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Fluid Dynamics of Carbon Dioxide Disposal into Saline Aquifers
Injection of carbon dioxide (CO{sub 2}) into saline aquifers has been proposed as a means to reduce greenhouse gas emissions (geological carbon sequestration). Large-scale injection of CO{sub 2} will induce a variety of coupled physical and chemical processes, including multiphase fluid flow, fluid pressurization and changes in effective stress, solute transport, and chemical reactions between fluids and formation minerals. This work addresses some of these issues with special emphasis given to the physics of fluid flow in brine formations. An investigation of the thermophysical properties of pure carbon dioxide, water and aqueous solutions of CO{sub 2} and NaCl has been conducted. As a result, accurate representations and models for predicting the overall thermophysical behavior of the system CO{sub 2}-H{sub 2}O-NaCl are proposed and incorporated into the numerical simulator TOUGH2/ECO{sub 2}. The basic problem of CO{sub 2} injection into a radially symmetric brine aquifer is used to validate the results of TOUGH2/ECO2. The numerical simulator has been applied to more complex flow problem including the CO{sub 2} injection project at the Sleipner Vest Field in the Norwegian sector of the North Sea and the evaluation of fluid flow dynamics effects of CO{sub 2} injection into aquifers. Numerical simulation results show that …
Date:
December 18, 2003
Creator:
Garcia, Julio Enrique
System:
The UNT Digital Library
Nitrogen doped zinc oxide thin film
To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO{sub 2} plasma or by N{sup +} implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zn{sub i}, a native shallow donor. In NO{sub 2}-grown ZnO films, the n-type conductivity is attributed to (N{sub 2}){sub O}, a shallow double donor. In NO{sub 2}-grown ZnO films, 0.3 atomic % nitrogen was found to exist in the form of N{sub 2}O and N{sub 2}. Upon annealing, N{sub 2}O decomposes into N{sub 2} and O{sub 2}. In furnace-annealed samples N{sub 2} redistributes diffusively and forms gaseous N{sub 2} bubbles in the films. Unintentionally doped ZnO films were grown at different oxygen partial pressures. Zni was found to form even at oxygen-rich condition and led to n-type conductivity. N{sup +} implantation into unintentionally doped ZnO film deteriorates the crystallinity and optical properties and leads to higher electron concentration. The free electrons in the implanted films are attributed to the defects introduced by implantation and formation of (N{sub 2}){sub O} and Zni. Although today there is still no reliable means to produce good …
Date:
December 15, 2003
Creator:
Li, Sonny X.
System:
The UNT Digital Library
Bioanalytical Applications of Real-Time ATP Imaging Via Bioluminescence
The research discussed within involves the development of novel applications of real-time imaging of adenosine 5'-triphosphate (ATP). ATP was detected via bioluminescence and the firefly luciferase-catalyzed reaction of ATP and luciferin. The use of a microscope and an imaging detector allowed for spatially resolved quantitation of ATP release. Employing this method, applications in both biological and chemical systems were developed. First, the mechanism by which the compound 48/80 induces release of ATP from human umbilical vein endothelial cells (HUVECs) was investigated. Numerous enzyme activators and inhibitors were utilized to probe the second messenger systems involved in release. Compound 48/80 activated a G{sub q}-type protein to initiate ATP release from HUVECs. Ca{sup 2+} imaging along with ATP imaging revealed that activation of phospholipase C and induction of intracellular Ca{sup 2+} signaling were necessary for release of ATP. Furthermore, activation of protein kinase C inhibited the activity of phospholipase C and thus decreased the magnitude of ATP release. This novel release mechanism was compared to the existing theories of extracellular release of ATP. Bioluminescence imaging was also employed to examine the role of ATP in the field of neuroscience. The central nervous system (CNS) was dissected from the freshwater snail Lymnaea stagnalis. …
Date:
December 12, 2003
Creator:
Gruenhagen, Jason Alan
System:
The UNT Digital Library
Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals
In this dissertation, they have undertaken the challenge to understand the unusual propagation properties of the photonic crystal (PC). The photonic crystal is a medium where the dielectric function is periodically modulated. These types of structures are characterized by bands and gaps. In other words, they are characterized by frequency regions where propagation is prohibited (gaps) and regions where propagation is allowed (bands). In this study they focus on two-dimensional photonic crystals, i.e., structures with periodic dielectric patterns on a plane and translational symmetry in the perpendicular direction. They start by studying a two-dimensional photonic crystal system for frequencies inside the band gap. The inclusion of a line defect introduces allowed states in the otherwise prohibited frequency spectrum. The dependence of the defect resonance state on different parameters such as size of the structure, profile of incoming source, etc., is investigated in detail. For this study, they used two popular computational methods in photonic crystal research, the Finite Difference Time Domain method (FDTD) and the Transfer Matrix Method (TMM). The results for the one-dimensional defect system are analyzed, and the two methods, FDTD and TMM, are compared. Then, they shift their attention only to periodic two-dimensional crystals, concentrate on their …
