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Asian and Pacific Conference on Synthetic Aperture Radar (APSAR)

作者： Ying Zhang Wei Xiong Xichao Dong Cheng Hu Chengxiang Liu Yang Sun Science and Technology on Complex Electronic System Simulation Laboratory Space Engineering University Beijing China School of Information and Electronics Beijing Institute of Technology Beijing China

ISBN: (数字)9781728129129

ISBN: (纸本)9781728129136

In some case, the azimuth spectrum bandwidth is larger than the pulse repetition frequency (PRF), leading to a whole azimuth spectrum has been folded into multiple subsegments and aliased. Therefore, the traditional Doppler ambiguous integer estimation method cannot be used directly. In this paper, the influence of Doppler ambiguous integer on residual range migrations' slope is analyzed. Based on the slope, the Doppler ambiguous integer estimation method for moving targets with azimuth spectrum aliasing is given. From the simulation results, the Doppler ambiguous integer can be estimated accurately by proposed method.

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Radial Accelerated Velocity Estimation for Moving Ship Target Imaging based on GRFT in Geosynchronous SAR

Radial Accelerated Velocity Estimation for Moving Ship Targe...

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International Applied Computational Electromagnetics Society Symposium (ACES)

ISBN: (数字)9780996007894

ISBN: (纸本)9781728146331

GEO SAR has great potential in marine surveillance. But the extremely low SNR of echo, resulting in the traditional signal integration method become invalid. This paper proposes an improved GRFT-based approach to realize the moving ship targets' radial accelerated velocity estimation. Firstly, the accurate slant range is constructed which has considered the curved synthetic aperture trajectory. Then, the GRFT-based estimation method is redefined to realize radial accelerated velocity estimation and imaging. Finally, the simulation results are given to verify the proposed methods.

关键词： Acceleration Marine vehicles Synthetic aperture radar Estimation Imaging systems simulation Aerospace electronics

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Line-point feature based structure-preserving image stitching

Line-point feature based structure-preserving image stitchin...

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Chinese Automation Congress (CAC)

作者： Longyun Chi Xujun Guan Xiaorong Shen Hai Zhang School of Automation Science and Electrical Engineering Beihang University Beijing China Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing China

The naturalness of the panoramic image is an important criterion for evaluating the result of image stitching. When the overlapping region of the image has a low-texture area, the alignment is hard to accomplish due to incorrect and inadequate feature point matching pairs, and the salient structures are easily destroyed due to the unreasonable position of the optimal seam. To solve the problem, we use line segment matching information to assist the alignment of low-texture regions and use superpixel segmentation regions to filter the unreliable point correspondences. An improved seam-finding algorithm is finally used to blend images together. The experimental results demonstrate that the proposed method can get more natural stitching results.

关键词： Image segmentation Strain Feature extraction Information filters Matched filters Optimization

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Amorphous alloys surpass E/10 strength limit at extreme strain rates

arXiv

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arXiv 2021年

作者： Zhu, Wenqing Li, Zhi Shu, Hua Gao, Huajian Wei, Xiaoding State Key Laboratory for Turbulence and Complex System Department of Mechanics and Engineering Science College of Engineering Peking University Beijing100871 China School of Mechanical and Aerospace Engineering College of Engineering Nanyang Technological University 70 Nanyang Drive 637457 Singapore Shanghai Institute of Laser Plasma China Academy of Engineering Physics Shanghai201102 China Institute of High Performance Computing A*STAR 138632 Singapore Beijing Innovation Center for Engineering Science and Advanced Technology Peking University Beijing100871 China Peking University Nanchang Innovation Institute Nanchang330000 China

