《供应链与物流管理》运作篇：仓储管理

Supplychainandlogisticsmanagement-8供应链与物流管理-8,Chapter8warehousingmanagement第八章仓储管理,8.1basicconceptionsproblem基本概念问题8.2inventorydecision库存决策8.3economicandtechnicalindexesofwarehousework仓储工作经济技术指标8.4developmenttrendofstoragetechnology仓储技术的发展趋势,Chapter8warehousingmanagement第八章仓储管理,8.1basicconceptionsproblem基本概念问题,1Warehousingandinventory仓储与库存2Warehouse仓库,1Warehousingandinventory仓储与库存,1warehousingimplementactivitiesofgoodsWarehousing,storage,ex-warehousebyusingthewarehouseandrelatedfacilitiesandequipment.(“Logisticsterms”,2006)仓储利用仓库及其相关设施设备进行物品的入库、存储、出库的活动。（物流术语2006）2inventory-Storagegoodsforfutureuseofpredeterminedobjectivebutinstateofidleornonproduction.库存储存作为今后按预定的目的使用而处于闲置或非生产状态的物品。3functionofstorage储备的作用(1)insurancestorage:surplusstorageandinsurancestorage保险储备:剩余储备和保险储备(2)reservestorage:aimedatturnover;makepreparationorserviceforimplementingofproductionandcurrency;foundationforproductionandcurrency.周转储备:目的是为了周转，是为生产和流通的进行作准备或服务，是生产和流通顺利进行的前提条件。,2Warehouse仓库,Concept概念Warehouseplacesforstorageofmaterials;Activitiesofreceiving,arranging,storing,keeping,deliveringcommodity,goods,materials;Generalusearchitecturalobjectsasawarehouse,alsouseofvehicles,ships,containersandotherequipment,andevendirectlyusegroundandsurfaceasawarehouse.仓库储存物资的场所，一般是以库房、货场及其他设施、装置为劳动手段对商品、货物、物资进行收进、整理、存储、保管和分发等工作。一般使用建筑物体作为仓库，但也有使用车辆、船舶、集装箱等设备，甚至直接利用地面和水面作为仓库。Warehouseintraditionalsensereferstoplacesassumingcustodialfunctioninthelogisticssystemandnodeofthelogisticsnetwork.Modernlogisticswarehouseisunderstoodasregionaldistributionbase,whichisoperationcenterofthelogisticsintheregion.传统意义上的仓库是指在物流系统中承担保管功能的场所，是物流网络中的结点。现代物流将仓库理解为区域分拨的基地，是区域内物流运作的中心。Inadditiontoarticlesstoragefunction,themainfunctionofwarehousealsoincludestransportportfolio,portfolio,circulationprocessing,service,creditinstitutionsandtransportregulationroleinthelogisticssystem,whichincreasestheaddedvalueoftheproducts.仓库的主要功能除了物品的存储保管功能之外，在物流系统中起着运输组合、产品组合、流通加工、服务、信用机构以及运输调节的作用，增加产品的附加值。,(2)Classificationofwarehouse仓库的分类,Warehouseisdividedasfollowsaccordingtothefunction,use,storagewarehousemorphology,structure,locationandotherstandard:按仓库的功能、用途、保管形态、结构、选址等标准划分如下：1classificationaccordingtofunction按仓库功能分类：(1)Storagewarehouse:Referstothespeciallong-termstorageofvariousreservematerials,warehouseforcompletingthereservetask.Suchasstrategicmaterialreserves,seasonalreservereserveseasonprepareagainstnaturaldisasters,flowregulatingreserveetc.储备仓库：是指专门长期存放各种储备物资，以保证完成各项储备任务的仓库。如战略物资储备、季节物资储备、备荒物资储备、流通调节储备等。储备仓库的功能是较长时间储存保管，主要追求储存效益。