Engineering: Theses and Dissertations

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  • ItemOpen Access
    Immersive virtual reality for children in formal education.
    (2023) Belter, Meike
    This PhD thesis explored the integration of virtual reality (VR) technology into formal education, specifically targeting school-aged children. While VR has gained traction primarily for entertainment, this study sought to harness its immersive potential for educational purposes within, for example, schools. Games have long been recognized as valuable tools for enhancing learning experiences. In recent years, schools have increasingly adopted them, particularly in subjects such as math. Not all learning methods and tools are inclusive to all learners. Common challenges for children in a school context are inattention and hyperactivity. VR, with its ability to create immersive and customizable environments, presents an intriguing avenue for addressing these challenges. To address this, a VR math game was developed for this research, drawing from established educational frameworks and insights garnered from subject matter experts. Through qualitative interviews and thorough requirement analysis, the game’s design was refined. Subsequently, two user studies were conducted within real-world school environments. The initial study focused on assessing usability and refining the prototype based on user feedback. Encouraging outcomes paved the way for a more extensive second study. This followup delved into the influence of a reward system and virtual agent on the user experience, and comparing the VR game against a non-VR counterpart. The findings demonstrated that the VR game not only cultivated positive user experiences but also heightened motivation and engagement. Despite these promising results, further exploration is necessary to determine the role of ‘peerpresence’ in VR learning, and the game’s suitability for children with clinically diagnosed attention and hyperactivity issues. This research adds valuable insights into the process of creating inclusive and effective VR learning experiences. Through a comprehensive research approach, including design, usability testing, and user studies, the thesis underscored the potential of VR to enhance user engagement and experiences within educational contexts.
  • ItemOpen Access
    Percolating networks of nanoparticles for neuromorphic computing.
    (2024) Heywood, Zachary
    Inspired by biology, neuromorphic (brain-like) computing aims to capture the incredible capabilities of the human brain with physical devices. The brain completes numerous complex tasks such as pattern recognition using a fraction of the time and energy of conventional computers. In order to build systems with similar computational abilities, it makes sense to investigate systems that have intrinsic brain-like qualities. Percolating networks of nanoparticles (PNNs) have many features that make them suitable for neuromorphic computing. The neuromorphic properties of PNNs have previously been demonstrated for simple two-electrode devices. Multiple electrodes are required, however, for the implementation of PNNs as the reservoir in a conventional reservoir computing (RC) scheme, where multiple inputs and outputs are used. This thesis focuses on simulations of PNNs and it is demonstrated that the neuromorphic properties are conserved in devices with multiple electrodes. RC utilises temporal correlations in a dynamical system in order to perform computation. A model for operating in the low-voltage tunnelling regime is described, which allows PNNs to be used as the physical reservoir. A range of benchmark tasks are successfully performed and the effect of network size on RC performance is investigated. The RC scheme is extended to the emulation of swarming behaviour, like that seen in flocks of birds. A number of approaches are investigated and a novel method is developed that produces ‘swarm-like’ behaviour with PNNs for the first time. The results presented in this thesis demonstrate that PNNs have capability for neuromorphic computing and show that there is promise for solving even complex problems.
  • ItemOpen Access
    Noodle : design of a modular and re-configurable serpentine robot, with series elastic actuators and modular ventral panels.
    (2023) Lay, Gordon
    In the field of mobile robotics, there is a substantial challenge surrounding reliable navigation of unstructured environments with irregularities. A robot capable of versatile and robust locomotion is required, in order to handle randomly cluttered environments, which may also vary in substrate. This problem has two interdependent components; the physical form of the robot, and its mode of locomotion, or gait. By observing nature, researchers can find inspiration in organisms that have spent decades of evolution becoming expertly adept in particular tasks, and manifest this through behaviours and physical features. As a species, snakes are fascinatingly versatile at locomoting; depending on the substrate and irregularities of the environment, various gaits are used. The physical features of biological snakes are also diverse; microscopic ventral scale structures vary with habitat and primary gait. These scale structures impact the frictional properties of the ventral scales, resulting in varying degrees of anisotropy. The physical form of biological snakes is also attractive from a design perspective; a slender form, instrinsic stability and hyper-redundancy make a snake-inspired robot (snake robot) ideal for navigating cluttered environments. A snake robot able to harness the diverse set of available snake gaits presents an appealing solution to versatile locomotion. The aforementioned relationships between substrate, gait and ventral scale structure are conflicting, however; for a snake robot to perform all snake gaits, it must also possess ventral scales that can vary in structure. This thesis presents Noodle; a cost-effective snake robot with modular ventral panels on the sides of its body. This enables configuration of the ventral contact surfaces prior to deployment onto a given substrate, and the ability to ‘select’ its ventral side simply by rolling. By modularising the contact surfaces into these panels, access to varying degrees of frictional anisotropy is granted simply by swapping them. The cross-section of Noodle ressembles a chamferred square; thus, there are up to 4 unique sets of panels able to equipped at a time. Two panel designs are 3D printed from PLA, to assess the effectiveness of altering geometry to achieve frictionally isotropic and anisotropic designs. The anisotropic design is able to achieve 3 times more friction in the lateral direction than longitudinal when interacting with carpet, which served as a textured, slightly yielding surface. The body of Noodle is modularised into identical single degree of freedom (DOF) segments, which may be appended to one another with the rotational axes in parallel, or alternating in pitch and yaw; these achieve the planar and 3D configurations, respectively. Through the inclusion of series elastic actuators (SEA), compliance and torque sensing are achieved. The SEA is realised by attaching a compliant element in between the servo motor and driven segment. A conventional hobby servo was used. Two designs of compliant element, or series elastic element (SEE), are presented: coil spring and elastomer, where the latter is used in the final design. The material properties of elastomers depend on temperature, while the elastomer itself exhibits dampening and hysteretic deformation; the coil spring SEE offers higher temperature invariance and no hysteresis, but meeting the stiffness requirements of the SEE were challenging. Furthermore, the elastomer SEE is much simpler to manufacture, and its shortcomings have been shown to be relatively minor in the use case of a snake robot SEE. The elastomer SEE is experimentally characterised to have a torsional stiffness constant of 3.54 [N·m/rad]; with a 12-bit rotary encoder resolution, a 0.005 [N·m] torque-measurement resolution is achieved. Each segment of Noodle consists of a custom embedded system, SEA, and 3D printed body. Special attachments to ressemble the head and tail are also included in the proposed design. These attachments, the segment bodies, and parts of the SEA, are 3D printed from PLA; a cost-effective manufacturing decision that also allows for rapid prototyping. To validate the design and assess gait-execution capabilities, Noodle is configured in the planar configuration, with a total of 8 joints. The average cost per segment module is 158 NZD. In the planar configuration, with the joints acting in the pitching direction, the rectilinear gait can be implemented; the robot propels itself by executing successive poses that ressemble a dorsally-propagating wave. The impacts of the wave parameters on average movement speed are investigated; keeping temporal frequency constant (which will self-evidently affect movement speed) and using a range of values for amplitude and phase shift, speeds between 2.5±0.1 and 5.2±0.1 [cm/s] are achieved. A control architecture and system are proposed, based on the embedded architecture and torquemeasuring SEAs. Local stiffness control (LSC) is implemented, which allows closed-loop control of the joint stiffnesses, which in turn achieves adaptive behaviour in response to environmental stimuli. The effectiveness of the LSC is evaluated across several experiments wherein Noodle successfully overcomes an obstacle approximately 70% of its own height, using the impedance variation of the LSC. The results show decreased time taken to conquer the obstacle with increasing torque control gain, to an extent; beyond a certain gain value, the decrements in the times taken become marginal. The implications of the control and embedded architectures on the control system responsiveness are also evaluated. Noodle, with its modular ventral panels, poses an appealing solution to the problem of conflicting snake gaits, ventral surface properties, and traversed substrate. Preliminary planar control with joint torque feedback is demonstrated, paving the way for the implementation of sophisticated 3D gaits. Ultimately, these elements make Noodle an excellent intermediate platform in the pursuit of mobile robots capable of navigating unstructured environments with irregularities.
