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  Partner: UNT Libraries
 Degree Discipline: Physics
 Collection: UNT Theses and Dissertations
Dipole Moments of Olefinic Esters

Dipole Moments of Olefinic Esters

Date: 1952
Creator: Poteet, Horace M.
Description: It is the purpose of this thesis to investigate the applicability of the Debye equation to measurements dipole moments of polar compounds in dilute solutions of non-polar solvents more fully than has been done by previous workers at this institution.
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Radar Scattering Cross-section of Triangular Corner Reflectors

Radar Scattering Cross-section of Triangular Corner Reflectors

Date: 1957
Creator: Budwine, Robert E.
Description: The series of experimental studies to be described has been carried out in order to determine the feasibility of using corner reflectors as laboratory standards for model cross-section measurements.
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Scattering Cross-sections of 4/1 Prolate Spheroids

Scattering Cross-sections of 4/1 Prolate Spheroids

Date: 1956
Creator: Tompkins, Keith W.
Description: This is a report of the second in a projected series of experiments at North Texas State College designed for obtaining information about the microwave scattering properties of various shaped objects.
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Backscattering from Prolate Spheroids at Microwave Frequencies

Backscattering from Prolate Spheroids at Microwave Frequencies

Date: 1956
Creator: Sybert, Jim
Description: This thesis examines backscattering from prolate spheroids at microwave frequencies.
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The Angular Distribution and Total Flux of Neutrons Obtained from the Deuterium-Tritium Reaction

The Angular Distribution and Total Flux of Neutrons Obtained from the Deuterium-Tritium Reaction

Date: 1956
Creator: Duggan, Jerome L.
Description: Mono-energetic neutrons have been produced with the low-voltage Cockroft-Walton accelerator at North Texas State College using two different reactions. It is the purpose of this paper to report the angular distribution and total flux of the neutrons obtained from the T(D,n) reaction.
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The Angular Distribution of the Deuterium-Deuterium Neutrons with 100 Kev Deuterons

The Angular Distribution of the Deuterium-Deuterium Neutrons with 100 Kev Deuterons

Date: 1956
Creator: Hackfield, Bobby J.
Description: It is the purpose of this paper to present the experimental techniques used in obtaining. 3.25 MeV neutrons from the H2(d,n)He3 reaction, as well as an analysis of the experimental data.
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Experimental Determination of the Scattering Cross-section of Ogives and Prolate Spheroids at Microwave Frequencies

Experimental Determination of the Scattering Cross-section of Ogives and Prolate Spheroids at Microwave Frequencies

Date: 1956
Creator: Rhoads, Wayne C.
Description: Because of the great difficulty of obtaining exact numerical values of cross-section, and because of the inherent uncertainties in interpreting and evaluating the approximate methods, accurate experimental cross-section data would be extremely useful to the radar engineer. It was with this purpose in mind that the present long-range research program in microwave scattering was undertaken. Of immediate interest were the scattering properties of the prolate spheroid, the ogive (formed by rotating the minor segment of a circle around the chord), and, for comparison, the long cylinder.
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An Investigation for Gamma Rays Resulting from the Bombardment of As75 with 14 Mev Neutrons

An Investigation for Gamma Rays Resulting from the Bombardment of As75 with 14 Mev Neutrons

Date: 1957
Creator: Givens, Wyatt Wendell
Description: It is the purpose of this paper to set forth the method and results of studying the gamma rays resulting from the bombardment of As75 with approximately 14 Mev neutrons. The source of these neutrons was the H3(d,n)He4 reaction. The deuterons of 325 Kev energy were obtained from a Van de Graff electrostatic accelerator. A NaI scintillation spectrometer was used to determine the gamma-ray energies.
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Gamma Rays from Neutron Excitation of Cs133

Gamma Rays from Neutron Excitation of Cs133

Date: January 1959
Creator: Lamb, Billy Leonard
Description: This thesis explores gamma rays from neutron excitation of Cs133.
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Design and Construction of a Positive Radio-Frequency Ion Source for the Production of Negative Ions

