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High Voltage 2024年第4期9卷 911-919页

作者： Haoliang Liu Boxue Du Meng Xiao Ke Chen Yanwei Ma School of Electrical and Information Engineering Tianjin UniversityTianjinChina Institute of Electrical Engineering Chinese Academy of SciencesBeijingChina

The dielectric performance of the pristine and the electrothermal-aged metallised polypropylene capacitors are investigated under different magnetic *** energy storage capacity decreases under the magnetic *** 12 T,the capacitance value of the pristine capacitors decreases by 8.4%-17%and that of the aged capacitors declines by 15%-20%.The dielectric loss is reduced by 2.6%-6.3%,but the equivalent series resistance shows an 8.3%-23.1%*** leakage conductivity increases to 202%-354%,which leads to a weakened voltage holding *** addition to the effects of the magnetic fields,the impacts of ageing have also been *** effects of the magnetic field and ageing on the electrical parameters of the capacitors are discussed *** molecular chains of the dielectric are oxidised and decomposed during the ageing process,which reduces the insulating properties of the *** magnetic field inhibits polarisation by changing the polarisation behaviour through Lorentz force and excites the electrons to enhance charge transmission.

关键词： magnetic performance fields

Dynamics of an impurity ion transport in oil-paper insulation under various electric fields

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High Voltage 2024年第1期9卷 66-80页

作者： Yuanyang Ren Yang Wang Qiankai Zhang Jiayu Xiong Wen Cao Zepeng Lv Kai Wu State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina School of Electronics and Information Xi'an Polytechnic UniversityXi'anChina State Grid Sichuan Electric Power Research Institute ChengduChina

The ionic transport process is an important counterpart to charge transport in oil-paper insulation,and it significantly impacts oil flow electrification at the oil-paper *** this,the dynamics of this phenomenon and the underlying mechanisms remain unclear,particularly at the molecular *** understand this fundamental aspect,we conduct Molecular Dynamics study on the transport behaviour of an impurity ion in different oil-paper insulation models under various external electric *** influence factors,such as external electric fields,temperatures,and local structural characteristics,are investigated in relation to the corresponding ionic mobility in different polymer *** to the simulations,ionic mobility and its response to electric fields are higher in weaker electrostatic *** a result,mineral oil exhibits the highest ionic mobility and the most substantial enhancement of ionic mobility by external electric fields,followed by vegetable oil,oil-paper blends,and insulating *** significant deviation in ionic mobility between oil and paper leads to the formation of an electric double layer near the oil-paper *** underlying physical mechanisms of different ionic mobility and its response to the electric field in different polymer models could be explained by the different polymer structural influences in terms of interaction energy and coordination numbers in a static manner,as well as by the interactions between the impurity ion and its surrounding atoms in terms of lifetime correlation functions and velocity autocorrelation functions in a dynamic *** addition,the influence of temperature on ionic mobility in mineral and vegetable oil is examined,and their activation energies are *** in the fundamental understanding of the dynamics of the ion transport process in oil-paper insulation is vital to improving their insulating properties for oil-impregnated power transformers.

关键词： insulation transport fields

On a Heuristic Point of View about the Generalization of Curie Law to Cosmic Higgs fields with the Casimir Effect

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Journal of Applied Mathematics and Physics 2024年第9期12卷 3135-3147页

作者： Hung-Te Henry Su Po-Han Lee Department of Physics National Chung Cheng University Chia-Yi Department of Electro-Optical Engineering National Taipei University of Technology Taipei City The Affiliated Senior High School of National Taiwan Normal University Taipei City

Condensed state physics demonstrates that the Curie temperature is the point at which spontaneous magnetization drops to zero, marking the critical transition where ferromagnetic or ferrimagnetic materials transform into paramagnetic substances. Below the Curie temperature, a material remains ferromagnetic;above it, the material becomes paramagnetic, with its magnetic field easily influenced by external magnetic fileds. For example, the Curie temperature of iron (Fe) is 1043 K, while that of neodymium magnets ranges from 583 to 673 K. From both physics and mathematics perspectives, examining the temperature properties of materials is essential, as it provides valuable insights into their electromagnetic and thermodynamic behaviors. This paper makes a bold assumption and, for the first time, carefully verifies the existence of a Casimir temperature at 0.00206 K under conditions of one-atomic spacing.

