Engineering: Theses and Dissertations
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Item Open Access Development and evaluation of machine learning tools to process an internet forum for clinical research of polycystic ovary syndrome(2024) Emanuel, Rebecca H. K.This thesis explores the possibility of using internet forums and machine learning (ML) for clinical research, specifically through the exploration of the PCOS subreddit to research polycystic ovary syndrome (PCOS). PCOS is a heterogenous condition that is estimated to effect up to 21 % of reproductive aged people with ovaries. It is diagnosed through the presence of at least two of the following: biochemical or clinical hyperandrogenism, menstrual irregularities or ovulatory dysfunction, and polycystic ovarian morphology (PCOM). Approximately 75% of people with PCOS have impaired insulin sensitivity. This relationship between PCOS and insulin resistance is not restricted to people who are overweight or obese. PCOS is also associated with subsequent metabolic disorders, infertility, pregnancy complications, sleep disturbances, decreased mental health, endometrial cancer, eating disorders and sexual dysfunction. Phenotypes can be derived from the inclusive nature of the diagnostic criteria, but clinically relevant phenotypes have not been agreed upon. There is currently worldwide dissatisfaction with the treatment of PCOS and the available research on the subject.Item Open Access Strain-induced stressing of concrete storage tanks(1990) Vitharana, Nihal DhamsiriIn this thesis, the effects of strain-induced loading on concrete liquid storage reservoirs are examined with particular regard to temperature. Although the research is primarily directed to thermally induced loads, the formulations and findings are applicable to other strain-induced loadings such as shrinkage and swelling. The investigation incorporated both experimental and theoretical studies. Current methods for predicting moment-curvature responses and strain induced loads are evaluated with respect to convenience of use and accuracy, and the ACI 318-83 Branson type approach was found to be suitable. Design aids are presented for calculating section properties and strain-induced loads. A method is proposed for the effective moment-curvature response of concrete reservoir wall elements subjected to combined axial force and flexural moment. A parametric best-fit formulation is also derived for bi-linear effective moment-curvature representation. Six half-scale wall specimens were tested under mechanically applied and thermally induced uni-directional and bi-directional moments with and without simultaneous applied tensile thrust. The measured responses were compared with theoretical predictions. No significant difference. between uni-directional and bi-directional or mechanically and thermally induced loads was observed. These properties were incorporated in the non-linear analyses of cylindrical reservoirs, and the results were compared with the predictions from the usual methods. Current code provisions were found to be inaccurate being either conservative or unconservative in different parts of the wall for different conditions. A basic study into the stress redistribution effects of circular rings is also reported. The detailed analysis of reservoirs rectangular in plan under strain induced loadings was carried out using a finite element shell analysis program. Nine reservoir aspect ratios were considered. The stress redistribution effects are discussed. Design aids and examples are presented for thermal stresses on rectangular reservoirs subjected to different loading patterns. Recommendations for future research are proposed.Item Open Access Thermal and emission performance studies on premixed meso-combustors for thermophotovoltaic applications.(2025) Rong, HuiThis study focuses on the thermal and emission performance of small-size premixed combustors by investigating the combustion and flow characteristics of various carbon-free and classical hydrocarbon fuels, including ammonia, hydrogen, and methane. More attention is given to the influence of combustor structure and inlet parameters on thermodynamic and emission performance. These novel structural designs demonstrated obvious improvements in combustor performance, offering valuable insights into the optimization of small-scale combustion systems. One of the designs include a reverse flow single-channel inlet and double-channel outlet (SIDO) combustor aining to enhance its thermal performances. Increasing the inlet pressure (Pin) improves thermal performance and exergy efficiency while reducing nitrogen oxide emissions. Increasing the inlet velocity (Vin) can enhance the temperature uniformity of the combustor wall. Increasing the equivalence ratio (Φ) leads to a reduction of nitrogen oxide emissions, and the micro-combustor has better overall performance, when Φ = 1.0. Increasing the blending ration of hydrogen give rise to a decayed advection but enhanced diffusion, and the pressure loss (Ploss) can be reduced. Another design is applying porous medium (PM) in the small-size combustors. In comparison with the system without PM, the application of PM is found to lead to a significant improvement on thermal performances. It is found that there is a substantial 37.5% reduction in the standard deviation of the outer wall temperature (ST,W) at Vin = 2.0 m/s. The optimal thermal performance is achieved as Φ=0.9. A higher porosity (σ) gives rise to a lower entropy production within the PM. The lowest entropy production resulting from heat conduction is shown to be achieved when σ = 0.8. By implementing PM, the exergy efficiency (ηexergy) is found to be increased by 23.9% at Vin = 2.0 m/s. In general, this present investigation shed physical insights on the entropy production and thermodynamic exergy performances of ammonia/methane-fueled micro-combustion systems with and without PM. For comparison, we proposed and studied a double-channel inlet and double-channel outlet (DIDO) combustor, which is shown to be capable of generating a vortex at the outlet, thereby reducing NOx emissions. Specifically, at a ammonia volumetric flow rate of 900 mL/min, the NO concentration at the outlet can be curtailed by 29.23%. The DIDO combustor yields a substantial enhancement in thermal performance, achieving a 51% reduction in ST,W when ammonia volumetric flow rate is set at 500 mL/min which significantly enhances the uniformity of wall temperature. The peak of thermal performance and maximum radiation efficiency (ηradiation) is reached at Φ = 0.9. Finally, we proposed and investigated a reverse-flow Tesla channel applied in a counter-flow combustor. It is found that such structured combustor has a remarkable improvement of 72.6% to the combustor wall temperature at hydrogen volume flow rate of 100 mL/min. The diodicity (Di) of the Tesla valve is found to be increased