检索结果-南通市图书馆

Preparation of TiC/Ni_3Al Composites by Upward Melt Infiltration

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2000年第4期16卷 387-392页

作者： Yi PAN (Department of Materials Science and Engineering, zhejiang university, hangzhou 310027, china) Kewei SUN (National Engineering Research center of Solid Waste Resources Recovery, Kunming university of Science and Technology,Kunming 650093, china) Department of Materials Science and Engineering Zhejiang University Hangzhou 310027 China National Engineering Research center of Solid Waste Resources Recovery Kunming University of Science and Technology Kunming 650093 China

TiC/Ni_3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni_3Al melt filling and TiC sintering during the infiltration. The dissolution of TiC in liquid Ni_3Al has been evidenced by finding Ni_3(Al,Ti)C after fast cooling in the TiC/Ni_3Al composites. The dissolution may be responsible for the infiltration and sintering. Compared with downward infiltration, the upward infiltration brought about higher strength and fracture toughness and shorter infiltration time. TiC/20 vol. pct Ni_3Al composite processed by upward infiltration had a flexural strength of 1476 MPa with a statistic Weibull modulus of 20.2 and a fracture toughness of 20.4 MPa . Better mechanical properties may be attributed to melt unidirectional movement in upward infiltration.

关键词： TiC Preparation of TiC/Ni3Al Composites by Upward Melt Infiltration Ni Al

Wake structures of two spheres in tandem arrangement at various gaps for Re=300

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第2期15卷 37-41页

作者： ZOU Jianfeng*, REN Anlu, DENG Jian and CHEN Wenqu(Department of Mechanics, zhejiang university, hangzhou 310027, china) Department of Mechanics Zhejiang University Hangzhou 310027 China

The virtual boundary method is extended to a 3D application and used to simulate the flow field of two spheres in tandem arrangement for a Reynolds number of 300. The wake structures and flow spectra at various gaps are investigated. The numerical results show that for small gaps (≈1.5), due to the mutual suppress between the wakes of the two spheres, the full flow field is stable and axisymmetric. As the gap is increased to 2.0, an asymmetric but stable flow is constructed through a certain bifurcation. The downstream wake structure is characterized by a double-thread vortex structure that comprises two slender parallel vortex tubes. The double-thread structure has a planar symmetry at gap 2.0. The hairpin-shape vortices are periodically shed from the downstream sphere at gap 2.5, but the planar symmetry persists. The vortex structures at gaps ranging from 3.0 to 4.0 are irregular and the flow field is undergoing a kind of 3D transition. It is up to the large gap 5.0 that the hairpin-shape structures are reconstructed behind the upstream and the downstream sphere, and the planar symmetry is resumed. All these numerical computations were performed on an SGI Origin3900 machine at the center for Engineering and Scientific Computation of zhejiang university.

关键词： virtual boundary method flow past two spheres wake structure flow spectra

Separation of Hydrophobic Neutral Compounds by Microemulsion Electrokinetic Chromatography

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1998年第11期9卷 0-0页

作者： Xiao Yun FU Xiu Zhu XU Jian De LU (Analytical and Testing center, zhejiang university, hangzhou 310027) zhejiang Univ Analyt & Testing Ctr Hangzhou 310027 Peoples R China

Microemulsion electrokinetic chromatography (MEEKC) was developed for the separation of hydrophobic neutral compounds. The effects of core phase and co-surfactant on the separations were investigated. Under the selected condition, good resolutions were obtained for the test mixtures. The separation efficiencies were higher than 105 theoretical plates per metre.

关键词： Microemulsion electrokinetic chromatography hydrophobic compounds

Kinetics and Mechanism of the Polymerization of Methyl Methacrylate in a Y(acac)_3/n-BuMgCl System

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2000年第1期16卷 61-66页

作者： PAN Zhi-da SUN Jun-quan and YANG Shi-lin (College of Chemical Engineering, zhejiang university, hangzhou 310027, china) zhejiang Univ Coll Chem Engn Hangzhou 310027 Peoples R China

Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)_3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as R_p=K_p[c][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with c_I=3. 6 × 10^(-4).