Theoretical predictions of the ideal strength of materials range from E/30 to E/10 (E is Young’s modulus). However, despite intense interest over the last decade, the value of the ideal strength that can be attained experimentally for metals remains a mystery (1-5). In this study, we demonstrated the unprecedented strength of an amorphous Cu-Zr alloy that surpassed the E/10 limit. Laser-induced shock experiments were conducted on Cu50Zr50 to explore its strength and failure mechanisms at ultrahigh strain rates. The material demonstrated a high spall strength of 9.8 GPa, approximately 1/13 of its P-wave modulus (~ E/6), at strain rates greater than 107 s−1, which sets a new record for the elastic limit of metallic materials. Electron microscopy and large-scale molecular dynamics simulations revealed that void nucleation and growth, not shear-banding, comprised the major failure mechanism for metallic glasses at extremely fast strain rates. A new model for void formation under the control of surface energy explained the rate dependence of the material strength. The results of this study reveal new possible ways to use the amorphous phase in nanostructured metals in future applications under demanding mechanical conditions. Copyright © 2021, The Authors. All rights reserved.

关键词： Copper alloys

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Research on the Radio Frequency Simulation Method for Wide-band Radar complex Target based on Physical Optics and Physical Diffraction Theory

Research on the Radio Frequency Simulation Method for Wide-b...

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

作者： Guijier, DIao Hong, Ni Tianming, Zhan Yajing, Zhang Liang, Yang Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing China Beijing Electro-mechanical Engineering Institute Beijing China Beijing Aerospace Smart Manufacturing Technology Development Co.Ltd. Beijing China Datang Mobile Communication Equipment Co. Ltd. Datang Telecom Group Beijing China

ISBN: (纸本)9781728123455

A radio frequency (RF) simulation technique based on high frequency hybrid method is proposed for complex target. Firstly, the radar cross section (RCS) of the target is obtained by vector addition of facets scattering field and wedges scattering field that are calculated respectively by physical optics (PO) method and physical theory of diffraction (PTD). Then, scattering centers of the target are extracted based on multi scattering center theory, and the radar echo signal is simulated through radio frequency simulation system (RFSS). This technique could improve the fidelity of radar signal simulation and the confidence of RF simulation test. At last, simulation results validate the technique. © 2019 IEEE.

关键词： Physical optics

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Optimal linear-quadratic guidance law considering autopilot first-order lag with terminal acceleration constraint

Optimal linear-quadratic guidance law considering autopilot ...

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Asia-Pacific International Symposium on Aerospace technology, APISAT 2018

作者： Zheng, Duo Xu, Xinghua Yan, Ruyi Lin, Defu Beijing Electro-Mechanical Engineering Institute Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing100074 China Beijing Institute of Automatic Control Equipment Beijing100074 China Unit 95806 PLA Air Force Beijing100070 China School of Aerospace Engineering Beijing Institute of Technology Beijing100081 China

ISBN: (纸本)9789811333040

In this paper, a new optimal linear-quadratic guidance law with terminal acceleration constraints is proposed for intercepting maneuvering target. Because the angle of attack is approximately proportional to the normal acceleration for aerodynamic control missile, not only miss distance, but also terminal acceleration is required to converge to zero for increasing effectiveness of the warhead for destroying armored target in the proposed guidance law. The gain characteristic of proposed guidance law is studied by comparing with traditional optimal guidance law with considering autopilot dynamics lags. Numerical simulations are performed to examine performance of the proposed optimal guidance law, and its robustness with respect to the time constant of autopilot dynamic lags is also studied by considering time constant typical errors. © Springer Nature Singapore Pte Ltd. 2019.

关键词： Angle of attack

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Time consistency technique of multi-aircrafts simulation system for cooperative mission

Time consistency technique of multi-aircrafts simulation sys...

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IEEE Conference on Industrial Electronics and Applications (ICIEA)

作者： Jian Han Hang Shi JiaHui Tong Qing Zhang Jing Li Beijing Electro-Mechanical Engineering Institute Beijing China Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing China

Aiming at the problem of time inconsistency problem exposed in multi-aircrafts simulation system during executing cooperative mission, a control solution of time consistency has been proposed to realize the unity of time information. On the basis of thoroughly analyzing the components and features of system, the factors that affect time synchronization are summarized and classified. After embedding a hardware of time synchronization system, a control solution is devised to maintain time consistency. Time synchronization and delay compensation are achieved from two aspects of hardware and software, which provides technical support for the following development and verification of cooperative control technology based on multiaircrafts simulation system.

