简介：当弹体表面安装喷管时,在喷管迎风条件下往往出现不利的侧向喷流干扰,翼梢安装喷管能减弱这种不利干扰.采用有限体积离散方法求解N-S方程,研究了旋成体-边条翼-舵组合体翼梢安装喷管的侧向喷流干扰特性和规律.分析了干扰流场结构和喷流干扰因子随Mach数、攻角、飞行高度等参数的变化特性.研究结果表明:翼梢喷流干扰形成了非常复杂的流场结构,虽然翼梢喷流远离弹体,仍对弹体、翼、舵上的载荷产生明显影响,在不同飞行条件下干扰范围和强度明显不同.喷流气动干扰因子规律复杂并呈非线性变化,干扰因子大于0.5的范围明显增加,有效增加了喷流控制使用范围.但在某些条件下仍然出现较大负值,产生严重不利干扰现象.

简介：盒式翼布局相对常规布局可以很大程度地减小诱导阻力,同时平滑的升力分布有利于减小跨声速激波阻力,但双翼间的气动干扰是跨声速盒式翼布局存在的主要问题.为掌握跨声速双翼气动干扰特性,选用超临界翼型RAE2822作为双翼翼型,对M=0.75,正负交错两种情况下双翼几何参数对布局升阻特性的影响进行数值研究.结果表明,增大双翼的纵向距离可以减弱双翼间气动干扰,使升阻比提高至无干扰升阻比.其中,前翼在下、后翼在上的负交错布局在双翼纵向距离为1.5倍上翼弦长时即可接近无干扰升阻比,更有利于提升布局的升阻特性.负交错时双翼的垂直间距对布局升阻比影响不大,无翼差角且减小前翼弦长有利于提高升阻比.

简介：为保持对目标接收机的持续有效欺骗,增强欺骗干扰的隐蔽性,从信号传播损耗、噪声基底、仰角因素等方面对欺骗干扰的功率控制问题进行了定量的分析,得出了一种欺骗功率控制策略。该方法通过实时调整欺骗干扰的总功率及各支路信号功率,使得噪声基底的抬高幅度和最大欺骗信号信噪比限制在一定范围内。仿真表明,通过实时调整欺骗功率,可以将噪声基底限制在3dB内,将最大欺骗信号信噪比限制在22dB内,实现持续有效欺骗。该方法可行性较强,对欺骗干扰机的研制具有重要的指导意义。

简介：ThecharacteristicsofsuspendedsedimentimagecanbereflectedbythecoefficientsofbiorthogonalwavelettransformofCDF(2,2).Basedonthepowerdistributionindifferentscales,anadaptivealgorithmisproposedinthispaper,wherebythecoefficientsareadjustednon-linearly.Theparticleinformationcanbewellretainedwhiletheuselessbackgroundisremoved.Inthisway,satisfactorybinaryimagecanbeobtainedforfurtheranalysisofthesedimentparticle.

简介：TheconstitutiveequationforasemiconcentratedfibresuspensionintheOldroyd-Bfluidhasbeenderivedfromastatisticalmodelofsuchasuspensionbyemployingthemoleculartheoryforpolymericliquids.Tocircumventtheoreticaldifficultiesinviscoelasticfluidmechanics,severalsimplifiedmodelsareusedtoaccountfortheinteractionsoffibresandpolymermolecules.Someofmaterialfunctionsarecalculatedintermsoftheconstitutiveequation.

简介：ThispaperestablishesthevelocityfieldandtheadequateshearstresscorrespondingtothemotionofanOldroyd-BfluidbetweentwoinfinitecoaxialcircularcylindersbymeansoffiniteHankeltransforms.Theflowofthefluidisproducedbytheinnercylinderwhichappliesatime-dependentlongitudinalshearstresstothefluid.Theexactanalyticalsolutions,presentedinseriesformintermsofBesselfunctions,satisfyallimposedinitialandboundaryconditions.ThegeneralsolutionscanbeeasilyspecializedtogivesimilarsolutionsforMaxwell,secondgradeandNewtonianfluidsperformingthesamemotion.Finally,somecharacteristicsofthemotionaswellastheinfluenceofthematerialparametersonthebehaviorofthefluidmotionaregraphicallyillustrated.

