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Journal of Iron and Steel Research International 2017年第5期24卷 483-489页

作者： Yu Xu En-gang Wang Zhuang Li An-yuan Deng Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education) Northeastern University Shenyang 110819 Liaoning China School of Metallurgy Northeastern University Shenyang 110819 Liaoning China School of Materials Science and Engineering Northeastern University Shenyang 110819 Liaoning China

The grain refinement and macrosegregation control of GCrl5 bearing steel were investigated under a type of rarely-used electromagnetic stirring, vertical electromagnetic stirring （V-EMS）, in continuous casting. V-EMS can create an upward electromagnetic force and generate longitudinal loop convection, which ena- bles the better mixing of the upper part with the lower part of the liquid steel. The results showed that ap- plying V-EMS can enlarge the region of the equiaxed grain, decrease the secondary dendrite arm spacing （SdaS） and reduce the segregation of both carbon and sulfur. After applying V-EMS, liquid steel with a high solute concentration is brought to the dendrite tips, making the dendrite arms partially melt. The length of the dendrite fragment is approximately 1.8 mm, 10 to 12 times the SdaS. Upon increasing the amount of cooling water from 2.0 to 3.5 m3/h, the dendrite fragments exhibit an obvious aggregation fol- lowing V-EMS. Finally, a criterion for dendrite fragmentation under V-EMS was derived based on the dendrite fragmentation theory of Campanella et al.

关键词： Vertical electromagnetic stirring Dendrite fragmentation Grain refinement Continuous casting Bearing steel Macrosegregation control

Optimal Policies for Quantum Markov Decision Processes

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International Journal of Automation and computing 2021年第3期18卷 410-421页

作者： Ming-Sheng Ying yuan Feng Sheng-gang Ying Centre for Quantum Software and Information University of Technology SydneyNSW 2007Australia State Key Laboratory of Computer Science Institute of SoftwareChinese Academy of SciencesBeijing 100190China Department of Computer Science and Technology Tsinghua UniversityBeijing 100084China

Markov decision process(MDP)offers a general framework for modelling sequential decision making where outcomes are *** particular,it serves as a mathematical framework for reinforcement *** paper introduces an extension of MDP,namely quantum MDP(q MDP),that can serve as a mathematical model of decision making about quantum *** develop dynamic programming algorithms for policy evaluation and finding optimal policies for q MDPs in the case of *** results obtained in this paper provide some useful mathematical tools for reinforcement learning techniques applied to the quantum world.

关键词： Quantum Markov decision processes quantum machine learning reinforcement learning dynamic programming decision making

A versatile model with three-dimensional triangular lattice for unconventional transport and various topological effects

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National Science Review 2024年第1期11卷 204-214页

作者： Jing-Yang You gang Su yuan Ping Feng Department of Physics National University of Singapore Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Centre for Advanced 2D Materials National University of Singapore

The finite Berry curvature in topological materials can induce many subtle phenomena, such as the anomalous Hall effect(AHE), spin Hall effect(SHE), anomalous Nernst effect(ANE), non-linear Hall effect(NLHE) and bulk photovoltaic effects. To explore these novel physics as well as their connection and coupling, a precise and effective model should be developed. Here, we propose such a versatile model—a 3D triangular lattice with alternating hopping parameters, which can yield various topological phases,including kagome bands, triply degenerate fermions, double Weyl semimetals and so on. We reveal that this special lattice can present unconventional transport due to its unique topological surface states and the aforementioned topological phenomena, such as AHE, ANE, NLHE and the topological photocurrent effect. In addition, we also provide a number of material candidates that have been synthesized experimentally with this lattice, and discuss two materials, including a non-magnetic triangular system for SHE, NLHE and the shift current, and a ferromagnetic triangular lattice for AHE and ANE. Our work provides an excellent platform, including both the model and materials, for the study of Berry-curvature-related physics.

关键词： three-dimensional triangular lattice different topological phases various topological effects Berry curvature

Locally Enhanced Flow and Electric Fields Through a Tip Effect for Efficient Flow‑Electrode Capacitive Deionization

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Nano-Micro Letters 2025年第2期17卷 1-17页

作者： Ziquan Wang Xiangfeng Chen yuan Zhang Jie Ma Zhiqun Lin Amor Abdelkader Maria‑Magdalena Titirici Libo Deng College of Chemistry and Environmental Engineering Shenzhen UniversityShenzhen 518060People’s Republic of China Research Center for Environmental Functional Materials College of Environmental Science and EngineeringTongji University1239 Siping RoadShanghai 200092People’s Republic of China Department of Chemical and Biomolecular Engineering National University of SingaporeSingapore 117585Singapore Department of Engineering Faculty of Science and TechnologyBournemouth UniversityTalbot CampusFern BarrowPooleEngland BH125BBUK Institut de Chimie de Nice UniversitéCôte d’AzurUMR CNRS 727228 Av.Valrose06108 NiceFrance Department of Chemical Engineering Imperial College LondonSouth Kensington CampusExhibition RdLondon SW72AZUK

