两点边值问题解的存在性

本文讨论两点边值问题解的存在性,在没有孤立性条件下,获得了不动点定理,作为应用实例,给出了反应扩散方程稳态解的存在性证明。     

Swelling of interpenetrating polymer networks

We have studied the densities, kinetics, and equilibrium degree of swelling in a number of different solvents of poly(carbonate urethane)/poly(methyl methacrylate) and poly(carbonate urethane)/poly(vinyl pyridine) interpenetrating polymer networks (IPN's). The kinetics of solvent uptake are often anomalous. The equilibrium extent of swelling reflects, among other factors, the number of phases present. © 1993 John Wiley & Sons, Inc.     

The Degree Theory of a New Operator

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Rh-catalyzed π-facial selective intermolecular hydroacylation of norbornenes

Rh-catalyzed π-facial selective intermolecular hydroacylations of norbornenes with salicylaldehyde have been attained. In the reaction with norbornylene, the exo-hydroacylated product was produced because of steric hindrance. In the case of norbornadiene, the endo-product was obtained because of chelation effect. Lastly, because of chelation and remote substituent effects, the product formed in the reaction of 7-tert-butoxynorbornadiene was the endo,syn-product. Deuterium-labeling experiments revealed that the hydroacylation stereoselectively proceeded via endo- and exo-intermediates.     

Automated parallel anionic polymerizations: Enhancing the possibilities of a widely used technique in polymer synthesis

Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec‐butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene‐b‐isoprene) and poly(styrene‐b‐methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005     

基于CCD探测机理的新的光学头与主轴间平面度调整方法

本文提出一种新的测量光盘存储器光学头与光盘主轴平面度的方法,新方法是直接运用CCD测量光学头光斑的位置,并用专门设计的算法来找出光斑的中心位置,通过计算光斑中心位置的变化来分析光盘光学头与主轴的平面度.     

NaIO4-mediated C-H activation of alkylbenzenes and alkanes with LiBr

NaIO₄ oxidizes lithium bromide efficiently under acidic conditions to functionalize alkylbenzenes and alkanes and produce the corresponding bromo and acetoxy derivatives in excellent yields. The protocol also demonstrates the direct conversion of cyclohexane into trans-1,2-dibromocyclohexane in moderate yield.     

基于相似度的样本分类算法

结合粗糙集理论中相似关系的思想,提出了一种基本相似度的样本分类算法.并通过实例说明了该分类算法的有效性。     

Application of model-fitting and model-free kinetics to the study of non-isothermal dehydration of equilibrium swollen poly (acrylic acid) hydrogel: Thermogravimetric analysis

The dehydration kinetics of equilibrium swollen poly (acrylic acid) hydrogel is analyzed by both model-fitting and model-free approaches. The conventional model-fitting approach assuming a fixed mechanism throughout the reaction and extract a single values of the apparent activation energy (E_a) and pre-exponential factor (A) and was found to be too simplistic. The values of Arrhenius parameters obtained in such a way are in fact an average that does not reflect changes in the reaction mechanism and kinetics with the extent of conversion. The model-free approach allows for a change of mechanism and activation energy, E_a, during the course of a reaction and is therefore more realistic. The complexity of the dehydration of poly (acrylic acid) hydrogel is illustrated by the dependence of E_a and A on the extent of conversion, α (0.05 ≤ α ≤ 0.98). Under non-isothermal conditions, E_a decreases with α for 0 ≤ α ≤ 0.50, followed by an approximately constant value of E_a during further dehydration. For 0 ≤ α ≤ 0.50, dehydration is complex, which probably involving a combination of several processes. In the constant-E_a region, non-isothermal dehydration follows the three-dimensional phase boundary model (R3). The complex hydrogen-bond pattern in poly (acrylic acid) hydrogel is probably responsible for the observed dehydration behavior. An existence of compensation effect is accepted and explanation of compensation effect appearance during the hydrogel dehydration is suggested.     

New coupling reagents for homogeneous esterification of cellulose

A group of known, but in cellulose chemistry new coupling reagents for homogeneous esterification has been investigated: 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride, N-methyl-2-bromopyridinium iodide, N-methyl-2-chloropyridinium iodide, and N-methyl-2-bromopyridinium tosylate. In order to study their ability to activate carboxylic acids in esterifications of cellulose they have been employed in synthesis of cellulose adamantate esters. Their effectiveness has been estimated in terms of degree of substitution of resulting esters and compared to that obtained with the commonly used N,N′-carbonyldiimidazole.