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IET International Radar Conference 2015

作者： Ai, Xia Zhang, Shengjun Wang, Mingliang Wang, Weidong Liu, Jiaqi Liu, Chengguo Liu, Xuemei National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical China

ISBN: (纸本)9781849199940

In this paper, a higher-order shift operater (SO) FDTD scheme with second-order accuracy in time and fourth-order in space has been proposed to accurately model scattering of perfect electronic conductor coated with cloaking structures. Several different electromagnetic parameters of the cloaks are taken into account using SO-FDTD method. numerical results indicate that the proposed method is more accuracy than the traditioinal method maintaining the same grid size. Scattering of different kinds of simplified cylindrical cloaks including thickness and loss are presented and could be served as further study on this subject.

关键词： Finite difference time domain method

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A New Formation Mechanism of Counterstreaming Mass Flows in Filaments and the Doppler Bullseye Pattern in Prominences

arXiv

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arXiv 2025年

作者： Zhou, Chengrui Shen, Yuandeng Xia, Chun Liu, Dongxu Tang, Zehao Yao, Surui Yunnan Observatories Chinese Academy of Sciences Kunming650216 China School of Aerospace Harbin Institute of Technology Shenzhen518055 China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of Technology Shenzhen518055 China State Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing100190 China School of Physics and Astronomy Yunnan University Kunming650500 China University of Chinese Academy of Sciences Beijing100049 China

The eruption of solar prominences can eject substantial mass and magnetic field into interplanetary space and cause geomagnetic storms. However, various questions about prominences and their eruption mechanism remain unclear. In particular, what causes the intriguing Doppler bullseye pattern in prominences has not yet been solved, despite some preliminary studies proposing that they are probably associated with counterstreaming mass flows. Previous studies are mainly based on single-angle and short timescale observations, making it difficult to determine the physical origin of Doppler bullseye patterns in prominences. Here, taking advantage of stereoscopic observations taken by the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory and a three-dimensional numerical simulation, we investigate the origin of prominence Doppler bullseye pattern by tracing a long-lived transequatorial filament/prominence from July 23 to August 4, 2012. We find that repeated coronal jets at one end of the prominence can launch the Doppler bullseye pattern. It is evidenced in our observations and simulation that during the forward traveling of jet plasma along the helical magnetic field structure of the prominence, part of the ejecting plasma can not pass through the apex of the prominence due to the insufficient kinetic energy and therefore forms a backward-moving mass flow along the same or neighboring magnetic field lines. This process finally forms counterstreaming mass flows in on-disk filaments. When the on-disk filament rotates to the solar limb to be a prominence, the counterstreaming mass flows are naturally observed as a Doppler bullseye pattern. Copyright © 2025, The Authors. All rights reserved.

关键词： Plasma magnetohydrodynamic waves

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The research on the effects of an active FSS with circle element on the characteristics of Radar Absorbing Materials

The research on the effects of an active FSS with circle ele...

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IET International Radar Conference 2015

作者： Wang, Ming-Liang Zhang, Sheng-Jun Liu, Jia-Qi Wang, Wei-Dong Ai, Xia Liu, Shengdong Liang, Wei National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing China

ISBN: (纸本)9781849199940

An active frequency selective surface (FSS) is designed, and is combined with Radar Absorbing Materials to form a composite absorbing structure. Based on the equivalent theory that the PIN diode can be regarded as resistance, the voltage-loading resistance of active FSS element is researched for RAM containing FSS, and the electromagnetic wave reflectivity performance is analyzed. The influence of active FSS design parameters on the reflectivity of RAM is researched, and the FSS design parameters include the voltage-loading manner, the resistance parameter, and the position in the RAM. The research result shows that the resonance frequency of RAM containing FSS can be dynamically adjusted from 3GHz to 4GHz by changing voltage-loading resistance of active FSS, and the reflectivity can be reduced from -13dB to -35dB.

关键词： Reflection

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Study on reflection selective structure on near infrared

Study on reflection selective structure on near infrared

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International Conference on Electronics and Optoelectronics

作者： Li, Yizhou Wang, Daorong Liu, Jiaqi Li, Hongjie Zhao, Juyan National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing China

ISBN: (纸本)9781612842738

The paper bring forward a design of multilayer structure which has a high reflectivity for 1.82μm laser beam and a high absorptivity for 1.48μm laser beam. The experiment reveal that the absorptivity of the film reach to 95% at incidence angle from 0 to 40 for 1.48μm laser beam and has a high reflectivity for 1.82μm high power laser at incidence angle of 30o at laser power density above 500w/cm2. © 2011 IEEE.

关键词： Reflection

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Unmanned aerial vehicle infrared detector simulation modelling and performance analysis

Unmanned aerial vehicle infrared detector simulation modelli...

