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Design and synthesis of polymer hydrogels for ultrasonic metrology applications
No full textThis thesis was previously held under moratorium from 28th August 2020 to 28th August 2022Ultrasonic probes for metrology are critical for the quality control of several products, such as airplane engine rotors. Currently, ultrasonic analysis is performed by means of immersion testing whereby the object to be measured is submerged in water and scanned with an ultrasonic probe to obtain morphological data. The immersion of individual objects in water is labour intensive, time-consuming, restrictive and can cause damage to valuable test objects.Herein, we report the development of a disruptive non-destructive testing technology using a novel coupling approach which utilises the unique properties of super-absorbent polymer (SAP) hydrogels. Unlike other coupling materials tested, SAP hydrogels can contain up to 99.9 % of coupling fluid while exhibiting exceptional mechanical strength and flexibility. The implementation of SAP hydrogels combines the precision of immersion testing with the mobility and ease of measurement of dry coupling techniques. An ultrasonic probe has been designed which is capable of attaching a modified tip for supporting the SAP couplant.Two-layer sedimentation polymerisation (TSLP) was developed to yield polymer hydrogels comprising various monomers, crosslink densities and compositions to yield spherical hydrogels with improved characteristics (e.g., mechanical strength, responsiveness). Spherical hydrogels prepared via TLSP showed outstanding swelling and ultrasound coupling character.Evaluation of promising high strength hydrogels enabled the synthesis of spherical high strength hydrogels by TLSP and moulding techniques. The high strength hydrogels showed excellent ultrasound coupling character, and outperformed all materials previously tested for this disruptive application, in terms of their mechanical strength.We anticipate that the materials, ideas and techniques described will lead to future non-destructive testing applications. Furthermore, the polymer synthesis techniques developed will broaden further the field of hydrogels.Ultrasonic probes for metrology are critical for the quality control of several products, such as airplane engine rotors. Currently, ultrasonic analysis is performed by means of immersion testing whereby the object to be measured is submerged in water and scanned with an ultrasonic probe to obtain morphological data. The immersion of individual objects in water is labour intensive, time-consuming, restrictive and can cause damage to valuable test objects.Herein, we report the development of a disruptive non-destructive testing technology using a novel coupling approach which utilises the unique properties of super-absorbent polymer (SAP) hydrogels. Unlike other coupling materials tested, SAP hydrogels can contain up to 99.9 % of coupling fluid while exhibiting exceptional mechanical strength and flexibility. The implementation of SAP hydrogels combines the precision of immersion testing with the mobility and ease of measurement of dry coupling techniques. An ultrasonic probe has been designed which is capable of attaching a modified tip for supporting the SAP couplant.Two-layer sedimentation polymerisation (TSLP) was developed to yield polymer hydrogels comprising various monomers, crosslink densities and compositions to yield spherical hydrogels with improved characteristics (e.g., mechanical strength, responsiveness). Spherical hydrogels prepared via TLSP showed outstanding swelling and ultrasound coupling character.Evaluation of promising high strength hydrogels enabled the synthesis of spherical high strength hydrogels by TLSP and moulding techniques. The high strength hydrogels showed excellent ultrasound coupling character, and outperformed all materials previously tested for this disruptive application, in terms of their mechanical strength.We anticipate that the materials, ideas and techniques described will lead to future non-destructive testing applications. Furthermore, the polymer synthesis techniques developed will broaden further the field of hydrogels
Housing Law M9313 exam papers
No full textAccess restricted to staff and registered students of the University of Strathclyde.PAST EXAM PAPERS ARE NO LONGER BEING ADDED TO STAX. PLEASE VISIT SUPRIMO TO ACCESS AN UP-TO-DATE COLLECTION OF PAST EXAM PAPERS: https://suprimo.lib.strath.ac.uk
Design and operation of Low Frequency AC (LFAC) transmission system for connecting offshore wind farms
