简介：Theanalysisoftheradiatednoiseofvesselsgiveninthispapershowssomestrongsuperposedlinecomponentsinlowfrequencyspeetrumbelow100Hzoccurringatdiscretefrequencieswhichcorrespondwiththerotationspeedofpropellershaft,orpropellerbladefrequency,ortheirharmonicfre-quencies.sincethelinecomponentsreflectpropeller＇workingcharacteristics,thepropller＇sfeaturescanbeextracteddirectlyfromlow-frequencylinecom-ponentsinadditiontodemodulatedlinecomponent.Sotherearetwowaystoextractthefeatures,oneisdirectway,theotherisdemodulationway.Detec-tionperformanceofthelinecomponentinbackground-noiseisdiscussedinthispaper.ThesignallevelisdefinedasthedifrerencebetweenthePDF＇s(ProbabilityDensityFunction)meanofthepeakofthelinecomponentandPDF＇smeanorthebackground-noise.Indircetwaythesignallevelofthelinecomponentisproportionaltothesignalnoiseratio(S/N).Indemodulationwaythesignallevelofdemodulatedlinecomponent

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简介：为有一个声学的向量传感器数组的二维的宽带Direction-of-Arrival(DOA)评价的一个靠近形式的算法被介绍。没有数组孔的损失，建议算法能应付协调消息提供者，并且不为DOA参数要求一个搜索过程。估计的方位角和举起角度能是自动地，paired.Simulation结果被介绍表明建议方法的有效性。

简介：Inthispaper,theoceanacousticchannelisconsideredasatime-variantchannel.Inordertoanalysetheconjointtime-shift-fre-quency-delaydistributionorthefadingandspreadstatisticalcharacteristicsofthechannel.TheTDWVS(TwoDimensionalWigner-VilleSpectrum)ofthetime-variantchannelisdefined.TherelationbetweentheWVS(Wigner-VilleSpectrum)oftheinputandtheoutputofthechannelisdiscussedandsomeexamplesforthespecificchannelareshown.Finally,theapplicationsonthedetectionofsignalsinnoiseusingtheWVSandTDWVSaregivenandtheadvantageisobvious,whenthedetectedsignalislinearfrequency-modulationsignal.

简介：Twocoupled-modemethods,namelyDGMCM(Direct-Global-MatrixCoupledModeMethod)andCCMM(ConsistentCoupled-ModeMethod),areanalyzedandcompared.First,bothofthesetwomethodsprovidetwo-waysolutions,andhencetheyareaccuratemodels.Second、theseriesoflocalverticalmodesinDGMCMconvergesasfastasthatinCCMM,whereasDGMCMhasamoretolerablerequirementofthenumberofsegmentsthanCCMM.Third,thesetwomodelsobtainthefieldsolutionbysolvingthecoupled-modesystemwithdifferentcoefficientmatrices,inwhichthecomputationaletfortfortherequiredparametersisalmostthesame.Finally,DGMCMcanhandlesomeproblemswhicharedifficultforCCMM,suchasinawaveguidewitharoughbottom,alinesourcelocatedrightontopofaslopingbottom,orinthepresenceofmultiplesources.InDGMCM,closed-formexpressionsforcouplingmatricesinatwo-layerwaveguidearegiven.Inaddition.theformulationfortheline-sourceprobleminplanegeometryisderivedtoupdateCCMM.

