UNT Libraries - 380 Matching Results
Search Results
- Galvanomagnetic Determination of Energy Bands in Arsenic
- A study of the transport properties of a substance requires the determination of a set of transport coefficients by experiment. From these coefficients, the elements of the electrical conductivity tensor, thermoelectric tensor, et cetera can be determined. In this experiment, measurements and analyses of galvanomagnetic effects in a single crystal of arsenic were performed. The measurements were made at liquid-helium temperatures in magnetic fields ranging to 25 kilogauss. The gross isothermal, electrical conductivities have been analyzed to determine various parameters characterizing the energy bands in arsenic.
- Solutions of the Equations of Radiative Transfer by an Invariant Imbedding Approach
- This thesis is a study of the solutions of the equations of radiative transfer by an invariant imbedding approach.
- Monte Carlo Calculations of Reflected Intensities for Real Spherical Atmospheres
- 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.
- Chlorine Nuclear Quadrupole Resonance Absorption of 3, 4, 5, 6 - Tetrachlorophthalimide and 1, 3, 6, 8 - Tetrachloropyrene
- In this study frequency modulation was used with a regenerative spectrometer and a super-regenerative spectrometer to detect the nuclear quadrupole resonance frequencies of chlorine in two commercially available compounds, 1, 3, 6, 8 - tetrachlorophyrene and 3, 4, 5, 6 - tetrachlorophthalimide.
- Quantized Hydrodynamics
- The object of this paper is to derive Landau's theory of quantized hydrodynamics from the many-particle Schroedinger equation. Landau's results are obtained, together with an additional term in the Hamiltonian.
- Virial Theorem for a Molecule
- The usual virial theorem, relating kinetic and potential energy, is extended to a molecule by the use of the true wave function. The virial theorem is also obtained for a molecule from a trial wave function which is scaled separately for electronic and nuclear coordinates.
- A Decay Scheme for 164 Ho
- The present investigation was prompted by several considerations. In previous studies there was considerable variance with regard to the reported values for the half-lives of the isomeric and ground states in 164 Ho. There was also considerable variance with regard to the values reported for the branching ratios and the relative intensities of the transitions. Thus a further study of the problem was needed.
- Pressure Dependence of Line Widths of Microwave Spectra of Sulphur Dioxide
- Measurements of line width parameters for eleven rotational transitions of type (J -- J + 1) of SO2 were made and are reported herein. The line width quantum number (J) trend was obtained. The microwave spectrograph used for these measurements of line width is described. Operational methods to operate the spectrograph are presented and discussed, with particular attention given to how to measure the line width. Suggestions for future avenues of probing this molecule to ascertain the non-uniform behavior of the line width parameter over the quantum number and frequency range are given.
- Cross-Section at 15.6 and 16.1 MeV
- The intent of this investigation is the determination of the values of the Cs-133 (n,2n)Cs-132 cross-section at neutron energies of 15.6 and 16.1 MeV. Neutrons of this energy are produced with comparative ease by means of the D-T reaction, in which deuterons of energy 500 and 750 keV, respectively, are impingent upon a tritium target.
- Recombination Rate Coefficient Measurements in the Helium Afterglow
- This thesis describes a method of determining the recombination rate coefficient experimentally, which does not depend on a specific model of the recombination process. With this method established, results are presented for the recombination rate coefficient measurements at 44.6 Torr.
- Measurement of the Atomic-oxygen Concentration under Simulated Upper Atmosphere Conditions
- This thesis describes an experimental technique for measuring the atomic-oxygen concentration under simulated upper atmosphere conditions.
- A Precision Angular Correlation Table and Calculation of Geometrical Correction Factors
- In recent years y-y angular correlations have been very useful in confirming the spins of excited nuclear states. Angular correlation techniques have also been employed to study the electric and magnetic character of excited nuclear states. With these things in mind, it was decided to design, construct, and test a precision angular correlation table.
- Cross Section for the 165/Ho (n, 2n) 164/Ho Reaction at 15.6 MeV
- It was the purpose of this investigation to bring together the ideas and procedures involved in the measurement of (n, 2n) reaction cross sections. Some of the inherent properties of the material under investigation (Holium) are involved in determining these relationships.
