7103 research outputs found
Sort by
Analysis of ship performance in deep and shallow waters using CFD
Get PDFHistorically, the prediction of ship resistance has received its fair share of attention by the scientific community. Although there is a significant body of literature devoted to the study of ship hydrodynamics, several open research questions of great practical relevance remain unanswered. Among these are the extrapolation of ship resistance from model to full-scale in restricted, and unrestricted waters, as well as shallow water ship flows. Most approaches used to predict the performance of a ship have typically relied on the assumptions inherent in potential flow theories, namely, the fluid is treated as inviscid and irrotational. In many cases, these are justifiable assumptions, yielding accurate predictions. However, there are equally many occasions, in which the analyst may not obtain a correct picture of the performance of a ship when relying on the assumptions of potential flow theory. Predicting scale effects, and shallow water influences on ship performance are prime examples of such cases. Numerical techniques based on the Navier-Stokes equations can be thought of as a solution in cases where it is important to model a greater proportion of the physical phenomena.;The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. The main advantages of using such an approach relate to the fact that it accounts for the action of viscosity and turbulence, and can therefore model scale effects and shallow water ship flows. However, with the rapid advent of computational methods in all fields of engineering, several areas have emerged as significant sources of ambiguity. Amongst these are the best approach to modelling turbulence, the numerical uncertainty induced as a result of mapping the continuous governing equations onto a discrete grid, and boundary conditions within the computational domain.;This thesis aims to address all of these issues using a commercially available Reynolds averaged Navier-Stokes solver. Firstly, a detailed literature review on the current methods and approaches to circumventing the problems mentioned above, both numerically and through the use of potential flow theory, is given. Then, studies on scale effects in deep and shallow waters are performed, supplemented by investigations into turbulence modelling and numerical uncertainty. Following these, the thesis' focus shifts towards shallow water phenomena. In particular, the modelling of ship flows without the use of Galilean relativity, and the determination of the Kelvin half-angle in restricted waters. Abrupt changes in the cross-section of the canal in which a ship propagates are also explored, with focus on ship resistance and the properties of the wave field. Finally, the main results obtained from each chapter are summarised and compared against the aims and objectives of this thesis, before recommendations for future work are suggested.Historically, the prediction of ship resistance has received its fair share of attention by the scientific community. Although there is a significant body of literature devoted to the study of ship hydrodynamics, several open research questions of great practical relevance remain unanswered. Among these are the extrapolation of ship resistance from model to full-scale in restricted, and unrestricted waters, as well as shallow water ship flows. Most approaches used to predict the performance of a ship have typically relied on the assumptions inherent in potential flow theories, namely, the fluid is treated as inviscid and irrotational. In many cases, these are justifiable assumptions, yielding accurate predictions. However, there are equally many occasions, in which the analyst may not obtain a correct picture of the performance of a ship when relying on the assumptions of potential flow theory. Predicting scale effects, and shallow water influences on ship performance are prime examples of such cases. Numerical techniques based on the Navier-Stokes equations can be thought of as a solution in cases where it is important to model a greater proportion of the physical phenomena.;The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. The main advantages of using such an approach relate to the fact that it accounts for the action of viscosity and turbulence, and can therefore model scale effects and shallow water ship flows. However, with the rapid advent of computational methods in all fields of engineering, several areas have emerged as significant sources of ambiguity. Amongst these are the best approach to modelling turbulence, the numerical uncertainty induced as a result of mapping the continuous governing equations onto a discrete grid, and boundary conditions within the computational domain.;This thesis aims to address all of these issues using a commercially available Reynolds averaged Navier-Stokes solver. Firstly, a detailed literature review on the current methods and approaches to circumventing the problems mentioned above, both numerically and through the use of potential flow theory, is given. Then, studies on scale effects in deep and shallow waters are performed, supplemented by investigations into turbulence modelling and numerical uncertainty. Following these, the thesis' focus shifts towards shallow water phenomena. In particular, the modelling of ship flows without the use of Galilean relativity, and the determination of the Kelvin half-angle in restricted waters. Abrupt changes in the cross-section of the canal in which a ship propagates are also explored, with focus on ship resistance and the properties of the wave field. Finally, the main results obtained from each chapter are summarised and compared against the aims and objectives of this thesis, before recommendations for future work are suggested
Supporting rational decision-making in civil engineering
