Other UNSW

Publication Search Results

Now showing 1 - 8 of 8
  • (2021) Webb, David
    Planetary waves play a role in a large variety of oceanic and climate dynamics. In particular, Kelvin waves can provide rapid teleconnections from large-scale climate and weather events to remote regions of the globe. Kelvin waves may be partially responsible for linking climatic changes in Southern Ocean winds to increases in subsurface warming around Antarctica that can lead to glacial ice-melt and increases in global sea level rise. Kelvin waves may also link changes in Southern Ocean winds to increases in North Atlantic Deep Water (NADW) formation and an enhancement of the Atlantic Meridional Overturning Circulation (AMOC), which is responsible for circulating a vast amount of the ocean’s heat and nutrient content. However, the exact role of Kelvin waves in these processes is unclear. This thesis aims to further clarify the role that Kelvin waves play in these high-latitude climate processes. First, we use a suite of idealized models in order to better understand the dynamics of barotropic Kelvin waves around Antarctica. We find that super-inertial (high frequency) barotropic Kelvin waves are nearly completely scattered away from the Antarctic coastline due to a combination of coastal geometry and bathymetry. Sub-inertial (low frequency) barotropic Kelvin waves are mostly scattered away from the Antarctic coastline due to bathymetry, however a significant amount of barotropic Kelvin wave energy remains at the Antarctic coastline after one circumnavigation of the continent, enabling a gradual build-up of energy along the coast and the ability to sustain a barotropic Kelvin wave signal around Antarctica over time. Secondly, we perform a diagnostic study using theory and a range of varying resolution model simulations to quantify the amount of subsurface warming along the West Antarctic Peninsula caused by barotropic Kelvin waves via an induced bottom Ekman flow that advects warm Circumpolar Deep Water onto the Antarctic continental shelf. We find that barotropic Kelvin waves can account for a substantial amount of warming within one year, depending on the background temperature gradients and thickness of the bottom Ekman layer. Lastly, we explore the role of Kelvin waves in linking Southern Ocean wind-stress to NADW formation and the AMOC by analysing ensemble simulations from a fully-coupled ocean-sea-ice model at 1/4 degree horizontal resolution (50 vertical levels). We find first mode baroclinic Kelvin waves to propagate along a global coastal and equatorial waveguide from the Southern Ocean forcing region to the North Atlantic, where downwelling waves initiate an enhancement of the AMOC by making surface waters denser.

  • (2021) Cai, Lin
    This thesis consists of three chapters that investigate the linkage between uncertainty and corporate investment decisions on an international basis. In first chapter, I investigate the extent of U.S. policy-related spillovers into 22 other real economies. I find that, after accounting for factors previously used to explain corporate investment, US Economic Policy Uncertainty (US EPU, hereafter) fluctuations affect foreign corporate investments through two channels. First, the single effect of US EPU on international corporate investment shows an unequivocal negative relation (the direct channel). Second, an increase in US EPU also attenuates the negative sensitivity of corporate investment towards the cost of capital (the indirect channel). Further, I find that while the direct channel of US EPU on corporate investment persists across several subsamples, its indirect channel relates to a high degree of dependence on the U.S. economy and opacity exhibited by local economies. The second chapter reconciles the contrary views on the foreign investors using local disaster shocks from 46 countries over the period 1998-2018. I find that local disaster shocks cause significant disruptions to corporate investments, but foreign institutional investors attenuate the costs of disaster risks. The benefits associated with foreign institutional investors are not uniformly held across all economies, where the role of foreign institutional investors is particularly measurable in countries with well-developed institutional environment. The third chapter focuses on the uncertainty at domestic level using national elections across 23 different countries. I find that the corporate investment cycle corresponds with the timing of national elections, but there is a cross-sectional difference in the firm-level investment sensitivity to elections. During election periods, while firms temporarily reduce investment expenditures relative to nonelection years, the decline is mainly sourced from firms with greater political exposures. Further, I find that the investment cycles are more volatile when the election outcomes are uncertain, and the institutional environments are weaker.

