Thermal, rheological, and mechanical properties of a polymer composite cured at different one-stage and two-stage cure cycles were studied in this dissertation. A commercial carbon-fiber prepreg, Cycom 977-2 UD, was used. This curing-toughened epoxy resin prepreg is formulated for autoclave or press molding. An encapsulated sample rheometer (ESR) was used to obtain its viscoelastic properties, including complex viscosity, gel time, and minimum viscosity time, as well as glass transition temperature (Tg) and pressure window time for onestage and two-stage cure cycles. A differential scanning calorimeter (DSC) was used to obtain the degree of cure (DOC) for one-stage and two-stage cure cycles. The mechanical properties of interest for specimens cured at one-stage cure cycles were short beam shear (SBS) strength, combined loading compression (CLC) strength, CLC modulus, CLC Poisson’s ratio, open-hole compression (OHC) strength, and OHC modulus. The SBS, CLC, and OHC tests were performed at room temperature to obtain the mechanical properties. For the one-stage cure cycles studied, it was observed that the mechanical properties, except SBS strength, did not vary significantly; therefore, no correlation with the viscoelastic properties or the DOC was found for them. Moreover, the failure mode for OHC specimens cured at different one-stage cure cycles was similar. Likewise, the failure mode for CLC specimens cured at different one-stage cure cycles was the same. However, the failure mode for the least-cured SBS specimens was different from that of other SBS specimens. Also, the SBS strength of the least-cured specimens was significantly less than that of other specimens. The complex viscosity of the specimens cured at one-stage cure cycles in the ESR showed a similar drop-off trend for the least-cured specimens. As such, SBS strength showed a good correlation with the complex viscosity. SBS strength showed a weaker correlation with the Tg and DOC for vii the same cure cycles. The Tg had a strong correlation with the DOC for all one-stage cure cycles. No correlation between gel time and other material properties was found. A considerable improvement in SBS strength, final complex viscosity, Tg, and DOC of the least-cured specimens was observed after the dwell time was increased enough to ensure that no further curing occurred. It was also observed that for the two-stage cure cycles, faster heat-up rates and higher first-stage dwell temperatures resulted in faster curing. The DOC for the entire cure cycle was modeled using the Springer-Loos cure kinetics model for one-stage and two-stage cure cycles. The complex viscosity up to the gel time was modeled using the Kenny viscosity model for one-stage and two-stage cure cycles. The modeling results agreed well with the experimental data. The results presented in this dissertation suggest that the ESR can be used as an ex-situ cure-monitoring instrument to mimic autoclave/oven curing and, hence, eliminate the need for multiple measurement instruments. The cure time-temperature data, provided by thermocouples attached to the composite part in the autoclave/oven would be the only input to the rheometer for cure monitoring. The complex viscosity as measured by the ESR was shown to be the best viscoelastic property for monitoring the state of the material during cure for the following reasons: (a) it could be precisely measured throughout the cure and post-cure cycles using the rheometer, (b) it could reveal the important changes in the material state during cure, (c) it could be modeled by sophisticated viscosity models, and (d) it could be correlated to the mechanical properties of the composite material. Utilizing the ESR as the main ex-situ cure-monitoring instrument makes it possible to offer a new approach to curing composites. In this new approach, called Material State Management (MSM), the acceptance of cured composite materials is based on the materials’ viscoelastic properties as measured by the ESR during cure and post-cure monitoring. Moreover, knowledge of the material’s viscoelastic properties during cure can be used to improve the current cure specifications. In the MSM approach, cure process confidence limits can be prescribed based on the viscoelastic properties of the material, thus addressing the shortcomings of the current time-temperature approach to curing. / Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

This sequential mixed methods study explored the role self-efficacy plays in students’ persistence to graduating high school. Framed within social cognitive theory, data collection included a self-efficacy scale, open-ended survey questions, and personal interviews. Data analysis consisted of descriptive statistics, comparative means of quartiles, and constant comparative methods for qualitative data. Findings were supported by the literature on selfefficacy and showed a relationship between student self-efficacy and locus of control, as well as increased academic persistence in high self-efficacy students. The higher self-efficacy quartiles of students were also found to have enhanced problem-solving skills to overcome obstacles affecting their ability to persist in school. No significant correlations were found between selfefficacy and grades or standardized assessment scores. Implications for practice in school settings are discussed. / Thesis (Ed.D.)--Wichita State University, College of Education, Dept. of Educational Leadership

This narrative inquiry focused on what four low-SES single mothers had to say about their aspirations for and support systems they have for their children. Discussions with the mothers involved a mix of topics. The four stories are unique in their own way yet similar themes emerged relating to the experiences they face being a single mother with children enrolled in and attending school in grades K-6. The theoretical perspective of social capital and the narrative inquiry approach to research provide the foundation for this study. Individual narratives of the four low-SES single mothers’ are shared. The mothers’ provided insightful and critical assessments of their experiences being a single mother of school age children in a society that tends to look at them in a different view. / Thesis (Ed.D.)--Wichita State University, College of Education, Dept. of Educational Leadership

