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**Partner:**UNT Libraries

**Department:**Department of Physics

**Collection:**UNT Theses and Dissertations

### Neutron Density Depression Due to an Oblate Spheroidal Detector

**Date:**January 1954

**Creator:**Trammell, Margaret Ruth

**Description:**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.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130362/

### Operation and Control of a Radiofrequency Ion Source

**Date:**August 1953

**Creator:**Paulissen, George T.

**Description:**This thesis examines the operation and control of a radiofrequency ion source.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130340/

### A Method for Calculating Foil Depression Factors

**Date:**June 1953

**Creator:**Workman, Billy J.

**Description:**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.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130315/

### Shubnikov-de Haas Effect in Arsenic

**Date:**August 1966

**Creator:**Miller, Ronald Eugene

**Description:**This thesis studies the Shubnikov-de Haas effect in arsenic.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130735/

### Homogeneous Canonical Formalism and Relativistic Wave Equations

**Date:**January 1967

**Creator:**Jackson, Albert A.

**Description:**This thesis presents a development of classical canonical formalism and the usual transition schema to quantum dynamics. The question of transition from relativistic mechanics to relativistic quantum dynamics is answered by developing a homogeneous formalism which is relativistically invariant. Using this formalism the Klein-Gordon equation is derived as the relativistic analog of the Schroedinger equation. Using this formalism further, a method of generating other relativistic equations (with spin) is presented.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130781/

### A Study and Critique of the Mean Position Concept in Relativistic Wave Mechanics

**Date:**January 1967

**Creator:**Gebhart, Hugh David

**Description:**The basic concept to be used in studying the question of one-particle interpretations of relativistic wave equations is that of observables and operator representations that are different from the more usual classically motivated observables and representations. In particular, the concept of a mean-position observable will be used to determine to what extent the one-particle "problems" can be resolved.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130778/

### Vertex Functions in K-Meson-Nucleon Scattering

**Date:**August 1966

**Creator:**Kang, Hsu Hsiung

**Description:**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.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc130726/

### Distribution of Nighttime F-region Molecular Ion Concentrations and 6300 Å Nightglow Morphology

**Date:**December 1970

**Creator:**Brasher, William Ernest, 1939-

**Description:**The purpose of this study is two-fold. The first is to determine the dependence of the molecular ion profiles on the various ionospheric and atmospheric parameters that affect their distributions. The second is to demonstrate the correlation of specific ionospheric parameters with 6300 Å nightglow intensity during periods of magnetically quiet and disturbed conditions.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278620/

### Charge State Distributions in Molecular Dissociation

**Date:**December 1998

**Creator:**Renfrow, Steven N. (Steven Neal)

**Description:**The present work provides charge state fractions that may be used to generate TEAMS relative sensitivity factors for impurities in semiconductor materials.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278340/

### Magnetomorphic Oscillations in Zinc

**Date:**August 1970

**Creator:**Waller, William Marvin

**Description:**In making this study it is important to search for ways to enhance and, if possible, make detection of MMO signals simpler in order that this technique for obtaining FS measurements may be extended to other materials. This attempt to improve measurement techniques has resulted in a significant discovery: the eddy-current techniques described in detail in a later section which should allow MMO to be observed and sensitively measured in many additional solids. The second major thrust of the study has been to use the newly discovered eddy-current technique in obtaining the first indisputable observation of MMO in zinc.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc279266/

### Quantum-Confined CdS Nanoparticles on DNA Templates

**Date:**May 1998

**Creator:**Rho, Young Gyu

**Description:**As electronic devices became smaller, interest in quantum-confined semiconductor nanostructures increased. Self-assembled mesoscale semiconductor structures of II-VI nanocrystals are an especially exciting subject because of their controllable band gap and unique photophysical properties. Several preparative methods to synthesize and control the sizes of the individual nanocrystallites and the electronic and optical properties have been intensively studied. Fabrication of patterned nanostructures composed of quantum-confined nanoparticles is the next step toward practical applications. We have developed an innovative method to fabricate diverse nanostructures which relies on the size and a shape of a chosen deoxyribonucleic acid (DNA) template.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc279352/

### Anisotropic Relaxation Time for Solids with Ellipsoidal Fermi Surfaces

**Date:**May 1971

**Creator:**Fuchser, Troy Denrich

**Description:**Many solids have Fermi surfaces which are approximated as ellipsoids. A comprehensive solution for the magnetoconductivity of an ellipsoid is obtained which proves the existence of a relaxation time tensor which can be anisotropic and which is a function of energy only.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278322/

### Fluorine Adsorption and Diffusion in Polycrystalline Silica

**Date:**December 1998

**Creator:**Jin, Jian-Yue

**Description:**The measurement of fluorine penetration into archeological flint artifacts using Nuclear Reaction Analysis (NRA) has been reported to be a potential dating method. However, the mechanism of how fluorine is incorporated into the flint surface, and finally transported into the bulk is not well understood. This research focuses on the study of the fluorine uptake phenomenon of flint mineral in aqueous fluoride solutions. Both theoretical and experimental approaches have been carried out. In a theoretical approach, a pipe-diffusion model was used to simulate the complicated fluorine transportation problem in flint, in which several diffusion mechanisms may be involved.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc277986/

