16168 research outputs found
Sort by
Valorization of wood ash for sustainable in situ reinforced Ti composites with tailorable mechanical behavior manufactured via powder metallurgy
No full textThe aim of this work is to investigate the feasibility of revalorizing commonly disposed wood ash as source to produce more sustainable in situ reinforced Ti composites. We propose a manufacturing process based on the powder metallurgy green technology and further increase the energy efficiency of the process by analyzing reactive induction sintering as the primary consolidation method. The feasibility of the proposed approach is demonstrated through the characterization of the physical, microstructural, and mechanical performance. It is found that compressibility decreases and the amount of residual porosity increases (6.0–11.7% for pressureless sintering) with the amount of wood ash used (0–0.25 wt%). However, the effective in situ creation of the reinforcement is always guaranteed by the proposed approach. Furthermore, minor adjustments of the manufacturing route can be used to maximize the amount of ash to be added for higher sustainability. The in situ reinforced Ti composites are commonly characterized by both elastic and plastic deformation and fail non-catastrophically, where for vacuum sintering ductility decreases (13.7 → 8.7%) but strength (497 → 653 MPa) and hardness (47.8 → 55.0 HRA) increase with the amount of ash used. The in situ reinforced Ti composites produced from revalorized wood ash have overall comparable or better mechanical properties in comparison to other Ti-based composites bearing a higher amount of generally more expensive reinforcements
Sill road
No full textNola Clark stays Inside, always.
She loves a few things about living on the Road: her big sister Lauren, her cat Milton and her friend Seb. She worries about a few things: the winnowing wind of the desert beyond her window, the gnarled hands of the travelling Mapper, and her sister’s inability to keep out of trouble. Set in an alternative reality to the Cold War, the world of Sill Road is one where people fear the Outside air will kill them. To protect themselves, houses are linked by covered-in Roads. These structures are advanced in large cities. In New Zealand’s Central Plateau, however, things are much more rickety.
Growing up, Nola’s neighbourhood is content to broil in the heat of their enclosed world. But the thing with Roads is that something’s always coming along them. In the unexplained absence of her sister, Nola and the whole community are forced to choose whose story to believe.
Sill Road is a novel about family, a closed door and relationships held together by firm beliefs. Toying with themes of faith, survival and love gone wrong, the story bores into the heart of group survival. It examines how we use narratives to build a world we can survive. It looks at what happens to the people who don’t fit inside those stories.
It is about the things we’ll do to save each other. It is about how there is nothing harder than changing our minds
Bones | Iwi
No full textPoetry written at Kāwhia featured in Issue 6 of The Quick Brown Dog Journal published by Hagley Writers' Institute, Christchurch, NZ
Proxy evidence of relative sea level change indicators and implications Raglan (Whaingaroa) harbour New Zealand
No full textGeological observations and macrofossil dating of 4 raised marine terraces reveal active tectonic displacement in the Raglan Harbour, New Zealand (NZ). The 120 km-long harbour shoreline displays multiple examples of block-faulting, stratigraphic displacement, and fresh stress release fracture zones within rock sea-cliffs. Tide-zone rock platforms are indicative of a long-term uplift trend within a major portion of the harbour. Vertical land movement (VLM) rates are found to vary at different locations, signifying active fault displacement. Six proxies establish VLM magnitude and timing constraints applicable to the last 7 decades. One further proxy establishes maximum relative sea level (RSL) throughout the last 23.5 Ka at a specific location in the harbour.
Seventeen 14C dated macrofossils from 4 raised marine terraces identified 2 groups of ages: pMC ~ 1 to 6.5 Ca yr BP and ̴ 6.5 Ka yr BP respectively. Tide dissolution notches in rocks identifiable in historical photographs are compared with modern equivalents at 2 locations. These depict no apparent change in the upper dissolution notch boundary elevations since 1910. Characterisation and U-Th dating of a speleothem located ̴ 0.4 m above the modern high tide level signifies that RSL is near its ̴ 23.5 Ka maximum at this location. Historic aerial imagery identifies a marine terrace that uplifted by < 0.4 m within the period 1979 to 1997. A fault demarcates this feature from a second terrace with stratigraphic evidence of a markedly different VLM history, indicating that the fault is active. Raised trace fossil castings exposed in the foreshore’s mid-tide zone further substantiates evidence of relatively recent uplift at this location
The reassembly of soil food web structure and functioning in restored urban forests across Aotearoa - New Zealand
No full textSoil food webs play a central role in the successful restoration of critical ecosystem processes. Yet, we lack an understanding of how these highly diverse and functionally complex belowground communities reassemble in forests undergoing restoration, and the factors responsible for varying trajectories of soil community reassembly. Even more poorly understood is the reassembly of soil invertebrates across multiple trophic levels after disturbance. Moreover, any potential effect of ecological succession on food web structural properties (connectance and maximum trophic level) and its implications on soil invertebrate trophic functions remains poorly understood. In this PhD thesis, I investigate the effect of restoration age and biotic and abiotic characteristics of restored forests on the reassembly of soil invertebrate communities across different trophic groups. I also explore the effect of the aforementioned predictors on soil food web structure and associated ecosystem functioning.
