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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Shengjun Zhang Mingliang Wang Xia Ai Yichun Cui Xin Liu Jiaqi Liu Gang Meng Zhaohui Qi Yuan Sun Yunhui Tang Hui Xue National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics Beijing China The Institute of Effectiveness Evaluation of Flying Vehicle Beijing China School of materials science and technology Beijing University of Technology Beijing China Beijing Institute of system engineering Beijing China

In this paper, the development history of metamaterials (MTMs) and Frequency selective surfaces (FSS) was sketched, and the two conception was discussed. Furthermore, state of the art of both terms was introduced and ... 详细信息

关键词： Frequency selective surfaces Metamaterials Lattices Crystals physics Electromagnetics Sun

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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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2017 International Conference on Radar Systems, Radar 2017

作者： Li, YuanHao Liu, XiangRong Hu, Cheng Dong, XiChao School of Information and Electronics Beijing Institute of Technology 100081 China 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)9781785615153

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. © 2017 Institution of Engineering and technology. All rights reserved.

关键词： Synthetic aperture radar

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Parallel pipeline algorithm of real time star map preprocessing

Parallel pipeline algorithm of real time star map preprocess...

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Chinese Society for Optical Engineering Conferences, CSOE 2016

作者： Wang, Hai-Yong Qin, Tian-Mu Liu, Jia-Qi Li, Zhi-Feng Li, Jian-Hua School of Aeronautics and Astronautics Beihang University Beijing100083 China Beijing Institute of Space Long March Vehicle Beijing100076 China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing100076 China

ISBN: (纸本)9781510610118

To improve the preprocessing speed of star map and reduce the resource consumption of embedded system of star tracker, a parallel pipeline real-time preprocessing algorithm is presented. The two characteristics, the mean and the noise standard deviation of the background gray of a star map, are firstly obtained dynamically by the means that the intervene of the star image itself to the background is removed in advance. The criterion on whether or not the following noise filtering is needed is established, then the extraction threshold value is assigned according to the level of background noise, so that the centroiding accuracy is guaranteed. In the processing algorithm, as low as two lines of pixel data are buffered, and only 100 shift registers are used to record the connected domain label, by which the problems of resources wasting and connected domain overflow are solved. The simulating results show that the necessary data of the selected bright stars could be immediately accessed in a delay time as short as 10us after the pipeline processing of a 496×496 star map in 50Mb/s is finished, and the needed memory and registers resource total less than 80kb. To verify the accuracy performance of the algorithm proposed, different levels of background noise are added to the processed ideal star map, and the statistic centroiding error is smaller than 1/23 pixel under the condition that the signal to noise ratio is greater than 1. The parallel pipeline algorithm of real time star map preprocessing helps to increase the data output speed and the anti-dynamic performance of star tracker. © 2017 SPIE.

关键词： Pipelines

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A method for feature extraction based on SVD and machine learning

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IOP Conference Series: Materials science and Engineering 2019年第5期569卷

作者： Wei Mao Shuxian Huang Xin Liu Hongyan Liu Jiaqi Liu Yi Shu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics 100076 China Beijing Institute of Precision Mechatronics and Controls 100076 China Beijing Institute of Long March Vehicle 100076 China

By studying the shortcomings of feature, which extracted from Radar-Cross Section(RCS),using mathematical and statistical method, using the idea of extracting abstract features in image recognition and speech recognition by artificial intelligence for reference[2][3]. This paper explores the possibility of extracting abstract features of target's RCS sequence, and proposes an abstract feature extraction method of RCS sequence based on singular value decomposition(SVD) feature decomposition. Because of the poor interpretability of abstract features, four different machine learning algorithms are used to classify the extracted Abstract features. The experimental results show that the machine learning algorithm can classify different types of spatial objects with high accuracy, which shows that the RCS features of different spatial objects can be characterized by abstract features.

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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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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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The Way from natural to artificial - the story of Periodic Electromagnetic Structures

The Way from natural to artificial - the story of Periodic E...

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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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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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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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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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