College of Science, Engineering and Food Science - Doctoral Theses

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    Sediment transport modelling and geomorphological assessments related to offshore renewable energy developments in the Irish Sea
    (University College Cork, 2022) Creane, Shauna; Murphy, Jimmy; O'Shea, Michael; Coughlan, Mark; Irish Research Council for Science, Engineering and Technology
    A combination of in-situ geophysical, geological and oceanographic datasets, and advanced numerical modelling tools are used to: improve the understanding of hydrodynamics and morphodynamics in the Irish Sea, develop new methods and approaches to investigate hydrodynamics and seabed morphodynamics in an offshore setting, collect and produce novel datasets that will contribute to this scientific field, and facilitate the sustainable growth of anthropogenic activities in the Irish Sea. These new methods and approaches include, using process-based indicators to understand sediment wave development and distribution, utilising ADCP-based suspended solids concentration as a numerical model calibration tool, and the application of a ‘sediment budget’ to an offshore sand bank to understand external influences on the stability of its morphodynamic system. Results provide hydrodynamic proof underpinning the presence of the bed load parting (BLP) in central Irish Sea and associated divergent sediment transport pathways driving sediment dispersal across this tidally-dominated continental shelf sea. Analysis of tidal propagation through the Irish Sea Basin concludes that the origin of the BLP is mainly attributed to the intersection of the north and south tidal fronts at an inclined angle due to Coriolis Forcing and coastline interactions. Minor factors impacting the shape and location of the BLP are the change in tidal character at (a) abrupt bathymetry changes, (b) headlands and intricate coastline topography, and (c) large-scale constrictions. These outcomes set the basis of understanding for the thesis. Building upon this knowledge, analysis of targeted, high resolution, time-lapse bathymetry datasets in the south-western Irish Sea reveals sediment waves in a range of sizes (height = 0.1 to 25.7 m, and wavelength = 17 to 983 m), occurring in water depths of 8.2 to 83 mLAT, and migrating at a rate of 1.1 to 79 m/yr. Combined with numerical modelling outputs, a strong divergence of sediment transport pathways from the previously understood predominantly southward flow in the south Irish Sea is revealed. Furthermore, a new source and sink mechanism are defined for offshore independent sediment wave assemblages, whereby each sediment wave field is supported by circulatory residual current cells originating from offshore sand banks. Reliable sediment transport modelling is required to investigate these physical processes further, therefore, the need for cost-effective sediment validation datasets for 2D sediment transport models is addressed, utilising ADCP-based datasets. A robust spatial timeseries of ADCP-based suspended solids concentration was successfully calculated in an offshore, tidally-dominated setting. Three new validation techniques are deemed advantageous in developing an accurate 2D suspended sediment transport, including i) validation of 2D modelled suspended sediment concentration using water sample-based suspended solids concentration, ii) validation of the flood-ebb characteristics of 2D modelled suspended load transport and suspended sediment concentration using ADCP-based datasets and iii) validation of the 2D modelled peak suspended sediment concentration over a spring-neap cycle using the ADCP-based suspended solids concentration. The robust coupled hydrodynamic and sediment transport model produced from this research is used as a tool of investigation in subsequent chapters. The complex hydrodynamic processes controlling upper slope mobility and long-term base stability of Arklow Bank are determined. Results reveal a flood and ebb tidal current dominance on the west and east side of the bank respectively, ultimately generating a large anticlockwise residual current eddy encompassing the entire bank. The positioning of multiple off-bank anticlockwise residual current eddies on the edge of this cell is shown to both facilitate and inhibit east-west fluctuations of the upper slopes of the bank and control long-term bank base stability. Within Arklow Bank’s morphological cell, eight morphodynamically and hydrodynamically unique bank sections or ‘sub-cells’ are identified, whereby a complex morphodynamic-hydrodynamic feedback loop is present. The local east-west fluctuation of the upper slopes of the bank is driven by migratory on-bank stationary and transient clockwise residual eddies and the development of ‘narrow’ residual current cross-flow zones. Together these processes drive upper slope mobility but maintain long term bank base stability. A sediment budget was successfully estimated for an offshore linear sand bank, Arklow Bank, whereby seven source and nine sink pathways are identified. The restriction of sediment sources off the southern extent of Arklow Bank impact erosion and accretion patterns in the mid and northern sections of the bank after just one lunar month simulation. Where tidal current is the primary driver of sand bank morphodynamics, wind- and wave-induced flow is shown to alter sediment distribution patterns. This advanced body of work forms a robust scientific evidence-base to facilitate the sustainable growth of offshore renewable developments.
