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Elucidating protein stabilization with fluorescence techniques
Get PDFInsulin is an important protein that controls blood glucose levels, but its function becomes ineffective during protein aggregation. Insulin readily undergoes protein aggregation and it contributes to hyperglycaemia. In long-term hyperglycaemia, glucose can alter the structure and stability of insulin via glycation.;In this thesis, fluorescence techniques have been used to monitor protein dynamics that are crucial to our understanding of protein aggregation and glycation. A synthetic protein that readily forms fibrous structures with homogenous growth kinetics is synthesized to simplify the interpretation of fluorescence kinetics. The conformational changes that both insulin and the protein model undergo throughout 700 hours have been monitored with a range of fluorescence techniques.;For the fibrillogenesis model, time-resolved emission spectra (TRES) measurements revealed two fluorescent species occurring around 33,000 and 31,500 cm-1 at 0.33 hours after preparation. After this time, the second component decreases to 30,500 cm-1and continues to emit at this range throughout 700 hours. This suggests that fibril formation occurs within a few hours (confirmed by structured illumination microscopy (SIM)) and remains stable. Long term stability of the model provides a measurement-supported basis for its use as a reference material in fluorescence studies of protein aggregation.;For free hexameric insulin, TRES measurements show drastic conformational changes. Two fluorescent components are shown at 33,000 cm-1 and 32,000 cm-1.The second component decreases to 31,000 cm-1 after 196 hours. This shows that the protein aggregates increase in size during this time. For free monomeric insulin, there is a lack of fluorescence intensity or TRES spectral changes, which show a lack of conformational change throughout 700 hours. In ThT studies and dSTORM images, there was no evidence to show amyloid fibrils were formed in both hexameric and monomeric insulin.;Spectral similarities are shown in TRES measurements between free hexameric insulin and insulin with glucose until 196 hours after preparation. At least two fluorescent species were observed around 33,000 and 31,500 cm-1. The second component decreases to 30,500 cm-1 at 196 hours and does not experience spectral shifts in 10 ns, which shows that glycation begin to cross link insulin aggregates, making them more rigid.;In dSTORMimages show there are an abundance of aggregates compared to free hexameric insulin which confirms cross linkage observed in the TRES measurements. For monomeric insulin with glucose, no significant changes were shown in the spectroscopy measurements and dSTORM images show smaller aggregates compared to free monomeric insulin. This demonstrates that glycation inhibits monomeric insulin aggregation.;The findings in this thesis hold promise for monitoring the storage of insulin and its application in the control of diabetes and may support the development of more effective therapeutics against amyloidosis.Insulin is an important protein that controls blood glucose levels, but its function becomes ineffective during protein aggregation. Insulin readily undergoes protein aggregation and it contributes to hyperglycaemia. In long-term hyperglycaemia, glucose can alter the structure and stability of insulin via glycation.;In this thesis, fluorescence techniques have been used to monitor protein dynamics that are crucial to our understanding of protein aggregation and glycation. A synthetic protein that readily forms fibrous structures with homogenous growth kinetics is synthesized to simplify the interpretation of fluorescence kinetics. The conformational changes that both insulin and the protein model undergo throughout 700 hours have been monitored with a range of fluorescence techniques.;For the fibrillogenesis model, time-resolved emission spectra (TRES) measurements revealed two fluorescent species occurring around 33,000 and 31,500 cm-1 at 0.33 hours after preparation. After this time, the second component decreases to 30,500 cm-1and continues to emit at this range throughout 700 hours. This suggests that fibril formation occurs within a few hours (confirmed by structured illumination microscopy (SIM)) and remains stable. Long term stability of the model provides a measurement-supported basis for its use as a reference material in fluorescence studies of protein aggregation.;For free hexameric insulin, TRES measurements show drastic conformational changes. Two fluorescent components are shown at 33,000 cm-1 and 32,000 cm-1.The second component decreases to 31,000 cm-1 after 196 hours. This shows that the protein aggregates increase in size during this time. For free monomeric insulin, there is a lack of fluorescence intensity or TRES spectral changes, which show a lack of conformational change throughout 700 hours. In ThT studies and dSTORM images, there was no evidence to show amyloid fibrils were formed in both hexameric and monomeric insulin.;Spectral similarities are shown in TRES measurements between free hexameric insulin and insulin with glucose until 196 hours after preparation. At least two fluorescent species were observed around 33,000 and 31,500 cm-1. The second component decreases to 30,500 cm-1 at 196 hours and does not experience spectral shifts in 10 ns, which shows that glycation begin to cross link insulin aggregates, making them more rigid.;In dSTORMimages show there are an abundance of aggregates compared to free hexameric insulin which confirms cross linkage observed in the TRES measurements. For monomeric insulin with glucose, no significant changes were shown in the spectroscopy measurements and dSTORM images show smaller aggregates compared to free monomeric insulin. This demonstrates that glycation inhibits monomeric insulin aggregation.;The findings in this thesis hold promise for monitoring the storage of insulin and its application in the control of diabetes and may support the development of more effective therapeutics against amyloidosis
Dense convolutional networks for efficient video analysis
