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5th IEEE International Conference on Computational Electromagnetics, ICCEM 2019

作者： Yang, Kunlong Li, Jianbing Liu, Xin College of Electronic Science National University of Defense Technology Changsha China National Key Laboratory of Science and Technology on Test Physics Numerical Mathematical Beijing Institute of Space Long March Vehicle Beijing China

ISBN: (纸本)9781538671115

The Oguchi method is an important tool for characterizing the transmission characteristics of polarized electromagnetic waves in precipitation. In this paper, the forward scattering matrix of chaff is calculated for the special random medium of chaff cloud. Then the transmission characteristics of polarized electromagnetic wave, including attenuation, (specific) differential phase, are studied by using Oguchi method. The obtained characteristics are consistent with the physical laws, and the feasibility of the Oguchi method in chaff characteristic analysis is preliminarily verified. © 2019 IEEE.

关键词： Forward scattering

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Ellipse Fitting Based on Neural Network Optimization 41

Ellipse Fitting Based on Neural Network Optimization

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第41届中国控制会议

作者： Chenrong Long Peng Liu Qinglei Hu School of Automation Science and Electrical Engineering Beihang University National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing Institute of Space Long March Vehicle School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China.

ISBN: (数字)9789887581536

ISBN: (纸本)9781665482561

Ellipse fitting is to estimate the parameters of the ellipse from a set of coplanar points,but the geometric distance from the plane point to the elliptic curve is difficult to calculate *** paper proposes a neural network optimization-based algorithm to estimate the geometric distances from plane points to elliptic curves to solve the ellipse fitting ***,the neural network is firstly applied to train the geometric distance between the plane point and the standard ellipse,and then obtain the geometric distance between the plane point and the general ellipse through the rotation and translation ***,use minimizing the sum of the Euclidean distances from the plane point to the elliptic curve as the objective function,and finally use the gradient descent method to iteratively solve the ellipse ***,the proposed method avoids the direct algebraic solution of the geometric distance from the plane point to the elliptic curve and the performance of the algorithm to gether with its robustness to noise are analysed via numerical simulation.

关键词： Ellipse Fitting Coplanar Points Geometric Distance Neural Network Optimization

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A novel GCV-based criterion for parametric PSF estimation

A novel GCV-based criterion for parametric PSF estimation

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International Conference on Signal Processing Proceedings (ICSP)

作者： Feng Xue Jiaqi Liu Zhifeng Li Gang Meng National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781479921898

We propose a generalized cross validation (GCV) as a novel criterion for estimating a point spread function (PSF) from the degraded image only. The PSF is obtained by minimizing this new objective functional over a family of Wiener processings. Based on this estimated PSF, we then perform deconvolution using our recently developed SURE-LET algorithm. The GCV-based criterion is exemplified with a number of parametric PSF, involving a scaling factor that controls the blur size. A typical example of such parametrization is the Gaussian kernel. The experimental results demonstrate that the GCV minimization yields highly accurate estimates of the PSF parameters, which also result in a negligible loss of visual quality, compared to that obtained with the exact PSF. The highly competitive results outline the great potential of developing more powerful blind deconvolution algorithms based on this criterion.

关键词： Optical filters Abstracts Estimation Fluorescence Noise reduction Integrated optics Optical imaging

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An Absorptive/Transmissive Frequency Selective Surface with Wide Transmission Band and Low Insertion Loss

An Absorptive/Transmissive Frequency Selective Surface with ...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Hang Song Jiaqi Liu Shengjun Zhang National Key Laboratory of Science & Technology on Test Physics and Numerical Mathematics Beijing China

The Absorptive/transmissive Frequency Selective Surface (ATFSS) is a multi-layer composite periodic structure with out-of-band absorption and in-band transmission characteristics, usually composed of a lossy resistive sheet (RS) and a lossless bandpass FSS. In this paper, an equivalent circuit method based on transmission line theory was used to design the ATFSS with idea of higher frequencies for transmission and lower frequencies for absorption, as well as the impedance conditions for satisfying wave transmission and absorption. Furthermore, the S-parameters was fitted, which verifies the design concept. Finally, the simulation was performed with numerical method. It is shown from the simulation that the broadband absorption of the ATFSS ranges from 2.00 GHz to 6.29 GHz, and the broadband transmission ranges from 8.46 GHz to 11.32 GHz with an insertion loss of less than 1 dB.

关键词： Frequency selective surfaces Absorption Insertion loss Power system stability Propagation losses Stability analysis Broadband communication

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Polar Coordinate Lattice Boltzmann Kinetic Modeling of Detonation Phenomena

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Communications in Theoretical physics 2014年第11期61卷 737-748页

作者：林传栋许爱国张广财李英俊 State Key Laboratory for GeoM echanics and Deep Underground Engineering China University of Mining and Technology National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Center for Applied Physics and Technology MOE Key Center for High Energy Density Physics Simulations College of Engineering Peking University State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology State Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences

A novel polar coordinate lattice Boltzmann kinetic model for detonation phenomena is presented and applied to investigate typical implosion and explosion processes. In this model, the change of discrete distribution function due to local chemical reaction is dynamically coupled into the modified lattice Boltzmann equation which could recover the Navier–Stokes equations, including contribution of chemical reaction, via the Chapman–Enskog *** the numerical investigations, the main focuses are the nonequilibrium behaviors in these processes. The system at the disc center is always in its thermodynamic equilibrium in the highly symmetric case. The internal kinetic energies in different degrees of freedom around the detonation front do not coincide. The dependence of the reaction rate on the pressure, influences of the shock strength and reaction rate on the departure amplitude of the system from its local thermodynamic equilibrium are probed.

