They have cooperated closely and mutually with me since the beginning of this research study to help me successfully finish this thesis.I am pleased to express my utmost gratitude and appreciation to my supervisors, Prof. Yuan Miao and Dr Khandakar Ahmed. They shared valuable knowledge and experience they had acquired over the years. They enabled me to choose an up-to-date research topic. Moreover, their continuous suggestions and helpful guidance made this difficult path easier for me. Without the support of these two prominent academics, it would have been impossible to follow this path. Dr Khandakar's unique personality and charisma have inspired me to pursue this research study professionally and full-time with more interest.Dr Khandakar has always devoted his time to my academic progress. He has always raised my spirit to study more, and after two years, I have concluded that research helps with my mental development, which is all due to Dr Khandakar. I would also like to thank Prof Yuan for suggesting a suitable and creative model that improves the research results.Since the beginning of this research study, I have lost some relatives and friends, including my father, grandfather, aunt and uncle, all of whom are in my mind and heart forever. Unfortunately, I could not meet them even for the last time due to the restrictions of Covid19. Here is probably a good opportunity to mention them, and I hope that one day I will be able to meet my family. I am also very grateful to my mother, who always encourages me to expand my knowledge on novel matters and serve humanity.