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Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

science china(Technological sciences) 2006年第5期49卷 521-536页

作者： CHEN Zhiyong1,2. CAI Hongnian1, ZHANG Xinming2. WANG Fuchi1 & TAN Chengwen1,3.1. school of {2. science and {3., Beijing Institute of Technology, Beijing 100081, china 2. school of {2. science and {3., Central South university, Changsha 410083. china 3. school of material science and engineering, Beijing university of {13. and astronautics, Beijing 1.0083, china 1. school of material {2. and {3. Beijing Institute of Technology Beijing 100081 China 2. school of material {2. and {3. Central South University Changsha 410083 China 3. school of material science and engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112.and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.

关键词： twinning slip face-centered cubic crystals axisymmetric co-deformation Bishop-Hill maximum work principle yield strength anisotropy

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Nonlinear Aeroelastic Response of High-aspect-ratio Flexible Wings

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Chinese Journal of aeronautics 2009年第4期22卷 355-363页

作者： Zhang Jian,Xiang Jinwu school of Aeronautic science and {2.,Beijing {3. of aeronautics and astronautics,Beijing 100191,china [a]school of Aeronautic science and {2. Beijing University of Aeronautics and Astronautics Beijing 100191 China

The aeroelastic analysis of high-altitude, long-endurance （HALE） aircraft that features high-aspect-ratio flexible wings needs take into account structural geometrical nonlinearities and dynamic stall. For a generic nonlinear aeroelastic system, besides the stability boundary, the characteristics of the limit-cycle oscillation （LCO） should also be accurately predicted. In order to conduct nonlinear aeroelastic analysis of high-aspect-ratio flexible wings, a first-order, state-space model is developed by combining a geometrically exact, nonlinear anisotropic beam model with nonlinear ONERA （Edlin） dynamic stall model. The present investigations focus on the initiation and sustaining mechanism of the LCO and the effects of flight speed and drag on aeroelastic behaviors. Numerical results indicate that structural geometrical nonlinearities could lead to the LCO without stall occurring. As flight speed increases, dynamic stall becomes dominant and the LCO increasingly complicated. Drag could be negligible for LCO type, but should be considered to exactly predict the onset speed of flutter or LCO of high-aspect-ratio flexible wings.

关键词： nonlinear aeroelasticity limit-cycle oscillation Galerkin methods geometrical nonlinearities dynamic stall HALEaircraft

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Key Parameters and Conceptual Configuration of Unmanned Combat Aerial Vehicle Concept

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Chinese Journal of aeronautics 2009年第4期22卷 393-400页

作者： Wang Ganglin Faculty 513.school of Aeronautic {2. and engineering,Beijing {3. of aeronautics and astronautics,Beijing 100191,china [a]Faculty 513 School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100191 China

The nature and characteristics of attack unmanned combat aerial vehicle （UCAV） are analyzed. The principles of selecting takeoff thrust-weight ratio and takeoff weight of attack UCAV are presented by analyzing the statistical data of weights for various main combat aircraft. The UCAV airborne weapons are analyzed, followed by the preliminary estimation of the payload weight. Various typical engines are analyzed and one of them is selected. Then the takeoff weight of the UCAV is determined. Based on some basic parameters and assumptions, the qualitative decomposition calculation for takeoff weight is completed. The key factors for obtaining longer endurance of aircraft with small aspect ratio configuration are found to be high lift-drag ratio and internal space. On the basis of the conclusions mentioned above, a highly blended flying-wing plus lifting body concept is proposed. According to this concept, the UCAV configuration is designed and optimized. Finally, the UCAV configuration with small aspect ratio, high lift-drag ratio, and high stealth characteristic is obtained.

关键词： aircraft design unmanned aerial vehicles unmanned combat aerial vehicles conceptual design aerodynamicsstealth

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Formation control for networked spacecraft in deep space:with or without communication delays and with switching topology

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science china(Information sciences) 2011年第3期54卷 469-481页

作者： WANG Nan 1,2. ZHANG TianWu 2.& XU JieQiong 1 1 school of Aeronautic science and {2., Beijing {3. of aeronautics and astronautics, Beijing 100191, china 2.Department of Computer science and {2., Henan Institute of {2., Zhengzhou 451191, china 1. school of Aeronautic science and {2. Beijing University of Aeronautics and Astronautics Beijing 100191 China2. Department of Computer Science and Engineering Henan Institute of Engineering Zhengzhou 451191 China

In this paper, several formation controllers are developed with constant and variable connected communication topology for six-degree-of-freedom (6-DOF) networked spacecraft flying in deep space with constant and time-varying communication delays considered. In the control algorithm, any explicit leader does not exist in the formation team and it is required that each spacecraft communicate only with its neighbors and therefore the required communication loads of the whole formation is greatly reduced. The proposed control strategies allow that each spacecraft can track its desired position and attitude and simultaneously the whole group moves to the desired formation and obtain its desired relative attitudes with its neighbors. Simulation results demonstrate the effectiveness of the proposed controllers.

