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Chapter2Portcapacityandships2.1Cargoscategorizedbymannerofshipmentandhandling(根據(jù)運輸和裝卸方式分類的貨物種類)2.2
Portcapacityandthroughput(港口通過能力及吞吐量)2.3
Determinationofberthrequirement(確定泊位數(shù))2.4
Introductiontoqueuingtheory(排隊論)2.5Moreapplicationcasesofqueuingtheory2.6
ShipsandtheirinfluenceonportdesignAccordingtothetransportationmode(運輸方式),wecanbasicallyclassify
cargo(貨物)intofourcategories:Drybulkcargo(干散貨)Liquidbulkcargo(液體散貨)Containercargo(集裝箱貨)General(break)cargo(雜貨)Drybulkcargo(干散貨)suchkindsofmaterialsascoal,metalore,structuralmaterials,grain,saltcharacterisedbystableandlargequantity(穩(wěn)定、大宗);specializedloading/unloadingequipmentandhighhandlingefficiency(特殊、高效的裝卸設(shè)備).Chapter2Portcapacityandships2.1Cargoscategorizedbytrafficandhandlingmanner(根據(jù)運輸和裝卸方式分類的貨物種類)Liquidbulkcargo(液體散貨)coverssuchkindsofmaterialsasPetroleum(石油)LPG(液化石油氣),LNG(liquifiednaturalgas,液化天然氣)Productsofpetroleum(石油產(chǎn)品)Vegetableoil(植物油)Characterisedbystableandlargequantity(穩(wěn)定、大宗);specializedloading/unloadingequipmentandhighhandlingefficiency(特殊、高效的裝卸設(shè)備);mostoftheliquidbulkcargosareflammable(可燃)andthusbelongtohazardous(危險)cargos.Somemayevenbetoxic(有毒).Chapter2Portcapacityandships2.1CategoriesofcargoContainercargoandContainerisation(集裝箱貨和集裝箱化):(/)
Aspecialkindofcargo,usinglargenumberofboxeswithstandarizedsizetocontainbreakormiscellaneousgoods.(是一種采用標(biāo)準(zhǔn)化尺寸來裝雜貨的特殊貨物)InventedintheUSduring1950s,originallyformilitaryuseandthenappliedtocommercialpurpose(上世界五十年代在美國發(fā)明,最初用于軍事目的,后用于商業(yè)).MaintypesintermsofsizeStandardtype:8×8×20ft.(width×height×length),calledtheTwenty-FootEquivalentUnit,TEU)Predominatedby20and40ftcontainers(以20和40噸箱為主);Specialsize45ftinlength8.5ftor9.5fthighTotalweight:20.3~32.5t,netcargoweightisstatistically8tChapter2Portcapacityandships2.1CategoriesofcargoAdvantagesofusingcontainerastransportationtoolTobeadaptabletostandardizedhandlingequipments
可適應(yīng)標(biāo)準(zhǔn)化裝卸設(shè)備Highhandlingefficiency(裝卸效率高)Toprovidesafeprotectionfordamageablegoods
為易損貨物提供安全保護(hù)Door-to-door(門到門)andmultimodaltransportation(多式聯(lián)運)servicesarepossible,cargoistransportedunderonethroughbill,issuedbytheshippingline;
可以實現(xiàn)門到門運輸以及多式聯(lián)運。Tobemoretimesavingincustomsprocessingandingoodshandover.
