简介：<正>Qingdao,itsnameissynonymouswithbeer.TsingtaoBeer,oneofthecountry’sfinest,hasputthecityfirmlyontotheinternationalscene.However,thereissomuchmoretothispearlonthecoastofShandongProvince.AsChinagoesforwardtothe2008Olympicsthecitywillbecomeevenbetterknownforithasbeenchosenasthevenuefortheoceansailingevents.QingdaooccupiesapeninsulajuttingintotheYellowSea.Itishilly,withacoastlineofrockyheadlandsconnectedbyfinecurvingsandybeaches.Itsnatural

简介：

简介：

简介：Inthispaperweproposeaspectralelement:vanishingviscosity(SEW)methodfortheconservationlawsonthesemi-infiniteinterval.Byusingasuitablemapping,theproblemisfirsttransformedintoamodifiedconservationlawinaboundedinterval,thenthewell-knownspectralvanishingviscositytechniqueisgeneralizedtothemulti-domaincaseinordertoapproximatethistrarsformedequationmoreefficiently.Theconstructiondetailsandconvergenceanalysisarepresented.Underausualassumptionofboundednessoftheapproximationsolutions,itisproventhatthesolutionoftheSEWapproximationconvergestotheuniciueentropysolutionoftheconservationlaws.Anumberofnumericaltestsiscarriedouttoconfirmthetheoreticalresults.

简介：

简介：Prestackreversetimemigration（RTM）isanaccurateimagingmethodofsubsurfacemedia.TheviscoacousticprestackRTMisofpracticalsignificancebecauseitconsiderstheviscosityofthesubsurfacemedia.OneofthestepsofRTMissolvingthewaveequationandextrapolatingthewavefieldforwardandbackward;therefore,solvingaccuratelyandefficientlythewaveequationaffectstheimagingresultsandtheefficiencyofRTM.Inthisstudy,weusetheoptimaltime-spacedomaindispersionhigh-orderfinite-difference（FD）methodtosolvetheviscoacousticwaveequation.Dispersionanalysisandnumericalsimulationsshowthattheoptimaltime-spacedomainFDmethodismoreaccurateandsuppressesthenumericaldispersion.Weusehybridabsorbingboundaryconditionstohandletheboundaryreflection.Wealsousesource-normalizedcross-correlationimagingconditionsformigrationandapplyLaplacefilteringtoremovethelow-frequencynoise.NumericalmodelingsuggeststhattheviscoacousticwaveequationRTMhashigherimagingresolutionthantheacousticwaveequationRTMwhentheviscosityofthesubsurfaceisconsidered.Inaddition,forthewavefieldextrapolation,weusetheadaptivevariable-lengthFDoperatortocalculatethespatialderivativesandimprovethecomputationalefficiencywithoutcompromisingtheaccuracyofthenumericalsolution.