- Electron Spin Resonance Absorption in Benzophenone Phenylhydrazone Negative Ion
- This thesis reports an electron spin resonance absorption study of the hyperfine interaction between nuclei and a single "nearly-free" electron in dilute solutions of the benzophenone phenylhydrazone free radical in tetrahydrofuran.
- Temperature Dependence of Line Widths of the Inversion Spectra of Ammonia
- One of the purposes of this work is to investigate modifications that have to be made to a standard source-modulation microwave spectrograph so that it can be used to study gases at various temperatures. Another objective in this work is to determine experimentally the function of temperature that describes how the line widths of microwave spectral lines vary with changing temperature. The most important segment of the study is the temperature dependence of the line width since from an accurate knowledge of this temperature dependence one is able to determine what molecular force fields are present and the relative importance of parts of the molecular force field.
- Size Dependence in the Electrical Conductivity of Bismuth
- In the present investigation, measurements were made at liquid-helium temperatures on single-crystal bismuth samples which had a stair-step geometry in order to study several thicknesses during one helium run. These samples were also thinned to extend the thickness range of the steps to a thinner region. In addition J.E. Parrott's theory is extended to include a diagonal anisotropic relaxation-time tensor and the effect of holes on the size effect. A discussion of the theory of Parrott, and the extension of Parrott's theory in connection with the experimental results is presented.
- Magnetomorphic Oscillations in Cadmium Cylinders
- The work presented here is an experimental investigation of the effect of cylindrical geometry on electrical conductivity, in which single-crystal samples of cadmium at the temperature of liquid helium are used, with the diameter on the order of the electron mean free path.
- Operation and Control of a Radiofrequency Ion Source
- This thesis examines the operation and control of a radiofrequency ion source.
- Analyzing Magnet System for the Electrostatic Accelerator
- This thesis describes the design and construction of a linear accelerator, specifically, a positive-ion source, a high voltage supply, an accelerating column, and the necessary associated vacuum system.
- Thermomagnetic Effects in Antimony at 4.2 [degrees]K
- The purpose of this investigation was to study the thermoelectric effects in a single crystal of antimony at liquid-helium temperatures.
- Vertex Functions in K-Meson-Nucleon Scattering
- The purpose of this study was to investigate some theoretical approaches to the scattering of positive k-mesons by nucleons in an attempt to explain the experimental data. In this work the problem has been investigated by the technique of the weak coupling approximation.
- A Computer Analysis of Complex Gamma-Ray Spectra
- The purpose of this investigation was to provide a method for determining the relative intensities of all gamma rays in a particular spectrum, and thereby determine the relative transition probabilities.
- A Calculation of the Kaon-Neutron Scattering Cross Section
- The purpose of this investigation was to study the scattering processes of K+ mesons with neutrons. In order to do such a study one must first make certain basic assumptions about the type of interaction involved and then proceed to calculate physically meaningful qualities which describe the processes. Thus, the problem is this: assuming the validity of Feynman's rules for these strongly interacting particles, calculate the differential and total scattering cross sections for the interaction of scalar K+ mesons and neutrons.
- Galvanomagnetic Phenomena in Arsenic at Liquid Helium Temperatures
- The purpose of this investigation was to study some of the transport effects in a single crystal of arsenic at liquid helium temperatures in a magnetic field up to twenty-four kilogauss. The experimental coefficients determined were the isothermal magnetoresistivity and the isothermal Hall resistivity.
- Dynamical Friction Coefficients for Plasmas Exhibiting Non-Spherical Electron Velocity Distributions
- This investigation is designed to find the net rate of decrease in the component of velocity parallel to the original direction of motion of a proton moving through an electron gas exhibiting a non-spherical velocity distribution.
- Electron Transport in Bismuth at Liquid Helium Tempratures
- To obtain information on the band structure of bismuth, galvanomagnetic potentials were measured in a single crystal at liquid-helium and liquid-nitrogen temperatures. These measurements were analyzed for information on the different carriers, particularly for the existence of a high-mobility band of holes.
