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简介：AlaminarpremixedPropane/Airflamewithafuelequivalenceratioof2.1wasemployedforanalysisofsootparticles.Zeroth-orderIognormaldistributions(ZOLD)wereusedintheanalysisofexperimentaldistributionphenomenaatdifferentresidencetimesduringsootformationintheflame.Rayleigh'stheoryandMie'sscatteringtheorywerecombinedwithagglomerateanalysisusingscatteringandextinctiondatatodeterminethefollowingsootcharacteristics:agglomerateparameters,volumetricfractions,massflowratesandsurfacegrowthrate.Sootdensitymeasurementswerecarriedouttodeterminedensityvariationsatdifferentstagesofgrowth.Themeasuredresultsshowthatmetricfractionandmassflowrateindicatethatthesurfacegrowthrateofsootparticlesexceedstheoxidationratesintheflamestudied.Thedataobtainedinthisworkwouldbeusedtostudysootoxidationrateunderflamingcondition.

简介：Atwo-dimensionalsteadyReynolds-averagedNavier–Stokes(RANS)equationwassolvedtoinvestigatetheeffectsofaGurneyflaponSFYT15thickairfoilaerodynamicperformance.Thisairfoilwasdesignedforflightvehicleoperatingat20kmaltitudewithfreestreamvelocityof25m/s.Thechordlength(C)is5mandtheReynoldsnumberbasedonchordlengthisRe=7.76×105.Gurneyflapswiththeheightsrangingfrom0.25%Cto3%Cwereinvestigated.Theshearstresstransport(SST)k-ωturbulencemodelwasusedtosimulatetheflowstructurearoundtheairfoil.ItisshowedthatGurneyflapcanenhancenotonlytheprestallliftbutalsolift-to-dragratioinacertainrangeofanglesofattack.Specially,atcruiseangleofattack(α=3°),Gurneyflapwith0.5%Cheightcanincreaselift-to-dragratioby2.7%,andliftcoefficientby12.9%,respectively.Furthermore,thesurfacepressuredistribution,streamlinesandtrailing-edgeflowstructurearoundtheairfoilareillustrated,whicharehelpfultounderstandthemechanismsofGurneyflaponairfoilaerodynamicperformance.Moreover,itisfoundthattheincreaseofairfoildragwithGurneyflapcanbeattributedtotheincreaseofpressuredragbetweenthewindwardandtheleewardsidesofGurneyflapitself.

简介：利用压力传感器测量扑翼的瞬时力,利用数字粒子测速仪（digitalparticleimagevelocimetry,DPIV）系统测量扑翼的前缘涡以及周围的流场,来揭示前缘涡在不同间距下对扑翼平均推力的影响.实验在-个低Reynolds数循环水洞中进行,两串列扑翼均做二维正弦平动.在固定的相位差下,当间距增加时,后翅前缘涡对前翅的影响具有相似性,均提高或者均降低前翅的平均推力.前翅平均推力的提高是由于后翅的前缘涡提高了前翅尾部的射流速度以及有效攻角.随着间距的增加,后翅前缘涡对前翅的影响急剧下降,使得前翅的平均推力快速接近于单翼值.在固定的相位差下,当间距增加时,前翅的脱落涡对后翅的影响变化非常大,后翅的平均推力可能先升高后降低,这是因为间距改变了前翅脱落涡作用于后翅的时间点.当前翅脱落涡遇到后翅,并且和后翅的前缘涡有相同的旋转方向时,前翅的脱落涡会抑制后翅前缘涡的形成,并且后翅的有效攻角减小,其平均推力降低.如果这两个涡的旋转方向相反,那么后翅有效攻角就会增大,平均推力值就会提高.

简介：Veryhighcyclefatigue(VHCF)propertiesofalowtemperaturetemperingbearingsteelGCr15withsmoothandhole-defectspecimensarestudiedbyemployingarotarybendingtestmachinewithfrequencyof52.5Hz.Bothsmoothandhole-defectspecimensbreakinVHCFregimewithsomedifferenceinfatiguecrackinitiation.Forsmoothspecimens,afinegranulararea(FGA)isobservednearthegrainboundaryinthefracturesurfaceofthespecimensbrokenafter10~7cycles.ButnoFGAisobservedinthehole-defectspecimensbrokeninVHCFregime,andtheVHCFcrackdoesnotinitiatefromthesmallholeatthesurfaceasitdoesatloworhighcyclefatigueregime.InternalstressisemployedtoexplaintheVHCFbehaviorofthesetwotypesofspecimens.Atlast,anadvanceddislocationmodelbasedonTanakaandMuramodelisproposedtoillustratetheinternalstressprocessandtopredictfatiguecrackinitiationlifewithFGAobservedinthefractureregion.

