7103 research outputs found
Sort by
On the financialisation of commodity markets
Get PDFAs they progressively emerged out of organised forward markets in staple commodities, commodity futures markets came together to address the needs of expert professionals. They are the place where the interests of commercial participants with concerns related to underlying physical commodities meet those of expert speculation; in other words, their essence originally lives in enabling commodity specialists to actively serve their needs. In the early 2000s however, a different type of less informed participation substantially expanded: institutional money entered these markets en masse with abnormally large investments. Participants behind this influx were typically no experts in commodity matters and sought exposures in sharp contrast with those typically assumed by traditional legacy participants. This phenomenon, commonly referred to as “financialisation” had ontological consequences for the commodity futures markets and its impact has been at the centre of heated debates in the policy, legislative, and regulatory spheres as well as in the academic literature. In this collection of studies, we strive to shed new lights on this phenomenon. In the first chapter we explore the issue of co-movement in financialised commodities and our results show that the metals sector was particularly affected.These findings are confirmed in the second chapter where we study the impact of financialisation from a macro viewpoint and our results further put forth the corporate sector as a potential transmission channel to the real economy. The breakdown of the financial crisis of 2008 tempered the commodity investment momentum and was followed by a series of extraordinary accommodative monetary regimes implemented by the US Federal Reserve. In our third chapter we study the financialisation process in this context and our results suggest that the crisis and its unorthodox monetary aftermath seem to have originated a process of definancialisation in the commodity complex.As they progressively emerged out of organised forward markets in staple commodities, commodity futures markets came together to address the needs of expert professionals. They are the place where the interests of commercial participants with concerns related to underlying physical commodities meet those of expert speculation; in other words, their essence originally lives in enabling commodity specialists to actively serve their needs. In the early 2000s however, a different type of less informed participation substantially expanded: institutional money entered these markets en masse with abnormally large investments. Participants behind this influx were typically no experts in commodity matters and sought exposures in sharp contrast with those typically assumed by traditional legacy participants. This phenomenon, commonly referred to as “financialisation” had ontological consequences for the commodity futures markets and its impact has been at the centre of heated debates in the policy, legislative, and regulatory spheres as well as in the academic literature. In this collection of studies, we strive to shed new lights on this phenomenon. In the first chapter we explore the issue of co-movement in financialised commodities and our results show that the metals sector was particularly affected.These findings are confirmed in the second chapter where we study the impact of financialisation from a macro viewpoint and our results further put forth the corporate sector as a potential transmission channel to the real economy. The breakdown of the financial crisis of 2008 tempered the commodity investment momentum and was followed by a series of extraordinary accommodative monetary regimes implemented by the US Federal Reserve. In our third chapter we study the financialisation process in this context and our results suggest that the crisis and its unorthodox monetary aftermath seem to have originated a process of definancialisation in the commodity complex
Design and engineering of myoglobin-based biocatalysts for controlled radical polymerisations
No full textThis thesis was previously held under moratorium from 1st February 2022 until 1st February 2023.Atom transfer radical polymerisation (ATRP) has attracted a lot of attentions since it was invented decades ago. Nowadays, it has been developed into the most efficient approach to synthesise the well-defined polymers. However, like other metal catalysis reactions, the metal contamination in polymer products and environment should be addressed. Our group has successfully applied several metalloenzymes to catalyse ATRP polymerisation. As an alternative solution, it not only greatly reduced the relative contamination, but also offered other potential benefits, such as selectivity. In this presented research project, myoglobin (Mb) has been discovered to catalyse ATRP polymerisations. To continue to liberate the enzyme’s power and increase the degree of control during the polymerisation, an engineering strategy has been designed based on the specific features of Mb. In conventional ATRP, the metal-ligand complex is the catalyst. Different species of metal and their ligands have a significant impact on polymerisation. Inspired by this, the cofactor of Mb could be replaced with a panel of artificial cofactors. By screening these Mb variants on bioATRP, the relationshipbetween metal ions, cofactor base and their performance in polymerisation might be found. This part of fundamental work would be useful to upgrade the current bioATRP system. As an ATRPase, the protein scaffold of Mb is not only a ‘cage’ to hold itscofactor, but also an extra element to introduce regulation and selectivity in polymerisations. During the reaction, the initiation and propagation happen in the active centre wrapped by protein scaffold. Thus, additional modifications on the key residues of the protein scaffold would be possible to create a suitable microenvironment for the initiator to attach and react with the metal centre. Ideally, this approach could improve the efficiency of initiation and propagation, leading to an enhanced degree of control of polymerisation Five Mb variants were identified with ATRPase functionality. Chlorin e6 (Ce6) was more supportive compared to native protoporphyrin as four variants werebased on Ce6 cofactor, including CuCe6-Mb. As a side project, the peroxidaseactivity of Mb variants was also investigated, FeCe6-Mb and MnCe6-Mb werecharacterised to have higher catalytic efficiency on guaiacol and TCP oxidisingreactions in comparison with wild-type Mb. A scoring system was developed for the screening of Mb mutants in bioATRP. As a result, four single mutants were characterised with first order reaction kinetics and improved degree of control of polymerisation. Double mutants and the final triple mutant were screened and some of the effects from single mutant were well maintained in them. As the first project exploring engineering of the biocatalyst in bioATRP, the outcomes essentially achieved the research aim. Modifications on metal centre and its surrounding environment have been shown to be effective in optimising controlled polymerisations. The lessons learned from the current study provided us inspiration to perfect the bioATRP system. It would also bebeneficial for researchers working in other areas of chemical biology, such asmetal-mediated catalysis and radical-mediated modifications on biomolecules.Atom transfer radical polymerisation (ATRP) has attracted a lot of attentions since it was invented decades ago. Nowadays, it has been developed into the most efficient approach to synthesise the well-defined polymers. However, like other metal catalysis reactions, the metal contamination in polymer products and environment should be addressed. Our group has successfully applied several metalloenzymes to catalyse ATRP polymerisation. As an alternative solution, it not only greatly reduced the relative contamination, but also offered other potential benefits, such as selectivity. In this presented research project, myoglobin (Mb) has been discovered to catalyse ATRP polymerisations. To continue to liberate the enzyme’s power and increase the degree of control during the polymerisation, an engineering strategy has been designed based on the specific features of Mb. In conventional ATRP, the metal-ligand complex is the catalyst. Different species of metal and their ligands have a significant impact on polymerisation. Inspired by this, the cofactor of Mb could be replaced with a panel of artificial cofactors. By screening these Mb variants on bioATRP, the relationshipbetween metal ions, cofactor base and their performance in polymerisation might be found. This part of fundamental work would be useful to upgrade the current bioATRP system. As an