Date:
December 12, 2003
Creator:
Foteinopoulou, Stavroula
System:
The UNT Digital Library
Homogeneous Precipitation of Nickel Hydroxide Powders
Precipitation and characterization of nickel hydroxide powders were investigated. A comprehensive precipitation model incorporating the metal ion hydrolysis, complexation and precipitation reactions was developed for the production of the powders with urea precipitation method. Model predictions on Ni{sup 2+} precipitation rate were confirmed with precipitation experiments carried out at 90 C. Experimental data and model predictions were in remarkable agreement. Uncertainty in the solubility product data of nickel hydroxides was found to be the large contributor to the error. There were demonstrable compositional variations across the particle cross-sections and the growth mechanism was determined to be the aggregation of primary crystallites. This implied that there is a change in the intercalate chemistry of the primary crystallites with digestion time. Predicted changes in the concentrations of simple and complex ions in the solution support the proposed mechanism. The comprehensive set of hydrolysis reactions used in the model described above allows the investigation of other systems provided that accurate reaction constants are available. the fact that transition metal ions like Ni{sup 2+} form strong complexes with ammonia presents a challenge in the full recovery of the Ni{sup 2+}. On the other hand, presence of Al{sup 3+} facilitates the complete precipitation of Ni{sup …
Date:
December 12, 2003
Creator:
Mavis, Bora
System:
The UNT Digital Library
Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors
Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.
Date:
December 12, 2003
Creator:
Kim, Chang-Hwan
System:
The UNT Digital Library
Organic Light-Emitting Devices (OLEDS) and Their Optically Detected Magnetic Resonance (ODMR)
Organic Light-Emitting Devices (OLEDs), both small molecular and polymeric have been studied extensively since the first efficient small molecule OLED was reported by Tang and VanSlyke in 1987. Burroughes' report on conjugated polymer-based OLEDs led to another track in OLED development. These developments have resulted in full color, highly efficient (up to {approx} 20% external efficiency 60 lm/W power efficiency for green emitters), and highly bright (> 140,000 Cd/m{sup 2} DC, {approx}2,000,000 Cd/m{sup 2} AC), stable (>40,000 hr at 5 mA/cm{sup 2}) devices. OLEDs are Lambertian emitters, which intrinsically eliminates the view angle problem of liquid crystal displays (LCDs). Thus OLEDs are beginning to compete with the current dominant LCDs in information display. Numerous companies are now active in this field, including large companies such as Pioneer, Toyota, Estman Kodak, Philipps, DuPont, Samsung, Sony, Toshiba, and Osram, and small companies like Cambridge Display Technology (CDT), Universal Display Corporation (UDC), and eMagin. The first small molecular display for vehicular stereos was introduced in 1998, and polymer OLED displays have begun to appear in commercial products. Although displays are the major application for OLEDs at present, they are also candidates for nest generation solid-state lighting. In this case the light source needs …
Date:
December 12, 2003
Creator:
Li, Gang
System:
The UNT Digital Library
Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes
This dissertation comprises two main research projects. The first project, presented in Chapter 1, involves the synthesis and thermochemistry of germacyclobutanes (germetanes). Four new germetanes (spirodigermetane, diallylgermetane, dichlorogermetane, and germacyclobutane) have been synthesized using a modified di-Grignard synthesis. Diallylgermetane is shown to be a useful starting material for obtaining other germetanes, particularly the parent germetane, germacyclobutane. The gas-phase thermochemistries of spirodigermetane, diallylgermetane and germacyclobutane have been explored via pulsed stirred-flow reactor (SFR) studies, showing remarkable differences in decomposition, depending on the substitution at the germanium atom. The second project investigates the thermochemical, photochemical, and catalytic additions of several digermanes to acetylenes. The first examples of thermo- and photochemical additions of Ge-Ge bonds to C{triple_bond}C are demonstrated. Mechanistic investigations are described and comparisons are made to analogous disilane addition reactions, previously studied in their group.
