Open Access Theses

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Open Access
Rewrite, Repurpose, Reclaim: The Intertextual Reweaving of Australia’s Colonial History in Leah Purcell’s First Nations Adaptation Film, The Drover’s Wife: The Legend of Molly Johnson
Milnes, Delaney
This thesis closely reads Leah Purcell’s The Drover’s Wife: The Legend of Molly Johnson (2022) as both a film adaptation and a Fourth Cinema film. Analysing the understudied intersection between these fields shows how the adaptation process and Indigenous filmmaking techniques methodologically complement each other, especially in their retelling of stories and complicating of single-story approaches to history. I argue that the film interweaves these practices so as to respond to Australia’s colonial history, creating an alternate version of Henry Lawson’s “The Drover’s Wife” (1892) that rewrites First Nations peoples’ perspectives and experiences back into the archive. As a critical response to and creative rewriting of the archive, I read the film as engaging in postcolonial decolonising practices, notably the “critical-creative” practices of First Nations women writing against the archive. By linking the fields of adaptation and Fourth Cinema to explore their combined decolonising potential, rather than closing a gap in the scholarship, this thesis creates a new interdisciplinary model that can be used in further studies focusing on indigenising adaptation films. The thesis concludes that through rewriting Lawson’s canonical piece, the film repurposes its story, so as to reclaim First Nations sovereignty of Australian history, storytelling, and land.
Open Access
Behavioural and neuronal correlates of spatial attention in the mouse whisker system
(2024) Dyce, Guthrie
In any given instant, our senses are bombarded by a surplus of information. Transforming this information into adaptive behaviour is imperative to the survival of all animals. The faculty of selective attention, which performs this function, exhibits both conceptual and neurophysiological parallels to the process of decision-making, except that it operates in information space. Decades of research have produced a rich literature on the behavioural and neuronal correlates of selective attention. Yet the precise microcircuitry and molecular mechanisms of attention remain to be elucidated. Mice represent an attractive model organism within which to study the mechanisms of attention owing to the availability of gene technologies designed for their species. However, attention is traditionally studied in the more complex brain of primates as studying attention in mice is experimentally challenging. The current thesis aims to investigate the behavioural and neuronal correlates of spatial attention using whisker touch as an ecologically relevant, structurally elegant, and functionally efficient model sensory system. I begin this thesis with a literature review on spatial attention and its neuronal correlates in primates and mice (Chapter 1). In Chapter 2, I explore a number of head-fixed experimental approaches to studying spatial attention in mice. I document the efficacy and limitations of two approaches (spatial cueing and spatial blocking) before presenting a novel approach that uses a stimulus-reward contingency as an ecologically relevant manipulation to induce spatial attention. Consistent with prior research, my results suggest that spatial cueing paradigms, directly borrowed from primate literature, can be effective in recruiting attention from rodents. However, these paradigms require extensive training if mice are to learn the task. The blocked spatial manipulation of target-stimulus probability is more effective than spatial cueing, yet it is limited by the occurrence of systematic spatial biases in mice. I then design and demonstrate the efficacy of an original, simplified behavioural paradigm for studying spatial attention in the whisker system of mice by directly manipulating stimulus-reward contingencies ("ecological prioritisation"). Chapter 3 optimises this behavioural paradigm, demonstrating that it reliably elicits rapid and spatially selective attentional engagement to the rewarded stimulus. Trained mice exhibited spatial attention in the form of elevated hit rates and perceptual sensitivities. In Chapter 4, I document extracellular recordings of neuronal activity in six behaving mice (n = 1461 responsive units) to demonstrate that neurons in the primary vibrissal cortex (vS1) exhibit spatially selective attentional gain modulation. Neuronal activity in vS1 increased with spatial attention, but not with spatially non-specific behavioural state. Spatial attention increased both pre-stimulus and evoked neuronal activity, although the greatest attentional gain modulation was observed in later activity (200-600 ms). The same time-course was present in the perceptual sensitivities to vibrissal stimuli. My data thus dissociates spatially non-specific behavioural state from spatial attention in the whisker system. In Chapter 5, I demonstrate that the frequency tagging approach which has been applied effectively to the macroscopic study of attention in humans can be usefully leveraged in the study of spatial attention at the neuronal level in mice. Finally, in Chapter 6, I provide a general discussion regarding the advantages of this ecological prioritisation paradigm and the identified neuronal correlates of spatial attention in the primary vibrissal cortex of mice. These experiments further validate the mouse as a model organism for studying spatial attention and lay a foundation for elucidating its mechanisms at the cellular and circuit level.
Open Access
Searching for a leaf in a forest: A taxonomic and phylogenetic revision of Phyllocnistis (Lepidoptera: Gracillariidae) leaf mining moths in Australia
(2024) Luo, Ying
The cosmopolitan genus Phyllocnistis Zeller comprises 117 species of tiny leaf mining moths, most of which are only known from small geographic areas. This first revision of the Australian fauna is based on morphological, biological and mitochondrial genome data, increasing the total number of species occurring in Australia from 15 to 39, 38 of which are endemic with the last species being the near cosmopolitan pest of Citrus, Phyllocnistis citrella Stainton. The new species are Phyllocnistis amateratsu sp. nov, P. aprica sp. nov., P. arcana sp. nov., P. aureola sp. nov., P. bolwarra sp. nov., P. conspicua sp. nov., P. convoluta sp. nov., P. cuprea sp. nov., P. curvata sp. nov., P. flexuosa sp. nov., P. geera sp. nov., P. gemina sp. nov., P. ignifera sp. nov., P. ignita sp. nov., P. incensa sp. nov., P. kalbarri sp. nov., P. laniyuk sp. nov., P. luminosa sp. nov., P. maiala sp. nov., P. mayari sp. nov., P. numerosa sp. nov., P. porongurup sp. nov., P. quinta sp. nov. and P. ulladulla sp. nov. Lectotypes are designated for P. acmias Meyrick, P. atractias Meyrick, P. diaugella Meyrick, P. dichotoma Turner, P. diplomochla Turner, P. ephimera Turner, P. eurymochla Turner, P. iodocella Meyrick and P. triortha Meyrick. All Australian species are illustrated, described and diagnosed, and an electronic LUCID identification key is provided. Here we also included previously unpublished records of host plant information, revealing that Australian Phyllocnistis are very host specific but also feed across 15 different plant families. A mitochondrial genome phylogeny, supplemented with global COX1 barcode sequences, provides first insights into the evolution of the Australian fauna.
