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International Applied Computational Electromagnetics Society Symposium in China

作者： Shengjun Zhang Mingliang Wang Xia Ai Weidong Wang Runhui Wu Xin Liu Jiaqi Liu Gang Meng Yuan Sun National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics The Institute of Effectiveness Evaluation of Flying Vehicle

In this paper, the general of artificial electromagnetic structure with analog to the natural materials were briefly reviewed. The lattice theory of artificial structure was suggested to be built.

ISBN: (纸本)9781509043118

In this paper, the general of artificial electromagnetic structure with analog to the natural materials were briefly reviewed. The lattice theory of artificial structure was suggested to be built.

关键词： Artificial structure Electromagnetic lattice Artificial structure lattice theory natural material ELECTROMAGNETIC

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Regional Meteorological Patterns for Heavy Pollution Events in Beijing

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Journal of Meteorological Research 2017年第3期31卷 597-611页

作者： ting you renguang wu gang huang guangzhou fan college of atmospheric sciences chengdu university of information technologyChengdu 610225 center for monsoon system research institute of atmospheric physicschinese academy of sciencesBeijing 100029 state key laboratory of numerical modeling for atmospheric sciences and geophysical fluid dynamics institute of atmospheric physicschinese academy of sciencesBeijing 100029 laboratory for regional oceanography and numerical modeling qingdao national laboratory for marine science and technologyQingdao 266237 joint center for global change studies Beijing100875 university of chinese academy of sciences Beijing 100049

The present study investigates meteorological conditions for the day-to-day changes of particulate matter （PM） concentration in Beijing city during the period 2008-2015. The local relationship of PM concentration to surface air temperature, pressure, wind speed, and relative humidity displays seasonal changes and year-to-year variations. The average correlation coefficient with PMI0 in spring, summer, fall, and winter is 0.45, 0.40, 0.38, and 0.30 for air tem- perature; -0.45, -0.05, -0.40, and -0.45 for pressure; 0.13, 0.04, 0.53, and 0.50 for relative humidity; and -0.18, -0.11, -0.45, and -0.33 for wind speed. A higher correlation with wind speed is obtained when wind speed leads by halfa day. The heavily polluted and clean days, which are defined as the top and bottom 10% of the PM values, show obvious differences in the regional distribution of air temperature, pressure, and wind. Polluted days correspond to higher air temperature in all the four seasons, lower sea level pressure and anomalous southerly winds to the south and east of Beijing in spring, fall, and winter, and a northwest-southeast contrast in the pressure anomaly and anom- alous southerly winds in summer. Higher relative humidity is observed on polluted days in fall and winter. The pol- luted days are preceded by an anomalous cyclone moving from the northwest, accompanied by lower pressure and higher air temperature, in all four seasons. This feature indicates the impacts of moving weather systems on local meteorological conditions for day-to-day air quality changes in Beijing.

关键词： PM10 Beijing local meteorology seasonal dependence weather system

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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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STATE OF THE CLIMATE IN 2021

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BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY 2022年第8期103卷 S1-S1页

作者： Blunden, Jessica NOAA/NESDIS National Centers for Environmental Information Asheville NC United States NOAA NESDIS National Centers for Environmental Information Silver Spring MD United States Met Office Hadley Centre Exeter United Kingdom Cooperative Institute for Satellite Earth System Studies North Carolina State University Asheville NC United States Communications and Outreach NOAA/NESDIS National Centers for Environmental Information Asheville NC United States Innovative Consulting and Management Services LLC NOAA/NESDIS National Centers for Environmental Information Asheville NC United States European Centre for Medium-Range Weather Forecasts Reading United Kingdom CMNS-Earth System Science Interdisciplinary Center University of Maryland College Park MD United States Department of Meteorology National Centre for Earth Observation University of Reading Reading United Kingdom Department of Atmospheric and Planetary Science Hampton University Hampton VA United States National Research Institute for Agriculture Food and Environment (INRAE) CARRTEL Université Savoie Mont Blanc Thonon les Bains France Graduate School of Life and Environmental Sciences Osaka Prefecture University Osaka Sakai Japan University of Bremen Bremen Germany NOAA Global Monitoring Laboratory Boulder CO United States Centro de Investigaciones sobre Desertificación Spanish National Research Council (CIDE CSIC-UV-Generalitat Valenciana) Climate Atmosphere and Ocean Laboratory (Climatoc-Lab) Moncada Valencia Spain Instituto de Geografía Pontificia Universidad Católica de Valparaíso Valparaíso Chile Climatic Research Unit School of Environmental Sciences University of East Anglia Norwich United Kingdom Joint Research Centre of the European Commission Ispra Italy GloH2O Almere Netherlands University of Reading Reading United Kingdom School of Engineering Newcastle University Newcastle-upon-Tyne United Kingdom Université de Paris Cité Institut de physique du globe de Paris CNRS IGN Paris

