1. Mechanical Engineering Department, University of the Basque Country UPV/EHU, Eibar, Spain
2. Mechanical Engineering Department, University of the Basque Country UPV/EHU, San Sebastian, Spain
3. Business Organization Department, University of the Basque Country UPV/EHU, San Sebastian, Spain
4. Mechanical Engineering Department, University of the Basque Country UPV/EHU, Bilbao, Spain