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Preprint
No Chaos in Dixon's System
(2020)
The so-called Dixon system is often cited as an example of a two-dimensional (continuous) dynamical system that exhibits chaotic behaviour, if its two parameters take their value in a certain domain. We provide first a rigorous proof that there is no chaos in Dixon's system. Then we perform a complete bifurcation analysis of the system showing that the parameter space can be decomposed into sixteen different regions in each of which the system exhibits qualitatively the same behaviour. In particular, we prove that ...
Dissertation
Symmetrien von Differentialgleichungen via Vessiot-Theorie
(2021-04)
Die übliche Definition des Symmetriebegriffs einer Differentialgleichung lautet wie folgt: Symmetrien sind Transformationen, die Lösungen wieder in Lösungen überführen. Modelliert man Differentialgleichungen als Untermannigfaltigkeiten eines Jetbündels, so lassen sich zwei Arten von Symmetrien unterscheiden: innere und äußere. Der erste Fall entspricht einer Transformation, die ausschließlich auf der Differentialgleichung definiert ist. Im zweiten Fall ist die betrachtete Transformation auf dem gesamten umgebenden ...
Working paper
Projektbericht QPL-Maßnahme I.3: QPL-Maßnahmen im Bereich der Mathematikpropädeutik
(2021-04)
Durch das Team des Fachs Quantitative Methoden/VWL des Fachbereichs Wirtschaftswissenschaften der Universität Kassel werden seit 2012 QPL-geförderte mathematikpropädeutische Maßnahmen angeboten (Vorkurse, Brückenkurse, offene Lernumgebung, Online-Tests), um Studienanfänger*innen den Einstieg in die universitäre Mathematik und die Aufarbeitung mathematischer Defizite zu erleichtern. Die Maßnahmen wurden jährlich von eigens erstellten Leistungstests und Befragungen begleitet. Mit den erhobenen Daten können weitreichende ...
Dissertation
Explicit Description Of Isogeny And Isomorphism Classes Of Drinfeld Modules Of Higher Rank Over Finite Fields
(2020)
When jumping from the number fields theory to the function fields theory, one cannot miss the deep analogy between rank 1 Drinfeld modules and the group of root of unity and the analogy between rank 2 Drinfeld modules and elliptic curves. But so far, there is no known structure in number fields theory that is analogous to the Drinfeld modules of higher rank r ≥ 3. In this thesis we investigate the classes of those Drinfeld modules of higher rank r ≥ 3 defined over a finite field L. We describe explicitly the Weil ...
Dissertation
Beliefs von Lehramtsstudierenden zur doppelten Diskontinuität
(2021-09)
Das Ziel der Forschungsarbeit ist die Untersuchung von Überzeugungen von Lehramtsstudierenden zur sogenannten doppelten Diskontinuität. Genauer geht es um die Beforschung von Überzeugungen zur Kohärenz zwischen Schulmathematik und Hochschulmathematik und die Überzeugungen zur Relevanz der universitären Mathematik für die spätere Tätigkeit als Lehrkraft in der Schule. Dabei soll erstens der Frage nachgegangen werden, welche Überzeugungen Lehramtsstudierende zur doppelten Diskontinuität haben und zweitens eine Antwort ...
Dissertation
Modeling of human vitreous as viscoelastic fluid considering the orientation of collagen fibers
(2021-11)
For the most common treatment of retinal diseases worldwide by drug distribution in the human vitreous we developed the mathematical model of the vitreous. Compare to previous works we focus on the vitreous as a viscoelastic fluid including its heterogeneous property due to the orientation of collagen fibers. By using the incompressible viscoelastic Burgers-type model based on experimental data as the specific constitutive equation in the setting of continuum mechanics we considered its non-Newtonian nature. This ...
Habilitation
Numerical Methods for Fluid Flow: High Order SBP Schemes, IMEX Advection-Diffusion Splitting and Positivity Preservation for Production-Destruction PDEs
(2021-01)
The current demands regarding the numerical simulation of fluid flow often require highly accurate computations to obtain a detailed resolution of the occurring physical phenomena. The basic concept for the construction of a fluid solver is to transfer the physical model into a numerical scheme which complies with the underlying physical principles such as conservation and balances of certain quantities. In addition, the numerical methods are required to be stable and efficient. Again, stability is often determined ...
Lehrmaterial
Skriptum zur Linearen Algebra und Analytischen Geometrie
(2020-07)
Vorlesungsskript zur Vorlesung „Lineare Algebra und Analytische Geometrie“ an der Universität Kassel im Sommersemester 2020. Es handelt sich um die Druckversion.
Preprint
Identifying critical demand scenarios for the robust capacitated network design problem using principal component analysis
(2021-11-30)
In this paper, we consider the single-commodity robust network design problem. Given an undirected graph with capacity installation costs on its edges and a set S of scenarios with associated flow balance vectors that represent different scenarios of node supplies and demands, the goal is to find integer edge capacities that minimize the total installation cost and permit a feasible single commodity flow for each scenario. This problem arises, for example, in the design of power networks, which are dimensioned to ...
Aufsatz
Quantification of the In Vitro Predisposition to Glistening Formation in One Manufacturer’s Acrylic Intraocular Lenses Made in Different Decades
(2021-02-05)
Introduction
Foldable hydrophobic acrylic intraocular lenses (IOLs) are prone to develop a long-term postoperative material change called glistenings. The aim of this study was to investigate the changes in the predisposition for glistening formation in one type of hydrophobic acrylic IOL material from its introduction to the present day.
Methods
In a laboratory setup, an in vitro model was used to induce glistenings in hydrophobic acrylic IOLs manufactured by one company (Alcon, Fort Worth, TX, USA) in different ...