,(2)Transfershed周转仓库,1)Productionwarehouse:Inthefieldofproduction,itsusedtotemporarystoretherawmaterialsundermainproductionandprocessingandfinishedgoodsneedtobesold.Itincludesrawmaterialwarehouse,WIPwarehouseandfinishedgoodswarehouse.生产仓库：在生产领域，主要暂时存放待生产加工的原材料和在制品、待销售的产成品。包括原材料仓库、在制品仓库和成品仓库。2)Distributionwarehouse:usedincirculationdomainespeciallyforstorageofgoodstobesold;includingwholesalewarehouse,retailwarehouseetc.流通仓库：在流通领域，专门存放待销售的货物。包括批发仓库、零售仓库等。3)Distributionwarehouse(distributioncenter):warehouseaimedatcollectinganddistributinggoods.集配型仓库(配送中心)：是以组织物资集货配送为主要目的的仓库。4)Transitgoodswarehouse:mainlyusedtoReconfigure,distributegoodsandtemporarystoregoodstobeshippedinconnectionpointofdifferentmodesoftransportandtransportdirection.中转分货型仓库：主要是在不同运输方式、不同运输方向的交接点用于重新组配、分货、暂存待运货物的仓库。5)Processingwarehouse:Themaindifferencewithproductionwarehouseisthatprocessingwarehouseismainlyusedforcirculationprocessing.加工型仓库：与生产仓库的主要区别是，加工仓库以流通加工为主要目的。,2classificationaccordingtouse按用途分类,(1)privatewarehousing:Referstowarehousethatenterprisesengageininternallogisticsbusiness.自用仓库：是指企业从事内部物流业务的仓库。(2)commercialwarehouse:referstoasocialwarehousethatobtainsabusinesslicenseinaccordancewiththerelevantregulationsandthewarehousestorageserviceisprovidedtothegeneralbusiness.营业仓库：是指按照相关管理条例取得营业许可,向一般企业提供保管服务的仓库，是一种社会化的仓库。(3)publicwarehouse:warehouseconstructedbystateandpublicorganizationsforthepublicinterest.公共仓库：是指国家和公共团体为了公共利益而建设的仓库。(4)bondedwarehouse：warehousetokeepingforeignimportswithouttaxofimportandexportgoodsaccordingtothetariff.保税仓库：是指根据关税法保管国外进口而未纳税的进出口货物的仓库。,3classificationaccordingtostoragemorphology按保管形态分类,(1)Ordinarywarehouse:Generallyreferstoawarehousewithgeneraltemperaturepreservation,naturalventilationandnospecialfunction.普通仓库：一般是指具有常温保管、自然通风、无特殊功能的仓库。(2)refrigeratedstoragehouse:generallyreferstowarehousewithrefrigerationequipment,agoodthermalinsulationperformancetomaintainlowtemperature,whichisspeciallyusedforstorageoffrozenmaterialwarehouse.冷藏仓库：一般指具有制冷设备，并有良好的保温隔热性能以保持较低温度的仓库，是专门用来储存冷冻物资的仓库。(3)warehousewithconstanttemperature:warehousethatcanmaintainacertaintemperatureandmoisturefunction恒温仓库：指具有保持一定温度和保湿功能的仓库。(4)dangerousgoodswarehouse:warehousethatstoreflammable,explosive,corrosive,toxicandradioactiveandotherdangerousmaterialswhichcauseacertaindangeronthehumanbody.危险品仓库：指存放具有易燃性、易爆性、腐蚀性、有毒性和放射性等对人体或建筑有一定危险的物资的仓库。,4classificationaccordingtostructureandtexture按结构和构造分类,(1)Bungalowwarehouse:referstowarehousewhosebuildingisbungalowwithsimplestructureandeffectiveheightlessthan5-6meters.平房仓库：平房仓库是指仓库建筑物是平房，结构简单，有效高度一般不超过56米的仓库。