简介：Synchronousgammaoscillationsarebelievedtoplayaprominentroleintheinformationprocessingofbiologicalneuralsystems.Experimentalobservationshavefoundthatthefrequencyandpowerofgammaoscillationsintheprimaryvisualcortex(V1zone)areregulatedbytheilluminationcontrastofvisualstimulus.However,theunderlyingmechanismofhowthesynchronousoscillationsdependontheilluminationcontrasthasnotbeenwellexplained.Weproposealocalexcitatory/inhibitory(E/I)neuronalnetworkofintegrate-and-fire(IAF)neuronswiththedifference-of-Gaussians(DOG)receptivefieldtounveilthismechanism.Simulationresultsdemonstratethatthehighertheilluminationcontrast,thehigherthefrequencyofgammaoscillations.Thepowerofgammaoscillationsalsoincreaseswiththeincreaseofilluminationcontrast.Theseresultsareconsistentwiththeexperimentalfindings.

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.

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简介：Thispaperestablishesanon-linearfiniteelementmodel(NFEM)ofL4-L5lumbarspinalsegmentwithaccuratethree-dimensionalsolidligamentsandintervertebraldisc.Forthepurpose,theintervertebraldiscandsurroundingligamentsaremodeledwithfour-nodalthree-dimensionaltetrahedralelementswithhyper-elasticmaterialproperties.Puremomentof10N·mwithoutpreloadisappliedtotheuppervertebralbodyundertheloadingconditionsoflateralbending,backwardextension,torsion,andforwardfle...

简介：为它的高氧化抵抗，钇硅酸盐是为在在1600°C上面的温度的carbon-fiber-reinforcedcomposites的保护的涂层的一个重要候选人。一个新奇方法，由一起沉淀组成，弄干水花，热处理和plasma-densification，被开发准备Y2SiO5粉末为热喷洒。作文，形态学和综合Y2SiO5粉末的流动能力被XRD，SEM和霍尔流量计分别地调查。结果证明综合Y2SiO5粉末与高纯净是将近球形的。分别地，Y2SiO5粉末的明显的密度和流动能力是1.87g/cm3和37s/50g它为大气的血浆喷洒导致多达80%的高免职效率。

简介：Inthisworktypicalmechanicalpropertiesforacatalystsupportmaterial,ZSM5(aspray-driedgranularzeolite),havebeenmeasuredinordertorelatethebulkbehaviourofthepowdermaterialtothesingleparticlemechanicalproperties.Particleshapeandsizedistributionofthepowders,determinedbylaserdiffractionandscanningelectronmicroscopy(SEM),confirmedthesphericalshapeofthespray-driedparticles.TheexcellentflowabilityofthematerialwasassessedbytypicalmethodssuchastheHausnerratioandtheCarrindex.Thiswasconfirmedbybulkmeasurementsoftheparticle-particleinternalfrictionparameterandflowfunctionusingaSchulzeshearcell,whichalsoillustratedthelowcompressibilityofthematerial.SingleparticlecompressionwasusedtocharacterizesingleparticlemechanicalpropertiessuchasreducedelasticmodulusandstrengthfromHertzcontactmechanicstheory.Comparisonwithsurfacepropertiesobtainedfromnanoindentationsuggestsheterogeneity,thesurfacebeingharderthanthecore.Inordertoevaluatetherelationshipbetweensingleparticlemechanicalpropertiesandbulkcompressionbehaviour,uniaxialconfinedcompressionwascarriedout.ItwasdeterminedthattheAdamsmodelwassuitablefordescribingthebulkcompressionandfurthermorethattheAdamsmodelparameter,apparentstrengthofsingleparticles,wasingoodagreementwiththesingleparticlestrengthdeterminedfromsingleparticlecompressiontest.

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

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简介：ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍｏｓｔｂａｓｉｃｃｏｎｄｉｔｉｏｎｓｆｏｒｆｅｅｄｂａｃｋｃｌｏｓｅｄ＿ｌｏｏｐｃｏｎｔｒｏｌｏｆｍａｎｉｐｕｌａｔｏｒｓａｒｅｔｈｅｆｉｎｅｓｔｒｕｃｔｕｒｅａｎｄｔｈｅｅｆｆｉｃｉｅｎｔｒｅａｌ＿ｔｉｍｅｃｏｍｐｕ...

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

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

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

简介：Duetotheirsize-dependentpropertiesandflexibleprocessingchemistry(Alivisatos,1996),monodispersednanocrystalshaveattractedconsiderableattentionfortheirdistinguishedroleinfundamentalstudiesandtechnicalapplications.AlthoughmuchhasbeenreportedonfabricationofmonodispersedinorganicnanocrystalssuchasFe2O3,CdSe,PbSeandZrO2(Peng&Peng,2002;Zhuetal.,2002;Niederbergeretal.,2002;Pangetal.,2001),littlepublishedonthepreparationofBaSO4nanocrystalsandtheircrystalsizeandmorphologywhichaffecttheirperformanceinapplication.PolymeradditiveswithcomplexfunctionshavebeenusedastemplatestodirectorientednucleationandgrowthofBaSO4(Xiaoetal.,2001;Yuetal.,2002;Summersetal.,2002),asanewclassoffunctionalpolymers,theso-calleddouble-hydrophilicblockcopolymers,designedtocontrolthemorphologyofBaSO4(Colfenetal.,2002),includingtheirnanofiberssynthesizedinAOTmicroemulsion(Li&Mann,2000).ThoughsomuchresearchhasbeendevotedtocontrollingtheBaSO4morphologies,thepresentnotewillreportonthesynthesisofBaSO4nanocrystalswithsizecontrolling.

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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.