1,130 research outputs found

    Graduate Catalog of Studies, 2023-2024

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    Assessing the Role and Regulatory Impact of Digital Assets in Decentralizing Finance

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    This project will explore the development of decentralized financial (DeFi) markets since the first introduction of digital assets created through the application of a form of distributed ledger technology (DLT), known as blockchain, in 2008. More specifically, a qualitative inquiry of the role of digital assets in relation to traditional financial markets infrastructure will be conducted in order to answer the following questions: (i) can the digital asset and decentralized financial markets examined in this thesis co-exist with traditional assets and financial markets, and, if so, (ii) are traditional or novel forms of regulation (whether financial or otherwise) needed or desirable for the digital asset and decentralized financial markets examined herein? The aim of this project will be to challenge a preliminary hypothesis that traditional and decentralized finance can be compatible; provided, that governments and other centralized authorities approach market innovations as an opportunity to improve existing monetary infrastructure and delivery of financial services (both in the public and private sector), rather than as an existential threat. Thus, this thesis seeks to establish that, through collaborating with private markets to identify the public good to which DeFi markets contribute, the public sector can foster an appropriate environment which is both promotive and protective of the public interest without unduly stifling innovation and progress

    Graduate Catalog of Studies, 2023-2024

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    Choreographing tragedy into the twenty-first century

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    What makes a tragedy? In the fifth century BCE this question found an answer through the conjoined forms of song and dance. Since the mid-twentieth century, and the work of the Tanztheater Wuppertal Pina Bausch, tragedy has been variously articulated as form coming apart at the seams. This thesis approaches tragedy through the work of five major choreographers and a director who each, in some way, turn back to Bausch. After exploring the Tanztheater Wuppertal’s techniques for choreographing tragedy in chapter one, I dedicate a chapter each to Dimitris Papaioannou, Akram Khan, Trajal Harrell, Ivo van Hove with Wim Vandekeybus, and Gisùle Vienne. Bringing together work in Queer and Trans* studies, Performance studies, Classics, Dance, and Classical Reception studies I work towards an understanding of the ways in which these choreographers articulate tragedy through embodiment and relation. I consider how tragedy transforms into the twenty-first century, how it shapes what it might mean to live and die with(out) one another. This includes tragic acts of mythic construction, attempts to describe a sense of the world as it collapses, colonial claims to ownership over the earth, and decolonial moves to enact new ways of being human. By developing an expanded sense of both choreography and the tragic one of my main contributions is a re-theorisation of tragedy that brings together two major pre-existing schools, to understand tragedy not as an event, but as a process. Under these conditions, and the shifting conditions of the world around us, I argue that the choreography of tragedy has and might continue to allow us to think about, name, and embody ourselves outside of the ongoing catastrophes we face

