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arXiv 2024年

作者： Lou, Zhefeng Zhao, Yingjie Gong, Zhihao Zhu, Ziye Wu, Mengqi Wang, Tao Wang, Jialu Qi, Haoyu Zuo, Huakun Xu, Zhuokai Shen, Jichuang Wang, Zhiwei Li, Lan Xu, Shuigang Kong, Wei Li, Wenbin Zheng, Xiaorui Wang, Hua Lin, Xiao Key Laboratory for Quantum Materials of Zhejiang Province Department of Physics School of Science Research Center for Industries of the Future Westlake University Hangzhou310030 China School of Physics Zhejiang University Zhejiang Province Hangzhou310027 China Institute of Natural Sciences Westlake Institute for Advanced Study Hangzhou310024 China Key Laboratory of 3D Micro/nano Fabrication and Characterization of Zhejiang Province School of Engineering Westlake University Zhejiang Province Hangzhou310024 China ZJU-Hangzhou Global Scientific and Technological Innovation Center School of Physics Zhejiang University Hangzhou311215 China Academy of Interdisciplinary Studies on Intelligent Molecules Tianjin Key Laboratory of Structure and Performance for Functional Molecules College of Chemistry Tianjin Normal University Tianjin300387 China Hangzhou Key Laboratory of Quantum Matters School of Physics Hangzhou Normal University Hangzhou311121 China Material Science Center Yangtze Delta Region Academy of Beijing Institute of Technology Jiaxing314011 China Wuhan National High Magnetic Field Center Huazhong University of Science and Technology Wuhan430074 China School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems Beijing Institute of Technology Beijing100081 China Center for Quantum Matter Zhejiang University Hangzhou310058 China

Two-dimensional (2D) materials with remarkable second-harmonic generation (SHG) hold promise for future on-chip nonlinear optics. Relevant materials with both giant SHG response and environmental stability are long-sought targets. Here, we demonstrate the enormous SHG from the phase engineering of a high-performance semiconductor, Bi2O2Se (BOS), under uniaxial strain. SHG signals captured in strained 20 nm-BOS films exceed those of NbOI2 and NbOCl2 of similar thickness by a factor of 10, and are four orders of magnitude higher than monolayer-MoS2, resulting in a significant second-order nonlinear susceptibility on the order of 1 nm V-1. Intriguingly, the strain enables continuous adjustment of the ferroelectric phase transition across room temperature. Consequently, an exceptionally large tunability of SHG, approximately six orders of magnitude, is achieved through strain or thermal modulation. This colossal SHG, originating from the geometric phase of Bloch wave functions and coupled with sensitive tunability through multiple approaches in this air-stable 2D semiconductor, opens new possibilities for designing chip-scale, switchable nonlinear optical devices. Copyright © 2024, The Authors. All rights reserved.

关键词： Harmonic generation

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Deep multimodal fusion by channel exchanging 20

Deep multimodal fusion by channel exchanging

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Proceedings of the 34th International Conference on Neural Information Processing systems

作者： Yikai Wang Wenbing Huang Fuchun Sun Tingyang Xu Yu Rong Junzhou Huang Beijing National Research Center for Information Science and Technology (BNRist) State Key Lab on Intelligent Technology and Systems Department of Computer Science and Technology Tsinghua University Tencent AI Lab

ISBN: (纸本)9781713829546

Deep multimodal fusion by using multiple sources of data for classification or regression has exhibited a clear advantage over the unimodal counterpart on various applications. Yet, current methods including aggregation-based and alignment-based fusion are still inadequate in balancing the trade-off between inter-modal fusion and intra-modal processing, incurring a bottleneck of performance improvement. To this end, this paper proposes Channel-Exchanging-Network (CEN), a parameter-free multimodal fusion framework that dynamically exchanges channels between sub-networks of different modalities. Specifically, the channel exchanging process is self-guided by individual channel importance that is measured by the magnitude of Batch-Normalization (BN) scaling factor during training. The validity of such exchanging process is also guaranteed by sharing convolutional filters yet keeping separate BN layers across modalities, which, as an add-on benefit, allows our multimodal architecture to be almost as compact as a unimodal network. Extensive experiments on semantic segmentation via RGB-D data and image translation through multi-domain input verify the effectiveness of our CEN compared to current state-of-the-art methods. Detailed ablation studies have also been carried out, which provably affirm the advantage of each component we propose.

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Cell-Free Massive MIMO with Normalized Conjugate Beamforming and Channel Non-Reciprocities 13

Cell-Free Massive MIMO with Normalized Conjugate Beamforming...

