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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Bifurcations, Normal Forms and their Applications

Chen, Jian 19 May 2005 (has links)
The first part is a study of an ecological model with one herbivore and $N$ plants. The system has a new type of functional response due to the speculation that the plants compete with each other and have different levels of toxin which inhibit the herbivore's ability to eat up to a certain amount. We first derive the model mathematically and then investigate, both analytically and numerically, the possible dynamics for this model, including the bifurcation and chaos. We also discuss the conditions under which all the species can coexist. The second part is a study in the normal form theory. In particular, we study the relations between the normal forms and the first integrals in analytic vector fields. We are able to generalize one of Poincare's classical results on the nonexistence of first integrals in an autonomous system. Then in the space of 2n-dimensional analytic autonomous systems with exactly n resonances and n functionally independent first integrals, we obtain some results related to the convergence and generic divergence of the normalizations. Lastly we give a new proof of the necessary and sufficient conditions for a planar Hamiltonian system to have an isochronous center.
32

Synchronization of the extended Kuramoto model

Lin, Huang-jyun 26 June 2009 (has links)
none
33

Iteration as an avenue for mathematical exploration

Joyoprayitno, Anne Christine 12 December 2013 (has links)
This report explores several applications of iteration and the various connections that can be made to different areas of mathematics. The ties iteration has to the Wada Property, bifurcation diagram, root finding, and applications in geometry are all investigated. Finally, a rationale for incorporating iteration into secondary mathematics courses to support a more robust curriculum is discussed. / text
34

Double Hopf bifurcations in two geophysical fluid dynamics models

Lewis, Gregory M. 05 1900 (has links)
We analyze the double Hopf bifurcations which occur in two geophysical fluid dynamics models: (1) a two-layer quasigeostrophic potential vorticity model with forcing and (2) a mathematical model of the differentially heated rotating annulus experiment. The bifurcations occur at the transition between axisymmetric steady solutions and non-axisymmetric travelling waves. For both models, the results indicate that, close to the transition, there are regions in parameter space where there are multiple stable waves. Hysteresis of these waves is predicted. For each model, center manifold reduction and normal form theory are used to deduce the local behaviour of the full system of partial differential equations from a low-dimensional system of ordinary differential equations. In each case, it is not possible to compute the relevant eigenvalues and eigenfunctions analytically. Therefore, the linear part of the equations is discretized and the eigenvalues and eigenfunctions are approximated from the resulting matrix eigenvalue problem. However, the projection onto the center manifold and reduction to normal form can be done analytically. Thus, a combination of analytical and numerical methods are used to obtain numerical approximations of the normal form coefficients, from which the dynamics are deduced. The first model differs from those previously studied with bifurcation analysis since it supports a steady solution which varies nonlinearly with latitude. The results indicate that the forcing does not qualitatively change the behaviour. However, the form of the bifurcating solution is affected. The second model uses the Navier-Stokes equations in the Boussinesq approximation, in cylindrical geometry. In addition to the double Hopf bifurcation analysis, a detailed axisymmetric to non-axisymmetric transition curve is produced from the computed eigenvalues. A quantitative comparison with experimental data finds that the computed transition curve, critical wave numbers and drift rates of the bifurcating waves are reasonably accurate. This indicates that the analysis, as well as the approximations which are made, are valid.
35

Étude d'un modèle de Gause généralisé avec récolte de proies et fonction de Holling type III généralisée

Etoua, Remy Magloire Dieudonné January 2008 (has links)
Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal
36

Backward bifurcation in HCV transmission dynamics

Nazari, Fereshteh 19 August 2014 (has links)
The thesis is based on the use of mathematical theories and techniques to gain qualitative and quantitative insight into the transmission dynamics of hepatitis C virus (HCV) in an IDU (injecting drug user) population. A deterministic model, which stratifies the IDU population into eight mutually-exclusive compartments (based on epidemiological status), is considered. Rigorous qualitative analysis of the model establishes, for the first time, the presence of the phenomenon of backward bifurcation in HCV transmission dynamics. Three routes (or causes) to such a dynamic phenomenon have been established. Furthermore, five main parameters that play a dominant role on the transmission dynamics of the disease have been identified. Numerical simulations of the model show that the re-infection of recovered individuals has marginal effect on the HCV burden (as measured in terms of the cumulative incidence and prevalence of the disease) in the IDU community.
37

A mathematical approach to axon formation in a network of signaling molecules for N2a cells /

Bani-Yaghoub, Majid, January 1900 (has links)
Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 88-93). Also available in electronic format on the Internet.
38

Bifurcations of equilibria in DNA elasticity

Biton, Yoav. January 2007 (has links)
Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Mechanics." Includes bibliographical references (p. 106-110).
39

Non-linear dynamics and power systems

Wilson, Jonathan P. January 2000 (has links)
No description available.
40

An experimental investigation of the bifurcation in twisted square plates

Howell, Robert A. January 1991 (has links)
The bifurcation phenomenon occurring in twisted square plates with free edges subject to contrary self-equilibrating corner loading was examined. In order to eliminate lateral deflection of the test plates due to their own weight, a special loading apparatus was constructed which held the plates in a vertical plane. The complete strain field occurring at the plate centre was measured using two strain gauge rosettes mounted on opposing sides of the plate at the centre. Principal curvatures were calculated and related to corner load for several plates with differing edge length/thickness ratios. A Southwell plot was used relating mean curvature to the ratio mean curvature/Gaussian curvature, from which the Gaussian curvature occurring at bifurcation was determined. The critical dimensionless twist ka was then calculated for each plate size. It was found that there is a linear relation between the critical dimensionless twist ka occurring at bifurcation, and the thickness to edge length ratio h/a ratio, specifically: ka = 10.8h/a. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

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