    New Porous Nanomaterials For Battery and Supercapacitor

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    Lithium-Sulfur batteries have a high energy storage capacity while their sulfur cathode suffers large volume change, polysulfides dissolution and shuttle effect, and capacity fading during long-term cycling. To help lock sulfur and mitigate these problems, we introduced halloysite, a natural clay material with a nanotube format, to disperse and confine sulfur nanoparticles as well as to suppress the dissolution and migration of polysulfides. Halloysite was made conductive by covering it with a glucose-derived carbon skin. Sulfur nanoparticles were then trapped in both the lumen and outside surface of individual nanotubes with a loading dosage up to 80 %. In this new halloysite/sulfur composites cathode, the hollow nanostructure of halloysite provides space to allow dimension changes of encapsulated sulfur nanoparticles during repeated lithiation while limiting their size up to the diameter of nanotube lumen (i.e., 25 nm or less). The stacked halloysite clusters further create many nanoscale voids to divide the sulfur-electrolyte interface into isolated domains and increase the migration tortuosity in electrolytes to suppress the dissolution and shuttle effect of polysulfides. These features together contribute to improved cycling stability, retaining nearly ~84% of the starting capacity over 250 cycles, though the diffusion of lithium ions going in and out of nanotubes show some differences. In project 2, we worked on the anode development for LIBs. Silicon-rich (e.g., \u3e30 wt.%) anodes are desired to leverage the current capacity of lithium-ion batteries (LIBs) towards commercial cell performance requirements in critical markets, such as the transportation sector. A new type of nanofiber-in-microfiber silicon/carbon composite electrode was prepared and tested as a potential silicon-rich anode candidate. A co-axial electrospinning setup was used to produce a unique hybrid composite fiber configuration, in which silicon nanoparticles were suspended in a polymer solution to serve as the middle stream while the sheath stream was comprised of another polymer solution. Polyvinyl alcohol (PVA) was chosen as the silicon dispersion fluid because of its limited viscosity increase even at a very high solid allowance, which after carbonization held those nanoparticles together as short, branched nanofibers. Polyacrylonitrile (PAN) sheath fluid helped wrap the formed short, silicon-rich nanofiber bundles to form a nonwoven, ductile microfiber mat. After being carbonized into composite anodes, the silicon-rich nanofibers were used to host the majority of lithium ions while their thin carbon skin, originating from carbonized PVA, promotes conductivity and charge transfer. The nanofibrous morphology and the mesoscale space in between help accommodate the notorious volume expansion issues in silicon anodes during lithiation/delithiation processes. The outside PAN-derived microfibers provide structural support for the encapsulated silicon-rich nanofibers and simultaneously serve as the three-dimensional current collector. The new composite anodes were confirmed on their unique fibrous configuration and improved electrochemical performance. With 40 wt% Si, such silicon-rich, nanofiber-in-microfiber anodes achieve ~900 mAhg-1 reversible capacity and ~90% capacity retention over 250 cycles by effectively balancing challenges on silicon-rich fibrous anode and electrode pulverization. Beside battery research, we also worked on supercapacitors with high power density in project 3. Despite the great benefits plastics have brought to our modern lives, a large volume of plastic wastes increasingly threatens our environment and human health. Through a hydrothermal carbonization and crystallization process involving nitric acid and ethanol, drinking bottles made of polyethylene terephthalate were successfully converted into carbon quantum dots (CQDs) and thin carbon sheets simultaneously, with the former well dispersed and intercalated in the latter as a ball-sheet carbon structure (BSCs). The formed unique, connected, and conductive carbon network allows rapid transport of ions and electrons besides their large surface area and numerous ion hosting sites. The electrodes made of such a plastic ball-sheet carbon structure (PBSCs) therefore exhibit pseudocapacitance behavior with the specific capacity reaching 237 F/g at the charge rate of 1 A/g. Superior cycling stability on the energy storage was also found. Our method offers a new avenue to upcycle some plastic wastes as valuable energy storage systems, to help boost the recycling of plastic waste, and move forwards to the sustainable deployment of various clean energy resources

    soMLier: A South African Wine Recommender System

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    Though several commercial wine recommender systems exist, they are largely tailored to consumers outside of South Africa (SA). Consequently, these systems are of limited use to novice wine consumers in SA. To address this, the aim of this research is to develop a system for South African consumers that yields high-quality wine recommendations, maximises the accuracy of predicted ratings for those recommendations and provides insights into why those suggestions were made. To achieve this, a hybrid system “soMLier” (pronounced “sommelier”) is built in this thesis that makes use of two datasets. Firstly, a database containing several attributes of South African wines such as the chemical composition, style, aroma, price and description was supplied by wine.co.za (a SA wine retailer). Secondly, for each wine in that database, the numeric 5-star ratings and textual reviews made by users worldwide were further scraped from Vivino.com to serve as a dataset of user preferences. Together, these are used to develop and compare several systems, the most optimal of which are combined in the final system. Item-based collaborative filtering methods are investigated first along with model-based techniques (such as matrix factorisation and neural networks) when applied to the user rating dataset to generate wine recommendations through the ranking of rating predictions. Respectively, these methods are determined to excel at generating lists of relevant wine recommendations and producing accurate corresponding predicted ratings. Next, the wine attribute data is used to explore the efficacy of content-based systems. Numeric features (such as price) are compared along with categorical features (such as style) using various distance measures and the relationships between the textual descriptions of the wines are determined using natural language processing methods. These methods are found to be most appropriate for explaining wine recommendations. Hence, the final hybrid system makes use of collaborative filtering to generate recommendations, matrix factorisation to predict user ratings, and content-based techniques to rationalise the wine suggestions made. This thesis contributes the “soMLier” system that is of specific use to SA wine consumers as it bridges the gap between the technologies used by highly-developed existing systems and the SA wine market. Though this final system would benefit from more explicit user data to establish a richer model of user preferences, it can ultimately assist consumers in exploring unfamiliar wines, discovering wines they will likely enjoy, and understanding their preferences of SA wine

    Organic-Inorganic Nanomaterial Based Highly Efficient Flexible Nanogenerator for Self-Powered Wireless Electronics

