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Influence factors of sparse microwave imaging radar system performance:approaches to waveform design and platform motion analysis

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Science china(Information sciences) 2012年第10期55卷 2301-2317页

作者： ZHANG Zhe 1,2,3,ZHANG BingChen 1,2,JIANG ChengLong 1,2,3,XIANG Yin 1,2,HONG Wen 1,2 & WU YiRong 1,2 1 Science and Technology on Microwave Imaging Laboratory,beijing 100190,china 2 Institute of Electronics,chinese academy of sciences,beijing 100190,china 3 graduate university,chinese academy of sciences,beijing 100190,china Science and Technology on Microwave Imaging Laboratory Beijing China Institute of Electronics Chinese Academy of Sciences Beijing China graduate university Chinese Academy of Sciences Beijing China

Sparse microwave imaging radar is a newly developed concept of microwave imaging system,which tries to combine the traditional radar imaging system with sparse signal processing theories,achieving the aim of reducing the complexity of microwave imaging systems and enhancing the system *** this paper,we introduce some basic concepts of sparse signal processing theory,and then apply it to the traditional radar imaging system to get the mathematical model of sparse microwave imaging *** analyze the factors that determine the performance of sparse microwave imaging radar,including scene,waveform and *** to the radar model,we analyze how these factors influence the radar system and how to optimize *** results of the sparse microwave imaging radar system are also provided.

关键词： sparse microwave imaging radar synthetic aperture radar compressive sensing Lq regularization waveform design

The impact of carrier leakage and spectral asymmetry distortions on the performance of navigation signals

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The impact of carrier leakage and spectral asymmetry distort...

A Decision Support for Target Country Selection of Future Generation Sovereign Wealth Funds:Hedging the Country Risk

第三届中国卫星导航学术年会

作者： HE Cheng-yan 1,2,3 , GUO Ji 1 , LU Xiao-chun 1,2 , WANG Xue 1,2 , LIU Feng 1,2,3 1 National Time Service Center, chinese academy of sciences, No.3 Shuyuan East Road, Lintong, Xi''an, Shaanxi, 710600, china 2 Key Laboratory for Precise Navigation, Positioning and Timing of chinese academy of sciences, Lintong, china 3 graduate university of chinese academy of sciences, beijing, 100190, china

In the process of analog modulation, carrier leakage will be possible if the carrier of orthogonal modulator leak to its output, with additional carrier appear at carrier frequency. What’s more, transmitter filters and power amplifier saturation may lead to spectral asymmetry. To further study the impact of these distortions on navigation signals performance, this paper begins to introduce the mechanism of carrier leakage and spectral asymmetry. Then based on a new Matlab platform and mathematical models, the impact of these distortions on signal performance is comprehensively demonstrated from different aspects from SNR （Signal-Noise-Ratio）, acquisition and tracing, to ranging accuracy, etc,. Results show that low degree of carrier leakage and spectral asymmetry won’t significantly affect signal performance, but when it deteriorates to a certain degree, the performance of navigation signals would exponentially decline. Those results and data we have obtained from this paper can also be used as a valuable reference for signal-on-board-generation designers in the process of signal design and optimization.

关键词： carrier leakage spectral asymmetry navigation signal performance affection simulation analysis

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A Decision Support for Target Country Selection of Future Ge...

Simulation of aerodynamic performance affected by vortex generators on blunt trailing-edge airfoils

第四届（2009）中国管理学年会--金融分会场

作者： Guangli Nie1,Haizhen Yang1,3,Ying Wang1,Wenjing Chen1,Yong Shi1,2 1. Research Center on Fictitious Economy and Data Science,CAS,beijing 100190,china 2. College of Information Science and Technology,university of Nebraska at Omaha,Omaha,NE 68182,USA 3. School of Management,graduate university of chinese academy of sciences,beijing 100190,china

This paper addresses the challenging problem of selecting target country for future Sovereign Wealth Fund （SWF） asset allocation to hedge the country risk,which is rarely studied in the field. The target country selection includes which country and how much to invest to obtain the objective of the funds and minimize the risk of these funds. In terms of the industrial perspective,an home country as the investor should consider SWF as part of its budget to make decision for long term. In order to control the risk,this paper measures the similarity between the home and the recipient country of SWF investment. The industrial risk of SWFs’ recipient country is also taken into consideration that is measured by a concentration ratio. The low industrial similarity does not necessarily mean low return. According to the criteria proposed in this approach,SWFs can realize the return objective and control the industrial risk. This paper also classifies the category of SWFs and summarizes possible investment transactions of available SWFs for their characteristics. Based on an analytical process of target country selection,the paper finds that Kazakhstan,India,Australia,Greece,Spain,United States,Austria,Portugal,Peru,Netherlands are the top 10 countries that china should consider as its investment priorities.

