简介:AnartificialdisturbanceisintroducedintotheboundarylayeroveraflatplatetoinvestigatetheeffectonthetransitionprocessintheMach6.5windtunnelatPekingUniversity.Alinearstabilitytheory(LST)isutilizedtopredicttheevolutionoftheeigenmodes,andthefrequencyoftheartificialdisturbanceischosenaccordingtotheLSTresults.Theartificialdisturbanceisgeneratedbyglowingdischargeonthesurfaceoftheplateclosetotheleadingedge.TheRayleigh-scatteringvisualizationandparticleimagevelocimetry(PIV)measurementsareperformed.Bycomparingtheexperimentalresultswithartificialdisturbanceswiththoseunderthenaturalcondition(withoutartificialdisturbances),thepresentpapershowsthatthesecond-modeinstabilitywavesaresignificantlystimulatedbytheartificialdisturbances,andtheboundarylayertransitioniseffectivelytriggered.
简介:-Aone-layertime-invarianteddyviscositymodelisspecifiedtodevelopamathematicalmodelfordescribingtheessentialfeaturesoftheturbulentwaveboundarylayeroveraroughbed.Thefunctionalformoftheeddyviscosityisevaluatedbasedoncomputationalresultsfromatwo-equationturbulencemodelinwhichtheeddyviscosityvarieswithtimeandspace.Thepresenteddyviscositymodelsimplifiesmuchofthemathematicalcomplexityinmanyexistingmodels.Predictionsfromthepresentmodelhavebeencomparedwithawiderangeofexperimentaldata.Itisfoundthattheeddyviscositymodeladoptedinthepresentstudyisphysicallyreasonable.
简介:沿着在长江的更低的活动范围的Meiyu前面的重降雨事件在2009年6月23日与一个mesoscale骚乱旋涡被连接,这被发现,它从行星的边界层(PBL)发源并且以后向上发展了并且被使用过滤方法的Shuman-Shapiro发现。在在这个过程的PBL(PMDV)的mesoscale骚乱旋涡在Doppler雷达回响对应于很好短时间的暴风雨。从先进天气研究和预报模型(ARW)的高分辨率的模拟结果的分析证明沿着在PMDV的产生以前的Meiyu前面的南部的温暖的节有几表面骚乱。PMDV与mesoscale交往了对流系统(MCS)并且加强了本地对流降水。在PBL的北方和西南流动在PMDV形成的时候收敛了。同时,到旋涡的南方方面的PBL的顶上的一口西南的喷气增强了上升运动和集中。因此,shear线的强壮的冷空气流动北方什么时候shear线向南遇到了西南流动,被结束PMDV被产生。在PBL,西南风的增强,和北方风的向南方的侵略的集中线为PMDV的发展是批评的。当它在底层便于集中,潜伏的热的版本为PMDV的形成被发现关键。
简介:BasedontheAfKdVequationofXuetal.,atheoryontheveloci-tiesoftheprecursorsolitongenerationintwo-layerflowovertopographyispresentedinthepresentpaper.Movingvelocitiesofprecursorsolitons,ofthefirstzero-crossingofthetailingwavetrainandoftheflowbehindthetopographyarefoundtheoretically.Itisshownthatforagiventopography,whenitsmovingvelocitiesareattheresonantpoints,wehavethefollowingrules:theratioofthemovingvelocityoftheprecursorsolitonstothatofthefirstzero-crossingofthetailingwavetrainequals-4/3.Atthesametime,theratioofthewidthofgeneratingregionoftheprecursorsolitonstothatofthedepressedwaterregionequalsalso-4/3.Thetheoreticalresultsareexaminedbymeansofnumericalcalculation.Thecomparisonbetweenthetheoreticalandnu-mericalresultsarefoundingoodagreement.Fordifferentstratifiedparametersoftwo-layerflow,thevelocitiesoftheprecursorsolitongenerationarealsopredictedintermsofthepresenttheoreticalresults.
简介:Non-lineardevelopmentofdoubletearingmodesinducedbyelectronviscosityisnumericallysimulated.MHDflowlayersaredemonstratedtomergeinthedevelopmentofthemodes.Theshearedflowsareshowntoliejustattheboundariesofthemagneticislands,andtohavesuffcientlevelsrequiredforinternaltransportbarrier(ITB)formation.PossiblecorrelationbetweenthelayerformationandtriggeringofexperimentallyobservedITBs,preferentiallyformedinproximitiesofrationalfluxsurfacesoflowsafetyfactors,isdiscussed.
