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Chinese Automation Congress (CAC)

作者： Yuting Lu Peng Liu Tuo Han Qinglei Hu School of Automation Science and Electrical Engineering Beihang University Beijing China National Key Laboratory of Science and Technology on Test Physics & Numerical Mathematics Beijing Institute of Space Long March Vehicle Beijing China School of Aeronautic Science and Engineering Beihang University Beijing China Beihang Hangzhou Innovation Institute (Yuhang) Hangzhou China

In order to meet the requirement of accurate intercept against the increased target maneuverability and external disturbance, a second-order inertial delay based incremental guidance law (IDIASMG) is proposed for an exo-atmospheric interceptor. Specifically, a three-dimensional guidance model is transformed into an incremental version. As a guidance design benchmark, a conventional sliding mode guidance law (SMG) is presented, and a sliding mode incremental guidance law (ISMG) is designed with gain adaptation. Moreover, a second-order inertial delay filter is utilized to estimate and compensate guidance perturbation including the target maneuver, system uncertainty, and external disturbance. Theoretical analysis shows that the incremental guidance requires smaller gains to ensure smaller system residual than the conventional SMG. Extensive numerical simulations validate the effectiveness and robustness of IDIASMG.

关键词： Solid modeling Uncertainty Adaptive systems Upper bound Navigation Perturbation methods numerical simulation

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A unified back-projection correction algorithm for squint SAR based on SPECAN processing

A unified back-projection correction algorithm for squint SA...

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2019 IEEE International Conference on Signal, Information and Data Processing, ICSIDP 2019

作者： Wang, Chao Sun, Heng Zhang, Xin-Yu Zhang, Ran National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781728123455

The missile-borne or airborne synthetic aperture radar (SAR) usually adopts the squint mode and subaperture to satisfy maneuvering and the real-time processing. A realtime imaging algorithm of squint SAR based on SPECAN processing is presented. It has high computational efficiency in low resolution. A unified back-projection algorithm is proposed to solve the problem of fan-shaped distortion and geometric distortion. Simulation results validate the effectiveness of the proposed method. © 2019 IEEE.

关键词： Computational efficiency

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A Triple-layer Frequency Selective Surface with Flat Wide Passband 5

A Triple-layer Frequency Selective Surface with Flat Wide Pa...

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5th IEEE International Conference on Computational Electromagnetics, ICCEM 2019

作者： Cui, Yichun Zhang, Shengjun Wang, Mingliang National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

ISBN: (纸本)9781538671115

In this paper, a novel triple-layer band-pass Frequency selective surface (FSS) with wide passband and low insertion loss is proposed. The proposed FSS is composed of three FSS layers and two dielectric substrates which are symmetric vertically. This structure realizes a three-order response and wide stop band with steep falling edge. Equivalent circuit analysis indicates that the three-order response is generated by resonance of FSS layers and coupling between layers, respectively. After optimization, the passband of proposed FSS ranges from 7.728GHz to 12.31GHz, whose fractional bandwidth reaches 44.5% with -0.044dB insertion loss. Meanwhile, this FSS has stable performance for TE polarization under oblique incidence. © 2019 IEEE.

关键词： Frequency selective surfaces

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Graph-GIC: A Smart and Parallelized Geomagnetically Induced Current Modelling Algorithm Based on Graph Theory for Space Weather Applications

arXiv

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arXiv 2024年

作者： Chen, Wen Yuan, Ding Feng, Xueshang Poedts, Stefaan Zou, Zhengyang Feng, Song Zhu, Yuxuan Yin, Tong Shenzhen Key Laboratory of Numerical Prediction for Space Storm School of Aerospace Harbin Institute of Technology Guangdong Shenzhen518055 China Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing China Centre for Mathematical Plasma Astrophysics Department of Mathematics KU Leuven LeuvenB-3001 Belgium State Key Laboratory of Lunar and Planetary Sciences Macau University of Science and Technology China Faculty of Information Engineering and Automation Kunming University of Science and Technology Kunming650500 China Institute of Physics University of Maria Curie-Sklodowska ul. Marii Curie-Sklodowskiej 1 Lublin20-031 Poland

