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Publication Open Access Investigating the effect of ground layer adaptive optics on speckle interferometry through computational simulations(University of Galway, 2026-04-30)Atmospheric turbulence limits the angular resolution of ground-based telescopes far below the diffraction limit. Speckle interferometry (SI) is a technique that recovers diffraction limited information under the turbulent atmosphere. This thesis investigates the performance of SI for recovering the parameters of binary star systems under photon-limited conditions and assesses the gains achievable with ground-layer adaptive optics (GLAO). Speckle images of both binary stars and reference stars were generated through numerical simulation, with atmospheric turbulence modelled by Kolmogorov phase screens. Fourier domain analysis of these images produced the corresponding power spectra, which—after calibration—were used to extract the binary separation, position angle, and intensity ratio, while a least-squares bispectrum algorithm recovered the Fourier phase to resolve the intrinsic 180° orientation ambiguity. Results show that SI reliably recovers binary parameters at high photon counts. Intensity-ratio estimates become biased and increasingly variable as the number of photoevents decreased to approximately 25,000 photoevents. Incorporating GLAO, modelled via removal of up to 120 Zernike modes from one of two phase screens, significantly improved fringe contrast and reduced the number of photoevents required for reliable recovery of binary parameters by more than an order of magnitude. These findings demonstrate that combining SI with GLAO correction enables diffraction limited measurements of binaries at visible wavelengths using relatively low photonevents. The study provides practical thresholds and error estimates for observing faint binaries with 4-m class telescopes and offers a computational framework readily extendable to real observational data and more advanced adaptive-optics configurations.Publication Open Access Iron-mediated autotrophic denitrification for nitrate removal: Product selectivity and microbial succession(University of Galway, 2026-04-30)Fe-mediated autotrophic denitrification has emerged as a promising technology for low carbon-to-nitrogen (C/N) wastewater treatment. It utilises solid-phase iron sources (zero-valent iron (Fe0) and iron minerals) and released ferrous ions (Fe2+) as electron donors to reduce nitrate (NO3-) or nitrite (NO2-) to nitrogen gas (N2) by autotrophic denitrifying bacteria, avoiding the high cost and secondary pollution risks associated with external organic matter addition, eliminating the generation of large volumes of sludge, and yielding by-products capable of adsorbing phosphorus and heavy metals. But Fe0 can reduce nitrate to ammonia by abiotic chemical reduction, resulting in NH4+ being retained rather than being permanently removed as N2. The contribution of microorganisms to enhanced iron-driven nitrate reduction and product selectivity remains unclear. Meanwhile, the low bioavailability and limited electron-donating capacity of Fe²⁺, especially when coexisting with more competitive electron donors such as thiosulfate, lead to the regulatory role of iron being overlooked. The objectives of this PhD research were to: (1) provide an up-to-date overview of Fe-mediated autotrophic denitrification; (2) explore the effects of unacclimated activated sludge on nitrate reduction and nitrogen product distribution in Fe and Fe/Biochar systems; (3) elucidate the regulatory role of iron in sulfur-mediated autotrophic denitrification, with a focus on denitrification performance, microbial succession, and metabolic pathways. The results showed that the introduction of unacclimated activated sludge significantly enhanced nitrate removal, reaching up to 100%, and improved N₂ selectivity to 79%. The Fe/BC/M group exhibited superior nitrate removal (ranging from 75% to 95%) across a broader pH range (from 2 to 10), with the preferable Fe/BC dosage set at 60 g/L. Microbial introduction increased electrochemical active surface area (ECSA), reduced electron transfer resistance and lowered corrosion potential, with a higher i0 value facilitating Hads generation, thereby enhancing nitrate reduction and N2 selectivity. The acclimation experiment demonstrated that iron modulated sulfur autotrophic denitrification efficiency, microbial succession, and key pathways. 1 mM Fe2+ enhanced denitrification efficiency to 91.1% while preventing cell encrustation. Metagenomic analysis indicated that phylum Campylobacterota (16.0%) and genus Sulfurimonas (14.4%) were enriched under iron-modulated conditions. Iron modulated nitrate reduction by improving the relative abundance of complete denitrification genes (napA, napB, and nosZ) and stimulating sulfur metabolism through the SOX complex pathway (soxZ and soxY). This PhD research supports the practical implementation of Fe-mediated autotrophic denitrification for low C/N wastewater treatment and contribute to the sustainable development of environmentally friendly biotechnologies for advanced nitrogen control.Publication Embargo Analysis and control of wide output voltage multi-level buck converters(University of Galway, 2026-04-28)Power supplies are a critical element of modern electrical systems. For emerging applications, conventional fixed-output power supplies may be unable to meet increasingly diverse load regulation requirements, particularly when it comes to ensuring the power supply’s output does not damage the load from unexpected voltage spikes or uncontrolled output current. This thesis investigates the development of a Wide Output Voltage converter capable of delivering a broad voltage and current range with precise control of the output voltage and current, that could be used in a modular, multiple-output ac-dc power supply, enabling a solution that combines the capabilities of multiple power converters into one. A comprehensive review of state-of-the-art wide output voltage architectures identified the Point of Load stage as the most effective location to increase the output voltage range without compromising independent operation. The Multi-Level buck converter emerged as a promising topology, offering improved efficiency, reduced component stress, and lower filter requirements compared to conventional “Two-Level” converter designs. A detailed loss analysis of multiple wide-output voltage converters using analytical models confirmed that the Three-Level buck converter outperforms equivalent single- and two-phase topologies across the whole output range, with significant gains in thermal headroom and potential power density. The power loss calculations were verified using three prototype converters, designed for a 1 V to 30 V, 0 A to 16 A, 300 W output range, which covers nearly 90 % of the duty cycle range of the converters. The literature review found that for wide output voltage operation, the control schemes available for the three-level converter were limited, particularly those that could provide cycle-by-cycle current control over the full output range. To