简介：Thedesignandoperationofhighvolumeconveyorsystemsindistributioncentersareimportantduetoitshighcost,largefootprintandcriticalroleinthesystem.However,thereisnoanalyticalmodelavailable.Inthispaper,westudythecharacteristicsoftheconveyorsortationsystem,developagenericmodelofacomplexconveyornetwork.WethenusetheDelayandStockabstractiontodevelopanapproximateanalyticalmethodusingsamplepathanalysisanddynamicnetworkflowmodel.Thedecisionvariablesincludelengthofaccumulationsegmentsandthespeedsofconveyorcomponentsaforementioneddecisionvariables.Thisanalyticalsolutionprovidesfasteranalysis,insightsandusefulsubgradientwithrespecttothedecisionvariables.

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简介：Particlemotioninascrewconveyorwassimulatedw让hthediscreteelementmethod.Theparticleflowbehaviorandtransportprocessesatdifferentscrewrotatingspeedsandfillinglevelswereinvestigatedinthisstudy.Thespatialdistributionsofparticlevelocitywerepredicted.Thepredictedmassflowrateincreasedw让hincreasingscrewrotatingspeedandfillinglevel.Thecontactforcesandgranulartemperaturesofparticleswerealsocalculated.Thesimulationresultsshowedthatthetranslationalgranularparticletemperatureswerehigherthantherotationalgranularparticletemperatures.Inadd让ion,theconfigurationaltemperaturesofparticleswerecalculatedfromsimulatedinstantaneousparticleoverlaps,andresultsindicatedthatdeformationofelasticparticlescontributedtotherateofenergydissipation.Goodagreementbetweenthenumericalsimulationandexperimentalresultswasachievedinthisstudy.

简介：AheavyrainstormnamedBeijing“7.21”heavyrainstormhitBeijingon21to22July2012,whichisrecordedasthemostsevererainstormsince1951.ThedailyprecipitationamountinmanystationsinBeijinghasbrokenthehistoryrecord.BasedontheNCAR/NCEPreanalysisdataandprecipitationobservation,thelarge-scaleconditionswhichcausedthe“7.21”heavyrainstormareinvestigated,withtheemphasisontherelationshipbetweenitandanequatorialconvergencezone,AsiansummermonsoonaswellasthetropicalcycloneovertheoceanfromthePhilippinestotheSouthChinaSea(SCS).TheresultsindicatedthatagreatdealofsoutherlywarmandwetmoisturecarriedbynorthwardmigratingAsiansummermonsoonprovidedplentyofmoisturesupplyingforthe“7.21”heavyrainstorm.Whenthewarmandwetmoisturemetwiththestrongcoldtemperatureadvectioninducedbycoldtroughsorvortexes,anobviouslyunstablestratificationformed,thusleadingtotheoccurrenceofheavyprecipitation.Withoutthiskindofintensemoisturetransport,therainstormonlyrelyingontheroleofthecoldairfrommid-andhigher-latitudescouldnotreachtherecord-breakingintensity.FurtherresearchsuggestedthatthenorthwardmovementofanAsianmonsoonalwarmandwetmoisturetransportconveyor(MWWTC)wascloselyrelatedwiththeactivephaseofa30-60dayintra-seasonaloscillationoftheAsiansummermonsoon.Duringthistime,themonsoonsurgetriggeredandmaintainedthenorthwardmovementoftheMWWTC.Inaddition,comparedwithanotherheavyrainstormnamed“63.8”heavyrainstorm,whichoccurredovertheHuaiheRiverBasininthemid-August1963andseriouslyaffectedNorthChina,asimilarMWWTCwasalsoobserved.ItwasjusttheintenseinteractionoftheMWWTCwithstrongcoldairfromthenorththatcausedthissevererainstorm.