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Changes of Population, Built-up Land, and Cropland Exposure to Natural Hazards in China from 1995 to 2015

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International Journal of Disaster Risk Science 2019年第4期10卷 557-572页

作者： Yimin Chen wei xie Xiaocong Xu School of Geography and Planning Sun Yat-sen UniversityGuangzhou 510275China Guangdong Key Laboratory for Urbanization and Geosimulation Sun Yat-sen UniversityGuangzhou 510275China

By using the latest China population grid and land-use data,we assess the changing exposure of China’s population and land uses to the hazards of storm surges,droughts,earthquakes,floods,and landslides from 1995 *** found that the single-hazard areas and the multihazard areas covered 43%and 26%of China’s territory,*** grew faster in the hazard-prone areas than in the non-hazard ***-up area expanded more rapidly in the areas prone to earthquakes and *** changed rapidly in many hazard-prone *** hazard-prone areas affected by floods featured the highest cropland loss rates,while the areas prone to earthquakes and landslides featured the highest cropland growth *** detected areas with significant exposure changes by using hot spot *** was found that population and built-up land in the Pearl River Basin were increasingly exposed to storm surges,floods,and *** Haihe River Basin and Huaihe River Basin also showed a consistent increase of population and built-up land exposure to droughts and *** findings can provide a foundation for the design and implementation of protection and adaptation strategies to improve the resilience of Chinese society to natural hazards.

关键词： China Exposure to natural hazards Population change Built-up land Cropland

A probability density function of liftoff velocities in mixed-size wind sand flux

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Science China(Physics,Mechanics & Astronomy) 2008年第8期51卷 976-985页

作者： ZHENG XiaoJing ZHU wei xie Li Key Laboratory of Mechanics on the Western Disaster and Environment Ministry of EducationLanzhou UniversityLanzhou 730000China

With the discrete element method(DEM) ,employing the diameter distribution of natural sands sampled from the Tengger Desert,a mixed-size sand bed was produced and the particle-bed collision was simulated in the mixed-size wind sand movement. In the simulation,the shear wind velocity,particle diameter,incident velocity and incident angle of the impact sand particle were given the same values as the experimental results. After the particle-bed collision,we collected all the initial velocities of rising sand particles,including the liftoff angular velocities,liftoff linear velocities and their horizontal and vertical components. By the statistical analysis on the velocity sample for each velocity component,its probability density functions were obtained,and they are the functions of the shear wind velocity. The liftoff velocities and their horizontal and vertical components are distributed as an exponential density function,while the angular velocities are distributed as a normal density function.

关键词： wind sand flux mixed-size particle diameter liftoff velocity probability density function(PDF) discrete element method(DEM)

Soil Aggregates and Fractal Features under Different Land Use Types in a Frequent Debris Flow Area

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Journal of Mountain Science 2013年第3期10卷 437-444页

作者： xie Xian-jian wei Fang-qiang School of Geography and Resources Science Neijiang Normal University Institute of Mountain Hazards and Environment Chinese Academy of Sciences

The stability of soil aggregates and the fractal characteristics of four typical land use types(farmland,grassland,woodland,and bare land) in the Jiangjiagou Ravine(Yunnan,China),a frequent debris flow occurring area,were studied according to the normal mean mass diameter and fractal *** present research showed that the stability of the soil aggregates was different for the different land use *** the soil depth was 0-30 cm,farmland soil formed more aggregates with diameters greater than 0.25 mm,i.e.,the farmland soil was more stable than that of the other three land *** the soil depth was 30-45 cm,the order of stability of the soil aggregates was woodland > grassland > farmland > bare *** fractal dimensions had a significant linear positive correlation with the amount of soil particles with diameters of <0.25 mm,and a significant negative linear correlation with the amount of soil particles with diameters of 0.25-0.5 mm,0.5-1 mm and 1-2 *** fractal dimensions of the soil particles correlated with more stable soil *** fractal dimensions had a positive linear correlation with the soil bulk density and a negative correlation with the concentration of organic *** results showed that soil aggregates can be used as a parameter for characterizing the soil structures and *** to these results,the soil particle fractal dimensions could not only objectively characterize the stability of the soil structure but also could be used to indicate soil structure and *** addition,these results have great significance for the discussion of the comprehensive evaluation of soil.