Design and Construction of a Positive Radio-Frequency Ion Source for the Production of Negative Ions

Date: August 1958
Creator: Thompson, B. Cecil
Description: It is the purpose of this paper to present a detailed account of the design and construction of this positive-ion source and associated equipment.
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Gamma Ray Response of a CsI(T1) Crystal to 14 Mev Neutrons

Gamma Ray Response of a CsI(T1) Crystal to 14 Mev Neutrons

Date: August 1958
Creator: Young, Jack Carter
Description: The purpose of this paper is to study the possible excited states in the nucleus of Cs133. At North Texas State College a 100-Kev Cockcroft-Walton accelerator has been constructed for use as a neutron source for exciting various nuclei and for studying the gamma spectra obtained to determine their energy levels.
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Magnetic Resonance of Protons in the Earth's Magnetic Field

Magnetic Resonance of Protons in the Earth's Magnetic Field

Date: August 1959
Creator: Crosby, Richard Hill
Description: The purpose of the work reported here was to determine the feasibility of applying the nuclear induction technique of Bloch to the direct observation of nuclear magnetic resonance in the very weak magnetic field of the earth.
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Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures

Date: May 2012
Creator: Llopis, Antonio
Description: III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN MQWs. the dependence on resonant interaction between the plasmons and the light emitter limits the applications of plasmonics for light emission. This dissertation presents a new non-resonant mechanism based on electrostatic interaction of carriers with induced image charges in a nearby metallic nanoparticle. Enhancement similar in strength to that of plasmonics is observed, without the restrictions imposed upon resonant interactions. in this work we demonstrate several key features of this new interaction, including intensity-dependent saturation, increase in the radiative recombination lifetime, and strongly inhomogeneous light emission. We also present a model for the interaction based on the aforementioned image charge interactions. Also discussed are results of work done in the course of this research resulting in the development of a novel technique for strain measurement ...
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Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Effects of Dissipation on Propagation of Surface Electromagnetic and Acoustic Waves

Date: May 2012
Creator: Nagaraj, Nagaraj
Description: With the recent emergence of the field of metamaterials, the study of subwavelength propagation of plane waves and the dissipation of their energy either in the form of Joule losses in the case of electomagnetic waves or in the form of viscous dissipation in the case of acoustic waves in different interfaced media assumes great importance. with this motivation, I have worked on problems in two different areas, viz., plasmonics and surface acoustics. the first part (chapters 2 & 3) of the dissertation deals with the emerging field of plasmonics. Researchers have come up with various designs in an efort to fabricate efficient plasmonic waveguides capable of guiding plasmonic signals. However, the inherent dissipation in the form of Joule losses limits efficient usage of surface plasmon signal. a dielectric-metal-¬dielectric planar structure is one of the most practical plasmonic structures that can serve as an efficient waveguide to guide electromagnetic waves along the metal-dielectric boundary. I present here a theoretical study of propagation of surface plasmons along a symmetric dielectric-metal-dielectric structure and show how proper orientation of the optical axis of the anisotropic substrate enhances the propagation length. an equation for propagation length is derived in a wide range of frequencies. ...
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Modification of Graphene Properties: Electron Induced Reversible Hydrogenation, Oxidative Etching and Layer-by-layer Thinning

Modification of Graphene Properties: Electron Induced Reversible Hydrogenation, Oxidative Etching and Layer-by-layer Thinning

Date: May 2012
Creator: Jones, Jason David
Description: In this dissertation, I present the mechanism of graphene hydrogenation via three different electron sources: scanning electron microscopy, e-beam irradiation and H2 and He plasma irradiation. in each case, hydrogenation occurs due to electron impact fragmentation of adsorbed water vapor from the sample preparation process. in the proposed model, secondary and backscattered electrons generated from incident electron interactions with the underlying silicon substrate are responsible for the dissociation of water vapor. Chemisorbed H species from the dissociation are responsible for converting graphene into hydrogenated graphene, graphane. These results may lead to higher quality graphane films having a larger band gap than currently reported. in addition, the dissertation presents a novel and scalable method of controllably removing single atomic planes from multi-layer graphene using electron irradiation from an intense He plasma under a positive sample bias. As the electronic properties or multi-layer graphene are highly dependent on the number of layers, n, reducing n in certain regions has many benefits. for example, a mask in conjunction with this thinning method could be used for device applications.
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Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