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简介：在舰载系统和机载系统，当子母惯导之间存在杆臂长度时，在传递对准中通常先消除杆臂效应误差再进行对准，以提高对准精度。在弹载环境中人们往往忽视杆臂效应，受制于弹体空间的限制，弹载惯组中的加速度计通常根据系统体积最小的原则寻找剩余空间布置，此时三个加速度计测量的是弹体三个不同点的加速度，不但存在外杆臂还存在内杆臂，导致惯组总体的杆臂误差。通过深入分析内外杆臂的形成机理，提出对弹载惯组也应进行杆臂效应误差补偿，对补偿算法进行了仿真和实验研究。系统半物理仿真表明补偿后在某些弹道条件下可以显著提高弹体攻击精度，其攻击目标误差由120m缩小为26m。

简介：BSTOdielectricceramicwaspreparedfromSrTiO3andBaTiO3powderssynthesizedbyhydrothermalmethod,aswellasfromBa0.6Sr0.4TiO3powdersynthesizedbyconventionalsolid-statereaction.Theformercanbesinteredatarelativelylowtemperatureof1120℃.CharacterizationbySEMshowedthatthegrainshapesofbothceramicsarecubical,thoughthegrainsizeoftheformerismuchsmaller.Dielectricconstantsmeasuredat20℃wereshowntovarywithfrequencyintherangefrom1kHzto2MHzanddcbiasfield,andfurtherthatthedielectriclossoftheformertobelessthan2×10-3inthefrequencyrangeof20kHzto1MHz,muchsmallerthanthatofthelattersample.Fortheformer,temperaturedependenceofdielectricconstantismuchflatterandthereexistsanextendedphasetransitiondiffusioncoveringawidetemperaturerangeofCurietemperatureTc.Thesmallergrainsizeoftheformerdepressesthedcbiaselectricalfielddependenceofdielectricconstant.Thetunabilityis7%underabiasfieldof0.6kV/mmdc.

简介：TiO2@ZrO2@Y2O3:有coremultishell结构的Eu3+合成粒子通过layer-by-layer(LBL)的联合被综合自己组装方法和一个solgel过程。获得的样品与扫描电子被描绘显微镜学(SEM)，传播电子显微镜学(TEM)，X光检查光电子光谱学(XPS)，X光检查衍射(XRD)，和荧光spectrophotometry。结果证明合成粒子有coremultishell结构，球形的形态学，和狭窄的尺寸分布。TiO2核心上的ZrO2层的存在能有效地阻止在TiO2核心和Y2O3壳之间的反应；为在在TiO2@ZrO2@Y2O3的TiO2核心和Y2O3壳之间的反应的温度:Eucoremultishell黄磷能被300提高

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简介：研究了利用双轴位置转台标定时，水平基准误差和北向基准误差对激光捷联惯组（LSIMU）标定精度的影响。首先建立了LSIMU标定模型和生成惯性器件信息的仿真算法，接着设计了LSIMU标定方案和数据处理方法，最后对LSIMU标定进行仿真和分析。仿真结果表明：水平基准误差为0．4’时，加速度计标定误差将达到116×10^-6；当北向基准误差大于5°时，陀螺标定误差将超过0．0001。

简介：3阶段的水动力学反的使流体化的床为不同液体和煤气的速度用低密度粒子试验性地被学习。水动力学特征学习了包括压力落下，最小的液体和气体使液化速度和阶段劫盗。用床压力坡度决定的最小的液体使液化速度，随气体的增加减少速度。液体劫盗沿着床高度增加的阶段劫盗表演的轴的侧面，而稳固的劫盗减少，击倒床。然而，煤气的劫盗在床上是几乎一致的。

简介：A3-DnonlinearproblemofsupercavitatingflowpastanaxisymmetricbodyatasmallangleofattackisinvestigatedbymeansoftheperturbationmethodandFourier-cosine-expansionmethod.Thefirstthreeorderperturbationequationsarederivedindetailandsolvednumericallyusingtheboundaryintegralequationmethodanditerativetechniques.Computationalresultsofthehydrodynamiccharacteristicsandcavityshapesofeachorderarepresentedfornonaxisymmetricsupercavitatingflowpastconeswithvariousapex-anglesatdiffer-entcavitationnumbers.Thenumericalresultsarefoundingoodagreementwithexperimentaldata.

