Liu Jun holds a doctor degree from Department of Engineering Mechanics, Northwestern Polytechnical University, China. He is now an associate professor at School of Mechanics and Civil Engineering & Architecture, NWPU. Zhufeng Yue is a professor at School of Mechanics and Civil Engineering & Architecture, NWPU. He was a Humboldt Scholar at Ruhr University Bochum in 1999 and Cheung Kung Scholar at NWPU in 2001. Xiaoliang Geng is an associate professor at School of Mechanics and Civil Engineering & Architecture, NWPU. Shifeng Wen is an associate professor at School of Mechanics and Civil Engineering & Architecture, NWPU. Wuzhu Yan is a lecturer at School of Mechanics and Civil Engineering & Architecture, NWPU.