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Frequency combs based on magnon-skyrmion interaction in magnetic nanotubes

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Chinese physics B 2024年第8期33卷 505-509页

作者： Tijjani Abdulrazak 刘雪娟金哲珺雨曹云姗严鹏 School of physics and State Key Laboratory of electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054China Department of physics Bayero UniversityKano-700006Nigeria School of Healthcare Technology Chengdu Neusoft UniversityChengdu 611844China

Within the magnonics community,there has been a lot of interests in the magnon–skyrmion *** and skyrmions are two intriguing phenomena in condensed matter physics,and magnetic nanotubes have emerged as a suitable platform to study their complex *** show that magnon frequency combs can be induced in magnetic nanotubes by three-wave mixing between the propagating magnons and *** study enriches our fundamental comprehension of magnon–skyrmion interactions and holds promise for developing innovative spintronic devices and *** frequency comb tunability and unique spectral features offer a rich platform for exploring novel avenues in magnetic nanotechnology.

关键词： ferromagnetic magnetic field magnon Mumax3 software skyrmion

Spin transport characteristics modulated by the GeBi interlayer in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures

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Chinese physics B 2024年第2期33卷 471-475页

作者：李明明张磊金立川郭海中 Key Laboratory of Materials physics Ministry of EducationSchool of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450052China State Key Laboratory of electronic Thin Films&Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054China Institute of Quantum Materials and physics Henan Academy of SciencesZhengzhou 450046China

For the past few years,germanium-based semiconductor spintronics has attracted considerable interest due to its potential for integration into mainstream semiconductor *** main challenges in the development of modern semiconductor spintronics are the generation,detection,and manipulation of spin ***,the transport characteristics of a spin current generated by spin pumping through a GeBi semiconductor barrier in Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures were investigated *** effective spin-mixing conductance and inverse spin Hall voltage to quantitatively describe the spin transport characteristics were *** spin-injection efficiency in the Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures is comparable to that of the Y_(3)Fe_(5)O_(12)/Pt bilayer,and the inverse spin Hall voltage exponential decays with the increase in the barrier ***,the band gap of the GeBi layer was tuned by changing the Bi *** spin-injection efficiency at the YIG/semiconductor interface and the spin transportation within the semiconductor barrier are related to the band gap of the GeBi *** results may be used as guidelines for the fabrication of efficient spin transmission structures and may lead to further studies on the impacts of different kinds of barrier materials.

关键词： spin current Y_(3)Fe_(5)O_(12)/GeBi/Pt heterostructures spin pumping inverse spin Hall effect

Effect of temperature and time on the precipitation ofκ-carbides in Fe-28Mn-10Al-0.8C low-density steels:Aging mechanism and its impact on material properties

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International Journal of Minerals,Metallurgy and Materials 2024年第10期31卷 2189-2198页

作者： Yulin Gao Min Zhang Rui Wang Xinxin Zhang Zhunli Tan Xiaoyu Chong School of Mechanical Electronic and Control EngineeringMaterials Science and Engineering Research CenterBeijing Jiaotong UniversityBeijing 100044China faculty of Materials science and Engineering Kunming University of Science and TechnologyKunming 650093China

In low-density steel,κ-carbides primarily precipitate in the form of nanoscale particles within austenite ***,their precipitation within ferrite matrix grains has not been comprehensively explored,and the second-phase evolution mechanism during aging remains *** this study,the crystallographic characteristics and morphological evolution ofκ-carbides in Fe-28Mn-10Al-0.8C(wt%)low-density steel at different aging temperatures and times and the impacts of these changes on the steels’microhardness and properties were comprehensively *** different heat treatment conditions,intragranularκ-carbides exhibited various morpho-logical and crystallographic characteristics,such as acicular,spherical,and short rod-like *** the initial stage of aging,acicularκ-carbides primarily precipitated,accompanied by a few spherical carbides.κ-Carbides grew and coarsened with aging time,the spherical carbides were considerably reduced,and rod-like carbides *** hardness testing demonstrated that the material’s hardness was affected by the volume fraction,morphology,and size ofκ-*** aging at higher temperatures led to an increase in carbide size and volume fraction,resulting in a gradual rise in *** deformation,the primary mechanisms for strengthening were dislocation strengthening and second-phase *** on these findings,potential strategies for improving material strength are proposed.