(2)multistoriedstorehouse(Buildingwarehouse):buildingswithmorethantwolayers;warehouseconstructedwithsteelreinforcedconcrete.Eachlayerbuildingofwarehouseisconnecteddependingontheverticaltransportationmachineryorconnectedbyrampscalledrampswarehouse.多层仓库(楼房仓库)：仓库为两层以上的建筑物，是钢筋混凝土建造的仓库。仓库楼房各层间依靠垂直运输机械联系，也有的楼层间以坡道相连，称坡道仓库。,（3）Highrackwarehouse(stereoscopicwarehouse)高层货架仓库(立体仓库),Acommonlyusedformofautomatedwarehousegenerallycomposedoffourparts,thataretopshelf,tunnelmachine,entryandhandlingsystemandmanagementcontrolsystemandhaswarehousestudiothatcanstorepalletswithmorethantenlayers.是一种常用的自动化仓库形式，一般由四个部分即高层货架、巷道机、周围出入搬运系统和管理控制系统组成，具有可以保管10层以上托盘的仓库棚。awarehousewithhighdegreeofautomationandstrongabilityofinventory.Stereoscopicwarehousemakesfulluseofthespaceintegratedwithinformationcollection,storage,management,usingmicroelectronicstechnologywithcharacteristicsofadvantagesofsmalloccupiedarea,quicklyandaccuratelywarehousingoperation.Itcompletelyrealizesautomationinthejudgmentoffault,parameterrecords,reportprintingandsoon.Comparedwiththebungalowwarehouse,warehouseautomationcansave70%oftheareaand70%ofthelaborforce.这是仓库中一种自动化程度较高、存货能力较强的仓库。立体仓库充分利用空间，集信息、存储、管理于一体，采用微电子技术，具有占地面积小、仓储作业迅速准确的特点，在故障判断、参数记录、报表打印等方面全部自动化。与平房仓库相比，自动化立体仓库可节约70的占地面积和70的劳动力。,(4)bulkwarehouse:Specializedstoragecontainerwarehousestoregranularorpowderymaterials;Granularorpowderedgoodssuchasgrain,feed,cement.散装仓库：是指专门保管散粒状或粉状物资的容器式仓库。如谷物、饲料、水泥等颗粒状、粉状货物的保管。此类仓库大多是混凝土结构。(5)Tankwarehouse:largecontainerwarehousestorageinavarietyoftank.罐式仓库：是指以各种罐体为储存库的大型容器型仓库。,5classificationofwarehouselocation按仓库选址分类,(1)Portwarehouse港口仓库(2)Inlandwarehouse内陆仓库(3)Hubstationwarehouse枢纽站仓库,8.2inventorydecision库存决策,1Outline概述2Economicorderquantity经济订货批量3Stochasticinventorycontrolmethod随机型库存控制方法4Quantitypricediscounts批量价格折扣5Inventorysimulationmethod库存模拟法,1Outline概述,(1)Inventoryandinventoryclassification库存和库存分类(2)Whytheturnoverwarehouseneedinventorycontrol为什么周转仓库要进行库存控制？(3)Inventoryprocessoverview库存过程概述(4)Principlesofinventorycontrol库存控制的原理(5)meaningoforderingstrategy订货策略的含义(6)storageexpenses库存费用,(1)Inventoryandinventoryclassification库存和库存分类,Inventory:numberofmaterialsinthestoragestate库存:处在储存状态的物资的数量。inventoryclassification:canbedividedintotwotypes:库存分类：按性质分，可以分为两大类：1reservestock(Safetyreserves,nationalreserves):Responsetothedisaster,waretc.储备库存（安全储备、国家储备）：应对灾害、战争等。2Inventoryturnover:temporaryreservesontemporarystand-byinordertocarryoutproductionordistributionineachlinkofproductionordistribution;Theyconstantlyputintoproductionandsales,andareconstantlyadded.周转库存：是为了生产或流通的进行、在生产或流通的各个环节上暂存待用的临时性储备，它们不断地投入生产和销售，又不断地补充进来。