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Chemical and structural stability of liquid-phase-exfoliated (LPE) two-dimensional (2D) materials
No full textAtomically thin two-dimensional (2D) materials have gathered massive attention owing to their unique properties that could benefit both the conventional semiconductor industry and wide-ranging nanotechnology-enable applications. At the atomically thin regime, 2D materials exhibit an array of unusual physiochemical, optical, and electronic phenomena enabling sustainable, high-performing, and faster devices, a prerequisite for future electronic and optoelectronic technologies. The emerging repertoire of 2D materials offers great flexibility in tuning these properties by allowing controlled fabrication of predetermined phases, compositions, and thicknesses. These properties are remarkably different from their bulk counterparts. These advancements have resulted in a large portfolio of 2D materials ranging from metals to semiconductors and insulators, offering possibilities to engineer and manoeuvre them for a specific purpose.
Largely, the properties of a 2D material depend on its crystal structure, composition and surface characteristics that authorise it to behave in a certain manner. Their atomistic nature makes them ultrasensitive to ambient conditions which influences their physico-chemistry and therefore affecting their performance. Hence, the topic of chemical and structural stability in 2D materials has undoubtedly become an unsettling question and receiving notable traction. The work presented in this thesis attempts to investigate the irregularities associated with the crystal structure and chemistry of materials at atomically thin regimes through their careful synthesis and characterisation. This is achieved by focussing on three technologically promising 2D materials, including black phosphorus (BP - phosphorene), lead monoxide (PbO), and lead (Pb - plumbene), which are discussed in three subsequent chapters, after discussing the state-of-the-art in the field in Chapter 1.
Chapter 2 introduces “few-layer black phosphorus (FLBP)”, a technologically promising 2D material with tuneable bandgap across the visible-infrared region. A major drawback with FLBP is its atmospheric instability as it has a high propensity to interact with its surrounding environment and rapidly degrade. Blocking direct exposure of FLBP to its environment remains a key method to achieve its protection against ambient oxidation. The work presented in this chapter proposes an alternative ambitious approach that not only ensures its protection but also allows to repair its surface to pristine conditions, if oxidised. This work has taken inspiration from naturally occurring processes in plants that produce antioxidant pigments such as β-carotene to defend them against photo-oxidative stresses. A similar protective and reparative mechanism of β-carotene is demonstrated to protect FLBP against photooxidation. The concept is demonstrated by first fabricating FLBP through a liquid-phase exfoliation (LPE) technique, followed by studying the interaction of FLBP with β-carotene molecules. β-carotene displayed exceptional protective ability, as illustrated by various microscopic and spectroscopic investigations, along with computational studies and biochemical assays. The outcomes from this study have created a potential opportunity to harness the strengths of naturally available antioxidant molecules in stabilising technologically important, yet environmentally sensitive 2D materials against ambient oxidation. This should enhance the opportunities for their deployment for various applications.
Chapter 3 of this thesis investigates PbO as a model system to evaluate the structural stability of 2D materials at atomically thin regimes. In contrast to FLBP investigated in the previous chapter that faces chemical instability, many other materials may undergo crystal phase transformations when reduced to atomically thin sizes. Despite the crystal structure al a material being a key determinant of its properties, an aspect that remains rather elusive is the influence of 2D crystal thickness on the structural stability of 2D materials. In particular, polymorphic crystals such as PbO that have a metastable crystal structure, make them an interesting candidate to study thickness-dependent phase transformations. To study these aspects, the work first developed an innovative reactive oxygen species (ROS) sequestration-mediated strategy to fabricate layered PbO crystals from a Pb foil. The thicker orthorhombic (β) PbO nanosheets obtained from this strategy were observed to gradually transform to tetragonal (α) PbO as the nanosheet thickness was reduced towards atomically thin layers by deploying an LPE method. These experimental findings from a range of microscopy and spectroscopy techniques were also supported by computational studies that indicated that a monolayer of α-PbO is thermodynamically more stable than β-PbO. An interesting observation was co-assembly of [001]-oriented α-PbO regions with [100]-oriented β-PbO regions within a single ultrathin nanosheet, suggesting the possibility to create interesting crystal structures at atomically thin regimes. Since the crystal structure of a material is the key determinant of its properties, the outcomes from this study offer opportunities to controllably create new 2D materials with unique crystal structures that have not been realised previously. Further, the polymorphic transformation of 2D PbO observed in this work highlights the need to carefully evaluate any potential changes in the crystal structure of materials at atomically thin levels.
