Mathematics Commons^™

Inversion Of The Broken Ray Transform, Roman Krylov

Electronic Theses and Dissertations

The broken ray transform (BRT) is an integral of a function along a union of two rays with a common vertex. Consider an X-ray beam scanning an object of interest. The ray undergoes attenuation and scatters in all directions inside the object. This phenomena may happen repeatedly until the photons either exit the object or are completely absorbed. In our work we assume the single scattering approximation when the intensity of the rays scattered more than once is negligibly small. Among all paths that the scattered rays travel inside the object we pick the one that is a union of …

Analytical Solutions To Nonlinear Differential Equations Arising In Physical Problems, Mathew Baxter

Electronic Theses and Dissertations

Nonlinear partial differential equations are difficult to solve, with many of the approximate solutions in the literature being numerical in nature. In this work, we apply the Homotopy Analysis Method to give approximate analytical solutions to nonlinear ordinary and partial differential equations. The main goal is to apply different linear operators, which can be chosen, to solve nonlinear problems. In the first three chapters, we study ordinary differential equations (ODEs) with one or two linear operators. As we progress, we apply the method to partial differential equations (PDEs) and use several linear operators. The results are all purely analytical, meaning …

An Explicit Construction Of Kleinian Groups With Small Limit Sets, Andrew Lazowski

Mathematics Faculty Publications

This paper provides an explicit construction of Kleinian groups that have small Hausdorff dimension of their limit sets. It is known that such groups exist and they can be constructed by results of Patterson. The purpose here is to work out the methods of calculation.

Function Of Several Variable, Weiting Li

A with Honors Projects

This Parkland A with Honors project discusses the function of several variables, it's limits and partial derivatives.

Global Convergence Of A Posteriori Error Estimates For A Discontinuous Galerkin Method For One-Dimensional Linear Hyperbolic Problems, Mahboub Baccouch

Mathematics Faculty Publications

In this paper we study the global convergence of the implicit residual-based a posteriori error estimates for a discontinuous Galerkin method applied to one-dimensional linear hyperbolic problems. We apply a new optimal superconvergence result [Y. Yang and C.-W. Shu, SIAM J. Numer. Anal., 50 (2012), pp. 3110-3133] to prove that, for smooth solutions, these error estimates at a fixed time converge to the true spatial errors in the L² -norm under mesh refinement. The order of convergence is proved to be k + 2, when k-degree piecewise polynomials with k ≥ 1 are used. As a consequence, we …

Small-World Properties Of Facebook Group Networks, Jason Wohlgemuth, Mihaela Teodora Matache

Mathematics Faculty Publications

Small-world networks permeate modern society. In this paper we present a methodology for creating and analyzing a practically limitless number of networks exhibiting small-world network properties. More precisely, we analyze networks whose nodes are Facebook groups sharing a common word in the group name and whose links are mutual members in any two groups. By analyzing several numerical characteristics of single networks and network aggregations, we investigate how the small-world properties scale with a coarsening of the network. We show that Facebook group networks have small average path lengths and large clustering coefficients that do not vanish with increased network …

Terminal Summation: Extending The Concept Of Convergence, Max Tran, Ayalur Krishnan

Publications and Research

This paper presents an atypical method for summing divergent series, and provides a sum for the divergent series log(n). We use an idea of T.E. Phipps, called Terminal Summation, which uses asymptotic analysis to assign a value to divergent series. The method associates a series to an appropriate difference equations having boundary conditions at infinity, and solves the difference equations which then provide a value for the original series. We point out connections between Phipps' method, the Euler-MacLaurin sum formula, the Ramanujan sum and other traditional methods for summing divergent series.

