I am deeply grateful to my wife Huiying Li for her unwavering support throughout my studies. The disruptions caused by the COVID-19 pandemic meant that she had to wait for me in China for over three years, and I am grateful for her understanding and determination to stand by me through it all. Without her support, I would not have been able to complete my studies. I also want to extend my heartfelt thanks to my family and friends for their love, encouragement, and understanding during this challenging time.