Microwave imaging has been used to observe optically obscured targets for over 40 years. Recently, there has been a push towards developing a microwave imaging technology for use in medical diagnostics. Microwave imaging technology has several advantages over current imaging modalities, including use of nonionizing radiation, and compact inexpensive electronics. However, no microwave diagnostic technology exists yet for clinical use. This is due to complications in estimating the complex near-field scattering of the microwave radiation. Recently, advancements in a direct inversion algorithm known as microwave holography have adapted it to operate on near-field measurements. This method, with simulations, has demonstrated the ability to estimate the relative permittivity of the imaged structures. The purpose of this work is to develop quantitative microwave holography for use in tissue imaging. In addition to the previous version of quantitative microwave holography using the Born approximation, a new version of the method using Rytov's approximation is derived, expanding the versatility of the algorithm. Filtering strategies are also developed to enhance the image-reconstruction quality. However, nonphysical permittivity values are still generated. One possible solution is a constrained optimization strategy, which is derived and implemented. Finally, experimental studies demonstrate the ability of quantitative microwave holography to produce reconstructions of several tissue phantoms. / Thesis / Master of Applied Science (MASc)

Plasma spray coatings are vital to the capabilities of jet engines. They allow engines to operate at combustion temperatures that would otherwise melt the superalloy components. Coatings tighten clearance between rotating components, increasing engine compression. They prevent chemical attack and physical erosion. Plasma spray coatings are imperative to the durability and efficient operation of the modern jet engine. In this application coating material property variation has a significant cost. In addition to the variation inherent in the process, some of the biggest contributors to coating property variation have been traced to spray gun nozzle wear and powder feed variation[3, 4]. Presented here are multiple methods utilizing flow induced acoustic signals to quantify noise parameters, measure component wear, diagnose the plasma spray process and detect coating property deviation. Methods have been developed for offline and online analysis of components in addition to online process analysis. These include characterization of nozzle wear by throat roughness measurements and nozzle casting, offline detection of nozzle wear by attenuation of discrete tone generation and broadband signal variation, and offline measurement of powder port wear by jet screech frequency variation. Online methods include pre-ignition nozzle degree of wear measurement by discrete frequency changes; online parameter change detection, process deviation detection with potential source identification, as well as variation in coating property detection by broadband acoustic signal changes. Offline methods allow for 100% accurate new nozzle manufacturer identification. By the same test nozzle wear state can be predicted with over 95% accuracy with the potential for a degree of wear determination. Internal diameter changes of less than 10 microns can similarly be detected. Analysis of online plasma spray acoustic signals as described here can distinguish nozzle state and powder feed variation with over 90% accuracy. The capabilities developed here will aid in plasma spray process variation detection and contribute to identifying the source of this variation. This will improve coating quality and consistency, reduce failures, lower operational costs and ultimately make jet engines more economical, safer, and more fuel efficient with significant environmental and financial cost reduction. / Ph. D.

Turbulent flows and turbulent flames are inherently multi-dimensional in space and transient in time. Therefore, multidimensional diagnostics that are capable of resolving such spatial and temporal dynamics have long been desired; and the purpose of this dissertation is to investigate three such diagnostics both for the fundamental study of flow and combustion processes and also for the applied research of practical devices. These multidimensional optical diagnostics are a 2D (two dimensional) two-photon laser-induced fluorescence (TPLIF) technique, a 3D hyperspectral tomography (HT) technique, and a 4D tomographic chemiluminescence (TC) technique. The first TPLIF technique is targeted at measuring temporally-resolved 2D distribution of fluorescent radicals, the second HT technique is targeted at measuring temperature and chemical species concentration at high speed, and the third TC technique is targeted at measuring turbulent flame properties. This dissertation describes the numerical and experimental evaluation of these techniques to demonstrate their capabilities and understand their limitations. The specific aspects investigated include spatial resolution, temporal resolution, and tomographic inversion algorithms. It is expected that the results obtained in this dissertation to lay the groundwork for their further development and expanded application in the study of turbulent flow and combustion processes. / Ph. D.

This work investigated the application of fiber-based endoscopes (FBEs) in combustion and flow measurements, especially for multidimensional and quantitative measurements. The use of FBEs offers several unique advantages to greatly reduce the implementation difficulty and cost of optical diagnostics. However, the use of FBEs requires registering the locations and orientations of the FBEs carefully for quantitative measurements, and degrades the spatial resolution of the images transmitted. Hence this work conducted a series of controlled tests to quantify the accuracy of the view registration process and the spatial resolution degradation for FBEs. The results show that, under the conditions tested in this work, the view registration process can be accurate within ±0.5 degree and the FBEs can resolve spatial features on the order of 0.25 mm. The combined effects of such view registration uncertainty and spatial resolution degradation are reflected in the re-projection error, which was shown to be within ±0.5 pixels under typical conditions used in this work. Finally, based on these understanding, experiments were conducted to obtain instantaneous measurements of flame structures at kHz temporal resolution using FBEs, demonstrating the capability of resolving flame features on the order of 0.2~0.3 mm in three-dimensional. / Master of Science

