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The sublimation energy of metal versus temperature and pressure and its influence on blow-off impulse

World Academy of science, Engineering and technology 2011年 81卷 620-623页

作者： Tang, Wenhui Wang, Daorong Huang, Xia Ran, Xianwen Institute of Technological Physics College of Science National University of Defense Technology Changsha 410073 China National Key Laboratory of Science and Technology Test Physics and Numerical Mathematics Beijing 100076 China

Based on the thermodynamic theory, the dependence of sublimation energy of metal on temperature and pressure is discussed, and the results indicate that the sublimation energy decreases linearly with the increase of temperature and pressure. Combined with this result, the blow-off impulse of aluminum induced by pulsed X-ray is simulated by smoothed particle hydrodynamics (SPH) method. The numerical results show that, while the change of sublimation energy with temperature and pressure is considered, the blow-off impulse of aluminum is larger than the case that the sublimation energy is assumed to be a constant.

关键词： Aluminum

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Progress and prospective of electromagnetic periodic structures 4

Progress and prospective of electromagnetic periodic structu...

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4th International Applied Computational Electromagnetics Society Symposium in China, ACES-China 2021

作者： Zhang, Shengjun Mu, Lei Shao, Chunshou Ai, Xia Wang, Weidong Chai, Song Cui, Yichun Liu, Shengdong Sun, Cuiyun Zhou, Nan Xie, Lei Li, Chunyu Jiao, Luting Wang, Yue Qi, Zhaohui Wang, Minghao Yong, Zhengyu Sun, Yuan Kong, Dewang National Key Laboratory of Science Technology on Test Physics and Numerical Mathematics Beijing China The Star of Aerospace Innovation Research Institute in Changsha Hunan Changsha China Beijing Institute of Space Long March Vehicles Beijing China Institute of Survival Technology Effectiveness Evaluation of Flying Vehicle Beijing China National Key Laboratory of Science Technology on Electromagnetic Scattering Beijing China

ISBN: (纸本)9781733509619

Periodic structures have attracted interests of researches for decades, and they were discovered more and more useful properties, and have been applied to many fields. Furthermore, more and more novel concept and phenomena based on periodic structures were proposed and found, such as tunable electromagnetic properties of some structures. In this paper, recent progress on two of the periodic structures, i.e., FSS and metamaterials and their variations, were revie, and the physical nature of these structures analog to materials were also suggested. © 2021 Applied Computational Electromagnetics Society (ACES).

关键词： Periodic structures

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RCS analysis of disk target covered with non-uniform plasma

RCS analysis of disk target covered with non-uniform plasma

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IET International Radar Conference 2015

作者： Runhui Wu Jiaqi Liu Xin Liu Gang Meng Aimin Ren Zhaohui Qi National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical Beijing 100076

ISBN: (纸本)9781510822023

This paper presents a model of RCS characteristic of non-uniform plasma sheltering disk target, by considering the absorption and refraction of electromagnetic wave, and combining graphic electromagnetic and ray tracking methods. The results show that: (1) RCS is reduced more than 10dB at wide-band frequency of electromagnetic wave, when the incident direction of electromagnetic wave is near the vertical surface. (2)For optimization of RCS reduction scheme, it is effective to optimize the relation between the plasma parameters (including electronic density, collision frequency, over-dense target scale) and incident wavelength. When the area of over-dense surface was larger than the target scale, the larger the collision frequency could lead to greater RCS reduction. When the area of over-dense scale was smaller than target, the RCS reduction has to be achieved by increasing electronic density and collision frequency.

关键词： Disk Target Electromagnetic Wave Non-uniform Plasma Radar Cross Section(RCS)

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Intercept Strategy for Maneuvering Target Based on Deep Reinforcement Learning

Intercept Strategy for Maneuvering Target Based on Deep Rein...

