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Research Commons is the University of Waikato's open access research repository, housing research publications and theses produced by the University's staff and students.
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Item Charge capacity characteristics of a Lithium Nickel-Cobalt-Aluminum Oxide battery show fractional-derivative behavior(Journal Article, 2021)Batteries experience capacity offset where available charge depends on the rate at which this charge is drawn. In this work we analyze the capacity offset of a 4.8 A h lithium nickel-cobalt-aluminium oxide battery using an equivalent circuit model of a fractional capacitor in series with a resistor. In this case, the available charge, in theory, becomes infinite in the limit of infinitesimal rate. We show that the fractional properties of the capacitor can be extracted from the charge against rate plot. We then use a network of RC elements to represent the fractional capacitor in order to simulate the data with Matlab. We find that the fractional exponent alpha obtained in this way, 0.971, agrees with that obtained in a more traditional manner from an impedance versus frequency plot, although the fractional capacity does not. Such an approach demonstrates the importance of a fractional description for capacity offset even when an element is nearly a pure capacitor and is valuable for predictions of state-of-charge when low currents are drawn.Publication Me ko Māui: Harnessing the sun to provide better outcomes for marae and communities(Thesis, The University of Waikato, 2024)Marae are the cultural centres of Māori communities, providing a space for important gatherings both joyful and sad. With the advent of solar energy capture technologies and rising electricity bills, many marae are becoming interested in whether a solar powered system will be beneficial for them. However, marae have unique electricity demand profiles, distinct from commonly modelled building types such as residential or commercial buildings. It is thus difficult to estimate an appropriate solar and battery system size based on annual or even monthly electricity usage data, which may be the only data readily available, requiring more in-depth analysis at a highly site-specific level to find an answer. This thesis aims to increase understanding around how solar power could benefit marae, first by investigating the characteristic electricity demand profile of marae, then by observing how proposed system configurations meet the demand. The potential community benefits arising from such a system was also investigated. Using a year’s worth of half-hourly data from three marae, five characteristic day types were found in the analysis of the demand profile, namely a “Non-Event” profile that maintained a low baseload and accounted for 70% of the days in a year, a “1-Day Event” profile that lasted only a few hours, and for events spanning multiple days a “Start”, “Middle” and “End” day profile that varied greatly in demand magnitude. The demand profiles were then used to develop an annual demand profile for an average marae that was broadly representative of a wide range of marae. Different configurations of solar and battery powered systems were then applied to the annual demand and a technoeconomic analysis performed to determine whether a specific configuration met the needs of the average marae or not, which then produced a range of acceptable system sizes based on the needs specified. Not many solar and battery configurations resulted in positive economic returns for the marae alone, but widening the scope of the analysis to the surrounding community allows other interests such as local grid resilience to be considered, some of which may justify a marae’s decision to invest in a non-economic system to gain better community benefits. While investigating the use of peer-to-peer energy trading and community energy scenarios, sharing excess energy generated by a system with the wider community was also found to improve the economic outlook of solar for marae.Publication Associative learning deficiencies underlying aberrant feeding in the valproate rat model of autism(Thesis, The University of Waikato, 2025-04)Autism spectrum disorder (ASD) is a heterogenous neurodevelopmental condition prevalent in over 1% of the global population. Aberrant feeding behaviours and feeding dysregulation are a prevalent and understudied difficulty. Individuals with ASD often present with poor health outcomes, including over/under eating, obesity, and restrictive feeding associated with poor dietary habits, however the underlying mechanisms are poorly understood. Here we propose an explanation for some neural mechanisms that may be responsible for feeding dysregulation present in ASD. We demonstrate that valproate rat models of ASD (VPA ASD) have a blunted neural response to LiCl-induced conditioned taste aversion and show transcriptional changes in the arcuate nucleus of the hypothalamus. Findings of this study also show that VPA ASD rats have significantly higher neural activation in the nucleus accumbens and the dorsal vagal complex in response to food, compared to controls. Our research