关键词： lattice Boltzmann method detonation wave nonequilibrium behavior polar coordinate

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An Experimental Study on the Object Shielding Performance of Discrete Metal Wire Array

An Experimental Study on the Object Shielding Performance of...

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2018 IEEE International Conference on Computational Electromagnetics, ICCEM 2018

作者： Wang, Weidong Liu, Xin Wang, Mingliang Liu, Jiaqi Meng, Gang Gao, Zhiyong Mu, Lei Ai, Xia Zhang, Shengjun Li, Jianbing Beijing Institute of Space Long March Vehicle National Key Laboratory of Science and Technology on Test Physics Numerical Mathematical Beijing China College of Electronic Science National University of Defense Technology Changsha China

ISBN: (纸本)9781538612415

In this paper, a method of shielding the object behind a discrete metal wire array is proposed and verified by anechoic chamber experiments. Results show that if the metal wire array is dense enough (cell size is smaller than half of the wavelength), the object behind it can be effectually shielded by the discrete metal wire array. The principle can be applied to electromagnetic camouflage and protection. © 2018 IEEE.

关键词： Electromagnetic shielding

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The propagation characteristic of the QPSK signals in reentry plasmas 67

The propagation characteristic of the QPSK signals in reentr...

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67th International Astronautical Congress, IAC 2016

作者： Wu, Runhui Liu, Jiaqi Liu, Xin Ren, Aimin Zhang, Shengjun Meng, Gang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical China Academy of Launch Vehicle Technology No 1 Nan Da Hong Men Road Beijing China

A spacecraft entering the Earth's atmosphere is enveloped by a plasma layer or sheath due to shock heating of the surrounding air and ablation of the heat shield material, and the plasma sheath may strongly effect the communication between the vehicles and receiver systems. In order to obtain the influence of communication system which is produced by reentry plasmas, a mechanism of QPSK signals through reentry plasmas which surround vehicles travelling at hypersonic velocities is proposed in this paper, and the simulation model of the QPSK signals propagation in plasma sheath is described. Then the energy attenuation and phase variable of QPSK signals which are transmitted by reentry plasmas are computed. The analysis results are shown that the QPSK signals would be shielded thoroughly if the plasma frequency is bigger than carrier frequency, and when the QPSK signals can propagate in reentry plasmas, the bit error probability (BEP) of communication systems would be improved by reentry plasmas which are ability to absorb the signals energy and vary signals phase. The simulation and analysis technique can also be used to calculate many other communication models such as FSK and ASK. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved.

关键词： Bit error rate

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Intelligent Counter Guidance Regulated by Deep Reinforced Learning

Intelligent Counter Guidance Regulated by Deep Reinforced Le...

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IEEE Metrology for Aerospace

作者： Runle Du Jiaqi Liu Li Zhang Jianhua Li National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (数字)9781728166360

ISBN: (纸本)9781728166377

In the game of pursuit and evasion in outer space, it is of utmost importance for the evader to make appropriate maneuver to survive this challenge. In previous publications, the common approach of guidance behavior recognition and counteracting evasion approach is based on model matching or multi-model matching. In that genre, due to the limitation of approximation from model matching and imperfection of state information, it is very difficult for the evader to take optimal maneuver when the pursuer uses unknown tracking algorithms. To solve this problem, in this article, deep neural network and reinforced learning are applied in counteractive maneuver. In the proposed approach, two networks are applied. Guidance recognition network is a pre-trained deep network able to estimate guidance behavior of pursuer vehicle, and the maneuver control network is trained by deep reinforced learning to perform counteract evading maneuver control. Exploring the policy space with Monte Carlo method, the maneuver controller deep neural network evolved to make optimal control acceleration and succeed in the evasion. Digital simulations confirmed that in the game of pursuit and evasion, deep reinforced learning with Monte Carlo method has the ability to guide the evader during the interception with improved chance of survival.

关键词： Neural networks Training Acceleration Monte Carlo methods Kinematics Games Space exploration

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A recursive predictive risk estimate for proximal algorithms

A recursive predictive risk estimate for proximal algorithms

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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Feng Xue Runle Du Jiaqi Liu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781479999897

For accurate signal reconstruction, proximal gradient methods generally require proper selection of regularization parameter. In this paper, we develop two data-driven optimization schemes, based on minimization of unbiased predictive risk estimate (UPRE). First, we propose a recursive UPRE to estimate the prediction error during the proximal iterations, which can be used to optimize the regularization parameter. Second, for fast optimization, we parametrize each proximal iterate as a linear combination of few elementary functions (LET), and solve the linear weights by minimizing recursive UPRE. We further exemplify the proposed approaches with the basic iterative shrinkage/thresholding (IST) algorithms for ℓ 1 -minimization. numerical experiments show that iterating this process leads to higher reconstruction accuracy with remarkably faster computational speed than standard IST.

关键词： Jacobian matrices Prediction algorithms Convergence Gradient methods Signal processing algorithms Standards

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Semantic Segmentation Algorithm of Street View Image Via Deep Learning

Semantic Segmentation Algorithm of Street View Image Via Dee...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Zihui Zhu Wenlin Cai Jianhua Li Feng Xue Lu Gao Jiaqi Liu National Key Laboratory Science and Technology on Test Physics and Numerical Mathematics Beijing China

Real-time semantic segmentation of street view images can be used as a visual aid system during autonomous driving. This paper proposes a multi-branch cross-layer fusion network (MCFNet). The model uses a multi-branch network to extract features, fuses the features of different stages of multiple branches for prediction, and uses a lightweight depthwise separable convolution to reduce the amount of computation. We use the Cityscapes dataset to train and evaluate the algorithm and get 61.6% mIoU and 115.3 fps.

关键词： Cross layer design Visualization Convolution Semantic segmentation Roads Semantics Feature extraction

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