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Characteristic analysis of unsteady viscous flow around a cavitating propeller

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science china(Technological sciences) 2010年第7期53卷 1983-1992页

作者： ZHU ZhiFeng1, 2, FANG ShiLang1 & WANG XiaoYan1 1 Key Laboratory of Underwater Acoustic Signal Processing of Ministry of Education, southeast university, nanjing 210096, china 2 school of Electrical engineering and Information, Anhui university of Technology, Maanshan 243002, china 1. Key Laboratory of Underwater Acoustic Signal Processing of Ministry of Education Southeast University Nanjing 210096 China2. School of Electrical Engineering and Information Anhui University of Technology Maanshan 243002 China

Based on viscous multiphase flow theory, this paper presents some recent validation results with a hybrid grid and sliding mesh solving Unsteady Navier-Stokes (N-S) and Bubble Dynamics equations as applied to prediction of pressure, velocity and vapor volume fraction in the wake in an uniform inflow. Comparable to experimental results, numerical predictions of sheet cavitation, tip vortex cavitation and hub vortex cavitation are in agreement with the corresponding experimental data, the same as numerical predictions of pressure in wake. Tip vortex cavitation is the most important to generate the pressure fluctuation within the near wake. The characteristics such as blade and shaft rate frequency of propeller pressure in wake coincide with its geometric model and parameters. With increasing distance from propeller disk, the pressure signals at blade frequency de-crease. The process of attenuation becomes fast with the decreased advance coefficient and cavitation number.

关键词： cavitating flow RANS propeller sliding mesh multiphase flow

A whisker-like carbon composite for the immobilization of laccase and its bioelectrochemistry

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science china Chemistry 2010年第6期53卷 1332-1336页

作者： MA GuoXian1,2,ZHONG QingDong2 & LU TianHong3 1Department of Chemical engineering,Shanghai Institute of Technology,Shanghai 200233,china 2school of Materials science and engineering,Shanghai university,Shanghai 200072,china 3Department of Chemistry,nanjing Normal university,nanjing 210097,china 1. Department of Chemical engineering Shanghai Institute of Technology Shanghai 200233 China2. School of Materials Science and Engineering Shanghai University Shanghai 200072 China3. Department of Chemistry Nanjing Normal University Nanjing 210097 China

A novel mesoporous carbon/whisker-like carbon (MCWC) composite was used for the immobilization of laccase (Lac) and its bioelectrochemical behaviors were *** was confirmed by XPS that Lac was strongly adsorbed on the surface of the MCWC *** cyclic voltammetric results showed that the immobilized Lac underwent a direct quasi-reversible electrochemical *** value of the electron transfer rate constant ks was estimated to be 0.770 s-1,indicating a reasonably fast electron transfer between the immobilized Lac and the underlying *** surface concentration (I-) of Lac was estimated to be 2.730 × 10-12 mol/*** experimental results showed that the immobilized Lac displayed an appreciable electrocatalytic activity to the electrochemical reduction of *** properties could be attributed to the particular structure of loosely packed nanometer-scale carbon whiskers and the existence of a large amount of oxygen-containing *** immo- bilization method and the novel carrier (MCWC) may find new applications in fabricating the biocatalysts for biofuel cells.

关键词： laccase whisker-like carbon composite direct electrochemical reaction oxygen bioelectrochemistry

Recent progress of solar physics research in china

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Research in Astronomy and Astrophysics 2011年第12期11卷 1377-1402页

作者： Cheng Fang 1 school of Astronomy and Space science,nanjing university,nanjing 210093,china 2 Key Laboratory of Modern Astronomy and Astrophysics(nanjing university),Ministry of Education,china school of Astronomy and Space science Nanjing University Nanjing 210093 China Key Laboratory of Modern Astronomy and Astrophysics (nanjing university) Ministry of Education China

Owing to the largely improved facilities and working conditions, solar physics research in china has recently shown marked development. This paper reports on the recent progress of solar physics research in china's Mainland, mainly focusing on several hot issues, including instrumentations, magnetic field observations and research, solar flares, filaments and their eruptions, coronal mass ejections and related processes, as well as active regions and the corona, small-scale phenomena, solar activity and its predictions. A vision of the future is also described.

关键词： Sun: general -- Sun: coronal mass ejections (CMEs) -- solar physics:recent progress

Review for dynamic researches in civil engineering in recent years

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science china(Technological sciences) 2010年第5期53卷 1450-1452页

作者： XU ZhaoDong RC&PC Key Laboratory of Education Ministry,southeast university,nanjing 210096,china 1. RC&PC Key Laboratory of Education Ministry Southeast University Nanjing 210096 China

Structure dynamic research is a hot field in civil *** involves in many challenge topics,such as dynamic analysis and tests under earthquake,wind or other dynamic *** paper introduces main dynamic researches in civil engineering in recent years,which will be classified into five aspects,especially for researches published in science in china Series E:Technological sciences.