简介：针对传统模型难以描述捷联惯组误差系数的复杂性、突变性和非线性特征这一问题,研究了其多重分形特征,并提出了一种自适应分形插值算法。利用盒维数和MF-DFA方法分析得出捷联惯组误差系数具有明显的多重分形特征。改进了适用于非等间隔数据的垂直比例因子求取算法,根据测试数据间隔大小赋予每个仿射变换不同的概率和使用次数,按照无放回抽样原则进行随机分形插值,在不增加迭代次数的条件下解决了分形插值点分布不均匀的问题。利用加权平均法得到指定时间的标定值。结果表明,所提算法插值准确性比常规分形插值至少提高了3倍。

简介：Soilconsolidationwouldinducevariationsofitstransportcoefficientssuchashydraulicconductivityanddiffusioncoefficient.Thispaperpresentsastudyoftheinfluenceofbarrierconsolidationontransportcoefficients,anda3Dtransportmodelbasedonmixturetheoryisproposedfordescribingthelinersthatinvolvecirculardefectsinthegeomembrane.TheelastoplasticALPHAmodelisrevisedbyusingthespatiallymobilizedplane(SMP)criterionforsimulatingthedeformationofthesoils.Then,the3Dmodelcouplingthenonlinearconsolidationandcontaminantadvection-diffusionissolvedusingthefiniteelementsoftwareABAQUS.Theresultsshowthattheimportanceofreducingthedefectsizeinthegeomembraneandthelinerporositytocontrolthecontaminantconcentrationincrease.

简介：TheIsodynetechniquebasedonthescatteredlightscanningfromathinlaserbeamcanbeusedtoobtaintheinformationinsidetheloadedobjectintheroomtemperaturenondestructively,soitisaverypowerfultechniquein3Dstressanalysis.Theproblemsarehowtointerprettheinformationandhowtogetsufficientinformationfromthefewinterferencefringe.Birefringencephaseshifttechniquecandistinguishthefringeordersautomaticallyandenrichtheinformationin256graylevelsbetweenmaximandminimlightintensity.InthepapertheIsodynebirefringencephaseshiftmethodwithanobliqueincidenceandequilibriumequationispresented,bywhichthe3DstressesinthemiddleplaneofaplatewithUshapenotchareseparatedsuccessfully.

简介：Basedonthegeneralconservationlawsincontinuummechanics,theEulerianandLagrangiandescriptionsofthejumpconditionsofshockwavesin3-dimensionalsolidswerepresentedrespectively.Theimplicationofthejumpconditionsandtheirrelationsbetweeneachother,particularlytherelationbetweenthemassconservationandthedisplacementcontinuity,werediscussed.Meanwhiletheshockwaveresponsecurvesin3-dimensionalsolids,i.e.theHugoniotcurveswereanalysed,whichprovidethefoundationforstudyingthecouplingeffectsofshockwavesin3-dimensionalsolids.

简介：The1/3subharmonicsolutionfortheDuffing'sequationisinvestigatedbyusingthemethodsofharmonicbalanceandnumericalintegration.Thesensitivityofparametervariationforthetransientprocessandthetransientprocessfortheperturbanceinitialconditionsarestudied.Overandabove,theprecisionofnumericalintegrationmethodisdiscussedandthenumericalintegrationmethodiscomparedwiththeharmonicbalancemethod.Finally,asymptoticalstabilityofthepuresubharmonicoscillationselementisinspected.

简介：Uniformlysizedα-Fe2O3hexagonalplateletsweresynthesizedbyahydrothermalprocessusingFe(OH)3suspensionandlargeamountofNaOH.ThereactionproductswerecharacterizedbyX-raydiffraction(XRD),scanningelectronmicroscopy(SEM),transmissionelectronmicroscopy(TEM),selectedareaelectrondiffraction(SAED),andavibratingsamplemagnetometer(VSM).Theresultsshowthatthehexagonalplateletsarefine,monodisperseandconsistingofsingle-crystals.Themagnetichysteresis(M-H)curveofthesamplesmeasuredatroomtemperatureindicatesthattheα-Fe2O3micro-plateletsexhibitferromagneticbehaviorswithrelativelylowcoercivity.

简介：Becausemostpiezoelectricdeviceshaveinterfaceswithfluidinengineering,itisvaluabletostudythecoupledfieldbetweenfluidandpiezoelectricmedia.Asthefundamentalproblem,the3DGreen'sfunctionsforpointforcesandpointchargeloadedinthefluidandpiezoelectricbimaterialsarestudiedinthispaper.Basedonthe3Dgeneralsolutionsexpressedbyharmonicfunctions,weconstructedthesuitableharmonicfunctionswithundeterminedconstantsatfirst.Then,thecouplefieldinthefluidandpiezoelectricbimaterialscanbederivedbysubstitutionofharmonicfunctionsintogeneralsolutions.Theseconstantscanbeobtainedbyvirtueofthecompatibility,boundary,andequilibriumconditions.Atlast,thecharacteristicsoftheelectromechanicalcoupledfieldsareshownbynumericalresults.