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第40届中国控制会议

作者： Xu Wang Yuanli Cai Yizhong Fang Yifan Deng School of Automation Science and Engineering Xi'an Jiaotong University National Key Laboratory of Science Technology on Test Physics & Numerical Mathematics

A novel interception strategy for high-speed maneuvering target based on reinforcement learning（RL） algorithm is proposed. With reshaped reward function and observation consisting solely of relative position information and path angle, the interception policy is trained by Deep Deterministic Policy Gradient（DDPG） algorithm. The results of training and test indicate that the proposed guidance law can approximate the optimal control model of the maneuvering target interception and show the superiority over traditional method.

关键词： Exoatmospheric Interception Maneuvering Target Deep Reinforcement Learning DDPG

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Insect wing-beat frequency automatic extraction and experimental verification with a Ku-band insect radar system

Insect wing-beat frequency automatic extraction and experime...

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IET International Radar Conference 2018, IRC 2018

作者： Zhang, Tianran Liu, XiangRong Hu, Cheng Wang, Rui Liu, Changjiang Li, Wenqing Radar Research Laboratory School of Information and Electronics Beijing Institute of Technology Beijing100081 China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing100076 China Key Laboratory of Electronic and Information Technology in Satellite Navigation Beijing Institute of Technology Ministry of Education Beijing100081 China

The wing-beat frequency is one of the most important behavioural parameters of migratory insects and is widely used to distinguish insect species due to the diversity of wing-beat frequency among different species. Traditional insect radar has been able to achieve automatic extraction of the wing-beat frequency. However, its low-range resolution and fixed threshold detection may cause false alarms and reduce the precision of wing-beat frequency. The authors' Ku-band insect radar system enables high-resolution, full-polarised detection of insects, but has not achieved automatic extraction of wing-beat frequency yet. The authors propose an insect wing-beat frequency automatic extraction algorithm based on a Ku-band insect radar system. The algorithm adopts the constant false alarm rate detector and tracks the association algorithm to get target echo automatically and combines the amplitude spectrum method and the phase spectrum method to achieve wing-beat frequency extraction. The authors carried out the outfield experiment using the radar system and used the collected data to test the proposed algorithm. The experiment results confirm that the algorithm can extract the wing-beat frequency of insects automatically based on the Ku-band insect radar system, which can improve system efficiency. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Errors

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The role of single loading dielectric layer on properties of frequency selective surfaces

The role of single loading dielectric layer on properties of...

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International Workshop on Metamaterials

作者： S. J. Zhang J. Q. Liu M. L. Wang W. M. Ms W. Liang X. M. Liu X. C. Hou National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Aerospace Science & Industry Defense Technology R & T Center

Frequency selective surfaces (FSS) have attracted researchers from many subjects for decades for its tempting applications such as for radome radar cross section (RCS) reduction, sub-reflector, ***. Many studies was focused on different type FSS, such as unit shape, dielectric loading, layers of FSS. And it is of popular consideration that double dielectric loading on both sides of FSS be an ideal configuration. In this paper, the type of single side loading, which is more similar to the practical configuration, was studied with the numerical method. And it is found that both the thickness of thick loading layer and the constant of the thin substrate play key roles to the properties of FSS.

关键词： Frequency selective surfaces Dielectrics Substrates Loading Load modeling Frequency modulation Equivalent circuits

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FSS design research for improving the wide-band stealth performance of radar absorbing materials

FSS design research for improving the wide-band stealth perf...

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International Workshop on Metamaterials

作者： Wang Ming-liang Zhang Sheng-jun Liu Jia-qi Liang Wei Liu Xue-mei X. W. Liang National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematical Beijing China

The frequency selective surface (FSS) is designed to improve the wide-band stealth performance of radar absorbing materials (RAM) at the frequency range from 2GHz to 12GHz. The FSS element structure is designed for thin RAM coating, and the electromagnetic wave reflectivity performance of RAM containing FSS is analyzed by using the numerical simulation. The influence of FSS design parameters on the reflectivity of RAM is researched, and the FSS design parameters include the element geometry parameter, the length of the array periods, and the permittivity of substrate material. The research results show that the three absorbing wide-bands can appear and that the reflectivity is lower than -10dB, so the wide-band stealth performance of RAM containing FSS can be improved at the frequency range from 2GHz to 12GHz.