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13th International Conference on Wireless Communications and Signal Processing, WCSP 2021

作者： Zhang, Yao Xia, Wenchao Zhu, Yongxu Zheng, Gan Gao, Feifei Zhejiang Normal University College of Physics and Electronic Information Engineering Jinhua321004 China Nanjing University of Posts and Telecommunications Department of Wireless Communication Key Lab of Jiangsu Province Nanjing210003 China London South Bank University Division of Computer Science and Informatics London United Kingdom Wolfson School of Mechanical Electrical and Manufacturing Engineering Loughborough University LeicestershireLE11 3TU United Kingdom Institute for Artificial Intelligence Tsinghua University State Key Lab of Intelligent Technologies and Systems Beijing National Research Center for Information Science and Technology Department of Automation Tsinghua University Beijing100084 China

ISBN: (纸本)9781665407854

This paper focuses on a generalized downlink cell-free massive multiple-input multiple-output (CF-mMIMO) system with normalized conjugate beamforming (NCB) and channel non-reciprocities, assuming the access points (APs) are equipped with low-resolution digital-to-analog converters (DACs). Specifically, the channel non-reciprocities consist of the amplitude and phase non-reciprocities at the APs and user equipments. Closed-form expressions of the achievable sum-rates are derived for evaluating the impacts of channel non-reciprocities and DAC resolutions and comparing against the conjugate beamforming (CB) counterpart. Simulation results reveal that the downlink sum-rates are immune to the amplitude non-reciprocity of transceivers but strongly sensitive to the AP phase non-reciprocity. In particular, a small degree of AP phase non-reciprocity can result in substantial rate degradations. Besides, 5-bit DACs are enough in CF-mMIMO systems to approach the same sum-rates as CF-mMIMO systems with high-resolution DACs. Moreover, the NCB scheme outperforms the CB scheme in terms of the downlink sum-rates for both reciprocal and non-reciprocal channels. © 2021 IEEE.

关键词： Beamforming

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Demagnetization analysis and magnet design of permanent magnet synchronous motor for electric power steering applications 1

Demagnetization analysis and magnet design of permanent magn...

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1st IEEE China International Youth Conference on Electrical Engineering, CIYCEE 2020

作者： Huang, Weihua Wang, Jin Zhao, Junchen Zhou, Libing Zhang, Zhiwei Huazhong University of Science and Technology State Key Laboratory of Advanced Elec-tromagnetic Engineering and Technology School of Electrical and Electronic Engineering Wuhan430074 China The Ohio State University Department of Electrical and Computer Engineering ColumbusOH43210 United States

ISBN: (纸本)9781728196596

The demagnetization analysis method of permanent magnet synchronous motor (PMSM) used in electric power steering (EPS) system is studied, and the size of permanent magnet (PM) is optimized considering demagnetization performance and manufacturing cost in this paper. PMSM has the advantages of high torque density and high efficiency, which is suitable for EPS system. However, the PMs may demagnetize at a high temperature or by a larger reverse magnetic field, which will affect the torque characteristics or output power of the motor, eventually resulting in the failure to drive the load and also reducing the reliability of the EPS system. In order to deal with these problems, it is necessary to consider demagnetization in the analysis stage. In addition, EPS systems are sensitive to cost since PM material is expensive, so it is necessary to restrain irreversible demagnetization under the condition of minimizing the volume of PM. A demagnetization analysis method based on 2D and 3D finite element analysis (FEA) for PMSM in EPS systems is proposed and the size of PM is mainly designed. Based on the computation of the distribution of magnetic flux density on the surface of PM, the demagnetization risk is evaluated. The simulation and experiment results clearly show that the proposed PMSM design can meet the requirements of EPS system. © 2020 IEEE.

关键词： Finite element method

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Feature refinement attention U-net for enhanced liver segmentation

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Engineering Applications of Artificial Intelligence 2025年 157卷

作者： Hui Wang Desheng Liu Zhilei Zhao Yue Wu Anil Baris Cekderi State Key Laboratory of Intelligent Control and Decision of Complex Systems School of Automation Beijing Institute of Technology Beijing 100081 People's Republic of China College of Information Science & Electronic Technology Jiamusi University Jiamusi 154007 People's Republic of China

Developing efficient and accurate automated liver segmentation methods is of far-reaching significance for the prevention, diagnosis, treatment, and prognostic assessment of liver diseases. Artificial intelligence (AI) technology has shown immense potential in various computer vision tasks and has been increasingly adopted in medical image segmentation in recent years. However, conventional neural networks often exhibit limitations in capturing global context capture, constraining their performance in medical image segmentation. To address this challenge, we propose a Feature Refinement Attention U-Net (FRAttU-Net). The architecture is designed with two key components: a High and Low Frequency Feature Fusion and Enhancement Module (HLF 3 EM) between the encoder and decoder to integrate the multilevel features and enhance the high-level feature representation using edge cues, and an Otsu Density Refinement Module in the output layer to strengthen density information representation and improve the prediction accuracy. Extensive experiments demonstrate that FRAttU-Net achieves state-of-the-art accuracy, outperforming existing methods on multiple datasets. This performance advancement holds considerable potential in improving clinical decision-making in liver disease diagnosis and treatment planning. The code is available at: https://***/HUI623/ FRAttU-Net.

