京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19487号 / 理博第4147号 / 新制||理||1596(附属図書館) / 32523 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 青山 秀明, 教授 田中 貴浩, 教授 畑 浩之 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21109号 / 工博第4473号 / 新制||工||1695(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 白石 誠司, 教授 木本 恒暢, 教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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A Thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy Johannesburg, 2018 / Two dimensional gravity models and a few magnetic models limited to short profiles in the eastern sections of the BC have been used to propose conflicting geometries for the Rustenburg Layered Suite (RLS), especially between the western and eastern lobes; one school argued for completely separate intrusions, while the other proposed that the outcropping lobes are connected at depth. These competing models suggest different emplacement models. They provide a valuable starting point, but, 2.5D potential field modelling is not well suited to modelling complex three dimensional geology. Also, in previous work the magnetics or only the gravity data were modelled independently. Here I present the first full three dimensional potential field forward modelling of the central and southern Bushveld Complex (BC) which has been used to test the geometry of the Bushveld Complex in areas obscured by younger geological cover. Both gravity and magnetic data have been used to develop a geological model that is consistent with both data sets. Joint 3D modelling of regional gravity and magnetic data combined with published crustal thickness models derived from broadband seismic tomography studies were used to create a 3D model of the central and southeastern sections of the BC, as well as the southern part of the northern lobe. Eight downhole logs with more than 730 000 new density and magnetic susceptibility measurements from the RLS were combined with existing data to determine values for Bushveld Complex lithologies that were used in the model. The 3D model has a complex geometry with thick continuous RLS in most of the western lobe, thinner RLS in the south-eastern lobe, but a disrupted RLS in the eastern lobe. Large domes of Transvaal dolomite or thicker granites and granophyre in the eastern lobe interrupt the continuity of the RLS. The western and eastern lobes are therefore broadly connected, with major disruptions largely in the eastern lobe. However, they are not separate intrusions, but represent a single magma chamber affected by pre-existing and syn-magmatic updoming. The model includes the whole thickness of the crust and requires dense material at the crust mantle boundary. Thus, for the first time, I have imaged the remnants of magma staging chambers. The chambers, constrained by the extent of the diffuse crust-mantle transition as determined from teleseismic data, underlie the whole Bushveld Complex, but is thickest under the northern, south-eastern and western parts of the complex. I propose feeders that correlate with the chambers in the northern lobe near the large gravity high near Polokwane and in the south-eastern lobe. / MT 2019

In this work, 2 + 1 dimensional Chern-Simons theory have been used in an attempt to describe superconductivity. It was examined if the two defining properties of superconductivity, infinite direct current (DC) conductivity and the Meissner effect, as well as the two characteristic length scales of superconductors, the London penetration depth and the coherence length, could be obtained. Three approaches modelling bulk properties of superconductivity were developed for this purpose. It was found that the London penetration depth could be obtained from a Maxwell-Chern-Simons theory, which explains the Meissner effect too, but not the mechanism responsible for the effect. Infinite DC conductivity was achieved by introducing a Proca mass term. The coherence length was not obtained. Although, the coherence length and the mechanism of the Meissner effect is expected to appear from an edge treatment.

Quasi-geostrophic (QG) analysis of the atmosphere utilizes predefined isobaric surfaces to ascertain vertical motion. One equation of the QG system is the omega equation that states that vertical forcing results from differential vorticity advection and thickness advection. Two problems arise when using the QG omega equation: the forcing terms are not independent and must be analyzed simultaneously, and vertical forcing is visually noisy. Both issues are resolved using a smoothing and quantification technique that applies the QG omega equation. The analysis fields from a selection of events were chosen from the North American Mesoscale model. Using a finite differencing methodology dependent on the wavelength of synoptic features, values of vertical forcing were calculated using the omega equation. The calculated omega field correlated well with model omega while also quantifying and visualizing large perturbations in vertical forcing. The method allows for quick diagnosis of forcing type and strength within the atmosphere.

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