The electric power system has experienced many changes in the last decade. The notable changes are deregulation of the industry, penetration of renewable energy sources, demand side management, stricter regulations on the system performance, investigation of smart-grid applications, emission regulations on generation and penetration of electric vehicles. These changes have forced the utilities to look for innovative ideas to incorporate the changes while ensuring the performance requirements. One way to measure the performance requirements is in terms of customer satisfaction. In other words the utility is expected to provide uninterrupted power supply on demand. The challenges in achieving this are limited by the increasing load / demand on the system and the aging of the components. In US on average 80% of consumer interruptions are attributed to the failures at the distribution level. Therefore, this work focuses on improving the performance of the distribution system using a preventive maintenance scheme based on the condition of the distribution level components. Impact on the system due to expected penetration of electric vehicles (EV) and the communication advancements for the smart-grid applications are also given noteworthy consideration in this work. / Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

A receptor able to selectively bind a phosphatidylglycerol head group of a bacterial membrane phospholipid, PPG is an attractive synthetic target as a modular component of an antimicrobial therapeutic. The major challenge to the preparation of such receptors, able to exclusively recognize this bacterial membrane component, is to create a binding motif that will complex a phosphorus anion, along with hydroxyl functionality, strongly and selectively in an aqueous environment. This study reports the synthesis and characterization of two families of charged hydrogen-bonding receptors. The first family of receptors contains different binding pocket sizes to accommodate the phosphate head group of the PPG anion while the second family of receptors contains multiple binding domains for the said phosphate head group and the glycerol hydroxyl functionality from the PPG. Following the synthesis and purification, the receptors were subjected to binding studies with inorganic dihydrogenphosphate anions and phosphatidylglycerol anions monitored with both proton NMR spectroscopy and isothermal titration calorimetry to reveal the binding stoichiometry and binding thermodynamics between each receptor and the anion. / Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry

In 2003 (Tellegen, Ben-Porath, McNulty, Arbisi, Graham, & Kaemmer) the MMPI-2 RCd scale was developed to independently measure the MMPI ―factor one,‖ an inherent technical problem within the Clinical scales. The developers renamed this factor ―demoralization‖ after exploratory factor analyses were utilized to extract this dimension from the basic nine MMPI-2 scales, creating a separate demoralization scale known as the Restructured Clinical Demoralization scale (RCd). This study examined a sample of 440 adult psychiatric inpatients to determine the relationship of the MMPI-2 RCd scale with the MCMI-III scales to assess the degree to which it may measure demoralization. Exploratory principal axis factoring with promax rotations were conducted resulting in a four factor solution. RCd loaded moderately (0.48, 0.43) on two of the four factors, Factor I named demoralized affect and Factor II named demoralized social functioning. This study indicated the presence of demoralization among several of the MCMI-III scales and supported the multidimensionality of demoralization suggested within the literature. / Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Psychology

Carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have an exceptional combination of properties that make them ideal materials for use as reinforcing particles in advanced composites. This investigation was aimed at obtaining fundamental understanding of the processing and properties of carbon nanoparticle/fiber-reinforced polymer composites ―defined as multiscalereinforced polymer composites (MRPCs)― manufactured through a practical and scalable process. Such process consists of two stages. The first stage involves the synthesis of multiscalereinforcement fabrics (MRFs) by electrophoretic deposition of carboxylic acid- or aminefunctionalized CNTs and CNFs onto the surface of carbon fiber layers in aqueous medium; while the second stage proceeds with the stacking of the MRFs and infusion of the resulting preforms with an epoxy-amine resin system to obtain the MRPC. MRPCs manufactured following the described approach were tested for mechanical and electrical properties. Mechanical test results showed an increase in interlaminar shear strength (ILSS), shear stiffness, and compressive strength of all panels manufactured. Panels containing amine-functionalized carbon nanoparticles had the highest increase in properties: 13% in ILSS, 2.5-4 fold in shear stiffness, and up to 15% in compressive strength. On the other hand, it was found that through-plane electrical conductivity of MRPCs increased by 100% when using unsized MRFs. Investigation into the enhancement mechanism of mechanical and electrical properties was also performed. Discussion of these mechanisms are presented with emphasis placed on the fiber/matrix interface and the load transfer mechanisms between matrix, carbon nanoparticles, and carbon fiber. / Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

