The nonlinear combined resonance problem of a ferromagnetic circular plate in a transverse alternating magnetic field is investigated. On the basis of the deformation potential energy, the strain potential energy, and...The nonlinear combined resonance problem of a ferromagnetic circular plate in a transverse alternating magnetic field is investigated. On the basis of the deformation potential energy, the strain potential energy, and the kinetic energy of the circular plate, the Hamilton principle is used to induce the magnetoelastic coupling transverse vibration dynamical equation of the ferromagnetic circular plate. Based on the basic electromagnetic theory, the expressions of the magnet force and the Lorenz force of the circular plate are presented. A displacement function satisfying clamped-edge combined with the Galerkin method is used to derive the Duffing vibration differential equation of the circular plate. The amplitude-frequency response equations of the system under various combined resonance forms are obtained by means of the multi-scale method, and the stability of the steady-state solutions is analyzed according to the Lyapunov theory. Through examples, the amplitude-frequency characteristic curves with different parameters, the amplitude of resonance varying with magnetic field intensity and excitation force, and the time-course response diagram, phase diagram, Poincar′e diagram of the system vibration are plotted, respectively. The effects of different parameters on the amplitude and stability of the system are discussed. The results show that the electromagnetic parameters have a significant effect on the multi-valued attribute and stability of the resonance solutions, and the system may exhibit complex nonlinear dynamical behavior including multi-period and quasi-periodic motion.展开更多
CONSPECTUS:Single-atom catalysts(SACs)represent a transformative advancement in heterogeneous catalysis,offering unparalleled opportunities for maximizing atomic efficiency and enhancing performance.SACs are character...CONSPECTUS:Single-atom catalysts(SACs)represent a transformative advancement in heterogeneous catalysis,offering unparalleled opportunities for maximizing atomic efficiency and enhancing performance.SACs are characterized by isolated metal atoms uniformly dispersed on suitable supports,ensuring each metal atom serves as an independent catalytic site.This dispersion mitigates metal atom aggregation,a common issue in conventional nanocatalysts,thus enabling superior activity,selectivity,and stability.Metal−organic frameworks(MOFs)have emerged as an ideal platform for SAC synthesis due to their structural diversity,tunable coordination environments,and high surface areas.MOFs provide well-defined coordination sites that facilitate the precise stabilization of single metal atoms,presenting significant advantages over traditional supports like metal oxides and metal materials.Carbonization of MOFs yields MOF-derived carbon materials that retain key structural characteristics while offering enhanced electrical conductivity and stability,making them suitable for various catalytic applications.Recent advances in the rational design and controlled synthesis of MOF-derived SACs have significantly improved their performance in electrocatalytic processes such as the oxygen reduction reaction(ORR)and carbon dioxide reduction reaction(CO_(2)RR).However,challenges remain,including maintaining structural integrity during high-temperature carbonization,enhancing mass and electron transport and ensuring the stability of isolated metal atoms under reaction conditions.To address these challenges,strategies such as using structure-directing agents to stabilize MOF frameworks,forming high-energy porous carbon networks,and optimizing support morphologies have been developed to maximize active site exposure and accessibility.On the other hand,the interplay between active metal sites and their coordination environments is crucial in determining the catalytic activity and selectivity of SACs.Advanced computational modeling,coupled with experimental validation,has provided insights into the electronic structure of SACs and the interactions between metal atoms and supports.These insights have enabled researchers to fine-tune local atomic coordination,leading to significant enhancements in performance.For instance,modifying the coordination environment of metal atoms optimizes the binding strength of reaction intermediates,thereby improving both activity and selectivity.This account highlights our group’s contributions to MOF-derived SACs,focusing on innovative design,functionalization,and synthesis approaches that enhance catalytic activity.Notable strategies include using structure-directing agents to maintain pore connectivity during carbonization,preserving high surface areas,and enhancing mass transport.We also discuss the design of high-energy MOFderived porous carbon networks that facilitate continuous electron transport and improve