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701.
光学活性N-肉桂酰R(S)-4-异丙基四氢噻唑-2-硫酮的合成及其 量子化学的研究 总被引:1,自引:0,他引:1
用KBH~4,CaCl~2为还原使D及L缬氨酸甲酯还原得到光学活性产物R-3-甲基-2-氨基丁醇(2a)及S-3-甲基-2-氨基丁醇(2b)。2a,2b同CS~2在KOH存在下反应得到(R)-4-异丙基四氢噻唑-2-硫酮(3a)及(S)-4-异丙基四氢噻唑-2-硫酮(3b)。肉桂酰氯分别同3a及3b在Et~3N存在下反应得到N-肉桂酰(R)-4-异丙基四氢噻唑-2-硫酮(4a)及N-肉桂酰(S)-4-异丙基四氢噻唑-2-硫酮(4b)。用半经验的量子化学PM3方法研究了反应物和产物的电子结构,得到了产物的最优构型和电荷键序分布以及反应焓变。 相似文献
702.
M.A.Chowdhury M.M.Alam M.F.Mina F.Akhtar S.E.Kabir 《高分子科学》2004,(3):253-258
Hydrogels have been synthesized from 10%, 20%, 30%, 40%, 50% and 60% aqueous solutions of acrylamide monomer by gamma radiation employing doses in the range of 0.2-30 kGy from a Co-60 source. The effect of solution concentration, y-ray dose, pH and time was studied in order to observe the optimizing conditions in the characterization of hydrogels. Gel fraction increases with dose for all concentrations indicating hundred-percentage conversion of gel at doses ≥5 kGy for homogenous solutions in the range of 20%-50% concentration. On the other hand, 10% solution provides conversion less than 86% even at 30 kGy, whereas 60% monomer makes an inhomogeneous solution which stile gives about 100% gel fraction. Swelling of hydrogels under water with respect to time varies with both the doses and concentrations due to the change of crosslinking density in the gels. The maximum volume change of hydrogels during swelling and water desorption mainly occurs within 24 h. Swelling is also enhanced with the rise of pH due to change of ionic content of the solvent. Considering the amount of gel fraction and the properties of hydrogel, the samples prepared from 20% solution at 5 kGy show better results. Moreover, the effect of bacteria on hydrogel was found to be nil, suggesting a prohibition of growth of microorganism in it. 相似文献
703.
704.
Radial Basis Function Neural Networks-Based Modeling of the Membrane Separation Process: Hydrogen Recovery from Refinery Gases 总被引:1,自引:0,他引:1 下载免费PDF全文
Lei Wang Cheng Shao Hai Wang Hong Wu 《天然气化学杂志》2006,15(3):230-234
Membrane technology has found wide applications in the petrochemical industry, mainly in the purification and recovery of the hydrogen resources. Accurate prediction of the membrane separation performance plays an important role in carrying out advanced process control (APC). For the first time, a soft-sensor model for the membrane separation process has been established based on the radial basis function (RBF) neural networks. The main performance parameters, i.e, permeate hydrogen concentration, permeate gas flux, and residue hydrogen concentration, are estimated quantitatively by measuring the operating temperature, feed-side pressure, permeate-side pressure, residue-side pressure, feed-gas flux, and feed-hydrogen concentration excluding flow structure, membrane parameters, and other compositions. The predicted results can gain the desired effects. The effectiveness of this novel approach lays a foundation for integrating control technology and optimizing the operation of the gas membrane separation process. 相似文献
705.
首先根据BP算法的基本原理,推导出了BP模型中输出对输入的偏导.然后基于已有数据,利用BP模型进行拟合,保留训练后的BP模型的权值和阈值.在此基础上,利用变步长梯度法实现了BP模型的最优化.本文是对BP模型优化方法的一种新的理论探讨. 相似文献
706.
Zhou Yan Pu Dingguo 《高校应用数学学报(英文版)》2007,22(4):425-433
In this paper,a smoothing QP-free infeasible method is proposed for nonlinear inequality constrained optimization problems.This iterative method is based on the solution of nonlinear equations which is obtained by the multipliers and the smoothing Fisher-Burmeister function for the KKT first-order optimality conditions.Comparing with other QP-free methods, this method does not request the strict feasibility of iteration.In particular,this method is implementable and globally convergent without assuming the strict complementarity condition and the isolatedness of accumulation points.Furthermore,the gradients of active constraints are not requested to be linearly independent.Preliminary numerical results indicate that this smoothing QP-free infeasible method is quite promising. 相似文献
707.
讨论求全局最优化问题的填充函数法,进一步提出了求全局最优化问题的一类单参数全局凸填充函数,它和目标函数同阶可微. 相似文献
708.
709.
Wen Song Bo-ying Wu Jian-mei Zhang 《应用数学学报(英文版)》2007,23(1):91-98
In this note,we prove that the efficient solution set for a vector optimization problem with acontinuous,star cone-quasiconvex objective mapping is connected under the assumption that the ordering coneis a D-cone.A D-cone includes any closed convex pointed cones in a normed space which admits strictly positivecontinuous linear functionals. 相似文献
710.
有限理性与多目标问题解的稳定性 总被引:1,自引:0,他引:1
文章对多目标最优化问题定义了理性函数,证明了大多数的最优化问题(在Baire分类意义上)都是结构稳定的,对ε-平衡也都是鲁棒的. 相似文献