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Cure Kinetics and Processing Parameters of Neat and Reinforced High Performance Epoxy Resins: Evaluation of Techniques

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Kinetic equation parameters for the curing reaction of a commercial glass fiber reinforced high performance epoxy prepreg composed of the tetrafunctional epoxy tetraglycidyl 4,4-diaminodiphenyl methane (TGDDM), the tetrafunctional amine curing agent 4,4’-diaminodiphenylsulfone (DDS) and an ionic initiator/accelerator, are determined by various thermal analysis techniques and the results compared. The reaction is monitored by heat generated determined by differential scanning calorimetry (DSC). The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC and temperature-modulated DSC (TMDSC), thermomechanical (TMA) and dynamic mechanical (DMA) analysis and thermally stimulated depolarization (TSD). Changes in viscosity, also indicative of degree of conversion, are monitored by DMA. Thermal stability as a function of degree of cure is monitored by thermogravimetric analysis (TGA). The parameters of the general kinetic equations, including activation energy and rate constant, are explained and used to compare results of various techniques. The utilities of the kinetic descriptions are demonstrated in the construction of a useful time-temperature-transformation (TTT) diagram for rapid determination of processing parameters in the processing of prepregs. Copyright is held by the author, unless otherwise noted. All rights reserved. Files: Thesis.pdf Special Conditions
Date: December 1999
Creator: Bilyeu, Bryan
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Hospitality Students' Attitudes and Behavioral Intentions toward Learning and Using Computer Technology

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Following Ajzen/Fishbein's 1980 Theory of Reasoned Action, influences of hospitality students' external variables (age, gender, university classification, and work experience) on computer attitudes, and relationships between computer attitudes and intentions to learn and use computers were tested. A sample of 412 hospitality students completed two measurements: Loyd/Gressard's 1984 Computer Attitude Scale, and Behavioral Intentions to Learn and Use Computers. Males and females had positive computer attitudes. Graduates had more positive computer attitudes. No interaction effect existed between gender and classification. No relationships existed between age and work experience on computer attitudes. Computer attitudes positively correlated with intentions to learn and use computers. Results supported the Theory of Reasoned Action. External variables partially influence attitudes and attitudes influence intentions.
Date: December 1999
Creator: Chuvessiriporn, Suttichai
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Development of a Coaxiality Indicator

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The geometric dimensioning and tolerancing concept of coaxiality is often required by design engineers for balance of rotating parts and precision mating parts. In current practice, it is difficult for manufacturers to measure coaxiality quickly and inexpensively. This study examines feasibility of a manually-operated, mechanical device combined with formulae to indicate coaxiality of a test specimen. The author designs, fabricates, and tests the system for measuring coaxiality of holes machined in a steel test piece. Gage Repeatability and Reproducibility (gage R&R) and univariate analysis of variance is performed in accordance with Measurement System Analysis published by AIAG. Results indicate significant design flaws exist in the current configuration of the device; observed values vary greatly with operator technique. Suggestions for device improvements conclude the research.
Date: December 1999
Creator: Arendsee, Wayne C.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Techniques of Sensual Perception: The Creation of Emotional Pathways

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Some artists strive to create artwork that has aesthetic value. If a piece of artwork has the ability to capture the attention of an audience, it must contain strong sensual attributes. Thus, understanding how to design an art form to contain strong sensual attributes may increase the possibility of an aesthetic experience. Since aesthetics is an experience of sensations perceived when in contact with a creative form in any artistic discipline, it is necessary for an artist to understand the nature of the sensual experience. In understanding the sensual experience, artists may be able to create techniques to enhance the aesthetic experience of their work. My video piece, entitled Ararat is a study of methods to enhance the sensual experience. I hope to accomplish this by means of using techniques that optimize an audience's perceptual experience.
Date: December 1999
Creator: Henry, Jon L.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Bird Bones and a Hatched Egg

