Other UNSW

Publication Search Results

Now showing 1 - 10 of 32
  • (2019) Taseidifar, Mojtaba
    Thesis
    Water sector demands for developing new, sustainable and low-cost technologies have resulted in a significant amount of research in engineering/chemical processes in this area. This project is aimed at making improvements in several water technologies. Desalination: Seawater desalination using hot gas bubbles to collect water vapour from a solution using a bubble column evaporator (BCE) offers a promising technique to provide access to clean and safe drinking water. Heated air can collect the same amount of water vapour as theoretically expected, but using helium as carrier gas can enhance evaporation at a 3 times higher rate for seawater. Additionally, a more efficient membrane technique for the closed-cycle regeneration of depleted ion-exchange resins, using ammonium bicarbonate, offers another new method for energy-efficient desalination. Water reuse: Cysteine’s high affinity to bind with heavy-metal ions was used as the basis for a study of the potential for using a surfactant synthesised with a cysteine head-group to remove heavy-metal ions in an ion-flotation process. Synthesis of related materials: An improved synthesis of a single-chain octanoyl-cysteine surfactant was developed based on a simple and efficient novel method, which should facilitate its use as a green surfactant in many environmental applications, and also as a general cleaning agent. The effects of adding an organic UV absorber was also investigated on the physical, chemical and mechanical properties of epoxy-diamine resins, which could be used as a basis for developing new membrane filters. Cavitation: A novel method for the complete visual and audible removal of cavitation effects around a rapidly moving propeller was discovered that uses the local release of de-gassed water directly onto the rotating propeller, immersed in normal water. Releasing the de-gassed water onto the leading edge of the low-pressure side of the rotating propeller forms a thin layer of de-gassed water covering the blade surface, preventing cavitation. As the film drains, due to the action of shear forces created by the rotation, the de-gassed fluid flows to the trailing edge of the blade (as opposed to the leading edge, which has a positive pressure), further protecting this negative-pressure region from cavitation.

  • (2017) Sadr Dadras, Arash
    Thesis
    Firms recognise agility as a crucial capability to survive and thrive in uncertain and turbulent markets. One of the reported enablers of agility, from an IT perspective, is the Service-Oriented Architecture (SOA). SOA with reliance on its characteristics has provided faster time to market and reduced system complexity. Review of SOA empirical results, however, suggested an increased process and system complexities which conversely inhibit achieving the goal of agility. The contradictory effect of SOA on complexity and lack of insight on IT sensing capability motivated this research to study the effects of SOA on the two-underlying sensing and responding capabilities of the IT agility. Due to the current limited theoretical perspectives in the extant SOA studies, the current study undertakes a theory-building research. With reliance on the real options theory, complemented by the dynamic capabilities, the current study develops an initial theoretical framework and argues that SOA characteristics, when embedded in a system at the design time, will provide future knowledge and process options. The embedded future options, when executed, will facilitate the IT sensing and responding capabilities. By collecting and analysing data from twenty-two in-depth interviews as well as project documents across multiple cases in a Bank, an Airline company, and an Airport, this study extends its initial conceptual framework to a mid-range theory that explains the interaction between SOA and IT agility. Results of the study contribute to the SOA literature by conceptualising the SOA in three sets of characteristics including: ‘information-centric’, flexibility-centric’ and ‘structure-centric’, as well as theorising the effects of each set on the effectiveness of process options and ‘change detection’ and ‘shared insight’ knowledge options. Furthermore, the study took steps to extend the options theory by developing a new concept called options depreciators, which represents the negative effect of options when there are multiple competing options. Finally, this dissertation contributes to the SOA governance literature by providing a novel view on the required governance structure for achieving agility. Under this perspective, this study presents an adaptive governance structure that is consistent with the SOA hierarchical layering and also appropriate to foster business autonomy and to create sustainable assets for future use.

