简介:分别以Bemstain多项式以及准均匀B样条为基函数,来逼近线性高振荡常微分方程。通过求解基函数对应的系数方程组,得到方程的近似解。通过数值实验表明用准均匀B样条函数的逼近效果要比Bemstain多项式要好。
简介:基于非结构/混合网格、耗散自适应2阶混合格式以及脱体涡模拟(detachededdysimulation,DES)方法开展了现代战斗机模型复杂分离流动的数值模拟,并与有限的平均气动力试验数据进行了对比,结果表明计算具有合理性,在此基础上进一步应用本征正交分解(properorthogonaldecomposition,POD)和动力学模态分解(dynamicmodedecomposition,DMD)方法对数值模拟流场的非定常特性进行了对比分析.研究表明飞行器背风区流场由一对边条涡的螺旋运动主导,旋涡破裂前在横向空间截面上流场是中性稳定的,同时主涡核的运动是多频耦合的.POD和DMD的对比分析则表明:两者模态配对的方式不同,但主要模态之间具有一定相关性;POD模态中包含多种频率的运动,而且能量较集中于主模态,流场重构效率更高;DMD则将流场的主要特征运动提取为一些单频模态的组合,同时能够给出模态的稳定性.
简介:Low-energypartial-waveπNscatteringdataisreexaminedwiththehelpoftheproductionrepresentationofpartial-waveSmatrix,wherebranchcutsandpolesarethoroughlyunderconsideration.Theleft-handcutcontributiontothephaseshiftisdetermined,withcontrolledsystematicerrorestimates,byusingtheresultsofO(p^3)chiralperturbativeamplitudesobtainedintheextended-onmass-shellscheme.InSnandPuchannels,severediscrepanciesareobservedbetweenthephaseshiftdataandthesumofallknowncontributions.Statisticallysatisfactoryfitstothedatacanonlybeachievedbyaddingextrapolesinthetwochannels.WefindthataSnresonancepolelocatesat√zr=(0.895±0.081)—(0.164±0.023)iGeV,onthecomplexs-plane.Ontheotherhand,aFnvirtualpole,asanaccompanyingpartnerofthenucleonbound-statepole,locatesat√zv=(0.966±0.018)GeV,slightlyabovethenucleonpoleontherealaxisbelowthreshold.Physicaloriginofthetwonewlyestablishedpolesisexploredtothebestofoiirknowledge.ItisemphasizedthattheO(p^3)calculationgreatlyimprovesthefitqualitycomparingwiththepreviousO(p^2)one.
简介:SupposethatCisthecomplexplaneandkisanon-negativeinteger.DefinefunctionsNk-(x)=|x|kifkisevenandNk(x)=x|x|k-1ifkisodd.SomeapproximationpropertiesofNk-(x)’sisdiscussedandanewexampleofaTchebycheffsystemisgivenout.
简介:研究了—(p,q)-Laplacian拟线性椭圆方程组.当连续函数V和W在两种情形下,利用Moser迭代技巧和Ljusternik-Schnirelmann畴数理论,建立了方程组正解的存在性和多重性结果.
简介:Polystyrenemacromonomerswithdifferentmolecularweightwerepreparedbyradicalpolymerizationofstyrene(St)inbenzeneusingβ-methacryloxylethyl2-N,N-diethyldithiocarbamylacetate(MAEDCA)asamonomer-iniferter.Characterizationofthemacromonomerby~1H-NMRshowedthattheendgroupswereα-methacrylyoxylethyloxycarbonyl-methylandω-(N,N-diethyldithiocarbamyl).Themacromonomerwasdifficulttohomopolymerize,butitwaseasilycopolymerizedwithmethylmethacrylate(MMA)initiatedbyAIBNtoformgraftcopolymers(PMMA-g-PSt)withPStbranchesrandomlydistributedalongthePMMAbackbone.CopolymerizationreactionandthestructureofthegraftcopolymerswerestronglyaffectedbyM_nandconcentrationofthemacromonomer.ThecompositionandM_nofthepurifiedgraftcopolymerweredeterminedby~1H-NMRandGPCanalysis.
简介:AnewkindofpolysiloxanecontainingN,N’-bis(diphenylsilyl)tetraphenylcyclodisilazanewaspreparedbyanionicnon-equilibriumpolymerizationwitha"seedsolution"asinitiator.Themonomer,N,N’-bis(hydroxydiphenylsilyl)-tetraphenyl-cyclodisilazane(BHPTPC),wassynthesizedviathehydrolysisofN,N’-bis(chlorodiphenylsilyl)tetraphenyl-cyclodisilazane(BCPTPC).AnewmethodforthepreparationofBCPTPCisalsoreportedherewithhighyieldandsimplermanipulation.ThesynthesizedpolysiloxanecontainingN,N’-bis(diphenylsilyl)tetraphenylcyclodisilazanewascharacterizedby1H-NMR,29Si-NMR,gelpermeationchromatography(GPC)andintrinsicviscosity.
简介:ReactionsofCuSCNwithtetramethylthiuramdisulfideinCH3CNinthepresenceofstyreneandN,N,N',N',N'-pentamethyldiethylenetriaminegaverisetoanewcopper(Ⅰ)complexofN,N'-dimethyldithio-cabamate{[Cu(S2CNMe2)]2}n.ThetitlecompoundcrystallizedinthetriclinicP-1spacegroupwithlatticeparametersα=0.7610(4)nm,b=0.8911(4)nm,c=0.9268(5)nm,α=68.66(1)°,β=83.88(2)°,γ=79.31(2)°,V=0.5748(5)nm^3,Z=2.Thecompoundhasaunique1DchainstructurecomposedofCuSCSCuSCSeight-memberedringsandapairofCu-Sbonds,thestructureofwhichhasbeendeterminedbysingle-crystalX-raycrystallography.Theisolationofthiscompoundmayprovidesomehelpfulinformationforthecauseoftheinductionperiodsofthereverseatomtransferradicalpolymerization.
简介:选取了常用洗涤助剂三聚磷酸钠(STPP)与柠檬酸钠(NaCA)为研究体系,通过实验测定和理论分析,对洗涤助剂的钙螯合能力进行了研究.实验研究采用铬黑T指示剂络合滴定法,分别测定以上2种助剂的钙螯合能力,结果表明:2种助剂均可与Ca2+离子形成稳定的螯合物,但螯合Ca2+离子的能力不同,三聚磷酸钠螯合能力较强.理论计算运用Gaussian09程序包,采用密度泛函的B3LYP方法,6-31G(d,p)基组,在溶剂化条件下计算出2种洗涤助剂与Ca2+离子形成螯合物的几何结构及其结合能,三聚磷酸钠和柠檬酸钠与Ca2+离子的螯合物均为六配位八面体结构,磷酸基团或羧酸基团与羟基参与配位.实验所得螯合能力的差异可以由理论计算得到的分子结构、结合能及前线分子轨道方面进行解释.