This thesis is not the end of my passion toward research, but marks a new
beginning of my constant enthusiasm for research. Through the entire process of the
thesis, I learned invaluable experience. As a baby learns to walk by falling down and as a
runner learns to win with every defeat, I realized that the best lessons in life do not come
easy. As the first publication ever in my life, this thesis might be immature like a new
born baby; however, I truly believe that it has tremendous potentials to grow up as my
enthusiasm for research grows up.