[1] Northwestern Polytech Univ, AIMCNT Res Ctr, Sch Automat, Xian 710129, Peoples R China
[2] Univ Edinburgh, Sch Engn, SMART Grp, Edinburgh EH9 3FG, Scotland
[3] Beijing Univ Technol, Fac Informat Technol, Res Ctr NDT&E, Beijing 100124, Peoples R China
[4] Univ Calif San Diego, Dept Comp Sci & Engn, La Jolla, CA 92093 USA