### Two-Fold Role of Randomness: A Source of Both Long-Range Correlations and Ordinary Statistical Mechanics

**Date:**December 1998

**Creator:**Rocco, A. (Andrea)

**Description:**The role of randomness as a generator of long range correlations and ordinary statistical mechanics is investigated in this Dissertation. The difficulties about the derivation of thermodynamics from mechanics are pointed out and the connection between the ordinary fluctuation-dissipation process and possible anomalous properties of statistical systems is highlighted.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278012/

### Synthesis and Study of Engineered Heterogenous Polymer Gels

**Date:**August 1998

**Creator:**Chen, Yuanye

**Description:**This dissertation studies physical properties and technological applications of engineered heterogenous polymer gels. Such gels are synthesized based on modulation of gel chemical nature in space. The shape memory gels have been developed in this study by using the modulated gel technology. At room temperature, they form a straight line. As the temperature is increased, they spontaneously bend or curl into a predetermined shape such as a letter of the alphabet, a numerical number, a spiral, a square, or a fish. The shape changes are reversible. The heterogenous structures have been also obtained on the gel surface. The central idea is to cover a dehydrated gel surface with a patterned mask, then to sputter-deposit a gold film onto it. After removing the mask, a gold pattern is left on the gel surface. Periodical surface array can serve as gratings to diffract light. The grating constant can be continuously changed by the external environmental stimuli such as temperature and electric field. Several applications of gels with periodic surface arrays as sensors for measuring gel swelling ratio, internal strain under an uniaxial stress, and shear modulus have been demonstrated. The porous NIPA gels have been synthesized by suspension technique. Microstructures of newly ...

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278503/

### Structural and Photoelectron Emission Properties of Chemical Vapor Deposition Grown Diamond Films

**Date:**August 1998

**Creator:**Akwani, Ikerionwu Asiegbu

**Description:**The effects of methane (CH4), diborone (B2H6) and nitrogen (N2) concentrations on the structure and photoelectron emission properties of chemical vapor deposition (CVD) polycrystalline diamond films were studied. The diamond films were grown on single-crystal Si substrates using the hot-tungsten filament CVD technique. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) were used to characterize the different forms of carbon in the films, and the fraction of sp3 carbon to sp3 plus sp2 carbon at the surface of the films, respectively. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the films. The photoelectron emission properties were determined by measuring the energy distributions of photoemitted electrons using ultraviolet photoelectron spectroscopy (UPS), and by measuring the photoelectric current as a function of incident photon energy.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc279053/

### On Delocalization Effects in Multidimensional Lattices

**Date:**May 1998

**Creator:**Bystrik, Anna

**Description:**A cubic lattice with random parameters is reduced to a linear chain by the means of the projection technique. The continued fraction expansion (c.f.e.) approach is herein applied to the density of states. Coefficients of the c.f.e. are obtained numerically by the recursion procedure. Properties of the non-stationary second moments (correlations and dispersions) of their distribution are studied in a connection with the other evidences of transport in a one-dimensional Mori chain. The second moments and the spectral density are computed for the various degrees of disorder in the prototype lattice. The possible directions of the further development are outlined. The physical problem that is addressed in the dissertation is the possibility of the existence of a non-Anderson disorder of a specific type. More precisely, this type of a disorder in the one-dimensional case would result in a positive localization threshold. A specific type of such non-Anderson disorder was obtained by adopting a transformation procedure which assigns to the matrix expressing the physics of the multidimensional crystal a tridiagonal Hamiltonian. This Hamiltonian is then assigned to an equivalent one-dimensional tight-binding model. One of the benefits of this approach is that we are guaranteed to obtain a linear crystal with a ...

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc278868/

### Scanning Tunneling Microscopy of Epitaxial Diamond (110) and (111) Films and Field Emission Properties of Diamond Coated Molybdenum Microtips

**Date:**May 1998

**Creator:**Lim, Seong-Chu

**Description:**The growth mechanism of chemical vapor deposition (CVD) grown homo-epitaxial diamond (110) and (111) films was studied using ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). In addition, the field emission properties of diamond coated molybdenum microtips were studied as a function of exposure to different gases.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc279160/

### Microscopic Foundations of Thermodynamics and Generalized Statistical Ensembles

**Date:**May 2008

**Creator:**Campisi, Michele

**Description:**This dissertation aims at addressing two important theoretical questions which are still debated in the statistical mechanical community. The first question has to do with the outstanding problem of how to reconcile time-reversal asymmetric macroscopic laws with the time-reversal symmetric laws of microscopic dynamics. This problem is addressed by developing a novel mechanical approach inspired by the work of Helmholtz on monocyclic systems and the Heat Theorem, i.e., the Helmholtz Theorem. By following a line of investigation initiated by Boltzmann, a Generalized Helmholtz Theorem is stated and proved. This theorem provides us with a good microscopic analogue of thermodynamic entropy. This is the volume entropy, namely the logarithm of the volume of phase space enclosed by the constant energy hyper-surface. By using quantum mechanics only, it is shown that such entropy can only increase. This can be seen as a novel rigorous proof of the Second Law of Thermodynamics that sheds new light onto the arrow of time problem. The volume entropy behaves in a thermodynamic-like way independent of the number of degrees of freedom of the system, indicating that a whole thermodynamic-like world exists at the microscopic level. It is also shown that breaking of ergodicity leads to microcanonical ...