,(2)Whytheturnoverwarehouseneedinventorycontrol为什么周转仓库要进行库存控制？,1Thedualityofturnoverwarehouse周转储备的二重性:Ononehand,itguaranteesuccessfullyimplementingofproductionandcurrency.一方面保障生产和流通的顺利进行；Ontheotherhand,itleavesunusedcausingdelayingproductionthatneedstopayfees.另一方面又闲置,延缓生产,需要付出费用。,Theinventorycostisamajorconstituentpartoflogisticscost,andlogisticscostaccountsformuchofthenationaleconomicoutput.Accordingtotheworldbankanalysis,thelogisticscostofdevelopedcountriesaccountsfor10%ofGDP库存成本是整个物流成本一个主要的组成部分，而物流成本又占国民经济产值的很大部分。据世界银行分析，发达国家物流成本占GDP的10左右,美国和加拿大普通公司物流成本占销售额比例(),CompositionoflogisticscostinUSAandCanadaCompany美国和加拿大公司物流成本构成情况,2turnoverwarehouseshouldhaveareasonablelimit周转储备应当有一个合理的限度：Toomuch,No:storagecostincreases;太多了,不行：保管费用增加；Toolittle,no:itwillcauseoutofstock;太少了,不行：会造成缺货。Shouldbenottoomuchortoolittleinthelimitationthatensureproductionandcirculation.应该不多不少,以能恰好保证生产和流通需要为限。3reasonableinventory:includesdistributionofreserves,reservevarietystructure,thenumberofreserves,reasonablereservecost.合理库存:包括储备分布,储备品种结构,储备数量,储备费用合理。,(3)Inventoryprocessoverview库存过程概述,Inventoryprocesscanbedividedinto：库存过程可以分成1orderprocess：beginwithsendingoutanorderandfinishwithordertransaction.订货过程：从发出订货到订货成交为止。商流过程（库存增加）2purchaseprocess:beginwithordertransactionandfinishwithstorageofgoods.Thelogisticsprocess(increaseinventory)进货过程：从订货成交到货物入库为止。物流过程（库存增加）3Storageprocess:beginwithgoodsstoredinwarehouseandfinishwithgoodsoutofwarehouse.Thelogisticsprocess(inventoryisunchanged)保管过程：从货物入库到货物出库为止。物流过程（库存不变）4Salesprocess:beginwithgoodshandingandfinishwithdischargefromwarehouse.销售出库过程：从货物点交到货物出库发运止,商、物流过程（库存减少）,(4)Principlesofinventorycontrol库存控制的原理,Inordertocontrolinventorylevel,fromtheinventoryprocesswecanknowthatwecancontroltheorderandpurchasingprocessandwecanalsocontrolsalesprocess.Bothofthemcanreachgoal.However,controllingisnotproperbecauseitmeanslimitingdemandofusersandinfluencesocialdemand.Soitsbettertocontrolinventorybycontroltheprocessoforderandpurchasing.Bythisway,itcannoonlycontrolinventorylevelbutalsonotaffectingsocialdemand.Therefor,thebasicideaistocontrolinventorylevelbycontrollingtheprocessoforderandpurchasing.为了控制库存量，由库存过程可知，可控制订货进货过程，也可控制销售出库过程。都可以达到目的。但是，控制销售出库过程，意味着限制用户的需求，影响社会需求，不好。所以最好采用通过控制订货进货过程的办法来控制库存量。这样，不但可主动控制库存量，而且不影响社会效益。因此，基本的思路，就是研究怎样通过控制订货进货过程的办法来控制库存量。,(5)meaningoforderingstrategy订货策略的含义,Itincludesthreeaspects:包括三个方面的内容：1whentoorder,namelyorderingtime.什么时侯订货，即订货时机。2howmuchtoorder,namelyorderingpoint.订多少，即订货点。Howtoimplement,namelyorderingmethod.如何实施，即订货方法。