简介:Globalseismicitycatalogsaresufficientforcharacterizingdoubleseismiczones(DSZs)insubductingslabandfacilitatetoestimatelayerseparationwithoutinconsistentuncertaintiesaslocalcatalogs.PreviousstudieshaveshownthecorrelationbetweenDSZslayerseparationandplateagewhilecorrelationforthoseyoungerthan~60Maissuspicious.ThelackingofDSZswithlayerseparationlessthan10kmfurthermakesitdifficulttopreciselyestimatesuchcorrelation.Thus,weincorporateeightDSZsdatadeterminedthroughlocalseismicityintoglobally-determineddatasetandreexaminesuchcorrelation.Thebestfittingresultsshowthatbothalinearmodelandasquarerootofplateagecanmathematicallyfitthelayerseparationwell.However,itisdifficulttodistinguishthesetwomodelswhenplateageisgreaterthan~20Masincetheirdifferenceislessthan2km.However,ifextrapolationispossible,bothmodelsshouldprovidephysicalinformationthatDSZswillnotformifthereisnosubductinglithosphere.Asaresult,theDSZscannotbeproduceduntiltheoceaniclithosphericagebecomesgreaterthan0.9Mainthesquarerootmodelwhilethelinearmodelgivesamisleadingresult.Assuchthesquarerootmodeldemonstratestherelationshipphysicallybetterthanthelinearone,itstillneedsfurthertestinthefuturewithmoreavailabledata,nevertheless,ourstudymightalsoprovideevidenceforthesuggestionthattheplateageisaprimarycontrolfactoroftheDSZsgeometryaswellasthesubductingprocesswhichdisregardsanylocaltectonicstresses.
简介:Weinvestigateeffectsofannealingonmagneticpropertiesofathick(Ga,Mn)Aslayer,andfindadramaticincreaseoftheCurietemperaturefrom65to115Kbypostgrowthannealingfora500-nm(Ga,Mn)Aslayer.AugerelectronspectroscopymeasurementssuggestthattheincreaseoftheCurietemperatureismainlyduetodiffusionofMninterstitialtothefreesurface.Thedouble-crystalx-raydiffractionpatternsshowthatthelatticeconstantof(Ga,Mn)Asdecreaseswithincreasingannealingtemperature.Asaresult,theannealinginducedreductionofthelatticeconstantismainlyattributedtoremovalofMninterstitial.
简介:Basedonexperimentalresults,thispaperpresentsthatunderspecificvibrationalandsolidifyingconditions,thereareseveralperiodiclayersappearinginthecrystallizationofA1-3%Mgalloy.Themechanismoftheformationofperiodiclayerisdiscussed.Furthermore,theuseofthelayerstoidentifythesolid-liquidinterfaceandtheeffectofsuchlayersonmechanicalpropertiesofalloyhavebeenstudied.
简介:Thegeneralequationsofsecondaryinstabilitywithrespecttothree-dimensionalsubharmonicdisturbancesarederivedandappliedtoBlasiusboundarylayerinthepresentpaper.Thetheoreticalresultsofevolutionandspatialdistributionofsubharmonicdisturbancesarecomparedwithexperimentaldata.There-suitsshowtheimportantroleoftheprocessofroutetotransitioninlow-disturbanceenvironments,andindi-catethatspatialmodeismorerationalthantemporalmode.
简介:Low-lyingstatesofaverticallycoupledthree-layerquantum-dotsystemarestudied.Eachlayercontainsoneelectron,andthetunnellingofelectronsbetweenlayersisneglected.EffectsoftheinterlayerseparationdandtheexternalmagneticfieldBareevaluatedbynumericalcalculations.Inthestrongcouplingcase(i.e.dissmall),asinasingledot,transitionsoftheangularmomentumLofthetruegroundstatesoccurwhenBincreases,whereasintheweakcouplingcasethetransitiondoesnotoccurandLremainszero.Furthermore,itisfoundthatthevariationofdmayalsoinducetheLtransition.Asaresult,aphasediagramofLofthetruegroundstateisgiveninthed-Bplane.
