- 學位論文
批量需求下發展存貨策略之研究
Development of Inventory Policies Subject to Non-unit sized Demands
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摘要
在以往許多存貨問題的研究中，多數都忽略了顧客批量需求的實際情況，因此對於許多存貨模型針對顧客的需求假設均是以單位(unit demand)的方式來探討其不同的存貨問題，可以將整個問題較為簡化許多，然後制定其系統之補貨策略或是總成本的關係等等；但是在實際的業界中所面對下游顧客需求，大部分是採用批量訂購，每次皆訂購相當數量的產品，這將連帶性的對於產品需求變異有放大的作用，會影響整個存貨補貨策略，也將問題給複雜化。 本研究將顧客到達人數服從卜瓦松分配，批量需求大小服從常態分配來接近實際顧客批量需求的情況，加以考慮在批量因素下所產生的undershoot，主要利用Matheus and Gelders (2000)研究中的離散型顧客需求機率函數，來建立本研究(R , Q)與(s , S)存貨策略成本模型，同時建立Exhaustive搜尋演算法與改進後的黃金切割搜尋法，以總成本最小為目標找到最佳的再訂購點與訂購批量，並且能滿足其服務水準限制。 另外設計兩種不同顧客批量需求的情境，第一個情境主要是顧客到達人數多而批量需求小；第二個情境主要供應少數顧客而其批量需求大；透過不同情境的實驗下，分別探討批量大小對於存貨系統的決策變數與相關成本上的影響，並在批量的顧客需求環境下找到最佳的存貨策略。了解不同的顧客批量需求對於存貨系統是不可忽略的，才能依據不同的顧客需求環境下做出正確的決策。
並列摘要
In most development of inventory management models, unit demand is assumed, in order to simplify problem complexity. However, in many cases, customers may demand more than one unit of item in one order. With non-unit sized demands, variations in demand increase as demand information moves from downstream to upstream in a supply chain. By neglecting non-unit demand, one may underestimate the magnitude of demand variations and the developed inventory models are less efficient. This research considers a two-echelon inventory system where demand from end customers is assumed to be non-unit sized. Customer arrival rate is assumed to be Poisson distributed. The work of Matheus and Gelders (2000) is utilized to derive system cost functions under reorder-point, fixed-order-quantity (R, Q) and reorder-point, order-up-to (s, S) inventory policies. Search algorithms are developed to find optimal control parameter values with an objective of minimizing total system costs and constraints on customer service levels. To explore the effect of non-unit demand, numerical experiment is conducted. Two scenarios with different demand patterns in terms of the batch size of demand are examined. The results show how inventory control policies and system costs are affected by various demand patterns.
參考文獻
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