二階層存貨系統導入緊急訂購機制之研究

Applying Emergency Order Policy toTwo-Echelon (R, S) Inventory System

鄭文彬(Wen-Ping Cheng)

指導教授 ： 蔡啓揚

元智大學/工程學院/工業工程與管理學系/碩士(2004年)

摘要

在供應鏈管理上，如何將貨品適時適地的送達到顧客的手上是一門重要的學問，管理階層通常會在每一階層的存貨點，以提高服務水準方式來降低缺貨發生，進而降低系統總成本。本研究將同時運用一緊急訂購策略，將此策略導入二階層(R, S)存貨系統中，目的是希望配合導入緊急訂購機制的方式能讓系統總成本可進一步降至更低。
二階存貨系統包含一個倉儲點與多個零售點，管理者根據期初剩餘存貨量是否滿足正常訂購前置時間的期望需求來判斷是否應進行緊急訂購，緊急訂購量會提前在正常訂購前置時間內到達，避免大量缺貨的發生。本論文將建構出系統在有無緊急訂購機制下的模型運作與系統相關成本表示式。將兩系統項目分別比較與分析，兩系統皆產生持有成本與缺貨成本，而執行緊急訂購機制時將產生緊急訂購成本。利用變動顧客的服務水準、需求變異、相關成本參數與前置時間參數來進行系統模擬的研究，分析兩系統在變動相關參數時，會有那些不同的趨勢變動所造成的影響。最後在比較中可證明緊急訂購策略能更進一步改善原存貨系統的總成本，此策略可提供供應鏈管理在改善系統成本的參考模式。

關鍵字

服務水準 ； R ； S ； 存貨系統 ； 緊急訂購策略 ； 二階層存貨系統

並列摘要

As one of the most important aspects of supply-chain management, delivering goods promptly and accurately to customers has always been the most essential study for every company. Managers often raise a company’s service level at every inventory cite in order to reduce the chance of inventory shortage, and to further reduce the system’s total cost. This research applies emergency order policy as a strategy into Two-echelon periodic-review (R, S) inventory system, and by introducing this strategy, aims to achieve reduction of the system’s total cost.
The two-echelon inventory system considered in this study contains one warehouse and multiple retailers. Managers need to determine whether to execute the emergency order process according to the current inventory at the review point. If the current inventory at a retailer can not satisfy the expected demand during the lead time of the regular orders, an emergency order will then be placed, and goods will arrive in a shorter lead time to avoid major shortage of inventory.
This research introduces two models of the system — one with emergency order policy and one without — to analyze and compare all the different aspects from both systems by constructing their correlation cost equations and model simulations. Both systems generate holding costs and shortage costs, and emergency order costs are also introduced into the systems when emergency order policies are implemented. Simulations of the two models are also conducted and sensitivity analysis is performed with respect to customer service levels, demands, correlation costs and lead times. The results are studied and discussed. This research shows that emergency order policy is capable of reducing the original system’s total cost, and should be taken as a serious strategy in supply-chain management to improve a system’s model.

並列關鍵字

service level ； periodic-reveiew (R ； S) inventory system ； emergency order policy ； two-echelon inventory system

參考文獻

【1】Axsäter, S. (1993), “Exact and approximate evaluation of batch ordering policies for two-level inventory systems,” Operations Research, 41, 777-785.

【2】Axsäter, S. (1998), “Exact analysis of continuous review (R, Q)- policies in two-echelon inventory systems with compound poisson demand,” Working Paper, Lund University.

【3】Axsäter, S. and Wen-Fa Zhang (1999), “A joint replenishment policy for multi-echelon inventory control,” International Journal of Production Economics, 59, 243-250.

【4】Axsater, S. (2001), “Scaling down multi-echelon inventory problem.” International Journal of Production Economics, 71, 255-261.

【5】Barankin, E. W. (1961), “A delivery-lag inventory model with an emergency provision,” Naval Research Logistics Quarterly, 8, 285-311.