Geomagnetically Induced Current (GIC) refers to the electromagnetic response of the Earth and its conductive modern infrastructures to space weather and would pose a significant threat to high-voltage power grids designed for the alternative current operation. To assess the impact of space weather on the power grid, one needs to calculate the GIC on a national or continental scale. In this study, we developed a smart and parallelized GIC modelling algorithm, Graph GIC. This algorithm deploys a graph representing a power grid in a single-line diagram, in which substations/transformers act as nodes and transmission lines as edges. With these denotations, a power grid and its electric parameters are mathematically represented with an adjacency matrix and an admittance matrix. We used sparse matrix and parallelisation techniques to expedite the intensive computation in cases of large-scale power grids. The Graph GIC was validated with a benchmark grid, applied to the GIC calculation of the 500 kV power grid of Guangdong, China, and conducted preliminary analysis on the grid’s susceptibility to geomagnetic storms. The Graph GIC algorithm has the advantage of an intuitive and highly scalable graph representation of a power grid at any scale. It achieves high-accuracy calculation and a speedup of about 18 times after parallelisation. This algorithm could be applied to assess the impact of space weather on a power grid up to continental scales and could be incorporated into global space weather modelling frameworks. Copyright © 2024, The Authors. All rights reserved.

关键词： Matrix algebra

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Resolved magnetohydrodynamic wave lensing in the solar corona

arXiv

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arXiv 2024年

作者： Zhou, Xinping Shen, Yuandeng Yuan, Ding Keppens, Rony Zhao, Xiaozhou Fu, Libo Tang, Zehao Wang, Jiaoyang Zhou, Chengrui College of Physics and Electronic Engineering Sichuan Normal University Chengdu610068 China Yunnan Observatories Chinese Academy of Sciences Kunming650216 China Shenzhen Key Laboratory of Numerical Prediction for Space Storm Institute of Space Science and Applied Technology Harbin Institute of Technology Guangdong Shenzhen China Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing China Centre for mathematical Plasma Astrophysics Department of Mathematics KU Leuven Celestijnenlaan 200B LeuvenB-3001 Belgium

Electromagnetic wave lensing, a common physical phenomenon recognized in visible light for centuries, finds extensive applications in manipulating light in optical systems such as telescopes and cameras. Magnetohydrodynamic wave is a common perturbation phenomenon in the corona. By using high spatio-temporal resolution observations from the Solar Dynamics Observatory, here, we report the observation of a magnetohydrodynamic wave lensing in the highly ionized and magnetized coronal plasma, where quasi-periodic wavefronts emanated from a flare converged at a specific point after traversing a coronal hole. The entire process resembles an electromagnetic wave lensing from the source to the focus. Meanwhile, the magnetohydrodynamic wave lensing is well reproduced through a magnetohydrodynamic numerical simulation with full spatio-temporal resolution. We further investigate potential applications for coronal seismology, as the lensing process encodes information on the Alfvén speed, in conjunction with favorable geometric and density variations. Copyright © 2024, The Authors. All rights reserved.

关键词： Electromagnetic waves

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南大洋增暖及其气候影响

引用

science Bulletin 2023年第9期68卷 946-960,M0004页

作者：蔡文炬高立宝罗义勇李熙晨郑小童张学斌程旭华贾凡 Ariaan Purich Agus Santoso 杜岩 David MHolland 石佳睿项宝强谢尚平 Frontiers Science Center for Deep Ocean Multispheres and Earth System and Key Laboratory of Physical Oceanography Ocean University of ChinaQingdao 266100China Laboratory for Ocean and Climate Dynamics Pilot National Laboratory for Marine Science and TechnologyQingdao 266237China Center for Southern Hemisphere Oceans Research Commonwealth Scientific and Industrial Research Organisation(CSIRO)Oceans and AtmosphereHobart 7004Australia First Institute of Oceanography and Key Laboratory of Marine Science and Numerical Modeling Ministry of Natural ResourcesQingdao 266061China Laboratory for Regional Oceanography and Numerical Modeling Pilot National Laboratory for Marine Science and TechnologyQingdao 266237China Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China College of Oceanography Hohai UniversityNanjing 210098China Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of SciencesQingdao 266071China Climate Change Research Centre University of New South WalesSydney 2052Australia Australian Research Council Centre of Excellence for Climate Extremes University of New South WalesSydney 2052Australia State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory Guangzhou 511458China Courant Institute of Mathematical Sciences New York UniversityNew York NY 10012USA Woods Hole Oceanographic Institution Woods Hole MA 02543USA NOAA/Geophysical Fluid Dynamics Laboratory Princeton NJ 08540USA University Corporation for Atmospheric Research Boulder CO 80307USA Scripps Institution of Oceanography University of California San DiegoLa Jolla CA 92093USA