海關(guān)貨物交接更省時.Chapter2Portcapacityandships2.1CategoriesofcargoGeneralcargo
Cargothatcannotbehandledwithspecializedequipments:不能用專業(yè)化裝卸設(shè)備進(jìn)行裝卸的貨物,如cartons(紙箱),crates(木箱),bales(捆),bags,drums(桶),etc.Characterisedby(特征是)Widely-varyingsizesandshapes(尺度、形狀變化大)Largely-varyingcapabilityofloading/unloadingequipmentstoadaptthemiscellaneouscargo.要求裝卸設(shè)備的能力變化大,以適應(yīng)各類貨物。Lowerhandlingefficiency.裝卸效率低Ausefulandefficientwaytoimprovehandlingefficiency(裝卸效率)istouselargeranduniformunits,whichiscalledunitizedhandlingorunitizedtransport
(成組裝卸或成組運輸).Oneunitweighsabout1.5-3tons.palletized(貨盤)cartonspre-slung(吊索)bagsChapter2Portcapacityandships2.1Categoriesofcargo2.2Portcapacityandvolumeofthroughput
(港口通過能力及吞吐量)Portcapacity:Definedastheabilityofaporttohandlecargoinoneyear;Dependingonthetotalnumberofberthsandtheirefficiencies(thenumberandhandlingefficiencyofloading/unloadingequipments)總泊位數(shù)和各個泊位的裝卸效率thestoragecapacity存儲容量thetransportationlinkswiththehinterland與腹地的交通聯(lián)系(集疏運系統(tǒng))Thecapacityoftheaccesschannel(itsdepth,width,andone-wayortwo-way)航道通過能力,與深度、寬度及單向雙向有關(guān)。thecustomsefficiency海關(guān)通關(guān)效率Chapter2Portcapacityandships2.2PortcapacityandthroughputNaturalconditions,suchasWinds(storms)Waves(swells)CurrentsFogNighttimerestrictionsforsomekindsofshipThus,agoodprotectionfromwavesandothernaturalenvironmentconditionswillgenerallyincreasetheworkabledayandhencethecapacityofaport.(因此,如果對于波浪或其它環(huán)境條件有良好保護(hù),好的泊穩(wěn)條件也會增加作業(yè)天數(shù),故也會增加港口通過能力。)Chapter2Portcapacityandships2.2PortcapacityandthroughputOperationsystemofamodernportManeuveringandNavigationsystemLoadingandunloadingsystemStoragesystemLinkingtransportationsystemServicesystemCapacityofaportCargothroughput
isdefinedasthetotalannualvolumeofcargo(年貨運量)loadedonandunloadedfromships.Insomeplaces,onetonofcargotransferredfromoneshiptotheotheriscountedtwice.Maininfluencingfactorsoncargothroughput
ofaport(影響港口貨物吞吐量的主要因素)Trafficdemandofthehinterland
(腹地)andnumberofcallingships(靠泊船舶).Thevolumeofcargothroughput
willincreasemorerapidlywheneconomy,especiallymanufactureindustryinthehinterland,increasesfast.Efficiency
ofportfacilities(orcapacityofaport)may,ontheotherhand,alsohavesignificanteffectonthecargothroughput.Portcapacityandcargothroughputaretwoimportantindicestodescribethescaleofaportindifferentsense.(港口通過能力和吞吐量是兩個描述港口規(guī)模大小的兩個不同參量)Chapter2Portcapacityandships2.2PortcapacityandthroughputPortcapacityVolumeofcargothroughput=><TheoceanHinterlandisdefinedasanareawherecargocomesfromorgoesinto.Directhinterland(直接腹地)Transshipmenthinterland(轉(zhuǎn)運腹地)ABPortPPortQFig.2.1DefinitionsketchofhinterlandCargoatMwhethertochoosePortAorBdependsonthetransportationcostsfromMtoAortoB.Chapter2Portcapacityandships2.2PortcapacityandthroughputForecastofportthroughput(吞吐量預(yù)測)Purposetoforecastportthroughput(港口吞吐量預(yù)測的目的)Todeterminethetypeandnumberofberthtobeconstructed.Toknowthecargotypeandthevolumepassingthroughaportandtheshiptype,tonnageandcallingfrequency.Methodofforecasting(預(yù)測方法)Quantitatively(定量方法):timeseriesforecasting,probabilityanalysismethod,casualrelationmethod,dynamicforecastingmethodandcombinedmethod.Qualitativemethod(定性方法):Delphiforecasting,expertinvestigationmethodChapter2Portcapacityandships2.2PortcapacityandthroughputTime-seriesforecasting(時間序列法)Assumingthatthethroughputisrelatedwiththeorderofyears,aregressionrelation(回歸關(guān)系)