Get PDFIn the past few years, artificial intelligence has ushered in the third climax, which is due to the improvement of hardware computing power, so that deep learning algorithm can be applied on a large scale. Before the large-scale use of deep learning, image feature engineering is more dependent on the experience of engineers, and it can't get good results in the face of random and complex environment. Through a large number of manual features, through SVM training to classify, detect, segment images. With the success of Alexnet [15], people began to realize that feature engineering can rely on neural network to extract itself. It has been proved that the neural network trained by big data has very strong robustness to image feature extraction.;This article is divided into four chapters. Chapter 1 mainly introduces the experimental significance and motivation of this article, and introduces the role of deep learning in computer vision. Chapter 2 introduces the application of deep learning algorithms, including image classification (AlexNet[8], VGGNet[34], ResNet[28]), target detection (FasterRCNN[35], YOLO[36], SSD[37]), video analysis (LSTM based,3DCNN), and introduces some of the most advanced algorithms The structure and their experimental results, the experimental results of the new structure can reach 790 FPS on the Tesla P100. Chapter 3 mainly introduces the achievements I made this year and the algorithms designed for effective video understanding. Chapter 4 is a summary of the entire process and points out what improvements can be made in the future.In the past few years, artificial intelligence has ushered in the third climax, which is due to the improvement of hardware computing power, so that deep learning algorithm can be applied on a large scale. Before the large-scale use of deep learning, image feature engineering is more dependent on the experience of engineers, and it can't get good results in the face of random and complex environment. Through a large number of manual features, through SVM training to classify, detect, segment images. With the success of Alexnet [15], people began to realize that feature engineering can rely on neural network to extract itself. It has been proved that the neural network trained by big data has very strong robustness to image feature extraction.;This article is divided into four chapters. Chapter 1 mainly introduces the experimental significance and motivation of this article, and introduces the role of deep learning in computer vision. Chapter 2 introduces the application of deep learning algorithms, including image classification (AlexNet[8], VGGNet[34], ResNet[28]), target detection (FasterRCNN[35], YOLO[36], SSD[37]), video analysis (LSTM based,3DCNN), and introduces some of the most advanced algorithms The structure and their experimental results, the experimental results of the new structure can reach 790 FPS on the Tesla P100. Chapter 3 mainly introduces the achievements I made this year and the algorithms designed for effective video understanding. Chapter 4 is a summary of the entire process and points out what improvements can be made in the future
Probability modelling of supplier development investment decisions under uncertainty
Get PDFSupplier development involves activities intended to improve a supplier's performance and to add value on a buying firm's business benefit. Typically, such activities require significant resource investment and there is a risk that the benefit to be obtained from supplier development may not be enough to offset the expenses incurred. This thesis develops quantitative models to inform buyer decisions on whether it is worth investing in a supplier development activity and, if so, how much should be invested. The proposed models are built from a buyer's perspective to support analysis of the benefit obtained from the development activity. In particular, the models take account of the uncertainty of the benefit and associate it with the stochastic characteristics of a supplier's performance.;More specifically, the two models are relevant for types of supplier performance data. The first model considers the case of developing a supplier whose undesirable performance is measured in categorical form, such as classes corresponding to degrees of late delivery. The multinomial distribution is used to represent the uncertainty of a supplier's performance. The second model considers a case of developing a supplier whose undesirable performance is measured in counting form, such as, the number of non-conformances. The non-homogenous Poisson process (NHPP) model is used to represent the uncertainty of a supplier's performance.;The two proposed models provide decision makers with an optimal investment level, which is the maximum amount of investment to be made for the development activity as well as an expected return. Numerical investigations are carried out to examine the behaviour of the models and to illustrate key theoretical properties. An industry case study is conducted to provide an empirical demonstration of modelling for analysis of supplier databases. This also qualitatively investigates how the models align with supplier development management decision making in practice.Supplier development involves activities intended to improve a supplier's performance and to add value on a buying firm's business benefit. Typically, such activities require significant resource investment and there is a risk that the benefit to be obtained from supplier development may not be enough to offset the expenses incurred. This thesis develops quantitative models to inform buyer decisions on whether it is worth investing in a supplier development activity and, if so, how much should be invested. The proposed models are built from a buyer's perspective to support analysis of the benefit obtained from the development activity. In particular, the models take account of the uncertainty of the benefit and associate it with the stochastic characteristics of a supplier's performance.;More specifically, the two models are relevant for types of supplier performance data. The first model considers the case of developing a supplier whose undesirable performance is measured in categorical form, such as classes corresponding to degrees of late delivery. The multinomial distribution is used to represent the uncertainty of a supplier's performance. The second model considers a case of developing a supplier whose undesirable performance is measured in counting form, such as, the number of non-conformances. The non-homogenous Poisson process (NHPP) model is used to represent the uncertainty of a supplier's performance.;The two proposed models provide decision makers with an optimal investment level, which is the maximum amount of investment to be made for the development activity as well as an expected return. Numerical investigations are carried out to examine the behaviour of the models and to illustrate key theoretical properties. An industry case study is conducted to provide an empirical demonstration of modelling for analysis of supplier databases. This also qualitatively investigates how the models align with supplier development management decision making in practice