关键词： sovereign wealth funds future generation industrial structure strategic asset allocation

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Science china(Technological sciences) 2010年第1期53卷 1-7页

作者： YANG Ke1,2,ZHANG Lei1,3 & XU JianZhong1,2 1 Institute of Engineering Thermophysics,chinese academy of sciences,beijing 100190,china 2 Key Laboratory of Wind Energy Utilization,chinese academy of sciences,beijing 100190,china 3 graduate School of chinese academy of sciences,beijing 100190,china Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing China Key Laboratory of Wind Energy Utilization Chinese Academy of Sciences Beijing China graduate School of chinese academy of sciences Beijing China

An investigation was carried out by numerical simulation on a wind turbine airfoil and a blunt trailing-edge airfoil with and without vortex generators (VGs), and the performance of the airfoils was analyzed. By the simulation of airfoil DU 91-W2-250 it was verified that the numerical method and model were credible. Based on this airfoil, a new one with a blunt trailing edge of 6% chord was blended by symmetrically adding thickness, and its characteristics curves were obtained through computing at key angles of attack. Additionally, the pressure distribution on blended airfoil was analyzed by comparing to the airfoil without blend. The interaction of streamwise vortices induced by VGs with trailing vortex or separation vortex was considered, followed by the uncovery of how VGs can suppress the boundary layer separation.

关键词： vortex generators airfoil blunt trailing-edge

Observation results of relativistic electrons detected by Fengyun-1 satellite and analysis of relativistic electron enhancement (REE) events

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Science china(Physics,Mechanics & Astronomy) 2008年第12期51卷 1947-1956页

作者： YANG XiaoChao1,2↑ & WANG ShiJin1 1 Center for Space Science and Applied Research, chinese academy of sciences, beijing 100190, china 2 graduate university of chinese academy of sciences, beijing 100049, china Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

The space particle component detector on Fengyun-1 satellite which works at the sun-synchronous orbit of about 870 km altitude has detected relativistic electrons for a long time. In comparison with the SAMPEX satellite observations during 1999–2004, the relativistic electron data from Fengyun-1 satellite from June 1999 to 2005 are used to analyze the relativistic electron enhancement (REE) events at the low earth orbit, and the possible correlation among REE events at the low earth orbit, high-speed solar wind and geomagnetic storms is discussed. The statistical result presents that 45 REE events are found in total during this time period, and the strong REE events with the maximum daily average flux > 400 cm?2·srt-1·s?1 occur mostly during the transition period from solar maximum to solar minimum. Among these 45 REE events, four strong REE events last a longer time period from 26-to 51-day and correlate closely with high speed solar wind and strong geomagnetic storms. Meanwhile, several strong geomagnetic storms occur continuously before these REE events, and these continuous geomagnetic storms would be an important factor causing these long-lasting strong REE events. The correlation analysis for overall 45 events indicates that the strength of the REE events correlates with the solar wind speed and the strength of the geomagnetic storm, and the correlation for strong REE events is much stronger than that for weak REE events.

关键词： relativistic electron enhancement low earth orbit high-speed solar wind geomagnetic storm

The solid lubricating material experiment device for Shenzhou-7 Spaceship

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Science china(Technological sciences) 2010年第9期53卷 2521-2527页

作者： WANG Ke1,2,REN WeiJia1,WANG ShiDa1 & WENG LiJun3 1 academy of Opto-Electronics,chinese academy of sciences,beijing 100190,china 2 graduate university of chinese academy of sciences,beijing 100049,china 3 Lanzhou Institute of Chemical Physics,chinese academy of sciences,Lanzhou 730000,china academy of Opto-Electronics Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou China

A solid lubricating material exposure experiment in space is one of the missions during the seventh manned spaceflight of china,and the key is to develop a device which can be fixed reliably outside of the orbital module and can be fetched conveniently by an astronaut during space *** solid lubricating material experiment device needs to be locked reliably in a vibrating and impacting environment during the launch phase,and should meet the requirement that it can be unlocked and fetched reliably by the astronaut wearing an extravehicular spacesuit via simple operations in orbit in an environment of high and low *** for the device we developed,the environmental characteristic of the mission was analyzed,the mechanical analysis and thermal analysis were carried out,and then a mechanism with functions of mechanical locking,structural self-locking and manual unlocking was *** device was verified by a sequence of experiments and was fetched by the astronaut during the flight of the Shenzhou-7 Spaceship.

