简介：Fromtheevolutionaryvectordeacriptionofslowlysime-varyingnoiseprocess,ameasurefornon-stationarityisdeveloped.Itincludesboththenon-stationaritiesofpowerandofspectrumshape.Asasingleparameter,itisacomparablequantityfordifferentprocesses.Applicationtotheanalysisofprecisegearboxisprescnted.

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简介：Thesonarsystemswhichworkinshallowwaterenvironmentsuffergreatlyfrominfluencesofoceanicnoises,acousticpropagationseesawandmultipath.Withshallowwaterenvironmentandhigherrange-bearingresolutionofsonarsystems,therearenotenoughindependentscattererswithinaresolutioncellforthecentrallimittheoremtohold.Thereverberationenvelopeprobabilitydensityfunction(pdf)divergesfromRayleighpdf.Thenon-Rayleighpdfwithheaviertailsiscomplicated,anditisdifficulttoestimatethefunctionparametersaccuratelyinrealtime.WithCFAR(ConstantFalseAlarmRate)processingofthereverberationenvelopedata,whichattenuatestheheaviertailsdatavaluestotheestimatedbackgroundpowervalues,thedatareverberationistransformedfromnon-RayleighdistributiontoapproximatelyRayleighdistribution.Sinceitgetsridoftheinterferenceswhichaffecttheestimationofbackgroundpower,thedetectorcanestimatetheoceanicbackgroundpowerlevelmoreaccurately.Withtherationalestimationofbackgroundpowerlevel,theCFARdetectioncapabilityisbetterandrobust.Withprocessingofhighresolutionsonardata,itisshownthattheproposedalgorithmisefficient.

简介：Usingthetimereversal(TR)-reversetimemigration(RTM)mixedmethod,thenumericalanalysistowardstheacousticfieldfordetectionandlocationoftargetsinlayeredmediaisperformed.Firsttheapproachesandstepsofthenumericalanalysisandsimulationforacousticfieldareproposed,then,theacousticfielddistributionofsingletargetandmultipletargetsarefurthercomputedbyusingtheapproachesofsingleemission-multiplereceivingandmultipleemission-multiplereceiving.Thenumericalsimulationresultsindicatethattargetdetectionandlocationcanbewellrealized.Bycomparison,goodresultsareobtainedfromthebothtwoapproaches,butlargetime-consumingisobservedinwayofmultipleemission-multiplereceiving,andsowouldbeunacceptable.Additionally,theimprovedwayisalsoproposedformultipletargetdetection.

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简介：Inanon-freefield,theexistenceofdisturbingsourceswoulddestroythefree-fieldconditionrequiredbynear-fieldacousticholography,andconfusetheidentificationoftargetsourceduetothescatteringeffectcausedbydisturbingsoundfallingonthetargetsource.Tototallyremovetheinfluenceofdisturbingsource,amethodforrecoveringandreconstructingthetargetsoundfieldinanon-freefieldwasproposedbasedontheequivalentsourcemethodandthepressure-velocitymeasurement.Intheproposedmethod,thesoundfieldseparationtechniquewasfirstlyusedtoseparatethemixedsoundfieldintotheoutgoingfieldcomingfromthetargetsourceandtheincomingfieldcomingfromthedisturbingsource.Thenthescatteredcomponentcontainedintheoutgoingfieldwascalculatedbyusingthedisturbingsoundandthesurfaceimpedanceofthetargetsource.Finally,thesoundfieldradiatedbythetargetsourceinafreefieldwasobtainedbysubtractingthescatteredcomponentfromtheoutgoingfieldandwasfurtherusedtoreconstructthesoundfieldofthetargetsource.Theproposedmethodwasnumericallyandexperimentallytestifiedandtheresultsofboththesimulationandtheexperimentdemonstratedthevalidityoftheproposedmethod.

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