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简介：Onthehypothesisthattheturbulentflowispracticallynotaffectedincharacterbypulsationoftheflow,theformulaforsoundpressurelevelofpulsedjetnoiseisobtainedin90°directionand1meterawayfromthenozzle.Thesteadyjetnoiseis,then,aspecialcasewhenthepulsatingfrequencyiszero.Theresultsagreewellwithexperiments.

简介：读故事，制造声音，并帮Zog解决怪物谜团。

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简介：Onthebasisofspectrummomentdescriptionofasignal,evolutionaryvectorisdeveopedtodescribeslowlytime-varyingnoiseprocesses.Itdescribesthemaintime-varyingpropertiesofasignal.Applicationstoaircraftflying-overnoisearepresented.

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简介：Consideringanopticalbistablesystemwithcross-correlatedadditivewhitenoiseandmultiplicativecolorednoise,westudytheeffectsofcorrelationbetweenthenoisesonthecorrelationfunctionC(s)usingtheunifiedcolorednoiseapproximationandtheStratonovichdecouplingansatzformalism.Theeffectsoftheself-correlationtimeTofthemultiplicativecolorednoiseandthecorrelationintensityλbetweenthetwonoisesarestudiedwithnumericalcalculation.ItisfoundthatC(s)increaseswiththeincreaseoftheself-correlationtimeT,butdecreaseswiththeincreaseofthecorrelationintensityλ.AtlargevalueofT,thereisalmostnochangeforC(s)whenTchanges.

简介：Inthispaperthepropertiesofspace-timecorrelationfunctionofthenoisefieldofmovingsourceinlayeredstatisticinhomogeneousmediumarestudiedandtheeffectsofrandomfluctuatingboundaryarecon-sideredaswell.Ithasbeenshown,theoreticallyandexperimentally,multi-pathpropergatingeffectscausethedispersionofthecorrelationfunctionandfluctuationsofthemediumrefractionindexandtheboundarycausethefluctuationofit.Theeffectofthemovementofthenoisesourceontheoutputofreal-timecorrelatorisequivalenttoalow-passfilteraddedthedriftofspace-timecorrelationfunction.Thesepropertiesofthecorrelationfunctioncausegravedegradationofthesignalprocessinggainofnoiserangingsonarsystem.Thefluctuatingandthedistortionofconrrelationfunctionmadeitdifficulttorealizethenoiseranging.Sointhispaper,amethodofspacecorrelationrangingbyalineararrayoffourpointswithshortseparationandlongspanandatechnigueofdual-correlationsignalp

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简介：在复杂添加剂噪音的环境的讲话端点察觉的一个方法被介绍。基于噪音的分析，静止噪音的一个适应模型被建议检测信号是nonstationary的节。然后，声音被它的泛音结构在这节检测，并且精确端点与典型算法用energy.Compared被寻找，这个算法在很真实的噪音环境可靠地操作。

简介：StabilizedorChebyshevexplicitmethodshavebeenwidelyusedinthepasttosolvestiffordinarydifferentialequations.MakinguseofspecialpropertiesofChebyshev-likepolynomials,thesemethodshavefavorablestabilitypropertiescomparedtostandardexplicitmethodswhileremainingexplicit.Anewclassofsuchmethods,calledROCK,introducedin[Numer.Math.,90,1-18,2001]hasrecentlybeenextendedtostiffstochasticdifferentialequationsunderthenameS-ROCK[C.R.Acad.Sci.Paris,345(10),2007andCommun.Math.Sci,6(4),2008].InthispaperwediscusstheextensionoftheS-ROCKmethodstosystemswithdiscretenoiseandproposeanewclassofmethodsforsuchproblems,theT-ROCKmethods.Onemotivationforsuchmethodsisthesimulationofmulti-scaleorstiffchemicalkineticsystemsandsuchsystemsarethefocusofthispaper,butournewmethodscouldpotentiallybeinterestingforotherstiffsystemswithdiscretenoise.TwoversionsoftheT-ROCKmethodsarediscussedandtheirstabilitybehaviorisanalyzedonatestproblem.ComparedtotheT-leapingmethod,asignificantspeed-upcanbeachievedforsomestiffkineticsystems.Thebehavioroftheproposedmethodsaretestedonseveralnumericalexperiments.

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简介：Theacousticperformanceofthestructureformeasuringcavitationnoiseistheoreticallyanalysed,andtwojudgingcriteriaoftheacousticperformanceofSTW（soundtransmissionwindow）arepresentedinthispaper.OneisofimpedancematchingbetweenworkingliquidandSTW:ρ1C1=ρ2C2.Theotherisofmaximumfrequency（orminimumwavelength）ofcavitationnoisespectrum:fmax≤c/60D(orλmin/D≥60).Ifeitherofthecriteriaismetreliablemeasuredresultsofcavitationnoisewillbeobtained.Thetheoreticalresultsareverifiedthroughexperi-ments.Accordingtothecriteria,thepaperanalysestheacousticperformanceofroutinelyusedplexiglassSTW.Theresultsshowthatintheresearchofclearwatercavitationtheimpedanceratio,2.18,doesnotsatisfyρ1C1=ρ2C2,andfmax≤C/60Dhardlyholdsforactualcavitationnoisespectrum.Therefore,plexiglassSTWisnotgoodenoughforsoundtransmission.Fromthispointofview,polyethyleneisbettersoundtransmissionmaterialthanplexi-glass.

简介：ThepaperestablishestwostochasticSIRSmodelswithjumpstodescribethespreadofnetworkvirusbycyberwar,terrorismandothers.First,addingrandomperturbationsproportionallytoeachvariable,wegetthedynamicpropertiesaroundthepositiveequilibriumofthedeterministicmodelandtheconditionsforpersistenceandextinction.Second,givingarandomdisturbancetoendemicequilibrium,wegetastochasticsystemwithjumps.BymodifyingtheexistingLyapunovfunction,weprovethepositivesolutionofthesystemisstochasticallystable.