This thesis is dedicated to all my beloved ones for supporting me throughout all my studies. For my father, who taught me that the best kind of knowledge to have is that which is learned for its own sake. It is also dedicated to my mother, who taught me that even the largest task could be accomplished if it is done one step at a time. They raised me, supported me, taught me, and loved me. I would like to thank to my brother who provided extraordinary encouragement and for supporting me spiritually throughout my life. For my fiancé, thank you for helping me to get through the difficult times, and for all the emotional support, entertainment, and caring you provided. iii