Low-electrode capacitive deionization(FCDI)is an emerging desalination technology with great potential for removal and/or recycling ions from a range of ***,it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes,both restricted by the current ***,a new tip-array current collector(designated as T-CC)was developed to replace the conventional planar current collectors,which intensifies both the charge transfer and ion transport *** effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy,which revealed the reduction of ion transport barrier,charge transport barrier and internal *** the voltage increased from 1.0 to 1.5 and 2.0 V,the T-CC-based FCDI system(T-FCDI)exhibited average salt removal rates(ASRR)of 0.18,0.50,and 0.89μmol cm^(-2) min^(-1),respectively,which are 1.82,2.65,and 2.48 folds higher than that of the conventional serpentine current collectors,and 1.48,1.67,and 1.49 folds higher than that of the planar current ***,with the solid content in flow electrodes increased from 1 to 5 wt%,the ASRR for T-FCDI increased from 0.29 to 0.50μmol cm^(-2) min^(-1),which are 1.70 and 1.67 folds higher than that of the planar current ***,a salt removal efficiency of 99.89%was achieved with T-FCDI and the charge efficiency remained above 95%after 24 h of operation,thus showing its superior long-term stability.

关键词： Flow-electrode Capacitive deionization Current collector Tip effect Desalination

3D stress simulation and parameter design during twin-roll casting of 304 stainless steel based on the Anand model

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 666-673页

作者： Jing Guo yuan-yuan Liu Li-gang Liu Yue Zhang Qing-xiang Yang State Key Laboratory of Metastable Materials Science & Technology Yanshan University Nanjing Iron & Steel Co. School of Material Science and Engineering University of Science and Technology Beijing

This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520℃, respectively.

关键词： stainless steel strip metal roll casting stress surface cracks numerical analysis

Joint Resource Allocation and Admission Control in Sliced Fog Radio Access Networks

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China Communications 2020年第8期17卷 14-30页

作者： yuan Ai gang Qiu Chenxi Liu Yaohua Sun State Key Laboratory of Network and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China LTE&5G Wireless Product R&D Institute ZTE CorporationShenzhen 518057China

Network slicing based fog radio access network(F-RAN) has emerged as a promising architecture to support various novel applications in 5 G-and-beyond wireless networks. However, the co-existence of multiple network slices in F-RANs may lead to significant performance degradation due to the resource competitions among different network slices. In this paper, the downlink F-RANs with a hotspot slice and an Internet of Things(Io T) slice are considered, in which the user equipments(UEs) of different slices share the same spectrum. A novel joint resource allocation and admission control scheme is developed to maximize the number of UEs in the hotspot slice that can be supported with desired quality-of-service, while satisfying the interference constraint of the UEs in the Io T slice. Specifically, the admission control and beamforming vector optimization are performed in the hotspot slice to maximize the number of admitted UEs, while the joint sub-channel and power allocation is performed in the Io T slice to maximize the capability of the UEs in the Io T slice tolerating the interference from the hotspot slice. Numerical results show that our proposed scheme can effectively boost the number of UEs in the hotspot slice compared to the existing baselines.

关键词： NOMA fog radio access networks resource allocation admission control

Improving the forming performance of incrementally formed sheet parts with customized heat treatment strategies

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Advances in Manufacturing 2023年第2期11卷 264-279页

作者： Hao yuan Yan-Le Li yuan-Yu Liu gang-Lin Zhao Fang-Yi Li Key Laboratory of High Efficiency and Clean Mechanical Manufacture Ministry of EducationSchool of Mechanical EngineeringShandong UniversityJinan250061People's Republic of China National Demonstration Center for Experimental Mechanical Engineering Education Shandong UniversityJinan250061People's Republic of China

Although incremental sheet forming(ISF)is an efficient way to manufacture customized parts,the forming performance and geometric accuracy of formed parts need to be improved to meet industrial *** feasible solution for these problems is to adopt proper heat treatment strategies for the sheet material both before and during the forming *** this paper,the effects of heat treatment before forming and heat-assisted forming on the formability and performance of formed parts were experimentally ***,TA1 sheets were heat-treated at different temperatures before forming,and then the sheets were incrementally formed into the target shape with variable angles at different *** heat treatment,the strength of sheets was decreased due to the occurrence of recrystallization and the growth of ***,the surface quality of formed parts was also improved with pre-heat treatment before *** the heat-assisted forming process,the sheet was softened and the deformation resistance was reduced with the increase of ***,the axial forming force was decreased obviously and the formability of the sheet was increased ***,by adopting both heat treatment and heat-assisted forming,it was found that the forming force could be further reduced and the formability of the sheet and surface quality could be further *** for geometric accuracy,heat treatment has a good effect on improving it,while heat-assisted forming has adverse *** findings provide an effective heat treatment strategy for improving the geometric accuracy and surface quality of the incrementally formed parts with lower forming force.

