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A Compton scatter camera for spectral imaging of 0.5 to 3.0 MeV gamma rays
A prototype Compton scatter camera for imaging gamma rays has been built and tested. This camera addresses unique aspects of gamma-ray imaging at nuclear industrial sites, including gamma-ray energies in the 0.5 to 3.0 MeV range and polychromatic fields. Analytic models of camera efficiency, resolution and contaminating events are developed. The response of the camera bears strong similarity to emission computed tomography devices used in nuclear medicine. A direct Fourier based algorithm is developed to reconstruct two-dimensional images of measured gamma-ray fields. Iterative ART and MLE algorithms are also investigated. The point response of the camera to gamma rays of energies from 0.5 to 2.8 MeV is measured and compared to the analytic models. The direct reconstruction algorithm is at least ten times more efficient than the iterative algorithms are also investigated. The point response of the camera to gamma rays energies from 0.5 to 2.8 MeV is measured and compared to the analytic models. The direct reconstruction algorithm is at least ten times more efficient than the iterative algorithms and produces images that are, in general, of the same quality. Measured images of several phantoms are shown. Important results include angular resolutions as low as 4.4{degrees}, reproduction of phantom …
Date:
December 31, 1994
Creator:
Martin, J.B.
System:
The UNT Digital Library
Evaluation of low-level radioactive waste characterization and classification programs of the West Valley Demonstration Project
The West Valley Demonstration Project (WVDP) is preparing to upgrade their low-level radioactive waste (LLW) characterization and classification program. This thesis describes a survey study of three other DOE sites conducted in support of this effort. The LLW characterization/classification programs of Oak Ridge National Laboratory, Savannah River Site, and Idaho National Engineering Laboratory were critically evaluated. The evaluation was accomplished through tours of each site facility and personnel interviews. Comparative evaluation of the individual characterization/classification programs suggests the WVDP should purchase a real-time radiography unit and a passive/active neutron detection system, make additional mechanical modifications to the segmented gamma spectroscopy assay system, provide a separate building to house characterization equipment and perform assays away from waste storage, develop and document a new LLW characterization/classification methodology, and make use of the supercompactor owned by WVDP.
Date:
December 31, 1994
Creator:
Taie, K.R.
System:
The UNT Digital Library
An experimental study of fluidelastic instability and draf force on a tube in two-phase cross flow
Two-phase cross flow over heat exchanger tubes creates vibrations which contribute greatly to the wear on the tubes. Fluidelastic instability is a major mechanism by which tubes can fail. In this work, the fluidelastic instability of a tube placed in an array subjected to two-phase cross flow has been studied. For the determination of fluidelastic instability, a triangular tube array was used. The tubes were made of acrylic and were 2.2 cm or 2.37 cm in diameter and 20 cm in length. Eighteen tubes and 4 half tubes formed 5 rows with a pitch to diameter ratio of 1.4. All of the tubes except the test tube were rigidly supported at the text section wall. The test tube was flexibly supported with two cantilever beams. By installing cantilever beams horizontally and vertically, drag and lift direction tube vibration were studied. Parameters of tube mass, structural stiffness, natural frequency, and pitch to diameter ratio were varied. The drag coefficients on a rigidly held tube in an array subjected to two-phase cross flow were measured. The tube in an array was located at displaced positions as well as at the normal position in order to study the variation of fluid force as …
Date:
December 31, 1994
Creator:
Joo, Youngcheol
System:
The UNT Digital Library
Further studies of the effects of oxidation on the surface properties of coal and coal pyrite
The objective of this research was to investigate the oxidation behavior of coal and coal pyrite and to correlate the changes in the surface properties induced by oxidation, along with the intrinsic physical and chemical properties of these organic and inorganic materials, with the behavior in physical coal cleaning processes. This provide more fundamental knowledge for understanding the way in which different factors interact in a medium as heterogeneous as coal. Fourteen coal samples of different ranks ranging from high to medium sulfur content were studied by dry oxidation tests at different temperatures and humidities, and by wet oxidation tests using different oxidizing agents. The concentration of surface oxygen functional groups was determined by ion-exchange methods. The changes in the coal composition with oxidation were analyzed by spectroscopic techniques. The wettability of as-received and oxidized coal and coal pyrite samples was assessed by film flotation tests. The electrokinetic behavior of different coals and coal pyrite samples was studied by electrokinetic tests using electrophoresis. Possible oxidation mechanisms have been proposed to explain the changes on the coal surface induced by different oxidation treatments.