Get PDFThe offshore power transmission market continuously grows as government incentives for Renewable Energy, and technological advancements lead to the exploitation of offshore wind for electricity generation due to its high capacity factors and the abundant offshore space. Currently, the High Voltage AC (HVAC) and High Voltage DC (HVDC) transmission systems (TS) are the commercial options for integrating the wind power to the onshore grid. The technical and economic efficiency of each approach is evaluated on a case-by-case basis and is mainly dependent on the Offshore Wind Power Plant (OWPP) capacity and its distance from shore, with HVAC TS being the most common solution for distances lower than 100km;The Low Frequency AC (LFAC) technology can provide an attractive transmission solution for exporting power from vast and remote OWPPs within a distance range of 80-300km. The basic idea of the LFAC system is to use lower AC frequency to reduce the effective electrical length of the equivalent HVAC subsea cable, so that its transmission capacity is increased, and also to eliminate the need for bulk offshore HVDC platforms, so that the installation, operation and maintenance costs are decreased. Despite the theoretical advantages of LFAC, the related research and its previous application in the rail and oil industries, there is no prior operational experience in similar type and scale networks, increasing the uncertainty for investors regarding the LFAC compliance capability and technology readiness level for offshore transmission purposes.;The aim of this industrial PhD Thesis is to result in robust and feasible LFAC TS options that can be realised by common industry practices and comply with typical Transmission System Operator's (TSO) grid code requirements. The LFAC TS is designed as a combined offshore HVAC system utilising an onshore Back-to-Back Modular Multilevel Converter (BtB MMC) scheme for frequency conversion. Point-to-Point (PtP) and Multi-Terminal (MT) LFAC topologies are examined for various cable lengths to export the nominal capacity of the OWPPs or interconnect different OWFs and different grids through single-cable connections to minimise costs. The technical feasibility of the LFAC TS is assessed through comprehensive steady-state, frequency and time-domain studies to optimise the system performance, its transmission capability and identify probable limitations.;Initially, the main transmission equipment specifications are appropriately adapted and rated for LFAC operation. Frequency scan studies are performed to investigate the low-order resonances of the LFAC TS, and suitable C-Type harmonic filter combinations are introduced to avoid potential harmonic stability issues. Power-flow cases are studied to calibrate the operating conditions of the system (e.g. reactive power compensation, control strategies, etc.) and optimise the schemes in terms of power losses and shunt cable compensation, placed only at the onshore side. It is yielded that by utilising the AC voltage control strategy of the OWPP inverters together with the reactive power capability of the BtB MMCs can maximise the power transfer through the cables.;Finally, detailed EMT models of the optimised PtP and MT-LFAC TS are simulated to evaluate its dynamic performance, stability and FRT capability against faults in the offshore LFAC and AC sides. It is concluded that if the LFAC grid-forming MMC employs a typical islanded control scheme without Inner Current Controllers (ICCs), it should always use harmonic filtering to avoid low order harmonic stability issues caused by the system resonance. Even then, its FRT response against an LFAC side fault would be unacceptable, due to its unconstrained LFAC fault current. However, by implementing high-bandwidth ICCs with appropriate current saturation and integrator anti-windup mechanisms to the islanded-control system, the LFAC TS rides through faults successfully and complies with the respective typical TSO limits. Also, depending on the system rating, DBRs may need to be applied in the DC sides of the OWTGs and the onshore BtB frequency converters.The offshore power transmission market continuously grows as government incentives for Renewable Energy, and technological advancements lead to the exploitation of offshore wind for electricity generation due to its high capacity factors and the abundant offshore space. Currently, the High Voltage AC (HVAC) and High Voltage DC (HVDC) transmission systems (TS) are the commercial options for integrating the wind power to the onshore grid. The technical and economic efficiency of each approach is evaluated on a case-by-case basis and is mainly dependent on the Offshore Wind Power Plant (OWPP) capacity and its distance from shore, with HVAC TS being the most common solution for distances lower than 100km;The Low Frequency AC (LFAC) technology can provide an attractive transmission solution for exporting power from vast and remote OWPPs within a distance range of 80-300km. The basic idea of the LFAC system is to use lower AC frequency to reduce the effective electrical length of the equivalent HVAC subsea cable, so that its transmission capacity is increased, and also to eliminate the need for bulk offshore HVDC platforms, so that the installation, operation and maintenance costs are decreased. Despite the theoretical advantages of LFAC, the related research and its previous application in the rail and oil industries, there is no prior operational experience in similar type and scale networks, increasing the uncertainty for investors regarding the LFAC compliance capability and technology readiness level for offshore transmission purposes.;The