A high resolution x-ray tomography system was used to study chopped fiber polymeric composites made of polypropylene resin, nickel coated carbon fiber and Eglass fiber. Procedures are developed to obtain micro-structured features of importance. In-situ tensile testing system was developed and integrated into the existing hardware for tomography equipment to study the evolution of damage and micro-structural features as a function of mechanical stress. High resolution x-ray tomographic images of glass fiber were collected and viewed on a micron scale. The radiographs were reconstructed to visualize the fiber content of the samples in three dimensional volume. In addition, glass fiber dogbone specimens were tested on a miniature tensile machine using x-ray tomography to view deformation of the samples in high resolution. Fractures in the chopped glass composite were observed for x-ray microscopy showing the dominant failure mechanism of the sample are low interfacial strength and adhesion between the fiber and matrix. Cracks were not observed until after failure by fiber pull-out using the digital microscopy method. Using SEM microscopy method, resin cracking and fiber debonding was observed for a carbon fiber with vinyl ester resin while under tensile loading. Important micro-structural information relationship with and mechanical behavior including variation modulus, yield and ultimate strength are discussed.

Within the scope of this thesis, an experimental system has been designed, developed and manufactured for the determination of the wetting behavior of liquids and polymer melts with solid surfaces (coated and uncoated) at high temperatures (> 200 ºC). The measurement system incorporates a modified Wilhelmy plate technique, using a precision weighing module, a vertical linear stage, custom developed application software using LabView with suitable hardware and a high temperature furnace with thermocouple feedback control. Experiments have been performed and are reported to evaluate the performance of the testing system, using liquids of known wetting properties. A suitable testing procedure based on dynamic Wilhelmy plate theory is proposed, involving investigation of advancing and receding liquid-probe interactive forces and hysteresis loops. Interfacial wetting and wicking behavior of polystyrene melt with clay based refractory coatings, as used in the lost-foam casting (LFC) process, are presented a function of temperature using this measurement system. Experiments of particular interest were performed for two different types of refractory coating and for polymer melts at processing temperatures between 220°C and 300°C, where they show pronounced viscoelastic behavior. Different variables, obtained from the hysteresis loops, were utilized as quantitative indicators for comparison, including the area under the loop from contact onwards, the slope of advancing and receding lines in the force-displacement domain, the force hysteresis at zero displacement and Fast Fourier Transform (FFT) analysis of the hysteresis loop.

Objective. To perform frequency response analysis of passive intact and rneniscectomized human knee joints under body mass. The knee dynamic system parameters and their alterations with different preloads and displacement amplitudes will be determined. Design. Using an Instron Mechanical Testing System, specially designed fixtures, and the following softwares: WaveMaker, Excel, LabView, and Matlab, the knees were dynamically tested and analyzed. Background. Studies have been performed to analyze the dynamic behavior of the human knee. However, no experimental study has investigated the dynamic response of the knee joint under an axial compressive dynamic loading condition considering the effect of the upper body mass. Methods. Ten human knee joints were each placed in fixtures and secured in the Instron equipment, with an added mass to simulate body weight. The dynamic testing sequence consisted of creep tests, a series of frequency sweeps at increasing amplitudes, and relaxation tests. This testing series was performed with the knee in full extension, and at a 25-degree flexion angle. A meniscectomy was performed on each specimen, and the testing trial was performed again. The data from testing was then analyzed, and the joint response was obtained. Results. The results indicated that the resonance frequency is significantly affected by change in preload and flexion angle. Increase in preload resulted with an increase in resonant frequency, but flexing the knee resulted in a decreased resonant frequency. The stiffness also decreased significantly when the knee was flexed. The joint compliance response increased up to two fold at resonant frequency compared with that of 1 Hz frequency at different joint conditions. Conclusion. The compliance graphs had similar shapes and had interesting trends that yielded results that can be used as reference data for future studies and rehabilitation means. The analysis indicated that there is a range in the dynamic factors depending on the testing conditions. The meniscectomy had a significant effect on the joint response as well.

