The presence of particles larger than the permissible dimensions of conventional laboratory specimens causes difficulty in the determination of shear strength of coarse-grained soils. In this research, the influence o...The presence of particles larger than the permissible dimensions of conventional laboratory specimens causes difficulty in the determination of shear strength of coarse-grained soils. In this research, the influence of particle size on shear strength of coarse-grained soils was investigated by resorting to experimental tests in different scale and numerical simulations based on discrete element method （DEM）. Experimental tests on such soil specimens were based on using the techniques designated as ＂parallel＂ and ＂scalping＂ to prepare gradation of samples in view of the limitation of laboratory specimen size. As a second approach, the direct shear test was numerically simulated on assemblies of elliptical particles. The behaviors of samples under experimental and numerical tests are presented and compared, indicating that the modification of sample gradation has a significant influence on the mechanical properties of coarse-grained soils. It is noted that the shear strengths of samples produced by the scalping method are higher than samples by the parallel method. The scalping method for preparing specimens for direct shear test is therefore recommended. The micromechanical behavior of assemblies under direct shear test is also discussed and the effects of stress level on sample behavior are investigated.展开更多
The coarse-grained discrete element method(DEM)is probably a feasible option for simulating an actual drum-type biomass boiler,which contains over 10 million cylinder particles.A multi-level study was conducted based ...The coarse-grained discrete element method(DEM)is probably a feasible option for simulating an actual drum-type biomass boiler,which contains over 10 million cylinder particles.A multi-level study was conducted based on particle and coarse-grained level data to evaluate the adequacy of the coarse-grained approach in terms of geometrical characteristics,kinematic features,and dynamic properties.Two scaling laws for contact parameters were used and compared during the simulations.The results show that the coarse-grained approach can accurately predict the positions of the free surface and active-passive interface,the mixing index,and the orientation properties.Deviations in the velocity fields may occur due to the worse flowability of coarse-grained particles near the free surface.The efficiency is significantly improved by the coarse-grained model compared with the corresponding original case(the same DEM code without a coarse-grained model was used for the original simulations).展开更多
Molecular simulations are now an essential part of modern chemistry and physics,especially for the investigation of macromolecules.They have evolved into mature approaches that can be used effectively to understand th...Molecular simulations are now an essential part of modern chemistry and physics,especially for the investigation of macromolecules.They have evolved into mature approaches that can be used effectively to understand the structure-to-property relationships of diverse macromolecular systems.In this article,we provide a tutorial on molecular simulations,focusing on the technical and practical aspects.Several prominent and classical simulation methods and software are introduced.The applications of molecular simulations in various directions of macromolecular science are thenfeatured by representative systems,including self-assembly,crystallization,chemical reaction,and some typical non-equilibrium systems.This tutorial paper provides a useful overview of molecular simulations in the rapid progress of macromolecular science,and suggests guidance for researchers who start exploiting molecular simulations in their study.展开更多
文摘The presence of particles larger than the permissible dimensions of conventional laboratory specimens causes difficulty in the determination of shear strength of coarse-grained soils. In this research, the influence of particle size on shear strength of coarse-grained soils was investigated by resorting to experimental tests in different scale and numerical simulations based on discrete element method （DEM）. Experimental tests on such soil specimens were based on using the techniques designated as ＂parallel＂ and ＂scalping＂ to prepare gradation of samples in view of the limitation of laboratory specimen size. As a second approach, the direct shear test was numerically simulated on assemblies of elliptical particles. The behaviors of samples under experimental and numerical tests are presented and compared, indicating that the modification of sample gradation has a significant influence on the mechanical properties of coarse-grained soils. It is noted that the shear strengths of samples produced by the scalping method are higher than samples by the parallel method. The scalping method for preparing specimens for direct shear test is therefore recommended. The micromechanical behavior of assemblies under direct shear test is also discussed and the effects of stress level on sample behavior are investigated.
基金funded by the National Natural Science Foundation of China(grant No.52205172 and 52075489)the Natural Science Foundation of Zhejiang Province of China(grant No.LY23E050015)the Basic Public Welfare Research Program of Zhejiang Province(grant No.LGG20E050017).
文摘The coarse-grained discrete element method(DEM)is probably a feasible option for simulating an actual drum-type biomass boiler,which contains over 10 million cylinder particles.A multi-level study was conducted based on particle and coarse-grained level data to evaluate the adequacy of the coarse-grained approach in terms of geometrical characteristics,kinematic features,and dynamic properties.Two scaling laws for contact parameters were used and compared during the simulations.The results show that the coarse-grained approach can accurately predict the positions of the free surface and active-passive interface,the mixing index,and the orientation properties.Deviations in the velocity fields may occur due to the worse flowability of coarse-grained particles near the free surface.The efficiency is significantly improved by the coarse-grained model compared with the corresponding original case(the same DEM code without a coarse-grained model was used for the original simulations).
基金financially supported by the National Natural Science Foundation of China(Nos.22025302 and 21873053).
文摘Molecular simulations are now an essential part of modern chemistry and physics,especially for the investigation of macromolecules.They have evolved into mature approaches that can be used effectively to understand the structure-to-property relationships of diverse macromolecular systems.In this article,we provide a tutorial on molecular simulations,focusing on the technical and practical aspects.Several prominent and classical simulation methods and software are introduced.The applications of molecular simulations in various directions of macromolecular science are thenfeatured by representative systems,including self-assembly,crystallization,chemical reaction,and some typical non-equilibrium systems.This tutorial paper provides a useful overview of molecular simulations in the rapid progress of macromolecular science,and suggests guidance for researchers who start exploiting molecular simulations in their study.