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A fifty page manuscript of poetry and a critical introduction detailing the poet's aesthetics. Using the idea of the double-image and eroticism, the poet places her work in the category of the surreal. She describes the process of writing poetry born of fragmentary elements as a feminist emergence of agency. The manuscript is composed of four sections, each an element in the inevitable breakdown of a love relationship: meeting, love-making, birth of a child, death. Quotes from various authors of anthropological and fictional texts begin each section to reinforce thematic structure in a process of unveiling the agency of the narrator. The poems are organized as a series, beginning and ending with sequence poems.
Date: December 2000
Creator: Skebe, Carolyn Alifair
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effect of Attachment on Preschooler's Emotion Understanding

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The purpose of this study was to identify the relationship between attachment and emotion understanding in preschoolers. Data was collected from 16 preschool children and their mothers recruited from a private learning center in a downtown metropolitan area. Attachment was measured by use of the Attachment Q-sort, 3.0 (Waters, 1995), while emotion understanding was assessed through use of Denham's (1986) affective perspective-taking task and interviews of children concerning naturally occurring emotions and emotion causes (Fabes et al., 1991). Results included a significant correlation (p < .05) between secure attachment and preschooler's ability to decipher the cause of another's emotion; however, a significant correlation was not found between secure attachment and preschooler's perspective-taking ability or ability to name other's emotions. Thus, conclusions about the impact of attachment upon emotion understanding were mixed, and more research on the subject was implicated.
Date: December 2000
Creator: Hernandez, Jennie R.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Logic Programming Tools for Dynamic Content Generation and Internet Data Mining

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The phenomenal growth of Information Technology requires us to elicit, store and maintain huge volumes of data. Analyzing this data for various purposes is becoming increasingly important. Data mining consists of applying data analysis and discovery algorithms that under acceptable computational efficiency limitations, produce a particular enumeration of patterns over the data. We present two techniques based on using Logic programming tools for data mining. Data mining analyzes data by extracting patterns which describe its structure and discovers co-relations in the form of rules. We distinguish analysis methods as visual and non-visual and present one application of each. We explain that our focus on the field of Logic Programming makes some of the very complex tasks related to Web based data mining and dynamic content generation, simple and easy to implement in a uniform framework.
Date: December 2000
Creator: Gupta, Anima
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Sarah T. Hughes: Her Influence in Texas Politics

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Conservative males traditionally dominated Texas politics. In 1930, however, Sarah T. Hughes, a liberal woman from Maryland, began a spectacular career in state politics despite obstacles because of her gender and progressive ideas. First elected to the Texas Legislature in 1930, she remained active in politics for the next fifty years. Hard work, intelligence, and ability allowed her to form solid friendships with Texas's most powerful politicians. She became the first woman in Texas to hold a district judgeship, the first woman from Texas appointed to the federal bench, and the only woman to swear in a U.S. president. Hughes profoundly influenced state politics, challenging the long-standing conservative male domination. She helped to create a more diverse political field that today encompasses different ideologies and both genders.
Date: December 2000
Creator: Justiss, Charnita Spring
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Effects of Reinforcement History on Stimulus Control Relations

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Ray (1969) conducted an experiment on multiple stimulus-response relations and selective attention. Ray's (1969) results suggested that stimulus-response relations function as behavioral units. McIlvane and Dube (1996) indicated that if stimulus-response relations are behavioral units the effects of environmental variables on stimulus-response relations should be similar to the effects of environmental variables on single response topographies. This experiment analyzed the effects of reinforcement history on the probability of stimulus-response relations with differing reinforcement histories. In separate conditions random-ratio schedules of reinforcement were contingent on each of four discriminated responses. To assess the effects of reinforcement, during test conditions stimuli controlling different topographies were present concurrently in composite form. Results show that reinforcement history affects the probability of each response topography and that the association between response topographies and their controlling stimuli tends to remain constant throughout variations in reinforcement probability.
Date: December 2000
Creator: Reyes, Fredy
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Effect of Engineered Surfaces on Valve Performance

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Performance of air operated valves is a major maintenance concern in process industries. Anecdotal information indicates that reliability of some high maintenance valves has been improved by using an ion deposition process to achieve engineered surfaces on selected components. This project compared friction for various surface treatments of selected valve components. Results indicate valve performance may be slightly more consistent when an engineered surface is applied in the valve packing area; however surface treatment in this area does not appear to have a dominant affect on reducing valve friction. Results indicate a linear relation between stem friction and torque applied to packing flange nuts, and even after a valve is in service, controlled packing adjustments can be made without significantly changing valve stroke time.
Date: December 2000
Creator: Pope, Larry G.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Texas Annexation and the Presidential Election of 1844 in the Richmond, Virginia, and New Orleans, Louisiana, Newspaper