Three dimensional pulsatile blood flow CFD simulations in geometrically genuine normal and non-normal (aneurysm) human neck-head vascular systems nominally spanning the aortic arch to the circle of Willis has been performed and studied. CT scans of the human aortic arch and the carotid arteries were interpreted to obtain geometric data defining the boundary for a vascular CFD simulation. This was accomplished by reconstructing the surface from the anatomical slices and by imposing pertinent boundary conditions at the various artery termini. Following automated formation of a non-conformal CFD mesh, steady and unsteady laminar and low turbulent simulations were performed both for the normal and aneurysm models. Atherosclerosis and atherosclerotic induced aneurysms can occur in the ascending aorta. The results showed marked differences in the flow dynamics for the two models. Secondary flow is induced in both of the models due to the curvature of the aortic arch which is distorted in three dimensions. Counter clockwise rotating vortex formation was seen at the aneurysm segment in the ascending aorta for the aneurysm model which was absent for the normal case. The effect of the aneurysm bulge was seen in regions proximal to it at peak reverse flow causing secondary flow. These secondary aortic blood flows are though to have an effect on the wall shear stress distribution. Maximum pressure regions for the aneurysm were observed at regions distal to it indicating the possible location for rupture. Wall shear force (WSF) values for the normal case at the aortic bend were low indicating the possible reason for the formation of the aneurysm in the first place. The WSF values at the aneurysm segment for the aneurysm case were also low supporting the low shear stress induced atherosclerotic aneurysms theory. These results may act as a precursor for a multiscale Large eddy simulation model (LES) for pulsatile blood flow eliminating the need for a priori definition of the flow as laminar or turbulent.

A high resolution x-ray tomography system was used to study chopped fiber polymeric composites made of polypropylene resin, nickel coated carbon fiber and Eglass fiber. Procedures are developed to obtain micro-structured features of importance. In-situ tensile testing system was developed and integrated into the existing hardware for tomography equipment to study the evolution of damage and micro-structural features as a function of mechanical stress. High resolution x-ray tomographic images of glass fiber were collected and viewed on a micron scale. The radiographs were reconstructed to visualize the fiber content of the samples in three dimensional volume. In addition, glass fiber dogbone specimens were tested on a miniature tensile machine using x-ray tomography to view deformation of the samples in high resolution. Fractures in the chopped glass composite were observed for x-ray microscopy showing the dominant failure mechanism of the sample are low interfacial strength and adhesion between the fiber and matrix. Cracks were not observed until after failure by fiber pull-out using the digital microscopy method. Using SEM microscopy method, resin cracking and fiber debonding was observed for a carbon fiber with vinyl ester resin while under tensile loading. Important micro-structural information relationship with and mechanical behavior including variation modulus, yield and ultimate strength are discussed.

Simulated, 3D gaming environments have been used for a wide-range of applications including training, entertainment, and experimentation in an assortment of domains for some time. This can be attributed to their unique ability to emulate multifaceted situations that may be difficult to control, while affording participants the opportunity to operate in a relatively safe environment. In cybersecurity research, investigation of insider threat behavior is an endeavor that has received little attention in terms of available environments and resources for experimental manipulation. This research effort aimed to close this gap. A simulated, 3D gaming environment and accompanying scenarios were developed for utilization as a research application for a verification study. These constitute crucial components for proper development of insider threat detection tools and training applications. The aim was to use knowledge of performance, user stress state, and user perceptions of the simulation's graphic and usability qualities to verify the simulation for use in insider threat detection work. The objective of this simulated, 3D gaming environment and scenarios was to serve as a realistic and valid context for the development of insider threat identification methods. The scenario narrative involved a reenactment of computer system exploitation by an employee who is trying to acquire private financial information without authorization. In each scenario, the participant assumed the role of a financial investigator employed at a large financial institution. There were two conditions associated with this verification study (control and insider threat). Participants in the control condition performed all of their tasking as regular bank employees while participants assigned to the insider threat condition had to carry out a portion of their tasking as an insider threat. Findings indicated that participants found the simulated, 3D gaming environment engaging, and the simulations graphics usable and immersive. Additionally, the role manipulation resulted in a significant difference in the time it took to perform critical tasking (tasking that was illicit in the insider threat condition). Role manipulation did not produce significant differences in stress between conditions, but it was influential regarding the perceptions of the stress sources. The results suggest that this simulated, 3D gaming environment meets the needs of insider threat investigation and can be used to advance understanding of the nature of insider threat behavior.