过去几十年南大洋在南极平流层臭氧消耗和大气二氧化碳浓度增加的共同作用下大幅增暖,显著影响着南极冰架和冰盖的融化、海平面上升、南北半球的降水分配以及热带海洋和大气环流等,引发了深远的气候效应.全球变暖背景下南大洋西风表现... 详细信息

过去几十年南大洋在南极平流层臭氧消耗和大气二氧化碳浓度增加的共同作用下大幅增暖,显著影响着南极冰架和冰盖的融化、海平面上升、南北半球的降水分配以及热带海洋和大气环流等,引发了深远的气候效应.全球变暖背景下南大洋西风表现为极向加强,同时进入南大洋的热辐射和淡水通量持续增加,由此上翻的海水可吸收更多的热量和碳,经由更强的平均流向北输送,更多地在45°S附近海域下沉并存储.当前对南大洋增暖背后诸多复杂的物理过程仍缺乏足够的理解,比如来自冰架、冰盖及海洋涡旋的作用、热带-极地相互作用、南大洋本身对全球变暖的响应等,尤其是有限的观测数据和较低分辨率的模式无法准确呈现快速变化的物理现象和机理.因此,南大洋的未来增暖存在很大的不确定性且可能长期持续,但近期的进展为深入认知南大洋增暖及其气候影响奠定了坚实的基础.

关键词：平流层臭氧南大洋物理现象物理过程全球变暖热带海洋南北半球低分辨率

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Diagnostics of the solar coronal plasmas by magnetohydrodynamic waves: Magnetohydrodynamic seismology

arXiv

引用

arXiv 2024年

作者： Nakariakov, Valery M. Zhong, Sihui Kolotkov, Dmitrii Y. Meadowcroft, Rebecca L. Zhong, Yu Yuan, Ding Centre for Fusion Space & Astrophysics Department of Physics University of Warwick CoventryCV4 7AL United Kingdom " Ventspils University of Applied Sciences VentspilsLV-3601 Latvia Shenzhen Key Laboratory of Numerical Prediction for Space Storm Harbin Institute of Technology Shenzhen Guangdong518055 China Key Laboratory of Solar Activity and Space Weather National Space Science Center Chinese Academy of Sciences Beijing100190 China

Macroscopic wave and oscillatory phenomena ubiquitously detected in the plasma of the corona of the Sun are interpreted in terms of magnetohydrodynamic theory. Fast and slow magnetoacoustic waves are clearly distinguished in observations. Properties of coronal magnetohydrodynamic waves are determined by local parameters of the plasma, including the field-aligned filamentation typical for the corona. It makes coronal magnetohydrodynamic waves reliable probes of the coronal plasma structures by the method of magnetohydrodynamic seismology. For example, propagating slow waves indicate the local direction of the guiding magnetic field. Standing, sloshing and propagating slow waves can be used for probing the coronal heating function and the polytropic index. Kink oscillations of coronal plasma loops provide us with the estimations of the absolute value of the magnetic field in oscillating plasma loops. This tutorial introduces several techniques of magnetohydrodynamic seismology of solar coronal plasmas. It includes the description of practical steps in the data acquisition, pre-processing, and processing using the open-access data of the Atmospheric Imaging Assembly on the Solar Dynamics Observatory spacecraft, and elaborated data analysis techniques of motion magnification and Bayesian statistics. © 2024, CC BY-NC-ND.

关键词： Seismology

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Research on dual-polarisation printed dipole antenna for spherical near-field measurements

Research on dual-polarisation printed dipole antenna for sph...

