【正文】 39 Q1 Stock level reviewed T T LT LT Order received Q2 M q 0 Quantity on hand Time M = maximum level最高庫存 M q = replenishment quantity補貨量 LT = lead time提前期 T = review interval盤點周期 q = quantity on hand持有庫存量 Qi = order quantity訂購量 ~ 單一產品定期盤點 Periodic Control for a Single Item 盤點時庫存 63 CR (2023) Prentice Hall, Inc. Estimate Q* from the EOQ formula as if under demand certainty conditions. Recall that this is Q* = 322 units. Now, T* = Q*/d = 322/50 = weeks Construct the demandduringleadtimeplusordercycletime distribution. T is order review time Periodic Review (Cont’d) 64 CR (2023) Prentice Hall, Inc. Periodic Review (Cont’d) P DD(T* + LT) X = d(T* + LT) LTTss *d39。盤點后的訂貨量就是最大值（ M)與盤點時所持有的庫存量之差。 ==?= xxsand sunit 3096)(263units 63(5)2(100)(1 0)=?=?===)z(s2QAILQ39。d得到修正公式 sLT是提前期的標準差 57 CR (2023) Prentice Hall, Inc. Supply Chain Example (Cont’d) Distributor Outbound transport Inbound transport Pool point Supplier X s p p = = 1 0 1 2 , . X s i i = = 4 1 0 2 , . X s o o = = 2 0 25 2 , . Processing time Transport time Transport time 供應商 內向運輸 集散地 加工時間 供應商 58 CR (2023) Prentice Hall, Inc. Pull Methods (Cont’d) Supply chain example Suppose that inventory is to be maintained on a distributor’s shelf for an item whose demand is forecasted to be d = 100 units per day and sd = 10 units per day. A reorder point is the method of inventory control. The supply channel is shown in the diagram. Determine the average inventory to be held at the distributor where we have: I = 10%/year C = $5/unit S = $10/order P = during lead time 59 CR (2023) Prentice Hall, Inc. Supply Chain Example (Cont’d) Solution The reorder point inventory theory applies. However, determining the statistics of the demandduringleadtime distribution requires taking the leadtime for the entire channel into account. Recall, days where=??=??=?=2o2i2p2LT2LT22dssss)(sd)LT(s39。 這可以通過將需求波動和提前期波動累加獲得。 LTd sdsLTs ?=Caution: Can result in very high safety stock levels when leadtime variability is high 937 在需求和提前期不確定的情況下找到正態(tài)分布的標準差 s39。d was previously calculated as 3,795 units 54 CR (2023) Prentice Hall, Inc. Reorder Point Control (Cont’d) units 12,872( ))() ](3,79 512)[(102(11,10 7)(=?=?=????????ICEks39?？捎梅磸偷姆椒? IC2DSQ =1 利用基本 EOQ公式得出訂貨量的近似值 Solve initially for Q 2 通過下式計算提前期內現(xiàn)貨供應的概率 Using Q, find DkQIC1P ?=如果缺貨允許 If backordering is allowed or QICDkQIC1 ??=如果銷售出現(xiàn)損失 If sales are lost 50 CR (2023) Prentice Hall, Inc. Reorder Point Control (Cont’d) 3 計算 Q的修正值 Using P, find revised Q IC](z)E39。 ( )11 d z d zD Q s E s ESLDQ180。=???=???=zEsQDkICrQICQDSTCwhere E(z) = from a unit normal loss table at a z value of 929 48 ? 服務水平 ? =1每年產品缺貨件數(shù)的期望值 /年需求總量 ( ) ( )( / ) ( 39。=?=?=?=======rXzsXROPLTssLTdXdwhere is the normal deviate at a probability of taken from a normal distribution table. 46 ? 平均庫存 =經常性庫存 +安全庫存 ? A/L=Q/2+z(s39。S’= 927 45 CR (2023) Prentice Hall, Inc. Reorder Point Control (Cont’d) units 190 )(17 .32150 Hence ,units units 150)3(50)(Now,39。 ? p是生產速率， d是需求速率 dppICDSQ p?=2*40 CR (2023) Prentice Hall, Inc. Q*和 ROP IC2DS=*QGood method for products: 1. Of high value 2. That are purchased from one vendor or plant 3. Having few economies of scale in production, purchasing, or transportation 924 Find Q* and ROP )39。 39 ? EOQ模型中有一個基本假設，即任何訂貨批量都可以及時補進。 ns LT SL TC z x s r z MAX T ROP Q P E s p k s C I S d D LT 39。庫存成本隨時間推移 Cost for holding the inventory over time 資金成本。 17 ? 虛擬庫存即將自己將來所可能需要而又沒有的東西的所有相關信息建立檔案，包括品名規(guī)格價格數(shù)量等，在需要時能使用上。 6 CR (2023) Prentice Hall, Inc. Reasons for Inventories ?Improve customer service Provides immediacy in product availability ?Encourage production, purchase, and transportation economies Allows for long production runs Takes advantage of pricequantity discounts Allows for transport economies from larger shipment sizes ?Act as a hedge against price changes Allows purchasing to take place under most favorable price terms ?Protect against uncertainties in demand and lead times Provides a measure of safety to keep operations running when demand levels and lead times cannot be known for sure ?Act as a hedge against contingencies Buffers against such events as strikes, fires, and disruptions in supply 7 CR (2023) Prentice Hall, Inc. Reasons Against Inventories ?第一，庫存被認為是一種浪費 ?第二，庫存可能掩蓋質量問題 ?第三，保有庫存鼓勵人們以獨立的觀點來看待物流渠道整體的管理問題 8 CR (2023) Prentice Hall, Inc. Reasons Against Inventories ?They consume capital resources that might be put to better use elsewhere in the firm ?They too often mask quality problems that would more immediately be solved without their presence ?They divert management’s attention away from careful planning and control of the supply and distribution channels by promoting an insular attitude about channel management 9 ?流通渠道 Pipeline （ Inventories in transit） ?投機 Speculative Goods purchased in anticipation of price increases ?定期性或周期性特征 Regular/Cyclical/Seasonal Inventories held to meet normal operating needs ?安全 Safety Extra stocks held in anticipation of demand and lead time uncertainties ?倉耗 Obsolete/Dead Stock Inventories that are of little or no value due to being out of date, spoiled, damaged, etc. Types of Inventories 10 ?持久性需求 Perpetual demand Continues well into the foreseeab