I sampled soil invertebrate communities from 70 urban restored forests, as well as three unrestored and three remnant urban forests. All forest sites were distributed across eight cities in Aotearoa, New Zealand and were historically occupied by native vegetation until cleared for either agriculture or urban development. The sites were then planted with native woody species between six and 60 years prior to this research, forming a chronosequence of forest succession. In addition to soil invertebrates, vegetation data (e.g., mean tree diameter, tree species richness) and site characteristics (e.g., litter depth, soil temperature) were also collected from these forests. I identified the soil invertebrates into major size-based functional groups (i.e., microfauna, mesofauna and macrofauna) and further into trophic levels: detritivores, fungivores, herbivores, omnivores and predators. Additionally, I quantified the abundance, biomass and mean body mass of all soil invertebrates. Finally, I constructed 70 local food webs across the restored forest sites and quantified the flux of energy between different feeding groups and their food sources to estimate five important ecosystem functions in soil food webs: detritivory, bacterivory, fungivory, herbivory and predation.
I analysed the relative importance of restored forest age and environmental variables as predictors of variation in soil invertebrate communities. I found that restoration age, in itself, had no discernible effect on the abundance, biomass or mean body size of soil invertebrate communities. Instead, site characteristics like mean tree diameter, tree species richness, litter depth and soil temperature were the main drivers of variability in soil communities. Notably, these factors influenced larger macrofauna and mesofauna more than nematodes. However, when I modelled the effects of restoration age on soil communities in a structural equation modelling framework, taking into account bottom-up effects from plant communities to invertebrate predators, restoration age was shown to have indirect effects on the biomass of mesofauna decomposers, omnivores and nematode predators. Finally, by investigating shifts in food web structure and resulting changes in energy fluxes across trophic levels, I found that forest restoration age did not directly influence either the structure (connectance, maximum trophic level) or the five examined trophic functions of the soil food webs. Instead, effects of forest restoration age occurred through changes in vegetation characteristics as forest succession progresses.
My results suggests that forest age is not a direct major driver of the reassembly of soil invertebrate communities. Instead, mean tree diameter, tree species richness, litter depth, and soil temperature play important roles in the process. My results show the significance of planting trees that can grow large, promoting species diversity and allowing leaf litter to accumulate naturally to support soil invertebrate community of different trophic functions. Through my results, I also show how the aforementioned vegetation characteristics can contribute to flow of energy in the soil food web. In addition to demonstrating how crucial food web structural properties are to energy flow via trophic interactions such as detritivory, fungivory and predation, this research also highlights the interconnectedness of above and belowground ecosystems. Taken together, my findings suggest that urban restoration efforts should focus on promoting these beneficial vegetation characteristics, alongside considering food web complexity, to optimize trophic functions performed by soil food webs
Weaving Mana Wahine and Masi methodology: Centring the embodied experiences of young Māori and Pasifika wāhine in physical activity and everyday life
No full textYoung Indigenous Māori and Pasifika wāhine (women) in Aotearoa New Zealand (hereafter Aotearoa) have too often been framed as vulnerable, ‘at risk’ and problematic in the media, policy and research. This thesis moves beyond these deficit framings and uses an Indigenous feminist, strengths-based approach by centring the voices and lived experiences of young Māori and Pasifika wāhine who are agentic in their everyday lives, celebrate their strong brown bodies and are physically active.
