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Cross-layer optimized Chord protocol for separated ring convergence in MANET

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The Journal of China Universities of Posts and Telecommunications 2009年第4期16卷 84-90页

作者： MEI jing-qing ji Hong li Ting Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

An optimized Chord protocol is proposed to solve the convergence problem for separated Chord rings over mobile Ad-hoc networks （MANETs）. This protocol exploits the information of topological neighbors in routing layer by utilizing a cross-layer design, and periodically detects whether there is any neighbor node that belongs to an alien Chord ring by sending detecting packets. The detection will be confirmed and then the corresponding predecessor node will be found out to initialize convergence of the Chord rings. Theoretical analysis and experiment results show that the proposed algorithm can detect separated Chord rings and implement the convergence process efficiently, and that a significant improvement in the successful lookup ratio is also achieved at an acceptable overhead for the system maintenance. Moreover, the proposed protocol can ensure the stability and scalability of the system.

关键词： convergence Chord mobile Ad-hoc network (MANET) cross-layer

CliMATIC FEATURES OF SUMMER TEMPERATURE IN NORTHEAST CHINA UNDER WARMING BACKGROUND

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Chinese Geographical Science 2005年第4期15卷 337-342页

作者： li ji GONG Qiang ZHAO lian-wei Shenyang Institute of Atmospheric Environment China Meteorological Administration Shenyang 110016 P. R. China Institute of Meteorological Energy Exploitation and Application Shenyang 110016 P. R. China liaoning Provincial Meteorological Observatory Liaoning Meterological Bureau Shenyang 110016 P. R. China

By using,summer temperature data in 26 stations from 1951 to 2003, the variation characteristics of summer temperature in Northeast China （NET） were analyzed based on the background of climate wanning. The results showed that the warming in summer was 0.15~C/10a in Northeast China, which was higher than that on the global, Northern Hemisphere or Northeast Asia scale in the recent 50 years. The responses of NET to global warming were shown in 3 aspects mainly. Firstly, it became warm and the average temperature increased in summer; secondly, the temperature variability increased, which displayed the increase of climatic instability; thirdly, the disaster of low temperature decreased and high temperature damage increased obviously, but the disaster of low temperature still existed in some areas under global warming background, which would be worthy of notice further.

关键词： Northeast China summer temperature climate features global warming disaster of low temperature

Analysis of the Attenuation Characteristics of an Elastic Wave Due to the Wave-Induced Fluid Flow in Fractured Porous Media

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Chinese Physics Letters 2014年第4期31卷 76-80页

作者： WANG Ding WANG li-ji ZHANG Mei-Gen Key Laboratory of Petroleum Resources Research Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 Key Laboratory of Middle Atmosphere and Global Environment Observation Institute of Atmospheric Physics Chinese Academy of sciences Beijing 100029 Ur~iversity of Chinese Academy of Sciences Beijing 100049

A theoretical model is presented to describe the elastic wave propagation characteristics in porous media of periodically arranged fractures. The effects of fracture geometric parameters on a compressional wave （p-wave） are considered through analysis of the wave induced fluid flow （WIFF） process between the fractures and the background media. The diffusion equation in porous media is used to reveal how the entire diffusion process affects the wave propagation. When the thickness proportion of fractures tends to 0 and 1, the WIFF does not take place almost between fractures and background matrix porosity, and therefore the media elasticity modulus is perfectly elastic. When the fracture thickness fraction achieves a certain value, the peak of the attenuation curve reaches the maximum value at a particular frequency, which is controlled by the fluid mass conservation and stress continuity conditions on each fracture boundary. That is, the inter-coupling of fluid diffusion between the adjacent layers is important for waves attenuation. Physically speaking, the dissipation of a wave is associated with the fluid flux essentially.

关键词： Media Analysis elastic

Control system design of flying-wing UAV based on nonlinear methodology

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Defence Technology（防务技术） 2017年第6期13卷 397-405页

作者： ji-guang li Xin CHEN Ya-juan li Rong ZHANG School of Automation Nanjing University of Aeronautics & Astronautics School of Electronic Engineering Nanjing XiaoZhuang University

In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear *** structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.

关键词： UAV paper flight validation

Mean shift based log-Gabor wavelet image coding

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第4期8卷 620-624页

作者： li ji-liang FANG Xiang-zhong HOU Jun Institute of Image Communication and Information Processing Shanghai Jiao Tong University Shanghai 200240 China

In this paper, we propose a sparse overcomplete image approximation method based on the ideas of overcomplete log-Gabor wavelet, mean shift and energy concentration. The proposed approximation method selects the necessary wavelet coefficients with a mean shift based algorithm, and concentrates energy on the selected coefficients. It can sparsely approximate the original image, and converges faster than the existing local competition based method. Then, we propose a new compression scheme based on the above approximation method. The scheme has compression performance similar to JPEG 2000. The images decoded with the proposed compression scheme appear more pleasant to the human eyes than those with JPEG 2000.