- A Correction Factor for the First Born Approximation
- This thesis looks at a Schroedinger equation and the Born approximation.
- Stochastic Mechanical Systems
- To understand the phenomena associated with such stochastic processes and to predict, at least qualitatively, the behavior of mechanical systems within environments which are completely random in time, new mechanical tools are necessary. Fortunately, the derivation of these tools does not necessitate a complete departure from existing theories. In fact, they may be considered as an extension of the well-defined theory of the integral transform, in particular, the exponential Fourier integral transform.
- D-D and D-T Neutron Excitation of Energy Levels in Cs133
- The purpose of this experiment was to make positive assignment of the Cs133 energy levels excited by the inelastic scattering of neutrons.
- Energy Losses of Protons Projected through a Plasma Due to Collisions with Electrons of the Plasma for a Variety of Non-Maxwellian Electron Velocity Distributions
- The purpose of this thesis is to study energy losses suffered by protons in traversing a plasma through collision with the electrons of the plasma. For these electrons a variety of non-Maxwellian velocity distributions are assumed.
- A Study of Emitter Drift in Transistors
- The purpose of this investigation was to determine the parameters of emitter drift and to suggest a mechanism for this phenomenon.
- Shubnikov-de Haas Effect in Arsenic
- This thesis studies the Shubnikov-de Haas effect in arsenic.
- Gurevich Magnetomorphic Oscillations in Single Crystals of Aluminum at Helium Temperatures
- The Sondheimer theory was tested by looking for oscillatory phenomena in a group of single crystals representing a range in dimensions from matchbox geometry to thin-film geometry. The single crystals were identical with respect to impurity content, strain, orientation, surface condition, and probe placement.
- Size Effect in the Electrical Conductivity of Bismuth
- 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.
- Effect of Sample Geometry on Magnetomorphic Oscillations in the Hall Effect in Cadium at Liquid-Helium Temperatures
- This thesis presents observations on size-effect oscillations in the Hall effect in an oriented single crystal of highly pure cadmium at liquid-helium temperatures. All measurements were made in transverse magnetic field.
- Boundary Scattering of Electrons in Thin Cadmium Single Crystals
- In the present investigation, zinc was plated onto a cadmium crystal to determine the effect on the scattering parameter.
- Cross Section Measurements in Praseodymium-141 as a Function of Neutron Bombarding Energy
- Using the parallel disk method of activation analysis, the (n,2n) reaction cross section in 141-Pr was measured as a function of neutron energy in the range 15.4 to 18.4 MeV. The bombarding neutrons were produced from the 3-T(d,n)4-He reaction, where the deuterons were accelerated by the 3-MV Van de Graff generator of the North Texas Regional Physics Laboratory in Denton, Texas.
- Phase Shift Determination for Elastic Potential Scattering, Using the IBM 360-50 Computer
- The primary objective of this paper is to present a computerized method for the extraction of phase shifts from an angular distribution. This was accomplished using a least squares curve fitting routine.
- Nuclear Reactions on the Palladium Isotopes
- The problem of interest in this investigation was to determine the cross sections of five nuclear reactions which occur when irradiating natural palladium with neutrons which have energy values of 15.1, 15.9, and 16.3 MeV. The cross sections were measured relative to a copper monitor which was "sandwitched" in with the palladium target.
- A Study of the Decay Levels of 169/Tm69
- 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.
- Carbon Contamination Measurements in Single Silicon Crystals
- The intent of this investigation was to directly measure the amount of carbon contamination in a single silicon crystal and, in so doing, develop a mathematical procedure that would be applicable to other contaminants in other substances.
- The Effects of Lead Placement and Sample Shape in the Measurement of Electrical Resistivity
- This thesis is a study of the effects of lead placement and sample shape in the measurement of electrical resistivity.
- A Method for Calculating Foil Depression Factors
- As disc-shaped detectors are one of the primary means of measuring the neutron density, a better solution is desirable if the error due to the depression factor is to be made negligible. In this paper, an attempt is made to solve this problem in the oblate spheroidal co-ordinate system which most nearly describes the disc-shaped detector, so that solutions may be obtained that describe depression factors for detectors of varying thicknesses and radii.
