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science china(Technological sciences) 2008年第8期51卷 1073-1086页

作者： ZHOU LiXing department of engineering {2., Tsinghua university, beijing 100084, china department of engineering {2. Tsinghua University Beijing 100084 China

The derivation and closure methods of the second-order moment (SOM) combus- tion model are proposed. The application of this model to Reynolds averaged (RANS) and large-eddy simulation (LES) of turbulent swirling diffusion combustion, jet diffusion combustion, and bluff-body stabilized premixed combustion is sum- marized. It is indicated that the SOM model is much better than the eddy-beak-up (EBU) and presumed PDF models widely used in commercial software and engi- neering. The SOM modeling results are close to those obtained using the most accurate but much more complex PDF equation model. Moreover, it can save much more computation time than the PDF equation model. Finally, the SOM model is validated by the direct numerical simulation (DNS) of turbulent reacting channel flows.

关键词： turbulent combustion second-order moment model Reynolds averaged simulation large-eddy simulation

IMPACT PROPERTIES OF METALLOCENE - CATALYZED ETHYLENE-α-OLEFIN COPOLYMERS

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Chinese Journal of Polymer science 2002年第5期20卷 473-480页

作者： Xu-rong Xu Jun-ting Xu Lin-xian Feng department of Polymer science and {2. Zhejiang university Hangzhou 31002.,china department of Polymer science and {2. College of Chemistry & Molecular {2. peking university beijing 100871, china Zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China

The impact properties of two selected metallocene-catalyzed ethylene-butene copolymers and one conventionalcopolymer were evaluated using Izod impact test. It is found that the metallocene-catalyzed copolymer shows superior impactproperties. This result was explained on the basis of the more homogeneous inter-molecular composition distribution andnarrower molecular weight distribution, which leads to more homogeneous morphology with fewer defects. Stepwisecrystallization improves the impact properties, especially in the crack propagation process, to a large extent. This is due to thedecrease of entanglements by stepwise crystallization, which is advantageous for the chain slip and shear. The polymer withheterogeneous intra-molecular composition distribution exhibits a more evident improvement of impact properties understepwise crystallization.

关键词： Metallocene-catalyzed ethylene-butene copolymer Impact properties Molecular heterogeneities Thermal treatment

Morita contexts on the Hopf algebroid

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science china Mathematics 2005年第7期48卷 958-971页

作者： YIN Yanmin School of Mathematical sciences, peking university,{2., china department of Mathematics, Shandong Institute of Architecture and engineering, Jinan 2.0101, china 1. School of Mathematical sciences Peking University 100871 Beijing China 2. department of Mathematics Shandong Institute of Architecture and Engineering 250101 Jinan China

We generalize the Morita theory to the Hopf algebroid and give the characterization of the surjectivity of one of the Morita context maps.

关键词： comodule algebra, generalized smash product, Morita context.

|m| Partial wave treatment for two-dimensional Coulomb-scattering and Regge pole

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science china(Physics,{2. & Astronomy) 2004年第6期47卷 676-684页

作者： WANG Jing & ZENG Jinyan department of Physics,Tsinghua university,{2. 100084,china School of Physics,peking university,{2. 100871,china department of Physics Tsinghua University Beijing 100084 China School of Physics Peking University Beijing 100871 China

The symmetry and |m| partial-wave analysis for two-dimensional (2.) Coulomb-scattering is investigated. As a function of energyE, the |m| partial-wave scattering amplitudef |m|(θ) is analytically continuated to the, negativeE (complexk) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles off |m|(θ) on the positive imaginaryk axis as is expected. In addition, as a function of |m|,f |m|(θ) is analytically continuated to the complex |m| plane, the bound state energy eigenvalues are just located at the poles off |m|(θ) on the positive real |m| axis.

关键词： two-dimensional Coulomb scattering, |m| partial-wave, Regge pole.

