A method of calculating copolymerization reactivity ratios

An improved linearization method is proposed for determining the monomer reactivity ratios of free-radical copolymerizations by fitting the data of cumulative copolymer compositions and overall weight fractional conversions, or cumulative copolymer compositions and residual monomer compositions of the reaction mixture. The reactivity ratios of monomers for four different copolymerization reactions are determined. The results are very close to those of literature reports and account well for the experimental results.     

A method for calculating the impact strength of sheet glass

Theoretical bases for calculating the dynamic strength of tempered sheet glass under the test conditions envisaged by GOST 5727-88 are considered. Methods for calculating the minimum height of a falling ball, the dynamic stresses appearing in specimens of tempered glass, and the minimum degree of tempering required for providing a specified dynamic strength of the glass are considered.     

烧结配料过程焦粉最低配比计算方法

提出了一种烧结过程焦粉最低配比计算方法。首先针对不同烧结终点位置、料层厚度的料层等温线数据建立烧结料层侧面温度场BP神经网络(back propagation neural network,BPNN)模型;然后采用最小二乘支持向量机(least squares support vector machine,LS-SVM)算法建立烧结终点位置、料层厚度等烧结过程状态变量与料层蓄热所需能量之间的关系模型;通过对烧结过程中主要物理、化学反应的分析,计算得到了水分蒸发与碳酸盐分解过程需要热量;最后通过对碳转换形式进行分析,计算得到烧结配料过程焦粉最低配比。仿真实验和工业实际数值算例表明,提出的焦粉最低配比计算方法能有效地反映实际生产所需的最低焦粉配比,从而为烧结过程节能减排提供重要的数值依据。     

一种计算含盐有机溶液气液相平衡的方法

提出了一种计算含盐混合溶剂气液相平衡的新模型,即把活度系数表示为盐的质量摩尔浓度ms和溶剂组成摩尔分数xi的函数,其中盐质量摩尔浓度项表示为盐质量摩尔浓度的二次函数,溶剂组成项由UNIQUAC模型计算。以文献中水-醇-盐和醇-醇-盐的11个体系为例,将新模型用于其气液平衡的计算,关联得到了各体系的模型参数。结果表明:将活度系数表示为ms和xi的函数是合适的;每种溶剂组分气相分压的计算值与实验值吻合良好,最大误差为0.928 k Pa。因此,新模型是一种可广泛用于含盐有机溶液体系气液相平衡计算的方法。     

A numerical method of calculating secondary current distributions in electrochemical cells

A numerical method is proposed based on the analogy between the potential distribution in an electrolytic solution and the temperature distribution in a heat-conducting medium. Thus the equation of non-steady-state heat conduction which contains a hypothetical temperaturev(x, y, t) is solved numerically with appropriate boundary conditions. In the steady state the distribution ofv(x, y, t) corresponds to the distribution of potentialφ _s (x,y) which satisfies Laplace's equation. The method is useful not only for conventional electrochemical cells but also for complicated systems such as a bipolar electrode for which boundary conditions provide neither the potential nor the current density at the electrode surface.     

A method of calculating fatty acid composition from ester fractionation analysis

Summary The calculations involved in ester fractionation analysis require the solution of sets of three simultaneous equations. Repeated solution of these equations is avoided by obtaining expressions for the proportions of the components. Frequent analysis of similar fractions is further simplified by the preparation of tables, slide rules, or nomograms. At the Applied Mathematics Laboratory, for the Fats Research Laboratory, Department of Scientific and Industrial Research.     

A method for preparing water soluble cyclic polymers

A novel ring-closure method was developed to specifically focus on the preparation of water soluble cyclic polymers. The well-defined linear polymers were synthesized by a standard RAFT polymerization using a functional RAFT agent 1. The cyclic polymers were then obtained by virtue of an efficient bromomaleimide-thiol substitution reaction to ring-close the linear precursors. This technique is unique in that it not only produces various well-defined water soluble cyclic polymers with high efficiency and topology purity, but also employs the environmentally benign solvent, water, as the ring-closure reaction media.     

A new catalytic method for crosslinking of silicone polymers

The aim of our work was to develop a gelation process for polymerizing polydimethylsiloxane-α,ω-diols for pharmaceutical purposes. Three different gelling agents has been tried; among them, the prehydrolyzed tetraethoxysilane (TES 40) had the best performance. As initiators, several amines were investigated. The gelling time has been found to be correlated with the basicity, solubility, and diffusibility of the amines. The correlation between the thickness of the oligomer layer and the gelling time has also been investigated. The amount of the remaining initiator after the completion of the network formation has been determined, together with the time needed for its complete removal from the matrix. By using thermogravimetric methods it has been shown that no initiator is left in the matrix. The elastomers obtained by the present method were compared to those obtained by the usual catalysts, resulting in identical properties. The procedure developed is able to produce silicone oligomers for pharmaceutical purposes either in a continous or in a discontinous way. The procedure has several advantages in comparison with the conventional methods. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1705–1709, 1998     

一种计算分子筛标准Gibbs生成自由能的新方法

引 言 自Mobil公司于20世纪60年代成功合成高硅分子筛β[1]及ZSM-5[2]以来,分子筛的合成及其应用便成为催化领域研究的热点.然而,对于分子筛的合成及其改性研究基本上都是凭着研究者的经验,而缺乏理论的有效指导.研究表明,分子筛的热力学性质(如生成焓、生成自由能等)对于分子筛的合成及其性能(如热稳定性等)的预测具有重要的指导意义.但由于分子筛的结构非常复杂,测定分子筛的热力学性质十分困难,到目前为止,只有少数分子筛的某些热力学参数已用实验测定[3].为此,人们一直在探索用各种方法直接计算或预测分子筛的热力学参数.     

A direct method for calculating ternary vapor compositions from total-pressure measurements

Ternary vapor compositions have been successfully calculated from total-pressure measurements for four systems by means of a modified direct method, which involves the previously proposed concept of hypothetical binary mixtures, and permits the numerical integration using a simple P-x relationship. The results of the systems tested further indicate that the ternary y values predicted from only binary P-x data are not significantly different from the y values obtained when binary together with ternary P-x values were used in the calculation, provided that the initial fit of binary P-x data is successful.     

一种计算平均毛管压力的方法及应用

毛管压力曲线在油气田勘探开发中已得到广泛应用。采用经验公式法中的＂J函数＂法对压汞毛管压力进行处理,得到平均毛管压力曲线。相比传统方法,该方法简便,精度高。它有利于及时确定代表性毛管压力曲线的变化趋势,能为油气田勘探开发可行性提供依据。     

Application of a chemical group contribution technique for calculating solubility parameters of polymers

A chemical group contribution technique, based on the principle of additivity of molar attraction constants for groups in a molecule, has been used for determining the solubility parameters for several polyesters, polyethers and a few other types of polymers. The solubility parameter for a polymer is calculated by using the contributions for chemical groups reported in the literature with the resultant values found to compare favorably. For geometrical isomers of polymers, the calculated solubility parameters are identical but differ for positional substitution.