A new membrane finite element method for modeling fluid flow in a porous medium is presented in order to quickly and accurately simulate the geo-membrane fabric used in civil engineering. It is based on discontinuous ...A new membrane finite element method for modeling fluid flow in a porous medium is presented in order to quickly and accurately simulate the geo-membrane fabric used in civil engineering. It is based on discontinuous finite element theory, and can be easily coupled with the normal Galerkin finite element method. Based on the saturated seepage equation, the element coefficient matrix of the membrane element method is derived, and a geometric transform relation for the membrane element between a global coordinate system and a local coordinate system is obtained. A method for the determination of the fluid flux conductivity of the membrane element is presented. This method provides a basis for determining discontinuous parameters in discontinuous finite element theory. An anti-seepage problem regarding the foundation of a building is analyzed by coupling the membrane finite element method with the normal Galerkin finite element method. The analysis results demonstrate the utility and superiority of the membrane finite element method in fluid flow analysis of a porous medium.展开更多
A membrane element model with bending modification based on element moment equilibrium is proposed for the first time by the authors, who apply the element model in one step inverse method and simulate the forming pro...A membrane element model with bending modification based on element moment equilibrium is proposed for the first time by the authors, who apply the element model in one step inverse method and simulate the forming process of a flower-shaped box using the membrane element model with and without this modification. The numerical results are compared with those of the incremental method to verify the validity of the element model developed in this paper.展开更多
Membrane diffractive optical elements formed by fabricating microstructures on the substrates have two important characteristics,ultra-light mass(surface mass density<0.1 kg/m2)and loose surface shape tolerances(su...Membrane diffractive optical elements formed by fabricating microstructures on the substrates have two important characteristics,ultra-light mass(surface mass density<0.1 kg/m2)and loose surface shape tolerances(surface accuracy requirements are on the order of magnitude of centimeter).Large-aperture telescopes using a membrane diffractive optical element as the primary lens have super large aperture,light weight,and low cost at launch.In this paper,the research and development on space-based diffractive telescopes are classified and summarized.First,the imaging theory and the configuration of diffractive-optics telescopes are discussed.Then,the developments in diffractive telescopes are introduced.Finally,the development prospects for this technology used as a high-resolution space reconnaissance system in the future are summarized,and the critical and relevant work that China should carry out is put forward.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50779012)
文摘A new membrane finite element method for modeling fluid flow in a porous medium is presented in order to quickly and accurately simulate the geo-membrane fabric used in civil engineering. It is based on discontinuous finite element theory, and can be easily coupled with the normal Galerkin finite element method. Based on the saturated seepage equation, the element coefficient matrix of the membrane element method is derived, and a geometric transform relation for the membrane element between a global coordinate system and a local coordinate system is obtained. A method for the determination of the fluid flux conductivity of the membrane element is presented. This method provides a basis for determining discontinuous parameters in discontinuous finite element theory. An anti-seepage problem regarding the foundation of a building is analyzed by coupling the membrane finite element method with the normal Galerkin finite element method. The analysis results demonstrate the utility and superiority of the membrane finite element method in fluid flow analysis of a porous medium.
基金Project supported by the National Natural Science Foundation of China (No. 51075187)
文摘A membrane element model with bending modification based on element moment equilibrium is proposed for the first time by the authors, who apply the element model in one step inverse method and simulate the forming process of a flower-shaped box using the membrane element model with and without this modification. The numerical results are compared with those of the incremental method to verify the validity of the element model developed in this paper.
基金Project supported by the National Natural Science Foundation of China(No.11874091)。
文摘Membrane diffractive optical elements formed by fabricating microstructures on the substrates have two important characteristics,ultra-light mass(surface mass density<0.1 kg/m2)and loose surface shape tolerances(surface accuracy requirements are on the order of magnitude of centimeter).Large-aperture telescopes using a membrane diffractive optical element as the primary lens have super large aperture,light weight,and low cost at launch.In this paper,the research and development on space-based diffractive telescopes are classified and summarized.First,the imaging theory and the configuration of diffractive-optics telescopes are discussed.Then,the developments in diffractive telescopes are introduced.Finally,the development prospects for this technology used as a high-resolution space reconnaissance system in the future are summarized,and the critical and relevant work that China should carry out is put forward.