关键词： manned spaceflight exposure experiment mechanism unlock

Applications of URANS on predicting unsteady turbulent separated flows

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Acta Mechanica Sinica 2009年第3期25卷 319-324页

作者： Jinglei Xu Huiyang Ma Department of Physics, graduate university of the chinese academy of sciences, 100049 beijing, china Department of Physics Graduate University of the Chinese Academy of Sciences Beijing China

Accurate prediction of unsteady separated turbulent flows remains one of the toughest tasks and a practi cal challenge for turbulence modeling. In this paper, a 2D flow past a circular cylinder at Reynolds number 3,900 is numerically investigated by using the technique of unsteady RANS （URANS）. Some typical linear and nonlinear eddy viscosity turbulence models （LEVM and NLEVM） and a quadratic explicit algebraic stress model （EASM） are evaluated. Numerical results have shown that a high-performance cubic NLEVM, such as CLS, are superior to the others in simulating turbulent separated flows with unsteady vortex shedding.

关键词： URANS Nonlinear eddy viscosity turbulencemodel ,Separated flows Circular cylinder

Strong decays of N~*(1535) in an extended chiral quark model

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Science china(Physics,Mechanics & Astronomy) 2009年第10期52卷 1452-1457页

作者： AN ChunSheng1,2,3 & ZOU BingSong1,2,3 1 Institute of High Energy Physics,chinese academy of sciences,beijing 100049,china 2 Theoretical Physics Center for Science Facilities,chinese academy of sciences,beijing 100049,china 3 graduate university of chinese academy of sciences,beijing 100049,china Institute of High Energy Physics Chinese Academy of Sciences Beijing China Theoretical Physics Center for Science Facilities Chinese Academy of Sciences Beijing China graduate university of chinese academy of sciences Beijing China

The strong decays of the N*(1535) resonance are investigated in an extended chiral quark model by including the low-lying $ qqqq\bar q $ components in addition to the qqq component. The results show that these five-quark components in N*(1535) contribute significantly to the N*(1535) → Nπ and N*(1535) → Nη decays. The contributions to the Nη decay come from both the lowest energy and the next-tolowest energy five-quarks components, while the contributions to the Nπ decay come from only the latter one. Taking these contributions into account, the description for the strong decays of N*(1535) is improved, especially for the puzzling large ratio of the decays to Nη and Nπ.

关键词： N*(1535) strong decays five-quark components

Teleconnection between the Indian summer monsoon onset and the Meiyu over the Yangtze River Valley

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Science china Earth sciences 2008年第7期51卷 1021-1035页

作者： LIU YunYun1,2,3 & DING YiHui2 1 chinese academy of Meteorological sciences, beijing 100081, china 2 National Climate Center, beijing 100081, china 3 graduate university of chinese academy of sciences, beijing 100049, china chinese academy of Meteorological sciences Beijing China National Climate Center Beijing China graduate university of chinese academy of sciences Beijing China

Based on the Indian and chinese precipitation data and the NCEP-NCAR reanalysis circulation data, the relationship between the Indian summer monsoon (ISM) onset and the Meiyu over the Yangtze River Valley has been discussed by the methods of correlation analysis and composite analysis. The results show that the date of ISM onset over Kerala in the southwestern coast of the Indian Peninsula is about two weeks earlier than the beginning of the Meiyu over the Yangtze River Valley. After the outbreak of ISM, the teleconnection mode sets up from the western coast of India via the Bay of Bengal (BOB) to the Yangtze River Valley and southern Japan. It is different both in time and space from the telecon- nection mode which is from the northwest of India via the Tibetan Plateau to northern china. The for- mer mode is defined as the "south" teleconnection of the Asian summer monsoon, forming in the pe- riod of ISM onset; while the latter mode is called the "north" teleconnection, mainly occurring in the Asian monsoon culminant period. During the process of the "south" teleconnection’s formation, the Asian monsoon circulation has experienced a series of important changes: ISM onset, the northward movement of the south Asia high (SAH), the onset vortex occurrence, the eastward extension of the stronger tropical westerly belt, and the northeastward jump of the western Pacific subtropical high (WPSH), etc. Consequently, since ISM sets up over Kerala, the whole Asian continent is covered by the upper SAH after about two weeks, while in the mid- and lower troposphere, a strong wind belt forms from the Arabian Sea via the southern India, BOB and the South china Sea (SCS), then along the western flank of WPSH, to the Yangtze River Valley and southern Japan. With the northward moving of the subtropical jet streams, the upper westerly jet stream and the low level jet have been coupled ver- tically over east Asia, while the Yangtze River Valley happens to locate in the ascending motion

关键词： Indian summer monsoon (ISM) the Meiyu over the Yangtze River Valley teleconnection mode