Get PDFThe management of civil engineering structures, such as bridges and dams, is fundamental for ensuring their continued safe and economical operation, where decisions such as whether or not to suspend operations are based on uncertain knowledge concerning the state of the structure. Modern development in technology has made available several accurate monitoring devices providing Structural Health Information, that can be used to support such decision-making through more informed assessment of the structural state. The wide-spread adoption of these devices has led to the development of Structural Health Monitoring (SHM) decision support system, to identify appropriate courses of action based on observed data from the monitoring system. Essentially, it is a two-step process, which includes the judgment of the structural state based on the SHM information, and the decision about the optimal action based on the knowledge of the structural state. When engineering knowledge concerning the state of the system is uncertain, as the monitoring system does not directly observe the state of the structure, Bayesian inference and Expected Utility Theory provide the only consistent way to judge and to make decisions, respectively, as all alternative inferential methods for decision support are susceptible to logical inconsistency.;However, we must recognize that in the real world the process followed by decision makers may be distorted. The goal of the research proposed in this contribution is twofold: we investigate how heuristic behaviours may affect human judgment and decision-making in civil engineering, and also how decision-making can be distorted when multiple agents, even rational but with different appetites for risk, are involved in the decision chain. Firstly, most agents in everyday life apply heuristic approaches rather than a formal Bayesian procedure in order to make inference to support decisions. In particular, without the use of formal algorithms to support rational interpretation of data, humans apply simple strategies or mental processes to interpret data, which are prone to systemic errors. This may happen with data that come from various data sources, such as SHM but also engineering expert knowledge. Innovative frameworks to support rational decision-making are then required, in order to minimize the risk of biased judgments or decisions. For instance, being able to predict the behavior of an irrational manager is necessary when we set a general policy for bridge management, and we know that someone else who is going to enact the policy may behave irrationally.;In this doctoral thesis, we start reviewing the literature of heuristics and cognitive biases in order to identify the most relevant as regards human judgment and decision-making for civil engineering structures. We identify Kahneman and Tversky's representativeness as a heuristic for which SHM-based decision-making is particularly susceptible, where simplified rules for updating probabilities can distort the decision maker's perception of risk. Therefore, we reproduce mathematically this observed irrational behavior to investigate how it distorts human judgment. In addition, it is recognized that heuristic behaviors may affect expert knowledge. Consequently, we propose a method for eliciting engineering expert knowledge in order to assess civilengineering structures: the process is required in order to support the collection of valid and reliable data, by minimizing the adverse impact of cognitive biases. Secondly, the decision process can be distorted when multiple agents are involved, not only in the case of irrational behaviors, where the distortion is expected, but even in the case of rational behaviors. Indeed, decision makers may differ in their decisions under uncertainty according to their different appetites for risk. Again, predicting the behavior of managers is required for instance when there is a management policy for which the final decision of an agent has to consider the opinion of other decision makers, who may behave differently.;In this thesis, we formalize an innovative rational method for quantifying the value of information (VoI) of SHM when two different agents are involved in the decision chain: this framework allows one to investigate how decisions may be distorted due to the different appetites for risk of decision makers. In addition, we understand that the interaction between rational agents with different appetites for risk may lead to a negative VoI, which is unexpected since it means that the monitoring information may be perceived as damaging. Therefore, we develop a mathematical formulation to investigate under which specific circumstances it is possible to achieve this unexpected outcome. Finally, all the studied theories and proposed frameworks are applied respectively to various civil engineering case studies. In summary: we evaluate the structural safety of a common type of bridge of the Autonomous Province of Trento stock, in Italy; we investigate the system reliability of the Mountain Chute dam and generating station in Ontario, Canada; we analyse the management of a pedestrian bridge in Princeton University campus equipped with a monitoring system, in USA. These applicationsallow us to demonstrate the operationalizability of the methods developed in this thesis, and to prove their relevance in various civil engineering case studies.The management of civil engineering structures, such as bridges and dams, is fundamental for ensuring their continued safe and economical operation, where decisions such as whether or not to suspend operations are based on uncertain knowledge concerning the state of the structure. Modern development in technology has made available several accurate monitoring devices providing Structural Health Information, that can be used to support such decision-making through more informed assessment of the structural state. The wide-spread adoption of these devices has led to the development of Structural Health Monitoring (SHM) decision support system, to identify appropriate courses of action based on observed data from the monitoring system. Essentially, it is a two-step process, which includes the judgment of the structural state based on the SHM information, and the decision about the optimal action based on the knowledge of the structural state. When engineering knowledge concerning the state of the system is uncertain, as the monitoring system does not directly observe the state of the structure, Bayesian inference and Expected Utility Theory provide the only consistent way to judge and to make decisions, respectively, as all alternative inferential methods for decision support are susceptible to logical inconsistency.;However, we must recognize that in the real world the process followed by decision makers may be distorted. The goal of the research proposed in this contribution is twofold: we investigate how heuristic behaviours may affect human judgment and decision-making in