关键词： Curie Temperature Curie Point Casimir Temperature Critical Point fields Materials One-Atomic Spacing

Accurate energy barriers for catalytic reaction pathways: an automatic training protocol for machine learning force fields

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npj Computational Materials 2023年第1期9卷 479-488页

作者： Lars L.Schaaf Edvin Fako Sandip De Ansgar Schäfer Gábor Csányi Engineering Laboratory University of CambridgeCB21PZ CambridgeUK BASF SE Carl-Bosch-Straße 3867056 LudwigshafenGermany

We introduce a training protocol for developing machine learning force fields(MLFFs),capable of accurately determining energy barriers in catalytic reaction *** protocol is validated on the extensively explored hydrogenation of carbon dioxide to methanol over indium *** the help of active learning,the final force field obtains energy barriers within 0.05 eV of Density Functional *** to the computational speedup,not only do we reduce the cost of routine in-silico catalytic tasks,but also find an alternative path for the previously established rate-limiting step,with a 40%reduction in activation ***,we illustrate the importance of finite temperature effects and compute free energy *** transferability of the protocol is demonstrated on the experimentally relevant,yet unexplored,top-layer reduced indium oxide *** ability of MLFFs to enhance our understanding of extensively studied catalysts underscores the need for fast and accurate alternatives to direct ab-initio simulations.

关键词： surface catalytic fields

Strain engineering of 2D semiconductors and graphene:from strain fields to band-structure tuning and photonic applications

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Light(Science & Applications) 2020年第1期9卷 130-154页

作者： Zhiwei Peng Xiaolin Chen Yulong Fan David J.Srolovitz Dangyuan Lei Department of Materials Science and Engineering City University of Hong Kong83 Tat Chee AvenueKowloonHong Kong 999077China Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityHung HomHong Kong 999077China

Two-dimensional(2D)transition metal dichalcogenides(TMDCs)and graphene compose a new family of crystalline materials with atomic thicknesses and exotic mechanical,electronic,and optical *** to their inherent exceptional mechanical flexibility and strength,these 2D materials provide an ideal platform for strain engineering,enabling versatile modulation and significant enhancement of their optical *** instance,recent theoretical and experimental investigations have demonstrated flexible control over their electronic states via application of external strains,such as uniaxial strain and biaxial ***,many nondestructive optical measurement methods,typically including absorption,reflectance,photoluminescence,and Raman spectroscopies,can be readily exploited to quantitatively determine strain-engineered optical *** review begins with an introduction to the macroscopic theory of crystal elasticity and microscopic effective low-energy Hamiltonians coupled with strain fields,and then summarizes recent advances in strain-induced optical responses of 2D TMDCs and graphene,followed by the strain engineering *** concludes with exciting applications associated with strained 2D materials,discussions on existing open questions,and an outlook on this intriguing emerging field.

关键词： strain fields discussions

Superchiral near fields detect virus structure

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Light(Science & Applications) 2020年第1期9卷 103-112页

作者： Tarun Kakkar Chantal Keijzer Marion Rodier Tatyana Bukharova Michael Taliansky Andrew J.Love Joel J.Milner Affar S.Karimullah Laurence D.Barron Nikolaj Gadegaard Adrian J.Lapthorn Malcolm Kadodwala School of Chemistry Joseph Black BuildingUniversity of GlasgowGlasgow G128QQUK Institute of Molecular Cell and Systems Biology and School of Life SciencesUniversity of GlasgowG128QQ GlasgowUK James Hutton Inst Cell&Mol SciDundee DD25DAUK Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS Moscow 117997Russia School of Engineering Rankine BuildingUniversity of GlasgowGlasgow G128LTUK

Optical spectroscopy can be used to quickly characterise the structural properties of individual ***,it cannot be applied to biological assemblies because light is generally blind to the spatial distribution of the component *** insensitivity arises from the mismatch in length scales between the assemblies(a few tens of nm)and the wavelength of light required to excite chromophores(≥150 nm).Consequently,with conventional spectroscopy,ordered assemblies,such as the icosahedral capsids of viruses,appear to be indistinguishable isotropic spherical *** limits potential routes to rapid high-throughput portable detection appropriate for point-of-care ***,we demonstrate that chiral electromagnetic(EM)near fields,which have both enhanced chiral asymmetry(referred to as superchirality)and subwavelength spatial localisation(∼10 nm),can detect the icosahedral structure of virus ***,they can detect both the presence and relative orientation of a bound virus *** illustrate the potential uses of the exquisite structural sensitivity of subwavelength superchiral fields,we have used them to successfully detect virus particles in the complex milieu of blood serum.

