College of Management;
Hebei University;
Baoding Hebei 071002;
China;
Dept. of Information Engineering;
Hebei Software Institute;
Baoding Hebei 071001;
China;
College of Mathematics & Computer;
Hebei University;
Baoding Hebei 071002;
China;
College of Mathematics & Computer;
Hebei University;
Baoding Hebei 071002;
China;