1. School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China
2. School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
3. Faculty of Printing, Packaging Engineering and Digital Media Technology, Xi'an University of Technology, Xi'an 710048, China
4. University of Nottingham, University Park, Nottingham NG72RD, UK