This thesis investigates how the processes of galaxy evolution combine to regulate gas content and drive the life cycle of nearby galaxies. We use a sample of 30,000 galaxies that is representative of gas content, star formation and environment in the local Universe and take advantage of the HI spectral stacking technique. Our findings demonstrate the importance of fast-acting gas stripping due to environment and gas supply fluctuations in regulating the star formation cycle. This thesis provides new insights into the relationships between galaxy properties and environment in the local Universe, providing strong constraints for galaxy formation and evolution models.
Power system stability is a major concern for the operation of power systems as the instability significantly affects both economic and technical benefits. The major challenge to maintain the power system stability is to match the continuously changing loads with the generation. Since power systems are mostly dominated by synchronous generators, excitation controllers have been useful to maintain this challenge including external disturbances. The excitation controllers need to be designed in such a way that these can provide robustness against all grid events. This thesis focuses to design a novel robust excitation controller for power systems to enhance transient stability.
The advancement of nanotechnology has enabled the miniaturization of electronic components to the extent of several nanometres, thus leading to heat dissipation issues which often result in device failure. This thesis involves a fundamental study on phonon and electron transport in semiconductor materials commonly used in electronic components. It proposes Monte Carlo phonon and electron transport simulation models to stochastically capture the physics of the transport mechanisms. Such information is essential to facilitate the study of heat distribution in sophisticated electronic devices in order to ensure optimum device performance and to prolong the device life.
This thesis’ experiment directed participants to drive a simulator while having their vision obstructed for various time intervals. The aim was to evaluate the effects that visual obstructions have on participants’ driving performance, subjective workload, and biological responses. Interviews were conducted to identify what strategies participants used to cope with the visual obstructions. This thesis has implications for defence domains, proposing that when multitasking within a vehicle, individuals will experience task performance decrements if they disengage from one task for 3 seconds or longer. Lastly, merging different types of data can develop better predictors of performance.
Number sense – the ability to discriminate between ‘fewer’ and ‘more’ objects beyond the range of counting is present from infancy (six months), and is the cornerstone of arithmetical and mathematical skills. Findings from this research revealed a relationship between number sense and neural mechanisms involved with sensory filtering (the removal of un-essential visual information). The conceptual synthesis between sensory filtering and number sense offers new insight toward developmental dyscalculia (mathematical learning disorder), where poor number sense – a symptom of developmental dyscalculia, is likely to be influenced by abnormal sensory filtering processes.
Internet-connected hosts commonly feature multiple network interfaces. Legacy data-transmission protocols are unable to take advantage of these when transmitting data. The Transmission Control Protocol Extensions for Multipath Operation with Multiple Addresses (MPTCP) specification retrofits such multipath capabilities, yet scope remains for exploring how data transmission across available paths ought to be coordinated through MPTCPs primary transmission mechanisms. This thesis outlines and evaluates a prototype MPTCP implementation for the FreeBSD operating system. The implementation augments FreeBSD with functionality that simplifies research on novel MPTCP transmission algorithms. The code is released publicly as a contribution to the FreeBSD community.
The offshore and shipping industry require accurate prediction of the shape of the largest waves and associated velocities to design and operate marine structures. Of particular interest are the so-called rogue waves, these waves are at least twice the height of the surrounding waves and often prone to breaking. The kinematic field associated with breaking rogue waves is responsible for the largest hydrodynamic loads on marine structures that, over the decades, have been responsible for many accidents recorded at sea.
This work demonstrates that the simple linear potential wave theory, used for decades by engineers, is not a reliable tool to predict wave induced velocities and consequently hydrodynamic forces during storm conditions when rogue waves are more likely to occur. Ultimately, the dissertation provides an enhanced description of the velocity field associated with breaking and non-breaking rogue waves to improve the current design practice.
This research targeted to improve the health and safety of workforce engaged in manual handing tasks, in construction and manufacturing industries.
Mainly, we conducted a questionnaire survey on certain health and safety risks associated with lifting and lowering tasks. This survey aims to collect perceptions or experiences based responses of participants and then explore the relationships between physical abilities of workforce, manual handing task requirements, postures and associated health and safety risks.
This thesis has developed quantitative methods to study stellar structures in galaxies, as seen in astronomical imaging at optical and infra-red wavelengths. These novel algorithms and techniques were used to gain new insight into evolutionary processes occurring in spiral galaxies, including our own Milky Way, with a focus on their stellar discs, bars and their dynamical (“buckling”) instabilities, their central bulges, and galaxy–(black hole) co-evolution in the previously unexplored regime of “intermediate-mass” black holes. The methods developed throughout are expected to be useful for a plethora of issues in extragalactic astrophysics, helping to further our understanding of galaxy evolution.
Obsessive-compulsive disorder (OCD) is a mental disorder characterised by unwanted intrusive thoughts (obsessions) and compulsions. The present thesis is that individuals may attempt to avoid, conceal, suppress, or neutralise intrusions not only to regulate aversive emotions such as anxiety and disgust, but to regulate shame. This dissertation addressed three primary questions. First, do individuals with OCD feel more shame than nonclinical populations when intrusions arise? Second, are individuals more likely to respond to frequent intrusions by performing compulsions if they feel shame? Third, is relief from shame associated with reduction in compulsions across the course of treatment?