civil engineering, and also how decision-making can be distorted when multiple agents, even rational but with different appetites for risk, are involved in the decision chain. Firstly, most agents in everyday life apply heuristic approaches rather than a formal Bayesian procedure in order to make inference to support decisions. In particular, without the use of formal algorithms to support rational interpretation of data, humans apply simple strategies or mental processes to interpret data, which are prone to systemic errors. This may happen with data that come from various data sources, such as SHM but also engineering expert knowledge. Innovative frameworks to support rational decision-making are then required, in order to minimize the risk of biased judgments or decisions. For instance, being able to predict the behavior of an irrational manager is necessary when we set a general policy for bridge management, and we know that someone else who is going to enact the policy may behave irrationally.;In this doctoral thesis, we start reviewing the literature of heuristics and cognitive biases in order to identify the most relevant as regards human judgment and decision-making for civil engineering structures. We identify Kahneman and Tversky's representativeness as a heuristic for which SHM-based decision-making is particularly susceptible, where simplified rules for updating probabilities can distort the decision maker's perception of risk. Therefore, we reproduce mathematically this observed irrational behavior to investigate how it distorts human judgment. In addition, it is recognized that heuristic behaviors may affect expert knowledge. Consequently, we propose a method for eliciting engineering expert knowledge in order to assess civilengineering structures: the process is required in order to support the collection of valid and reliable data, by minimizing the adverse impact of cognitive biases. Secondly, the decision process can be distorted when multiple agents are involved, not only in the case of irrational behaviors, where the distortion is expected, but even in the case of rational behaviors. Indeed, decision makers may differ in their decisions under uncertainty according to their different appetites for risk. Again, predicting the behavior of managers is required for instance when there is a management policy for which the final decision of an agent has to consider the opinion of other decision makers, who may behave differently.;In this thesis, we formalize an innovative rational method for quantifying the value of information (VoI) of SHM when two different agents are involved in the decision chain: this framework allows one to investigate how decisions may be distorted due to the different appetites for risk of decision makers. In addition, we understand that the interaction between rational agents with different appetites for risk may lead to a negative VoI, which is unexpected since it means that the monitoring information may be perceived as damaging. Therefore, we develop a mathematical formulation to investigate under which specific circumstances it is possible to achieve this unexpected outcome. Finally, all the studied theories and proposed frameworks are applied respectively to various civil engineering case studies. In summary: we evaluate the structural safety of a common type of bridge of the Autonomous Province of Trento stock, in Italy; we investigate the system reliability of the Mountain Chute dam and generating station in Ontario, Canada; we analyse the management of a pedestrian bridge in Princeton University campus equipped with a monitoring system, in USA. These applicationsallow us to demonstrate the operationalizability of the methods developed in this thesis, and to prove their relevance in various civil engineering case studies
Corpus vile or corpus personae? The status of the human body, its parts and its derivatives in Scots Law
Get PDFScots law, as it pertains to the human body, its parts and its derivatives, is said to be 'as settled as the law of England'. It has been juridically asserted that there can be 'no property in a corpse' in either jurisdiction. This rule precluding 'property' in cadavers has been extended, in Anglo-American jurisdictions, to hold that parts of bodies and separated human tissue are also, prima facie, legal non-entities. The suggestion that Scots law is as settled as - indeed, is the same as - the law of England in respect of this matter is puzzling, however. Scots property law is 'resolutely Civilian in character': the word 'property' holds a distinctly different meaning to a Scots lawyer than to an Anglo-American lawyer.;Furthermore, again due to Scotland's institutional connection to the Civil law, Scots law has the potential to afford redress and remedy in situations in which the Common law has been unable to do so. The actio iniuriarum served in Roman law - and serves in modern South African law - as a means of safeguarding the 'dignity' of persons. Scots law, too, thus has the potential to safeguard individuals' interests in 'dignity'. This thesis argues that the distinct legal history of Scotland makes any assumption of commonality between Scots and English law simplistic at best and offers the first comprehensive account of the law relating to the human body, its parts and derivatives in Scotland.;Ultimately, the thesis concludes that Scotland's mixed legal heritage affords scope for the law to develop a 'mixed approach': while it can sometimes be appropriate to recognise the human body, its parts and derivatives as 'property', in other cases it is more logical to regard them as continuing to form a part of a legal 'person'.Scots law, as it pertains to the human body, its parts and its derivatives, is said to be 'as settled as the law of England'. It has been juridically asserted that there can be 'no property in a corpse' in either jurisdiction. This rule precluding 'property' in cadavers has been extended, in Anglo-American jurisdictions, to hold that parts of bodies and separated human tissue are also, prima facie, legal non-entities. The suggestion that Scots law is as settled as - indeed, is the same as - the law of England in respect of this matter is puzzling, however. Scots property law is 'resolutely Civilian in character': the word 'property' holds a distinctly different meaning to a Scots lawyer than to an Anglo-American lawyer.;Furthermore, again due to Scotland's