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This thesis examines the issue of Texas annexation from the viewpoints of two southern cities: Richmond, Virginia, and New Orleans, Louisiana. It looks primarily at four major newspapers, two in each city: the Richmond Enquirer and the Richmond Whig; and the New Orleans Times-Picayune and the New Orleans Whig. These four newspapers were examined thoroughly from January 1844 to July 1845. In addition to the above newspapers, the Congressional Globe and national voting patterns on Texas annexation were examined. Analysis of the editorial articles in the above newspapers offers the best possibility of understanding public sentiment toward Texas annexation and the presidential election of 1844. The evidence examined in this study indicates that Texas annexation became a decisive issue in the presidential election of 1844. It also shows that, although the press and elements within both Democratic and Whig parties were aware that the slavery question was intricately linked to the Texas annexation issue, slavery and sectional politics were not the primary factors influencing annexation. Ultimately, fundamental concerns regarding western expansion in general, especially for the Whigs, and political party loyalty proved the decisive factors in the presidential election of 1844 and Texas annexation. The evidence gathered in this study …
Date: December 2001
Creator: Short, Steven W.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels

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Aerogels are highly porous, low dielectric constant (low k) materials being considered by the semiconductor industry as an interlayer dielectric. Low k materials are needed to overcome capacitance problems that limit device feature sizes. Precursors triethoxyfluorosilane (TEFS) and tetraethoxysilane (TEOS) were used to prepare bulk aerogels. Samples were prepared by sol-gel methods, and then carbon dioxide supercritically-dried. Effects of varying the water to precursor ratio were studied with respect to aerogel properties and microstructure. Methods of analysis for this study include FTIR-ATR, TEM, RBS, EDS, SEM, dielectric constant determination by impedance and surface area by gas adsorption. Si-F bonds were determined to be present in both acid- and base-catalyzed TEFS as well as HF-catalyzed TEOS. Fluorine promotes a fractal network microstructure as opposed to a particle-like microstructure. Surface area and dielectric constant were determined to increase slightly with increases in the water to precursor ratio.
Date: December 2001
Creator: Roepsch, Jodi Ann
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Immediate and subsequent effects of fixed-time food presentations on automatically maintained mouthing.

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Several studies have demonstrated that fixed-time (FT) schedules of stimulus delivery can function to reduce a variety of behaviors. The purpose of this study was to evaluate the immediate and subsequent effects of FT food deliveries on mouthing. In Phase 1, a preference assessment showed that caramel popcorn, chocolate cookies and pretzels were highly preferred food items. Thus, providing the basis for use of food items during treatment. In Phase 2, a functional analysis showed that mouthing was a nonsocially maintained problem behavior. Phase 3 demonstrated the use of FT schedules of food deliveries as treatment for nonsocially maintained mouthing. Results indicated that FT schedules of food significantly reduced mouthing. In addition, levels of mouthing observed during post-FT observations were reliably lower than pre-FT observations. Treatment effects, operative mechanisms responsible for the treatment effects and the experimental arrangement used to investigate varying FT schedules are discussed.
Date: December 2001
Creator: Simmons, Jason N.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Microwave Cavity Test for Superconductivity

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The first part of this paper describes the Meissner effect in superconductors which serves as the most definitive evidence for superconductivity. It is shown that the microwave perturbation technique may be used to demonstrate this effect. By measuring the changes of resonant frequency and inverse quality factor Q of a microwave cavity with a small volume of sample loading, the Meissner effect can be shown by using the Slater perturbation equation. The experimental system is described with details and the basic principle of each component discussed. The second part of this work describes the technique employed to do the actual measurements. The experiments were conducted on samples of Gallium Arsenide (GaAs) and lead zirconate titanate (PZT) to look for the possible high temperature superconductivity properties. Results of these experiments are presented and discussed. Conclusion and suggestions to future exploration are made.
Date: December 2001
Creator: Tang, Shan
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Mineral-filled polypropylene: Improvement of scratch resistance

