Affiliation: | 1.School of Mathematics and Statistics, Qingdao University, Qingdao, 266071, People’s Republic of China ;2.Institute of Applied Mathematics of Shandong, Qingdao, 266071, People’s Republic of China ;3.Institute of Applied Mathematical Research, Karelian Research Center, Russian Academy of Sciences, Pushkinskaya str. 11, Petrozavodsk, Russia, 185910 ; |