BIO-DATA OF Prof.S. RAJASEKAR Date of birth : 15, July 1963 Designation : Professor Address : School of Physics Bharathidasan University Tiruchirapalli 620 024 Tamilnadu, India Education : M.Sc., M.Phil., Ph.D. e-mail : [email protected], [email protected] Mobile Number : 9442539305 May 21, 1993 -- May 20, 2002 – Lecturer Department of Physics Manonmaniam Sundaranar University Tirunelveli 627 012. May 21, 2002 -- July 12, 2005 - Reader Department of Physics Manonmaniam Sundaranar University Tirunelveli 627 012. From July 13, 2005 - Professor School of Physics Bharathidasan University Tiruchirapalli 620 024. December 2014 – June 2019 -- Director of IQAC 1 RESUME OF RESEARCH Specialized area of research: Nonlinear Resonances In recent years stochastic and vibrational resonances were investigated in certain nonlinear oscilllators. The role of shape of periodic forces and depths and widths of the double-well potentials on the characteristics of stochastic resonance has been investigated. It has been shown that multifractal analysis can also be used for characterization of stochastic resonance. The utility of stochastic resonance in multi-scroll system in detecting additional ac or dc signal present in the input signal was explored. In multi-scroll systems the signal-to-noise ratio is found to be maximum when the equilibrium point is six and stochastic resonance is observed only for the number of equilibrium points < 20. Both theoretically and numerically, vibrational resonance has been investigated in monostable, bistable, three-well and spatially periodic potential systems, time-delay systems and nonlinear biological maps. Specifically, analytical expression for the control parameters at which resonance occurs was derived. Multiple resonances in monostable systems and sequential resonances in pendulum system and undamped signal propagation in coupled maps were found due to vibrational resonance. The effect of depth and width of the potential wells and asymmetry in the potential of the Duffing oscillator has been investigated. Theory for the analysis of vibrational resonance in time-delay system has been developed. The theoretical treatment allows us to predict the values of the control parameters at which resonance occurs, the number of resonances, the parametric choices for which resonance cannot occur, the maximum value of the response amplitude and explains the mechanism for vibrational resonance. The influence of (i) single constant, (ii) multiple, (iii) gamma distributed, (iv) integrative, (v) random and (vi) different types of state-dependent time-delayed feedbacks on vibrational resonance has been investigated. Ghost-stochastic resonance in single Bellows map and unidirectionally coupled n Bellows maps, and ghost-vibrational resonance in single Duffing oscillator and unidirectionally coupled n Duffing oscillators were analysed. Multiple resonance and antiresonance were investigated both theoretically and through analog circuit simulation of two-coupled and n coupled Duffing oscillators. 2 LIST OF PUBLICATIONS 1. Period doubling route to chaos for a BVP oscillator with periodic external force. S. Rajasekar and M .Lakshmanan, J. Theor. Biol. 133 (1988) 473—477. 2. Period doubling bifurcations, chaos, phase-locking and devil's staircase in a BVP oscillator. S. Rajasekar and M. Lakshmanan, Physica D 32(1988)146—152. 3. Bifurcations and chaotic motion of soliton in a long Josephson junction oscillator. S. Rajasekar and M. Lakshmanan, Physica A 167 (1990) 793—809. 4. Multiple attractors and their basins of attraction of long Josephson junction oscillator. S. Rajasekar and M. Lakshmanan, Physics Letters A 147 (1990) 264—268. 5. Controlling of chaos in BVP oscillator. S. Rajasekar and M. Lakshmanan, Int. J. Bifur. and Chaos 2 (1992) 201—204. 6. Prediction of horseshoe chaos in BVP and DVP oscillators. S. Rajasekar, S. Parthasarathy and M. Lakshmanan, Chaos, Solitons and Fractals 2 (1992) 271—280. 7. Routes to chaos and mode-locking in interferometers with nematic film inserts. S. Rajasekar, Pramana J of Physics 39 (1992) 509—520. 8. Algorithms for controlling chaotic motion: application for the BVP oscillator. S. Rajasekar and M. Lakshmanan, Physica D 67 (1993) 282—300. 9. Fractal measures of first passage time of a simple random walk. K.P.N. Murthy, S. Rajasekar, M.C. Valsakumar, V. Sridhar and R. Krishnan, Physica A 199 (1993) 55—66. 10. Controlling of chaos by weak periodic perturbations in Duffing--van der Pol oscillator. S. Rajasekar, Pramana J of Physics 41 (1993) 295—309. 11. Diffusion in disordered systems. K.P.N. Murthy, K.W. Kehr and S. Rajasekar, Proceeding of Ordering in Disorder: Prospects and Retrospects in Condensed Matter Physics. (Eds.) V. Srivastava, A.K. Bhatnagar and D.G. Naugle (Amer. Inst. Phys., New York, 1994) pp.243—245. 12. Fractal measures of mean first passage time in the presence of Sinai disorder. K.P.N. Murthy, S. Rajasekar and K.W. Kehr, J. Phys. A 27 (1994) L107--L112. 3 13. Bifurcation, chaos and suppression of chaos in FitzHugh--Nagumo nerve condition model equation. S. Rajasekar and M.Lakshmanan, J. Theor. Biol. 166 (1994) 275—288. 