Electrostatic Effects in III-V Semiconductor Based Metal-optical Nanostructures

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Date: May 2012
Creator: Gryczynski, Karol Grzegorz
Description: The modification of the band edge or emission energy of semiconductor quantum well light emitters due to image charge induced phenomenon is an emerging field of study. This effect observed in quantum well light emitters is critical for all metal-optics based light emitters including plasmonics, or nanometallic electrode based light emitters. This dissertation presents, for the first time, a systematic study of the image charge effect on semiconductor–metal systems. the necessity of introducing the image charge interactions is demonstrated by experiments and mathematical methods for semiconductor-metal image charge interactions are introduced and developed.
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Transport Phenomena in Indium Arsenide at Low Temperatures

Transport Phenomena in Indium Arsenide at Low Temperatures

Date: August 1968
Creator: Luke, Paul Jacob
Description: This thesis looks at the transport phenomena in indium arsenide at low temperatures.
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Solutions of the Equations of Radiative Transfer by an Invariant Imbedding Approach

Solutions of the Equations of Radiative Transfer by an Invariant Imbedding Approach

Date: January 1969
Creator: Adams, Charles N.
Description: This thesis is a study of the solutions of the equations of radiative transfer by an invariant imbedding approach.
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Monte Carlo Calculations of Reflected Intensities for Real Spherical Atmospheres

Monte Carlo Calculations of Reflected Intensities for Real Spherical Atmospheres

Date: January 1969
Creator: Montgomery, John A.
Description: To calculate the emergent radiation field, a realistic atmospheric model and algorithm must be developed. The radiation field may be characterized by the emergent intensities of scattered light. This is possible only if the algorithm determines these intensities as dependent upon atmospheric and angular parameters.
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Boundary Scattering of Electrons in Thin Cadmium Single Crystals

Boundary Scattering of Electrons in Thin Cadmium Single Crystals

Date: August 1968
Creator: Fortmayer, Gary William
Description: In the present investigation, zinc was plated onto a cadmium crystal to determine the effect on the scattering parameter.
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Size Effect in the Electrical Conductivity of Bismuth

Size Effect in the Electrical Conductivity of Bismuth

Date: August 1967
Creator: Vaughn, Bobby J.
Description: If a physical dimension of a metallic specimen is comparable with, or smaller than, the mean free path of the conduction electrons, then the observed electrical conductivity will be less than that of a conventional bulk sample. This phenomenon is called a size effect, and is the result of electron scattering from the specimen surfaces. In the present investigation, measurements were made on electropolished monocrystalline specimens ranging from matchbox geometry to thick-film geometry in order to obtain further information on the size effect in bismuth at liquid helium temperatures.
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The Effects of Lead Placement and Sample Shape in the Measurement of Electrical Resistivity

The Effects of Lead Placement and Sample Shape in the Measurement of Electrical Resistivity

Date: August 1970
Creator: Stephens, Anthony E.
Description: This thesis is a study of the effects of lead placement and sample shape in the measurement of electrical resistivity.
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A Determination of the Bothe Depression Factor for Discs in Water

A Determination of the Bothe Depression Factor for Discs in Water

Date: August 1950
Creator: Patton, Bob
Description: The purpose of this work is to determine experimentally the depression of the neutron density by a detecting foil. The depression factor is known as the "self-shading" of the foil.
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A Study of the Decay Levels of 169/Tm69

A Study of the Decay Levels of 169/Tm69

Date: December 1970
Creator: Harris, Robert J.
Description: The purpose of this investigation was to study the radiations of the 169/Tm nucleus as it de-excites after the electron capture decay of the 169/Yb. Numerous unreported gammas were present in the sample. The origins of these gamma rays were found.
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