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ACKNOWLEDGEMENT

Thanks and indebtedness is directed first and always to ALLAH
for all his graves, without the power he gave me, the accomplishment of
this work would have been certainly impossible.

I would like to thank my adviser, Prof. Dr. S. K. El-Labany
Professor of theoretical physics, Physics Department, Faculty of Science, Damietta
University for his support and encouragement throughout this work. I have learned
so much from him in so many ways, especially how to be a free thinker and an
independent scientist.

I would like to express special thanks to Prof. Dr. M. M. Selim, Professor of
theoretical Physics, Physics Department, Faculty of Science, Damietta University,
for his help, support, and guiding me during this work.
I would like to express special thanks to Dr. N. A. El-Bedwehy, Associate

Professor of Applied Mathematics, Mathematics Department, Faculty of Science,
Damietta University, for her help, support, and guiding me during this work.
I would like to express special thanks to Dr. H. G. Abdelwahed , Associate

Professor of Physics, Physics Department, Faculty of Science, Mansoura
University, for his help, support, and guiding me during this work.
I can`t express my thanks to Prof. Dr. E. K. ElShewy, Professor of

theoretical Physics, Physics Department, Faculty of Science, Mansoura University,
for his great support and encouragement while preparing the thesis from the
inception phase till the end.
Let me also express my indeed thank to all the members of the
theoretical physics group at Damietta University Specially Prof. Dr. W. F. El-
Taibany, Port Said University specially Prof. Dr. W. Moslem and Mansoura
University specially Prof. Dr. S. A. El Wakil for providing me with a good
atmosphere to work.

Finally, and to all of those, I would really like to say:
There are no words to match my gratitude'.

Thank you
Mohamed Awad Youssef Elattafi