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Carrier-driven magnetic and topological phase transitions in twodimensional III-V semiconductors

Nano Research 2023年第2期16卷 3443-3450页

作者： Yan Li Xinru ma Hongwei Bao Jian Zhou Fei ma Jingbo Li State Key Laboratory for mechanical Behavior of materials Xi’an Jiaotong UniversityXi’an 710049China Center for Alloy Innovation and Design Xi’an Jiaotong UniversityXi’an 710049China Institute of Semiconductors South China Normal UniversityGuangzhou 510631China

III-V semiconductors such as GaAs are widely studied as promising candidates for high-speed integrated *** these applications for conventional bulk structures,their fundamental physical properties in the nanoscale limit are still in scarcity,which is of great importance for the development of *** this work,we demonstrate that the III-V semiconductor mX(m=Al,Ga,In;X=P,As,Sb)in its two-dimensional(2D)limit could exhibit double layer honeycomb(DLHC)configuration and distorted tetrahedral coordination,according to our first-principles calculations with HSE06 hybrid *** is found that surface reconstruction endows 2D III-V DLHCs with pronouncedly different electronic and magnetic properties from their bulk counterparts due to strong interlayer ***-hat-shape bands emerge at the top valence bands of pristine AlP,GaP,InP,AlAs,and InAs DLHCs,inducing the density of states showing a sharp van Hove singularity near the Fermi *** a result,these DLHCs exhibit itinerant magnetism upon moderate hole doping,while the rest GaAs,AlSb,GaSb,and InSb DLHCs become magnetic under tensile strain with hole *** an exchange splitting of the localized pz states at the top valence bands,the hole-doped III-V DLHCs become half-metals with 100%***,the InSb DLHC shows inverted band structure near the Fermi level,bringing about nontrivial topological band structures in stacked InSb DLHC due to the strong spin-orbital *** III-V DLHCs expand the members of 2D material family and their exotic magnetic and topological properties may offer great potential for applications in the novel electronic and spintronic devices.

关键词： III-V semiconductors HSE06 hybrid functional mexican-hat-shape bands magnetism topological bands

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ACHIEVING ADVERSARIAL ROBUSTNESS REQUIRES AN ACTIVE TEACHER

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Journal of Computational mathematics 2021年第6期39卷 880-896页

作者： Chao ma Lexing Ying Department of mathematics Stanford UniversityCaliforniaUSA

A new understanding of adversarial examples and adversarial robustness is proposedby decoupling the data generator and the label generator (which we call the teacher). Inour framework, adversarial robustness is a conditional concept—the student model is notabsolutely robust, but robust with respect to the teacher. Based on the new understanding, we claim that adversarial examples exist because the student cannot obtain sufficientinformation of the teacher from the training data. Various ways of achieving robustness iscompared. Theoretical and numerical evidence shows that to efficiently attain robustness,a teacher that actively provides its information to the student may be necessary.

关键词： Adversarial robustness Decoupled supervised learning Active teacher

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mODIFIED ALTERNATING POSITIVE SEmIDEFINITE SPLITTING PRECONDITIONER FOR TImE-HARmONIC EDDY CURRENT mODELS

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Journal of Computational mathematics 2021年第5期39卷 733-754页

作者： Yifen Ke Changfeng ma College of mathematics and Informatics FJKLmaA Fujian Normal UniversityFuzhou 350117China

In this paper,we consider a modified alternating positive semidefinite splitting preconditioner for solving the saddle point problems arising from the finite element discretization of the hybrid formulation of the time-harmonic eddy current *** eigenvalue distribution and an upper bound of the degree of the minimal polynomial of the preconditioned matrix are studied for both simple and general *** results demonstrate the effectiveness of the proposed preconditioner when it is used to accelerate the convergence rate of Krylov subspace methods such as GmRES.

关键词： Time-harmonic eddy current model Saddle point problem Eigenvalue distribution Preconditioner

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RNA methylation preserves ES cell identity by chromatin silencing of retrotransposons

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Signal Transduction and Targeted Therapy 2021年第8期6卷 2259-2260页

作者： Zhaofa Xu Annabel ma Yongchao C.ma Departments of Pediatrics Neurology and PhysiologyNorthwestern University Feinberg School of MedicineAnn&Robert H.Lurie Children’s Hospital of ChicagoChicagoILUSA

RNA methylation on N6-methyladenosine(m6A)and histone methylation are critical mechanisms regulating gene expression at epitranscriptomic and epigenetic levels,***,how RNA methylation modulates histone methylation,and in which biological processes,is *** a recent study published in Nature,Liu et al.1 identified the critical roles of m6A and its reader YTHDC1 in mediating histone methylation and chromatin silencing of retrotransposon genes to preserve embryonic stem(ES)cell identity.