the interaction between active sites and reactants,ultimately boosting catalytic efficiency.Techniques such as electrospinning have also been employed to create hierarchical porous structures and one-dimensional nanofibers,enhancing mass transport and electron transfer.The rational design of SACs requires a comprehensive understanding of the microenvironment surrounding active sites,and by leveraging computational and experimental tools,researchers can precisely control these microenvironments to achieve desired outcomes.MOF-derived SACs hold substantial promise for energy conversion and chemical synthesis.Continued research is essential to optimize their design,improve scalability,and explore new applications,ultimately advancing sustainable catalysis.This account provides an overview of the latest advancements in MOF-derived SACs,highlighting their potential as next-generation electrocatalysts and their role in sustainable energy technologies.展开更多
The landslides have an important influence on the force and deformation of existing tunnels,which may adversely affect the liner structures and even endanger normal operation.Current scholars have made few efforts to ...The landslides have an important influence on the force and deformation of existing tunnels,which may adversely affect the liner structures and even endanger normal operation.Current scholars have made few efforts to investigate the reinforcement measures for existing tunnels in the landslide region,and even paid less attention to probe into the pile-anchor strengthening mechanics.A new kind of pile-anchor strengthening system for existing tunnels has been proposed in this paper considering the influences of deforming land-slides,in which the anti-slide pile,the anchor cable and the tunnel lining were integrated as one force whole.In order to observe the pile-anchor strengthening mechanics,three physical model tests for comparative analyses were established in case of the tunnel axis parallel to the sliding direction of landslide,including the conditions without reinforcements,only with anti-slide pile and full with the pile-anchor strengthening system.Specially for the pile-anchor strengthening model tests,the extra experimental evaluation for the interaction mechanics between existing tunnel and landslide was added,such as,the tunnel diameter of 40 and 50 mm and the pile-anchor of three and six pairs.In addition,three-dimensional numerical models were implemented to analyze the landslide deformation and the internal force of tunnels after installing the pile-anchor strengthening system.Comparing with non-reinforcement,the bending moment of tunnel and contact stress at interface between tunnel and landslide at the position of 200 m away from tunnel entrance with six pairs pile-anchor reinforcement dropped by 97.2% and 50%.The results show that the deformation of landslide,the bending moment of existing tunnel and the contact stress at the interface between tunnel and landslide pronouncedly diminish after taking the pile-anchor strengthening measures.The new combined pile-anchor system has higher bearing capacity and stability,which can further improve the operation safety of existing tunnels in landslide region.展开更多
基金Project supported by the National Natural Science Foundation of China(No.11472239)
文摘The nonlinear combined resonance problem of a ferromagnetic circular plate in a transverse alternating magnetic field is investigated. On the basis of the deformation potential energy, the strain potential energy, and the kinetic energy of the circular plate, the Hamilton principle is used to induce the magnetoelastic coupling transverse vibration dynamical equation of the ferromagnetic circular plate. Based on the basic electromagnetic theory, the expressions of the magnet force and the Lorenz force of the circular plate are presented. A displacement function satisfying clamped-edge combined with the Galerkin method is used to derive the Duffing vibration differential equation of the circular plate. The amplitude-frequency response equations of the system under various combined resonance forms are obtained by means of the multi-scale method, and the stability of the steady-state solutions is analyzed according to the Lyapunov theory. Through examples, the amplitude-frequency characteristic curves with different parameters, the amplitude of resonance varying with magnetic field intensity and excitation force, and the time-course response diagram, phase diagram, Poincar′e diagram of the system vibration are plotted, respectively. The effects of different parameters on the amplitude and stability of the system are discussed. The results show that the electromagnetic parameters have a significant effect on the multi-valued attribute and stability of the resonance solutions, and the system may exhibit complex nonlinear dynamical behavior including multi-period and quasi-periodic motion.
基金financially supported by the National Natural Science Foundation of China(52332007Z).
