1. Department of Physics, PRIST University, Thanjavur 614 904, India
2. Centre for Nonlinear Dynamics, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, India
3. P.G. and Research Department of Physics, A.V.V.M. Sri Pushpam College, Poondi, Thanjavur 613 503, India