A DSC STUDY OF PHOTOPOLYMERIZATION OF POLYESTERS CONTAINING CONJUGATED DIACETYLENES

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Chinese Journal of Polymer science 2000年第4期18卷 351-356页

作者： Yao-wen Bai Xiao-fang Chen Dong Zhang Xin-hua Wan Qi-feng Zhou department of Polymer science and {2., College of Chemistry, peking university, beijing 100871, china peking Univ Coll Chem Dept Polymer Sci & Engn Beijing 100871 Peoples R China

The photopolymerization of two kinds of prepolyesters containing conjugated diacetylene (PDA-6 and PDA-12. was investigated using DSC. By measuring the endothermic enthalpy of the prepolymers after different UV-irradiation times, the polymerizations were found to follow the first-order rate law which agreed with the results of other investigators using a different method. The endothermic enthalpy measurements of PDA-6 and PDA-12.before UV-irradiation precluded the possibility that the decrease of endothermic enthalpy was caused by thermal polymerization.

关键词： diacetylene-containing polyesters DSC enthalpy

The influence of thermal radiation on MHD station-point flow past a stretching sheet with heat generation

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Acta Mechanica Sinica 2011年第4期27卷 502-509页

作者： Jing Zhu.Lian-Cun Zheng.Xin-Xin Zhang department of Mathematics and mechanics,{2. of science and Technology beijing,100083 beijing,china Thermal engineering department,{2. of science and Technology beijing,100083 beijing,china Zheng department of Mathematics and mechanics University of Science and Technology Beijing Beijing China Thermal engineering department University of Science and Technology Beijing Beijing China

This letter is concerned with the plane and axisymmetric stagnation-point flows and heat transfer of an electrically-conducting fluid past a stretching sheet in the presence of the thermal radiation and heat generation or absorption. The analytical solutions for the velocity distribution and dimensionless temperature profiles are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter, Prandtl number, thermal radiation parameter, the suction and injection velocity parameter and magnetic parameter and dimensionality index in the series form with the help of homotopy analysis method （HAM）. Convergence of the series is explicitly dis- cussed. In addition, shear stress and heat flux at the surface are calculated.

关键词： Thermal radiation MHD Laminar boundarylayers - Homotopy analysis method

New direction of computational fluid dynamics and its applications in industry

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science china(Technological sciences) 2007年第5期50卷 521-533页

作者： CHEN YaoSong1, SHAN XiaoWen2.& CHEN HuDong2.1 department of mechanics,{2., beijing 100871, china 2.Exa Corporation, Burlington, MA 01803 USA 1. department of mechanics Peking University Beijing 100871 China 2. Exa Corporation Burlington MA 01803 USA

For the past ten years there has been much progress in computational fluid dy- namics (CFD), among which the formation and development of the lattice Boltz- mann method (LBM) are an important new direction. We give a review on the main aspect and the latest development of this method in this article, and at the same time we also discuss the related development of scientific software and its impact on the real-world applications in industry.

关键词： lattice method, Boltzmann equation, CFD

SYNTHESIS OF NOVEL LIQUID CRYSTALLINE POLY(METH)ACRYLATES CONTAINING SILOXANE SPACER AND TERPHENYLENE MESOGENIC UNIT

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Chinese Journal of Polymer science 2000年第2期18卷 101-107页

作者： Zhi-qian Zang Yu-fei Luo Dong Zhang Xin-hua Wan Qi-feng Zhou department of Polymer science & {2., College of Chemistry, peking university, beijing 100871, china peking Univ Coll Chem Dept Polymer Sci & Engn Beijing 100871 Peoples R China

Novel side-chain liquid-crystalline poly(meth)acrylates were synthesized using 1-(3-hydroxyl-propyl)-3-[(4 '-cyano-p-terphenyloxycarbonyl)alkyl]-1,1,3,3-tetramethyldisiloxane as the key intermediate. The polymers used a disiloxane moiety as decoupling spacer with cyano-p-terphenyl as mesogenic unit. The products were characterized by NMR, GPC, DSC and polarizing optical microscopy. All the polymers with cyano-p-terphenyl mesogens formed a stable mesophase. However, if the mesogenic unit is replaced by cyano-p-biphenyl, the liquid crystalline character will be lost. The results also showed that the decoupling is incomplete even if a complex and very flexible decoupling spacer is deliberately incorporated to obtain the highest possible decoupling effect.

