在存貨管理的領域中，由傳統的EOQ模式開始不斷地被發展及應用，但是其過於理想化的考量，並不能有效地應用在多變的實際情況。其中一個不合理的假設即為所訂購的商品皆為良品，而不去考慮訂購量中含有不良品項；另外一個不合理的假設為自有倉庫的容量是無所限制的。在實務上，企業的自有倉庫容量是有限的，一旦訂購批量超過容量限制，就必須向外租借倉庫來存放存貨。
因此，本研究將Salameh和Jaber [14]的條件加以修改及延伸，考慮在兩個倉庫情況下加入個別隨機不良率的假設，並經由在檢查期間內確保不缺貨的假設條件，來判斷在兩個倉庫間之個別不良率的範圍，以建立此存貨模型的相關成本函數。另外，當不良率為固定值時，則依據在兩個倉庫中所具有的個別不良率來分別討論在不同區間下的訂購量；而當不良率為服從某一機率分配的隨機變數時，則建立一可行之演算法，來求取其訂購週期內之最小的期望每單位時間總成本以及最佳訂購量。最後，以數值範例來驗證所推論的各種結果。

In the field of inventory management, the traditional EOQ model is constantly developed and applied, but it’s unsuitable to use in real-life situations because of the ideal consideration. One of the unreasonable assumptions is that all the order items are of good quality and ignore that they may have imperfect items. Another unrealistic assumption is that the capacity of own warehouse is unlimited. In fact, the rented warehouse is needed whenever the storage capacity of own warehouse is insufficient.
In this paper, we modify and extend the Salameh and Jaber’s [14] model, and consider the assumption of different random defective rates for two warehouses. In order to set up the relevant cost function of this inventory model, we can use the assumption of no shortage during the screening time to determine the range of the different defective rates for two warehouses. In addition, when the total defective rate is fixed, the optimal order quantity in different ranges is discussed detailly on the basis of the two defective rates under different warehouses. When the total defective rate is a random variable that follows some probability distribution, we also provide a feasible algorithm to find the minimum expected total cost per unit time and the optimal order size during the whole cycle time. At last, numerical examples are presented to illustrate these discussions.

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