suggests that some of the feeding abnormalities seen in people with ASD may stem from signalling deficiencies in brain areas involved in associative learning responses following ingestion of foods that cause malaise. Extremely restrictive feeding behaviours seen in ASD phenotypes may be caused by difficulties identifying foods that make them sick. These findings contribute to understanding neuromolecular drivers of anomalous feeding behaviours in people with ASD.Publication Talking in circles: Examining co-rumination in parent-child reminiscing and future event conversations as an intergenerational transmission pathway for internalising symptoms(Thesis, The University of Waikato, 2025)Middle childhood is a salient period of development (Mah & Ford-Jones, 2012). Internalising difficulties such as depression and anxiety often occur before the age of 15 (Lijster et al., 2017; Liu et al., 2011), and the burden of these difficulties continue into adolescence and adulthood (Caputi & Schoenborn, 2018; Garber & Horowitz, 2002). Previous research highlights the integral role that parent-child interactions play in the development of mental health concerns in children (Eisenberg et al., 1998; Goodman & Gotlib, 1999), with the discussion of emotions identified as a pathway which might support children’s capacity to cope with emotional distress and buffer against the development of mental health difficulties in children (Bray et al., under review; Russell et al., 2024b; Swetlitz et al., 2021). On the other hand, parents may pass on their own cognitive biases through conversations about emotions with their child (Bray et al., under review). This study aimed to examine co-rumination within parent-child conversations about past and future negative emotional events, and whether this might act as a potential pathway for the intergenerational transmission of internalising difficulties between parents and their children. Participants were parent-child dyads from New Zealand (n = 51) and Australia (n = 54). Children were aged between 8 and 12-years-old. Parents and children completed relevant measures for mental health difficulties and engaged in two reminiscing conversations (one positive and one negative) and two future event conversations (one positive and one negative). Parent-child conversations were coded for co-rumination utilising an adapted co-rumination coding scheme (Rose et al., 2014). A series of Pearson correlations and simple mediation models were conducted to examine associations between parent and child mental health and co-rumination, and to test a potential pathway of intergenerational transmission of internalising difficulties through co-rumination. Results indicated that parent and child rumination were correlated, suggesting a dyadic style of rumination developing during middle childhood. No empirical support was identified for an indirect effect of parent to child internalising symptoms through co-rumination. Recommendations for future research are discussed.Publication Planning for the protection and enhancement of marine environments' wellbeing(Thesis, The University of Waikato, 2025-04-16)The wellbeing of marine environments has a direct relationship with the types of whenua (land, placenta) use and management practices that go from the mountains to the sea. In Aotearoa, activities that are carried out in this land-marine interface, including those related to Nature-based Solutions (NbSs), are regulated by national, regional, and district policies (e.g., New Zealand Coastal Policy Statement, regional plans, and district plans). However, due to its novel character, not all current policies account for the realisation of NbSs nor are NbSs’ potential for addressing the wellbeing of our marine environments well understood. This dissertation focuses on Tauranga Moana (the seas of Tauranga) as the chosen locality for the case study area, to: i) investigate how the Ngapeke 7 Trust’s community participants in the Ngāti Pūkenga area of Tauranga Moana understand and value NbSs for addressing the wellbeing of their marine systems; and, ii) review current planning policies and mechanisms to identify barriers, enablers, and gaps that support or hinder the implementation of NbSs in Tauranga Moana, observing through a Kaupapa Māori lens. Findings emphasize that integrating mātauranga Māori and Māori Ecological Knowledge (MEK) with scientific knowledge offers a holistic approach to environmental management, enhancing decision-making, education, and policy. Key Māori values, including whakapapa, mauri, and kaitiakitanga, are central to this approach. The research identifies gaps in policies regarding NbS realization and a need for greater understanding of NbS potential and Māori perspectives. Implications include the necessity of integrating MEK into environmental practices and policies, and the value of NbSs for effective and equitable environmental outcomes. Limitations include sample size and scope, which focused on the Ngapeke 7 block. This research contributes valuable insights for environmental planning and management by centring mātauranga Māori and values in NbS implementation for marine health.
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