Liquid crystal (LC) droplets show great potential as an optical probe for sensor applications due to their large surface areas and stimuli-response director configurations. Bile acids with amphipathic properties, which are formed in liver and secreted into the small intestine, play an important role in the digestion of fats and fat-soluble vitamins. After the digestion process, most of bile acids are recycled back to the liver and ready for the next digestion. Only a few of them are excreted into body fluids. However, there is significant increases in the concentration level of bile acids in body fluids for patients with liver and intestinal diseases, which makes bile acids a biomarker for the early diagnosis of liver and intestinal diseases. Chromatography-mass spectrometry and electrochemical sensors are common methods for the detection of bile acids. However, these detection methods are time consuming, require relatively large sample volumes, and expensive instruments. To date, there is still a demand in the development of simple, low-cost and user-friendly sensing platforms for the rapid detection of bile acids in clinical settings. In this dissertation, two simple and low-cost LC droplet-based sensing platforms were developed for the rapid and real-time detection of bile acids with a small sample volume. First, a miniaturized LC droplet-based sensor platform was designed and fabricated by the integration of polyelectrolytes/surfactant/sulfate β-cyclodextrin (β-CD) complex-stabilized LC droplets into a microfluidic channel for the selective detection of bile acids in a small amount of solution, in which the β-CD immobilized at the surface of the LC droplets acts as a selective barricade and the director configuration of the LC droplets serves as an optical probe. Second, a flexible LC droplet-based sensor platform was formed by the integration of surfactant-stabilized LC droplets in biopolymer hydrogel films. The LC droplet-based hydrogel film was cut into small sheets for the real-time detection of bile acids in a small amount of solution, in which the configuration transition of LC droplets induced by the interaction of bile acids with the surfactants absorbing on the surface of LC droplets serves as an optical probe. Cholic acid (CA) and deoxycholic acid (DCA), which are the most related to the liver and intestinal diseases, were detected in phosphate buffered saline (PBS) solution in the presence of the interference species of uric acid (UA) and ascorbic acid (AA) in this dissertation. These miniaturized LC droplet-based sensor platforms can be used to selectively detect CA and DCA in the presence of UA and AA. The detection limit of these sensor platforms for CA and DCA can be tuned by the number of LC droplets and the nature of surfactants. Furthermore, we find that these sensor platforms are more sensitive for DCA with the shorter response time and lower detection limit over CA due to their difference in hydrophobicity. These miniaturized 5CB droplet-based sensor platforms are easily handled, allowing the rapid and real-time detection of bile acids in a small sample volume in the presence of interference species, which are highly desirable for the "point-of-care" analysis of bile acids.