betweenthethroughputandtheorderofyearscanbeobtainedbasedontheavailabledataofthroughput假定吞吐量與年序相關(guān),以已有吞吐量資料為基礎(chǔ),建立吞吐量與年序回歸關(guān)系。Probabilityanalysismethod(概率分析法)Theportthroughputdependsonmanyfactorsthatcontainrandomeffects.Basedontheavailabledataandestimationofthefuturedevelopmenttrend,itispossibletoevaluatethesubjectiveprobabilityofcertainthroughputvalue.吞吐量依賴于很多包含隨機(jī)性的因子,根據(jù)已有資料和對未來發(fā)展趨勢的預(yù)測,可以給出某吞吐量值的主觀概率估計。Casualrelationmethod(因果關(guān)系法)Theportthroughputdependsonsocialandeconomicindices,suchasGDPandforeigntradevolume,etc.,fromthefuturetrendofthoseindices,portthroughputcanbeforecasted.港口吞吐量依賴于社會和經(jīng)濟(jì)指標(biāo),如GDP、外貿(mào)額等,從這些指標(biāo)的未來發(fā)展趨向,可以預(yù)測港口吞吐量。Chapter2Portcapacityandships2.2PortcapacityandthroughputDelphiforecastingDevelopedbyRandCorporationin1950sMainprocedures:Aquestionnaireabouttheissuedesignedbyamonitorteamissenttoaselectedgroupofexperts.首先進(jìn)行專家問卷調(diào)查。Aftertheresponsesaresummarized,theresultsaresentbackagaintotherespondentsforpossiblereevaluation.答卷匯總后,再送給答卷者,進(jìn)行可能的重新評估。Therespondentsaregiventheopportunitytodefendtheiroriginalopinionortochangetheirpositiontoagreewiththemajorityinthesubsequentroundofquestionnaires.在接下來的問卷中,答卷者可以堅持其最初觀點,也可以轉(zhuǎn)為同意多數(shù)意見。Chapter2Portcapacityandships2.2PortcapacityandthroughputAssignmentICollectenoughdataofcontainerthroughputforaportthatyouchoose,basedonwhichperformpredictionofthethroughputofcontaineroftheyear2015and2020byatleastonemethodofthroughputforecast.Chapter2PortcapacityandshipsInconstructionofaport,themostimportantindextobedecidedinthefirststepmaybethenumberofberthstobeconstructedforgiventhroughput,cargotype,shipsize,andshiptonnage.建港時,最重要的指標(biāo)就是給定吞吐量、貨物種類以及船型建幾個泊位。Ingeneral,thenumberofberthsshouldbedeterminedbasedontheconsiderationoffollowingfactors(確定泊位數(shù)時主要考慮以下因素):predictedthroughputofvariouscargo(不同貨物的吞吐量)averageshiptonnage(平均單船裝載量)averagecargo-handlingrate(servicetime)anditsprobabilitydistributions(平均裝卸效率及其概率分布)totalstayingtimeanditsprobabilitydistributions(總在港時間及其概率分布)probabilitydistributionsofships’arrivalrates(船舶到船率的概率分布)Chapter2Portcapacityandships2.3DeterminationofberthrequirementAsaruleofthumb,theberthnumbercanbecalculatedfromthepredicted
throughputofaportandthedesigned
handlingefficiency(裝卸效率)ofasingleberth.(2.1)Chapter2Portcapacityandships2.3DeterminationofberthrequirementIntheplanningstage,thehandlingefficiencyofaberthPt
maybeestimatedfromempiricaldata,whichdependsonthecargotype,shiptonnage,andloading/unloadingoperation.TobemorepreciselyPtcanbecalculatedby(2.2)
Tyannualtotalservicetime(days);
tzservicetimeofoneship(hr.),;Chapter2Portcapacityandships2.3Determinationofberthrequirement
tf
auxiliaryoperation(輔助操作)time(hr.),includingmooringtime;
Rhandlingrateofaberth;
G
tonnageofshipment;thenon-servicetime(hr.),includingbreak,dining,etc.;