Enhanced protection and location techniques for enabling wider implementation of LVDC distribution networks
No full textWith the increasing penetration of renewable generation in power systems and the electrification of heat and transport, LV distribution networks are under pressure to host a growing number of low carbon technologies. Alternative Low Voltage Direct Current(LVDC) distribution networks have been considered as an effective approach to release the pressure on existing LV distribution networks. Meanwhile, the fast development of power electronics and increasing LVDC applications facilitate the transition to LVDC distribution networks. However, DC fault protection and location have been identified as key technical challenges by a number of research works and industrial groups. This thesis works toward the development of a fast and selective protection scheme and a reliable and accurate fault location technique that are to ensure secure and reliable LVDC operations, thereby facilitating the transition towards the widespread implementation of LVDC distribution networks. As LVDC protection solutions are influenced by AC/DC interface converters, existing protection solutions are mainly based on conventional two-level voltage source converters. Recently, new converter technologies such as solid-state transformers (SST) have been implemented, their unique fault characteristics introducing new requirements in understanding the impact of new converters. This is presenting the need for new recommendations and guidelines, and for developing new protection solutions. Therefore, this thesis presents an approach for fault characterisation and protection evaluation of future LVDC distribution networks. The SST is selected in this thesis to conduct case studies due to its unique fault characteristics, enhanced fault current control capabilities, great potential to replace existing LV transformers, and additional ancillary services. The derived understanding of the impact of SST on DC fault response and the effectiveness of existing protection solutions gives recommendations for future LVDC protection design. These help the development of a novel voltage-based protection scheme that uses the combination of sign of current derivative, voltage magnitude, and voltage concavity. The proposed protection scheme only relies on local measurements without any communications. The enhanced protection selectivity and the fast protection speed have been proven by simulation studies. The improved performance of the proposed protection scheme compared to existing methods allows LVDC distribution networks to have faster power restoration during fault events thus enabling resilient LVDC operations. In addition, a fault let-through energy (FLTE) based fault location technique is developed that uses FLTE in conjunction with a 'critical point' concept that is based on the capacitor ratio of local and remote converters. This achieves improved accuracy and reliability over the most of the proposed fault distance estimation techniques during the fault transient period. The enhanced performance of the proposed fault location technique has been verified based on simulation studies. This improved accuracy and reliability allows DC faults to be accurately located and facilitates rapid network reconfiguration and post fault cable maintenance.With the increasing penetration of renewable generation in power systems and the electrification of heat and transport, LV distribution networks are under pressure to host a growing number of low carbon technologies. Alternative Low Voltage Direct Current(LVDC) distribution networks have been considered as an effective approach to release the pressure on existing LV distribution networks. Meanwhile, the fast development of power electronics and increasing LVDC applications facilitate the transition to LVDC distribution networks. However, DC fault protection and location have been identified as key technical challenges by a number of research works and industrial groups. This thesis works toward the development of a fast and selective protection scheme and a reliable and accurate fault location technique that are to ensure secure and reliable LVDC operations, thereby facilitating the transition towards the widespread implementation of LVDC distribution networks. As LVDC protection solutions are influenced by AC/DC interface converters, existing protection solutions are mainly based on conventional two-level voltage source converters. Recently, new converter technologies such as solid-state transformers (SST) have been implemented, their unique fault characteristics introducing new requirements in understanding the impact of new converters. This is presenting the need for new recommendations and guidelines, and for developing new protection solutions. Therefore, this thesis presents an approach for fault characterisation and protection evaluation of future LVDC distribution networks. The SST is selected in this thesis to conduct case studies due to its unique fault characteristics, enhanced fault current control capabilities, great potential to replace existing LV transformers, and additional ancillary services. The derived understanding of the impact of SST on DC fault response and the effectiveness of existing protection solutions gives