aim of this industrial PhD Thesis is to result in robust and feasible LFAC TS options that can be realised by common industry practices and comply with typical Transmission System Operator's (TSO) grid code requirements. The LFAC TS is designed as a combined offshore HVAC system utilising an onshore Back-to-Back Modular Multilevel Converter (BtB MMC) scheme for frequency conversion. Point-to-Point (PtP) and Multi-Terminal (MT) LFAC topologies are examined for various cable lengths to export the nominal capacity of the OWPPs or interconnect different OWFs and different grids through single-cable connections to minimise costs. The technical feasibility of the LFAC TS is assessed through comprehensive steady-state, frequency and time-domain studies to optimise the system performance, its transmission capability and identify probable limitations.;Initially, the main transmission equipment specifications are appropriately adapted and rated for LFAC operation. Frequency scan studies are performed to investigate the low-order resonances of the LFAC TS, and suitable C-Type harmonic filter combinations are introduced to avoid potential harmonic stability issues. Power-flow cases are studied to calibrate the operating conditions of the system (e.g. reactive power compensation, control strategies, etc.) and optimise the schemes in terms of power losses and shunt cable compensation, placed only at the onshore side. It is yielded that by utilising the AC voltage control strategy of the OWPP inverters together with the reactive power capability of the BtB MMCs can maximise the power transfer through the cables.;Finally, detailed EMT models of the optimised PtP and MT-LFAC TS are simulated to evaluate its dynamic performance, stability and FRT capability against faults in the offshore LFAC and AC sides. It is concluded that if the LFAC grid-forming MMC employs a typical islanded control scheme without Inner Current Controllers (ICCs), it should always use harmonic filtering to avoid low order harmonic stability issues caused by the system resonance. Even then, its FRT response against an LFAC side fault would be unacceptable, due to its unconstrained LFAC fault current. However, by implementing high-bandwidth ICCs with appropriate current saturation and integrator anti-windup mechanisms to the islanded-control system, the LFAC TS rides through faults successfully and complies with the respective typical TSO limits. Also, depending on the system rating, DBRs may need to be applied in the DC sides of the OWTGs and the onshore BtB frequency converters
Investigating the genome complexity of Streptomyces clavuligerus
Get PDFStreptomyces clavuligerus is the producer of clavulanic acid; a β-lactamase inhibitor that isused in combination with the antibiotic amoxicillin to treat many bacterial infections. The unique genome of S. clavuligerus includes a chromosome, and four linear plasmids pSCL1, pSCL2, pSCL3 and the megaplasmid pSCL4, which is the largest linear plasmid ever identified at 1.8 Mb in size. In order to study the genomic architecture of S. clavuligerus strains, we established an optimised method of pulsed-field gel electrophoresis, which allowed visualisation of the three giant linear plasmids pSCL2, pSCL3 and pSCL4, as well as chromosomal fragments in order to establish the physical map of the S. clavuligerus genome.;Furthermore, to establish a foundation on which the genomic analyses of industrial strains of this species could be carried out, we closed the genome sequence of the S. clavuligerus type strain DSM 738, using a combination of short-read Illumina sequencing and long-read PacBio technology. Additionally, the telomeres of the five replicons were purified by a self ligation method, and identification of the sequences confirmed that the five replicons carry archetypal telomeres, with the chromosome and megaplasmid sharing identical telomeric sequences. Streptomycetes telomeres are maintained by the terminal proteins Tap and Tpg, however, while copies of the genes encoding these proteins were identified in pSCL4, pSCL3 and pSCL2, the chromosome carries none, making these the only known essential elements missing from the chromosome.;Moreover, in order to investigate the essentiality of the megaplasmid in S. clavuligerus, we cured pSCL4 by targeting parB with CRISPR/Cas9. This caused deletion of the chromosomal ends and circularisation, confirming that pSCL4 Tap-Tpg are required for maintaining the chromosome telomeres, and cannot be complemented by the proteins encoded on the other two plasmids. In addition, pSCL4-free strains were confirmed to be non-sporulating as well as presenting a phenotype of short and thin hyphae, in addition to higher branching frequency. Some mutant strains also exhibited reduced clavulanic acid production which confirmed that the loss of pSCL4 has important effects onmorphological development and secondary metabolism of S. clavuligerus. Overall, with this study we have closed the genome sequence of S. clavuligerus type strain and optimised a method for rapid screening of the S. clavuligerus mutant strains that will greatly benefit the industry for