In this talk, numerical methods to solve second-order elliptic partial dierential equations will be presented. First, some of the existing methods, such as the standard Galerkin method, mixed nite element methods etc., will be briey discussed. Then, a new hybrid mixed nite element method will be introduced for ecient and accurate approximations of the ux variables. In many applications, the ux variables are the main quantities of interest. The method is a two{step method. On a coarse mesh, the primary variable is approximated. Then, the approximation is used as a data for the ux approximation on a ne mesh. It will be shown that the ne mesh size can be taken as the square of the coarse mesh size, or a higher power with a proper choice of parameter. This means that the computational cost for the coarse-grid solution is negligible compared to that for the ne-grid solution. This is a joint work with Dr. Young Ju Lee and Dr. Dongwoo Sheen.