简介：针对风场对临近空间伪卫星导航精度影响的问题，提出伪卫星抗风场干扰自主导航算法，以提高伪卫星的导航精度。首先，将风场模型加入伪卫星SINS/CNS/SAR组合导航的量测模型中，建立风场干扰下的SINS/CNS/SAR组合导航系统模型；然后，设计自适应UPF非线性滤波算法，将该算法用于SINS/CNS/SAR组合导航解算中，分别在考虑风场干扰和不考虑风场干扰的情况下，利用UKF、UPF和自适应UPF算法对临近空间伪卫星组合导航系统误差进行估计。仿真结果表明，在考虑风场干扰的条件下，提出的自适应UPF算法在东向、北向和天向的速度误差均控制在±0.21m/s以内，误差大小分别是现有的UKF和UPF的1/5和1/3。该算法能有效抑制风场对导航解算精度的影响，提高伪卫星的定位精度。

简介：TheintrinsicphysicalrelationshipofvorticitybetweenmodesAandBinthethree-dimensionalwaketransitionisinvestigated.Directnumericalsimulationsfortheflowpastasquare-sectioncylinderarecarriedoutatReynoldsnumbersof180and250,associatedwithmodesAandB,respectively.Basedontheanalysisofspacialdistributionsofvorticityinthenearwake,characteristicsoftheverticalvorticityinmodesAandBareidentified.Moreover,therelationshipofthreevorticitycomponentswithspecificsignsissummarizedintotwosignlaws,asintrinsicphysicalrelationshipsbetweentwoinstabilitymodes.Bythetheoryofvortex-inducedvortex,suchtwosignlawsconfirmthattherearetwoandonlytwokindsofvortex-sheddingpatternsinthenearwake,justcorrespondingtomodesAandB.Inbrief,alongthefreestreamdirection,modeAcanbedescribedbytheparallelsheddingverticalvorticeswiththesamesign,whilemodeBisdescribedbytheparallelsheddingstreamwisevorticeswiththesamesign.Finally,itisfoundoutthatthe-typevortexisabasickindofvortexstructureinbothmodesAandB.

简介：

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

简介：文章采用热流率测量和纹影拍摄技术,对高超声速层流湍流边界层条件下钝舵干扰流场进行了实验研究.实验在高超声速炮风洞内完成,来流Mach数为6,8.研究结果表明层流与湍流干扰流场之间存在较大差别,层流状态下干扰流场存在分离,平板干扰区内热流率存在负增量,舵面上存在明显的热流率峰值;湍流状态下干扰流场无分离,干扰对平板干扰区内热流率影响较小,舵面上无明显峰值.

简介：有沿着一张拉长的表的混合传送对流的非牛顿的液体的不可压缩的流动被分析。热转移现象通过热放射被讨论。融化的热转移和热产生/吸收的效果也被拿。合适的转变被利用达到非线性的平常的微分表情。会聚的系列答案被介绍。液体流动，温度，和表面热转移率图形地被检验。当时，松驰时间什么时候增加，被观察速度减少当延迟时间是不变的时，增加。当放射参数增加时，结果也表明温度分发减少。

简介：TheinfluenceofNa2SO4ontheformationofZnOwhiskerswasinvestigatedinthispaper.ZnOwhiskerswithaspectratiosofupto50weresynthesizedbydissolvingε-Zn（OH）2precursorinNaOH/Na2SO4solutionatroomtemperature,followedbyagingoftheresultingsolutionat140℃for6h.Fouriertransforminfraredspectroscopy,Ramanspectroscopy,andX-rayphotoelectronspectroscopyanalysesrevealedthatSO42-ionswereprimarilyadsorbedonthe（100）planeoftheZnOwhiskersviaanouter-spherecomplexconfiguration（O-H…O）,therebypromotingtheone-dimensionalgrowthofZnOwhiskersalongthec-axis.

简介：为研究转捩与湍流对激波边界层干扰及底部流动结构的影响,文章选取了二维与三维高超声速双斜面进气道模型与大钝头着陆器模型,并使用γ-Reθ转捩模型开展数值模拟研究.研究表明,对于二维进气道模型,随着前缘钝度的增加,激波边界层干扰位置前移,分离区变大,与层流流动情况相比,有转捩流动发生时,激波边界层干扰位置后移,同时分离流动强度变弱,分离区缩小;对于三维进气道模型,其拐角附近的分离流动呈现明显的三维特征,转捩流动也存在三维流动结构,与静风洞状态相比,噪音风洞状态下,有转捩流动发生,对壁面热流影响较大,对激波系影响很小.对于着陆器模型,底部流动发生转捩,使得底部流动由不稳定非定常的流动结构变为稳定定常的流动结构,这有益于姿态控制设计.

