欢迎来到人人文库网! | 帮助中心 人人文库renrendoc.com美如初恋!
人人文库网
首页 人人文库网 > 资源分类 > PDF文档下载

外文资料--Numerical Simulation Method of Acoustic Field Positive Problem based on Magnetoacoustic Tomography with Magnetic Induction.PDF

  • 资源大小:319.56KB        全文页数:4页
  • 资源格式: PDF        下载权限:游客/注册会员    下载费用:1
游客快捷下载 游客一键下载
会员登录下载
下载资源需要1

邮箱/手机:
温馨提示:
支付成功后,系统会根据您填写的邮箱或者手机号作为您下次登录的用户名和密码(如填写的是手机,那登陆用户名和密码就是手机号),方便下次登录下载和查询订单;
特别说明:
请自助下载,系统不会自动发送文件的哦;
支付方式: 微信支付    支付宝   
验证码:   换一换

 
友情提示
2、PDF文件下载后,可能会被浏览器默认打开,此种情况可以点击浏览器菜单,保存网页到桌面,既可以正常下载了。
3、本站不支持迅雷下载,请使用电脑自带的IE浏览器,或者360浏览器、谷歌浏览器下载即可。
4、本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰   

外文资料--Numerical Simulation Method of Acoustic Field Positive Problem based on Magnetoacoustic Tomography with Magnetic Induction.PDF

