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Chern Number Tunable Quantum Anomalous Hall Effect in Compensated Antiferromagnets

Physical Review Letters 2025年第11期134卷 116603-116603页

作者： Wenhao Liang Zeyu Li Jiaqi An Yafei Ren Zhenhua Qiao Qian Niu International Centre for Quantum Design of Functional Materials CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics and Department of Physics University of Science and Technology of China Hefei Anhui 230026 China Department of Physics The Hong Kong University of Science and Technology Clear Water Bay Hong Kong China Hefei National Laboratory University of Science and Technology of China Hefei 230088 China Department of Physics and Astronomy University of Delaware Newark Delaware 19716 USA

We propose to realize the quantum anomalous Hall effect (QAHE) in two-dimensional compensated antiferromagnets without net spin magnetization. We consider antiferromagnetic MnBi2Te4 as a concrete example. By breaking the parity-time (PT) symmetry of even-layer MnBi2Te4, we find that the system can host the QAHE with a nonzero Chern number. We show that by controlling the antiferromagnetic spin configuration—for example, down/up/up/down that breaks PT symmetry—tetralayer MnBi2Te4 can host a Chern number |C|=1. Such spin configuration can be stabilized by pinning the spin orientations of the surfaces. Furthermore, via tuning the on-site orbital energy and vertical electric fields, we find rich QAHE phases with tunable Chern number of |C|=1,2,3. In addition, we reveal that the edge states are layer selective and primarily located at the boundaries of the bottom and top layers. Our Letter not only proposes a scheme to realize Chern number tunable QAHE in antiferromagnets without net spin magnetization but also provides a platform for layer-selective dissipationless transport devices.

关键词： Antiferromagnetism

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Study on Transient Electromagnetic Characteristics Based on Typical Soft Magnetic Material for EMS Maglev Train 13

Study on Transient Electromagnetic Characteristics Based on ...

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13th International Symposium on Linear Drives for Industry Applications, LDIA 2021

作者： Bo, Kai Xiong, Youxing Yu, Xiwen Wu, Jiasi Wang, Yu National Key Laboratory of Science and Technology on Vessel Integrated Power System Naval University of Engineering Wuhan430043 China

ISBN: (纸本)9781728172101

It was established that a complete 2D transient electromagnetic field model of linear synchronous motor for EMS (electric-magnetic suspension) maglev train. The validity of the simulation model was analyzed by comparing the dynamic electromagnetic force with different calculation methods. The influence of typical soft magnetic materials as suspension electromagnetic iron core materials on levitation force and core loss was analyzed. The typical soft magnetic material order of the dynamic levitation force as core materials is 18RK070 > 1J22> 35WW270 > 50WW800 > 30Q130. The research provide a reference for the optimization design of electromagnetic system of EMS maglev train. © 2021 IEEE

关键词： Coremaking

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A Reinforcement Learning PID Compound Protocol design Method for Ultrasonic Motor Control*

A Reinforcement Learning PID Compound Protocol Design Method...

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Control Conference (ANZCC), Australian and New Zealand

作者： Qiang Wang Yunlong Yang Xiongjun Wu Jinqi Wang Guanyu Liu The 802 Institute of Shanghai Academy of Space Flight Technology The Eighth Academy of China Aerospace Science and Technology Corporation National Defense Key Laboratory of Science and Technology on Electromagnetic Scattering Shanghai Department of Automation Key Laboratory of System Control and Information Processing Ministry of Education of China Shanghai Jiao Tong University Shanghai China

Aiming at overcoming drawback brought by the nonlinear and time-varying characteristics of ultrasonic motor, this paper proposed a PID compound controller of ultrasonic motor based on reinforcement learning to improve the dynamic performance and adaptability of the system. In practice, the output control value of the reinforcement learning controller is observed in general to be uncertain, and sometimes even destroys the learning strategy, which makes the system unstable. To overcome this limitation, this paper ultilized the idea of expert rules to improve the controller performance, and the Lyapunov stability is also guaranteed. The simulation results show that the improved composite control algorithm can significantly improve the learning efficiency, and meanwhile shorten the number of learning iterations. At the same time, the composite controller based on expert rules significantly improves the control performance of the system, in terms of reducing the rise time and adjustment time of the system, as well as reducing the steady-state error of the system.

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design and Analysis of Terminal Guidance Law for Kinetic Interceptors based on Pulse Engine

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Journal of Electronic Research and Application 2024年第5期8卷 95-108页

作者： Shixin Li Jia Ma Shuai Yue School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094China Aerospace System Engineering Shanghai Shanghai 201100China Shanghai Key Laboratory of Spacecraft Mechanism Shanghai 201108China National Key Laboratory of Space Intelligent Control Beijing 100048China

A new terminal guidance law is proposed based on a solid propellant pulse engine and an improved proportional navigation method to address the terminal guidance issue for kinetic *** this basis,the start-stop curve of the pulse motor during the terminal guidance process is designed,along with its start-up *** effectiveness of the proposed guidance strategy is verified through simulation.