  • (2022) Mostyn, Benjamin
    The adoption of the United Nations Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances 1988 (“the 1988 Convention”) has been widely viewed as the final step in establishing global drug prohibition. This thesis provides an examination of Australia’s decision to support and sign the Convention which has not been analysied before. It also provides a detailed history of the development of the Convention as Australia was a key participant in UN drug meetings at the time. This thesis is based on the first research to access archival files, primarily from Foreign Affairs but also from the AFP and Department of Health. Nearly 180 folders, totalling approximately 35,000 pages, were copied from the Australian archives. These files provide detailed reports of almost all meetings and drafts that progressed the 1988 Convention. Interviews with key participants were also conducted. It provides an interdisciplinary legal history of Australia’s involvement in the 1988 Convention using the lens of the international relations theory of neorealism and the political theory of historical institutionalism. Through process tracing, it uses the theories to examine whether neorealist geopolitical forces and institutional forces caused Australia to support and sign the Convention. The analysis finds that geopolitical considerations trumped early concerns that a third convention was not necessary. The analysis also demonstrates that institutional forces within the UN benefitted financially from drug prohibition and played an unusually strong role in encouraging the development of the 1988 Convention. It also finds that institutional forces within the Australian government, such as the AFP and Foreign Affairs, supported the new Convention to increase their own jurisdiction and powers. Lastly, it looks at whether alternative policies such as regulation or decriminalization were considered by key policymakers. It finds that key individuals did support decriminalization but were overpowered by institutional and geopolitical forces. The significance of the dissertation includes: large amounts of new data to explain the development of the 1988 Convention; it increases knowledge around the institutional forces of criminalization and global criminalization; it significantly increases our knowledge of the role of the United Nations in waging the War on Drugs; and it increases knowledge around how mid-level nations interact with global institutions.

  • (2022) Zheng, Zhaozhi
    Urban stormwater runoff possesses the properties of intermittent occurrence, unexpectable volume and variable pollution which lead to different environmental issues, including flooding and waterlogging, pollution transportation, damage to downstream and contamination of the receiving waters. On the other hand, the low-level contamination (relative to sewerage) and large volume supply of stormwater makes it suitable as an alternative water resource to relieve the water shortage in the urban areas. Stormwater harvesting is under the concept of Water Sensitive Urban Design (WSUD) trying to treat stormwater properly for the different end-uses (like irrigation, toilet flushing and even for the uses close to human contact). Several treatment technologies (e.g., biofilters, constructed wetlands) have already been implemented to purify the stormwater with effective performance prior to reuse. However, the refractory organic micropollutants (especially herbicides) presented resistance to these nature-based solutions by showing variable treatment outcomes. In order to provide harvested stormwater for end-uses with high quality requirement (e.g., close to human contact recreational waters), a reliable treatment technology for organic micropollutants is desired as a post-treatment method in the stormwater harvesting system. This thesis aims to develop advanced oxidation processes (AOPs), in particular, photoelectrochemical oxidation (PECO), as the post-WSUD treatment approach for stormwater using its oxidation capacity towards the refractory organic micropollutants. Following the technology development procedure, three steps have been conducted: (1) testing the feasibility of AOPs for stormwater herbicides treatment; (2) investigating the intrinsic mechanism in the stormwater herbicides degradation process; and (3) assessing the operation conditions impact towards PECO stormwater treatment system. Boron-doped diamond (BDD) anode was used in the preliminary lab-scale tests for the feasibility study of AOPs towards stormwater organic micropollutants (two representative herbicides, diuron and atrazine - selected as the target pollutants in the study). The results showed that the effective herbicides degradation could be achieved by PECO process under 5 V operation (which was regarded as the optimal voltage in the system). The positive impact coming from voltage increase has been found in the study. BDD showed a remarkably durable property with stable removal performance under challenging voltage application (9 V) without observed deterioration. The catalysts loading showed negligible effect in removal performance. While the thermal effect was observed as a supporting factor for the process (higher temperature supported the oxidation process). Since BDD is not a perfect choice for scaled-up implementation due to its high manufacture cost, carbon fiber anode was chosen in the following studies and operated under low voltage (2 V) to avoid the possible anode deterioration under high voltage application. In the mechanism investigation, the superoxide radicals were found to be the major reactive species in PECO process. Meanwhile, hydroxyl radicals and free chlorine also demonstrated supporting impact for the oxidation process. With the identified intermediate products, degradation pathways of diuron and atrazine were proposed for the first time for three AOPs (PECO, electrochemical oxidation (ECO) and photocatalytic oxidation (PCO)) in stormwater herbicides degradation process. PECO was certified to be the preferrable stormwater treatment technology with the ability for further oxidation reactions towards herbicides degradation compared with ECO and PCO. In the third study, a flow reactor was designed and used to test the impacts of operational conditions (flow rate, light intensity, and initial pollutant concentration) for PECO process. An obvious improvement was observed for flow rate towards removal performance, while the light intensity was found to influence atrazine removal only. The initial pollutant concentration study demonstrated the robust performance of PECO flow reactor towards herbicides removal under challenging (240 μg L-1) pollutant concentration condition. The real stormwater experiments suggested the possible impacts coming from the stormwater chemistry towards PECO process. Further based on the energy consumption analysis, high flow rate (610 mL min-1) and normal light intensity (100 mW cm-2) were regarded as the optimal operational conditions for flow reactor system. Also, the effective PECO degradation performance of herbicides under the real stormwater environment has been verified by using the stormwater collected from field as supporting electrolyte in the experiments. Overall, this thesis confirms PECO as a promising stormwater herbicides treatment technology (potentially for all organic micropollutants) to provide further purification for stormwater high-quality targets. It also discusses the implications for the practical implementation and points out the future research directions for the system optimization.

