均匀橡胶弹性体隔声量的理论计算

由于材料在水声介质中的隔声性能的测试方法和测试设备较复杂，目前还没有在水声介质中的隔声量的标准测试方法。笔者从理论上研究了材料在水声介质中的隔声性能(隔声量)的计算方法，利用该方法计算了所合成的材料在不同厚度下的隔声量。计算结果表明：随着厚度的增加，材料的隔声量增加，但在低频下，当厚度增加到40mm以后，隔声量随厚度的增加而变化得很缓慢，在低频下不符合厚度每增加一倍，隔声量增加6dB这一规律。     

基于交叠社团相似性的生物网络关键节点识别

生物网络是研究生物特性的一个重要工具,目前已经有许多方法用于研究生物网络,关键节点分析是其中最常用的方法之一。关键节点分析通常是根据一定的规则为网络中的各节点分配一个函数值,并由此来确定网络中各节点的重要程度,目前已经发表了一些方法。然而,这些方法在单独使用的情况下,获得的关键节点的生物学意义一般较低,存在一定的缺陷。本文从节点对社团贡献的角度建立关键节点识别方法,首先提取网络中富含生物学功能意义的社团,然后依据交叠社团的相似性为各节点分配贡献值,最后通过两个生物网络实例论证了方法的有效性。     

有效增强重组腈代谢酶系表达活性的策略

讨论并提出了有效增强重组腈代谢酶系表达活性的多种策略。根据所选用的载体和宿主的不同表达特性,同时克隆目的基因上、下游的正向调控序列可直接增强酶表达水平;强化翻译后的修饰,可有效提高活性;除了常用的大肠杆菌克隆表达体系外,开发新型宿主-载体系统可为重组酶的活性表达提供新的途径;随着生物信息学技术的迅速发展,利用已知三维结构的蛋白对目标酶进行突变位点设计及结构与功能预测,将有望加快腈代谢酶系的定点突变研究进程。     

具有时延和丢包的NCS鲁棒H∞控制

针对一类含有不确定参数的网络控制系统(NCS),研究网络中存在时延与丢包情况下的鲁棒?∞控制问题.构造一个新的Lyapunov-Krasovskii泛函,并基于改进的Wirtinger不等式推导出闭环NCS渐近稳定且满足?∞性能的充分条件,该条件能得到比已有文献保守性更小的结果.给出线性锥补算法以实现次优鲁棒?∞控制器增益的求解.最后通过多个数值实例验证了所提出方法的有效性.     

聚合物乳液的稳定性

简要讨论了乳液稳定性的原理,综述了乳液配方、乳胶粒组成和结构对聚合物乳液电解质稳定性、机械稳定性、冻融稳定性和贮存稳定性的影响。     

离子水--21世纪的保健品

离子水是一种新型的保健饮用水.本文主要对饮用水、离子水的功能和作用进行了概述,阐述了离子水对人类生活和健康的影响,且指出了离子水具有良好的发展、开发和推广的前景.     

Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles

A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H₂ production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H₂ with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH₃OH→H₂COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.     

Anionic synthesis of poly(epichlorohydrin-g-styrene) and chemical modification of polyepichlorohydrin

Poly(epichlorohydrin-g-styrene) copolymers, P(ECH-g-S)s, have been prepared in solution by two different methods of coupling polyepichlorohydrin, PECH, with polystyrene, PS, containing a functional end group. In the first method, polystyryl carboxylic acid, PSCOOH, prepared from living polystyrene, was converted to the corresponding potassium salt which was coupled with PECH in dimethyl formamide solution usually at 60°C. In the second method, polystyryl potassium, PS^?K⁺, in tetrahydrofuran solution was end-capped with propylene sulphide to form PSCH₂CH(CH₃)S^?K⁺ which was coupled directly with PECH in tetrahydrofuran at 40°C. Grafting by the first reaction was relatively slow but occurred without significant adverse side reactions. The grafting by the second reaction was relatively fast, but side reactions occurred resulting in a cleavage of the graft copolymer. The graft copolymers were purified by fractional precipitation and extraction procedures and were characterized by infra-red and ultra-violet spectroscopy, microanalysis, gel permeation chromatography, differential scanning calorimetry, solution viscometry, dynamic mechanical testing, and electron microscopy. Solution properties of the graft copolymers in benzene-carbon tetrachloride and toluene-cyclohexane mixtures were studied. There was evidence of micelle formation in dilute solutions of the mixed solvents and microphase separation of components in the solid state. Nucleophilic substitution of chlorine atoms in PECH by phenyl acetate (C₆H₅ CH₂COO-) and thiophenoxide (C₆H₅S-) groups was performed.     

胺烷基化聚羟基酸酰胺类超分散剂的研制及应用

对胺烷基化聚羟基酸酰胺的合成方法进行研究，确立了反应条件与制得的聚羟基酸酯特征之间的一些相互关系。并为获得适当长度的聚酯链选择了最佳合成条件。同时扼要论述了这类超分散剂的结构特性，以及对于颜料粒子表面吸附作用、分散体系的稳定作用以及对涂料、油墨生产的重要意义。     

纤维素科学与技术研究进展

本文综述纤维素科学与技术的研究进展。阐述了纤维素结构、纤维素的合成、纤维素液晶、功能纤维素、纤维素溶剂、纤维素裂解和纤维素的废物利用等的最新动态。