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Articles 1 - 7 of 7
Full-Text Articles in Physical Sciences and Mathematics
Efficient Cone Beam Reconstruction For The Distorted Circle And Line Trajectory, Souleymane Konate
Efficient Cone Beam Reconstruction For The Distorted Circle And Line Trajectory, Souleymane Konate
Electronic Theses and Dissertations
We propose an exact filtered backprojection algorithm for inversion of the cone beam data in the case when the trajectory is composed of a distorted circle and a line segment. The length of the scan is determined by the region of interest , and it is independent of the size of the object. With few geometric restrictions on the curve, we show that we have an exact reconstruction. Numerical experiments demonstrate good image quality.
Optimal Dual Frames For Erasures And Discrete Gabor Frames, Jerry Lopez
Optimal Dual Frames For Erasures And Discrete Gabor Frames, Jerry Lopez
Electronic Theses and Dissertations
Since their discovery in the early 1950's, frames have emerged as an important tool in areas such as signal processing, image processing, data compression and sampling theory, just to name a few. Our purpose of this dissertation is to investigate dual frames and the ability to find dual frames which are optimal when coping with the problem of erasures in data transmission. In addition, we study a special class of frames which exhibit algebraic structure, discrete Gabor frames. Much work has been done in the study of discrete Gabor frames in Rn, but very little is known about the l2(Z) …
The Sheffer B-Type 1 Orthogonal Polynomial Sequences, Daniel Galiffa
The Sheffer B-Type 1 Orthogonal Polynomial Sequences, Daniel Galiffa
Electronic Theses and Dissertations
In 1939, I.M. Sheffer proved that every polynomial sequence belongs to one and only one type. Sheffer extensively developed properties of the B-Type 0 polynomial sequences and determined which sets are also orthogonal. He subsequently generalized his classification method to the case of arbitrary B-Type k by constructing the generalized generating function A(t)exp[xH1(t) + · · · + xk+1Hk(t)] = ∑∞n=0 Pn(x)tn, with Hi(t) = hi,iti + hi,i+1t i+1 + · · · , h1,1 ≠ 0. Although extensive research has been done on characterizing polynomial sequences, no analysis has yet been completed on sets of type one or higher …
Almost Regular Graphs And Edge Face Colorings Of Plane Graphs, Lisa Macon
Almost Regular Graphs And Edge Face Colorings Of Plane Graphs, Lisa Macon
Electronic Theses and Dissertations
Regular graphs are graphs in which all vertices have the same degree. Many properties of these graphs are known. Such graphs play an important role in modeling network configurations where equipment limitations impose a restriction on the maximum number of links emanating from a node. These limitations do not enforce strict regularity, and it becomes interesting to investigate nonregular graphs that are in some sense close to regular. This dissertation explores a particular class of almost regular graphs in detail and defines generalizations on this class. A linear-time algorithm for the creation of arbitrarily large graphs of the discussed class …
Weighted Lp-Stability For Localized Infinite Matrices, Qiling Shi
Weighted Lp-Stability For Localized Infinite Matrices, Qiling Shi
Electronic Theses and Dissertations
This dissertation originates from a classical result that the lp-stability of the convolution operator associated with a summable sequence are equivalent to each other for different p . This dissertation is motivated by the recent result by C. E. Shin and Q. Sun (Journal ofFunctional Analysis, 256(2009), 2417-2439), where the lp-stability of infinite matrices in the Gohberg-Baskakov-Sjostrand class are proved to be equivalent to each other for different p. In the dissertation, for an infinite matrix having certain off-diagonal decay, its weighted lp-stability for different p are proved to be equivalent to each other and hence a result by Shin …
Analytical And Numerical Solutions Of Differentialequations Arising In Fluid Flow And Heat Transfer Problems, Erik Sweet
Analytical And Numerical Solutions Of Differentialequations Arising In Fluid Flow And Heat Transfer Problems, Erik Sweet
Electronic Theses and Dissertations
The solutions of nonlinear ordinary or partial differential equations are important in the study of fluid flow and heat transfer. In this thesis we apply the Homotopy Analysis Method (HAM) and obtain solutions for several fluid flow and heat transfer problems. In chapter 1, a brief introduction to the history of homotopies and embeddings, along with some examples, are given. The application of homotopies and an introduction to the solutions procedure of differential equations (used in the thesis) are provided. In the chapters that follow, we apply HAM to a variety of problems to highlight its use and versatility in …
Standing Waves Of Spatially Discrete Fitzhugh-Nagumo Equations, Joseph Segal
Standing Waves Of Spatially Discrete Fitzhugh-Nagumo Equations, Joseph Segal
Electronic Theses and Dissertations
We study a system of spatially discrete FitzHugh-Nagumo equations, which are nonlinear differential-difference equations on an infinite one-dimensional lattice. These equations are used as a model of impulse propagation in nerve cells. We employ McKean's caricature of the cubic as our nonlinearity, which allows us to reduce the nonlinear problem into a linear inhomogeneous problem. We find exact solutions for standing waves, which are steady states of the system. We derive formulas for all 1-pulse solutions. We determine the range of parameter values that allow for the existence of standing waves. We use numerical methods to demonstrate the stability of …