简介:不同尺寸的喷雾器被一个安德森空气刺绣花样收集观察黑碳(BC)的详细形态学与另外的伴随的喷雾器化学上被分开的喷雾器,用与一个精力DispersiveX光线分光计(SEM-EDX)装备的一台扫描电子显微镜。结果显示大多数BC喷雾器是在直径并且与同类的表面的大约50nm的球形的粒子。结果也证明这些粒子与另外的喷雾器或与自己一起聚集形成更大在测微计范围聚结。这些50-nmBC球形的粒子的形状被发现很类似于免除石油动力的车辆的内燃机的BCparticles的。这些球形的BCparticles被显示与发现帮助usingMatrix的激光解吸附作用/电离蒂米夫莱特·马斯·斯佩克特罗梅特里(MALDI-TOF-MS)的以前报导的fullerenes不同。
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简介:骨胶原纤维提供成为强壮的一个好例子微--或从nanoscaletropocollagen分子通过的mesoscale纤维一蹒跚并且以一种自底向上的方式的cross-linked组织。骨胶原纤维的建筑上的特征被显示出是一条有希望的途径开发高效的碳nanotube(CNT)纤维的Mimicking。在现在的工作,一个有弹性的模型被开发在bioinspiredCNT捆以内描述负担转移和失败繁殖,并且与象CNT方面比率和纵的差距那样的很多个几何、物理的参数建立捆的机械性质的关系,接口交叉结合密度,和在CNT的导致functionalization的降级,等等。与模型一起,沿着CNTCNT接口以及在每单个CNT的压力分布是捕获的井,和沿着CNT捆的机械性质上的接口和它的效果的失败繁殖被预言。工作可以在实践为新奇CNT纤维的设计提供有用指南。
简介:Carbonnanotubemacro-filmsaretwo-dimensionalfilmswithmicrometerthicknessandcentimeterbycentimeterin-planedimension.Thesecarbonnanotubemacroscopicassemblieshaveattractedsignificantattentionfromthematerialandmechanicscommunitiesrecentlybecausetheycanbeeasilyhandledandtailoredtomeetspecificengineeringneeds.Thispaperreportstheexperimentalmethodsonthepreparationandcharacterizationofsingle-walledcarbonnanotubemacro-films,andastatisticalmechanicsmodelon...
简介:Heattransportisakeyenergeticprocessinmaterialsanddevices.Thereducedsamplesize,lowdimensionoftheproblemandtherichspectrumofmaterialimperfectionsintroducefruitfulphenomenaatnanoscale.Inthisreview,wesummarizerecentprogressesintheunderstandingofheattransportprocessinlow-dimensionalmaterials,withfocusontherolesofdefects,disorder,interfaces,andthequantummechanicaleffect.Newphysicsuncoveredfromcomputationalsimulations,experimentalstudies,andpredictablemodelswillbereviewed,followedbyaperspectiveonopenchallenges.
简介:Thispapergivesanoverviewonnonlinearporousflowinlowpermeabilityporousmedia,revealsthemicroscopicmechanismsofflows,andclarifiespropertiesofporousflowfluids.Itshowsthat,deviatingfromDarcy’slinearlaw,theporousflowcharacteristicsobeyanonlinearlawinalow-permeabilityporousmedium,andtheviscosityoftheporousflowfluidandthepermeabilityvaluesofwaterandoilarenotconstants.Basedonthesecharacters,anewporousflowmodel,whichcanbetterdescribelowpermeabilityreservoir,isestablished.Thismodelcandescribevariouspatternsofporousflow,asDarcy’slinearlawdoes.Alltheparametersinvolvedinthemodel,havingdefinitephysicalmeanings,canbeobtaineddirectlyfromtheexperiments.
简介:TheaerodynamicforcesandflowstructureofamodelinsectwingisstudiedbysolvingtheNavier-Stokesequationsnumerically.Afteraninitialstartfromrest,thewingismadetoexecuteanazimuthalrotation(sweeping)atalargeangleofattackandconstantangularvelocity.TheReynoldsnumber(Re)consideredinthepresentnoteis480(Reisbasedonthemeanchordlengthofthewingandthespeedat60%winglengthfromthewingroot).Duringtheconstant-speedsweepingmotion,thestallisabsentandlargeandapproximatelyconstantliftanddragcoefficientscanbemaintained.Themechanismfortheabsenceofthestallorthemaintenanceoflargeaerodynamicforcecoefficientsisasfollows.Soonaftertheinitialstart,avortexring,whichconsistsoftheleading-edgevortex(LEV),thestartingvortex,andthetwowing-tipvortices,isformedinthewakeofthewing.Duringthesubsequentmotionofthewing,abase-to-tipspanwiseflowconvertsthevorticityintheLEVtothewingtipandtheLEVkeepsanapproximatelyconstantstrength.ThispreventstheLEVfromshedding.Asaresult,thesizeofthevortexringincreasesapproximatelylinearlywithtime,resultinginanapproximatelyconstanttimerateofthefirstmomentofvorticity,orapproximatelyconstantliftanddragcoefficients.Thevariationoftherelativevelocityalongthewingspancausesapressuregradientalongthewingspan.Thebase-to-tipspanwiseflowismainlymaintainedbythepressure-gradientforce.