关键词： Incremental sheet forming(ISF) Heat-assisted forming Heat treatment Forming force Formability

A multi-stage regulation strategy of space manipulators with a free-swinging joint failure

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Chinese Journal of Aeronautics 2021年第5期34卷 573-584页

作者： gang CHEN Yingzhuo FU Qingxuan JIA Bonan yuan dan LIU School of Automation Beijing University of Posts and TelecommunicationsBeijing 100876China

To ensure tasks can be completed after a free-swinging joint failure occurs,a multi-stage regulation strategy of space manipulators is *** all terms of the dynamics equation,an evaluation model of the regulation ability(EMRA)of active joints over the fault joint is established based on the fuzzy *** then a multi-stage regulation strategy based on the EMRA is designed to regulate the fault *** strategy divides the regulation process into several stages,and select a certain active joint to regulative the fault joint in every *** this multi-stage regulation strategy,the fault joint can be regulated to the desired angle without huge torque on regulative *** simulation is carried out with a 7-DOF space manipulator,verifying the correctness and effectiveness of the multi-stage regulation *** strategy has three advantages:Coriolis and centrifugal terms are both considered for the first time in selecting the regulative joint,making the selection result more in line with the actual regulation process;The influence of the model uncertainty is eliminated in establishing the EMRA,making the evaluation of regulative ability more precise;The fault joint is successfully regulated to the desired angle without huge torque on regulative joints.

关键词： Free-swinging joint failure Fuzzy entropy Multi-stage regulation strategy Regulation ability Space manipulator

Observation-Driven Multiple UAV Coordinated Standoff Target Tracking Based on Model Predictive Control

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Tsinghua Science and Technology 2022年第6期27卷 948-963页

作者： Shun Sun Yu Liu Shaojun Guo gang Li Xiaohu yuan Department of Control Science and Technology Naval Aviation UniversityYantai 264001China Department of Electronic Engineering Tsinghua UniversityBeijing 100084China National Institute of Defense Technology Innovation Academy of Military Sciences PLABeijing 100091China Department of Automation Tsinghua UniversityBeijing 100084China

An observation-driven method for coordinated standoff target tracking based on Model Predictive Control(MPC)is proposed to improve observation of multiple Unmanned Aerial Vehicles(UAVs)while approaching or loitering over a *** acquiring a fusion estimate of the target state,each UAV locally measures the observation capability of the entire UAV system with the Fisher Information Matrix(FIM)determinant in the decentralized *** facilitate observation optimization,only the FIM determinant is adopted to derive the performance function and control constraints for coordinated standoff ***,a modified iterative scheme is introduced to improve the iterative efficiency,and a consistent circular direction control is established to maintain long-term observation performance when the UAV approaches its *** experiments with simulated and real trajectories validate that the proposed method can improve observation of the UAV system for target tracking and adaptively optimize UAV trajectories according to sensor performance and UAV-target geometry.

关键词： coordinated tracking standoff tracking observation-driven Model Predictive Control(MPC) multiple UAVs Fisher Information Matrix(FIM)

Continuation Finite Element Simulation of Second Harmonic Generation in Photonic Crystals

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Communications in Computational Physics 2011年第6期10卷 57-69页

作者： gang Bao Zhengfu Xu Jianhua yuan Department of Mathematics Zhejiang UniversityHangzhou 310027China Department of Mathematics Michigan State UniversityEast LansingMI 48824USA Department of Mathematics Beijing University of Posts and TelecommunicationsBeijing 100876China

A computational study on the enhancement of the second harmonic generation(SHG)in one-dimensional(1D)photonic crystals is *** mathematical model is derived from a nonlinear system of Maxwell’s equations,which partly overcomes the shortcoming of some existing models based on the undepleted pump *** designed an iterative scheme coupled with the finite element method which can be applied to simulate the SHG in one dimensional nonlinear photonic band gap structures in our previous *** the case that the nonlinearity is strong which is desirable to enhance the conversion efficiency,a continuation method is introduced to ensure the convergence of the iterative *** convergence of our method is *** experiments also indicate the conversion efficiency of SHG can be significantly enhanced when the frequencies of the fundamental and the second harmonic wave are tuned at the photonic band *** maximum total conversion efficiency available reaches more than 50%in all the cases studied.

关键词： Photonic crystals second harmonic generation photonic band gap conversion effi-ciency finite element methods fixed-point iterations continuation method