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Effects of acid deposition control in China:a review based on responses of subtropical forests

Frontiers of Environmental Science & Engineering 2024年第6期18卷 115-126页

作者： Danni Xie Xiaodong Ge Lei Duan Jan Mulder School of Land Engineering Chang’an UniversityXi’an 710064China State Key Laboratory of Environmental Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex Beijing 100084China Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life SciencesBox 5003NO-1432ÅsNorway

For many decades,acid deposition used to pose a significant regional air pollution challenge in China.After substantial emission control of anthropogenically derived sulfur and nitrogen containing gasses,both sulfur and nitrogen deposition,as well as the acid rain-affected area,have significantly decreased compared to their peak levels.Forests,particularly in the humid subtropics,are sensitive to acid deposition,as evidenced by soil acidification,sulfate and nitrate leaching in stream water,and elevated soil nitrous oxide emission.Reduction in the total deposition of sulfur and nitrogen,caused a significant decline in sulfate and nitrate leaching from subtropical forest and subsequently in sulfate and nitrate concentrations in stream water,although there was about a 5-year delay.This delay may be attributed to the desorption of accumulated sulfate and continued elevated mineralization of accumulated nitrogen pools.Emissions of nitrous oxide,a potent greenhouse gas,also declined in nitrogen-saturated subtropical forest soils,as soil water nitrate concentration decreased.Therefore,subtropical forests in China suffering from elevated acid deposition have begun to recover.Yet,the current levels of sulfur and nitrogen deposition continue to exceed the critical loads,i.e.,the assigned threshold levels in accordance with emission control policies,in more than 10%of the country’s land area,respectively,indicating remaining risks of acidification and eutrophication.Thus,further emission reductions are urgently needed,also because they will help achieving goals related to air quality and nitrous oxide emissions.

关键词： Acidification critical load Nitrous oxide Surface water chemistry Recovery

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THE INFLUENCE OF IMPERFECTIONS UPON THE critical load OF STRUCTURES

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Applied Mathematics and Mechanics(English Edition) 1999年第10期20卷 1108-1115页

作者：朱正佑丛玉豪 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai P R China Department of Mathematics Shanghai University Shanghai P R China College of Mathematical Sciences Shanghai Normal University Shanghai P R China

By means of the theory of universal unfolding, the influence of multi-imperfections upon the critical load of structure in engineering is analysed in this paper. For the pitchfork problem, a lower bound of increments of the critical loads caused by imperfections of the structures is given. A simple and available numerical method for computing the lower bound is described.

关键词： imperfections critical load pitchfork universal unfolding

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critical transitions in the shape morphing of kirigami metallic glass

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Journal of Materials Science & Technology 2021年第2期61卷 204-212页

作者： D.X.Han L.Zhao S.H.Chen G.Wang K.C.Chan Advanced Manufacturing Technology Research Center Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HornKowloonHong KongChina School of Mechanical Engineering Hefei University of TechnologyHefei230009China Laboratory for Microstructures Institute of MaterialsShanghai UniversityShanghai200444China

Kirigami, the ancient Japanese paper cutting technique, has been applied to achieve high stretchability and low energy loss of designed metallic glass. Despite the exploration of the underlying deformation mechanism of kirigami-inspired structures from the energy point of view, the morphable responses of the kirigami patterns and the origin of the kirigami response are yet to be fully understood. This study reveals the mechanical driven-forms of the kirigami structure with the corresponding deformation stages. Based on the beam deflection theory, the elastic buckling behavior of kirigami metallic glass is manifested and a critical force prediction model is developed. Moreover, a force concentration parameter is introduced in the rigid-plastic deformation stage, predicting the nominal ultimate force. The kirigami-inspired facture force is firstly proposed. The findings of these models are in good agreement with the experimental sizedependent kirigami responses, and expected to provide significant insights into the understanding of the deformation behavior and the design of kirigami metallic glasses.

