I would like to express my deepest appreciation and acknowledgment to my advisor Dr. Nadeem Javaid, for his invaluable support, guidance, encouragement, patience, and life teachings. I will internalize all he has taught me in my future life, because it is something that will help me to achieve even greater objectives. Their vigilance guidance also helped me a lot to achieve my objective. I heartily dedicate my dissertation to my late father Mr. Khadim Hussain and late aunt Miss. Safia Begum whose endless efforts brought me to this stage. My deepest gratitude to my wife who always remained a source of inspiration and support for me. My heartily thanks to my mother, brothers, sisters, my loving children and other family members for their worthy love, support and company. Last but not the least, I thank God for giving me the opportunity to keep growing and improving myself, with the ultimate goal of better service of humanity.