/library/oar/handle/123456789/77202 2025-11-04T18:55:47Z 2025-11-04T18:55:47Z /library/oar/handle/123456789/104434 2023-01-13T10:23:48Z 2009-01-01T00:00:00Z

Title: The impact of radial migration on the vertical profiles of disk galaxies Abstract: Recent work (Sellwood & Binney 2002; Roskar et al. 2008) has shown that disk stars can undergo large migrations across the disks within which they reside, even though they maintain nearly circular orbits. Roskar et al. (2008) showed that this migration leads to positive age gradients outside the break radius of the disk; this picture is starting to obtain some observational support. However, the full consequences of such migration have yet to be worked out. In this dissertation we examine the effect migration has on the vertical profiles of disks. Is the height of the disk driven primarily by heating mechanisms, or does migration play a more primary role in setting the thickness of the disk? Description: B.SC.(HONS)PHYSICS

2009-01-01T00:00:00Z /library/oar/handle/123456789/104050 2024-01-30T12:48:07Z 2010-01-01T00:00:00Z

Title: Developing a capacity for storm surge forecasting in the Maltese islands Abstract: The aim of this project is to develop components of a prototype system for the forecasting of sea level variations and extreme mean sea levels in the area of the Maltese Islands. The system makes use of a high resolution coastal numerical model nested to the storm surge operational model run by the Spanish (Nivmar) covering the full Mediterranean Sea. The coastal model makes use of a finite element mesh which allows the resolution to focus with more grid cells on geographical areas of higher interest, thus allowing coastal embayment to be resolved. This work is conducted within a research project at the Physical Oceanography Unit (PO-Unit) in collaboration with international partners. Tasks include the configuration of the coastal model and the formulation and tuning of suitable boundary conditions from the coarse model. The system is implemented to run in pre-operational mode and validated against observations. The validation involves the creation of a beta version of the model where a series of numerical experiments are conducted to validate against observations. The objective is to fine tune the performance of the sea level forecasts. This higher resolution sea level forecasting model is intended to be subsequently linked to the operational forecast system run by the PO-Unit. Storm surges are related to atmospheric disturbances and result in extreme conditions of high mean sea levels which put high risks to inundation and render storm water floods more severe, especially in low lying areas such as Msida and Burmarrad. The work includes conducting statistics on the occurrence of storm surges in Malta. This kind of research is a precursor to applications of storm surge modelling in coastal areas and offers a potential application to other areas in Mediterranean. Description: M.SC.PHYSICS

2010-01-01T00:00:00Z /library/oar/handle/123456789/101840 2022-09-27T07:33:21Z 2007-01-01T00:00:00Z

Title: An integrated geophysical study of the Ionian Basin western margin : new insights on its Permo-Triassic origin Abstract: The origin and evolution of the Ionian Basin of the Central Mediterranean have been the subject of intense study and debate in the last three decades. The principal unsettled issues include the nature of the crust underlying the basin, the location of the presumed continent ocean boundary in the west, the timing of its opening and subsequent spreading, and the exact mechanism of its evolution to the present-day configuration. The structural complexity of its northern and eastern subduction margins has added to the difficulty in fully understanding this enigmatic province. The crust underlying the basin has been variously described as being either continental, oceanic or transitional. Earlier models for its evolution postulated a thinned continental crust linking the Pelagian Shelf to the west and the Apulian Shelf to the northeast to form a promontory of the north African plate. However, more recent seismic reflection and refraction surveys and potential field studies conducted in the 1980's and 1990's reveal features that are more reminiscent of a basin underlain by oceanic crust. This would imply the presence of two conjugate continent-ocean boundaries separating the crust underlying the basin from the Pelagian and Apulian Shelves. The location of the western boundary is uncertain although it is often considered to coincide with the Sicily-Malta Escarpment and its southeast continuation towards the Libyan coast. The eastern boundary is located offshore southwest Puglia in Italy in the direction of Albania and Greece. The age of the basin is even more controversial, with a time for the initiation of rifting that could be as early as the Permo-Triassic, the early Jurassic or as recent as the middle Cretaceous. This thesis presents new geophysical data from a study area covering regions of the Ionian Basin in its westernmost bathymetric limits with the Pelagian Shelf. Gravity modelling confirms the oceanic nature of the crust beneath the basin and also shows a progressive increase in crustal density from the Pelagian Shelf and the Sirt Rise towards the Ionian Basin. The crustal thickness is in agreement with published results from deep-penetrating seismic surveys. Moreover, the relatively high density of the crust of the Shelf suggests that it is made up of oceanic accretions rather than continental-derived terranes. Interpretation of regional gravity and seismic data indicates that the location of the western continent-ocean boundary lies significantly to the east of the Sicily-Malta Escarpment and extends in a southeast direction towards the Cyrenaica Ridge. North of the Medina Ridge, east-west dextral wrenching in the Plio-Quaternary is deemed to have shifted the boundary further east with respect to the boundary in the south. Integrated seismic and well data show the presence of a series of en echelon fault blocks, igneous mounds, syn-rift deposits of probable late Palaeozoic to early Mesozoic age and a thick sequence of late Mesozoic to Tertiary post-rift sediments coinciding with the western margin of the basin. The age of the syn-rift sediments suggests that although the foundering of the basin to its present bathymetric depths may have started in the late Miocene, its opening occurred much earlier and has an origin in the Permo-Triassic during the :fragmentation of the north African margin in the break-up of Pangaea. Description: PH.D.PHYSICS

2007-01-01T00:00:00Z /library/oar/handle/123456789/101830 2022-09-16T07:52:50Z 2009-01-01T00:00:00Z

Title: The characterization of a fibre-optic gyroscope Abstract: A fibre-optic gyroscope is an optoelectronic device that is mainly utilized to determine the angular motion and orientation of a rotating system. The principle of operation of this optical gyroscope is based on the Sagnac effect in which a phase difference proportional to the angular rate is produced between two counter-propagating beams. The main aim in this dissertation is that of characterizing one particular fibre-optic gyroscope model (which is a Fizoptika rotational sensor), where by means of different experiments its specific features can be established. An electrical assembly together with an experimental setup had to be constructed in order to operate the fibre-optic gyroscope and provide the rotational motion required. Moreover, the introduction of a lock-in amplifier in this electrical assembly turned out to be indispensable in retrieving the output signal emitted by the fibre-optic gyroscope especially in determining the different terms of the characteristic equation. The electrical components present in the fibre-optic gyroscope model were also tested and characterized in order to obtain their specific and individual characteristics. This was also done in order to obtain one of the essential identifications of an optical gyroscope which is that of the optical scale factor which determines the correlation between the Sagnac phase difference and the angular rate of the system. Description: B.SC.(HONS)PHYSICS

2009-01-01T00:00:00Z