Date:
December 31, 1994
Creator:
Herrera, Miguel Nicholas
System:
The UNT Digital Library
Measurements of granular flow dynamics with high speed digital images
The flow of granular materials is common to many industrial processes. This dissertation suggests and validates image processing algorithms applied to high speed digital images to measure the dynamics (velocity, temperature and volume fraction) of dry granular solids flowing down an inclined chute under the action of gravity. Glass and acrylic particles have been used as granular solids in the experiment. One technique utilizes block matching for spatially averaged velocity measurements of the glass particles. This technique is compared with the velocity measurement using an optic probe which is a conventional granular flow velocity measurement device. The other technique for measuring the velocities of individual acrylic particles is developed with correspondence using a Hopfield network. This technique first locates the positions of particles with pattern recognition techniques, followed by a clustering technique, which produces point patterns. Also, several techniques are compared for particle recognition: synthetic discriminant function (SDF), minimum average correlation energy (MACE) filter, modified minimum average correlation energy (MMACE) filter and variance normalized correlation. The author proposes an MMACE filter which improves generalization of the MACE filter by adjusting the amount of averaged spectrum of training images in the spectrum whitening stages of the MACE filter. Variance normalized correlation …
Date:
December 31, 1994
Creator:
Lee, J.
System:
The UNT Digital Library
Modeling the effects of atmospheric emissions on groundwater composition
A composite model of atmospheric, unsaturated and groundwater transport is developed to evaluate the processes determining the distribution of atmospherically derived contaminants in groundwater systems and to test the sensitivity of simulated contaminant concentrations to input parameters and model linkages. One application is to screen specific atmospheric emissions for their potential in determining groundwater age. Temporal changes in atmospheric emissions could provide a recognizable pattern in the groundwater system. The model also provides a way for quantifying the significance of uncertainties in the tracer source term and transport parameters on the contaminant distribution in the groundwater system, an essential step in using the distribution of contaminants from local, point source atmospheric emissions to examine conceptual models of groundwater flow and transport.
Date:
December 31, 1994
Creator:
Brown, T. J.
System:
The UNT Digital Library
Plasma destruction of North Carolina`s hazardous waste based on hazardous waste generated between the years of 1989 and 1992
The purpose of this research is to analyze the applicability of the plasma waste destruction technology to North Carolina hazardous waste streams. This study outlines the current regulations, existing technologies, and innovative technologies being considered as hazardous waste treatment alternatives. From this foundation, the study proceeds to identify the superiority of the plasma waste destruction technology. Specific areas of discussion include: temperature capabilities, waste residence time requirements, destruction removal efficiencies, operational efficiencies, economic issues, safety, and maintenance. This study finds the plasma destruction technology to be fully effective and superior to conventional facilities. The technology completely destroys hydrocarbons and can reduce the volume of many other hazardous wastes on the order of one part per million. The required residence time of waste in a plasma facility for effective destruction is a fraction of a second, while the rotary kiln incinerator maintains an average residence time of approximately 5 seconds. Also mass and heat balance calculations are performed to quantify the effectiveness and efficiency of this technology. It is found that one day`s average amount of hazardous waste generated in the state of North Carolina can be destroyed in approximately thirty seconds using a standard one megawatt power source. Yet, before …
Date:
December 31, 1994
Creator:
Williams, D.L.
System:
The UNT Digital Library
{sup 222}Rn in water: A comparison of two sample collection methods and two sample transport methods, and the determination of temporal variation in North Carolina ground water
Objectives of this field experiment were: (1) determine whether there was a statistically significant difference between the radon concentrations of samples collected by EPA`s standard method, using a syringe, and an alternative, slow-flow method; (2) determine whether there was a statistically significant difference between the measured radon concentrations of samples mailed vs samples not mailed; and (3) determine whether there was a temporal variation of water radon concentration over a 7-month period. The field experiment was conducted at 9 sites, 5 private wells, and 4 public wells, at various locations in North Carolina. Results showed that a syringe is not necessary for sample collection, there was generally no significant radon loss due to mailing samples, and there was statistically significant evidence of temporal variations in water radon concentrations.