关键词： preserve identity.

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Goosegrass (Eleusine indica) density effects on cotton (Gossypium hirsutum)

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Journal of Integrative Agriculture 2015年第9期14卷 1778-1785页

作者： ma Xiao-yan WU Han-wen JIANG Wei-li ma Ya-jie ma Yan State Key Laboratory of Cotton Biology Institute of Cotton ResearchChinese Academy of Agricultural Sciences Wagga Wagga Agricultural Institute NSW Department of Primary Industries

Goosegrass is one of the worst agricultural weeds on a worldwide basis. Understanding of its interference impact in crop ifeld wil provide useful information for weed control programs. Field experiments were conducted during 2010–2012 to determine the inlfuence of goosegrass density on cotton growth at the weed densities of 0, 0.125, 0.25, 0.5, 1, 2, and 4 plants m–1 of row. Seed cotton yield tended to decrease with the increase in weed density, and goosegrass at a density of 4 plants m–1 of row signiifcantly reduced cotton yields by 20 to 27%. A density of 11.6–19.2 goosegrass plant m–1 of row would result in a 50%cotton yield loss from the maximum yield according to the hyperbolic decay regression model. Bol production was not affected in the early growing season. But bol numbers per plant were reduced about 25%at the den-sity of 4 plants m–1 of row in the late growing season. Both cotton bol weight and seed numbers per bol were signiifcantly reduced (8%) at 4 goosegrass plants m–1 of row. Cotton plant height, stem diameter and sympodial branch number were not affected as much as cotton yields by goosegrass competition. Seed index, lint percentage and lint ifber properties were unaffected by weed competition. Intraspeciifc competition resulted in density-dependent effects on weed biomass per plant, 142–387 g dry weight by harvest. Goosegrass biomass m–2 tended to increase with increasing weed density as indicated by a quadratic response. The adverse impact of goosegrass on cotton yield identiifed in this study has indicated the need of effective goosegrass management.

关键词： competition goosegrass cotton yield fiber properties weed biomass

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Influence of processing parameters on the phase composition of ZrN-Si_3N_4 synthesized from zircon

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Rare metals 2009年第4期28卷 367-371页

作者： ma Beiyue YU Jingkun School of materials and metallurgy Northeastern University Shenyang 110004 China

The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.

关键词： inorganic non-metal materials nitrides carbothermal reduction-nitridation zircon processing parameters phase composition

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Spatiotemporal Trends and Ecological Determinants in Population by Elevation in China Since 1990

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Chinese Geographical Science 2021年第2期31卷 248-260页

作者： ma Chaoqun HE Yanfen College of Earth Science and Resources Chang’an UniversityXi’an 710054China Yellow River Institute of Shaanxi Province College of Urban and Environment SciencesNorthwest UniversityXi’an 710127China

It is very important to understand the ecological and socio-economic factors in population distribution and their changes over time for the compilation of regional development planning and the guidance of rational population *** surface-based population data for China from 1990 to 2015,the national distribution and dynamics of the human population by elevation are quantified based on 1-km cell-size gridded distribution datasets and 1-km cell-size DEm(digital elevation model).A geographical detector model is used to quantitatively analyze the dominant role of natural geographical factors,such as topography and climate,on the spatial distribution of *** show that:1)the population size and density decrease rapidly with elevation below 1000 m above the sea level,and the gap in population density between low-altitude areas and high-altitude areas increases with time because of the continuous growth of population density in low-altitude areas;2)the distribution of the population can be divided into five steps according to integrated population density(IPD),in proportions of 43∶35∶21∶1∶0,and that these proportions have remained stable over the last 25 yr;3)the basic pattern of population spatial distribution is determined by natural geographical environment factors,such as topography,climate,geomorphology,and their interactions;and 4)the development of society and the economy are the driving forces for the dynamic change in the population distribution during the study period,with the distribution pattern and dynamics of population by altitude in China providing a comprehensive reflection of various geographical elements on different spatial scales.