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    Participation and triangulation: learning from non-institutional international Architecture Live Projects through a comparative case approach
    (University College Cork, 2022) Lehane, Jack R.; Mulrooney, Sarah; Linehan, Denis; Mccartney, Kevin
    Noticeable opportunities for architecture education are opening up in the world, markedly non-institutional international Live Project networks that practice independently of university course structures. As distinct from conventional volunteer-based construction in the humanitarian development sector, this emergent and ‘independent’ model of international architecture education represents a unique intersection between the Live Project and new spatial agency. However, despite the increasingly participative nature of Live Project initiatives, there is still a lack of research into the role stakeholder participation plays in the first place, exacerbating this emergent model’s underrepresentation within formal research and literature not least due to its recent and decentralised nature. To address this knowledge gap — and in line with calls for a departure from traditional understandings of participation in an era of globalisation — this thesis employs a first principles reasoning and (re)turns to the fundamental question: What constitutes stakeholder participation for this new model of Live Project in the first place? Through real world participation and a comparative case study approach, this thesis embarks beyond the boundary of the university structure and engages multiple stakeholder groups across three real world Live Project cases in Lebanon, Fiji and Nepal. Each case is investigated according to three sub-research questions: • What can the built artefact reveal about the stakeholder participation? • How are these aspects of stakeholder participation experienced by the stakeholders? • What are the extended implications of this participation for the organisation and the community? Mixed methods were utilised for concurrent data collection during and after each case study — participant observation, semi-structured interviews and post-occupancy participatory walking probe. Following this, three phases of sequential data analysis were employed to measure, contextualise, and assess the implications of stakeholder participation in the projects. The findings offer an original and measurable understanding of stakeholder participation, as revealed through the built artefact. As a result, this research formalises this emergent typology of Live Project through comparative measure; demonstrating distinctions from, and extendedly limitations of, Architecture Live Projects in academic institutions. This extends our current knowledge of how stakeholder participation in these Live Projects operates, informing participation for the organisations and the communities within future initiatives, and offers an empirical basis to broader participatory conditions of an emerging architectural space.
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    Lead toxicity in Mute swans: Cygnus olor (Gmelin)
    (University College Cork, 1987) O'Halloran, John; Myers, A. A.
    Lead toxicity in Mute swans Cygnus olor (Gmelin) was investigated. Two methods for the assessment of lead exposure were used: (1) blood lead level and (2) free red blood cell protoporphyrin. An accurate estimation of haemoglobin was found to be a prerequisite to determining lead exposure. A measurement of haemoglobin based on converting all haem species to alkaline haematin was found to give accurate and reproducible results. Variation in blood lead during the diel cycle in caged birds was investigated. Blood lead levels in a flock of Mute swans at a coarse-fish angling site were examined over a two year period. Forty-two percent of blood samples (n = 870) from this site were shown to have elevated lead. X-ray examination of swans revealed the source of contamination to be ingested lead pellets. Post mortem examination showed that 68% (n = 101) of all Mute swans examined died from lead poisoning. Two sources of lead were identified: spent gunshot and lost or discarded anglers' weights. Biochemical and haematological aspects of swan blood were also investigated. Reference haematological and biochemical values were established from 'normal' healthy Mute swans. These reference values were used as a baseline against which changes in lead poisoned birds could be measured. Moulting and immaturity were identified as causing natural variation, while acute lead poisoning was found to increase protoporphyrin, cholesterol and two serum enzymes: lactate dehydrogenase and aspartate amino transferase. Hypochromic anaemia was noted in swans suffering from acute lead poisoning. The possible role of lead in causing other sub-lethal effects, for example collisions, is also discussed.
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    Synthesis of novel cycloperoxides
    (University College Cork, 2023) Hennessy, Mary C.; O'Sullivan, Tim; Irish Research Council
    Cycloperoxides represent an important class of compounds for synthetic chemists. Their asymmetric synthesis will be the focus of this thesis, specifically using organocatalysis. Chapter 1 contains a review of organocatalysed peroxidations from the literature and within the research group to date. The key aims and objectives of this project are also outlined. Chapter 2 describes the generation of a diverse library of trans-γ,δ-unsaturated β-keto esters. The preparation of these compounds involves both Wittig chemistry and Lewis acid-catalysed C-H insertion strategies. The synthesis of a cis-γ,δ-unsaturated β-keto ester and a non-enolisable α,α-disubstituted β-keto ester are also outlined. The optimisation of the organocatalysed peroxidation of γ,δ-unsaturated β-keto esters in terms of enantioselectivity and yields is described in Chapter 3. To determine the enantioselectivity of the peroxidation reaction, a robust chiral HPLC methodology is required. The development of a suitable separation methodology is outlined in this chapter. Chapter 4 describes a novel synthetic route to 3,5-substituted 1,2-dioxolane ethyl esters through the chemoselective reduction of a δ-peroxy-β-keto ester to the corresponding δ-peroxy-β-hydroxy ester, and subsequent phosphorus pentoxide-mediated cyclisation. Chapter 5 outlines our preparation of several novel 1,2-dioxolane carboxylic acids and various attempts at subsequently introducing an N-acyl sulfonamide to the 1,2-dioxolane core. Chapter 6 details the main conclusions of this work and proposes several avenues of research to investigate in future. Chapter 7 contains all relevant experimental procedures, including spectroscopic and analytical data.