Date:
December 31, 1994
Creator:
Hightower, J. H., III
System:
The UNT Digital Library
Analysis of dynamic testing performed on structural clay tile infilled frames
The behavior of two structural clay tile infilled frames subjected to dynamic loading is investigated. The testing was performed by USACERL using a biaxial shake table machine on which two framed infills were spaced nine feet apart and connected by steel trusses and an eight inch concrete roof slab. The infills were composed of structural clay tile block which were laid with the cores horizontal. The specimen was loaded in both the out-of-plane and in-plane directions using a site specific time history record. The testing focused on determining frame and panel load-deflection behavior, acceleration amplification, and frequency degradation characteristics. The out-of-plane tests resulted in little degradation of frequency which means there was little loss of stiffness. There was no evidence of the infill {open_quotes}walking-out{close_quotes} of the steel frame; in fact the infill still had substantial stability after completion of the out-of-plane tests. As a result of the gradual increase in ground motion in the in-plane testing, the stiffness of the specimen gradually decreased. Strength and stiffness characteristics obtained from the dynamic testing were comparable to results and behavior seen in static tests. Degradation in the panel was much more rapid under the stronger ground motions which were produced during the …
Date:
December 18, 1994
Creator:
Fowler, J. J.
System:
The UNT Digital Library
Differential geometry on Hopf algebras and quantum groups
The differential geometry on a Hopf algebra is constructed, by using the basic axioms of Hopf algebras and noncommutative differential geometry. The space of generalized derivations on a Hopf algebra of functions is presented via the smash product, and used to define and discuss quantum Lie algebras and their properties. The Cartan calculus of the exterior derivative, Lie derivative, and inner derivation is found for both the universal and general differential calculi of an arbitrary Hopf algebra, and, by restricting to the quasitriangular case and using the numerical R-matrix formalism, the aforementioned structures for quantum groups are determined.
Date:
December 15, 1994
Creator:
Watts, P.
System:
The UNT Digital Library
Accelerator Mass Spectrometry Studies of Highly Charged Molecular Ions
The existence of singly, doubly, and triply charged diatomic molecular ions was observed by using an Accelerator Mass Spectrometry (AMS) technique. The mean lifetimes of 3 MeV boron diatomic molecular ions were measured. No isotopic effects on the mean lifetimes of boron diatomic molecules were observed for charge state 3+. Also, the mean lifetime of SiF^3+ was measured.
Date:
December 1994
Creator:
Kim, Yong-Dal
System:
The UNT Digital Library
Accounting Measurement Bias and Executive Compensation Systems
This dissertation presents empirical evidence intended to help answer two research questions. The first question asks whether executive compensation systems appear to exploit the bias in accounting-based performance measures in order to reduce the volatility in executive compensation and to allocate incentives more effectively across the range of activities performed by the executive. The second question asks whether compensation systems systematically differ between firms that use alternative accounting methods and whether any such systematic difference helps explain accounting choice. Parameters estimated in fixed-effects endogenous switching regression models were used to test the risk-shielding and incentive-allocation hypotheses. The models were estimated across a dataset consisting of 1151 executive-year observations of annual compensation paid to 222 top-level executives in 40 oil and gas firms. The dataset was partitioned by accounting method and separate models estimated for the full cost and successful efforts partitions. The tests provided modest support for the risk-shielding and incentive-allocation hypotheses, revealing that accounting measurement bias is used to focus incentives for effort in the exploration activity and to reduce executives' exposure to production risk. The design also allowed an estimate of the proportional change in compensation that was realized from the accounting choice actually made.
Date:
December 1994
Creator:
Boone, Jeffery Paul
System:
The UNT Digital Library
Actinide cation-cation complexes
The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO{sub 2}{sup +}) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO{sub 2}{sup +}; therefore, cation-cation complexes indicate something unique about AnO{sub 2}{sup +} cations compared to actinide cations in general. The first cation-cation complex, NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO{sub 2}{sup +} species, the cation-cation complexes of NpO{sub 2}{sup +} have been studied most extensively while the other actinides have not. The only PuO{sub 2}{sup +} cation-cation complexes that have been studied are with Fe{sup 3+} and Cr{sup 3+} and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, NpO{sub 2}{sup +}{center_dot}Th{sup 4+}, PuO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, …
Date:
December 1994
Creator:
Stoyer, N. J. & Seaborg, G. T.