development of production strains. Additionally, we have confirmed that pSCL4 is a dispensable plasmid, but is yet necessary for maintaining optimum fitness of this bacterium.Streptomyces clavuligerus is the producer of clavulanic acid; a β-lactamase inhibitor that isused in combination with the antibiotic amoxicillin to treat many bacterial infections. The unique genome of S. clavuligerus includes a chromosome, and four linear plasmids pSCL1, pSCL2, pSCL3 and the megaplasmid pSCL4, which is the largest linear plasmid ever identified at 1.8 Mb in size. In order to study the genomic architecture of S. clavuligerus strains, we established an optimised method of pulsed-field gel electrophoresis, which allowed visualisation of the three giant linear plasmids pSCL2, pSCL3 and pSCL4, as well as chromosomal fragments in order to establish the physical map of the S. clavuligerus genome.;Furthermore, to establish a foundation on which the genomic analyses of industrial strains of this species could be carried out, we closed the genome sequence of the S. clavuligerus type strain DSM 738, using a combination of short-read Illumina sequencing and long-read PacBio technology. Additionally, the telomeres of the five replicons were purified by a self ligation method, and identification of the sequences confirmed that the five replicons carry archetypal telomeres, with the chromosome and megaplasmid sharing identical telomeric sequences. Streptomycetes telomeres are maintained by the terminal proteins Tap and Tpg, however, while copies of the genes encoding these proteins were identified in pSCL4, pSCL3 and pSCL2, the chromosome carries none, making these the only known essential elements missing from the chromosome.;Moreover, in order to investigate the essentiality of the megaplasmid in S. clavuligerus, we cured pSCL4 by targeting parB with CRISPR/Cas9. This caused deletion of the chromosomal ends and circularisation, confirming that pSCL4 Tap-Tpg are required for maintaining the chromosome telomeres, and cannot be complemented by the proteins encoded on the other two plasmids. In addition, pSCL4-free strains were confirmed to be non-sporulating as well as presenting a phenotype of short and thin hyphae, in addition to higher branching frequency. Some mutant strains also exhibited reduced clavulanic acid production which confirmed that the loss of pSCL4 has important effects onmorphological development and secondary metabolism of S. clavuligerus. Overall, with this study we have closed the genome sequence of S. clavuligerus type strain and optimised a method for rapid screening of the S. clavuligerus mutant strains that will greatly benefit the industry for development of production strains. Additionally, we have confirmed that pSCL4 is a dispensable plasmid, but is yet necessary for maintaining optimum fitness of this bacterium
Architectures for securing low-cost IoT
No full textThis PhD study proposes various solutions to enable low-cost Internet of Things (IoT) devices to employ end-to-end encryption, with consideration to the financial and practical requirements of such devices. Manufacturers of IoT devices often sacrifice security in favour of features, user friendliness, time to market or cost, in order to stay ahead of their competitors. However, numerous recent hacks on IoT devices have shown this is unwise. Extremely low-cost, microcontroller-based devices, in particular struggle to create sufficient random data required for state-of-the-art security features. This is in stark contrast to common internet connected devices such as smartphones, and personal computers, which with their high-performance processors can generate sufficient randomness to implement state of the art security features. Through taking advantage of existing devices this PhD study enables these extremely low-cost devices implement state of the art security features. One such existing device is a smartphone which are abundant and have multiple sources of randomness for strong key generation. This abundance and power enables two discrete architectures to be proposed which offload key generation and transfer to the user's smartphone, removing the requirement for constrained IoT devices to participate in public key infrastructure. The first proposed architecture takes advantage of the ubiquity of Wi-Fi in consumer devices, and employs it as a key transfer mechanism. The design only requires a 1 general-purpose microcontroller and a Wi-Fi module. The performance of such an architecture was modelled, and a threat analysis conducted. The design allows all communication to and from the device to be encrypted, without any additional manufacturing cost or sacrificing user experience. Since the architecture does not require any additional hardware, it can be retroactively applied and deployed to existing devices through a firmware update. This architecture has been integrated into a smart light switch product. The second architecture targeted at increasingly popular low-power wide-area networks (LPWAN) technologies, such as LoRaWAN. Future utility networks will require much greater levels of machine to-machine interaction to