institutional connection to the Civil law, Scots law has the potential to afford redress and remedy in situations in which the Common law has been unable to do so. The actio iniuriarum served in Roman law - and serves in modern South African law - as a means of safeguarding the 'dignity' of persons. Scots law, too, thus has the potential to safeguard individuals' interests in 'dignity'. This thesis argues that the distinct legal history of Scotland makes any assumption of commonality between Scots and English law simplistic at best and offers the first comprehensive account of the law relating to the human body, its parts and derivatives in Scotland.;Ultimately, the thesis concludes that Scotland's mixed legal heritage affords scope for the law to develop a 'mixed approach': while it can sometimes be appropriate to recognise the human body, its parts and derivatives as 'property', in other cases it is more logical to regard them as continuing to form a part of a legal 'person'
Adopting a care ethics approach to fill the void between formal and substantive equality for women solicitors, an analysis of policies of the Law Societies of Scotland, and England & Wales
Get PDFThis research explores workplace policy at the sectoral level which is intended to provide gender equality in a professional setting. More women have been entering the legal profession than men for decades, and more than half of solicitors in the UK are now women. However, there is a leaky pipeline as many women leave the profession, or move in-house, or to other legal roles outside of private practice when they become parents and/or require flexibility. Those women that remain, are not making it to partnership in the same proportion as men, as only 28% of partners are female.;This study is based on the premise that employment laws in the UK provide formal but not substantive equality, so specific workplace policies are required to deliver substantive equality. This study provides a critical analysis of the relevant policies of the Law Societies of Scotland, and England and Wales. It seeks to uncover whether and, to what extent, the regulators are committed to improving substantive equality by way of equal outcomes for women solicitors compared with their male counterparts, seeking promotion to partner. The findings will be of use to the national regulators and to law firms in determining their strategic approaches to gender equality and to those in other jurisdictions and professional sectors.;Firstly, this study sets out a theoretical framework using care ethics based on a cross-disciplinary analysis of relevant literature. Secondly, it uses this framework to provide a content and critical discourse analysis of the relevant policies of the two Law Societies. These are compared and contrasted to identify examples of 'good practice' and areas requiring development according to the theoretical framework. This analysis determines whether the approaches adopted by the regulators are likely to lead to substantive equality for women solicitors and whether lessons can be learned from adopting a care ethics approach to policy-making.This research explores workplace policy at the sectoral level which is intended to provide gender equality in a professional setting. More women have been entering the legal profession than men for decades, and more than half of solicitors in the UK are now women. However, there is a leaky pipeline as many women leave the profession, or move in-house, or to other legal roles outside of private practice when they become parents and/or require flexibility. Those women that remain, are not making it to partnership in the same proportion as men, as only 28% of partners are female.;This study is based on the premise that employment laws in the UK provide formal but not substantive equality, so specific workplace policies are required to deliver substantive equality. This study provides a critical analysis of the relevant policies of the Law Societies of Scotland, and England and Wales. It seeks to uncover whether and, to what extent, the regulators are committed to improving substantive equality by way of equal outcomes for women solicitors compared with their male counterparts, seeking promotion to partner. The findings will be of use to the national regulators and to law firms in determining their strategic approaches to gender equality and to those in other jurisdictions and professional sectors.;Firstly, this study sets out a theoretical framework using care ethics based on a cross-disciplinary analysis of relevant literature. Secondly, it uses this framework to provide a content and critical discourse analysis of the relevant policies of the two Law Societies. These are compared and contrasted to identify examples of 'good practice' and areas requiring development according to the theoretical framework. This analysis determines whether the approaches adopted by the regulators are likely to lead to substantive equality for women solicitors and whether lessons can be learned from adopting a care ethics approach to policy-making
Using cognitive dissonance inducing interventions to change drivers' attitudes towards speeding and reduce speeding behaviour
Get PDFThis research investigated the effects of cognitive dissonance (Festinger, 1957) inducing interventions on drivers' attitudes and speeding behaviour. Chapter 1 discusses the applied context (road safety) and the negative impact of speeding. Chapter 2 discusses the attitude-behaviour relationship and emphasises the need for both attitude-change interventions (for drivers whose speeding is potentially dictated by their generally pro-speeding attitudes) and attitude-conversion interventions (for drivers who speed despite holding generally anti-speeding attitudes). Chapter 3 introduces the theory of cognitive dissonance and reviews associated research relating to attitude-change (induced compliance) and attitude-conversion (hypocrisy induction) interventions;Chapter 4 presents study 1, which was conducted to pilot test measures for the subsequent studies and investigate the components of attitude that predict speeding on the basis that this would have a bearing on how best to develop cognitive dissonance-based interventions (e.g., which components should be targeted?).;Chapter 5 presents study 2, which tested an induced compliance intervention in a sample of drivers with pro-speeding attitudes. As expected, the intervention