简介:Weconductedmeasurementsofblackcarbon(BC)aerosolinJiaxing,ChinaduringautumnfromSeptember26toNovember30,2013.WeinvestigatedtemporalanddiurnalvariationsofBC,anditscorrelationswithmeteorologicalparametersandothermajorpollutants.ResultsshowedthathourlymassconcentrationsofBCrangedfrom0.2to22.0μg/m3,withanaverageof5.1μg/m3.ThediurnaivariationofBCexhibitedabimodaldistribution,withpeaksat07:00and18:00.Themorningpeakwaslargerthantheeveningpeak.ThemasspercentagesofBCinPM2.5andPM10were7.1%and4.8%,respectively.TheabsorptioncoefficientofBCwascalculatedtobe44.4Mm-1,whichaccountedfor11.1%ofthetotalaerosolextinction.BCwasmainlyemittedfromlocalsourcesinsouthwesternJiaxingwhereBCconcentrationsweregenerallygreaterthan11μg/m3duringthemeasurementperiod.CorrelationanalysisindicatedthatthemainsourcesofBCweremotorvehicleexhaust,anddomesticandindustrialcombustion.
简介:Thisworkfocusesonthestudyoftheeffectofhydrophobicityonthewaterflowincarbonnanotubes(CNTs)usingamoleculardynamics(MD)approachforawiderangeofpotentialapplicationssuchaswaterpurificationandhighefficiencyofnanofluidenergyabsorptionsystems(NEAS).ThehydrophobicitybetweenliquidwaterandsurfaceofCNTswascharacterizedbyinteraction-energy-coefficient(IEC)—aparameterdescribingtheenergyinteractionstrengthbetweenwatermoleculesandcarbonatoms.Itisshownthatthestaticcontactanglesbetweenwaterandcarbonsurfacedecreasefrom155°to44°whenthevaluesofIECincreasefrom0.042kJ/molto2.196kJ/mol.Inaddition,thepressuredropsinCNTbecameindependentofIECwhentheIECvaluewashigherthan1.192kJ/molforagivenflowrate.ItwasfoundthatthehydrophobicityofCNTsurfacehasasignificantimpactonthepressuredropofwaterflowintheCNTsandMDmethodprovidesaquantitativeevaluationoftheimpact.
简介:Holloworderedporouscarbonspheres(HOPCS)withahierarchicalstructurewerepreparedbytemplatingwithholloworderedmesoporoussilicaspheres(HOMSS).Scanningelectronmicroscopy(SEM)andtransmissionelectronmicroscopy(TEM)showedthatHOPCSexhibitedasphericalhollowmorphology.High-resolutionTEM,smallangleX-raydiffraction(SAXRD)andN2sorptionmeasurementsconfirmedthatHOPCSinverselyreplicatedtheunconnectedhexagonal-stackedporestructureofHOMSS,andpossessedorderedporosity.HOPCSexhibitedahigherstoragecapacityforLi+ionbattery(LIB)of527.6mAh/g,andgoodcyclingperformance.Alargecapacitylossduringthefirstdischarge-chargecyclewasfoundattributedtothehighcontentofmicropores.Thecyclingperformancewasderivedfromthehierarchicalstructure.