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A potential alternative to acrylonitrile-butadiene-styrene (ABS) and polycarbonate+ABS (PC+ABS), pigmented mineral-filled polypropylene (PP) finds an opening in automotive interior components such as instrument panels, knee bolsters, consoles, etc. Because of the lack of surface aesthetics, pigmented mineral-filled PP is experiencing a limitation to its acceptance in many applications. This study focuses on exploring various mineral fillers and additives in polypropylene to provide a material with enhanced scratch resistance. Several physical properties including Rockwell and Shore D hardness are investigated, and it is determined that Filler W improves scratch resistance. It is also determined that Filler T-filled-PP has poor scratch resistance even with the addition of a lubricant.
Date: December 2001
Creator: Khatib, Jamal F.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effect of Punishment Threat on Children's Ability to Resist Temptation to Transgress and Lie

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Children's response to a resistance-to-temptation (RTT) task was investigated under three punishment threat conditions: negative consequence, removing an anticipated reward, and no explicit punishment. Ninety first and second graders participated in the RTT task and seventy-three parents completed the Behavior Assessment System for Children and the Psychopathy Screening Device. As only 4% of children transgressed, results are unclear. Hypotheses tested using approximations of transgression showed no differences in RTT. Children with temperaments characterized by hyperactivity, impulsivity, attention problems, and conduct problems (HIA-CP) had the highest levels of psychopathic traits compared to all others. In addition, spanked children were rated as having significantly more behavioral problems than non-spanked children. Limitations of the current study and suggestions for future research are discussed.
Date: December 2001
Creator: Collins, Michelle
Object Type: Thesis or Dissertation
System: The UNT Digital Library

A laboratory course in experimental genetics for the biology major.

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This manual has been designed for a class of twenty- four students concurrently enrolled in the lecture course. The laboratory aids in the learning process and fosters an interest in the science of genetics. This manual and the experiments contained within are both informative and fun. The manual correlates with and expands upon the genetics course. Each investigation, with the exception of the Drosophila melanogaster project, can be completed in a 3-4 hour timeframe. This manual provides a “hands on” experience of theories simply discussed in the lecture course. This manual is intended to be a one-source manual where each investigation is designed to include an adequate introduction. Special attention has been given for each investigation with both the student and instructor in mind.
Date: December 2001
Creator: Lux, Melissa McNeil
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effects of Color Concentrate in Polyolefins.

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Throughout history consumer products were generally manufactured from wood and metal. They either had to hold their natural color or become subject to painting. When plastics entered the industry, it was recognized for its ease of shaping, re-usability, physical properties and its low cost. One of plastics' greatest benefits is its ability to hold a given color from within allowing it to avoid use of paint. This paper will give a brief overview on the effects of pigments when incorporated in a polyolefin. It will provide a classification of the main types of pigments and how each effect the properties of the product through: crystallization, weatherability, opacity, coloristic values and of course viscosity.
Date: December 2001
Creator: Flora, Paul
Object Type: Thesis or Dissertation
System: The UNT Digital Library

An Etiology of Juvenile Homicide in Dallas, Texas: 1988-1997

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This research analyzed all juveniles involved in a homicide, both victims and offenders, in the city of Dallas, Texas from the years 1988 through 1997. This study addressed several research questions including the identification of risk factors common to both victims and offenders. Data for this study was obtained from the homicide files of the Dallas Police Department. The findings in part identify specific profiles of the victims and offenders, as well as identifying comparisons of risk factors between the two groups. Also identified are the relationships between the offenders and victims. Conclusions from this research present implications for law enforcement agencies, as well as furthering the etiology of juvenile homicide.
Date: December 2001
Creator: Haynes, Joseph
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Development of a Pre-Impact Environmental Site Characterization for the Bryan Mound, Texas Strategic Petroleum Reserve

