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951.
Cai-hong Xu Ning Zhou Ze-min Xie Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2000,(5):449-452
A new silazane oligomer containing cyclotrisilazane was synthesized by KH-catalyzed dehydro-coupling reactionsbetween diphenylsilane and 1,1,3,3,5,5-hexamethylcyclotrisilazane (D_3~N). 相似文献
952.
A novel complex [Cu(acac)(dppe)]n (1) [acac = acetylacetone; dppe = 1,2-bis(diphenylphosphino)ethane] was obtained by solution reactions and structurally characterized by X-ray diffraction. The crystal structure analysis indicates that the title complex is characteristic of a polymeric chain formed by the dppe ligands bridging neighboring copper centers. The copper atom is in a distorted tetrahedral geometry. Photoluminescent investigation reveals that the title complex displays a strong emission in bluelight region. 相似文献
953.
本文利用分子动力学方法研究了KCl晶体在ρ=ρ0时的温度相变。面心立方(fcc)和体心立方(bcc)两种结构的径向分布函数随温度的变化的情况说明,在高压下,发生着bcc结构相fcc结构的转变,bcc结构是不稳定的。为了选取合理的势参数,利用了分子动力学程序在T=0时的性质,计算了NaCl和KCl晶体的零温状态方程,研究了它们在压力作用下发生的多形性相变。计算表明,NaCl和KCl晶体将分别于18.8 GPa和5.9 GPa发生从fcc到bcc的多形性相变,这些值相当接近实验结果。着说明本文选用的势参数势有一定精度的。 相似文献
954.
Zitian Xie 《Journal of Mathematical Analysis and Applications》2008,343(2):1154-1160
In this paper, we give a new reverse Hilbert-type inequality with a best constant factor and some parameters. As application, we consider the equivalent form and some particular results. 相似文献
955.
Continuous-time portfolio selection with liability: Mean–variance model and stochastic LQ approach 总被引:1,自引:1,他引:0
In this paper we formulate a continuous-time mean–variance portfolio selection model with multiple risky assets and one liability in an incomplete market. The risky assets’ prices are governed by geometric Brownian motions while the liability evolves according to a Brownian motion with drift. The correlations between the risky assets and the liability are considered. The objective is to maximize the expected terminal wealth while minimizing the variance of the terminal wealth. We derive explicitly the optimal dynamic strategy and the mean–variance efficient frontier in closed forms by using the general stochastic linear-quadratic (LQ) control technique. Several special cases are discussed and a numerical example is also given. 相似文献
956.
The electronic structure and properties of polypyrrole (p-Pyr) based substituting by the group of pyrazine (Pyz) and their
model compounds were studied by the density functional theory (DFT) at the B3LYP level with 6-31G* basis set. The bond length,
the topological analyses and nucleus-independent chemical shifts (NICS) were analyzed and correlated with the electronic properties.
The bond length of all compounds is reduced with the increase in the degree of polymerization, and the band gap of these compounds
is decreased. The change of NICS shows that the conjugation degree in central section of the polymeric axis is stronger than
that in outer section, and the structure of central part was close to quinoid structure in polymers. The theoretical results
suggest that the band gap of p-Pyz (polymer of Pyz) (0.37 eV) is much smaller than the band gap of polypyrrole (1.84 eV).
The narrow band gap, large HOMO and LUMO bandwidths and small effective masses make p-Pyz have a remarkable elevation of the
conductivity, so it may be considered as a very good candidate for conducting material. 相似文献
957.
A novel reactive polyorganosiloxane containing nitro groups was first prepared by acid-catalyzed equilibration polymerization. The monomer, 3-(4-nitrophenoxy)propylmethyldichlorosilane (NPPMS), was synthesized by hydrosilylation reaction with dicyclopentadienylplatinum(II) chloride (Cp2PtC12) catalyst in high yield. The synthesized polynitroorganosiloxane, which has potential application as a precursor for synthesizing advanced functional polymers, was characterized by FTIR, 1H-NMR, 13C-NMR, 29Si-NMR, vapor pressure osmometry (VPO) and gel permeation chromatography (GPC). 相似文献
958.
谢帕莎 《广东微量元素科学》1999,6(7):24
总结了抢救急性心肌梗塞猝死的体会,包括:及早确诊及有效的心肺脑复苏、合理使用复苏药物和警惕老年性心梗的不典型性。 相似文献
959.
960.