with higher hydrogen volume flow rate, and a lower Φ contributes to a higher Di. Besides, Di decreases when Φ goes up, stabilizing at Φ = 0.9. The reverse-flow Tesla valve exhibits a more uniform pressure distribution and entropy production than the forward-flow Tesla valve. At Φ = 0.9, the hydrogen-to-air ratio maximized heat release, producing the highest entropy. Tesla-valve structured combustors demonstrate near complete combustion before Φ reaching 0.9, the combustion efficiency (ηcombustion) gradually decreasing after Φ getting to 1.0. Additionally, the effect of blending ammonia with various ratio of hydrogen was studied. To achieve a stable ammonia-hydrogen combustion within the reverse and forward flow Tesla valves, ammonia ratio can reach 20% for the reverse flow Tesla valve, whereas the ratio for a stable combustion in the forward flow configuration is 10%. The increased flow resistance inside the reverse flow structure promotes more complete fuel-depleted combustion, thereby increasing the wall temperature. In contrast, the forward flow structure, due to its lower flow resistance, extends the flame area of the mixed fuel, thereby improving wall temperature uniformity. The Double-layer Tesla Valve structure improves wall temperature uniformity by over 55% across varying flow rates. Both double-layer and single-layer structures demonstrate a significant enhancement in the combustor's thermal performance and overall performances characterized with Nusselt and Peclet numbers.Item Open Access Forming metal organic framework glass membranes for gas separation.(2025) Stone, Dana M.This thesis investigates the fundamental factors affecting the use of glass transformations to repair defective crystalline metal organic framework (MOF) membranes. This work aims to clarify our understanding of the major limitation that prevents MOF materials being used for gas separation membranes: intercrystalline defects. The research aimed to produce MOF membranes within tubular ceramic supports and evaluate the differences in gas separation performance between crystalline and glass (ag) forms. A four-stage method was adapted to produce glass membranes, including the use of an -alumina tubular support, ZnO precursor deposition via Atomic Layer Deposition (ALD), in-situ solvothermal synthesis of ZIF-62, and defect healing through glass transformation. The gas separation performance of ZIF-62 and agZIF-62 membranes showed low permeance (10⁻⁸ & 10⁻¹⁰ mol m⁻²s⁻¹Pa⁻¹ respectively) and selectivities (e.g. H₂/CO₂ of 3.5 & 4.3 respectively) which were seen as significant areas for improvement. To address the low permeance, ALD conditions to control membrane thickness were developed, reducing crystalline membranes thicknesses from 38 μm to 16 μm. The glass transition process led to further membrane thinning, down to 2 μm, due to a capillary effect. To address low selectivity, the relationship between isothermal hold times, porosity, and macroscopic melting was examined via PALS, adsorption studies, and visual imaging. These results showed that only limited retention of porosity was possible, and that isothermal treatments offered no control over pore structure. These results highlighted challenges in reproducibility during glass transformation by revealing the variability in agZIF-62 samples, including pore aperture size which ranged from 3.2 to 3.7 Å. Finally, a pioneering alternative synthesis approach using chemical vapor deposition (CVD) was explored for the multi-ligand ZIF-62 to address the poor quality of ZIF-62 membranes. However, the polymorphic nature and high energy state of ZIF-62 prevented its synthesis via CVD, instead resulting in the formation of the dense ZIF-zni. Overall, this research provides foundational insights for enhancing the performance and scalability of ZIF-based membranes for gas separation.Item Open Access A new approach to model locomotive kit set instructional design.(2025) Bennet, CelynModel locomotive construction offers a rewarding and intellectually stimulating activity within the broader context of railway modelling. Despite its benefits for cognitive and manual skill development, model locomotive construction is increasingly overshadowed by the prevalence of ready-made models. One reason they are overshadowed is that there is a significant barrier to entry for newcomers. This barrier arises from the lack of adequate support offered by commercially available “beginner” model locomotive kit sets, which do not address the challenges newcomers encounter during the construction process. This research investigates the challenges associated with model locomotive construction for four user groups (Non-Makers, Makers, Railway Modellers, and Locomotive Constructors) and proposes a redesigned instructional and product approach to bridge the identified gap between railway modelling and locomotive construction. Using the Stanford design methodology, this research empathised with novice constructors, investigated product and instructional design principles, as well as iterating through ideation and prototyping, to create a product that supports users who are participating for the first time. User observation sessions were conducted across a range of participants from all skill levels using a commercially available model locomotive kit set. This identified that Non-Makers, Makers, Railway Modellers, and experienced Locomotive Constructors all struggled with the construction process due to a lack of communication and synergy. The main issues participants experienced during the commercial kit observation session were related to the comprehension of the instructions. This led to errors being made, with some participants being unable to complete the construction task. Focus groups and iterative prototyping were employed to redefine the Product Design Specification (PDS) and incorporate refined instructional and design principles to simplify the construction process. The final design outcome comprised an instructional system which embedded information into the packaging. This meant that not only was the user instructed during construction but also supported them, building trust and confidence in the participant. The instructional system redesigned the kit set components to incorporate design principles for communication and engagement such as Constraints. These served to limit the options for user engagement therefore building affordances and reducing errors.. Additionally, the kit set packaging was redesigned and evolved from merely protecting components to incorporating instructional information and enabling assembly visualisation. The final design was validated through user testing sessions with participants across the four skill categories. The redesigned system demonstrated a significant reduction in errors and assembly time, as well as improved comprehension and user satisfaction. These findings confirm the effectiveness of incorporating instructional and design principles into the development of beginner-friendly model locomotive kits. Future research would further investigate the refinement of the final design and explore other concepts presented during the ideation and prototyping rounds.Item Open Access Synthesis and characterisation of poly glycerol sebacate bioelastomers.