Numerical Modeling and Data Assimilation of Soil Water Flow

Soil water flow is a key process in Earth's hydrological cycle and an essential part of many ecosystem services. Soils are porous media and exhibit a heterogeneous, multi-scale architecture. Their non-linear material properties have a significant influence on the soil water dynamics, which poses difficulties for numerical models. These material properties cannot be measured directly, but data assimilation methods can estimate them by combining information from measurements of soil hydraulic states and from numerical models. The validity of the estimation results can be strongly affected by model errors. This dissertation (i) presents a versatile software package for modeling soil water flow and analyzes the accuracy and efficiency of its numerical discretization schemes, and (ii) employs this software in synthetic data assimilation tasks to investigate the effects of unrepresented dynamics, topography, and small-scale heterogeneity on estimated material properties and forecasts conducted with them. The results reveal that favoring low-order numerical methods over more accurate ones can be justified for use cases in soil hydrology. Moreover, the findings indicate that one-dimensional models with estimated effective material properties can reasonably replicate the dynamics of heterogeneous, two-dimensional domains with complicated topography, if boundary conditions are represented correctly

Erreichbarkeit von Bildungs-, Gesundheits- und kulturellen Einrichtungen : Einkommensunterschiede, Wünsche nach Investitionen und Einfluss auf die Wohnzufriedenheit

Die ungleiche Verteilung von Bildungschancen wird nicht erst seit Beginn der Covid-19-Pandemie diskutiert. Doch haben die langen Phasen von Homeschooling während der Lockdowns deutlicher offengelegt, mit welch unterschiedlichen Voraussetzungen die gut acht Millionen Schülerinnen und Schüler in Deutschland ins Leben starten. Die Debatte darum, Schule in Präsenzunterricht stattfinden zu lassen, hat neben ungleich verteilten Chancen auch die Erreichbarkeit von Bildungseinrichtungen in den Fokus gerückt. Grund- und weiterführenden Schulen sowie Kinderbetreuungseinrichtungen bilden einen wichtigen Teil der als Daseinsvorsorge bereitgestellten staatlichen Leistungen, die wiederum regelmäßiger Diskussionsgegenstand sind, wenn es um den politischen Leitbegriff der „Gleichwertigkeit der Lebensverhältnisse“ geht. Traditionell werden in diesem Kontext neben der Daseinsvorsorge auch die Arbeits-, Wirtschafts- und Konsumverhältnisse berücksichtigt. Die vorliegende Kurzexpertise untersucht die Erreichbarkeit von Kindergärten und Schulen sowie von Ärzten/Krankenhäusern und kulturellen Einrichtungen insbesondere im Hinblick auf Einkommensunterschiede zwischen den nutzenden Haushalten

Shiftwork and Alcohol Consumption: A Systematic Review of the Literature

Introduction: Shiftwork can be a risk factor for a number of different somatic and psychological health conditions, especially sleep disorders. Shiftworkers sleep less than dayworkers, and 20–40% of them suffer from difficulties initiating and maintaining sleep, which result in reduced capacity for work and social life. A common coping strategy might be the use of alcohol, which presents a health and safety hazard as it further impairs sleep quality and exacerbates sleepiness in the workplace. This review aimed to assess the extent of such possible connections. Methods: We performed a systematic search of the scientific literature on shiftwork and alcohol consumption in PubMed, PsycInfo, and Cochrane Library. Only original studies comparing shiftworkers with non-shiftworkers were included. The recommendations of the Preferred Reporting Items of Systematic Reviews and Meta-Analyses were followed. Results: Fourteen articles are included in this review. Six studies report some kind of connection between shift- or nightwork and alcohol consumption, especially as a sleep aid. Conflicting or negative results are reported by 3 studies. Discussion: Shiftwork, especially working at night and in rotation shifts, is associated with binge drinking disorder in different professions. The reasons for pathological consumption of alcohol can be self-medication of sleep problems or coping with stress and psychosocial problems typical for shiftwork. Nurses aged over 50 years represent one important risk group. These results can be important for preventive programs against sleep disorders, including measures other than drinking alcohol as a sleep aid in the workplace of shiftworkers

Experimental investigation of flow-induced sound of kite lines

In times of increasing importance of renewable energies, airborne wind energy (AWE) systems represent an emerging extension to conventional wind turbines. Many AWE systems use powerful kites to provide tether traction to mechanically unwind the tether, generating electricity on the ground. In addition to the traction tether, a large number of kite lines spanning the kite are moved through the air at high speed. This can produce a loud unpleasant whistling noise on the ground, which is due to a superposition of the aeolian tones of the many different lines. In the present work, differently structured kite lines were investigated in the aeroacoustic wind tunnel with respect to their sound radiation when they were exposed to a flow at up to 34 ms−1 resulting in Re ≦ 7300 and angles of attack (AOA) in the range of 90° ≧ AOA ≧ 45°. It was found that greater surface roughness increases sound radiation while line tension has negligible influence. By weaving a single-helix-shaped protrusion into the sheath of the kite line, the total radiated sound pressure level can be reduced by up to 9 dB. If the line itself has a helical contour, even a reduction of up to 11.5 dB is reachable. For decreasing AOA the noise suppression effect of helical surface protrusions and helical line shape is significantly reduced. The results provide initial guidelines on how to effectively reduce sound radiation from aircraft kites. Further investigations should consider the individual contributions of fluid and structural sounds to the total radiated sound of a flying kite

