Hochschule Bonn-Rhein-Sieg
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Reduction of outflow boundary influence on aerodynamic performance using neural networks
No full textThe accurate treatment of outflow boundary conditions remains a critical challenge in computational fluid dynamics when predicting aerodynamic forces and/or acoustic emissions. This is particularly evident when employing the lattice Boltzmann method (LBM) as the numerical solution technique, which often suffers from inaccuracies induced by artificial reflections from outflow boundaries. This paper investigates the use of neural networks to mitigate these adverse boundary effects and enable truncated domain requirements. Two distinct NN-based approaches are proposed: (1) direct reconstruction of unknown particle distribution functions at the outflow boundary; and (2) enhancement of established characteristic boundary conditions by dynamically tuning their parameters. The direct reconstruction model was trained on data generated from a two-dimensional (2D) flow over a cylindrical obstruction. The drag, lift, and Strouhal number were used to test the new boundary condition. We analyzed results for various Reynolds numbers and restricted domain sizes, where it demonstrated significantly improved predictions when compared with the traditional Zou and He boundary condition. To examine the robustness of the NN-based reconstruction, the same condition was applied to the simulation of a National Advisory Committee for Aeronautics 0012 airfoil, again providing accurate aerodynamic performance predictions. The neural-enhanced characteristic boundary condition (CBC) was evaluated on a 2D convected vortex benchmark and showed superior performance in minimizing density errors compared to CBCs with fixed parameters. These findings highlight the potential of NN-integrated boundary conditions to improve accuracy and reduce computational expense of aerodynamic and acoustic emission simulations with the LBM
Herausforderungen und Chancen für Träger der Ganztagsbetreuung bei der aktuellen Anpassung an das Ganztagsförderungsgesetz am Fallbeispiel der Katholischen Jugendagentur Bonn gGmbH
No full textDie vorliegende empirische Arbeit wurde von einer Forscherin mit persönlicher Nähe zum Feld geschrieben. Die Nähe zum Forschungsfeld ergibt sich aus einer mehrjährigen Tätigkeit in der untersuchten Trägerin. Die Tätigkeit beinhaltete ein Freiwilliges Soziales Jahres sowie eine folgende Anstellung als pädagogische Ergänzungskraft während des Studiums. Trotz des Fehlens einer Qualifikation im sozialpädagogischen Bereich ermöglichten mir die praktischen Erfahrungen ein vertieftes Verständnis für das Arbeitsfeld. Diese Vorerfahrungen bilden die zentrale Grundlage für die vorliegende Untersuchung. Aus meinen mehrjährigen praktischen Erfahrungen entstand so zum einen der persönliche Wunsch, mich mit diesem Thema theoretisch und empirisch zu beschäftigen. Zum anderen beeinflussten diese meine Haltung im Forschungsprozess. Zum Zeitpunkt der Entstehung der Arbeit bestand kein Arbeitsverhältnis zur untersuchten Trägerin. Die frühere Tätigkeit ermöglichte zwar einen praxisnahen Zugang zum Feld, war jedoch bewusst zeitlich vom Forschungsprozess getrennt, um Rollenkonflikte zu vermeiden
Cytokine-induced killer (CIK) cells inhibit Plasmodium falciparum parasitemia through cytolytic effector activity in vitro
No full textCytokine-induced killer (CIK) cells, with dual traits resembling natural killer (NK) and T cells, have shown a promising clinical efficacy against cancer in clinical application leading to licensing of CIK cells in many countries. Here, we demonstrated that CIK cells can also inhibit the growth of Plasmodium falciparum in vitro, leading to a significant reduction in parasitemia levels after 24 h. We found that CIK cells cytotoxicity against infected RBCs is mostly dependent on their secretions rather than cell to cell communication, as they are a substantial repository of lytic agents, including granzyme B, granulysin, as well as perforin. We found that these components in the recombinant form acted synergistically, with granulysin and perforin facilitating granzyme B entry into target cells, resulting in parasite death. Moreover, we observed that priming CIK cells with dendritic cells pulsed with P. falciparum lysate antigen led to diminished CIK cell cytotoxicity against pRBCs. And finally, we found that although combination of CIK cells with chloroquine cannot be synergistic, CIK cells showed a comparable efficacy to chloroquine. Artemisinin combined with effector cells exhibited a slight enhancement in cytotoxicity compared to artemisinin alone. These results propose CIK cells as a potential alternative cell therapeutic approach in the preclinical and clinical setting against malaria and potentially other infections
