1. School of Mechanical and Precision Instrument Engineering; Xi'an University of Technology; Xi'an 710048 China
2. State Key Laboratory for Strength and Vibration of Mechanical Structures; Xi'an Jiaotong University; Xi'an 710049 China
3. College of Engineering; Michigan State University; East Lansing MI 48824 USA
4. School of Printing and Packaging Engineering; Xi'an University of Technology; Xi'an 710048 China
5. Robert R. McCormick School of Engineering and Applied Science; Northwestern University; Evanston IL 60208 USA