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2017 IASTED International Conference on Modelling, Identification and Control, MIC 2017

作者： Liu, Fang Liu, Xin Liu, Jiaqi National Key Laboratory of Science and Technology On Test Physics and Numerical Mathematics Nandahongmen Road No.1 Beijing China

ISBN: (纸本)9780889869882

An observation model of unmanned aerial vehicle(UAV) infrared detector is developed. The visibility criterion is derived via geometric relationships between the infrared detector, target and earth, the constraint of the detector's frame angle, and the detection range of infrared detector. Because of the infrared sensor can only obtain the angular information of the target, so it is impossible for one detector to locate position of the target. The position of the target is obtained by two or more detectors. The least square method based multi-sensor target tracking method is introduced. It is important to set a filter before using the tracking data as there are observation errors caused by UAV position error, UAV attitude error, sensor pointing error and sensor image plane position error. The extend Kalman Filter (EKF) algorithm is used to smooth the tracking signals. Finally, two UAV infrared detectors observing a low-orbit target is simulated for their observation performance. The result shows that the infrared detectors can observe the target within the scope of the detection range. When the target flies off the top of the UAV, the detectors can't observe it because of the constraint of the frame angle. The observation error is reduced substantially after the EKF is used.

关键词： Infrared detectors

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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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2022 International Applied Computational Electromagnetics Society Symposium, ACES-China 2022

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

ISBN: (纸本)9781665452366

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. © 2022 IEEE.

关键词： Radar cross section

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China's promotion on space security and safety 66

China's promotion on space security and safety

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66th International Astronautical Congress 2015: Space - The Gateway for Mankind's Future, IAC 2015

作者： Zhang, Shengjun Liu, Jiaqi Liu, Xin China Academy of Launch Vehicle Technology National Key Laboratory on Test Physics and Numerical Mathematics China

ISBN: (纸本)9781510818934

As the development of the activities in space, militarization on space and space debris bring more and more risks and danger to the world. It is a worldwide problem to keep space in a security and safety situation. With years of development in astronautics, more and more space activities actualized in China as well as the cooperation on space items between China and many other countries, both academic groups and government of China now pay more attentions on the activities itself and the space environment for peace use of space and the convenient life in the information days. Many researches have been sponsored by the government in recent three decades. There are two types of research groups, including the academic part (such the professors and their students) and space organizations, concerning on topics such as legal affairs, space debris and other. The study of these groups as well as their cooperation with international groups contributed much to concerning and the decision-making of the government, even leading to the TCBM and PPWT.

关键词： Space debris

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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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2012 International Workshop on Metamaterials, Meta 2012

作者： Wang, Ming-Liang Zhang, Sheng-Jun Liu, Jia-Qi Liang, Wei Liu, Xue-Mei Liang, X.W. National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical BeiJing 100076 China

ISBN: (纸本)9781467328081

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. © 2012 IEEE.

关键词： Frequency selective surfaces

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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： Wu, Runhui Liu, Jiaqi Liu, Xin Meng, Gang Ren, Aimin Qi, Zhaohui National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematical Beijing100076 China

ISBN: (纸本)9781849199940

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： Radar cross section

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Generative Decoding for Quantum Error-correcting Codes

arXiv

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arXiv 2025年

作者： Cao, Hanyan Pan, Feng Feng, Dongyang Wang, Yijia Zhang, Pan CAS Key Laboratory for Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Centre for Quantum Technologies National University of Singapore 117543 Singapore Science Mathematics and Technology Cluster Singapore University of Technology and Design 8 Somapah Road 487372 Singapore School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced Study UCAS Hangzhou310024 China

Efficient and accurate decoding of quantum error-correcting codes is essential for fault-tolerant quantum computation, however, it is challenging due to the degeneracy of errors, the complex code topology, and the large space for logical operators in high-rate codes. In this work, we propose a decoding algorithm utilizing generative modeling in machine learning. We employ autoregressive neural networks to learn the joint probability of logical operators and syndromes in an unsupervised manner, eliminating the need for labeled training data. The learned model can approximately perform maximum likelihood decoding by directly generating the most likely logical operators for k logical qubits with O(2k) computational complexity. Thus, it is particularly efficient for decoding high-rate codes with many logical qubits. The proposed approach is general and applies to a wide spectrum of quantum error-correcting codes including surface codes and quantum low-density parity-check codes (qLDPC), under noise models ranging from code capacity noise to circuit level noise. We conducted extensive numerical experiments to demonstrate that our approach achieves significantly higher decoding accuracy compared to the minimum weight perfect matching and belief propagation with ordered statistics on the surface codes and high-rate quantum low-density parity-check codes. Our approach highlights generative artificial intelligence as a potential solution for the real-time decoding of realistic and high-rate quantum error correction codes. © 2025, CC BY.

关键词： Qubits

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