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The UC Research Repository collects, stores and makes available original research from postgraduate students, researchers and academics based at the University of Canterbury.

 

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ItemOpen Access
Open clusters as tracers of galactic chemical evolution.
(2024) Boucher, Kyle
In this thesis, we investigate the formation and evolutionary history of the Milky Way, with a focus on separating the inner and outer galactic regions as well as the thin and thick disk formation. To do this we use FGK stars from the Open Cluster (OC) program of the Gaia-ESO spectroscopic survey to constrain numerical simulations of the chemical evolution of the Milky Way. Our Galactic Chemical Evolution (GCE) numerical simulations use Markov Chain Monte Carlo (MCMC) sampling to infer the galactic formation parameters for each open cluster. These simulations are constrained by the observational abundance measurements of C, N, O, Mg, Si, Ca, Ti, Fe, Mn, Zn, Y, and Ba from the Gaia-ESO DR5 data. The results of our simulations reveal distinct formation histories between the inner and outer galactic regions. The observed galactic metallicity gradient aligns with the trends we find in the slope of the IMF and the rate of Type Ia supernovae. We also corroborate the galactic formation theory of the star formation history being early and intense in the inner galaxy followed by minimal star formation, and the outer galaxy showing a more sustained star formation throughout the history of the Milky Way. While we were unable to conclusively split the thin and thick disks, our results reveal potential regions where mixing between the thin and thick disks is high. Additionally, the outliers in our results broadly agree with the evidence of galactic mergers and accretion events.
ItemOpen Access
Parental love withdrawal and relational aggression in preschool age children : the role of normative beliefs about relational aggression.
(2024) Lawerance, Preethi
Parental psychological control encompasses several dimensions, such as invalidation of feelings, shaming/disappointment, guilt induction, and love withdrawal. These parenting behaviours have been shown to influence young children’s aggressive behaviours, such as relational aggression (RA). Parental love withdrawal is similar to RA, where the threat is often directed towards the possibility of damaging social relationships. Social Learning Theory suggests that parental love withdrawal may be observed by children, and subsequently modelled in peer interactions as RA. Additionally, the Social Information Processing Model for aggressive behaviours posits that children turn to their memory for cognitive schemas to guide their behavioural choices. Exposure to parental love withdrawal is likely to impact children's belief behaviour pathways and their normative beliefs about relational aggression (NBRA). This study used data from a larger three-year longitudinal study called THRIVE and examined the association between parental love withdrawal and preschool age children’s (2-5 years) RA via NBRA. Parents participated in interviews regarding their parenting styles. Teacher reports were used to measure child RA, and children’s NBRA were assessed using hypothetical vignettes and a social cognitive interview. The results showed no significant associations between parental love withdrawal and children's RA. However, children more disapproving of RA showed significantly higher levels of RA. Similarly, older children were more likely to perceive RA as wrong, but also exhibited greater levels of RA compared to younger children. Older children with greater exposure to parental love withdrawal were more likely to be accepting of RA. Overall, the study highlights the nuances of the belief behaviour pathway in preschool children, and the need to examine different precursors and mechanisms of child RA.
ItemOpen Access
The role of avalanche deposition on the mass balance of Rolleston Glacier, Arthur’s Pass, New Zealand.
(2024) Spera, Alison
Avalanches are a crucial source of nourishment for cirque mountain glaciers, supplementing their accumulation and delaying melt. However, their role in glacier mass balance is highly under-studied and overlooking their influences may inaccurately assess glacier health. This thesis investigates the role of avalanches on the Rolleston Glacier mass balance using an Energy Balance Model (EBM) coupled to a mass transport and deposition (MTD) algorithm. A 12-year climate record (2010 – 2022) was used as model input with precipitation factors and temperature lapse rates as tuning parameters. Annual (Bn) and winter balances (Bw) were compared for the glaciological years 2010/11, 2012/13 and 2018/19 with and without the MTD algorithm. The MTD performed better for positive balance years, with optimum precipitation factors and lapse rates applied for different years. To quantify the proportion of winter balance attributed to avalanches, the model was run over the 12-year period. Excluding gravitational processes produced results that were within 1.81 m w.e of directly measured mass balance, while activating the MTD yielded estimates within 0.64 m w.e of the observed. In general, the spatial distribution of the winter balance was improved under the MTD, contributing an additional 1.47 m w.e to the average winter balance across 2010 – 2022. A comparison against probe measurements showed more bias was incurred (2.04 m w.e) when discarding the MTD from the model. The model was validated against cumulative mass balance measurements showing strong R2 relationships when coupled to the MTD (R2 = 0.9) as opposed to scenarios without the MTD (R2 = 0.65). Future work should incorporate a comprehensive sensitivity analysis and parameter optimisation procedures to advance the applications of mass transport algorithms to mass balance models. The results demonstrate that including the MTD has useful applications to simulating more accurate mass balance estimates to avalanche-fed glaciers like Rolleston Glacier and enhances understanding of local-scale alpine processes.
ItemOpen Access
Simulating Solar Storms via Active DC Injection from the HVDC Link
(2023) Lapthorn, Andrew; Hardie , Stewart; Agger , Paul; Subritzky , Soren; Dalzell , Mike; Clilverd , Mark; Cobbett , Neil; Beggan , Ciaran; Huebert , Juliane; Eaton , Eliot; Brundell, James; Rodger , Craig
As part of the MBIE Endeavour programme “Solar Tsunamis: Space-Weather Prediction and Risk Mitigation for New Zealand’s Energy Infrastructure,” we are interested in the effects of geomagnetically induced currents (GICs) on New Zealand’s electrical infrastructure. GICs appear as quasi-dc currents on the power system and can lead to problems in the network as a result of transformer saturation such as increased reactive power demand, increased harmonics, and even overloading of the transformers. Studies have shown that, depending on the severity of the solar storm, these effects could potentially be widespread. Different transformer designs behave differently under these quasi-dc conditions, with single phase designs the worst, and three-limb core designs proving the most resilient. Furthermore, several transformers in New Zealand have neutral earthing resistors (NERs) installed. Therefore, it is difficult to say at what point do GICs start becoming a problem, and how much current is too much current. In January 2023, with the support of Transpower, we were able to utilise New Zealand’s high voltage DC (HVDC) link to inject current directly into the ground at Haywards substation and monitor the effects on two 216 MVA, 220/110 kV autotransformers, along with monitoring of associated transmission lines. Over the span of nine days, six injection tests were carried out lasting between one and two hours each time. The peak current injected into the ground was about 621 A. This paper provides an overview of the testing plan, procedure, and initial results from the collected data.