,(6)storageexpenses库存费用,1Orderingcost订货费2Custodycharges保管费3Replenishexpensesandpurchasefee进货费与购买费4Shortagepenaltycost缺货费5Restockingfee补货费Totalcost总费用,1Orderingcost订货费,Meaning:thetotalcostoforderingprocess.Includingtravel,orderingfees,communicationexpenses,hospitalityandrelatedorderpersonnelcosts.含义：订货过程中发生的全部费用。包括差旅费，订货手续费，通讯费，招待费以及订货人员有关费用。Features:orderingcostofeveryorderisindependentwithorderingquantity.Thetotalorderingcostofseveraltimesisrelatedwithordernumber.特点：每一次订货中订货费与订货量的多少无关。若干次订货的总订货费与订货次数有关。Formula公式：设一次订货费为C0,且每次订货费都相等,如在期间内共订了次货，每次订货量为，期间内的总需求量(也即期间内的总订货量)为，则期间内的总订货费为：如平均单位时间需求量（也即平均需求速率为），则期间内的平均订货费为：,ItsobviousthatwhentotaldemandDisconstantduringT,theaveragesizeoftheorderingcostisinverselyproportionaltotheaverageorderquantity.可见，如期间的总需求量确定不变时，平均订货费的大小与订货批量成反比。,2Custodycharges保管费,Meaning:allcostsincurredintheprocessofstorage.Include:含义：保管过程中发生的全部费用。包括:inspectionfeewhenhandlingstackinginthelibrary入、出库时的装卸搬运堆码检验费用；Storageappliancematerialcost保管用具用料费用；Warehouserentutilities仓库房租水电费；Therelatedcustodialstaffexpenses保管人员有关费用；Thedamageorlossofcustodyintheprocess保管过程中的货损货差；Storageofmaterialsandfundsofbankinterest保管物资资金的银行Features:Custodychargesisrelatedwithstoragequantityandthelengthofstoragetime.特点：保管费用与保管数量的多少和保管时间的长短有关。,设单位物资单位时间的保管费为c1，平均库存量为，则期间的总保管费C1为：,如每次订货量为0。对于瞬时到货的情况，如图4-3，则平均库存量：,可见平均保管费与订货批量成正比。如图所示：,而期间内的平均保管费为：,对于持时到货的情况（图4），设进货的速率为p、销售的速率为R，订货批量为Q0，则所能达到的最高库存量Qmax为：,T期间的平均库存量等于：,所以T期间的平均保管费等于：,图3,图4,3Replenishexpensesandpurchasefee进货费与购买费,Meaning:theso-calledpurchasefeesisallcostsinpurchaseprocess,namelythetransportfees.Including:freight,packagingfees,handlingfees,rentalfees,feesforthedamageorloss,delayetc.Purchasefee,namelyoriginalpriceofgoods.含义：所谓进货费，就是进货途中的全部费用，即运杂费。包括：运费、包装费、装卸费、租赁费、延时费、货损货差等。购买费，即物资的原价。Features:stockcostandpurchasefeesareindependentwithorderbatch,numberorderbatchwillnotaffectthetotalstockcostandpurchasecost.Wecallthiscostsindependentwithorderquantityasfixedcosts,whilethoseexpensesrelatedwithorderquantityiscalledvariablecost.Therefore,thepurchasecostandpurchasecostisfixed,andtheorderingcost,storagefee,shortagecost,variablecostarevariablefees.特点：进货费与购买费都与订货批量无关，批量订多订少都不影响其总进货费和购买费。我们把这种与订货批量无关的费用称为固定费用，而把那些与订货批量有关的费用称作可变费用。因此，进货费与购买费是固定费用，而订货费、保管费、缺货费、补货费是可变费用。设单位物资的进货费为c3，单价为k，订货批量为0，则总进货费与购买费3为：3=（c3+k）0如为简化起见，用表示固定费用，则3可表示为：3=（c3+k）00则平均固定费用：,4Shortagepenaltycost缺货费,Theso-calledshortageisphenomenonoflossingofthesalesopportunitybecauseofnospotgoodssupplywhentheuserbuyingthegoods.Shortagecausesthestocklossandshortagecost.Inthiscase,companysaleswhentherearegoodsinthewarehousebutnotsaleswithoutgoodsinwarehouse.Inventorycanbereducedtozero.