I declare that I have adhered to the rules of Qassim University, including those of its systems and websites related to preparing a scientific theses. I prepared my dissertation personally in a manner consistent with scientific integrity and all internationally recognized ethical standards regarding the writing of scientific dissertations and scientific research. I also declare that this thesis is not copied, borrowed, or plagiarized from letters, books, research, or any scientific publications that have been published or stored in any form of media. It has not previously been submitted for the purpose of obtaining any other academic degree, and I bear all responsibility if it transpires otherwise.