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A gauge theory for two-band model of Chern insulators and induced topological defects

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Communications in Theoretical Physics 2022年第1期74卷 124-133页

作者： zhi-wen chang Wei-chang Hao Xin Liu Institute of Theoretical Physics Faculty of SciencesBeijing University of TechnologyBeijing 100124China School of Physics Beihang UniversityBeijing 100191China

In this paper a gauge theory is proposed for the two-band model of Chern *** on the so-calle't Hooft monopole model,a U(1)Maxwell electromagnetic sub-field is constructed from an SU(2)gauge field,from which arise two types of topological defects,monopoles and e2 *** focus on the topological number in the Hall conductance σ_(xy)=e^(2)/hC,where C is the Chern *** is discovered that in the monopole case C is indeterminate,while in the meron case C takes different values,due to a varying on-site energy *** a typical example,we apply this method to the square lattice and compute the winding numbers(topological charges)of the defects;the C-evaluations we obtain reproduce the results of the usual ***,based on the gauge theory we propose a new model to obtain the high Chern numbers|C|=2,4.

关键词： Chern insulator Chern number monopole meron

Decorating carbon nanofibers with Mo_2C nanoparticles towards hierarchically porous and highly catalytic cathode for high-performance Li-O_2 batteries

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Science Bulletin 2018年第7期63卷 433-440页

作者： Zhen-Dong Yang zhi-wen chang Qi Zhang Keke Huang Xin-Bo Zhang Key Laboratory of Automobile Materials Ministry of Education Department of Materials Science and Engineering Jilin University State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences Hunan Key Laboratory for Micro-Nano Energy Materials and Device Xiangtan University State Key Laboratory of Inorganic Synthesis & Preparative Chemistry Jilin University

A facile synthesis of the hierarchically porous cathode with Mo2C nanoparticles through the electrospinning technique and heat treatment is proposed. The carbonization temperature of the precursors is the key factor for the formation of M02C nanoparticles on the carbon nanofibers （MCNFs）. Compared with the Mo2N nanoparticles embedded into N-doped carbon nanofibers film （MNNFs） and N-doped carbon nanofibers film （NFs）, the battery with MCNFs cathode is capable of operation with a high-capacity （10,509 mAhg-1 at 100 mAg-l）, a much reduced discharge-charge voltage gap, and a long-term life （124 cycles at 200 mA g-1 with a specific capacity limit of 500 mAh g -1）. These excellent performances are derived from the synergy of the following advantageous factors：（1） the hierarchically self-standing and binder-free structure of MCNFs could ensure the high diffusion flux of Li＋ and O2 as well as avoid clogging of the discharge product, bulk Li202; （2） the well dispersed M02C nanoparticles not only afford rich active sites, but also facilitate the electronic transfer for catalysis.

关键词： Li-O2 battery Carbon nanofibers film Mo2C nanoparticles Electrospinning Binder-free

Anchoring Iron-EDTA Complex on Graphene toward the Synthesis of Highly Efficient Fe-N-C Oxygen Reduction Electrocatalyst for Fuel Cells

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Chinese Journal of Chemistry 2018年第4期36卷 287-292页

作者： zhi-wen chang Fan-Lu Meng Hai-Xia Zhong Xin-Bo Zhang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun Jilin 130022 China University of Chinese Academy of Sciences Beijing 100049 China

Developing nonprecious carbon electrocatalysts as alternatives to platinum for cathodic oxygen reduction reaction in fuel cells is of signifi- cance. Herein, an efficient precursor-controlled synthesis strategy based on extremely rapid nucleation and deposition process assisted by the liquid nitrogen freeze drying method is explored to anchor cheap iron-EDTA complex evenly dispersed on graphene to realize mJcrostructural homogeneity of the derived Fe-N-C oxygen reduction electrocatalyst. The prepared electrocatatyst possesses excellent performance including high activity with more positive onset and half-wave potential, a long-term stability, and anti-poisoning effect compared to commercial Pt/C. The activity correlates well with the unique sheet-shaped morphology, high surface area, hierarchical porous structure, and the introduction of Fe-Nx/C species. Especially, both the assembled practical alkaline and acid fuel cells based on the synthesized cathode catalysts reveal excellent performance with high open-circuit voltage and power density.

