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Explicit analytical solutions of the anisotropic Brinkman model for the natural convection in porous media(Ⅱ)

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Science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 422-430页

作者： CAI Ruixian1, GOU Chenhua1, 2.& ZHANG Na1 1. institute of Engineering Thermophysics, chinese academy of sciences, {2., china 2. Graduate School, chinese academy of sciences, {2., china institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Graduate School Chinese Academy of Sciences Beijing China

Some algebraically explicit analytical solutions are derived for the anisotropic Brinkman model―an improved Darcy model―describing the natural convection in porous media. Besides their important theoretical meaning (for example, in analyzing the non-Darcy and anisotropic effects on the convection), such analytical solutions can be the benchmark solutions that can promote the development of computational heat and mass transfer. Some solutions considering the anisotropic effect of permeability have been given previously by the authors, and this paper gives solutions including the anisotropic effect of thermal conductivity and the effect of heat sources.

关键词： explicit analytical solution, porous medium, natural convection, Brinkman model, anisotropic.

Interfacial behaviors of PMMA-PEO block copolymers at the air/water interface

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Science china chemistry 2005年第6期48卷 567-573页

作者： CHENG Caixia1, JIAO Tifeng2. TANG Rupei1, LIU Minghua2.& XI Fu1 1. State Key Laboratory of Polymer Physics and chemistry, Joint Laboratory of Polymer Science and Materials, institute of chemistry, chinese academy of sciences, beijing 100080, china 2. CAS Key Laboratory of Colloid and Interface Science, institute of chemistry, chinese academy of sciences, beijing 100080, china State Key Laboratory of Polymer Physics and chemistry Joint Laboratory of Polymer Science and Materials Institute of Chemistry Chinese Academy of Sciences Beijing China CAS Key Laboratory of Colloid and Interface Science Institute of Chemistry Chinese Academy of Sciences Beijing China

Diblock copolymer of PMMA2.1-b-PEO114 and triblock copolymer of PMMA12.-b- PEO2.7-b-PMMA12. were synthesized and their interfacial properties at the air-water interface were investigated, where both blocks of polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are surface active but the former is soluble in water while the latter is not. Both the block copolymers could form monolayers with two obvious transition regions. The first transition point is around 10 mN/m, which could be assigned to the pancake-brush change of the PEO chains. The other is around 18 mN/m, which could be ascribed to the condensed packing of PMMA. The surface morphological changes during the compression of the Langmuir monolayers are inves-tigated by using the AFM and SEM methods for the films deposited at different surface pressure or molecular areas. At a lower surface pressure, a typical morphology of PEO-con- taining lipopolymers is observed. Upon compression, sphere-dominant morphologies were observed. While the diblock copolymer is easy to folding, the triblock copolymer is in favor of formation of circular domains through vesiculation.

关键词： PMMA-PEO, block copolymers, monolayer, Langmuir-Blodgett films, AFM.

COPOLYMERIZATION OF ETHYLENE AND PROPYLENE WITH (CpCH_2.H_2.H=CH_2._2.Cl_2.M=Zr,Hf)AND Cp_2.rCl_2.CATALYSTS

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chinese Journal of Polymer Science 2000年第2期18卷 169-175页

作者： Hui Yao Shi-jing Xiao institute of chemistry, {2., beijing 100080, china 中科院化学所北京

(CpCH_2.H_2.H = CH_2._2.Cl_2.M=Zr, Hf)/MAO and Cp_2.rCl_2.MAO (Cp=cyclopentadienyl; MAO=methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and copolymer properties. For both CH_2.H_2.H=CH_2.substitutedcatalysts the catalytic activity decreased with increasing propene concentration in the feed. The activity of the hafnocenecatalyst was 6～8 times lower than that of the analogous zirconocene catalyst, ^(13)C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2.rCl_2.has greater incorporatien of propene than those produced byCH_2.H_2.H=CH_2.substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecularweight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2.H_2.H= CH_2.substitutedZr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However,there are significant differences between the two zirconocene catalysts. The copolymer produced by Cp_2.rCl_2.catalyst havemuch lower T_m and X_c than those obtained with the (CpCH_2.H_2.H=CH_2._2.rCl_2.catalyst. The density and molecular weightof the copolymer decreased in the order: (CpCH_2.H_2.H=CH_2._2.fCl_2.(CpCH_2.H_2.H=CH_2._2.rCl_2.Cp_2.rCl_2. The kineticbehavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst.

关键词： Metallocene catalyst Ethylene/propylene copolymerization Methylaluminoxane

MULTIVARIATE FOURIER SERIES OVER A CLASS OF NON TENSOR-PRODUCT PARTITION DOMAINS

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Journal of Computational Mathematics 2003年第1期21卷 53-62页

作者： Jiachang Sun(Parallel Computing Division, institute of Software, chinese academy of sciences, {2., china) Parallel Computing Division Institute of Software Chinese Academy of Sciences 北京 100080

This paper finds a way to extend the well-known Fourier methods, to so-called n+1 directions partition domains in n-dimension. In particular, in 2.D and 3-D cases, we study Fourier methods over 3-direction parallel hexagon partitions and 4-direction parallel parallelogram dodecahedron partitions, respectively. It has pointed that, the most concepts and results of Fourier methods on tensor-product case, such as periodicity,orthogonality of Fourier basis system, partial sum of Fourier series and its approximation behavior, can be moved on the new non tensor-product partition case.

