简介：Itisusuallydifficulttomeasureacousticvelocitiesthroughacasing,especiallywhenthecasingispoorlybondedwithformation.AnacousticloggingtechniqueusingthedualsourceofoppositepolarityisproposedtoenhancetheSignaltoNoiseRatiooftheformationsignalandtoreducethecasingwaveinthedataacquisitionprocess.Inwhatfollows,atheoreticalmodelingisusedtocaculatethewavefromsofcasedwells.Andthen,ascaledexperimentwasconductedinthe1:10scaledexperimentalwellusingtheproposedtechniqueinthepoorlybondedcondition.Theresultsshowthatthistechniquecaneffectivelysuppressthecasingwaveandenhancetheformationwave,eveninthepoorly-bondedcondition.Byanalyzingthemeasuredwavefroms,theamplitudeofcasingwaveisreducedto12%comparedtotheconventionalone-sourcetechnique,andthecompressionalwavevelocitycanbeeasilyobtainedbyusingthistechnique.Boththetheoreticalmodelingandexperimentresultsdemonstratethefeasibilityoftheproposedtechnique.Thisstudyestablishesthetheoreticalandexperimentalfoundationforthecased-hole,dualsourceofoppositepolarity,acousticloggingtooldevelopment.

简介：Adual-excitedfull-wavelengthpiezoceramicultrasonictransducerasacascadeoftwohalf-wavelengthsandwichpiezoceramictransducersisstudied.Therelevantparameters'expressionsofthefigureofmeritNforthetransducerarederived,andtheeffectsofthestructureandmaterialparametersofthetransduceronitscharacteristicsarefurtheranalyzedbynumericalcalculation.Theresultsshowthatwhenthetwopiezoceramicstacksarerespectivelylocatedatthedisplacementnodesoftheirownhalf-wavelengthtransducers,orthetwopiezoceramicstackshavethesamenumberofpiecesinthecaseofacertainnumberofpiezoceramicpieces,thefigureofmeritofthetransducercanreachamaximum.Withincreasingofthenumberofpiezoceramicpiecesinafairlylargerange,thefigureofmeritofthetransducerslightlydecreases,buttheforcefactorofthetransducerincreasesrapidly.Themetalmaterialsofthetransducerhavelittleeffectonitsfigureofmerit.Thusitcanbeseenthatthedual-excitedfull-wavelengthtransducercaneffectivelyincreasethevolumesofthepiezoceramicstacksinthecaseofthatthetransducer'scomprehensiveperformancehasonlyalittlebitofdegradation,soit'spowercapacityandloadcapabilitycanbedramaticallyimproved,whichmeansthetransducerismoresuitableforhighpowerandheavyloadapplications.

简介：双交换边界元素方法(DRBEM)被使用与三维的潜在的流动预言管和silencers的声学的特征，并且基本原则和建议方法的数字过程是到常规边界元素方法(CBEM)的introduced.Compared，DRBEM在声学的管理方程考虑流动马赫数字的第二个顺序术语，它对有更高的马赫数字的状况合适亚声的flow.The四杆的parame