关键词： Debris flow Land use pattern Aggregates Fractal dimension

Normalized Wolfe-Powell-type local minimax method for finding multiple unstable solutions of nonlinear elliptic PDEs

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Science China Mathematics 2023年第10期66卷 2361-2384页

作者： wei Liu Ziqing xie Wenfan Yi Key Laboratory of Computing and Stochastic Mathematics(Ministry of Education) Hunan Normal UniversityChangsha 410081China School of Mathematics Hunan UniversityChangsha 410082China

The local minimax method(LMM)proposed by Li and Zhou(2001,2002)is an efficient method to solve nonlinear elliptic partial differential equations(PDEs)with certain variational structures for multiple *** steepest descent direction and the Armijo-type step-size search rules are adopted in Li and Zhou(2002)and play a significant role in the performance and convergence analysis of traditional *** this paper,a new algorithm framework of the LMMs is established based on general descent directions and two normalized(strong)Wolfe-Powell-type step-size search *** corresponding algorithm framework,named the normalized Wolfe-Powell-type LMM(NWP-LMM),is introduced with its feasibility and global convergence rigorously justified for general descent *** a special case,the global convergence of the NWP-LMM combined with the preconditioned steepest descent(PSD)directions is also ***,it extends the framework of traditional *** addition,conjugate-gradient-type(CG-type)descent directions are utilized to speed up the ***,extensive numerical results for several semilinear elliptic PDEs are reported to profile their multiple unstable solutions and compared with different algorithms in the LMM’s family to indicate the effectiveness and robustness of our *** practice,the NWP-LMM combined with the CG-type direction performs much better than its known LMM companions.

关键词： semilinear elliptic PDE multiple unstable solution local minimax method normalized strong Wolfe-Powell-type search rule conjugate-gradient-type descent direction general descent direction global convergence

Effects of flux on crystal structure and luminescent properties of nitroxides phosphors

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Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2228-2234页

作者： xie An SHI Yu WANG Yu wei School of Materials Science and Engineering Xiamen University of Technology Fushun Electronics Co. Ltd.

Yellow-green-emitting Sr Si2O2N2:Eu2+phosphors were synthesized with Sr2Si O4:Eu2+as *** effects of flux and the concentration of Eu2+on the crystal structure and luminescent properties of the phosphors were *** suggested that the optimal content of flux Na2CO3 was 1 wt%and the optimal doping concentration of Eu2+was 0.05 *** emission spectra showed the most intense peaks located at 535 nm which corresponded to the 4f65d→4f7 transition of Eu2+.The excitation spectra showed that these phosphors could be effectively excited by near-ultraviolet and blue light,whichwas consistent with the widely applied output wavelengths of near-ultraviolet and blue-white light-emitting diode(LED)*** the influence of flux on the luminescent properties of Sr Si2O2N2:Eu2+phosphor was analyzed,the X-ray diffraction(XRD)patterns indicated that the flux could help the crystallization of the *** other phases except the triclinic structure of Sr Si2O2N2 were *** thermal stability and the emission intensity of synthesized Sr Si2O2N2:Eu2+phosphor were examined and compared with commercial YAG yellow *** results indicate that the yellow-green-emitting phosphor is a suitable candidate for the fabrication of white LEDs.