关键词： Cascading style sheets Synchronization Delays Clocks Benchmark testing Delay effects

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DOUBLE PHASE IMPLICIT OBSTACLE PROBLEMS WITH CONVECTION AND MULTIVALUED MIXED BOUNDARY VALUE CONDITIONS

arXiv

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arXiv 2021年

作者： Zeng, Shengda Rǎdulescu, Vicenţiu D. Winkert, Patrick Guangxi Colleges Universities Key Laboratory of Complex System Optimization and Big Data Processing Yulin Normal University Guangxi Yulin537000 China Jagiellonian University in Krakow Faculty of Mathematics and Computer Science ul. Lojasiewicza 6 Krakow30-348 Poland Faculty of Applied Mathematics Agh University of Science and Technology Kraków30-059 Poland Department of Mathematics University of Craiova Craiova200585 Romania Technische Universität Berlin Institut für Mathematik Straße des 17. Juni 136 Berlin10623 Germany

In this paper we consider a mixed boundary value problem with a nonhomogeneous, nonlinear differential operator (called double phase operator), a nonlinear convection term (a reaction term depending on the gradient), three multivalued terms and an implicit obstacle constraint. Under very general assumptions on the data, we prove that the solution set of such implicit obstacle problem is nonempty (so there is at least one solution) and weakly compact. The proof of our main result uses the Kakutani-Ky Fan fixed point theorem for multivalued operators along with the theory of nonsmooth analysis and variational methods for pseudomonotone operators. Copyright © 2021, The Authors. All rights reserved.

关键词： Fixed point arithmetic

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Finite Time Cooperative Guidance Law for Multiple UAVs with Intermittent Communication Topologies

Finite Time Cooperative Guidance Law for Multiple UAVs with ...

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IEEE International Conference on Unmanned systems (ICUS)

作者： Teng LYU Cheng XU Hongchun LI Song HU Daochi ZHANG Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory Beijing China Beijing Electro-mechanical Engineering Institute Beijing China

ISBN: (纸本)9781728137933

To solve the problem of multiple Unmanned Aerial Vehicles (UAVs) with intermittent communication topologies simultaneously attack a stationary target, a time cooperative guidance law is studied in this paper. First, a novel time cooperative guidance model for multiple UAVs is constructed based on UAVs-target relative motion equations. Then, a cooperative guidance law is designed based on consensus theory, which can ensure multiple UAVs' impact times realize finite time consensus under intermittent topologies. After UAVs' impact times become to be the same, traditional PN guidance law is applied in all UAVs to guarantee that the UAVs can attack the target precisely without influencing the consensus of impact times. Finally, the validity of the proposed method is shown by numerical simulations.

关键词： Multiple UAVs Cooperative guidance Intermittent communication topologies Finite time consensus Unmanned Aerial Vehicle Guidance

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Resource Allocation for Threat Defense in Cyber-security IoT system

Resource Allocation for Threat Defense in Cyber-security IoT...

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International Conference on Wireless and Optical Communications ( WOCC)

作者： Manxi Wang Bingjie Liu Haitao Xu Electromagnetic Environment Effects on Electronics and Information System State Key Laboratory of Complex Luoyang China University of Science and Technology Beijing Beijing China

In this paper, we design a model for resource allocation in IoT system considering the cyber security, to achieve optimal resource allocation when defend the attack and threat. The resource allocation problem is constructed as a dynamic game, where the threat level is the state and the defend cost is the objective function. Open loop solution and feedback solutions are both given to the defender as the optimal control variables under different solutions situations. The optimal allocated resource and the optimal threat level for the defender is simulated through the numerical simulations.

关键词： Internet of Things Security Resource management Mathematical model Games Wireless communication Dynamic scheduling

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