rtheutilizationfactorofaberth,theratiooftheutilizedtimetothetotaltime.Fordifferenttypeofberth,differenttypeofformulaareavailable.ConceptsofoptimumberthnumberandberthutilizationThepreviousruleofthumbindeterminationofberthnumbermaybemisleadingastheyignoretheinterestofshipownerswhilemakingthemawaitavailableberth.Sometimesthismaybeaveryseriousproblemwhentheutilizationisextraordinarily(異常地)highbecauseofthetworandomeventsinvolvinginportoperation:randomlengthofservicetime(loading/unloading),randomintervalofshiparrivals.Optimumberthnumbermustbeatradeoff(折中)oftheinterestsoftheportpartytheshipownerpartyInotherwords,theoptimumberthnumbermustbeafunctionthattakestheinterestofboththetwopartiesintoconsideration.Chapter2Portcapacityandships2.3DeterminationofberthrequirementTheoptimumberthnumber(最優(yōu)泊位數(shù))shouldbecorrespondingtothenumberwhenthetotalexpenseoftheberthsandthecallingvesselsgainstheminimum.Thereasonsare:最優(yōu)泊位數(shù)應(yīng)該對應(yīng)于泊位費和船舶待泊費之和最小的情況下的泊位數(shù),原因是Iftheberthnumberincreasedbyone,theportpartywilllosemoneyastheyinvesttoomuchinconstructionofberths.如果泊位數(shù)增加一個,港方會因為泊位太多而虧損。Whereasifitisdecreasedbyone,theshipownerpartymaybecomeunbearable(難以承受的)becauseoftoomuchwaitingtimeforavailableberth.而如果減少一個泊位,則船方會因為待泊時間過長而難以接受。Chapter2Portcapacityandships2.3DeterminationofberthrequirementOptimumberthutilization(最優(yōu)泊位利用率)istheberthutilizationwhenberthnumberistheoptimum.0.47~0.75DependingonnumberandtypeofberthAsimplewaytodeterminetheoptimumberthnumber
isbycomparingthetotalexpenses
ofthetwopartiesunderthefollowingthreeconditions:KeeptheberthnumberunchangedLettheberthnumberincreaseoneLettheberthnumberdecreaseoneChapter2Portcapacityandships2.3DeterminationofberthrequirementMathematicalexpressionoftheoptimumberthnumberDenotethedailyexpenseofasingleberthbycb,whichincludestotalinitialinvestmentofthefixedfacilities(固定設(shè)備初投資)maintenanceexpenseoftheport(營運費)Denotethetotaldailyexpenseofashipbycs,whichincludesfixedcosts(固定費用):
totalinitialinvestmentofthefixedfacilitiesoperationandmaintenanceexpenses(營運費)Thefixedcostsincludestheexpensesofshipfacilities,laborage,stuff(材料),broking(經(jīng)紀(jì)),insurance,loaninterest,andetc.Theoperationandmaintenanceexpensesincludethecostsoffuel,electricity,andothersupplies.Chapter2Portcapacityandships2.3DeterminationofberthrequirementExpressionoftotalexpensesTotalberthnumberSnumberofshipsunderservice
+numberofships
waitingforberthvacancyTotaloperationdaysNinayearExpenseofaberthgroup
Cb=cbNS (2.3)Expenseofcallingships
Cs=csNns (2.4)Totalexpenseofboththeberthgroupandthecallingships (2.5)Chapter2Portcapacityandships2.3DeterminationofberthrequirementDefinitionoftheoptimumberthnumberSmustsatisfyand (2.6)Thusweobtain(2.7)and(2.8)Afteralittlemanipulation,wehave(2.9)Chapter2Portcapacityandships2.3DeterminationofberthrequirementThekeyproblemishowtoestimatethevaluesofns-1,ns,ns-1,andthelengthoftime
thatshipsstayatportforknownvaluesofcbandcsandotherbasicparameters,whichareallrandomvariables(隨機(jī)變量).CombiningEq.(2.8)and(2.9),wehave(2.10)QueuingtheorymodelOriginallydevelopedfordesigningtelephoneexchangesystembyA.N.Erlanginthelastcentury.Thecommoncharacteristicsofthetwoprocesses:randomarrivalsandrandomlengthofservicetime,correspondingtothetworandomevents:therandomarrivaltimeintervalofshipstherandomhandlingtimeofcargo2.4IntroductiontoqueuingtheoryChapter2Portcapacityandships??????????DepartureUnderserviceTotalnumberofshipsatportns=nw,s+nb,s
Givenquantities:ThroughputQAveragehandlingrateofship
mAveragevolumeofshipment
GAveragehandlingcapacityofcargo
RWedefinethe
averagearrivalrate(日到船率)andtrafficintensity(船流密度)
rs