关键词： Pulse engine Terminal guidance law Kinetic interceptor Proportional navigation method

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Analysis of the Axial Fan Performance Mounted on a 4.5kW Aviation Motor

Analysis of the Axial Fan Performance Mounted on a 4.5kW Avi...

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2021 International Conference on Mechanical Engineering, Intelligent Manufacturing and Automation technology, MEMAT 2021

作者： Liu, Bin Yu, Zhongjun Fu, Jia Chen, Zutao National Key Laboratory of Science and Technology on Vessel Integrated Power System Naval University of Engineering Wuhan430033 China

Integrating an axial flow fan with the rotor is a sufficient cooling method for high-speed and high power density motors. Different from the axial fan design work under ideal intake condition, i.e. the intake flow of the fan is axial and uniform, the flow in actual engineering is more complex, which means the flow characteristics of an integrated fan are changed and disturbed. It leads to a performance penalty of the fan, and in some conditions it makes the fan stall, so it is important to get a knowledge of the flow characteristics and the performance of the integrated fan. A certain 4.5kW aviation motor with integrated axial fan is taken as the research object. Firstly, the motor-fan coupling simulation model and ideal axial intake simulation model are established, in which the mass flow rates are same, then calculation is conducted. Secondly, the simulation results are analyzed and compared, focusing on the performance of the axial fan, especially the static pressure rise, and the conclusion is obtained that the static pressure rise in ideal axial intake situation is higher than that in coupling situation. Furthermore, the reasons for the characteristics change are explored, finding that the increase of flow turbulence due to the more complex wind road structure is the main cause for these changes. This paper investigates the flow characteristics and axial fan performance mounted a whole motor, making a contribution to better understand the changes in fan performance under motor-fan coupling situation. © Published under licence by IOP Publishing Ltd.

关键词： Fans

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NUMERICAL SIMULATION AND EXPERIMENTAL RESEARCH OF SHEAR-DRIVEN WATER FILM ON FLAT PLATE

NUMERICAL SIMULATION AND EXPERIMENTAL RESEARCH OF SHEAR-DRIV...

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2024 CSAA/IET International Conference on Aircraft Utility systems, AUS 2024

作者： Li, Qinyang Guan, Ning Ning, Bo Zhu, Guangya Zhang, Dalin Chen, Weijian Key Laboratory of Aircraft Environment Control and Life Support MIIT Nanjing University of Aeronautics and Astronautics Nanjing China College of Aeronautics Shandong Jiaotong University Changqing University Science and Technology Park No.5001 Haitang Road Jinan China Utility System Design and Research Department Jiangxi Hongdu Aviation Industry Group Company Ltd. Nanchang China

The supercooled water droplets in the air will form a water film on the aircraft during flight, which will then form icing, which will have an impact on the aerodynamic performance of the aircraft and even endanger the flight safety. In this paper, based on the Eulerian Wall Films model, the partial wetting effect is introduced, and the water film flow on flat plates driven by airflow shear force is investigated. The flow behaviours of water film with different contact angles under different flow rates were explored through water film test. The effectiveness of the calculation method for water film flow characteristics in this paper was verified by comparison between numerical simulation and test records, which laid a foundation for the anti-icing calculation in subsequent studies. © The Institution of Engineering & technology 2024.

关键词： Shear flow

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ODLPIM: A Write-Optimized and Long-Lifetime ReRAM-Based Accelerator for Online Deep Learning

ODLPIM: A Write-Optimized and Long-Lifetime ReRAM-Based Acce...

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design, Automation and Test in Europe Conference and Exhibition

作者： Heng Zhou Bing Wu Huan Cheng Wei Zhao Xueliang Wei Jinpeng Liu Dan Feng Wei Tong Wuhan National Laboratory for Optoelectronics Key Laboratory of Information Storage System Engineering Research Center of Data Storage Systems and Technology School of Computer Science and Technology Huazhong University of Science and Technology Ministry of Education of China Wuhan China

ReRAM-based Processing-In-Memory (PIM) architectures have demonstrated high energy efficiency and performance in deep neural network (DNN) acceleration. Most of the existing PIM accelerators for DNN focus on offline batch learning (OBL) which requires the whole dataset to be available before training. However, in the real world, data instances arrive in sequential settings, and even the data pattern may change, which calls concept drift. OBL requires expensive retraining to solve concept drift, whereas online deep learning (ODL) is evidenced to be a better solution to keep the model evolving over streaming data. Unfortunately, when ODL optimizes models over a large-scale data stream in the PIM system, unbalanced writes are more severe than OBL, due to the heavier weight updates, resulting in the amplification of unbalanced writes and lifetime deterioration. In this work, we propose ODLPIM, an online deep learning PIM accelerator that extends the system lifetime through algorithm-hardware co-optimization. ODLPIM adopts a novel write-optimized parameter update (WARP) scheme that reduces the non-critical weight updates in hidden layers. Besides, a table-based inter-crossbar wear-leveling (TIWL) scheme is proposed and applied to the hardware controller to achieve wear-leveling between crossbars for lifetime improvement. Experiments show that WARP reduces weight updates on average to 15.25% and up to 24% compared to that without WARP, and eventually prolongs system lifetime on average to 9.65% and up to 26.81%, with a negligible rise in cumulative error rate (up to 0.31%). By combining WARP with TIWL, the lifetime of ODLPIM is improved by an average of $\mathbf{12}.\mathbf{59}\times$ and up to $\mathbf{17}.\mathbf{73}\times$ .