(2025) Mohsin, HammadContext: Surgical meshes have been used in multiple areas of the human body, especially to treat hernia defects. However they are controversial regarding postoperative complications. Research Motivation: Bioelastomers are not currently used in the commercial production of surgical meshes. Nonetheless they have potential advantages in that the mechanical properties of bioelastomers may provide mechanical stimuli that promote faster wound healing in soft tissue applications. Objectives: There is need to better characterise the bioelastomers, i.e. determine those properties that are important to biomedical engineering designers who are considering potential future implant applications. Results: This thesis describes the characterisation of one of the bioelastomers, specifically polyglycerol sebacate (PGS), by reporting on chemical structure, thermal behaviour (glass transition temperature, crystallisation temperature, shrinkage, decomposition temperature), and mechanical properties (Young’s Modulus, strength, elongation). The work also reports on the use profile for the material, i.e. the medical implications (hydroscopic properties), manufacturability of meshes, and the product design implications. Findings: Two synthesis routes were attempted, microwave and conventional inert gas and oven. This work e established that the microwave route is not currently reliable. Conventional synthesis for PGS using inert atmosphere and curing in a vacuum oven, was successful. Originality: This work makes the novel contribution of showing a comprehensive characterisation of poly glycerol sebacate, including the rheology which has not previous been reported in the literature. In addition, the work shows that the curing temperature of 140 oC as cited in the literature, resulted in a material with the correct chemical composition but showing different molecular segmental thermal behaviour. The work makes an additional contribution of offering a conceptual model of how the factors affect mesh infection, chronic pain, and hernia recurrence. Using this a risk assessment framework was developed. This quantifies risk of complications, based on the frequencies reported in the literature.Item Open Access A multimodal approach to investigate cognitive and neural mechanisms of construction hazard recognition : the roles of attention, situation awareness, and experience.(2025) Zhang, ZheThe construction industry is hazardous due to its high-risk nature, with many fatalities attributed to the failure of hazard recognition. A review of existing research in the construction reveals the following limitations: (1) Limited understanding of hazard recognition in dynamic environments, (2) Insufficient consideration of the combined impact on situation awareness (SA) transition and hazard recognition, (3) Subjective and static SA measurement methods, (4) Lack of consideration of temporal SA transitions, (5) Insufficient integration with cognitive psychology and neuroscience, and (6) Limited understanding of the role of technologies in enhancing SA. The research aims to investigate how the experience and interplay between endogenous (top-down) and exogenous (bottom-up) factors affect SA transitions and hazard recognition in dynamic virtual construction environments. The objectives are to (1) Identify key cognitive factors underlying construction hazard recognition and the mechanisms by which digital technologies enhance SA. (2) Investigate the effects of the interplay between bottom-up attention (B-U) and top-down attention (T-D) on hazard recognition. (3) Examine the effects of augmented stimuli and safety goal setting on SA transition (from Level 1 to Level 3 SA) and hazard recognition. (4) Compare the differences in SA, path selection, and hazard recognition between novice and experienced workers under different conditions of augmented stimuli and safety goal settings. A mixed-methods approach was employed, combining a systematic review, scientometric analysis, and experiment. Systematic review and scientometric analysis were employed to identify cognitive factors that influence hazard recognition in dynamic virtual construction sites. The experiment employed innovative technologies such as Immersive Virtual Reality (IVR), eye tracking, electroencephalography (EEG), and event-related potentials (ERP) to examine how three key factors - B-U, T-D, and SA - affect hazard recognition in dynamic virtual construction sites. The research found that augmented stimuli and safety goal setting significantly improve B-U, T-D, SA transition, and hazard recognition. Moreover, experienced workers demonstrated a superior ability to recognize hazards, characterized by faster response times, increased fixation on hazardous objects, and heightened activity in brain regions associated with SA. This research makes significant contributions to both construction site safety practices and academic literature by shifting traditional safety management approaches towards human-centered ones. This paradigm shift has the potential to revolutionize how researchers, government agencies, construction companies, and industries prioritize worker safety. Specifically, by transitioning from rigid protocols and regulations to a deeper understanding of cognitive processes, this work introduces a worker-centric approach that leverages digital technology to enhance hazard recognition. Future research should focus on developing multimodal assessment tools that integrate various neurophysiological measures to understand SA transitions in real-time. Understanding the neural mechanisms underlying SA processing is crucial for developing targeted interventions. Techniques such as functional magnetic resonance imaging or magnetoencephalography can be employed to identify subcortical brain regions involved in SA transitions. Research should also investigate SA transitions in complex environments with high workload, time pressure, or uncertainty, to develop more effective safety protocols. It is highly recommended that a worker-centric approach be adopted in safety management practices, where safety protocols and training programs are tailored to meet the specific needs, abilities, and experiences of individual workers.Item Open Access Measurement and modelling of calcium tartrate precipitation in wine.