简介：UltrasonicvelocitieshavebeenmeasuredinsinglephaseBi1.7Pb0.3Sr2CaCu2O8+xandBi1.7Pb0.3Sr2Ca2O10+xpolycrystallinesamples.Anomalouschangesofbothlongitudinalandtransversevelocitieswereobservednear200K,whichindicatesthatsomestructuralphasetransitiomightoccur.Theelasticconstantsofthesesampleshavebeendeterminedfromthemeasuredultrasonicvelocitydata,whicharemuchsmallerthanthoseofYBa2Cu3O7-yandBaTiO3,manifestingthattheinterlayercoup-lingwilldramaticallydecreasewhenthec-axesoftheunitcellsoftheseperovstite-likemultilayerceramicsincrease.ThevaluesofPoissonratio,however,ofthoseceramicsareveryclose,implyingsimilarinteratomicbondingforces.Correctedtovoid-freestate,theDebyetemperatureofthesematerialsisestirnatedas270±20k.ThetemperaturedependenceofDebyetemperaturesforthesematerialsisalsocalculatedbyusingthesamemethodandreportedforthefirsttime.

简介：

简介：

简介：Numericalanalysisofthree-dimensionalsoundpropagationinsoft-softorsoft-hardcircularductswithcircumferentialandaxialmodesofsoundsourcesattheinlethasbeencarriedout.Inthispaper,thenumericalmethodandthesamplesareofferedandtheeffectsofcircumferentialandaxialmodesonnumericalresultsarediscussedindetail.

简介：Regardforthefuzzinessandtherandomnessinsomeacousticfields,amethodforthenumericalanalysisofthe2DacousticfieldwithFuzzy-Randomparameterswasproposedbasedontheequivalentconversionofinformationentropy.Intheproposedmethod,afuzzyrandomacousticfieldwastreatedasapurefuzzyacousticfieldorapurerandomacousticfieldbytransformingallthevariablesintofuzzyvariablesorrandomvariables.Perturbationfiniteelementmethodsforanalyzingthetwo-dimensionalacousticfuzzyandrandomfieldarededuced.Thesoundpressureresponseofa2Dacoustictubeandthe2Dacousticcavityofacarwithfuzzy-randomparameterswereanalyzedbytheproposedmethodandtheMonteCarlomethod,theresultsshowthattheproposedmethodcanbewellappliedtothenumericalanalysisofthe2Dacousticfieldwithfuzzy-randomparameters,andhasgoodprospectofengineeringapplication.

简介：Foraccuracyandrapidityofaudioeventdetectioninthemass-dataaudioprocessingtasks,agenericmethodofrapidlyrecognizingaudioeventbasedon2D-HaaracousticsuperfeaturevectorandAdaBoostisproposed.Firstly,itcombinescertainnumberofcontinuousaudioframestobean'acousticfeatureimage',secondly,usesAdaBoost.MHorfastRandomAdaBoostfeatureselectionalgorithmtoselecthighrepresentative2D-Haarpatterncombinationstoconstructsuperfeaturevectors;thirdly,analyzesthecommonalityanddifferencesbetweensubcategories,thenextractscommonfeaturesandreducesdifferentfeaturestoobtainagenericaudioeventtemplate,whichcansupporttheaccurateidentificationofmultiplesub-classesanddetectandlocatethespecificaudioeventfromtheaudiostreamaccurately.Experimentalresultsshowthattheuseof2D-Haaracousticfeaturesupervectorcanmakerecognitionaccuracy5%higherthanonesthatMFCC,PLP,LPCCandothertraditionalacousticfeaturesyielded,andcanmakethetrainingprocessing7-20timesfasterandtherecognitionprocessing5-10timesfaster,itcanevenachieveanaverageprecisionof93.38%,anaveragerecallof95.03%undertheoptimalparameterconfigurationfoundbygridmethod.Aboveall,itcanprovideanaccurateandfastmass-dataprocessingmethodforaudioeventdetection.

简介：Anewapproachtodeterminealltheelectro-elasticconstantsofthepiezoelectriccrystalsinclass4mmhasbeenputforward.Asanexample,alltheconstantsofLithiumTetraborate（Li2B4O7）crystalhavebeenmeasuredbymeansoftheapproach.Theoutstandingadvantageoftheapproachisthatiton-lyneedstoemployinmeasurementthreecrystalplatesdifferentlyoriented.