1. Faculty of Engineering, University of Deusto , 48007 Bilbao, Spain, ollorente@opendeusto.es
2. Faculty of Engineering, Mondragon Unibertsitatea , 20500 Arrasate-Mondragon, Spain; HP Labs, BS34 8QZ Bristol, UK, isantos@mondragon.edu ; igor.santos.grueiro@hp.com
3. Faculty of Engineering, University of Deusto , 48007 Bilbao, Spain, iker.pastor@deusto.es
4. Faculty of Engineering, University of Deusto , 48007 Bilbao, Spain, pablo.garcia.bringas@deusto.es