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Achieving Privacy-Preserving and Scalable Graph Neural Network Prediction in Cloud Environments

Achieving Privacy-Preserving and Scalable Graph Neural Netwo...

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IEEE International Conference on Communications (ICC)

作者： Yanli Yuan Dian Lei Chuan Zhang Ximeng Liu Zehui Xiong Liehuang Zhu School of Cyberspace Science and Technology Beijing Institute of Technology Beijing China Guangdong Provincial Key Laboratory Novel Security Intelligence Technologies Guangdong China College of Mathematics and Computer Science Fuzhou University Fuzhou China School of Information Systems Singapore Management University Singapore Information System and Technology Design Pillar Singapore University of Technology and Design Singapore

ISBN: (数字)9781728190549

ISBN: (纸本)9781728190556

Graph neural networks (GNNs) have been widely applied in various graph analysis tasks. To provide more convenient and faster predictive services, many enterprises are choosing to deploy GNNs in cloud environments. However, given the increasing privacy concerns about GNNs models and graph data, as well as the need to quickly generate embeddings for new nodes in real-world applications, a critical issue in this emerging paradigm is to ensure the security and scalability of GNN predictions. In this paper, we propose a privacy-preserving and scalable GNN prediction scheme, named PS-GNN, to address the privacy issues in cloud environments. Specifically, PS-GNN utilizes a customized array structure to store graph data and employs secret sharing to preserve the confidentiality of both the GNN model and graph data. Besides, the scalability of PS-GNN is achieved by aggregating feature information from local node neighborhoods in parallel. Through a detailed analysis, we demonstrate the security of PS-GNN. Extensive experiments on real-world datasets demonstrate that PS-GNN outperforms existing schemes in terms of computational and communication overhead, and reaches state-of-the-art performance on large graphs.

关键词： Privacy Data privacy Scalability Computational modeling Predictive models Graph neural networks Data models

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CorcPUM: Efficient Processing Using Cross-Point Memory via Cooperative Row-Column Access Pipelining and Adaptive Timing Optimization in Subarrays

CorcPUM: Efficient Processing Using Cross-Point Memory via C...

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design Automation Conference

作者： Chengning Wang Dan Feng Wei Tong Jingning Liu Wuhan National Laboratory for Optoelectronics Key Laboratory of Information Storage System Engineering Research Center of Data Storage Systems and Technology Ministry of Education of China School of Computer Science and Technology Huazhong University of Science and Technology Wuhan China

Emerging cross-point memory can in-situ perform vector-matrix multiplication (VMM) for energy-efficient scientific computation. However, parasitic-capacitance-induced row charging and discharging latency is a major performance bottleneck of subarray VMM. We propose a memory-timing-compliant bulk VMM processing-using-memory design with row access and column access co-optimization from rethinking of read access commands and µ-op timing. We propose row-level-parallelism-adaptive timing termination mechanism to reduce tail latency of tRCD and tRP by exploiting row nonlinear charging and bulk-interleaved row-column-cooperative VMM access mechanism to reduce tRAS and overlap CL without increasing column ADC precision. Evaluations show that our design can achieve 5.03× performance speedup compared with an aggressive baseline.

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Research on Optimization of Momentum Source Model to Supercritical Carbon Dioxide Flow in Wire Wrapped Rods Bundle

SSRN

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SSRN 2023年

作者： Liu, Sichao Liu, Yu Yang, Xiaolei Li, Xiaochang Tian, Ruifeng College of Nuclear Science and Technology Harbin Engineering University Harbin150001 China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu601213 China College of Aerospace and Civil Engineering Harbin Engineering University Harbin150001 China

Wrapped wire is widely used in new reactor core design. Simulation with traditional body fitted grid needs a large number of grids, which requires more computing resources. By optimizing the basic mathematical model of momentum source method, simulation of wire wrapped rod bundle with arbitrary wire shape can be carried out. By simulating the experimental data of 3 wire wrapped rod bundle, the model adaptability of momentum source method and mesh sensitivity analysis are carried out. Then optimized momentum source method and original momentum source method are compared based on simulation of supercritical carbon dioxide flow and heat transfer in wire wrapped rod bundle with different wire shapes. Through comparison with body fitted grid, the improvement of accuracy of optimized momentum source model can be proved. In conclusion, optimized momentum source method can greatly save the computational resources and calculated results is more accurate than original momentum source method. © 2023, The Authors. All rights reserved.

关键词： Wire

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