检索结果-南通市图书馆

An SGS Model and Its Application

在线全文

学校读者我要写书评

暂无评论

Communications in Nonlinear Science and Numerical Simulation 1999年第2期4卷 87-90页

作者： Zhengtong XIE Jiachun LI (institute of Mechanics, chinese academy of sciences, {2., china) institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Based on the turbulent energy and structure function model, a subgridstress model named transitional structure function (TSF) is proposed, which exhibitsmore satisfactory performance than the previous one when applied in turbulent flow withinand above forest *** time and horizontal averaged statistics such as mean verticalprofiles of wind velocity, Reynolds stress, turbulent kinetic energy etc., and instantaneousfields as well are in general agreement with earlier observations, at least in a qualitativesense.

关键词： Large-Eddy simulation SGS model turbulent flow canopy

Effect of concentration on surfactant micelle shapes——A molecular dynamics study

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china chemistry 2005年第5期48卷 470-475页

作者： GAO Jian1,2. GE Wei1 & LI Jinghai1 1. Multiphase Reaction Laboratory, institute of Process Engineering, chinese academy of sciences, {2., china 2. Graduate School of The chinese academy of sciences, beijing 100085, china Multiphase Reaction Laboratory Institute of Process Engineering Chinese Academy of Sciences Beijing China Graduate School of The chinese academy of sciences Beijing China

Many aspects of the behavior of surfactants have not been well understood due to the coupling of many different mechanisms. Computer simulation is, therefore, attractive in the sense that it can explore the effect of different mechanisms separately. In this paper, the shapes, structures and sizes of sodium dodecylbenzenesulfonate (SDBS) micelles under different con-centrations in an oil/water mixture were studied via molecular dynamics (MD) simulations using a simplified atomistic model which basically maintains the hydrophile and lipophile properties of the surfactant molecules. Above the critical micellar concentration (cmc), surfactant molecules ag-gregate spontaneously to form a wide variety of assemblies, from spherical to rodlike, wormlike and bilayer micelles. Changes in their ratios of the principle moments of inertia (g1/g3, g2.g3) in-dicated the transition of micelle shapes at different concentrations. The aggregation number of micelle is found to have a power-law dependence on surfactant concentration.

关键词： surfactant, MD simulation, sodium dodecylbenzenesulfonate, micelle shape.

Flow Instability and Its Control in Compression Systems

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2003年第1期12卷 1-9页

作者： Jingyi Cheninstitute of Engineering Thermophysics, chinese academy of sciences, {2., china institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China

This paper reviews the development in the research of flow instability and its control over the recent ten or more years. This development was largely stimulated by the novel idea of active control of the aerodynamic instability in compressors. Three topics are covered in the paper, which appeared as the major themes towards the goal of stability enhancement. The first topic is the pre-stall behavior of rotating stall, which plays a vital role in designing the control scheme and discovering the convenient route to find the causal factors of flow disturbances potentially leading to stall. The second topic is the mechanism of blade passage flow during stall and its inception, which is the basic knowledge needed to manipulate the blade design for the stability improvement and eventually to predict the unsteady performance of the compressor system. The third topic is the recent trend of the control strategy based on the learning of active vs. passive methods. To introduce to the discussion of these topics, a brief description of the history of the recent development is given at the beginning of the paper. In discussing each topic, future works are also highlighted to enhance the further development of this long-standing problem in turbomachinery research and application.

关键词： compressors rotating stall pre-stall active/passive control wavelet.

Experimental investigation and numerical simulation on the effect of fissure water pressure in vertical sliding surface

在线全文

学校读者我要写书评

暂无评论

Science china(Technological sciences) 2005年第z1期48卷 53-64页

作者： ZHANG Lei1,2. LI Shihai1, LIAN Zhenzhong1,2.& WANG Yuannian1 1. institute of Mechanics, chinese academy of sciences, {2., china 2. Graduate School, chinese academy of sciences, beijing 100060, china institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

This paper studies the effect of fissure water pressure in different fractures on the critical angle of landslide by laboratory investigation and numerical simulation in order to understand the mechanisms of fissure water pressure on landslide stability. Laboratory observations show that the effect of fissure water pressure on the critical angle of landslide is little when the distance between water-holding fracture and slope toe is three times greater than the depth of fissure water. These experimental results are also simulated by a three-dimensional face-to-face contact discrete element method. This method has included the fissure water pressure and can accurately calculate the critical angle of jointed slope when fissure water pressure in vertical sliding surface exists. Numerical results are in good agreement with experimental observations. It is revealed that the location of water-holding structural surface is important to landslide stability. The ratio of the distance between water-holding fissure and slope toe to the depth of fissure water is a key parameter to justify the effect of fissure water pressure on the critical angle of landslide.

关键词： jointed rock slope, discrete element method, fracture in vertical sliding surface, model experiment,fissure water pressure.

ON THE CENTRAL RELAXING SCHEMES I:SINGLE CONSERVATION LAWS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2000年第3期18卷 313-324页

作者： Hua-zhong Tang (LSEC, institute of Computational Mathematics and Scientific /Engineering Computing, academy of Mathematics and System {2., chinese academy of sciences, beijing, 100080, china) 中科院计算数学与科学工程计算所科学与工程计算国家重点实验室北京 100080

Presents a central relaxing scheme for scalar conservation laws. Details on the preliminary equations; Properties of the relaxed schemes; Conclusions.

