学科分类
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491 个结果
  • 简介:设G是一个图.设g和f是两个定义在V(G)上的整值函数使得对V(G)所有的顶点x有g(x)f(x).图G被称为(g,f,n)-临界图,如果删去G的任意n个顶点后的子图都含有G的(g,f)-因子.本文给出了图是(a,b,n)-临界图几个充分条件.进一步指出这些条件是最佳的.例如,如果对V(G)所有的顶点x和y都有g(x)<f(x),n+g(x)dG(x)和g(x)/(dG(x)-n)f(y)/dG(y),则G是(g,f,n)-临界图.

  • 标签: (G F)-因子 (g f n)-临界图
  • 简介:Inthispaper,weareconcernedwiththesymmetricpositivesolutionsofa2n-orderboundaryvalueproblemsontimescales.Byusinginductionprinciple,thesymmetricformoftheGreen’sfunctionisestablished.Inordertoconstructanecessaryandsufficientconditionfortheexistenceresult,themethodofiterativetechniquewillbeused.Asanapplication,anexampleisgiventoillustrateourmainresult.

  • 标签: SYMMETRIC positive solutions boundary value problems
  • 简介:Anumbilicalfreeorientedhypersurfacex:M→Rnwithnon-zeroprincipalcurvaturesiscalledaLaguerreisoparametrichypersurfaceifitsLaguerreformC=iCiωi=iρ1(Ei(logρ)(rri)Ei(r))ωivanishesandLaguerreshapeoperatorS=ρ1(S1rid)hasconstanteigenvalues.Hereρ=i(rri)2,r=r1+r2+···+rn1n1isthemeancurvatureradiusandSistheshapeoperatorofx.{Ei}isalocalbasisforLaguerremetricg=ρ2IIIwithdualbasis{ωi}andIIIisthethirdfundamentalformofx.Inthispaper,weclassifyallLaguerreisoparametrichypersurfacesinRn(n>3)withtwodistinctnon-zeroprincipalcurvaturesuptoLaguerretransformations.

  • 标签: 等参超曲面 主曲率 非零 拉格朗日 曲率半径 特征值
  • 简介:我们构造N=从歧管的概括Calabi-Yau的2superconformal顶点代数学(SCVA)并且计算它的联系拓扑的顶点代数学的BRSTcohomology。我们证明BRSTcohomology与概括Dobeaultcohomology与一致。我们证明二拓扑的顶点代数学由A和B扭曲从N=构造了2SCVA分别地是镜子对。

  • 标签: 镜面对称 广义 顶点代数 上同调 代数拓扑 拓扑构造
  • 简介:在这份报纸,我们学习最少的精力的存在包含部分拉普拉斯算符操作员的一个Kirchhoff类型问题的改变症状的解决方案。由使用限制变化方法和量的变丑词根,我们获得一个最少的精力节的答案u为给定的问题的b。而且,我们证明ub严格地比大两次扎根的州的精力。我们也给u是的bb0,在b被认为是一个积极参数的地方。

  • 标签: Kirchhoff 方程 部分拉普拉斯算符 改变症状的答案
  • 简介:采用普通溶液法合成了锰配位聚合物[Mn(C_(10)H_8N_2)(CHO_2)_2]_n,并用红外光谱、紫外光谱、X-射线单晶衍射、热重分析和电化学分析对其进行表征.晶体结构表明:该配合物属于单斜晶系,Pn空间群,晶胞参数a=0.7828(6)nm,b=0.8650(6)nm,c=0.9021(7)nm,β=90.304(7)°,V=0.6108(8)nm3,Z=1.Mn(Ⅱ)离子的配位多面体呈变形的八面体几何结构.配合物由配体甲酸根离子和4,4'-联吡啶桥联为三维网状结构.

  • 标签: 配位聚合物 4 4'-联吡啶 甲酸 晶体结构 电化学性质
  • 简介:Asidechainliquidcrystallinecopolysiloxane,whichwouldshowelectro-opticeffectsasknownfromlowmassliquidcrystal,wassynthesizedbyhydrosilylationreaction,andthetwohomologousmonomerswithdifferentlengthspacerscontainingSchiff’sbasemesogenwith—NO2terminatedgroupweregraftedtoapolysiloxanemainchain.Residualmonomerincrudeproductiseffectiveinreinforcingtheresponsetoanelectricfieldoverthatofpurepolymericliquidcrystal.

  • 标签: Liquid Crystalline POLYSILOXANE Schiff’s BASE MESOGENS
  • 简介:设∑A,∑B,∑C是n维欧氏空间En(n≥3)中三个n维单形,它们的棱长分别是ai,bi,ci(i=1,2,…,c2n+1),体积分别是VA,VB,VC。本文证明了下列定理。设实数α≥0,β≤an(n≥3)且α,β不全为零。(1)如果θ1,θ2,θ3∈[0,1],那末(1)并且(1)中等号成立当且仅当ΣA,ΣB,ΣC都是正则单形,(2)当θ1∈(1,2],θ2,θ3∈(0,1]且ΣA的的每一个三角形侧面都是锐角三角形时,不等式(1)仍成立。

  • 标签: 不等式 单形体积 欧氏空间 锐角三角形 正则单形 联系
  • 简介:LetM^nbeaclosedspacelikesubmanifoldisometricallyimmersedindeSitterspaceSp^(n+p)(c),DenotebyR,HandSthenormalizedscalarcurvature,themeancurvatureandthesquareofthelengthofthesecondfundamentalformofM^n,respectively.SupposeRisconstantandR≤c.ThepinchingproblemonSisstudiedandarigiditytheoremforM^nimmersedinSp^(n+p)(c)withparallelnormalizedmeancurvaturevectorfieldisproved.Whenn≥3,thepinchingconstantisthebest.Thus,themistakeofthepaper“Space-likehypersurfacesindeSitterspacewithconstantscalarcurvature”(seeManusMath,1998,95:499-505)iscorrected.Moreover,thereductionofthecodimensionwhenM^nisacompletesubmanifoldinSp^(n+p)(c)withparallelnormalizedmeancurvaturevectorfieldisinvestigated.

  • 标签: 类空间子流形 常量曲率 平行正则 边量场 SITTER空间
  • 简介:Thebilinearformofthe(2+1)-dimensionalnon-isospectralAKNSsystemisderived.ItsN-solitonsolutionsareobtainedbyusingtheHirotamethod.Asareduction,a(2+1)-dimensionalnon-isospectralSchrdingerequationanditsN-solitonsolutionsareconstructed.

  • 标签: 孤立子解 Hirota法 等光谱 SCHRODINGER方程
  • 简介:W,N共同做TiO2nanoparticles被一个solgel方法综合。准备样品被X光检查衍射(XRD)描绘,域排放扫描电子显微镜学(FE-SEM),传播电子显微镜学(TEM),Fourier变换红外线的光谱学(英尺红外),X光检查光电子光谱学(XPS)和弥漫的反射spectrophotometry(医生)。结果证明共同做的光催化剂是有22.5nm的最小的粒子尺寸的实质上一致的球形的粒子。比作未做的TiO2,N-TiO2和P-25,W的吸收边,N共同做转移到更长的波长的TiO2和它为在Xe灯(350W)下面的甲基橘子(瞬间)的降级的photocatalytic活动更高。

  • 标签: N-TiO2 光催化剂 共掺杂 场发射扫描电子显微镜 光驱动 傅里叶变换红外光谱
  • 简介:Aseriesofcopper(Ⅱ)complexeswithpyridineN-oxide-2-ylmethylidened-ithiocarbazatesasligandsweresynthesizedandcharacterizedbyIRspectra,electronicspectraandmagneticmomentsmeasurementatroomtemperature.Variabletemperaturemagneticsusceptibilites(3-300K)offourcomplexsweremeasuredandfittedwiththeBleaney-Bowersdimerequationbyconsideringthemagneticinteractionbetweenmolecules.Thefittingresultsshowtheexistenceofintramolecularferromagneticinteractionsandintermolecu-laranti-ferromagneticinteractionsinthesecopper(Ⅱ)complexes.

  • 标签: PYRIDINE N-oxide-2-ylmethylidenedithiocarbazate Copper(Ⅱ) complex MAGNETIC SUSCEPTIBILITY
  • 简介:ThispaperstudiestheequilibriumgeometriesandelectronicpropertiesofBenandBenLiclusters,upton=15,byusingdensity-functionaltheory(DFT)atB3LYP/6-31G(d)level.Thelowest-energystructuresofBenandBenLiclustersweredetermined.Theresultsindicatethatasinglelithiumimpurityenhancesthestabilityandchemicalreactivityoftheberylliumclusters.Itfindsthatthegeometriesofthehostclusterschangesignificantlyaftertheadditionofthelithiumatomforn≥8.Thelithiumimpuritypreferstobeontheperipheryofberylliumclusters,andoccupiesvertexsites.BothBe4Li,Be9Li,andBe13Liwerefoundtobeparticularlystablewithhigheraveragebindingenergy,localpeaksofsecond-orderenergydifferenceandfragmentationenergies.ForalltheBenLiclustersstudied,wefoundchargetransfersfromtheLitoBesiteandco-existenceofcovalentandmetallicbondingcharacteristics.更多还原

  • 标签: 低能构造 电子特征 密度泛涵理论
  • 简介:TwoN-dichloroacetyloxazolidinesweresynthesizedwithasimple,mildandconvenientmethod.AllthecompoundswerecharacterizedbyIR,^1HNMRandelementalanalysis.Thepreliminarybiologicaltestshowedthatthecompoundsprotectedmaizeagainstinjurybysomeherbicidestosomeextent.

  • 标签: 合成 N-二氯-乙酰基唑烷 生物活性 核磁共振 元素分析