NumericalSimulationMethodofAcousticFieldPositiveProblembasedonMagnetoacousticTomographywithMagneticInductionHuiXia1,GuoqiangLiu1,YanhongLi1,YangZhang1,ShiqiangLi1andLaifuZhang21.InstituteofElectricalEngineering,ChineseAcademyofSciencesBeijing,China2.ShanxiElectricPowerResearchInstituteShanxi,Chinaxiahuimail.iee.ac.cnAbstractMagnetoacousticimpedancetomographywithmagneticinductionMAT-MIisanewimagingmethod.Itsimagesreflectconductivitydistribution.Inthispaper,wefirstlyproposedthenumericalsimulationmethodofmulti-physicsfieldscouplingtoobtainthedistributionofacousticfieldinMAT-MIwithoutthestaticmagneticfield.Simpleacousticdetectionexperimentsareconductedtovalidatethealgorithm.Theresultsdemonstrateditsfeasibility,andmayprovidesometheoreticalfoundationforthefurtherresearchonthereal-timedetectionofacousticsignalsandthereconstructionmethodoftheMAT-MI.Keywords-magnetoacoustictomographywithmagneticinductionMAT-MI,Multi-physicsfieldscoupling,two-dimensionalaxisymmetricmodel,numericalsimulationofacousticfieldI.INTRODUCTIONAsakindoffunctionalimaging,ElectricalimpedancetomographyEIThasmanypredominancecomparedwithconventionalimagingmeans,suchasnon-invasivediagnose,highimagingqualityandsoon.ButEIThasnotbeenusedinclinicalapplicationbecauseofit’slowresolutionnow[1-3].Inordertoresolvetheproblem,MagnetoacoustictomographywithmagneticinductionMAT-MIisproposedbyBinHeetal[4],whichisshowninFig.1.InMAT-MI,imagingtargetisplacedinastaticmagneticfieldwithpulsedmagneticstimulationimposedonit,thepulsedcurrentinduceseddycurrentinthesample,andtheinducededdycurrentinstaticmagneticfieldgeneratesLorentzforce.TheLorentzforcecausesacousticvibration,andthegeneratedacousticwavecanbemeasuredaroundthesampletoreconstructtheconductivitydistributionofthesample.Figure1.TheillustrationofMAT-MIquotedfrom[4]OnthebasisoftheprincipleMentionedabove,weproposeanewnon-static-magnetMAT-MImethod.Inthispaper,weanalyzetheprinciplesofmulti-physicsfieldscoupling,includingthetwo-dimensionalaxisymmetrictransientelectromagneticfield,displacementfield,soundfield,andputforwardthemethodofmulti-physicscalculations.Onthebasicofaboveall,theformulaforcalculatingthevariousfieldsarederivedindetail,andconductthesimpleacousticdetectionexperimentstovalidatethemethod.II.THENUMERICALSIMULATIONMETHODOFMULTI-PHYSICSFIELDSCOUPLINGThemethodadoptsimpulsingpowersourceasthedrivingsource,excitingcoilgeneratesalternatingelectromagneticfieldwhichexcitesLorentzforceinthesample.TheLorentzforcecausesvibrationofsampleboundary,thenacousticwavesisexcitedintheair.Wecaninversethesampleresistivitybydetectingacousticwavesignal.Thesoundfielddistributionofthesamplecanbesimulatedthroughsolvingthemulti-physicalequationwhichincludeselectromagneticequation,wienerequationofelasticsolidsandsoundfieldequationintheair.A.TheequationofaxisymmetricelectromagneticfieldsTheexcitingcoilishollowcylindricalcoil,androundcoppersheetisselectedasthesample,thesimulationmodelhasaxialsymmetry,sothevectormagneticpotentialAKonlyhascircumferentialcomponent,labeledasA,thecorrespondingaxisymmetricelectromagneticequationis22s2A1AAAAJrrrrzt∂∂∂∂−−σ−∂∂∂∂1Whereismagneticpermeability,σiselectricalconductivity,andsJiscurrentdensityoftheexcitingcoil.Althoughthecurrentdensityoftheexcitingcoilgeneratesonlycircumferentialcomponent,magneticfluxdensityincludesradialandaxialcomponent,wecangetAJt∂−σ∂978-1-4244-4713-8/10/25.002010IEEErABz∂−∂zAABrr∂∂2Inordertoavoidthesingularityattheboundarywhichrequalstozero,sosupposeuistheratioofAandr,thentheEq.2becomes222suuuuur3rrrJrrztt∂∂∂∂∂−σ−ε−∂∂∂∂∂3OnbothsidesoftheEq.3aremultipliedby2r,wecanget222323332suuuuur3rrrrJrrrztt∂∂∂∂∂−σ−ε−∂∂∂∂∂4Ifnotetherandzforxandyrespectively,weget233332s2uuuuxxxxJxxxyytt⎛⎞∂∂∂∂∂∂⎛⎞−σ−ε−⎜⎟⎜⎟∂∂∂∂∂∂⎝⎠⎝⎠5FromtheEq.5,wecansee⎟⎟⎠⎞⎜⎜⎝⎛∂∂∂∂⎟⎠⎞⎜⎝⎛∂∂∂∂yuxyxuxx33isthe3ux∇⋅∇underrectangularcoordinatesystem,wecanget23332s2uuxuxxJxtt∂∂∇∇−σ−ε−∂∂6AccordingtothesolvingrangeoftheFig2a,wecanseethatΩ1istheairrange,Ω2isthesampleposition,Ω3istheexcitingcoilposition.IntheΩ1area,conductivityequalszero,andthereisnoexcitingsource.IntheΩ2area,thereisalsonoexcitingsource.IntheΩ3area,thecurrentinthecoilisthesourcecurrent.Thenequationofthethreesolvingareascanbewroterespectively3xu0∇−∇7−133uxux0t∂∇−∇σ∂7−232sxuJx∇−∇7−3Atthesymmetryaxisandinfinityboundary,theboundaryconditionisthatuequalszero.So,afterobtainingtheu,substitutingrAU/intoEq.1,wecangetelectricfieldintensityandmagneticfluxdensityAuErtt∂∂−−∂∂,ruBrz∂−∂,zuBr2ur∂∂81Ω2Ω3Ω2Γ3Γ2Ω3Ω2Γ3Γ1Γ1Ω2Ω3Ω2Γ3ΓFigure2.Solvingmodels(aElectromagneticfieldsolvingmodel(bdisplacementfieldsolvingmodel(cSoundfieldsolvingmodelBasedonEq.8,wecanget.sFJBKKK9B.AxisymmetricNavierequationsofelasticsolidsAcordingtothetheoryofcontinuummechanics,thewienerequationofelasticsolidcanbederivedthroughusingmomentumconservationprinciple,lawofconservationofmassandconstitutiveequationofmechanicalpropertiesinaninertialreferenceframe.Thevectorformofthewienerequationcanbewroteas222uGGuuFt12v∂ρ∇∇∇⋅∂−KKKK10Whereuurzt,,Kisdisplacementfield,FKisunitvolumeforce,ρisdensityofcoppersheet,Gisshearmodulus,andvisPoisson’sratio.Underthecylindricalcoordinates,Eq.10canbewrote22rrrr22uuGGuF12rrt∂∂θ⎛⎞∇−ρ⎜⎟−ν∂∂⎝⎠10−122zzz2uGGuF12zt∂∂θ∇ρ−ν∂∂10−2rrzuuuurrz∂∂θ∇10−3Where2ru∇、2zu∇、r∂θ∂andz∂θ∂canbewrote222rrrr22uuu1urzrr∂∂∂∇∂∂∂11−1222zzzz22uuu1urzrr∂∂∂∇∂∂∂11−2rzrr2uuuu1rrrzrrr∂∂∂∂θ∂⎛⎞−⎜⎟∂∂∂∂∂⎝⎠11−3rzruuu1zzrzrz∂∂∂∂θ∂⎛⎞⎜⎟∂∂∂∂∂⎝⎠11−4Inordertovoidthesingularityattheboundary,supposeorruur,andsubstitutingroruuintoEq.10-1,andOnbothsidesoftheequationmultipliedbythe2r,wecanget22323ororor22223orzr22G1uuur3rGr12rrzuuGrFr12rzt−ν⎛⎞∂∂∂⎜⎟−ν∂∂∂⎝⎠∂∂ρ−ν∂∂∂12Thesolvingrangeisshowninfigure2b,theboundaryconditionscanbewroteatthe2Γand3ΓsFnp−KK13WheresnKisunitnormalvectorwhichpointingtheoutsideofthesampleorcoil.C.AxisymmetricacousticwaveequationIntheexperiment,becausethereisnoLorentzforceintheair,theacousticwaveequationinthesolvingrangeofFig2ccanbewroteas222210ppct∂∇−∂14Inthecylindricalcoordinate,wecanget2222222110∂∂∂∂−−−∂∂∂∂ppppctrrrz15Wheretheboundaryconditionisr0attheaxisofsymmetry,andp0attheinfinitepoint.Onthe2Γand3Γ,theboundaryconditionareasfollows,22unpnt∂⋅∇⋅∂KK16AccordingtotheEq.10Eq.16,wecansolvethesoundwavedistributioninthesoundfieldofthesample.III.EXPERIMENTSA.SimulationexperimentInthesimulationprocess,thewaveformofexcitingcurrentcanbeshownasfollow0sin−tVItetLαωω17wheredischargevoltage0V1000V,inductionL7.7μH,resistanceR8.06e-3Ω,capacityC200μF,αR/2L,21/LCωα−.Inthecourseofpracticalapplication,thecurrentwaveformisinterceptedbyathyristor,andonlyreservesthefirstpositivespike.Theimpulsewidthisabout120μS,numericalsimulationresultofsoundfielddistributionat60μSisshownbelowinFig.3.Figure3a.Atthetimeof60μs,soundfielddistributionoftheexcitingcoilitselfFigure3b.Atthetimeof60μs,soundfielddistributionofthesampleFromtheFig.3a,wefindthatthesoundfielddistributionofexcitingcoilcanbeapproximatelyconsideredasacircularringwhosecenteristhecoil’stheinsideandoutsideboundaries,andatthesymmetryaxis,thesoundfieldisthestrongest.Atthesametime,wefind,inthedisplacementy0,theacousticsignalstrengthgeneratedbycoilitselfisweak,itcanbeshieldedbymeansofsomemeasuresthatcaneffectivelyeliminatetheinfluenceofacousticsignalgeneratedbythecoilitself.0.000000.000030.000060.000090.00012-250