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An exploration for the macroscopic physical meaning of entropy

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Science china(Technological Sciences) 2010年第7期53卷 1809-1816页

作者： WU Jing1 & GUO ZengYuan2 1 college of energy and power engineering, nanjing university of aeronautics and astronautics, nanjing 2.0016, china 2 Key Laboratory for Thermal Science and power engineering of Ministry of Education, School of Aerospace, Tsinghua university, Beijing 100084, china 1. college of energy and power engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education School of Aerospace Tsinghua University Beijing 100084 China

The macroscopic physical meaning of entropy is analyzed based on the exergy (availability) of a combined system (a closed system and its environment), which is the maximum amount of useful work obtainable from the system and the environment as the system is brought into equilibrium with the environment. The process the system experiences can be divided in two sequent sub-processes, the process at constant volume, which represents the heat interaction of the system with the environment, and the adiabatic process, which represents the work interaction of the system with the environment. It is shown that the macroscopic physical meaning of entropy is a measure of the unavailable energy of a closed system for doing useful work through heat interaction. This statement is more precise than those reported in prior literature. The unavailability function of a closed system can be defined as T0S and p0V in volume constant process and adiabatic process, respectively. Their changes, that is, AiTgS) and A (p0V) represent the unusable parts of the internal energy of a closed system for doing useful work in corresponding processes. Finally, the relation between Clausius entropy and Boltzmann entropy is discussed based on the comparison of their expressions for absolute entropy.

关键词： entropy macroscopic physical meaning exergy heat interaction

EXPERIMENTAL STUDY ON THE INFRARED RADIATION CHARACTERISTICS FROM HOT JET

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Chinese Journal of aeronautics 1996年第3期9卷 187-192页

作者： Shan Qixiang Bu Man(college of Science, nanjing university of aeronautics and astronautics, nanjing, chinaa, 2.0016)Zhen Libao(Department of power engineering, nanjing university of aeronautics and astronautics, nanjing, china, 2.0016) college of Science Nanjing Univ. Aero. and Astronaut. Nanjng 210016 China Department of power engineering Nanjing Univ. Aero. and Astronaut. Nanjing 210016 China

An experimental study on infrared radiation from the hot jet by means of model test is presented. The infrared detection system of the universal infrared instruments. the testing method and experimental results of infrared radiation from the hot jet are introduced. The space distribution of infaed radiant energy. the spectrum of infrared radiation from the hot jet. the distribution of the radiant energy of the hot jet against the wavebands and the characteristic difference of the hot jet radiaton between the 2-D jet tube and the circular jet tube are obtained. It is indicated that the testing system and the method are valid and the results are in accord with the theoretical analysis.

关键词： hot jets infrared radiation tests spectrum analysis

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 2.0016, 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

NUMERICAL CALCULATION FOR 2-DIMENSIONAL HEAT TRANSFER IN KEYHOLE LASER WELDING

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Chinese Journal of Mechanical engineering 1998年第3期11卷 20-25页

作者： Xu Jiuhua Zhang Jingzhou Jiang Chengyu Luo Yumei Mechanical engineering Institute, nanjing university of aeronautics and astronautics nanjing Univ of aeronautics and Astronautics Nanjing China

A numerical method is presented for analysing 2 dimensional quasi steady state heat transfer in high power density laser keyhole welding processes. The mathematical model is established according to the conservation of mass, momentum and energy. Computation is performed by using the finite control volume method in the curvilinear coordinate system. A position prediction correction procedure is employed to identify the solid liquid interface location. This method is applied to the study of a typical keyhole welding process of an AISI 304 stainless steel plate and its feasibility is verified.

关键词： Laser welding Heat transfer Keyhole Temperature distribution

Preparation and characterization of nanostructured Al_2O_3-13wt.%TiO_2 ceramic coatings by plasma spraying

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Rare Metals 2009年第5期28卷 465-470页

作者： WANG Dongsheng TIAN Zongjun SHEN Lida LIU Zhidong HUANG Yinhui Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China college of Mechanical and Electrical engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Nanostructured and conventional Al2O3-13wt.%TiO2 ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions （a three-dimensional net or skeleton-like structure： Al2O3-rich submicron particles embedded in the TiO2-rich matrix） and solid-phase sintered regions （remained nanoparticles）. The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO2 nanoparticles during plasma spraying. On the other hand, the TiO2 and Al2O3 nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.

关键词： surface coating nanostructured coating plasma spraying microstructure microhardness wear resistance

PIV EXPERIMENTAL RESEARCH OF INSTANTANEOUS FLOW CHARACTERISTICS OF CIRCULAR ORIFICE SYNTHETIC JET

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Journal of Hydrodynamics 2007年第4期19卷 453-458页

作者： XU Jing-lei SHA Jiang LIN Chun-feng ZHANG Kun-yuan School of energy and power engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The instantaneous flow characteristics of circular orifice synthetic jet was experimentally studied by a phase-locked Particle Image Velocimetry （PIV） system. The instantaneous flowfields, including the forming, developing and breaking down of the vortex for the jet were clearly shown by the PIV experimental results. As the basis of the study of the instantaneous flow, 36 images were taken and phase-averaged for each condition. The PIV experiment was mainly focused on the time evolution of the vortex pairs formed in the push cycle, the saddle point existing in the suck cycle, the variation of the centerline velocity in the whole cycle and the cross-stream velocity profiles and their self-similarity. Finally, the orifice depth was changed from 1.5 mm to 2 mm and 3.5 mm in order to study the effect of different orifice depths on the flow structure, which shows that at all stream wise sections, the peak of the mass flux and momentum flux increases as the orifice depth increases. Furthermore, the nondimensional distance of the mass flux from the exit is the maximum, while the nondimensional distance of the centerline velocity peak from the exit is the minimum, and nondimensional distance of the momentum flux from the exit section is between them.

关键词： circular synthetic jet Particle Image Velocimetry (PIV) phase-locked

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风力机振荡翼型动态失速特性的CFD研究

太阳能学报 2010年第3期31卷 367-372页

作者：雷延生周正贵南京航空航天大学能源与动力学院南京210016

为采用CFD方法研究风力机振荡翼型出现的流动动态失速现象,首先依据实验结果,对比分析了Baldwin-Lomax、Johnson-King、K-ωSST、S-A和K-ω5种紊流模型计算结果,结果表明:K-ωSST模型由于考虑到分离流动的非平衡作用,针对动态失速的计... 详细信息

为采用CFD方法研究风力机振荡翼型出现的流动动态失速现象,首先依据实验结果,对比分析了Baldwin-Lomax、Johnson-King、K-ωSST、S-A和K-ω5种紊流模型计算结果,结果表明:K-ωSST模型由于考虑到分离流动的非平衡作用,针对动态失速的计算精度较高。通过对NACA0012翼型振荡运动的流场进行计算,详细分析了振荡运动过程中翼型表面分离涡的形成、放大直至造成翼型失速以及失速区涡结构。

关键词：动态失速 NACA0012翼型 CFD方法 K-ω SST模型

A Novel Dual-Rate Sampling Switched-Capacitor Configuration and Its Application

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Journal of Electronic Science and Technology of china 2003年第1期1卷 74-79页

作者： CAO Kunyong YU Shenglin(college of Automation engineering,nanjing university of aeronautics and astronautics nanjing 2.0016 china) School of Microelectronics and Solid-state Electronics UESTC Chengdu 610054 China

In order to realize accurate bilinear transformation from s- to z-domain,a novelswitched-capacitor configuration is proposed in the light of principles of dual-rate sampling and chargeconservation,which has also been used for building a 5th-order elliptic lowpass *** filter issimulated and measured in typical 0.34 μm/3.3 V Si CMOS process models,special full differentialoperational amplifiers and CMOS transfer gate switches,which achieves 80 MHz sampling rate,17.8MHz cutoff frequency,0.052 dB maximum passband ripple,42.1 dB minimum stopband attenuation and74 mW quiescent power *** the same time,the dual-rate sampling topology breaks thetraditional restrictions of filter introduced by unit-gain bandwidth and slew rate of operational amplifiersand also improves effectively their performances in high-frequency *** has been applied forthe design of an anti-alias filter in analog front-end of video decoder IC with 15 MHz signal frequencyyet.

关键词： a novel SC configuration dual-rate sampling 80MSPS 0.34μm Si CMOS switched capacitor filter(SCF)

NUMERICAL SIMULATION OF SLOSHING IN RECTANGULAR TANK WITH VOF BASED ON UNSTRUCTURED GRIDS

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Journal of Hydrodynamics 2010年第6期22卷 856-864页

作者： MING Ping-jian DUAN Wen-yang college of power and energy engineering Harbin Engineering University Harbin 150001 China college of Shipbuilding engineering Harbin Engineering University Harbin 150001 China

A new method for sloshing simulation in a sway tank is present, in which the two phase interface is treated as a physical discontinuity, which can be captured by a well-designed high order scheme. Based on Normalized Variable Diagram （NVD）, a high order discretization scheme with unstructured grids is realized, together with a numerical method for free surface flow with a fixed grid. This method is implemented in an in-house code General Transport Equation Analyzer （ GTEA ） which is an unstructured grids finite volume solver. The present method is first validated by available analytical solutions. A simulation for a 2-D rectangular tank at different excitation frequencies of the sway is carried out. A comparison with experimental data in literature and results obtained by commercial software CFX shows that the sloshing load on the monitor points agrees well with the experimental data, with the same grids, and the present method gives better results on the secondary peak. It is shown that the present method can simulate the free surface overturning and breakup phenomena.

关键词： sloshing numerical simulation unstructured grid Volume Of Fluid (VOF)