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    As the world progresses towards artificial intelligence and the Internet of Things (IoT), self‐powered sensor systems are increasingly vital for sensing and detection. Nanogenerators, a new technology in energy research, enable the harvesting of normally wasted energy from the environment. This technology scavenges a wide range of ambient energies, meeting the ever-expanding energy demands as conventional fossil fuel sources are depleted. This research involves designing and fabricating high-performance flexible piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), using novel organic-inorganic hybrid nanomaterials for wireless electronics. Structural health monitoring (SHM) is crucial in the aerospace industry to enhance aircraft safety and consistency through reliable sensor networks. PENGs are promising for powering wireless sensor networks in aerospace SHM applications due to their sustainability, durability, flexibility, high performance, and superior reliability. This research demonstrated a self-powered wireless sensing system based on a porous PVDF (polyvinylidene fluoride)-based PENG, which is ideal for developing auto-operated sensor networks. The porous PVDF film-based PENG, enhanced output current by ~ 11 times and output voltage by ~ 8 times, respectively, compared to a pure PVDF-based PENG. The PENG device generated sufficient electrical energy to power a customized wireless sensing and communication unit and transfer sensor data every ~ 4 minutes. This PENG could harness energy from automobile vibration, reflecting the potential for real-life SHM systems. Subsequently, a novel, self-assembled, highly porous perovskite (FAPbBr2I)/polymer (PVDF) composite film was designed and developed to fabricate high-performance piezoelectric nanogenerators (PENGs). The porous structure enlarged the bulk strain of the piezoelectric composite film, resulting in a 5-fold enhancement of the strain-induced piezo potential and a 15-fold amplification of the output current. This highly-efficient PENG achieved a peak output power density of 10 ”W/cm2 and enabled to run a self-powered integrated wireless electronic node (SIWEN). The PENG was applied to real-life scenarios including wireless data communication, efficient energy harvesting from automobile vibrations as well as biomechanical motion. This low-temperature, full-solution synthesis approach could lead to a paradigm shift in sustainable power sources, expanding the realms of flexible PENGs. One of the remaining concerns is the highly soluble lead component, which is one of the constituents of the PENGs that poses potential adversary impacts on human health and the environment. To address this concern, lead-free organic-inorganic hybrid perovskite (OIHP) based flexible piezoelectric nanogenerators (PENGs) have been developed. The excellent piezoelectric properties of the FASnBr3 NPs was demonstrated with a high piezoelectric charge coefficient (d33) of ~ 50 pm/V through piezoelectric force microscopy (PFM) measurements. The device’s outstanding flexibility and uniform distribution properties resulted in a maximum piezoelectric peak-to-peak output voltage of 94.5 V, peak-to-peak current of 19.1 ÎŒA, and output power density of 18.95 ÎŒW/cm2 with a small force of 4.2 N, outperforming many state-of-the-art halide perovskite-based PENGs. For the first time, a self-powered RF wireless communication between smartphones and a nanogenerator solely based on a lead-free PENG was demonstrated and serves as a stepping-stone towards achieving self-powered Internet of Things (IoT) devices using environment-friendly perovskite piezoelectric materials. Likewise, triboelectric nanogenerators (TENGs) are also promising energy-harvesting devices for powering the next generation of wireless electronics. TENGs’ performance relies on the triboelectric effect between the tribonegative and tribopositive layers. In this study, a natural wood-derived lignocellulosic nanofibrils (LCNF) tribolayer was reported to have high tribonegativity (higher than polytetrafluoroethylene (PTFE)) due to the presence of natural lignin on its surface and its nanofibril morphology. LCNF nanopaper-based TENGs produced significantly higher voltage (160%) and current (120%) output than TENGs with PTFE as the tribonegative material. Assembling LCNF nanopaper into a cascade TENG generated sufficient output to power a wireless communication node to send a radio-frequency signal to a smartphone every 3 mins. This study demonstrates the potential of using LCNF as a more environmentally friendly alternative to conventional tribonegative materials based on fluorine-containing petroleum-based polymers. Overall, this thesis explores the design and development of highly efficient and flexible nanogenerators for self-powered wireless electronics. By combining highly electroactive nanomaterials with flexible polymer matrix structures, NGs with high electric output performance and flexibility were successfully obtained. The synthesizing process for the electroactive nanomaterials was carefully designed and adopted to sustain the inherent advantages of flexible electronics. The various type of high performance flexible NGs developed in this research work, including ZnO/PVDF porous PENGs, FAPbBr2I/PVDF based PENGs, FASnBr3/PDMS based PENGs, and LCNF nanopaper-based TENGs, provide promising solutions for energy harvesting and self-powered sensing

