简介:Acoupledmodel,whichisemployedtostudythedominatingfactorandkeyareaofElNinocycleformation,consistsofadynamicaloceanmodelandastatisticalatmosphericmodel.ThecoupledmodelwithseasonalforcingsuccessfullyreproducestheElNinoeventcyclewhichexhibitsquasi-regularoscillationswithapreferredperiodofabout4years.Theresultsshowthattheheatcontent(HC)istransportedbetweentheeasternandthewesterntropicalPacificareas.ThespatialdistributionofHCanomaliesforfourphasesofthewholecycleclearlyshowsapossibleformationmechanismofElNino.ExperimentsfurthersuggestthatseasurfacetemperatureinthetropicalPacificandHCinthecentraltropicalPacificarethemostimportantfactorsandthecentraltropicalPacificisthemostimportantareafordeterminingformationofElNinocycle.
简介:LongbeforethediscoveryofHelicobacterpylori,thereweremanyexcellentobservationalstudiesthatdocumenteddifferencesinthepatternsofgastroduodenaldisease.Itwasclearthatinthedevelopingworld,gastriculcerandgastriccancerweremorecommonthaninthedevelopedworldwhereduodenalulcerpredominated.Thiscorrelatedwiththedistributionofgastritisinduodenalulcerpatientswheretheinflammationwasantralpredominantwhileingastriculcerpatientsthegastritiswasmoreevenlydistributedthroughthestomach.Gastriculcersusuallyappearedinafairlyrestricteddistributioninthestomachneartheangulusandclosetothetransitionalzonebetweenantrumandbodymucosa.Asasocietydevelopedsothesepatternsofdiseasechanged.
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简介:Anumericalsimulationisperformedtofindoutakeyvorticalstructureinthelaminar-turbulenttransition.Alow-speedstreakisgeneratedinsidealaminarboundarylayerusinganisolatedcuboidroughness,aimedatprovidinganenvironmentunstabletoouterdisturbances.Then,ashortdurationjetisissuedintotheboundarylayer.Whenthejetvelocityislow,somevorticesappearintheboundarylayer,butthetransitionoftheboundarylayerdoesnottakeplace.However,whenthejetvelocityexceedsacertainthreshold,twovorticesnewlyappearabovetheelongatedlegsofaV-shapedvortexandonlyoneofthemisstretchedandsurvives.Afterthat,vorticesaregeneratedoneafteranotheraroundthesurvivedone.Bycomparingthedecayedandthesurvivedvortices,itisfoundthatthedifferenceintheirheightsisthekeycharacteristicwhichleadstothetransition.