(2025) Muir, JackPrecipitates in wine are considered undesirable by the wine industry as consumers perceive them as indicators of poor wine quality. Calcium tartrate precipitation is difficult to predict and can occur months after bottling, which makes it hard for winemakers to prevent. The levels of calcium and tartrate are important for predicting the precipitation of calcium tartrate, but wine also contains many interacting components that will influence its formation and solubility in solution. Any attempts to model and predict the precipitation of calcium tartrate must account for these interactions. A system of equations for ion equilibria, electroneutrality, and conservation of mass was solved using Newton’s Method. This used activity coefficients calculated with the mean spherical approximation method, which provides good estimates for a wide range of concentrations and neutral molecules. The model accounted for the major species present in wine, including water, ethanol, the major organic acids, inorganic anions and cations, glucose, and fructose. Automatic pH adjustment was implemented to ensure the model correctly predicted the measured pH of the wine. Heun’s method was incorporated to solve precipitation rate equations and demonstrated how a solution with a low supersaturation could suddenly form crystals after a long period. Wines with and without crystals were analysed using high-performance liquid chromatography, ion chromatography, and microwave plasma atomic emission spectroscopy. The pH, ethanol, calcium, tartrate, and malate concentrations were individually compared for the wines that formed calcium tartrate and the wines that formed no crystals. This showed that there was no significant difference between the groups for any of these factors. However, the model was able to account for the interactions between the wine components and predicted significantly higher supersaturation ratios for wines that formed calcium tartrate. There was overlap between the groups but the model could still provide a useful indication of a wine’s risk level. A reduced model containing only water, ethanol, calcium, tartrate, malate, and lactate was tested to see how many compounds were required for an adequate prediction. This reduced model was still able to predict significantly higher supersaturation ratios for wines that formed calcium tartrate and would be more practical for winemakers to use. It was harder to do pH adjustment using the reduced model, so a sequential search was implemented to ensure that the code could solve automatically for every wine. A range of juices and wines were analysed to see if the model could be used early in the winemaking process to predict calcium tartrate formation. No relationship was found between the supersaturation ratio of the juice and the final wine, demonstrating that the model could only be used for prediction after most of the winemaking processes were finished. Ideally, the model would be used after cold stabilisation (when potassium bitartrate is precipitated) and close to the bottling of the wine. Some of the major factors that increase the risk of calcium tartrate precipitation are high pH, calcium, tartaric acid, ethanol, and low malic acid. These factors all interact, so no simple ranges can be given where there is no risk of precipitation. Winemakers can lower the likelihood of crystals forming by avoiding additives containing calcium, avoiding deacidification, considering acidification for high pH wines, creating a wine with a lower ethanol content, and avoiding malolactic fermentation.Item Open Access Machine learning for automated trading.(2025) Semple, WilliamThis thesis uses three machine learning algorithms to construct automated trading systems to predict the direction of share prices using technical analysis. Random forest, gradient boosting, and BART methods were chosen. We use a strategy of buying and selling stocks over 5-day windows over the span of the trading period, using some set of pre-determined shares. We considered the buy-hold strategy of buying all of the predetermined shares at the start of the trading period and selling them at the end of the period, to be the baseline against which our systems were measured. Each machine learning algorithm had their hyperparameters tuned, with gradient boosting using three different tuning algorithms. The final results are promising; each of the three methods resulted in greater returns and risk-adjusted returns than the buy-hold strategy. iItem Open Access Aerodynamic performance investigations of UAV propellers at low Reynolds number.(2025) Dougherty, SamThis thesis summarizes a comprehensive methodology for analysing low Reynolds number propellers using the Blade Element Momentum Theory (BEMT), aiming to predict these propellers’ aerodynamic performances more accurately in climbing and hovering conditions. Since many commercially available propellers lack published geometric data, a scanning method was developed first to extract this critical information. This method involved 3D laser scanning the propeller, meshing in Geomagic Wrap, and extracting chord length and pitch angle data in SolidWorks. The accuracy of this method was validated through visual/deviation analyses and comparison to manufacturers data. Then we outline the fundamental BEMT equations along with methodologies for aerodynamic polar generation, extensions, and general BEMT corrections. This detailed methodology allows general users to implement BEMT in their own software and produce more accurate propeller predictions. Three key contributions to BEMT accuracy were identified: 1) polar generation and extension, 2) general corrections, and 3) spanwise airfoil section/Reynolds number considerations. Suggestions on the optimisation of these elements is provided to improve model prediction accuracy. For this, polars were generated first using XFOIL software, with an 𝑁𝑐𝑟𝑖𝑡 value of 6 found to improve the agreement with the experimental data of Brandt. An extension method was then applied to the unstalled XFOIL polars to account for the blade elements reaching angles of attack (AOA) beyond the unstalled region. An investigation of the Viterna & Corrigan and AERODAS extension methods found them to be largely interchangeable, however AERODAS was favoured due to its simpler implementation. As far as the general BEMT corrections are concerned, the Prandtl tip-loss correction was found to improve the agreement by mitigating over-predictions of thrust in low advanced ratio conditions. The Prandtl-Glauert compressibility correction had no effect on performance prediction, as none of the propellers tested reached conditions that warranted application (𝑀𝑎>0.3). Reynolds number corrections had a minimal impact on performance predictions, but were computationally inexpensive, which justified their inclusion. The employment of a rotational correction improved the BEMT accuracy, where the Corrigan & Schilling’s stall delay model was found to provide a better agreement than Snel’s 3D correction model. However, using the stall delay model with the Viterna & Corrigan’s polar extension method was