关键词： Metamaterial Kirigami metallic glass critical load Size effect Beam deflection

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RESEARCH PROGRESS ON THE IMPACT OF NITROGEN DEPOSITION ON GLOBAL GRASSLANDS

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Frontiers of Agricultural Science and Engineering 2022年第3期9卷 425-444页

作者： Carly J.STEVENS Sofía BASTO Michael DBELL Tianxiang HAO Kevin KIRKMAN Raul OCHOA-HUESO Lancaster Environment Centre Lancaster UniversityLancasterLA14YQUK Unidad de Ecologia y Sistematica Departamento de BiologiaFacultad de CienciasPontificia Universidad JaverianaCarrera 7 No.43-82 Ed.Jesus Emilio Ramirez(53)BogotaColombia National Park Service Air Resources DivisionLakewoodCO 80235USA Synthesis Research Center of Chinese Ecosystem Research Network Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environmental Sciences National Academy of Agriculture Green DevelopmentKey Laboratory of Plant-Soil Interactions of Ministry of EducationBeijing Key Laboratory of Farmland Soil Pollution Prevention and RemediationChina Agricultural UniversityBeijing 100193China School of Life Sciences University of KwaZulu-NatalDurban4041South Africa Departamento de Biologia-IVAGRO Universidad de CadizCampus Rio San Pedro11510 Puerto RealSpain Department of Terrestrial Ecology Netherlands Institute of Ecology(NIOO-KNAW)P.O.Box 506700 ABWageningenthe Netherlands

Grasslands are globally-important ecosystems providing critical ecosystem services.The species composition and characteristics of grasslands vary considerably across the planet with a wide variety of different grasslands found.However,in many regions grasslands have been impacted by atmospheric nitrogen deposition originating from anthropogenic activities with effects on productivity,species composition and diversity widely reported.Impacts vary across grassland habitats but many show declines in species richness and increases in biomass production related to soil eutrophication and acidification.At a continental level,there is considerable variation in the research effort that has been put into understanding the impacts of nitrogen deposition.In Europe,North America and parts of Asia,although there are unanswered research questions,there is a good understanding of N deposition impacts in most grassland habitats.This is not the case in other regions with large knowledge gaps in some parts of the world.This paper reviews the impacts of N deposition on grasslands around the world,highlighting recent advances and areas where research is still needed.

关键词： acidification biomass production critical load eutrophication species composition species richness

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CLASSICAL AND HOMOGENIZED EXPRESSIONS FOR BUCKLING SOLUTIONS OF FUNCTIONALLY GRADED MATERIAL LEVINSON BEAMS

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Acta Mechanica Solida Sinica 2015年第5期28卷 592-604页

作者： Shirong Li Xuan Wang Zeqing Wan Department of Civil Engineering Yangzhou University

The relationship between the critical buckling loads of functionally graded material （FGM） Levinson beams （LBs） and those of the corresponding homogeneous Euler-Bernoulli beams （HEBBs） is investigated. Properties of the beam are assumed to vary continuously in the depth direction. The governing equations of the FGM beam are derived based on the Levinson beam theory, in which a quadratic variation of the transverse shear strain through the depth is included. By eliminating the axial displacement as well as the rotational angle in the governing equations, an ordinary differential equation in terms of the deflection of the FGM LBs is derived, the form of which is the same as that of HEBBs except for the definition of the load parameter. By solving the eigenvalue problem of ordinary differential equations under different boundary conditions clamped （C）, simply-supported （S）, roller （R） and free （F） edges combined, a uniform analytical formulation of buckling loads of FGM LBs with S-S, C-C, C-F, C-R and S-R edges is presented for those of HEBBs with the same boundary conditions. For the C-S beam the above-mentioned equation does not hold. Instead, a transcendental equation is derived to find the critical buckling load for the FGM LB which is similar to that for HEBB with the same ends. The significance of this work lies in that the solution of the critical buckling load of a FGM LB can be reduced to that of the HEBB and calculation of three constants whose values only depend upon the through- the-depth gradient of the material properties and the geometry of the beam. So, a homogeneous and classical expression for the buckling solution of FGM LBs is accomplished.

关键词： FCM beam Levinson beam theory buckling critical load Euler-Bernoulli beam

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Nonlinear stability of sensor elastic element--corrugated shallow spherical shell in coupled multi-field

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Applied Mathematics and Mechanics(English Edition) 2017年第6期38卷 877-888页

作者： Yongan ZHU Fan WANG Renhuai LIU Institute of Applied Mechanics Jinan University Guangzhou 510632 China Key Laboratory of Disaster Forecast and Control in Engineering of Ministry of Education Jinan University Guangzhou 510632 China

Nonlinear stability of sensor elastic element- corrugated shallow spherical shell in coupled multi-field is studied. With the equivalent orthotropic parameter obtairled by the author, the corrugated shallow spherical shell is considered as an orthotropic shallow spherical shell, and geometrical nonlinearity and transverse shear deformation are taken into account. Nonlinear governing equations are obtained. The critical load is obtained using a modified iteration method. The effect of temperature variation and shear rigidity variation on stability is analyzed.