Date:
December 12, 2003
Creator:
Chubb, Andrew Michael
System:
The UNT Digital Library
Protein Structure Recognition: From Eigenvector Analysis to Structural Threading Method
In this work, they try to understand the protein folding problem using pair-wise hydrophobic interaction as the dominant interaction for the protein folding process. They found a strong correlation between amino acid sequences and the corresponding native structure of the protein. Some applications of this correlation were discussed in this dissertation include the domain partition and a new structural threading method as well as the performance of this method in the CASP5 competition. In the first part, they give a brief introduction to the protein folding problem. Some essential knowledge and progress from other research groups was discussed. This part includes discussions of interactions among amino acids residues, lattice HP model, and the design ability principle. In the second part, they try to establish the correlation between amino acid sequence and the corresponding native structure of the protein. This correlation was observed in the eigenvector study of protein contact matrix. They believe the correlation is universal, thus it can be used in automatic partition of protein structures into folding domains. In the third part, they discuss a threading method based on the correlation between amino acid sequences and ominant eigenvector of the structure contact-matrix. A mathematically straightforward iteration scheme provides …
Date:
December 12, 2003
Creator:
Cao, Haibo
System:
The UNT Digital Library
Quantification of Soil Physical Properties by Using X-Ray Computerized Tomography (CT) and Standard Laboratory (STD) Methods
The implementation of x-ray computerized tomography (CT) on agricultural soils has been used in this research to quantify soil physical properties to be compared with standard laboratory (STD) methods. The overall research objective was to more accurately quantify soil physical properties for long-term management systems. Two field studies were conducted at Iowa State University's Northeast Research and Demonstration Farm near Nashua, IA using two different soil management strategies. The first field study was conducted in 1999 using continuous corn crop rotation for soil under chisel plow with no-till treatments. The second study was conducted in 2001 and on soybean crop rotation for the same soil but under chisel plow and no-till practices with wheel track and no-wheel track compaction treatments induced by a tractor-manure wagon. In addition, saturated hydraulic (K{sub s}) conductivity and the convection-dispersion (CDE) model were also applied using long-term soil management systems only during 2001. The results obtained for the 1999 field study revealed no significant differences between treatments and laboratory methods, but significant differences were found at deeper depths of the soil column for tillage treatments. The results for standard laboratory procedure versus CT method showed significant differences at deeper depths for the chisel plow treatment …
Date:
December 12, 2003
Creator:
Sanchez, Maria Ambert
System:
The UNT Digital Library
SPA-LEED Study of the Morphology and Nucleation of a Novel Growth Mode and the ''devil's staircase'' on Pb/Si(111)
This thesis was developed to address the following questions for the Pb/Si(111) system: (1) Is it possible to control the nano-structure growth by changing the initial substrate; (2) is the nucleation theory applicable to the case of the 7-step growth mode; and (3) what phase or phases could be formed between coverage 6/5 ML and 4/3 ML? The first question was answered in chapter 2, different growth results were observed for different initial substrate, suggesting the possibility of controlling nano-structure growth by selecting the initial substrate. The applicability of nucleation theory was determined to be unclear in chapter 3, from the results that the saturation island density does not depend on deposition rate, in contrary to the prediction of nucleation theory. Chapter 4 revealed a novel ''devil's staircase'' in Pb/Si(111) within the coverage range 6/5 ML and 4/3 ML. Low temperature deposition experiments showed high order of self-organization in such a system. Theoretical studies are needed to understand such a low temperature behavior. In general, this thesis provides possibilities of controlling nano-structure growth, which can be possibly an indication for future application. It also raises interesting questions in fundamental researches: a modified theory of nucleation is needed, and a detailed …
Date:
December 12, 2003
Creator:
Yeh, Wang-Chi Vincent
System:
The UNT Digital Library
Thermal Properties of Starch From New Corn Lines as Impacted by Environment and During Line Development
The objectives of this research were to further characterize exotic by adapted corn inbreds by studying the impact of environment on their starch thermal properties, and investigating the development of starch thermal properties during kernel maturation by using differential scanning calorimetry (DSC). A method to expedite identification of unusual starch thermal traits was investigated by examining five corn kernels at a time, instead of one kernel, which the previous screening methods used. Corn lines with known thermal functions were blended with background starch (control) in ratios of unique starch to control starch, and analyzed by using DSC. Control starch was representative of typical corn starch. The values for each ratio within a mutant type were unique ({alpha} < 0.01) for most DSC measurements. These results supported the five-kernel method for rapidly screening large amounts of corn germplasm to identify unusual starch traits. The effects of 5 growing locations on starch thermal properties from exotic by adapted corn and Corn Belt lines were studied using DSC. The warmest location, Missouri, generally produced starch with greater gelatinization onset temperature (T{sub oG}), narrower range of gelatinization (R{sub G}), and greater enthalpy of gelatinization ({Delta}H{sub G}). The coolest location, Illinois, generally resulted in starch …
Date:
December 12, 2003
Creator:
Lenihan, Elizabeth M.