关键词： Application of artificial intelligence Deep learning Density refinement Feature refinement attention Liver segmentation

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Bi-Mapper: Holistic BEV Semantic Mapping for Autonomous Driving

arXiv

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arXiv 2023年

作者： Li, Siyu Yang, Kailun Shi, Hao Zhang, Jiaming Lin, Jiacheng Teng, Zhifeng Li, Zhiyong The School of Robotics Hunan University Changsha410082 China The State Key Laboratory of Modern Optical Instrumentation Zhejiang University Hangzhou310027 China The Institute for Anthropomatics and Robotics Karlsruhe Institute of Technology Karlsruhe76131 Germany The Department of Engineering Science University of Oxford OxfordOX1 3PJ United Kingdom The School of Computer Science and Electronic Engineering Hunan University Changsha410082 China

A semantic map of the road scene, covering fundamental road elements, is an essential ingredient in autonomous driving systems. It provides important perception foundations for positioning and planning when rendered in the Bird's-Eye-View (BEV). Currently, the prior knowledge of hypothetical depth can guide the learning of translating front perspective views into BEV directly with the help of calibration parameters. However, it suffers from geometric distortions in the representation of distant objects. In addition, another stream of methods without prior knowledge can learn the transformation between front perspective views and BEV implicitly with a global view. Considering that the fusion of different learning methods may bring surprising beneficial effects, we propose a Bi-Mapper framework for top-down road-scene semantic understanding, which incorporates a global view and local prior knowledge. To enhance reliable interaction between them, an asynchronous mutual learning strategy is proposed. At the same time, an Across-Space Loss (ASL) is designed to mitigate the negative impact of geometric distortions. Extensive results on nuScenes and Cam2BEV datasets verify the consistent effectiveness of each module in the proposed Bi-Mapper framework. Compared with exiting road mapping networks, the proposed Bi-Mapper achieves 2.1% higher IoU on the nuScenes dataset. Moreover, we verify the generalization performance of Bi-Mapper in a real-world driving scenario. The source code is publicly available at BiMapper. Copyright © 2023, The Authors. All rights reserved.

关键词： Autonomous vehicles

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Data-driven resilient predictive control under denial-of-service

arXiv

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arXiv 2021年

作者： Liu, Wenjie Sun, Jian Wang, Gang Bullo, Francesco Chen, Jie State Key Lab of Intelligent Control and Decision of Complex Systems The School of Automation Beijing Institute of Technology Beijing100081 China State Key Lab of Intelligent Control and Decision of Complex Systems The School of Automation Beijing Institute of Technology Beijing100081 China The Beijing Institute of Technology Chongqing Innovation Center Chongqing401120 China Mechanical Engineering Department The Center of Control Dynamical Systems and Computation UC Santa Barbara CA93106-5070 United States Department of Control Science and Engineering Tongji University Shanghai201804 China State Key Lab of Intelligent Control and Decision of Complex Systems The School of Automation Beijing Institute of Technology Beijing100081 China

The study of resilient control of linear time-invariant (LTI) systems against denial-of-service (DoS) attacks is gaining popularity in emerging cyber-physical applications. In previous works, explicit system models are required to design a predictor-based resilient controller. These models can be either given a priori or obtained through a prior system identification step. Recent research efforts have focused on data-driven control based on pre-collected input-output trajectories (i.e., without explicit system models). In this paper, we take an initial step toward data-driven stabilization of stochastic LTI systems under DoS attacks, and develop a resilient model predictive control (MPC) scheme driven purely by data-dependent conditions. The proposed data-driven control method achieves the same level of resilience as the model-based control method. For example, local input-to-state stability (ISS) is achieved under mild assumptions on the noise and the DoS attacks. To recover global ISS, two modifications are further suggested at the price of reduced resilience against DoS attacks or increased computational complexity. Finally, a numerical example is given to validate the effectiveness of the proposed control method. © 2021, CC BY.