Open Access
From Pandemic to Endemic: Applied Epidemiology of Communicable Diseases in Australia
(2024) Hassall, Jenna
This thesis presents public health activities, experiences, and projects that satisfy the competencies for the Master of Philosophy (Applied Epidemiology) undertaken during my 22-month field placement at the Australian Government Department of Health and Aged Care. From February 2022 to December 2023, I carried out fieldwork in the National Incident Centre at the Office of Health Protection, which is responsible for coordinating national surveillance and control of communicable diseases in Australia during emergency periods. Across 2022 to 2023, Australia transitioned its response to the coronavirus disease 2019 (COVID-19) pandemic from national emergency response to one focused on the prevention and management of severe disease, death, and health impact associated with COVID-19, consistent with other common communicable diseases. My experiences and responsibilities within my field placement changed over time and were heavily influenced by this transition. This thesis describes the public health activities and experiences undertaken during my field placement including repeated epidemiological analyses of multiple public health datasets; data quality improvement activities; involvement in several national surveillance committees or working groups; and designing an epidemiological study to validate use of the screening method for vaccine effectiveness against severe disease associated with COVID-19 in Australia. The projects presented here comprised of analyses of public health datasets, an evaluation of the National Notifiable Disease Surveillance System for severe disease associated with COVD-19; investigating trends in community behaviours associated with self-reported COVID-19 in Australia using repeated cross-sectional surveys; and conducting an outbreak investigation of SARS-CoV-2 in a hospital setting. The public health activities and experiences undertaken during my field placement, and the findings from my projects have contributed to the body of knowledge regarding applied epidemiology and informed public health policy, decision-making, and action for COVID-19 in Australia.
Open Access
Lodging at the Government's house: Understanding the state from the standpoint of evicted and relocated residents of Jakarta's rented social housing
(2024) Siagian, Clara
Between 2013 and 2017, Jakarta's government forcibly evicted around 18,000 households from informal settlements (kampung). While existing scholarship provides insights into the grassroots resistance against eviction and its influences on Jakarta's electoral politics, it overlooks important questions regarding the residents' lives after eviction. This research addresses this gap by examining the lives of Jakarta residents who were displaced from kampung and relocated to rented social housing (rusunawa). The study is situated at the under-researched intersection of slum clearance and social housing in the Global South. To explore this intersection, I formulate a research question, "How do rusunawa residents understand and engage with the state as both a political idea and a collection of practices through their experiences of eviction and relocation?" I conducted eighteen months of ethnographic fieldwork from 2019 to 2021 in three rusunawa in Jakarta, gaining insights into how the residents understand and reflect on their relationship with the state in the wake of their eviction. I present three arguments: First, the eviction and relocation represent major encounters with the state, shaping the residents' ideas of the state and their engagement with it in ambivalent, diverse, and sometimes contradictory ways. Second, the residents' various and conditional engagements with the state enable similarly diverse and provisional articulations of agency. I demonstrate that while the residents are involved in everyday forms of resistance, their sense of agency is also expressed in their enthusiastic engagements with state programs. Third, and finally, the residents exercise their agency outside conventional mechanisms. Instead of invoking their rights through formal political avenues, they advance claims by appealing to the tacit yet sacred covenant binding the state and its subjects, nestled in the nation's deep-seated political culture. By teasing out the contingency of residents' entanglements with the state, I demonstrate the complexity and intimacy of rights, care, agency, and community, and their conflicting realizations. My thesis explores the diverse articulations of agency among the urban poor which align their individual desires within existing structures while simultaneously complicating and undermining the possibility of collective political subjectivities and action. My thesis also reveals the limited appeal of human rights and formal political avenues in the residents' narratives and the prominence of ethics, morality, and affect in the everyday politics of the urban poor amid their yearning for paternalistic state care.
Open Access
Spatial Multizone Soundfield Reproduction using Higher Order Loudspeakers
(2012) Chakraborty, Debashish
Spatial multizone sound field reproduction aims to regenerate desired sound fields as multiple independent sound fields in isolated zones without unpremeditated interference within a zone from other zones. Such attempts over an extended region of open have proved to be quite arduous and intricate. At high frequencies, significantly large numbers of loudspeakers are required for the reproduction of the sound field over significant areas. This thesis is aimed at using higher order (up to 𝑁th) loudspeakers, with polar responses up to cos (𝑁𝜙) and sin (𝑁𝜙) to resolve the high frequency reproduction issue. The thesis includes the design of the system along with any equations derived to verify the performance of the system for arbitrary sound fields. The equations have been defined with respect to the frequency content of the sound fields and the order and number of sources used. Numerical simulations to verify the equations and corresponding results have also been included.
Open Access
Antibiotic resistance in Vanuatu: Developing an evidence base to inform locally relevant strategies to respond to the growing challenge.
