1. School of Materials Science and Engineering Beijing Institute of Technology Beijing 100081 P. R. China
2. School of Mechanical and Material Engineering North China University of Technology Beijing 100144 P. R. China
3. School of Science Yanshan University Qinhuangdao Qinhuangdao 066004 P. R. China
4. Department of Communication Engineering Communication University of China Beijing 100024 P. R. China
5. Chinese Acad Sci Inst Coal Chem State Key Lab Coal Convers 27 Taoyuan South Rd Taiyuan Shanxi 030001 P. R. China
6. School of Information Engineering Minzu University of China Beijing 100081 P. R. China