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500 个结果
  • 简介:在组成的部件之间的有瑕疵的结合能极大地影响合成结构的性质。处于2Dfibrereinforced的问题产生的有瑕疵的接口的不同类型的asymptotic分析合成材料被建议。执行学习基于管理biharmonic问题的asymptotic减小进二个泛音问题。所有答案在一种关上的分析形式被获得。获得的结果能被用于撤退和pushout测试的计算,以及为合成材料的破裂的调查。

  • 标签: 复合材料界面 纤维增强 2D 复合材料结构 双调和问题 组成成分
  • 简介:Open-loopflowcontrolmethodwasusedtoaffectthedevelopmentofaturbulentwakebehindaD-shapedbluffbody.Loudspeakerswereembeddedinsidethebluffbodytoproducetwozero-net-massfluxjetsthrough2mm-widespan-wiseslotslocatedalongtheupperandloweredgesontherearwall.Thedragforcesfordifferentactuationamplitudes(C_μtheratiobetweenthemomentumoftheactuatingjetsandthemomentdeficitcausedbythebluffbody)andfrequencies(Sr_A)wereexamined.Theeffectsofthephasedifferenceinthetwojets(0andπ)werealsostudied.ItwasfoundthatwhenC_μwas0.1%,adragreductionupto5%wasachievedwhenthevelocitiesofthetwojetsvariedinphaseatafrequencyofSt_A=0.16.Whenthevelocitiesofthetwojetsvariedrroutofphase,significantdragincreasewasobserved.

  • 标签: 动阻力 钝体 喷气式飞机 谐波 振幅 速度变化
  • 简介:AbstractFortheweaklyinhomogeneousacousticmediuminΩ={(x,y,z):z>0},weconsidertheinverseproblemofdeterminingthedensityfunctionρ(x,y).Theinversioninputforourinverseproblemisthewavefieldgivenonaline.Wegetanintegralequationforthe2-Ddensityperturbationfromthelinearization.Byvirtueoftheintegraltransform,weprovetheuniquenessandtheinstabilityofthesolutiontotheintegralequation.Thedegreeofill-posednessforthisproblemisalsogiven.

  • 标签: LINEARIZATION INVERSION INTEGRAL GEOMETRY ILL-POSEDNESS
  • 简介:M.Randic首先引入了Wiener.Hosoya指标,该指标可用于对分子的结构,性质和活跃性等方面进行研究.有且仅有一个顶点的度大于或等于3的树称为spider.本文对直径为d,且具有最大Wiener-Hosoya指标的spider进行了刻划.

  • 标签: Wiener-Hosoya指标 直径 SPIDER
  • 简介:Basedonconsolidationequationsproposedforunsaturatedsoil,ananalyticalsolutionfor1Dconsolidationofanunsaturatedsingle-layersoilwithnonhomogeneousmixedboundaryconditionisdeveloped.Themixedboundaryconditioncanbeusedforspecialapplications,suchastestsoccurinlaboratory.Theanalyticalsolutionisobtainedbyassumingallmaterialparametersremainconstantduringconsolidation.Inthederivationoftheanalyticalsolution,thenonhomogeneousboundaryconditionisfirsttransformedintoahomogeneousboundarycondition.Then,theeigenfunctionandeigenvaluearederivedaccordingtotheconsolidationequationsandthenewboundarycondition.Finally,usingthemethodofundeterminedcoefficientsandtheorthogonalrelationoftheeigenfunction,theanalyticalsolutionforthenewboundaryconditionisobtained.Thepresentmethodisapplicabletovarioustypesofboundaryconditions.Severalnumericalexamplesareprovidedtoinvestigatetheconsolidationbehaviorofanunsaturatedsingle-layersoilwithmixedboundarycondition.

