[1] Hunan Univ Technol, Coll Sci, Zhuzhou 412007, Peoples R China
[2] Chinese Acad Sci, Natl Time Serv Ctr, Key Lab Time & Frequency Primary Stand, Xian 710600, Shaanxi, Peoples R China
[3] Univ Electrocommun, Dept Engn Sci, Tokyo 1828585, Japan
[4] Univ Chinese Acad Sci, Sch Astron & Space Sci, Beijing 100049, Peoples R China