1. PhD candidate, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal, Telephone: +351 225081286; Telefax: +351 225081446;(Corresponding author)
2. Assistant Professor, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal, Telephone: +351 225081586; Telefax: +351 225081446;(Corresponding author)
3. Professor, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal, Telephone: +351 225081564; Telefax: +351 225081446;