关键词： low-density steel κ-carbide solution-aging treatment hardness

Performance of pulsed plasma thruster at low discharge energy

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Plasma science and Technology 2024年第4期26卷 122-132页

作者：李鸿俊林泽豪胡浩俊吴文东陈爱虹杜德扬 Department of physics Faculty of ScienceUniversity of MalayaKuala Lumpur 50603Malaysia faculty of Engineering The University of Nottingham Malaysia CampusSemenyih 43500Malaysia faculty of Engineering Multimedia UniversityCyberjaya 63100Malaysia

As the size of satellites scales down, low-power and compact propulsion systems such as the pulsed plasma thruster(PPT) are needed for stabilizing these miniature satellites in orbit. Most PPT systems are operated at 2 J or more of discharge energy. In this work, the performance of a PPT with a side-fed, tongue-flared electrode configuration operated within a lower discharge energy range of 0.5-2.5 J has been investigated. Ablation and charring of the polytetrafluoroethylene propellant surface were analyzed through field-effect scanning electron microscopy imaging and energy-dispersive X-ray spectroscopy. When the discharge energy fell below 2 J, inconsistencies occurred in the specific impulse and the thrust efficiency due to the measurement of the low mass bit. At energy ≥2 J, the performance parameters are compared with other PPT systems of similar configuration and discussed in depth.

关键词： pulsed plasma thruster low discharge energy performance parameters

Critical behavior and Joule-Thomson expansion of charged AdS black holes surrounded by exotic fluid with modified Chaplygin equation of state

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Chinese physics C 2024年第6期48卷 179-190页

作者：张梦瑶陈浩 Hassan Hassanabad 隆正文杨辉 School of Mathematics and Statistics Guizhou UniversityGuiyang 550025China School of physics and electronic science Zunyi Normal UniversityZunyi 563006China faculty of physics Shahrood University of TechnologyShahroodIran Department of physics University of Hradec KrálovéRokitanského 6250003 Hradec KrálovéCzechia College of physics Guizhou UniversityGuiyang 550025China

By considering the concept of a unified single fluid model,referred to as modified Chaplygin gas(MCG),which amalgamates dark energy and dark matter,we explore the thermodynamic characteristics of charged anti-de Sitter(AdS)black holes existing in an unconventional fluid accompanied by *** accomplish this objective,we derive the equations of state by regarding the charge Q^(2) as a thermodynamic *** effects of MCG parameters on the critical thermodynamic quantities(ψ_(c),T_(c),Q_(c)^(2))are examined,followed by a detailed analysis of the Q^(2)-ψ *** provide a clearer explanation of the phase transition,we present an analysis of the Gibbs free *** is important to note that if the Hawking temperature exceeds the critical temperature,a distinct pattern is observed known as swallowtail *** indicates that the system undergoes a first-order phase transition from a smaller black hole to a larger *** critical exponent of the system is found to be in complete agreement with that of the van der Waals fluid ***,we investigate the impact of MCG parameters and black hole charge on Joule-Thomson(J-T)expansion in the extended phase *** J-T coefficient is examined to pinpoint the exact region experiencing cooling or heating,and the observation reveals that the presence of negative heat capacity results in the occurrence of a cooling *** impact of MCG on the inversion curve of charged black holes exhibits a striking resemblance to that observed in most multi-dimensional black hole *** addition,it is worth noting that certain parameters exert a significant influence on the ratio T_(min)/*** specific values of the MCG parameters,the ratio is consistent with the charged AdS black *** parametersγandβhave a non-negligible effect on the isenthalpic curve.

关键词： black hole dark matter dark energy phase transition Joule-Thomson expansion

Fairness in machine learning: definition, testing,debugging, and application

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science China(Information sciences) 2024年第9期67卷 41-61页

作者： Xuanqi GAO Chao SHEN Weipeng JIANG Chenhao LIN Qian LI Qian WANG Qi LI Xiaohong GUAN faculty of electronic and Information Engineering Xi'an Jiaotong University School of Cyber science and Engineering Wuhan University Institute for Network sciences and Cyberspace Tsinghua University

In recent years, artificial intelligence technology has been widely used in many fields, such as computer vision, natural language processing and autonomous driving. Machine learning algorithms, as the core technique of AI, have significantly facilitated people's lives. However, underlying fairness issues in machine learning systems can pose risks to individual fairness and social security. Studying fairness definitions, sources of problems, and testing and debugging methods of fairness can help ensure the fairness of machine learning systems and promote the wide application of artificial intelligence technology in various fields. This paper introduces relevant definitions of machine learning fairness and analyzes the sources of fairness problems. Besides, it provides guidance on fairness testing and debugging methods and summarizes popular datasets. This paper also discusses the technical advancements in machine learning fairness and highlights future challenges in this area.

