需求具季節循環及趨勢成長特性下損耗性產品之存貨模式

The Inventory Models for Deteriorating Items with Cyclic and Linear Trend Demand

金介中(Jie-Zhong Jin)

指導教授 ： 黃惠民

中原大學/工學院/工業工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200473

摘要

古典的存貨訂購模式策略假設需求量固定。但是由產品之生命週期(product life cycle)來看，只有在成熟期(maturity cycle)時需求量才趨近一固定常數。
本研究探討再一個有限的規劃時間之下，需求具有週期性波動以及線性趨勢成長的損耗性產品之存貨政策，例如空調冷氣、啤酒、夏季之清涼飲料、假期間之汽油銷售等等，這些商品的訂購時間點也隨著季節或某時間週期而改變。
大部分文獻中，這類型存貨模式均為補貨率無限的訂購政策，並且加上訂購週期固定以及不允許缺貨的假設。本研究分為兩個模式進行，首先探討週期變動及允許缺貨之訂購模式，然後再延伸為補貨率有限之生產批量模式。並且比較補貨率有限與否、週期變動與否以及允許缺貨與否三種條件下對於存貨成本的影響。模式是以總變動成本最低為目標，以傳統最佳化方法得到滿足最佳解的必要條件，然而封閉形式解(closed form)無法得到，因此用啟發性方法與數值方法搜尋最佳解。
本研究結果可知補貨率有限、週期變動及允許缺貨時之存貨政策其成本是較低的。

關鍵字

循環性需求 ； 補貨率 ； 損耗 ； 缺貨 ； 最佳化 ； 線性趨勢 ； 存貨

並列摘要

The demand in conventional inventory replenishment policy is assumed to be a constant. For product with product life cycle, however, demand is constant only in the maturity cycle.
This study considers the inventory models for deteriorating items with cyclic and linear trend demand during a finite planning horizon. The present models can be useful for all such deteriorating items with a seasonal demand, such as air conditioner, beers, drinking consumption during summer, petrol consumption during holidays. Since demand changes for different seasons, the order time period of the product is varies.
Many researches have considered replenishment policies in which the replenishment rate is infinite, the replenishment periods are fixed, and the shortages are not allowed. This study assumes flexible demand and flexible order time period, and proceeds to develop two models. The first model assumes instantaneous replenishment with variable, replenishment periods, and shortages. The second, production lot size models assume finite replenishment rate. The objective of the models is to minimize the total variable cost. The necessary conditions of the optimization problems are derived by using classical optimizations theory. Since the closed-form solutions cannot be obtained, the optimal solutions are derived by using heuristic procedures and numerical methods.
The result of this study shows that the inventory cost is lower for model with finite replenishment, variable cycles and shortages.

並列關鍵字

deteriorating ； optimization ； shortages ； linear trend ； cyclic demand ； replenishment rate ； inventory

參考文獻

[38] Mak, K. L.,1982, “A production lot size inventory model for deteriorating item”, Computers and Industrial Engineering, Vol. 6, No. 4, pp.309-317.

[1] Aggarwal, S. P., 1979, “A note on an order level lot size inventory model for deteriorating items by Y. K. Shah”, AIIE Transactions, Vol. 11, pp. 344-346.

[3] Aggarwal, S.C., 1972, “A review of current inventory theory and its applications”, International Journal of Production Research. Vol.20, pp. 443-482.

[4] Aggarwal, V. and Bahari-Kashani, H., 1991, "Synchronized production policies for deteriorating items in a declining market”, IIE Transactions, Vol.23, No.2, pp. 185-197.

[5] Bahari-Kashani, H., 1989, “Replenishment schedule for deteriorating items with time proportional demand”, Journal of The Operational Research Society, Vol.40, pp. 75-81.