feodex2l.m

大量的有限元法求解偏微分方程的实例程序

function [k]=feodex2l(xl,xr)

%-------------------------------------------------------------------
%  Purpose:
%     element matrix for (x^2 u'' - 2x u' - 4 u)
%     using linear element
%
%  Synopsis:
%     [k]=feodex2l(xl,xr) 
%
%  Variable Description:
%     k - element matrix (size of 2x2)   
%     xl - coordinate value of the left node of the linear element 
%     xr - coordinate value of the right node of the linear element     
%-------------------------------------------------------------------

% element matrix

 eleng=xr-xl;
 k=(1/eleng^2)*[ (4*xr^2*xl-6*xr*xl^2-xr^3+3*xl^3) ...
                 (2*xr^2*xl-xr^3-xl^3);...
                 (-2*xr*xl^2+xr^3+xl^3) ...
                 (6*xr^2*xl-4*xr*xl^2-3*xr^3+xl^3)];