14. Controlling of chaos in BVP and DVP oscillators. S. Rajasekar, Proceedings of Computational Aspects in Chaos and Nonlinear Dynamics} (Eds) G. Ambika and V.M. Nandakumaran (Wiley Easter Limited, New Delhi, 1994) pp.72--82 15. Controlling of chaotic motion by chaos and noise signals in a logistic map and BVP oscillator. S. Rajasekar, Phys. Rev. E 51 (1995) 775—778. 16. Conversion of chaotic attractor into a strange nonchaotic attractor in an one dimen- sional map and BVP oscillator. S. Rajasekar, Pramana J of Physics 44(1995) 121—131. 17. Dynamic behaviour of the critical attractor and characterization of chaotic attractors at bifurcation in a one-dimensional map. S. Rajasekar, Phys. Rev. E 52 (1995) 3234—3237. 18. Controlling unstable periodic orbits in a Bonhoeffer--van der Pol equation. S. Rajasekar, Chaos, Solitons and Fractals 5 (1995) 2135—2144. 19. Painleve analysis and integrability of the damped anharmonic oscillator equation. S. Paul Raj and S. Rajasekar, Pramana J of Physics 45 (1995) 305—309. 20. Dynamic behaviours of attractor and q-phase transitions at bifurcations in logistic map. P. Philominathan and S. Rajasekar, Physica A 229 (1996) 244—254. 21. Experimental observation and characterization of chaos in the unstable plastic flow domain during tensile testing. S. Rajasekar, S. Venkadesan and K.P.N. Murthy, J. Mater. Sci. Letts. 15 (1996) 597—599. 22. Lyapunov exponent analysis in an one-dimensional map and BVP equation. S. Rajasekar, Indian J Physics 70B (1996) 51—57. 23. Dynamical structure functions at critical bifurcations in a Bonhoeffer—van der Pol equation. S. Rajasekar, Chaos, Solitons and Fractals 7 (1996) 1799—1805. 4 24. Evidence for chaos in an experimental time series from serrated plastic flow. S. Venkadesan, M.C. Valsakumar, K.P.N. Murthy and S. Rajasekar, Phys. Rev. E 54 (1996) 611—616. 25. The Painleve property, integrability and chaotic behaviour of a two-coupled Duffing oscillators. S. Rajasekar and S. Paulraj, Pramana J Physics 47 (1996) 183—198. 26. Directing chaotic systems to regular motion. M. Lakshmanan and S. Rajasekar, Proc.Nat.Acad.Sci.India 66(A) (1996) 37—56. 27. Characterization and control of chaotic dynamics in a nerve conduction model equation. S. Rajasekar, Pramana J Physics 48 (1997) 249—258. 28. Analytical prediction of horseshoe chaos in two coupled Duffing oscillators. S. Rajasekar and S. Paulraj, Indian J Physics 71(B) (1997) 49—58. 29. Migration control in two coupled Duffing oscillators. S. Paulraj and S. Rajasekar, Phys. Rev. E 55 (1997) 6237--6240 30. Statistical dynamics of sine-square map. P. Philominathan, P. Neelamegam and S. Rajasekar, Physica A 242 (1997) 391- 408. 31. Control of chaos by nonfeedback methods in a simple electronic circuit system and the FitzHugh--Nagumo equation. S. Rajasekar, K. Murali and M. Lakshmanan, Chaos, Solitons and Fractals 8 (1997) 1545—1558. 32. Dynamical evolution of escape probability in the presence of Sinai disorder. S. Rajasekar and K.P.N. Murthy, Phys. Rev. E 57 (1998) 1315—1318. 33. Probability distribution characteristics of chaos in a simple population model and the BVP oscillator. S. Parthasarathy and S. Rajasekar, Phys. Rev. E 58 (1998) 6839—6842. 34. Noise-induced jumps in two coupled Duffing oscillators. S. Rajasekar, M.C. Valsakumar and S. Paulraj, Physica A 261 (1998) 417—434. 35. Statistical dynamics at critical bifurcations in Duffing--van der Pol oscillator. V. Chinnathambi and S. Rajasekar, Pramana J Physics 52 (1999) 561—577. 36. Coexisting chaotic attractors, their basin of attractions and synchronization of chaos in a two coupled Duffing oscillators. S. Paulraj, S. Rajasekar and K. Murali, Physics Letters A 264 (1999) 283—288. 5 37. Variation of certain statistical quantities near critical bifurcations. S. Rajasekar and V. Chinnathambi, Chaos, Solitons and Fractals 11 (2000) 859--870 38. Variation and fluctuation dynamics of state variables near bifurcations of chaos. S. Rajasekar, in Nonlinear Dynamics: Integrability and Chaos (Eds.) M. Daniel, K.M. Tamizhmani and R. Sahadevan (Narosa Publ. House, New Delhi, 2000) pp. 245—251. 39. Normal and anomalous diffusions in web map driven by a constant external force. S. Rajasekar and V. Chinnathambi, Physica A 282 (2000) 137—154. 40. Diffusion in a periodically driven damped and undamped pendulum. R. Harish, S. Rajasekar and K.P.N. Murthy, Phys. Rev. E 65 (2002) 046214 -- 9 pages. 41. Diffusion in periodically driven damped and undamped pendulum S. Rajasekar, R. Harish and K.P.N. Murthy in Nonlinear Systems. (Eds.) R. Sahadevan and M. Lakshmanan (Narosa, New Delhi, 2002) pp 329—341. 42. Resonance behaviour and jump phenomenon in a two-coupled Duffing--van der Pol oscillators. S. Rajasekar and K. Murali, Chaos, Solitons and Fractals 19 (2004) 925-934. 43. Painleve analysis and integrability of a two-coupled nonlinear oscillators. S. Rajasekar, Pramana J of Physics 62 (2004) 1—12. 44. Stochastic resonance in overdamped two coupled anharmonic oscillators V.M.