关键词： liquid crystalline polymers polyacrylates 4 ''-cyano-p-terphenyl

Phase relationship of complex multi-component system in chromate cleaner production

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Progress in Natural science:Materials International 2007年第7期17卷 845-850页

作者： Ge Xinlei~1 Wang Xidong~(1,3**) Zheng Shili~2.Zhang Mei~1 Zhang Yi~2.(1.department of Physical Chemistry,university of {2. and Technology beijing,beijing 100083,china 2.Institute of Process engineering,Chinese Academy of {2.s,beijing 100080,china 3.College of engineering,peking university,beijing 100871,china) [a]department of Physical Chemistry University of Science and Technology Beijing Beijing China [b]College of engineering Peking University Beijing China [c]Institute of Process engineering Chinese Academy of Sciences Beijing China

The phase relationships of the complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production are investigated theoretically and *** phase diagram of main system Fe- Cr2.4-KOH-O2.f oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated.A se- ries of phase diagrams of the separation process at different temperatures,such as K（Na）OH-K（Na）2.rO4-H2.,KOH-KAlO2.H2., K（Na）OH-K（Na）2.O3-H2.,K（Na）OH-K（Na）HCO3-H2. and K（Na）HCO3-K（Na）2.rO4-H2. have also been *** ex- periments are carried out to verify the calculated *** results showed that the sub-molten salt media are suitable for the oxidization and separation processes;FeCr2.4can be oxidized across a wide range of temperature;K（Na）2.rO4can be separated from K（Na）AlO2.ystem at appropriate temperature and proper concentration;the crystallization of carbonate is easier than that of K（Na）2.rO4.

关键词： chromite chromate system thermodynamics calculation phase diagram

Water demand for ecosystem protection in rivers with hyper-concentrated sediment-laden flow

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science china(Technological sciences) 2004年第z1期47卷 186-198页

作者： LUO Huaming, LI Tianhong, NI Jinren & WANG Yudong department of Environmental engineering,{2., beijing 100871, china The Key Laboratory of Water and Sediment sciences, Ministry of Education, beijing 100871, china peking Univ Dept Environm Engn Beijing 100871 Peoples R China Key Lab Water & Sediment Sci Minist Educ Beijing 100871 Peoples R China

Sediment transport is one of the main concerns in a river system with hyper-concentrated flows. Therefore, the water use for sediment transport must be considered in study on the water demand for river ecosystem. The conventional methods for calculating the Minimum Water Demand for River Ecosystem (MWDRE) are not appropriate for rivers with high sediment concentration. This paper studied the MWDRE in wet season, dry season and the whole year under different water-and-sediment conditions in the Lower Yellow River, which is regarded as a typical river with sediment-laden flows. The characteristics of MWDRE in the river are analyzed. Firstly, the water demand for sediment transport (WDST) is much larger than the demands for other riverine functions, the WDST accounts for the absolute majority of the MWDRE. Secondly, in wet season when the WDST is satisfied, not only most of the annual incoming sediment can be transported downstream, but also the water demands for other river functions can be satisfied automatically, so that the MWDRE in wet season is identical to the WDST. Thirdly, in dry season, when the WDST is satisfied, the water demands for other river functions can also be satisfied, but the low sediment transport efficiency results in significant waste of water resources. According to these characteristics and aiming at decreasing sediment deposition in the riverbed and improving the utilization efficiency of water resources, hydrological engineering works can be used to regulate or control flow and sediment so that the sediment incoming in dry season can be accumulated and be transported downstream intensively and thus efficiently in wet season.

关键词： sediment-laden flow, the Lower Yellow River, water demand for river ecosystem, water demand for sediment transport