Department of Physics,College of Science,Yanbian University,Yanji 133002;
Department of Physics,College of Science,Yanbian University,Yanji 133002;
Department of Physics,College of Science,Yanbian University,Yanji 133002;
Department of Physics,College of Science,Yanbian University,Yanji 133002;
Department of Physics,College of Science,Yanbian University,Yanji 133002;