engendered cognitive dissonance and engendered a change in the components of attitudes that were found to be the biggest predictors of speeding in study 1 at both immediate and one-month post-intervention. It also reduced one-month post-intervention (self-reported) speeding. Although the intervention did not result in immediate post-intervention (objective) behaviour-change and the changes in attitudes were not attributable to the changes in cognitive dissonance, the one-month post-intervention behaviour-change was attributable to attitude-change.;Chapter 6 presents study 3, which tested a hypocrisy induction intervention. As expected, the intervention was found to generate reductions in speeding behaviour, in a sample of regular speeders with anti-speeding (i.e., hypocritical) attitudes at both immediate post-intervention (objective behaviour) and one-month post-intervention (self-reported behaviour). However, the intervention was not found to generate changes in cognitive dissonance.;Chapter 7 discusses the implications of this research for theory and enhancing road safety. Avenues for future research are also discussed.This research investigated the effects of cognitive dissonance (Festinger, 1957) inducing interventions on drivers' attitudes and speeding behaviour. Chapter 1 discusses the applied context (road safety) and the negative impact of speeding. Chapter 2 discusses the attitude-behaviour relationship and emphasises the need for both attitude-change interventions (for drivers whose speeding is potentially dictated by their generally pro-speeding attitudes) and attitude-conversion interventions (for drivers who speed despite holding generally anti-speeding attitudes). Chapter 3 introduces the theory of cognitive dissonance and reviews associated research relating to attitude-change (induced compliance) and attitude-conversion (hypocrisy induction) interventions;Chapter 4 presents study 1, which was conducted to pilot test measures for the subsequent studies and investigate the components of attitude that predict speeding on the basis that this would have a bearing on how best to develop cognitive dissonance-based interventions (e.g., which components should be targeted?).;Chapter 5 presents study 2, which tested an induced compliance intervention in a sample of drivers with pro-speeding attitudes. As expected, the intervention engendered cognitive dissonance and engendered a change in the components of attitudes that were found to be the biggest predictors of speeding in study 1 at both immediate and one-month post-intervention. It also reduced one-month post-intervention (self-reported) speeding. Although the intervention did not result in immediate post-intervention (objective) behaviour-change and the changes in attitudes were not attributable to the changes in cognitive dissonance, the one-month post-intervention behaviour-change was attributable to attitude-change.;Chapter 6 presents study 3, which tested a hypocrisy induction intervention. As expected, the intervention was found to generate reductions in speeding behaviour, in a sample of regular speeders with anti-speeding (i.e., hypocritical) attitudes at both immediate post-intervention (objective behaviour) and one-month post-intervention (self-reported behaviour). However, the intervention was not found to generate changes in cognitive dissonance.;Chapter 7 discusses the implications of this research for theory and enhancing road safety. Avenues for future research are also discussed
Fatigue design criteria for austenitic stainless steels based on simplified elastic-plastic analysis
Get PDFPressure-retaining components of civil light-water reactor (LWR) plants are susceptible to low-cycle fatigue damage throughout their operational life. In the UK civil nuclear industry, the assurance of such components against fatigue failure has traditionally been achieved by satisfying the elastic design-by-analysis (DBA) criteria outlined in Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). The demonstration of a fatigue usage factor of unity against an S-N fatigue design curve forms the basis for establishing acceptable designs.;The ASME III procedure is deterministic, and it is presumed that uncertainties are accounted for by conservatism arising from the largely unquantified margins imposed by the original Code authors, and accumulated from the use of pessimistic input variables and methodological assumptions in the assessment. Whilst this conservatism was tolerable in the past, the emergent industry understanding of the deleterious effect of the LWR coolant environment on fatigue life and its strong dependence on strain rate and temperature for austenitic stainless steels has spawned additional regulatory requirements to incorporate LWR environmental effects into traditional Code fatigue assessments.;Consequently, the application of extant assessment methods, now exacerbated by environmental fatigue penalty factors, can pose difficulties in satisfying Code requirements for some critical components, potentially introducing unnecessary design constraints and an additional in-service inspection burden.;It is well understood that the current ASME III procedure for fatigue evaluation neglects several key variables, is often very conservative and provides an unquantified design margin, and thus does not provide a consistent measure of component risk. The desire for longer plant design life and the potential for civil plants to adopt flexible modes of operation has increased the urgency to develop a more accurate fatigue evaluation procedure, recognising that the traditional design margins, and indeed the acceptance criterion itself, may not be fit for purpose when considering modern plant performance requirements and economic constraints;Accordingly, several actions have been initiated as part of the 'ASME 2025 Nuclear Code' initiative to modernise the existing fatigue design rules. This includes future code development to adopt a risk-informed design methodology based on probabilistic methods with target reliability as an acceptance criterion for fatigue. To this end, ASME has commenced development of a new plant system design standard for establishing plant system and component reliability targets.;In the UK, probabilistic methods for fatigue assessment are also gaining traction within industry, and are currently under consideration by the Department for Business, Energy and Industrial Strategy (BEIS) and the Technical Advisory Group on the Structural Integrity of High Integrity Plant (TAGSI) in anticipation of their future application in nuclear plant safety cases. Adopting a risk-informed design methodology will require improved accuracy of predicting fatigue crack initiation, which in pressure vessels is strongly influenced by the plastic strain range experienced on the component surface.;ASME III prescribes simplified elastic-plastic analysis procedures wherein the plastic strain range may be estimated from elastic analysis using a plasticity correction factor (Ke). However, the existing approach is recognised to be very conservative, especially for ductile materials such as austenitic stainless steels.;The aim of this work is to investigate these conservatisms and develop alternative approaches for simplified elastic-plastic fatigue analysis of austenitic stainless steel components with improved accuracy and practicality, suitable for future application to probabilistic fatigue initiation analysis. Extant Ke methods prescribed within various nuclear and non-nuclear codes and standards are reviewed to understand their relative advantages and limitations. A framework is proposed for calculating the actual plasticity correction factor (KeFEA) implied by detailed elastic-plastic analysis.;A large number of elastic-plastic finite element analyses are performed for a range of case studies considering plant representative components and loading conditions. The performance of the various code Ke factors are evaluated and compared. Two alternative approaches - the Global Plasticity Correction Factor (Fg) and Stress-Modified Neuber (SMN) methods - are proposed and validated against the compiled KeFEA results. Both approaches are shown to be fully compatible with existing methods for assessing environmentally assisted fatigue. Through a benchmark problem, the proposed methods are demonstrated to give a more appropriate evaluation of fatigue usage, enabling significant improvements in component design lifePressure-retaining components of civil light-water reactor (LWR) plants are susceptible to low-cycle fatigue damage throughout their operational life. In the UK civil nuclear industry, the assurance of such components against fatigue failure has traditionally been achieved by satisfying the elastic design-by-analysis (DBA) criteria outlined in Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). The demonstration of a fatigue usage factor of unity against an S-N fatigue design curve forms the basis for establishing acceptable designs.;The ASME III procedure is deterministic, and it is presumed that uncertainties are accounted for by conservatism arising from the largely unquantified margins imposed by the original Code authors, and accumulated from the use of pessimistic input variables and methodological assumptions in the assessment. Whilst this conservatism was tolerable in the past, the emergent industry understanding of the deleterious effect of the LWR coolant environment on fatigue life and its strong dependence on strain rate and temperature for austenitic stainless steels has spawned additional regulatory requirements to incorporate LWR environmental effects into traditional Code fatigue assessments.;Consequently, the application of extant assessment methods, now exacerbated by environmental fatigue penalty factors, can pose difficulties in satisfying Code requirements for some critical components, potentially introducing unnecessary design constraints and an additional in-service inspection burden.;It is well understood that the current ASME III procedure for fatigue evaluation neglects several key variables, is often very conservative and provides an unquantified design margin, and thus does not provide a consistent measure of component risk. The desire for longer plant design life and the potential for civil plants to adopt flexible modes of operation has increased the urgency to develop a more accurate fatigue evaluation procedure, recognising that the traditional design margins, and indeed the acceptance criterion itself, may not be fit for purpose when considering modern plant performance requirements and economic constraints;Accordingly, several actions have been initiated as part of the 'ASME 2025 Nuclear Code' initiative to modernise the existing fatigue design rules. This includes future code development to adopt a risk-informed design methodology based on probabilistic methods with target reliability as an acceptance criterion for fatigue. To this end, ASME has commenced development of a new plant system design standard for establishing plant system and component reliability targets.;In the UK, probabilistic methods for fatigue assessment are also gaining traction within industry, and are currently under consideration by the Department for Business, Energy and Industrial Strategy (BEIS) and the Technical Advisory Group on the Structural Integrity of High Integrity Plant (TAGSI) in anticipation of their future application in nuclear plant safety cases. Adopting a risk-informed design methodology will require improved accuracy of predicting fatigue crack initiation, which in pressure vessels is strongly influenced by the plastic strain range experienced on the component surface.;ASME III prescribes simplified elastic-plastic analysis procedures wherein the plastic strain range may be estimated from elastic analysis using a plasticity correction factor (Ke). However, the existing approach is recognised to be very conservative, especially for ductile materials such as austenitic stainless steels.;The aim of this work is to investigate these conservatisms and develop alternative approaches for simplified elastic-plastic fatigue analysis of austenitic stainless steel components with improved accuracy and practicality, suitable for future application to probabilistic fatigue initiation analysis. Extant Ke methods prescribed within various nuclear and non-nuclear codes and standards are reviewed to understand their relative advantages and limitations. A framework is proposed for calculating the actual plasticity correction factor (KeFEA) implied by detailed elastic-plastic analysis.;A large number of elastic-plastic finite element analyses are performed for a range of case studies considering plant representative components and loading conditions. The performance of the various code Ke factors are evaluated and compared. Two alternative approaches - the Global Plasticity Correction Factor (Fg) and Stress-Modified Neuber (SMN) methods - are proposed and validated against the compiled KeFEA results. Both approaches are shown to be fully compatible with existing methods for assessing environmentally assisted fatigue. Through a benchmark problem, the proposed methods are demonstrated to give a more appropriate evaluation of fatigue usage, enabling significant improvements in component design lif
