I would like to express my sincere thanks to my thesis advisor, Aj. Malcolm Charles Perry for his invaluable help and constant encouragement throughout the course of this research. I am most grateful for his teaching and advice. I would not have achieved this far and this thesis would not have been completed without all the support that I have always received from him and others person for suggestions and all their help. Finally, I most gratefully acknowledge my parents and my friends for all their support throughout the period of this research.