Submitted on: 19 June 2007.
Revised on: 18 August 2007.
Accepted on: 10 October 2007.
___________________Ingenieria y Competitividad---UNIV VALLE, FAC INGENIERIA
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Submitted on: 18 November 2012.
Revised on: 31 January 2013.
Accepted on: 03 March 2013.
___________________Ingenieria y Competitividad---UNIV VALLE, FAC INGENIERIA
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Submitted on: 23 December 2014.
Revised on: 17 February 2015.
Accepted on: 24 March 2015.
___________________Ingenieria y Competitividad---UNIV VALLE, FAC INGENIERIA