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简介：Responsespectralmomentsareusefulforsystemreliabilityanalysis.Usually,spectralmo-mentsarecalculatedbythefrequencydomainmethod.Basedonthetimedomainmodalanalysisofrandomvibrations,theauthorspresentanewmethodforcalculatingresponsespectralmomentsthroughresponsecorrelationfunctions.Themethodcanbeappliedtobothclassicalandnon-classicaldampingcasesandtothreekindsofrandomexcitations,i.e.,whitenoise,band-limitedwhitenoise,andfilteredwhitenoise.

简介：Globalpropertyisthenecessaryconditionwhichmustbesatisfiedbytheprovableformulas.Itcanhelptofindoutsomeunprovableformulathatdoesnotsatisfysomeglobalpropertybeforeprovingitusingformalautomatedreasoningsystems,thustheefficiencyofthewholesystemisimproved.ThispaperpresentssomeglobalpropertiesofvalidformulasinmodallogicK.Suchpropertiesarestructurecharactersofformulas,sotheyaresimpleandeasytocheck.Atthesametime,someglobalpropertiesofKunsatisfiableformulasetarealsogiven.

简介：Forsomelarge-scaleengineeringstructuresinoperatingconditions,modalparametersestimationmustbaseitselfonresponse-onlydata.Thisproblemhasreceivedaconsiderableamountofattentioninthepastfewyears.Itiswellknownthatthecross-correlationfunctionbetweenthemeasuredresponsesisasumofcomplexexponentialfunctionsofthesameformastheimpulseresponsefunctionoftheoriginalsystem.Sothispaperpresentsatime-domainoperatingmodalidentificationglobalschemeandafrequency-domainschemefromoutput-onlybycouplingthecross-correlationfunctionwithconventionalmodalparameterestimation.Theoutlinedtechniquesareappliedtoanairplanemodeltoestimatemodalparametersfromresponse-onlydata.

简介：Afrequencyandspatialdomaindecompositionmethod(FSDD)foroperationalmodalanalysis(OMA)ispresentedinthispaper,whichisanextensionofthecomplexmodeindicatorfunction(CMIF)methodforexperimentalmodalanalysis(EMA).ThetheoreticalbackgroundoftheFSDDmethodisclarified.Singularvaluedecompositionisadoptedtoseparatethesignalspacefromthenoisespace.Finally,anenhancedpowerspectrumdensity(PSD)isproposedtoobtainmoreaccuratemodalparametersbycurvefittinginthefrequencydomain.Moreover,asimulationcaseandanapplicationcaseareusedtovalidatethismethod.

简介：Theboundaryelementmethodforthemodalanalysisoffreevibrationfor3-Danisotropicstructuresusingparticularsolutionshasbeendeveloped.Thecompletepolynomialsofordertwoareusedtoconstructtheparticularsolutionsforgeneralanisotropicmaterials.Thenumericalresultsfor3-Dfreevibra-tionanalysisofanisotropiecantileverbeambythemethodpresentedisingoodagreementwiththeresultsus-ingtheRitztechnique.Foranisotropicmaterials,thenumericalresultscalculatedfromtheproposedmethodareingoodagreementwiththeresultsfromMSC.NASTRAN.

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简介：Thepropagationofmultipolemodalwavesalongthewell-axisinafluid-filledboreholesurroundedbyelasticandnonelastic,infiniteandfiniteformationisanalysedbyusingthewaveequations.Thephasevelocitydispersionandtheexcitationcurvesarenumericallycalculated.Thewaveformsexcitedbyattenuatingburstsarealsocalculated.Themeasurementswithlong-spaceddipoletransducersmadeofPZTthindisksvibratinginbendingmodearecarriedoutinaconcretemodelwellandtheexperimentalresultsarecomparedwiththetheoreticalresults.

简介：ＡＭＯＤＥＬＩＤＥＮＴＩＦＩＣＡＴＩＯＮＭＥＴＨＯＤＯＦＶＩＢＲＡＴＩＮＧＳＴＲＵＣＴＵＲＥＳＦＲＯＭＩＮＣＯＭＰＬＥＴＥＭＯＤＡＬＩＮＦＯＲＭＡＴＩＯＮＺｈｅｎｇＸｉａｏｐｉｎｇ（郑小平）ＹａｏＺｈｅｎｈａｎ（姚振汉）ＱｕＳｈｉｓｈｅｎｇ（蘧时胜）...

简介：Weconductedalong-termmonitoringexperimentontheLutuanxiluBridgelocatedinChangpingDistrictofBeijing,employingourrecentlydevelopedreal-timebridgemonitoringsystembasedontheGuralpCMG-6TDbroadbandseismometer.Weidentifiedthemodalparameterswiththestochasticsubspaceidentification(SSI)algorithm,andcontinuouslymonitoredthetemporalvelocityvariationwithcodawaveinterferometry.Theresultsshowthat:(1)thehighlysensitiveGuralpCMG-6TDbroadbandseismometer,whichrecordsthethree-componentvibrationsignalwithinbroadfrequencyrange,iswellsuitedforlong-termbridgehealthmonitoring.(2)Withthecontinuousvibrationsignalfromambientexcitation,thestochasticsubspacealgorithmcanrobustlyidentifythelow-ordermodalparametersandthecodawaveinterferometrycanaccuratelymonitorthetinyvelocityvariation.(3)Theelasticmodulusofbridgematerialschangessignificantlyassociatedwithvaryingtemperature,leadingtodiurnalvelocityvariationwithamplitudeofapproximately1%.Thevelocityvariationshowsstrongnegativecorrelationwithtemperaturefluctuation.Meanwhile,themodalfrequenciesremainquitestable,suggestingthatthevelocityvariationmaybeamoresensitivequantitativedamageindex.(4)Whilethemodalfrequenciesreflecttheintegratedhealthstatusofthebridge,thevelocityvariationcanbeutilizedtomonitorthelocalelasticmodulus.Therefore,itiscrucialforbridgehealthmonitoringtocontinuouslymonitorthetwokeydamageindexesunderambientexcitation.

