College of Mathematics and Physics, Jinggangshan University, Ji'an 343009, China;
College of Mathematics and Physics, Jinggangshan University, Ji'an 343009, China;
College of Mathematics and Physics, Jinggangshan University, Ji'an 343009, China;
College of Mathematics and Physics, Jinggangshan University, Ji'an 343009, China;
College of Mathematics and Physics, Jinggangshan University, Ji'an 343009, China;