关键词： Sparse approximation Log-Gabor Image coding Mean shift Overcomolete

Structure design of high-performance Cu-based shape memory alloys

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Rare Metals 2015年第9期34卷 607-624页

作者： jian-Xin Xie ji-li liu Hai-You Huang State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing Laboratory of Metallic Materials and Processing for Modern Transportation

The effects of various structure factors on the properties(superelasticity mainly) of Cu-based shape memory alloys(SMAs) were systematically evaluated in this review article through literatures combining with our work. It is concluded that besides the decisive role of grain orientation, the grain boundary(GB) characteristics also play important roles in the superelasticity, which include GB area, GB type, GB morphology and GB direction in descending order of the effect significance. According to the above results, the prior principles of structure design are proposed for high-performance Cu-based SMAs from most to least important:(1) obtaining grain orientation with high phase transformation strain;(2) increasing grain size or reducing GB area;(3) obtaining straight low-energy GBs, especially low-angle GBs;(4) trying to make GB direction parallel to external stress. Consistent with the main or all principles, the bamboo-like-grained and columnar-grained(CG) Cu-based SMAs show excellent comprehensive properties.

关键词： Cu-based shape memory alloy Superelasticity Cu–Al–

Effects of aging treatment on the microstructure and superelasticity of columnar-grained Cu71Al18Mn11 shape memory alloy

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International Journal of Minerals,Metallurgy and Materials 2016年第10期23卷 1157-1166页

作者： ji-li liu Hai-you Huang jian-xin Xie Beijing Laboratory of Metallic Materials and Processing for Modern Transportation Beijing 100083 China Department of Mechanics and Engineering Structure Wuhan University of Technology Wuhan 430070 China

The effect of aging treatment on the superelasticity and martensitic transformation critical stress in columnar-grained Cu_（71）Al_（18）Mn_（11） shape memory alloy（SMA） at the temperature ranging from 250°C to 400°C was investigated. The microstructure evolution during the aging treatment was characterized by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results show that the plate-like bainite precipitates distribute homogeneously within austenitic grains and at grain boundaries. The volume fraction of bainite increases with the increase in aging temperature and aging time, which substantially improves the martensitic transformation critical stress of the alloy, whereas the bainite only slightly affects the superelasticity. This behavior is attributed to a coherent relationship between the bainite and the austenite, as well as to the bainite and the martensite exhibiting the same crystal structure. The variations of the martensitic transformation critical stress and the superelasticity of columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with aging-temperature and aging time are described by the Austin-Rickett equation, where the activation energy of bainite precipitation is 77.2 kJ ·mol1. Finally, a columnar-grained Cu_（71）Al_（18）Mn_（11） SMA with both excellent superelasticity（5%-9%） and high martensitic transformation critical stress（443-677 MPa） is obtained through the application of the appropriate aging treatments.

关键词： copper aluminum manganese alloys shape memory effect columnar grains aging bainite superelasticity

Ballistic performance of tungsten particle/metallic glass matrix composite long rod

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Defence Technology（防务技术） 2019年第2期15卷 132-145页

作者： ji-cheng li Xiao-wei Chen Feng-lei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Institute of Systems Engineering China Academy of Engineering Physics Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province

In the present manuscript numerical analysis on the ballistic performance of a tungsten particle/metallic glass matrix(WP/MG) composite rod is conducted by integrating with related experimental investigations. In the corresponding finite element method(FEM) simulations a modified coupled thermomechanical constitutive model is employed to describe the mechanical properties of metallic glass(MG)matrix, and geometrical models of the WP/MG composite rod are established based on its inner structure. The deformation and failure characteristics of the rod and target materials are analyzed in detail,and the influences of various factors on the ballistic performance of the WP/MG composite long rod are discussed. Related analysis demonstrates that the penetrating performance of the WP/MG rod is similar to that of the tungsten fiber/metallic glass matrix(WF/MG) composite long rod, i.e., a "self-sharpening" behavior also occurs during the penetration process, and correspondingly its penetrating capability is better than that of the tungsten heavy alloy(WHA) rod. However, the mass erosion manner of the WP/MG rod is different and the erosion is relatively severe, thus its penetrating capability is a little lower compared with that of the WF/MG one. Moreover, the impact velocity and the target strength have significant influences on the ballistic performance of the WP/MG composite rod, whereas the effect of initial nose shape is very little.

关键词： Tungsten particle/metallic glass matrix (WP/MG)composite Ballistic performance Shear band Self-sharpening Numerical analysis

Effects of physical parameter range on dimensionless variable sensitivity in water flooding reservoirs

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Acta Mechanica Sinica 2006年第5期22卷 385-391页

作者： Yu Hu Bai jia Chun li ji Fu Zhou Division of Engineering Sciences Institute of MechanicsChinese Academy of Sciences Beijing 100080 China

The similarity criterion for water flooding reservoir flows is concerned with in the present paper. When finding out all the dimensionless variables governing this kind of flow, their physical meanings are subsequently elucidated. Then, a numerical approach of sensitivity analysis is adopted to quantify their corresponding dominance degree among the similarity parameters. In this way, we may finally identify major scaling law in different parameter range and demonstrate the respective effects of viscosity, permeability and injection rate.

关键词： Physical parameter range Dimensionless variable Sensitivity analysis Water flooding reservoir Two-phase flow in porous media