ATRPase, the protein scaffold of Mb is not only a ‘cage’ to hold itscofactor, but also an extra element to introduce regulation and selectivity in polymerisations. During the reaction, the initiation and propagation happen in the active centre wrapped by protein scaffold. Thus, additional modifications on the key residues of the protein scaffold would be possible to create a suitable microenvironment for the initiator to attach and react with the metal centre. Ideally, this approach could improve the efficiency of initiation and propagation, leading to an enhanced degree of control of polymerisation Five Mb variants were identified with ATRPase functionality. Chlorin e6 (Ce6) was more supportive compared to native protoporphyrin as four variants werebased on Ce6 cofactor, including CuCe6-Mb. As a side project, the peroxidaseactivity of Mb variants was also investigated, FeCe6-Mb and MnCe6-Mb werecharacterised to have higher catalytic efficiency on guaiacol and TCP oxidisingreactions in comparison with wild-type Mb. A scoring system was developed for the screening of Mb mutants in bioATRP. As a result, four single mutants were characterised with first order reaction kinetics and improved degree of control of polymerisation. Double mutants and the final triple mutant were screened and some of the effects from single mutant were well maintained in them. As the first project exploring engineering of the biocatalyst in bioATRP, the outcomes essentially achieved the research aim. Modifications on metal centre and its surrounding environment have been shown to be effective in optimising controlled polymerisations. The lessons learned from the current study provided us inspiration to perfect the bioATRP system. It would also bebeneficial for researchers working in other areas of chemical biology, such asmetal-mediated catalysis and radical-mediated modifications on biomolecules
Norway lobster and Hematodinium sp. in the Clyde, modelling the population dynamics of a commercially important host-parasite system
Get PDFThe Norway lobster, Nephrops norvegicus, also commonly known as the Dublin Bay prawn, langoustine or scampi, is a burrow-dwelling crustacean abundant in muddy areas across the North-East Atlantic. The species has a high commercial value for human consumption. Trawl and creel fisheries for Nephrops are among the most valuable in the UK, especially in Scotland. The Clyde Sea Area, on the west coast of Scotland, supports a particularly productive Nephrops fishery. In recent years, over 5000 tonnes of Nephrops have been landed annually in this region. However, Nephrops in the Clyde Sea Area carry a particularly high prevalence of a parasitic dinoflagellate species (Hematodinium sp.).This parasite causes drastic changes in the organs, tissues and haemolymph of infected individuals and is ultimately fatal. The overall meat quality of infected animals is also significantly reduced which leads to a drop in commercial value. Understanding the dynamics of the host-parasite relationship between Nephrops and Hematodinium and how this may change over time is therefore important for assessing the economic potential of Nephrops fisheries in the Clyde Sea Area. This thesis describes the development of a Nephrops-Hematodinium population model which simulates the coupled dynamics of Nephrops and Hematodinium in the Clyde Sea Area.;This includes a representation of harvesting by fisheries. The model involves a dynamic energy budget approach to modelling the moult cycle of Nephrops, embedded in an Escalator-Box-Car type representation of the development of annual cohorts of individuals. Resolving the moult cycle is critical since the life-cycle of the parasite is synchronised with moulting. Nephrops are vulnerable to infection by Hematodinium spores immediately following a moult event whilst their shell is still in a soft, post-moult condition. Furthermore, the Nephrops moult hormone, methyl farnesoate, is thought to cause Hematodinium to switch from the growth phase into the spore production phase. This ultimately leads to the mass release of parasitic spores which in turn leads to the death of the infected host. Observational detection of Hematodinium in sampled Nephrops is a complex process. Visual effects of infection only manifest once the host is heavily-infected. In the early stages of infection, molecular and immunological tests are required to detect the parasite. The Nephrops-Hematodinium population model is designed to mimic the detection thresholds for the various tests, so that the model can be directly tested against field data on Hematodinium prevalence collected by field surveys. Analysis of the performance of the Nephrops-Hematodinium population model relative to observational data leads to a paradigm-shift regarding understanding of the parasite lifecycle within the host. The existing assumption that infection to sporulation must occur within a single year is shown to be unsustainable. The parasite life-cycle can take up to 2 years or more, depending on the moulting rate of the host - which in turn depends on its size at infection. Inter-moult intervals increase with size, but follow different schedules for males and females. As a result, Hematodinium prevalence is strongly dependent on size and sex, with females and smaller individuals more vulnerable to infection. This is an emergent property of the Nephrops-Hematodinium population model and is also replicated in field observations.;As a corollary of this, population-level prevalence estimates obtained from the various diagnostic tests are dependent on the size-selectivity of fishing gears used to sample animals in the field. Furthermore, the Nephrops-Hematodinium population model is also used to conduct scenario experiments on the effects of parasite prevalence for fishery yields. The presence of the parasite in the Clyde Sea Area was estimated to cause a 10-15% reduction in potential yields. In the actual fishery, visually infected animals are typically discarded at sea since they detract from the value of the catch. However, it is estimated that a proportion of these survive and go on to release spores and perpetuate the infection. The Nephrops-Hematodinium population model was used to assess the consequences of ceasing this discarding practice and instead bringing infected animals ashore for disposal. The results showed that this operation change could lead to a small reduction in overall prevalence alongside a small increase in yield. Supporting investigations in this thesis include the development of a new method for predicting suitable Nephrops habitat in the Clyde Sea Area. Larval-transport connectivity between patches of suitable sediment is investigated using particle tracking methodology, driven by output from a high resolution hydrodynamic model of the region. The results show a high rate of larval retention from patches in the northern regions of the Firth of Clyde. Patches of suitable sediment in the southern regions of the Firth of Clyde, on the other hand, were found to export a greater proportion of larvae, with some larvae from this region settling on suitable sediment in the Sound of Jura. These results provide a basis for a future implementation of the Nephrops-Hematodinium population model in spatially discrete patches, interconnected by the larval transport simulations.The Norway lobster, Nephrops norvegicus, also commonly known as the Dublin Bay prawn, langoustine or scampi, is a burrow-dwelling crustacean abundant in muddy areas across the North-East Atlantic. The species has a high commercial value for human consumption. Trawl and creel fisheries for Nephrops are among the most valuable in the UK, especially in Scotland. The Clyde Sea Area, on the west coast of Scotland, supports a particularly productive Nephrops fishery. In recent years, over 5000 tonnes of Nephrops have been landed annually in this region. However, Nephrops in the Clyde Sea Area carry a particularly high prevalence of a parasitic dinoflagellate species (Hematodinium sp.).This parasite causes drastic changes in the organs, tissues and haemolymph of infected individuals and is ultimately fatal. The overall meat quality of infected animals is also significantly reduced which leads to a drop in commercial value. Understanding the dynamics of the host-parasite relationship between Nephrops and Hematodinium and how this may change over time is therefore important for assessing the economic potential of Nephrops fisheries in the Clyde Sea Area. This thesis describes the development of a Nephrops-Hematodinium population model which simulates the coupled dynamics of Nephrops and Hematodinium in the Clyde Sea Area.;This includes a representation of harvesting by fisheries. The model involves a dynamic energy budget approach to modelling the moult cycle of Nephrops, embedded in an Escalator-Box-Car