1. School of Mathematics and Computational Science, Xiangtan University, Xiangtan 411105, People's Republic of China
2. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. National Institute of Technology, Hachinohe College, Hachinohe, Aomori 039-1192, Japan