所谓缺货，就是当用户来买货时，仓库因为没有现货供应而丧失了这次销售机会，这种现象就叫缺货，缺货，会造成缺货损失，也就是缺货费用。在这种情况下，仓库中有货就销售，没有货物就不销售。库存量可以降到零。Characteristicsoftheshortagecost:Inthespecificcase,shortagecostmayhavethreekindsofaspects:缺货费用的特点：在具体情况下，缺货费可能有三种情况：(1)Associatedwiththeshortagequantity与缺货量有关；(2)Mayassociatedwiththeshortagefrequency可能与缺货次数有关；(3)Mayassociatedwiththeshortagetime可能与缺货时间有关。计算缺货费用时，可以简化计算，不考虑长久影响。,5Restockingfee补货费,Theso-calledrestockingistorequiretheuserstillsetongoodsherebyloansandpromisetoimmediatelyreplenishgoodsincaseoflosingofsalesopportunitieswhenthereisnotenoughspotsupplyinwarehouseandtheusersbuythegoods.Afterreplenishment,sellerimmediatelysellsittotheuser.Sointhereplenishmentsituation,inventorydropstonegative.Andinreplenishmentstagefollowingthepurchase,inventoryrisesagainfromnegativetopositive.所谓补货，就是当用户来买货时，仓库没有现货供应，但不丧失销售机会，而是要求用户仍然在这里订上货，进行欠账经营，答应马上进货，待进货后，马上补货给用户。所以补货情况下，在欠账阶段，库存量可以下降到负值，在进货后的补货阶段，库存由负值再上升到正值。Restockingcostmayhavethreekindsofaspects:补货费可能有三种情况：(1)Associatedwiththerestockingquantity与补货量有关；(2)Mayassociatedwiththerestockingfrequency可能与补货次数有关；(3)Mayassociatedwiththeshortagetime可能与补货时间有关。,Totalfeeswithoutshortageandreplenishment没有缺货与补货时总费用,即各项费用的总和。即：o13总平均费用为：,Whenshortageorreplenishmenthappens,itsfeesshouldalsobeaddedtothetotalfees.(Note:shortageandreplenishmentaremutuallyexclusive)当有缺货或补货发生时，总费用还需要加进去。（注意：缺货与补货是互斥的）,2Economicorderquantity经济订货批量,(1)Outline概述(2)Economicorderquantityincaseofinstantaneousarrival瞬时到货情况下的经济订货批量(3)Economicorderquantityincaseofdurativearrival持时到货情况下的经济订货批量,(1)Outline概述,1Whatiseconomicorderquantity?什么叫经济订货批量？Considerhowtochoosetheorderquantitytomakeinventorytotalcostmosteconomic.Theorderquantityenablesinventorytotalcostthemosteconomiciscalledtheeconomicorderquantity考虑怎样选择订货批量，使得库存总费用最省最经济。把这个使得库存总费用最省最经济的订货批量，叫经济订货批量。2FoundationtouseEconomicOrderQuantityFormula应用经济订货批量公式的前提条件：1)Theformulaisapplicabletoconditionofunrestrictedorder.Thatisyoucanordergoodsatanytimeandanywhere.公式适用于订货不受限制的情况。即什么时侯想订货就能订到货，想到哪里订就能到那里订。2)Theformulaisapplicableforsingleproduct.公式适用于单一品种的情况。3)Theformulaisapplicablenotonlyfordeterministictypebutalsorandomtype.3)公式不但适用于确定型，也适用于随机型。,Datum:economicorderquantitymodel资料：经济订货批量模型(EOQ),Economicorderquantitymodelwasfirstputforwardby.W.Harrisin1915;Themodelhasthefollowinghypothesis:经济订货批量模型(EconomicOrderQuantity,EOQ)最早由F.W.Harris于1915年提出的，该模型有如下假设：(1)Thedemandrateisknownasconstant.AnnualdemandisrepresentedbyD,demandrateinunittimeisexpressedbyd.需求率已知，为常量。年需求量以D表示，单位时间需求率以d表示。(2)Nolimitationtoorderquantity.一次订货量无最大最小限制。(3)Nopricediscountinpurchasingandtransportation采购、运输均无价格折扣。(4)Leadtimeisknownasconstant.