System:
The UNT Digital Library
Agent Extensions for Peer-to-Peer Networks.
Peer-to-Peer (P2P) networks have seen tremendous growth in development and usage in recent times. This attention has brought many developments as well as new challenges to these networks. We will show that agent extensions to P2P networks offer solutions to many problems faced by P2P networks. In this research, an attempt is made to bring together JXTA P2P infrastructure and Jinni, a Prolog based agent engine to form an agent based P2P network. On top of the JXTA, we define simple Java API providing P2P services for agent programming constructs. Jinni is deployed on this JXTA network using an automated code update mechanism. Experiments are conducted on this Jinni/JXTA platform to implement a simple agent communication and data exchange protocol.
Date:
December 2003
Creator:
Valiveti, Kalyan
System:
The UNT Digital Library
Analysis of a Cotton Gene Cluster for the Antifungal Protein Osmotin
Three overlapping genomic clones covering 29.0 kilobases of cotton DNA were found to encompass a cluster of two presumptive osmotin genes (OSMI and OSMII) and two osmotin pseudogenes (OSMIII and OSMIV). A segment of 16,007 basepairs of genomic DNA was sequenced from the overlapping genomic clones (GenBank Accessions AY303690 and AF304007). The two cotton osmotin genes were found to have open reading frames of 729 basepairs without any introns, and would encode presumptive osmotin preproteins of 242 amino acids. The open reading frames of the genes are identical in sequence to two corresponding cDNA clones (GenBank Accessions AF192271 and AY301283). The two cDNA inserts are almost full-length, since one lacks codons for the four N-terminal amino acids, and the other cDNA insert lacks the coding region for the 34 N-terminal amino acids. The cotton osmotin preproteins can be identified as PR5 proteins from their similarities to the deduced amino acid sequences of other plant osmotin PR5 preproteins. The preproteins would have N-terminal signal sequences of 24 amino acids, and the mature 24 kilodalton isoforms would likely be targeted for extracellular secretion. Prospective promoter elements, including two ethylene response elements, implicated as being positive regulatory elements in the expression of a …
Date:
December 2003
Creator:
Wilkinson, Jeffery Roland
System:
The UNT Digital Library
An Analysis of Motivational Cues in Virtual Environments.
Access:
Use of this item is restricted to the UNT Community
Guiding navigation in virtual environments (VEs) is a challenging task. A key issue in the navigation of a virtual environment is to be able to strike a balance between the user's need to explore the environment freely and the designer's need to ensure that the user experiences all the important events in the VE. This thesis reports on a study aimed at comparing the effectiveness of various navigation cues that are used to motivate users towards a specific target location. The results of this study indicate some significant differences in how users responded to the various cues.
Date:
December 2003
Creator:
Voruganti, Lavanya
System:
The UNT Digital Library
Analysis of Special Education Compliance and Special Education Funding in Four Texas Open-Enrollment Charter Schools.
