College of Information Science and Technology;
Nanjing University of Aeronautics and Astronautics;
Nanjing 210098;
P.R. China;
College of Computer and Information Engineering;
Hohai University;
Nanjing 210016;
P.R. China;
College of Information;
Shandong Agricultural University;
Tai' an 271000;
P.R. China;