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简介：Acoupled-modesoundpropagationmodelwithcomplexeffectivedepthispresented,inordertoinvolvetheeffectofbranchlineintegralforacousticfieldinarange-dependentwaveguide.Theequationsofmotionandcontinuityareusedtoobtainthecoupledequations,whichsatisfyboundaryconditionsinthewaveguidewithvaryingtopographyandcontainonecouplingmatrix.Meanwhile,thecouplingsbetweendiscreteandcontinuousspectrumaredealtwithbasedoncomplexeffectivedepththeory.Numericalsimulationsshowthattheaccuracyoftransmissionlossisimprovedbythecoupledmodemodelwheneigenvaluesoftrappedmodesarelocatednearthebranchpoint.Theacousticfieldinanon-horizontallystratifiedwaveguidecanbecalculatedefficientlyandaccuratelybythismodel,andtheenergycorrespondingtotrappedmodes,leakymodesandbranchlineintegralcanbeconsideredadequately.

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简介：AmethodtoidentifycomplexYoung’smodulusofviscoelasticmaterialsusingforcedlongitudinalvibrationofslenderrodsisproposed.Themethoddiffersfromthebeamone.Experimentaltestswerecarriedoutatroomtemperaturewithdifferentlengthsin108mm,100mm,90mm,83.5mm,80mm.74.5mm,70mmforthepolycarbonatebars,andthecurvesofratiosA2/A1betweentwoendsofaviscoelasticbarversusfrequenciesareobtained,furthermore,thecorresponding3dBbandwidthandthestorageandlossmoduluscanbecalculated.SufficientnumberofobtainedcomplexYoung’smodulusatdifferentfrequencyallowsustocalculateotheronesusingtheleastsquaremethod.Ifthestepofthetestedfrequencyis5Hz,themaximumerrorofresultscanbelessthan6%.Bycomparisonwiththemeasurementmethodswhichthepreviousliteraturementioned,thisnewmethodsimplifiesthecalculation,andthephysicalmeaningappearsapparentlyandclearly.

简介：ThispaperreportsastudyofcomplexfocussingacousticfieldsofaconvexphasedarrayprobewidelyusedinultrasonicdiagnosticB-scanner.Thetimedelaynecessaryforelectronicfocussingandforgeometricfocussingofcomplexfocussingisgiven.BymeansofHelmholtz‘sintegralformula,theexpressionsofacousticfieldswereobtainedfortheelectronicfocussingandcomplexfocussing.Withsimpson‘snumericalintegral,agreatdealofcomputationswascarriedoutwithan86/330computer.Bymeansofusingdifferentparameters,anoptimumfocalrangeandbeamwidthofa4sequenceselectronicandcomplexfocussingacousticsystemwasselected.WithanEUB-40ultrasounddiagnosticB-scannerproducedbytheHitachicompany,thelateralfocussingacousticfieldandlateralresolutioninanechoictankwerephotographedbylatticingmethodandtheexperimentalresultiscon-sistentwiththetheory.