Universität Stuttgart
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Item Open Access Microbial biostabilization in fine sediments(2022) Gerbersdorf, Sabine Ulrike; Wieprecht, Silke (Prof. Dr.-Ing.)Microbial biostabilization has increasingly received attention over the last years due to its significance for the dynamics of fine sediments in fluvial and coastal systems with implications for ecology, economy and human-health. This habilitation thesis highlights the contributions of the applicant and her team to this multi-disciplinary research area and is based on eight core publications that are presented in seven chapters. First, the topic of biofilm and biostabilization is introduced and second, the materials and methods applied are presented before own research findings are discussed. To start with, the stabilization potential of heterotrophic bacterial assemblages has been emphasised as well as the adhesive properties of the protein moieties within the EPS (extracellular polymeric substances) that are more significant than previously thought. Furthermore, the engineering potential of estuarine prokaryotic and eukaryotic assemblages has been studied separately and combined to reveal the effective cooperation of mixed biofilm that resulted in highest substratum stabilization although the effects were not clearly synergistic (=more than additive). The significance of biostabilization could be evidenced as well for freshwaters where highest adhesive capacity and sediment stability occurred during spring. Microbial community composition differed accordingly to result in mechanically highly diverse biofilm. Moreover, the importance of two of the most influential abiotic conditions, light intensity and hydrodynamics, was shown for biofilm growth, species composition and functionality - here biostabilization. In order to test adhesive properties at the relevant mesoscale (mm-cm) but non-destructively and highly sensitive, MagPI (Magnetic Particle Induction) has been applied. The last chapter concerns technical aspects to further improve its performance while demonstrating the impact of material and geometry and the importance of both, magnetic field strength and field gradient for the physics of the MagPI approach.Item Open Access Advanced methods for a sustainable sediment management of reservoirs(Stuttgart : Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung der Universität Stuttgart, 2022) Haun, Stefan; Wieprecht, Silke (Prof. Dr.-Ing.)As a result of an increasing demand on storing water, sustainable reservoir management will become more and more important in the future. Minimizing, or in the best case avoiding, the loss of storage due to sedimentation is a challenging task because each reservoir has unique boundary conditions. Hence, not every management strategy is suitable for a given reservoir. Due to the combination of state of the art measurement methods and hydro‐morphodynamic models, reservoir sedimentation can be better predicted in the future and the success of sediment management strategies can be assessed. The development of advanced measurement methods makes it possible to obtain data with a high accuracy, but also with a high spatial and temporal resolution. The combination of recent measurement approaches with reliable hydro‐morphodynamic numerical prediction models, enhances a highly accurate prediction and understanding of governing processes. This opens new possibilities for an objective selection of important parameters, essential spatial domains as well as for the temporal resolution of measurements. This will finally lead to more reliable predictions about the future of reservoirs that provide water for human life, health and wealth. The presented scientific work gives an overview of recent developments to investigate hydromorphological processes in reservoirs.Item Open Access Circuit complexity of group theoretic problems(2021) Weiß, Armin; Diekert, Volker (Prof. Dr. rer. nat.)In dieser kumulativen Habilitationsschrift werden sechs Arbeiten zum Thema "Schaltkreiskomplexität von Gruppentheoretischen Problemen" zusammengefasst. An vorderster Stelle steht hierbei das Wortproblem: Gegeben ein Wort über den Erzeugern einer Gruppe, ist die Frage, ob das Wort das Einselement der Gruppe darstellt. Daneben werden noch weitere Probleme, wie das Konjugationsproblem, das Power-Wortproblem (wie das Wortproblem, aber die Eingabe wird in komprimierter Form gegeben) und das Lösen von Gleichungen betrachtet. Die meisten der hier zusammengefassten Arbeiten betrachten die genannten Probleme für spezielle Klassen von Gruppen und klassifizieren deren Komplexität mit Methoden der Schaltkreiskomplexität. Eine Ausnahme bildet die letzte Arbeit zum Thema Gleichungen: hier liegt der Zusammenhang zur Schaltkreiskomplexität darin, dass sich das Erfüllbarkeitsproblem für Gleichungen in endlichen auslösbaren Gruppen ähnlich verhält wie das Erfüllbarkeitsproblem für CC^0 Schaltkreise.Item Open Access State of the art of the co-incineration of waste-derived fuels and raw materials in clinker/cement plants(2021) Schönberger, Harald; Garrecht, Harald (Prof. Dr.-Ing.)The treatise is about the co-incineration of waste-derived fuels and raw materials in clinker/cement production plants and its impact on emissions to air. Depending on the incineration conditions, emissions to air can exceed existing requirements. This is demonstrated and explained by both conventional parameters such as dust, nitrogen oxides, sulphur dioxide, carbon monoxide, volatile organic carbon, mercury and other heavy metals, ammonia and hydrogen chloride and special organic pollutants such as benzene, polychlorinated dibenzo-p-dioxins and furans (PCCD/F), polychlorinated biphenyls (PCB), hexachlorobenzene (HCB) and polycyclic aromatic hydrocarbons (PAH).Item Open Access Multiscale modeling and simulation of transport processes in porous media(2022) Bringedal, Carina; Helmig, Rainer (Prof. Dr.-Ing.)Item Open Access Gas-solid reactions for energy storage and conversion(2022) Linder, Marc; Thess, André (Prof. Dr.)Reversible gas-solid reactions could offer relevant technological contributions to an energy system predominantly based on renewable energy. However, our current understanding of this technology is mainly based on fundamental material research and generic application concepts. Therefore, the first part of this work summarizes the current state of knowledge in order to identify unique advantages that could arise from reversible gas-solid reactions for energy storage and conversion. Starting with a technological differentiation between various reversible processes used for energy storage, a classification of different reactor designs and a generic approach for thermal integration and necessary reaction gas supply, three main directions are derived that currently seem most promising to transfer the specific properties of gas-solid reactions to technical systems: (1) open configurations to reduce system complexity, (2) utilization of available pressure differences to adjust the reaction temperature and (3) combination of abundant materials with the intrinsic possibility of lossless storage. Based on these considerations, the second part of this work summarizes our approach to transfer material properties to technical systems, e.g. by developing storages that utilize oxygen from air, by taking advantage of the pressure dependency of the reaction temperature of metal hydrides and salt hydrates or by combining the long-term energy storage possibility with abundant and costefficient reactants such as calcium oxide and water.Item Open Access Continuum mechanics of multicomponent materials : modelling, numerics and applications for biological materials in the framework of the theory of porous media(Stuttgart : Institut für Mechanik (Bauwesen), Lehrstuhl für Kontinuumsmechanik, Universität Stuttgart, 2021) Wagner, Arndt; Ehlers, Wolfgang (Prof. Dr.-Ing. Dr. h. c.)Item Open Access Thermofluids with porous media(2024) Chu, Xu; Weigand, Bernhard (Prof. Dr.-Ing. habil.)