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arXiv 2019年

作者： Yu, Zhou Cui, Yuhao Yu, Jun Tao, Dacheng Tian, Qi Key Laboratory of Complex Systems Modeling and Simulation School of Computer Science and Technology Hangzhou Dianzi University China UBTECH Sydney AI Centre School of Computer Science Faculty of Engineering University of Sydney Australia Noah's Ark Lab Huawei China

Learning an effective attention mechanism for multimodal data is important in many vision-and-language tasks that require a synergic understanding of both the visual and textual contents. Existing state-of-the-art approaches use co-attention models to associate each visual object (e.g., image region) with each textual object (e.g., query word). Despite the success of these co-attention models, they only model inter-modal interactions while neglecting intra-modal interactions. Here we propose a general 'unified attention' model that simultaneously captures the intra- and inter-modal interactions of multimodal features and outputs their corresponding attended representations. By stacking such unified attention blocks in depth, we obtain the deep Multimodal Unified Attention Network (MUAN), which can seamlessly be applied to the visual question answering (VQA) and visual grounding tasks. We evaluate our MUAN models on two VQA datasets and three visual grounding datasets, and the results show that MUAN achieves top level performance on both tasks without bells and whistles. Copyright © 2019, The Authors. All rights reserved.

关键词： Deep learning

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Directed momentum current induced by the PT-symmetric driving

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Physical Review E 2019年第4期99卷 042201-042201页

作者： Wen-Lei Zhao Jiaozi Wang Xiaohui Wang Peiqing Tong School of Science Jiangxi University of Science and Technology Ganzhou 341000 China Department of Modern Physics University of Science and Technology of China Hefei 230026 China School of Information Engineering Jiangxi University of Science and Technology Ganzhou 341000 China Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing 210023 China Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing Jiangsu 210023 China

We investigate the directed momentum current in the quantum kicked rotor model with PT-symmetric deriving potential. For the quantum nonresonance case, the values of quasienergy become complex when the strength of the imaginary part of the kicking potential exceeds a threshold value, which demonstrates the appearance of the spontaneous PT symmetry breaking. In the vicinity of the transition point, the momentum current exhibits a staircase growth with time. Each platform of the momentum current corresponds to the mean momentum of some eigenstates of the Floquet operator whose imaginary parts of the quasienergy are significantly large. Above the transition point, the momentum current increases linearly with time. Interestingly, its acceleration rate exhibits a kind of “quantized” increment with the kicking strength. We propose a modified classical acceleration mode of the kicked rotor model to explain such an intriguing phenomenon. Our theoretical prediction is in good agreement with numerical results.

关键词： Coherent control Cold atoms & matter waves Light-matter interaction Wave chaos

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Ellipticity control of terahertz high-harmonic generation in a Dirac semimetal

arXiv

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arXiv 2022年

作者： Germanskiy, Semyon Dantas, Renato M.A. Kovalev, Sergey Reinhoffer, Chris Mashkovich, Evgeny A. van Loosdrecht, Paul H.M. Yang, Yunkun Xiu, Faxian Surówka, Piotr Moessner, Roderich Oka, Takashi Wang, Zhe Institute of Physics II University of Cologne Cologne50937 Germany Max Planck Institute for the Physics of Complex Systems Dresden01187 Germany Department of Physics University of Basel Basel4056 Switzerland Institute of Radiation Physics Helmholtz-Zentrum Dresden-Rossendorf Dresden01328 Germany State Key Laboratory of Surface Physics Department of Physics Fudan University Shanghai China Shanghai Qi Zhi Institute No. 701 Yunjin Road Xuhui District Shanghai200232 China Department of Theoretical Physics Wroclaw University of Science and Technology Wroclaw50-370 Poland Institute for Theoretical Physics University of Amsterdam Amsterdam1090 GL Netherlands University of Amsterdam Amsterdam1090 GL Netherlands The Institute for Solid State Physics The University of Tokyo Chiba Kashiwa277-8581 Japan Max Planck Institute for Chemical Physics of Solids Dresden01187 Germany Department of Physics TU Dortmund University Dortmund44227 Germany

We report on terahertz high-harmonic generation in a Dirac semimetal as a function of the driving-pulse ellipticity and on a theoretical study of the field-driven intraband kinetics of massless Dirac fermions. Very efficient control of third-harmonic yield and polarization state is achieved in electron-doped Cd3As2 thin films at room temperature. The observed tunability is understood as resulting from terahertz-field driven intraband kinetics of the Dirac fermions. Our study paves the way for exploiting nonlinear optical properties of Dirac matter for applications in signal processing and optical communications. Copyright © 2022, The Authors. All rights reserved.

