<有限元编程>一书中例题程序代码，p40-p53，包括杆单元，梁单元，简单平面三角形单元，四边形单元的简单有限元计算。-The finite element programming>　Example program code, p40-p53, including rod elements, beam elements, a simple plane triangular element, quadrilateral element simple finite element calculation.