  • ItemOpen Access
    Sequential of acid, alkaline and torrefaction of wood pre-treatments to improve bio oil quality through fast pyrolysis.
    (2023) Mohd Safaai, Nor Sharliza
    Alternative and renewable energy sources have been explored and investigated over the world to meet the sustained increase in energy demand of and to abate the environmental problems due to heavy reliance on fossil fuels. Woody biomass has abundant resources and is renewable, therefore attracting great interest in the production of energy and fuels. In New Zealand, radiata pine is a dominant species in plantation forests, and residues from forest harvesting and wood processing have a strong potential for energy conversion because it is readily available at relatively low costs. Fast pyrolysis offers a promising way to turn the woody biomass into a liquid product called bio-oil at high yield, together with non-condensable gases (NCGs) and solid char as byproducts. Bio-oil has an extremely complex composition, consisting of hundreds of organic oxygenate compounds as well as water. The qualities of the bio-oil degrade with time during storage. In order to improve the bio-oil quality, bio-oil upgrading has been investigated, however, this normally operates at high temperatures and high pressure thus is a costly operation. Biomass pretreatments have also been reported in which some undesirable components in the biomass are removed before the pyrolysis thus better quality of bio-oil can be produced in the pyrolysis. This study aims to investigate the effects of various biomass pretreatments on bio-oil yield and composition from the subsequent pyrolysis. The biomass pretreatments include solely torrefaction and chemical pretreatments, as well as their combinations. In the chemical pretreatments, sulfuric acid (0.5%, 1.0%, 1.5% and 2.0%) and sodium hydroxide (4%, 7%, 10% and 13%) were used, while torrefaction was performed at 220 and 250 oC. These pretreatments produced treated biomass samples identified as AC (acid), AL (alkaline), ACAL (acid followed by alkaline), ALAC (alkaline followed by acid), ACTO (acid followed by torrefaction), ALTO (alkaline followed by torrefaction), ACALTO (acid + alkaline + torrefactoion) and ALACTO (alkaline + acid + tporrefaction), representing the pretreatment methods. Based on the analyses, the sample treated with solely acid (AC) showed high volatile matter (80.2%), indicating high volatilization during the subsequent pyrolysis. Biomass treated with alkaline (AL) illustrated a slight reduction of volatile matter (76.8%), which would hinder the volatilization process in the subsequent pyrolysis. ACAL and ALAC samples had 76.6% and 85.7% volatile matters, respectively. With torrefaction pretreatment, the volatile matter was further reduced, ranging from 72.9% to 80.02%. The reduction of inorganic elements in the biomass was also observed after the chemical pretreatments. Upon torrefaction as the last step, each studied sample portrayed a unique behaviour upon degradation, reflecting its unique elemental composition attained from earlier chemical pretreatment. Of all the samples including the torrefaction, the ACTO-250 sample showed more cracked fragments which could be linked to the effective inorganic removal and small molecular compounds by acid due to low lignin content. All treated samples showed changes in concentration of alkali metals and alkaline earth metals (AAEMs) recorded after analysis using ICP-OES unit. Morphological images from SEM recorded massive destruction after pretreatments that was obviously due to the elimination of lignin and hemicellulose during pretreatments. Thermogravimetric analysis (TGA) tests of all samples were conducted to investigate the pyrolysis kinetics by determination of the activation energies (Ea) and pre-exponential factors (A) in various kinetic models, including Kissinger, Kissinger-Akahira-Sunose (KAS), Flynn- Wall-Ozawa (FWO), and simplified Distributed Activation Energy Model (DAEM) methods. The results show that the Ea values for all of the treated samples ranged between 170.9 and 270.9 kJ mol−1 for Kissinger model 170.1–262.3 kJ mol−1 for KAS model, 186.2–259.2 kJ mol−1 for FWO model and 169.3–266.3 kJ mol−1 for DAEM model, respectively. The mean Ea values of the pretreated samples increased in comparison with that of the Control sample. In general, the Ea values increased over the degree of conversion from 0.2 to 0.8 attributed to the crystallinity and carbonisation effects upon the pretreatments. The A values determined for all of the treated biomass samples varied over a broad magnitude ranging from 105 to 1026 s−1 for the adopted kinetic models. Fast pyrolysis of the pretreated biomass samples and the Control sample were conducted in a lab-scale fluidized bed reactor at 400, 450 and 500oC for the production of bio-oil. The bio-oil was analysed for its chemical composition using GC-MS, NMR, FTIR and ICP-MS. Water content, acidity and viscosity were also determined using corresponding techniques. For the chemically-treated samples, the highest bio-oil yield was recorded from AC (39.72 wt%) at pyrolysis temperature of 450°C whereas the highest bio-oil yield from pyrolysis of pretreated samples including torrefaction was 34.05 % for the ACTO sample at the same pyrolysis temperature of 450°C. The bio-oil yields in these two cases were higher than that from pyrolysis of the Control sample (32.79±7.93%) at the same pyrolysis temperature. This study revealed that both chemical pretreatment and torrefaction of biomass were required to overcome the drawbacks of bio-oil from raw biomass. Using acid as the medium of pretreatment is preferable than using alkaline due to the suppression of inorganic matters in biomass and subsequent bio-oil. Torrefaction lowers the cost of biomass grinding, which is essential in balancing the higher process costs for pretreating biomass. Therefore, the combinatorial approach of pretreatments is required to improve the quality of crude bio-oil, depending on the final usage. By comparing to the Control bio-oils and other fuels, the results proved that less works are required to further upgrade the oils from ACTO and ALACTO pretreatments. Thus, ACTO and ALACTO bio-oils have the potential to be applied as transportation fuel with further upgrading process. Other applications are bio-adhesive (phenol), bio-based pesticides and biodegradable plastics.
  • ItemOpen Access
    Computational modeling of 3D printed porous media for process engineering.
    (2023) Kadzungura, Luckmore
    Triply periodic minimal surface (TPMS) structures, known for their unique geometric properties such as high surface area, customizable pore structures, and continuous networks, are evaluated as promising candidates for process engineering applications, including separation, heat exchange, and fluid flow management. This thesis details a computational approach to model and analyze TPMS structures in the Open- FOAM environment using the Finite Volume Method (FVM). Phenomena such as pressure drop, particulate flow, residence time distribution, heat transfer in TPMSbased heat exchangers, and adsorption were all simulated, with the computational results validated by experimental studies. The investigation centered on the Schoen Gyroid, Schwarz Primitive, and Schwarz Diamond surfaces, generated by implicit mathematical functions and parameterized to manipulate pore size, unit cell size, and overall shape. Insights were derived on how the selection of TPMS structures and geometric parameters impact process engineering applications. The determination of pressure drop across different TPMS structures, for both laminar and turbulent flows, was found to be influenced by their inherent pore connectivity and tortuosity. The contrast between low and high Reynolds numbers clearly illustrated as the transitional fluid flow behaviour at about Reh = 20. Additionally, particle flow behaviour was seen to be affected by variables such as pore size, velocity, particle size, and surface properties. A study of the residence time distribution in TPMS structures showed that cell orientations pose effects on the perfomances and also provided insights into their potential use in mixing and reaction engineering. The performance of TPMS-based heat exchangers was evaluated, with findings showing efficient operation at low Reynolds numbers 20 Reh 300, pointing to their potential for effective heat transmission due to the extensive surface area and interconnected channels. In separation processes, the adsorption capabilities of TPMS structures were analyzed, highlighting the importance of customized surface qualities for enhanced selectivity and capacity. Experimental tests conducted to validate the computational findings supported the projected performance of TPMS structures in various process engineering applications, particularly in the areas of fluid flow and heat transfer, which validates the credibility of the computational models. In conclusion, the research offers an in-depth, experimentally validated computational methodology for modeling TPMS structures for process engineering applications, placing emphasis on their performance across diverse applications. The groundwork is laid for the development and optimization of innovative TPMS-based materials with application-specific advantages, thereby contributing to the advancement of more efficient and sustainable process engineering solutions.