The purpose of this study was to conduct an in-depth examination of special education services in open-enrollment charter schools in north Texas and to examine relationships between special education compliance and funding. Six questions guided the research: How have the charter schools designed special education services, and do these services meet individual needs of students with disabilities? Have federal education and disability laws affected charter schools' admissions, operations, or student performance ratings? What were the levels of special education funding and compliance with federal and state regulations? Is there a relationship between special education funding and special education compliance with rules and regulations? Studies at the national and state levels have frequently been conducted in the form of surveys, and provide only preliminary information about the status of special education in charter schools. There is a paucity of case specific information about the management and delivery of special education services in open-enrollment charter schools. A within-case study research design was used for this investigation utilizing qualitative methods of structured open-ended interviews, observations at the schools, and document analysis. Administrators at four open-enrollment charter schools were interviewed to gather data for this multi-case study. The data supported the hypotheses related to …
Date:
December 2003
Creator:
Rudebusch, Judith
System:
The UNT Digital Library
An analysis of the effects of high school student concurrent enrollment at Collin County Community College District.
Access:
Use of this item is restricted to the UNT Community
As efforts to provide seamless transitions from high school to college grow, so do the numbers of high school students who concurrently enroll in college courses across the country. The purpose of this study was to evaluate the effectiveness of various aspects of the concurrent enrollment program at Collin County Community College District in Texas. Six research questions were designed to address student success and continuing enrollment patterns after high school graduation, as well as evaluate differences in the various models of dual credit classes offered by the college. Literature related to concurrent enrollment and dual credit programs, senior year of high school, and part-time faculty effectiveness was reviewed. Student issues addressed include: grade performance of concurrent enrollment students compared to the general college population; the percentage of concurrent enrollment students who continue at the college after high school graduation; and a comparison of continuing concurrent enrollment students with a matched sample (based on high school class rank), on the student success factors of fall-to-spring retention rates, fall-to-fall retention rates, grade point averages, and completion rates. Findings were generally positive related to the impact of concurrent enrollment on students and their subsequent success at the college. Various models of offering …
Date:
December 2003
Creator:
Swanson, Kathrine Bridgett
System:
The UNT Digital Library
An Annotated Bibliography of Selected Chamber Music For Saxophone, Winds and Percussion with Analyses Of Danses Exotiques by Jean Françaix, and Nonet by Fisher Tull
An expansive repertoire of original chamber works is available for ensembles comprised of saxophone, wind and percussion instruments. Many musicians, including saxophonists and conductors, are unaware of this enormous body of literature. This produces a compelling need for sources of identification available to conductors, performers and teachers. This study begins to provide such a source through the presentation of selected works and the accompanying annotated bibliography. The lack of awareness of available scores for chamber music with saxophone, winds and percussion among conductors and many performers often contributes to the absence of these works in concert halls. The objective of this lecture-recital document is to make available a tool that includes only original works for the saxophone in a variety of chamber ensemble settings. The nature of this study will be descriptive. The literature chosen for this project reveals varying levels of performance difficulty, compositional techniques, form, and instrumentation. Chosen works employ an ensemble size that requires a conductor or are more successfully performed with a conductor. Selected compositions are illustrated in which the saxophone is identified as a vital ingredient in an already existing repertoire of serious chamber literature. Works in this study include original compositions using from seven …
Date:
December 2003
Creator:
Fryer, Cheryl A.
System:
The UNT Digital Library
The aquatic insect communities of Holbrook Creek and Cochetopa Creek in Colorado.
The first objective for this problem in lieu of thesis project was to gather, identify to the lowest practical taxonomic level and organize all available aquatic insects collected from high altitude Colorado aquatic systems during the summers of 1994, 1996, 1998, and 2002 for the University of North Texas Environmental Science Field Course (BIOL 5650). The curated collection will be housed in the Elm Fork Natural History Museum, located at the University of North Texas. The second objective was to provide a summary and discussion of the occurrence and distribution of the aquatic insects collected from Mt. Blanca in 1994, 1996, and 1998 and to create a taxa list of aquatic insects collected from Cochetopa Creek during the summer of 2002.