istheberthutilization(berthoccupancy)(2.11)Chapter2Portcapacityandships2.4Introductiontoqueuingtheory(2.12)(2.13)Shiparrivalmaybeaheadofordelayedtothescheduleduetometeorologicalfactorsorotherunforeseenevents.Poissondistributionisusuallyagoodrepresentationfortheprobabilityofshiparrival.Thelengthofservicetimemayalsobedelayedwithrespecttoitsmeanbecauseofmeteorologicalinfluence,tidesandrandomnessincargohandlingoperations.Negative-exponentialdistribution
(負(fù)指數(shù)分布)isoftenusedforthedwelling(停留)timeofshipsatberth.Chapter2Portcapacityandships2.4Introductiontoqueuingtheory(2.14)ThusresultedmodeliscalledM/M/Smodel,inwhichtheprobabilityofnshipsdwellingatporthasananalyticalsolutionandcanbeexpressedasindicatesthesituationthatnoshipisatport.(2.15)Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryTheaveragenumberofwaitingshipscanthusbeexpressedas (2.16)Theaveragewaitingtimepershipcanbecalculatedby (2.17)Tb
istheservicetimepership,calculatedby (2.18)Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryThetotalnumberofshipsdwellingatportis(2-19)Fortheconvenienceofcalculation,atableiscreatedintermsofratioofwaitingtimetoservice-timeTw/TbnumberofberthsSberthoccupancyrs
BerthnumberUtilizationrs1234560.10.1110.0100.0010.0000.0000.0000.20.2500.0420.0100.0030.0010.0000.30.4290.0990.0330.0130.0060.0030.40.6670.1900.0780.0380.0200.0110.51.0000.3330.1580.0870.0520.0330.61.5000.5620.2960.1790.1180.0820.72.3330.9610.5470.3570.2520.1870.84.0001.7781.0790.7460.5540.4310.99.0001.2632.7241.9691.5251.234Table2.1Ratioofwaitingtimetoservice-time(M/M/Smodel)Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryProcedurestocalculatetheoptimumberthnumber:GivenvaluesofThroughputofaberthgroupQAveragehandlingcapacityofshipsmAveragetonnageofshipmentGAveragehandlingrateofcargoRBerthnumberSBerthutilizationrsChapter2Portcapacityandships2.4IntroductiontoqueuingtheoryExample1CalculatetheoptimumberthnumberforPortA,giventhethroughputQ=146×104ton/a,supposingshiparrivalsconformtoPoissondistributionandberthoccupationtimeconformstonegative-exponentialdistribution.Otherrelatedparametersareasfollows:Presentberthnumberis3.BerthhandlingrateR=2000ton/day·berthVolumeofshipmentG=5000ton/shipcs=2.92×104CNY/day·berthcb=8.00×104CNY/dayAnalysisThecapacityofasingleberth:48.7×104tons/yr.Inthiscase,theutilization(berthoccupancy)ishighupto67%thewaitingtimeofshipmaybetoolongthattheportwilllosecompetitiveability.Constructionofanewberthbecomesnecessary.Thiscanbeshownmoreclearlybythequeuingtheory.Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryForberthnumberof3,4,and5,therelatedparametersareshowninthefollowingtable.Table2.2Resultsofexample1Chapter2Portcapacityandships2.4IntroductiontoqueuingtheorySrsTwnw.snsns-ns+130.671.1380.9102.9140.500.2180.1742.1750.400.0500.0402.040.740.13TheoptimumberthnumberisthusS=4.Example2Estimatethewaitingcostofshipsinexample1forberthnumberS=3,4,and5,respectively.WhenS=4,theexpenselostofberthvacancy(泊位閑置損失)isTheexpenselostofshipwaitingforberthvacancyisChapter2Portcapacityandships2.4IntroductiontoqueuingtheoryDiscussionsTheberthexpenseisproportionaltotheberthnumber;Whiletheexpenseofthewaitingshipissharplydegressivewiththeincreaseofberthnumber;ThetotalexpenseofbothshipsandberthsgainsitsminimumwhenberthnumberS=4.Table2.3Resultsofexample2Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryS345Cb(×104CNY)1055.22131.63191.4Cs(×104CNY)2657.2508.1116.8Cb+Cs(×104CNY)3712.42639.73308.2ProbabilityofshiparrivalratePoissondistributionProbabilityofservicetimeSecond-orderErlangdistributionSelectionamongdifferentmodelsNegative-exponentialdistributionChapter2Portcapacityandships2.4IntroductiontoqueuingtheoryProbabilityofshiparrivalrateSecond-orderErlangdistributionProbabilityofservicetimeSecond-orderErlangdistributionStatisticdatashowsthatshiparrivaldistributionofgeneralcargoinmostportsconformsto(符合)Poisson