  • (2017) Danker, Joanne
    Thesis
    Students with a sense of well-being are socially, emotionally, and academically competent. As adults, they are likely to contribute to the nation's social capital. On the other hand, students with a low sense of well-being are prone to depression, suicide, and may engage in antisocial behaviours such as drug and alcohol abuse and criminal activities. Recognising the impact of student well-being, the Australian government is committed to enhancing the well-being of all Australian students. The purpose of this qualitative study was to explore what constitutes the well-being of students with autism spectrum disorder (ASD), 'Level 1: Requiring support’ in mainstream high schools, the barriers to, and assets of the well-being of these students from the perspectives of teachers, parents, and students with ASD. To collect data, semi-structured interviews were conducted with 20 teachers, 13 parents, and 16 students with ASD. Students with ASD also participated in a Photovoice project. Grounded theory approaches were used to analyse the data. Findings revealed seven domains of student well-being, five categories of barriers, community and organisational external assets, and internal assets comprising of individual qualities and skills. Implications for practice, policy, theory, and research, were discussed.

  • (2018) Datta, Ananya
    Thesis
    Microbes often contaminate contact lens storage cases during use. Up to 85% of contact lens storage cases show contamination by bacteria and contaminated lens cases may be associated with corneal infections and inflammation. This thesis sets out to understand how bacteria colonise cases, the kinetics and patterns of bacterial interactions during colonisation and determines how antimicrobial strategies might limit storage case contamination and deliver safer contact lens wear, both in laboratory studies and clinical trials. The rate of contact lens case contamination was estimated using a relatively new povidone iodine (cleadew™) based disinfecting system. Contact lens case contamination was low, with 30% of cases having no culturable microbes, but higher level of Gram-negative bacteria than some other disinfecting solutions. However, use of cleadew™ resulted in the recovery of multiple bacterial species from the same lens case. Subsequent experiments were designed to understand how multiple species may attach and colonise lens cases. My research demonstrated for the first time that ocular isolates of P. aeruginosa, S. aureus, A. radioresistens, M. luteus and Staphylococcus spp. could coaggregate. For P. aeruginosa and S. aureus coaggregation was not related to the build-up of biofilms in contact lens cases as there was no evidence that the coaggregation was associated with cohesion between the strains. However, A. radioresistens, M. luteus and Staphylococcus spp. coaggregated and cohered. Overall, these findings suggest that coaggregation and cohesion may occur and contribute to the coexistence of different microbial types in contact lens cases. Then I examined, whether antimicrobial silver-impregnated barrel cases could reduce the level of case contamination in vitro and in vivo. Silver was very effective in cases and resulted in significant decreases level of microbial colonization and lower levels of multispecies recovery from lens cases. This thesis revealed that the combined efficacy of silver in cases along with a disinfecting solution could be an approach to reduce overall bacterial contamination, particularly contamination by Gram positive bacteria. Further investigations are required to understand whether the microbes formed multispecies biofilms in lenses cases, and whether the reductions in lens case contamination result in reduced complications during lens wear.

  • (2018) Chen, Ssu-Han
    Thesis
    This dissertation reports the development of a MEMS PZT-based piezoelectrically driven microlens actuator for potential use in micro-optics applications. The actuator consists of six uniquely arranged piezoelectric beams configured in d31 mode. One end of the beam is fixed to the substrate and the other end connected to a serpentine spring supporting a microlens holding platform. The microlens actuator exhibits large out-of-plane displacement of 145 um at 100kV/cm (22V) with a high resonance frequency of 1.96 kHz when it is free from a microlens loading, and 0.673 kHz with a 330 ug PDMS lens loading. The parameters governing the design and fabrication conditions to obtain an optimum actuation performance are discussed in detail. As part of the microlens actuator development, a series of original studies have been conducted. These include: (i) The study of Ultra-High Vacuum E-beam Evaporated Polysilicon (UHVEEPoly) thin-film for forming Lead Zirconate Titanate (PZT) based piezoelectric MEMS. The film is used as a passive structural layer in a unimorph PZT micro-cantilever actuator to demonstrate its suitability as an alternative platform for forming PZT based devices. In particular, this technique enables a cost-effective process and versatility of forming MEMS structures compared to conventional platforms. (ii) The development of PZT bimorph actuator with polysilicon as the passive structural layer. This novel arrangement has been made possible due to the low stress and low thermal budget properties of the UHVEEPoly film which can be formed without influencing the quality of the piezoelectric layer deposited prior. This configuration has unique suitability for the micro-actuation mechanism presented in this work that enables the possibility of bi-directional actuation and reduction in device footprint area. (iii) A novel approach to enhance the out-of-plane uni-directional actuation without compromising resonance frequency or changing the overall actuator design has been demonstrated. The study exploits the use of the UHVEEPoly and RF-sputtered SiO2 films as the passive structural layer to manipulate the residual moment created from the residual stress in the multi-layered thin-film structure. By residual stress manipulation of the passive layer, an enhancement of more than 36% in the displacement range has been obtained from the microlens actuator; (iv) The proposed microlens actuator has demonstrated the capability to function as an optical focusing mechanism by changing the focus of a laser pointer with actuation; (v) Studies on the development to implement an integration of on-chip piezoresistive sensor with the microlens actuator has been discussed.