Weight Modules Of Orthosymplectic Lie Superalgebras, Thomas Lynn Ferguson

Mathematics Dissertations - Archive

A long-standing problem in representation theory is the classification of all simple weight modules of the classical Lie superalgebras. This problem was reduced to the classification of simple bounded highest weight modules. The latter classification has been accomplished for all classical Lie superalgebras except for the orthosymplectic series osp(m|2n) where m = 1, 3, 4, 5, 6. In this thesis, we complete the classification of the simple bounded highest weight modules of osp(1|2n) (i.e., for m = 1). The classification is obtained by developing constraints on primitive vectors in tensor products of bounded (Weyl) and finite-dimensional osp(1|2n)-modules.

Differential Equation Models Of Foreign Body Fibrotic Reactions For Assessing Roles Of Macrophage Phenotypes And Mesenchymal Stem Cells, Larrissa Owens

Mathematics Dissertations - Archive

Implant failure due to fibrotic encapsulation is an ongoing challenge in the bio-medical field. We develop two mathematical models based on partial differential equations in two spatial dimensions, and use them to gain quantitative insights regarding the dynamics of immune cells and proteins following the insertion of a foreign body. We focus heavily on incorporating a distinction between varied phenotypes of macrophage cells and analyzing their effects on healing processes. We extend our research to a new model that incorporates mesenchymal stem cells that influence the chemical reactions of immune regulators. Stability analysis is conducted on a family of equilibria …

Numerical Les For Mvg Controlled Supersonic Ramp Flow, Xiao Wang

Mathematics Dissertations - Archive

An implicitly implemented large eddy simulation by using the fifth order bandwidth-optimized WENO scheme is applied to make comprehensive studies on ramp flows with micro-ramp vortex generators (MVG) at Mach 2.5 and Re=5760. Detailed mechanism and topology of flow structure after MVG was studied to make better understanding. A series of new findings are obtained about the MVG-ramp flow including the three-dimensional vortex structure generated by MVG. The mechanism about the formation of vortex ring structure and momentum deficit after MVG is deeply studied. Small scale vortical structures in the rear separation and wake near the trailing edge of MVG …

On The Dimension Of A Certain Measure Arising From A Quasilinear Elliptic Partial Differential Equation, Murat Akman

Theses and Dissertations--Mathematics

We study the Hausdorff dimension of a certain Borel measure associated to a positive weak solution of a certain quasilinear elliptic partial differential equation in a simply connected domain in the plane. We also assume that the solution vanishes on the boundary of the domain. Then it is shown that the Hausdorff dimension of this measure is less than one, equal to one, greater than one depending on the homogeneity of the certain function. This work generalizes the work of Makarov when the partial differential equation is the usual Laplace's equation and the work of Lewis and his coauthors when …

A Characterization Of Serre Classes Of Reflexive Modules Over A Complete Local Noetherian Ring, Casey R. Monday

Theses and Dissertations--Mathematics

Serre classes of modules over a ring R are important because they describe relationships between certain classes of modules and sets of ideals of R. We characterize the Serre classes of three different types of modules. First we characterize all Serre classes of noetherian modules over a commutative noetherian ring. By relating noetherian modules to artinian modules via Matlis duality, we characterize the Serre classes of artinian modules. A module M is reflexive with respect to E if the natural evaluation map from M to its bidual is an isomorphism. When R is complete local and noetherian, take E as …

Homogeneous Gorenstein Ideals And Boij Söderberg Decompositions, Sema Güntürkün

Theses and Dissertations--Mathematics

This thesis consists of two parts. Part one revolves around a construction for homogeneous Gorenstein ideals and properties of these ideals. Part two focuses on the behavior of the Boij-Söderberg decomposition of lex ideals.