Editors note: For easy download the posted pdf of the State of the Climate in 2021 is a low-resolution file. A high-resolution copy of the report is available by clickinghere. Please be patient as it may take a few mi... 详细信息

关键词： Greenhouse gases

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Study of RF structure and Beam Wave Interaction system for a W-band Sheet Beam EIK

Study of RF structure and Beam Wave Interaction system for a...

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International Conference on Radar Systems

作者： Shuyuan Chen Jiaqi Liu Lu Gao Jinliang Bai Zhiye Jiang Feng Xu Peng Qin Hongyan Liu Xin Liu Hu Li Jingpeng Gao National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing 100076 P. R. China

ISBN: (纸本)9781785616723

Sheet beam Extended Interaction Klystron (EIK) is an attractive Millimeter Waves (MMW) amplifier because of its high gain per unit length and compact configuration, which can be used in radar transmission system. In this paper, RF structure and beam wave interaction system of W band sheet beam EIK has been designed. A new and effective method of designing and studying the beam wave interaction system is presented in this paper. The whole tube consists of one single-gap cavity, six tri-gaps cavities and one five-gaps cavity. By optimizing the position of cavities, the output power can achieve 30 kW and high gain of 50 dB, which is calculated by three dimensional particle in cell (3D-PIC) software. It provides a powerful basis for the subsequent study of sheet beam EIK.

关键词： RF EIK Dumbbell cavity Interaction system

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Evolution of Surface Sensible Heat over the Tibetan Plateau Under the Recent Global Warming Hiatus

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Advances in Atmospheric sciences 2017年第10期34卷 1249-1262页

作者： Lihua ZHU Gang HUANG Guangzhou FAN Xia QU Guijie ZHAO Wei HUA State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China School of Atmospheric Sciences/Plateau Atmosphere and Environment Key Laboratory of Sichuan Province/Joint Laboratory of Climate and Environment Change Chengdu University of lnformation TechnologyChengdu 610225China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and TechnologyQingdao 266237China Joint Center for Global Change Studies Beijing 100875China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

Based on regular surface meteorological observations and NCEP/DOE reanalysis data, this study investigates the evolution of surface sensible heat（SH） over the central and eastern Tibetan Plateau（CE-TP） under the recent global warming hiatus. The results reveal that the SH over the CE-TP presents a recovery since the slowdown of the global warming. The restored surface wind speed together with increased difference in ground-air temperature contribute to the recovery in *** the global warming hiatus, the persistent weakening wind speed is alleviated due to the variation of the meridional temperature gradient. Meanwhile, the ground surface temperature and the difference in ground-air temperature show a significant increasing trend in that period caused by the increased total cloud amount, especially at night. At nighttime, the increased total cloud cover reduces the surface effective radiation via a strengthening of atmospheric counter radiation and subsequently brings about a clear upward trend in ground surface temperature and the difference in ground-air ***–radiation feedback plays a significant role in the evolution of the surface temperature and even SH during the global warming hiatus. Consequently, besides the surface wind speed, the difference in ground-air temperature becomes another significant factor for the variation in SH since the slowdown of global warming, particularly at night.

关键词： surface sensible heat Tibetan Plateau ground-air temperature difference surface wind speed global warming hiatus

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Electromagnetic scattering characteristics of the plasma sheath around Re-entry hypersonic vehicles

Electromagnetic scattering characteristics of the plasma she...

