Datum des Promotionskolloquiums:

First of all, I would like to express my deep gratitude to my supervisor Prof. Dr. Peter Maass for his valuable advice from my first to my final steps in conducting the work that leads to this thesis. Under his supervision, I have become stronger in developing new ideas as well as joining the research community. I have learned a lot from him not only in research and education but also in life. I would like to thank Prof. Dr. Dirk Lorenz, Prof. Dr. Dinh Nho Hào and Dr. Bangti Jin for many valuable suggestions and useful discussions. Prof. Dirk Lorenz gave some suggestions and discussions about the algorithms studied in the thesis. Prof. Dr. Dinh Nho Hào introduced and suggested me to consider Nesterov’s algorithm and sent me his papers. Some ideas of his papers are used in my thesis. He also read the draft of my thesis and gave some useful remarks and suggestions. Dr. Bangti Jin discussed with me about electrical impedance tomography and sent me his program. Based on his ideas, I developed the MATLAB programs in the thesis. I would like to thank Dr. Ronald Stöver, Dr. Thomas Bonesky and Mrs. Sabine Pfarr for great help during my first days in Bremen. I sincerely thank all members of ”Zentrum für Technomathematik ” and the group of scientific computing in engineering, who have created a wonderful environment for researching and living. I would like to thank the participating institutes of the project “Scientific Computing in Engineering ” for supporting the PhD scholarship during my study in Germany. To do Ph.D in University of Bremen, I received the agreement of the leader boards at m