简介：TiO2nanoparticlesweresynthesizedbyahomogeneouscontrolledprecipitationmethodusingindustrialtitaniumsulfate(Ti(SO4)2).TheobtainedpowderswerecharacterizedbyX-raydiffraction(XRD),transmissionelectronmicroscope(TEM),Fouriertransforminfraredspectroscopy(FTIR)andICPplasmaspectrometer.EDTAwasusedascomplexingagenttoimprovethepurityandtheformationofTiO2nanoparticles.Experimentalresultsindicatedthatthehigh-purityTiO2nanoparticleswere20nminmeansizeandnearlymonodispersed.

简介：PureAl2O3-2SiO2powderswerepreparedbysol-gelandcoprecipitationmethods,andtheiralkaliactivationreactivitieswerecompared.Thealkali-activationreactivityofthepowderpreparedbythesol-gelmethodwashigherthanthatofthepowderpreparedbythecoprecipitationmethod.Thepowderswereinvestigatedby27AIand29Simagic-anglespinningnuclearmagneticresonancespectroscopy（MASNMR）tounderstandtherelationshipbetweentheirstructureandalkali-activationreactivity.The27AlMASNMRdatashowedthatthefive-coordinateAIcontentofthepowderpreparedbythesol-gelmethodwashigherthanthatofthepowderpreparedbycoprecipitation.Thehighercontentoffive-coordinateAlcorrespondedtohigheralkali-activationreactivity.The29SiMASNMRdatashowedthatforthepowderpreparedbythesol-gelmethod,siliconwasreplacedbyaluminumatsecondarycoordinationsitesofthecentralSiatomsduringcalcination.However,forthepowderpreparedbysingle-batchcoprecipitation,themainchangewasfromalowdegreeofpolycondensationtoahighdegreeofpolycondensation.

简介：

简介：HomogeneousNi2+-dopedtitaniagelwassynthesizedbyasol-gelprocess,andthexerogelwasthenobtainedthroughaginganddrying,leadingtotheformationofNi/TiO2nanocompositeafterheattreatmentunderasuitablereducingatmosphere.TheresultingnanocompositewascharacterizedbyTGA-DSC,TEM,XRDandBETmethods.Theresultsshowthatthestructureandgrainsizeofthenanocompositescouldbemanipulatedbyalteringtheheat-treatmentconditions,andthatthenanocompositepossessesamesoporousstructurewithaporeradiusofca.28nmandaspecifictheanatase-rutilephasetransformation.

简介：DrivenbycuriosityaboutpossibleflightoptionsfortheChang’e-2spacecraftafteritremainsattheSun-EarthL2point,effectiveapproachesweredevelopedfordesigningpreliminaryfuel-optimalnear-Earthasteroidflybytrajectories.Theapproachesincludetheuseofmodifiedunstablemanifolds,gridsearchofthemanifolds’parameters,andatwo-impulsemaneuverfororbitalphasematchingandz-axisbiaschange,andaredemonstratedtobeeffectiveinasteroidtargetscreeningandtrajectoryoptimization.Asteroidflybysareexpectedtobewithinadistanceof2×107kmfromtheEarthowingtotheconstrainedEarth-spacecraftcommunicationrange.Inthiscase,thespacecraft’sorbitalmotionissignificantlyaffectedbythegravitiesofboththeSunandtheEarth,andtherefore,theconceptofthe"heliocentricoscillating-Keplerorbit"isproposed,becausetheclassicalorbitalelementsoftheflybytrajectoriesreferencedintheheliocentricinertialframeoscillatesignificantlywithrespecttotime.Theanalysisandresultspresentedinthisstudyshowthat,amongtheasteroidswhoseorbitsarethemostaccuratelypredicted,"Toutatis","2005NZ6",or"2010CL19"mightbeencounteredbyChang’e-2inlate2012or2013withtotalimpulseslessthan100m/s.

简介：在laminar的非线性的传送对流的效果三维的Oldroyd-B液体流动被探讨。热转移现象被考虑非线性的热放射和热产生/吸收探索。边界层假设被考虑管理流动分析的数学模型。一些合适的类似变量被介绍把部分微分方程转变成平常的微分系统。有射击方法的Runge-Kutta-Fehlberg第四顺序、第五顺序的技术被用来获得无尺寸的速度和温度的答案。液体速度和温度上的各种各样的物理参数的效果被阴谋并且检验。比较与准确并且homotopy不安答案被做为粘滞液体大小写，和一根优秀火柴被注意。墙的数字价值砍在墙的压力和热转移率被公布并且调查。在德卜拉数字的价值的改进在液体速度上显示出反向的行为。当非线性的传送对流参数增加时，结果证明温度和热边界层被减少。Nusselt数字的价值比处于线性放射状况的那些处于非线性的放射状况是更高的。