determine if this affected the output regulation of the three-level converter, its dynamic performance was compared with that of other converters, using both Voltage Mode Control and Current Mode Control schemes to quantify their output regulation performance fully. This was achieved analytically using simulated models to characterise the frequency-domain and time-domain performance of the converters in both load and voltage steps. The dynamic performance evaluation revealed that existing control schemes for Three-Level converters suffer from poor transient response, particularly during large voltage steps, which was verified with the same prototype converters. To address this, a novel Hysteretic Current Mode Control scheme was developed, enabling proper cycle-by-cycle current regulation over the entire output range while maintaining high efficiency and robust stability. This control method was validated through simulation and experimental prototypes, demonstrating compatibility with an existing modular ac–dc system with minimal impact on its own regulation during load transients or input voltage variations. The results establish that a Three-Level buck converter with HCMC can deliver a wide range of output voltages while providing higher efficiency and robust load handling in a modular system. The work described in this thesis presents a validated topology and control scheme that can be applied to wider voltage and current output converters, including potential extensions to higher-level converter architectures to leverage the benefits of multi-level converters further.Publication Open Access An investigation into the performance and robustness of intelligent transportation system infrastructure node sensors(University of Galway, 2026-04-28)This thesis investigates the performance and robustness of sensors deployed in Intelligent Transportation System (ITS) infrastructure nodes to enhance the safety of all road users, particularly in the context of intelligent and increasingly autonomous vehicles. Despite the ubiquity of surveillance cameras, phone cameras, and ADAS sensors, infrastructure sensor nodes capable of robust and reliable environmental perception are not yet commonplace, prompting the central research question: why? One hypothesis explored in this thesis is that there are still several open questions about the individual sensor or combination of sensors that will enable safety-critical Infrastructure-to-Vehicle (I2V) ITS applications. A comprehensive review of the literature on infrastructure nodes reveals that, as yet, no single sensor exists that is capable of meeting the diverse requirements of all I2V applications. Contemporary autonomous vehicles predominantly deploy one or more RGB cameras, RADAR, or LIDAR sensors for safety-critical perception tasks; consequently, these sensors set the benchmark for infrastructure node sensors in this thesis. However, this thesis also examines thermal and event-based cameras to evaluate their potential for I2V systems. Event-based cameras exhibit particular promise due to their capacity to capture asynchronous events associated with moving objects, thus reducing bandwidth while preserving dynamic range at low latency, whereas thermal sensors have been shown to significantly improve night-time performance. Given the experience of the automotive and security industries to date, RGB frame-based cameras will most likely be one of the core sensors of ITS infrastructure, and this thesis examines a number of the challenges associated with their deployment. For example, subtle issues such as the variability in image signal processing (ISP) parameters across different RGB surveillance datasets raise concerns regarding the generalisability of deep learning models trained on such data. Another example is performance degradation in camera perception performance due to low-quality, inexpensive lenses or temperature-induced misalignment between the sensor and lens, resulting in blurred images. The impact of lens blur on deep learning perception performance is characterised by employing a physically realistic lens blur model to evaluate the correlation between image sharpness and perception accuracy. Results demonstrate that perception performance correlates significantly with sharpness, a factor that can be taken into account in determining the expected performance or capabilities of downstream perception algorithms. In conclusion, this thesis addresses several key challenges in safety-critical perception from an infrastructure perspective, focusing on sensor selection, configuration, and tolerances in the context of object detection performance on an ITS node.Publication Open Access Direct Flux via Virtual Faces (DFVF-overset): An interpolation-free, fully conservative scheme for overset CFD with direct calculation of intergrid flux(University of Galway, 2026-04-28)In this thesis a new, conservative and interpolation-free, method for computation of solutions to partial differential equations on overset grids is presented. Conventional overset approaches rely on discretising and solving the governing equations on each grid separately. Communication between the grids is then realised through interpolation from one grid to another. This is a source of error in the solution, and compromises the conservative properties of the system. The new technique, termed Direct Flux via Virtual Faces, or DFVF-overset, eliminates the need for interpolation. Instead, flux between overlapping cells on overset grids is calculated directly. A term for intercell face area is derived for overlapping cells which do not share faces, using a generalised, meshless form of the finite volume method. The composite system of overlapping grids can thus be discretised as one monolithic system. The errors associated with interpolation are eliminated and strict conservation is maintained. The method is implemented for the open-source CFD library OpenFOAM, and its performance is benchmarked against solutions using existing, interpolation-based overset techniques, as well as single-grid solutions. The accuracy of the technique is verified against analytical or published experimental results. In the solution of the Poisson equation, the method shows second-order convergence. For incompressible lid-driven cavity flow, DFVF-overset produces results close to single-grid solutions and displays similar grid convergence properties. In static and dynamic multiphase cases solved with a volume-of-fluid method, conventional overset schemes display loss of liquid mass, whereas DFVF-overset demonstrates strict conservation of mass and close agreement with single-grid solutions. The new technique produces continuous and smooth velocity and pressure fields, whereas existing interpolation-based techniques show discontinuities at the overset boundary. DFVF-overset shows potential to provide enhanced accuracy in any application where overset grids have utility, and to enable the use of overset in cases where current interpolation-based techniques are unsuitable, by combining the accuracy and conservative properties of a single-grid solver with the practical benefits of overset.