Submitted on: 14 May 2004.
Revised on: 24 June 2004.
Accepted on: 16 July 2004.
___________________Advances in Electrical and Computer Engineering
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Submitted on: 13 February 2006.
Revised on: 27 March 2006.
Accepted on: 26 May 2006.
___________________Advances in Electrical and Computer Engineering
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Submitted on: 27 July 1999.
Revised on: 07 November 1999.
Accepted on: 18 December 1999.
___________________Advances in Electrical and Computer Engineering
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