(2024) Foxlee, Nicola
Antimicrobial resistance including antibacterial resistance (ABR) is a major global health problem. Increased use and misuse of antibiotics are key drivers of ABR. Surveillance and research, optimising the use of antibiotics through antibiotic guidelines and antibiotic stewardship programmes (ASPs), and infection prevention and control programs are all essential to containing ABR. Evidence suggested antibiotics were over and unnecessarily prescribed during COVID-19, especially in some LMICs. The aim of this thesis is to develop an evidence base to inform locally relevant strategies to manage and respond to ABR in Vanuatu. The five objectives involved in achieving this aim are addressed in the following paragraphs. First, to understand the epidemiological situation regarding ABR in PICTs, I conducted a scoping review and found evidence of widespread ABR in Pacific Island Countries and Territories (PICTs). The most frequently occurring gram-positive pathogen was Staphylococcus aureus (S. aureus) and rates of methicillin resistant S. aureus (MRSA) were highly variable. Several gram-negative bacteria listed on the World Health Organization's (WHO) Priority Pathogen List were present. Second, to investigate the epidemiology of ABR in Vanuatu, I conducted a descriptive study into pathogen occurrence and ABR in specimens collected for culture and testing at Vila Central Hospital (VCH) laboratory from January 2017 to December 2019. The findings showed S. aureus was the major pathogen, and the rate of MRSA was low at 3%. Data about ABR was scarce, suggesting surveillance and research across all health settings is urgently needed for monitoring and reporting. Third and fourth, to investigate the influence of COVID-19 on Ni-Vanuatu health workers' knowledge, beliefs, and practices (KBPs) regarding antibiotic prescribing and awareness of ABR and antibiotic consumption at VCH, respectively. Firstly, I conducted a before-after mixed methods study by administering a KBPs survey and in-depth interviews at baseline (2018) and follow-up (2022). I found that COVID-19 influenced antibiotic prescribing and awareness of ABR. Health workers' knowledge and beliefs about antibiotic prescribing improved and their awareness of ABR was heightened. I also collected the monthly quantities of antibiotics dispensed, before (2018 - 2020) and during the COVID-19 pandemic (2020 - 2021), from the dispensary at VCH. Using WHO's ATC/DDD index, I calculated the number of DDDs prescribed to inpatients and outpatients during the two study periods and used interrupted time series analysis to assess the impact of the pandemic on consumption. I found that inpatient consumption increased during the pandemic. Finally, I conducted a systematic review into the strategies used to implement and promote adherence to guidelines in low- and lower-middle-income countries (LLMICs). I found multifaceted interventions to be the most effective including audit and feedback, combined with other quality strategies. Clinical decision support systems, used with mobile technologies were shown to be easy to implement, but impediments in LLMICs must be overcome before widespread use can be realised. I found few studies reported prescriber involvement in guideline development, and little evidence of formalised ASPs in LLMICs. These results provide robust evidence to support the following recommendations: strengthen laboratory infrastructure, capacity, capability, and expertise; establish systems for surveillance of ABR, and antibiotic consumption and usage; complete Vanuatu's national antibiotic prescribing guidelines with an active implementation plan; formalise ASPs and strategies in all healthcare settings; and provide opportunities for continuing inter- and intra-professional development. Together, these recommendations will contribute towards optimising antibiotic prescribing, containing ABR, and supporting Vanuatu's ongoing preparedness efforts to manage future public health events.
Open Access
The use of fallout radionuclides to estimate soil redistribution in a logged coupe in the south east of NSW
(1997) Roddy, Brendan
An investigation into the effects of logging on a native forest in the south east of NSW was carried out. The principle aim was to measure the five years of soil redistribution and soil loss that has occurred due to the harvesting process. Fallout radionuclide technology was employed to quantify soil redistribution, in particular the anthropogenic radioisotop 137Cs and the lithogenic radioisotope 210Pbex. These tracers are distributed onto the earth's surface principally by wet precipitation, and move about the surface not in solution but in association with soil particles. The landscape units that result from logging are identified as the snig tracks, log landings, buffer strip, cross banks and general harvest area. Reference values were determined for the two tracers from unlogged, undisturbed forests adjacent to the study area. The reference activity values were then conrpared to the activity of the logged landscape units to determine a sediment budget. The 137Cs sediment budget result was 111% (± 14), and the 210Pbex sediment budget was 78% (± 12). Various options were investigated to account for the 20% difference in the two budgets. From two point estimates it was found that more of the 210Pbex total activity inventory (17% and 5%) resided in the surface organic layer than did 137Cs (1.3% and 0.1%). It was possible that the differences between the two sediment budget could be balanced by a loss of the surface organic layer (due to fire) and some associated soil loss. The two point estimates total areal concentration for each tracer was compared to the total areal concentrations derived from 30 spatially representative reference cores. While 137Cs point estimate values were within uncertainty of the 30 cores, the 2l0Pbex point estimates were not. It was concluded that the two sediment budgets could not be balanced as the two point estimates for 210Pbex activity inventory were not a confident estimate. It was further concluded that the 210Pbex tracer is more variable in this environment and not enough samples have been taken to confidently characterise it. Consequently, only the 137Cs sediment budget was used to quantify soil edistribution. Areas of soil loss were the log landing (- 2%) and snig tracks (-10%). Areas of soil gain were the general harvest area (18%), and the buffer strip (4%). The cross banks (2%) were considered part of the snig track activity. Soil loss was quantified from the log landings and snig tracks using the 137Cs areal concentration reference curve. The mean areal concentration for the two landscape units was plotted against the depth dependent curve to yield a soil loss result of 23-49 mm for the snig tracks and 49-59 mm for the log landing.