recommendations for future LVDC protection design. These help the development of a novel voltage-based protection scheme that uses the combination of sign of current derivative, voltage magnitude, and voltage concavity. The proposed protection scheme only relies on local measurements without any communications. The enhanced protection selectivity and the fast protection speed have been proven by simulation studies. The improved performance of the proposed protection scheme compared to existing methods allows LVDC distribution networks to have faster power restoration during fault events thus enabling resilient LVDC operations. In addition, a fault let-through energy (FLTE) based fault location technique is developed that uses FLTE in conjunction with a 'critical point' concept that is based on the capacitor ratio of local and remote converters. This achieves improved accuracy and reliability over the most of the proposed fault distance estimation techniques during the fault transient period. The enhanced performance of the proposed fault location technique has been verified based on simulation studies. This improved accuracy and reliability allows DC faults to be accurately located and facilitates rapid network reconfiguration and post fault cable maintenance
The utility of an integrated model to explore the mediating role of religious coping between illness perceptions and psychosocial outcomes of Omani women newly diagnosed with breast cancer
No full textDevelopment of computational and experimental techniques to Investigate the effect of biofouling on ship hydrodynamic performance
Get PDFHull and propeller roughness can be caused by various factors such as mechanical causes, chemical and electrochemical processes (e.g. corrosion), and finally the colonisation of biofouling, which is often the most critical. The associated economic and environmental problems include increases in ship resistance, fuel consumption, and greenhouse gas emissions. The mitigation measures are also associated with costly antifouling coatings and dry docking. Therefore, accurate predictions of the roughness effect on ship performance are of great importance in the economic and environmental perspectives. Although many studies have been carried out to investigate the roughness effect since the age of William Froude, our understanding in this field is still limited. More specifically, the validations of the two most prevalent prediction methods are not complete. Also, the conventional studies have mainly focussed on the roughness effect on ship resistance, whereas the impact on propulsion performance has been less highlighted.;Furthermore, the hull surfaces have been treated as uniformly rough in the conventional studies, while real ships' surfaces are not uniform as they are exposed to heterogeneous fouling accumulation. Based on the above background, this PhD study aims to develop computational and experimental techniques to investigate the effect of biofouling on ship hydrodynamic performance. This aim has been realised by achieving several milestones using Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD).;This PhD thesis consists of three distinct parts. Part I includes experimental validations by means of tank testing to demonstrate the suitability of the methods for the added resistance prediction due to hull roughness: Granville's similarity law scaling method and the CFD method involving modified wall-functions. Part II presents the full-scale applications of the CFD approach to predict the effect of biofouling on the full-scale ship hydrodynamic problems, including ship resistance, propeller performance and ship self-propulsion performance. Finally, extended investigations are presented in Part III, including the investigations into the effect of heterogeneous distributions of hull roughness on ship resistance as well as the roughness effect with the variations of hull forms, ship lengths and speeds.Hull and propeller roughness can be caused by various factors such as mechanical causes, chemical and electrochemical processes (e.g. corrosion), and finally the colonisation of biofouling, which is often the most critical. The associated economic and environmental problems include increases in ship resistance, fuel consumption, and greenhouse gas emissions. The mitigation measures are also associated with costly antifouling coatings and dry docking. Therefore, accurate predictions of the roughness effect on ship performance are of great importance in the economic and environmental perspectives. Although many studies have been carried out to investigate the roughness effect since the age of William Froude, our understanding in this field is still limited. More specifically, the validations of the two most prevalent prediction methods are not complete. Also, the conventional studies have mainly focussed on the roughness effect on ship resistance, whereas the impact on propulsion performance has been less highlighted.;Furthermore, the hull surfaces have been treated as uniformly rough in the conventional studies, while real ships' surfaces are not uniform as they are exposed to heterogeneous fouling accumulation. Based on the above background, this PhD study aims to develop computational and experimental techniques to investigate the effect of biofouling on ship hydrodynamic performance. This aim has been realised by achieving several milestones using Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD).;This PhD thesis consists of three distinct parts. Part I includes experimental validations by means of tank testing to demonstrate the suitability of the methods for the added resistance prediction due to hull roughness: Granville's similarity law scaling method and the CFD method involving modified wall-functions. Part II presents the full-scale applications of the CFD approach to predict the effect of biofouling on the full-scale ship hydrodynamic problems, including ship resistance, propeller performance and ship self-propulsion performance. Finally, extended investigations are presented in Part III, including the investigations into the effect of heterogeneous distributions of hull roughness on ship resistance as well as the roughness effect with the variations of hull forms, ship lengths and speeds
