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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Functional photoacoustic tomography of animal brains

Wang, Xueding 01 November 2005 (has links)
This research is primarily focused on laser-based non-invasive photoacoustic tomography of small animal brains. Photoacoustic tomography, a novel imaging modality, was applied to visualize the distribution of optical absorptions in small-animal brains through the skin and skull. This technique combines the high-contrast advantage of optical imaging with the high-resolution advantage of ultrasonic imaging. Based on the intrinsic optical contrast, this imaging system successfully visualized three-dimensional tissue structures in intact brains, including lesions and tumors in brain cerebral cortex. Physiological changes and functional activities in brains, including cerebral blood volume and blood oxygenation in addition to anatomical information, were also satisfactorily monitored. This technique successfully imaged the dynamic distributions of exogenous contrast agents in small-animal brains. Photoacoustic angiography in small-animal brains yielding high contrast and high spatial resolution was implemented noninvasively using intravenously injected absorbing dyes. In the appendix, the theory of Monte Carlo simulation of polarized light propagation in scattering media was briefly summarized.
162

One- and Three-dimensional P- and S-wave Velocity Models of Central and Southern Sweden Based on SNSN Data

Chan, Ne Xun January 2014 (has links)
The velocity structures of southern and central part of Sweden have been derived with the local tomography (LET) method. The region has been divided into two study areas and the datasets come from the P- and S-wave traveltimes recorded by the Swedish National Seismic Network (SNSN). Man-made explosions and earthquakes occurring over the period of 5 years and 10 years, respectively, within the study areas have been used. One-dimensional starting models were derived based on an a priori model obtained from the SNSN, that were later used for starting models in the inversion for the 3-D crustal structures of the study areas. Attempts were also made to invert for Moho topography in the areas. The study areas are found to have an upper-crustal thickness of approximately 20 to 25 km and the Moho boundaries vary from 42 to 46 km in depth. The Vp/Vs ratios varies from about 1.68 to 1.78. The LET method appear to resolve the different between the Sveconorgwegian and Svecofennian orogen regions, but the stations and sources are too sparsely distributed for higher resolution models. The seismicity in the study areas are distributed in two distinctive depth ranges. The focal depth of the SNSN catalogued earthquakes concentrated in approximately 5 km and 15 - 20 km depth. Relocations of the earthquakes using a global search method reduced this tendency. The results also show that using 3-D models produces less biased results than using 1-D models with the same relocation method.
163

The acquisition and analysis of craniofacial data in three dimensions / Amanda Helen Abbott

Abbott, Amanda Helen January 1988 (has links)
Typescript (Photocopy) / A stereo-viewer is provided ... to facilitate fusing of the three dimensional CT reconstructions and the stereo wire frame models--Pref. v. 2 / Bibliography: leaves [244]-263 / 3 v. : ill ; 30 cm. + 1 viewer (Taylor-Merchant stereopticon 707) in back pocket of vol. 2 / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Dentistry, University of Adelaide, 1990
164

Trends in CT abdominal doses in Malaysian practices

Ali, Mohd. Hanafi January 2005 (has links)
Doctor of Health Science / An investigation of clinical Abdominal Computed Tomography (CT)dose, and associated clinical diagnostic protocols, has been ndertaken. This research was carried out to study the pattern of CT dose from routine abdominal examinations in Malaysian practices. From this study it is hoped to establish a Dose Reference Level (DRL) to assist in optimising radiation dose for CT abdominal examination in Malaysia
165

Tomographic imaging for the visualization of multiphase flows /

Butler, Jason Edward, January 1998 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 184-191). Available also in a digital version from Dissertation Abstracts.
166

Electrical impedence tomography for temperature measurement in hyperthermia

Blad, Börje. January 1994 (has links)
Thesis--Lund Institute of Technology, 1994.
167

Electrical impedence tomography for temperature measurement in hyperthermia

Blad, Börje. January 1994 (has links)
Thesis--Lund Institute of Technology, 1994.
168

Teleseismic tomographic images of the Central Andes at 21⁰S and 25.5⁰S : an inside look at the Altiplano and Puna plateaus /

Heit, Benjamin S. January 1900 (has links)
Thesis (doctoral)--Freie Universität Berlin, 2005. / "Febuar 2006"--P. [2] of cover. Vita. Includes bibliographical references (p. [99]-111). Also available via the World Wide Web.
169

Inspection techniques for determining graphite core deterioration for nuclear applications

Penny, Sarah January 2016 (has links)
Graphite bricks make up a significant part of the core of an Advanced Gas-cooled Reactor (AGR). The graphite moderates the neutrons vital to the continuation of the fission chain reaction and provides support and stability for the entire core. During operation, the graphite can be oxidised due to the extreme conditions inside the core and so undergo weight loss. Differential shrinkage caused by neutron interaction throughout the brick can also cause radial cracking to occur. The effects of the oxidation, weight loss and cracking reduce the ability of the graphite to function as a moderator. The effects also have the potential of reducing the structural integrity of the brick, causing movement and structural instability of the entire core. It is, therefore, vital to monitor the condition of the graphite bricks and to understand how the changes in the graphite's properties and structure may affect the safe operation of the reactor. This report firstly looks briefly at the effect of irradiation on the graphite brick; the mechanisms leading to weight loss and cracking. The report then considers various methods which can be used to inspect the deterioration of graphite blocks within the cores of AGRs deriving quantitative and qualitative information on density and crack profiling. These methods will be considered for use both on small samples trepanned from the core and in-situ blocks within the reactor core, requiring non-destructive techniques. The inspection methods considered in this report are: Electrical Impedance Tomography (EIT); Four point probes; Eddy Current Tomography; and Electromagnetic Inductance Tomography (EMT).There are two main contributions of this thesis. First, the development an EIT methodology using outward facing probes, which were best suited to the geometry of the graphite bricks within the AGR. Proof of principle was established using both modelling and laboratory testing. The second contribution is the development of commercial grade EMT equipment, which can be used on-site to determine the conductivity of trepanned samples. The method was successfully demonstrated in the laboratory; however, further development will be required for use on-site, due to the sampling speed required.
170

Desenvolvimento de um sistema de tomografia por coerencia optica no dominio de Fourier sensivel a polarizacao e sua utilizacao na determinacao das matrizes de mueller / Development of an polarization sensitive Fourier domain optical coherence tomography and it utilization on the Mueller matrix determination

RAELE, MARCUS P. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:26:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:18Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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