学科分类
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2453 个结果
  • 简介:Whethertheconceptofeffectivestressandstraininelastic-plastictheoryisstillvalidundertheconditionoffinitedeformationwasmainlydiscussed.Theuni-axialcompressionexperimentsinplanestressandplanestrainstateswerechosenforstudy.Inthetwokindsofstressstates,thestress-straincurvedescribedbylogarithmstrainandrotatedKirchhoffstressmatchestheexperimentsdatabetterthanthecurvesdefinedbyotherstressstraindescription.

  • 标签: 有效压力 有效张力 有限变形 弹塑性理论 固体力学 体积不变性
  • 简介:Twodimensionalequationsofsteadymotionforthirdorderfluidsareexpressedinaspecialcoordinatesystemgeneratedbythepotentialflowcorrespondingtoaninviscidfluid.Fortheinviscidflowaroundanarbitraryobject,thestreamlinesarethephicoordinatesandvelocitypotentiallinesarepsi-coordinateswhichformanorthogonalcurvilinearsetofcoordinates.Theoutcome,boundarylayerequations,isthenshowntobeindependentofthebodyshapeimmersedintotheflow.Asafirstapproximation,assumptionthatsecondgradetermsarenegligiblecomparedtoviscousandthirdgradeterms.Secondgradetermsspoilscalingtransformationwhichisonlytransformationleadingtosimilaritysolutionsforthirdgradefluid.ByusingLiegroupmethods,infinitesimalgeneratorsofboundarylayerequationsarecalculated.Theequationsaretransformedintoanordinarydifferentialsystem.NumericalsolutionsofoutcomingnonlineardifferentialequationsarefoundbyusingcombinationofaRunge-Kuttaalgorithmandshootingtechnique.

  • 标签: 李群 边界层方程 第三级流体 非牛顿流体 流体力学
  • 简介:Thestructuraldynamicsproblems,suchasstructuraldesign,parameteridentificationandmodelcorrection,areconsideredasakindoftheinversegeneralizedeigenvalueproblemsmathematically.Theinverseeigenvalueproblemsarenonlinear.Ingeneral,theycouldbetransformedintononlinearequationstosolve.Thestructuraldynamicsinverseproblemsweretreatedasquasimultiplicativeinverseeigenalueproblemswhichweresolvedbyhomotopymethodfornonlinearequations.Thismethodhadnorequirementsforinitialvalueessentiallybecauseofthehomotopypathtosolution.Numericalexampleswerepresentedtoillustratethehomotopymethod.

  • 标签: 结构力学 同伦解 反转问题 结构设计
  • 简介:AfastadaptivesymplecticalgorithmnamedMultiresolutionSymplecticScheme(MSS)wasfirstpresentedtosolvetheproblemofthewavepropagation(WP)incomplexmedia,usingthesymplecticschemeandDaubechies'compactlysupportedorthogonalwavelettransformtorespectivelydiscretisethetimeandspacedimensionofwaveequation.TheproblemwassolvedinmultiresolutionsymplecticgeometryspaceundertheconservativeHamiltoniansystemratherthanthetraditionalLagrangesystem.Duetothefascinatingpropertiesofthewaveletsandsymplecticscheme,MSSisapromisingmethodbecauseoflittlecomputationalburden,robustnessandrealityoflong-timesimulation.

  • 标签: 小波变换 自适应耦对算法 波动力学 波传播 哈密顿系统 复合介质
  • 简介:Fromsuchactualconditionsastheeffectsofcharacteristicsofmiltilayerpetroleumgeologyandpermeationfluidmechanics,anewnumericalmodelisputforwardandcouplingsplitting-upimplicitinteractiveschemeisformed.FortheactualsituationofDongyinghollow(four-layer)andTanhairegion(three-layer)ofShengliPetroleumField,thenumericalsimulationtestresultsandtheactualconditionsarecoincident.

  • 标签: 数值模拟 并行算法 多层结构 胜利油田 石油形成
  • 简介:Adirectnumericalsimulationisperformedon2563gridsfordecayingisotropicturbulence.Thetotalkinematicenergy,Taylormicro-scale,Taylormicro-scaleReynoldsnumberandthevelocityderivativeskewnessarecalculated.Thesnapshotsofenergyspectraandenergytransferspectraareplotted.ThesemeasurementsverifytheDIApredictions:decayingisotropicturbulencehastheenergypropagationandoccupiesthefinaldecayperiods.Theskewnessremainstosomelevelwithsmallvariationeveninthefinaldecayperiod.