enable smart grid applications, and ultimately increase the efficiency of the network. In response a low-cost LPWAN module was developed to be retrofitted to existing monitoring device, Fault Passage Indicators (FPI), creating an automatic remote detection and location system for medium voltage faults, reducing the time to find faults from hours to minutes. This prototype device was then tested on a physical 11kV overhead line network, where the device demonstrated it was robust and suitable for mass deployment on a live network. The finalised prototype module costs roughly 5% of a single FPI unit, making the solution cost effective. The system additionally features the ability to remotely reconfigure the FPI, making the installation and future maintenance more convenient. Two high costs in a full-scale LPWAN deployment are the cost of deployment and the potential cost of re-keying the compromised network. Therefore, this thesis also explores methods of decentralising sensor device deployment using commonly available hardware. It details a procedure which uses a smartphone's camera ash to transfer the necessary credentials to such low-cost sensor devices. As with the domestic Wi-Fi-based solution, smartphones were chosen as a transfer mechanism since they are both abundant and suitably powerful to generate random keys. Using smartphone's LED ash removes the need for a wired connection, a laptop, and programming software, allowing devices to be provisioned out in the _eld without the need for specialised tools or knowledge. An implementation with a Long Range Wide Area Network (LoRaWAN) device was created as this is a prime candidate given its requirement for cryptographic keys and lack of ability to partake in public key infrastructure. The solution allows non-specialists to securely program and re key devices without specialised tools. A security audit is then conducted on the system as a whole. The final part of the thesis considers the dependency IoT devices currently have on centralised architecture. This reliance has made numerous devices non-functional when their infrastructure ceased to operate. Recent research into the security of internet-connected consumer equipment has showed the extent to which many of these devices remain highly vulnerable to remote compromise. The Mirai botnet highlighted this risk of having large numbers of vulnerable devices, all connected to high-speed internet connections, capable of performing Distributed Denial of Service (DDoS) attacks. A distributed hash table (DHT) based architecture is proposed, where an intermediary device provides access control and secure remote access of IoT devices located in the home. This design removes the need for a centrally operated server and improves longevity. Software running the intermediary separates vulnerable IoT devices from the rest of the home network, and coordinates with the DHT to publish and listen for messages. An implementation of this system was created, and demonstrated that the network overhead would be minimal, and the system would be able to integrate with existing IoT ecosystems
An investigation of stock market volatility in Chinese stock markets and the effects of institutional investors
Get PDFThis thesis contributes to the literature on the investigation of stock market volatility in Chinese stock markets and the effects of institutional investors.;Chapter 2 focuses on the key characteristics of China's stock market that the volatility of stock returns tends to be greater, and to persist for longer, than is typical in 'western' markets. We provide persuasive arguments and evidence in support of the view that volatility persistence in part reflects the opacity of the information environment the majority of investors operate within. We go on to show that continuing reforms of state ownership and control, along with growth in the proportion of shares held by active institutional investors, look to be promising ways to mitigate the persistence in China's stock market volatility going forward.;Chapter 3 investigates the trading behaviour of institutional investors on extreme market movement days. Using daily cash flow data on the largest category of trades by value we construct a proxy for institutional trading and demonstrate that institutional trading behaviour consistently destabilizes both markets on extreme market movement days. We go on to highlight the conflating influence of regulator imposed daily limits to individual stocks' price movements. We conclude that binding price limits act to exacerbate the destabilising effects of institutional trading in Chinese stock markets.;Chapter 4 disaggregates the volatility of common stocks at the market, industry and firm levels by using daily stock return data of all listed firms in Chinese stock market. We find the time-series behaviour of idiosyncratic volatility in Chinese stock market is associated with large stock trading activities by institutional investors. Finally, we provide new evidence from industry-level study and show that much of the idiosyncratic volatility is concentrated in China's manufacturing industry, which is a leading