Jorge Miguel Tavares Couceiro de SousaDepartament of Physics and Mathematics of the Coimbra Institute of Engineering (ISEC - Instituto Superior de Engenharia de Coimbra)Polythecnic of Coimbra (IPC - Instituto Politécnico de Coimbra)
Candida Maria dos Santos Pereira MalcaPolytechnic Institute of CoimbraCoimbra Institute of Engineering