The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pu...The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260？？ under the optimal processing conditions.A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software.The pulsed electric circuit was first solved and then it is substituted into the magnetic field model.The fluid flow model was solved with the acquired electromagnetic force.The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied.The pulsed magnetic field increases melt convection,which stirs and fractures the dendritic arms into pieces.These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement.The Joule heat effect produced by the electric current also participates in the microstructural refinement.展开更多
The refined explicit finite element scheme considering various strengthening mechanisms and damage modes is proposed for simulation of deformation processes and mechanical properties of carbon nanotube(CNT)-reinforced...The refined explicit finite element scheme considering various strengthening mechanisms and damage modes is proposed for simulation of deformation processes and mechanical properties of carbon nanotube(CNT)-reinforced bimodal-grained aluminum matrix nanocomposites.Firstly,the detailed microstructure model is established by constructing the geometry models of CNTs and grain boundaries,which automatically incorporates grain refinement strengthening and load transfer effect.Secondly,a finite element formulation based on the conventional theory of mechanical-based strain gradient plasticity is developed.Furthermore,the deformation and fracture modes for the nanocomposites with various contents and distributions of coarse grains(CGs)are explored based on the scheme.The results indicate that ductility of the composites first increases and then decreases as the content of CGs rises.Moreover,the dispersed distribution exhibits better ductility than concentrated one.Additionally,grain boundaries proved to be the weakest component within the micromodel.A series of interesting phenomena have been observed and discussed upon the refined simulation scheme.This work contributes to the design and further development of CNT/Al nanocomposites,and the proposed scheme can be extended to various bimodal metal composites.展开更多
Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed...Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged througll the tube. A narrow section of the, boat is assmned to be exposed to a constant heat rate produced b v an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of tile molten zone, required power and temperature gradient in the system.展开更多
Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainab...Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainable development of urban water resources,which makes the current construction efficiencies unsatisfactory.Outcomes:This review highlights the importance of establishing a multi-scale urban distributed eco-hydrological model by analyzing the connotations of sponge city construction.Hydrological models that can be configured for sponge city construction were selected.Traditional models have limitations in coupling ecological and hydrological processes,multi-scale and landscape-based simulations,refined simulations,and computational efficiency.By contrast,cellular automaton has a discrete data structure in space,time,and states,is capable of bottom-up computing,and provides a new conceptual framework for simulating complex urban eco-hydrological processes.Discussion and Conclusion:Future model development may focus on the conduction of multi-scale simulation systems,the simulation of coupled urban eco-hydrological processes,the quantification of eco-hydrological responses to land cover composition,spatial configuration and low impact development practices,and improving simulation accuracy.展开更多
Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainab...Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainable development of urban water resources,which makes the current construction efficiencies unsatisfactory.Outcomes:This review highlights the importance of establishing a multi-scale urban distributed eco-hydrological model by analyzing the connotations of sponge city construction.Hydrological models that can be configured for sponge city construction were selected.Traditional models have limitations in coupling ecological and hydrological processes,multiscale and landscape-based simulations,refined simulations,and computational efficiency.By contrast,cellular automaton has a discrete data structure in space,time,and states,is capable of bottom-up computing,and provides a new conceptual framework for simulating complex urban eco-hydrological processes.Discussion and Conclusion:Future model development may focus on the conduction of multi-scale simulation systems,the simulation of coupled urban eco-hydrological processes,the quantification of eco-hydrological responses to land cover composition,spatial configuration and low impact development practices,and improving simulation accuracy.展开更多
The lattice Boltzmann method （LBM） has gained increasing popularity in the last two decades as an alternative numerical approach for solving fluid flow problems. One of the most active research areas in the LBM is i...The lattice Boltzmann method （LBM） has gained increasing popularity in the last two decades as an alternative numerical approach for solving fluid flow problems. One of the most active research areas in the LBM is its application in particle-fluid systems, where the advantage of the LBM in efficiency and parallel scalability has made it superior to many other direct numerical simulation （DNS） techniques. This article intends to provide a brief review of the application of the LBM in particle-fluid systems. The numerical techniques in the LBM pertaining to simulations of particles are discussed, with emphasis on the advanced treatment for boundary conditions on the particle-fluid interface. Other numerical issues, such as the effect of the internal fluid, are also briefly described. Additionally, recent efforts in using the LBM to obtain closures for particle-fluid drag force are also reviewed.展开更多
基金Project(50774075)supported by the National Natural Science Foundation of ChinaProject(2006BAE04B01-4)supported by Key Technologies R&D Program,China
文摘The effects of a pulsed magnetic field on the solidified microstructure of pure Mg were investigated.The results show that microstructure of pure Mg is considerably refined via columnar-to-equiaxed growth under the pulsed magnetic field and the average grain size is refined to 260？？ under the optimal processing conditions.A mathematical model was built to describe the interaction of the electromagnetic-flow fields during solidification with ANSYS software.The pulsed electric circuit was first solved and then it is substituted into the magnetic field model.The fluid flow model was solved with the acquired electromagnetic force.The effects of pulse voltage frequency on the current wave and on the distribution of magnetic and flow fields were numerically studied.The pulsed magnetic field increases melt convection,which stirs and fractures the dendritic arms into pieces.These broken pieces are transported into the bulk liquid by the liquid flow and act as nuclei to enhance grain refinement.The Joule heat effect produced by the electric current also participates in the microstructural refinement.
基金supported by the National Natural Science Foundation of China(51931009)the Shandong Provincial Natural Science Foundation(ZR2023ME097).
文摘The refined explicit finite element scheme considering various strengthening mechanisms and damage modes is proposed for simulation of deformation processes and mechanical properties of carbon nanotube(CNT)-reinforced bimodal-grained aluminum matrix nanocomposites.Firstly,the detailed microstructure model is established by constructing the geometry models of CNTs and grain boundaries,which automatically incorporates grain refinement strengthening and load transfer effect.Secondly,a finite element formulation based on the conventional theory of mechanical-based strain gradient plasticity is developed.Furthermore,the deformation and fracture modes for the nanocomposites with various contents and distributions of coarse grains(CGs)are explored based on the scheme.The results indicate that ductility of the composites first increases and then decreases as the content of CGs rises.Moreover,the dispersed distribution exhibits better ductility than concentrated one.Additionally,grain boundaries proved to be the weakest component within the micromodel.A series of interesting phenomena have been observed and discussed upon the refined simulation scheme.This work contributes to the design and further development of CNT/Al nanocomposites,and the proposed scheme can be extended to various bimodal metal composites.
文摘Three-dimensional thermal a nalysis simulation of a horizontal zone refining system is conducted for germanimn semiconductor materials. The considered geometry includes a g＇ral）hite boat filled with germanium placed in a cylindrical quartz tube. A flow of Ar and H2 gas mixture is purged througll the tube. A narrow section of the, boat is assmned to be exposed to a constant heat rate produced b v an rf coil located outside the quartz tube. The results of this analysis provide essential information about various parameters such as the shape of tile molten zone, required power and temperature gradient in the system.
基金This work was supported by the Beijing Natural Science Foundation[8181001]Special Fund for Scientific Research Cooperation between Colleges and Institutes of University of Chinese Academy of Sciences[Y65201NY00].
文摘Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainable development of urban water resources,which makes the current construction efficiencies unsatisfactory.Outcomes:This review highlights the importance of establishing a multi-scale urban distributed eco-hydrological model by analyzing the connotations of sponge city construction.Hydrological models that can be configured for sponge city construction were selected.Traditional models have limitations in coupling ecological and hydrological processes,multi-scale and landscape-based simulations,refined simulations,and computational efficiency.By contrast,cellular automaton has a discrete data structure in space,time,and states,is capable of bottom-up computing,and provides a new conceptual framework for simulating complex urban eco-hydrological processes.Discussion and Conclusion:Future model development may focus on the conduction of multi-scale simulation systems,the simulation of coupled urban eco-hydrological processes,the quantification of eco-hydrological responses to land cover composition,spatial configuration and low impact development practices,and improving simulation accuracy.
基金supported by the Beijing Natural Science Foundation 8181001Special Fund for Scientific Research Cooperation between Colleges and Institutes of University of Chinese Academy of Sciences Y65201NY00
文摘Introduction:Understanding complex urban eco-hydrological processes through models is an important approach in sponge city construction.However,the research on this has not kept pace with the urgent need for sustainable development of urban water resources,which makes the current construction efficiencies unsatisfactory.Outcomes:This review highlights the importance of establishing a multi-scale urban distributed eco-hydrological model by analyzing the connotations of sponge city construction.Hydrological models that can be configured for sponge city construction were selected.Traditional models have limitations in coupling ecological and hydrological processes,multiscale and landscape-based simulations,refined simulations,and computational efficiency.By contrast,cellular automaton has a discrete data structure in space,time,and states,is capable of bottom-up computing,and provides a new conceptual framework for simulating complex urban eco-hydrological processes.Discussion and Conclusion:Future model development may focus on the conduction of multi-scale simulation systems,the simulation of coupled urban eco-hydrological processes,the quantification of eco-hydrological responses to land cover composition,spatial configuration and low impact development practices,and improving simulation accuracy.
文摘The lattice Boltzmann method （LBM） has gained increasing popularity in the last two decades as an alternative numerical approach for solving fluid flow problems. One of the most active research areas in the LBM is its application in particle-fluid systems, where the advantage of the LBM in efficiency and parallel scalability has made it superior to many other direct numerical simulation （DNS） techniques. This article intends to provide a brief review of the application of the LBM in particle-fluid systems. The numerical techniques in the LBM pertaining to simulations of particles are discussed, with emphasis on the advanced treatment for boundary conditions on the particle-fluid interface. Other numerical issues, such as the effect of the internal fluid, are also briefly described. Additionally, recent efforts in using the LBM to obtain closures for particle-fluid drag force are also reviewed.