Being an Indigenous feminist early career researcher of Māori-Samoan ancestry, I intentionally weave Mana Wahine (Māori) and Masi (Pasifika) methodologies throughout all aspects of this research. Employing wānanga (focus group discussions), individual interviews and digital methods, I gather knowledge from a total of 31 young Māori and Pasifika wāhine residing in two low socio-economic urban regions (Porirua and South Auckland) in Te Ika-a-Maui, the North Island of Aotearoa. Centring their voices and lived experiences, I examine how the young wāhine embrace and weave their intersectional identities with culture, body image and physical activity.
This is a PhD with publication. It begins with an introductory chapter and a literature review chapter that locates the project in the context of Aotearoa and the local and international literature. In the methods chapter, which is a published article, I focus on the importance of creating culturally safe and supportive spaces for young wāhine to participate in research that feels meaningful to them. The empirical chapters are presented in three different manuscripts. Chapter Four contains a manuscript (currently under review) that focuses on the intersectional identities of the young wāhine. It is structured using three key themes, including 1) ethnic and cultural identities, 2) navigating, and 3) how they embrace cultural pride, particularly through family values, customs and responsibilities. Chapter Five is a published manuscript that explores body image through an intersectional Indigenous feminist lens. This publication examines cultural perspectives that influence their views on body image and provides insights into how the young wāhine navigate body image stereotypes. Chapter six is the final empirical manuscript (currently under review) that evaluates the motivations the young wāhine have for participation in physical activity. It examines the types of activities they enjoy and provides insights into how and why they use cultural knowledge as a motivator for participation.
This research contributes to international literature conducted with, for and by Indigenous feminist scholars on young women’s identities, body image and physical activity. It responds to the limited academic scholarship that explores the lived experiences of young Māori and Pasifika wāhine in Aotearoa and their nuanced cultural knowledge of their bodies. In so doing, this research offers insights and new ways of understanding the complex lives of young Māori and Pasifika wāhine, and highlights the importance of intersectional approaches and localized Indigenous methods that listen to, and amplify the voices of young wāhine
Natural and Experimental Admixture of Invasive Blowflies in New Zealand and Australia
Get PDFAcross the globe, native species are being outcompeted and often reach extinction due to introduced species becoming invasive. Previously confined to their native areas due to geographical, ecological, or environmental barriers that have prevented them from expanding, human impacts have resulted in a significant increase in the number of introduced species. Such species become invasive when they begin to expand their range demographically and typically cause negative impacts in the new environment. There is no current model that allows us to predict and prevent future biological invasions, though next generation sequencing, population genomics analysis, and experimental laboratory manipulations are helping to fill critical gaps in our understanding of the invasion process.
My first analysis (Chapter 2) explored the ability of population genetics analyses of single nucleotide polymorphism (SNP) data to identify hybridisation levels and the rate of admixture occurring in wild populations of Calliphora hilli and Calliphora stygia – two invasive blowflies found in New Zealand and originally from Australia. I analysed samples from various locations and found patterns of population genetic connectivity and structure that supported Australia as the source of the New Zealand invasion for both species. This research provided highly valuable new insights into the population structure of these two species, with hybridisation and gene flow playing a key role in their respective biological invasions.
My second analysis (Chapter 3) first explored the population structure of the highly invasive blowfly species, Callipohra vicina, using SNP data to analyse population genomic patterns, such as genetic diversity and admixture. Following this, low genetic diversity colonies were generated from isofemale lines to simulate an invasive population that had undergone a genetic bottleneck. These low diversity lines were compared to relatively high diversity lines for a number of traits, including fecundity, body size, developmental rate, and lifespan to determine the effects of genetic diversity on population fitness. We found genetic differentiation between North and South Island New Zealand populations in the wild, while high diversity lines outcompeted low diversity lines for all measured traits in the laboratory. These results demonstrated the importance of genetic bottlenecks on invasion scenarios and suggested interesting new ideas for follow-up research.
Predicting and preventing future invasions is a significant current gap in invasion biology. Population genomic and ecological assays can together help to fill this gap to help us identify the mechanisms underlying invasive success
Words on walls: The linguistic landscape of Kirikiriroa primary school classrooms
No full textLanguage contact between te reo Māori and English has resulted in one of the central features of New Zealand English (NZE): the integration of loanwords from the Indigenous, donor language, te reo Māori, into a dominant Lingua Franca (Hay et al., 2008). Previous works have analysed the presence and presentation of these loanwords across a number of mediums. Our study, however, examines data directed at a previously unexamined demographic: primary school-aged children.