distribution.統(tǒng)計數(shù)據(jù)顯示,多數(shù)港口雜貨船到達(dá)符合泊松分布。Theoccupationtime(servicetime)ofshipsusuallyconformstoErlangdistribution.Insomeports,itconformstonegative-exponential
distribution.船舶在泊位時間(服務(wù)時間)一般愛爾蘭分布。某些港符合負(fù)指數(shù)分布。Thearrivalrateoflinerships(班輪)oftenconformstothesecond-orderErlangdistributionbecauseshipandcargoownersareusuallyfixedandaremoreeasilytobescheduled.Randomnessusuallycomesfromnaturalfactors.So,theE2/E2/Smodeloftengivesmorerationalforecastresults.班輪到船率經(jīng)常符合二階愛爾蘭分布,因為船和貨主一般都是固定的,行程比較容易確定。隨機(jī)性主要來自于自然因素。所以,
theE2/E2/S模型經(jīng)常給出合理預(yù)報結(jié)果。Chapter2Portcapacityandships2.4IntroductiontoqueuingtheoryItisimportantfortheplannerstobeawareofthefactthattheforecastedresultsbymathematicalmodelreflectsonlythemosttypicalsituationandisasimplificationofthecomplexpicture.對于規(guī)劃者來說,了解到數(shù)學(xué)模型預(yù)報結(jié)果只是反映了最典型情況和對復(fù)雜實際情況的簡化是很重要的。Sometimesitmaybeoversimplifiedandthustheresultsmaybeunreasonable.有時甚至?xí)蜻^于簡化而使結(jié)果不合理。Inthissense,theforecastedresultsisonlyofvaluesofreferenceratherthanpreciseresults.在這個意義上,預(yù)報結(jié)果只能作為一種參考,而不能認(rèn)定為精確結(jié)果。Chapter2Portcapacityandships2.4Introductiontoqueuingtheory2.5MoreapplicationcasesofqueuingtheoryConceptofberthgroupDuetotherandomfeaturesincargohandlingrateandshiparrivalrate,theservicequalitywilllikelybeimprovedifseveralberthsinaquayaremanagedasaunit(integratively,集中管理)
accordingtothequeuingtheory.Thiscanbeseenclearlyfromthefollowingdiscussions.由于在貨物裝卸及船舶到達(dá)中存在隨機(jī)特征,根據(jù)排隊論原理,如果幾個泊位集中管理,服務(wù)質(zhì)量很可能會提高。這可以從以下討論中看出來。Chapter2PortcapacityandshipsExample3StrategyofmanagementCertainporthastwosectionsandeachhastwocontainerberths,respectively.Eachsectionhasthethroughputamountingto500,000TEU/a.TheshipmentisG=1000TEUpership.Theloading/unloadingtime1/m=0.8days/ship.某港有兩個港區(qū),每個港區(qū)有兩個泊位,每個港區(qū)吞吐量為50萬TEU,每艘船的平均裝載量為1000TEU,裝卸時間為1/m=0.8天/艘。UseM/E2/Smodel(PoissondistributionforshiparrivalandErlangdistributionforservicetime)tocomparetheadvantagesanddisadvantagesofintegrativeandindependentmanagement.用M/E2/S模型(船舶到達(dá)符合泊松分布,裝船時間符合愛爾蘭分布),對比集中和分散管理的優(yōu)缺點。Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryManagedindependentlyFromTable4-8(textbook),itisinterpolatedshipsperdayChapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryManagedasaunitFromTable4-8(textbook),itisinterpolateddaysFromtheresults,wecanseethatalthoughtheequipmentsremainunchanged,thewaitingtimepershipisreducedby:從結(jié)果看出,盡管設(shè)備未變,待泊時間減少了0.244-0.0704=0.174day/shipTheannualamountofsavedtimeis(一年節(jié)約時間)Thecorrespondingexpense
