The objective is to find the optimal replenishment and pricing strategies
maximizing the net present value of total profit over the infinite horizon. It is assumed that the capacity of the own warehouse is unlimited in Chapter 2 and Chapter 3. In
Chapter 4, a deterministic inventory model is developed for deteriorating items with capacity constraint and time-proportional backlogging rate. A rented warehouse is used
when the ordering quantity exceeds the limited capacity of the own warehouse. In all inventory models, the existence and uniqueness of the optimal solution are proved and numerical examples are provided to illustrate the proposed models. Finally, in Chapter 5, we provide some conclusions of this thesis and future research topics. |