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc6128/

### Multifunctional Organic-Inorganic Hybrid Nanophotonic Devices

**Date:**May 2008

**Creator:**Garner, Brett William

**Description:**The emergence of optical applications, such as lasers, fiber optics, and semiconductor based sources and detectors, has created a drive for smaller and more specialized devices. Nanophotonics is an emerging field of study that encompasses the disciplines of physics, engineering, chemistry, biology, applied sciences and biomedical technology. In particular, nanophotonics explores optical processes on a nanoscale. This dissertation presents nanophotonic applications that incorporate various forms of the organic polymer N-isopropylacrylamide (NIPA) with inorganic semiconductors. This includes the material characterization of NIPA, with such techniques as ellipsometry and dynamic light scattering. Two devices were constructed incorporating the NIPA hydrogel with semiconductors. The first device comprises a PNIPAM-CdTe hybrid material. The PNIPAM is a means for the control of distances between CdTe quantum dots encapsulated within the hydrogel. Controlling the distance between the quantum dots allows for the control of resonant energy transfer between neighboring quantum dots. Whereby, providing a means for controlling the temperature dependent red-shifts in photoluminescent peaks and FWHM. Further, enhancement of photoluminescent due to increased scattering in the medium is shown as a function of temperature. The second device incorporates NIPA into a 2D photonic crystal patterned on GaAs. The refractive index change of the NIPA hydrogel as ...

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc6108/

### Emergence of Complexity from Synchronization and Cooperation

**Date:**May 2008

**Creator:**Geneston, Elvis L.

**Description:**The dynamical origin of complexity is an object of intense debate and, up to moment of writing this manuscript, no unified approach exists as to how it should be properly addressed. This research work adopts the perspective of complexity as characterized by the emergence of non-Poisson renewal processes. In particular I introduce two new complex system models, namely the two-state stochastic clocks and the integrate-and-fire stochastic neurons, and investigate its coupled dynamics in different network topologies. Based on the foundations of renewal theory, I show how complexity, as manifested by the occurrence of non-exponential distribution of events, emerges from the interaction of the units of the system. Conclusion is made on the work's applicability to explaining the dynamics of blinking nanocrystals, neuron interaction in the human brain, and synchronization processes in complex networks.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc6107/

### Perturbation of renewal processes

**Date:**May 2008

**Creator:**Akin, Osman Caglar

**Description:**Renewal theory began development in the early 1940s, as the need for it in the industrial engineering sub-discipline operations research had risen. In time, the theory found applications in many stochastic processes. In this thesis I investigated the effect of seasonal effects on Poisson and non-Poisson renewal processes in the form of perturbations. It was determined that the statistical analysis methods developed at UNT Center for Nonlinear Science can be used to detect the effects of seasonality on the data obtained from Poisson/non-Poisson renewal systems. It is proved that a perturbed Poisson process can serve as a paradigmatic model for a case where seasonality is correlated to the noise and that diffusion entropy method can be utilized in revealing this relation. A renewal model making a connection with the stochastic resonance phenomena is used to analyze a previous neurological experiment, and it was shown that under the effect of a nonlinear perturbation, a non-Poisson system statistics may make a transition and end up in the of Poisson basin of statistics. I determine that nonlinear perturbation of the power index for a complex system will lead to a change in the complexity characteristics of the system, i.e., the system will reach ...

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc6140/

### Temporal Properties Of Dynamic Processes On Complex Networks

**Date:**December 2011

**Creator:**Turalska, Malgorzata A.

**Description:**Many social, biological and technological systems can be viewed as complex networks with a large number of interacting components. However despite recent advancements in network theory, a satisfactory description of dynamic processes arising in such cooperative systems is a subject of ongoing research. In this dissertation the emergence of dynamical complexity in networks of interacting stochastic oscillators is investigated. In particular I demonstrate that networks of two and three state stochastic oscillators present a second-order phase transition with respect to the strength of coupling between individual units. I show that at the critical point fluctuations of the global order parameter are characterized by an inverse-power law distribution and I assess their renewal properties. Additionally, I study the effect that different types of perturbation have on dynamical properties of the model. I discuss the relevance of those observations for the transmission of information between complex systems.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc103403/

### The Use of Mossbauer Effect for the Study of Recoilless Rayleigh Scattering of Low-Energy Gamma Rays from Sodium Chloride

**Date:**August 1963

**Creator:**Fowler, Eugene Franklin

**Description:**Evidence that recoilless emission and absorption exist may be shown by an experiment in which the source gamma rays are allowed to pass through a suitable absorber to a detector.

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**Permallink:**digital.library.unt.edu/ark:/67531/metadc108227/