  • ItemOpen Access
    Modular multilevel converters for electric vehicle applications.
    (2024) Omar, Alaa
    The increasing focus and global support for the transition to electric vehicle traction systems drive rapid advancements in electric vehicle technologies. One essential component of electric vehicles is the main traction converter, which controls the power flow and drives the electric motor. Additionally, a dedicated arrangement is required for managing the batteries state of charge and the charging process. The modular multilevel converter with submodules that comprises half-bridges and batteries is currently being investigated for its suitability in traction systems. This converter offers many advantages in terms of integration, modularity, and redundancy. It combines multiple functions of various electrical components within the vehicle, and it can partially support vehicle operation even during undesired battery conditions. In this research, a real-time emulation approach of the modular multilevel converter is developed using MicroLabBox/dSPACE to investigate the operation of the converter. A physical prototype of the converter is also constructed in the laboratory and compared to the real-time model to validate its accuracy and effectiveness. This model is implemented by utilising a single look-up table in each arm of the converter. The dynamic performance of the converter in the emulated system resembles the dynamic operation of the converter prototype, confirming its fidelity and suitability for further investigations. The developed model is then integrated into a simplified real-time model of the vehicle to demonstrate the converter’s potential in driving the motor, balancing battery state of charge, and regenerative braking. Furthermore, the research investigates a novel approach for balancing the average state of charge of the converter phases and demonstrates the override capability of the converter through the integration of an override subroutine in the central control and balancing system. The balancing arrangement is independent on the system parameters and reduces the number of controllers required in the converter’s conventional balancing arrangement. This approach balances the average state of charge of the converter legs during different vehicle driving conditions. This investigation also shows that a balanced converter operation can be achieved while overriding particular submodules due to undesired conditions. A practical approach to minimise the sensing devices in the converter is developed in this thesis. Instead of using hundreds of sensors, only six sensors are utilised to estimate the voltage of the individual submodules. This approach reduces the cost and minimises the potential points of failure in the system. Also, this approach reduces the required analogue inputs in the controller system, particularly for systems with a large number of submodules. Finally, this research investigates the utilisation of the converter as an onboard charger without altering the converter connection or adding extra components. This charging arrangement enables faster charging of batteries with a lower state of charge and ensures equalised charging of all batteries in the converter. The charging arrangement is for a single-phase source and can be used for three-phase source charging if needed. In summary, this thesis studies the utilisation of the modular multilevel converter as a central traction converter in electric vehicles. The investigation provides an optimal and reliable converter integration to achieve multiple functions in the electric vehicle system. The optimisation includes a balanced converter operation under various driving conditions and implementing a submodule override algorithm. The reduced number of sensors enhances the overall reliability of the converter while reducing the cost. The research is conducted using a validated real-time emulated model of the converter in conjunction with a laboratory prototype converter. This work can also be extended to investigate many potential electric vehicle drive system optimisations.
  • ItemOpen Access
    Using field based power meter data to model track cycling performance.
    (2023) Ferguson, Hamish
    Track cycling events, both sprint and endurance, are primarily focused on performance of high and medium power durations, and it is suggested, measures of peak power govern performance in the sprint and pursuit cycling events. Various tests and metrics in the laboratory have been used to try and model track cycling. With the advent of power meters cyclists have been able to record power output in the field and several basic tests have evolved to use as a means to get started with training and racing with power. This thesis proposes a linear model based on total least squares regression, to evaluate these models and provide an option for coaches to see what durations are key for performance, and for sprint cyclists what types of training should be performed at a given part of a training build up. This analysis is applied to sprint cycling, male and female sprint cyclists, and pursuit cyclists to evaluate field-based data compared to lab and model derived metrics. The key conclusions from this thesis are: 1. For each specific power duration along the hyperbolic power-duration curve shows field-based data offers a better model for both sprint and pursuit durations. The linear model has a parabolic relationship the closer the inputs get to the specific duration assessed. 2. This disproves the contention of a linear process governed by peak power being the key metric of sprint cycling. The data in this thesis shows not only is this relationship incorrect, but strong relationships with sprint cycling durations hold for durations as long as 20-min. 3. This thesis finds there are sex differences for the model showing women have a higher variation of sprint power than men. 4. The linear model is applied to track endurance cycling to show, again, how a peak power (or maximal sprinting power or 𝑉̇O2max) does not govern performance, more a broad base of capacity reflected by a high lactate threshold, ventilatory threshold, critical power or other estimates of the maximal metabolic steady state. 5. Based on an understanding of the importance of capacity as well as peak power Chapter 6 shows this information can successfully be applied to the performance of sprint cyclists training towards peak performance.
  • ItemOpen Access
    The effects of applied stress and heat treatment on the stress corrosion cracking behaviour of manganese bronze.
    (2023) Manz, Olaf
    Stress corrosion cracking (SCC) is a cracking mechanism requiring a tensile stress on a susceptible material in a corrosive environment. Changes to, or the removal of, any of these three conditions can cause significant impacts on the SCC susceptibility. The propagation of SCC is typically described as being predominately transgranular (TG) or intergranular (IG). AW Fraser is an original equipment manufacturer (OEM) that produces extrusions and precision machined components from bronze alloys. The particular alloy used for this project’s investigations is a manganese bronze designated as UNS C86300, which is primarily used in high-wear engineering applications such as bushings in earthmoving equipment due to its excellent strength and wear resistance. The material consists of equiaxed grains of the BCC β-phase, with iron-rich κ-phase precipitates within the grains and at grain boundaries. Cracks were discovered in parts of rough-machined UNS C86300 after as little as 24 hours when stored outside. A failure analysis determined the cracking mode to be intergranular SCC due to the residual stresses from rough machining. A preliminary project found UNS C86300 to be susceptible to SCC in an environment of deionised water. The current method AW Fraser uses to prevent SCC in these parts is to cast sections far thicker than the final part to reduce the residual stresses induced by the clamping force of the lathe chuck, yet this process increases production time and cost significantly. SCC in copper-based alloys has been extensively researched after first being documented in the late 19th century, and the effects of the environment, material, and stress are well understood. However, the majority of the research focuses on α-phase alloys. Although there are some documented cases of β-phase brass alloys experiencing SCC in deionised water, there is a gap in the literature concerning this phenomenon. To contribute towards filling this gap in the literature and to provide valuable data to AW Fraser, the effects of applied stress and heat treatment on the SCC behaviour of UNS C86300 have been investigated. As-received, stress-relieved, annealed, and quenched C-ring specimens were tested in deionised water at applied stresses ranging from 25–95% of the material’s yield strength. Dezincification susceptibility tests and various analytical methods have been conducted on selected specimens to determine any relationships between failure time and applied stress or heat treatment.