简介：Identificationofmodalparametersofalinearstructurewithoutput-onlymeasurementshasreceivedmuchattentionoverthepastdecades.Inthepaper,theNaturalExcitationTechnique(NExT)isusedforacquisitionoftheimpulsesignalsfromthestructuralresponses.ThenEigensystemRealizationAlgorithm(ERA)isutilizedformodalidentification.(SAMFM),isdevelopedtodistinguishthetruemodesfromnoisemodes,andtoimprovetheprecisionoftheidentifiedmodalfrequenciesofthestructure.Anoffshoreplatformismodeledwiththefiniteelementmethod.Thetheoreticalmodalparametersareobtainedforacomparisonwiththeidentifiedvalues.ThedynamicresponsesoftheplatformunderrandomwaveloadingarecomputedforprovidingtheoutputsignalsusedforidentificationwithERA.Resultsofsimulationdemonstratethattheproposedmethodcandeterminethesystemmodalfrequencywithhighprecision.

简介：Inthispaper,modalanalysistheory,equivalentdynamicmodelofthejointsurfaceofassemblyandidentificationmethodsofjointsurfaceparametersarethemaintheories.StaticandmodalanalysisoftheworkingtablecomponentsoftheFM6324machiningcenterisdone.Thethree-dimensionalmodeloftheworkingtablecomponentsisestablishedusingProEatfirst,thenstaticcharacteristicsisobtainedthroughANSYScontactanalysis;finally,thedynamicmodelisestablishedinANSYS,anditsdynamiccharacteristicsisobtainedthroughANSYSmodalanalysis.

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简介：柔韧的损坏察觉方法为的发展近海结构是关键的阻止结构的失败引起的大祸。在这研究，我们为检测损坏在开发了一个改进形式的紧张精力(IMSE)方法近海站台基于一个传统的形式的紧张精力方法(Stubbs索引方法)组织。从Stubbs索引方法的最重要的差别是形式的频率的应用程序。目标是改进传统的方法的坚韧性。表明建议IMSE方法的有效性和实物，数字、试验性的研究用夹克衫站台结构为不同损坏情形被进行。当仅仅有限、空间地不完全、弄脏噪音的形式的数据是可得到的时，结果在损坏地点表明了IMSE方法的有效性。比较研究证明IMSE索引超过了Stubbs索引并且展出了更强壮的坚韧性，证实建议途径的优势。

简介：Platestructuresareemployedasimportantstructuralcomponentsinmanyengineeringapplications.Hence,assessingthestructuralconditionsofin-serviceplatestructuresiscriticaltomonitoringglobalstructuralhealth.Modalcurvature-baseddamagedetectiontechniqueshaverecentlygarneredconsiderableattentionfromtheresearchcommunity,andhavebecomeapromisingvibration-basedstructuralhealthmonitoringsolution.However,computingerrorsarisewhencalculatingmodalcurvaturesfromlateralmodeshapes,whichresultfromunavoidablemeasurementerrorsinthemodeshapesasidentifiedfromlateralvibrationsignals;thismakescurvature-basedalgorithmsthatusealateralmeasurementonlytheoreticallyfeasible,butpracticallyinfeasible.Therefore,inthisstudy,long-gaugefiberBragggratingstrainsensorsareemployedtoobtainamodalcurvaturewithoutanumericaldifferentiationprocedureinordertocircumventthecomputingerrors.Severaldamageindicesbasedonmodalcurvaturesthatweredevelopedtolocatebeamdamageareemployed.Bothnumericalandexperimentalstudiesareperformedtovalidatetheproposedapproach.However,althoughpreviousstudieshavereportedrelativesuccesswiththeapplicationofthesedamageindicesonasimplebeam,onlyonedamageindexdemonstratedthecapabilitytolocatedamagewhenthestiffnessofthelocalregionchangednearthesensor.

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简介：以赛络纺和环锭纺两种不同方式生产的18texModel纯纺纱为例，对比测试其性能，比较选择不同的牵伸倍数，提高成纱质量，改善纱线毛羽条干等问题。实践表明：在牵伸倍数为1．30时，纱线最光洁，毛羽少，纱线的棉结最小。牵伸倍数为1．25时成纱的强伸性能最好。

简介：Basedonthemultivariatecontinuoustimeautoregressive(CAR)model,thispaperpresentsanewtime-domainmodalidentificationmethodoflineartime-invariantsystemdrivenbytheuniformlymodulatedGaussianrandomexcitation.Themethodcanidentifythephysicalparametersofthesystemfromtheresponsedata.First,thestructuraldynamicequationistransformedintoacontinuoustimeautoregressivemodel(CAR)oforder3.Second,basedontheassumptionthattheuniformlymodulatedfunctionisapproximatelyequaltoaconstantmatrixinaveryshortperiodoftimeandonthepropertyofthestrongsolutionofthestochasticdifferentialequation,theuniformlymodulatedfunctionisidentifiedpiecewise.Twospecialsituationsarediscussed.Finally,byvirtueoftheGirsanovtheorem,weintroducealikelihoodfunction,whichisjustaconditionaldensityfunction.Maximizingthelikelihoodfunctiongivestheexactmaximumlikelihoodestimatorsofmodelparameters.Numericalresultsshowthatthemethodhashighprecisionandthecomputationiseffcient.