620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
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We present a novel unimorph deformable mirror with a diameter of only 10 mm that will be used in adaptive resonators of high power solid state lasers. The relationship between applied voltage and deformation of a unimorph mirror depends on the piezoelectric material properties, layer thicknesses, boundary conditions, and the electrode pattern. An analytical equation for the deflection of the piezoelectric unimorph structure is derived, based on the electro-elastic and thin plate theory. The validity of the proposed analytical model has been proven by numerical finite-element modelling and experimental results. Our mirror design has been optimized to obtain the highest possible stroke and a high resonance frequency.
In the German design code ATV-M 127-2, three host pipe states are differentiated: State I for leaky sewers without cracks, state II for sewers with longitudinal cracks but a stable soil pipe system, and state III for cracked pipes with larger deformations and considerable risk of collapse in the near future. State II sewers that are close to the traffic surface must be calculated as a state III situation. On the other hand, the US Standard ASTM F 1216 defines two states: structurally safe and fully deteriorated sewers. This paper examines the common aspects and differences between the two codes. A simple non-linear numerical approach is presented to evaluate the actual safety of the host pipe-soil system based on the following parameters: 1. the pipe material (e. g. age, corrosion depth, state of the contact zones), 2. the measured or estimated pipe deformations, 3. the soil group, stiffness, and possible voids occurring next to the springlines of the pipe, 4. the loading to be applied on the deteriorated pipe-soil system. Using stability and ultimate stress criteria, the safety of the system can be defined in a rational way. Missing parameters have to be introduced into the algorithm conservatively. Case studies are presented to demonstrate safe estimations for the host pipe state. The consequences on the required wall thickness of a lining and the application of non-circular linings are shown. The wall thicknesses resulting from a design for the fully deteriorated state as defined by the design codes in both the USA and Germany are compared and discussed.
Nach einer kurzen Bestandsaufnahme zur Ingenieurmathematik an Hochschulen werden langjährige Testergebnisse zu den Mathematik-Vorkenntnissen der Studienanfänger im Fach Bauingenieurwesen dargestellt. Auf eine Diskussion über die Folgen der aufgezeigten Defizite werden zunächst allgemeine organisatorische und inhaltliche Vorschläge gemacht, wie diese Defizite im Ingenieurstudium abgebaut werden können. Anschließend wird ein detailliertes Lehrkonzept für die Ingenieurmathematik beschrieben, das der Autor zusammen mit Kollegen entwickelt und viele Jahre lang erfolgreich durchgeführt hat. Im Anhang wird ein vom Autor entworfener Fragebogen zur Evaluation der Mathematik-Lehrveranstaltung vorgestellt und kommentiert.