Exploring subsurface ground water and geochemical rock interactions during drainage of a surface water reservoir in Switzerland
No full textThis thesis was previously held under moratorium from 05/08/2020 to 5/08/2021.This thesis examines the spatial and temporal controls on groundwater chemistry in a fractured granitic environment. The research was conducted at the Grimsel Test Site, Switzerland (GTS), where draining and refilling of a nearby surface water reservoir induced microseismicity In the surrounding rocks. The GTS is a network of closely monitored tunnels and boreholes approx 300-500m below ground surface.Characterisation of background geochemical conditions over a two-year period consisted of a time series of physiochemical, major and minor dissolved ion chemistry, stable isotope analysis and dissolved organics, for boreholes spanning the length of the GTS. Results show poor fracture connectivity; physiochemical and dissolved ion chemistry are dominated by water-rock reactions between infiltrating meteoric waters and spatially varying host rock lithology.A new technique is developed that compares the differing signatures of dissolved organic compounds (2D-gas chromatographs) found within surface soils, river sediments and the lake, to those found in groundwater samples from the GTS. Results show that organic signatures are well-preserved and that different groundwater samples can be traced to different surface infiltration sites. This organic fingerprinting technique has the potential to be a powerful new tool for determining groundwater origins. Analysing the groundwater data over time, identified no changes to major or minor ion chemistry, but repeated drops in groundwater pH (1-3 units) were observed during periods of reservoir drainage.These drops were concurrent with nearby shallow (<1 km below ground surface) microearthquakes -1.2 < ML <1. Experiments to crush granite from the GTS in the presence of equilibrated groundwater, and in the absence of oxygen, were able to reproduce similar pH drops with no changes to water chemistry. This is the first evidence that microseismic events cause substantial pH drops, these findings have significant implications for a wide variety of geological processes.This thesis examines the spatial and temporal controls on groundwater chemistry in a fractured granitic environment. The research was conducted at the Grimsel Test Site, Switzerland (GTS), where draining and refilling of a nearby surface water reservoir induced microseismicity In the surrounding rocks. The GTS is a network of closely monitored tunnels and boreholes approx 300-500m below ground surface.Characterisation of background geochemical conditions over a two-year period consisted of a time series of physiochemical, major and minor dissolved ion chemistry, stable isotope analysis and dissolved organics, for boreholes spanning the length of the GTS. Results show poor fracture connectivity; physiochemical and dissolved ion chemistry are dominated by water-rock reactions between infiltrating meteoric waters and spatially varying host rock lithology.A new technique is developed that compares the differing signatures of dissolved organic compounds (2D-gas chromatographs) found within surface soils, river sediments and the lake, to those found in groundwater samples from the GTS. Results show that organic signatures are well-preserved and that different groundwater samples can be traced to different surface infiltration sites. This organic fingerprinting technique has the potential to be a powerful new tool for determining groundwater origins. Analysing the groundwater data over time, identified no changes to major or minor ion chemistry, but repeated drops in groundwater pH (1-3 units) were observed during periods of reservoir drainage.These drops were concurrent with nearby shallow (<1 km below ground surface) microearthquakes -1.2 < ML <1. Experiments to crush granite from the GTS in the presence of equilibrated groundwater, and in the absence of oxygen, were able to reproduce similar pH drops with no changes to water chemistry. This is the first evidence that microseismic events cause substantial pH drops, these findings have significant implications for a wide variety of geological processes
"NEET" or left out?, disadvantaged young people, everyday experiences of marginalisation and "accelerated" transitions in urban Scotland
Get PDFWhile social, economic and political transformations inscribed in current neoliberal capitalism have significantly changed contemporary young adulthood, social divisions continue to shape young people's lives and transitions. A considerable body of research has linked socio-economic inequalities with experiences of a group of young people often described as being 'Not in Education, Employment or Training' (NEET). Yet, comparatively little is known about the everyday lives and transitions of young people identified as NEET from their own perspective and in a distinctive Scottish policy context.;This thesis aims to address this gap by exploring : (1) young people's everyday lives and circumstances, and their relationships with place, institutions and others ; (2) their school experiences and impact of these experiences on their transitions ; and (3) their practices of looking for work and learning. Moreover, the role technologies playin lives and transitions of young people identified as NEET is critically examined. This additional dimension to youth transitions was of particular interest because it has beenso far under researched in relation to this group, while policy responses frame technologies as a panacea for erasing socio-economic inequalities.;The thesis employs narrative inquiry methodology and adopts thinking tools from Pierre Bourdieu. The data from qualitative interviews with 22 young people aged 16-24, who were predominantly white and identified as NEET allowed for the intimate study of their everyday lives and transitions, how they understand and relate to the world around them. The Bourdieusian framework positioned young people within unequal power structures and broader socio-economic and political contexts. Interviews with 11 service providers overseeing youth transitions offered an