Submitted on: 14 October 2006.
Revised on: 17 November 2006.
Accepted on: 05 January 2007.
___________________Advances in Electrical and Computer Engineering
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Submitted on: 30 November 1999.
Revised on: 03 February 2000.
Accepted on: 21 February 2000.
___________________Advances in Electrical and Computer Engineering
Submitted on: 23 December 2008.
Revised on: 05 February 2009.
Accepted on: 21 February 2009.
___________________Advances in Electrical and Computer Engineering
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