iosr-JECE   Volume-10 ~ Issue-4 ~ July-August 2015

Abstract: In our present article the concentration is given to the superconducting behaviour of CNTs. The superconductivity of a material depends on transition temperature Tc. the impact of coulomb interaction is also taken into account. A theory have been developed with resistivity and coherence length from the earlier experimental curve between transition temperature and resistivity for a single wall nanotube.The curvature of CNTs leads to the creation of new electron –phonon interaction can introduce superconductivity. In this part the resistivity of carbon nanotube has been derived theoretically with relaxation time and Fermi velocity.

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Abstract: In Wireless/Mobile networks various kinds of encoding schemes were used for transmission of data over a bandwidth. The desired quality and generated traffic varies with the requirement with this bandwidth. A generic video telephony may require more than 40 kbps whereas a low motion video telephony may require about 25 kbps for data transmission. From the designing point of view these requirements demands for an alternative resource planning, especially for bandwidth allocation in wireless networks. In wireless network where bandwidth is a scare resource, the system may need to block incoming user if all of the bandwidth has been used to provide highest quality of service to existing users. However this bandwidth resource planning may be unacceptable for larger application.

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Abstract: Free space optical communication (FSO) is the future technology for high speed and highly secure data communication. Terrestrial operation is one of the applications of FSO where data communication is established between ground to ground platforms. But the FSO has to face challenges against atmosphere in form of attenuation and turbulent channel. The atmospheric attenuation is mainly caused by scattering. The atmospheric attenuation affects the overall quality of the system. In this paper the effects of scattering on the terrestrial FSO which have a link length of 2 km, is simulated using OptiSystem 7.0.

[1] Arun K. Majumdar and Jenifer C. Ricklin. "Free-Space Laser communications, Principles and Advances". Number ISBN: 987-0-387-28652-5. Springer, 2008.
[2] Hennes Henninger and Otakar Wilfert. "An Introduction to Free-space Optical Communications". Radio Engineering, 19(2):203-212, June 2010.
[3] Abdulsalam Alkholidi and Khalil Altowij. "Effect of Clear Atmospheric Turbulence on Quality of Free Space Optical Communications in Western Asia", Optical Communications Systems, Dr. Narottam Das (Ed.), ISBN: 978-953-51-0170-3, InTech, DOI: 10.5772/351 86, 2012.
[4] Ghassemlooy Z. and Popoola W. O. "Terrestrial Free-Space Optical Communications, Mobile and Wireless Communications Network Layer and Circuit Level Design", Salma Ait Fares and Fumiyuki Adachi (Ed.), ISBN: 978-953-307-042-1, InTech, DOI: 10.5772/7698, 2010.
[5] Isaac I. Kim, Bruce McArthur, and Eric Korevaar, Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications, Optical Access Incorporated, Web: http://www.opticalac cess.com.