关键词： hyperbolic conservation laws the relaxing scheme TVD cell entropy inequality

An efficient chiral synthesis of (R)-N-[3-acetyl-4-(2.hydroxy-3-isopropylamino-propoxy)phenyl]-butanamide with high enantioselectivity

在线全文

学校读者我要写书评

暂无评论

Science china chemistry 2009年第8期52卷 1216-1219页

作者： WANG NaiXing1,2.& TANG XinLiang1,3 1 Technical institute of Physics and chemistry,{2.,beijing 100080,china 2.College of chemistry and Chemical Engineering,Graduate University of {2.,beijing 100049,china 3 School of Chemical Engineering and Environment,beijing institute of Technology,beijing 100081,china Technical institute of Physics and chemistry Chinese Academy of Sciences Beijing China College of chemistry and Chemical Engineering Graduate University of Chinese Academy of Sciences Beijing China School of Chemical Engineering and Environment Beijing Institute of Technology Beijing China

R-Enantiomer of the β-receptor antagonist N-[3-acetyl-4-(2.hydroxy-3-isopropylamino-propoxy)phenyl] butanamide with high enantioselectivity was synthesized from cheap starting materials and enantiopure chiral reagent through an efficient,convenient and practical synthetic *** product was detected by 1H NMR,13C NMR,and MS,and the enatiomeric excess was determined by chiral HPLC analysis using a chiracel AD-H column.

关键词： chiral synthesis enantioselectivity enatiomeric excess chiral HPLC analysis

Physical aging in Zr_(46.75)Ti_(8.2.)Cu_(7.5)Ni_(10)Be_(2..5) typical bulk metallic glass manifested as enthalpy relaxation

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2008年第4期51卷 356-364页

作者： WEN Ping,ZHAO ZuoFeng & WANG WeiHua institute of Physics,chinese academy of sciences,{2.,china institute of Physics Chinese Academy of Sciences Beijing China

Enthalpy recovery is not only an important characteristic of physical aging of glass,but also a good tool to investigate the physical aging. Using differential scanning calorimeter (DSC),the enthalpy recovery of Zr46.75Ti8.2.Cu7.5Ni10Be2..5 bulk metallic glass (BMG) was studied. The typical characteristics of enthalpy recovery of glass including the sub-Tg peak and ‘overshot’ were found in BMG. The evolution of the sub-Tg peak and ‘overshot’ were described by the free volume theory and Hodge’s model,respectively. It was found that the former failed to describe the enthalpy recovery in the BMG,while the latter could give a qualitative explanation. In com-bination with the dynamics in the BMG,the origin of the enthalpy recovery in the BMG was discussed. The results show that BMGs are an ideal material to investi-gate the physical aging. The further understanding of physical aging of BMGs is useful to clarify the nature of glass and improve the application and device of new types of BMGs.

关键词： bulk metallic glass enthalpy recovery physical aging

Topography and functional information of plasma membrane

在线全文

学校读者我要写书评

暂无评论

Science china(Life sciences) 2008年第2期51卷 95-103页

作者： SUN DeLan1, CHEN JianMin1, SONG YanMei1, ZHU ChuanFeng2. PAN GeBo2.& WAN LiJun2.1 Key Laboratory of Photosynthesis and Environmental Molecular Physiology, institute of Botany, chinese academy of sciences, {2. 100093, china 2.institute of chemistry, chinese academy of sciences, beijing 100080, china Key Laboratory of Photosynthesis and Environmental Molecular Physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 Chin

By using atomic force microscope (AFM), the topography and function of the plasmalemma surface of the isolated protoplasts from winter wheat mesophyll cells were observed, and compared with dead protoplasts induced by dehydrating stress. The observational results revealed that the plasma membrane of living protoplasts was in a state of polarization. Lipid layers of different cells and membrane areas exhibited distinct active states. The surfaces of plasma membranes were unequal, and were characterized of regionalisation. In addition, lattice structures were visualized in some regions of the membrane surface. These typical structures were assumed to be lipid molecular complexes, which were measured to be 15.8±0.09 nm in diameter and 1.9±0.3 nm in height. Both two-dimensional and three-dimensional imaging showed that the plasmalemma surfaces of winter wheat protoplasts were covered with numerous protruding particles. In order to determine the chemical nature of the protruding particles, living protoplasts were treated by proteolytic enzyme. Under the effect of enzyme, large particles became relatively looser, resulting that their width was increased and their height decreased. The results demonstrated that these particles were likely to be of protein nature. These protein particles at plasmalemma surface were different in size and unequal in distribution. The diameter of large protein particles ranged from 2.0 to 440 nm, with a central micropore, and the apparent height of them was found to vary from 12.to 40 nm. The diameter of mid-sized protein particles was between 40―60 nm, and a range of 1.8―5 nm was given for the apparent height of them. As for small protein particles, obtained values were 12.40 nm for their diameter and 0.7―2.2.nm for height. Some invaginated pits were also observed at the plasma membrane. They were formed by the endocytosis of protoplast. Distribution density of them at plasmalemma was about 16 pits per 15 μm2. According to their size, we clas

关键词： atomic force microscope winter wheat protoplast plasma membrane surface membrane protein invaginated pits

ARCHITECTURE OF LADDER,TUBULAR AND SIEVE-PLATE POLYMERS PREPARED BY STEPWISE COUPLING POLYMERIZATION

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Polymer Science 2000年第3期18卷 195-206页

作者： Rong-ben Zhang Ping Xie Dao-rong Dai Chun-qing Liu institute of chemistry, {2., beijing 100080, china 中科院化学所北京

'Stepwise-coupling polymerization' (SCP) is a very useful approach for preparing microstructure-controllable ordered network polymers, including soluble one-dimensional ladderlike polymers (LP) and tubular polymers (TP), and two-dimensional sieve-plate polymers. The novel reactive LPs are important precursors of micro-structure controllable polymers such as 'fishbone-' or 'rowboat-' like mesomorphic polymers and their metal complexes as well as tubular polymers (TPs). They are full of great potential for use as advanced materials.

关键词： stepwise coupling polymerization ladder polysiloxane tubular polymers