关键词： modified iteration method corrugated shallow spherical shell multi-field,stability critical load temperature variation

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Local Strain Energy Density Applied to Bainitic Functionally Graded Steels Plates Under Mixed-Mode(Ⅰ+Ⅱ) loading

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Acta Metallurgica Sinica(English Letters) 2015年第2期28卷 164-172页

作者： H.Salavati Y.Alizadeh F.Berto Department of Mechanical Engineering Amirkabir University of Technology Department of Management and Engineering University of Padova

In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loading. The studied FGSs contain ferritic and austenite phases in addition to bainitic layer produced by electroslag remelting. The mechanism- based strain gradient plasticity theory is used to determine the flow stress （yield stress or ultimate stress） of each layer. The Young＇s modulus and the Poisson＇s ratio have been assumed to be constant, while other mechanical properties vary exponentially along the specimen width. The control volume is centered in relation to the maximum principal stress present on the notch edge and assumes a crescent shape. The points belonging to the volume perimeter are obtained numerically. In the present contribution, the effects of notch radius and notch depth on the SED and the critical load are studied. The notch radius varies from 0.2 to 2.0 mm, and the notch depth varies from 5 to 7 ram. By using the SED approach and finite element simulations, the critical load is determined, and the obtained results show a sound agreement with the experimental results.

关键词： Functionally bainitic graded steel Strain energy density Mechanism-based strain gradientplasticity theory critical load Notch radius Notch depth

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Co-based Amorphous/Nanocrystalline Composite Coatings Deposited by Arc Ion Plating

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Journal of Materials Science & Technology 2013年第9期29卷 806-812页

作者： Zhengkai Chang Jun Gong Chao Sun State Key Laboratory for Corrosion and Protection Institute of Metal ResearchChinese Academy of Sciences

Cobalt-based amorphous/nanocrystalline composite coatings have been grown by arc ion plating together with a specimen cooling system. With decreasing substrate temperature, the coatings undergo significant structure evolution. The degree of crystallization first decreases and subsequently increases as confirmed by X-ray diffraction. The cluster size first decreases and then remains constant as confirmed by transmission electron microscopy. The effect of substrate temperature on the evolution of the structure has been studied as a result of a competition between nucleation thermodynamics and kinetics of crystalline growth. With decreasing the substrate temperature, the microhardness and the critical load of the composite coatings firstly increased, and then remained almost constant. And the saturation magnetization revealed the opposite trend over the same range. The essence of these phenomena was ascribed to the microstructural variations caused by the decrease of the substrate temperature.

关键词： Amorphous/nanocrystalline composite coatings Arc ion plating Thermodynamics Kinetics Microhardness critical load

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Dynamical response of hyper-elastic cylindrical shells under periodic load

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Applied Mathematics and Mechanics(English Edition) 2008年第10期29卷 1319-1327页

作者：任九生 Department of Mechanics Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

Dynamical responses, such as motion and destruction of hyper-elastic cylindrical shells subject to periodic or suddenly applied constant load on the inner surface, are studied within a framework of finite elasto-dynamics. By numerical computation and dynamic qualitative analysis of the nonlinear differential equation, it is shown that there exists a certain critical value for the internal load describing motion of the inner surface of the shell. Motion of the shell is nonlinear periodic or quasi-periodic oscillation when the average load of the periodic load or the constant load is less than its critical value. However, the shell will be destroyed when the load exceeds the critical value. Solution to the static equilibrium problem is a fixed point for the dynamical response of the corresponding system under a suddenly applied constant load. The property of fixed point is related to the property of the dynamical solution and motion of the shell. The effects of thickness and load parameters on the critical value and oscillation of the shell are discussed.

关键词： hyper-elastic cylindrical shells nonlinear differential equation periodic oscillation quasi-periodic oscillation critical load

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NONLINEAR VIBRATION OF CIRCULAR SANDWICH PLATES UNDER CIRCUMJACENT load

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Applied Mathematics and Mechanics(English Edition) 2006年第10期27卷 1417-1424页

作者：杜国君马建青 Yanshan University Qinhuangdao 066004Hebei ProvinceP.R.China

Based on von Karman plate theory, the issue about nonlinear vibration for circular sandwich plates under circumjacent load with the loosely clamped boundary condition was researched. Nonlinear differential eigenvalue equations and boundary conditions of the problem were formulated by variational method and then their exact static solution can be got. The solution was derived by modified iteration method, so the analytic relations between amplitude and nonlinear oscillating frequency for circular sandwich plates were obtained. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.

关键词： sandwich plate nonlinear vibration critical load buckling amplitude frequency-load characteristic relation

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