Li dynamics in carbon-rich polymer-derived SiCN ceramics probed by nuclear magnetic resonance

We report $^{7}$Li, $^{29}$Si, and $^{13}$C NMR studies of two different carbon-rich SiCN ceramics SiCN-1 and SiCN-3 derived from the preceramic polymers polyphenylvinylsilylcarbodiimide and polyphenylvinylsilazane, respectively. From the spectral analysis of the three nuclei at room temperature, we find that only the $^{13}$C spectrum is strongly influenced by Li insertion/extraction, suggesting that carbon phases are the major electrochemically active sites for Li storage. Temperature and Larmor frequency ($\omega_L$) dependences of the $^7$Li linewidth and spin-lattice relaxation rates $T_1^{-1}$ are described by an activated law with the activation energy $E_A$ of 0.31 eV and the correlation time $\tau_0$ in the high temperature limit of 1.3 ps. The $3/2$ power law dependence of $T_1^{-1}$ on $\omega_L$ which deviates from the standard Bloembergen, Purcell, and Pound (BPP) model implies that the Li motion on the $\mu$s timescale is governed by continuum diffusion mechanism rather than jump diffusion. On the other hand, the rotating frame relaxation rate $T_{1\rho}^{-1}$ results suggest that the slow motion of Li on the ms timescale may be affected by complex diffusion and/or non-diffusion processes.Comment: 28 pages with double line spacing, 7 figures and 2 tables, accepted version in Journal of Power Source

Transition-Metal-Doping of CaO as Catalyst for the OCM Reaction, a Reality Check

In this study, first-row transition metal-doped calcium oxide materials (Mn, Ni, Cr, Co., and Zn) were synthesized, characterized, and tested for the OCM reaction. Doped carbonate precursors were prepared by a co-precipitation method. The synthesis parameters were optimized to yield materials with a pure calcite phase, which was verified by XRD. EPR measurements on the doped CaO materials indicate a successful substitution of Ca2+ with transition metal ions in the CaO lattice. The materials were tested for their performance in the OCM reaction, where a beneficial effect towards selectivity and activity effect could be observed for Mn, Ni, and Zn-doped samples, where the selectivity of Co- and Cr-doped CaO was strongly reduced. The optimum doping concentration could be identified in the range of 0.04-0.10 atom%, showing the strongest decrease in the apparent activation energy, as well as the maximum increase in selectivity

Transition-Metal-Doping of CaO as Catalyst for the OCM Reaction, a Reality Check

In this study, first-row transition metal-doped calcium oxide materials (Mn, Ni, Cr, Co., and Zn) were synthesized, characterized, and tested for the OCM reaction. Doped carbonate precursors were prepared by a co-precipitation method. The synthesis parameters were optimized to yield materials with a pure calcite phase, which was verified by XRD. EPR measurements on the doped CaO materials indicate a successful substitution of Ca2+ with transition metal ions in the CaO lattice. The materials were tested for their performance in the OCM reaction, where a beneficial effect towards selectivity and activity effect could be observed for Mn, Ni, and Zn-doped samples, where the selectivity of Co- and Cr-doped CaO was strongly reduced. The optimum doping concentration could be identified in the range of 0.04-0.10 atom%, showing the strongest decrease in the apparent activation energy, as well as the maximum increase in selectivity.DFG, 390540038, EXC 2008: Unifying Systems in Catalysis "UniSysCat

Machbarkeitsstudie und Ableitung von Forschungsfragen zu Bedeutung, Inanspruchnahme und Verteilungswirkungen von gesellschaftlich notwendigen Dienstleistungen: Endbericht

Dienstleistungen der öffentlichen Hand machten Mitte der 2000er Jahre im Durchschnitt 13% des Bruttoinlandsprodukts aus und damit leicht mehr als die Geldleistungen mit 11% und die kostenfreie oder vergünstigte Versorgung mit Gütern und Dienstleistungen durch die öffentliche Hand hat einen beträchtlichen Einfluss auf das Niveau und die Verteilung von Wohlstand. Dieser Expertise arbeitet den aktuellen wirtschaftswissenschaftlichen Forschungsstands zur Inanspruchnahme und den Verteilungswirkungen gesellschaftlich notwendiger Dienstleistungen auf. Davon ausgehend werden weitergehende Forschungsbedarfe aufgezeigt und die für Deutschland zur Durchführung weitergehender Forschung potentiell geeigneten Datenquellen vorgestellt und beschrieben

Strategic Technology Switching under Risk Aversion and Uncertainty

Firms devising green investment strategies within a deregulated environment must take into account not only economic and technological uncertainty, but also strategic interactions due to competition. Also, further complicating green investment decisions is the fact that firms are likely to exhibit risk aversion, since alternative energy technologies entail risk that cannot be diversified. Therefore, we develop a utility-based, real options framework for pre-emptive and non-pre-emptive competition in order to analyse how economic and technological uncertainty interact with risk aversion to impact the adoption of an existing technology in the light of uncertainty over the arrival of an improved version. We confirm that greater risk aversion delays investment and show that technological uncertainty accelerates the follower’s entry, delays the entry of the pre-emptive leader, and, intriguingly, does not affect the non-pre-emptive leader’s investment decision. Also, we show how the relative loss in the leader’s value due to the follower’s entry is affected by economic and technological uncertainty as well as risk aversion, and how the risk of pre-emption under increasing economic uncertainty raises the value of direct investment in the new technology relative to stepwise investment