  • ItemOpen Access
    Kōpaki Waiora Tamaiti o Aotearoa | New Zealand Child Wellbeing Project
    (2023) Knight, Ashley Rose
    The aim of this MProdDesign project was to design an intervention product and/or service that supports childrens’ emotional regulation (ER) learning within primary education in Aotearoa. Aotearoa has cultural and environmental influences that have greatly affected our tamariki (children’s) development. Aotearoa has a history of colonization and ongoing coloniality that has caused inequities in educational and health societies that has impacted behavioural and social norms (Hobbs et al., 2019). These influences have caused wellbeing and mental health deficiencies for tamariki that may inhibit their behavioural, social, and emotional skills as they grow. Emotional regulation (ER) is the extrinsic and innate processes responsible for monitoring, evaluating, and modifying emotional reactions (Thompson, 1991). Thus, ER is important in aiding a tamaiti (child’s) ability to identify, understand and integrate emotional information while managing behavioural responses (e.g., anger, sadness, distress) to different situations (Adrian, Zeman, & Veits, 2011). Progressive (and government supported) Modern Learning Environments (MLE) have shifted towards holistic pedagogies. Some holistic teaching approaches promote ER techniques to support the development of behavioural, emotional, and social capacities. One way that MLEs integrate teaching of ER skills is through the practice of mindfulness. Mindfulness refers to a state of awareness that is focus on one’s present moment experiences, with an attitude of non-judgement. (Shapiro, Carlson, Astin, Freedman, 2006). Mindful awareness is cultivated through formal meditation practices (e.g., focusing on relaxation sounds like heartbeats, breathing patterns) and through formal practices that involve bringing mindful awareness to everyday activities (e.g., showering). Mindfulness has previously been linked to emotional regulation by promoting enhanced attention in the present moment. Mindfulness can improve an individual’s ability to attend to specific aspects of a situation, as well as aspects of their own experience (e.g., mental and/or physical awareness) (Roemer, 2015; Roemer, Williston, Rollins, 2015). Using a product design-focused codesign framework, this project facilitated research focus groups that directed design decisions and developments from learner and education facilitator insights. As a result, mindfulness-based wearable prototypes were produced and play-tested with young learners and education facilitators over a 5-week period. The qualitative testing data conveyed what functional, aesthetic, sensorial and ergonomic aspects were successful and what were shortcomings for both young learners to use and for education facilitators to deliver within a Modern Learning Environment. Thematic analyses of the testing data proved that the learner participants maintained consistent engagement with the prototypes over the testing period and found them an effective tool to aid in refocusing their attention to the present moment during their school day and mindfulness lessons. This project opens future opportunities to explore lesson plans and projects that are framed with both learners and their education facilitator teams to grow their familiarity and engagement with their mindfulness journeys together.
  • ItemOpen Access
    Ground motion simulations validation via response of complex structures.
    (2023) Loghman, Vahid
    This dissertation addresses a diverse range of applied aspects in ground motion simulation validation via the response of complex structures. In particular, the following topics are addressed: (i) the investigation of similarity between recorded and simulated ground motions using code-based 3D irregular structural response analysis, (ii) the development of a framework for ground motion simulations validation to identify the cause of differences between paired observed and simulated dataset, and (iii) the illustration of the process of using simulations for seismic performance-based assessment. The application of simulated ground motions is evaluated for utilisation in engineering practice by considering responses of 3D irregular structures. Validation is performed in a code-based context when the NZS1170.5 (NZS1170.5:2004, 2004) provisions are followed for response history analysis. Two real buildings designed by engineers and physically constructed in Christchurch before the 2010-2011 Canterbury earthquake sequence are considered. The responses are compared when the buildings are subjected to 40 scaled recorded and their subsequent simulated ground motions selected from 22 February 2011 Christchurch. The similarity of recorded and simulated responses is examined using statistical methods such as bootstrapping and hypothesis testing to determine whether the differences are statistically significant. The findings demonstrate the applicability of simulated ground motion when the code-based approach is followed in response history analysis. A conceptual framework is developed to link the differences between the structural response subjected to simulated and recorded ground motions to the differences in their corresponding intensity measures. This framework allows the variability to be partitioned into the proportion that can be “explained” by the differences in ground motion intensity measures and the remaining “unexplained” variability that can be attributed to different complexities such as dynamic phasing of multi-mode response, nonlinearity, and torsion. The application of this framework is examined through a hierarchy of structures reflecting a range of complexity from single-degree-of-freedom to 3D multi-degree-of-freedom systems with different materials, dynamic properties, and structural systems. The study results suggest the areas that ground motion simulation should focus on to improve simulations by prioritising the ground motion intensity measures that most clearly account for the discrepancies in simple to complex structural responses. Three approaches are presented to consider recorded or simulated ground motions within the seismic performance-based assessment framework. Considering the applications of ground motions in hazard and response history analyses, different pathways in utilising ground motions in both areas are explored. Recorded ground motions are drawn from a global database (i.e., NGA-West2 Ancheta et al., 2014). The NZ CyberShake dataset is used to obtain simulations. Advanced ground motion selection techniques (i.e., generalized conditional intensity measure, GCIM) are used for ground motion selection at a few intensity levels. The comparison is performed by investigating the response of an example structure (i.e., 12-storey reinforced concrete special moment frame) located in South Island, NZ. Results are compared and contrasted in terms of hazard, groundmotion selection, structural responses, demand hazard, and collapse risk, then, the probable reasons for differences are discussed. The findings from this study highlight the present opportunities and shortcomings in using simulations in risk assessment. i
  • ItemOpen Access
    Deteriorated capacity assessment of aging bridge structures in seismic areas complimented by artificial intelligence modeling.