Open Access
How Do People Perceive MNCs? Development and Validation of a Multidimensional Attitudes towards MNCs Scale
(2024) Zhang, Shuojia
This research program investigates host nationals' attitudes towards multinational corporations (MNCs) and their antecedents and consequences. MNCs have rapidly expanded worldwide. As external agents, MNCs inevitably bring different cultures, values and styles of governance into host countries. Such differences can influence members of the general public' attitudes towards MNCs (ATM). These attitudes can have significant consequences for MNCs in host countries regarding talent attraction and retention, stakeholder relationships and consumer choices, ultimately leading to financial viability of MNCs. However, there is little known about host nationals' ATM. Through three studies, this research program creates and validates a scale on individuals' ATM in host nations. I conduct this research in the context of China. China is one of the largest recipients of foreign direct investment (FDI), with MNC units from various countries. Hence, China serves as an excellent context to study ATM. Study 1 is inductive (interviews, N = 55) and helps identify general and specific attitudes towards MNCs. This study's findings also help generate items for each scale component. Then, Study 2 validates the scale in three steps: 1/ item generation, item reduction and external content validation; 2/ psychometric properties; and 3/ nomological network validity assessment at seven multiple time points through survey research based on ten separate samples (N = 1404). Finally, Study 3 undertakes empirical research (i.e., multiple time points, two survey-based studies) with 691 participants to apply the ATM Scale developed in Study 2 to test the proposed models described in Study 1 (abductively developed based on the literature and the inductive study) in a recruitment context. As a point of clarification, the present study comprehensively investigates host nationals' ATM as a whole, rather than individual MNCs, without considering heterogeneity of MNCs, such as the nature of FDI, country of origin or specific sector. When referring to 'host nationals', this research program does not distinguish them based on demographics, including educational background, residential location or the nature of their profession or work experience. The three studies collectively contribute to the attitudes, international business and management theory literature. This research program makes three contributions to the attitudes literature by providing a tool to measure ATM. Then, the study contributes to organisational attraction as well as legitimacy of MNCs in the host location. Last, it introduces a new informal institution, ATM, contributing to signalling and institutional theory. The research program has practical implications for managers and practitioners. It helps understand ATM, which may in turn aid in comprehending corporate image, marketing strategy, MNC employee training programs and recruitment in the host context.
Open Access
Deep learning convolutional neural networks for Landsat-derived land cover mapping
(2024) Boston, Tony
Deep learning is an area of machine learning research that can be applied to image analysis and feature extraction. It uses neural networks (NNs) with many layers (hence deep learning) that can extract feature representations from data and, for example, undertake image segmentation into categorical classes as required to produce land cover maps from satellite imagery. A major advance in the accuracy of convolutional neural networks (CNNs) for computer vision image classification occurred in 2012, supported by advances in processing such as GPUs. This was subsequently adopted by the remote sensing community from 2014 for a variety of tasks including: image classification, segmentation, object detection, image fusion, change detection, building or road extraction from high resolution imagery and pan-sharpening. To date, almost 90% of studies have applied CNNs to higher resolution imagery (less than 10m resolution) with a majority of studies using imagery finer than 2m. Landsat imagery which is freely available globally enables long-term studies of changes in land cover. Such studies have been undertaken for over 40 years at continental and, more recently, global scales using a variety of machine learning methods. This project chose to use Landsat data for a number of reasons: its long time series enables estimation of land cover change over time; application of CNNs for land cover mapping using medium resolution Landsat data in Australia was limited; and benchmark land cover datasets built using performant pixel-based methods such as Random Forest (RF) decision trees were available for comparison. Label/ training data for model development supporting supervised machine learning were derived using current best-available national-scale government mapping including: Catchment scale Land Use of Australia (CLUM), Forests of Australia (FoA) from ABARES; and National Vegetation Information System (NVIS) from DCCEEW. CNN models were built using input annual Landsat 8 geomedian data for 2018 from Geoscience Australia to produce land cover maps for a study area in SE Australia, and compared to leading alternative machine learning techniques such as pixel-based RFs. The most accurate CNN model was applied for 34 years (1987-2020) using input annual Landsat 5, 7 and 8 geomedian imagery and tested for its spatial and temporal stability. A third experiment compared the capacity of CNNs and RFs to map natural vegetation and major forest types in the study area. Key findings include the ability of CNNs to detect land cover in the absence of accurate label data using proxy data (e.g., land use translated into land cover), superior spatial and temporal stability of CNN models compared to RFs, and the ability of CNNs to partially compensate for label data errors. Of broad-scale land cover and forest types mapped using CNNs, Eucalyptus/ Forest, Plantation and Grassland showed high accuracy (>80%), Built-up, Crop, Horticulture and Water as well as Callitris, Mangrove and Rainforest moderate accuracy (20-80%) and Bare, Acacia, Casuarina and Melaleuca exhibited low accuracy (<20%). CNNs are capable of broad-scale land cover mapping and change detection using Landsat resolution input data. CNNs produce coherent maps operating at a coarser spatial resolution than RFs, whereas RFs are better for fine-scale variations, for example, vegetation in urban areas. CNNs have potential for validation of existing national and global land use and land cover datasets. CNNs rather than pixel-based mapping approaches have sufficient temporal stability and spatial consistency for use in natural resource management at regional, continental and global scales and applications such as environmental accounting. This project has demonstrated that deep learning CNNs have the potential to exploit the long time series of Landsat data globally to produce robust broad-scale land cover maps of change over time.
Open Access
Decision making under conflictive uncertainty
(2024) Zhu, Guangyu
Living in a post-truth era, individuals are increasingly exposed to conflicting information. Such conflict can induce "conflictive uncertainty", a state of uncertainty about which information and source to trust. Conflictive uncertainty can impact emotions (e.g., frustration, distress), cognition (e.g., suspicion, distrust), and behaviours (e.g., reluctance to follow health-promoting advice). Yet, the psychological mechanisms driving these impacts are not well understood. Particularly, there are limited studies exploring why people are averse to conflicting information and conflictive uncertainty. Previous studies have suggested that decreased perceived source credibility may be a factor in conflict aversion. Sources who provide conflicting information are usually perceived as less credible compared to sources who provide other types of information, such as ambiguous or risky information. The decreased perceived source credibility may further diminish people's preference for options involving conflictive uncertainty, causing conflict aversion. Therefore, the aim of this thesis is to examine the mediation relationship between conflictive uncertainty, decreased perceived source credibility, and conflict aversion. It addresses three main questions: (1) validation of a cross-domain measure of conflict aversion; (2) identification of an appropriate method to study causality in a mediation relationship; and (3) empirical testing of the cause of conflict aversion. To validate a cross-domain measure of conflict aversion, this thesis assessed the convergent validity and test-retest reliability of three uncertainty preference measures: forced binary choice, certainty equivalent, and matching probability. The results showed that these measures exhibited unsatisfactory convergent validity and test-retest reliability in one-off assessments but achieved relatively satisfactory validity in repeated measurement conditions. Despite the limited reliability, matching probability consistently captured average preferences over two measurement periods. Thus, matching probability was selected for further experimental studies due to its consistency and cross-domain applicability. To identify an appropriate method for studying causality in a mediation relationship, this thesis first reviews the advantages and disadvantages of commonly used regression-based mediation approaches in psychology, such as Baron and Kenny's criteria, Sobel test, and structural equation modelling. It also discussed the challenges associated with using psychological states as mediators. To address these challenges, this thesis introduces some alternative causal approaches from recent causal inference literature, including the counterfactual framework, encouragement design, blockage design and so on. Using these advanced approaches, the thesis conducted four experiments to examine the mediation relationship between conflictive uncertainty, decreased perceived source credibility, and conflict aversion. Experiment 1 found a significant indirect effect from conflictive uncertainty to conflict aversion via decreased source credibility. Experiment 2 and 3 demonstrated that interventions on perceived source credibility significantly altered participants' degree of conflict aversion. Experiment 4 showed that by blocking the decrease in perceived source credibility, conflict aversion can be weakened or even eliminated. These experiments support the hypothesis that decreased perceived source credibility under conflictive uncertainty is a cause for conflict aversion. The findings of this thesis have significant implications for managing the impact of conflicting information. Additionally, the application of advanced causal approaches provides valuable guidance for studies aiming to explore different types of evidence supporting causality within a psychological mechanism.
Open Access
Optimisation of collector locations and pipe networks for dish–Rankine power plants
(2016) Cumpston, Jeffrey
The thermal efficiency of the collector field of a concentrating solar thermal power plant is strongly dependent on the geometry of the chosen collector. Paraboloidal dish collectors are realisations of the ideal reflective imaging concentrator geometry, and offer the highest possible optical efficiency of all collector geometries. The feasibility of multi-megawatt scale dish–Rankine power plants incorporating Big Dish collectors is investigated in this thesis by optimising collector placement, energy transport network pipe diameters, and network branching, accounting for shading, network heat loss, network pressure drop, network capital costs, and land costs. The thermal performance of the optimised collector field is assessed against respective fields comprised of linear Fresnel collectors, parabolic trough collectors, and central receiver systems. We find that the annual thermal energy delivered to the central power block by the optimised dish-Rankine field is approximately 120% of that delivered by a central receiver system with the same nameplate generation capacity, which is the technology that offers the next-highest field thermal efficiency. Field optimisation comprises optimisation of dish collector placement for minimal annual shading for a range of ground cover ratios. We find that collectors arranged in diamond-shaped layouts collect up to 1.4 percentage points more annual solar energy than those in rectangular layouts for ground cover ratios above 0.23. Using a layout informed by our shading optimisation work, we use a nested optimisation to optimise energy transport network pipe diameters for each network used in a genetic optimisation of network branching. Network exergy costs, pipe material costs, and installation costs are estimated using an exergoeconomic model. The optimal network tree is then found for a 10 MWe collector field and a 20 MWe network. Extra east-west pipe branches correspond to a lower cost for the 20 MWe field, despite the longer overall network pipe length. Exergy costs from heat loss and pressure drop account for approximately 60% of total network cost in both cases, where the remaining fraction is comprised of pipe material costs, installation costs, insulations costs, and pumping irreversibilities. Total annual network costs are, respectively, 8.9% and 9.5% of potential plant revenue for the 10 MWe and the 20 MWe networks. Annual simulations of power plant performance using the optimal 20 MWe network are performed for a range of collector separations. The rectangular layout corresponding to the highest annual plant income is relatively closely spaced in the north–south direction, and east–west separation is sensitive to land cost. The annual thermal performance of the optimised dish field is compared to values found in the literature for parabolic trough, linear fresnel, and central receiver systems. Thermal efficiencies associated with each collector type enable the comparison between the annual thermal energy delivered by equivalent power plants utilising the respective collectors.
Open Access
The impact of mesoscale flows on the identification, energy partitioning and propagation of near-inertial internal waves
(2024) Rama, Jemima
Near-inertial waves (NIWs) contain a significant fraction of the ocean internal wave energy and can propagate long distances from their source before breaking. The dissipation of those waves contributes to the lightening of abyssal water masses and is thus important for sustaining the overturning circulation. Despite the crucial contribution of near-inertial waves to the ocean energy budget, a complete understanding of the physical processes that determine the waves generation, propagation and destruction is still lacking. Past studies have highlighted the influence of background flows, in the form of mesoscale eddies and jets, on NIWs. Mesoscale flows not only affect the generation mechanism of the waves but also refract the waves once generated, thereby imprinting on the near-inertial energy distribution. The deep propagation of NIWs in anticyclonic eddies has been observed in numerical simulations while the ability of eddies and jets to amplify the waves has been demonstrated in idealised configurations. However, the magnitude of wave amplification by eddies in more realistic conditions is yet to be quantified and uncertainties remain regarding how background flows affect the partitioning of near-inertial energy across different wavelengths. Lastly, the impact of turbulent background flows is often neglected when identifying NIWs; this exclusion consequently leads to an inaccurate estimate of their energy content. In this thesis, we employ a realistic eddy-resolving numerical simulation of the North Pacific to address those research gaps in relation to wind-generated NIWs. We first study the impacts of background mean flows on NIWs as a function of the waves horizontal wavelength. Two distinct cases are analysed: the propagation and energetics of large-scale NIWs in negative relative vorticity flows and the behaviour of small-scale NIWs in high shear. The large-scale waves rapidly propagate to depth in negative vorticity areas, while their small-scale counterparts are confined to shallower depths in high shear regions. Additionally, the results show that the mean-to-wave energy exchanges provide a considerable source of energy, similar in magnitude to wind-work, to NIWs. Secondly, we study the inherent intermittency and localised variations of NIWs . Traditional Fourier analysis falls short in resolving the temporal evolution of the waves frequency and in detecting the localised variations of NIWs of different wavelengths. Wavelet analysis is utilised to overcome these limitations and to characterise the near-inertial wave field across various temporal and spatial scales. The propagating behaviour, whether dispersive or trapped, of waves with a particular wavenumber is found to be depend on the scales of the dominant background flow. Furthermore, the dominant wavelengths of NIWs being generated are found to be dependent on the scales of the prevailing eddies. Lastly, the thesis examines how a varying background flow velocity can alter the NIWs properties. Background relative vorticity modifies the lower bound of the frequency bandwidth over which the waves can exist, while Doppler shifts alter the wave intrinsic frequency. Both effects complicate the identification of the waves and the estimation of their energy content. We employ different types of adaptive frequency filters to isolate the effects of relative vorticity and Doppler shift on the apparent near-inertial wave energy. Spectral filters neglecting background vorticity effects result in an underestimation of near-inertial energy by 40% in anticyclonic structures and an overestimation by 100% in cyclonic flows. The findings presented in this thesis advance our understanding of the influence of realistic turbulent background flows on the energetics, partitioning and propagation of near-inertial waves, and provide a new analysis tool for quantifying these effects in future studies.