Magnetic targeted drug delivery, the science concerned with the design, characterization and use of magnetic materials as carriers of therapeutic agents presents promising advances in the study of drug delivery and pharmacokinetics. This is made possible by use of nanotechnology in the areas, such as engineering, biotechnology, chemistry and other sciences to develop new materials and mechanisms that can be channeled to improve the way diseases are identified and treated. The aim of this research was to introduce the use of cobalt zinc ferrite (Co₀․₅Zn₀․₅Fe₂O₄) nanoparticles as magnetic materials that could be formulated and used for targeted drug delivery, and compare the results with the commonly used magnetite. This study focused on the preparation, characterization, particle flow characteristics and cytotoxicity evaluation of magnetic materials. Cobalt zinc ferrite and magnetite (Fe₃O₄) nanoparticles (~10 nm) were synthesized by chemical co-precipitation of initial reagents. An oil-in-oil emulsion/solvent evaporation technique was used to embed the magnetic nanoparticles (MNP) plus a sample drug in a biodegradable polymer poly (DL-lactide-co-glycolide) (PLGA) to produce a magnetic nanocomposite (MNC) spheres. MNC spheres with different MNP concentrations (10%, 15%, 20%, and 25%) were prepared and characterized to determine their physical and magnetic properties by various techniques including; X-ray diffraction, dynamic laser light scattering (DLLS), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Mossbauer spectroscopy(MS) and superconducting quantum interference magnetometer (SQUID). The hydrodynamic flow characteristics of MNP and MNC spheres were also evaluated using experimental techniques. The cytotoxicity effects of these materials on normal cells were further determined from in-vitro cell trials. Results show that MNC spheres (200 nm to 1.1 μm in diameter) retained superparamagnetic properties when embedded with Co₀․₅Zn₀․₅Fe₂O₄ nanoparticles, and had a blocking temperature ranging from 120K to 140K and a saturation magnetization above 2,000 Oe. The magnetic properties of the embedded Co₀․₅Zn₀․₅Fe₂O₄ were close to those of magnetite. The effectiveness of these nanomaterials as carrier particles in drug delivery under various flow conditions depended on the vessel diameter, strength of magnetic field and concentration of MNP. An increase in the number of MNC captured could be achieved by increasing the MNP content, vessel diameter and magnetic field at optimal flow conditions. Cytotoxicity testing showed that the use of cobalt zinc ferrite delivery systems was viable though with some identifiable constraints when compared with magnetite. A reduction in sample concentration improved cell viability significantly making it potentially useful in drug delivery. / Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

The research presented in this dissertation deals with the syntheses, characterization, electrochemical, computational and photophysical studies of carbon nanostructures such fullerenes, single-wall carbon nanotubes (SWCNT) and highly colored pigment containing donor-acceptor supramolecular assembles. Using these fascinating chromophores, we have designed and synthesized donor-acceptor systems to mimic natural photosynthesis. Photosynthesis involves two major steps, absorption and transportation of light energy to the reaction center, and photoinduced electron transfer (PET) to generate charge separated entities by using the electronic excitation energy. We have designed elegant photosynthetic architectures using fullerene as carbon nanostructure based material for mimicry of antenna, mimicry of reaction center and mimicry of 'combined antenna-reaction center' functionalities in the natural photosynthetic system. Semiconducting single-wall carbon nanotube (SWNT)-based supramolecular nanoarchitectures are constructed using photosensitizing donor and acceptor molecules which reveal efficient photoinduced charge separation. The kinetic and thermodynamic data suggests feasibility of these nanohybrids for the construction of photovoltaic cell and other devices. Interestingly, the photoelectrochemical behavior of the nanohybrids indicates that by choosing nanotubes of appropriate diameter, it is possible to improve the light-harvesting conversion efficiency. / Thesis (Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry

The purpose of this study was to investigate possible associations between the application of word emphasis and risk-taking behaviors of adult Japanese English-language learners (ELLs) in the scope of foreign accent modification. The investigation was conducted through comparing 30 adult Japanese ELLs "first readings of a scenario with 30 age- and gender-matched native American-English speakers (NESs), the ELLs" first readings and second readings with an instruction to apply emphasis, and the ELLs' scores for a risk-taking questionnaire. Acoustical data were gathered from the recorded readings of the speakers for vowel duration, fundamental frequency (F0), and intensity of the pre-determined target words in the scenario. A second measurement tool involved seven listeners‟ evaluations of comprehensibility and foreign accentedness for each recorded token and their identification of the emphasized words. Results indicated that there were no significant differences in vowel duration, F0, and intensity of the pre-determined target words between the ELLs‟ and NESs‟ first readings. Although the Japanese ELLs made significant increases in the three acoustical elements on the target words after receiving instruction to apply emphasis in their second readings, the listeners‟ evaluations of comprehensibility and foreign accentedness did not correlate with the changes. Also, no correlation was found between changes the ELLs made and their scores on the risk-taking questionnaire. The findings may provide additional perspectives for foreign accent modification in addition to conventional methods. Overall outcomes may also be beneficial to help the increasing number of nonnative English speakers be more comprehensible and adaptable for American society. / Thesis (Ph.D.)--Wichita State University, College of Health Professions, Dept. of Communication Sciences and Disorders