    (2023) Matthews, Benjamin James
    Chloride-induced deterioration of reinforced concrete (RC) structures severely depreciates the mechanical advantages provided by the composite action of concrete and steel reinforcing. Degradation of the embedded steel and succedent effects on the surrounding concrete occur naturally over several decades, depending on the in-situ environmental conditions and construction quality. As many RC structures are reaching the end of their initial design lives, progressive deterioration of the reinforcing steel over time has created a far-reaching issue of compromised structural reliability, particularly in seismically active zones. Transverse reinforcement faces additional susceptibility to decay, due to its geometric and physical design relative to the longitudinal steel. The increased vulnerability alludes to an accelerated loss of shear and confinement-related mechanical properties as degradation advances with time. This Ph.D. research explores the implications of chloride-induced corrosion on the mechanical response of degrading RC members. The project is separated into two primary scopes. The first involves a comprehensive multi-phase experimental program to characterize the effect of corrosion on the cyclic shear degradation of affected circular RC columns. The second explores machine learning as a high-performing alternative to conventional modeling approaches, for predicting key mechanical properties in degrading RC members. Artificially accelerated methodologies have become indispensable for achieving a broad spectrum of corrosion damages, enabling researchers to analyze the performance of affected reinforced concrete elements. However, an issue exists in over- accelerating the process, which creates unrealistic morphologies, limiting the experimental value of the test. An experimental study is undertaken to investigate the effects of the degree of acceleration on the corrosion morphology, sectional properties, and crack distribution of laboratory-scale RC elements. Twenty-four RC cylinders were constructed, corroded at two current densities, two concrete cover thicknesses, and using two variations of the impressed-current method. Results suggest a maximum upper bound threshold of 300 µA/cm2 should be used to ensure realistic corrosion morphologies and crack behavior. It is recommended that wet-dry phasing be implemented as the primary variant of the impressed-current method because of its superiority in producing morphologies, sectional properties, and cracking that adequately reflect those found in naturally corroding elements. This experimental phase also serves as a calibration benchmark for the proceeding artificial corrosion implementation on large-scale RC circular columns. The ever-growing volume of experimental and field data continually enables advances in the field through deeper micro-macro analyses and various modeling applications. Machine learning offers powerful and robust methodologies for improving the predictive capabilities of complex phenomena, with the additional benefit of continual adaptability as more data emerges. An experimental phase is introduced, describing the tensile testing of 284 artificially corroded, 25 mm diameter deformed Grade500E reinforcing bars. Next, the mechanical characteristics of corroded bars are predicted through a collection of regression-based machine-learning algorithms. Models are trained and tested on a database of 1,387 tensile tests compiled from 25 other experimental programs available in the literature. The complete database includes 19 input parameters used to predict nine key mechanical properties of the corroded steel bars: yield force, ultimate force, effective yield stress, residual engineering yield stress (%), effective ultimate stress, residual engineering ultimate stress (%), ultimate strain, elastic modulus, and ductility. Nine machine learning models were selected from a balanced assortment of algorithm typologies to determine the most appropriate methodology for each response variable. Literature-supplied decay laws serve as null models for statistical analysis. Results indicate that machine learning applications can drastically improve the predictive accuracy for both strength and displacement-based characteristics. The adaptive-neuro fuzzy inference system (ANFIS) model was found to have the strongest individual predictive ability across all models. Meanwhile, ensemble tree-based learning algorithms categorically provided the most consistently high-performing models over the selected response variables. Following on from the small-scale corrosion phase, a similar comparative assessment of two artificial corrosion techniques was undertaken in large-scale circular RC columns to quantify the authenticity of the induced damage patterns. The impressed-current method was divided into two subgroups – constant saturation and wet-dry phasing, at two imposed current densities of 200 µA/cm2 and 300 µA/cm2. The assessment was applied over a large-scale experimental program, testing the cyclic shear behavior of eight circular RC concrete piers. Analyses were conducted from the local corrosion distribution and morphology scale through to each test specimen’s global structural behavior and cyclic response. The seismic shear response of fourteen scaled circular RC piers subjected to artificial chloride-induced corrosion is then investigated. Each pier was designed to trigger a shear-dominated failure and artificially corroded at two current densities. A further parametric study is undertaken, investigating the influence of confinement effective- ness, spiral diameter size effect, and pier aspect ratio on the rate of cyclic shear loss. As corrosion increases, a shift in failure mode towards a more brittle mechanism is consistently observed. Significant reductions in shear capacity were observed, with significant implications on the ultimate deflection capacity at severe levels of deterioration. In the most severe case, a maximum reduction of 37.5 % and 70.9 % were recorded in peak shear capacity and ultimate deflection, respectively. A series of empirical modifications to an existing three-step analytical model is proposed to derive the cyclic shear capacity of circular RC columns considering corrosive conditions. The results of sixteen shear-critical RC columns, artificially corroded to various degrees and tested under quasi-static reversed cyclic loading, were used for model verification. Two simplified degradation models are developed to serve as performance benchmarks. The final model is proposed in a stepwise format relative to the measured damage of the steel reinforcement. New empirical decay law coefficients were derived for determining the degraded material properties based on the extensive database of over 1,380 corroded tensile tests. An additional experimental database of 45 corroded RC circular piers, with displacement ductilities ranging between 1.4 to 11.9, was collected to assist in the modification of ductility- based parameters. The results of the model, compared to experimental tests failing in shear-dominated modes, indicate that the peak shear capacity can be predicted well across a range of deterioration severities (0 – 58.5 % average transverse mass loss). As corrosion damage increases, the distribution of the corrosion relative to the location of the shear plane becomes a critical performance consideration, increasing predictive variance. Lastly, an extensive database is introduced, aggregating 54 experimental programs with 804 test specimens and 45 input parameters, investigating the implications of chloride-induced corrosion on the deteriorated response of corroded reinforced concrete beams. Several statistical models are explored to determine the highest performing predictor for five key response variables – the residual ultimate moment capacity, residual capacity factor, yield load, yield displacement, and the ultimate displacement. Three existing analytical approaches were included for comparative purposes to test the efficacy of the trained statistical models. The optimized machine learning models outperformed conventional analytical approaches and achieved high levels of predictive accuracy. Ensemble tree-based learning algorithms consistently produced the best predictions.
  • ItemOpen Access
    Understanding and reducing drying collapse in difficult-to-dry plantation-grown eucalypt timber
    (2023) Ghildiyal, Vikash
    Eucalyptus plantations are one of the largest wood resources, and while they are typically primarily grown for fibre or biomass, there is an increasing interest in using this resource for solid wood products. However, timber from such short-rotation eucalyptus plantations is often ‘difficult-to-dry’, suffering collapse during drying. To make such timber suitable for higher- value solid wood products, this thesis explored two strategies for reducing collapse in plantation-grown eucalypts: reducing collapse through a breeding programme by selecting genetically less-collapse-prone planting stock; and technical solutions to allow the drying of collapse-prone timber with reduced collapse. Additionally, the influence of ions on water transport in wood and collapse was explored. Chapter 1 provides an overview of timber drying, collapse mechanisms during drying, amelioration of this problem, and different methods of assessing collapse in wood. Review of the literature on collapse suggested that there was no practical method that could solve this problem, even though this issue was identified more than 100 years ago. Finding a solution for drying collapse is topical since the New Zealand Dryland Forests Innovation (NZDFI) is working to establish a domestic ground-durable eucalypt resource for use in high-value solid wood products. Chapter 2 investigates the reliability of collapse assessment methods used in tree breeding. This chapter reports on correlations, especially the genetic correlation, between different shrinkage and collapse measurements in E. quadrangulata samples cored from a breeding population. Strong correlations would allow the choice of the least resource-consuming assessment method. Maximum tangential shrinkage, the most convenient measure tested in this study, was shown to be a reliable predictor of true (recoverable) collapse because of its comparable heritability and strong phenotypic and genetic correlations with the true collapse. The strong correlation between these traits in E. quadrangulata samples also indicated that most genetic variation in maximal tangential shrinkage was explained by true collapse rather than normal shrinkage when cores were dried at 60°C. Moreover, checking in sawn timber is likely to be related to maximal tangential shrinkage rather than a volumetric measure. The maximal tangential shrinkage in cores was positively correlated to both recoverable collapse and normal shrinkage. This indicated that selection for lower maximal tangential shrinkage would reduce both normal shrinkage and collapse in a breeding population. Chapter 3 explored the genetic parameters and amount of genotype by environment interaction for drying collapse, extractive content, basic density, core length, and heartwood diameter in two ~9-year-old E. quadrangulata breeding trials, as well as evaluating the relationships between collapse and other traits. Collapse was confirmed and was prominent in the heartwood of E. quadrangulata cores. Heartwood collapse and other wood properties