关键词： iron-EDTA complex iron-nitrogen-doping carbon porous nanosheets oxygen reduction reaction fuel cells

CeO2@NiCo2O4 nanowire arrays on carbon textiles as high performance cathode for Li-O2 batteries

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Science China Chemistry 2017年第12期60卷 1540-1545页

作者： Zhen-Dong Yang zhi-wen chang Ji-Jing Xu Xiao-Yang Yang Xin-Bo Zhang State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Key Laboratory of Automobile Materials(Jilin University) Ministry of EducationDepartment of Materials Science and EngineeringJilin UniversityChangchun 130022China University of Chinese Academy of Sciences Beijing100049China

The successful development of Li-O_2 battery technology depends on developing a stable and efficient cathode. As an important step toward this goal, for the first time, we report the development of CeO_2 nanoparticles modified NiCo_2O_4 nanowire arrays(NWAs) grown on the carbon textiles as a new carbon-free and binder-free cathode system. In this study, the Li-O_2 battery with the CeO_2@NiCo_2O_4 NWAs has exhibited much reduced overpotentials, a high discharge capacity, an improved cycling stability,outperforming the Li-O_2 battery with NiCo_2O_4 NWAs. These improvements can be attributed to both the tailored morphology of discharge product and improved oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) activity after CeO_2 NPs deposition. To a considerable extent, this idea of cathode construction including structure design and composition optimization can provide guidance for further researches in developing more powerful cathode for Li-O_2 battery.

关键词： Li-O2 battery efficient cathode design CeO2 nanoparticles NiCo2O4 nanowire arrays improved electrochemical performances

A new two-step variational model for multiplicative noise removal with applications to texture images

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Applied Mathematics(A Journal of Chinese Universities) 2024年第3期39卷 486-501页

作者： ZHANG Long-hui YAO wen-juan SHI Sheng-zhu GUO zhi-chang ZHANG Da-zhi School of Mathematics Harbin Institute of TechnologyHarbin 150001China

Multiplicative noise removal problems have attracted much attention in recent *** additive noise,multiplicative noise destroys almost all information of the original image,especially for texture *** by the TV-Stokes model,we propose a new two-step variational model to denoise the texture images corrupted by multiplicative noise with a good geometry explanation in this *** the first step,we convert the multiplicative denoising problem into an additive one by the logarithm transform and propagate the isophote directions in the tangential field *** the isophote directions are constructed,an image is restored to fit the constructed directions in the second *** existence and uniqueness of the solution to the variational problems are *** these two steps,we use the gradient descent method and construct finite difference schemes to solve the ***,the augmented Lagrangian method and the fast Fourier transform are adopted to accelerate the *** results show that the proposed model can remove the multiplicative noise efficiently and protect the texture well.

关键词： multiplicative noise removal texture images total variation two-step variational method aug-mented Lagrangian method

Reducing Operation Emissions and Improving Work Efficiency Using a Pure Electric Wheel Drive Tractor

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Engineering 2024年第6期37卷 230-245页

作者： chang-Kai wen wen Ren Qing-Zhen Zhu Chun-Jiang Zhao Zhen-Hao Luo Sheng-Li Zhang Bin Xie zhi-Jun Meng Research Center of Intelligent Equipment Beijing Academy of Agriculture and Forestry SciencesBeijing 100097China State Key Laboratory of Intelligent Agricultural Power Equipment Beijing 100097China BYD Company Limited Shenzhen 518118China College of Agricultural Engineering Jiangsu UniversityZhenjiang 212013China College of Engineering China Agricultural UniversityBeijing 100083China

In response to the problems of excessive greenhouse-gas and particulate emissions and the low traction efficiency of conventional diesel tractors in the field,a purely electric wheel-side drive tractor was studied,including an electric motor drive system,a battery ballast system,and an electro–hydraulic suspension *** paper develops a dynamics model of an electric tractor-ploughing unit under complex soil conditions,leading to the proposal of an active control method for drive wheel torque and a joint control method for the traction force of the suspension system and the front-and rear-axle loads of a ***,the tractor is prototyped and assembled,and ploughing tests are carried *** ploughing results show that the active torque-distribution control method proposed in this study reduces the tractor slip by 14.83%and increases the traction efficiency by 10.28%compared with the average torquedistribution *** with the conventional traction control mode,the joint control method for traction and ballast proposed in this paper results in a 3.7%increase in traction efficiency,a 15.05%decrease in slip,and a 4.9%reduction in total drive motor energy *** study will help to improve the operation quality and traction efficiency of electric tractors in complex soil conditions.