savedperyearis(supposingtheexpenseofwaitingshipstobecb=172000CNY/ship·day):YuanRemarksAlthoughtheresultscannotbeabletoaccountforthecompletesituation,itdoinspireusthatsimilarberthsinaquaymanagedasaunitwillbesuperiortomanagedindependentlyintermsoftheirefficiency.雖然結(jié)果不能說明問題的全部,但給我們的啟示是一個泊位組的相似的泊位綜合管理優(yōu)于分散管理。Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryAdvantageofincreasingloading/unloading(handling)efficiency提供裝卸效率的好處Inordertocompletetheincreasingthroughputofaport,oneisoftenconfrontedwiththechoiceofwhethertoincreaseberthnumberortoimprovetheefficiencyofeachloading/unloadingequipmentsoastosatisfytheincreaseinportthroughput.為了完成不斷增長的吞吐量要求,我們經(jīng)常面臨選擇增加泊位數(shù)還是提高裝卸效率Byusingthequeuingtheory,thequestioncanbeclarified(闡明)easily.運用排隊論,問題可以得到澄清。Asshowninexample1,tocarryoutthethroughputof146×104tons,onesolutionistobuildanewberthwhilekeepingtheefficiencyofloading/unloadingfacilitiesunchanged.如例1所示,要完成146萬噸的吞吐量,一種方案是新建一個泊位,而裝卸效率不變。Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryWiththe4berths(3oldonesplus1newly-builtone),theberthutilizationfactorrs=50%andtheratioofwaitingtimetoservicetimeis0.087.Theportnowbecomesmorereadytoprovideserviceforcallingships.4個泊位情況下(3個已有,1個新建),泊位利用率為50%,待泊時間與范圍時間之比為0.087,港口接近隨到隨靠。Isitthebestwaytoincreaseportcapacity?Ifnot,thenwhatwillhappenifweinvestmoreintheloading/unloadingfacilitiesinsteadofinconstructionofanewberth?增加泊位是最好辦法嗎?如果不是,那么如果投到裝卸設(shè)備,而不是建新泊位會怎么樣呢?Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheorySupposingthehandlingrateisincreasedfrom2000ton/dayto3000ton/daybyaddingonemorehandlingline,inwhichcase,FromTable4-8(textbook),itisinterpolatedday/shipdaydayTheaveragetimeofashipatportisChapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryImprovedOriginalfacilities0.218+2.5=2.720.2180.5S=4;Increasingoneberth0.142+1.67=1.810.1420.44S=3;Increasinghandlingrateby50%Table2.4ComparisonamongdifferentstrategyChapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryConcludingremarks:Thetotaltimeofshipsstayingatportbeforeanyinvestmentisthelargestsinceboththewaitingtimeandtheservicetimearemorethanthoseafterinvestmentofnewfacilities;在任何投資實施之前,船舶全部在港時間為最大,因為待泊時間和服務(wù)時間都比改善之前都大。Thewaitingtimeisdecreasedsignificantlyaftertheconstructionofonemoreberth,howevertheservicetimestillremainsunchanged,consequentlythetotaltimeisstillatahighlevel;建成一個泊位后待泊時間顯著減小,但服務(wù)時間不變,因此,總在港時間仍然較大。Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryByincreasingonesetofloading/unloadingline,i.e.,thehandlingrateisincreasedby50%,boththewaitingtimeandtheservicetimearereducedeffectivelyandthetotaltimegainsminimum;增加一套裝卸設(shè)備后,裝卸效率提高50%,待泊時間和服務(wù)時間都顯著減少,總在港時間也達(dá)到最小。Theexampleindicatesthatimprovementofhandlingrateismoreeffectiveinsavingstaytimethanincreasingberthnumber.
這個例子表明,提高裝卸效率比起增加泊位對于節(jié)省在港時間更有效。Thisiswhymodernportprefersusinghighly-efficientloading/unloadingequipmentstosolelyincreasingberthnumberwhilekeepingusingloading/unloadingequipmentsoflow-efficiency.這就是為什么現(xiàn)代港口大都采用高效率的裝卸機(jī)械,而不是靠單純增加泊位數(shù)量,而裝卸機(jī)械維持原狀。Chapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryHowtoarrangethechanceofimprovingportcapacity
怎樣安排提高港口通過能力的時機(jī)Berthutilizationfactorhassignificantinfluenceontheservicequalityofaport.泊位利用率對于港口的服務(wù)質(zhì)量有很大影響Fromtheformula,itcanbeseenthatifthehandlingrate
Randtheberthnumber
Sremainunchanged,theutilizationfactorhastobeincreasedinordertosatisfythedesignatedthroughput.從公式可以看出,如果泊位數(shù)保持不變,為了完成吞吐量,必須提高泊位利用率。RatioofwaitingtimetoservicetimeUtilizationfactorChapter2Portcapacityandships2.5MoreapplicationcasesofqueuingtheoryItcanbeconcludedthatthelowertheutilizationfactoris,thebetterservicequalityaportwillpossess.泊位利用率越低,服務(wù)質(zhì)量越好。Whentheutilizationfactorreachessuchahighdegreeastheservicequalityofaportisseriouslyaffected,const
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