Acknowledgments

First of all, I want to acknowledge Professor José Dias Rodrigues for his guidance and sup-port during the development of this master thesis. Without his contribution, the execution of this work would never been possible. To my laboratory colleague Luis Cardoso for the help and opinions that he had given me during this work which were fundamental in some fields. To all my colleagues from Faculdade de Engenharia da Universidade do Porto (FEUP) for their friendship and attendance during these five years of course which is now ending. Lastly, thanks a lot to my dear family for all the support and conditions they have given and provided me along these years.