The application of quantum simulation to topological and open many-body systems
Get PDFQuantum simulation is the notion of experimentally controlling and manipulating physical quantum mechanical resources such that their evolution can be mapped onto a problem that is much harder to solve by any other means. Realising a fully general quantum computer is still a work in progress but we can currently use devices that are purpose built to solve particular classes of problems, so called analogue quantum simulators, to investigate many-body quantum systems. In this thesis we first consider benchmarking the performance of realistic hardware implementations of quantum simulators through simulations of many-body dynamics, where we are able to demonstrate that even with current levels of experimental errors, analogue simulators in ongoing experiments are able to out-perform the best classical algorithms. We next propose how to use these devices in order to study strongly correlated phases induced by interactions in topological band structures, where we place a strong emphasis on how to experimentally realise, prepare and detect these phases for atoms in a Creutz ladder and in a Lieb lattice.;We find that in these systems there is an enhanced tendency for interaction induced pairing, allowing for novel pair superfluid phases to be prepared in experiments with ultracold atoms. Finally, we consider additions to these simulators such that they map more closely to many-body systems in realistic solid state settings by including dissipative mechanisms. Specifically, we demonstrate that we are able to classically simulate this behaviour by modifying and hybridising existing numerical methods to allow for the simulation of open many-body systems beyond the Born-Markov approximation. We benchmark this numerical approach by simulating the dynamicsof electrons coupled to a phonon environment, where we find substantial qualitative differences compared to standard open system techniques.Quantum simulation is the notion of experimentally controlling and manipulating physical quantum mechanical resources such that their evolution can be mapped onto a problem that is much harder to solve by any other means. Realising a fully general quantum computer is still a work in progress but we can currently use devices that are purpose built to solve particular classes of problems, so called analogue quantum simulators, to investigate many-body quantum systems. In this thesis we first consider benchmarking the performance of realistic hardware implementations of quantum simulators through simulations of many-body dynamics, where we are able to demonstrate that even with current levels of experimental errors, analogue simulators in ongoing experiments are able to out-perform the best classical algorithms. We next propose how to use these devices in order to study strongly correlated phases induced by interactions in topological band structures, where we place a strong emphasis on how to experimentally realise, prepare and detect these phases for atoms in a Creutz ladder and in a Lieb lattice.;We find that in these systems there is an enhanced tendency for interaction induced pairing, allowing for novel pair superfluid phases to be prepared in experiments with ultracold atoms. Finally, we consider additions to these simulators such that they map more closely to many-body systems in realistic solid state settings by including dissipative mechanisms. Specifically, we demonstrate that we are able to classically simulate this behaviour by modifying and hybridising existing numerical methods to allow for the simulation of open many-body systems beyond the Born-Markov approximation. We benchmark this numerical approach by simulating the dynamicsof electrons coupled to a phonon environment, where we find substantial qualitative differences compared to standard open system techniques
Multi-modality feature fusion and unsupervised hyperspectral band selection for effective classification of remote sensing images
Get PDFIn recent years, Hyperspectral image (HSI) has been widely applied in a range of applications due to its contained rich spectral information. As a fundamental topic in HSI analysis, HSI classification has attracted increasing attention. An effective classification algorithm without too much computational cost is always desired, especially under the circumstance of insufficient training samples. As a result, this thesis aims to design and implement novel techniques to reduce the high dimensionality of the HSI data and improve the classification performance with limited training samples.;In this thesis, first, a superpixel-based feature specific sparse representation framework (SPFS-SRC) is proposed for spectral-spatial classification of HSI at superpixel level, which can improve the classification performance with less training samples and better efficacy. The proposed online learning strategy can better reflect the effect of each extracted feature. Second, a superpixel-based multiple feature fusion framework has been developed to generate an effective fused feature with a reduced dimension.;In addition, two novel methods are also proposed for unsupervised band selection for dimensionality reduction in HSI. First, an adaptive distance enabled tree-based band hierarchy framework (ADBH) has been developed to obtain desired band subset of the HSI, which can help to avoid the noisy bands. With the proposed tree hierarchy-based framework, any number of band subset can be acquired. By introducing a novel adaptive distance into the hierarchy, the similarity between bands and band groups can be computed straightforward whilst reducing the effect of noisy bands.;Furthermore, a deep learning-based framework has been designed to determine the optimal band subset by utilizing the concrete autoencoder (CAE). The band subset with the most information can be chosen as the desired result. For performance evaluation, several remote sensing HSI datasets