关键词： artificial intelligence security machine learning security machine learning fairness model testing model debugging

Simultaneously enhancing erosion and compression resistance:designing AlCoCrFeNi high-entropy alloy strengthened Ag-based contacts

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Rare Metals 2024年第9期43卷 4476-4492页

作者： Xiao-Yang Xue Zhe Wang Hui-Ling Nie Zhao Yuan Jun Wang Chang-Hu Xu Kai Wen Cong-Hao Yu School of Materials science and Engineering Xi’an Polytechnic University School of physics Xi’an Jiaotong University Key Laboratory of Pulsed Power Technology School of Electrical and Electronic EngineeringHuazhong University of Science and Technology State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic EngineeringHuazhong University of Science and Technology

Designing microstructures and unveiling dynamic erosion mechanisms remain important challenges for Ag-based contacts. To simultaneously enhance erosion and compression resistance, an Al Co Cr Fe Ni high-entropy alloy(HEA) is introduced into Ag-based materials to fabricate novel Ag-HEA contacts with island-and skeletonrestricted microstructures. The arc erosion experimental results reveal that the skeleton-restricted HEA microstructure is the key factor in reducing the hill and crater morphologies of the contact surface, effectively delaying material transfer between the movable and stationary contacts. The molten bridge evolution and compressive deformation behavior of Ag-HEA contacts with various microstructures are investigated using molecular dynamics(MD) simulations. MD results indicate that the constraint of Ag atom diffusion in the molten pool and the involvement of HEA atoms in the molten bridge are the primary mechanisms for improving erosion resistance. The skeleton-restricted HEA microstructure reduces the total energy and structural stability of the molten bridge system and promotes its fracture and disintegration. Moreover, the synergistic effect of the twin and Lomerz–Cottrell lock structures can hinder dislocation glide, generating dispersed and small-area stacking faults in the Ag matrix and mitigating the concentration of shear strains. Thus, the skeleton-restricted HEA microstructure contributes positively to compression resistance. This study presents a novel approach to designing Ag-based contacts.

关键词： Arc erosion Electrical contact materials High entropy alloys Microstructures Molecular dynamics

Pressure-triggered stacking dependence of interlayer coupling in bilayer WS_(2)

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science China(physics,Mechanics & Astronomy) 2024年第8期67卷 177-186页

作者： Zejuan Zhang Chenyin Jiao Shenghai Pei Xilong Zhou Jiaze Qin Wanli Zhang Yu Zhou Zenghui Wang Juan Xia School of Integrated sciences and Engineering(Exemplary School of Microelectronics) University of Electronic Science and Technology of ChinaChengdu 610054China Institute of Fundamental and Frontier sciences University of Electronic Science and Technology of ChinaChengdu 610054China State Key Laboratory of electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 611731China School of physics and electronics Hunan Key Laboratory of Nanophotonics and DevicesCentral South UniversityChangsha 410083China

Tungsten disulfide(WS_(2))has been reported to show negligible stacking dependence under ambient conditions,impeding its further explorations on physical properties and potential ***,we realize efficient modulation of interlayer coupling in bilayer WS_(2)with 3R and 2H stackings by high pressure,and find that the pressure-triggered interlayer coupling and pressure-induced resonant-to-nonresonant transition exhibit prominent stacking dependence,which are experimentally observed for the first time in *** work may unleash the stacking degree of freedom in designing WS_(2)devices with tailored properties correlated to interlayer coupling.

关键词： tungsten disulfide pressure engineering stacking order interlayer coupling

Influence of extraction voltage on electron and ion behavior characteristics

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Chinese physics B 2024年第4期33卷 553-559页

作者：徐翱甘娉娉石元杰陈磊 Institute of electronic Engineering China Academy of Engineering PhysicsMianyang 621999China

The characteristics of the extracted ion current have a significant impact on the design and testing of ion source *** this paper,a 2D in space and 3D in velocity space particle in cell(2D3V PIC)method is utilized to simulate plasma motion and ion extraction characteristics under various initial plasma velocity distributions and extraction voltages in a Cartesian coordinate *** plasma density is of the order of 10^(15)m^(-3)-10^(16)m^(-3)and the extraction voltage is of the order of 100 V-1000 *** study investigates the impact of various extraction voltages on the velocity and density distributions of electrons and positive ions,and analyzes the influence of different initial plasma velocity distributions on the extraction *** simulation results reveal that the main reason for the variation of extraction current is the spacecharge force formed by the relative aggregation of positive and negative net *** lays the foundation for a deeper understanding of extraction beam characteristics.

关键词： extraction voltage plasma ion beam ion current