For finite elements the elementwise assembly is carried out by the quadrature of all integral expressions which are related to a common cell . In the case of a triangular cell which contains three vertex values, nine integrals have to be calculated. When Galerkin schemes are used, the calculation can be reduced to six integrals, because of the symmetry of the local matrix. The matrix can be written in the following manner, where the vertices of the cell are denoted as , and
In the notation according to Chapter 2, such a local element matrix can be assembled using the vectorization command in order to retrieve a matrix.
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Michael 20080116