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Submitted on: 23 March 2011.
Revised on: 03 July 2011.
Accepted on: 13 August 2011.
___________________International Journal of Energy Optimization and Engineering
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Submitted on: 26 March 2008.
Revised on: 27 June 2008.
Accepted on: 15 July 2008.
___________________International Journal of Energy Optimization and Engineering
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