Acknowledgments

I would like to thank to all that directly or indirectly contributed to the conclusion of this thesis. Without them this work would be more poor and difficult. I would like to express my gratitude to my supervisor, professor João Lemos for taking the responsi-bility for this dissertation and whose expertise, understanding and patience added considerably to my graduate experience. A very special thanks to professor José Fernando Silva for the weekly meetings where several issues were discussed in order to promote my critical spirit. I must also acknowledge my friend engineer Ricardo Melro, for suggesting me the theme for this thesis and for his availability and provision of the font materials evaluated in this study. Appreciation also goes out to my dear-est colleagues and friends Ana Clara Lopes, Catarina Cruz, Lúcia Cordeiro, Joana Gomes and José Jerónimo for their friendship and all the instances in which their assistance helped me along the way. I would also like to thank my family for the support they provided me through my entire life and in particular, I must acknowledge my parents and sister, without whose love and encouragement I would not have finished this thesis. In conclusion, I recognize that this research would not have been possible without the assistance of INESC-ID (Lisbon), where this thesis was performed