Before revision:  To overcome these problems, this paper discusses competent techniques to determine the optimal \mathcal{H}_2 error norm efficiently for the second-order system. The efficiency and applicability of the proposed techniques are validated by applying them to several large-scale dynamical systems .
After revision:  To overcome these problems, this paper discusses competent techniques to determine the optimal \mathcal{H}_2 error norm efficiently for the second-order systems. The applicability and efficiency of the proposed techniques are validated by applying them to several large-scale dynamical systems .