文摘CONSPECTUS:Single-atom catalysts(SACs)represent a transformative advancement in heterogeneous catalysis,offering unparalleled opportunities for maximizing atomic efficiency and enhancing performance.SACs are characterized by isolated metal atoms uniformly dispersed on suitable supports,ensuring each metal atom serves as an independent catalytic site.This dispersion mitigates metal atom aggregation,a common issue in conventional nanocatalysts,thus enabling superior activity,selectivity,and stability.Metal−organic frameworks(MOFs)have emerged as an ideal platform for SAC synthesis due to their structural diversity,tunable coordination environments,and high surface areas.MOFs provide well-defined coordination sites that facilitate the precise stabilization of single metal atoms,presenting significant advantages over traditional supports like metal oxides and metal materials.Carbonization of MOFs yields MOF-derived carbon materials that retain key structural characteristics while offering enhanced electrical conductivity and stability,making them suitable for various catalytic applications.Recent advances in the rational design and controlled synthesis of MOF-derived SACs have significantly improved their performance in electrocatalytic processes such as the oxygen reduction reaction(ORR)and carbon dioxide reduction reaction(CO_(2)RR).However,challenges remain,including maintaining structural integrity during high-temperature carbonization,enhancing mass and electron transport and ensuring the stability of isolated metal atoms under reaction conditions.To address these challenges,strategies such as using structure-directing agents to stabilize MOF frameworks,forming high-energy porous carbon networks,and optimizing support morphologies have been developed to maximize active site exposure and accessibility.On the other hand,the interplay between active metal sites and their coordination environments is crucial in determining the catalytic activity and selectivity of SACs.Advanced computational modeling,coupled with experimental validation,has provided insights into the electronic structure of SACs and the interactions between metal atoms and supports.These insights have enabled researchers to fine-tune local atomic coordination,leading to significant enhancements in performance.For instance,modifying the coordination environment of metal atoms optimizes the binding strength of reaction intermediates,thereby improving both activity and selectivity.This account highlights our group’s contributions to MOF-derived SACs,focusing on innovative design,functionalization,and synthesis approaches that enhance catalytic activity.Notable strategies include using structure-directing agents to maintain pore connectivity during carbonization,preserving high surface areas,and enhancing mass transport.We also discuss the design of high-energy MOFderived porous carbon networks that facilitate continuous electron transport and improve the interaction between active sites and reactants,ultimately boosting catalytic efficiency.Techniques such as electrospinning have also been employed to create hierarchical porous structures and one-dimensional nanofibers,enhancing mass transport and electron transfer.The rational design of SACs requires a comprehensive understanding of the microenvironment surrounding active sites,and by leveraging computational and experimental tools,researchers can precisely control these microenvironments to achieve desired outcomes.MOF-derived SACs hold substantial promise for energy conversion and chemical synthesis.Continued research is essential to optimize their design,improve scalability,and explore new applications,ultimately advancing sustainable catalysis.This account provides an overview of the latest advancements in MOF-derived SACs,highlighting their potential as next-generation electrocatalysts and their role in sustainable energy technologies.
基金National Natural Science Foundation of China(Grant Nos.41977247 and 41772331)Project of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(No.SKLGP2015K015,Chengdu University of Technology)Project of Key Laboratory of Geohazard Prevention of Hilly Mountains,Ministry of Natural Resources(No.FJKLGH2020K004,Fujian Key Laboratory of Geohazard Prevention).
文摘The landslides have an important influence on the force and deformation of existing tunnels,which may adversely affect the liner structures and even endanger normal operation.Current scholars have made few efforts to investigate the reinforcement measures for existing tunnels in the landslide region,and even paid less attention to probe into the pile-anchor strengthening mechanics.A new kind of pile-anchor strengthening system for existing tunnels has been proposed in this paper considering the influences of deforming land-slides,in which the anti-slide pile,the anchor cable and the tunnel lining were integrated as one force whole.In order to observe the pile-anchor strengthening mechanics,three physical model tests for comparative analyses were established in case of the tunnel axis parallel to the sliding direction of landslide,including the conditions without reinforcements,only with anti-slide pile and full with the pile-anchor strengthening system.Specially for the pile-anchor strengthening model tests,the extra experimental evaluation for the interaction mechanics between existing tunnel and landslide was added,such as,the tunnel diameter of 40 and 50 mm and the pile-anchor of three and six pairs.In addition,three-dimensional numerical models were implemented to analyze the landslide deformation and the internal force of tunnels after installing the pile-anchor strengthening system.Comparing with non-reinforcement,the bending moment of tunnel and contact stress at interface between tunnel and landslide at the position of 200 m away from tunnel entrance with six pairs pile-anchor reinforcement dropped by 97.2% and 50%.The results show that the deformation of landslide,the bending moment of existing tunnel and the contact stress at the interface between tunnel and landslide pronouncedly diminish after taking the pile-anchor strengthening measures.The new combined pile-anchor system has higher bearing capacity and stability,which can further improve the operation safety of existing tunnels in landslide region.
