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Thesis (Ph.D.)--University of Texas at Dallas, 2007. / Includes vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Dept. of Mathematics, June 2000. / Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--Washington State University, May 2006. / Includes bibliographical references (p. 57-63).

Although the Global Position System (GPS) can help to navigate around the world, it cannot provide useful information in an indoor environment. I developed an indoor localization system using wireless sensor networks (WSNs). This system has two goals: (1) to make a system that runs for long duration without changing or charging batteries, and (2) to obtain more accurate position estimates of the target nodes using received signal strength indicator (RSSI) values than other localization systems using different localization algorithms. I chose ANT radio due to its lower power consumption. I applied a fingerprinting-based algorithm and used the parameters of the closest point to the estimated target node to calculate the final position of a target node. A local weighted k-Nearest Neighbour algorithm was proposed to estimate the position of a mobile node. I compared my system to other indoor localization systems to assess its performance. / February 2016

Abstract In this work, the homogeneity of both the B0 and B1 fields was studied. Both B0 and B1 field homogeneities are the basic assumptions of high resolution liquid state NMR. Although some inhomogeneity of both of the fields is always present, the spectrometers can be operated, with the help of the developed spectral purging techniques, without giving any thought to the field inhomogeneities or the necessary actions to minimize their adverse effects. Although the effect of B0 inhomogeneity can occasionally be seen, the B1 fieldin a modern probe head is often assumed to be sufficiently homogenous for any practical purpose. By using the method used in this study the B1 field strength along one axis, typically the z-axis, can be easily mapped. Based on the information gathered from a single experiment, one can obtain reliable and valuable information about the B1 field distribution, e.g. homogeneity of the coil. From such information, the degree of required artifact suppressing methods for successful NMR experiments can be determined. Since normal pulse length calibration also requires the acquisition of several 1-D spectra, the required experimentation time is not increased. Although the maximum amount of signal from an NMR experiment is obtained when the signal is acquired from a maximum number of resonating spins, the results presented show that significantly more homogenous B1 field along the active sample volume is achieved by rejection of the signal originating from the outer parts of the coil length. Although the total amount of signal obtained from the outer parts of the RF-coil is not very high, some loss of signal is associated with the spatially selective acquisition. The rejected signal, however, is a significant source of artifacts, and if no precautions were taken, the artifacts would severely decrease the quality of the acquired data. If the sample concentration can be increased, it would be advantageous to dissolve the amount of sample available in as small an amount of solvent as is possible and place the sample in the most B1 homogenous part of the probe-head RF-coil. With the same amount of nuclear spins concentrated into a smaller volume, the sensitivity of an NMR experiment can be increased manifold. As an application of a spatially selective data acquisition, a versatile method capable of producing a map of the B0 field strength and its variation along the sample volume is presented.

Sound source localization with microphone arrays has received considerable attention as a means for the automated tracking of individuals in an enclosed space and as a necessary component of any general-purpose speech capture and automated camera pointing system. A novel computationally efficient method compared to traditional source localization techniques is proposed and is both theoretically and experimentally investigated in this research. This thesis first reviews the previous work in this area. The evolution of a new localization algorithm accompanied by an array structure for audio signal localization in three dimensional space is then presented. This method, which has similarities to the structure of the eye, consists of a novel hemispherical microphone array with microphones on the shell and one microphone in the center of the sphere. The hemispherical array provides such benefits as 3D coverage, simple signal processing and low computational complexity. The signal processing scheme utilizes parallel computation of a special and novel closeness function for each microphone direction on the shell. The closeness functions have output values that are linearly proportional to the spatial angular difference between the sound source direction and each of the shell microphone directions. Finally by choosing directions corresponding to the highest closeness function values and implementing linear weighted spatial averaging in those directions we estimate the sound source direction. The experimental tests validate the method with less than 3.10 of error in a small office room. Contrary to traditional algorithmic sound source localization techniques, the proposed method is based on parallel mathematical calculations in the time domain. Consequently, it can be easily implemented on a custom designed integrated circuit. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The history of the discovery of the visual cortex is reviewed and previous investigations on the corticofugal fibre connections from the visual cortex to the brain stem area presented. Efferent fibres from the visual striate cortex to the lateral geniculate body of the monkey have been investigated, following striate cortex ablation. Sections at five different points through the lateral geniculate body were stained with Del-Rio-Hortega’s double impregnation method and have been examined for fibre and "bouton terminaux" degeneration. Two other stains, Nauta and Gygax silver stain to further determine degenerating fibres, and Einarson's chrom alum stain to differentiate the structures within the sections, were used for this investigation. Experimental results showed that there was a consistent increase (with an exception of one section) in the number of boutons on the side corresponding to the lesion. This increase is statistically significant. The presence of a substantial volume of degenerating fibres and an abundance of heavily stained, almost solid type of "bouton terminaux" occurring on the side of the lesion has strongly suggested that there are actually a number of corticofugal or efferent fibres from the striate area to the lateral geniculate body. / Medicine, Faculty of / Graduate

In the present investigation the effect on brightness discrimination of ablations of various parts of the cerebral cortex of cats has been examined. The background for this project lay in the work of Kluver and Bucy (1939) who observed "psychic blindness” in monkeys with bilateral temporal ablations and that of Chow, Blum and Blum (1951) and Riopelle, Alper, Strong and Ades (1953) who found no such loss of simple visual properties from similar ablations in monkeys. Since it is not possible to subject the cat to the complex experimental tests of the monkey, and since a rigorous control of the stimulus situation was desired, the present investigation deals with brightness discrimination only. It was found that bilateral ablations of the cerebral cortex had a deleterious effect on brightness discrimination. The specific test did not differentiate among the effects of ablations of the frontal, temporal and parietal association areas although the total post-operative behavior of the animals easily indicated the specific site of the lesions. / Medicine, Faculty of / Graduate

Three topics in localization theory and group ring theory are investigated. In Chapter I, it is proved that every symmetric kernel functor in a left Noetherian ring is induced by a prime ideal. A sufficient condition for the ring of quotients with respect to a prime kernel functor to be semi-simple Artinian is found. &n analogous result for guasi-prime kernel functors is obtained in Section 5. In Chapter II, the idea of controlling subgroups is applied to group ring localization. Some sufficient conditions for the descent of the maximal ring of quotients and of the classical ring of quotients are obtained in Section 8. In Chapter III, characterizations of group rings, over nilpotent groups of transfinitely bounded cardinality, whose left global dimension is finite are obtained. As an application, this homological result is used to get information on the torsion elements of an M-group. / Science, Faculty of / Mathematics, Department of / Graduate