Anantharaman, M R; Swapna, Nair S; Mercy, Mathews; Joy, P A; Kulkarni, S D(Elsevier, July 26, 2004)
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Abstract:
Superparamagnetic nanocomposites based on g-Fe2O3 and sulphonated polystyrene have been synthesized by ion
exchange process and the preparation conditions were optimized. Samples were subjected to cycling to study the effect
of cycling on the magnetic properties of these composites. The structural and magnetization studies have been carried
out. Magnetization studies show the dependence of magnetization on the number of ion exchange cycles. Doping of
cobalt at the range in to the g-Fe2O3 lattice was effected in situ and the doping was varied in the atomic percentage
range 1–10. The exact amount of cobalt dopant as well as the iron content was estimated by Atomic Absorption
Spectroscopy. The effect of cobalt in modifying the properties of the composites was then studied and the results
indicate that the coercivity can be tuned by the amount of cobalt in the composites. The tuning of both the
magnetization and the coercivity can be achieved by a combination of cycling of ion exchange and the incorporation of
cobalt
Description:
Journal of Magnetism and Magnetic Materials 283 (2004) 344–352
Jijo, P U; Dr.Nandakumaran,V M(Cochin University of Science & Technology, August , 2008)
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Abstract:
This thesis presents analytical and numerical results from studies based on the multiple
quantum well laser rate equation model. We address the problem of controlling chaos produced
by direct modulation of laser diodes. We consider the delay feedback control methods
for this purpose and study their performance using numerical simulation. Besides the control
of chaos, control of other nonlinear effects such as quasiperiodicity and bistability using
delay feedback methods are also investigated.A number of secure communication schemes based on synchronization of chaos semiconductor
lasers have been successfully demonstrated theoretically and experimentally. The current
investigations in these field include the study of practical issues on the implementations of
such encryption schemes. We theoretically study the issues such as channel delay, phase mismatch
and frequency detuning on the synchronization of chaos in directly modulated laser
diodes. It would be helpful for designing and implementing chaotic encryption schemes using
synchronization of chaos in modulated semiconductor lasers.
Description:
International School of Photonics,
Cochin university of Science & Technology