简介:高度强制的钴铁酸盐nanoparticles被他们的暂停的直接注射为加热为磁性的过高热综合并且学习进一个强壮的听觉频率的磁场的一个肿瘤和应用。物理(在液体和稳固的分散的动态磁性的磁滞现象和热产生),生物(在进老鼠肿瘤织物的治疗学的数量的粒子的毒性和穿入)象其它一样,粒子的性质被学习。一个模型被开发为Brownian和常规旋转与一篇报道在磁性的nanoclusters的暂停描述magnetodynamics,到提供观察现象的理解。开发的试验性、理论的技术为低频率的热产生为磁性的nanoparticles的可控制的合成形成了一个基础在医药并且另外的应用程序。
简介:Coherentstructuresareessentialforthemomentumexchangeandturbulenceproductioninwall-boundedturbulentflows.Diversifiedcoherentstructureshavebeenobservedinturbulentboundarylayers,andhairpin-basedvorticesdominatemostoftherelevantliterature.However,thereisnoconsensusyetontheoriginandformingmechanismofhairpinvortices.Herein,fivecornerstonespertainingtotheframeworkofhairpin-basedcoherentstructuresarereviewed,andthreedifferenthairpingenerationmechanismsareclarified.Next,thetime-resolvedtomographicparticleimagevelocimetry(Tomo-PIV)isusedinanearlyturbulentboundarylayer(Reθ=420)toinvestigatetheoriginofhairpinvortices.Thetimelinesrevealatriangularbulgeinthelow-speedstreak(LSS),andtheinitialroll-upoccursattwosidesofit.Meanwhile,thematerialsurfacesmanifestasathree-dimensional(3D)wavestructureintheLSS,whichmaysupportthemodelofasoliton-likecoherentstructure(SCS).Subsequently,themethodofLagrangian-averagedvorticitydeviationisusedtodetectearlyvortices.Wefindthatthe3Dwavestructureisflankedbytwovortices,thusconfirmingtheroll-upoftimelinesanddemonstratingtheadvantageoftheLagrangiancriteriaincapturingstructuresincomplexflows.Theseresultssuggestthatvariouscoherentstructuresmayevolvefromthemetamorphosisof3Dwavestructuresandtheirlaterinteraction.Finally,thelimitationsoftraditionalexperimentalandpost-processingtoolsarediscussed.
简介:Analumina-supportedcobaltaerogelcatalystpreparedfromasol-gelandasupercriticaldryingmethodwasusedinthecatalyticdecompositionofmethane.Thephysical-chemicalpropertiesofthecatalystwerecharacterizedanditsactivityformethanedecompositionwasinvestigated.Theeffectsofcalcinationandreactiontemperaturesontheactivityofthecatalystandthemorphologyofthecarbonnanotubesproducedwerediscussed.ACoAl2O4spinelstructureformedinthecalcinedcatalyst.Thequantityofthenanotubesproducedinthereactionincreaseswiththeamountofcobaltinthereducedcatalyst.Ahigherreactiontemperatureleadstoahigherreactionrate,thoughfasterdeactivationofthecatalystoccurswiththechange.Thecarbonnanotubesgrownonthecatalysthavesmoothwallsanduniformdiameterdistribution.
简介:Thediscoveryofdrawablecarbonnanotubeforestsopenedupthepossibilityofconstructingawiderangeofpurecarbonnanotubemacrostructuresandsparkedinterestsindevelopingapplicationsfromthesestructures,especiallypurecarbonnanotubeyarns.Thisreviewexaminesthevariousfacetsofthedrawablecarbonnanotubeforests,synthesisanddrawability,andtheirresultingyarns,structure,production,propertiesandapplications.Thestructure,formationandpropertiesofcarbonnanotubeyarnsarecomparedwiththoseofconventionaltextileyarnsinordertoobtainabetterunderstandingofthescience,structuralmechanicsandprocessingtechnologyinvolvedincarbonnanotubeyarns.
简介:Thepolarlowandtropicalcyclonetypevorticesovertopographyareassumedtobetheaxisymmetricalandthermal-windbalancedsystems,whicharesolvedasaninitialvalueproblemofalinearizedvortexequationsetincylindricalcoordinates.Therolesofthesensibleandlatentheating,friction,andtopographyinthestructureandintensificationofthepolarlowandtropicalcyclonetypevorticesareanalyzed.Theradialvelocity,verticalvelocity,azimuthalvelocity,andtheunstablegrowthrateincludingthetopographyeffectsareobtained.Itisshownthattheinteractionbetweentheflowandthetopographyplaysasignificantroleinthestructureandintensificationofthepolarlowandtropicalcyclonesystem.Theanalysisofthetopographytermindicatesthat,intheup-slopesideofthemountain,theradialinflowandtheverticalascentforcedbythemountaincanintensifythepolarlowandtropicalcyclonetypevortexandincreasetheunstablegrowthrate.However,intheleesideofthemountain,theradialinflowandtheverticaldescentforcedbythemountaincanweakenthepolarlowandtropicalcyclonetypevortexanddecreasetheunstablegrowthrateofthepolarlowandtropicalcyclonesystem.Inaddition,theevolutionaryprocessandthespatialstructureofthepolarlowobservedovertheJapanSeaon19December2003areinvestigatedwiththeobservationaldatatoverifythistheoreticalresult.
简介:Spacecraftsciencemissionstoplanetsorasteroidshavehistoricallyvisitedonlyoneorseveralcelestialbodiespermission.Theresearchgoalofthispaperistocreateatrajectorydesignalgorithmthatgeneratestrajectoryallowingaspacecrafttovisitasignificantnumberofasteroidsduringasinglemission.Fortheproblemofglobaltrajectoryoptimization,evenwithrecentadvancesinlow-thrusttrajectoryoptimization,afullenumerationofthisproblemisnotpossible.Thisworkpresentsanalgorith...