Date:
December 2003
Creator:
Wallace, Mark Allen
System:
The UNT Digital Library
Assessment of Resident and Staff Activity in a State Residential Setting
Previous studies have demonstrated the use of momentary time-sampling methods for the objective measurement of naturally occurring events (Zarcone, Iwata, Rodgers & Vollmer, 1993; Shore, Lerman, Smith, Iwata & DeLeon, 1995). These studies have provided information about observed levels and characteristics of direct care services, supervision, resident activity and facility conditions. The present study evaluated the utility of these assessment procedures in a residential facility for developmentally delayed adults. The procedure was further evaluated for sensitivity to changes relative to an intervention designed to increase staff and client interaction. A multiple baseline design was used to assess a data collection procedure in the context of intervention in four residences on a state facility campus. Intervention included the use of scheduling, modeling and performance feedback. Results indicate an overall increase of staff and client interaction and demonstrate the utility of the assessment procedure for the evaluation of multiple, on-going activities as well as intervention effects.
Date:
December 2003
Creator:
Galletta, Katharine Lena
System:
The UNT Digital Library
Ballistic Deposition: Global Scaling and Local Time Series.
Complexity can emerge from extremely simple rules. A paradigmatic example of this is the model of ballistic deposition (BD), a simple model of sedimentary rock growth. In two separate Problem-in-Lieu-of Thesis studies, BD was investigated numerically in (1+1)-D on a lattice. Both studies are combined in this document. For problem I, the global interface roughening (IR) process was studied in terms of effective scaling exponents for a generalized BD model. The model used incorporates a tunable parameter B to change the cooperation between aggregating particles. Scaling was found to depart increasingly from the predictions of Kardar-Parisi-Zhang theory both with decreasing system sizes and with increasing cooperation. For problem II, the local single column evolution during BD rock growth was studied via statistical analysis of time series. Connections were found between single column time series properties and the global IR process.
Date:
December 2003
Creator:
Schwettmann, Arne
System:
The UNT Digital Library
Case-Based Reasoning for Children Story Selection in ASP.NET
This paper describes the general architecture and function of a Case-Based Reasoning (CBR) system implemented with ASP.NET and C#. Microsoft Visual Studio .NET and XML Web Services provide a flexible, standards-based model that allows clients to access data. Web Form Pages offer a powerful programming model for Web-enabled user interface. The system provides a variety of mechanisms and services related to story retrieval and adaptation. Users may browse and search a library of text stories. More advanced CBR capabilities were also implemented, including a multi-factor distance-calculation for matching user interests with stories in the library, recommendations on optimizing search, and adaptation of stories to match user interests.
Date:
December 2003
Creator:
Hu, Demin
System:
The UNT Digital Library
Characterization of Cure Kinetics and Physical Properties of a High Performance, Glass Fiber-Reinforced Epoxy Prepreg and a Novel Fluorine-Modified, Amine-Cured Commercial Epoxy.
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) and by high speed DSC when the reaction rate is high. The changes in physical properties indicating increasing conversion are followed by shifts in glass transition temperature determined by DSC, temperature-modulated DSC (TMDSC), step scan DSC and high speed DSC, 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 and a continuous heating transformation (CHT) diagram for rapid determination of processing parameters in the processing of prepregs. Shrinkage …
Date:
December 2003
Creator:
Bilyeu, Bryan
System:
The UNT Digital Library
Clinical and Educational Efficacy of a University-Based Biofeedback Therapy Clinic.
This study is a qualitative analysis and a quantitative analysis of all peripheral biofeedback client data files of the University of North Texas Biofeedback Research and Training Laboratory since its establishment in 1991 and through the year of 2002. The purpose of this study is to evaluate the clinical and educational efficacy of the BRTL. Clients' electromyography and temperature measures, self-report of homework relaxation exercises and progress, and the pre- and post-Stress Signal Checklist were reviewed and analyzed. In regard to clinical efficacy, results indicate statistically significant changes in both temperature training and muscle tension training as a whole group. When divided into subtypes based on the clients' primary presenting problem, findings indicate statistical significance in chronic pain, tension headache, and temporomandibular jaw pain on temperature training, and show statistical significance in chronic pain, tension headache, hypertension, migraine headache, stress, and temporomandibular jaw pain on muscle tension training. When analyzing the Stress Signal Checklist, only 25% of clients had complete information on both pre- and post-Stress Signal Checklist. For these 25%, 87.5% reported symptoms decreased. When reviewing the clients' self-reported progress in therapist's session notes, there is no procedure for computing a treatment success to failure ratio due to the …
Date:
December 2003
Creator:
Shiau, Shwu-Huey
System:
The UNT Digital Library