  • (2018) Chen, Weijian
    Thesis
    This thesis investigates the photophysics of InGaN/GaN multiple quantum wells (MQW) on top of GaN nanorods. InGaN/GaN MQW is a promising candidate material for high-performance light-emitting diodes and solar cells. In this thesis, InGaN/GaN MQW nanorods were fabricated by nanosphere lithography, a top-down method using reactive ion etching (RIE) of c-plane GaN with InGaN quantum wells. The nanorod arrays presents a hexagonal perodicity with uniform morphology. InGaN/GaN MQW nanorods demonstrate significantly improved optical and electronic properties compared to their planar counterparts. However, the exact nature of the processes whereby nanorod structures impact the carrier dynamics in InGaN quantum wells is not well understood. Using a confocal microscopy, associated with time-resolved spectroscopy, combining selective one- and two- photon excitations steady and time-resolved photoluminescence characterization provides detailed carrier dynamic analysis. The depth- and spatial-resolution at the nanoscale is helpful for understanding the optical properties of InGaN/GaN MQW nanorods. While nanostructured surfaces enhance luminescence performances of InGaN/GaN MQW, the increased surface defects impair the device performance, which is dealt with by surface treatments in this thesis. By studying the intensity-dependent PL of InGaN/GaN MQW, this thesis proves that photoexcited electrons and holes are strongly bound by Coulomb interactions (i.e., excitons) in planar MQWs due to the large exciton binding energy in InGaN quantum wells. In contrast, free electron-hole recombination becomes the dominant mechanism in nanorods, which is ascribed to efficient exciton dissociation. The nanorod sidewall provides an efficient pathway for exciton dissociation that significantly improves the optical performance of InGaN/GaN MQW. This thesis provides new insights into excitonic and charge carrier dynamics of quantum confined materials as well as the influence of surface states. The optical characterization techniques provide depth-resolved and time-resolved carrier dynamics with nanoscale spatially-resolved mapping, which is crucial for a comprehensive and thorough understanding of nanostructured materials.

  • (2018) Chilton, Angela
    Thesis
    The increased accessibility of genomics has enabled unparalleled exploration of the microbial world. Taxonomic diversity is proving to be vast beyond expectations, with extrapolations from genomes indicating functional diversity to be even greater. In the face of multi-drug resistance, this promising frontier is galvanising the pursuit of microbes for novel anti-infectives and other socially beneficial compounds. Given the immense scope of the microbial world, there is an imperative to identify and prioritise promising avenues for future work. Arid soils have been identified as diversity hotspots for the nonribosomal megasynthase genes responsible for producing a large array of microbial bioactive compounds (secondary metabolites). Biocrusts are top-soil microbial niches within arid lands that present as compelling candidates for bioprospecting given their extremotolerance, enrichment with cyanobacteria, and use as model systems. This thesis takes direction from prior research to specifically target arid Australian biocrusts and profile their genetic capacity for small molecule production. Next generation sequencing was used to target the 16S rRNA gene as well as conserved domains within two nonribosomal biosynthetic pathways. Examination of biocrusts at the local scale showed visually distinct stages were defined by distinct bacterial communities. However, no difference was found in the biosynthesis genes between the stages. At the intra-continental scale, seasonality of precipitation was found to control biocrust community assembly and drive the distribution of secondary metabolite genes, suggesting possible functional roles involving water cycles. Overall, functional richness correlated with taxonomic richness. Network analysis was used to identify influential bacteria and genes as targets for future bioprospecting efforts. This thesis identified underlying patterns in taxonomic and functional diversity to further narrow the search field and contribute to a biosynthetic atlas of Australia.