System:
The UNT Digital Library
Addition, Omission and Revision: the Stylistic Changes Made to Zehn Variationen über ein Präludium von Chopin by Ferruccio Busoni
This study examines what Busoni meant by "formal deficiencies" when he described his 1884 version of Chopin Variations, and reveals that changes made to the 1884 version during its process of revision in 1922 correct the "formal deficiencies" and show a fundamental change in Busoni's compositional style and perception of musical motion. Including a detailed analysis of the modifications, omissions, and additions made to the 1922 version (including an examination of the Chopin Prelude in C minor, op. 28, No. 20 as a theme to reveal aspects of its construction used in the variation process), which shows how these changes affect the work's compositional structure.
Date:
December 1994
Creator:
Yoon, Soomee
System:
The UNT Digital Library
Adsorbate-enhanced Corrosion Processes at Iron and Iron Oxide Surfaces
This study was intended to provide a fuller understanding of the surface chemical processes which result in the corrosion of ferrous materials.
Date:
December 1994
Creator:
Murray, Eric
System:
The UNT Digital Library
Adult Survivors of Childhood Sexual Abuse : Characteristics of the Mother-child Relationship
This qualitative study examined the characteristics of the mother-child relationship of adult survivors of childhood sexual abuse at the time of the abuse. The study consisted of data from the McMaster Family Assessment Device (FAD), the Family of Origin Scale (FOS), and a set of structured interview questions designed by the researcher. Autonomy/intimacy concepts from the FOS examined constructs of clarity of expression, responsibility, respect, openness, acceptance of loss and separation, expression of a wide range of feelings, conflict resolution, mood and tone, and empathy.
Date:
December 1994
Creator:
Motley, Rebecca Roper
System:
The UNT Digital Library
Advanced far infrared detector and double donor studies in Ge
This has application to astronomy and astrophysics. Selenium in Ge has been studied with a doping technique which limits complex formation. Only one ionization level has been found to correspond to selenium, which presumably occupies a substitutional site. This level is extremely unstable and its concentration decreases after annealing at 400C. Future work is planned to anneal the fast neutron damage before much selenium has formed in the {sup 74/76}Ge samples. It is expected that the observed selenium level can be better characterized and the missing selenium level is more likely to be discovered if other defects are removed before {sup 77}Se formation.
Date:
December 1, 1994
Creator:
Olsen, C.S.
System:
The UNT Digital Library
An Analysis of the Management and Leadership Development Training Needs of Texas Principals on the Texas State Board of Education's Core Curriculum
The problem of this study was to determine training priorities as mandated by the Texas Legislature on the CORE Curriculum for Management and Leadership Development and their implications for Texas public school principals. Purposes of the study were to validate an instrument for assessing principals' training needs, to provide data for planning and delivering training for principals, to provide results to staff developers, and to develop a profile of similarities and differences in the perceptions of principals and their superordinates.
Date:
December 1994
Creator:
Morris, Amelia Marie
System:
The UNT Digital Library
An Application of Grundgestalt Theory in the Late Chromatic Music of Chopin: a Study of his Last Three Polonaises
The late chromatic music of Chopin is often difficult to analyze, particularly with a system of Roman numerals. The study examines Schoenberg's Grundgestalt concept as a strategy for explaining Chopin's chromatic musical style. Two short Chopin works, Nocturne in E-flat major. Op. 9, No. 2, and Etude in E major, Op. 10, No. 3, serve as models in which the analytic method is formulated. Root analysis, in the manner of eighteenth-century theorist Simon Sechter, is utilized to facilitate harmonic analysis of chromatic passages. Based upon the analytic method developed, the study analyzes the last three polonaises of Chopin: Polonaise in F-sharp minor, Op. 44, Polonaise in A-flat major, Op. 53, and Polonaise-Fantasie in A-flat major, Op. 61. The Grundgestalt-based analysis shows harmonic, melodic and rhythmic connections in order to view Chopin's chromaticism and formal structure from a new perspective. With this approach, the chromaticism is viewed as essential to the larger form.