Degassing is a critical heat treatment process in aluminum powder metallurgy, where powders are subjected to high temperature in vacuum to remove volatile gaseous species absorbed in and adsorbed on powders. For cryomilled aluminum alloy powders with nanoscale features, degassing can cause accelerated microstructural and chemical changes including removal of volatiles, grain growth, dislocation annihilation, and formation of dispersoids. These changes can significantly alter the mechanical behavior of consolidated components based on their contributions to strength. In this study, cryomilled AA5083 (0.4 wt.% Mn; 4.5 wt.% Mg; minor Si, Fe, Cu, Cr, Zn, Ti; balance Al) powders were degassed at 200, 300, 350, 410 and 500°C at a ramp rate of 68.3 °C?hr-1 for a soak time of 8 hours with a vacuum at or below 6.5 x 10-3 Pa. Grain size, dislocation density and dispersoid phase constituents were examined as a function of degassing temperature by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, equipped with high angle annular dark field detector and X-ray energy dispersive spectroscopy. Inert gas fusion and thermal conductivity analysis were employed to determine the oxygen, nitrogen and hydrogen concentrations as a function of degassing temperature. Grain size in as-cryomilled powders (21 ~ 34 nm) increased as a function of degassing temperature, and reached a maximum value of 70 ~ 80 nm for powders degassed at 500°C for 8 hours. The dislocation density of 1.11 x 1015 m-2 in as-cryomilled powders decreased to 1.56 x 1014 m-2 for powders degassed at 500°C for 8 hours. The Al6(MnFeCr) phase was the most commonly observed dispersoid, mostly on samples degassed at or above 300°C. Volume fraction increased with degassing temperature up to 5 vol.% and the size of the dispersoids grew up to ~ 280 nm. Oxygen and nitrogen content after cryomilling were unaffected by the change in degassing temperature, but the hydrogen content decreased and reached a minimum of 45 ± 3.16 ppm for cryomilled powders degassed at 500°C for 8 hours. Grain growth was quantitatively analyzed based on the general grain growth formula and Burke's model in the presence of pinning forces. Degassing occurred in two different kinetic regimes: Harrison A kinetics at higher temperatures and Harrison B in the lower with a transition temperature of about 287°C. Burke's model exhibited a poor fit to the experimental results in higher temperature regime. Desorption of impurities during degassing was analyzed using Fickian diffusion in a spherical coordinate system and an empirical expression based on the exponential decay of average concentration. The activation energy for degassing was estimated to be 16.2 ± 1.5 kJ?mol-1. Evolutions in composition and microstructure in cryomilled powders as a function of degassing temperature were further analyzed and quantitatively correlated to the strengthening mechanisms of solid solution, grain size reduction (i.e., Hall-Petch), dislocation forest and Orowan. For consolidated AA5083 derived from cryomilled powders, strengthening by grain size reduction was the dominant mechanism of strengthening.

Thermal poling is a technique which involves the application of a strong DC electric field to a glass substrate heated below its glass transition temperature (Tg). Following the treatment, a static electric field is frozen inside the glass matrix, effectively breaking its centrosymmetry. Historically, this treatment has been used as a way to gain access to second order non-linear optical properties in glasses. However, recent efforts have shown that the treatment was responsible for structural changes as well as surface property modifications. Our study was focused on using this technique to tailor surface properties in oxide (borosilicate and niobium borophosphate) and chalcogenide glasses. A strong emphasis was put on trying to control all changes at the micrometric scale. After poling, property changes were assessed using a set of characterization tools: the Maker fringes technique (a Second Harmonic Generation ellipsometry technique), micro-Second Harmonic Generation (µ-SHG), vibrational spectroscopy and Secondary Ion Mass Spectroscopy (SIMS). Surface reactivity in borosilicate glasses was effectively changed while in niobium borophosphate and chalcogenide glasses, the optical properties were controlled linearly and non-linearly. Finally, property changes were effectively controlled at the micrometric scale. This opens up new applications of thermal poling as a mean to design glass substrate for integrated photonics and lab-on-a-chip devices.

Characterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line applications for research and development, and module/system level applications to evaluate long-term reliability. A frame work was developed to assess the cost and potential value of metrology within a manufacturing line. This framework has been published to an on-line calculator in an effort to provide the solar industry with an intuitive and transparent method of evaluating the economics of in-line metrology. One important use of metrology is in evaluating spatial non-uniformities, as localized defects in large area solar cells often reduce overall device performance. Techniques that probe spatial uniformity were explored and analysis algorithms were developed that provide insights regarding process non-uniformity and its impact on device performance. Finally, a comprehensive suite of module level characterization was developed to accurately evaluate performance and identify degradation mechanisms in field deployed photovoltaic modules. For each of these applications, case-studies were used to demonstrate the value of these techniques and to highlight potential use cases.