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A wideband beamforming method based on directional uniform circular arrays

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Science china(Information Sciences) 2010年第12期53卷 2600-2609页

作者： MU PengCheng ,YIN QinYe & ZHANG JianGuo Ministry of Education Key Lab for Intelligent Networks and Network Security,school of Electronics and Information Engineering,xi’an jiaotong university,xi’an 710049,china 1. Ministry of Education Key Lab for Intelligent Networks and Network Security School of Electronics and Information Engineering Xi’an Jiaotong University Xi’an 710049 China

A new method for solving the wideband beamforming problem is proposed in this paper based on directional uniform circular *** basic idea is designing a narrowband beamforming spatial filter at a specific frequency and using the obtained filter weights directly to wideband signals,which reduces the complexities of designing and *** the premise of knowing signals’ direction information,this paper uses the method of least square with linear constraints to design the narrowband spatial *** the directional uniform circular array is insensitive to the variation of frequency,coincident beams and notches are obtained at different frequencies of the wideband signal by using the obtained narrowband spatial filter *** computation complexity of array signal processing can be greatly reduced by using the method proposed in this paper,which is convenient for real-time signal processing.

关键词： array signal processing wideband beamforming uniform circular array spatial filter least square

AN INVESTIGATION ON COMPUTER-CONTROLLED TURNING AND CONTOUR DESIGNING OF SHAPED CONNECTION

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Chinese Journal of Mechanical Engineering 2000年第4期13卷 278-284页

作者： He xiaojiaDing Chongsheng He Yue (school of Mechanical Engineering, xi’an jiaotong university) 西安交通大学陕西西安

The computer-controlled turning technique of shaped connection (keyless connection), shaft and hole, is discussed. By using the method, a clearance free fit with a taper is obtained. After the comparison of the mechanical behavior and the turning machinability of the contours, it is found that the present contour needs further improvement, and a new contour is presented.

关键词： Shaped connection Profiling turning Computer-controlled machining

Inferring playback rate and rate resets of P2P video streaming transmissions by piecewise line envelope approximation

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The Journal of china Universities of Posts and Telecommunications 2009年第2期16卷 58-62,79页

作者： LI Chun-xi CHEN Chang-jia school of Electronics and Information Engineering,Beijing jiaotong university,Beijing 100044,china [a]school of Electronics and Information Engineering Beijing jiaotong university Beijing 100044 china

Conventionally, P2P video is regarded as CBR traffic. However, our measurements have shown that the rate reset cannot be neglected in a practical IPTV system because each rate reset often leads to performance degradation. Thus, addressing the problem of inferring playback rate and rate reset in a P2P video system is significant. In this article, an algorithm termed piecewise linear envelope approximation （PLEA） is proposed, in which a follow-up time is introduced to smooth rate fluctuations in a small time scale and to adapt rate jumps in a large time scale automatically. With the PLEA algorithm, discontinuity introduced by blind segmentations adopted by current methods is avoided. Furthermore, unlike existing algorithms in which both segmentation and combinations are performed in multiple runs, only a single computation path is involved in the PLEA algorithm. This makes PLEA algorithm amenable to implementation of low complexity by either software or hardware. Both theoretical analysis and experiment based on measured data show that the PLEA outperforms existing algorithms based on segmentation.

关键词： P2P video playback rate rate reset convex hull linear program

Improvement of Heating Method for Measuring the Wetness of Flowing Wet Steam

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Journal of Thermal Science 1998年第3期7卷 202-207页

作者： Li YanFeng Wang xinJun Xu Tingxiang(school of Energy and Power Engineering, xi’an jiaotong university xi’an, Shed, 710049, china) school of Energy and Power Engineering Xi’an Jiaotong University Xi’an China

In this paper, an improvement of heating method for measuring wetness of the flowing wet steam is developed, the basic principle of the heating method is presented and the mathematical model has been built for analyzing the thermodynamics problezns during the process of heating. Moreover, an instru-ment for measuring wetness of wet steam flow was designed and made out. This instrument has been used for measuring wetness of the wet steam flow at the outlet of the nozzle rig in Thermal TUrbine Laboratory xi’an jiaotong university. By analyzing the relative error of the result, it was found that this instrument has fairly high accuracy it can be used as the prototype of practical instrument and has an important applicable value in engineering.

关键词： wetness measurement heating method wet steam flow

Assigning Task by Parallel Genetic Algorithm Based on PVM

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Wuhan university Journal of Natural Sciences 2001年第Z1期6卷 579-584页

作者： Zheng Zhi jun, Dong xiao she, Zheng Shou qi Department of Computer Science and Technology,xi’an jiaotong university,xi’an 710049,china Department of Computer Science and Technology Xi'an Jiaotong University Xi'an 710049 China

Genetic algorithm has been proposed to solve the problem of task assignment. However, it has some drawbacks, e.g., it often takes a long time to find an optimal solution, and the success rate is low. To overcome these problems, a new coarse grained parallel genetic algorithm with the scheme of central migration is presented, which exploits isolated sub populations. The new approach has been implemented in the PVM environment and has been evaluated on a workstation network for solving the task assignment problem. The results show that it not only significantly improves the result quality but also increases the speed for getting best solution.