关键词： deep space graph theory formation control communication topology delays

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Reliability analysis of ship structure system with multi-defects

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science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2113-2124页

作者： AN Hai 1,AN WeiGang 1 & ZHAO WeiTao 2.1 school of Aerospace and Civil engineering,Harbin engineering {3.,Harbin 150001,china 2.school of aeronautics and astronautics,Shenyang Institute of Aeronautical engineering,Shenyang 11003.,china 1. school of Aerospace and Civil engineering Harbin Engineering University Harbin 150001 China2. School of Aeronautics and Astronautics Shenyang Institute of Aeronautical Engineering Shenyang 110034 China

This paper analyzes the influence of multi-defects including the initial distortions,welding residual stresses,cracks and local dents on the ultimate strength of the plate element,and has worked out expressions of reliability calculation and sensitivity analysis of the plate *** analysis is made for the system with multi-defects plate *** mechanism,failure paths and the calculating approach to global reliability index are also worked *** plate elements with multi-defects fail,the formula of reverse node forces which affect the residual structure is deduced,so are the sensitivity expressions of the system reliability *** ensures calculating accuracy and rationality for reliability analysis,and makes it convenient to find weakness plate elements which affect the reliability of the structure ***,for the validity of the approach proposed,we take the numerical example of a ship cabin to compare and contrast the reliability and the sensitivity analysis of the structure system with multi-defects with those of the structure system with no *** approach has implications for the structure design,rational maintenance and renewing strategy.

关键词： initial distortions welding residual stresses cracks and local defects ultimate strength reverse node forces sensitivity expression reliability analysis

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Theory and techniques of data mining in CGF behavior modeling

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science china(Information sciences) 2011年第4期54卷 717-731页

作者： YIN YunFei 1,2.GONG GuangHong 2.& HAN Liang 2.1 College of Computer science,Chongqing university,Chongqing 400044,{2. 2.{3. of Automation science and Electrical engineering,Beijing university of aeronautics and astronautics,Beijing 1.0083,{2. 1. College of Computer science Chongqing University Chongqing 400044 China2. School of Automation Science and Electrical Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

For the large quantity of data,rules and models generated in the course of computer generated forces (CGFs) behavior modeling,the common analytical methods are statistical methods based on the tactical rules,tactical doctrine and empirical ***,from the viewpoint of data mining,we can find many of these analytical methods are also each-and-every different data mining *** this paper,we survey the data mining theory and techniques that have appeared in the course of CGF behavior modeling from the viewpoint of data ***,we redefine and reclassify these theories and techniques according to the research requirements of data mining (the knowledge structure of data mining).We aim to help the CGF investigators to learn the key points and the research methods of the data intelligent processing in the CGF behavior modeling,and thus we can provide the references for the colleagues who are engaged in the research and practice of the CGF behavior modeling by this *** also introduce our ongoing work on the CGF behavior modeling based on data mining.

关键词： CGF CGF behavior modeling data mining theory and techniques

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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 {2. and {3.,Nanjing 2.0016,china 2.school of Civil engineering,Nantong university,Nantong 2.6019,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

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Manifold contraction for semi-supervised classification

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science china(Information sciences) 2010年第6期53卷 1170-1187页

作者： HU EnLiang 1,2., CHEN SongCan 1 & YIN XueSong 1 1 school of Computer science & {2., Nanjing {3. of aeronautics & astronautics, Nanjing 2.0016, china 2.school of Mathematics, Yunnan Normal {3., Kunming 650092. china 1. school of Computer science & {2. Nanjing University of Aeronautics & Astronautics Nanjing 210016 China2. School of Mathematics Yunnan Normal University Kunming 650092 China

The generalization ability of classification is often closely related to both the intra-class compactness and the inter-class *** to the fact that many current dimensionality reduction methods, regarded as a pre-processor, often lead to the poor classification performance on real-life data, in this paper, a new data preprocessing technique called manifold contraction(MC) is proposed for the classification-oriented learning *** main motivation behind MC lies in seeking a proper mapping of contracting the given multiple-manifold data such that the ratio of the intra-class to the inter-class scatters is ***, in order to properly control the contraction level in MC, an adaptive MC(AMC) criterion is developed in the semi-supervised *** to its generality, MC can be not only applied in original space and reproducing kernel Hilbert space(RKHS), but also easily incorporated with dimensionality reduction method for further improvement of classification *** final experimental results show that MC, as a data preprocessor, is effective and promising in the subsequent classification learning, especially in small-size labeled sample case.

关键词： manifold learning dimensionality reduction lower-dimensional embedding semi-supervised learning classification manifold contraction adaptive manifold contraction

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Nonlinear flutter analysis of stiffened composite panels in super-sonic flow

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science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 336-344页

作者： YUAN KaiHua & QIU ZhiPing school of Aeronautic science and {2.,Beijing {3. of aeronautics and astronautics,Beijing 100191,china 1. school of Aeronautic science and {2. Beijing University of Aeronautics and Astronautics Beijing 100191 China

The flutter instability of stiffened composite panels subjected to aerodynamic forces in the supersonic flow is investigated. Based on Hamilton's principle,the aeroelastic model of the composite panel is established by using the von Karman large deflection plate theory,piston theory aerodynamics and the quasi-steady thermal stress theory. Then,using the finite element method along with Bogner-Fox-Schmit elements and three-dimensional beam elements,the nonlinear equations of motion are derived. The effect of stiffening scheme on the flutter critical dynamic pressure is demonstrated through the numerical example,and the nonlinear flutter characteristics of stiffened composite panels are also analyzed in the time domain. This will lay the foundation for design of panel structures employed in aerospace vehicles.

关键词： panel flutter piston theory finite element method quasi-steady thermal stress critical dynamic pressure stiffened composite panel

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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 {2. and {3., 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

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