Gorenstein ideals are known for their nice duality properties. For codimension two and three, the structures of Gorenstein ideals have been established by Hilbert-Burch and Buchsbaum-Eisenbud, respectively. However, although some important results have been found about Gorenstein ideals of higher codimension, there is no structure theorem proven for higher codimension cases. Kustin and Miller showed how to construct a Gorenstein ideals in local Gorenstein rings starting …

Spin Cobordism And Quasitoric Manifolds, Clinton M. Hines

Theses and Dissertations--Mathematics

This dissertation demonstrates a procedure to view any quasitoric manifold as a “minimal” sub-manifold of an ambient quasitoric manifold of codimension two via the wedge construction applied to the quotient polytope. These we term wedge quasitoric manifolds. We prove existence utilizing a construction on the quotient polytope and characteristic matrix and demonstrate conditions allowing the base manifold to be viewed as dual to the first Chern class of the wedge manifold. Such dualization allows calculations of KO characteristic classes as in the work of Ochanine and Fast. We also examine the Todd genus as it relates to two types of …

Homological Algebra With Filtered Modules, Raymond Edward Kremer

Theses and Dissertations--Mathematics

Classical homological algebra is done in a category of modules beginning with the study of projective and injective modules. This dissertation investigates analogous notions of projectivity and injectivity in a category of filtered modules. This category is similar to one studied by Sjödin, Nǎstǎsescu, and Van Oystaeyen. In particular, projective and injective objects with respect to the restricted class of strict morphisms are defined and characterized. Additionally, an analogue to the injective envelope is discussed with examples showing how this differs from the usual notion of an injective envelope.

Algebraic Properties Of Formal Power Series Composition, Thomas S. Brewer

Theses and Dissertations--Mathematics

The study of formal power series is an area of interest that spans many areas of mathematics. We begin by looking at single-variable formal power series with coefficients from a field. By restricting to those series which are invertible with respect to formal composition we form a group. Our focus on this group focuses on the classification of elements having finite order. The notion of a semi-cyclic group comes up in this context, leading to several interesting results about torsion subgroups of the group. We then expand our focus to the composition of multivariate formal power series, looking at similar …

A Generalization Of Poincaré-Cartan Integral Invariants Of A Nonlinear Nonholonomic Dynamical System, Muhammad Usman, M. Imran

Mathematics Faculty Publications

Based on the d'Alembert-Lagrange-Poincar\'{e} variational principle, we formulate general equations of motion for mechanical systems subject to nonlinear nonholonomic constraints, that do not involve Lagrangian undetermined multipliers. We write these equations in a canonical form called the Poincar\'{e}-Hamilton equations, and study a version of corresponding Poincar\'{e}-Cartan integral invariant which are derived by means of a type of asynchronous variation of the Poincar\'{e} variables of the problem that involve the variation of the time. As a consequence, it is shown that the invariance of a certain line integral under the motion of a mechanical system of the type considered characterizes the …

Lyapunov Functionals That Lead To Exponential Stability And Instability In Finite Delay Volterra Difference Equations, Catherine Kublik, Youssef Raffoul

Mathematics Faculty Publications

We use Lyapunov functionals to obtain sufficient conditions that guarantee exponential stability of the zero solution of the finite delay Volterra difference equation.

Also, by displaying a slightly different Lyapunov functional, we obtain conditions that guarantee the instability of the zero solution. The highlight of the paper is the relaxing of the condition |a(t)| < 1. Moreover, we provide examples in which we show that our theorems provide an improvement of some recent results.

2014 Alumni Presenters, University Of Dayton. Department Of Mathematics

Biennial Alumni Seminar

No abstract provided.

Conjugate Points For Fractional Differential Equations, Paul W. Eloe, Jeffrey T. Neugebauer

Mathematics Faculty Publications

Let b > 0. Let 1 < α ≤ 2. The theory of u 0-positive operators with respect to a cone in a Banach space is applied to study the conjugate boundary value problem for Riemann-Liouville fractional linear differential equations D 0+α u + λp(t)u = 0, 0 < t < b, satisfying the conjugate boundary conditions u(0) = u(b) = 0. The first extremal point, or conjugate point, of the conjugate boundary value problem is defined and criteria are established to characterize the conjugate point. As an application, a fixed point theorem is applied to give sufficient conditions for existence of a solution of a related boundary value problem for a nonlinear fractional differential equation.