简介:无线网络在更宽的光谱利用的时尚下面被开发(例如,认知无线电)并且多跳跃通讯(例如,无线网孔网络)。在这些范例,怎么有效地与最小化的相互的干扰分配光谱到不同传播连接成为关键担心。在这份报纸,我们在认知收音机网络(CRN)经由光谱分配学习产量优化。以前的研究合并冲突图或SINR模型描绘干扰关系。然而,以前的模型忽视积聚的干扰效果并且导致讨厌的干扰和非最优的结果,当工作在所有潜在的连接之中在估计的RSS(收到的信号力量)的精确性上基于后者模型忽视它的重信赖时。两个是不适当的描绘在干扰和产量之间的复杂关系。到这个目的,由考虑CR的特征,象光谱差异和间断OFDM一样,我们建议一个帮助测量的基于SINR的跨层的产量优化答案。我们的工作在不同的层使特征担心:在物理层,我们在场改进SINR模型的精确性的一个有效RSS评价算法;在上面的层,流动水平为WMN的基于SINR的产量优化问题作为一个混合整数被建模被证明NP难的非线性的编程问题。解决这个问题,一集中(1)最佳的算法和一个有效分布式的算法被提供。评估算法表演,真实世界的踪迹被用来说明我们的计划的有效性。
简介:Theperfectlymatchedlayer(PML)isaneffectivetechniquefortruncatingunboundeddomainswithminimalspuriousreflections.Afluidparabolicequation(PE)modelapplyingPMLtechniquewaspreviouslyusedtoanalyzethesoundpropagationprobleminarange-dependentwaveguide(LuandZhu,2007).However,LuandZhuonlyconsideredastandardfluidPEtodemonstratethecapabilityofthePMLanddidnottakeimprovedone-waymodelsintoconsideration.Theyapplieda[1/1]Padéapproximanttotheparabolicequation.Thehigher-orderPEsaremoreaccuratethanstandardoneswhenaverylargeanglepropagationisconsidered.Asforrange-dependentproblems,thetechniquestohandletheverticalinterfacebetweenadjacentregionsaremainlyenergyconservingandsingle-scattering.Inthispaper,thePMLtechniqueisgeneralizedtothehigherorderelasticPE,asistothehigherorderfluidPE.Thecorrectionofenergyconservingisusedinrange-dependentwaveguides.Simulationismadeinbothacousticcasesandseismo-acousticcases.Range-independentandrange-dependentwaveguidesarebothadoptedtotesttheaccuracyandefficiencyofthismethod.ThenumericalresultsillustratethataPMLismuchmoreeffectivethananartificialabsorbinglayer(ABL)bothinacousticandseismo-acousticsoundpropagationmodeling.
简介:mesoscale在边界层和表面流动的狂暴的交换系数的计算在被改进的数字天气预言模型(MM4),被用来在mesoscale模型的预兆的结果上学习边界层parameterization计划的影响。七个不同实验计划(包括原来的MM4模型)在这份报纸设计了被几大雨格的观察数据测试以便发现改进边界层parameterization在mesoscale的计划气象学的模型。结果证明所有七个不同边界层parameterization计划在降水紧张,雨区域的分发,垂直速度,涡度和分叉地的预报上有一些影响,并且在这的改进计划糊能改进降水预报。关键词边界层parameterization-Mesoscale数字天气预言(MNWP)-狂暴的交换系数-表面流动-大雨这份报纸被中国(资助号码49875005和号码49735180)的国家自然科学基础支持。
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简介:TheeffectofseedlayerontheorientationofZnOfilmwasinvestigated.BeforethepreparationofZnOfilmusingsol-gelmethod,seedlayerofZnOwaspreparedinasimilarwayusingtheprecursorataratherlowconcentration.ExperimentsshowthattheexistenceofseedlayercanimprovetheorientationofthefinallypreparedZnOfilm,whilebakingtemperature,bakingtimeandprecursorconcentrationallhaveeffectsonthefinalresults.
简介:作为在许多设计应用程序的一个基本问题,到骚乱的从laminar的转变在计算液体动力学(CFD)仍然是一个困难的问题。一过渡流动在的数字研究二维被雷纳兹进行在这份报纸的平均数字模拟(RANS)。骚乱模型戏在复杂流动模拟的一个重要角色,和四个先进骚乱模型被评估。摩擦抵抗系数的数字答案与在过渡地区的测量那个相比,它显示有修正的那个威尔科克斯(2006)k-模型是最好的候选人。平均无尺寸的速度介绍的streamwise的无尺寸的速度表演的数字、分析的解决方案的比较在过渡区域很快改正形状。而且,象骚乱动能,旋涡粘性,和雷纳兹应力那样的骚乱数量也被学习,它是有用的学习转变行为。