000-200000-150000-100000-50000050000100000150000Signalintensity/a.uTime/s0.00050.0010.0020.0050.0080.01Figure4a.Atx0,thesimulationacousticsignal0.000000.000030.000060.000090.00012-200000-1000000100000Signalintensity/a.uTime/s00.00050.0020.0050.010.15Figure4b.Aty0.0005,thesimulationacousticsignalInFig.3b,wecanseethatsoundfielddistributionconcentratearoundtheaxisofsymmetry.Inordertofurtherunderstandthecharacteristicsofacousticsignals,weselectthedifferentcoordinatepointstosimulatetheacousticsignal,andthetime-stepsetto10μS.Afterachievingtheacousticsignalofthevariouspoint,thecontinuous120μSdataweresegmentedinto0.1μSepochsforFFTtransformandobtainthesignalfrequency.Intheaxisofx0,weobtainthesimulationacousticsignalshowninFig.4a,andintheaxisofy0.0005m,weobtainthesimulationacousticsignalshowninFig.4b.Afteranalysisandcalculation,wefindthatthefrequencyofacousticwavesignalmainlyconcentrateintherangeof3-5KHzinthesphericalsoundfieldrangewhosecenteristhesample’scenterandradiusisapproximately0.005m.B.AcousticdetectionexperimentWeadopttheexperimentalsystemtodetectthesoundfieldofthecoppersheetsample.Withregardtoadetaileddescriptionoftheexperimentcanrefertoliterature[5].Inthesphericalsoundfieldrangewhosecenteristhesample’scenterandtheradiusisapproximately0.005m,theacousticsignalunderexcitationisdetected.ThenweprocessthedetectedsoundsignalbyFFT,andobtainsignalspectrum.TheacousticsignalofmeasurementpointtisshowninFig.5.Figure5.Detectedacousticwavesignalandit’sspectrumAftermulti-pointmeasurementandanalysis,wefindthatthefrequencyofdetectedsoundwavesignalmainlyconcentrateinthespectrumrangeof3-5KHz,itisconsistentwiththesimulationresults.Itprovesthatthesimulationmethodofmulti-physicalfieldcouplingiscorrect,themethodofMAT-MIisfeasible.IV.CONCLUSIONMedicalimagingisaresearchdomainwithbroaddevelopmentprospect,itisessentialtotheadvancementofmedicineandimprovementofpeople’slife.Inthispaper,ourmethodshowsthatitispossibletocompletetwo-dimensionalaxisymmetricacousticwavepositionproblemofMAT-MIwithoutthestaticmagneticfield.ItcanbeseenasthetheoreticalreferenceforthefuturestudyonMAT-MI.ACKNOWLEDGEMENTSTheauthorsthanktheNationalNaturalScienceCouncilofChinaforfinancialsupportGrantNo.60802086,50977084,FoundationofChinaPostdoctorGrantNo.20090450570,BeijingNovaProgramGrantNo.2009B48andtheNationalHighTechnologyResearchandDevelopmentCouncilofChinaGrantNo.2007AA06Z212.REFERENCES[1]V.Cherepeninetal.A3DelectricalimpedancetomographyEITsystemforbreastcancerdetection[J],Physiol.Meas.,2001.221,918.[2]J.P.MorucciandB.Rigaud.BioelectricalimpedancetechniquesinmedicinepartIIIImpedanceimagingthirdsectionMedicalapplications[J].Crit.Rev.Biomed.Eng,1996.244-6655677[3]A.D.Seagar,D.C.Barber,B.H.Brown.TheoreticalLimitstoSensitivityandResolutioninImpedanceImaging[J].Clin.Phys.Physiol.Meas.,1987.81331.[4]X.Yuan,B.He.MagnetoacousticTomographywithMagneticInductionMAT-MI[J].Phys.Med.Biol.,2005.5051755187.[5]H.Xia,G.Liu.etal.ImagingMethodofNewMagneto-acousticImpedanceTomographywithMagneticInductionProcedingsofsecondinternationalconferenceonSportsScienceandSportsEngineeringSSSE2009,99-103

注意事项

本文(外文资料--Numerical Simulation Method of Acoustic Field Positive Problem based on Magnetoacoustic Tomography with Magnetic Induction.PDF)为本站会员(英文资料库)主动上传,人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知人人文库网(发送邮件至[email protected]或直接QQ联系客服),我们立即给予删除!

温馨提示:如果因为网速或其他原因下载失败请重新下载,重复下载不扣分。

关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服客服 - 联系我们

网站客服QQ:2846424093    人人文库上传用户QQ群:460291265   

[email protected] 2016-2018  renrendoc.com 网站版权所有   南天在线技术支持

经营许可证编号:苏ICP备12009002号-5