    Recent advances in expression and purification strategies for plant made vaccines

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    Plants have been explored as a platform to produce pharmaceutical proteins for over 20 years. Important features such as the cost-effectiveness of production, the ease of scaling up to manufacturing capacity, the lack of cold chain requirements and the ability to produce complex therapeutic proteins which are biologically and functionally identical to their mammalian counterparts, make plants a strong alternative for vaccine production. This review article focuses on both the expression as well as the downstream purification processes for plant made vaccines. Expression strategies including transgenic, transient and cell suspension cultures are outlined, and various plant tissues targeted such as leaves and seeds are described. The principal components used for downstream processing of plant made vaccines are examined. The review concludes with a reflection of the future benefits of plant production platforms for vaccine production

    Examining the Relationship Between Lignocellulosic Biomass Structural Constituents and Its Flow Behavior

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    Lignocellulosic biomass material sourced from plants and herbaceous sources is a promising substrate of inexpensive, abundant, and potentially carbon-neutral energy. One of the leading limitations of using lignocellulosic biomass as a feedstock for bioenergy products is the flow issues encountered during biomass conveyance in biorefineries. In the biorefining process, the biomass feedstock undergoes flow through a variety of conveyance systems. The inherent variability of the feedstock materials, as evidenced by their complex microstructural composition and non-uniform morphology, coupled with the varying flow conditions in the conveyance systems, gives rise to flow issues such as bridging, ratholing, and clogging. These issues slow down the conveyance process, affect machine life, and potentially lead to partial or even complete shutdown of the biorefinery. Hence, we need to improve our fundamental understanding of biomass feedstock flow physics and mechanics to address the flow issues and improve biorefinery economics. This dissertation research examines the fundamental relationship between structural constituents of diverse lignocellulosic biomass materials, i.e., cellulose, hemicellulose, and lignin, their morphology, and the impact of the structural composition and morphology on their flow behavior. First, we prepared and characterized biomass feedstocks of different chemical compositions and morphologies. Then, we conducted our fundamental investigation experimentally, through physical flow characterization tests, and computationally through high-fidelity discrete element modeling. Finally, we statistically analyzed the relative influence of the properties of lignocellulosic biomass assemblies on flow behavior to determine the most critical properties and the optimum values of flow parameters. Our research provides an experimental and computational framework to generalize findings to a wider portfolio of biomass materials. It will help the bioenergy community to design more efficient biorefining machinery and equipment, reduce the risk of failure, and improve the overall commercial viability of the bioenergy industry

    Development of the C-GEN generator technology for vertical axis wind turbines

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    In this thesis, 5 MW, 7.5MWand 10MWat 6 rpm C-GEN generator models were designed and optimized respectively for a vertical axis wind turbine. Although VAWTs have lower rotational speed than HAWTs, the offered C-GEN VAWT generators have significant higher power density compared to conventional PM and superconducting HAWT generators of equivalent power. The inner radius of the 5 MW C-GEN generator is 5.35 m and mass is 41.2 tonnes. The inner radius of the 7.5 MW C-GEN generator is 5.35 m and active mass is 44.1 tonnes. The inner radius of the 10 MW C-GEN generator is 7.50 m and active mass is 41.6 tonnes. Annual generation results show that offshore VAWT can generate as much energy as HAWT of the same power. In addition, by the end of 2022, the most powerful single offshore HAWT is 14 MW and due to the tower head mass of HAWTs, it is limited to increase the power further. Multi-power platform VAWTs can take the power of a single turbine further. The C-GEN model with wavy and comb steel structure has higher power density than the C-GEN model with straight steel structure. In addition, in the multi-stage C-GEN models, the comb steel structure will allow the passage of air between the stages, and since the wavy steel structure has more surface area than straight steel, it can help to increase the thermal performance of the machine. Since machine mass is an important factor in aviation, automotive propulsion systems and renewable energy converters, these structures can provide advantage. The machines are analysed and optimised electromagnetically using 2-D FEA simulations. A software algorithm has been developed for the simulations. This algorithm allows any electrical machine to be modelled and optimized easily and quickly. In addition, this algorithm can be applied to 3-D models and other branches of engineering such as mechanical, civil, naval, aircraft and etc. for use CAD and FEA models
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