学科分类
/ 18
346 个结果
  • 简介:1.联系生活实例,认识杠杆是一根在力的作用下,可绕固定点转动的硬棒,能从常见的工具中辨识出杠杆.

  • 标签: 杠杆 生活实例 定点转动
  • 简介:On △I=4 Bifurcation PhenomenaOn△I=4BifurcationPhenomena¥ZhangJingye;YangSunandMikeGuidryTheexperiments-bythenew7--raydetector...

  • 标签:
  • 简介:1.运用实例分析,认识运动的物体能够做功,所具有的能量称为动能.2.通过探究实验,知道动能的大小与物体的质量和运动速度有关.能运用动能与质量、速度的关系解释简单的生活现象.

  • 标签: 动能 机械能 势能 运动速度 探究实验 生活现象
  • 简介:ThecapacitytocaptureCO2wasdeterminedinseveralstoichiometriccompositionsintheLi2O–Bi2O3system.Thecompounds(Li7BiO6,Li5BiO5,Li3BiO4andLiBiO2phases)weresynthesizedviasolid-statereactionandcharacterizedbyX-raydiffraction,scanningelectronmicroscopyandN2adsorptiontechniques.Thesampleswereheat-treatedattemperaturesfrom40to750°CundertheCO2atmospheretoevaluatethecarbonateformation,whichisindicativeofthecapacityofCO2capture.Moreover,Li7BiO6showsanexcellentCO2capturecapacityof7.1mmol/g,whichisconsiderablyhigherthanthoseofotherpreviouslyreportedceramics.Li7BiO6isabletoreactwithCO2from240°Ctoapproximately660°CshowingahighkineticreactionevenatCO2partialpressurevaluesaslowas0.05.

  • 标签:
  • 简介:Carbonnanotubeswithjunctionsmayplayanimportantroleinfuturenanoelectronicsandfuturenanodevices.Inparticular,junctionsconstructedwithmetalandsemiconductingnanotubeshavepotentialapplications.Basedontheorthogonaltight-bindingmoleculardynamicsmethod,wepresentourstudyofthestructurestabilityofI-typecarbonnanotubejunctions.

  • 标签: 碳纳米管 结构稳定性 纳米器件
  • 简介:ThecorrelationbetweenphasestructuresandsurfaceacidityofAl2O3supportscalcinedatdifferenttemperaturesandthecatalyticperformanceofNi/Al2O3catalystsintheproductionofsyntheticnaturalgas(SNG)viaCOmethanationwassystematicallyinvestigated.Aseriesof10wt%NiO/Al2O3catalystswerepreparedbytheconventionalimpregnationmethod,andthephasestructuresandsurfaceacidityofAl2O3supportswereadjustedbycalciningthecommercialγ-Al2O3atdifferenttemperatures(600–1200C).COmethanationreactionwascarriedoutinthetemperaturerangeof300–600Catdifferentweighthourlyspacevelocities(WHSV=30000and120000mL·g-1h-1)andpressures(0.1and3.0MPa).ItwasfoundthathighcalcinationtemperaturenotonlyledtothegrowthinNiparticlesize,butalsoweakenedtheinteractionbetweenNinanoparticlesandAl2O3supportsduetotherapiddecreaseofthespecificsurfaceareaandacidityofAl2O3supports.Interestingly,NicatalystssupportedonAl2O3calcinedat1200C(Ni/Al2O3-1200)exhibitedthebestcatalyticactivityforCOmethanationunderdifferentreactionconditions.LifetimereactiontestsalsoindicatedthatNi/Al2O3-1200wasthemostactiveandstablecatalystcomparedwiththeotherthreecatalysts,whosesupportswerecalcinedatlowertemperatures(600,800and1000C).ThesefindingswouldthereforebehelpfultodevelopNi/Al2O3methanationcatalystforSNGproduction.

  • 标签: Ni catalyst ALUMINA CO METHANATION synthetic
  • 简介:A60%Fe/Al2O3catalystwaspreparedbytheco-precipitationmethod.ItwasreducedbyH2toproducemetallicFe,whichwasthensulfidedbyCS2toFe0.96SandFe3S4orphosphidedbytriphenylphosphine(PPh3)inliquidphasestoFe2PandFeP.Itwasfoundthattheironsulfides(Fe0.96SandFe3S4)exhibitedthelowactivityforthehydrodesulfurization(HDS)reactions.TheHDSactivitywasalsolowontheFe(metal)/Al2O3andFe2P/Al2O3catalystssincetheywereconvertedintoFe0.96SandFe3S4duringtheHDSreactions.Incontrast,theFeP/Al2O3wasfoundtobestableandactivefortheHDSreactions.Inparticular,FeP/Al2O3possessedsignificantlysmallerFePparticlesthanFeP/C,leadingtothesignificanthigherHDSactivityofFeP/Al2O3thanFeP/C.