  • 标签: 数值模拟 Navior-Stokes方程 流体力学 DIA 动能 势能
  • 简介:Inthispaper,wecarryoutananalysisofthestructuralpropertiesofthesolutionstothespeedgradient(SG)trafficflowmodel.Undertheconditionthattherelaxationeffectcanbeneglected,itisshownthata1-shockora1-rarefactionisassociatedwiththefirstcharacteristic,butontheotherhand,acontactdiscontinuityratherthana2-shockora2-rarefactionisassociatedwiththesecondcharacteristic.Sincetheexistenceofa2-shockor2-rarefactionviolatesthephysicalmechanismofthetrafficflow,theSGmodelismorereasonable.Iftherelaxationeffectcannotbeneglected,itissomewhatdifficulttocarryouttheanalyticalanalysisandthenumericalsimulationresultsshouldbeobtained.

  • 标签: 交通流 速度梯度交通流模型 弛豫条件 交通密度 结构解
  • 简介:Inordertoinvestigatetheinfluenceoftheverticalvibrationloadingontheliquefactionofsaturatedsand,onedimensionalmodelforthesaturatedsandwithaverticalvibrationispresentedbasedonthetwophasecontinuousmediatheory.Thedevelopmentoftheliquefactionandtheliquefactionregionareanalyzed.Itisshownthattheverticalvibrationloadingcouldinduceliquefaction.Therateoftheliquefactionincreaseswiththeincreaseoftheinitiallimitstrainorinitialporosityoramplitudeandfrequencyofloading,andincreaseswiththedecreaseofthepermeabilityorinitialmodulus.Itisshownalsothatthereisaphaselaginthesandcolumn.Whenthesandpermeabilitydistributionisnon-uniform,theporepressureandthestrainwillrisesharplywherethepermeabilityisthesmallest,andfracturemightbeinduced.Withthedevelopmentofliquefaction,thestrengthofthesoilfoundationbecomessmallerandsmaller.Inthelimitingcase,landslidesordebrisflowscouldoccur.

  • 标签: 融解 振动负载 饱和沙 断裂 固体力学
  • 简介:AnFEanalysisprocedurewaspresentedtopredictthebehaviorofsoilogeogridinterctionunderautomobileloading.Thedynamicinteractionsbetweenthetransversebars,thelongitudinalribsandthesoilweresimulatedbyasystemconsistingofnonlinearsprings,dashpotsandmasses,tostudythedeformationpropertiesofthereinforcedsoil.Theequivalentstiffnessanddampingratioscouldbedeterminedwiththeshakingtable.Thedynamicresponsesofareinforcedsubgradewereanalyzedwiththe3Dfiniteelementapproach.Thisapproachisprogrammedandappliedtoanalyzethesoilogeogridinteractionunderdynamicloading.Thecomparativeanalysisoftheresponseofthereinforcedsubgradeandthatofthesubgradewithoutreinforcementshowsthatthegeogridplacedatthebottomofthebaselayermayeffectivelyreducetheaccumulativeplasticdeformationduetothecyclicautomobileloading.

  • 标签: 道路力学 车辆负载 路基加固 变形 弹性减阻装置系统
  • 简介:AconstitutiveequationtheoryofOldroydfluidBtype,i.e.theco-rotationalderivativetype,isdevelopedfortheanisotropic-viscoelasticfluidofliquidcrystalline(LC)polymer.Analyzingtheinfluenceoftheorientationalmotiononthematerialbehaviorandneglectingtheinfluence,theconstitutiveequationisappliedtoasimplecaseforthehydrodynamicmotionwhentheorientationalcontributionisneglectedinitandtheanisotropicrelaxation,retardationtimesandanisotropicviscositiesareintroducedtodescribethemacroscopicbehavioroftheanisotropicLCpolymerfluid.UsingtheequationfortheshearflowofLCpolymerfluid,theanalyticalexpressionsoftheapparentviscosityandthenormalstressdifferencesaregivenwhichareinagoodagreementwiththeexperimentalresultsofBaeketal.Forthefiberspinningflowofthefluid,theanalyticalexpressionoftheextensionalviscosityisgiven.

  • 标签: 各向异性粘性流体 非牛顿流 各向异性材料方程 外延流 液晶聚合体
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  • 简介:ThesedimentationsoftwocylindricalparticlesinthreedifferentinitialrelativepositionsarenumericallysimulatedusingthelatticeBoltzmannmethod.Themovementcharacteristicsandparticleinteractionsduringtheirsedimentationarepresentedanddiscussedindetail.Theresultsshowthat,(i)ifthetwoparticlesarereleasedparallelbutseparatedhorizontally,theypushawayeachother,rotateinwardsandseparatehorizontallyastheyfall;(ii)ifthetwoparticlesarereleasedparallelbutseparatedvertically,thesedimentationbehaviorcanbeclassifiedintothreestages:trailing,tumblingandseparating;(iii)ifthetwoparticlesarereleasedperpendicularbutseparatedvertically,thesedimentationbehaviorcanbecharacterizedas:trailingandrotating,touchingandsliding.Inordertovalidateoursimulation,experimentswerealsoconductedandtheresultsagreewellwiththenumericalones.

