\chapter*{Acknowledgements}
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I wish to thank my parents Edda and Francesco for their support during my studies and because they have been sure and wise guide throughout
my life. 
I express gratitude also to my siblings Elisabetta and Giuseppe because preceding me with their studies, they were an excellent example and
constant reference point. Thanks to the invaluable suggestions and teachings of my family I was able to achieve this ambitious goal. 

I wish to express my considerable gratitude to my advisor Prof. Ruggero Frezza for his availability and trust in me and because he gave me the
 wonderful opportunity to do research in the United States of America. 
 
 I am especially grateful to my advisor Prof.~Pietro~Perona  at
 California~Institute~of~Technology who gave me hospitality for seven months in the Computer~Vision~Laboratory. His patient and inspired guide, generosity and
creativity are a landmark in my human and professional experience. 

I thank also all the Computer Vision group and staff at Caltech for their friendliness, availability and help: Melissa~Slemin, Silvio~Savarese, 
Anelia~Angelova, Lihi~Zelnik, Pierre~Moreels, Michael~Fink, Ueli~Rutishauser, Fei~Fei~Li, Marco~Andretto, Claudio~Fanti, Ulrik~Beierholm and Alex~Holub.

I must acknowledge Prof.~Gian~Antonio~Mian and Prof.~Gaudenzio \linebreak[4] Meneghesso's contribution to my educational and 
professional growth, they will be always an example of people who love science and their work of research and teaching. 

I express a last thought for my friends and colleagues at University~of~Padua because we shared together these years of study and 
many joyful moments.  



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