We aim to establish which loanwords children are regularly exposed to, and thus examine a most relevant domain: the classroom. Considering the linguistic landscape of classrooms (schoolscapes) offers insight into the language use that occurs within them. Further, the classroom is educational in the traditional sense, but also in the developmental sense, in the acquisition of broader social meaning. Previous schoolscapes research has highlighted not only their pedagogical importance, but their influence in the construction and transmission of language ideologies (Pzymus and Huddleston 2021; Brown 2012), making these particularly valuable spaces to study.
This study presents a schoolscape investigation of nine Waikato classrooms by analysing loanwords arising in educational artefacts directed at primary-aged children (7-11) in an English-medium school setting. We make the following contributions: (1) a systematic schoolscape method for analysing contact-induced language phenomena; (2) quantitative and qualitative analyses of loanwords identified in our data; (3) a detailed taxonomic expansion of te reo Māori loanword categories (semantic and syntactic) in present day NZE.
In this talk, we ask the following questions:
RQ1) What type of te reo Māori (loan)words are children regularly exposed to through schoolscapes in A/NZ?
RQ2) What is their distribution across schools/classrooms/years?
We find that, in the classes examined, children encounter both high levels of exposure to te reo Māori (loan)words and high levels of variation in the types of words present. On average, children encounter one te reo Māori token for every ten English tokens. As in previously identified trends (Macalister, 2006b), most loanwords found are nouns belonging to semantic categories pertaining to the environment, place names and social culture items. However, we also identify prominently occurring words and word types that have not previously been identified in corpora. We show that, within classrooms, children regularly encounter a landscape richer in te reo Māori (loan)words than previously seen, but also one characterised by substantial variation
The integration of heat pumps with biomass boiler flue gas for generating hot water
No full textAchieving the goal of net zero greenhouse gases by 2050 requires reducing demand and switching from fossil fuels to renewables. Process heat in New Zealand is a significant source of greenhouse gas emissions. Transitioning to biomass boilers could lower emissions and offer opportunities for waste heat recovery by integrating heat pumps with the flue gas.
This thesis evaluates heat pump integration for hot water production, supplying low temperature process heat. Using an industrial case study, a boiler model is developed and confirmed against industrial measurements. Flue gas composition is modelled to determine temperature-enthalpy profiles, and therefore the heat available for recovery and upgrade. Combustion is modelled for different biomass fuels and varying flue gas oxygen levels. The higher moisture fuels showed increased availability of heat for utilisation, which decreased as flue gas oxygen levels increased.
Three heat pump cycles are explored to maximise efficiency. Refrigerant selection is considered with respect to environmental factors and thermodynamic suitability. Using a basic cycle heat pump the three most promising refrigerants, ammonia, propane and cyclopropane, were identified and considered in more detail for the industrial case. Subcooling improved efficiency and should be maximised. An internal heat exchanger also improves efficiency and reliability and should be considered. Two zeotropic mixtures were investigated to take advantage of the temperature glide. The propane-pentane (50wt%-50wt%) blend matched the temperature profile more closely and provided increases in COP.
To make the most of the latent heat in the flue gas, the evaporator temperature must be much lower than the dew point. However, absorbing heat from low source temperatures results in lower COPs, but higher volumes of hot water generated
The impact of patchiness on plant-flow interactions and consequences for seagrass habitat suitability: a multiscale study
No full textSeagrasses are among the most productive marine ecosystems, providing essential ecological services. As ecosystem engineers, these flowering plants modify their environment through physical, chemical, and biological processes. A key physical mechanism involves stabilizing sediments by reducing near-bed flows, which result from the resistance created by plant stems. Flow attenuation increases sedimentation and reduces erosion of seabed, making seagrasses valuable for coastal protection in the face of climate change. Additional ecological services provided by seagrasses include improving water quality by cycling nutrients, providing habitat and feeding grounds for marine species, and sequestering carbon. However, the ability of seagrasses in providing these ecological services is strong influenced by the extent and spatial distribution of vegetation coverage. Patchiness in seagrass beds alters interactions between seagrass and water flow, with areas of varied flow resistance creating heterogeneous flow and turbulence conditions. This thesis assesses the impacts of patchiness, and in particular, the effect of gaps (bare sediment) in otherwise, continuous vegetation coverage, on plant-flow interactions through field measurements, numerical hydrodynamic modelling, and machine-learning classification methods. A multiscale approach is employed: First, a small-scale, field-based study explores the impacts of a bare patch on flow and turbulence, and the links with the spatial distribution of the surrounding seagrass. Second, a suite of numerical modelling simulations was undertaken to investigate the hydraulic interactions of multiple bare patches in a meadow-scale domain. Finally, estuary-scale species distribution models were developed based on topographic and sediment property variables to evaluate seagrass habitat suitability in a large tidal estuary, while also correlating habitat suitability with seagrass patchiness at a larger spatial scale.
