This collection of 25 research papers is dedicated to Professor Klaus Ritter of the Technical University of Munich on the occasion of his 60th birthday. The contributions provide a broad spectrum of research in nonlinear optimization problems, including theoretical aspects, automatic differentiation, and practical applications. It is dealt with quadratic optimization and with multiobjective decision-making. Further topics are parallelizing of algorithms and their implementation on transputer workstations. Special attention is paid to applications of parallel algorithms in the field of robotics. New results in statistics are also presented.