The following presentations and discussion contributions were delivered at the working conference organized by the Association of German Engineers (VDI), which took place on November 22 and 23, 1990, in Stuttgart. Upon reviewing the audio recordings, the participants in the discussions kindly limited themselves to purely editorial corrections, ensuring that the spontaneous and pointed character of the contributions was fully preserved. The conference was made possible through the financial support of the Federal Ministry for Research and Technology. The organizational management was handled by Mr. Dipl. Pol. Volker Brennecke. Ms. Sigrid Korf-Breitenstein, M.A., took on the challenging task of editorially processing the discussion contributions. Our thanks go to all of them from the authors, the conference participants, and the editor. Introduction: First, some general remarks.