indicator of the idiosyncratic volatility in other individual industries.This thesis contributes to the literature on the investigation of stock market volatility in Chinese stock markets and the effects of institutional investors.;Chapter 2 focuses on the key characteristics of China's stock market that the volatility of stock returns tends to be greater, and to persist for longer, than is typical in 'western' markets. We provide persuasive arguments and evidence in support of the view that volatility persistence in part reflects the opacity of the information environment the majority of investors operate within. We go on to show that continuing reforms of state ownership and control, along with growth in the proportion of shares held by active institutional investors, look to be promising ways to mitigate the persistence in China's stock market volatility going forward.;Chapter 3 investigates the trading behaviour of institutional investors on extreme market movement days. Using daily cash flow data on the largest category of trades by value we construct a proxy for institutional trading and demonstrate that institutional trading behaviour consistently destabilizes both markets on extreme market movement days. We go on to highlight the conflating influence of regulator imposed daily limits to individual stocks' price movements. We conclude that binding price limits act to exacerbate the destabilising effects of institutional trading in Chinese stock markets.;Chapter 4 disaggregates the volatility of common stocks at the market, industry and firm levels by using daily stock return data of all listed firms in Chinese stock market. We find the time-series behaviour of idiosyncratic volatility in Chinese stock market is associated with large stock trading activities by institutional investors. Finally, we provide new evidence from industry-level study and show that much of the idiosyncratic volatility is concentrated in China's manufacturing industry, which is a leading indicator of the idiosyncratic volatility in other individual industries
Investigation of focused Very High Energy Electrons (VHEEs) as a new radiotherapy method
No full textCurrently, external beam radiotherapy is faced with the challenge of delivering doses which exceed standard clinical fractions to target radioresistant tumours. However, any dose escalation in the tumour is limited by radiation tolerance of healthy tissues,including skin, which is among the most sensitive tissue. An improved efficiency can be accomplished at the cost of irreversible damage to these tissues. A similar problem is found when high doses are delivered to deep-seated tumours while trying to avoid intolerable doses in surrounding tissue.;This thesis investigates a new treatment modality that uses a single Very High Energy Electron (VHEE, 50 - 250 MeV) beams focused by a magnetic lens to create a high dose region in a small volume, which is referred to here as a volumetric element. This can be scanned over the radioresistant regions of a tumour at typical depths of deep-seated cancers. Monte Carlo simulations were performed to model irradiation of a tissue-equivalent phantom with focused VHEE beams. These are confirmed by an experimental investigation of this treatment method that was undertaken at the CLEAR user facility at CERN. The results show a significant enhancement of the target dose and a simultaneous reduction of the dose to surrounding healthy tissue.;The experimental part of this study required a new dosimetry protocol to be established for VHEEs. The energy dependence and dose response of radiochromic films up to 50 MeV were studied using the electron research accelerator at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig and the clinical accelerator at the National Physical Laboratory (NPL) in London. The response of radiochromic films in the VHEE range was cross-calibrated against alanine based secondary standard.Currently, external beam radiotherapy is faced with the challenge of delivering doses which exceed standard clinical fractions to target radioresistant tumours. However, any dose escalation in the tumour is limited by radiation tolerance of healthy tissues,including skin, which is among the most sensitive tissue. An improved efficiency can be accomplished at the cost of irreversible damage to these tissues. A similar problem is found when high doses are delivered to deep-seated tumours while trying to avoid intolerable doses in surrounding tissue.;This thesis investigates a new treatment modality that uses a single Very High Energy Electron (VHEE, 50 - 250 MeV) beams focused by a magnetic lens to create a high dose region in a small volume, which is referred to here as a volumetric element. This can be scanned over the radioresistant regions of a tumour at typical depths of deep-seated cancers. Monte Carlo simulations were performed to model irradiation of a tissue-equivalent phantom with focused VHEE beams. These are confirmed by an experimental investigation of this treatment method that was undertaken at the CLEAR user facility at CERN. The results show a significant enhancement of the target dose and a simultaneous reduction of the dose to surrounding healthy tissue.;The experimental part of this study required a new dosimetry protocol to be established for VHEEs. The energy dependence and dose response of radiochromic films up to 50 MeV were studied using the electron research accelerator at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig and the clinical accelerator at the National Physical Laboratory (NPL) in London. The response of radiochromic films in the VHEE range was cross-calibrated against alanine based secondary standard
