This dissertation outlines work taken towards the understanding, implementation, and improvements to the process of creating of quantitative images of the bulk-electrical parameters of the interior of unknown objects via the use of electromagnetic scattering data. Improvements are considered to both theory and experiments using low-power radiation in the microwave frequency range, known as Microwave Tomography (MWT). A detailed derivation of the Multiplicative-Regularized Contrast-Source Inversion (MR-CSI) method is given, and we compare the performance of MR-CSI with the other leading inversion technique used in MWT: the Gauss Newton/Distorted Born Iterative Method. The inversion results of the two algorithms are very similar, and thus most of the differences between them are in the relative ease of implementation and computational resource use. We further introduce a new version of the CSI algorithm, based on the Finite-Difference method. Using this algorithm, we show that when accurate information about a scatterer is known before the inversion process, this information is best utilized as an artificial computational background, as opposed to an initial guess of the scatterer. The MWT problem is also formulated inside of a conductive enclosure, which significantly changes the physics, and resultant Green's function, of the MWT problem. The implications and possible advantages of this type of MWT are discussed, and synthetic inversion results for a circular enclosed system are presented. These results show that the enclosure is capable of improving the inversion in some regions, although more research is required to realize the full potential of conductive-enclosure MWT. In the final section, experimental results from both open-region and conductor-enclosed type MWT systems developed at the University of Manitoba are shown. For the open-region system, we show that antenna coupling is a major factor affecting the data collection, and provide a simple method for avoiding the frequencies where this coupling is too strong to prevent effective imaging. For the conductor-enclosed type system, we have found the system to be extremely sensitive to presence of antennas in the chamber, and show that effective MWT imaging is possible in this type of system by taking the antenna elements into account in the inverse solver.

This dissertation outlines the development of static and dynamic tomographic wave-front (WF) reconstructors tailored to Multi-Object Adaptive Optics (MOAO). They are applied to Raven, the first MOAO science and technology demonstrator recently installed on an 8m telescope, with the goal of increasing the limiting magnitude in order to increase sky coverage. The results of a new minimum mean-square error (MMSE) solution based on spatio-angular (SA) correlation functions are shown, which adopts a zonal representation of the wave-front and its associated signals. This solution is outlined for the static reconstructor and then extended for the use of standalone temporal prediction. Furthermore, it is implemented as the prediction model in a pupil plane based Linear Quadratic Gaussian (LQG) algorithm. The algorithms have been fully tested in the laboratory and compared to the results from Monte- Carlo simulations of the Raven system. The simulations indicate that an increase in limiting magnitude of up to one magnitude can be expected when prediction is implemented. Two or more magnitudes of improvement may be achievable when the LQG is used. These results are confirmed by laboratory measurements. / Graduate

No description available.

Most EIT machine operates at high frequencies above 10 kHz. Biological systems demonstrate dispersions of electrical impedance characteristics at very low frequencies below 2 kHz due to the presence of membrane surrounding the cells and diffusion polarisation effects. A study was made on the feasibility of the use of low frequencies in a range of 1.12 Hz to 4.55 kHz in EIT. One high frequency of 77.712 kHz similar to that normally used in common EIT was also used as a comparison. The impedance measurements employed a four-terminal method using the BULFIS, an ultra low frequency impedance spectrometer and used conducting and insulating material as the objects/phantoms. The results show that the conductance and capacitance of a metal object disperses at frequency range of 0.1 -10 kHz, which is consistent to the electrical properties of a double layer forming at the metal-electrolyte interface similar to the electrical properties of a membrane. The reconstructed images reveal that at low frequencies the conducting and the insulating bodies were indistinguishable. They appear differently at high frequencies above 4.55 kHz indicating that the use of multi frequency instrumentation in EIT covering the very low frequency range provides information that instrumentation restricted to frequencies above 10 kHz does not supply. While the internal structure of the double layers could not be delineated, the presence of the double layers could be readily detected by the behaviour of the images as the frequency was varied. This has potential for EIT because it might allow the detection of structures from the variation of the images with frequency. This variation with frequency does not occur at the higher frequencies more usually used for EIT.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 47-51).

Thesis (Ph.D.)--Tufts University, 2005. / Advisers: David A. Boas; Yaacov Shapira. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 113-126). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (M.S.)--Ohio University, March, 1985. / Title from PDF t.p.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves157-159).

Thesis (M. Med. Sc.)--University of Hong Kong, 2005. / Also available in print.

Thesis (M.S.)--Ohio University, March, 1987. / Title from PDF t.p.