引用

IET International Radar Conference 2018, IRC 2018

作者： Zheng, Pei Liu, JiaQi Wang, ShangYue Zhang, Ran Fan, Hu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

Here a dual-polarisation printed dipole antenna for spherical near-field measurements is proposed. The printed dipole employs double-layered structure to obtain low cross-polarisation and uses irregular patch to get wide bandwidth. Two such dipoles are cross arranged to form a dual-polarisation dipole antenna. Simulated results show that the bandwidth is over 72% when VSWR is less than 3, the cross-polarisation ratio is better than 30 dB, the port isolation between two dipoles is better than −26 dB, while good radiation performance is also obtained. All the results above prove that the crossed arrangement structure will not affect the performance of the printed dipole, and the strength of mutual coupling between probes can be neglected. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Dipole antennas

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Research on near-field focusing algorithm of reconfigurable reflect-array

Research on near-field focusing algorithm of reconfigurable ...

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IET International Radar Conference 2018, IRC 2018

作者： Liu, Hong Yan Zheng, Pei Wang, Chao Guo, Lei Zhang, Xin Yu National Key Laboratory of Science and Technology on Test Physics and Numerical Mathematics Beijing China

In this study, the near-field beam focusing algorithm of reconfigurable reflect array for security imaging application is proposed. The proposed near-field focusing algorithm is based on classic array method, which is usually adopted for far-field pattern calculation. In order to satisfy the near-field imaging application, the imaging distance is added to array method, and the improved formula can calculate the shifting phase of every array element precisely. In addition, due to discrete phase characteristic of reconfigurable reflect array, a phase choice method based on trigonometric function is used in authors' design. Based on the proposed algorithm, the shifting phase of every element is calculated and obtained the simulated beam focusing patterns. Meanwhile, the calculated shifting phase is written to whole array by field-programmable gate array, the near-field beam scanning patterns is measured and the measured results are in good agreement with the simulated ones. © 2019 Institution of Engineering and technology. All rights reserved.

关键词： Field programmable gate arrays (FPGA)

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Four-Fold Composite Structures and Triple Coherent Interfaces Endow Exceptional Mechanical Properties of an Fecrnialti High-Entropy Alloy

SSRN

引用

SSRN 2024年

作者： Wen, Donghui Jiang, Beibei Gao, Mengqi Huang, Zhaowen Kong, Fengyu Wang, Anding Wang, Qing Wang, Biao Liu, Chain-Tsuan Research Institute of Interdisciplinary Science School of Materials Science and Engineering Dongguan University of Technology Dongguan523808 China Analysis and Test Center Guangdong University of Technology Guangzhou510006 China Xinjiang Key Laboratory of Solid State Physics and Devices School of Physical Science and Technology Xinjiang University Ürümqi830046 China Hong Kong Institute for Advanced Study Mechanical Behavior Division Shenyang National Laboratory for Materials Science City University of Hong Kong Hong Kong School of Materials Science and Engineering Dalian University of Technology Dalian116024 China Department of Materials Science and Engineering China Sino-French Institute of Nuclear Engineering and Technology China

Introducing additional phases and constructing composite structures in BCC-based high-entropy alloys (HEAs) have recently been a hot spot for synergistically enhancing the strength and ductility at room and elevated temperatures. Here, we report a novel cost-efficiency (FeCrNi)85(AlTi)15 HEA that composed of four-fold composite structures with triple BCC/L21, L21/BCC and FCC/L12 coherent interfaces. The rationally introduction of ductile FCC phase in brittle BCC and L21 phases endows this composite alloy with an exceptional compressive plasticity of 37% at room-temperature. The well-controlled L21, BCC and L12 nano-particles coherently precipitate in BCC, L21 and FCC matrix phases, respectively, resulting in the super-high strength of 1850 MPa, outperforming other B2/L21-strengthened BCC HEAs. The triple coherent interfaces stabilize the composite microstructures and lead to the excellent yield strength at elevated temperatures (850 MPa at 700 °C, 395 MPa at 800 °C and 190 MPa at 900 °C). It is found that the FCC/L12 and L21/BCC composite phases can exhibit a high thermal stability even at 900 °C, which can partially compensate the strength decline from BCC/L21 phase dynamic recrystallization. These results obtain a new strategy for overcoming the drawback of inadequate deformability in BCC-based alloys and developing new composite materials for high-temperature applications. © 2024, The Authors. All rights reserved.

关键词： Precipitation (chemical)

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