  • 标签: 英文摘要 编辑工作 优秀论文 医学期刊
  • 简介:Inthispaper,ahigh-orderfinite-volumeschemeispresentedfortheone-dimensionalscalarandinviscidEulerconservationlaws.TheSimpson’squadratureruleisusedtoachievehigh-orderaccuracyintime.TogetthepointvalueoftheSimpson’squadrature,thecharacteristictheoryisusedtoobtainthepositionsofthegridpointsateachsub-timestagealongthecharacteristiccurves,andthethird-orderandfifth-ordercentralweightedessentiallynon-oscillatory(CWENO)reconstructionisadoptedtoestimatethecellpointvalues.Severalstandardone-dimensionalexamplesareusedtoverifythehigh-orderaccuracy,convergenceandcapabilityofcapturingshock.

  • 标签: EULER方程 有限体积格式 准一维 特征 基础 高阶精度
  • 简介:用Co2(CO)8与CH3CSNH2反应制得产物Ⅰ,又用Na2Fe(CO)4与Ⅰ反应制得产物Ⅱ(Ⅰ:Co3(μ3-S)(CO)7(CH3CSNH),Ⅱ:Co2Fe(μ3-S)(CO)7(CH3CSNH).通过元素分析。IR、UV、1HNMR、MS表征并用X射线衍射法测得Ⅱ的单晶结构.该簇合物属三斜晶系、PT空间群,晶胞参数:a=0.9203(1),b=1.1296(2),c=1.1425(2)nm;α=116.40°(2),β=101.92°(2),γ=92.58°(1);z=2,V=1.2162nm3,Dc=1.698cm3,μ=21.89cm-1.结构分析表明,Co2FeS构三角锥分子骨架,所有CO均为端基配体,S1为面桥基配体,CH3CSNH为双齿配体,与Co、Fe形成五元环结构.

  • 标签: 簇合物 三角锥分子骨架 硫代乙酰胺
  • 简介:采用直接动力学的方法,对多通道反应体系Br+CH3S(O)CH3进行了理论研究.在BH&H-LYP/6-311G(2d,2p)水平下获得了优化几何构型、频率及最小能量路径(MEP),能量信息的进一步确认在MC-QCISD(单点)水平下完成.利用正则变分过渡态理论,结合小曲率隧道效应校正(CVT/SCT)方法计算了该反应的两个可行的反应通道在200K~2000K温度范围内的速率常数.在整个反应区间内,生成HBr的反应通道与生成CHa的反应通道存在着竞争,前者是主反应通道,后者是次反应通道.变分效应和小曲率隧道效应对反应速率常数的计算影响都很小.理论计算得到的两个反应通道的反应速率常数与实验值符合得很好.

  • 标签: 直接动力学方法 速率常数 小曲率隧道效应 正则变分过渡态理论
  • 简介:路易斯底能从CF3SiMe3和包含羰基的混合物催化-trifluoromethyl酒精的形成。-trifluoromethyl白酒能也被用来处于基本条件支持合成,这被发现。

  • 标签: 有机合成 有机化学 催化反应
  • 简介:USINGFINITEGEOMETRIESTOCONSTRUCT-PBIB(2)DESIGNSAND-DESIGNS¥YANGBENFU(DepartmentofMathematics,ChengduTeachersCollege,Chengdu...

  • 标签: FINITE GEOMETRY design.
  • 简介:BSTOdielectricceramicwaspreparedfromSrTiO3andBaTiO3powderssynthesizedbyhydrothermalmethod,aswellasfromBa0.6Sr0.4TiO3powdersynthesizedbyconventionalsolid-statereaction.Theformercanbesinteredatarelativelylowtemperatureof1120℃.CharacterizationbySEMshowedthatthegrainshapesofbothceramicsarecubical,thoughthegrainsizeoftheformerismuchsmaller.Dielectricconstantsmeasuredat20℃wereshowntovarywithfrequencyintherangefrom1kHzto2MHzanddcbiasfield,andfurtherthatthedielectriclossoftheformertobelessthan2×10-3inthefrequencyrangeof20kHzto1MHz,muchsmallerthanthatofthelattersample.Fortheformer,temperaturedependenceofdielectricconstantismuchflatterandthereexistsanextendedphasetransitiondiffusioncoveringawidetemperaturerangeofCurietemperatureTc.Thesmallergrainsizeoftheformerdepressesthedcbiaselectricalfielddependenceofdielectricconstant.Thetunabilityis7%underabiasfieldof0.6kV/mmdc.