关键词： flux nitrogen oxides yellow-green-emitting white LEDs

PhIO-mediated Synthesis of Ketones from Aikynes and Alkenes

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Chemical Research in Chinese Universities 2019年第1期35卷 26-32页

作者： wei Ying ZHENG Xiangping xie Xinmiao Center for Molecular Systems and Organic Devices(CMSOD) Key Laboratory for Organic Electronics and Information Displays &Jiangsu Key Laboratory for BiosensorsInstitute of Advaneed Materials(LAM) Jiangsu National Synergetie Innovation Center for Advaneed Materials(SICAM) Nanjing University of Posts & TelecommunicationsNanjing 210023P.R.China

A facile and efficient method for the preparation of methyl ketones was developed in the reaction of alkynes and alkenes with PhIO-BF3·*** reaction features mild conditions,short time and metal-free *** possible mech... 详细信息

关键词： Alkyne Alkene Ketone Hydration reaction

Finite Element Error Estimation for Parabolic Optimal Control Problems with Pointwise Observations

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Numerical Mathematics(Theory,Methods and Applications) 2022年第1期15卷 165-199页

作者： Dongdong Liang wei Gong Xiaoping xie School of Mathematics Sichuan UniversityChengdu 610064China LSEC Institute of Computational MathematicsAcademy of Mathematics and Systems ScienceChinese Academy of Sciences&School of Mathematical SciencesUniversity of Chinese Academy of SciencesBeijing 100190China

In this paper,we consider parabolic distributed control problems with cost functional of pointwise observation type either in space or in ***,we show the well-posedness of the optimization problems and derive the first order optimality systems,where the adjoint state can be expressed as the linear combination of solutions to two backward parabolic equations that involve the Dirac delta distribution as source either in space or in ***,we use a space-time finite element method to discretize the control problems,where the state variable is approximated by piecewise constant functions in time and continuous piecewise linear polynomials in space,and the control variable is discretized by following the variational discretization *** obtain a priori error estimates for the control and state variables with order O(k 12+h)up to a logarithmic factor under the L ***,we perform several numerical experiments to support our theoretical results.

关键词： Parabolic optimal control problem pointwise observation space-time finite element method parabolic PDE with Dirac measure error estimate

Stochastic 3D Leray-α model with fractional dissipation

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Science China Mathematics 2023年第11期66卷 2589-2614页

作者： Shihu Li wei Liu Yingchao xie School of Mathematics and Statistics/Research Institute of Mathematical Science Jiangsu Normal UniversityXuzhou 221116China

In this paper,we establish the global well-posedness of the stochastic 3D Leray-αmodel with general fractional dissipation driven by multiplicative *** model is the stochastic 3D Navier-Stokes equations regularized through a smoothing kernel of orderθ1 in the nonlinear term and theθ2-fractional *** the case ofθ1≥0 andθ2>0 withθ1+θ2≥5/4,we prove the global existence and uniqueness of strong *** main results not only cover many existing works in the deterministic cases,but also generalize some known results of stochastic models such as the stochastic hyperviscous Navier-Stokes equations and classical stochastic3D Leray-αmodel as the special cases.

关键词： stochastic Leray-Q model fractional Laplacian stochastic Navier-Stokes equation well-posedness

He-Ar-S-Pb Isotopic Compositions of Pyrite：Constraints on the Source of Ore-forming Materials of the Chengchao Skarn Iron Deposit,SE Hubei Province,Eastern China

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Acta Geologica Sinica(English Edition) 2016年第5期90卷 1780-1794页

作者： LI wei xie Guiqing ZHU Qiaoqiao Faculty of Earth Resources China University ofGeosciences Wuhan 430074 China Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 100037 China MLR Key Laboratory of Metallogeny and Mineral Assessment Beijing 10003 7 China

The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product *** obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of *** results indicate that the δ34S values（ranging from 14.0‰ to 17.6‰） of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur *** δ34S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt（MLYRB）.The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of 208Pb/204Pb,207Pb/204Pb,and-206Pb/204Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle *** He-Ar results exhibit different compositions of the two stages：the -3He/-4He（R/Ra） and 40Ar/-36Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,*** stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water（MASW） during fluid *** Triassic evaporites played an important role in the mineralization process.

关键词： He-Ar-S-Pb isotopes evaporites mineralization Chengchao skarn Fe deposit southeastern Hubei Province