1. School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 P. R. China
2. Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen 518055 P. R. China
3. School of Microelectronics Southern University of Science and Technology Shenzhen 518055 P. R. China
4. Department of Mechanical Engineering Iowa State University Ames IA 50011 USA