  • 标签: 钛酸锶钡陶瓷 钛酸钡粉体 介电性能 水热合成 介电常数测量 高频
  • 简介:利用Gaussian-94计算程序中的B3LYP方法,在6-311+G(2d)6d基组下,对Si5,Si5H3,Si5H6,Si5Li3和Si5Na3原子簇的几何结构进行优化和频率计算.结果表明,Si5原子簇中最稳定的具有D3h对称性的结构中,位于同一平面上的3个Si原子确实具有剩余的成键能力,可以与3个H,Li,Na原子和6个H原子形成稳定的化合物.研究还发现,虽然H,Li和Na都属同一主族,但它们与Si5原子簇中Si原子的键连方式却不同,而且它们的加入,对Si5原子簇的'三角双锥'结构也有不同的影响.

  • 标签: Si5H3 Si5H6 Si5Li3 Si5Na3 硅原子簇 结构
  • 简介:Temperature-dependentphotoluminescencecharacteristicsoforganic-inorganichalideperovskiteCH3NH3PbI3-xClxfilmspreparedusingatwo-stepmethodonZnO/FTOsubstrateswereinvestigated.Surfacemorphologyandabsorptioncharacteristicsofthefilmswerealsostudied.Scanningelectronmicroscopyrevealedlargecrystalsandsubstratecoverage.Theorthorhombic-to-tetragonalphasetransitiontemperaturewas140K.Thefilms’excitonbindingenergywas77.6±10.9meVandtheenergyofopticalphononswas38.8±2.5meV.TheseresultssuggestthatperovskiteCH3NH3PbI3-xClxfilmshaveexcellentoptoelectroniccharacteristicswhichfurthersuggeststheirpotentialusageinperovskitebasedoptoelectronicdevices.

  • 标签: 金属卤化物 有机-无机 光致发光 钙钛矿 氧化锌 两步法
  • 简介:让M是紧缩的orientable无法缩减的3-manifold,和F是在把M切成二manifoldsM1和M2的M的必要连接关上的表面。如果Mi有最小的Heegaard切开Mi=$V_i\cup_{H_i}$V_i\cup_{H_i}有d(H1)的Wi+d(H2)2(g(M1)+g(M2)?g(F))+1,然后g(M)=g(M1)+g(M2)?g(F)。

  • 标签: Heegaard分裂 流形 合并 不可约 表面 H2
  • 简介:TwopossiblereactionmechanismsofVS~+(~3∑~-,~1Γ)withCOinthegasphasehavebeenstudiedbyusingB3LYP/TZVPandCCSD(T)/6-311+G(3dr,3pd)methods:theO/Sexchangereaction(VS~++CO→VO~++CS)andtheS-transferreaction(VS~++CO→V~++COS).Thetworeactionsproceedviatwo-stepandone-stepmechanism,respectively.ThebarriersofthetripletandsingletPESsare30.6and50.9kcal/mol,respectively,forO/Sexchangereactionand7.3and50.2kcal/mol,respectively,fortheS-transferreaction.Theresultsindicatethatthetripletgroundstatereactionismorefavorable,andtheS-transferreactionismorefavorablethantheO/Sexchangereaction,whichisingoodagreementwiththeexperimentalobservation.

  • 标签: 钒元素 铅矿 硫化物 理论研究
  • 简介:Generally,ROSareregardedashostdefensemoleculesthatarereleasedbyneutrophilstodestroyexogenouspathogenssuchasbacteriaandtoactassecondarymessengersinsignaltransduction.However,increasedproductionofROSisalsoinvolvedininducingpathophysiologicalchangessuchasapoptosis,cellcycledisruption,andnecrosis.Forthisreason,inductionofROS-mediateddamageincancercellsbypharmacologicalagentsthateitherpromoteROSgenerationordisablethecellularantioxidantsystemisconsideredapotentialtherapeuticstrategyforpreferentiallykillingcancercells[1].

  • 标签: ROLE Redox STATUS