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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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Impacts of Cumulus Momentum Transport on MJO Simulation

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Advances in Atmospheric sciences 2009年第5期26卷 864-876页

作者：凌健李崇银贾小龙 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Graduate University of the Chinese Academy of Sciences Institute of Meteorology PLA University of Science and Technology National Climate Center

Vertical cumulus momentum transport is an important physical process in the tropical atmosphere and plays a key role in the evolution of the tropical atmospheric system. This paper focuses on the impact of the vertical cumulus momentum transport on Madden-Julian Oscillation （MJO） simulation in two global climate models （GCMs）. The Tiedtke cumulus parameterization scheme is applied to both GCMs [CAM2 and Spectral Atmospheric general circulation Model of LASG/IAP （SAMIL）]. It is found that the MJO simulation ability might be influenced by the vertical cumulus momentum transport through the cumulus parameterization scheme. However, the use of vertical momentum transport in different models provides different results. In order to improve model＇s MJO simulation ability, we must introduce vertical cumulus momentum transport in a more reasonable way into models. Furthermore, the coherence of the parameterization and the underlying model also need to be considered.

关键词： Madden Julian Oscillation vertical cumulus momentum transport propagation characteristics

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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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The Relationship between Deterministic and Ensemble Mean Forecast Errors Revealed by Global and Local Attractor Radii

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Advances in Atmospheric sciences 2019年第3期36卷 271-278,339页

作者： Jie FENG Jianping LI Jing ZHANG Deqiang LIU Ruiqiang DING School of Meteorology University of Oklahoma College of Global Change and Earth System Science (GCESS) Beijing Normal University Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Cooperative Institute for Research in the Atmosphere GSD/ESRL/OAR/NOAA Fujian Meteorological Observatory Wuyishan National Park Meteorological Observatory State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Plateau Atmosphere and Environment Key Laboratory of Sichuan Province Chengdu University of Information Technology

It has been demonstrated that ensemble mean forecasts, in the context of the sample mean, have higher forecasting skill than deterministic(or single) forecasts. However, few studies have focused on quantifying the relationship between their forecast errors, especially in individual prediction cases. Clarification of the characteristics of deterministic and ensemble mean forecasts from the perspective of attractors of dynamical systems has also rarely been involved. In this paper, two attractor statistics—namely, the global and local attractor radii(GAR and LAR, respectively)—are applied to reveal the relationship between deterministic and ensemble mean forecast errors. The practical forecast experiments are implemented in a perfect model scenario with the Lorenz96 model as the numerical results for verification. The sample mean errors of deterministic and ensemble mean forecasts can be expressed by GAR and LAR, respectively, and their ratio is found to approach2^(1/2) with lead time. Meanwhile, the LAR can provide the expected ratio of the ensemble mean and deterministic forecast errors in individual cases.

关键词： attractor radius ensemble forecasting ensemble mean forecast error saturation

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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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A MULTI-AGENT JAMMING DECISION-MAKING METHOD BASED ON SP-HASAC

A MULTI-AGENT JAMMING DECISION-MAKING METHOD BASED ON SP-HAS...

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IET International Radar Conference 2023, IRC 2023

作者： Gao, Jingpeng Shen, Chen Gao, Lu Jiang, Zhiye College of Information and Communication Engineering Harbin Engineering University Harbin China Beijing Institute of Electronic System Engineering Beijing China National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing Institute of Space Long March Vehicle Beijing China

ISBN: (纸本)9781839539954

In the study of the multi-UAV penetration mission decision method, the Heterogeneous Agent Soft Actor-Critic algorithm uses the HAML framework and the maximum entropy principle to enable UAVs to have stronger anti-jamming capability and exploration capability. However, it is difficult to accurately evaluate the action value of UAVs and the training stability is poor. To address this issue, this paper proposes a multi-agent based on the state prediction-HASAC(SP-HASAC) jamming decision method. Based on the idea of advantage function decomposition and environmental dynamics model, the state prediction network is designed to extract more abundant spatial information of penetration battlefield and achieve accurate evaluation of the action value of multi-UAV. Combining with the negative domain activation theory, the ReLU function is improved to realize the stable training of multi-UAV. The simulation results show that in the electronic penetration scenario of three UAVs against a single radar, the training convergence time of the proposed improved algorithm is reduced by 22% compared with the original algorithm. Three UAVs penetration to twice the burn-through distance still has more than 70% penetration success rate. © The Institution of Engineering & technology 2023.

关键词： Jamming

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Factors contributing to rapid decline of Arctic sea ice in autumn

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Advances in Polar science 2021年第2期32卷 96-104页

作者： LI Shuyao CUI Hongyan XU Junli GONG Xiang QIAO Fangli YANG Yanzhao WANG Ping HAN Yuqun SHAN Feng College of Mathematics and Physics Qingdao University of Science and TechnologyQingdao 266061China Research Institute for Mathematics and Interdisciplinary Sciences Qingdao University of Science and TechnologyQingdao 266061China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China The First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China

Autumn Arctic sea ice has been declining since the beginning of the era of satellite sea ice *** this study,we examined the factors contributing to the decline of autumn sea ice *** the Beaufort Sea to the Barents Sea,autumn sea ice concentration has decreased considerably between 1982 and 2020,and the rates of decline were the highest around the Beaufort *** calculated the correlation coefficients between sea ice extent(SIE)anomalies and anomalies of sea surface temperature(SST),surface air temperature(SAT)and specific humidity(SH).Among these coefficients,the largest absolute value was found in the coefficient between SIE and SAT anomalies for August to October,which has a value of−*** second largest absolute value was found in the coefficient between SIE and SH anomalies for September to November,which has a value of−*** the correlation coefficients between SIE and SST anomalies,the largest absolute value was found in the coefficient for August to October,which has a value of−*** conducted empirical orthogonal function(EOF)analyses of sea ice,SST,SAT,SH,sea level pressure(SLP)and the wind field for the months where the absolute values of the correlation coefficient were the *** first EOFs of SST,SAT and SH account for 39.07%,63.54%and 47.60%of the total variances,respectively,and are mainly concentrated in the area between the Beaufort Sea and the East Siberian *** corresponding principal component time series also indicate positive *** first EOF of SLP explains 41.57%of the total *** is mostly negative in the central *** the Beaufort,Chukchi and East Siberian seas,the zonal wind weakened while the meridional wind *** from the correlation and EOF analyses further verified the effects of the ice-temperature,ice-SH and ice-SLP feedback mechanisms in the *** mechanisms accelerate melting and decrease the rate of formation of sea *** addition,stronger m

关键词： Arctic sea ice rapid decline empirical orthogonal function feedback mechanisms

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