草地生态系统为重要的陆地碳库,其碳源/汇动态直接影响全球碳循环过程。为深入了解全球草地碳源/汇研究的现状、热点及前沿趋势,本研究利用文献计量法,借助CiteSpace可视化软件对Web of Science数据库中1995年1月1日至2025年5月14日期...草地生态系统为重要的陆地碳库,其碳源/汇动态直接影响全球碳循环过程。为深入了解全球草地碳源/汇研究的现状、热点及前沿趋势,本研究利用文献计量法,借助CiteSpace可视化软件对Web of Science数据库中1995年1月1日至2025年5月14日期间发表的3215篇文献进行分析。结果表明,过去30年间全球草地碳源/汇研究的发文量持续增长,以中国、美国和德国为主要研究力量,并形成了稳定的高产作者群体,其发展轨迹与国际和国内政策导向高度契合;研究热点主要集中在青藏高原等典型区域,研究方法以涡度相关技术为主,重点关注碳源/汇估算以及土壤碳库动态、植被生产力变化、凋落物分解及土壤呼吸等核心过程。后续应着力于草地碳源/汇的薄弱区填补与多尺度整合、驱动机制与多因子互作、退化草地恢复碳汇潜力与调控机制、畜牧业温室气体排放特征与减排路径、牧区产业转型与碳汇市场化机制等方面,并持续强化政策引领作用,不断拓展研究的深度与广度,从而提升对全球气候变化的应对能力。展开更多
To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite col...To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.展开更多
Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistanc...Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.展开更多
文摘草地生态系统为重要的陆地碳库,其碳源/汇动态直接影响全球碳循环过程。为深入了解全球草地碳源/汇研究的现状、热点及前沿趋势,本研究利用文献计量法,借助CiteSpace可视化软件对Web of Science数据库中1995年1月1日至2025年5月14日期间发表的3215篇文献进行分析。结果表明,过去30年间全球草地碳源/汇研究的发文量持续增长,以中国、美国和德国为主要研究力量,并形成了稳定的高产作者群体,其发展轨迹与国际和国内政策导向高度契合;研究热点主要集中在青藏高原等典型区域,研究方法以涡度相关技术为主,重点关注碳源/汇估算以及土壤碳库动态、植被生产力变化、凋落物分解及土壤呼吸等核心过程。后续应着力于草地碳源/汇的薄弱区填补与多尺度整合、驱动机制与多因子互作、退化草地恢复碳汇潜力与调控机制、畜牧业温室气体排放特征与减排路径、牧区产业转型与碳汇市场化机制等方面,并持续强化政策引领作用,不断拓展研究的深度与广度,从而提升对全球气候变化的应对能力。
基金The National Natural Science Foundation of China(No.51278118)the Natural Science Foundation of Jiangsu Province(No.BK2012756)+1 种基金the Key Project of Ministry of Education of China(No.113029A)the Third Five-Year Major Scientific and Technological Project of China Metallurgical Group Corporation
文摘To improve the seismic performance of columns, engineered cementitious composite （ECC） is introduced to partially substitute concrete at the base of the columns to form ECC,/reinforced concrete （ RC） composite columns. The mechanical behaviors of the ECC/RC composite columns are numerically studied under low-cyclic loading with the finite element analysis softwareof MSC. MARC. It is found that the ECC/RC composite columns can significantly enhance the load capacity, the ductility ad energy dissipation of columns. Then, the effects of the height of the ECC, the axial compression ratio and the longitudinal reinforcement ratio on the seismic behaviors of the composite columns are parametrically studied. The results show that the ECC/RC composite column with a height of the ECC layer of 0. Sh（h is the height to the cross-section） can achieve similar seismic performance of a full ECC column. The peak load of the composite column increases significantly while the ductility decreases with the increase of the axial compression ratio. Increasing the longitudinal reinforcement ratio within a certain range can improve the ductility and energy dissipation capacity and almost has no effect on load capacity. The aalysis results ae instructive and valuable for reference in designing ECC structures.
基金supported by the National Natural Science Foundation of China(Grant No.51278118)the Natural Science Foundation of Jiangsu Province(Grant No.BK2012756)the Scientific Research Project of Ministry of Education of China(Grant No.113029A)
文摘Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.
