@misc{Proell2013, type = {Master Thesis}, author = {Pr{\"o}ll, Sebastian}, title = {Stability of Switched Epidemiological Models}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-108573}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {In this thesis it is shown how the spread of infectious diseases can be described via mathematical models that show the dynamic behavior of epidemics. Ordinary differential equations are used for the modeling process. SIR and SIRS models are distinguished, depending on whether a disease confers immunity to individuals after recovery or not. There are characteristic parameters for each disease like the infection rate or the recovery rate. These parameters indicate how aggressive a disease acts and how long it takes for an individual to recover, respectively. In general the parameters are time-varying and depend on population groups. For this reason, models with multiple subgroups are introduced, and switched systems are used to carry out time-variant parameters. When investigating such models, the so called disease-free equilibrium is of interest, where no infectives appear within the population. The question is whether there are conditions, under which this equilibrium is stable. Necessary mathematical tools for the stability analysis are presented. The theory of ordinary differential equations, including Lyapunov stability theory, is fundamental. Moreover, convex and nonsmooth analysis, positive systems and differential inclusions are introduced. With these tools, sufficient conditions are given for the disease-free equilibrium of SIS, SIR and SIRS systems to be asymptotically stable.}, subject = {Gew{\"o}hnliche Differentialgleichung}, language = {en} } @misc{Forster2013, type = {Master Thesis}, author = {Forster, Johannes}, title = {Mathematical Modeling of Complex Fluids}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-83533}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {This thesis gives an overview over mathematical modeling of complex fluids with the discussion of underlying mechanical principles, the introduction of the energetic variational framework, and examples and applications. The purpose is to present a formal energetic variational treatment of energies corresponding to the models of physical phenomena and to derive PDEs for the complex fluid systems. The advantages of this approach over force-based modeling are, e.g., that for complex systems energy terms can be established in a relatively easy way, that force components within a system are not counted twice, and that this approach can naturally combine effects on different scales. We follow a lecture of Professor Dr. Chun Liu from Penn State University, USA, on complex fluids which he gave at the University of Wuerzburg during his Giovanni Prodi professorship in summer 2012. We elaborate on this lecture and consider also parts of his work and publications, and substantially extend the lecture by own calculations and arguments (for papers including an overview over the energetic variational treatment see [HKL10], [Liu11] and references therein).}, subject = {Variationsrechnung}, language = {en} } @misc{Englert2009, type = {Master Thesis}, author = {Englert, Stefan}, title = {Sch{\"a}tzer des Artenreichtums bei speziellen Erscheinungsh{\"a}ufigkeiten}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71362}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2009}, abstract = {Bei vielen Fragestellungen, in denen sich eine Grundgesamtheit in verschiedene Klassen unterteilt, ist weniger die relative Klassengr{\"o}ße als vielmehr die Anzahl der Klassen von Bedeutung. So interessiert sich beispielsweise der Biologe daf{\"u}r, wie viele Spezien einer Gattung es gibt, der Numismatiker daf{\"u}r, wie viele M{\"u}nzen oder M{\"u}nzpr{\"a}gest{\"a}tten es in einer Epoche gab, der Informatiker daf{\"u}r, wie viele unterschiedlichen Eintr{\"a}ge es in einer sehr großen Datenbank gibt, der Programmierer daf{\"u}r, wie viele Fehler eine Software enth{\"a}lt oder der Germanist daf{\"u}r, wie groß der Wortschatz eines Autors war oder ist. Dieser Artenreichtum ist die einfachste und intuitivste Art und Weise eine Population oder Grundgesamtheit zu charakterisieren. Jedoch kann nur in Kollektiven, in denen die Gesamtanzahl der Bestandteile bekannt und relativ klein ist, die Anzahl der verschiedenen Spezien durch Erfassung aller bestimmt werden. In allen anderen F{\"a}llen ist es notwendig die Spezienanzahl durch Sch{\"a}tzungen zu bestimmen.}, subject = {Statistik}, language = {de} }