Bøker utgitt av Cuvillier

Biofilms play a major role in material cycles and contribute to technical systems significantly. Despite their interference with the functionality of technical equipment or the product quality their ability to catabolize toxins and metabolize pharmaceutically relevant substances increases the interest in biofilm-based biotransformations. However, so far there is a lack of appropriate models that allow anticipating the mechanical stability of biofilms in particular during detachment processes.The main objective of this work was the development of a hydrogel based physico-chemical and growth independent biofilm imitate to investigate mechanical, primarily fluid dynamical stresses and their influence on growth and detachment effects of biofilms. Verification was achieved by comparison with real single culture biofilms. Single culture biofilms of Pseudomonas putida KT2440 were cultivated in a biofilm tube reactor and grown on different surfaces, e.g., tube walls, surface-modified object slides, plastic and iron nettings as well as membrane filters. The establishment of on-line analytics allowed the automatic measurement of dissolved oxygen, pH, temperature and planktonic cell growth by optical density in the cultivation broth. Image acquisition of the biofilm surface supported the observation of biofilm development in terms of growth and detachment.A hydrogel based on gellan was established as simplified artificial biofilm system, which behaves like a viscoelastic fluid. The degree of cross-linking at different gellan levels was modified by the addition of mono-and divalent ions (Na+, Mg2+) and the influence on the material constants in terms of storage (G¿) and loss (G¿¿) modulus was determined. Experiments and evaluation in the predefined design space were supported by Central Composite Design (CCD), an experimental design technique.The developed gellan-based hydrogel allows mimicking the mechanical properties of a biofilm excluding biological growth effects. It can now be used to validate further characterization methods or to test slowly growing biofilms where systematic errors are often smaller than the biological variances. Eventually this method enables a fast and reliable mechanical testing of biofilm systems.

Automotive control software is developed according to the AUTomotive Open System ARchitecture (AUTOSAR) standard. High development costs require the re-use of existing software when the hardware platform changes from a single-core to a multicore electronic control unit (ECU).This Ph.D. thesis focuses on the migration of AUTOSAR legacy software to a multicore ECU. Different parallelization methods are proposed and evaluated; RunPar and Supertasks on runnable-level, timed implicit communication on task-level, and the parallel schedule quality metric for quantification of combinations. The methods respect data dependencies and still enable parallel execution, they exploit the energy-saving potential of the processor, they guarantee latency constraints, and they reproduce the reference data-flow.

Polymer electrolyte membrane (PEM) fuel cell stack was analyzed from a mechanical point of view with the help of measurements and simulations in this study.The deflection of the fuel cell stack was measured with the help of the experimental set-up under operating conditions. The effects of cell operating parameters and cyclic conditions on the mechanical properties of the fuel cell stack were investigated.In order to extend the mechanical analysis of the fuel cells, two computational models were established containing the geometrical features in detail. A large-scale fuel cell stack model was built for the thermomechanical analysis. The second model was built on a cross-section geometry for the electrochemical analysis including fluid dynamics. The internal stress distribution and buckling of fuel cell stack were examined. The influence of the mechanical compression on the cell performance and squeezing of the gas diffusion layers are investigated. A design procedure is developed for fuel cell stack regarding the durability and performance from a mechanical point of view.