Where,λ is the eigenvalue and φ is the corresponding eigenvector. Both eigenvalues and eigenvectors may be complex. In order
to solve the complex eigenproblem, this system is symmetrized by ignoring the damping matrix C and the asymmetric
contributions to the stiffness matrix K. Then this symmetric eigenvalue problem is solved to find the projection subspace. The N
eigenvectors obtained from the symmetric eigenvalue problem are expressed in a matrix as[ , ,........ ] 1 2 N φ φ φ . Next, the original
matrices are projected onto the subspace of N eigenvectors