经济决策定量方法第三章课件.ppt

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1、Chapter3InventoryModels★deterministicmodel★stochasticmodelInventoryModelsThestudyofinventorymodelsisconcernedwithtwobasicquestions:HowmuchshouldbeorderedeachtimeWhenshouldthereorderingoccurTheobjectiveistominimizetotalvariablecostoveraspecifiedtimeperiod(assu

2、medtobeannualinthefollowingreview).InventoryCostsOrderingcost--salariesandexpensesofprocessinganorder,regardlessoftheorderquantityHoldingcost--usuallyapercentageofthevalueoftheitemassessedforkeepinganitemininventory(includingfinancecosts,insurance,securitycos

3、ts,taxes,warehouseoverhead,andotherrelatedvariableexpenses)Backordercost--costsassociatedwithbeingoutofstockwhenanitemisdemanded(includinglostgoodwill)Purchasecost--theactualpriceoftheitemsOthercostsDeterministicModelsThesimplestinventorymodelsassumedemandand

4、theotherparametersoftheproblemtobedeterministicandconstant.Thedeterministicmodelscoveredinthischapterare:Economicorderquantity(EOQ)EconomicproductionlotsizeEOQwithplannedshortagesEOQwithquantitydiscountsEconomicOrderQuantity(EOQ)Themostbasicofthedeterministic

5、inventorymodelsistheeconomicorderquantity(EOQ).Thevariablecostsinthismodelareannualholdingcostandannualorderingcost.FortheEOQ,annualholdingandorderingcostsareequal.DeterministicModel★EconomicOrderQuantity,（EOQ）Asimplemodelrepresentingthemostcommoninventorysit

6、uationfacedbymanufacturers,retailers,andwholesalersistheEOQ(EconomicOrderQuantity)model.(Itsometimesisalsoreferredtoastheeconomiclot-sizemodel.)EconomicOrderQuantityAssumptionsA:Annualnumberofitemsdemanded,c:Unitcostofprocuringanitem,T:Timebetweenorders,h:Ann

7、ualcostperdollarvalueofholdingitemsininventory.K：fixedcostperorderTheorderquantity(Q)toreplenishinventoryarrivesallatoncejustwhendesired,namely,whentheinventoryleveldropsto0.PlannedshortagesarenotallowedTheobjectiveistodeterminewhenandhowmuchtoreplenishinvent

8、orysoastominimizethetotalcost.EconomicOrderQuantityTheMathematicalModelT=Q/AOrderpointsQTime(years)InventoryLevelSlope=-AFigure3-1InventorysystemforthesimpleeconomicorderquantitymodelDete