Open Access
Indium Phosphide Nanowire Arrays for Gas Sensing Applications
(2024) Wei, Shiyu
Semiconductor chemiresistive gas sensor is one of the most promising technologies for the development of next-generation chemical sensing, with applications ranging from explosive detection and environmental monitoring to industrial safety, healthcare and the Internet of Things (IoTs). Recently, there have been growing efforts in developing room temperature chemiresistive gas sensors with high sensitivity, selectivity, long-term stability, and low power consumption. In this thesis, we develop indium phosphide (InP) nanowire (NW) array based chemiresistive gas sensors and demonstrate that they represent a new and promising platform for achieving high-performance gas sensing for real-world applications. Firstly, by carefully engineering the NW geometry (i.e., diameter and pitch), we demonstrate a NO2 sensor with superior sensitivity (limit of detection 3.1 ppb) at room temperature, with outstanding selectivity and long-term stability. Kinetic analysis and electrical simulation reveal the array geometry correlated sensing mechanism. To minimize the device power consumption, a novel axial p-i-n homojunction self-powered photovoltaic (PV) NO2 NW sensor was further designed through numerical simulation and optimization. The fabricated InP NW array PV sensor achieved 84% sensing response to 1 ppm NO2 with a record limit of detection down to sub-ppb level even under <5% of 1 sun illumination. With such high atmospheric light fidelity, the sensor was integrated onto a commercial microchip interface for dynamic self-powered monitoring of on-field motor vehicle exhaust. Not only for oxidizing gas such as NO2, we have also shown that by applying surface-modification, the InP NW array can also be fabricated into highly sensitive sensors to reducing gases such as acetone. This is critical for the development of breath ketone sensors for diabetes monitoring and diagnostics. This acetone sensor was then integrated into a breath testing apparatus, named Ketowhistle, and proven to be highly effective across an ultrabroad range of acetone concentrations from the simulated breath. Finally, a wearable multipixel InP nanowire array sensor was fabricated on a flexible substrate. A signal decoupling strategy was designed and implemented through careful device fabrication control, surface-functionalisation and different contact metal selection. This approach has led to the demonstration of a multipixel sensor device consisting of four sensing elements with integrated functionality, including NO2 and acetone sensing, as well as simultaneous pulse and body temperature measurements. The thesis work indicates that III-V compound semiconductor nanowire array presents a promising chemical sensing platform for the development of high performance, miniaturized, low power consumption, multiplexing on-chip sensing system for future large-scale implementation of IoT technology.
Open Access
Measles incidence and measles vaccine coverage in WHO South East Asia Region, 2017-2021
(2024) Zar Nyi, Ei
Abstract Introduction Measles is a highly contagious disease caused by the measles virus of the paramyxovirus family. Measles remains one of the leading causes of childhood morbidity and mortality worldwide, accounting for more than 140,000 deaths in 2018. There was global concern about the high risk of measles outbreaks occurring due to the disruption of immunisation services during the COVID-19 pandemic. This study aimed to describe the incidence and immunisation coverage of measles in South East Asia Region (SEAR) between 2017 and 2021. Methods A cross-sectional descriptive study was undertaken using publicly available data from WHO, UNICEF, World Bank, and Our World in Data. Analysis included measles cases, estimated measles vaccine coverage, supplementary immunisation activities. Statistical analysis was conducted using STATA17. Results During the study period, a global measles peak was seen in 2019; regional peaks varied between 2018-2019. Global and regional measles incidence fell during 2020-2021. Globally, measles incidence was reported to be >80% lower in 2020 and 2021 than in 2019, with regions ranging from 61% to 91.5% lower. A large decline in incidence was seen in SEAR with a 67.3% drop in 2020 and 78.2% in 2021. Globally, measles vaccine coverage fell during the study period. Global MCV1 coverage reduced by 3.5% in 2020 and 5.8% in 2021, but global MCV2 coverage rose by 1.4% in 2020 and remained unchanged in 2021. In 2020, the estimated national immunisation coverage (MCV1) declined in six SEAR countries ranging from 3% in Sri Lanka to 13.6% in Indonesia, while MCV2 coverage dropped in five SEAR countries ranging from 2.5% to 15.5%. There was a statistically significant negative correlation between country's population and elimination status (p<0.006). The association between incidence and MCV1 coverage was not significant. Discussion Although a drop in cases was detected in SEAR, India and Indonesia were included in top 10 countries globally with multiple reported measles outbreaks during June-November 2022. During a global pandemic, we would expect disruption to health systems including surveillance and access to routine health services, therefore the findings reported in this study could be under reporting and may not reflect the real situation. Conclusion This study found a decrease in measles incidence as well as reduced measles immunisation coverage in SEAR countries. This appears contradictory as low measles immunisation coverage may increase disease transmission causing large measles outbreaks in some SEAR countries. The findings are likely impacted by COVID-19 pandemic disruptions to measles surveillance and immunisation. The true situation may be clearer to see in the coming years as we emerge from the pandemic and reinstate health and data systems in countries. All countries need to focus on building stronger health systems and restoring immunisation and surveillance system for measles to allow progress to elimination to continue.
