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Climate-Vegetation Interannual Variability in a Coupled Atmosphere-Ocean-Land Model

Advances in Atmospheric sciences 2009年第3期26卷 599-612页

作者：智海王盘兴丹利俞永强徐永福郑伟鹏 Nanjing University of Information Science and Technology Nanjing 210044 The National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029 START Regional Center for Temperate East Asia and Key Laboratory of Regional Climate-Environmentfor Temperate East Asia Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029 The State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

The coupled models of both the Global Ocean-Atmosphere-Land System （GOALS） and the Atmosphere- Vegetation Interaction Model （GOALS-AVIM） are used to study the main characteristics of interannual variations. The simulated results are also used to investigate some significant interannual variability and correlation analysis of the atmospheric circulation and terrestrial ecosystem. By comparing the simulations of the climate model GOALS-AVIM and GOALS, it is known that the simulated results of the interannual variations of the spatial and temporal distributions of the surface air temperatures and precipitation are generally improved by using AVIM in GOALS-AVIM. The interannual variation displays some distinct characteristics of the geographical distribution. Both the Net Primary Production （NPP） and the Leap Area Index （LAI） have quasi 1-2-year cycles. Meanwhile, precipitation and the surface temperatures have 2-4- year cycles. Conditions when the spectrum density values of GOALS are less than those of GOALS-AVIM, tell us that the model coupled with AVIM enhances the simulative capability for interannual variability and makes the annual cycle variability more apparent. Using Singular Value Decomposition （SVD） analysis, the relationship between the ecosystem and the atmospheric circulation in East Asia is explored. The result shows that the strengthening and weakening of the East Asian monsoon, characterized by the geopotential heights at 500 hPa and the wind fields at 850 hPa, correspond to the spatiotemporal pattern of the NPP. The correlation between NPP and the air temperature, precipitation and solar radiation are different in interannual variability because of the variation in vegetation types.

关键词： interannual variability net primary production atmosphere-vegetation interaction model twoway interaction

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A Novel Deceptive Jamming Method Via Frequency Diverse Array

A Novel Deceptive Jamming Method Via Frequency Diverse Array

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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： Wei Mao Hui Wang Shunsheng Zhang Xiangrong Liu National Key Laboratory of Science and Technology Test Physics and Numerical Mathematics Beijing China Research Institute of Electronic Science and Technology University of Electronic Science and Technology of China Chengdu China

Different from traditional single-element and phased-array antennas, frequency diverse array (FDA) uses a slight frequency offset across the elements to produce angle-, range- and even time-dependent transmit beampattern, which provides promising potentials to develop new jamming techniques on synthetic aperture radar (SAR) imaging. In this paper, we propose a novel deception jamming method against SAR imaging, which uses FDA to quickly generate false targets. Moreover, the position of the false target is controlled by the jammer, and the number of false targets is determined by the number of FDA elements. The proposed methods are validated by extensive simulation results with range-Doppler imaging algorithm.

关键词： Jamming Synthetic aperture radar Imaging Azimuth Interference Radar imaging

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Composite data fusion algorithm for miniature vehicles building navigation base in formation flying

Composite data fusion algorithm for miniature vehicles build...

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IEEE Workshop on Signal Processing Systems (SIPS)

作者： Runle Du Jiaqi Liu Zhifeng Li Zhenhong Niu Zhiye Jiang Yadong Yang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China (100076) China Academy of Launch Vehicle Technology Beijing China (100076)

When multiple miniature vehicles with individual position and inter-vehicle distance measurement ability collaborate in a formation, navigation base can be established by data fusion in a decentralized and standalone scheme. A Composite Data Fusion (CDF) algorithm which combines Least Square Error and Kalman Filtering is proposed in this paper to build navigation base with optimized computing stress. In CDF, Enhanced LSE is incorporated as the preprocessing stage to build a coarse estimation and handle temporary or permanent group number failure. KF stage is then built to further alleviate noises in the pre-processed estimations In CDF, the dynamic model can be much simpler than KF, so the computation load is reduced while the result still has the advantage of high precision. Simulation results show that, when the fault rate of measurement in each vehicle goes 5 thousandth, the result is still acceptable. The computation time of the proposed method is less than three percent of that of KF, while its precision is almost the same to that of KF.