identified as a combination that could potentially lead to thrust over-predictions at low advanced ratios. Finally, considerations of the airfoil section and Reynolds number variation across the blade span with regards to polar inputs was analysed. Using a single airfoil at 75% blade span produced comparable results to considering airfoil section variation across blade span, but further testing would be required to test the necessity of considering spanwise airfoil shape variation on other propeller geometries. Considering only a single Reynolds number at the 75% span position was found to produce better agreement than considering Reynolds number variation along the blade. This finding is likely applicable to other propeller designs given that the approximate location of the average force on the blade is likely to be consistent across propeller geometries. It is worth noting that all interesting findings reported in this work are based on APC propellers, and so further validation is required for different propeller sizes and geometries. Regardless, the established methodology provides a solid foundation for future BEMT-based propeller analysis and optimisation.Item Open Access Enhancing Autonomous Sensory Meridian Response (ASMR) through personalised triggers in virtual reality.(2025) Ling, JiaxuanThis research investigates the effectiveness of personalised Autonomous Sensory Meridian Response (ASMR) triggers in enhancing users’ ASMR sensations within virtual reality (VR), addressing the central question: Do personalised triggers enhance ASMR sensations in VR? The study compares personalised and non-personalised triggers in a VR-based ASMR application across four dimensions: effectiveness, efficiency, duration, and subjective emotional responses. A mixed-methods approach with a primary focus on quantitative analysis was employed, supplemented by qualitative insights. Participants engaged with an immersive VR application featuring ASMR content and personalised elements. They completed an in-game task, followed by a self-report questionnaire to gather quantitative data, and participated in short semi-structured interviews to provide qualitative feedback. Quantitative results revealed that personalised triggers slightly improved ASMR tingling intensity, onset time, duration, and pleasantness, though enhancements were not necessarily significant. Qualitative results concurred with these findings, as participants preferred the personalised triggers due to its customised nature and calming properties. Distraction, absence of diversity in triggers, and minor design flaws were noted as well, pointing to areas for improvement. Other findings further revealed connections between emotional tendencies and ASMR responsiveness, i.e., the pre-experiment calmness level and the likelihood of musical frisson are positively correlated with ASMR tingling intensity. The study highlights the potential of personalisation in immersive ASMR applications through VR, demonstrating its tendency to enhance the overall ASMR experience while outlining a clear pathway for future optimisation.Item Open Access Automating the assessment of Level One NCEA Programming.(2025) Hickman, HenryThis thesis investigates the implementation of an automated high school programming assessment system, designed to assess the new programming Achievement Standard, AS92004. This is a nationally recognised standard, outlined by the New Zealand Qualifications Authority (NZQA) for New Zealand’s National Certificate of Educational Achievement (NCEA). The goal of automating assessment is to reduce teachers’ workload, and increase the equity and availability of programming education nationwide. This provides a case study of developing an automated assessment system that must conform to externally set criteria. We first explore automated programming assessment systems, and determine which assessment systems are suitable for assessing the achievement standard. This starts with an investigation of what tools teachers are currently using in the classroom, and what programming languages they are using to assess programming. This revealed that Python is the most common choice. We then investigate 23 different automated assessment systems by a literature search, and through teacher forum postings, to determine which may be suitable for assessing the standard. We find that several systems could be adapted to assess the standard, and ultimately proceed with CodeRunner, a Moodle plugin designed to automatically grade code. We develop a custom question type, and make some changes to CodeRunner, to better assess AS92004, referring to this modified version of CodeRuner as NCEA-CodeRunner. We then investigate assessment integrity, specifically through the use of randomisation techniques. We provide a taxonomy of randomisation techniques, and identify which contexts they are most relevant to based on the intended assessment scenario. We also discuss four different assessment scenarios, based on the combinations of formative and summative assessment, paired with invigilated and non-invigilated assessment. We find that randomisation techniques serve different purposes in each assessment scenario, based on the assessor’s goals, and use this information to choose randomisation techniques suited to AS92004. We then explore experienced teachers’ views of using NCEA-CodeRunner for assessment. We interview four experienced programming teachers to understand their thoughts. We perform an inductive coding of these interviews to identify relevant themes and sub-themes. From these four teachers, there was little agreement on what levels of context we should have in our questions, with each teacher having differing views for differing reasons. There was also a range of views on how to interpret some of the more ambiguous aspects of the standard, and how it should be marked. However, there was agreement that the way NCEA-CodeRunner assesses AS92004 was valid, and should be released to the wider teaching community. While NCEA-CodeRunner is designed to reduce teacher workload, and move away from manual grading, some aspects of the standard were difficult to fully automate. Therefore, after the initial release of the system, we analyse student submissions to determine if these aspects can be automated. First we investigate the effective use of conditions and control structures. We analyse 2,500 pieces of student work, at both a university and high school level, and manually grade whether their code effectively uses conditions and control structures. We then use pre-existing code quality metrics to determine if there is a correlation between a manual analysis of code, and an automated one. Finding no strong correlations, we turn to Machine Learning techniques. We develop and evaluate multiple models to assess whether students are effectively using conditions and control structures. We find that, while there are