First and foremost, I would like to express my sincere gratitude to my supervisor Prof Premchand Dommaraju for his guidance, motivation, and knowledge to support me to complete this thesis. It is truly my luck to have you as my supervisor, I appreciate all the time and effort you have put in to guide me in the past 2 years.Next, I would like to thank my family, whom I have not met in the past 7 months due to the ongoing COVID-19 crisis, thank you all for the unconditional love and support. A special thanks to Youjun, long distance relationship in the past few years has not been easy, but we survived from it, and thank you for your love, support and accompany all along.Then, my sincere thanks to all the professors whom I have met in the past two years, every lecture, seminar, research opportunity, advice from you is invaluable to me and they will always be my lifelong inspiration.In addition, I would like to thank NTU School of Social Sciences and the graduate office for the most efficient backup support on earth and all the academic resources that you have provided.Last but not least, thanks to my fellow graduate students: Haoyu, Jingwen, Xingyan, Victoria and Polo, it is lucky to meet you and work together with you in NTU, wishing you guys all the best in the coming days. This thesis would not have been possible without the support from any of you.