Chapter 4 focuses on investigating the synthesis and stability of monolayer and few-layer thin lead (FLPb), commonly referred as “plumbene”. Free-standing plumbene has been proposed as an interesting 2D material to realise quantum spin hall phenomenon, which is critical for spintronics applications. While plumbene has been previously grown epitaxially on palladium surface, and a plethora of theoretical work has emphasised upon the importance of free-standing (substrate-free) plumbene, FLPb and plumbene have remained unrealised in the form of free-standing nanosheets. To address this gap, in this chapter, a cryo-mediated LPE strategy is discussed to produce FLPb by exfoliation of bulk Pb, a non-layered, non-van der Waal crystal. The cryogenic temperature along with mechanical forces (grinding and sonication) induced a ductile-to-brittle transition in Pb crystal and created higher DMF binding sites, favouring its cleaving between the (100) planes. The obtained FLPb nanosheets were found preferentially oriented along the [z00] direction. The strategy could achieve production of free-standing plumbene monolayers with a thickness of ~0.6 nm and average lateral dimension of ~450 nm. The work also revealed that FLPb is prone to surface oxidation, leading to the formation of lead oxides on its surface. In particular, radiation-induced surface oxidation of FLPb was noted during spectroscopic analysis of FLPb, suggesting that electrons, x-rays, and even visible light may oxidise plumbene during analysis and characterisation. This poses challenges in confidently determining whether the as-synthesised FLPb was free of surface oxides or was inherently stabilised by an oxide layer. Nevertheless, the access to free-standing plumbene to the 2D materials community is likely to offer opportunities to explore this exciting material for emerging applications.
Chapter 5 discusses the overall conclusions from this thesis and propose directions for future research. Overall, the investigations made during this thesis have enhanced our understanding of the chemistry of materials at atomically thin regimes by selecting three model systems, phosphorene, lead oxide, and plumbene. Phosphorene represents a material class that can undergo complete oxidative degradation, lead oxide is representative of materials that can exhibit remarkable crystal transformations, and plumbene belongs to those 2D materials whose surface can perhaps be controllably oxidised to create a shield that protects them from further deterioration. The knowledge generated from this thesis is likely to influence further studies in this area, where efforts will be made to understand the chemistry of 2D materials deeply and carefully. The learnings from these studies will expedite the technological translation of 2D materials
Techno-economic Analysis of Conformal Tooling via Hybrid Manufacturing
No full textInjection molding is an important polymer manufacturing process known for its efficiency in producing complex and precise components at high volumes and with good quality. However, the traditional approach to designing advanced injection molding (IM) tools, particularly their in-situ cooling systems, has resulted in inaccurate approximations that are only discovered after prototype tooling is manufactured and tested. Identifying these design failures during operation often leads to expensive redesigns to meet performance metrics such as manufacturing cycle time, part consistency, and part accuracy.
To avoid poor return on investment (ROI) for IM tool purchasers and operators, a superior design optimisation methodology is necessary. The optimisation should focus on maximising and homogenising the performance of the cooling system by optimising the heat flux across the cavity/core surface and the IM process parameters. Conformal cooling channels (CCCs), which follow the cavity surface, have emerged as a critical solution for achieving these goals, but this ‘smart’ design of CCCs is still in its infancy. This thesis proposes a novel generative design (GD) approach to IM tooling that optimises CCC design to enhance performance. This approach reduces design labour and costs, which are particularly high in Australia's manufacturing sector, and significantly increases ROI for IM tool purchasers. The GD algorithm developed here combines evolution-based optimisation methods with iterative routing optimisation based on surface temperature gradients—a novel combination not explored in existing literature. Compared to conventional tools, the GD tool achieved cooling time reductions of 20% (predicted worst case) and over 50% (measured) for a molded polymer part with a simplified geometry.
While advanced IM tool designs with complex CCCs can now be created, manufacturing them is challenging due to their sophisticated internal geometry. Additive manufacturing (AM) technologies can build somewhat sophisticated internal geometries in a near net-shape manner with low raw material wastage, but hybrid manufacturing (HM), which combines additive and subtractive manufacturing technologies, offers increased productivity and potentially reduced costs. This capability is particularly relevant for building GD-designed IM tools with highly complex internal geometries. Therefore, this thesis determines the "manufacturability" requirements that GD-designed tooling must meet to be manufactured using a modern hybrid directed energy deposition (DED) printer. The key aspect is having self-supported profile shapes with a maximum overhang angle of 35° from the vertical. Additionally, process parameters for multimaterial tools are developed, and tool material selection considers composite (bi-metallic) builds suitable for modern AM alloys.