Bürokratieaufwand und Einsparpotenziale an Hochschulen
No full textDer Beitrag liefert eine quantitative Abschätzung des derzeitigen Bürokratieaufwands für Lehrende mit Professur an Hochschulen für angewandte Wissenschaften (HAW). Hierzu wird eine „repräsentative“ Größe einer HAW hergeleitet und ein „professoraler Stundensatz“ von 100 €/h definiert. Der Bürokratieaufwand für die exemplarisch behandelten 17 Themenfelder, wie z. B. Akkreditierung, Berichtspflichten, Drittmittelverwaltung summiert sich dabei auf 20.450 Arbeitszeitstunden oder umgerechnet 2 Mio. € jährlich pro HAW mit repräsentativer Größe. Verursacht wird dieser Aufwand teils durch behördliche Vorgaben (z. B. Ministerien, Projektträger), teils durch eigene Vorgaben (z. B. Hochschulleitung, Verwaltung). Würden alle vorgeschlagenen Maßnahmen umgesetzt, könnten bis zu 53 % dieser Arbeitszeit eingespart werden – wertvolle Zeit, die den Lehrenden direkt für qualitativ bessere Lehre und intensivere Forschung zur Verfügung stünde
Evaluating the effect of reactive power injection on power factor and system losses reduction in an optimally sized PV grid-connected solar photovoltaic system
No full textAlthough rooftop grid-connected solar PV systems (RGCSPVS) play a crucial role in the global energy transition to mitigate climate change, reactive power imbalance remains a significant power quality challenge, intensifying as the system approaches its optimal penetration limit. This study examines the amount of reactive power an optimally sized GCSPVS can accommodate without exceeding voltage limits. A Python-based dynamic programming approach placed optimally, shunt capacitor (SC) targeting high loads, voltage drops, and losses nodes. The Conditional New Adaptive Foraging Tree Squirrel Search Algorithm (CNAFTSSA) otherwise applied to determine the most effective SC injection locations. In the high-load scenario, 46.20 kVAR of SC injection reduced system losses from 72.36 % to 82.87 %, improving the power factor from 0.51 to 0.69. The high-voltage-drop scenario introduced 10.27 kVAR, reducing losses from 71.57 % to 73.03 % and enhancing the power factor from 0.53 to 0.55. For high-loss nodes, 66.73 kVAR reduced losses from 68.21 % to 82.27 % and improved the power factor from 0.31 to 0.68. The CNAFTSSA scenario injected 65.70 kVAR, reducing losses from 68.34 % to 82.88 % and improving the power factor from 0.31 to 0.67. These results highlight SCs’ role in minimizing losses and enhancing power quality, with the CNAFTSSA approach demonstrating superior performance
Proton-selective conductance and gating of the lysosomal cation channel TMEM175
No full textThe lysosomal cation channel TMEM175 plays a key role in luminal pH homeostasis and lysosome function, with aberrant activity linked to Parkinson's disease. Although initially described as a K+-selective channel, TMEM175 exhibits substantial H+ permeability. Here, we dissect complex changes affecting human TMEM175 conductance and ionic properties of TMEM175-mediated current in response to pH shifts on the luminal side of the protein. A drop in pH from 7.4 to 4.7 on the side equivalent to the lysosomal lumen triggers a sustained increase in TMEM175-mediated inward and outward currents, which is accompanied by a transient shift in the reversal potential (Erev) toward the theoretical equilibrium voltage for H+, yet remaining ~100 mV below the expected value even in the absence of K+. This discrepancy, along with low sensitivity of Erev to the concentration gradient for K+, supports a model in which TMEM175-mediated H+ flux rapidly collapses the lysosomal pH-gradient. Molecular dynamics simulations identify H57 as a key residue on the luminal side of the open channel, which forms intra- and intersubunit salt bridges with D279 and E282. Supporting the functional importance of these interactions, the TMEM175 mutant H57Y displayed reduced H+- and K+-conductance and a reduced H+/K+ selectivity in whole-cell and lysosomal electrophysiological analyses. Our findings contribute to a better understanding of TMEM175's complex electrophysiological properties, thereby expanding the possibilities of understanding the channel's function in lysosomal physiology and pathophysiology