关键词： civil engineering structures dynamic researches

Large-eddy simulations and vortex structures of turbulent jets in crossflow

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science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 118-132页

作者： GUAN Hui1,2 & WU ChuiJie2 1 school of Mechanical and Power engineering,East china university of science and Technology,Shanghai 200237,china 2 Research Center for Fluid Dynamics,PLA university of science and Technology,nanjing 211101,china 1. school of Mechanical and Power engineering East China University of Science and Technology Shanghai 200237 China 2. Research Center for Fluid Dynamics PLA University of Science and Technology Nanjing 211101 China

Using the method of large-eddy simulation, the 3-dimensional turbulent jets in crossflow with stream-wise and transverse arrangements of nozzle are simulated, emphasizing on the dynamical process of generation and evolution of vortex structures in these flows. The results show that the basic vortex structures in literatures, such as the counter-rotating vortex pair, leading-edge vortices, lee-side vortices, hanging vortices, kidney vortices and anti-kidney vortices, are not independent physical substances, but local structures of the basic vortex structure of turbulent jets in crossflow-the 3-D stretching vortex rings originating from the orifice of the nozzle, which is discovered in this study. Therefore, the most important large-scale structures of turbulent jets in crossflow are unified to the 3-D vortex rings which stretch and twist in stream-wise and swing in transverse directions. We also found that the shedding frequencies of vortex rings are much lower than the one corresponding to the appearance of leading-edge and lee-side vortices in the turbulent jets.

关键词： turbulent jet in crossflow coherent structure large-eddy simulation

The Testing Strength Curves of Lightweight Aggregate Concrete by Rebound Method and Ultrasonic-rebound Combined Method

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Journal of Wuhan university of Technology(Materials science) 2011年第5期26卷 1010-1017页

作者：荣辉 school of Materials science and engineering Southeast University

The strength curves of lightweight aggregate concrete （LWAC） were tested based on detecting LWAC with density of 1 400-1 900 kg/m3 and LWAC with strength grade of LC15-LC50 by rebound method and ultrasonic-rebound combined *** results show that the common measured strength curves tested by above two methods can not satisfy the required accuracy of LWAC strength *** addition,specified compressive strength curves of testing LWAC by rebound method and ultrasonic-rebound combined method are obtained,respectively.

关键词： lightweight aggregate concrete compressive strength rebound method testing-strength curve ultrasonic-rebound combined method

On the general expressions of finite Hankel transform

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science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2125-2130页

作者： JIANG Quan 1,2 & GAO CunFa 1 1 College of Aerospace engineering,nanjing university of Aeronautics and Astronautics,nanjing 210016,china 2 school of Civil engineering,Nantong university,Nantong 226019,china 1. College of Aerospace engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. School of Civil Engineering Nantong University Nantong 226019 China

The general expressions of finite Hankel transform are naturally deduced with the help of the property of Bessel *** equations in this paper can degenerate into three kinds of boundaries since all the coefficients in the boundary conditions are taken into *** results can be adopted in solving physics problems involving the finite Hankel transform.

关键词： hankel transform bessel function finite integral

Low-complexity distributed differential spacetime coding scheme for amplify-and-forward cooperative networks

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science in china(Series F) 2009年第8期52卷 1418-1427页

作者： YU XiangBin1,2, BI GuangGuo3 & XU WeiYe4 1 College of Information science and Technology, nanjing university of Aeronautics and Astronautics, nanjing 210016, china 2 Department of Electronic engineering, City university of Hong Kong, Hong Kong, china 3 National Mobile Communications Research Laboratory, southeast university, nanjing 210096, china 4 Department of Communication engineering, nanjing Institute of Technology, nanjing 211167, china College of Information science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Electronic engineering City University of Hong Kong Hong Kong China National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China Department of Communication engineering Nanjing Institute of Technology Nanjing 211167 China

By introducing a space-time coding scheme based on amicable orthogonality, we develop a distributed differential space-time coding scheme with the amplify-and-forward （AF） method for wireless cooperative networks. The scheme requires no knowledge of the channel state information at both transmitters and receivers, and effectively decreases the realization complexity due to no channel estimation. Moreover, it has lower decoding complexity and higher coding advantage than the existing scheme, thus avoiding the shortcoming of exponential decoding complexity of some existing schemes. According to the pairwise error probability （PEP） analysis of the system, the power allocations of source and relay terminals are jointly optimized, and as a result, the PEP is minimized, which will provide a helpful guideline for system design. Numerical calculation and simulation results show that the developed scheme is superior to the existing scheme. Moreover, the scheme with optimal power allocation yields obvious performance improvement over that with equal power allocation.

关键词： differential space-time coding cooperative communication amplify-and-forward method power allocation

Stability of a linear oscillator with damping force of the fractional-order derivative

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science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 345-352页

作者： WANG ZaiHua1,2 & HU HaiYan1 1 Institute of Vibration engineering Research,nanjing university of Aeronautics and Astronautics,nanjing 210016,china 2 Institute of science,PLA university of science and Technology,nanjing 211101,china 1. Institute of Vibration engineering Research Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. Institute of Science PLA University of Science and Technology Nanjing 211101 China

It begins with the study of damping representation of a linear vibration system of single degree of freedom (SDOF),from the view point of fractional calculus. By using the idea of stability switch,it shows that the linear term involving the fractional-order derivative of an order between 0 and 2 always acts as a damping force,so that the unique equilibrium is asymp-totically stable. Further,based on the idea of stability switch again,the paper proposes a scheme for determining the stable gain region of a linear vibration system under a fractional-order control. It shows that unlike the classical velocity feedback which can adjust the damping force only,a fractional-order feedback can adjust not only the damping force,but also the elastic re-storing force,and in addition,a fractional-order PDα control can either enlarge the stable gain region or narrow the stable gain region. For the dynamic systems described by integer-order derivatives,the asymptotical stability of an equilibrium is guaranteed if all characteristic roots stay in the open left half-plane,while for the systems with fractional-order derivatives,the asymptotical stability of an equilibrium is guaranteed if all characteristic roots stay within a sector in the complex plane. Analysis shows that the proposed method,based on the idea of stability switch,works effectively in the stability analysis of dynamical systems with fractional-order derivatives.

关键词： vibration system fractional-order derivative asymptotical stability stability switch