关键词： Electric tractor Ploughing unit Torque distribution Active ballast Traction performance

Exciton Bose–Einstein Condensation in Transition Metal Dichalcogenide Monolayer under In-Plane Magnetic Fields

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Chinese Physics Letters 2024年第8期41卷 69-76页

作者： Dengfeng Wang Yingda Chen zhi-Chuan Niu wen-Kai Lou Kai chang SKLSM Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China College of Materials Science and Opto-electronic Technology Center of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of SciencesBeijing 100049China School of Physics Zhejiang UniversityHangzhou 310027China

Based on the Gross–Pitaevskii equation,we theoretically investigate exciton Bose–Einstein condensation(BEC)in transition metal dichalcogenide monolayers(TMDC-MLs)under in-plane magnetic *** observe that the in-plane magnetic fields exert a strong influence on the exciton BEC wave functions in TMDC-MLs because of the mixing of the bright and dark exciton states via Zeeman *** leads to the brightening of the dark exciton BEC *** competition between the dipole–dipole interactions caused by the long-range Coulomb interaction and the Zeeman effect induced by the in-plane magnetic fields can effectively regulate dark exciton BEC *** findings emphasize the utility of TMD-MLs as platforms for investigating collective phenomenon involving excited states.

关键词： effect Einstein dipole

Transition metals for stabilizing lithium metal anode:advances and perspectives

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Tungsten 2024年第1期6卷 212-229页

作者： Si-Cheng Miao Ye Jia zhi-wen Deng Yan Deng Ruo-Xuan Chen Xue-Mei Zhang chang-Haoyue Xu Meng Yao wen-Long Cai Department of Advanced Energy Materials College of Materials Science and EngineeringSichuan UniversityChengdu 610064China

As the capacity of lithium-ion batteries gradually reaches its limit,the high-capacity characteristics of lithium metal batteries(LMBs)make them one of the most promising electrochemical energy storage devices ***,uncontrolled lithium dendrite growth can cause poor cell performance and severe safety issues,seriously slowing down the commercialization of *** metals(TMs)are lithiophilic materials that effectively stabilize lithium metal anode(LMA)and inhibit dendrite ***,the growth of lithium dendrites and the performance of TMs in stabilizing lithium metals are comprehensively discussed in this ***,we elucidated the formation mechanisms of lithium dendrite,and we put forward several strategies to suppress lithium dendrite formation based on the understanding of these ***,the application of TMs and their compounds to stabilize LMA and their corresponding mechanisms are comprehensively ***,further research perspectives of TMs in stabilizing LMA are emphasized in detail.

关键词： Transition metals Lithium metal batteries Lithium dendrite Solid electrolyte interphase Formation mechanism

Amplification effect of intra-seasonal variability of soil moisture on heat extremes over Eurasia

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Advances in Climate change Research 2024年第1期15卷 1-8页

作者： Yi-Nuo WANG zhi-Yan ZUO Liang QIAO Kai-wen ZHANG Mei-Yu chang Dong XIAO Zou-Xing LIN Huan WANG Department of Atmospheric and Oceanic Sciences Institute of Atmospheric SciencesFudan UniversityShanghai 200438China CMA-FDU Joint Laboratory of Marine Meteorology Shanghai 200438China Key Laboratory of Cites Mitigation and Adaptation to Climate change in Shanghai China Meteorological AdministrationShanghai 200030China Collaborative Innovation Centeron Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 211800China Shanghai Frontiers Science Center of Atmosphere-Ocean Interaction Shanghai 200123China College of Geography and Resources Science Sichuan Normal UniversityChengdu 610101China National Observations and Research Station for Wetland Ecosystems of the Yangtze Estuary Shanghai 202183China Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081China

Drying soil has been conducive to a high frequency of extreme high-temperature events over many regions worldwide in recent ***,changes in the intraseasonal variability of soil moisture can also influence the likelihood of extremely high *** previous investigators have examined the association between extremely high temperatures and large-scale atmospheric circulation variability,the role of land-atmosphere coupling dominated by soil moisture variability in extremely high temperatures,particularly over the Eurasian continent,is not well *** this study,on the basis of the Land Surface,Snow,and Soil Moisture Model Intercomparison Project,we found that land-atmosphere feedback amplified the variability of soil moisture in most regions of Eurasia during summer from 1980 to *** amplification of soil moisture variability is closely correlated with more intensive intraseasonal variability of surface air temperature and more frequent occurrences of extreme high-temperature events,particularly in Europe,Siberia,Northeast Asia,and the Indochina *** correlation implies that increasing the intraseasonal variability of soil moisture results in a high likelihood of heat extremes during summer in most parts of Eurasia except Asian desert *** the intraseasonal timescale,the land-atmosphere coupling increases the variability of surface sensible heat flux and net long-wave radiation heating the atmosphere by intensifying the soil moisture variability,thus amplifying the variability of surface air temperature and enhancing the extreme high-temperature *** finding demonstrates the importance of changes in intraseasonal soil moisture variability for the increasing likelihood of heat extremes in summer.

关键词： Soil moisture Intraseasonal variability Land-atmosphere coupling Heat extremes