1. School of Software, Northwestern Polytechnical University, Xi’an 710129, China
2. School of Computer Science, Shaanxi Normal University, Xi’an 710119, China
3. College of Computer Science and Technology, Huaqiao University, Xiamen 361021, China
4. School of Computer Science and Engineering, Xi’an University of Technology, Xi’an 710048, China
5. Institute of Mathematics, Silesian University of Technology, Kaszubska 23, Gliwice 44-100, Poland
6. Czestochowa University of Technology, Al. Armii Krajowej 36, Czestochowa 42-200, Poland