1. Department of Mathematics, KGISL Institute of Technology , Coimbatore 641 035, Tamilnadu , India
2. Department of Mathematics, Bharathiar University , Coimbatore 641 046 , India
3. Department of Applied Mathematics, Kongju National University , Chungcheongnam-do 32588, Republic of Korea
4. National Research Base of Intelligent Manufacturing Service, Chongqing Technology and Business University , Chongqing 400067 , China