1. School of Mathematics and Big Data , Foshan University , Foshan , Guangdong 528000 , P. R. China
2. Mathematics with Computer Science Program , Guangdong Technion , 241 Daxue Road, Jinping District , Shantou , Guangdong 515063 , P. R. China ; and Department of Mathematics, Technion – Israel Institute of Technology, Haifa 32000, Israel