type representation of the development of annual cohorts of individuals. Resolving the moult cycle is critical since the life-cycle of the parasite is synchronised with moulting. Nephrops are vulnerable to infection by Hematodinium spores immediately following a moult event whilst their shell is still in a soft, post-moult condition. Furthermore, the Nephrops moult hormone, methyl farnesoate, is thought to cause Hematodinium to switch from the growth phase into the spore production phase. This ultimately leads to the mass release of parasitic spores which in turn leads to the death of the infected host. Observational detection of Hematodinium in sampled Nephrops is a complex process. Visual effects of infection only manifest once the host is heavily-infected. In the early stages of infection, molecular and immunological tests are required to detect the parasite. The Nephrops-Hematodinium population model is designed to mimic the detection thresholds for the various tests, so that the model can be directly tested against field data on Hematodinium prevalence collected by field surveys. Analysis of the performance of the Nephrops-Hematodinium population model relative to observational data leads to a paradigm-shift regarding understanding of the parasite lifecycle within the host. The existing assumption that infection to sporulation must occur within a single year is shown to be unsustainable. The parasite life-cycle can take up to 2 years or more, depending on the moulting rate of the host - which in turn depends on its size at infection. Inter-moult intervals increase with size, but follow different schedules for males and females. As a result, Hematodinium prevalence is strongly dependent on size and sex, with females and smaller individuals more vulnerable to infection. This is an emergent property of the Nephrops-Hematodinium population model and is also replicated in field observations.;As a corollary of this, population-level prevalence estimates obtained from the various diagnostic tests are dependent on the size-selectivity of fishing gears used to sample animals in the field. Furthermore, the Nephrops-Hematodinium population model is also used to conduct scenario experiments on the effects of parasite prevalence for fishery yields. The presence of the parasite in the Clyde Sea Area was estimated to cause a 10-15% reduction in potential yields. In the actual fishery, visually infected animals are typically discarded at sea since they detract from the value of the catch. However, it is estimated that a proportion of these survive and go on to release spores and perpetuate the infection. The Nephrops-Hematodinium population model was used to assess the consequences of ceasing this discarding practice and instead bringing infected animals ashore for disposal. The results showed that this operation change could lead to a small reduction in overall prevalence alongside a small increase in yield. Supporting investigations in this thesis include the development of a new method for predicting suitable Nephrops habitat in the Clyde Sea Area. Larval-transport connectivity between patches of suitable sediment is investigated using particle tracking methodology, driven by output from a high resolution hydrodynamic model of the region. The results show a high rate of larval retention from patches in the northern regions of the Firth of Clyde. Patches of suitable sediment in the southern regions of the Firth of Clyde, on the other hand, were found to export a greater proportion of larvae, with some larvae from this region settling on suitable sediment in the Sound of Jura. These results provide a basis for a future implementation of the Nephrops-Hematodinium population model in spatially discrete patches, interconnected by the larval transport simulations
The urban atlas, methodological foundation of a morphometric taxonomy of urban form
No full textNo two cities in the world are alike. Each urban environment is characterised by a unique variety and heterogeneity as a result of its evolution and transformation, reflecting the differences in needs human populations have had over time manifested, in space, by a plethora of urban patterns.;Traditionally, the study of these patterns over time and across space is the domain of urban morphology, a field of research stretching from geography to architecture. Whilst urban morphology has considerably advanced the current understanding of processes of formation, transformation and differentiation of many such patterns, predominantly through qualitative approaches, it has yet to fully take advantage of quantitative approaches and data-driven methods recently made possible by advances in geographic data science and expansion of available mapping products.;Although relatively new, these methods hold immense potential in expanding our capacity to identify, characterise and compare urban patterns: these can be rich in terms of information, scalable (applicable to the large scale of extent, regional and national) and replicable, drastically improving the potential of comparative analysis and classification.;Different disciplines with more profound quantitative methods can help in the development of data-driven urban morphology, as now, for the first time, we are in the position where we can rely on a large amount of data on the built environment, unthinkable just a decade ago. This thesis, therefore, aims to link urban morphology and methodologically strong area of quantitative biological systematics, adapting its concepts and methods to the context of built-up fabric. That creates an infrastructure for numerical description of urban form, known as urban morphometrics, and a subsequent classification of urban types.;Conceptually building on the theory of numerical taxonomy, this research progresses the development of urban morphometrics to automate processes of urban form characterisation and classification. Whilst many available methods are characterised by significant limitation in applicability due to difficulties in obtaining necessary data, the proposed method employs only minimal data input - street network and building footprints - and overcomes limitations in the delineation of plots by identifying an alternative spatial unit of analysis, the morphological tessellation, a derivative of Voronoi tessellation partitioning the space based on a composition of building footprints.;As tessellation covers the entirety of urban space, its inherent contiguity then constitutes a basis of a relational framework aimed at the comprehensive characterisation of individual elements of urban form and their relationships. Resulting abundant numerical description of all features is further utilised in cluster analysis delineating urban tissue types in an unrestricted urban fabric, shaping an input for hierarchical classification of urban form - a taxonomy.;The proposed method is applied to the historical heterogeneous city of Prague, Czechia and validated using supplementary non-morphological data reflecting the variation of built-up patterns. Furthermore, its cross-cultural and morphological validity and expandability are tested by assessment of Amsterdam, Netherlands and a combination of both cases into a unified taxonomy of their urban patterns. The research is accompanied by a bespoke open-source software momepy for quantitative assessment of urban form, providing infrastructure for replicability and further community-led development.;The work builds a basis for morphometric research of urban environment, providing operational tools and frameworks for its application and further development, eventually leading to a coherent taxonomy of urban form.No two cities in the world are alike. Each urban environment is characterised by a unique variety and heterogeneity as a result of its evolution and transformation, reflecting the differences in needs human populations have had over time manifested, in space, by a plethora of urban patterns.;Traditionally, the study of these patterns over time and across space is the domain of urban morphology, a field of research stretching from geography to architecture. Whilst urban morphology has considerably advanced the current understanding of processes of formation, transformation and differentiation of many such patterns, predominantly through qualitative approaches, it has yet to fully take advantage of quantitative approaches and data-driven methods recently made possible by advances in geographic data science and expansion of available mapping products.;Although relatively new, these methods hold immense potential in expanding our capacity to identify, characterise and compare urban patterns: these can be rich in terms of information, scalable (applicable to the large scale of extent, regional and national) and replicable, drastically improving the potential of comparative analysis and classification.;Different disciplines with more profound quantitative methods can help in the development of data-driven urban morphology, as now, for the first time, we are in the position where we can rely on a large amount of data on the built environment, unthinkable just a decade ago. This thesis, therefore, aims to link urban morphology and methodologically strong area of quantitative biological systematics, adapting its concepts and methods to the context of built-up fabric. That creates an infrastructure for numerical description of urban form, known as urban morphometrics, and a subsequent classification of urban types.;Conceptually building on the theory of numerical taxonomy, this research progresses the development of urban morphometrics to automate processes of urban form characterisation and classification. Whilst many available methods are characterised by significant limitation in applicability due to difficulties in obtaining necessary data, the proposed method employs only minimal data input - street network and building footprints - and overcomes limitations in the delineation of plots by identifying an alternative spatial unit of analysis, the morphological tessellation, a derivative of Voronoi tessellation partitioning the space based on a composition of building footprints.;As tessellation covers the entirety of urban space, its inherent contiguity then constitutes a basis of a relational framework aimed at the comprehensive characterisation of individual elements of urban form and their relationships. Resulting abundant numerical description of all features is further utilised in cluster analysis delineating urban tissue types in an unrestricted urban fabric, shaping an input for hierarchical classification of urban form - a taxonomy.;The proposed method is applied to the historical heterogeneous city of Prague, Czechia and validated using supplementary non-morphological data reflecting the variation of built-up patterns. Furthermore, its cross-cultural and morphological validity and expandability are tested by assessment of Amsterdam, Netherlands and a combination of both cases into a unified taxonomy of their urban patterns. The research is accompanied by a bespoke open-source software momepy for quantitative assessment of urban form, providing infrastructure for replicability and further community-led development.;The work builds a basis for morphometric research of urban environment, providing operational tools and frameworks for its application and further development, eventually leading to a coherent taxonomy of urban form
Enhanced active power control of photovotaic systems
Get PDFThe share of electrical power generation from renewable energy sources is increasing and is expected to keep on increasing as various countries intensify their efforts to reduce CO2 emissions. Differences in the nature and characteristics of some renewable generation affect the ability of power systems to maintain frequency stability. This is because some renewable generation sources do not have inertia or are converter connected and decoupled from grid frequency. Solar Photovoltaic system do not have any stored inertia and usually operate at maximum power. There is need for control method for solar PV systems to contribute to frequency stability. This thesis proposes operation methodologies for photovoltaic (PV) systems to carry out active power control functions - including frequency control and proposes a framework for comparing frequency support ability of different generation sources. First, a modification to the conventional Perturb and Observe (P&O) maximum power point tracking (MPPT) algorithm is proposed to avoid leftward and rightward from maximum power. Results presented show that PV systems employing P&O with the proposed modification avoid both leftward and rightward drift when subjected to rapidly increasing irradiance, sinusoidal irradiance, and real irradiance. This drift-free P&O enables the PV system to participate in active power control function at rapidly increasing irradiance. An offline MPPT that uses the characteristics of PV modules to determine the maximum power point offline and reduce online computation is proposed for frequency support. Two methods for achieving de-loaded operation of a PV system using the offline MPPT are presented and compared for accuracy. The ability of offline MPPT and the P&O with proposed modification to maintain a power reserve under different irradiance conditions are compared. Second, this thesis examines the ability of a PV system to contribute to frequency support. Different methods for frequency support from a PV power plant under different penetration levels are examined. Results show with the appropriate amount of reserve and support parameters, PV systems can contribute to frequency support. The results also show that PV power plants with the proper support parameters can adequately compensate for the loss of inertia with regards to its effect on the nadir of frequency response. A variable droop control method for frequency support is proposed to reduce the amount of reserve required for frequency support. The effect of MPPT choice on frequency support is evaluated by comparing responses from PV systems with the offline MPPT, P&O with proposed modification, and the constant voltage MPPT. Lastly, this thesis proposes a framework for comparing the frequency support ability of different generating units based on their response speed and support parameters. Different response speeds are emulated by changing one the time constant of a Second-order system. The effect of response speed, support method, and support parameters on the nadir of frequency response and maximum power increase are evaluated for different response speeds. A method for comparing support ability by considering the economic cost and benefit for support is also presented.The share of electrical power generation from renewable energy sources is increasing and is expected to keep on increasing as various countries intensify their efforts to reduce CO2 emissions. Differences in the nature and characteristics of some renewable generation affect the ability of power systems to maintain frequency stability. This is because some renewable generation sources do not have inertia or are converter connected and decoupled from grid frequency. Solar Photovoltaic system do not have any stored inertia and usually operate at maximum power. There is need for control method for solar PV systems to contribute to frequency stability. This thesis proposes operation methodologies for photovoltaic (PV) systems to carry out active power control functions - including frequency control and proposes a framework for comparing frequency support ability of different generation sources. First, a modification to the conventional Perturb and Observe (P&O) maximum power point tracking (MPPT) algorithm is proposed to avoid leftward and rightward from maximum power. Results presented show that PV systems employing P&O with the proposed modification avoid both leftward and rightward drift when subjected to rapidly increasing irradiance, sinusoidal irradiance, and real irradiance. This drift-free P&O enables the PV system to participate in active power control function at rapidly increasing irradiance. An offline MPPT that uses the characteristics of PV modules to determine the maximum power point offline and reduce online computation is proposed for frequency support. Two methods for achieving de-loaded operation of a PV system using the offline MPPT are presented and compared for accuracy. The ability of offline MPPT and the P&O with proposed modification to maintain a power reserve under different irradiance conditions are compared. Second, this thesis examines the ability of a PV system to contribute to frequency support. Different methods for frequency support from a PV power plant under different penetration levels are examined. Results show with the appropriate amount of reserve and support parameters, PV systems can contribute to frequency support. The results also show that PV power plants with the proper support parameters can adequately compensate for the loss of inertia with regards to its effect on the nadir of frequency response. A variable droop control method for frequency support is proposed to reduce the amount of reserve required for frequency support. The effect of MPPT choice on frequency support is evaluated by comparing responses from PV systems with the offline MPPT, P&O with proposed modification, and the constant voltage MPPT. Lastly, this thesis proposes a framework for comparing the frequency support ability of different generating units based on their response speed and support parameters. Different response speeds are emulated by changing one the time constant of a Second-order system. The effect of response speed, support method, and support parameters on the nadir of frequency response and maximum power increase are evaluated for different response speeds. A method for comparing support ability by considering the economic cost and benefit for support is also presented
Development of feature extraction algorithms for real-time brain computer interface
Get PDFBrain-computer interface (BCI) research is a multidisciplinary field of biomedical engineering that incorporates information from neuroscience, computer engineering, and electrical engineering. A BCI attempts to decode the brain’s electrical activity to comprehend the neural system’s function and transform it into outputs that augment, replace, repair, or improve human activities. The primary focus of BCI research is on creating robust, dependable, and user-friendly real-time systems. One of the most challenging aspects of developing real-time BCI is minimising the delay introduced by processing pipelines, which often decreases a system’s computing performance. The thesis focuses on developing a real-time BCI signal processing method, particularly on the acceleration of the feature extraction phase. The purpose of the study is three-fold: a) to evaluate a feature extraction method that could be potential for real-time BCIs b) to modify the existing feature extraction algorithms in order to support real-time processing using different accelerating techniques c) to demonstrate the use of modified algorithms for real-time BCI applications. The first study examined potential methods for real-time BCI feature extraction using a publicly available EEG data set. The findings established a difference between time and frequency domain techniques for a BCI with two classes of motor imaginary. Furthermore, the key findings show that although varying feature extraction methods did not result in a significant increase in classification accuracy, they did result in a considerable decrease in computation time. An additional examination is parallel computing to address the remaining complexity issues in the selected feature extraction methods. As a result, boosting computing time using a parallel processing technique is theoretically possible and flexible enough for real-time processing. However, in order to further reduce system latency, both hardware and software must be optimised when utilised in a real-time environment. Additionally to the assessment findings, the discrete Fourier transform technique offered comparable classification accuracy but was computationally costly. This almost eliminates the possibility of processing in real time. Another study solved this problem by proposing a new technique known as the “enhanced sliding discrete Fourier transform (eSDFT).” The eSDFT method is optimal for processing time varying physiological data in real-time or near-real-time. The computational complexity analysis revealed that the proposed approach outperformed the traditional method. Furthermore, the suggested approach can be utilised for large-scale, real-time signal processing that uses a distributed computing infrastructure comprised of many compute units. Apart from the Fourier transform-based feature extraction method, a straightforward Fourier transform cannot be used effectively for BCI processing because of the high temporal resolution of EEG signals, which often results in the loss of time information. Hence, the discrete wavelet transform (DWT) was selected to study, as it operates in both the time and frequency domains. This study examined the feasibility of creating a parallel computing approach for extracting time-frequency domain characteristics. A modification of the DWT method has been proposed to enable parallel computing. The results show how effective hardware acceleration is in handling enormous computational demands. The suggested processing technique maybe utilised to speed up any signal processing methodology. The last study shows how to handle real-time signal processing using recursive approaches and parallel computing technologies. On a sliding window basis, the first and second generations of DWT algorithms were chosen for research. A variation of the conventional DWT method has been suggested to minimise duplication in the computation of coefficients. The findings indicate that the recursive approach has the shortest runtime and the most outstanding speedup ratio for all input lengths. Additionally, the proposed technique may be used for a wide variety of wavelet functions without degrading performance.Brain-computer interface (BCI) research is a multidisciplinary field of biomedical engineering that incorporates information from neuroscience, computer engineering, and electrical engineering. A BCI attempts to decode the brain’s electrical activity to comprehend the neural system’s function and transform it into outputs that augment, replace, repair, or improve human activities. The primary focus of BCI research is on creating robust, dependable, and user-friendly real-time systems. One of the most challenging aspects of developing real-time BCI is minimising the delay introduced by processing pipelines, which often decreases a system’s computing performance. The thesis focuses on developing a real-time BCI signal processing method, particularly on the acceleration of the feature extraction phase. The purpose of the study is three-fold: a) to evaluate a feature extraction method that could be potential for real-time BCIs b) to modify the existing feature extraction algorithms in order to support real-time processing using different accelerating techniques c) to demonstrate the use of modified algorithms for real-time BCI applications. The first study examined potential methods for real-time BCI feature extraction using a publicly available EEG data set. The findings established a difference between time and frequency domain techniques for a BCI with two classes of motor imaginary. Furthermore, the key findings show that although varying feature extraction methods did not result in a significant increase in classification accuracy, they did result in a considerable decrease in computation time. An additional examination is parallel computing to address the remaining complexity issues in the selected feature extraction methods. As a result, boosting computing time using a parallel processing technique is theoretically possible and flexible enough for real-time processing. However, in order to further reduce system latency, both hardware and software must be optimised when utilised in a real-time environment. Additionally to the assessment findings, the discrete Fourier transform technique offered comparable classification accuracy but was computationally costly. This almost eliminates the possibility of processing in real time. Another study solved this problem by proposing a new technique known as the “enhanced sliding discrete Fourier transform (eSDFT).” The eSDFT method is optimal for processing time varying physiological data in real-time or near-real-time. The computational complexity analysis revealed that the proposed approach outperformed the traditional method. Furthermore, the suggested approach can be utilised for large-scale, real-time signal processing that uses a distributed computing infrastructure comprised of many compute units. Apart from the Fourier transform-based feature extraction method, a straightforward Fourier transform cannot be used effectively for BCI processing because of the high temporal resolution of EEG signals, which often results in the loss of time information. Hence, the discrete wavelet transform (DWT) was selected to study, as it operates in both the time and frequency domains. This study examined the feasibility of creating a parallel computing approach for extracting time-frequency domain characteristics. A modification of the DWT method has been proposed to enable parallel computing. The results show how effective hardware acceleration is in handling enormous computational demands. The suggested processing technique maybe utilised to speed up any signal processing methodology. The last study shows how to handle real-time signal processing using recursive approaches and parallel computing technologies. On a sliding window basis, the first and second generations of DWT algorithms were chosen for research. A variation of the conventional DWT method has been suggested to minimise duplication in the computation of coefficients. The findings indicate that the recursive approach has the shortest runtime and the most outstanding speedup ratio for all input lengths. Additionally, the proposed technique may be used for a wide variety of wavelet functions without degrading performance
Identity and the multi-levelled structure of disadvantage among Chinese female migrant entrepreneurs in Scotland
Get PDFIssues surrounding diversity and entrepreneurship have received much interest in research and public policy over the last couple of decades. This thesis aims to contribute to this body of work by studying Chinese female migrant entrepreneurs (CFMEs)’s and how with their multiple identities cope with barriers faced in both their business and family contexts. This thesis used grounded theory to investigate CFMEs’ experience by unpacking the multiple layers of disadvantage they contend with. First, the micro-level explores the patriarchal culture in Chinese families and households and its implications for female entrepreneurs. Second, themeso-level evaluates how CFMEs cope with limited access to resources for their business as well as unfair treatment in the community. Lastly, our analysis of how CFMEs experience the macro-level assesses whether it is challenging for CFMEs to integrate into local business networks. This research followed the interpretive method to explore Chinese female migrant entrepreneurs’ experience between business and family multiple identities. Seventeen interviews were conducted to analyse the participants’ narrative. Data was systematically accumulated through an inductive approach to ensure accuracy. Overall, the contributions are developed in three aspects. First, it makes a theoretical contribution to entrepreneurship and identities fields by introducing a novel concept, identity switch, to extend multiple identities concept. The thesis posits that CFMEs use and switch their multiple identities in a dynamic way to cope with the barriers and disadvantage they face at the micro, meso and macro levels. Second, the identity switch concept helps explain CFMEs’ identity work. Further, it helps articulate the coping methods CFMEs use to deal with “trouble” between business and family. Finally, this study makes a bridge to link social identity theory and intersectionality theory to explore CFMEs’ coping methods to navigate disadvantage and expand access and employment of business resources to become successful entrepreneurs.Issues surrounding diversity and entrepreneurship have received much interest in research and public policy over the last couple of decades. This thesis aims to contribute to this body of work by studying Chinese female migrant entrepreneurs (CFMEs)’s and how with their multiple identities cope with barriers faced in both their business and family contexts. This thesis used grounded theory to investigate CFMEs’ experience by unpacking the multiple layers of disadvantage they contend with. First, the micro-level explores the patriarchal culture in Chinese families and households and its implications for female entrepreneurs. Second, themeso-level evaluates how CFMEs cope with limited access to resources for their business as well as unfair treatment in the community. Lastly, our analysis of how CFMEs experience the macro-level assesses whether it is challenging for CFMEs to integrate into local business networks. This research followed the interpretive method to explore Chinese female migrant entrepreneurs’ experience between business and family multiple identities. Seventeen interviews were conducted to analyse the participants’ narrative. Data was systematically accumulated through an inductive approach to ensure accuracy. Overall, the contributions are developed in three aspects. First, it makes a theoretical contribution to entrepreneurship and identities fields by introducing a novel concept, identity switch, to extend multiple identities concept. The thesis posits that CFMEs use and switch their multiple identities in a dynamic way to cope with the barriers and disadvantage they face at the micro, meso and macro levels. Second, the identity switch concept helps explain CFMEs’ identity work. Further, it helps articulate the coping methods CFMEs use to deal with “trouble” between business and family. Finally, this study makes a bridge to link social identity theory and intersectionality theory to explore CFMEs’ coping methods to navigate disadvantage and expand access and employment of business resources to become successful entrepreneurs
Improvements to iontophoresis devices for transdermal glucose monitoring
No full textPreviously held under moratorium from 1st June 2021 until 30th June 2023.Self-monitoring of blood glucose plays a crucial role in diabetes care. Currentmethods apply invasive means, which causes pain and discomfort to the people withdiabetes. Therefore, non-invasive methods are in high demand. Reverse Iontophoresis(RI) is a technique for non-invasive transdermal glucose monitoring. Thereby, electriccurrent is applied across the skin to extract glucose from the interstitial fluid into a gelreservoir, where it is measured with an in situ glucose sensor. One of the key problemsin RI based wearable sensors, is the glucose build-up in the gel-reservoir, which resultsin poor correlation between the extracted glucose and blood glucose level. ActivatedCarbon (AC) has excellent adsorption capabilities to organic molecules and couldtherefore act as a glucose binding agent in the RI devices leading to more accurateglucose readings and ultimately better correlation between the extracted and bloodglucose levels.The overall aim was to study and compare glucose fluxes in in vitro RIexperiments using the developed AC-integrated electrodes to the standard electrodeswithout AC. The extracted glucose was quantified using glucose assay kits.Furthermore, this study involved embedding a biosensor in the electrode system toallow direct glucose measurements.In vitro RI experiments using the newly developed AC-integrated electrodesshowed increased glucose fluxes of 61% in the high glucose concentration level in thediffusion cell. Besides, the extracted glucose correlated well with increasing glucoseconcentrations in the diffusion cell (R2=0.90). Thus, confirming AC’s suitability as aglucose binding agent in the RI environment.In vitro RI experiments with an integrated mediated enzymatic glucose sensor inthe electrode system showed limited success for electrochemical glucosequantification of the extracted glucose. However, a thorough electrochemicalcharacterisation of the developed glucose sensor using cyclic voltammetry wasperformed, which may provide good basis to make improvements for future glucosesensors.Self-monitoring of blood glucose plays a crucial role in diabetes care. Currentmethods apply invasive means, which causes pain and discomfort to the people withdiabetes. Therefore, non-invasive methods are in high demand. Reverse Iontophoresis(RI) is a technique for non-invasive transdermal glucose monitoring. Thereby, electriccurrent is applied across the skin to extract glucose from the interstitial fluid into a gelreservoir, where it is measured with an in situ glucose sensor. One of the key problemsin RI based wearable sensors, is the glucose build-up in the gel-reservoir, which resultsin poor correlation between the extracted glucose and blood glucose level. ActivatedCarbon (AC) has excellent adsorption capabilities to organic molecules and couldtherefore act as a glucose binding agent in the RI devices leading to more accurateglucose readings and ultimately better correlation between the extracted and bloodglucose levels.The overall aim was to study and compare glucose fluxes in in vitro RIexperiments using the developed AC-integrated electrodes to the standard electrodeswithout AC. The extracted glucose was quantified using glucose assay kits.Furthermore, this study involved embedding a biosensor in the electrode system toallow direct glucose measurements.In vitro RI experiments using the newly developed AC-integrated electrodesshowed increased glucose fluxes of 61% in the high glucose concentration level in thediffusion cell. Besides, the extracted glucose correlated well with increasing glucoseconcentrations in the diffusion cell (R2=0.90). Thus, confirming AC’s suitability as aglucose binding agent in the RI environment.In vitro RI experiments with an integrated mediated enzymatic glucose sensor inthe electrode system showed limited success for electrochemical glucosequantification of the extracted glucose. However, a thorough electrochemicalcharacterisation of the developed glucose sensor using cyclic voltammetry wasperformed, which may provide good basis to make improvements for future glucosesensors
Novel representations for modelling free-form objects under constraints : a parametric modelling tool for computer-aided ship design
Get PDFPreviously held under moratorium from 23rd June 2021 until 3rd July 2023.Digital design of engineering systems, using Computer-Aided Design (CAD) tools fordeveloping and optimising products, has been used in the manufacturing process since1957, when Patrick Hanratty built the first commercial numerical-control programmingsystem known as PRONTO, while he was working for General Electric. One year later,the French physicist and mathematician Paul de Casteljau invented a system basedon the use of Bernstein polynomials, during his employment with the Frenchautomobile manufacturer Citro¨en. In 1968, another French engineer named PierreB´ezier, launched on behalf of the automobile manufacturer Renault the CAD/CAMUNISURF system for surface design, which was fully in use by 1975. The steppingstone of Computer-Aided Ship Design (CASD) was set in 1963, when the NorwegianCAD/CAM software Autokon was first used, developed by Trygve Reenskaug. It was 14years later when parametric modelling in ship design introduced by Prof. H. Nowackiwho pioneered in CASD via coupling form parameters with the then novel technologyof B-splines. Since then, Parametric Modellers (PM) play a crucial role in the development and -most importantly- shape optimisation of free-form objects with increasedcomplexity such as ship-hulls, for they have to represent robustly and efficiently everysolid object.The purpose of the current work is three-fold:Firstly, it is meant to develop and present the corresponding methodology of twotools:a) an innovative, robust, and cost-efficient parametric modelling tool for containerand tanker ship-hulls, which are hull forms of increased complexity. The tool is named TshipPM and is an extension of the work presented in,b) a ship-hull shape optimisation tool based on geometric criteria, namely volumemoments up to 2nd order.Secondly, to evaluate the performance of TshipPM by comparing it with a wellestablished, commercial parametric modelling tool, CAESES®1, opting for itsNURBS functionality.Finally, was to provide an easy to follow ”handbook” for developers and users onthe development of parametric modelling tools, illustrating as well how a PM canbe utilised for the construction of a given ship-hull.The key findings of the current work which also coincide with the main objectives, are:A method of constructing a T-splines-based parametric modelling tool (TshipPM)for complex ship-hull design, the development of which is taking into consideration the detailed characteristics of two different ship-hull types, i.e., tankers andcontainers.A set of geometric and design constraints imposed to TshipPM to tackle theintricate and complex issue of Geometric Validity, ascertaining the production ofvalid models for the whole design space the modeller covers.A step-by-step method to remodel (using TshipPM) a great variety of complexhulls with complexity not-higher than that of tankers and containers.The exceptional performance of TshipPM. A comparative study is conductedto evaluate the performance of TshipPM against CAESES, a well-establishedcommercial parametric modeller for ship design. This work is published in theOcean Engineering2international journal, titled ”A T-splines-based parametricmodeller for computer-aided ship design”.A method for ship-hull shape optimisation with respect to geometric criteriaand especially volume moments up to 2nd order, utilising TshipPM and a multiobjective Teaching-Learning-based optimisation tool. This part of the work alsostresses the insufficiency of 2nd order moments to perform as complex-shape optimisers.TshipPM is a parametric modelling tool for ship-hull design under geometric and designconstraints. It uses as a mathematical representation of surfaces -and to some extendsolids- the fairly new technology of T-splines, introduced by Sederberg et al. in 2003, which constitutes a generalisation of NURBS, exhibiting several advantages overthe latter. T-splines technology aids towards the development of modellers for complexship forms, by providing geometrically valid objects with smooth surfaces and increasedfairness throughout the model’s surface, and much lower complexity in comparison withPMs employing the standard NURBS technology. TshipPM uses 27 external (or input)parameters to produce the control cage of the ship-hull, 3 of which are global anddimensional, while 24 are non-dimensional and of local nature. It employs Autodesk®T-splines plug-in® v.4.0 for Rhino5® 3D to create the final, smooth T-splines surfacesusing as input the control cage created by TshipPM.The PhD thesis consists of 6 Chapters, structured in the following way:The Novelties of the current work and its contribution to the field of parametricmodelling in CASD.Chapter 1, after a brief discussion on the historical background of splines, it delivers acomparison between T-splines, the representation underlying TshipPM, and NURBS,the industrial standard in CAD, which is also used in the context of CAESES (§1.1).In addition, it introduces the reader to parametric modelling, reviewing in brief themain advancements in the field (§1.2).Chapter 2, after the necessary introduction to TshipPM’s features and characteristics(§2.1), analyses the structure of TshipPM regarding the parameters involved (§2.2),making the distinction into internal and external, dimensional (or physical) and nondimensional. §2.3 demonstrates the process of creating a ship-hull model, starting frombuilding the control cage along with its link to external parameters, which are used asinput for TshipPM, up to its conversion into the resulting ship-hull surface with theaid of T-splines plug-in.Chapter 3, after a brief introduction on the importance of robust PMs (§3.1), definesthe constraints encountered in ship-hull design and introduces the reader to the concept of geometric validity, illustrating examples of invalid ship-hull models (§3.2). §3.3presents the geometric and design constraints imposed to TshipPM to ascertain itsrobustness as far as the production of geometrically valid models is concerned. In §3.4we provide an experimental indication of the robustness of TshipPM in its response tostrong parameter values variation. Finally, in the last section (§3.5), we present theoutput of a Monte Carlo sampling of 200,000 ship-hull instances produced by TshipPMfor both containers and tankers, and we analyse its output information to determine thedesign space of the PM, by measuring TshipPM’s flexibility with regards to geometriccharacteristics, namely volume centroid and moments of inertia.Chapter 4 begins by stressing the need of remodelling a given ship-hull with PMs touse it as basis for optimisation (§4.1), while §4.2 refers to the remodelling evaluationcriteria. The remodelling process is thoroughly described in §4.3 using as a case studythe MOERI KCS container ship-hull, and aims to the reconstruction of a parentship-hull CAD model; we use TshipPM for the construction of model’s control cageand we feed it into Rhino5 to create the corresponding surfaces with the aid of theT-splines plug-in. Finally, in §4.4 the evaluation of the remodelled MOERI KVLCCtanker [10] ship-hull is conducted, under a predefined set of criteria, providing feedbackto users and developers for any adjustments and their specific locations. The evaluationof MOERI KCS container hull is conducted in Chapter 5.In Chapter 5, TshipPM is compared against CAESES with regards to their outputsagainst a parent hull, the KCS container ship-hull, which has been extensively usedby the research community for CAD and Computational Fluid Dynamics (CFD) benchmarking purposes. The comparison criteria are described in §5.1. §5.2 presents the basiccharacteristics of the CAESES parametric modelling tool, as well as a description of thephysical (or dimensional) parameters CAESES uses to remodel KCS ship-hull and thecorresponding external non-dimensional parameters, while §5.3 refers to the commonexternal parameters both PMs use. Finally, in §§5.4 - 5.8 the comparison of both PMsis conducted.Lastly, Chapter 6 presents an in-house, C#-built, shape-optimisation tool usingTshipPM and an adjusted to the needs of the current work Multi-objective TeachingLearning-based Optimisation (MO-TLBO) method. TshipPM MO-TLBO is optimisingthe shape of a given hull (MOERI KCS) against a set of ship-design criteria, and especially volume moments up to 2nd order. After the required introduction to the chapter(§6.1), a brief presentation of the TLBO method is conducted (§6.2). The set of theobjective functions against which the optimisation is conducted is provided in §6.3,while in §6.4 the method of building TshipPM MO-TLBO, its features and functionality are presented in detail. The chapter concludes with §6.5, illustrating the resultedKCS-ship-hull instances produced by TshipPM MO-TLBO.The thesis concludes with the Discussion and Summary of the current work, highlighting its key points, stressing the delivered novelties and main contributions to thefield of parametric modelling in CASD.Digital design of engineering systems, using Computer-Aided Design (CAD) tools fordeveloping and optimising products, has been used in the manufacturing process since1957, when Patrick Hanratty built the first commercial numerical-control programmingsystem known as PRONTO, while he was working for General Electric. One year later,the French physicist and mathematician Paul de Casteljau invented a system basedon the use of Bernstein polynomials, during his employment with the Frenchautomobile manufacturer Citro¨en. In 1968, another French engineer named PierreB´ezier, launched on behalf of the automobile manufacturer Renault the CAD/CAMUNISURF system for surface design, which was fully in use by 1975. The steppingstone of Computer-Aided Ship Design (CASD) was set in 1963, when the NorwegianCAD/CAM software Autokon was first used, developed by Trygve Reenskaug. It was 14years later when parametric modelling in ship design introduced by Prof. H. Nowackiwho pioneered in CASD via coupling form parameters with the then novel technologyof B-splines. Since then, Parametric Modellers (PM) play a crucial role in the development and -most importantly- shape optimisation of free-form objects with increasedcomplexity such as ship-hulls, for they have to represent robustly and efficiently everysolid object.The purpose of the current work is three-fold:Firstly, it is meant to develop and present the corresponding methodology of twotools:a) an innovative, robust, and cost-efficient parametric modelling tool for containerand tanker ship-hulls, which are hull forms of increased complexity. The tool is named TshipPM and is an extension of the work presented in,b) a ship-hull shape optimisation tool based on geometric criteria, namely volumemoments up to 2nd order.Secondly, to evaluate the performance of TshipPM by comparing it with a wellestablished, commercial parametric modelling tool, CAESES®1, opting for itsNURBS functionality.Finally, was to provide an easy to follow ”handbook” for developers and users onthe development of parametric modelling tools, illustrating as well how a PM canbe utilised for the construction of a given ship-hull.The key findings of the current work which also coincide with the main objectives, are:A method of constructing a T-splines-based parametric modelling tool (TshipPM)for complex ship-hull design, the development of which is taking into consideration the detailed characteristics of two different ship-hull types, i.e., tankers andcontainers.A set of geometric and design constraints imposed to TshipPM to tackle theintricate and complex issue of Geometric Validity, ascertaining the production ofvalid models for the whole design space the modeller covers.A step-by-step method to remodel (using TshipPM) a great variety of complexhulls with complexity not-higher than that of tankers and containers.The exceptional performance of TshipPM. A comparative study is conductedto evaluate the performance of TshipPM against CAESES, a well-establishedcommercial parametric modeller for ship design. This work is published in theOcean Engineering2international journal, titled ”A T-splines-based parametricmodeller for computer-aided ship design”.A method for ship-hull shape optimisation with respect to geometric criteriaand especially volume moments up to 2nd order, utilising TshipPM and a multiobjective Teaching-Learning-based optimisation tool. This part of the work alsostresses the insufficiency of 2nd order moments to perform as complex-shape optimisers.TshipPM is a parametric modelling tool for ship-hull design under geometric and designconstraints. It uses as a mathematical representation of surfaces -and to some extendsolids- the fairly new technology of T-splines, introduced by Sederberg et al. in 2003, which constitutes a generalisation of NURBS, exhibiting several advantages overthe latter. T-splines technology aids towards the development of modellers for complexship forms, by providing geometrically valid objects with smooth surfaces and increasedfairness throughout the model’s surface, and much lower complexity in comparison withPMs employing the standard NURBS technology. TshipPM uses 27 external (or input)parameters to produce the control cage of the ship-hull, 3 of which are global anddimensional, while 24 are non-dimensional and of local nature. It employs Autodesk®T-splines plug-in® v.4.0 for Rhino5® 3D to create the final, smooth T-splines surfacesusing as input the control cage created by TshipPM.The PhD thesis consists of 6 Chapters, structured in the following way:The Novelties of the current work and its contribution to the field of parametricmodelling in CASD.Chapter 1, after a brief discussion on the historical background of splines, it delivers acomparison between T-splines, the representation underlying TshipPM, and NURBS,the industrial standard in CAD, which is also used in the context of CAESES (§1.1).In addition, it introduces the reader to parametric modelling, reviewing in brief themain advancements in the field (§1.2).Chapter 2, after the necessary introduction to TshipPM’s features and characteristics(§2.1), analyses the structure of TshipPM regarding the parameters involved (§2.2),making the distinction into internal and external, dimensional (or physical) and nondimensional. §2.3 demonstrates the process of creating a ship-hull model, starting frombuilding the control cage along with its link to external parameters, which are used asinput for TshipPM, up to its conversion into the resulting ship-hull surface with theaid of T-splines plug-in.Chapter 3, after a brief introduction on the importance of robust PMs (§3.1), definesthe constraints encountered in ship-hull design and introduces the reader to the concept of geometric validity, illustrating examples of invalid ship-hull models (§3.2). §3.3presents the geometric and design constraints imposed to TshipPM to ascertain itsrobustness as far as the production of geometrically valid models is concerned. In §3.4we provide an experimental indication of the robustness of TshipPM in its response tostrong parameter values variation. Finally, in the last section (§3.5), we present theoutput of a Monte Carlo sampling of 200,000 ship-hull instances produced by TshipPMfor both containers and tankers, and we analyse its output information to determine thedesign space of the PM, by measuring TshipPM’s flexibility with regards to geometriccharacteristics, namely volume centroid and moments of inertia.Chapter 4 begins by stressing the need of remodelling a given ship-hull with PMs touse it as basis for optimisation (§4.1), while §4.2 refers to the remodelling evaluationcriteria. The remodelling process is thoroughly described in §4.3 using as a case studythe MOERI KCS container ship-hull, and aims to the reconstruction of a parentship-hull CAD model; we use TshipPM for the construction of model’s control cageand we feed it into Rhino5 to create the corresponding surfaces with the aid of theT-splines plug-in. Finally, in §4.4 the evaluation of the remodelled MOERI KVLCCtanker [10] ship-hull is conducted, under a predefined set of criteria, providing feedbackto users and developers for any adjustments and their specific locations. The evaluationof MOERI KCS container hull is conducted in Chapter 5.In Chapter 5, TshipPM is compared against CAESES with regards to their outputsagainst a parent hull, the KCS container ship-hull, which has been extensively usedby the research community for CAD and Computational Fluid Dynamics (CFD) benchmarking purposes. The comparison criteria are described in §5.1. §5.2 presents the basiccharacteristics of the CAESES parametric modelling tool, as well as a description of thephysical (or dimensional) parameters CAESES uses to remodel KCS ship-hull and thecorresponding external non-dimensional parameters, while §5.3 refers to the commonexternal parameters both PMs use. Finally, in §§5.4 - 5.8 the comparison of both PMsis conducted.Lastly, Chapter 6 presents an in-house, C#-built, shape-optimisation tool usingTshipPM and an adjusted to the needs of the current work Multi-objective TeachingLearning-based Optimisation (MO-TLBO) method. TshipPM MO-TLBO is optimisingthe shape of a given hull (MOERI KCS) against a set of ship-design criteria, and especially volume moments up to 2nd order. After the required introduction to the chapter(§6.1), a brief presentation of the TLBO method is conducted (§6.2). The set of theobjective functions against which the optimisation is conducted is provided in §6.3,while in §6.4 the method of building TshipPM MO-TLBO, its features and functionality are presented in detail. The chapter concludes with §6.5, illustrating the resultedKCS-ship-hull instances produced by TshipPM MO-TLBO.The thesis concludes with the Discussion and Summary of the current work, highlighting its key points, stressing the delivered novelties and main contributions to thefield of parametric modelling in CASD
Access Repository Dashboard
Do you manage STAX (Strathclyde Repository)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!