Date:
December 1994
Creator:
Spicer, Mark Joseph
System:
The UNT Digital Library
The Application of Statistical Classification to Business Failure Prediction
Bankruptcy is a costly event. Holders of publicly traded securities can rely on security prices to reflect their risk. Other stakeholders have no such mechanism. Hence, methods for accurately forecasting bankruptcy would be valuable to them. A large body of literature has arisen on bankruptcy forecasting with statistical classification since Beaver (1967) and Altman (1968). Reported total error rates typically are 10%-20%, suggesting that these models reveal information which otherwise is unavailable and has value after financial data is released. This conflicts with evidence on market efficiency which indicates that securities markets adjust rapidly and actually anticipate announcements of financial data. Efforts to resolve this conflict with event study methodology have run afoul of market model specification difficulties. A different approach is taken here. Most extant criticism of research design in this literature concerns inferential techniques but not sampling design. This paper attempts to resolve major sampling design issues. The most important conclusion concerns the usual choice of the individual firm as the sampling unit. While this choice is logically inconsistent with how a forecaster observes financial data over time, no evidence of bias could be found. In this paper, prediction performance is evaluated in terms of expected loss. Most …
Date:
December 1994
Creator:
Haensly, Paul J.
System:
The UNT Digital Library
An Assessment of Employee Satisfaction within a Major Unit of a Worldwide Hotel and Resort Management Company
The purpose of this study was to assess the satisfaction level of 240 employees of a single hotel property. The questionnaire, administered by the Corporate Director of Training, determined if a significant difference exists between overall satisfaction and individual departmental satisfaction regarding 11 dimensions: customer satisfaction, employee involvement/teamwork, work environment, training/development/evaluation, communication, compensation/benefits, supervision, resources, planning/goal setting, general, and departmental interaction. Percentages and t tests were used to analyze the data. Results of the study will help management recommend courses of action needed to address identified problem areas.
Date:
December 1994
Creator:
Aranson, Anne (Anne Elizabeth)
System:
The UNT Digital Library
Assimilation of Baroque and Classical Essence with Romantic Sentiment: a Structural Analysis of Felix Mendelssohn-Bartholdy's Sonata in C Minor for Organ, Opus 62, No. 2
The purpose of this study is to examine Sonata No. 2 in detail from many analytical perspectives including melodies, rhythms, harmonic progressions, tonal plans, voice leading, and cadential patterns on macro- and micro-levels. It is believed that a more in-depth discussion of the composition from the perspective of harmony and voice leading may provide answer for the questions raised, and correct some misinterpretations in the works of certain writers. Furthermore, through analysis of Sonata No. 2. this study will show the relationship of the use of formal, stylistic, harmonic features between Mendelssohn and other composers of the eighteenth and nineteenth centuries.
Date:
December 1994
Creator:
Chou, Kwong-Yan Godwin
System:
The UNT Digital Library
Attenuation of Escherichia Coli Aspartate Transcarbamoylase Expressed in Pseudomonas Aeruginosa Mutant and Wild Type Strains
No apparent repression of pyr gene expression in Pseudomonas aeruginosa is observed upon addition of exogenous pyrimidines to the growth medium. Upon introduction of the subcloned Escherichia coli pyrBI genes for aspartate transcarbamoylase (ATCase) into a P. aeruginosa pyrB mutant strain, repression was observed in response to exogenously fed pyrimidine compounds. The results proved that it is possible to bring about changes in pyrimidine nucleotide pool levels and changes in transcriptional regulation of gene expression as a result. Thus, the lack of regulatory control in P. aeruginosa pyr gene expression is not due to an inability to take up and incorporate pyrimidine compounds into metabolic pools, or to an inability of the RNA polymerase to respond to regulatory sequences in the DNA but is probably due to a lack of specific regulatory signals in the promoter of the genes themselves.
Date:
December 1994
Creator:
Liu, Haiyan, 1966-
System:
The UNT Digital Library
Booker T. Washington and the Myth of Accommodation
Since his rise to fame in the late nineteenth century, Booker T. Washington has been incorrectly labeled a compromiser and power-hungry politician who sacrificed social progress for his own advancement. Through extensive research of Washington's personal papers, speeches, and affiliations, it has become apparent that the typical characterizations of Washington are not based exclusively in fact. The paper opens with an overview of Washington's philosophy, followed by a discussion of Washington's rise to power and consolidation of his "Tuskegee Machine," and finally the split that occurred within the African-American community with the formation of the NAACP. The thesis concludes that, while Washington's tactics were different from and far less visible than those of more militant black leaders, they were nonetheless effective in the overall effort.
Date:
December 1994
Creator:
Brennan, Douglas C. (Douglas Carl)
System:
The UNT Digital Library