improvements to be made, no models can be implemented without introducing the risk of failing students who should pass. A second aspect of the standard that is challenging to automate is whether or not students are “documenting their code with comments that clarify the purpose of code sections”. We again perform a human analysis of high school students’ code submissions, and manually rate each comment. We find that students are over-documenting their code, and their behaviour in formative and summative assessment differs, with summative assessment having worse code comments. We then develop a prompt for GPT-4, and evaluate if it is a suitable way of assessing this aspect of the standard, ultimately finding it to not align with a manual analysis of code comments. Finally, NCEA-CodeRunner was used to assess AS92004 by over 30 teachers, assessing over 900 students, and we sought their feedback on the system. This was done via a survey of both teachers that used the system, and teachers that did not. We find a variety of reasons for not using the system, even amongst a small group of responses. However, many of them are willing to use NCEA-CodeRunner in future years. From teachers that did use our system, we find that they felt it was a fairer, less stressful, and less time consuming method of assessing AS92004. While there were some issues, such as moderation feedback, many were willing to use the system in the future. We also make suggestions for modifying the standard in future years, in order to make it more amenable to automated assessment, without losing the intent of the standard. From this, we appear to have achieved our goal of saving teachers’ scarce resource of time, and increasing the equity and availability of programming education nationwide.Item Open Access Ductility of concrete frames under seismic loading(1975) Thompson, Kevin JosephThe object of this thesis is to investigate some aspects of the behaviour of prestressed, partially prestressed and reinforced concrete structures under severe earthquake loading. An experimental study was made of the performance of ten prestressed, partially prestressed and reinforced concrete interior beam-column joint specimens under high intensity cyclic loading, in order to assess the possible advantages of incorporating nonprestressed (mild) steel in prestressed concrete members as a means of increasing the ductility and energy dissipation capacities of such members. Analytical methods are developed to predict the moment-curvature characteristics of prestressed, partially prestressed and reinforced concrete sections under both monotonic and cyclic loading. Moment- curvature characteristics predicted using these analytical methods showed good correlation with experimental results. The monotonic and cyclic loading analyses are used to study the effect of a number of section variables on the moment-curvature characteristics. An idealisation of the moment-curvature characteristics of cyclically loaded partially prestressed concrete members is presented for use in dynamic analyses of structures responding to seismic motions. Dynamic analyses are performed on single degree of freedom structures responding to three different earthquakes in order to compare the relative displacement responses of partially prestressed concrete structures-ranging from fully prestressed to ordinary reinforced concrete.Item Open Access Exploring pedestrian movement through colour for everyone(2025) Harding, Nicholas R.With the rise of aging populations and urban densification, the need to communicate and analyse pedestrian crowd’ data is becoming increasingly important, particularly to researchers and professionals in fields such as Pedestrian Evacuation, Human Crowd Modelling, Urban Planning, Crowd Safety, Disaster Planning, Building Insurance Assessment, and Fire Safety Science, especially concerning Human Behaviour. A typical method for communicating and analysing crowd movement models involves data visualisations, commonly represented as heatmaps or animated 2D or 3D visualisations of simulated crowd model outputs. While these visualisations utilise widely accepted techniques and practices within the fields, they are not always accessible to all viewers. This research specifically addresses accessibility challenges related to Colour Vision Deficiency (CVD), a condition characterised by difficulty or inability to perceive certain wavelengths of the visible spectrum, typically red, green, or blue. CVD arises from abnormalities or absence of cones (long, medium, or short wavelength-sensitive photoreceptors) within the eye. Advancements in software and hardware increasingly support sophisticated 3D graphical representations of crowd simulations, providing greater clarity and context to users and audiences. Building upon this, the research proposes a novel 3D real-time visualisation technique incorporating height dynamics into traditional heatmaps. Furthermore, the research investigates potential environmental design guidelines to enhance accessibility for individuals with CVD. This thesis explores the effectiveness of a colour correction algorithm to determine if it can adequately replace traditional colour-dependent heatmap visualisations, highlighting areas for improvement in accessibility. Participants were randomly assigned to four groups to investigate visualisation challenges experienced by individuals with CVD: Non-Colour, Protanopia, Deuteranopia, and Tritanopia Deficient. Instead of recruiting participants with actual CVD, a validated simulation technique was employed to emulate colour vision deficiencies. Experiments utilised validated crowd modelling software ('Simulex') and building geometries created in Building Information Modelling (BIM) software ('Revit') to ensure realistic scenarios. Conducting experiments within Virtual Reality (VR) created an immersive experience, yielding unexpected insights and enhancing awareness regarding accessibility considerations. Participant responses and feedback were collected through questionnaires, surveys, and structured debrief interviews throughout the experimental process. Findings from this research offer preliminary design guidelines and highlight areas for further investigation to improve the accessibility of heatmaps, particularly in pedestrian crowd modelling contexts. Although the results presented in this thesis are indicative, they clearly demonstrate that the topic warrants continued research and development.Item Open Access Nonparametric instrumental variable estimator performance evaluation in econometrics(2025) Kim, KwanhoInstrumental Variables are a tool widely used in statistics and econometrics, most often utilized to address the problem of endogeneity. The aim is to achieve consistent estimation with the knowledge that the dependent variables have a correlation of unknown degree with the error terms in a model. This would make the expectation of the error non-zero, which violates standard modelling assumptions. Instrumental variables are variables that they can be utilized in said models such that the expectation of the error of a model given the instrumental variable returns to zero, allowing for consistent estimation. Many methods of performing instrumental variables estimation are available in academic literature. Some popular ones are kernel estimators (Singh 2019 [9], Meunier 2024 [10]), series estimators (Crain 1974 [3], Efromovich 2010 [2]) and spline estimators (Beyhum 2024 [1]). Estimation via nonparametric methods (Newey 1988 [11], Horowitz 201 [8], Darolles 2011 [4], Chetverikov 2018 [5], Loh 2023 [7]) is of particular interest as they do not enforce any assumed form of an underlying relationship between the explanatory and dependent variables and relies on the data itself for modelling the underlying distribution, at the cost of requiring data of large sample sizes for effective utilization. In previous works, academics have focused on comparing single methods to a naive baseline. Much of the work is silent on how to choose different methods of NPIV estimators in the face of differing datasets. The contribution of this thesis is the comparison by performance evaluation of several methods, with an emphasis on methods that are nonparametric by nature and offer indirect solutions or some other compromising workarounds to common problems arising in this topic such as the computational intensity of algorithms and the ill-posedness of inverse problems. Specifically, we will implement, evaluate and compare the performance of four nonparametric estimation methods in literature to handle regression problems with an instrumental variable on data stemming from different data generating processes. This thesis is divided into four main parts. Chapters 1 and 2 offer an introduction to the topic, motivation and mathematics of nonparametric instrumental variable regression. Chapters 3 and 4 discuss the background and algorithm of four popular methods, two apiece. Chapter 5 supplies the metric and computational comparison of the performance of the four methods against simulated data. Chapter 6 concludes the thesis with a summary of what has been covered and what further work there is to be done.Item Open Access Efficient image reconstruction techniques for a multiple-receiver synthetic aperture sonar(2001) Wilkinson, David R. (David Ross)Fast and efficient imaging techniques have been developed for reconstructing data from the single-receiver synthetic aperture sonar (SAS). Therefore, it is advantageous to be able to combine multiple-receiver SAS data into the single-receiver data equivalent to employ these existing algorithms. In this thesis, a method is developed for combining the data efficiently. This method can be used with SAS systems containing any number of hydrophones arbitrarily located in a linear array and with the imaging platform travelling at any velocity. Motion errors resulting from the towed platform deviating from its straight path need to be determined and compensated accordingly. Sway and yaw are the primary motion errors of concern in low glancing angle side-looking sonar, since they are the major cause of image errors and artifacts in the reconstructions. Algorithms for estimating both sway and yaw are presented based on prominent points. These have shown to work well in simulations. Efficient implementations of the algorithms are also outlined using the mathematical software package Matlab. To achieve fast and efficient code, the importance of knowing the capabilities of the software being used is demonstrated. The use of the Fourier transform package FFTW in conjunction with Matlab shows performance gains of two to three times over Matlab's existing methods.Item Open Access Cascading risks of climate change to the natural domain.(2024) Sharp, PortiaClimate change poses complex risks to the natural environment, requiring an integrated and holistic approach to risk assessment strategies that can capture the relationships within ecosystems. This study satisfies an important gap in New Zealand’s current climate risk approach, by investigating cascading risks to the natural environment. While there is ample research into climate change, current methodologies typically follow a siloed approach to lacking in-depth consideration of ecosystem types and cross-domain effects. The research design is a mixed method analysis using literature review, systems thinking, participatory workshops and narrative-based system diagrams to explore potential cascades to New Zealand’s natural domain. Focusing on the interdependencies between domains and within ecosystems, this work hopes to further the understanding of how climate-change risks cascade through natural systems. There are three research questions which underpin this thesis, 1. What are the gaps/challenges in the current framework for assessing climate risk to the natural environment in Aotearoa, New Zealand? 2. How can the integration of cascading risks into climate risk assessments improve the evaluation of the natural environment in Aotearoa, New Zealand? 3. How could the consideration of cascades influence climate adaptation? The research highlights the limitations of current risk assessment approaches, which often treat the natural environment as a singular domain and fail to account for historical context, Indigenous knowledge systems, and complex ecological dynamics. By looking at marine, freshwater, terrestrial and estuarine ecosystems, the thesis illustrates how cascades can occur across domains, and the importance of intrinsic ecosystem interdependencies. The findings contribute to a more nuanced understanding of climate risks, emphasising the need for integrated, cross-domain assessment frameworks that acknowledge the complex feedback between ecological systems and human interventions. By providing insight into ecosystem vulnerability and adaptation opportunities, this research contributes to insights on how to inform policymakers and environmental managers on more sustainable strategies for climate change.Item Open Access Utilising black soldier fly fat as a sustainable ingredient in personal care products.(2025) Newell, CourtneyThe sustainability of ingredients in personal care products is becoming an important issue as consumers become more concerned about the effect their products are having on the environment. BSF provides a viable solution to this problem as it can be farmed more sustainably, and they have an ability to efficiently reduce organic waste and convert it into valuable components. These components can be extracted via different methods with juicing providing the easiest up-scalability for fat that can be later used in personal care products compared to chemical and mechanical methods. It requires the least amount of processing time and produces a light-coloured fat with a high lauric acid content. This composition is similar to coconut and palm kernel oil making it ideal as an ingredient in products such as cleansers where it can help with skin conditions such as acne. This study found that the BSF could be easily incorporated into products with little effect on the performance. Additionally focus group and sensory study results show it is difficult for consumers to tell if it is in a product as it has little effect on the appearance which means they are more willing to accept it.Item Open Access A study on cybersickness and immersion in a VR game with 360-degree motion simulator.