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

作者： Run-hui Wu Jia-qi Liu Gang Meng Xin Liu Ai-min Ren Xia Ai Song Chai Ju-yan Zhao Ya-nan Li Ming-liang Wang National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical No.1 Dahongmen South Road Fengtai District Beijing 100076 China

ISBN: (纸本)9781538616093

In order to analyze electromagnetic scattering of reentry vehicle, models of the expected electromagnetic scattering properties of the aircrafts must be developed. This paper begins with a discussion of the plasma sheath characteristics, and the interactions between electromagnetic wave and plasma sheath, and the simulation model of plasma sheath scattering is described by using physical optics and hierarchical approximation technique. Then rigorous calculations of radar cross section(RCS) for a double conical target, plasma-clad body, 30km, 40km, 50km altitude, 4km/s, 5km/s velocity are presented in context with 9.8GHz, 5.8GHz, 3.2GHz, 1.5GHz of incident wave frequency. The results are shown that plasma sheath can increase or decrease the RCS of vehicles for different altitude, velocity and wave frequency. When the aircraft has a low altitude and high-speed flight, electron density of plasma sheath will increase continuously. Influenced by it, the RCS of vehicles shows a decreasing trend.

关键词： Plasma sheaths Electromagnetic scattering Atmospheric modeling mathematical model Radar cross-sections

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Frequency divided adaptive Kalman filter in guidance law recognition 24

Frequency divided adaptive Kalman filter in guidance law rec...

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24th European Navigation Conference, ENC 2016

作者： Run-Le, Du Jia-Qi, Liu Zhi-Feng, Li Zhen-Hong, Niu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781479989157

Recognition of guidance law on non-cooperative vehicle is drawing research interest among the literature, while insufficient accuracy of modeling and measurement makes it a hard problem. In this paper, a Frequency Divided Adaptive Kalman Filter is proposed to implement guidance law recognition. In FD-AKF, a Low Pass Filter is applied to extract the noise directly from state vector and measurement vector, and estimate the co-variance matrices of observation noise and prediction noise online. Without intertwined iterating equation of prediction noise and observation noise, FD-AKF decouples the estimation on prediction noise and observation noise, and thus avoids the risk of bias and divergence. Simulation results show that, FD-AKF improves robustness of guidance recognition significantly over Kalman Filter and Sage-Husa. © 2016 IEEE.

关键词： Forecasting

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Optimal selection of regularization parameter for 1-based image restoration based on SURE

Optimal selection of regularization parameter for 1-based im...

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International Symposium on Infrared technology and Application and the International Symposiums on Robot Sensing and Advanced Control

作者： Xue, Feng Liu, Xin Liu, Hongyan Liu, Jiaqi National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China

ISBN: (纸本)9781510607729

To exploit the sparsity in transform domain (e.g. wavelets), the image deconvolution can be typically formulated as a 1-penalized minimization problem, which, however, generally requires proper selection of regularization parameter for desired reconstruction quality. The key contribution of this paper is to develop a novel data-driven scheme to optimize regularization parameter, such that the resultant restored image achieves minimum prediction error (p-error). First, we develop Stein's unbiased risk estimate (SURE), an unbiased estimate of p-error, for image degradation model. Then, we propose a recursive evaluation of SURE for the basic iterative shrinkage/thresholding (IST), which enables us to find the optimal value of regularization parameter by exhaustive search. The numerical experiments show that the proposed SURE-based optimization leads to nearly optimal deconvolution performance in terms of peak signal-to-noise ratio (PSNR). © 2016 SPIE.

关键词： Image reconstruction

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Suppressing the Effects of Ionospheric Scintillation on Geosynchronous SAR by Optimised Orbit Design

Suppressing the Effects of Ionospheric Scintillation on Geos...

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International Conference on Radar Systems

作者： YuanHao Li XiangRong Liu Cheng Hu XiChao Dong Beijing Institute of Technology Beijing Beijing CN National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China Beijing Key Laboratory of Embedded Real-time information Processing Technology 100081 China

ISBN: (纸本)9781785616723

An L band geosynchronous synthetic aperture radar (GEO SAR) will be sensitive to ionosphere scintillation because of its low carrier frequency. Meanwhile, because of the high orbit, GEO SAR has a higher probability to meet ionospheric scintillation. In this paper, we propose an orbit strategy for eliminating the impacts of ionospheric scintillation. It is realized by selecting a proper orbit element (time past perigee) to avoid imaging for the sensitive region of ionospheric scintillation during the eruption time interval of ionospheric scintillation with the highest probability. Finally, the simulation based on systems tool kit (STK) software was conducted to verify the effectiveness of the method.

关键词： Geosynchronous SAR Ionospheric scinitllation Orbit design SAR imaging

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