关键词： Model predictive control

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Sum-Rate Maximization of RIS-Aided Multi-User MIMO systems with Statistical CSI

arXiv

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arXiv 2021年

作者： Zhang, Huan Ma, Shaodan Shi, Zheng Zhao, Xin Yang, Guanghua The State Key Laboratory of Internet of Things for Smart City The Department of Electrical and Computer Engineering University of Macau 999078 China The Institute of Physical Internet The School of Intelligent Systems Science and Engineering Jinan University Zhuhai519070 China The School of Information and Electronics Beijing Institute of Technology Beijing100081 China The Department of Electrical and Computer Engineering University of Macau Taipa 999078 China

This paper investigates a reconfigurable intelligent surface (RIS)-aided multi-user multiple-input multiple-output (MIMO) system by considering only the statistical channel state information (CSI) at the base station (BS). We aim to maximize its sum-rate via the joint optimization of beamforming at the BS and phase shifts at the RIS. However, the multi-user MIMO transmissions and the spatial correlations make the optimization cumbersome. For tractability, a deterministic approximation is derived for the sum-rate under a large number of the reflecting elements. By adopting the approximate sum-rate for maximization, the optimal designs of the transmit beamforming and the phase shifts can be decoupled and solved in closed-forms individually. More specifically, the global optimality of the transmit beamforming can be guaranteed by using water-filling algorithm and a sub-optimal solution of phase shifts can be obtained by using projected gradient ascent (PGA) algorithm. By comparing to the case of the instantaneous CSI assumed at the BS, the proposed algorithm based on statistical CSI can achieve comparable performance but with much lower complexity and signaling overhead, which is more affordable and appealing for practical applications. Moreover, the impact of spatial correlation is thoroughly examined by using majorization theory. © 2021, CC BY.

关键词： MIMO systems

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Mean Field Game-based Waveform Precoding Design for Mobile Crowd Integrated Sensing, Communication, and Computation systems

arXiv

引用

arXiv 2023年

作者： Wang, Dezhi Huang, Chongwen He, Jiguang Chen, Xiaoming Wang, Wei Zhang, Zhaoyang Han, Zhu Debbah, Mérouane The College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China The State Key Laboratory of Integrated Service Networks Xidian University Xi’an710071 China Hangzhou310027 China Technology Innovation Institute Masdar City Abu Dhabi9639 United Arab Emirates The Department of Electrical and Computer Engineering The University of Houston HoustonTX77004 United States Khalifa University of Science and Technology P O Box 127788 Abu Dhabi United Arab Emirates

Data collection and processing timely is crucial for mobile crowd integrated sensing, communication, and computation (ISCC) systems with various applications such as smart home and connected cars, which requires numerous integrated sensing and communication (ISAC) devices to sense the targets and offload the data to the base station (BS) for further processing. However, as the number of ISAC devices growing, there exists intensive interactions among ISAC devices in the processes of data collection and processing since they share the common network resources. In this paper, we consider the environment sensing problem in the large-scale mobile crowd ISCC systems and propose an efficient waveform precoding design algorithm based on the mean field game (MFG). Specifically, to handle the complex interactions among large-scale ISAC devices, we first utilize the MFG method to transform the influence from other ISAC devices into the mean field term and derive the Fokker-Planck-Kolmogorov equation, which models the evolution of the system state. Then, we derive the cost function based on the mean field term and reformulate the waveform precoding design problem. Next, we utilize the G-prox primal-dual hybrid gradient algorithm to solve the reformulated problem and analyze the computational complexity of the proposed algorithm. Finally, simulation results demonstrate that the proposed algorithm can solve the interactions among large-scale ISAC devices effectively in the ISCC process. In addition, compared with other baselines, the proposed waveform precoding design algorithm has advantages in improving communication performance and reducing cost function. Copyright © 2023, The Authors. All rights reserved.

关键词： Cost functions

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A diffuse-interface lattice Boltzmann method for thermal particulate flows with Dirichlet boundary conditions

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Physics of Fluids 2025年第6期37卷

作者： Liu, Jiao Liu, Xi Chai, Zhenhua School of Mathematics and Computer Science Nanchang University Jiangxi Nanchang330031 China School of Mathematics and Statistics Huazhong University of Science and Technology Wuhan430074 China Institute of Interdisciplinary Research for Mathematics and Applied Science Huazhong University of Science and Technology Wuhan430074 China Hubei Key Laboratory of Engineering Modeling and Scientific Computing Huazhong University of Science and Technology Wuhan430074 China The State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan430074 China

The lattice Boltzmann method has been widely used to study thermal particulate flows that are usually observed in both nature and engineering, while how to efficiently and accurately treat the fluid-solid boundary conditions is still an important and not well-resolved issue. In this paper, a diffuse-interface lattice Boltzmann method (DI-LBM) is developed for complex thermal particulate flows with Dirichlet boundary conditions. Unlike the previous works where the fluid-solid boundary is treated as a sharp interface, the fluid-solid boundary in the DI-LBM is implemented as a diffuse interface such that the physical variables and transport coefficients in the fluid and solid regions are varied smoothly. To depict the diffuse interface, a smooth function is introduced, and simultaneously, an additional source term is added in the evolution equation to reflect the effect of Dirichlet boundary condition imposed on the fluid-solid boundary. The present method is also tested by several classical problems, and the numerical results show that the DI-LBM is not only of second-order convergence rate in space, but also efficient in the study of complex thermal particulate flows. © 2025 Author(s).

关键词： Kinetic theory of gases

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