were under varying degrees of genetic control, with heritability ranging from 0.19–0.40. In accordance with theory, heartwood collapse was negatively correlated with basic density and positively correlated with extractive content. Significant genetic gain could be expected for heartwood diameter, core length, basic density, and heartwood collapse. However, improving extractive content for this species might be challenging as low heritability was observed, but it should be noted that the low number of families included in these breeding trials partly contributed to low heritability. Chapter 4 investigated genetic control of collapse and other tree features at mid-rotation age of the emerging plantation species E. globoidea. Using a 14-mm diameter corer, thousands of E. globoidea trees representing 163 families were sampled from a breeding population established at three sites, and genetic parameters for heartwood and sapwood collapse, extractive content, and heartwood diameter were estimated. Heartwood collapse was under genetic control, with a narrow-sense heritability ranging from 0.22 to 0.44. Considering the coefficient of genetic variability of ~13% to 23%, heartwood collapse in E. globoidea can be reduced through selection. The significant genetic correlation between sites for heartwood collapse (rg = 0.73 to 0.83) suggested low genotype by environment (G × E) interaction. In line with the physical causes of collapse, heartwood collapse was positively correlated with extractive content. Extractive content and heartwood diameter are other traits of interest, since E. globoidea is grown for its ground-durable heartwood. The heritability of extractive content ranged from 0.40 to 0.71. Heartwood diameter was shown to be negatively correlated to extractive content. No significant genotype by environment (G × E) interaction was found for extractive content, while genotype by environment (G × E) interactions for heartwood and sapwood diameter were small. Finally, 12 families were identified with above-average heartwood diameter, extractive content, and below-average heartwood collapse. In summary, this study has shown that genetic selection for collapse and other wood properties of E. globoidea is feasible. Chapter 5 investigated Joule heating as a technical solution to mitigate drying collapse, an energy-efficient method to heat timber by passing electric current through it. All electric energy is converted into heat inside the wood avoiding losses caused by unfocused electromagnetic fields in microwave heating or the long timeframes and consequent energy losses through imperfect insulation in conventional heating. The effect of Joule heating on collapse, shrinkage, water absorption, and compressive strength of timber was investigated. Tangential and volumetric collapse in E. nitens reduced significantly by ~53% and ~48%, respectively, with Joule heating. Maximum tangential shrinkage was significantly lower, due to the reduction of collapse in Joule-heated samples, because normal shrinkage was not affected by Joule heating. A reduction in collapse was achieved without a statistically significant increase in water absorption capacity or decrease in compressive strength. Further, the estimated costs for Joule heating pretreatment were estimated to be competitive when compared with conventional steam recovery of collapse. Chapter 6 examined the influence of replacing sap with potassium chloride (KCl) solution or deionised water on drying collapse, wood permeability, and streaming potential of never-dried wood. Ion-mediated response in xylem is considered a major factor in sap-flow regulation. Volumetric and tangential collapse in KCl-treated E. nitens logs decreased significantly by 42%–62% and by 51%, respectively. Improvement in shrinkage properties was dependent on the KCl concentration, with a maximum at a concentration (20 mM) in the range of total ionic strength found in living trees. Logs treated with deionised water showed higher normal shrinkage than the control, without affecting recoverable collapse. Consistent with reduced collapse in KCl-treated logs, E. globoidea stem cores showing low collapse contained significantly more inorganic cations than the high-collapsed wood. The decrease in collapse when treated with KCl solution coincided with increased green wood permeability evident in a higher sap flow rate. Sap conductivity affected the streaming potential, with the polarity of the induced electric potential varying between concentrations and matching literature reports of electric potential measurements in living trees and laboratory experiments. In summary, this study confirmed that drying collapse was negatively correlated to sap flow, and a potential technical solution to drying collapse in E. nitens could be sap replacement as a pre-drying treatment, and/or nutrient management of the plantations.
  • ItemOpen Access
    The control and program unit of a small capacity medium speed digital computer designed for instructional use
    (1967) Justice, N. A. (Nicholas Alexander)
    This project, along with three other similar projects was created so that in the second year, a small capacity (16 x 16 decimal digits) medium speed (100 Kc/s clock rate) digital computer would be built. It would be used within the Electrical Engineering Department both as an aid to large computations and as a teaching device for undergraduates.
  • ItemOpen Access
    Feeling moved in VR concerts.
    (2023) Aguilar, David J.
    This research explores the user experience design elements necessary to evoke the emotion called kama muta, most commonly known as” being moved” or “being touched”, in a virtual reality concert. Previous research has been able to mediate this emotion using video, nevertheless, to the best of my knowledge, no work has been done related to evoking kama muta in Virtual Reality. Accordingly, a VR experience prototype was created to simulate the performance of a fictional pop singer called X-ABC, who would have been dealing with grief as a consequence of his brother being missing and decides to share his feelings with the audience. Twenty participants took part in a between subjects’ study, in which they reported their emotional state using the KAMMUS Two, and Bailenson’s social presence questionnaires. Ultimately, participants’ answers were analysed using quantitative and qualitative methods. Overall, the findings suggest that it is possible to elicit kama muta in a simulation by featuring a narrative that increases the intensity of communal sharing relationships, such as loss, reunion, or memories of loved ones. It was also found that the user-experience design elements that contributed the most to the emotional response were a set of floating screens with portraits of the siblings when they were children, a believable voice acting and a character with emotional facial animations which were also lip-synced with the acted voice.
  • ItemOpen Access
    Two generalisations of the wheels-and-whirls theorem.
    (2023) Toft, Gerry
    One of the most famous results in matroid theory is Tutte’s Wheels-and-Whirls Theorem. It states that every 3-connected matroid has an element which can either be deleted or con- tracted while retaining 3-connectivity, except for two families of matroids: the eponymous wheels and whirls. The Wheels-and-Whirls Theorem is a powerful tool for inductive argu- ments on 3-connected matroids. We consider two generalisations of the Wheels-and-Whirls Theorem. First, what are the k-connected matroids such that the deletion and contraction of every element is not k-connected? Motivated by this problem, we consider matroids in which every element is contained in a small circuit and a small cocircuit, and, in particular, when these circuits and cocircuits have a cyclic structure. The first part of this thesis is concerned with matroids in which have a cyclic ordering σ of their ground set such that every set of s − 1 consecutive elements of σ is contained in an s-element circuit and every set of t − 1 consecutive elements of σ is contained in a t-element circuit. We show that these matroids are highly structured by proving that they are “(s, t)-cyclic”, that is, their s-element circuits and t-element cocircuits are consecutive in σ in a prescribed way. Next, we provide a characterisation of these matroids by showing that every (s, t)-cyclic matroid is a weak-map image of a particular (s, t)-cyclic matroid. Secondly, what are the 3-connected matroids such that such that the deletion and con- traction of every 2-element subset is not 3-connected? In the second part of this thesis, we find all such matroids. Roughly speaking, these matroids can be constructed in one of four ways: by attaching fans to a spike, by attaching fans to a line, by attaching particular matroids to M (K3,m), or by attaching particular matroids to each end of a fan.
  • ItemOpen Access
    Redirected hands for reducing arm fatigue during mid-air interactions in virtual reality.
    (2023) Hobson, Alex
    Muscle fatigue is a major impediment to the long-term usage and acceptance of Virtual Reality (VR). Users must routinely manipulate objects, perform repeated teleportations, and interact with user interface elements using prolonged arm and hand gestures. One leading strategy for reducing arm fatigue is ray-casting, which gives the user a laser pointer metaphor, allowing them to select objects with a comfortable position of the arms, but limits the fidelity of interactions by deviating from how hands are used in the real world. In this thesis a lesser-explored strategy to address arm fatigue is explored: hand redirection. “Hand redirection” is a technique made possible with VR, where the user can be fooled into believing their hand is in a different location to where it is in the real world, since people are visually dominant and VR completely immerses a person’s vision. Existing hand redirection literature mainly relates to being able to redirect the hand to a sparse haptic proxy, allowing the user to feel objects in VR, however its impact on arm fatigue is lesser explored. In this thesis, hand redirection is explored as a practical mitigation strategy addressing arm fatigue in VR, which still supports natural hand interactions (unlike ray-casting). A system was built that provides hand tracking and a physical surface at different heights, such that the user can touch the lower or tilted surface, and still see themselves touching an upright surface at eye level in VR. A between-subjects study was then conducted with 48 participants across six conditions, using a 2×3 mixed-factorial design, with two levels of redirection (Tilted, Redirected) and a control (No Redirection), with (Present) and without (Not Present) a physical surface on which to tap. The findings show that hand redirection is a valid way to reduce arm fatigue in VR, since arm fatigue was dramatically reduced without a significant impact on task performance. This behaviour differs when looking at results when the surface was present versus when it was not, suggesting that the way in which users behave in the presence of hand redirection is different when there is a physical surface to touch. Finally, the Tilted condition (where the board was rotated but not moved vertically) did not reduce arm fatigue, suggesting that the main way to reduce arm fatigue is to introduce a vertical offset rather than changing the angle that the hand interacts with the virtual content.