  • 标签: Fe2P/Al2O3 CATALYST FeP/Al2O3 CATALYST Liquid phase
  • 简介:Pureandneodymium-dopedgadoliniumcalciumoxoboratecrystalsofhighqualityweregrownbytheCzochralskimethod.Theorientationofcrystalwaspreciselydetermined,andthesamplesformeasurementswereprepared.Throughsynchrotronx-raytopographyandhigh-resolutionx-raydiffractometry,thetwinstructurewasdiscovered.Somepropertiessuchasthefigureofmeritvalue,anddielectric,piezoelectric,andelasticconstantsweremeausuredalongwithadiscussionoftheanisotropyofthelaserproperties.

  • 标签: GdCa4O(BO3)3晶体 钕掺杂 硼酸盐晶体 Nd:GdCa4O(BO3)3晶体 晶体生长 形貌学
  • 简介:Aseriesofoxygenpermeabledual-phasecompositeoxides60wt%Ce0.8Gd0.2O2-δ-40wt%LnBaCo2O5+δ(CGO-LBCO,Ln=La,Pr,Nd,Sm,GdandY)weresynthesizedthroughasol-gelrouteandeffectsoftheLn3+cationsontheirphasestructure,oxygenpermeabilityandchemicalstabilityagainstCO2wereinvestigatedsystemicallybyXRD,SEM,TG-DSCandoxygenpermeationexperiments.XRDpatternsrevealthatthelargerLn3+cations(La3+,Pr3+andNd3+)successfullystabilizedthedouble-layeredperovskitestructureofsinteredLBCO,whilethesmallerones(Sm3+,Gd3+,andY3+)resultedinthepartialdecompositionofLBCOwithsomeimpuritiesformed.CGO-PBCOyieldsthehighestoxygenpermeationflux,reaching2.8×10-7mols-1cm-2at925?Cwith1mmthicknessunderair/Hegradient.TheTG-DSCprofilesin20mol%CO2/N2andoxygenpermeabilityexperimentswithCO2assweepgasshowthatCGO-YBCOdemonstratesthebestchemicalstabilityagainstCO2,possiblyduetoitsminimumbasicity.ThestableoxygenpermeationfluxofCGO-YBCOunderCO2atmosphererevealsitspotentialapplicationintheoxy-fuelcombustionrouteforCO2capture.

  • 标签: CO2 透氧性 双相 化学稳定性 TG-DSC 渗透实验
  • 简介:充分一致的相对论的连续统随机阶段近似(RCRPA)以格林的功能技术被构造。在到原子刺激的连续统光谱的贡献完全被单个粒子对待的这个方法,格林是功能,它也在迪拉克海包括否定状态在没有海近似。RCRPA和数字细节的理论形式主义被介绍。单个粒子格林的功能被迪拉克方程的常规、不规则的答案的一个合适的产品数字地计算。数字细节和在动量表示的RCRPA的形式主义被介绍。

  • 标签: 形式主义 相对论 随机 格林函数方法 狄拉克方程 计算数值
  • 简介:TomoreindepthunderstandthedopingeffectsofoxygenonSiGealloys,boththemicro-structureandpropertiesofO-dopedSiGe(including:bulk,(001)surface,and(110)surface)arecalculatedbyDFT+Umethodinthepresentwork.Thecalculatedresultsareasfollows.(i)The(110)surfaceisthemainexposingsurfaceofSiGe,inwhichOimpuritypreferstooccupythesurfacevacancysites.(ii)ForOinterstitialdopingonSiGe(110)surface,theexistencesofenergystatescausedbyOdopinginthebandgapnotonlyenhancetheinfraredlightabsorption,butalsoimprovethebehaviorsofphoto-generatedcarriers.(iii)ThefindingaboutdecreasedsurfaceworkfunctionofO-dopedSiGe(110)surfacecanconfirmpreviousexperimentalobservations.(iv)Inallcases,Odoingmainlyinducestheelectronicstructuresnearthebandgaptovary,butisnotdirectlyinvolvedinthesevariations.Therefore,thesefindingsinthepresentworknotonlycanprovidefurtherexplanationandanalysisforthecorrespondingunderlyingmechanismforsomeoftheexperimentalfindingsreportedintheliterature,butalsoconducetothedevelopmentofμc-SiGe-basedsolarcellsinthefuture.

  • 标签: SIGE 计算结果 电子结构 掺杂 O型 锗硅合金
  • 简介:合成了六铝酸盐SrNiAl11O19并用XRD、UVDRS、TGDTA和TEM等技术对其进行了表征。在750℃于SrNiAl11O19上进行的甲烷与二氧化碳重整反应表明,这类催化剂较Ni/SrAl12O19具有较大活性和低积碳能力,在催化反应过程中可有效地抑制Ni颗粒的增大。

  • 标签: 六铝酸盐甲烷重整Ni催化剂
  • 简介:TheNd2O3nanoparticleswhichmodifiedbyAOTwaspreparedusingmicrioemulsionmethodinthesystemofwater/xylene.L3edgeXAFSwasusedtodeterminethedifferenceofthelocalstructurearundNd^3+ionandtheelectricalstructurebetweenthenanocystallineNd2O3andthecoarsebulkmicrocrystallineNd2O3.ItwasfoundthatNd-Odistanceincreasedwiththeformofnanocrystalliteandtheintensityofabsorptionedgealsoenhancedatthesametime.

  • 标签: EXAFS研究 ND2O3 毫微米粒子