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11.
12.
一类Narcissistic反应过渡态的优化 总被引:1,自引:0,他引:1
我们对一类narcissistic 反应XCH_2-CH_2Y→[过渡态TS]→YCH_2—CH_2X (1)进行了研究,结果表明其过渡态能在对称性限制下由能量极小化方法较容易地给出. 采用IMSPAK分子轨道从头算程序,在IBM VM/370计算机系统上用STO—3G极小基组以平衡几何构型的能量梯度优化方法,在对称性限制下对反应(1)的几种反应体系的过渡态构型进行了优化,其结果列于表1. 相似文献
13.
14.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
15.
Jiaqiang Wang Hua Fang Ying Li Junjie Li Zhiying Yan 《Journal of molecular catalysis. A, Chemical》2006,250(1-2):75-79
Cobalt-doped mesoporous titania with a crystalline framework synthesized by surfactant templating method presented highly selective (99%) and reasonable conversion rate (49%) of catalytic oxidation of para-chlorotoluene to para-chlorobenzaldehyde in acetic acid using aqueous hydrogen peroxide as oxidant for the first time. Recycling of the catalyst indicates that the catalyst can be used a number of times without losing its activity to a greater extent. By contrast, cobalt-doped mesoporous titania without a crystalline structure and cobalt doped the commercial titania, Degussa P25 prepared by impregnation method with the similar concentration of cobalt were found inactive. The effects of catalyst concentration, reaction time, reaction temperature, and solvents on the performance of the catalyst were also investigated. 相似文献
16.
This study presents a compact optical configuration that can generate a multiplex dot-matrix hologram with complex interlaced images for anti-counterfeiting applications on valuable paper. Varying the orientation of the interference plane can enable the multiplex hologram to be recorded without changing the interference angle of two laser beams. With its simple asymmetric optical setup, a multiplex hologram with many interlaced images can be efficiently fabricated, increasing the cost of imitation. Experimental details of the asymmetric optical setup are also described. 相似文献
17.
ChunXiaLI YingXiaLI LingBoYU HuaZHANG SiftDongCHU HuaShiGUAN 《中国化学快报》2003,14(8):776-778
A convenient synthetic route was developed for the synthesis of the novel glycolipids: 1,2-di-O-acyl-3-O-(2‘-acylamide-2‘-denxy-ct-D-glucopyranosyl)-sn-glycerols. 10 new compounds of glycolipids with different acyl groups were obtained. 相似文献
18.
基于Lee等人的离子温度梯度模导致的反常热能输运系数,本文研究了辅助加热托卡马克等离子体的能量约束行为,并对自举电流的效应作了初步考虑。结果表明,计算得到的能量约束时间随等离子体电流I_p和托卡马克大半径R增大而增长,随注入功率P_t、环向场B_t以及等离子体小半径α的增大而缩短。这些结果与Kaye-Goldston的经验约束定标具有相同的趋势。自举电流的存在总是导致能量约束时间的增加,当自举电流与总电流的比值γ较小时,能量约束时间的增加率约为γ/2。此外,自举电流将造成锯齿反转半径的减小。 相似文献
19.
Xiao‐Hui Liu Yan‐Guo Li Ying Lin Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2007,45(7):1272-1281
The reversible addition–fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANs were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. 1H NMR analysis confirmed the high chain‐end functionality of the resultant polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1272–1281, 2007 相似文献
20.
物理实验课程考核、评估体系初探 总被引:4,自引:0,他引:4
对物理实验课程考核、评估方法进行了探讨,提出了物理实验课程考核、评估体系及实施细则.重点介绍了体系中的核心部分——正规的物理实验课程考试. 相似文献