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This thesis presents a model for developing site-specific contingency plans to be used during spill response, remediation, and post-spill monitoring using the Strategic Petroleum Reserve's Bryan Mound site as a case study. Bird and vegetation observations provide baseline data for biological conditions, and sediment sampling for total petroleum hydrocarbons serves as a chemical component of the model. Results demonstrate previously unknown conditions that would hinder remediation and affect the persistence of petroleum contaminants. Results also established previously unmapped dominant bird and vegetation types likely to be impacted by a spill at the site. This model points to a reconsideration of individual facilities' responsibilities when planning for large-scale disasters and protecting the sensitive ecosystems surrounding their sites.
Date: December 2001
Creator: Hernandez, Sylvia A.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Characterization of Moraxella bovis Aspartate Transcarbamoylase

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Aspartate transcarbamoylase (ATCase) catalyzes the first committed step in the pyrimidine biosynthetic pathway. Bacterial ATCases have been divided into three classes, class A, B, and C, based on their molecular weight, holoenzyme architecture, and enzyme kinetics. Moraxella bovis is a fastidious organism, the etiologic agent of infectious bovine keratoconjunctivitis (IBK). The M. bovis ATCase was purified and characterized for the first time. It is a class A enzyme with a molecular mass of 480 to 520 kDa. It has a pH optimum of 9.5 and is stable at high temperatures. The ATCase holoenzyme is inhibited by CTP > ATP > UTP. The Km for aspartate is 1.8 mM and the Vmax 1.04 µmol per min, where the Km for carbamoylphosphate is 1.05 mM and the Vmax 1.74 µmol per min.
Date: December 2001
Creator: Hooshdaran, Sahar
Object Type: Thesis or Dissertation
System: The UNT Digital Library

The Effects of Reinforcing Operant Variability on Task Acquisition

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Neuringer, Deiss, and Olson (2000) was replicated and extended to determine the effect of variability contingencies on task acquisition for twelve 7-9 year old children. Subjects first learned to press a computer's shift keys with increasing response variation. Each subject was then exposed to one of three experimental conditions during which they received a point for target responses. Variability condition subjects received additional points on a variable interval schedule for nontarget responses occurring less than 3% of the time. The any condition subjects received additional points on a variable interval schedule for any nontarget response. Control subjects received points only for target responses. All variability condition and two control subjects learned the target response. All any condition subjects and two control subjects did not.
Date: December 2002
Creator: Seymour, Kail H.
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Performance Evaluation of MPLS on Quality of Service in Voice Over IP (VoIP) Networks

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The transmission of voice data over Internet Protocol (IP) networks is rapidly gaining acceptance in the field of networking. The major voice transmissions in the IP networks are involved in Internet telephony, which is also known as IP telephony or Voice Over IP (VoIP). VoIP is undergoing many enhancements to provide the end users with same quality as in the public switched telephone networks (PSTN). These enhancements are mostly required in quality of service (QoS) for the transmission of voice data over the IP networks. As with recent developments in the networking field, various protocols came into market to provide the QoS in IP networks - of them, multi protocol label switching (MPLS) is the most reliable and upcoming protocol for working on QoS. The problem of the thesis is to develop an IP-based virtual network, with end hosts and routers, implement MPLS on the network, and analyze its QoS for voice data transmission.
Date: December 2002
Creator: Chetty, Sharath
Object Type: Thesis or Dissertation
System: The UNT Digital Library

Integrating life cycle analysis and the ecological footprint calculator to foster sustainable behaviors

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Many tools have been developed to assess global, national or regional sustainable development policies. However, as governments develop sustainable policies, individuals must also feel empowered to affect their personal impact on the planet. This thesis integrates three sustainability concepts that lend themselves to individual sustainability: The natural step, life cycle assessment, and the ecological footprint. TNS serves to provide the meaning and substance toward sustainable development. LCA helps provide the framework for assessing sustainability. The EF calculator determines the driving components and measures the qualitative decisions made through TNS and LCA. From the analysis of the household footprint calculator a simplified footprint calculator was developed to assist individuals and communities in setting benchmarks and goals as they move away from over-consumption and towards a sustainable lifestyle.
Date: December 2002
Creator: Anderle, Kathryn
Object Type: Thesis or Dissertation
System: The UNT Digital Library