1. Dipartimento di Innovazione Meccanica e Gestionale, Universita´ di Padova, Padova 35131, Italy
2. Department of Design, Manufacture and Engineering Management, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, Scotland
3. Departamento de Engenharia Mecaˆnica, Instituto Superior Te´cnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal