Engineering: Theses and Dissertations

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Open Access
Triadic human-agent dynamics in collaborative decision-making within extended reality
(2024) Han, Binyang
The convergence of Extended Reality (XR) and Artificial Intelligence (AI), particularly Large Language Models (LLMs), offers exciting opportunities to enhance collaborative decision-making processes. XR, encompassing virtual, augmented, and mixed reality, combined with LLMs, can power Embodied Virtual Agents (EVAs), virtual characters that communicate naturally with users in real time. This project investigates the role of LLM-driven EVAs in supporting group decision-making. We developed the XMAC Framework, a multiscale, multiuser VR system integrated with an LLM-powered embodied agent. This framework allows users to switch perspectives, interact with virtual objects, and communicate directly with the agent. A user study was conducted to investigate the effects of virtual agents on collaborative decision-making within an XR office design task. The study aimed to assess how the presence and embodiment of a virtual agent influence collaborative behaviours and teamwork efficiency, as well as how different user perspectives (Regular and Giant) affect interaction patterns and engagement with both embodied and disembodied agents. This study examined the effects of virtual agents, their embodiment, and user perspectives on collaborative decision-making tasks. The findings revealed that virtual agents influence key aspects of collaboration. The embodied agent enhanced the sense of co-presence, creating a more immersive experience for users. Additionally, participants communicated more frequently with the agent and spent more time in the regular perspective. Qualitative data highlighted varied user preferences, with some favouring the embodied agent’s engagement, while others preferred the disembodied agent’s less intrusive nature or no agent at all for greater autonomy. These results underscore the complexity of designing virtual agents in collaborative environments, as user preferences and working styles play a crucial role in their perceived effectiveness. The findings suggest that including a virtual agent influenced aspects of collaboration, such as perceived closeness and group effectiveness, but had no significant impact on task completion time or overall user satisfaction, suggesting that the agent shapes collaboration dynamics without necessarily improving task performance. Moreover, the embodied agent enhanced co-presence and made interactions more immersive, but it did not improve teamwork efficiency or interaction frequency, indicating that while embodiment boosts user engagement, it may not lead to better collaboration outcomes. Also, different perspectives affected user behaviour, with the Regular Perspective fostering more frequent interactions, longer engagement, and a stronger sense of co-presence. The Giant Perspective was useful for spatial awareness but less conducive to detailed interactions. Overall, virtual agents, virtual agent embodiment and user perspectives significantly influence collaboration and interaction in XR environments, with varied effects on user behaviour and engagement.
Open Access
Patient-specific parameter identification of mechanically ventilated neonates.
(2024) McDonald, Mariah Aroha
The “breath of life” is a narrative weaving throughout many cultures, signifying the beginning of humanity. Across nearly all known lifeforms, oxygen is essential for survival. When a newborn human enters the world, their first significant action is to breathe. However, the lungs of a neonate are delicate and there are many reasons one may struggle to breathe independently. Relative to other mammals, humans are born with underdeveloped lungs, which is of particular concern in cases of prematurity and can lead to acute respiratory distress syndrome (ARDS). Birth complications or abnormalities may also result in ARDS. Respiratory issues can cause permanent injury and are one of the leading causes of infant mortality. However, rates of infant mortality have drastically decreased with the continued development of mechanical ventilation (MV). MV is a respiratory therapy where a ventilator takes over some, or all, work of breathing. MV maintains oxygenation when a patient is unable to do so independently, such as during respiratory distress or sedation. It is an essential therapy in the intensive care unit (ICU) and the neonatal intensive care unit (NICU). Current MV approaches administer a positive pressure of air at the airway via a mask, nasal prongs, or invasive intubation. There are many modes and settings which are chosen by the clinicians. Modes range from non-invasive and patient driven, to invasive and fully automated. Once the mode of ventilation is chosen, settings may include: driving pressure; positive end-expiratory pressure; tidal volume inspired per breath; rate of air flow; inspiratory and expiratory time; percentage of oxygen delivered; trigger sensitivity; and fraction of inspired oxygen. Ideal MV mode and settings are dependent on the individual patient’s needs. Suboptimal settings can result in inadequate oxygenation, ventilator-induced lung injury (VILI)and sustained need for MV, ultimately conflicting with MV goals and patient wellbeing.
Open Access
Biomechanics of sport climbing : development and validation of instrumented mounting screw for holistic evaluation of climbers.
(2025) Pernus Weber, Nina
Sport climbing has gained popularity over the past decade, which is expected to grow since its inclusion in the Tokyo 2020 and Paris 2024 Olympic Games. This has created increased interest in quantitative climber performance data for coaching, athlete feedback, and ensuring safety. Although coaches currently rely on their trained observational skills, there is a lack of detailed data on the interactions between climbers' limbs and holds. Additionally, beginners often start climbing without guided support, resulting in poor techniques and elevated injury risk. Thus, there is a need for methods that provide a comprehensive evaluation of climbing performance by combining measurements of climbers' interactions with holds and their overall movements. This thesis describes the design conceptualisation, fabrication, and validation of a low-cost instrument for measuring forces exerted on climbing holds. Previous designs for measuring forces on climbing holds were often limited to laboratory settings due to their high cost and the need for specialised sensors. More recently, low-cost and unobtrusive designs have emerged, but there is a recognised gap in instrumented climbing holds that are affordable, non-intrusive, and easy to install on existing climbing walls without requiring structural modifications. In this study, a standard M10 socket head cap screw was modified to function as an instrumented mounting screw (IMS). The screw shank was machined to have a smaller diameter, and a channel was milled down the threads. Finite element analysis (FEA) proved the machined IMS was still fit for purpose (FOS = 1.128). Initially, three strain gauges were bonded to the shank at 0°, 120° and 240°, orientated in the axial direction. Benchtop testing determined the optimal strain gauge configuration around the shank to accommodate variable load magnitudes and directions on the climbing hold. These tests also identified the effect of the point of force application on strain measurements, with anteroposterior centre of pressure (COP) changes being the most influential. Consequently, the IMS design was modified to feature a double-triplet strain gauge configuration, with two sets of three strain gauges bonded at 0°, 120° and 240° around the shank and positioned at 15 and 20mm from the screw head. Sensors were connected to a data acquisition system via flexible printed circuit boards (PCBs) routed through the channel to the back of the climbing wall. All sensors and PCBs were mechanically protected with epoxy. An additional washer was inserted between the climbing hold and the wall to enhance strain measurements. Due to the complex behaviour of the screw, hold, washer, and climbing wall system, a calibration procedure using neural networks (NN) was developed to address non-linearities and minimise crosstalk in the strain gauge measurements. Reference measurement systems with off-the-shelf sensors were used to optimise the NN architecture and hyperparameters. The NN was trained and verified for estimating 3D forces with resulting relative errors of 10%, 17%, and 17.6% in the vertical, lateral, and anteroposterior directions. R2 values for the force measurements were 0.89 for the lateral direction, 0.92 for the vertical direction, and 0.88 for the AP direction. Further testing for force magnitude recognition yielded more accurate results, with a relative error of 7%. Angles measured with the IMS compared to true values in the coronal and sagittal planes achieved R² values of 0.80 and 0.70, respectively. A special calibration rig, utilising a wooden dry tool axe and load cell, was developed for on-wall calibration. Final testing demonstrated that the modified screw could reliably measure force magnitudes above 30N with a mean relative error of <6% across the loading scenarios tested. The loads from the IMS and two motion capture methods were also tested. The first motion capture method was a wearable IMU-based (inertial measurement unit) approach, and the second method utilised smart device cameras with a human pose estimation (HPE) algorithm. A study with 32 participants across three proficiency groups (beginner, intermediate, and advanced) was conducted. The study was used to identify distinguishing kinetic and kinematic parameters and provide a holistic evaluation of climber performance. Three proficiency groups were tested with equal numbers of male and female climbers. Climbers were given three attempts to climb each of three routes of increasing difficultly. Most beginner climbers were unable to complete the moderate and advanced climbs, which limited comparison of the proficiency groups to the easy climbing route. All experiments were conducted under ethical approval from the University of Canterbury Human Ethics Committee. Results from the easy climbing route showed that the IMS could identify differences in climbers' proficiency through statistical analysis of performance parameters. Significant differences in contact time, Higuchi fractal dimension (HFD), and pulse count were observed on individual climbing holds (p<0.05), with experienced climbers exhibiting lower values indicative of their more fluent and efficient styles. Novel parameters such as power spectral density (PSD) and force rate of change (FRC) also revealed significant differences (p<0.05), with advanced climbers demonstrating higher FRC values and greater power at lower frequencies, while beginners exhibited more prominent higher frequencies, indicating increased force fluctuations. Additionally, a binary classifier and SHAP (SHapley Additive exPlanations) analysis for all holds’ identified mean normalised force magnitude as the most significant feature to distinguish beginners from advanced climbers. Beginners displayed lower mean normalised force values on both footholds and handholds, indicative of less dynamic climbing, which was confirmed with kinematic observations. SHAP analysis found that FRC and PSD were valuable in distinguishing between intermediate and advanced climbers, with advanced climbers showing higher FRC values on handholds and lower PSD values on footholds. Furthermore, the IMS also provided additional observations, identifying the crux of the climb through increased contact time, HFD, and pulse count, highlighting challenging holds. It also detected changes over three climbs, showing the ability to monitor the effect of familiarisation. The system also analysed dynamics between upper and lower body normalised forces, revealing advanced climbers' more dynamic approaches, confirmed by greater fluctuations of normalised total force. A Bland-Altman analysis of the IMU and HPE kinematic measurements revealed limits of agreement (LoA) in displacement measurements of ±0.05m, ±0.06m, and ±0.10m for the mediolateral (ML), anteroposterior (AP), and vertical directions, respectively. The study also assessed whether both methods could distinguish proficiency groups based on climbers' centre of gravity (COG) parameters. Results indicated that average position values were more comparable between the methods (relative percentage difference RPD < 1%) than peak value comparisons (RPD > 10%). Average vertical and AP velocities were more consistent (RPD < 6%), whereas the ML direction showed greater differences (RPD > 12%). Similar RPDs were observed in average acceleration. These findings suggest that while both methods are suitable for separate motion analysis, their results are not identical, particularly for peak displacement and dynamic parameters. The kinematic analysis of climbers across different proficiency levels identified several distinguishing parameters. Advanced climbers displayed greater COG displacement in the AP direction, higher velocities, and increased lateral oscillations as measured by mean absolute deviation (MAD) with p<0.05, indicating a more dynamic and efficient climbing style. Beginners, on the other hand, showed higher geometric index of entropy (GIE), time-normalised jerk coefficients, and immobility ratios, reflecting less fluent and more erratic movements with frequent stops. Advanced climbers also demonstrated greater power throughout the climb, making it a promising parameter for performance evaluation. Significant differences between intermediate and advanced groups were observed in the ML MAD parameter, with advanced females exhibiting greater lateral oscillations than the intermediate male group, suggesting a more conservative climbing style in the latter. Additionally, head orientation observations indicated that beginners had prolonged neck flexion from gazing at their feet rather than handholds, which reduced climbing efficiency. The last objective was holistic observation of climbers’ performance. By employing Markov models to analyse combined kinematic and kinetic data, differences in climbing behaviours between proficiency groups were detected. The analysis compared normalised forces on footholds during mobility phases, normalised forces on handholds relative to COG lateral displacement, and total normalised forces versus AP displacement. Advanced climbers exhibited higher normalised forces on footholds during the traction phase (15% higher probability), while beginners showed increased foothold forces during the postural regulation phase (6% higher probability). Advanced climbers also demonstrated 4% higher probability to be in a state with greater lateral COG displacement, resulting in higher normalised forces on handholds, compared to beginners and intermediate climbers who had 4% higher probability to be in a state that relied more on their upper bodies when their COG was closer to the midline. Further examination of COG in the AP direction also revealed that advanced climbers had higher probability (9%) to be in a state with their COG positioned farther from the wall, contributing to greater total normalised forces in comparison to the state of COG closer to the wall. These findings emphasise the importance of a holistic evaluation, as forces exerted on holds are intricately linked to COG trajectory. Overall, based on the results of this thesis, the instrumented mounting screw was found to be an effective tool for measuring climbing performance parameters. While it was less precise than other climbing hold instrumentation methods reported in the literature, this reduced precision was offset by its low cost and ease of installation on existing climbing walls, which could lead to widespread adoption. Although each climbing hold required calibration, this could be completed quickly. Hence, the proposed instrumentation will be suitable for use in climbing gyms for assessing recreational climbers and as a coaching tool.
Open Access
Axial cyclic behaviour of RC prisms representing wall boundary zones.
(2025) Gokhale, Rohit
Structural reinforced concrete (RC) walls effectively provide lateral load resistance in regions of medium to high seismicity owing to their relatively high in-plane stiffness. A flexure-dominated RC wall (shear-span ratio ≥ 3.0) relies on the response of its confined end regions against in-plane lateral cyclic actions. These confined end regions (also known as boundary zones) are subjected to tensile and compressive strain reversals during seismic events. A more desirable deformation capacity of a structural wall can be achieved by suppressing the premature compression failure modes in its boundary regions. Adequacy of prevailing design practice is often studied through scaled wall panel testing under in-plane lateral cyclic loading. While such wall panel experiments provide comprehensive insights into the wall behaviour, conducting parametric studies are deemed cumbersome due to the complex test setup and its resource intensive nature. Alternatively, a simplified approach of treating these end boundary zones as isolated columns (or prisms) and testing them under axial loading has been introduced in the past. Subsequently, several experimental studies have been conducted using this approach to study the parameters influencing not only the global instability but also localized compression failure modes. Therefore, the research presented in this thesis is centred around examining the various aspects associated with the idealized RC prism approach. A typical quasi-static uniaxial cyclic loading protocol often employed during prism test comprises of multiple cycles (mostly 2 to 3) at progressively increasing axial displacement amplitudes, even though an earthquake loading pattern is characterised by large number of small magnitude cycles and fewer large magnitude cycles. Inclusion of a more realistic loading history representative of earthquake demand seems warranted in the test program, however a procedure to develop such loading history for idealized wall boundary zones has not been explored adequately in the literature. This study presents a numerical procedure leading to the development of uniaxial cyclic earthquake loading protocol that comprises of realistic strain cycles representative of a chosen earthquake-type, both in terms of relationship between the tensile and compressive peaks and the corresponding cycle count at each strain range. With an increasing emphasis on performance-based design, the proposed loading protocol is structured around inelastic strain demands generated at the performance-based drift limit for structural walls. Analytical studies are conducted on a prototype wall model and the resulting axial cyclic loading protocols having near-fault and far-fault characteristics are presented. Moreover, parametric study results involving effect of some critical parameters on the cycle content are also discussed and then expressions are proposed to aid development of the loading protocol. Applicability of these proposed expressions are then scrutinized through analytical studies conducted on a different reference wall model using both, same as well as different, suites of ground motions. A review of previous experimental studies on RC prisms involving cyclic tension-compression loading suggests that most of the loading protocols differed in terms of their compression to tension strain ratios. The strain ratios were either held constant or varied with each increasing level of strain range. However, a specific study involving comparative evaluation of the inelastic demands imposed by conventional and earthquake loading protocols is missing in the literature. In this study, uniaxial cyclic tests were performed on doubly reinforced prisms idealised as the boundary elements of rectangular flexure-dominated walls to evaluate the effect of various loading histories on different compression failure modes. The uniaxial cyclic loading histories applied to these specimens included a conventional loading protocol (obtained directly from lateral cyclic loading test of a prototype wall) as well as two earthquake loading histories comprising cycle content representative of the cyclic demand expected from near-fault and far-fault earthquakes. Experiment results highlighted the low-cycle fatigue damage caused by the conventional loading protocol in comparison to the earthquake loading histories. In some of these tests, the level of compressive strains in the adopted loading protocol was reduced to study their impact on the global instability failure mode. Review of previous experimental research on idealized prisms also highlighted inconsistency in the prism height adoption. Typically, the prism height has been either considered based on the floor-to-floor unsupported height or theoretical plastic hinge length of the representative wall. Selecting an appropriate column height representative of the compression failure mode (global buckling or local instability) under consideration seems crucial to avoid experiencing failure modes different from the research objective, as observed during some of the past experiments. This study experimentally scrutinizes the role of prism slenderness (height-to-thickness) in altering the compression failure mode sequence. Unique relationships between the effective prism slenderness ratio and different compression failure modes are established using the results of this study as well as previous experimental investigations conducted by other researchers. While previous experimental studies have mainly focussed on investigating the influence of various parameters ranging from reinforcement detailing to loading history on the prism response, studies comparing the response of idealized prisms with the corresponding wall boundary zones have been rarely conducted. The underlying assumption with the prism testing concept is that the results obtained from the prism experiments are conservative and considered representative of the wall response. But a past experimental study on wall specimen and corresponding idealized boundary prism has shown that meaningful results may not be obtained without the consideration of strain gradient along the height, which was found to be a key influencing factor. This study proposes an approach to overcome this shortcoming and presented a procedure that can facilitate reliable prediction of the wall ultimate drift capacity deduced from the prism results using a material-strain limit approach by assuming constant strains over the theoretical plastic hinge length (i.e., prism height in this case). Finally, all findings from the experimental and analytical studies conducted as part of this research study are consolidated and recommendations for future research are also summarised.
Open Access
Risk-informed and data-driven adaptation : quantitative advancements in spatial risk analysis at the intersection of built and human systems.
(2024) Anderson, Mitchell
The increasing frequency and severity of climate-related natural hazards worldwide threatens the lives and wellbeing of billions. It is this notion that underscores the urgent need for equitable and effective adaptation planning, which, as described in this thesis, requires accessible and advanced spatial risk assessment methodologies. This thesis explores and advances methodologies for modelling quantitative impacts on infrastructure and communities during and after natural hazard events. The research aims to improve the effectiveness of spatial risk assessments and subsequent decision-making in climate adaptation, infrastructure management, land use planning, and emergency response. The overarching objective is to enhance the understanding of how risks cascade between built and human systems. This is achieved through a systematic examination and strengthening of methodologies used within climate risk and adaptation assessments to date. Specifically, this research integrates the modelling of natural hazards with social vulnerability, interconnected infrastructure networks, supply chain disruptions, and community access to essential services. Key methodological advancements include the development of techniques for modelling residents and assets that become isolated during hazard events, the introduction of the concept of functional isolation, and the incorporation of distributional justice considerations into direct and indirect risk assessments. These innovations address critical gaps identified in a systematic review of 86 global climate risk and adaptation assessments, particularly in addressing indirect impacts and equity considerations. Case studies in New Zealand and the United States demonstrate the practical utility of these methodologies in real-world scenarios. Analysis of coastal flooding in New Zealand reveals that including indirect impacts increases the at-risk population from 61,993 to 217,002 in a present-day event, with disproportionate effects on Māori communities. In Christchurch, the concept of functional isolation uncovers a three-fold increase in affected residential buildings when considering cascading infrastructure failures on critical amenities such as health-related and educational facilities. By addressing critical gaps in current risk analysis practices, this research contributes to a more comprehensive understanding of community resilience in the face of increasing climate-related risks. The findings have significant implications for equitable and effective climate adaptation strategies, emergency preparedness, and long-term urban planning. As climate change escalates global risks, the approaches and insights presented become increasingly critical for building resilient communities worldwide. The thesis concludes by discussing future research directions and the potential for wider application of these methodologies in future risk assessments and adaptation plans around the world.
Open Access
Performance of tree height measurement instruments & technology in New Zealand forestry.
(2025) Deering, Matthew H.
There are a range of popular tree hypsometer or height finding devices in popular use in the New Zealand forestry sector, but they have not been rigorously testing in New Zealand plantation forestry conditions against independently measured tree height via direct measurement after felling. Using instruments provided by the University of Canterbury’s School of Forestry that represent the diversity of contemporary hypsometers used in New Zealand forestry, the research explored the bias and precision via parametric and non-parametric statistical testing as appropriate of said instruments in ideal measuring conditions, as well as in actual radiata pine (Pinus radiata D.Don) plantations in the Christchurch area. The study instruments were evaluated on 100 radiata pine stems located across three different sites, and multiple measurements were taken by three operators using all five instruments. In addition to the intended use by hand, the study instruments were used with a monopod to test if height measurement bias and precision were affected and time taken to measure stems was recorded for each method. Additionally, given the increasing ubiquity of drone-based LiDAR use in forestry, fair comparisons were made between its height measurement bias and precision results and those of the study instruments using the same statistical methods. In field conditions the EC II-D, Vertex 5, and Vertex Laser Geo stood out as having less bias than other instruments (p > 0.05) while not being different from each other in terms of bias and precision (p < 0.05). Drone-based LiDAR bias of tree height measurements was not significantly different from the study instruments (p < 0.05) except for the Forestry Pro II. Ultimately, which technology to use for forest management will be decided by foresters and other stakeholders based on time, budget, and level of metric fidelity dictated by management goals.
Open Access
Non-Euclidean statistics in the space of phylogenetic time trees.
(2024) Berling, Lars
Reconstructing evolutionary histories is crucial across disciplines such as biology and linguistics. Traditionally, research has focused on finding the best phylogenetic tree from large collections, but less attention has been given to treating these collections as distributions within the complex treespace. Advances in software and data have made it possible to infer phylogenies with hundreds or even thousands of taxa, increasing treespace complexity and highlighting the need to view tree collections as samples from broader distributions within treespace. Despite progress, developing statistics over treespace remains challenging due to its complex geometry, limiting the application of conventional methods and leading to reliance on heuristics. In this thesis, we introduce new statistical methods for analysing ranked and unranked time trees and examine their impact on phylogenetic analyses. We present an algorithm for approximating a mean tree in the space of ranked time trees and explore its properties. Additionally, we extend our results to assess the convergence of phylogenetic Markov chain Monte Carlo (MCMC) analyses by comparing variances of tree distributions. We also revisit the parametrization of posterior tree distributions using conditional clade distributions (CCDs) and show that CCDs accurately estimate the full tree distribution and the mean tree (point estimate). We introduce a new CCD parametrization and highlight that its effectiveness varies with sample size and problem dimensionality. Through extensive simulations and real data applications, we demonstrate that our methods outperform existing state-of-the-art approaches.
Open Access
Geotechnical characterisation and liquefaction potential of sand-gravel mixtures
(University of Canterbury, 2023) Pokhrel, Abilash
The ground is shaken by thousands of earthquakes every year around the world. While most of them are small and low in magnitude and acceleration, a few could cause liquefaction even in gravelly soils, causing damage to several buildings and infrastructures. For example, earthquake-induced liquefaction, lateral spreading and ground deformation of gravelly soil in reclamation areas took place at Wellington's CentrePort during the 2016 Mw7.8 Kaikoura Earthquake, causing detrimental damage to the buildings and wharf (Cubrinovski et al. 2017). Worldwide, one of the issues that has continuously been brought to the attention of the engineering community is the lack of guidance for the characterisation and evaluation of gravelly soils (i.e. gravelly sands, sandy gravels, and uniform gravels). Such soils are often referred to as ‘problematic’ because their behaviour is still poorly understood. Due to the deficiency of well-documented case histories and the minimal availability of field assessment data, the current practice of evaluating the liquefaction resistance of gravelly soils relies on the assumption that liquefiable gravelly soil behaves like sandy ones (Abbaszadeh 2018). However, existing clean sand-based empirical correlations based on sands may not work to characterise gravelly soils and could be misleading engineering assessments. Therefore, research in studying the liquefaction mechanism and developing proper analysing techniques for gravelly soils is critical (not only in New Zealand) to characterise hazards presented by these materials so that engineers may effectively and economically minimise damage and loss caused by liquefaction of saturated gravelly soils. This study concentrated on the characterisation and critical assessment of the liquefaction potential of sand-gravel mixtures. In order to make recommendations for the use of suitable frameworks in practical applications, the objectives of this study were defined. The objectives of this study are (1) to characterise the selected sand–gravel mixtures (SGM) using the shear wave velocity method, (2.a) to identify a suitable physical and/or state parameter framework for the accurate liquefaction assessment of SGM using a cyclic stress approach, (2.b) to find the applicability of shear wave velocity-based liquefaction triggering curve developed for gravelly soil, and (2.c) to explore the applicability of energy based approach (EBM) for the liquefaction assessment of SGM. To achieve the objectives mentioned earlier, this study carried out a series of shear wave velocity and undrained cyclic triaxial tests on selected SGMs with different gravel content (GC) and relative density (Dr) were carried out. SGM were prepared by mixing a medium sand (New Brighton Sand), a coarse sand (Dalton River Washed Sand) and a commercially available round gravel (Gravel) having mean diameters of 0.2mm, 0.75mm and 5mm, respectively. Shear wave velocity (VS) of SGM specimens having gravel content (GC) 0, 10, 25, 40, 60, 80 and 100% with global relative density (Dr) 20, 30, 45 and 60% were measured at the mean effective stress (σ’) of 50, 100, 150 and 200 kPa. The laboratory results indicated that the VS of SGMs increases with increasing both the Dr and σ’, whereas the effect of GC would be marginal to significant depending on the limiting and threshold sand content. However, the intergrain state concept, equivalent void ratio (𝑒𝑓(𝑒𝑞)) and equivalent relative density (𝐷𝑟𝑓(𝑒𝑞)) are the suitable parameters to describe the VS of SGMs uniquely by combining the effects of GC and Dr. Further, the VS of SGM can be evaluated using a relation of equivalent void ratio and VS of clean sand with reasonable accuracy. In the second stage of this study, a series of stress-controlled undrained cyclic triaxial tests were conducted along with the measurement of VS on reconstituted SGM specimens with GC = 0, 10, 25 and 40%, and Dr ranging from 25 to 55%. The experimental results confirmed that both the GC and Dr have marginal to significant effects on the cyclic resistance ratio (CRR) of SGM, and highlighted the need to consider the GC and Dr effects together. In this regard, the use of the equivalent void ratio (𝑒𝑓(𝑒𝑞)) was found to be a suitable approach to describe the combined effect of GC and Dr on CRR as it provides a unique correlation for SGM. This study also compared the laboratory-based CRR- VS correlations with existing field-based liquefaction triggering curves developed based on clean sand and gravelly soil liquefaction case histories. The laboratory result is consistent with existing field-based curves for gravelly soils. The pore pressure generation and liquefaction resistance were then interpreted using an energy based method (EBM) of liquefaction assessment. It was shown that the rate of pore pressure development is influenced by the cyclic stress ratio (CSR), GC, and Dr of SGM depending on the GC and Dr conditions. However, a unique correlation exists between the pore pressure ratio and cumulative normalised dissipated energy during liquefaction. Further, the cumulative normalised energy was found to be a promising parameter to describe the CRR of gravelly soils for various strain levels, considering the integrated effect of GC and Dr on liquefaction resistance.
Open Access
Generating upgraded texture maps from old Video game textures using machine learning
(2024) Illingworth, Catherine
One of the major areas of development in game engines over the past few decades has been graphical advancements allowing for the rendering of increasingly high quality environments in real time. While this has enabled new games to be increasingly visually impressive, there is increasing interest in modifying and redeveloping older video games to run on these advanced rendering frameworks. Due to graphical limitations of older games and game engines, the art assets they utilised were often low resolution and simplistic to fit the capabilities of consumer hardware of the time. Due to these limitations, simply using old game art assets in modern game engines will not result in a game that looks as good as games designed for a modern engine from the start, requiring the assets to be recreated either manually or through automatic processes. Recent advancements in Artificial Intelligence (AI) and Deep Learning, including but not limited to Generative AI, offer new user directed solutions for improving existing assets or creating new assets from scratch, or using various text and image based sources as input. This research aims to explore how AI can be used to upgrade older game textures which is ideal for modern rendering techniques. Specifically, this project will be investigating using AI to take diffuse textures with baked lighting which is common in games, and using these as a basis to create textures required for Physically-Based Rendering (PBR). We will be focusing on AI models which can create normal, roughness, specular and diffuse textures for video games.
Open Access
Traffic estimation for large-scale heterogeneous urban networks with sparse data
(2024) Mousavizadeh, Omid
Urban traffic congestion is a prevalent concern, carrying significant implications for economic efficiency, environmental integrity, and societal welfare. Unlike traditional approaches which favour infrastructure enhancements for traffic congestion mitigation, contemporary solutions emphasize the implementation of traffic management and control strategies. This attention has given rise to diverse and adaptive traffic control and management strategies, emphasizing the importance of comprehending the system’s state, whether at the level of links, intersections, corridors, or the overall network. In recent years, attention has been shifted towards the network-level traffic flow models due to the emergence of control strategies based on the notion of the Network Macroscopic Fundamental Diagram (NMFD). This evolution has transitioned from analyzing traffic congestion in heterogeneous single-reservoir systems to more uniformly distributed multi-reservoir systems. Despite significant efforts in this direction, it has been found that the prediction accuracy of network-level traffic flow models in large-scale urban networks requires extensive calibration efforts, leading to less accurate simulation of traffic states in such systems. This thesis is an attempt towards the direction to provide a better representation of traffic state evolution in such complex systems by taking advantage of real-time sparse data from the network. The initial step towards a better understanding of traffic states in urban networks lies in introducing a framework for NMFD estimation, with a particular focus on reduced NMFD estimation due to limited data availability. Although it is well-established that the NMFD of a network is influenced by various factors, encompassing trafficrelated and topological characteristics, existing literature predominantly directs its efforts towards estimating the reduced NMFD through the utilization of traffic-related features. More importantly, prevailing methodologies often prioritize the loading period in reduced NMFD estimation, neglecting the crucial significance of the unloading period. These shortcomings have been addressed in the proposed method in this thesis, in which the simultaneous influences of traffic and topological characteristics are evaluated to estimate the reduced NMFD. Unlike existing approaches, the proposed method also takes into consideration the effect of the unloading period, thus offering a more accurate representation of the network performance during this period. Previous works on traffic dynamics simulation in heterogeneous urban networks have evolved from relying on significant assumptions about prior trip knowledge to utilizing either path flow distribution methods or state estimation techniques that take into account the presence of loop detectors on the periphery of regions. In this study, however, the focus is shifted towards identifying the evolution of Turning Rate (TR) at macroscopic nodes along the perimeter of the reservoirs with the aim to leverage the outputs to comprehend flow exchanges in multi-reservoir networks. In contrast to previous approaches, the proposed data-driven TR estimation method offers networkwide estimations at intersections capable of detecting both low and high-frequency variations. This approach allows us to better identify outflow/transfer flow ratios across multi-reservoir networks by integrating TR estimates with local penetration rate estimates using sparse Floating Car Data (FCD). Moreover, our results showcase the potential to directly estimate the outflow-NMFD of the network using sparse FCD. To address potential errors in model predictions, a model-driven state estimator is introduced which comprises two steps: (i) prediction step and (ii) update step. In the former step, the accumulation-based model regulates the system dynamics by considering estimated outflow-NMFD and real-time estimates of transfer flow ratios based on FCD. In the latter step, the sparse LDD is integrated with model predictions to minimize the model’s prediction errors and provide more accurate estimates of traffic states (i.e. accumulation and transfer flows).
Open Access
Bimanual Interaction, Passive-haptic Feedback, 3D Widget Representation, and Simulated Surface Constraints for Interaction in Immersive Virtual Environments
(1999) Lindeman , Robert William
The study of human-computer interaction within immersive virtual environments requires us to balance what we have learned from the design and use of desktop interfaces with novel approaches that allow us to work effectively in three dimensions. This dissertation presents empirical results from four studies into different techniques for indirect manipulation in immersive virtual environments. These studies use a testbed called the Haptic Augmented Reality Paddle (or HARP) system to compare different immersive interaction techniques. The results show that the use of hand-held windows as an interaction technique can improve performance and preference on tasks requiring head movement. Also, the use of a physical prop registered with the visual representation of an interaction surface can significantly improve user performance and preference compared to having no physical surface. Furthermore, even if a physical surface is not present, constraining user movement for manipulating interface widgets can also improve performance. Research into defining and classifying interaction techniques in the form of a taxonomy for interaction in immersive virtual environments is also presented. The taxonomy classifies interaction techniques based on three primary axes: direct versus indirect manipulation; discrete versus continuous action types; and the dimensionality of the interaction. The results of the empirical studies support the classification taxonomy, and help map out the possible techniques that support accomplishing real work within immersive virtual environments.
Open Access
Rethinking respiratory diagnostics and monitoring: From hardware to model-based therapeutics
(2024) Guy, Ella Frances Sophia
Respiratory disease poses a large and increasing global burden, directly effecting approximately 450 million people. Respiratory disease can be described by combinations of obstructive, respiratory, and neuromuscular dysfunction modes. It follows that mechanically this disease can be described by mechanical airway resistance, lung elastance, or neuromuscular abnormalities. However, direct measurement of these variables is difficult and often impractical in spontaneously breathing (unsedated) patients, and has significant added economic and social costs. Mechanical respiratory parameters have been successfully identified in invasively ventilated, sedated, patients in intensive care units. However, in spontaneous, unsedated, patients, patient effort dominates inspiratory drive, and is difficult to elucidate from passive elastic and restrictive mechanics. The ability to establish an identifiable model of respiratory function in terms of airway resistance, lung elastance, and neuromuscular contributions could be expected to enable faster, more accurate patient-specific diagnoses, testing, and treatment adjustment, but only if it does not require added sensors, measurements, or cost. Overall, this thesis presents developments towards an identifiable and clinically informative model of respiratory function. With the aim of facilitating more frequent respiratory testing to establish patient-specific baseline functions and track progressions with time, without requiring clinical visits and multiple intrusive tests for each data point. Hardware was developed to collect appropriate data for model identification, using simple methods which could be easily followed and thus applied outside clinical settings without specialist operation. In addition, a number of small-scale low-risk trials, with a combined total 160 subjects, were conducted to collect spontaneous breathing data for model and testing methodology development. The first section of this thesis centred on the investigation of appropriate methods of identifying active respiratory mechanics. First, active muscular components of spontaneous breathing were described by scaled second order b-splines within a linear single compartment model framework. These methods were adapted from a technique applied to Neurally Adjusted Ventilatory Assist invasive mechanical ventilation data. Significant parameter trade-off was observed when applying this method in spontaneously breathing subjects. Thus, a fixed literature based resistance value was used and elastance was identified from expiratory data and extrapolated to inspiration. However, the accuracy of identified patient drive was consequently highly dependent on the accuracy of estimated elastances and resistances. Subsequently, the identified patient muscular effort profiles were used to assess a subject’s muscular contributions to work of breathing. Patient-ventilator interactions were then investigated using patient driving pressure relative to positive airway pressure therapy. These modelling efforts provide a foundation for positive airway pressure therapy titration to optimise subject-specific work of breathing profiles, and thus to optimise care. Another practical difficulty in respiratory assessment is differentiation of the symptoms of disease from disordered breathing patterns. Thus, investigation of abdominal and thoracic contributions to respiration were made using externally located dynamic circumference tape measures created specifically for this research, and which are very low cost and simple to use. A key outcome was the graphical differentiation of laboured from resting breathing modes by comparison of abdomino-thoracic pattern between inspiration and expiration. In future, clinical testing of neuromuscular disease could augment these results and prove further differentiation of muscular recruitment modes and their underlying causes. The active respiratory mechanics investigation portion of this thesis resulted in a promising model framework and increased understanding of patient-ventilator mechanics in NIMV, as well as an understanding of variations and trends in breathing mode. However, the identification of active mechanics was highly-dependent on the accuracy of estimated resistance and elastance values from the pulmonary mechanics models. Thus, the second portion of the thesis targeted methods of improving the accuracy of elastance and resistance identification to reduce parameter trade-off and improve clinical applicability and efficacy. Elastances and resistances were fit to rapid expiratory occlusion instances, adapted from interrupter technique methods, using a low-cost shuttering hardware system developed specifically for this research. Occlusion-based elastance and resistance values were identified in mechanical lung bench testing data and in subject spontaneous cases. In both cases, identified elastances and resistances were within expected ranges and were more reliable than compared methods, and performed better with the application of NIMV. The combined active and passive respiratory mechanics identification provides a comprehensive model-based respiratory assessment framework. The combined model was applied to a small spontaneous breathing dataset to illustrate the combined methodology. The combined comprehensive model-based respiratory assessment framework has many associated clinical implications which have the potential to improve patient-specific care across diagnostic, monitoring, and treatment of disease. Overall, the model-based methods and corresponding high-function, low-cost hardware developed in this thesis have shown the ability differentiate key parameters of respiratory function breath-wise in spontaneous breathing data. The identified parameters are closely related to physiological function (and dysfunction), and due to the simplistic physiological base model framework, they are clinically relevant and identifiable. These outcomes demonstrate the clinical utility of these methods and potential to guide and improve patient-specific respiratory care, by providing patients and clinicians with clear metrics, which can be obtained at greater frequency with lower burden to patients and healthcare systems.
Open Access
Dependence on Wood Properties of Log Sterilization by Joule Heating
(2014) Fischer , S B
When passing current through conductors, such as metals, with the purpose of heating, they uniformly heat up and heat disperses quickly. This would enable a process to easily control and maintain a desired temperature and temperature distribution. However, in contrast to metals, wood is a very heterogeneous material. Experiments performed to investigate the influence of electrotreatment on fungi in Pinus radiata by Mellsop [11] revealed that high temperature variation occurred while heating. The findings of that work were further investigated by another student, Fiona Crook [12]. In her work, the influence of some key properties of wood, namely moisture content and density on the temperature during Joule heating were examined. However, her findings were that the examined properties were independent of the observed temperature. The reason for these results was believed to have a statistical cause, specifically insufficient observations. In response to that conclusion, the objective of this research is to re-examine the properties and identify additional ones, such as extractives content, that may cause the observed temperature differences in Pinus radiata boards. Moreover, a conclusive and reproducible methodology has to be developed. After determining the different distribution of properties in green logs, for example by CT scans [13], the correlations could then be used to predict temperature distributions in logs, to develop a controlled heating scheme in order to satisfy ISPM-15 regulations.
Open Access
Estimating seismic demand of reinforced concrete wall buildings : a simplified approach
(2023) Gurung Shrestha, Srijana
Seismic loss estimation of a building requires information regarding its damage potential for a given earthquake scenario. Damage in a building is directly related to its seismic demands/response which invokes the need for non-linear static or dynamic analysis with relatively accurate model according to the current performance based earthquake engineering (PBEE) approach. While these complex analysis methods exist, simplified approaches are needed for practical engineering applications. It is impractical for practicing engineers to conduct structural analysis of every single building as it requires lots of computational time and in-depth knowledge about modeling and analysis. A comprehensive review of existing methodologies for estimating seismic demands, highlights that only limited methods are available for RC wall structures. To address this gap this PhD thesis focuses on developing practical and simplified approaches to predict two crucial engineering demand parameters (EDPs): maximum inter-storey drift ratio (IDR) and peak floor acceleration (PFA) in reinforced concrete (RC) walls. RC walls are commonly used as lateral load-resisting systems in seismically active regions, making their prediction of seismic demands crucial for assessing seismic performance of the buildings. The research begins by identifying a suitable modeling approach for RC walls, selecting the Shear-Flexure Interaction Multiple Vertical Line Element Model (SFIMVLEM) due to its ability to capture shear-flexure interaction. A comprehensive parametric study is conducted on RC walls to investigate the effects of different structural parameters (number of storeys, shear span ratio, axial load ratio, longitudinal reinforcement ratio in the boundary zone, and boundary zone length) on drift and acceleration demands. Among these parameters, shear span ratio (SSR) is identified as the most crucial for predicting IDR and PFA profiles accurately. The study also discusses the differences between pushover analysis and incremental dynamic analysis, highlighting the limitations of conventional pushover analysis in estimating shear capacity of RC walls. The study then proposes prediction equations for IDR and PFA profiles using over 10,000 non-linear response history analysis results. The IDR prediction equation incorporates the normalized height and shear span ratio (SSR) of RC walls, providing a practical and reliable estimation of drift profiles. The PFA prediction equation accounts for different critical points along the height of the wall, considering the SSR of RC walls and ground motion intensity. The proposed equations are based on extensive numerical simulations and are validated against numerical and instrumented data. The simplified approaches demonstrate reasonable accuracy and outperform existing methods in terms of efficiency, and practicality. Furthermore, this research contributes to the development of a set of generic ground motions for conducting hazard-consistent incremental dynamic analysis (HCIDA). These ground motions can be used to assess the seismic performance of buildings in Wellington, New Zealand or regions with similar site characteristics, eliminating the need for time-consuming ground motion selection processes. In conclusion, this PhD thesis proposes practical and simplified approaches for predicting the seismic response of RC walls, focusing on IDR and PFA. The developed models offer accurate estimations and demonstrate superior performance compared to existing methods. These simplified approaches have the potential to enhance the efficiency and effectiveness of seismic design and assessment in earthquake engineering practice.
Open Access
Stream depletion from groundwater pumping.
(1999) Weir, Julian J.
Stream depletion due to groundwater pumping has been recognised as a significant environmental concern by water resource managers for some time. Methods currently used in New Zealand to estimate stream depletion overestimate the actual stream depletion, as no allowance is made for streambed clogging or partial stream bed penetration of the aquifer. A solution has been obtained by Hunt (1999) for streamflow depletion created by pumping from a well beside a stream. This solution differs from earlier stream depletion solutions by the inclusion of a semipervious clogging layer along the streambed and partial streambed penetration of the aquifer. The aim of this research was to investigate the use of the solution by Hunt (1999) for analysing stream depletion field data. Field work was undertaken adjacent to the Doyleston Drain during August - September 1998. Tests undertaken consisted of aquifer step and constant discharge tests, streamflow measurements, aquifer and stream water level measurements, and adaptations from data obtained from previous soakage testing in the dry streambed. Two methods have been presented to estimate aquifer and streambed parameters from the constant discharge test. Method I used drawdown data only. Method 2 further developed the results obtained from Method I and incorporated the measured stream depletion data in an iterative technique. It was found that Method 2 almost simulates the actual measured stream depletion (△Q ). Two additional independent methods to estimate the streambed leakage coefficient (λ) were investigated. Theoretical stream depletion estimated by Theis (1941) and Hunt (1999) were compared with the actual stream depletion measured during the constant discharge test. Hunt (1999) Method 2 was found to more accurately estimate stream depletion than both Method 1 and Theis (1941). Variations in the estimation of △Q between Method 1 and Method 2 were a function of the value calculated for λ . It was found that significant stream depletion can occur from streams that partially intercept confined or semi-confined aquifers. Hunt (1999) is applicable to any aquifer with a partially penetrating stream ( either naturally or artificially formed) that is not perched above the aquifer piezometric surface. It is recommended that Hunt (1999) be introduced as a standard water resource management tool to better assess stream depletion effects from groundwater pumping.
Open Access
Studies of liquefaction in 1929 Murchison and 1968 Inangahua, New Zealand earthquakes
(1988) Bienvenu, Véronique
Two major New Zealand earthquake cases both related to liquefaction of sand layers during shaking are presented in this report. First a general background about liquefaction is given. Then a second chapter deals with cases of liquefaction in the 1929 Murchison earthquake. A literature survey has been carried out, completed by verbal reports of eyewitnesses as well as by some light site investigation. In a third chapter liquefaction in a well-studied earthquake, the 1968 Inangahua earthquake, is reviewed, and work done by E. Ooi (1987) is completed with new field test data with the standard penetration test. In this chapter, emphasis is put on field data correlations for liquefaction potential assessment. The necessary different corrections applied to the data, before correlation, are described and discussed. Then different method of liquefaction potential assessment are tested and compared, Finally an analysis of the pore pressure measurements and dissipation, obtained with a recently-developed piezocone, is attempted, A brief summary of preliminary results obtained for the recent Edgecumbe earthquake (1987) is given in an appendix at the end of this report.
Open Access
Structural design of rocking systems, including higher mode eﬀects.
(2023) Kordani, Reza
This thesis provides an insight into the design and analysis of controlled rock- ing structures. Rocking structures are allowed to uplift from the base under the seismic load, while the upper levels typically remain elastic. Therefore, the seismic energy can be dissipated using supplemental energy dissipaters at the base level. This localisation of energy dissipation protects the upper levels and particularly structural elements from absorbing response energy through sacri cial damage. The base rocking mechanism can be used in the design of a wide variety of structures including buildings, bridges, tanks, etc. Several experimental and numerical studies have shown the robustness of these rocking systems in mitigating the seismic excitations in a repeatable manner without any degradation in sti ness or strength. The herein thesis explores some design methods that are currently being used by engineering practitioners particularly in New Zealand and studies some recent attempts in developing simpli ed design procedures for rocking systems. Several com- puter models are developed to perform a large number of earthquake simu- lations to capture the behaviour of rocking structures. The modelling tech- nique is veri ed using analytical solutions and an experimental test by other researchers. The e ects of numerous structural properties on the accuracy of the design methods are investigated and their limitations and advantages are highlighted and improved methods are proposed. The improved methods are unique, simple to implement, and are in line with current New Zealand standards. Overall, signi cant progress is made towards the technology of rocking systems receiving uptake by the profession.
Open Access
Seismic performance of high-capacity screwed hold-down connections in mass timber buildings.
(2024) Wright, Thomas D. W.
Cross-laminated timber (CLT) shear walls are a common lateral load-resisting system for mass timber buildings. The performance of the connections between CLT elements primarily governs the ability of CLT shear walls to resist lateral load. CLT shear walls have been widely used in residential structures, where the large number of walls available to resist lateral load means only low-capacity connections are required. High-capacity connection systems are required to achieve open floor plans with a reduced number of walls and fully utilise the high in-plane strength of the CLT shear wall. In this study, the seismic performance of high-capacity mixed-angle screw hold-down connections is investigated. These mixed-angle screw connections combine the high strength and stiffness of screws installed at an inclined angle to the grain, with the high ductility and displacement capacity of screws installed at 90 degrees to the grain for an overall strong, stiff, and ductile connection system. To investigate the performance of these connections, four stages of experimental testing were undertaken along with further numerical non-linear time-history analyses. The first experimental stage was comprised of component testing of screws in withdrawal, while the other three stages consisted of small (Fmax ≈ 200 kN), medium (Fmax ≈ 600 kN), and large-scale (Fmax ≈ 1200 kN) testing of mixed-angle screw connections. The connections were tested under both monotonic and cyclic loading. It was found that the mixed-angle self-tapping screws can provide a robust hold-down solution with high strength, high stiffness, and high ductility (component μ=10 to 20), with no significant difference in performance between monotonic and cyclic loading. Various configurations and combinations of mixed-angle screws were tested. It was found that partially threaded inclined screws should be used to facilitate the gradual withdrawal failure and load transfer between inclined screws and 90° screws. Considering the partially threaded screws used in this study, the optimal ratio between Ø12 mm inclined screws and Ø10 mm 90° screws was found to be 2:1, and the optimal ratio between the Ø12 mm inclined screws and Ø12 mm 90° screws was found to be 1:1.5. Analytical prediction equations were compared to the experimental testing results. It was found that the actions of inclined and 90° screws can be superimposed, but that the rope effect term for 90° screws should be omitted due to the high displacement required to activate this mechanism. Generally, prediction equations provided conservative estimates relative to the experimental results. However, when prediction equations were used with input parameters derived from experimental component testing, the connection capacity could be predicated accurately with a mean error of only 4%. The overstrength of mixed-angle screw connections was found to range from 1.92-2.22 and it was discussed how this could be lowered if there was less inherent conservatism in the input parameters. Two repair methodologies were trialled to determine if they could be used to repair these connections after they were damaged in an earthquake. It was found that connections could be easily repaired using a simple repair methodology that involved repairing the damaged screw holes with epoxy, and then installing new fasteners at a small offset (half a spacing) to the original faster holes. Non-linear time history analysis was undertaken to assess the dynamic performance hold-down connections with pinched hysteretic behaviour. For CLT walls with mixed-angle screw hold-downs, peak displacements were found to be slightly higher than those with equivalent elastic or bilinear hysteretic behaviour. Proposed amplification factors for pinched hysteretic response were assessed and found to overpredict the displacements observed in analyses, so they are not recommended for design. Overall, it was shown that the mixed-angle screw hold-down connections investigated can provide a strong, stiff, and ductile connection system for CLT shear walls.
Open Access
From lab to lineout : a study of headgear and brain injury biomechanics in rugby.
(2024) Stitt, Danyon
Rugby union is well recognised as New Zealand’s unofficial national game. As such it is one of the most popular sports in New Zealand. Unfortunately, concussion, a form of traumatic brain injury (TBI), is an inherent risk of participating in contact, combat or collision sports. Children exposed to TBIs can face long-term developmental, health and quality of life difficulties extending into adulthood. Even a single TBI may disrupt the neurological mechanisms underlying ongoing development. Despite the acknowledged high incident rates of TBI, important gaps in the research remain evident, especially for junior rugby players. In the past few years, there has been increased attention on possible concussion mitigation through using protective headgear, with World Rugby introducing new testing standards for headgear as a medical device. This allows innovative headgear designs to be tested for medical benefits such as potential concussion mitigation. However, the methods used in this standard to simulate rugby head impacts lack rigorous scientific backing, and the standard does not define the measurable medical benefit it aims to assess. Using a head impact simulation method that lacks any real-world validation limits the conclusions regarding headgear effectiveness during gameplay and hinders the progress of headgear development. The lack of data surrounding head impact kinematics in rugby union, data-driven head impact simulation methods, and biomechanical analyses of the link between brain injury metrics and head impacts in rugby does not facilitate an increase in player safety. This thesis presents several streams of novel work, covering the analysis of the impact mitigation of rugby headgear during laboratory testing, a comparison between these current testing methods and youth rugby head impacts, the relationship between head impact kinematics, gameplay scenarios, and brain strain, and finally, puts forward a set of recommendations for more accurate head impact reconstruction in the laboratory and areas of the game to look to reduce the severity of head impact exposure. Under a laboratory drop testing regime that covered 5 impact locations over 3 impact surface angles at 4 different heights, all rugby headgear significantly lowered the peak linear and rotational accelerations. Headgear that incorporates low-density, closed-cell foams (also described as traditional headgear) and has received World Rugby approval did not reduce peak linear acceleration or HIC to the same extent as the new generation headgear that used denser open-cell foams. The results of this study show that the headgear tested can lower the peak linear acceleration by up to 50%, and the peak rotational acceleration by up to 60%. The results lacked the same clarity when looking at the peak rotational velocities and brain strain metrics. Headgear constructed with lightweight, closed-cell foam only lowered the peak rotational velocity and regional brain strain reduction in isolated cases. In contrast, the newer generation headgear, which employed higher-density, viscoelastic, open-cell foam, consistently demonstrated significant reductions in peak rotational velocity and regional brain strain. However, drop testing onto the MEP pad impact surface may not adequately reflect the impact conditions specific to rugby gameplay. This underscores the need for a well-validated impact test methodology tailored to rugby-specific head impacts. Analysing the difference in impact kinematics between common drop test methods, we found that the impact surface stiffness greatly affected the peak linear accelerations and the duration of the linear acceleration peak. The inclusion of the neck significantly affected the rotational kinematics in both duration and kinematic profile. Peak linear accelerations showed the highest variation between drop test conditions with steel impacts creating the highest linear accelerations, and 45° MEP impacts creating the lowest. Peak rotational accelerations showed less variance than linear accelerations between drop-test conditions while peak rotational velocities did not vary between drop test conditions. Angled impacts produced the highest rotational velocities for a given linear acceleration, and steel impacts produced the lowest. When comparing these drop-test conditions to those measured in the field, peak linear and rotational kinematics were significantly higher than the field head impacts while the durations of the acceleration peaks were significantly lower on average. Peak linear and rotational accelerations diverged vastly from those on the field as the change in linear velocity increased. Peak rotational velocities showed lower divergence with increasing linear velocity but were still significantly higher during drop tests. Drop testing with a neck onto an angled impact surface produced peak linear acceleration durations similar to head impacts to bony areas of the body and the ball. Drop testing without a neck failed to recreate the appropriate duration of the peak linear and rotational kinematics. Drop tests with the neck resulted in a much closer approximation of the durations of the on-field rotational kinematic peaks. Those onto the angled impact surface simulated most male and female head impact conditions.
Open Access
Towards improving BDD and ATDD teaching in a university project course.
(2024) Filipovic, Marina
Software testing is a fundamental part of the software development process, as it is considered an assurance gate for product quality. Research shows that testing and quality assurance are generally the most expensive tasks in the software life cycle. So far, at universities, software testing is approached mainly as a subtopic of the subjects of Software Engineering or Software Quality. Behavior Driven Development (BDD) was introduced about two decades ago in the agile software development context. BDD is a process used to achieve a common understanding of the system under development among stakeholders and to automate testing. It still has ever increasing interests from both academic and industrial communities; therefore, it has become necessary to include this development practice in the software engineering curriculum. The objective of this research is to understand the state-of-the-art Behavior-Driven Development and Acceptance Test-Driven Development teaching and training so that young developers can be best prepared to face the challenges and demands of the industry in the field of automated acceptance testing. We will also present our approach to teaching these practices and investigate how compliant junior developers are with BDD principles in a year-long project course. We will then make recommendations on how to improve the teaching of these practices to achieve greater learning outcomes.