关键词： Vehicles Kalman filters Navigation Mathematical model Equations Data integration

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Dual-band checkerboard plasma electromagnetic surface for radar cross section reduction

Dual-band checkerboard plasma electromagnetic surface for ra...

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IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP)

作者： Qiang Xu Zhifeng Li Jinjun Mo National University of Defense Technology Changsha China National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical Beijing China

ISBN: (纸本)9781538616093

Radar cross section (RCS) can be reduced along the principal planes by applying electromagnetic band gap (EBG) structures. Checkerboard plasma electromagnetic surface (PES), combining with EBG and plasma layer, can realize a narrow band near 3 GHz and a wide band 10-dB radar cross section reduction (RCSR) covered X-band, by redirecting the scattered fields towards four quadrants. Bistatic RCS of the checkerboard PES is simulated and the results compared to the corresponding perfect electric conductor (PEC) surface show that the maxima of the bistatic RCS pattern are reduced by 5.4 dB at fixed frequency 10 GHz.

关键词： Plasmas Periodic structures Metamaterials Electromagnetics Radar cross-sections Electromagnetic scattering

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Differences in Meteorological Conditions between Days with Persistent and Non-Persistent Pollution in Beijing, China

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Journal of Meteorological Research 2018年第1期32卷 81-98页

作者： Ting YOU Renguang WU Gang HUANG Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 College of Atmospheric Sciences Chengdu University of Information Technology Chengdu 610225 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Qingdao 266237 Joint Center for Global Change Studies Beijing 100875 University of Chinese Academy of Sciences Beijing 100049

We compared the regional synoptic patterns and local meteorological conditions during persistent and non-persistent pollution events in Beijing using US NCEP–Department of Energy reanalysis outputs and observations from meteorological stations. The analysis focused on the impacts of high-frequency（period 〈 90 days） variations in meteorological conditions on persistent pollution events（those lasting for at least 3 days）. Persistent pollution events tended to occur in association with slow-moving weather systems producing stagnant weather conditions, whereas rapidly moving weather systems caused a dramatic change in the local weather conditions so that the pollution event was short-lived. Although Beijing was under the influence of anomalous southerly winds in all four seasons during pollution events, notable differences were identified in the regional patterns of sea-level pressure and local anomalies in relative humidity among persistent pollution events in different seasons. A region of lower pressure was present to the north of Beijing in spring, fall, and winter, whereas regions of lower and higher pressures were observed northwest and southeast of Beijing, respectively, in summer. The relative humidity near Beijing was higher in fall and winter, but lower in spring and summer. These differences may explain the seasonal dependence of the relationship between air pollution and the local meteorological variables. Our analysis showed that the temperature inversion in the lower troposphere played an important part in the occurrence of air pollution under stagnant weather *** results from this study are based on a limited number of events and thus require validation using more data.

关键词： persistent and non-persistent pollution events regional synoptic patterns local meteorological conditions temperature inversion stability index Beijing

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Plasma Diagnosis Method Based on Microwave Reflection Characteristics By GA-ANN

Plasma Diagnosis Method Based on Microwave Reflection Charac...

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International Conference on Microwave and Millimeter Wave technology Proceedings

作者： Yu-hang Shi Run-hui Wu Jin-jun Mo School of Information And Communication Guilin University of Electronic Technology Guilin China National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing China

ISBN: (数字)9798350389968

ISBN: (纸本)9798350389975

In this paper, a microwave reflection method based on fusion algorithm is proposed to diagnose the peculiarity of plasma. This fusion algorithm is composed of genetic algorithm (GA) and neural network (ANN), that is GA-ANN. Only a single horn antenna is used to emit spherical waves to the preset plasma, and the scattering peculiarity of the horn antenna (impedance bandwidth, resonance point and gain) and the corresponding plasma characteristics (characteristic frequency, collision frequency) are obtained. The weight and bias of ANN are optimized by GA screening mechanism. Then GA-ANN is used to establish the mapping relationship between the scattering characteristics of antenna and plasma, which is finally used to diagnose the unknown plasma characteristics. The experimental results show that the relative error of plasma diagnosis using GA-ANN is 0.7 lower than that using ANN alone.