关键词： task assignment genetic algorithm parallel process PVM

Simulation on the Melt Flow in Laser Full Penetration Welding with a Model Including a Non-Rotational Symme-try Keyhole Based on Energy Balance

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稀有金属材料与工程 2011年第S4期40卷 120-124页

作者： Zhang L J1,Zhang J X1,Wu B1,2,Chen L2,Gong S L2,Wang H R3 1 State Key Laboratory of Mechanical Behavior for Materials,xi’an jiaotong university,xi’an 710049,china2 Power Beam Processing Dept.,Avic Beijing Aeronautical Manufacturing Technology Research Institute,Beijing 100024,china3 school of Energy and Power Engineering,xi’an jiaotong university,xi’an 710049,china xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Peoples R China xi An Jiao Tong Univ State Key Lab Mech Behav Mat Xian 710049 Peoples R China Avic Beijing Aeronaut Mfg Technol Res Inst Power Beam Proc Dept Beijing 100024 Peoples R China

A three dimensional model including a non-rotational symmetry keyhole of which the geometry is calculated base on the energy balance at keyhole wall is created to simulate the heat transfer and fluid flow within the molten pool during laser full penetration welding of titanium alloy *** order to take into account the effects of multiple reflections within the keyhole,a ray tracing method is employed and the coordinate dependent heat flux obtained is exerted on keyhole wall during the simulation on the heat transfer and fluid flow within molten ***,the computed weld cross sectional profile is compared with the experimental result to verify the model and it is fond that the simulation result is consists with experimental result.

关键词： laser welding titanium alloy non-rotational symmetry keyhole simulation

STOCHASTIC RESONANCE MEASURED BY THEMUTUAL INFORMATION IN THE NEURONSTHAT TRANSMIT CHAOTIC SPIKE TRAINS

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生物物理学报 1999年第4期15卷 726-732页

作者： Gong Pulin Xu Jianxue Hu Sanjue(Institution of Nonlinear dynamics, school of Civil Engineering and Mechanics,xi’an jiaotong university, xi’an 710049, china)(Department of Physiology, Fourth Military Medical university, xi’an, 710032, china)

The spike trains generated by a neuron model are studied by the methods of nonlinear time series analysis. The results show that the spike trains are chaotic. To investigate effect of noise on transmission of chaotic spike trains, this chaotic spike trains are used as a discrete subthreshold input signal to the integrate-and-fire neuronal model and the FitzHugh-Nagumo(FHN) neuronal model working in noisy environment. The mutual information between the input spike trains and the output spike trains is calculated, the result shows that the transformation of information encoded by the chaotic spike trains is optimized by some level of noise, and stochastic resonance(SR) measured by mutual information is a property available for neurons to transmit chaotic spike trains.

关键词：神经元随机共振传输放电序列

Structure and electrochemical properties of low-cobalt La_(1-x)Li_xNi_(3.2)Co_(0.3)Al_(0.3) (0≤x≤0.2) hydrogen storage electrode alloys

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Rare Metals 2006年第z1期25卷 1-6页

作者： WEI Xuedong LIU Yongning ZHANG Peng State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi''an Jiaotong University Xi''an 710049 China

The structure and electrochemical properties of a new low cobalt hydrogen storage electrode alloys La1-xLixNi3.2Co0.3Al0.3 (0≤x≤0.2) were investigated with a different additions of Li in replacement of La. With the increase of Li contents the maximum discharge capacity increases from 240 mAh·g-1(x=0) to 328.4 mAh·g-1(x=0.1) and the cycle stability is improved correspondingly. The capacity decay can remain 28.6% (x=0.2) after 230 charge/discharge cycles. The high rate discharge(HRD) ability of the alloys(x≤0.1) is improved and the best HRD is 34.1%(x=0.1) under the discharge current density 1200 mA·g-1. It is found that the prepared alloys are basically composed of LaNi5 as matrix phase and LaNi3 as second phase(x≤0.1). But the abundance of LaNi3 phase dramatically decreases with increasing x. When x=0.2, a new phase Al(NiCo)3 is formed.

关键词： hydrogen storage alloy microstructure high rate discharge ability cycling stability

The application of geographic information technology to coastal geomorphology

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Acta Oceanologica Sinica 2009年第5期28卷 49-57页

作者： GUO Wei LI Shuheng ZHU Dakui school of Human Settlements and Civil Engineering Xi＇an Jiaotong University Xi＇an 710049 China Department of Computer Sciences Xi＇an Jiaotong University Xi＇an 710049 China Department of Urban and Resources Sciences Northwest University Xi＇an 710032 China Faculty of Environmental Sciences University of Waterloo Waterloo N2L3G1 Canada Key Laboratory of Coast ＆ Island Development of Ministry of Education Nanjing University Nanjing 210093 China

With the development of modern oceanic observation technologies, coastal survey data have been experiencing a substantial growth. The integration management of the data from different disciplines, different sources and different formats has become a major research field in coastal geomorphology by using Geographic Information System （GIS）. This paper puts forward a new methodology framework of GIS techniques in coastal ocean geomorphology, including data acquisition, process, analysis, and representation. It focuses on some major GIS techniques to study the land-ocean interaction mechanism, such as spatial analysis, submarine topography model and three-dimension （3D） visualization, and apply its result to coastal urban planning, harbor site selection and geomorphology environment about coral reef and islands on the continental shelf. The case studies cover the whole coastal ocean to serve the social community, economical development and diplomatic rights for decision-making all round in the coastal zone. The research shows clearly that the application of coastal multi-source geospatial platform has changed the traditional coastal geomorphology science dramatically from its research scope, fields and methods, however, as made clear in this paper, extracting accurate information from remote sensing data and GIS databases for coastal geomorphological applications is a nontrivial challenge that requires the combined knowledge and skills of information scientists and geomorphologists.

关键词： coastal geomorphology geographic information system (GIS) spatial analysis threedimensional visualization