1. Chengdu Development Center of Science and Technology of CAEP Chengdu, Sichuan 610207 P. R. China
2. Institute of Electronic Engineering China Academy of Engineering Physics Mianyang, Sichuan 621000 P. R. China
3. Shanghai Synchrotron Radiation Facility Shanghai Advanced Research Institute Chinese Academy of Sciences Shanghai 201204 P. R. China
4. Department of Mechanical and Materials Engineering University of Western Ontario London Ontario N6A 5B9 Canada