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71.
Lanthanide Complexes for Oligomerization of Phenyl Isocyanate 总被引:1,自引:0,他引:1
IntroductionThestudyonthereactivitiesoflanthanidecomplexesto wardisocyanateshasattractedmuchattention .Ithasbeenre portedthatlanthanidealkoxides,1anddivalentdiaza pentadi enyllanthanidecomplexes2 canbeusedasthesinglecompo nentinitiatorsforisocyanatespolymerization .Recentlyourre searchgrouphasalsofoundthatlanthanoceneamide ,3diva lentaryloxideofsamarium4 ,5anddivalentsamarocene6 areallactivefortheoligomerizationofphenylisocyanate,andtheactivespeciesforthesethreesystemswereallsuccessfullyisolat… 相似文献
72.
Strong limit-point criteria for singular Hamiltonian differential expressions with complex coefficients are obtained. The main results are extensions of the previous results due to Everitt, Giertz, and Weidmann for scalar differential expressions.
73.
74.
Q. H. Liu W. H. Qi T. G. Liu Z. H. Zhu 《International Journal of Theoretical Physics》2003,42(4):783-791
Expectation values of physical quantities in a wave packet involving few stationary states in an infinite square well are calculated. Explicit results show that the expectation values in the classical limit go over to the corresponding classical quantity in the form of the arithmetic mean (in mathematical term, the Fejér's average) of the partial Fourier series converging to the classical quantity. The number of the stationary states is that of the partial Fourer series in the Fejér's average. The quantum uncertainty is then demonstrated to have a classical counterpart. 相似文献
75.
In this paper we consider the problem of estimating an unknown joint distribution which is defined over mixed discrete and continuous variables. A nonparametric kernel approach is proposed with smoothing parameters obtained from the cross-validated minimization of the estimator's integrated squared error. We derive the rate of convergence of the cross-validated smoothing parameters to their ‘benchmark’ optimal values, and we also establish the asymptotic normality of the resulting nonparametric kernel density estimator. Monte Carlo simulations illustrate that the proposed estimator performs substantially better than the conventional nonparametric frequency estimator in a range of settings. The simulations also demonstrate that the proposed approach does not suffer from known limitations of the likelihood cross-validation method which breaks down with commonly used kernels when the continuous variables are drawn from fat-tailed distributions. An empirical application demonstrates that the proposed method can yield superior predictions relative to commonly used parametric models. 相似文献
76.
Two homologous series of mesogenic materials which incorporate a 1,4-tetrafluorophenylene moiety and a terminal cyano- or nitro-substituent have been synthesized by using palladiumcatalysed coupling procedures. The compounds exhibit nematic and/or smectic A phases. 相似文献
77.
A perturbation wave solution of the Robinson-Trautman equations is proved to be a perturbation of the Schwarzschild black hole which describes an outgoing axial gravitational wave and corresponds to a special case of Chandrasekhar's algebraically special perturbation of the Schwarzschild metric. 相似文献
78.
A problem in extremal quasiconformal extensions 总被引:2,自引:0,他引:2
Yi Qi 《中国科学A辑(英文版)》1998,41(11):1135-1141
A constantK
0
(m)
(h) is introduced for every quasisymmetric mappingh of the unit circle and every integerm≥4 which contains the constantK
0(h) (indicated by the change in module of the quadrilaterals with vertices on the circle) as a special case. A necessary and
sufficient condition is established forK
0
(m)
(h) =K
1(h). It is shown that there are infinitely many quasisymmetric mappings of the unit circle having the property thatK
0
(m)
(h)<K
1(h), wherek
1(h) is the maximal dilatation ofh. 相似文献
79.
研究了L∞模的拟凸性质,利用极大熵方法得到极小化L∞模的Q算法.这是一种具有显式搜索方向的变尺度算法,在非线性参数估计中取得较好效果. 相似文献
80.
缺失功能性p35基因的苜蓿尺蠖核形多角体病毒(AcNPV)突变体(vΔP35K/pol+)感染草地夜蛾细胞(Sf9和Sf21)[1]及海灰翅夜蛾细胞(SL2)[2]时,引起细胞凋亡,从而使病毒的感染流产.我们发现海灰翅夜蛾核形多角体病毒(SlNPV)... 相似文献