关键词： chiral detect fields

Trajectory analysis of few-cycle strong field ionization in two-color circularly polarized fields

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Chinese Physics B 2019年第9期28卷 16-21页

作者： Yan Huang Chaochao Qin Yizhu Zhang Xincheng Wang Tian-Min Yan Yuhai Jiang College of Physics and Materials Science Henan Normal UniversityXinxiang 453007China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China ShanghaiTech University Shanghai 201210China Key Laboratory of Opto-electronics Information and Technical Science Tianjin UniversityTianjin 300072China

Bichromatic circularly polarized fields provide a useful tool to probe the ionization *** this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different *** spectral features are analyzed with semiclassical trajectories derived from the strong field *** particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released *** types of trajectories that contribute to the interference fringes are elucidated.

关键词： strong field ionization semiclassical trajectories bicircularly polarized fields photoelectron momentum

Heavy fermions in high magnetic fields

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Chinese Physics B 2019年第1期28卷 25-38页

作者： M Smidman B Shen C Y Guo L Jiao X Lu H Q Yuan Center for Correlated Matter and Department of Physics Zhejiang UniversityHangzhou 310058China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

Heavy fermion materials are prototypical strongly correlated electron systems, where the strong electron–electron interactions lead to a wide range of novel phenomena and emergent phases of matter. Due to the low energy scales, the relative strengths of the Ruderman–Kittel–Kasuya–Yosida(RKKY) and Kondo interactions can often be readily tuned by non-thermal control parameters such as pressure, doping, or applied magnetic fields, which can give rise to quantum criticality and unconventional superconductivity. Here we provide a brief overview of research into heavy fermion materials in high magnetic fields, focussing on three main areas. Firstly we review the use of magnetic fields as a tuning parameter,and in particular the ability to realize different varieties of quantum critical behaviors. We then discuss the properties of heavy fermion superconductors in magnetic fields, where experiments in applied fields can reveal the nature of the order parameter, and induce new novel phenomena. Finally we report recent studies of topological Kondo systems, including topological Kondo insulators and Kondo–Weyl semimetals. Here experiments in magnetic fields can be used to probe the topologically non-trivial Fermi surface, as well as related field-induced phenomena such as the chiral anomaly and topological Hall effect.

关键词： heavy fermions high magnetic fields quantum phase transitions heavy fermion superconductivity topological Kondo systems

Helicity of harmonic generation and attosecond polarization with bichromatic circularly polarized laser fields

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Chinese Physics B 2019年第10期28卷 321-326页

作者： Jun Zhang Tong Qi Xue-Fei Pan Jing Guo Kai-Guang Zhu Xue-Shen Liu College of Instrumentation and Electrical Engineering Jilin UniversityChangchun 130026China Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China

We theoretically investigate the high-order harmonic generation(HHG) of helium atom driven by bichromatic counterrotating circularly polarized laser fields. By changing the intensity ratio of the two driving laser fields, the spectral chirality of the HHG can be controlled. As the intensity ratio increases, the spectral chirality will change from positive-to negativevalue around a large intensity ratio of the two driving fields when the total laser intensity keeps unchanged. However, the sign of the spectral chirality can be changed from positive to negative around a small intensity ratio of the two driving fields when the total laser intensity changes. At this time, we can effectively control the helicity of the harmonic spectrum and the polarization of the resulting attosecond pulses by adjusting the intensity ratio of the two driving laser fields. As the intensity ratio and the total intensity of the driving laser fields increase, the relative intensity of either the left-circularly or right-circularly polarized harmonic can be enhanced. The attosecond pulses can evolve from being elliptical to near linear correspondingly.

关键词： high-order harmonic generation bichromatic circularly polarized laser fields spectral chirality attosecond polarization

Constitutive parameters identification of thermal barrier coatings using the virtual fields method

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Acta Mechanica Sinica 2019年第1期35卷 78-87,I0003页

作者： Mengmeng Zhou Huimin Xie Luming Li School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

Thermal barrier coatings (TBCs) are widely applied in thermal components to protect metallic components. Owing to the complex layered structure of TBCs and difficult preparation of coating, the mechanical characterization of TBCs should be of primary importance. With regard to TBCs, this study deals with the constitutive parameters identification of bi-material. Considering the complex construction and boundary of bi material, the virtual fields method (VFM) was employed in this study. A methodology based on the optimized virtual fields method combined with moire interferometry was proposed for the constitutive parameters identification of bi-material. The feasibility of this method is verified using simulated deformation fields of a two-layer material subjected to three point ben ding loading. As an application, the deformation fields of the TBC specimens were measured by moire interferometry. Then, lhe mechanical parameters of the coating were identified by the proposed method. The identification results indicate that Young's modulus of the TBC top coating is 89.91 GPa, and its Poisson's ratio is 0.23.

关键词： Virtual fields Method Thermal barrier coatings Mechanical parameters identification Moiré interferometry