1. Department of Materials Science and EngineeringCity University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 P. R. China
2. Harbin Institute of Technology (Shenzhen) Shenzhen 518055 P. R. China
3. Chengdu Research InstituteCity University of Hong Kong Chengdu 999077 P. R. China