  • ItemOpen Access
    Augmented reality for alternative measuring techniques in geospatial field work.
    (2023) Turton, David
    This thesis assesses the value of a LiDAR application created for the the collection of data in geospatial field work. Several interfaces were developed for this tool with the purpose of determining the best method of selection in 3D space using augmented reality for data collection. Background research evaluates multiple tools and the validity of mobile LiDAR for measuring and data collection. Selection in 3D space using augmented reality is complex and multiple tools were analyzed for how they could be adapted for this task. Two user studies were performed. The first user study was performed with non- professional users aiming to evaluate the effectiveness of the different interfaces developed based on time taken, efficiency, accuracy, and user experience. The second user study consisted of interviews and test runs with GIS developers who analyzed the interfaces, gave feedback on them, and discussed how they compare to existing workflows in GIS data collection. Feedback from these studies was used to determine the best possible interface for the application, how the interfaces can be improved, and if it can operate as a potential alternative measuring tool to existing workflow.
  • ItemOpen Access
    Playing with uncertainty : participatory modelling to facilitate social and technical investment negotiations for resilience planning.
    (2023) Avendano Uribe, Bryann Esteban
    BACKGROUND: Resilience has become a fundamental paradigm for communities to deal with disaster planning, particularly in the face of increasing climate change impacts. While formal methods are employed to prioritise and decide about investments for resilience planning, developing strategies to negotiate that go beyond formal modelling is essential. Participatory Modelling (PM) has emerged as an effective approach in facilitating data-driven decision-making, enabling stakeholders to create, adjust, and learn from interactive models and to use this experience to inform their decisions. THE PROBLEM: When making decisions related to disaster planning, experts, managers, and policymakers face challenges in recognising interdependence within and between social and technical systems. Therefore, a socio-technical systems approach is crucial to understand the challenge of integrating social and technical assets in resilience planning, their interactions, and interdependencies to make informed decisions. Thus, there is a need for an integrated set of investments that increase social resilience and, at the same time, improve critical infrastructure before natural hazard-caused or human-caused disasters. THE AIM: This PhD thesis aims to develop and trial a Participatory Modelling methodology that engages participants in the process of deciding where or whether to invest in technical and social resilience. The objective of this work is to simulate the decision-making process and understand the trade-offs when negotiating between technical/infrastructure and social resilience investments. The study focused on creating a collaborative process that ensures that the diverse interests and concerns of stakeholders are represented and integrated into the planning process. THE APPROACH: To achieve these objectives, the study developed a tailored methodology called Playing with Uncertainty, which includes role-playing simulations and game elements to enhance participant engagement. The methodology involved several steps, including a workshop to identify the interests and concerns of key stakeholder groups, a survey to capture participants' perceptions of the importance of different resilience factors, a simulation exercise to explore different flood management strategies and a debriefing session to discuss the results and lessons learned. The participation model considered the challenge of investment planning for a small coastal community at risk of sea level rise. A total of Five workshops were conducted between 2020 and 2022. Workshops were held at the Human-Interface Technology Lab HITLab NZ at the University of Canterbury. Each tailored session involved three categories of role-played stakeholders: community leaders or locals, policymakers, and resilience experts. Participants included students from the University of Canterbury, resilience experts, industry professionals and planners, and policymakers from the local government in New Zealand. This research was conducted under human ethics permission HEC-2020/88. Triangulation between three data collection methods was used: 1) Role-playing negotiations, 2) Investment decisions, and 3) Prospective Structural Analysis (PSA). In addition, observations from the facilitator and comments from participants during debriefing sessions in the workshops were used to refine the methodology. KEY FINDINGS: This exploratory research found why and how the Participatory Modelling methodology developed: Playing with Uncertainty engaged participants in the decision-making process for the problem tackled in this thesis. Three key findings can be summarised as follows: 1) The use of various methods adapted aimed at enhancing engagement and eliciting knowledge from participants indicates that Playing with Uncertainty could facilitate negotiations among participants on the inherent dilemma of Socio-Technical Systems (STS). The evidence presented on the implementation of game elements and the triangulation of methods: role- playing negotiations, PSA, and investment decisions; suggests why PM has the potential to enhance STS trade-off analysis. 2) It is crucial to determine the level of detail in the information provided to participants when facilitating trade-off negotiations in STS. Drawing on observations and participants’ comments during the trials of Playing with Uncertainty, striking a balance of information in PM could benefit stakeholders’ engagement, and the need to understand how much detailed and realistic information is provided could improve the practice of PM in the field. Hence, implementing better practices of PM could bridge the gap between scientific, local and policymakers expertise when conducting decision-making. 3) Implementation and use of game elements could be synergistically integrated into the methodology development base on its refinement process. Methodological considerations for developing and trialling Playing with Uncertainty suggest the need for refinement. Participatory modellers should prioritise refinement as an ongoing process to inform their creative "polishing approach" when engaging with multiple stakeholders. A framework is proposed for PM in STS. CONCLUDING THOUGHTS: This study contributes to the growing literature on Participatory Modelling as an attempt to approach community resilience planning. Before this research, little research had been conducted on STS in New Zealand, and an international research gap in this area inspired the endeavour to challenge the civil systems engineering community to produce participatory methods to desirable enhance community cohesion while also building resilience in a holistic manner. This work provides a framework for joint investment analysis in STS. The proposed framework and lessons presented in this thesis, along with the importance of refining the methodology, have broader applications and can guide scholars in implementing participatory approaches that foster interdisciplinary collaboration and encourage creative problem-solving. However, limitations on the use of PM in STS remain, and a debate over the need for a consensus on standards and guidelines in PM persists with no clear resolution in sight. FUTURE RESEARCH: It is recommended to conduct additional trials involving a broader range of participants to provide a more comprehensive perspective within the STS context. It is recommended to polish the use of methods to identify specific challenges and opportunities within PM methodologies. Moreover, it is crucial to refine the limitations when integrating game elements and explore immersive technologies in PM to help visualise aspects that enhance a holistic understanding of STS by creating engaging and interactive experiences. This approach could attract PM practitioners from diverse engineering fields and foster collaboration and innovation for community-driven engineering solutions in resilience planning.
  • ItemOpen Access
    Ionic liquid antifouling coating for marine environment.