  • (2018) Do Duy, Tho
    Thesis
    There is occasionally an absorption feature around 11μm in the spectra of forming stars and probably ISM sightlines. The carrier is still debated to be possibly water ice, polycyclic aromatic hydrocarbons, silicon carbide, carbonates or crystalline silicates all of which have been detected in cosmic dust. In this thesis, we present over 60 new ground-based spectra from 8-13μm of more than 40 objects, including three evolved stars which is considered as dust factories, several embedded young stellar objects in which dust involve in star formation and planet formation, and several objects whose sightlines intersects with many dense an/or diffuse clouds. Our observations were made with a variety of spectrographs on different telescopes, including Michelle on Gemini North, Michelle on UKIRT, TReCS on Gemini South, TIMMI2 on the ESO 3.6 m telescope and COMICS on Subaru. Most of the spectra are compared with the data obtained with the Infrared Space Observatory (ISO) on these and other targets; they show an inflection around 11μm. We aim to identify the carrier of this feature. By comparing the strength of that feature with those at other wavelengths, we are able to exclude all of the possible carriers above but crystalline silicate. The evidence includes the similarity in shape between the 11μm band profile and the emissivity of crystalline olivine, the correlation between this band and the amorphous silicate band at 9.7μm and the best model fit of the spectra, which determines the mass fraction of rystalline silicates in each object. We propose that crystalline silicates exist in the embedded YSO phase and even in the ISM, which was thought to have amorphous silicates only. This result leads to several implications on the life cycle of silicates in particular and cosmic dust in general. There are probably several possibilities, for instance, the destruction of the ISM silicates is not complete or the crystalline silicates can form in the ISM due to a low-temperature crystallisation process. We also investigate self-absorption in the spectra of an embedded young stellar objects (YSOs) and a post-AGB star using an optically thin models with absorption on the sightline and a modified version of the radiative transfer model by Towers et al. (2009). These models, each of which has its own advantages and disadvantages, not only can reproduce the shapes of the spectra, but also reveal the properties of the dust surrounding the objects such as the composition, temperature and thickness.

  • (2018) Priyambodo, Bayu
    Thesis
    Spiny lobster farming is an emerging industry in Indonesia. However, its dependence on wild puerulus (an intermediate larval–juvenile phase) supply is critical and the industry has been constrained by the underdeveloped skills of puerulus fishers. The overall aim of this study was, first, to address the development of the spiny lobster aquaculture in Indonesia by understanding barriers to puerulus collection through a study tour involving an Indonesian spiny lobster stakeholder group to Vietnam; second, to address the assessment of the lobster puerulus resource and its potential for sustainable exploitation to support aquaculture; and finally, to identify the most effective collection devices and techniques, and understand puerulus behaviour and ecology. The study tour appeared a highly effective method for improving the knowledge of participants, particularly in regard to detailed technical information on puerulus collection. The most important outcome of the study tour was the substantial increase in lobster puerulus catch, attributed to improved (adopted) techniques involving modified equipment and application of light to attract pueruli to the fishing equipment. Many new Indonesian puerulus hotspots have been identified, including the entire south coast from Sumbawa to Java. Puerulus exporters have played an important role in the expansion of new puerulus fishing grounds throughout the country by delivering skilled puerulus fishers from Lombok elsewhere around Indonesia to disseminate information about new puerulus catching techniques. However, although the number of caught puerulus has increased dramatically, this has not generated positive effects for development of the grow-out sector because collected pueruli are designated for more lucrative international markets. Additionally, as both grow-out and collection of pueruli became illegal under Indonesian legislations introduced in 2015 and 2016, a puerulus black market has emerged. Removal of pueruli for the purpose of aquaculture is unlikely to negatively affect future catches or the breeding stock because of the extremely low wild survival rate of this larval stage. However, growing pueruli on to market-size lobsters provides significant benefits for both humans and the environment. Given that the natural mortality of pueruli in Indonesia is likely to be >99%, combining lobster grow-out of wild-caught pueruli and restocking a certain percentage of farmed lobsters back into the wild provides a win–win solution. Indonesia has a puerulus resource exceeding 100 million individuals, which is 20 times greater than that of Vietnam where a large, stable and sustainable lobster farming industry based on the puerulus resource is established. If 50% of the Indonesian fishable lobster puerulus resource (i.e., 50 million pueruli) was allowed to be fished, this would be sufficient to support production of 12,500 tonnes of market size lobsters—assuming 50% survival from puerulus to a harvest size of 500 g. This could provide a livelihood for more than 50,000 households. Spiny lobster farming is an emerging industry in Indonesia. However, its dependence on wild puerulus (an intermediate larval–juvenile phase) supply is critical and the industry has been constrained by the underdeveloped skills of puerulus fishers. The overall aim of this study was, first, to address the development of the spiny lobster aquaculture in Indonesia by understanding barriers to puerulus collection through a study tour involving an Indonesian spiny lobster stakeholder group to Vietnam; second, to address the assessment of the lobster puerulus resource and its potential for sustainable exploitation to support aquaculture; and finally, to identify the most effective collection devices and techniques, and understand puerulus behaviour and ecology. The study tour appeared a highly effective method for improving the knowledge of participants, particularly in regard to detailed technical information on puerulus collection. The most important outcome of the study tour was the substantial increase in lobster puerulus catch, attributed to improved (adopted) techniques involving modified equipment and application of light to attract pueruli to the fishing equipment. Many new Indonesian puerulus hotspots have been identified, including the entire south coast from Sumbawa to Java. Puerulus exporters have played an important role in the expansion of new puerulus fishing grounds throughout the country by delivering skilled puerulus fishers from Lombok elsewhere around Indonesia to disseminate information about new puerulus catching techniques. However, although the number of caught puerulus has increased dramatically, this has not generated positive effects for development of the grow-out sector because collected pueruli are designated for more lucrative international markets. Additionally, as both grow-out and collection of pueruli became illegal under Indonesian legislations introduced in 2015 and 2016, a puerulus black market has emerged. Removal of pueruli for the purpose of aquaculture is unlikely to negatively affect future catches or the breeding stock because of the extremely low wild survival rate of this larval stage. However, growing pueruli on to market-size lobsters provides significant benefits for both humans and the environment. Given that the natural mortality of pueruli in Indonesia is likely to be >99%, combining lobster grow-out of wild-caught pueruli and restocking a certain percentage of farmed lobsters back into the wild provides a win–win solution. Indonesia has a puerulus resource exceeding 100 million individuals, which is 20 times greater than that of Vietnam where a large, stable and sustainable lobster farming industry based on the puerulus resource is established. If 50% of the Indonesian fishable lobster puerulus resource (i.e., 50 million pueruli) was allowed to be fished, this would be sufficient to support production of 12,500 tonnes of market size lobsters—assuming 50% survival from puerulus to a harvest size of 500 g. This could provide a livelihood for more than 50,000 households.