Hybrid micro-LED devices enabled by elastomeric micro-transfer printing
No full textThe work presented in this thesis focuses on the development of hybrid micron-sized light emitting diode (micro-LED) devices by elastomeric micro-transfer printing. The main body of this work is divided into the development of dual-colour micro-LED devices and the integration of micro-LEDs with control electronics, mainly for optical communication and optogenetics applications.;Individually addressable III-nitride based blue-green and blue-violet micro-LED arrays and in-series connected blue-green micro-LED arrays were fabricated by microtransfer printing a blue micro-LED platelet onto to the substrate a pre-fabricated green (or violet) micro-LED. Gigabit per second (Gbps) error-free data rates in free-space visible light communication (VLC) and up to 200 Mbps in highly turbid underwater media have been demonstrated using these dual-colour arrays. Gbps VLC based on III-phosphide red micro-LEDs micro-transfer printed onto diamond and glass substrates is also presented.;Furthermore, the integration of III-phosphide red micro-LEDs onto a III-nitride based optrode for dual-colour excitation of different neural populations is also demonstrated. III-nitride based singulated micro-LEDs were directly integrated onto a silicon complementary metal oxide semiconductor (CMOS) drive chip containing a monolithic single photon avalanche diode detector, by elastomeric micro-transfer printing. An 8x8 array was realised with excellent uniformity both in brightness and modulation performance across the full array, which has led to a 128 kbps optical camera communication link, and to a time-of-flight ranging demonstration with cm-scale resolution.The work presented in this thesis focuses on the development of hybrid micron-sized light emitting diode (micro-LED) devices by elastomeric micro-transfer printing. The main body of this work is divided into the development of dual-colour micro-LED devices and the integration of micro-LEDs with control electronics, mainly for optical communication and optogenetics applications.;Individually addressable III-nitride based blue-green and blue-violet micro-LED arrays and in-series connected blue-green micro-LED arrays were fabricated by microtransfer printing a blue micro-LED platelet onto to the substrate a pre-fabricated green (or violet) micro-LED. Gigabit per second (Gbps) error-free data rates in free-space visible light communication (VLC) and up to 200 Mbps in highly turbid underwater media have been demonstrated using these dual-colour arrays. Gbps VLC based on III-phosphide red micro-LEDs micro-transfer printed onto diamond and glass substrates is also presented.;Furthermore, the integration of III-phosphide red micro-LEDs onto a III-nitride based optrode for dual-colour excitation of different neural populations is also demonstrated. III-nitride based singulated micro-LEDs were directly integrated onto a silicon complementary metal oxide semiconductor (CMOS) drive chip containing a monolithic single photon avalanche diode detector, by elastomeric micro-transfer printing. An 8x8 array was realised with excellent uniformity both in brightness and modulation performance across the full array, which has led to a 128 kbps optical camera communication link, and to a time-of-flight ranging demonstration with cm-scale resolution
Reliability-based optimization of floating wind turbine support structures
Get PDFFloating offshore wind technology has high potential due to the renewable energy goals and the vast deep water ocean areas, however, still faces several challenges until achieving commercial market uptake. Floating concepts have to gain economic competitiveness and deal with more complex coupled system dynamics and greater uncertainties. This makes modeling, simulation, and reliability-based design optimization indispensable. However, reliability assessment and design optimization of floating wind turbines has not yet been coupled. - This is precisely the focus of this thesis. The overall aim is to derive guidelines for reliability-based design optimization of floating wind turbine support structures, taking target safety levels and failure mechanisms from existing standards into account and applying them in such novel concepts. To achieve this, reliability methods applied in the offshore and marine renewable energy industry are reviewed, classified, and investigated with respect to suitable procedures for reliability assessment of offshore wind turbine systems. Addressing the aspect of floating wind, the large diversity of existing floating support structures is assessed, focusing on their suitability for offshore wind farm deployment. Based on this, a reference floating wind turbine system is defined, for which an aero-hydro-servo-elastic coupled model of dynamics is developed and verified. Additionally, a holistic framework for automated simulation and optimization is developed and applied to different design optimization tasks: based on global limit states, addressing innovative design solutions or the future trend towards larger MW-class wind turbines, and finally including reliability criteria. The developed model, framework, and approaches - especially the concept for combining floating wind turbine design optimization with reliability assessment in a computationally and time-efficient manner - are of high value for both research and industry. The knowledge and outcomes of this thesis offer a broad range of future applications and pave the way towards economic and reliable floating support structure designs.Floating offshore wind technology has high potential due to the renewable energy goals and the vast deep water ocean areas, however, still faces several challenges until achieving commercial market uptake. Floating concepts have to gain economic competitiveness and deal with more complex coupled system dynamics and greater uncertainties. This makes modeling, simulation, and reliability-based design optimization indispensable. However, reliability assessment and design optimization of floating wind turbines has not yet been coupled. - This is precisely the focus of this thesis. The overall aim is to derive guidelines for reliability-based design optimization of floating wind turbine support structures, taking target safety levels and failure mechanisms from existing standards into account and applying them in such novel concepts. To achieve this, reliability methods applied in the offshore and marine renewable energy industry are reviewed, classified, and investigated with respect to suitable procedures for reliability assessment of offshore wind turbine systems. Addressing the aspect of floating wind, the large diversity of existing floating support structures is assessed, focusing on their suitability for offshore wind farm deployment. Based on this, a reference floating wind turbine system is defined, for which an aero-hydro-servo-elastic coupled model of dynamics is developed and verified. Additionally, a holistic framework for automated simulation and optimization is developed and applied to different design optimization tasks: based on global limit states, addressing innovative design solutions or the future trend towards larger MW-class wind turbines, and finally including reliability criteria. The developed model, framework, and approaches - especially the concept for combining floating wind turbine design optimization with reliability assessment in a computationally and time-efficient manner - are of high value for both research and industry. The knowledge and outcomes of this thesis offer a broad range of future applications and pave the way towards economic and reliable floating support structure designs
Lynching and ladies in the American South, white women's complicity in white supremacy, racial violence, and suffrage from the progressive era to the great depression
No full textThis thesis explores the under examined area of white women who worked for white supremacy, by focusing on the period between the Progressive Era to the Great Depression in the American South. It examines white women's participation in two key areas, lynching and suffrage in order to argue that embracing white supremacy allowed white women firstly to become publicly empowered through their participation in lynching and the debate surrounding it, and secondly to become active in suffrage.Discourse on rape and racial violence became a way to discuss white women's rights and status in post-slavery South, which in turn evolved into discussions on suffrage.Overall this thesis, by examining both of themes, argues that white women were complicit and key in maintaining white supremacy, and that they used it to their ownadvantage as a group to be embraced into public life in the South.This thesis explores the under examined area of white women who worked for white supremacy, by focusing on the period between the Progressive Era to the Great Depression in the American South. It examines white women's participation in two key areas, lynching and suffrage in order to argue that embracing white supremacy allowed white women firstly to become publicly empowered through their participation in lynching and the debate surrounding it, and secondly to become active in suffrage.Discourse on rape and racial violence became a way to discuss white women's rights and status in post-slavery South, which in turn evolved into discussions on suffrage.Overall this thesis, by examining both of themes, argues that white women were complicit and key in maintaining white supremacy, and that they used it to their ownadvantage as a group to be embraced into public life in the South
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