The combined benefits of GD and HM on the predicted and achievable ROI of IM tool designs are substantial. However, the cost analysis of these modern IM tools and their manufacturing is crucial. This thesis provides an economic assessment of GD-designed and hybrid-manufactured IM tooling with CCCs. The assessment includes a whole-of-life costing model and concludes that, for the sample part evaluated, a minimum of 80,000 molded parts is required to offset the higher costs of hybrid manufacturing compared to conventional methods. The predicted ROI for this tool, considering its usage frequency, leads to an estimated 127% ROI within a year for producing 100,000 parts annually, which is relevant to an Australian tool design and manufacturing SME
A Framework of Facilitators and Barriers to Career Adaptability: Migrant Hotel Workers During COVID-19
No full textWe examine internal and external factors that build or thwart the career adaptability resources of migrant hotel workers. Drawing on qualitative data at two points in time over a 12-month period during COVID-19, results show that while some migrant workers changed roles and exited hotels, for most, job changes were a shorter-term, separation phenomenon, with migrants transitioning back to their employer within a year. Psychological, social, and human capital resources facilitated career adaptability, while psychoemotional support from managers and peers fostered the confidence of temporary migrants, and facilitated positive affect, which was integral to their openness to exploring alternate hospitality careers. Inhibitors to career adaptability included a lack of agency among temporary migrants, and career entrenchment of mid-career permanent migrants. Our model provides a fine-grained, holistic understanding of the antecedents of career adaptability, enriching career construction theory by clarifying the contexts that drive career adaptability in the evolving, COVID-19 context
Meat texture modification for dysphagia management and application of hydrocolloids: A review
No full textDysphagia is a medical condition that describes the difficulty of swallowing food, and texture modified food (TMF) is the best intervention for dysphagia. The relevant guidelines to identify dysphagia food are provided by the International Dysphagia Diet Standardization Initiative (IDDSI). Developing texture modified meat is a challenging task due to its fibrous microstructure and harder texture. Various meat tenderization attempts are therefore evaluated in the literature. Meat texture modification for dysphagia is not just limited to tenderization but should be focused on safe swallowing attributes as well. The application of hydrocolloids for designing TMF has a major research focus as it is a cost-effective method and offers an opportunity for careful control. The present review focuses on the meat texture modification attempts that have been used in the past and present, with special attention to the use of hydrocolloids. Several studies have shown improvements in texture upon the addition of various hydrocolloids; however, few studies have attempted to develop texture modified meat for people with dysphagia. This area has to be further developed along with the sensory evaluations conducted with the dysphagia population, to validate the industrial application of hydrocolloids to TMF
CSR Intent, CSR Strategies, and Their Effect on Multinational Mining Firms’ CSR Performance in Africa
No full textABSTRACT
The global demand for minerals is on the rise, driven mainly by developed countries. As a result, multinational corporations (MNCs) are turning their attention to developing countries with untapped mineral reserves. In today's business world, MNC managers must employ corporate social responsibility (CSR) strategies to navigate the complex global environment. The MNCs face pressure to fulfil economic, legal, ethical, and philanthropic obligations to the societies in which they operate. The extractive mining sector has drawn significant CSR attention due to its adverse effect on mining communities worldwide, notably in Africa. This study has noted the body of literature exploring the innovation of subsidiary managers and the micro-foundations of CSR in parallel. Therefore, this research combines these two dimensions to investigate how subsidiary managers' CSR intent influence their CSR strategies and firms' performances. These findings support the academic decision to view subsidiary managers as strategic human resources responsible for CSR strategy decisions which influence firm CSR performances.
Micro-foundations are gaining traction in various academic fields, but literature on psychological micro-foundations and their application in CSR studies is scarce. This noticeable research gap underscores the need to explore further how managers' CSR intent shapes their CSR strategies and their firms' overall CSR performance. This research has addressed the micro-foundations of CSR literature by exploring individual CSR determining factor, manager's CSR intent according to the theory of planned behaviour (TPB). The approach has opened an opportunity for CSR, management, and international business to work together with social psychology discipline through the lens of TPB theory and CSR intent. Therefore, the CSR intent concept has created interdisciplinary cooperation while fusing micro-CSR factors at meso and macro-level level of analysis. Consequently, the study has demonstrated the complementary capacity of managers` CSR intent and TPB for other CSR theoretical approaches – for example, Caroll's CSR typology and the theory of corporate social performance – and other theoretical levels of analysis at the institutional, industrial, managerial capabilities and firm levels.