关键词： Multivariate Fourier methods Non tensor-product partitions Multivariate Fourier series

Stability of proton and maximally symmetric minimal unification model for basic forces and building blocks of matter

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Science china(Physics,Mechanics & Astronomy) 2007年第3期50卷 303-310页

作者： WU YueLiang institute of Theoretical Physics, chinese academy of sciences, {2., china institute of Theoretical Physics Chinese Academy of Sciences Beijing China

With the hypothesis that all independent degrees of freedom of basic building blocks should be treated equally on the same footing and correlated by a possible maximal symmetry, we arrive at a 4-dimensional space-time unification model. In this model the basic building blocks are Majorana fermions in the spinor repre- sentation of 14-dimensional quantum space-time with a gauge symmetry GM4D = SO(1,3)×SU(32.×U(1)A×SU(3)F. The model leads to new physics including mirror particles of the standard model. It enables us to issue some fundamental questions that include: why our living space-time is 4-dimensional, why parity is not con- served in our world, how the stability of proton is, what the origin of CP violation is and what the dark matter can be.

关键词： gauge symmetry space-time symmetries beyond standard model and unification

SYNTHESIS OF NOVEL SOLUBLE AROMATIC POLYPYROMELLITIMIDE CONTAINING ORDERED 1,2.4-TRIAZINE IN THE MAIN CHAIN

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chinese Journal of Polymer Science 2002年第3期20卷 219-224页

作者： Xiao-bing Yi Guo-shi Wu Feng-cai Lu Department of chemistry Tsinghua University, beijing 100084 {2. institute of chemistry chinese academy of sciences, beijing 100080, {2. Tsing Hua Univ Dept Chem Beijing 100084 Peoples R China

A new heat-resistant, soluble polymer, poly(phenyl-1,2.4-triazine imide), has been prepared via a two-step method of polycondensation of N,N'-bis(4-benzil)pyromellitimide and terephthalamidrazone in cresol, followed by curing at higher temperature. The rigid 1,2.4-triazine group increases the solubility of the polyimide so that the polymer is soluble in cresol, N-methyl-2.pyrrolidone (NMP), trifluoroacetic acid and concentrated sulfuric acid, etc. Thermogravimetric analysis (TGA) indicates that this novel polyimide has good thermal stability with a high decomposition temperature of 447degreesC in air and of 42. degreesC in N-2. It has a tensile strength of 107.4 MI'a with an elongation at break of around 7.6%.

关键词： polyimides N,N '-bis(4-benzil)pyromellitimide rigid-rod group 1,2.4-triazine

TRIMETHYLSILYLATED SILICA AS RHEOLOGY MODIFIER FOR SILICONE RESINS

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chinese Journal of Polymer Science 2000年第1期18卷 51-55页

作者： Wei Huang Ying Huang Yunzhao Yu Center for Molecular Science, institute of chemistry, {2., beijing 100080, china 中科院化学所北京

Trimethylsilylated silica was synthesized. through hydrolytic condensation of tetraethoxysilane followed by trimethylsilylation. Rheological properties of the silicone resin with trimethylsilylated silica as modifier were studied. It turned out that the particle size of silica was important to the rheological behavior of the modified resin. Trimethylsilylated silica of medium particle size shows the strongest tendency of forming physical network in the resin.

关键词： silica trimethylsilylation rheology modifier silicone resins

A new approach of cascade utilization of the chemical energy of fuel

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Progress in Natural Science:Materials International 2006年第5期16卷 518-523页

作者： HAN Wei, JIN Hongguang and LIN Rumou ( institute of Engineering Thermophysics, chinese academy of sciences, {2., china Graduate School of the chinese academy of sciences, {2., china) institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100080 China Graduate School of the chinese academy of sciences Beijing 100080 China

The indirect release of chemical energy of fuel is investigated, and a new mechanism is proposed to identify the cascade utilization of chemical energy of fuel more clearly. Based on the concept of energy level, the internal phenomenon of the indirect chemical energy release is disclosed, and the equations of energy level describing the utilization of chemical energy and thermal energy during the indirect chemical energy release process are obtained. From theoretical analysis, we find that the superiority of the indirect chemical energy release of fuel comes from the cascade utilization of the fuel's chemical energy. Moreover, the cascade utilization of chemical energy is verified by the investigation of CRGT (chemically recuperated gas turbine). As a result, the thermal exergy obtained from the chemical energy release of fuel increases by 2.% -3 % . The results obtained here may help a deeper understanding of indirect chemical energy release of fuel and provide a theoretical basis for the synthesis of innovative energy systems.

关键词： chemically recuperated gas turbine methane/steam reforming chemical energy level cascade utilization.

THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF POLYMERS WITH PHYSICAL CROSSLINKS

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chinese Journal of Polymer Science 1999年第3期17卷 203-213页

作者： Mao Xu Feng-kui Li Polymer Physics Laboratory, institute of chemistry, {2., beijing 100080, china 中科院化学所高分子物理及化学国家重点实验室北京 100080 中科院化学所高分子物理及化学国家重点实验室北京

The shape memory effect of polymers was investigated for the purpose of improving the processing conditions of their preparation and broadening the list of polymers for shape memory applications. Emphasis was put on the possibility of using polymers with physical crosslinks as shape memory materials and their structure-function relationships. Segmented block polyurethanes and polyethylene/nylon 6 graft copolymers were used as examples of polymers with physical crosslinks. It was found that these copolymers can really be used as thermally stimulated shape memory materials with large recoverable strain and high final recovery rate. The main advantage of using copolymers is their improved processing conditions as compared with polymers with chemical crosslinks. As only physical crosslinks are introduced, all conventional processing techniques for thermal plastics can be used, and the materials become easily reusable. The results indicate that the high crystallinity of these copolymers at room temperature and the formation of stable physical crosslinks are the two prerequisites for these polymers to exhibit shape memory effect. The successful use of block and graft copolymers imply the possibility of using polymers of various structure and properties as shape memory materials.

关键词： shape memory effect segmented polyurethanes polyethylene nylon graft copolymers