  • (2022) Maranan, Noahlyn
    The 2016 vice-presidential election in the Philippines was contested on Facebook, the nation’s most prominent social media platform. Among the contenders was Ferdinand ‘Bongbong’ Marcos, son of former president Ferdinand Marcos Sr, who ruled between 1965 and 1986. Memes played a significant role in the election. They potentially enriched participatory engagement and information dissemination to a broader public. Through them, opposing camps worked through different versions of the Philippines’ past, present, and future. This case presents a novel opportunity to contribute to the growing scholarly debate about the relationship between social media and democratic politics. This study asks, “Can social media contribute to strengthening democracy in the Philippines?” It approaches this question through a conceptual framework that integrates work on democracy and political memory while also taking seriously the propensity of social media to be enlisted in information campaigns of a propagandist nature. Having analysed a sample of Facebook memes for their form and content, the study comes to an ambivalent conclusion. As immensely pliable and flexible texts, created and circulated with ease, the thesis finds that memes play a dual role in democratic politics. In the 2016 Philippine election, they (a) allowed for the inclusion of competing perspectives, narratives, and voices about Marcos Sr’s past regime and his son’s electoral bid. Rational and passionate voices, as one would expect from models of deliberative and agonistic democracy, were visible in this study. Enabled by digital platforms, memes became an important medium for the creative, potentially deliberative, and agonistic (if not outwardly antagonistic) articulation of sidelined memories about the regime of Marcos Sr. At the same time, (b) memes served as instruments for persuasive networked influence. While this may seem contrary to democratic communication, such propagandistic communication carries the potential to enrich reasoned argumentations in the broader public sphere when viewed from the lens of the wider literature on deliberative democracy. This potential, however, also depends on other factors, which include the techno-discursive platform in which propagandistic content circulates and the characteristics of the electorate.

  • (2006) Doran, Michael
    The transplantation of ex vivo expanded mobilized peripheral blood haematopoietic stem cells (PBSC), in place of unmanipulated cells following high dose chemotherapy, reduces the period of cytopenia associated with the therapy’s hemotoxicity. In this thesis the development and optimization of a preclinical prototype hollow fiber bioreactor (HFBR) for the ex vivo expansion of PBSC is described. Mass transport measurements and model of metabolite profiles demonstrate that Cuprophan and Polyflux are suitable membrane material for high-density cell expansion in a HFBR. Materials selected for the HFBR were found to be non-toxic following a 20-day saline extraction. Growth factor (GF) adsorption to the Polyflux membrane makes it unsuitable for expansion of GF dependent cells. However, the GF retention and minimal adsorption characteristics of the Cuprophan membrane are appropriate for this application. Cell-free medium degrades at 37ºC by an oxygen dependent process generating byproducts that inhibit cell growth. This process is relevant to perfusion bioreactors where the bulk of the medium is maintained at 37ºC and is cell-free. Albumin was shown to slow the degradation process but was itself degraded by shear damage inflicted during recirculation. Treating recirculating medium with dialysis against albumin was shown to be a more effective way to mitigate the effects of degradation and lengthen the functional life of albumin over conventional suspension of albumin in the recirculating medium. The preclinical prototype HFBR utilised dialysis against albumin to expand KG-1a cultures from densities as low as 3.5x10^5 cells/ml up to as high as 2x10^8 cells/ml with expansion rates equivalent to T-flask cultures. This process was then applied to PBSC where the targeted 100-fold expansion was achieved. Process optimization was continued using cord blood (CB) CD34+ cells. Growth factor loading sufficient for PBSC expansion in the HFBR was inadequate for CB expansions due to greater than anticipated CB uptake rates. The cell product from the HFBR contained significantly greater yields of CD34+ cells than attained using T-flask cultures. The HFBR platform is suitable for PBSC expansion and appears promising for CB expansion.