关键词： Nonlinear optics

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Hazard-evaluation-oriented Moving Horizon Parallel Steering Control for Driver-Automation Collaboration During Automated Driving

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IEEE/CAA Journal of Automatica Sinica 2018年第6期5卷 1062-1073页

作者： Hongyan Guo Linhuan Song Jun Liu Fei-Yue Wang Dongpu Cao Hong Chen Chen Lv Partick Chi-Kwong Luk State Key Laboratory of Automotive Simulation and Control and the Department of Con-trol Science and Engineering Jilin University(Campus Nanling)Changchun130025China State Key Laboratory of Management and Control for Complex Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China Research Center for Military Computational Experiments and Parallel Systems Technology National University of Defense TechnologyChangsha 410073China Mechanical and Mechatronics Engineering Department at the University ot Waterloo 200 University Avenue West WaterlooONNZL3G1Canada Department of Automotive Engineering Cranfield UniversityBedfordshire MK43 0ALUK School of Water Energy and EnvironmentCranfield UniversityBedfordshire MK43 0ALUK

Prompted by emerging developments in connected and automated vehicles, parallel steering control, one aspect of parallel driving, has become highly important for intelligent vehicles for easing the burden and ensuring the safety of human drivers. This paper presents a parallel steering control framework for an intelligent vehicle using moving horizon *** framework considers lateral stability, collision avoidance and actuator saturation and describes them as constraints, which can blend the operation of a human driver and a parallel steering controller effectively. Moreover, the road hazard and the steering operation error are employed to evaluate the operational hazardous of an intelligent vehicle. Under the hazard evaluation,the intelligent vehicle will be mainly operated by the human driver when the vehicle operates in a safe and stable *** automated steering driving objective will play an active role and regulate the steering operations of the intelligent vehicle based on the hazard evaluation. To verify the effectiveness of the proposed hazard-evaluation-oriented moving horizon parallel steering control approach, various validations are conducted, and the results are compared with a parallel steering scheme that does not consider automated driving situations. The results illustrate that the proposed parallel steering controller achieves acceptable performance under both conventional conditions and hazardous conditions.

关键词： Hazard evaluation intelligent vehicle atera stability moving horizon optimization paralle steering control

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Singularity structure simplification of hexahedral mesh via weighted ranking

arXiv

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arXiv 2019年

作者： Xua, Gang Ling, Ran Zhang, Yongjie Jessica Xiao, Zhoufang Ji, Zhongping Rabczuk, Timon School of Computer Science and Technology Hangzhou Dianzi University Hangzhou310018 China Key Laboratory of Complex Systems Modeling and Simulation Ministry of Education Hangzhou310018 China Department of Mechanical Engineering Carnegie Mellon University United States Institute of Structural Mechanics Bauhaus-Universitat Weimar Germany

In this paper, we propose an improved singularity structure simplification method for hexahedral (hex) meshes using a weighted ranking approach. In previous work, the selection of to-be-collapsed base complex sheets/chords is only based on their thickness, which will introduce a few closed-loops and cause an early termination of simplification and a slow convergence rate. In this paper, a new weighted ranking function is proposed by combining the valence prediction function of local singularity structure, shape quality metric of elements and the width of base complex sheets/chords together. Adaptive refinement and local optimization are also introduced to improve the uniformity and aspect ratio of mesh elements. Compared to thickness ranking methods, our weighted ranking approach can yield a simpler singularity structure with fewer base-complex components, while achieving comparable Hausdorff distance ratio and better mesh quality. Comparisons on a hex-mesh dataset are performed to demonstrate the effectiveness of the proposed method. Copyright © 2019, The Authors. All rights reserved.

关键词： Aspect ratio

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Dynamical energy equipartition of the Toda model with additional on-site potentials

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Chinese Physics B 2017年第10期26卷 107-111页

作者：张振俊唐春梅康静童培庆 College of Science Hohai University School of Physics and Technology Nanjing Normal University Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University

We study the dynamical energy equipartition properties in the integrable Toda model with additional uniform or disordered on-site energies by extensive numerical simulations. The total energy is initially equidistributed among some of the lowest frequency linear modes. For the Toda model with uniform on-site potentials, the energy spectrum keeps its profile nearly unchanged in a relatively short time scale. On a much longer time scale, the energies of tail modes increase slowly with time. Energy equipartition is far away from being attached in our studied time scale. For the Toda model with disordered on-site potentials, the energy transfers continuously to the high frequency modes and eventually towards energy equipartition. We further perform a systematic study of the equipartition time teq depending on the energy density ε and the nonlinear parameter α in the thermodynamic limit for the Toda model with disordered on-site potentials. We find teq∝ （1/ε）^a（1/α）^b, where b≈ 2a. The values of a and b are increased when increasing the strengths of disordered on-site potentials or decreasing the number of initially excited modes.

