庫存管理(生產(chǎn)與運作管理丁斌)-資料下載頁
2025-02-28 11:58本頁面
【正文】 xg xXPxGXEXDq?q? (Q,r)模型中庫存水平的變化 Q Inventory Time l r (Q,r)模型中庫存水平的變化 (續(xù) ) r q + Q Inventory Time l r r q (Q,r)模型中的成本 ? 固定訂貨成本 :每年訂購 D/Q次 ? 保管成本 :平均庫存水平約為 故 AQD cos t setu p fixed annu al ? q???????? rQsQssQ222)(Inventory Average ?????? ??? qrQh2cost holdi ng annual (Q,r)模型中的成本 (續(xù) ) ? 缺貨成本 – 若訂貨提前期內(nèi)的需求為 x,則每周期間的缺貨次數(shù)為 : 故 ???????rxrxrx if , if ,0backo rders ofnumbe r )(cos tbacko rder annu al)(yearper backo rders ofnumbe r expec ted)()()(/cyc lebacko rders avernQbDrnQDdxxgrxrnr????? ?? (Q,r)模型的成本最小化 (*)))((22)(0)(2),()(2),(222hrbnADQhQrbDnDAQrbDnhQDAQrQYrnQDbrQhAQDrQY?????????????????????? q (Q,r)模型的成本最小化 (續(xù) ) 由于 故 或 或 ))(1()()()()(rGdxxgdxxfrxrrnrr??????????????0)(),( ?????? rnQbDhr rQY 0))(1( ?? rGQbDhbDhQrG ?? )(1 (**)1)(bDhQrG ?? 求解 Q與 r 0. 1. 計算 2. 計算 rt作為 r的值代入 3. 2. If |Qt Qt 1| 1 and |rt rt1| 1, stop and set Q* = Qt, r* = rt. Else, set t = t + 1 and go to (1). . 1 )( satisfi es that of value thebe to and 2Set 000???tbDhQ rGrrhADQhrbnADQ tt))((2 1???bDhQrG t?? 1)( (Q,r)模型舉例 D = 100 units per year c = $100 per unit h = 100 = $10 per unit l = 30 days q = (100 30)/365 = units during replenishment lead time A = $10 b = $100 Demand during lead time is Poisson Poisson分布的值 r p ( r ) G ( r ) n ( r ) r p ( r ) G ( r ) n ( r )0 11 1 12 2 13 3 14 4 15 5 16 6 17 7 18 8 19 9 20 10 ))(1)(()()()()(2 ,1 ,)1(!)(0rGrrprnkprGrrrprerprkr????????????qqqqq? 例題求解 ? Step (0) Use EOQ formula to pute Q0: and find smallest r such that From Table, r0 = 15 1001022 ??????? hADQ t 100100141011)( 0 ???????bDhQrG 例題求解 (續(xù) ) ? Step (1) Compute Q1 as and calculate r1 as the smallest r such that From Table, r1 = 15. ? Step (2) The value of r did not change from step (0) to step (1), so STOP. The optimal solution is Q* = 15, r* = 15. safety stock = 15 = )(1002))((2 01 ???????? h rbnADQ 100100151011)( 1 ???????bDhQrG (Q,r)模型啟示 ? 基本啟示 – 安全庫存可減少缺貨 – 周期庫存增加可減少訂貨次數(shù) ? 其它啟發(fā) – 增加 q 將增加最優(yōu)訂貨點 (注 :增加 D或 l將增加 q ) – 增加需求的變異性將增加最優(yōu)訂貨點 – 增加保管成本將減少最優(yōu)訂貨點和批量
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