关键词： Microwave antennas Microwave integrated circuits Horn antennas Scattering Resonant frequency Reflection Resonance

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Design of Non-uniform Flexible Meta-surface for Antenna Beam-steering

Design of Non-uniform Flexible Meta-surface for Antenna Beam...

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IEEE International Conference on Electronic Information and Communication technology (ICEICT)

作者： Yuwei Qiu Zhiye Jiang Pei Zheng School of Electronic Information Northwestern Polytechnical University Xi'an China National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing China

ISBN: (数字)9781728190457

ISBN: (纸本)9781728190464

Design of non-uniform flexible meta-surface for antenna beam-steering is presented in this paper. By properly tuning the dimensions of quasi-I-shaped unit cells on meta-surface, we propose a bi-layer meta-surface that can achieve beam deflection of up to 34°. Horn antenna is adopted as the feed antenna to illuminate the meta-surface which is printed on flexible plastic sheet. The meta-surface is fixed on the outside surface of horn antenna with an electric motor, making it possible to slide relative to the aperture of feed antenna. The horn antenna together with the meta-surface will work like a projector when operating, the main-beam of the horn antenna can be steered when different frames of the meta-surface cover the horn aperture and the steering range is ±34°. Radiation reconfigurable is thus achieved through a simple structure. Prototype will be fabricated in the following research.

关键词： Horn antennas Prototypes Antenna feeds Aperture antennas Information and communication technology Plastics Tuning

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A Physical Layer key Generation method with Reliable Negotiation

A Physical Layer Key Generation method with Reliable Negotia...

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Signal, Information and Data Processing (ICSIDP), IEEE International Conference on

作者： Yuchen Wang Xuanli Wu Zhicong Xu Wei Wu Hu Li Ran Zhang School of Electronics and Information Engineering Harbin Institude of Technology Harbin China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (数字)9781728123455

ISBN: (纸本)9781728123462

There is a risk of information leakage in the process of wireless communication. The introduction of key generation in the physical layer can effectively improve the security of wireless communication. This paper proposes a new physical layer key generation method in the TDD (time division duplex) communication system. Assume that the uplink and downlink channels are reciprocal. Through LDPC (Low Density Parity Check)channel coding and negotiation algorithm, the inconsistency rate of key generation between Alice and Bob is reduced. Simulation and analysis results show that the method improves the key generation rate and reduces the key inconsistency rate.

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Piecewise Linear Recursive Convolution Method Applied in One-dimensional Unmagnetized Plasma

Piecewise Linear Recursive Convolution Method Applied in One...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Jiaqi Liu Gang Meng Lei Mu Lu Gao Jinjun Mo Runhui Wu Weidong Wang National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing China School of Information and Communication Guilin University of Electronic Technology Guilin China

The piecewise linear recursive convolution(PLRC) method based on finite difference time domain(FDTD) is used to calculate the reflection and transmission characteristics of electromagnetic waves from one-dimensional unmagnetized plasma. The results are shown that this method has obvious advantages in accurately calculating the electromagnetic problems of one-dimensional, small-scale and thin-layer dielectric materials.

关键词： Convolution Electromagnetic scattering Dielectric materials Computational electromagnetics Reflection Plasmas Electromagnetics

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A Radiation Pattern-Reconfigurable Patch Antenna with Tunable CSRR based on Liquid Metal and 3-D Printed Microfluidics

A Radiation Pattern-Reconfigurable Patch Antenna with Tunabl...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Yumeng Wang Lu Gao Pei Zheng Lingnan Song School of Electronic and Information Engineering Beihang University Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In this article, a radiation patternreconfigurable patch antenna with tunable complementary split-ring resonators (CSRR) based on liquid metal (LM) and 3-D printed microfluidics is presented. The antenna is composed of three layers, a top coaxial fed rectangular patch, a middle ground plane with two CSRRs etched symmetrically, and two bottom microfluidics channels each adhered underneath the corresponding CSRR. Pattern reconfiguration is achieved by filling the microfluidic channels with the liquid metal plugs to change the physical parameters of the CSRR structure. By adjusting the length of the slot stubs in CSRRs, the main beam of the double CSRR-loaded antenna can be continuously scanned from -46° to 46° in elevation plane.

关键词： Liquids Slot antennas Patch antennas Simulation Metals Filling Resonators

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