关键词： population distribution vertical distribution hypsographic demography geographical detector model China

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Different Diffusion Behavior of Cu and Ni Undergoing Liquidesolid Electromigration

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Journal of materials Science & Technology 2014年第12期30卷 1235-1242页

作者： m.L.Huang Z.J.Zhang H.T.ma L.D.Chen Electronic Packaging materials Laboratory School of Materials Science & Engineering Dalian University of Technology IC Packaging Department Xi'an Institute of Microelectronic Technology

The diffusion behavior of Cu and Ni atoms undergoing liquidesolid electromigration（L-S Em） was investigated using Cu/Sn/Ni interconnects under a current density of 5.0 103A/cm2 at 250℃. The flowing direction of electrons significantly influences the cross-solder interaction of Cu and Ni atoms, i.e., under downwind diffusion, both Cu and Ni atoms can diffuse to the opposite interfaces; while under upwind diffusion,Cu atoms but not Ni atoms can diffuse to the opposite interface. When electrons flow from the Cu to the Ni, only Cu atoms diffuse to the opposite anode Ni interface, resulting in the transformation of interfacial intermetallic compound（ImC） from Ni3Sn4into（Cu,Ni）6Sn5and further into [（Cu,Ni）6Sn5t Cu6Sn5], while no Ni atoms diffuse to the opposite cathode Cu interface and thus the interfacial Cu6Sn5 *** electrons flow from the Ni to the Cu, both Cu and Ni atoms diffuse to the opposite interfaces,resulting in the interfacial ImC transformation from initial Cu6Sn5into（Cu,Ni）6Sn5and further into[（Cu,Ni）6Sn5t（Ni,Cu）3Sn4] at the anode Cu interface while that from initial Ni3Sn4into（Cu,Ni）6Sn5and further into（Ni,Cu）3Sn4at the cathode Ni interface. It is more damaging with electrons flowing from the Cu to the Ni than the other way.

关键词： Cu/Sn/Ni Electromigration Cross-solder interaction Interfacial reaction Diffusion

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Phase composition of SiC-ZrO2 composite materials synthesized from zircon doped La2O3

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Journal of Rare Earths 2009年第5期27卷 806-810页

作者： ma Beiyue YU Jingkun School of materials and metallurgy Northeastern University Shenyang 110004 China School of Materials and Metallurgy Northeastern University Shenyang 110004 China

A study was carried out to determine the optimum parameters for synthesis of SiC-ZrO2 composite materials by carbothermal re-duction of zircon. Test samples were prepared by mixing average mesh size of less than 30 μm of carbon black and 40 μm of zircon with C/ZrSiO4 mass ratio of 0.2 and the extra addition amount of La2O3 was 0, 1 wt.% and 2 wt.%. Prepared samples were subjected to the car-bothermal reduction process at temperatures of 1723, 1753, 1773 and 1803 K for 4 h, respectively. The carbothermal reduction process was conducted in an atmosphere controlled tube furnace at an argon flow of 1.5 L/min. All products were examined by X-ray diffraction (XRD) to determine the transformation. The results showed that the best transformation of SiC-ZrO2 composite materials occurred at 1803 K for 4 h with the amount of 2 wt.%La2O3.

关键词： composite materials carbothermal reduction zircon lanthanum oxide rare earths

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Effect of Initial Vortex Intensity Correction on Tropical Cyclone Intensity Prediction:A Study Based on GRAPES_TYm

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Journal of meteorological Research 2020年第2期34卷 387-399页

作者： Liwen WANG Suhong ma Key Laboratory for Aerosol–Cloud–Precipitation of China meteorological Administration School of Atmospheric PhysicsNanjing University of Information Science&TechnologyNanjing 210044 National meteorological Center China Meteorological AdministrationBeijing 100081

Predicting the intensity of tropical cyclones(TCs)is challenging in operational weather prediction systems,partly due to the difficulty in defining the initial *** an attempt to solve this problem,this study investigated the effect of initial vortex intensity correction on the prediction of the intensity of TCs by the operational numerical prediction system GRAPES_TYm(Global and Regional Assimilation and Prediction System_Typhoon model)of the National meteorological Center of the China meteorological *** statistical results based on experiments using data for major TCs in 2018 show that initial vortex intensity correction can reduce the errors in mean intensity for up to 120-h integration,with a noticeable decrease in the negative bias of intensity and a slight increase in the mean track *** correction leads to an increase in the correlation coefficient of Vmax(maximum wind speed at 10-m height)for the severe typhoon and super typhoon *** of the errors in intensity at different stages of intensity(including tropical storms,severe tropical storms,typhoons,severe typhoons,and super typhoons)show that vortex intensity correction has a remarkable positive influence on the prediction of super typhoons from 0 to *** of the errors in intensity for TCs with different initial intensities indicate that initial vortex correction can significantly improve the prediction of intensity from 24 to 96 h for weak TCs(including tropical storms and severe tropical storms at the initial time)and up to 24 h for strong TCs(including severe typhoons and super typhoons at the initial time).The effect of the initial vortex intensity correction is more important for developing TCs than for weakening TCs.

关键词： vortex intensity correction intensity bias intensity error tropical cyclones

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