1. Assistant, Faculty of Engineering, Univ. of Porto, Rua Dr. Roberto Frias, 4200 Porto, Portugal.
2. Associate Professor, Faculty of Engineering, Univ. of Porto, Rua Dr. Roberto Frias, 4200 Porto, Portugal.
3. Professor, Faculty of Engineering, Univ. of Porto, Rua Dr. Roberto Frias, 4200 Porto, Portugal.