1. School of Mechanical Engineering, Xi’an Jiaotong University, Xi'an, P.R. China
2. Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
3. Department of Neurology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, P.R. China
4. Department of Mechanical Engineering, University of Bath, Bath, UK