江汉盆地是长江出三峡后第一个大型卸载区,近2.77 Ma以来堆积了近300 m的碎屑沉积物,主要由河流相和湖沼相组成,形成了多个沉积旋回。选择江汉盆地中心位置的ZL钻孔,利用ICP—MS方法展开微量元素组成分析,细粒组分中微量元素含量与各粒...江汉盆地是长江出三峡后第一个大型卸载区,近2.77 Ma以来堆积了近300 m的碎屑沉积物,主要由河流相和湖沼相组成,形成了多个沉积旋回。选择江汉盆地中心位置的ZL钻孔,利用ICP—MS方法展开微量元素组成分析,细粒组分中微量元素含量与各粒组含量相关性并不明显,主要是5～7粒级组分表现出微弱的相关性.可见,粒度并非ZL钻孔微量元素丰度的主控因素。钻孔岩心中大部分亲石元素、亲硫元素相对上部陆壳均出现明显富集,亲铁元素总体低于上部陆壳,可能与江汉盆地总体上更多地接受了来自上游而非扬子古陆本地深源物质风化碎屑沉积有关。Sr、V/Ni和Sr/Ba值的变化则表明江汉盆地在2.6～2.43 Ma B.P.时可能有咸化湖的发育,而在2.1 Ma B.P.左右存在过一段大湖发育期。展开更多
Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including th...Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including the particle contact stiffness and the particle-particle friction. These parameters cannot easily be measured in the laboratory or directly related to measurable, physical material parameters. Therefore, a calibration process is typically used to determine the values for use in simulations of physical systems. This paper focuses on how to define the particle stiffness for the discrete element modelling in order to perform realistic simulations of granular materials in the case of linear contact model. For that, laboratory tests and numerical discrete element modelling of triaxial compression tests have been carried out on two different non-cohesive soils i.e. poorly graded fine sand and gap graded coarse sand. The results of experimental tests are used to calibrate the numerical model. It is found that the numerical results are qualitatively and quantitatively in good agreement with the laboratory tests results. Moreover, the results show that the stress dependent of soil behaviour can be reproduced well by assigning the particle stiffness as a function of the particle size particularly for gap graded soil.展开更多
This paper analyzes nanobridge tests with consideration of adhesive contact deformation, which occurs between a probe tip and a tested nanobeam, and deformation of a substrate or template that supports the tested nano...This paper analyzes nanobridge tests with consideration of adhesive contact deformation, which occurs between a probe tip and a tested nanobeam, and deformation of a substrate or template that supports the tested nanobeam.Analytical displacement-load relation, including adhesive contact deformation and substrate deformation, is presented here for small deformation of bending.The analytic results are confirmed by finite element analysis.If adhesive contact deformation and substrate deformation are not considered in the analysis of nanobridge test data, they might lead to lower values of Young＇s modulus of tested nanobeams.展开更多
The main objective of this paper is to introduce a new theory called size-dependent thermopiezoelectricity for smart nanostructures.The proposed theory includes the combination of thermoelastic and piezoelectric influ...The main objective of this paper is to introduce a new theory called size-dependent thermopiezoelectricity for smart nanostructures.The proposed theory includes the combination of thermoelastic and piezoelectric influences which enable us to describe the deformation and mechanical behaviors of smart nanostructures subjected to thermal,and piezoelectric loadings.Because of difficulty of experimental research problems associated with the proposed theory.Therefore,we propose a new boundary element method(BEM)formulation and algorithm for the solution of such problems,which involve temperatures,normal heat fluxes,displacements,couple-tractions,rotations,force-tractions,electric displacement,and normal electric displacement as primary variables within the BEM formulation.The computational performance of the proposed methodology has been demonstrated by using the generalized modified shift-splitting(GMSS)iteration method to solve the linear systems resulting from the BEM discretization.GMSS advantages are investigated and compared with other iterative methods.The numerical results are depicted graphically to show the size-dependent effects of thermopiezoelectricity,thermoelasticity,piezoelectricity,and elasticity theories of nanostructures.The numerical results also show the effects of the sizedependent and piezoelectric on the displacement components.The validity,efficiency and accuracy of the proposed BEM formulation and algorithm have been demonstrated.The findings of the current study contribute to the further development of technological and industrial applications of smart nanostructures.展开更多
