1. State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi'an Jiaotong University, Xi'an, China
2. Department of Mechanical and Electrical Engineering, Ningxia Polytechnic, Yinchuan, China
3. Institute of Fluid Science, Tohoku University, Sendai, Japan
4. The Kansai Electric Power Co., Fukui-ken, Japan