- A Determination of the Bothe Depression Factor for Discs in Water
- 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.
- Variational Wave Function for Sodium
- The practical method of applying the variation principle to the calculation of the energy of an atom demands a trial function which contains variable parameters. The previous work done using this approach was based on the use of some combination of hydrogenic wave functions containing parameters inserted in appropriate places. The present calculation of the energy of the eleven-electron atom has been brought about using this method.
- Neutron Density Depression Due to an Oblate Spheroidal Detector
- In this paper, two projects have been undertaken. First, Workman's calculations have been checked to a higher degree of approximation to determine the accuracy of his method. Second, a new set of boundary conditions has been developed for obtaining solutions of the neutron diffusion equation which do not depend on the solution of the equation inside the detector.
- Foil Depression Factors for Disc-shaped Detectors
- The generalized data which are presented in this thesis are the culmination of the determination of the foil depression factor using oblate spheroidal coordinates.
- Ultrafast Spectroscopy of Hybrid Ingan/gan Quantum Wells
- Group III nitrides are efficient light emitters. The modification of internal optoelectronic properties of these materials due to strain, external or internal electric field are an area of interest. Insertion of metal nanoparticles (MNPs) (Ag, Au etc) inside the V-shaped inverted hexagonal pits (IHP) of InGaN/GaN quantum wells (QWs) offers the potential of improving the light emission efficiencies. We have observed redshift and blueshift due to the Au MNPs and Ag MNPs respectively. This shift could be due to the electric field created by the MNPs through electrostatic image charge. We have studied the ultrafast carrier dynamics of carriers in hybrid InGaN/GaN QWs. The change in quantum confinement stark effect due to MNPs plays an important role for slow and fast carrier dynamics. We have also observed the image charge effect on the ultrafast differential transmission measurement due to the MNPs. We have studied the non-linear absorption spectroscopy of these materials. The QWs behave as a discharging of a nanocapacitor for the screening of the piezoelectric field due to the photo-excited carriers. We have separated out screening and excitonic bleaching components from the main differential absorption spectra of InGaN/GaN QWs.
- A Non-equilibrium Approach to Scale Free Networks
- Many processes and systems in nature and society can be characterized as large numbers of discrete elements that are (usually non-uniformly) interrelated. These networks were long thought to be random, but in the late 1990s, Barabási and Albert found that an underlying structure did in fact exist in many natural and technological networks that are now referred to as scale free. Since then, researchers have gained a much deeper understanding of this particular form of complexity, largely by combining graph theory, statistical physics, and advances in computing technology. This dissertation focuses on out-of-equilibrium dynamic processes as they unfold on these complex networks. Diffusion in networks of non-interacting nodes is shown to be temporally complex, while equilibrium is represented by a stable state with Poissonian fluctuations. Scale free networks achieve equilibrium very quickly compared to regular networks, and the most efficient are those with the lowest inverse power law exponent. Temporally complex diffusion also occurs in networks with interacting nodes under a cooperative decision-making model. At a critical value of the cooperation parameter, the most efficient scale free network achieves consensus almost as quickly as the equivalent all-to-all network. This finding suggests that the ubiquity of scale free networks in nature is due to Zipf's principle of least effort. It also suggests that an efficient scale free network structure may be optimal for real networks that require high connectivity but are hampered by high link costs.
- Theoretical and Experimental Investigations Concerning Microgels of Varied Spherical Geometries
- Polymer gels have been studied extensively due to their ability to simulate biological tissues and to swell or collapse reversibly in response to external stimuli. This work presents a variety of studies using poly-N-isopropylacrylamide (PNIPA) hydrogels. The projects have been carried out both in the lab of Dr. Zhibing Hu and in collaboration with others outside of UNT: (1) an analysis of the swelling kinetics of microgel spherical shells prepared using a novel design of microfluidic devices; (2) a comparison of the drug-release rates between nanoparticle structures having either core or core-with-shell (core-shell) designs; (3) an investigation into the thermodynamics of swelling for microgels of exceedingly small size.