A quantitative methodological approach was used to research a population of subsidiary firms of MNCs operating in Africa. A study included 820 operational mining MNC subsidiaries operating in the African market. The study obtained responses from 214 participants who completed the online surveys. Additionally, 214 community leaders participated in the survey to provide their opinions on the CSR performance of MNCs in the African market. For research robustness, the measurement scales of each construct were subjected to reliability and validity tests. These tests included scale reliability assessment, confirmatory factor analysis, correlation analysis, and a meticulous evaluation of common method bias. The study further conducted a hypothesis-testing phase, investigating direct, mediation, and multiple moderating relationships. Structural equation modelling was used to test the hypotheses, ensuring a thorough and rigorous data analysis. The validity of the findings was ensured by cross-referencing the conclusions from primary data and secondary sources, confirming convergence validity.
The study also highlighted the bottom-up approach to strategy planning, emphasising the significance of subsidiary unit innovation and community engagement in host countries. The African community's positive involvement in the study showcased how CSR managerial strategies can uniquely benefit local communities. This favourable response from the community positions mining subsidiary units as an asset for the firm's overall reputation and a safeguard against potential issues between head offices and subsidiaries. The fact that the firms studied operate in various parts of the world but align in the African market lends credibility to the study's findings, potentially influencing mining communities in developed and developing countries.
Companies can utilise the results of this study to streamline their human resources activities, including training, recruitment, selection, and talent management. Additionally, a manager's CSR intent can bring value and practical application to management and business, as in previous research that considers micro-determinant factors like CSR attitudes, ideology, sense-making, person-job fit, personality, and mindset. As a result, managers can use CSR intent assessment to enhance the talent management process, just as management assessments and measures use intelligence tests, personality tests, aptitude tests, integrity tests, and social acumen tests, blending business, social psychology, and organisational psychology. Through inter-rater validity tests, managers can standardize CSR intent measurements, and managers, MNCs, governments, and other CSR stakeholders can utilise these concepts to select managers for subsidiary management positions.</p
Performing the Self: Parafictional Persona and the Comedian Comedy
No full textThis thesis draws on the concept of parafictional persona to examine the increasingly pervasive phenomenon of
comedians playing themselves in fictional media. With reference to case studies selected from American comedy
from the dawn of broadcast media to the present day, I identify and describe five distinct but closely interrelated
“modes” of parafictional persona: parafictional stardom (George Burns and Gracie Allen in The George Burns
and Gracie Allen Show); performative parafiction (Larry David in Curb Your Enthusiasm); proximate parafiction
(Tig Notaro in One Mississippi); parodic parafiction (Tim Heidecker and Gregg Turkington in On Cinema at the
Cinema); and parareality (Nathan Fielder in Nathan for You).
I adopt a persona studies approach to investigate each of these comedians, aligning theories of self,
celebrity, and performance to analyse the construction and enactment of their polysemic public selves across
fictional, nonfictional, parafictional, and social media. Within this approach I consider parafictional persona as a
construct, noting common attributes and effects across the case studies, but also observing how they differ from
each other and how they separately fit into wider structures of media and culture.
My research reveals these performers and texts to be emblematic of growing tensions in how we
categorise and make sense of contemporary media, challenging traditional understandings of stardom, comic
persona, and the self. By identifying and articulating these five modes of parafictional persona in comedy, this
thesis illuminates the historical and contemporary meanings and significance of a highly self-reflexive mode of
comic performance, representing a significant advance in the theorisation of persona and a novel contribution to
persona studies, comedy studies, and media studies more broadly.</p
Improving Neural Network Performance Through Accelerated Learning and Simplified Architecture for Big Data Applications
No full textWith the continuous growth in computational power, the field of machine learning, particularly in neural networks, has seen remarkable advancements. However, improving model performance through faster training and simplified architecture remains application-dependent, with specific needs in areas such as time-sensitive tasks or resource-limited environments. This thesis addresses these needs by accelerating neural network learning and simplifying architectures in the context of big data applications, focusing on both improving computational efficiency and practical usability. To accommodate the increasingly large model structures and meet the demands for faster computation, extensive research has been conducted on algorithms that accelerate learning and architecture search methodologies that simplify model designs, thereby enhancing the overall performance of neural networks. The work is broadly categorized into three parts spanning problems of convergence speed to architecture search, as well as their application on big data scenario. Firstly, by modifying the gradients of recently proposed finite time algorithms, attempts are made to incorporate the terminal slide