中文摘要：

这份报纸在 Hilbert-Schmidt-Hankel 标准的意义认为矩阵秒顺序的最佳的模型减小问题是线性系统，与保存原来的系统的结构的减少的顺序系统。错误功能和它的坡度的表情被导出。二个数字例子被给说明介绍模型减小技术。

英文摘要：

This paper considers the optimal model reduction problem of matrix second-order linear systems in the sense of Hilbert-Schmidt-Hankel norm, with the reduced order systems preserving the structure of the original systems. The expressions of the error function and its gradient are derived. Two numerical examples are given to illustrate the presented model reduction technique.