Hochschule Bonn-Rhein-Sieg
Publikationsserver der Hochschule Bonn-Rhein-Sieg - pub H-BRSNot a member yet
7939 research outputs found
Sort by
Lattice-Boltzmann-Verfahren hoher Ordnung zur Simulation kompressibler Strömungen
No full textIn dieser Arbeit wird eine kompressible Semi-Lagrangesche Lattice-Boltzmann-Methode neu entwickelt und erprobt. Die Lattice-Boltzmann-Methode ist ein Verfahren zur numerischen Strömungssimulation, das auf einer Modellierung von Partikeldichten und deren Interaktion untereinander basiert. In ihrer Ursprungsform ist die Methode jedoch auf schwach kompressible Strömungen mit niedriger Machzahl beschränkt. Wesentliche Nachteile der bisherigen Versuche zur Erweiterung auf supersonische Strömungen sind entweder mangelhafte Stabilität der Verfahren, unpraktikabel große Geschwindigkeitssätze oder die Beschränktheit auf kleine Zeitschrittweiten. Als Alternative zu bisherigen Ansätzen wird in dieser Arbeit ein Semi-Lagrangescher Strömungsschritt eingesetzt. Semi-Lagrangesche Verfahren entkoppeln mittels Interpolation die Orts-, Zeit- und Geschwindigkeitsdiskretisierung der ursprünglichen Lattice-Boltzmann-Methode. Nach der Einleitung wird im zweiten und dritten Kapitel dieser Arbeit zunächst auf die Grundlagen und Prinzipien der Lattice-Boltzmann-Methode eingegangen sowie bisherige Ansätze zur Simulation kompressibler Strömungen aufgeführt. Im Anschluss wird die kompressible Semi-Lagrangesche Lattice-Boltzmann-Methode entwickelt und beschrieben. Die Erweiterung erfolgt im Wesentlichen durch die Verknüpfung der Methode mit geeigneten Gleichgewichtsfunktionen und Geschwindigkeitssätzen. Im vierten Kapitel der Arbeit werden neue Kubatur-basierte Geschwindigkeitssätze entwickelt und getestet, darunter ein D3Q45-Geschwindigkeitssatz zur Berechnung kompressibler Strömungen, der den Rechenaufwand gegenüber konventionellen Geschwindigkeitsdiskretisierungen erheblich verringert. Im fünften Kapitel der Arbeit werden zur Validierung Simulationen von eindimensionalen Stoßrohren, zweidimensionalen Riemann-Problemen und Stoß-Wirbel-Interaktionen durchgeführt. Im Anschluss zeigen Simulationen von dreidimensionalen, kompressiblen Taylor-Green-Wirbeln sowie von wandgebundenen Testfällen die Vorteile der Methode für kompressible Strömungssimulationen. Zu diesem Zweck werden die Überschallströmung um ein zweidimensionales NACA-0012-Profil und um eine dreidimensionale Kugel sowie eine supersonische Kanalströmung untersucht. Dem Simulationsteil folgt eine umfangreiche Diskussion der Semi-Lagrangeschen Lattice-Boltzmann-Methode im Vergleich zu anderen Methoden. Die Vorteile der Methode, wie vergleichsweise große Zeitschrittweiten, körperangepasste Netze und die Stabilität der Methode, werden hier herausgearbeitet.In this thesis, a compressible semi-Lagrangian lattice Boltzmann method is newly developed and tested. The lattice Boltzmann method is a rapidly advancing numerical method for computational fluid dynamics. However, in its original form, the lattice Boltzmann method is limited to weakly compressible flows with low Mach number. Previous attempts to extend the lattice Boltzmann method to supersonic flows suffered either from poor stability, from impractically large velocity sets, or from small time step sizes. As an alternative to previous approaches, a semi-Lagrangian streaming step is used in this work. Semi-Lagrangian methods decouple the spatial, time, and velocity space discretization of the original lattice Boltzmann method by interpolation during the streaming step. Following the introduction, the second and third chapters of this thesis first detail the basics of the lattice Boltzmann method and list previous approaches to simulate compressible flows. Subsequently, the compressible semi-Lagrangian lattice Boltzmann method is developed and described. In the fourth chapter of the thesis, new cubature-based velocity sets are developed and tested, including a D3Q45 velocity set for the computation of compressible flows, which significantly reduces the computational cost compared to conventional velocity discretizations. In the fifth chapter of the thesis, simulations of one-dimensional shock tubes, two-dimensional Riemann problems, and shock-vortex interactions are performed for validation. Thereafter, simulations of compressible Taylor-Green vortices as well as wall-bounded problems demonstrate the advantages of the method for compressible flow simulations. The latter include the supersonic flow around a two-dimensional NACA-0012 profile and around a three-dimensional sphere as well as a supersonic channel flow. The simulation section is followed by an extensive discussion of the semi-Lagrangian lattice Boltzmann method in comparison to other methods. The advantages of the method include comparatively large time step sizes, compatibility with body-fitted meshes, and the intrinsic stability of the method even without artificial viscosity