mode. This is aiming to achieve faster convergence in shallow neural networks. To extend the benefits of accelerated convergence to deep neural net-works, the rescaled gradient descent is further modified by altering the norm types. When evaluated across various benchmarks, this approach yields significantly improved convergence speeds compared with methods utilizing momentum or Nesterov accelerated gradient. Secondly, this work simplifies model neural network through architecture search. Genetic algorithms are employed with flexible genotype encoding, featuring different numbers of potential neurons in hidden layers, and finds a satisfactory balance between a large search space and rapid convergence by adjusting mutation and crossover operations. Several multi-layer patterns are discovered through time series prediction tasks on four real-world datasets. Different search space architectures across benchmarks are compared to validate their reliability. Lastly, to meet the demands of big data environments, distributed and parallel learning are thoroughly discussed respectively. For distributed learning, a combination of various acceleration techniques maximizes GPU efficiency and significantly reduces computation time. Parallel genetic algorithms and GPU grouping strategies are proposed and compared across various image recognition datasets. The results offer recommendations for GPU grouping under limited resources based on search space coverage and the avoidance of premature convergence to local optimal solution.</p
Growth Areas Liveability Scorecard for Melbourne
No full textThis report is the first series of Growth Areas Liveability Scorecard
Reports developed in partnership with the National Growth Areas
Alliance. The Growth Area Liveability Scorecards have been
developed for the capital cities of Adelaide, Brisbane, Melbourne,
Sydney and Perth include indicators and maps from the
Australian Urban Observatory measuring the liveability of 21
Australian cities. The Scorecards focus on the fastest growing
Local Government Areas located in outer metropolitan and
peri-urban regions of Australia’s five largest capital cities. The
Growth Area Liveability Scorecards identify differences between
Growth Areas and Non-Growth Areas across Australian capital
cities. Results are based on previous City Liveability Scorecards
developed by the Australian Urban Observatory @ RMIT University
and are based on 2021 indicator results.
More detailed neighbourhood, suburb, and Local Government
Area results across Australian cities are available online at
auo.org.au.</p
Tan Quy Market
No full text"Tan Quy Market" is a cinematic exploration that delves into the heart of Vietnamese culture through the bustling life of a traditional market. The market, a cornerstone of Vietnamese society, is portrayed as a vibrant hub of human interaction, cultural exchange, and communal bonding. This film captures the market's essence, illustrating how it embodies the spirit of being human in its most fundamental form.Set against the backdrop of a large wet market, the narrative follows the daily rituals of shopping, predominantly conducted on motorcycles, reflecting the unique and dynamic ways in which the community engages with this essential space. The market's atmosphere is palpable, with an intensity that stems from the crucial role food plays in familial and communal life. The freshness and quality of the goods on offer, unmatched by industrialised supermarkets, are central to the market's appeal and vitality.The film intricately examines the decision-making processes of shoppers as they navigate the market, comparing prices, assessing freshness, and evaluating quality. These decisions are informed by a deep, tacit knowledge passed down through generations, highlighting the cultural importance of these skills and the wisdom inherent in everyday market transactions."Tan Quy Market" transcends traditional documentary storytelling by weaving in and out of abstraction. The use of layered colours mimics a painter's technique, building a visual intensity that mirrors the market's vibrant atmosphere. This artistic approach creates a rich tapestry of sights, sounds, and sensations, drawing viewers into the visceral experience of the market.Through its immersive and visually captivating style, "Tan Quy Market" offers a profound reflection on the act of being human in the context of a street market. It celebrates the market not just as a place of commerce, but as a vital cultural asset that fosters community, preserves traditions, and enriches the daily lives of those who partake in its bustling, colourful world.</p
Micro X-ray fluorescence (μ-XRF) methodology for quantitative elemental imaging of Al–Zn–Mg–Cu alloys with varying chemical compositions
No full textThe preparation and characterization of Al–Zn–Mg–Cu alloys with varying chemical compositions are helpful for rapid screening of the optimal compositions in the research and development of new materials. The traditional testing methods cannot accurately determine the composition gradient in samples because they have a low spatial resolution or are semi-quantitative and time-consuming. The micro X-ray fluorescence (μ-XRF) methodology has been used for the elemental imaging of Al–Zn–Mg–Cu alloys with varying chemical compositions. The experimental conditions, including testing voltages, testing currents and the dwell time for each pixel, were optimized systematically to improve the repeatability and accuracy of the μ-XRF methodology. The quantitative elemental imaging of an Al–Zn–Mg–Cu alloy rod sample using μ-XRF was performed, and the results were validated by conducting spark optical emission spectroscopy. The limits of detection of μ-XRF for Zn, Mg, and Cu were 0.007 wt%, 0.068 wt%, and 0.002 wt%, respectively. This versatile elemental imaging technique provided an effective means for the component analysis and process evaluation of alloy samples with a composition gradient and thus for research and development of new materials