关键词： Polymerization Kinetics Mechanism Methyl methacrylate Rare earth catalyst

Some results on numerical divided difference formulas

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2005年第11期48卷 1441-1450页

作者： Wang Xinghua,Wang Heyu & Ming-Jun Lai Department of Mathematics, zhejiang university, hangzhou 310028, china Computing center, zhejiang university, hangzhou 310012, china Department of Mathematics, university of Georgia, Athens, GA 30602-7403, USA 1. Department of Mathematics Zhejiang University 310028 Hangzhou China 2. Computing center Zhejiang University 310012 Hangzhou China 3. Department of Mathematics University of Georgia 30602-7403 Athens GA USA

The remainder estimates of numerical divided difference formula are given for the functions of lower and higher smoothness, respectively. Then several divided difference formulas with super-convergence are derived wit... 详细信息

关键词： numerical divided difference remainder estimate functions of lower smoothness sufficiently smooth functions super convergence.

Rational surface charge engineering of haloalkane dehalogenase for boosting the enzymatic performance in organic solvent solutions

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2024年第1期65卷 276-285页

作者： yin Wu Yan Sun Department of Biochemical Engineering School of Chemical Engineering and Technology and Key Laboratory of Systems Bioengineering and Frontiers Science Center for Synthetic Biology(Ministry of Education)Tianjin UniversityTianjin 300350China

Biocatalysis in organic solvents(OSs)has numerous important applications,but native enzymes in OSs often exhibit limited catalytic ***,we proposed a computation-aided surface charge engineering strategy to improve the catalytic performance of haloalkane dehalogenase DhaA in OSs based on the energetic analysis of substrate binding to the DhaA *** variants with enhanced OS resistance were obtained by replacing negative charged residues on the surface with positive charged residue(Arg).Particularly,a four-substitution variant E16R/E93R/E121R/E257R exhibited the best catalytic performance(five-fold improvement in OS resistance and seven-fold half-life increase in 40%(vol)dimethylsulfoxide).As a result,the overall catalytic performance of the variant could be at least 26 times higher than the wild-type *** spectroscopy and molecular dynamics simulation studies revealed that the residue substitution mainly enhanced OS resistance from four aspects:(a)improved the overall structural stability,(b)increased the hydrophobicity of the local microenvironment around the catalytic triad,(c)enriched the hydrophobic substrate around the enzyme molecule,and(d)lowered the contact frequency between OS molecules and the catalytic *** findings validate that computationaided surface charge engineering is an effective and ingenious rational strategy for tailoring enzyme performance in OSs.

关键词： Surface charge engineering Organic solvent resistance Molecular dynamics simulation Haloalkane dehalogenase

The three-dimensional structure of Infectious flacherie virus capsid determined by cryo-electron microscopy

在线全文

学校读者我要写书评

暂无评论

Science china(Life sciences) 2009年第12期52卷 1186-1191页

作者： XIE Li1,4, ZHANG QinFen2·, LU XingMeng3, DAI XinHong2, LI KunPeng2, HONG Jian1,4· & ZHOU XuePing11 Institute of Biotechnology, zhejiang university, hangzhou 310029, china 2 State Key Laboratory of Biocontrol, School of Life sciences, Sun Yat-Sen university, Guangzhou 510275, china 3 College of Animal sciences, zhejiang university, hangzhou 310029, china 4 center of Analysis and Measurement, zhejiang university, hangzhou 310029, china Institute of Biotechnology Zhejiang University Hangzhou 310029 China State Key Laboratory of Biocontrol School of Life Sciences Sun Yat-Sen University Guangzhou 510275 China College of Animal sciences Zhejiang University Hangzhou 310029 China center of Analysis and Measurement Zhejiang University Hangzhou 310029 China