additional dimension into how the policy agenda is implemented and exercised 'on the ground' in Scotland and what consequences this has for young people's trajectories.;A number of significant findings emerged from the study. Participants' everyday lives and circumstances were complex and diverse, and so were the ways they made sense of themselves and the world around them. Yet, the thematic analysis also identified a set of commonalities in the young people's lives and transitions through and into employment, and in their labouring subjectivities (the way the self is constructed and performed in relation to the labour market). Particularly, participants relationship with schooling was that of unease and struggle, resulting in most cases in 'accelerated' transitions towards vocational pathways. Furthermore, segregation processes embedded within the education system and the post-16 transitions policy and practice landscape were found to strongly shape their trajectories.;Concurrently, uncertainties about the rules and presuppositions of the realm of work, the 'proper' ways of conduct and of performance of the self, constituted a strong feature of the young people's labouring subjectivities. Consequently, seeing the labour market as an 'alien' environment was also reflected in the ways the young people engaged with technologies while looking for opportunities. Specifically, while the young people described complex patterns of technology use in their everyday lives, their engagement with technologies for accessing opportunities was underpinned by uncertainties and struggles that derived from their distinctive (classed) social identities. However, even when participants acquired (digital) employability skills through engagement with numerous skills initiatives, these had very little impact on their career choices, transitions and chances of accessing secure employment.;Once again, social divisions combined with other external factors proved to be of much stronger influence. Consequently, the findings provide significant evidence on the real challenges faced by young people who find themselves not in education or employment from a relatively young age and identifies recommendations for policy and practice, in addition to future opportunities for research.While social, economic and political transformations inscribed in current neoliberal capitalism have significantly changed contemporary young adulthood, social divisions continue to shape young people's lives and transitions. A considerable body of research has linked socio-economic inequalities with experiences of a group of young people often described as being 'Not in Education, Employment or Training' (NEET). Yet, comparatively little is known about the everyday lives and transitions of young people identified as NEET from their own perspective and in a distinctive Scottish policy context.;This thesis aims to address this gap by exploring : (1) young people's everyday lives and circumstances, and their relationships with place, institutions and others ; (2) their school experiences and impact of these experiences on their transitions ; and (3) their practices of looking for work and learning. Moreover, the role technologies playin lives and transitions of young people identified as NEET is critically examined. This additional dimension to youth transitions was of particular interest because it has beenso far under researched in relation to this group, while policy responses frame technologies as a panacea for erasing socio-economic inequalities.;The thesis employs narrative inquiry methodology and adopts thinking tools from Pierre Bourdieu. The data from qualitative interviews with 22 young people aged 16-24, who were predominantly white and identified as NEET allowed for the intimate study of their everyday lives and transitions, how they understand and relate to the world around them. The Bourdieusian framework positioned young people within unequal power structures and broader socio-economic and political contexts. Interviews with 11 service providers overseeing youth transitions offered an additional dimension into how the policy agenda is implemented and exercised 'on the ground' in Scotland and what consequences this has for young people's trajectories.;A number of significant findings emerged from the study. Participants' everyday lives and circumstances were complex and diverse, and so were the ways they made sense of themselves and the world around them. Yet, the thematic analysis also identified a set of commonalities in the young people's lives and transitions through and into employment, and in their labouring subjectivities (the way the self is constructed and performed in relation to the labour market). Particularly, participants relationship with schooling was that of unease and struggle, resulting in most cases in 'accelerated' transitions towards vocational pathways. Furthermore, segregation processes embedded within the education system and the post-16 transitions policy and practice landscape were found to strongly shape their trajectories.;Concurrently, uncertainties about the rules and presuppositions of the realm of work, the 'proper' ways of conduct and of performance of the self, constituted a strong feature of the young people's labouring subjectivities. Consequently, seeing the labour market as an 'alien' environment was also reflected in the ways the young people engaged with technologies while looking for opportunities. Specifically, while the young people described complex patterns of technology use in their everyday lives, their engagement with technologies for accessing opportunities was underpinned by uncertainties and struggles that derived from their distinctive (classed) social identities. However, even when participants acquired (digital) employability skills through engagement with numerous skills initiatives, these had very little impact on their career choices, transitions and chances of accessing secure employment.;Once again, social divisions combined with other external factors proved to be of much stronger influence. Consequently, the findings provide significant evidence on the real challenges faced by young people who find themselves not in education or employment from a relatively young age and identifies recommendations for policy and practice, in addition to future opportunities for research
Numerical modelling of rubber hyperelasticity, parameter identification and finite element implementations
Get PDFThe aim of the presented research is to investigate and develop methods to model rubber hyperelasticity. Accurate numerical modelling of the hyperelastic behaviour of rubber requires a capable constitutive model and experimental data from the material or component of interest. This research focuses on three areas: hyperelastic constitutive modelling with homogeneous experimental parameter identification, implementing hyperelasticity in the Finite Element Method and simulating the hyperelastic behaviour of industrial rubber components.;Postulated conditions are proposed to ensure the physical plausibility of hyperelastic homogeneous experimental data. Using experimental data from literature deemed to meet these conditions, the connection between constitutive model, the extent of experimental data and the ability to predict the complete hyperelastic behaviour is investigated. A more efficient means of experimental parameter identification is suggested, which uses only 'sufficient' experimental data. This data encompasses the expected range of deformations for a material or component. To develop this method for industrial rubber components, the Finite Element Method is used.;Open-source user subroutines are developed to enable the implementation of hyperelastic constitutive models in the Finite Element Method. Analytical implementations are developed for hyperelastic constitutive models defined by two common strain measures, Cauchy-Green invariants and principal stretches. Implementations are also developed for two complimentary real-domain approximation methods. All implementations are validated in terms of their numerical accuracy and computation time. The implementations are accurate to double precision and analytical methods are more computationally efficient than approximation methods.;A methodology for simulating rubber components using sufficient experimental data is developed. The approach uses prototype simulations to identify the strain region of the component under operating conditions. A modification is proposed for simulating strain-loaded and stress-loaded components, as the latter affects the strain region. The method is demonstrated by simulating two industrial components, one for each loading type.The aim of the presented research is to investigate and develop methods to model rubber hyperelasticity. Accurate numerical modelling of the hyperelastic behaviour of rubber requires a capable constitutive model and experimental data from the material or component of interest. This research focuses on three areas: hyperelastic constitutive modelling with homogeneous experimental parameter identification, implementing hyperelasticity in the Finite Element Method and simulating the hyperelastic behaviour of industrial rubber components.;Postulated conditions are proposed to ensure the physical plausibility of hyperelastic homogeneous experimental data. Using experimental data from literature deemed to meet these conditions, the connection between constitutive model, the extent of experimental data and the ability to predict the complete hyperelastic behaviour is investigated. A more efficient means of experimental parameter identification is suggested, which uses only 'sufficient' experimental data. This data encompasses the expected range of deformations for a material or component. To develop this method for industrial rubber components, the Finite Element Method is used.;Open-source user subroutines are developed to enable the implementation of hyperelastic constitutive models in the Finite Element Method. Analytical implementations are developed for hyperelastic constitutive models defined by two common strain measures, Cauchy-Green invariants and principal stretches. Implementations are also developed for two complimentary real-domain approximation methods. All implementations are validated in terms of their numerical accuracy and computation time. The implementations are accurate to double precision and analytical methods are more computationally efficient than approximation methods.;A methodology for simulating rubber components using sufficient experimental data is developed. The approach uses prototype simulations to identify the strain region of the component under operating conditions. A modification is proposed for simulating strain-loaded and stress-loaded components, as the latter affects the strain region. The method is demonstrated by simulating two industrial components, one for each loading type
The development of intelligent hull forms of large ships for energy efficient transportation
Get PDFIt is not usual that the interests of ship owners are aligned with maritime legislation requirements with the incentives to make ships more efficient. Owners seek to reduce the ship operating costs whilst entities, such as the IMO, push for a more environment friendly marine industry.;A ship's efficiency can be improved by optimising the hull form and/or by installing Energy Saving Devices (ESD) in order to improve the hydrodynamic performance and fluid flow of a vessel. These two areas are not new to the industry and have been investigated using various methods, including computational fluid dynamics (CFD) procedures. The use of CFD for ship performance analyses is becoming more popular in the maritime industry due to its cost-effective capabilities. The continuous development of numerical simulation (CFD) as well as high performance computing opens doors to new areas of investigation and allows research to further study topics that have been previously looked into as well as research questions that have never been explored.;The general aim of this PhD thesis is to contribute to the body of knowledge by shedding light on improving the hydrodynamic performance of large ships for energy efficient transportation. This was achieved by accomplishing a series of objectives and case studies that addressed various research questions.;This study initially proposes an intelligent state-of-the-art methodology for predicting and