关键词： energy transport behaviors Toda model uniform or disordered on-site potentials

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A distributed MIMO radar oriented barrage jamming strategy

A distributed MIMO radar oriented barrage jamming strategy

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Signal, Information and Data Processing (ICSIDP), IEEE International Conference on

作者： Guangyong Zheng Siqi Na Tianyao Huang Lulu Wang State Key Laboratory of Complex Electromagnetic Environment Effects on Electronic Information Systems (CEMEE) Luoyang China Tsinghua University Beijing China Artificial Intelligence Research Center National Innovation Institute of Defense Technology Academy of Military Science Beijing China

ISBN: (数字)9781728123455

ISBN: (纸本)9781728123462

Distributed multiple input multiple output (MIMO) radar has attracted much attention for its improved detection and estimation performance as well as enhanced Electronic Counter-Counter Measures (ECCM) ability. In order to protect the target from being detected and tracked by such radar, we consider a barrage jamming strategy orienting towards a distributed MIMO. We first derive the Cramer-Rao bound (CRB) of target parameters estimation using a distributed MIMO under barrage jamming environments. We then set maximizing the CRB as the criterion for jamming resource allocation, aiming at degrading the accuracy of target parameters estimation. Particle swarm optimization is utilized to solve the maximizing problem. simulation results demonstrate the advantages of the the proposed strategy over traditional jamming methods.

关键词： Barrage jamming Distributed MIMO radar Cramer-Rao bound Cramer-Rao bounds MIMO radar complementary return to bias multiple input multiple output systems Parameter estimation Distribute Targets radar jamming

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Distributed circle formation control over directed networks with communication constraints ⁎

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IFAC-PapersOnLine 2019年第3期52卷 108-113页

作者： Peng Xu Jiayan Wen Chen Wang Guangming Xie College of Electrical and Information Engineering Guangxi University of Science and Technology Liuzhou 545006 China National Engineering Research Center for Software Engineering Peking University Beijing 100871 China The State Key Laboratory of Turbulence and Complex Systems Intelligent Biomimetic Design Lab College of Engineering Peking University Beijing100871 China

This paper investigates distributed circle formation problems of multi-agent systems (MAS) subject to limited information communication under a class of weight-unbalanced directed graphs, in which the communication topology contains a directed spanning tree and each agent can only perceive the distances from itself to the nearest neighbor in counterclockwise direction as well as the counterpart in the clockwise direction. Towards this end, a novel algorithm combined with an encoder-decoder framework has been proposed. We show that, under the proposed policy, the resulting network executions can drive the states of all mobile agents to converge to some expected equilibrium point. Numerical simulation results have been given to demonstrate the effectiveness of the proposed algorithm.

关键词： Multi-agent systems Communication Bandwidth Directed Network Circle Formation Control

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Directed momentum current induced by the PT -symmetric driving

arXiv

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arXiv 2019年

作者： Zhao, Wen-Lei Wang, Jiaozi Wang, Xiaohui Tong, Peiqing School of Science Jiangxi University of Science and Technology Ganzhou341000 China Department of Modern Physics University of Science and Technology of China Hefei230026 China School of Information Engineering Jiangxi University of Science and Technology Ganzhou341000 China Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing Jiangsu210023 China

We investigate the directed momentum current in the quantum kicked rotor model with PT symmetric deriving potential. For the quantum non-resonance case, the values of quasi-energy become to be complex when the strength of imaginary part of the kicking potential exceeds a threshold value, which demonstrates the appearance of the spontaneous PT symmetry breaking. In the vicinity of the transition point, the momentum current exhibits a staircase growth with time. Each platform of the momentum current corresponds to the mean momentum of some eigenstates of the Floquet operator whose imaginary parts of the quasi-energy are significantly large. Above the transition point, the momentum current increases linearly with time. Interestingly, its acceleration rate exhibits a kind of "quantized" increment with the kicking strength. We propose a modified classical acceleration mode of the kicked rotor model to explain such an intriguing phenomenon. Our theoretical prediction is in good agreement with numerical results. Copyright © 2019, The Authors. All rights reserved.

关键词： Momentum

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HeROS: A simulation platform for heterogeneous robotic swarms

HeROS: A simulation platform for heterogeneous robotic swarm...

引用

第三十八届中国控制会议

作者： Shuai Li Yuanfang Wan Pengzhou He Chen Wang Jinan Sun Yanling Zhang Xuyang Li Guangming Xie The State Key Laboratory of Turbulence and Complex Systems Intelligent Biomimetic Design Lab College of Engineering Peking University School of Automation and Electrical Engineering University of Science and Technology Beijing National Engineering Research Center for Software Engineering Peking University Xi'an Bibang Intelligent Technology Co. Ltd.

This paper presents HeROS, which is a novel simulation platform for heterogeneous robotic swarms. Compared with some existing simulation platforms, our HeROS(Heterogeneous Robotic Swarms simulation) platform is more efficient due to its special designed communication methods and framework. Besides, it's convenient for use since we provide many kinds of control functions with free API's. It also supports many external libraries, which can be used to develop different simulation tasks. Using our developed platform, a mission of target search and tracking is realized as a case study, where a UAV-UGV heterogeneous system consisting of a UAV and two UGVs is required to search for a ground target and then move close to *** implementation of the task successfully shows the effectiveness and performance of the HeROS platform.

关键词： Heterogeneous robotic swarms simulation platform UAV UGV cooperation

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