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Sepsis is commonly caused by bacteria, fungi or both present in the blood stream during inflammation. In response, inflammatory cascades are released in multiple organ systems which if prolonged causes sepsis and can eventually lead to organ failure and death. The major diagnostic technique of sepsis is blood culturing. However, the technique is time consuming and lacks sensitivity; especially in patients under antimicrobial therapy. Molecular techniques particularly PCR could possibly become implemented in sepsis diagnostics in the future. The aim of the thesis was to compare the effect on PCR sensitivity by different PCR kits, with optimized PCR conditions to find an ideal Real-time PCR applicable for direct detection of rRNA or rDNA in whole blood, using the 16S rDNA gene. The study also surveyed the overall background flora of bacterial species circulating in the blood. During the optimization Haemophillus influenzae and Streptococcus pneumoniae were added to whole blood, rRNA or rDNA was isolated and extracted and subsequently processed by Real-time PCR. Four commercially available PCR kits were compared. Attempts using rRNA did not significantly increase the PCR sensitivity. LightCycler FastStart DNA Master SYBR Green I kit (Roche Diagnostics) used for rDNA, generated low cp-values, the cleanest sequences and the finest separation between amplification curves. Twenty whole blood and pre-cultured patient samples were processed by the optimized PCR. The effect on PCR sensitivity by pre-culturing patient blood samples was studied and no statistical difference was noted. Increased PCR sensitivity is essential for implementation of PCR techniques in sepsis diagnostics.

The performance of the Acoustic Emission (AE) technique was investigated to establish its reliability in detecting and locating fatigue crack damage as well as distinguishing between different AE sources in potential SHM applications. Experiments were conducted to monitor the AE signals generated during fatigue crack growth in coupon 2014 T6 aluminium. The influence of stress ratio, stress range, sample geometry and whether or not the load spectrum was of constant or variable amplitude were all investigated. Timing filters were incorporated to eliminate extraneous AE signals produced from sources other than the fatigue crack. AE signals detected were correlated with values of applied cyclic load throughout the tests. Measurements of Time difference of arrival were taken for assessment of errors in location estimates obtained using time of flight algorithms with a 1D location setup. It was found that there was significant variability in AE Hit rates in otherwise identical samples and test conditions. However common trends characteristic of all samples could be observed. At the onset of crack growth high AE Hit rates were observed for the first few millimetres after which they rapidly declined to minimal values for an extended period of crack growth. Another peak and then decline in AE Hit rates was observed for subsequent crack growth before yet another increase as the sample approached final failure. The changes in AE signals with applied cyclic load provided great insights into the different AE processes occurring during crack growth. AE signals were seen to occur in the lower two-thirds of the maximum load in the first few millimetres of crack growth before occurring at progressively smaller values as the crack length increased. These emissions could be associated with crack closure. A separate set of AE signals were observed close to the maximum cyclic stress throughout the entire crack growth process. At the failure crack length AE signals were generated across the entire loading range. Novel metrics were developed to statistically characterise variability of AE generation with crack growth and at particular crack lengths across different samples. A novel approach for fatigue crack length estimation was developed based on monitoring applied loads to the sample corresponding with generated AE signals which extends the functionality of the AE technique in an area which was previously deficient. It is however limited by its sensitivity to changes in sample geometry. Experiments were also performed to validate the performance of the AE technique in detecting and locating fatigue crack in a representative wing-box structure. An acousto-ultrasonic method was used to calibrate the AE wave velocity in the structure which was used to successfully locate the 'hidden' fatigue crack. A novel observation was made in the series of tests conducted where the complex propagation paths in the structure could be exploited to perform wide area sensing coverage in certain regions using sensors mounted on different components of the structure. This also extends current knowledge on the capability of the AE technique.

Currently microseismic monitoring is widely used for fracture diagnosis. Since the method monitors the propagation of shear failure events, it is an indirect measure of the propped fracture geometry. Our primary interest is in estimating the orientation and length of the ‘propped’ fractures (not the created fractures), as that is the primary driver for well productivity. This thesis presents a new Low Frequency Electromagnetic Induction (LFEI) method that has the potential to estimate the propped length, height, orientation of hydraulic fractures, and vertical distribution of proppant within the fracture. The proposed technique involves pumping electrically conductive proppant (which is currently available) into the fracture and then using a specially built logging tool to measure the electromagnetic response of the formation. Results are presented for a proposed logging tool that consists of three sets of tri-directional transmitters and receivers at 6, 30 and 60 feet spacing respectively. The solution of Maxwell’s equations shows that it is possible to use the tool to determine both the orientation and the length of the fracture by detecting the location of these particles in the formation after hydraulic fracturing. Results for extensive sensitivity analysis are presented in this thesis to show the effect of different propped lengths, height and orientation of planar fractures in a shale environment. Multiple numerical simulations, using a state-of-the-art electromagnetic simulator (FEKO) indicate, as this work show, that we can detect and map fractures up to 250 feet in length, 0.2 inches wide, and with a 0 to 45 degree of inclination with respect to the wellbore. Special cases such as proppant banking, non-symmetrical bi-wing fractures, and wells with steel casing in place were studied. / text

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