  • 标签: 沉积作用 圆柱形粒子 相互作用 静态流 流体力学
  • 简介:TheaerodynamicforcesandflowstructureofamodelinsectwingisstudiedbysolvingtheNavier-Stokesequationsnumerically.Afteraninitialstartfromrest,thewingismadetoexecuteanazimuthalrotation(sweeping)atalargeangleofattackandconstantangularvelocity.TheReynoldsnumber(Re)consideredinthepresentnoteis480(Reisbasedonthemeanchordlengthofthewingandthespeedat60%winglengthfromthewingroot).Duringtheconstant-speedsweepingmotion,thestallisabsentandlargeandapproximatelyconstantliftanddragcoefficientscanbemaintained.Themechanismfortheabsenceofthestallorthemaintenanceoflargeaerodynamicforcecoefficientsisasfollows.Soonaftertheinitialstart,avortexring,whichconsistsoftheleading-edgevortex(LEV),thestartingvortex,andthetwowing-tipvortices,isformedinthewakeofthewing.Duringthesubsequentmotionofthewing,abase-to-tipspanwiseflowconvertsthevorticityintheLEVtothewingtipandtheLEVkeepsanapproximatelyconstantstrength.ThispreventstheLEVfromshedding.Asaresult,thesizeofthevortexringincreasesapproximatelylinearlywithtime,resultinginanapproximatelyconstanttimerateofthefirstmomentofvorticity,orapproximatelyconstantliftanddragcoefficients.Thevariationoftherelativevelocityalongthewingspancausesapressuregradientalongthewingspan.Thebase-to-tipspanwiseflowismainlymaintainedbythepressure-gradientforce.

  • 标签: 空气动力学 NAVIER-STOKES方程 雷诺数 昆虫翅膀 边界涡流
  • 简介:在干扰大的外界环境中,传统滤波法对组合导航系统进行状态估计的精度难以满足要求,为此提出了引入Elman神经网络.描述了它的状态估计的设计方法,对如何获取训练样本及网络的训练算法给予了详细的介绍,并把优化后的算法与原有方法进行仿真对比.最后以INS/GPS组合导航系统为例,分别用传统滤波法与Elman神经网络法进行状态估计.仿真结果证明了该法的有效性和实用性.

  • 标签: 组合导航系统 神经网络 卡尔曼滤波 状态估计
  • 简介:在三轴整体式速率偏频激光陀螺无法进行输出轴冗余配置的情况下,为实现陀螺的元件级故障检测与隔离,提出了由三轴整体式速率偏频激光陀螺和挠性陀螺组构成的双惯性系统的故障检测与隔离方案,给出了双惯性系统的量测方程,并以此为基础推导了用于进行故障检测与隔离的奇偶方程.提出一种基于奇偶方程的双惯性系统故障检测与隔离方法,并针对一类无法用奇偶方程进行隔离的故障,给出一种搜索无故障陀螺输出轴的故障检测与隔离新方法.

  • 标签: 双惯性系统 故障检测 速率偏频 激光陀螺 奇偶方程 故障隔离
  • 简介:提出了一种利用GPS定位与测速相结合的动态定位方法.引入模糊人工神经网络技术对GPS数据进行处理,利用BP网络实现模糊化知识集的记忆和模糊判决的功能;最后,对处理前后的结果进行了对比.试验结果表明,该方法可以有效地提高GPS在开阔场地的定位精度.

  • 标签: 卫星定位技术 GPS 模糊控制 人工神经网络 动态定位
  • 简介:TheChineseSocietyofParticuologyisavoluntaryorganizationofworkersinresearch,developmentandapplicationofthescienceandtechnologyofparticles.TheSocietyisdedicatedtofostedngliaisonandexchangeamongitsmembersthroughscientificandtechnicalsymposiaandseminarsofbothanationalandinternationalnatureandtodisseminatingknowledgeonparticlesthroughcontinuingeducationandpublicationintheformofscientifictransactionsandofjournalsonnewsandotheritemsofcurrentinterest.Itsultimateobjectiveistoservethecountry'sneedsformodernization.

  • 标签: 中国颗粒学报协会 国际会议 学术交流 国内会议
  • 简介:publishesonlypapersofthehighestquality.Allpaperssubmittedaresenttorefereesfamiliarwiththerespectivesubjectsforadviceastotheireligibilityforpublicationandneededimprovement.TheEditorsmakethefinaldecisiononpublicationinthelightofsuchadvice.Non-nativeEnglish-speakingauthorsareadvisedtoseeknecessarylinguisticassistancebeforesubmissionoftheirmanuscripts,althoughtheEditorsarepreparedtohelpupgradeworksofexceptionalexcellence.Inadditiontofulllengthpapersofupto5000words,thejournalwelcomesreviews,correspondenceandshortercommunicationsoflessthan2500wordsdealingwithnovelresearchtechniques,analysisofcurrentresearch,newconcepts,etc.

  • 标签: 中国颗粒学报 论文要求 参考文献 版权 论文结构