对于一个给定了质量矩阵和刚度矩阵的系统,利用该函数可求出模态参数.- Purpose:

　　　The function subroutine femodal.m calulates modal parameters

　　　for a given structural system. It calculates natural frequency and

　　　eigenvector. The eigenvectors are normalized so that the modal

　　　mass matrix becomes an indentity matrix.