zur Erlangung des akademischen Grades

The topic was my interest, the journey was my choice. After five years (three intensive years) of effort, I finally stand on the top of the mountain. Looking back on the way I went, I feel I was very lucky. I fully appreciate all guides and supporters that helped me throughout this endeavor. First of all, my greatest thanks go to Prof. Herrmann, my doctoral supervisor, for guiding my research in an efficient and practical way. His careful academic attitude and his application-focused thinking vigorously showed me the characteristics of a Doctor Engineer. The atmos-phere of open discussion and idea exchange he created in the team greatly benefited my en-tire work. I would like to deeply thank Prof. Friesdorf for taking over the responsibility of the chairman of the doctoral examination committee. I am grateful to Prof. Mertins for his careful review of my thesis as well as the constructive feedback. It is my pleasure to acknowledge the efforts of Mr. Gropp, Mr. Majetic, the colleagues in the institute, for the discussion and their suggestions. My special thanks go to Ms. Sveceny for her friendly and highly efficient management support. She is always like the sunshine in