Open Access
Exploring Genetic and Environmental Drivers of Variation in Wheat Growth and Carbon Metabolism
(2024) Garcia, Andres
Business-as-usual agricultural performance is failing to keep up with the demand for crops in a growing global population. At the same time, climate change is increasing the frequency and severity of extreme weather events that disrupt agriculture. In Chapter 1, we underscore the importance of plant physiology in enhancing crop performance, particularly focusing on carbon assimilation and the efficiency with which that carbon is converted to biomass. There is untapped potential to enhance crop yields through improvements this efficiency closer to its theoretical maximum. Because much less is known about respiration than photosynthesis with regards to the mechanisms controlling rates, this thesis focuses on respiration as a trait of interest that could boost yield potential. However, measuring respiration was traditionally slow - yet, using high-throughput measurement techniques, it becomes more viable to explore the relationship between respiration and other growth traits on the larger scale necessary. This thesis therefore explores respiration across various plant tissue types and aims to relate Rdark with carbohydrate status of leaves and associated transport costs; biomass allocation and the contributions of shoot- and root-respiration to whole-plant properties; and relative growth rates across a range of environmental conditions across 8 wheat genotypes. Chapter 2 explores the influence of different light environments and growth temperatures on respiration and starch levels in wheat flag leaves. We found that starch levels are significantly affected by the two environmental variables we manipulated, with reduced-irradiance treatments showing lower starch accumulation and degradation rates. However, respiration rates showed little thermal acclimation. Importantly, the export costs in a mature flag leaf were non-linear and point to substrate-dependent rates of export in wheat leaves. Chapter 3 extends the analysis to the whole shoot and root systems to correlate growth and respiration at the whole-plant level. Heat treatments generally negatively impact growth rate in DNA #1704, a heat-intolerant genotype, but commercially high-performing genotypes show more resilience. Contrary to prior findings, warmer days had some limited exidence of exhibiting greater acclimation than warmer nights. In Chapter 4, eight wheat genotypes are assessed in field settings, revealing variation in leaf respiration and aboveground relative growth rate across environments and developmental stages. Importantly, the ranking of Rdark showed some consistency across sites. Lastly, Chapter 5 discusses the implications of these findings for improving crop yield, emphasizing the need for high-throughput physiological measurements and advanced digital phenotyping in the field. Overall, understanding respiration and its response to changing climates is essential for enhancing crop productivity.
Open Access
Topics on Survival Analysis with Long-term Survivors
(2024) Zhao, Muzhi
This thesis focuses on various topics in survival analysis when there are both "immunes" or "cured" individuals, those who will never experience the event of interest, and susceptibles, those who will eventually experience the event of interest, present in the dataset. Traditional survival models are unsuitable for datasets where immunes are present. In those cases, cure models should be used instead. We introduce some of the commonly used cure models in practice in Chapter 2. The issues that mixture cure models may face under insufficient follow-up are discussed in Chapter 3. Some existing tests and methods to detect insufficient follow-up are also reviewed. The generalised F distribution embeds most of the commonly used parametric lifetime distributions as special cases. However, the connections between the generalised F distribution and its sub-models have never been clearly formulated in literature. We fill this gap by clearly outlining such connections in Chapter 4. In Chapter 5, we provide a detailed methodology for researchers to select a parametric mixture cure model for the data given using a generalised F distribution. Using the results, we demonstrate the application of parametric mixture cured models in practice using real data examples, where we conduct tests for sufficient follow-up, parametric cure model selection and covariate analysis. Cure proportion estimation is usually of interest to researchers. However, when the assumption that the follow-up period is sufficient does not hold, the parametric cure proportion estimator will be extremely unstable, and the nonparametric cure proportion estimator designed using the Kaplan-Meier estimator will overestimate the cure proportion. In Chapter 6, we develop a nonparametric cure proportion estimator under insufficient follow-up for models in the Gumbel maximum domain of attraction. We show our estimator is asymptotically consistent and normally distributed under reasonable assumptions and performs well in simulation studies with data under both sufficient and insufficient follow-up. We also demonstrate its use with an application to survival data where patients with different stages of breast cancer have varying degrees of follow-up.