Werkstoffeigenschaften für die Simulation von Fertigungsprozessen - Ein Ausflug in die Kreuzritterzeit
No full text
Factors Affecting the Violence Against Women: Evidence from Rural Bangladesh
No full textThe present study investigates the phenomenon of domestic violence perpetrated against women in Bangladesh, and endeavors to identify potential determinants that may underlie its prevalence. By employing a multivariate logistic regression model and utilizing a national representative dataset comprising 5044 households in rural Bangladesh, the present study reveals noteworthy correlations between domestic violence and various factors, including but not limited to women's age, poultry farming, total land ownership, working in rural areas, and women's decision-making authority in agriculture. The age of female individuals is a crucial factor in the occurrence of domestic violence, as there exists a positive correlation between age and the likelihood of experiencing such violence, with older women being more susceptible to it. Nevertheless, the probability of violent behavior decreases after a specific period. The rearing of poultry in farms seems to have a noticeable effect on the incidence of violence, whereas the possession of extensive land holdings reduces the probability of violent occurrences. Men who work in rural areas are more likely to engage in violent behavior, possibly due to economic instability and adherence to traditional gender norms. Research indicates that female individuals who possess decision-making power in the realm of agricultural production tend to experience reduced levels of violence. In general, the aforementioned discoveries illuminate the intricate mechanisms that underlie domestic violence in rural areas of Bangladesh
RoboCup 2023 dataset
No full textThis is the YOLO format version of the robocup2023 competition dataset. The dataset is annotated using the Anylabeling tool (Link: https://github.com/vietanhdev/anylabeling)
RoboCup @work 2023 dataset
No full textThis is the YOLO format version of the robocup2023 competition dataset. The dataset is annotated using the Anylabeling too
Live-in migrant home care workers in Germany: Stressors and resilience factors
No full textBACKGROUND
Thousands of Eastern Europeans find employment caring for older individuals as transmigrating live-in home care workers in private households in Germany. Studies have shown that the stressors threatening their well-being are multifaceted and include inequalities and a high practical and emotional workload, but research on protective factors is still scarce.
AIM & METHODS
This qualitative descriptive study focuses on both the stressors and factors that promote care workers' well-being and contribute to their psychological resilience. In guideline-based interviews, 14 female and one male care workers were asked about their stressors and the factors that help them cope.
RESULTS
Identified stressors included separation from their own family, strained relationship with either or both the care recipient (dementia) and their relatives (violation of worker´s rights and devaluation of care work), and permanent availability and lack of free time due to a 24-h care schedule. Resilience factors were both external and internal and included positive social relationships, self-determination, experience in care work, and intrinsic job motivation.
CONCLUSION
Live-ins reside in an ambiguous setting, exposed to both structural and individual strains. However, external and internal resilience factors contribute to a generally positive attitude toward their job and indicate the agency of this precariously employed group. A socially anchored appreciation of their work and an officially controlled expansion of free time are mandatory to improve the working conditions of live-in care workers
Simultaneous occurrence of intermittent and incipient faults
No full textDiagnosis and prognosis of intermittent faults, in general, is difficult as it is unknown when and for how long intermittent faults will reappear. This paper addresses the case of parametric incipient faults and simultaneously occurring intermittent faults with a magnitude that increases over time so that they may reach a failure alarm threshold and may eventually lead to a component or even a system failure.
The presented Bond Graph-based approach consists of two parts. First, a Diagnostic Bond Graph (DBG) is developed offline for an online diagnosis of intermittent faults by means of Analytical Redundancy Relations (ARRs). Due to the magnitude of intermittent faults increasing with time, the time evolutions of ARRs indicate a degradation trend. In a second, data-based, part, values of this trend over a moving time window stored in a buffer are extrapolated concurrently to the monitoring and to the fault detection and isolation (FDI) part in a repeated failure prognosis resulting in a sequence of Remaining Useful Life (RUL) estimates. A case study considers a small switched electronic circuit
