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Full-Text Articles in Physical Sciences and Mathematics
Time-Resolved Magnetic Flux And Ac-Current Distributions In Superconducting Yttrium Barium Copper Oxide Thin Films And Multifilaments, Ran Yang
Dissertations, Theses, and Masters Projects
Time-resolved magneto-optical imaging (TRMOI) technique allows dynamic ac transport measurements on superconductors. The high time and spatial resolutions of the measurements also offer good quantitative data analysis of the MO images. YBa2Cu 3O7-delta (YBCO) was discovered as a high-temperature superconductor (HTSC) which has wide applications due to its high critical temperature of Tc = 91 K, and high critical current density Jc in the order of 106-7 Acm-2. Many of the applications require high ac current load and a high magnetic field. We study the interaction behavior of YBCO thin films in an ac transport current and a dc magnetic …
Topics In Mode Conversion Theory And The Group Theoretical Foundations Of Path Integrals, Andrew Stephen Richardson
Topics In Mode Conversion Theory And The Group Theoretical Foundations Of Path Integrals, Andrew Stephen Richardson
Dissertations, Theses, and Masters Projects
This dissertation reports research about the phase space perspective for solving wave problems, with particular emphasis on the phenomenon of mode conversion in multicomponent wave systems, and the mathematics which underlie the phase space perspective. Part I of this dissertation gives a review of the phase space theory of resonant mode conversion. We describe how the WKB approximation is related to geometrical structures in phase space, and how in particular ray-tracing algorithms can be used to construct the WKB solution. We further review how to analyze the phenomena of mode conversion from the phase space perspective. By making an expansion …
Methods For Stabilizing High Reynolds Number Lattice Boltzmann Simulations, Brian Robert Keating
Methods For Stabilizing High Reynolds Number Lattice Boltzmann Simulations, Brian Robert Keating
Dissertations, Theses, and Masters Projects
The Lattice Boltzmann Method (LBM) is a simple and highly efficient method for computing nearly incompressible fluid flow. However, it is well known to suffer from numerical instabilities for low values of the transport coefficients. This dissertation examines a number of methods for increasing the stability of the LBM over a wide range of parameters. First, we consider a simple transformation that renders the standard LB equation implicit. It is found that the stability is largely unchanged. Next, we consider a stabilization method based on introducing a Lyapunov function which is essentially a discrete-time H-function. The uniqueness of an H-function …
As Particles Collide: Extra Dimensions And Heavy Leptons, Erin Kathleen De Pree
As Particles Collide: Extra Dimensions And Heavy Leptons, Erin Kathleen De Pree
Dissertations, Theses, and Masters Projects
Despite excellent agreement with experiment, the Standard Model leaves several issues unresolved. These issues will be explored and several extensions to the Standard Model introduced: models with extra dimensions and a fourth family of particles.;In extra dimensional models, there are Fourier modes of the Standard Model particles. We study the detection of bound states of one of the modes and its Standard Model particle.;We then explore a particular model of extra dimensions known as Randall-Sundrum or warped extra dimensions. We will see how this model affects top quark measurements at the proposed International Linear Collider.;Finally we will study the detection …
The Semiclassical Description Of The Energy Spectrum Of Hydrogen In Near-Perpendicular Fields, Christopher Robert Schleif
The Semiclassical Description Of The Energy Spectrum Of Hydrogen In Near-Perpendicular Fields, Christopher Robert Schleif
Dissertations, Theses, and Masters Projects
We examine the energy spectrum of hydrogen in weak near-perpendicular electric and magnetic fields using quantum computations and semiclassical analysis. The structure of the quantum spectrum is displayed in a lattice constructed by plotting the difference between total energy and first order energy versus first order energy, for all states of a given principal quantum number n. For some field parameters, the lattice structure is not regular, but has a lattice defect structure which may be characterized by the transport of lattice vectors. We find that in near-perpendicular fields the structure of the spectrum is divided into six distinct parameter …
Measurement Of Inclusive Proton Double -Spin Asymmetries And Polarized Structure Functions, Robert G. Fersch
Measurement Of Inclusive Proton Double -Spin Asymmetries And Polarized Structure Functions, Robert G. Fersch
Dissertations, Theses, and Masters Projects
The scattering of polarized electrons from a polarized proton target provides a means for studying the internal spin structure of the proton. The CLAS (CEBAF Large Acceptance Spectrometer) EG1b experiment in Hall-B at Jefferson Laboratory measured double-spin inclusive and exclusive electron-nucleon scattering asymmetries using longitudinally polarized frozen NH3 and ND3 targets and a longitudinally polarized electron beam at 4 different energies (1.6, 2.5, 4.2, 5.6 GeV). Extraction of the virtual photon asymmetry Ap1 (for 0.05 GeV2 < Q2 < 5.0 GeV2) provides precision measurements of the polarized proton spin-structure function gp1 in and above the resonance region. Linear regression of data between the varying energies yields new constraints on the virtual photon asymmetry Ap2 (and thus the structure function gp2 ) in the resonance region (for 0.3 GeV2 < Q2 < 1.0 GeV2). Measurements of these structure functions and their moments allows testing of perturbative Quantum Chromodynamics (pQCD) models and evaluation of moments of the structure functions in the Operator Product Expansion. Testing of Chiral Perturbation Theory (chiPT) at Q2 < 0.2 GeV 2 is enabled by the new data. Other applications of polarized structure functions include measurement of foward-spin polarizability, evaluation of high-order corrections in 1H hyperfine splitting, and testing of quark-hadron duality.
Synthesis And Field Emission Properties Of Carbon Nanostructures, Kun Hou
Synthesis And Field Emission Properties Of Carbon Nanostructures, Kun Hou
Dissertations, Theses, and Masters Projects
This dissertation focuses on developing carbon nanostructures for application as the electron emissive material in novel back-gated triode field emission devices. The synthesis, characterization, and field emission properties of carbon nanostructures, including 1-D carbon nanofibers (CNF), 2-D carbon nanosheets (CNS), and chromium oxide coated carbon nanosheets (CrOx-CNS), are presented in this work.;First, we have fabricated aligned carbon nanofiber based back-gated triode field emission devices and confirmed the operation of these devices. 1-D carbon nanofibers were directly synthesized on blank TiW substrates using direct current plasma enhanced chemical vapor deposition. It was found that the morphology of carbon nanofibers could be …
Correction Of Finite Size Errors In Many-Body Electronic Structure Calculations, Hendra Kwee
Correction Of Finite Size Errors In Many-Body Electronic Structure Calculations, Hendra Kwee
Dissertations, Theses, and Masters Projects
Electronic structure calculations using simulation cells for extended systems typically incorporate periodic boundary conditions as an attempt to mimic the real system with a practically infinite number of particles. Periodic boundary conditions introduce unphysical constraints that give rise to finite-size errors. In mean-field type calculations, the infinite size limit is achieved by simple quadrature in the Brillouin zone using a finite number of k-points. Many-body electronic structure calculations with explicit two-particle interactions cannot avail themselves of this simplification. Direct extrapolation is computationally costly while size correction with less accurate methods is frequently not sufficiently accurate. The Hartree-Fock method neglects the …