School of Mathematics;
Beijing Institute of Technology;
Pedagogical Department E.E.;
Section of Mathematics and Informatics;
National and Capodistrian University of Athens;
4;
Agamemnonos Str.;
Aghia Paraskevi;
Athens 15342;
Greece;
School of Communication and Information Engineering;
University of Electronic Science and Technology of China;
Department of Electrical and Computer Engineering;
College of Engineering;
University of Kentucky;
Lexington 40506;
USA;