(2025) Zhang, ZiyangVirtual Reality (VR) is an emerging technology that enables immersive simulated experiences. With improvements in hardware, development accessibility, and application availability, VR technology has become increasingly capable of realistically simulating both real and virtual environments (VE), thereby enhancing training and entertainment experiences. Nevertheless, cybersickness remains a significant challenge, triggering numerous physical discomfort symptoms in users. Moreover, most VR simulators have limitations in motion experience: they cannot perfectly simulate user movement in the virtual world. This limitation leads to reduced realism when attempting to simulate the physical world. This thesis aims to evaluate how different mapping methods in a 360-degree motion simulator (NOVA Ball) affect motion sickness and immersion, and to assess the advantages of various mapping methods in reducing motion sickness and enhancing user immersion. This study designed and tested hypotheses regarding immersion and motion sickness. The experiment utilized a simulated flight game where users flew through a VE. Three different motion mapping modes were applied: No Rotation, Rotation Only, and Motion Cueing. The experiment employed a between-groups design, with participants randomly assigned to three conditions. In total, 45 participants completed the experiment, during which heart rate and flight data were recorded. After the experiment, participants completed questionnaires relating to discomfort and presence. The results showed that the Rotation Only condition exhibited the lowest levels of simulator sickness, while the Motion Cueing condition reported the highest simulator sickness scores. However, there were no significant differences in presence across the three conditions. Interestingly, the heart rate of the Rotation Only group was higher than that of the other two groups, suggesting that physical exertion in the 360-degree motion simulator might have had a greater influence on heart rate than cybersickness.Item Open Access Experimental, numerical and theoretical studies of the aerodynamic performance of small-size UAV propellers for general forward flight conditions.(2024) Liu, XiranIn recent years, the use of unmanned aerial vehicles (UAVs) has increased in civil and military applications. Currently, propeller-driven UAVs still dominate this market because propellers generate thrust efficiently and directly. Additionally, continuous advancements in electric motor technology have greatly improved the efficiency and performance of propeller-driven UAVs. While alternative propulsion systems are being explored, the utility and reliability of propellers continue to demonstrate their significance in the UAV industry. Accurately predicting the aerodynamic performance parameters of the propeller under different operating conditions can help to improve the flight performance of the whole UAV and provide vital safety guarantees. The present research begins with an extensive historical review of rotary-wing development, illustrating the evolution of propeller technology and its enduring relevance in UAV propulsion. Following that, the present research employs an integrated methodology combining wind tunnel experiments, computational fluid dynamics (CFD) simulations, and blade element momentum theory (BEMT) models, culminating in the development of an extended BEMT (eBEMT) model that incorporates turbulence effects. Wind tunnel experiments are conducted first on an APC 1045MR-Thin Electric propeller to characterize thrust (𝑇), torque (𝑄), power (𝑃), and efficiency (𝜂) across varying rotational speeds (𝜔 = 3,000 – 7,000 rpm) and freestream velocities (𝑉∞ = 2 – 14 m/s). The experiments indicate a strong correlation between aerodynamic performance and the advance ratio (𝐽). Also, a significant decline in 𝜂 is observed at higher 𝐽 values. All these observations provide a robust dataset for validating the numerical and theoretical models. The conventional BEMT model in this work has been validated across a wide range of 𝜔 and various onset values of 𝑉∞, represented by 𝐽. It can produce results that are as accurate as those obtained from experimental methods and CFD within specific operating limits. The rapid feedback provided by this model offers a significant advantage in design iteration for any multi-rotor configuration when compared to CFD and experimental approaches. However, the conventional BEMT method fails to make a sufficiently accurate result in a particular scenario at higher values of 𝐽>~ 0.6. The CFD simulations are conducted to verify the accuracy of the conventional BEMT model. The results obtained from the CFD model are considerably closer to the wind tunnel measurements, with the associated percentage difference of thrust coefficient |Δ𝐶𝑇(%)_𝐶𝐹𝐷| ~ 5% and power coefficient |Δ𝐶𝑃(%)_𝐶𝐹𝐷| ~ 4%, compared to |Δ𝐶𝑇(%)_𝐵𝐸𝑀𝑇| ~ 15% and |Δ𝐶𝑃(%)_𝐵𝐸𝑀𝑇| ~ 11%. This result is justified by the fact that in the CFD model, computations are complemented by the effects of turbulence and the 3D nature of the flow, which are missing in the BEMT model. However, at the same time, CFD models can be computationally expensive, especially for calculating unsteady flow models in full 3D conditions. The present eBEMT model is furthermore developed to address the deficiencies of the conventional approach. This model incorporates azimuthal variability and accounts for unsteady aerodynamic forces and moments, achieving predictions for 𝑇, 𝑄, and 𝑃 within a 15% error margin, especially where the conventional model struggles. It also includes the wake skew effect to better represent real-world UAV flight. Additionally, the present eBEMT-turbulence model integrates turbulence models like Dryden and Von Karman to simulate broadband turbulence. The propeller blade’s response to turbulent inflow is modelled as a specific filter, targeting specific turbulence frequencies that affect aerodynamic performance. Finally, the recommendations of this thesis suggest objectives and directions for future research. The introduction of advanced turbulence modelling by extending the CFD or BEMT models to include different flight conditions for propellers and exploring material and flexibility effects will all improve the understanding of UAV aerodynamics.