On the Existence of Positive Solution for n OrderSingular Boundary Value Problems

§１．　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｅｘｉｓｔｅｎｃｅｆｏｒｔｈｅｂｏｕｎｄａｒｙｖａｌｕｅｐｒｏｂｌｅｍｓｈａｖｅｂｅｅｎｗｉｄｅｌｙｓｔｕｄｉｅｄｒｅｃｅｎｔｌｙ．Ｉｎｔｈｉｓｐａｐｅｒ，ｗｅｗｉｌｌｄｉｓｃｕｓｓｔｈｅＢＶＰｏｆｔｈｅｆｏｌｌｏｗｉｎｇｃｏｎｄｉｔｉｏｎｓ：ｕ（ｎ）＋ａ（ｔ）ｆ（ｕ）＝０，０＜ｔ＜１，ｕ（ｋ）（０）＝０，０ｋｎ－２（１．１）ｕ（１）＝０，　ｗｈｅｒｅ（ｈ１）ａ：（０，１）→（０，∞）ｉｓａｃｏｎｔｉｎｕｏｕｓｆｕｎｃｔｉｏｎ．（ｈ２）ｆ：［０，∞）→［…     

加权总体最小二乘问题的解集和性质

本文讨论了加权总体最小二乘问题的等价解集，分析了加权总体最小二乘解与加权最小二乘问题的解之间的关系。推广了Ｇｏｌｕｂ和Ｖａｎ Ｌｏａｎ，Ｖａｎ Ｈｕｆｆｅｌ和Ｖａｎｄｅｗａｌｌｅ，及Ｗｅｉ的相应结果。     

Difference in enzyme activity and conformation of glucose oxidase before and after purification

Enzyme activity of commercial glucose oxidase was enhanced after purification through a strong anionic exchange resin. In order to get a better insight into this phenomenon, surface pressure–area (π–A) isotherms and surface pressure–time (π–t) isotherms was used to study the interaction and the absorption at different pH values of the subphases between octadecylamine and glucose oxidase purified by a styrene system quaternary ammonium type strongly basic anionic exchange resin. Circular dichroism (CD), electrophoresis and enzyme activity measurements were conducted to study these phenomena. A preliminary hypothesis has been suggested to explain why the enzyme activity of purified glucose oxidase was higher than that of the commercial one.     

Elution Behaviour of Monocarboxylic Acids on a Cation-exchange Resin Column

The retention mechanism of monocarboxylic acids on a cation-exchange resin column was investigated. It was assumed that both Donnan membrane equilibrium and adsorption equilibrium were involved in the chromatographic process. On the basis of the proposed mechanism, an equation was derived for correlating distribution coefficient, Kd, dissociation constant, Aa, and adsorption equilibrium constant, K, of the analyzed acid. By this approach, retention data for some aliphatic acids under different operating conditions were predicted. Results are reasonably in agreement with experiment.     

测自来水的电阻率

研究性学习是新课程教学改革的核心，它既是一种教学活动形式，也是一种学习活动方式。研究性主题不同于一般教学中的课外活动，而是强调学生动手动脑的实践过程。在这一过程中，在教师的指导下，学生从自然现象、社会、生活中遇到的问题出发，提出问题，并应用已有的知识设法解决问题，从中主动获取新知识，达到培养学生提出和解决问题能力的目的。本着这一教学思想我们组织开展了一次研究性学习课，将学习课全程总结浓缩成文，仅以此供同仁商榷。     

NURBS approximation of surface/surface intersection curves

We use a combination of both symbolic and numerical techniques to construct degree boundedC ^k -continuous, rational B-spline ε-approximations of real algebraic surface-surface intersection curves. The algebraic surfaces could be either in implicit or rational parametric form. At singular points, we use the classical Newton power series factorizations to determine the distinct branches of the space intersection curve. In addition to singular points, we obtain an adaptive selection of regular points about which the curve approximation yields a small number of curve segments yet achievesC ^k continuity between segments. Details of the implementation of these algorithms and approximation error bounds are also provided. Supported in part by NSF Grants CCR 92.22467, DMS 91-01424, AFOSR Grant F49620-10138 and NASA Grant NAG-1-1473. Supported in part by K.C. Wong Education Foundation, Hong Kong.     

THERMODYNAMIC AND PARTICLE-DYNAMIC STUDIES ON SYNTHESIS OF SILICA NANOPARTICLES USING MICROWAVE-INDUCED PLASMA CVD

1. Introduction1.1 Silica nanoparticles and synthesis methods Silica (SiO2) nanoparticles are widely used in industry asan active filler for polymer reinforcement, a rheologicaladditive in fluids, a free flow agent in powders, and anagent for chemical mechanical polishing during IC (inte-grated circuit) fabrication (Sniegowski & de Boer, 2000).Silica powder is also used for producing silicon carbide(Koc & Cattamanchi, 1998) or opaque silica aerosols (Leeet al., 1995). Many methods can …     

FI催化剂配体的研究进展

FI催化剂作为一类新型聚烯烃催化剂,具有高活性、耐高温等特性,在催化聚合方面表现出良好的性能,不但可以催化乙烯与极性及非极性单体共聚,而且可以通过改变主催化剂苯氧基亚胺配体的结构,得到具有不同结构的聚合物。本文介绍了FI主催化剂的基本结构、合成方法、结构与催化性能的关系以及基于苯氧基亚胺配体基本结构的新型催化剂的研究进展。     

柠檬酸镧的合成及其对SBR橡胶硫化性能的影响

以氯化镧和柠檬酸为原料,合成柠檬酸镧,探究反应条件对柠檬酸镧产率的影响,得到反应体系p H值4~5之间,柠檬酸与氯化镧的摩尔比1.2∶1,反应体系温度50℃为较优的反应条件。并将合成的柠檬酸镧添加到SBR混炼胶中,研究其对混炼胶的硫化特性和硫化胶物理机械性能的影响;结果表明,添加2.5%的柠檬酸镧可使混炼胶的硫化速率t90达到943 s,比未添加柠檬酸镧的快了31 s,当添加量为7.5%时硫化胶的物理机械性能达到最佳,比未添加相比提高了将近50%。通过红外光谱表征产物结构,并采用硫化仪、万能试验机对混炼胶进行硫化性能及物理机械性能测试,研究结果表明,柠檬酸镧可提高混炼胶的硫化性能、硫化胶物理机械性能及抗硫化还原性。因此,柠檬酸镧可以作为SBR橡胶硫化剂的一种补充。