订货提前期已知，为常量。(5)Orderfeeisindependentwithorderquantity.订货费与订货批量无关。(6)InventoryMaintenancecostsislinearfunctionofstockquantity.维持库存费是库存量的线性函数。(7)Replenishmentrateisinfinite,allordersarecompletedonce.补充率为无限大，全部订货一次交付。(8)Shortageisnotallowed.不允许缺货。(9)Usingthefixedquantitysystem采用固定量系统。,Economicorderquantitymodel经济订货批量模型(EOQ),费用,订货批量Q,CR=S(D/Q),CH=H(Q/2),CR+CH,Q*,(2)Economicorderquantityincaseofinstantaneousarrival瞬时到货情况下的经济订货批量,Instantaneousarrivalrefersthatorderingandpurchasingcanbecompletedinsecondsandgoodsbookedcanarriveonce.Thatistosay,thepurchasingrateisinfinity,purchasingtimeequalszero,andinventorysuddenlyincreaseaorderquantityQ0.瞬时到货，指订货进货，都能够在很短的时间内完成、而且所订货物一次全部到货。也就是说，进货速率无穷大、进货时间等于0，库存突然增长一个订货批量Q0,Q0就是常说的经济订货批量，特记为,根据前面的成本公式，求导计算可得,并且可求得,分别称作经济订货周期和瞬时到货的平均总变动费用。,(3)Economicorderquantityincaseofdurativearrival持时到货情况下的经济订货批量,Inventorymodelisshowninchartsix.Theso-calleddurativearrivalisthatorderingandpurchasingneedsaperiodoftimetogetthegoodsarrivalinwarehousingandgraduallyinventoryincrease.Thatistosay,purchaseratePisequaltoafinitenumber,orderingandpurchasingtimeT1isnotequalto0.库存模型如图6。所谓持时到货，就是订货进货需要一段时间、所订货物逐渐到货入库、库存逐渐升高。也就是进货速率p等于一个有限数、订货进货时间t1不等于0。,设一次订购量(或生产量)为Q，商品分批进货率为I(kgd)，库存商品耗用率为O(kg/d)，并且IO。一次连续补充库存需要的时间为t1。直至最高库存量；该次停止进货并不断耗用库存呈直至最低库存量(甚至为零)的时间为t2。由此可以计算出以下指标：t1=Q/h；在t1时间内的最高库存量为（I-O）t1；在一个库存周期(t1+t2)内的平均库存量为(I-O)t1/2：,Theaveragecostofstoragecanbecalculatedaccordingtopreviousformula;Soeconomicquantitycanbederivedthroughbyderivatewarehousestoragecostsas:根据前面公式可以计算出仓库的平保管费用；所以通过对仓库储存费用求导得到，经济批量为,3Stochasticinventorycontrolmethod随机型库存控制方法,(1)Outline概述(2)Stochasticinventorycontrolmethod随机型库存控制方法1、ABCclassificationmethodABC分类法2、Fixed-quantityorderingmethod定量订货法3、Periodicorderingmethod定期订货法,(1)Outline概述,1Randompattern:Thatisinventorymodelthatthereisatleastonerandomvariableininventoryparameters.Theso-calledrandomvariableisthevalueisrandomvariationwithtime,whoseexactvalueinafuturetimecannotbeknowninadvance.随机型：即库存参数中，至少有一个是随机变量的库存模型。所谓随机变量是其值是随时间而随机变化的，不能预先知道它在将来某一时刻确切的取值。2Themainparametersofthestochasticinventory:主要的随机型库存参数有：1)demandrateR:demandinunittime.需求速率：单位时间的需求量。2)Orderleadtimek:timespanfromsendingoutanordertogoodsarrivinginwarehouse.订货前置期k：从发出订货到所订货物入库为止的时间间隔。3)demandinleadtime：totaldemandinleadtime前置期需求量L：订货前置期中的总需求量。,4)determinationoforderpoint订货点Qk的确定OrderpointQkistherealinventorywhensendingorder.订货点Qk是发出订货时的实际库存量。控制订货点Qk的高低，可以控制库存量。如Qk取得高，则所订货物到达入库时，原来库存物资还没销售完，从而库存水平升高，保管费用增加；如Qk太低，则所订货物到达入库时，原来的库存物资早已销售一空，产生了缺货，影响销售利润和库存满足率。所以Qk是一个进行库存控制的决策变量。Qk的最佳值最好是恰好等于“DL”，即：Qk“DL”但“DL”是随机变量（由相关需求所