Cryo-electron microscopy and image reconstruction were used to determine the three-dimensional structure of Infectious flacherie virus (IFV). 5047 particles were selected for the final reconstruction. The FSC curve showed that the resolution of this capsid structure was 18 ·. The structure is a psuedo T=3 (P=3) icosahedral capsid with a diameter of 302.4 · and a single shell thickness of 15 ·. The density map showed that IFV has a smooth surface without any prominent protrude or depression. Comparison of the IFV structure with those of the insect picorna-like virus-Cricket paralysis virus (CrPV)and human picornavirus-Human rhinovirus 14 (HRV 14) revealed that the IFV structure resembles the CrPV structure. The "Rossmann canyon" is absent in both IFV and CrPV particles. The polypeptide topology of IFV VP2, IFV VP3 was predicted and the subunit location at the capsid surface was further analyzed.

关键词： Infectious flacherie virus cryo-electron microscopy three-dimensional structure polypeptide folding

Quasi-static Analysis of Thrust-loaded Angular Contact Ball Bearings Part Ⅱ:Results and Discussion

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2012年第1期25卷 81-87页

作者： CHEN Wenhua1,2,MA Zikui1,GAO Liang1,LI Xinglin3,and PAN Jun2 1 Institute of Mechanical Design,zhejiang university,hangzhou 310027,china 2 Institute of Mechanical Design and Manufacturing,zhejiang Sci-Tech university,hangzhou 310018,china 3 State Testing Laboratory of hangzhou Bearing Test & Research center,hangzhou 310022,china 1. Institute of Mechanical Design Zhejiang University Hangzhou 310027 China 2. Institute of Mechanical Design and Manufacturing Zhejiang Sci-Tech University Hangzhou 310018 China 3. State Testing Laboratory of hangzhou Bearing Test & Research center Hangzhou 310022 China

Ball bearings are widely employed mechanical components characterized by high precision and quality,and usually play important roles in various rotary machines and *** advanced applications require a deep understanding of their various kinematic and tribological characteristics that are essential to predict the fatigue endurance,relieve the vibration and minimize the power dissipation of ball bearings in particular *** angular contact ball bearing under a specified operating condition is simulated with the quasi-static/creepage analytical model proposed in the preceding *** results demonstrate that the ball bearing is a statically determinate *** the balls spin on both inner and outer races means the ball is controlled by neither the inner nor the outer *** friction between the ball and raceway renders the inner and outer contact angles *** larger the coefficient of friction is,the larger the angle *** tangential traction perpendicular to the rolling direction due to the spin induces a gyro-like rotation of the ball with respect to the raceway even if no inertial effects are *** tangential elastic compliance of contacting surfaces gives rise to locked areas within the contact patch and transforms the sliding lines from circles into *** differential slip due to the close conformity of the ball and raceway makes the sliding and traction distributions asymmetric,which will influence the location of the spinning center of the ball with respect to the *** quasi-static/creepage model can be used to reveal the operating behaviors of ball bearings running under steady conditions and to optimize the design of ball bearings for specific applications.

关键词： ball bearing quasi-static creepage differential slip tangential elastic compliance

同方期刊数据库

The Retention Behaviors of Benzene and Its Alkyl Homologues in Microemulsion Electrokinetic Chromatography

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2000年第6期11卷 549-550页

作者： Xiao Yun FU Wei YUAN Xiu Zhu XU Jian De LU(Analytical and Testing center, zhejiang university, hangzhou 310027) zhejiang Univ Analyt & Testing Ctr Hangzhou 310027 Peoples R China

The retention behaviors of benzene and its alkyl homologues in microemulsion electrokinetic chromatography were investigated in both anionic and cationic surfactant MEEKC systems. The effects of the composition of microemulsion on retention time and selectivity were studied. A good linear relationship was obtained between log k and the carbon number of alkyl chain.

关键词： microemulsion electrokinetic chromatography alkyl benzene