1. Professor School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, China e-mail:
2. Department of Mechanical Engineering, The University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada
3. Professor Fellow ASME Department of Mechanical Engineering, The University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada e-mail: