简介：通过理论推导提出了一种评价高速流动PIV示踪粒子随流能力的松弛特性分析模型,在法向Mach数大于1.4时具有良好的适用性.将新模型应用于试验测量,发展了高速流动PIV系统和示踪粒子布撒技术,验证了高速流动PIV的定量化测量能力.针对空间发展的二维超声速气固两相混合层,数值模拟了不同Stokes数和对流Mach数（M_c）下的粒子跟随性以及弥散和迁徙运动,结果表明：相同对流Mach数,粒径越小的示踪粒子跟随性越好,Stokes数在[1,10]范围内的粒子有最大扩散距离.示踪粒子的直径大小决定其在超声速混合层大涡拟序结构中的分布特征,且粒径越小,气体与粒子的掺混越剧烈.相同粒径的粒子,对流Mach数越大跟随性越差.

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.

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

简介：W，N共同做TiO2nanoparticles被一个solgel方法综合。准备样品被X光检查衍射(XRD)描绘，域排放扫描电子显微镜学(FE-SEM)，传播电子显微镜学(TEM)，Fourier变换红外线的光谱学(英尺红外)，X光检查光电子光谱学(XPS)和弥漫的反射spectrophotometry(医生)。结果证明共同做的光催化剂是有22.5nm的最小的粒子尺寸的实质上一致的球形的粒子。比作未做的TiO2，N-TiO2和P-25，W的吸收边，N共同做转移到更长的波长的TiO2和它为在Xe灯(350W)下面的甲基橘子(瞬间)的降级的photocatalytic活动更高。

简介：NanofluidswerepreparedbydispersingCunanoparticles(~20nm)inn-tetradecanebyatwo-stepmethod.Theeffectivethermalconductivitywasmeasuredforvariousnanoparticlevolumefractions(0.0001-0.02)andtemperatures(306.22-452.66K).TheexperimentaldatacompareswellwiththeJangandChoimodel.Thethermalconductivityenhancementwaslowerabove391.06Kthanforthatbetween306.22and360.77K.Theinterfacialthermalresistanceincreasedwithincreasingtemperature.Theeffectivethermalconductivityenhancementwasgreaterthanthatobtainedwithamoreviscousfluidasthebasemediaat452.66KbecauseofnanoconvectioninducedbynanoparticleBrownianmotionathightemperature.