关键词： Frequency selective surfaces Random access memory Reflectivity Resonant frequency Arrays Substrates

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Effects of discharge types on plasma collisional absorption of electromagnetic waves

Effects of discharge types on plasma collisional absorption ...

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International Workshop on Metamaterials

作者： Runhui Wu Shengjun Zhang Jiaqi Liu Aimin Ren Gang Meng Wei Liang Xuemei Liu National Key Laboratory of Science and Technology on test physics & numerical mathematical Beijing China

In this paper, the collisional absorption mechanism of electromagnetic wave in plasma of different types is studied with numerical methods. The collision frequency and electromagnetic wave which is made by RF discharge in the obturator or DC discharge around the opening space. The computation models are founded for calculating the absorption by the plasma. The FDTD method is presented for simulating the collisional absorption of electromagnetic wave power for one-dimensional homogeneous/inhomogeneous plasma. The emulational results illustrate that there are two conclusions: 1) the homogeneous plasma which is produced by RF discharge in the obturator on collisional absorption of electromagnetic wave can absorb the energy of electromagnetic wave effectively in the finite bandwidth; 2) the inhomogeneous plasma which is produced by DC discharge around the opening space can absorb the energy of electromagnetic wave availably both in the wide bandwidth and from low-frequency to high-frequency.

关键词： Plasmas Discharges (electric) Absorption Radio frequency Nonhomogeneous media Electromagnetic scattering Attenuation

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Performance analysis of one-step prediction-based cognitive jamming in jammer-radar countermeasure model

Performance analysis of one-step prediction-based cognitive ...

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IET International Radar Conference 2018, IRC 2018

作者： Gao, Lu Liu, Li Cao, Yang Wang, Shangyue You, Shixun National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China DFH Satellite Co. Ltd Beijing China Harbin Engineering University 145 Nantong Street Nangang District Harbin China

Strong adaptive radar, such as cognitive radar (CNR), can perform various missions while ensuring its own security in electronic warfare, via detecting environments and changing the radar parameters in real time. Unfortunately, most of the current military countermeasures, such as jamming-based electronic countermeasures, have rarely been related to jamming for CNR. Since the behaviours of radar in the traditional design of the jammer-radar scenario are always static, it is easy to create a subjective or local optimal jamming effect. In order to dynamically analyse the execution process of a complete jamming radar mission, this work establishes an equivalent attack-defence game in which the radar is regarded as a defence decision agent, and the jammer is an attack decision agent. The attributes of the game's players, the rules of the game, and the conditions for the end of the game are set clearly by setting reasonable parameters. After searching for antagonism strategies by exhaustive method, it can be found that the survivability of the predictive cognitive jamming is much stronger than that of the normal jamming based on real-time sampling data of radars. This conclusion is demonstrated through a 1 ms simulation of the game process. © This is an open access article published by the IET under the Creative Commons Attribution License (http://***/licenses/by/3.0/)

关键词： Jamming

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Application of Graphic Electromagnetic Computing in Electrically Large Scale Composite Target Scattering

Application of Graphic Electromagnetic Computing in Electric...

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International Applied Computational Electromagnetics Society Symposium (ACES)

作者： Lu Gao Ning Fang Mingliang Wang Jiaqi Liu Yanan Li Runhui Wu Yinfang Xu National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing China Academy of electronic information engineering Beihang University Beijing China National Key Laboratory of Science and Technology on Test Physics Beijing China

The radar cross section(RCS) calculation model of electrically large-scale composite target is established by combining graphic electromagnetic computing(GRECO) with high-frequency optical approximation and physical diffraction. Using different illumination modes, the normal vector at each point on the target surface is obtained, and the total scattering field of the target is acquired by the coherent superposition of the scattering field and the diffraction field at each point on the target surface.

关键词： Graphics Optical diffraction Laser radar Diffraction Computational modeling Lighting Optical computing

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