الفهرس 
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Abstract
Acknowledgement All acknowledgements and gratitude are due to Allah almighty for giving me the strength to finish this thesis. I would like to express my deepest thanks and appreciation to Prof. Mohamed Abdel-Latif Soliman, for his constructive guidance, valuable discussions throughout all the stages of this work and for his excellent help I could wish for. My sincere thanks and gratitude are dedicated to Prof. Nassar Hassan Abdel- All, for his continuous encouragements, valuable discussions throughout all the stages of this work, helpful guidance and his trust in me in such a simple way. Also, I’d like to thank Dr. Soad Ali Hassan, for her most valuable help in writing this thesis and her excellent help. Moreover, My deepest thanks to prof. Also, I’d like to thank all the staff members of Mathematics Departm.