  • (2019) Pinto, Angie
    Thesis
    Background: Primary HIV infection (PHI) is a unique time to study clinical, virological and public health aspects of HIV. Data on long term outcomes in this cohort are limited. New South Wales is at a crossroads in HIV strategy and more detailed insight is needed into molecular epidemiology, drug resistance and the role of PHI in driving the epidemic. Aims: 1) To determine mortality in a cohort of PHI in NSW 2) To establish a state-wide drug resistance database and evaluate rates of transmitted and acquired drug resistance (TDR & ADR) 3) To understand the role of PHI in molecular epidemiology of NSW Methods: Chapter Two describes data linkage methods used to link PHI cohort to deaths notifications. It also describes data linkage used to link HIV sequence dataset with HIV notifications. Chapter Three uses univariate and multivariate analysis to assess factors associated with mortality in a PHI cohort. Chapter Four evaluates the rates of transmitted and acquired drug resistance over ten years. Chapter Five uses univariate and multivariate analysis to assess factors associated with TDR. Chapter Six uses maximum likelihood phylogenetic inference and univariate and multivariate analysis to determine factors associated with cluster membership. Key findings: Treatment with antiretrovirals within one year of PHI is associated with decreased mortality. Overall rate of prevalent drug resistance is decreasing, most markedly with ADR, while TDR rates have been stable. People residing in non-metropolitan regions and those aged 19-29 years had the highest odds of pre-treatment drug resistance. Acquisition in Australia, diagnosis post- 2012, early infection stage (but not laboratory defined PHI) are factors associated with cluster membership in NSW. Conclusion: Primary HIV cohorts can provide valuable insights into the natural history of HIV, and the role of therapies commenced during this period. Ongoing surveillance of drug resistance mutations combined with molecular epidemiology in NSW is critical in an era of immediate universal treatment and widespread community access to pre exposure prophylaxis to understand where to focus public health interventions. Future research should focus on establishment on national HIV resistance surveillance and integration of molecular epidemiology into public health strategies.