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    Integration of anaerobic digestion with bio-electrochemical technologies in cascading circular bioeconomy systems producing biofuel and chemicals
    (University College Cork, 2023) Ning, Xue; Murphy, Jerry; Lin, Richen; O'Shea, Richard; Sustainable Energy Authority of Ireland; Gas Networks Ireland
    Anaerobic digestion is a waste treatment technology, which can alleviate greenhouse gas emissions, reduce environmental pollution whilst simultaneously generating biomethane (a clean energy source which can be used as a direct replacement for natural gas), biofertilizer (which can reduce fossil fertiliser use), and biogenic CO2 (which can be further valorised). However, many anaerobic digestion systems are implemented as standalone systems without optimizing circularity in system design. Conventional anaerobic digestion systems can face challenges such as: low biomethane production rate (in particular from feedstocks with high portions of lignin and cellulose), and inefficient biogas upgrading to biomethane. In an endeavour to simultaneously increase biogas production and upgrading, the potential for integrating anaerobic digestion with three emerging bio-electrochemical technologies in a circular cascading bioeconomy was assessed, including for power to gas, microbial electrolysis cell, and microbial electrosynthesis. An energy balance assessment indicated that these three circular cascading bio-electrochemical systems could display positive energy outputs if the electricity used would have been otherwise curtailed or constrained. This drove the thesis to develop bio-electrochemical cascading anaerobic digestion systems for value-added biofuel and chemical production. Anaerobic digestion is a complex microbial process that involves multiple syntrophic interactions with interspecies electron transfer as a crucial factor influencing digestion efficiency. Biochar has been shown to support direct interspecies electron transfer between fermentative bacteria and methanogenic archaea, thereby increasing biomethane production and reducing reaction times. The first experimental work investigated the biomethane potential in batch two-stage co-digestion of grass silage and cattle slurry, with varying dosages of biochar supplementation. Biochar addition at the optimal dosage of 10 g/L in two-stage digesters led to the highest methane yield of 253 L per kilogram (kg) volatile solid (VS), which was 24% higher than that from two-stage digesters without biochar supplementation. Continuous single-stage and two-stage co-digestion of grass silage and cattle slurry with 10 g/L biochar supplementation were compared in the second experimental work. In continuous trials, operated at an organic loading rate of 4.0 g VS/L/d, the second-stage digester in two-stage digestion produced a methane yield of 237 L/kg VS with 10 g/L biochar addition; this was 7% higher than the second-stage digester without biochar addition. The incorporation of two-stage anaerobic digestion and the addition of biochar was shown to be a promising approach to enhance system stability and improve biomethane production. To expand on the application of conductive materials in improving biogas production in anaerobic digestion, biochar was added to an integrated microbial electrolysis cell and anaerobic digestion system (the MEC-AD system) in the third experimental work. The results demonstrated that the biomethane yield and methane content in biogas in the MEC-AD system (with plain graphite cathode) increased by 68% and 17%, respectively, compared to conventional anaerobic digestion when co-digesting grass silage and cattle slurry. Biochar supplement (10g/L) in the MEC-AD system was shown to further increase biomethane yield by 9% as compared to the MEC-AD system without biochar addition. The combination of an enhanced electric field and biochar addition in the MEC-AD system provides a pathway for effective in-situ bioconversion of carbon dioxide to biomethane and improved substrate utilisation. The overall carbon utilisation of biomass conversion in AD and MEC-AD can be limited by the presence of carbon dioxide (CO2; approximately 30–45%) in the off-gas. This residual CO2 can be upgraded into valuable chemical products (such as acetic acid and ethanol) in microbial electrosynthesis, a process by which microorganisms utilize electrical energy to convert CO2 into value-added compounds. A 3D cobalt and nickel coated carbon felt (CoNi-CF) cathode was developed in this last experimental work and applied in microbial electrosynthesis reactors. The highest acetate concentration obtained from the microbial electrosynthesis reactor was 18.4 mmol/L, with a carbon conversion efficiency (C in acetate) of 75.4%, while the maximum ethanol production achieved was 4.5 mmol/L, with a carbon conversion efficiency (C in ethanol) of 18.6%. This thesis explored the synergistic integration of anaerobic digestion and bio-electrochemical technologies in cascading circular bioeconomy systems, and demonstrated that simultaneously enhanced biogas production and CO2 upgrading can be achieved through efficient direct interspecies electron transfer by adding biochar and/or by imposing an external electricity supply. The results from this thesis can provide guidance on designing future cascading circular bio-systems to produce advanced biofuel and value-added chemicals.