简介：Simpleandefficientsurfaceacousticwave(SAW)two-portresonatorswithlowinsertionlossandhighQ-valuesonST-Xquartzsubstrateusingacorrosion-proofA1/Au-stripeelectrodestructurearedevelopedforgassensing.Itwascomposedoftwoshortedgratingreflectorsandadjacentintedigitaltransducers(IDT),andanactivemetalfilminthecavitybetweentheIDTsforthesensitivefilmcoating.Thedevicesareexpectedtoprovidegoodprotectiontowardsmetalelectrodeforgassensorsapplicationinchemicallyreactiveenvironments.Excellentdeviceperformanceaslowinsertionloss,highQfactorandsingle-modeareachievedbycarefullyselectingthemetallicelectrodethickness,cavitylengthandacousticaperture.Priortofabrication,thecouplingofmodes(COM)modelwasperformedfordevicesimulationtodeterminetheoptimaldesignparameters.Thefabricatedsingle-modeSAWresonatoratoperationfrequencyof300MHzrangeexhibitsmatchedinsertionlossof~6.5dBandloadedQfactorinthe3000range.Usingthefabricatedresonatorasthefeedbackelement,adualresonator-oscillatorwithexcellentfrequencystability(0.1ppm)wasdevelopedandevaluatedexperimentally,anditissignificantforperformanceimprovementofSAWgassensor.

简介：在坚硬地在任意的角度连接的二个无限的盘子的角落接口的颤动精力传播被波浪途径学习以便调查堵住使用减少把波浪传播弄弯的飞机的质量的效果。二个本地坐标系统被介绍，暗示管理盘子的典型阻抗或堵住质量的相应比率的六个新非维的系数被介绍简化传播和思考系数的明确的表达。五件样品在experiment.Discussions被测试以插入损失基于在预言和实验之间的比较被执行。在角落接口堵住质量象“一个lowpass过滤器”一样行动，这被结束，为在某些频率上面的颤动变细有效。在“变细乐队”的TL和IL的价值每每统一一些堵住的团在惯性的集体时刻统一“变细乐队”的长度和乐队宽度主要取决于质量。

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简介：Withtheadvantagesoftransmittingenergyfrommultipledirectionstoonedirectionandtransformingvibrationfromonesourcetomultipledirections,thetwo-dimensionalvibrationdirectionconverterhasimportantapplicationsinpowerultrasonictechnology.However,forthecomplexityofusingthewaveequationtodesignandanalysisthetwo-dimensionalvibrationdirectionconverter,aconciseequivalentcircuitfortheconverterisinvestigated.Byintroducingthetwo-dimensionalmechanicalcouplingcoefficientandthelongitudinalforcetransformcoef-ficient,andusingtheelectromechanicalanalogyprinciple,theequivalentcircuitandresonancefrequencyequationofthetwo-dimensionalvibrationdirectionconvertervibratinginanti-phaseandin-phasetwo-dimensionalcoupledvibrationarededuced.Theresonancefrequenciesofthevibrationdirectionconvertersoftwodifferentmaterialsarecalculatedbyusingtheproposedfrequencyequation,whichareinagreementwiththeresultsfromthefiniteelementmethodandtheexperimentaltest.Itprovidesaconcisemethodforthedesignandapplicationsofsuchultrasonicvibrationsystem.

简介：Thefinite-dmerencetime-domam（FDTD）methodisproposedforanalyzingthesurfaceacousticwave（SAW）propagationintwo-dimensional（2D）piezoelectricphononiccrystals（PCs）atradiofrequency（RF）,andalsoexperimentsareestabhshedtodemonstrateitsanalysisresultofthePCs’bandgaps.TheFDTDmethodtakesthepiezoelectriceffectofPCsintoaccount,inwhichperiodicboundaryconditionsareusedtodecreasememory/timeconsumptionandtheperfectlymatchedlayerboundaryconditionsareadoptedastheSAWabsorberstoattenuateartificialreflections.TwoSAWdelaylinesareestabhshedwith/withoutpiezoelectricPCslocatedbetweeninterdigitaltransducers.Byremovingseveralechoeswithwindowgatingfunctionintimedomain,delaylinestransmissionfunctionisachieved.ThePCs’transmissionfunctionsandbandgapsareobtainedbycomparingtheminthesetwodelaylines.WhenAluminum/128°YX-LiNbO3isadoptedasscatterandsubstratematerial,thePCs’bandgapiscalculatedbythisFDTDmethodandCOMSOLrespectively.ResultsshowthatcomputationalresultsofFDTDagreewellwithexperimentalresultsandarebetterthanthatofCOMSOL.