  • (2022) Fan, Hui
    The integration of variable distributed energy resources and vehicle electrification has come to focus over the last few years. While much work has been done to address the challenges that arise in modern distribution system planning and operation, continuous improvement to the models with the change is essential. The objective of this thesis is to improve the distribution network planning and operation models in the presence of distributed generation and electric vehicles. It aims to build stochastic models including the power generation and the charging demand, determine the location and sizing of the energy resources and charging stations in the coupled systems, and evaluate the impacts of the new low-carbon technologies on the network. Using a mixed-integer nonlinear programming framework through an optimal power flow analysis, this thesis presents three major methodological contributions including uncertainty modelling, coordinated mathematical formulation, and conflicting objective solutions. First, a multivariate stochastic process based on the notion of copula is applied to derive probabilistic charging patterns and to obtain the stochastic charging profiles. Second, a two-stage stochastic program based on statistical analysis and numerical simulation is introduced to generate synthetic time series of solar and wind power generation. The continuous distributions are discretized to generate the scenarios and the number of scenarios is reduced using Kantorovich metrics. Third, a two-dimensional Pareto front of dominant solutions is given for the competing objectives using a multiobjective Tchebycheff decomposition-based evolutionary algorithm. Case studies are conducted to evaluate the effectiveness of the proposed methods. An optimal charging scheduling problem is formulated to assess the stochastic charging models. The problem is formulated as a conic quadratic optimal power flow model and solved with a convex optimization algorithm. Network expansion planning problems are presented with carsharing and non-carsharing models, as well as the distributed energy generations. Overall, these problems aim to minimize the planning and operational cost of feeder routing, and substation alterations while maximizing the utilization of charging stations. It is found that an accurate estimation of the randomness intrinsic to the network is critical to ensure the secure and economic operation and planning of the distribution system intertwined with the transport network.

  • (2022) Ali, Muhammad
    This thesis addresses a key challenge for creating synthetic distribution networks and open-source datasets by combining the public databases and data synthesis algorithms. Novel techniques for the creation of synthetic networks and open-source datasets that enable model validation and demonstration without the need for private data are developed. The developed algorithms are thoroughly benchmarked against existing approaches and validated on industry servers to highlight their usefulness in solving real-world problems. A review using novel techniques that provides unique insights into the literature is conducted to identify research gaps. Based on this review, three contributions have been made in this thesis. The first contribution is the development of a data protection framework for anonymizing sensitive network data. A novel approach is proposed based on the maximum likelihood estimate for estimating the parameters that represent the actual data. A data anonymization algorithm that uses the estimated parameters to generate realistic anonymized datasets is developed. A Kolmogorov-Smirnov test criteria is used to create realistic anonymized datasets. Validation is carried out by collecting actual network data from an energy company and comparing it to anonymized datasets created using the methods developed in this thesis. The application of this method is shown by performing simulation studies on the IEEE 123-node test feeder. The second contribution is developing a practical approach for creating synthetic networks and datasets by integrating the open-source data platforms and synthesis methods. New data synthesis algorithms are proposed to obtain the network datasets for electricity systems in a chosen geographical area. The proposed algorithms include a topology for designing power lines from road infrastructure, a method for computing the lengths of power lines, a hub-line algorithm for determining the number of consumers connected to a single transformer, a virtual layer approach based on FromNode and ToNode for establishing electrical connectivity, and a technique for ingesting raw data from the developed network to industrial data platforms. The practical feasibility of the proposed solutions is shown by creating a synthetic test network and datasets for a distribution feeder in the Colac region in Australia. The datasets are then validated by deploying them on industry servers. The results are compared with actual datasets using geo-based visualizations and by including feedback from industry experts familiar with the analysis. The third contribution of this thesis is to address the problem of electric load profile classification in the context of buildings. This classification is essential to effectively manage energy resources across power distribution networks. Two new methods based on sparse autoencoders (SAEs), and multi-stage transfer learning (MSTL) are proposed for load profile classification. Different from conventional hand-crafted feature representations, SAEs can learn useful features from vast amounts of building data in an unsupervised automatic way. The problems of missing data and class imbalance for building datasets are addressed by proposing a minority over-sampling algorithm that effectively balances missing or unbalanced data by equalizing minority and majority samples for fair comparisons. The practical feasibility of the methodology is shown using two case studies that include both public benchmark and real-world datasets of buildings. An empirical comparison is conducted between the proposed and the state-of-the-art methods in the literature. The results indicate that the proposed method is superior to traditional methods, with a performance improvement from 1 to 10 percent.