Open Access
Borders and Belonging: Visions of Relationality and Community by Contemporary Korean Artists in Australasia
(2024) Shim, Soo-Min
Current prevailing art historical narratives continue to constrain the interpretation of works by overseas artists of Korean heritage, narrowly fixating on national identity and essentialist categories. This thesis challenges normative categorisations such as 'Korean-Australian' or 'Korean-New Zealand' which often fail to capture the complexity and fluidity of identity and artistic practices. It explores the artistic practices of contemporary Korean artists currently based in Australasia, with a particular focus on the practices of Lisa Myeong-Joo, Haji Oh, and Yona Lee. This research uncovers the artists' intricate negotiations of diasporic citizenship, ethno-nationalism and their intellectual explorations of belonging, mobility, and migration. It pays close attention to artists' own visions of themselves as global actors. By proposing an expanded application of Hijoo Son and Jooyeon Rhee's methodology of the micro, meso, and macro, I argue for an art historical framework that seriously considers artists' positions and expressions in the broader world beyond the 'local' and the 'nation-state'. Son and Rhee's micro, meso, and macro levels of analysis attend to the nuances and differing historical circumstances that inform the creation, production, and reception of artworks without forcing differences into a false or monolithic homogeneity. A balanced consideration of all three levels allows for the critical analysis of the works of artists who speak back to ideas of Korean-ness but at the same time eschew them all together. This tripartite model generates interpretations that assess the artists' personal lived experiences that are in turn shaped by broader social, economic, cultural, and historical forces. Opposed to the logic of the binary of the 'global' and the 'local,' this thesis asserts that only by appreciating the singularity of the granular and its role in the wider tapestry of global meta-narratives are we able to fully grasp the complexity of global art histories. The discussion begins with an analysis of the artists' re-negotiation of geographical and historical paradigms paying particular attention to the tropes of cartography, historiography, and archival material that are manipulated to produce conscious un-belonging and de-territorialisation. As overseas artists contend with nationalist exclusion, they not only expose the lacunae of nationalist, institutionalised history and geography but participate in creating their own subjective spaces and personal archives through memory. By doing so, they prove that their experiences in Korea at a micro level are simply an entry point into their practices. Rather than visualising place as static, tangible, or geographically bound, the artists in this thesis operate via a productive mode of refusal to be situated in a single place altogether. This is an important point to make in contradistinction to studies that continue to focus on the elements of 'Korean' history, culture and politics in the works of overseas Korean artists, omitting the fact that the micro is part of the meso and macro. I argue that from their disparate migratory journeys and experiences of varied forms of alienation and domination, overseas Korean artists speak back to nationalist conceptions of communities and belonging by forging their own subjective structures of belonging. I propose that one method of resisting conventional notions of community is through the concept of a 'transnational sorority,' as theorised by Naoki Sakai and Hyon Joo Yoo. Through the potential for building a transnational sorority that challenges traditional gendered practices, I espouse a feminist methodology as a means to explore alternative forms of belonging outside the nation-state. The thesis reimagines the concept of belonging in the global art world, calling for a broader and more inclusive perspective that acknowledges the artists' claims and contributions to world-building and building the world.
Open Access
Fundamentals and applications of ion tracks and nanopores in solid state membranes
(2024) Dutt, Shankar
Solid-state nanopore membranes have emerged as pivotal tools in a wide array of technological domains, including the analysis of biomolecules, advanced filtration, osmotic energy generation, and environmental monitoring. This thesis reports on the fabrication and characterisation of solid-state nanopore membranes, as well as their application for single-molecule sensing. The focus is on two classes of membrane materials: polymer foils and silicon-based membranes. The nanopore formation in these foils/windows was achieved through the ion-track etching and the controlled breakdown (CBD) techniques. In the ion-track etching method, membranes were irradiated with swift heavy ions. At these energies, the ions generate long, narrow columnar defect regions along their trajectory, called 'ion tracks'. These ion tracks are often highly susceptible to chemical etching, which can be used to fabricate nanopores with a high aspect ratio. The CBD method fabricates nanopores by applying an electric field across a thin dielectric membrane, which causes localised breakdown and formation of nanopores with precise control over their size. A detailed investigation of ion tracks in polypropylene foils was conducted, particularly how their structure changes with varying antioxidant concentrations. Notably, foils with high antioxidant content show a cylindrical track structure with a highly damaged core with significant mass loss and a gradual transition to the undamaged material while a core-shell structure and increase in foil mass over time was observed in polypropylene foils with lower antioxidant content. The increased mass, located in the shell region is attributed to an oxidation chain reaction, which occurs as primary radicals capture oxygen in the absence of hindered phenols, which typically act as antioxidants. Knowledge of the track structure is important for controlled nanopore fabrication. This thesis then delves into elucidating the detailed structure of nanopores in polycarbonate membranes, a challenge that has persisted for over four decades. Using small-angle X-ray scattering with a new form factor model, the shape of the nanopores was found to be tapered towards the surface of the foils while the center of the nanopores is cylindrical in nature. It was found that the size distribution of the pores increases with increasing ion fluence, and the pore dimensions slightly decrease when the fluence exceeds a certain value. The latter effect is attributed to a halo around the track core which exhibits crosslinking of polymer chains. The research then transitions to silicon-based materials, studying the annealing of ion tracks in amorphous silicon dioxide and their impact on the etching of the tracks. The annealing kinetics of the ion tracks were explored, examining the effects of the ambient atmosphere, annealing temperature, and duration. It was discovered that the ion tracks in amorphous silicon dioxide anneal preferentially near the surface. A combination of stress relaxation and oxygen diffusion was suggested as the driving mechanism for this behavior. Furthermore, an etching model was developed that can accurately predict the shape and size of the resulting nanopores. Subsequently, the thesis delves into the development of ultra-thin nanopore membranes, employing controlled dielectric breakdown to create single nanopores. The study further ventured into single biomolecule sensing using these nanopores. Membranes with different stoichiometry of silicon nitride were studied and found to have different surface charges, which is important for biomolecule translocation. Finally, the thesis reports on the integration of solid-state nanopore sensing with machine learning for the label-free identification of proteins. High F-values and specificity were achieved for combinations of four proteins similar in size and weight through the combined use of high bandwidth instruments, advanced clustering and machine learning methods.
Open Access
Parameter Estimation and Adaptive Design of an Autonomous Racing Car
Zhao, Boyu
This thesis proposes a parameter estimation method for a scale-down autonomous racing car. The dynamic single-track model of Euler integration method is used for parameter estimation based on the measurements generated by the multi-body model in state-space form. By implementing optimization methods, the vehicle mass, moment of inertia for entire mass about z axis, distance from centre of gravity to rear/front axle, centre of gravity height of total mass and cornering stiffness coefficients of front/rear tires have been successfully estimated. The accuracies of the estimated parameters were also demonstrated. Moreover, an idea of adaptive design for the estimated parameters have been proposed in this thesis. By adjusting the selected parameters, the vehicle can achieve the performance of a complex model under a simple model.