This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is...This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.展开更多
Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material throu...Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material through a series of equilibrium configurations. The motion brings energy into the coronal magnetic field until the system ceases to be in equilibrium. The catastrophe theory for solar eruptions indicates that loss of mechanical equilibrium constitutes the main trigger mechanism of major eruptions, usually shown up as solar flares, eruptive prominences, and coronal mass ejections （CMEs）. Magnetic reconnection which takes place at the very beginning of the eruption as a result of plasma instabilities/turbulence inside the current sheet, converts magnetic energy into heating and kinetic energy that are responsible for solar flares, and for accelerating both plasma ejecta （flows and CMEs） and energetic particles. Various manifestations are thus related to one another, and the physics behind these relationships is catastrophe and magnetic reconnection. This work reports on recent progress in both theoretical research and observations on eruptive phenomena showing the above manifestations. We start by displaying the properties of large-scale structures in the corona and the related magnetic fields prior to an eruption, and show various morphological features of the disrupting magnetic fields. Then, in the framework of the catastrophe theory, we look into the physics behind those features investigated in a succession of previous works, and discuss the approaches they used.展开更多
Progres in ion beam analysis at Fudan University in the recent years is briefly reviewed. Presented as examples of the research activities performed in this field are the following projects: (1) Nuclear potential reso...Progres in ion beam analysis at Fudan University in the recent years is briefly reviewed. Presented as examples of the research activities performed in this field are the following projects: (1) Nuclear potential resonance scattering of 6.25 MeV and 4.25 MeV helium ions for simultaneous compositional analysis of carbon and oxygen in a Mylar, a SnInO, and some other film samples: (2) Determination of stoichiometry of a high-temperature superconducting Y-Ba-Cu-O sample by backscattering of 8.8 MeV helium ions; (3) Backscattering and channeling analysis of multilayered structures periodically consisting of layers of pure Si and alternate layers of Ge and Si, grown on (100) Si substrates by molecular beam epitaxy: (4) Studies of surface structure of Al(100) by the use of MeV ions backscattering and channeling surface peak: and (5) MeV ion microbeam analysis and the use of PIXE method in DNA study. etc.展开更多
基金supported by the Specialized Fund for the Doctoral Program of Higher Education of China (200802131046)China Postdoctoral Science Foundation Funded Major Project (200801290)+1 种基金Development Program of Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2008.004)Specialized Fund for Innovation Talents of Science and Technology in Harbin (2008RFQXG057).
文摘This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.
基金the National Natural Science Foundation of China.
文摘Large-scale magnetic structures are the main carrier of major eruptions in the solar atmosphere. These structures are rooted in the photosphere and are driven by the unceasing motion of the photospheric material through a series of equilibrium configurations. The motion brings energy into the coronal magnetic field until the system ceases to be in equilibrium. The catastrophe theory for solar eruptions indicates that loss of mechanical equilibrium constitutes the main trigger mechanism of major eruptions, usually shown up as solar flares, eruptive prominences, and coronal mass ejections （CMEs）. Magnetic reconnection which takes place at the very beginning of the eruption as a result of plasma instabilities/turbulence inside the current sheet, converts magnetic energy into heating and kinetic energy that are responsible for solar flares, and for accelerating both plasma ejecta （flows and CMEs） and energetic particles. Various manifestations are thus related to one another, and the physics behind these relationships is catastrophe and magnetic reconnection. This work reports on recent progress in both theoretical research and observations on eruptive phenomena showing the above manifestations. We start by displaying the properties of large-scale structures in the corona and the related magnetic fields prior to an eruption, and show various morphological features of the disrupting magnetic fields. Then, in the framework of the catastrophe theory, we look into the physics behind those features investigated in a succession of previous works, and discuss the approaches they used.
文摘Progres in ion beam analysis at Fudan University in the recent years is briefly reviewed. Presented as examples of the research activities performed in this field are the following projects: (1) Nuclear potential resonance scattering of 6.25 MeV and 4.25 MeV helium ions for simultaneous compositional analysis of carbon and oxygen in a Mylar, a SnInO, and some other film samples: (2) Determination of stoichiometry of a high-temperature superconducting Y-Ba-Cu-O sample by backscattering of 8.8 MeV helium ions; (3) Backscattering and channeling analysis of multilayered structures periodically consisting of layers of pure Si and alternate layers of Ge and Si, grown on (100) Si substrates by molecular beam epitaxy: (4) Studies of surface structure of Al(100) by the use of MeV ions backscattering and channeling surface peak: and (5) MeV ion microbeam analysis and the use of PIXE method in DNA study. etc.