The first chapter examines the effects of seagrass patchiness on plant-flow interactions. Data on vegetation cover, bed elevation, and hydrodynamics were collected within and around a bare gap in the natural intertidal seagrass meadows of Tauranga Harbour, New Zealand. The small-scale, high-frequency measurements of flow and turbulence revealed faster flow speeds within bare gaps, and slower flow speeds above the surrounding seagrass, during the incoming flood phase of the tidal cycle. Although flow speeds were slower above the seagrass adjacent to the gap, turbulence, as characterised by the dissipation rate of turbulent kinetic energy, remained elevated above the vegetation These turbulence levels were dominated by down-deceleration events, which directed water and nutrient fluxes downward into the canopy, potentially explaining the presence of denser seagrass along the sides of the gap. We observed a spatial alignment between tidal flows and spatial distribution of seagrass: NDVI-derived maps of seagrass coverage demonstrated that the axis of seagrass continuity coincided with the dominant flow direction during flood tide at both the gap scale (O(100)m) and meadow scale (O(102)m), thus suggesting that small-scale plant-flow interactions are also strongly modulated by large-scale processes, such as tidal asymmetry. These findings suggest a feedback mechanism in which seagrass patchiness and spatial structure are shaped by flow transience, which then also influence ecological conditions associated with the survival and growth of the plants.
The work examining the impact of a single bare patch on plant-flow interactions was extended to investigate the collective impacts of multiple bare gaps at the meadow scale. This section used numerical modelling, focusing on unidirectional flows within emergent vegetation. Simulations with single gaps showed that horizontal flows were accelerated within the modelling domain, with the flow acceleration increasing up to a critical gap size. Beyond this critical size, further gap enlargement did not increase flow speeds. Paired-gaps simulations revealed that flow interactions occurred when the gaps were separated by distances less than or equal to two gap diameters, especially when aligned in the streamwise direction, where wakes of accelerated flow interconnected, and flow changes were maximised. Minimal flow changes were observed for laterally aligned gaps. Hydrodynamic simulations involving multiple gaps assessed the effects of fragmentation, defined by the number and size of gaps, on flow at fixed levels of bare bed coverage. The results showed that the flow dynamics within aquatic canopies if also driven by spatial configuration of gaps, rather than bare bed coverage alone. Models with fewer, larger gaps caused greater flow acceleration within the idealised meadow than those with more numerous smaller gaps at the same coverage ratio. These effects were more pronounced at higher bare coverage levels, demonstrating that the arrangement of gaps is one of the driving factors in modifying flow and influencing ecosystem stressors linked to flow modification and habitat degradation.
Lastly, as feedback mechanisms are species- and system-specific, understanding the relationship between seagrass distribution and environmental factors across different systems is essential. To address this need, a regional-scale study was conducted to explore how topography and sediment composition determine the distribution and the habitat suitability of the temperate, shortleaf species Zostera muelleri in Tauranga Harbour, New Zealand. Using Random Forest species distribution models, the influences of twenty topographic and substrate variables on seagrass habitat suitability were assessed across a large (~240 km²), predominantly intertidal (~60%) estuary. The models showed strong predictive performance as assessed by a mean area under the curve (AUC) of 0.84. Elevation emerged as the most significant factor (mean importance score = 0.29), followed by sediment composition (mean importance score = 0.17 to 0.22), while other topographic variables had a lesser impact (mean importance score < 0.17). Suitable habitats were predominantly located in sandy areas near mean sea level, within a narrow optimal elevation range. The study also revealed that broad-scale patchiness (minimum patch size = 0.1 ha) was significantly influenced by these environmental factors, with seagrass forming smaller, clustered patches in areas of lower habitat suitability, where patches also exhibited a higher presence of bare gaps.
The combined findings of the three chapters highlight the controls of the spatial heterogeneity of aquatic vegetation, and in particular, the presence of gaps on the seagrass dynamics across scales. Understanding the links between spatial distributions and environmental drivers can be used to inform frameworks for targeted conservation and restoration of Zostera muelleri