文摘江汉盆地是长江出三峡后第一个大型卸载区,近2.77 Ma以来堆积了近300 m的碎屑沉积物,主要由河流相和湖沼相组成,形成了多个沉积旋回。选择江汉盆地中心位置的ZL钻孔,利用ICP—MS方法展开微量元素组成分析,细粒组分中微量元素含量与各粒组含量相关性并不明显,主要是5～7粒级组分表现出微弱的相关性.可见,粒度并非ZL钻孔微量元素丰度的主控因素。钻孔岩心中大部分亲石元素、亲硫元素相对上部陆壳均出现明显富集,亲铁元素总体低于上部陆壳,可能与江汉盆地总体上更多地接受了来自上游而非扬子古陆本地深源物质风化碎屑沉积有关。Sr、V/Ni和Sr/Ba值的变化则表明江汉盆地在2.6～2.43 Ma B.P.时可能有咸化湖的发育,而在2.1 Ma B.P.左右存在过一段大湖发育期。
文摘Discrete element modelling is commonly used for particle-scale modelling of granular or particulate materials. Developing a DEM model requires the determination of a number of micro-structural parameters, including the particle contact stiffness and the particle-particle friction. These parameters cannot easily be measured in the laboratory or directly related to measurable, physical material parameters. Therefore, a calibration process is typically used to determine the values for use in simulations of physical systems. This paper focuses on how to define the particle stiffness for the discrete element modelling in order to perform realistic simulations of granular materials in the case of linear contact model. For that, laboratory tests and numerical discrete element modelling of triaxial compression tests have been carried out on two different non-cohesive soils i.e. poorly graded fine sand and gap graded coarse sand. The results of experimental tests are used to calibrate the numerical model. It is found that the numerical results are qualitatively and quantitatively in good agreement with the laboratory tests results. Moreover, the results show that the stress dependent of soil behaviour can be reproduced well by assigning the particle stiffness as a function of the particle size particularly for gap graded soil.
基金supported by an Earmarked Research Grant (No.622506) from the Research Grants Council of the HongKong Special Administrative Region,China
文摘This paper analyzes nanobridge tests with consideration of adhesive contact deformation, which occurs between a probe tip and a tested nanobeam, and deformation of a substrate or template that supports the tested nanobeam.Analytical displacement-load relation, including adhesive contact deformation and substrate deformation, is presented here for small deformation of bending.The analytic results are confirmed by finite element analysis.If adhesive contact deformation and substrate deformation are not considered in the analysis of nanobridge test data, they might lead to lower values of Young＇s modulus of tested nanobeams.
文摘The main objective of this paper is to introduce a new theory called size-dependent thermopiezoelectricity for smart nanostructures.The proposed theory includes the combination of thermoelastic and piezoelectric influences which enable us to describe the deformation and mechanical behaviors of smart nanostructures subjected to thermal,and piezoelectric loadings.Because of difficulty of experimental research problems associated with the proposed theory.Therefore,we propose a new boundary element method(BEM)formulation and algorithm for the solution of such problems,which involve temperatures,normal heat fluxes,displacements,couple-tractions,rotations,force-tractions,electric displacement,and normal electric displacement as primary variables within the BEM formulation.The computational performance of the proposed methodology has been demonstrated by using the generalized modified shift-splitting(GMSS)iteration method to solve the linear systems resulting from the BEM discretization.GMSS advantages are investigated and compared with other iterative methods.The numerical results are depicted graphically to show the size-dependent effects of thermopiezoelectricity,thermoelasticity,piezoelectricity,and elasticity theories of nanostructures.The numerical results also show the effects of the sizedependent and piezoelectric on the displacement components.The validity,efficiency and accuracy of the proposed BEM formulation and algorithm have been demonstrated.The findings of the current study contribute to the further development of technological and industrial applications of smart nanostructures.