enhancing the hull-propeller interaction of a vessel using numerical techniques (CFD), optimisation procedures and high-performance computing to identify optimal stern designs as well as understanding the physics and impact of Energy Saving Device/s that could help improve the stern flow characteristics.;The CFD method, that was used to predict the performance for all the various case studies, was validated and verified using well established procedures. The implementation of the recently available curvature correction feature in the numerical model and its enhanced wake prediction capabilities were clearly demonstrated.;Moreover, various types of post-processing CFD analyses that were deemed useful to understand the hydrodynamic performance of a vessel were listed and outlined.;A practical full-scale stern form optimisation procedure for a bulk carrier was developed and demonstrated. Furthermore, whether the quality of a nominal wake can provide any insight into the propeller performance of a vessel was investigated and evaluated.;With regards to the case studies investigating Energy Saving Devices, Propeller Boss Cap Fins were analysed in open water full-scale conditions to understand the physics, function and working principles of such technologies. A state-of-the-art full-scale PBCF optimisation procedure was also demonstrated. The performance of a Wake Equalising Duct at different scale conditions was investigated and compared. The study indicated that the duct is not as effective in full-scale. The reasons and findings were thoroughly discussed and outlined.;The thesis also focused on the research questions regarding the installation of multiple Energy Saving Devices on a ship system. Whether the benefits are directly cumulative or whether the ESDs affect the flow regimes of one another? Thus, a case study was carried out by investigating seven combinations using PBCF, a duct and stator fins. The performance of each condition was clearly outlined, discussed and explained.;This author believes that this study has exhibited and proven the ability and applicability of computational fluid dynamics (CFD) to better understand the hydrodynamics of a ship system and improve hull-propeller interaction dynamics. The studies and research in this thesis contribute to the industry as well as academia by shedding more light on large ship hydrodynamic systems.It is not usual that the interests of ship owners are aligned with maritime legislation requirements with the incentives to make ships more efficient. Owners seek to reduce the ship operating costs whilst entities, such as the IMO, push for a more environment friendly marine industry.;A ship's efficiency can be improved by optimising the hull form and/or by installing Energy Saving Devices (ESD) in order to improve the hydrodynamic performance and fluid flow of a vessel. These two areas are not new to the industry and have been investigated using various methods, including computational fluid dynamics (CFD) procedures. The use of CFD for ship performance analyses is becoming more popular in the maritime industry due to its cost-effective capabilities. The continuous development of numerical simulation (CFD) as well as high performance computing opens doors to new areas of investigation and allows research to further study topics that have been previously looked into as well as research questions that have never been explored.;The general aim of this PhD thesis is to contribute to the body of knowledge by shedding light on improving the hydrodynamic performance of large ships for energy efficient transportation. This was achieved by accomplishing a series of objectives and case studies that addressed various research questions.;This study initially proposes an intelligent state-of-the-art methodology for predicting and enhancing the hull-propeller interaction of a vessel using numerical techniques (CFD), optimisation procedures and high-performance computing to identify optimal stern designs as well as understanding the physics and impact of Energy Saving Device/s that could help improve the stern flow characteristics.;The CFD method, that was used to predict the performance for all the various case studies, was validated and verified using well established procedures. The implementation of the recently available curvature correction feature in the numerical model and its enhanced wake prediction capabilities were clearly demonstrated.;Moreover, various types of post-processing CFD analyses that were deemed useful to understand the hydrodynamic performance of a vessel were listed and outlined.;A practical full-scale stern form optimisation procedure for a bulk carrier was developed and demonstrated. Furthermore, whether the quality of a nominal wake can provide any insight into the propeller performance of a vessel was investigated and evaluated.;With regards to the case studies investigating Energy Saving Devices, Propeller Boss Cap Fins were analysed in open water full-scale conditions to understand the physics, function and working principles of such technologies. A state-of-the-art full-scale PBCF optimisation procedure was also demonstrated. The performance of a Wake Equalising Duct at different scale conditions was investigated and compared. The study indicated that the duct is not as effective in full-scale. The reasons and findings were thoroughly discussed and outlined.;The thesis also focused on the research questions regarding the installation of multiple Energy Saving Devices on a ship system. Whether the benefits are directly cumulative or whether the ESDs affect the flow regimes of one another? Thus, a case study was carried out by investigating seven combinations using PBCF, a duct and stator fins. The performance of each condition was clearly outlined, discussed and explained.;This author believes that this study has exhibited and proven the ability and applicability of computational fluid dynamics (CFD) to better understand the hydrodynamics of a ship system and improve hull-propeller interaction dynamics. The studies and research in this thesis contribute to the industry as well as academia by shedding more light on large ship hydrodynamic systems
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