    (2023) Kaniyadan Baiju, Sajith
    Biofouling, a phenomenon characterized by the accumulation of marine organisms on submerged surfaces, has spurred extensive research into innovative solutions. This study endeavours to assess the effectiveness of phosphonium ion gels, which consist of phosphonium monomers ([P444VB][AOT] and [P888VB][AOT]), as well as free ionic liquid ([P444n][AOT] and [P888n][AOT]) at varying concentrations (ranging from 10% to 50% by weight). Additionally, it explores the impact of altering the length of alkyl chains (with values of n= 8 and 14) and varying the concentration of copper(II) oxide biocide (ranging from 0% to 2% by weight). Another factor under investigation is the role of the docusate anion [AOT] in enhancing hydrophobicity. To evaluate the efficacy of these formulations, a seachest simulator was employed, positioned in New Zealand coastal waters and shielded from both light and tidal currents. The testing period encompassed the summer and autumn seasons. The performance of these anti-fouling formulations was subsequently correlated with the hydrophobic nature of the submerged surfaces, determined by the water contact angle, which ranged from 14° to 131°, and the concentration of the biocide. Notably, formulations exhibiting higher levels of hydrophobicity, achieved through a reduction in free ionic liquid content and the incorporation of longer alkyl chain substituents, demonstrated superior anti-fouling performance. Intriguingly, the presence of the copper (II) biocide had an adverse effect on anti-fouling performance by increasing the surface's hydrophilicity. Importantly, no significant correlation was identified between antimicrobial activity and anti-fouling performance in this context. In summary, this research underscores the potential of phosphonium ion gels as a promising avenue for combining anti-fouling and foul release properties, offering a multifaceted approach to addressing the persistent challenge of biofouling in marine environments.
  • ItemOpen Access
    Quantifying variation in paropsine defoliation within Eucalyptus.
    (2023) Mann, Leslie
    This thesis developed various methods to quantify and better understand paropsine (Coleoptera: Chrysomelidae) defoliation within Eucalyptus, with the overarching goal of reducing herbivore damage in plantation forests. To date, paropsine preferences and impacts on Eucalyptus in New Zealand remain poorly understood with only a few published studies (Lin et al., 2017a; Radics et al., 2018; T. Withers et al., 2017). Furthermore, defoliation was previously measured with visual ground-based assessment; as a consequence, quantifying defoliation is semi-subjective. Research needs to be undertaken to fill these knowledge gaps. This thesis expands on the work of Lin (2017) and includes E. bosistoana families and other Eucalyptus species identified as priority species by the New Zeland Dryland Forest Initiative (NZDFI). This thesis is composed of five chapters, which seek to improve our knowledge of Eucalyptus tolerance and resistance to paropsine defoliation. The first chapter is a review of previous literature, followed by four separate, but interconnected chapters detailing experimental results, which are summarised in a final concluding chapter. In chapter one, my literature review identifies knowledge gaps, especially with regard to Eucalyptus tolerance and resistance (Lin (2017a) already reviewed differences in Eucalyptus species resistance in the North Island) to paropsine beetles in the South Island, what drives paropsine beetle preferences, and the way that defoliation is currently assessed in the field. These gaps led me to develop four main research questions, each of which was explored by one of the four subsequent chapters. My research questions were: 1. Are there Eucalyptus species, Eucalyptus bosistoana families, clones or even provenances that are more resistant or tolerant to paropsine defoliation? 2. Are there Eucalyptus species more tolerant to controlled artificial defoliation at different water deficit? 3. Is there a relationship between Eucalyptus foliar chemistry and paropsine defoliation? 4. Can remote sensing be used to reliably quantify Eucalyptus paropsine defoliation? In chapter two, seven Eucalyptus species from two subgenera (Symphyomyrtus subg.: E. bosistoana, E. camaldulensis, E. tricarpa, E. quadrangulata, and E. cladocalyx; Eucalyptus subg.: E. globoidea and E. macrorhyncha), 74 Eucalyptus bosistoana families and 132 Eucalyptus bosistoana genotypes (clones) were measured in the Marlborough region between December 2019 and March 2021 to investigate variation in their resistance and tolerance to paropsine defoliation. Resistance was measured with the Crown Damage Index (CDI) and tolerance was measured with growth (height gain, DBH gain and new stem length) over time. Compared to the Symphyomyrtus subgenus, the Eucalyptus subgenus was generally more resistant to paropsine defoliation, with the exception of E. cladocalyx. Eucalyptus cladocalyx, E. macrorhyncha and E. globoidea were the most resistant to paropsine defoliation. Eucalyptus bosistoana’s most resistant family and genotype were family 805 and genotype 839a. Eucalyptus quadrangulata, E. bosistoana, E. tricarpa and E. camaldulensis were all potentially tolerant regarding the new stem growth, whereas E. cladocalyx, E. macrorhyncha and E. globoidea were the most tolerant regarding the height and DBH growth. The E. bosistoana family 835 and genotype 24a were potentially tolerant. In chapter three, two Eucalyptus species (E. bosistoana and E. globoidea) were placed in a greenhouse for 101 days to test defoliation and water tolerance in a more controlled environment. Three artificial defoliation severity levels, two water levels and two defoliation frequency levels were applied. Tree growth (height and diameter gain), dry biomass (total, leaf, stem, root) as well as leaf carbon and nitrogen content were measured. Both species were negatively affected by water stress, meaning that planting these species in drylands will likely exacerbate the negative impact of paropsines. Nevertheless, E. globoidea was more resistant to water deficit and defoliation than E. bosistoana. Low levels of defoliation stimulated E. bosistoana biomass (overcompensation), but high levels of defoliation negatively impacted this species. E. globoidea may generate taller trees as a mechanism to tolerate defoliation, whereas E. bosistoana may produce trees with denser overall biomass (stem in particular) and narrower trunk. Compared to trees that had only been defoliated once, trees that had been defoliated twice grew less. This demonstrated that both species exhibit some elements of tolerance to defoliation, but E. globoidea is more tolerant than E. bosistoana. In chapter four, leaves from seven Eucalyptus species from two subgenera (Symphyomyrtus subg.: E. bosistoana, E. camaldulensis, E. tricarpa, E. quadrangulata, and E. cladocalyx; Eucalyptus subg.: E. globoidea and E. macrorhyncha) were collected in a trial from the Marlborough region to study the potential relationship between foliar chemistry and paropsine defoliation. The leaves were then oven-dried, ground, extracted with ethanol and analysed with a High Performance Liquid Chromatography (HPLC). The Eucalyptus subgenus Symphyomyrtus and Eucalyptus foliar compound diversity were distinct. These preliminary experimental results suggest a relationship between foliar chemicals and paropsine defoliation. Defoliated species had higher foliar compound concentration and richness than non-defoliated species, except for E. camaldulensis, which displayed low foliar compound concentration and richness despite being significantly defoliated. Two compounds specific to E. cladocalyx may be paropsine repellent. In chapter five, six Eucalyptus species from two subgenera (Symphyomyrtus subg.: E. bosistoana, E. camaldulensis, E. tricarpa, E. quadrangulata, and E. cladocalyx; Eucalyptus subg.: E. globoidea) were measured in a trial from the Canterbury region with three LiDAR sensors to assess the potential of this technology to accurately detect defoliation. LiDAR data were compared to Crown Damage Index (CDI) field measurements to assess its prediction accuracy. The 5 % accuracy difference among the three LiDAR sensors under evaluation indicated that each could be useful for predicting paropsine defoliation and show good promise for further experiments. The most effective LiDAR metrics for predicting paropsine defoliation on Eucalyptus trees were itot, zimean, imax, imean, and isd, with zkurt, zpcum2 to zpcum9, p1th to p3th, pzabovemean, pzabove2, and ipcumzq10 to 70 being less useful. All of these metrics are related to either tree height or foliage density (canopy cover). My results contributed to a better understanding of tolerance and resistance to paropsine beetles within Eucalyptus. This contributes to limiting the effect of paropsines on the Eucalyptus forest industry. These findings are a valuable starting point to deeper exploration and guiding future Eucalyptus breeding in terms of paropsine herbivory.