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양희수,봉수찬,조경석,최성환,박종엽,김지헌,백지혜,나자경,Mingzhe Sun,Qian Gong 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.2
In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun Because the intensity of the solar outer corona is $10^{-6}$ to $10^{-10}$ times of that of the solar disk (\ir), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of $7.6\times10^{-10}$ \ir~when the cone angle $\theta_c$ was about $0.39\degree$. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of $6\times10^{-9}$ \ir~at $\theta_c=0.40\degree$. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be $0.05\degree$, the lateral alignment tolerance was $45$\,\um, and the angular alignment tolerance was $0.043\degree$. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.
A FINITE ELEMENT SOLUTION FOR THE CONSERVATION FORM OF BBM-BURGERS' EQUATION
Yang Ning,Mingzhe Sun,GUANG-RI PIAO 영남수학회 2017 East Asian mathematical journal Vol.33 No.5
With the accuracy of the nonlinearity guaranteed, plenty of time and large memory space are needed when we solve the finite ele- ment numerical solution of nonlinear partial differential equations. In this paper, we use the Group Element Method (GEM) to deal with the non- linearity of the BBM-Burgers Equation with Conservation form and per- form a numerical analysis for two particular initial-boundary value (the Dirichlet boundary conditions and Neumann-Dirichlet boundary condi- tions) problems with the Finite Element Method (FEM). Some numerical experiments are performed to analyze the error between the exact solution and the FEM solution in MATLAB.
A FINITE ELEMENT SOLUTION FOR THE CONSERVATION FORM OF BBM-BURGERS' EQUATION
Ning, Yang,Sun, Mingzhe,Piao, Guangri The Youngnam Mathematical Society 2017 East Asian mathematical journal Vol.33 No.5
With the accuracy of the nonlinearity guaranteed, plenty of time and large memory space are needed when we solve the finite element numerical solution of nonlinear partial differential equations. In this paper, we use the Group Element Method (GEM) to deal with the non-linearity of the BBM-Burgers Equation with Conservation form and perform a numerical analysis for two particular initial-boundary value (the Dirichlet boundary conditions and Neumann-Dirichlet boundary conditions) problems with the Finite Element Method (FEM). Some numerical experiments are performed to analyze the error between the exact solution and the FEM solution in MATLAB.