have been utilized to evaluate the proposed algorithms, where improved performance has proved the superiority of proposed methodologies.;In summary, the outcome of this thesis make contributions in the HSI community by proposing two multi-modality feature fusion algorithms and two unsupervised band selection methods for the effective dimensionality reduction and data classification in HSI, the novelty and robustness of the proposed technologies have been fully demonstrated by extensive experiments. Relevant approaches also have great potential to be applied in other signal and image analysis tasks,especially dimensionality reduction, data fusion and data classification.In recent years, Hyperspectral image (HSI) has been widely applied in a range of applications due to its contained rich spectral information. As a fundamental topic in HSI analysis, HSI classification has attracted increasing attention. An effective classification algorithm without too much computational cost is always desired, especially under the circumstance of insufficient training samples. As a result, this thesis aims to design and implement novel techniques to reduce the high dimensionality of the HSI data and improve the classification performance with limited training samples.;In this thesis, first, a superpixel-based feature specific sparse representation framework (SPFS-SRC) is proposed for spectral-spatial classification of HSI at superpixel level, which can improve the classification performance with less training samples and better efficacy. The proposed online learning strategy can better reflect the effect of each extracted feature. Second, a superpixel-based multiple feature fusion framework has been developed to generate an effective fused feature with a reduced dimension.;In addition, two novel methods are also proposed for unsupervised band selection for dimensionality reduction in HSI. First, an adaptive distance enabled tree-based band hierarchy framework (ADBH) has been developed to obtain desired band subset of the HSI, which can help to avoid the noisy bands. With the proposed tree hierarchy-based framework, any number of band subset can be acquired. By introducing a novel adaptive distance into the hierarchy, the similarity between bands and band groups can be computed straightforward whilst reducing the effect of noisy bands.;Furthermore, a deep learning-based framework has been designed to determine the optimal band subset by utilizing the concrete autoencoder (CAE). The band subset with the most information can be chosen as the desired result. For performance evaluation, several remote sensing HSI datasets have been utilized to evaluate the proposed algorithms, where improved performance has proved the superiority of proposed methodologies.;In summary, the outcome of this thesis make contributions in the HSI community by proposing two multi-modality feature fusion algorithms and two unsupervised band selection methods for the effective dimensionality reduction and data classification in HSI, the novelty and robustness of the proposed technologies have been fully demonstrated by extensive experiments. Relevant approaches also have great potential to be applied in other signal and image analysis tasks,especially dimensionality reduction, data fusion and data classification
'Where's the storytelling factory?' A social enterprise blueprint for our older people's last 1000 days
No full textProblem Statement : If each of us knew that we had only 1,000 days left to live, I wonder how we might like to spend such time? The chances are that we might like to spend our time along with our families and engaged, should we so choose, with pursuits that we may find fulfilling. If this is the case, then perhaps a public strategy for the social care for older people might configure the resources that may be to hand in order to best enable these outcomes for us. My thesis examines how a strategy can be configured as to achieve these outcomes better.;That people are living longer worldwide is to be celebrated, but along with this success comes significant challenges for individuals, families and society. To illustrate the scale of this challenge, consider that in the UK, one person in six born today are expected to live to be 100 years old, some 10 million people,rising from some 13,000 today. Such rapid growth has been evident in Northern Ireland where the Northern Ireland Statistics and Research Agency found that between 2007 and 2017, the number of people aged between 90 and 98 grew by 55% from 1,956 to 3,029 (NISRA, 2019).;In this cohort, a great many find themselves at the 'interface' between care-at-home and care home, torn between their deep-seated desire to maintain their quality of life through remaining in control, and their capability to do so. Many are forced to trade in their independence in return for the security and standardised interventions of institutional care.;Regrettably, such care is not well suited to maximise the individuals' quality of life. Nor is it financially sustainable. Mean care costs for 65-year-olds are £2,000 per year, whereas costs for 85-year-olds are closer to £12,000 per year (Bengoa et al., 2016). Such expense is partially due to unplanned acute care events by older people living at home at this interface, as well as the costs relating to the number living their last 1,000 days in institutional care.;Demographics, costs of institutional care, plus non-elective and extended stays in acute care are significant reasons behind the health and social care system finding itself on an unsustainable trajectory. The resulting pressures on the acute care system mean that a different strategy is sorely needed. Such a strategy may well be an approach that enables older people's autonomy, but with security. It may likely take the form of a housing-with-care environment that enables the well-being contributions of the home, autonomy and relationships.;Accordingly, it has been long recognised that for those older people at the interface between care-at-home and care home, enabling them to remain in control via housing with care both maximises their quality of life and constitutes cost-effective care. Indeed, as I detail within Section 1 of my enclosures companion document, in Northern Ireland, there have been successive policy initiatives for over 30 years that have advocated creating more clusters of housing-with-care.;Therein, it has been long recognised that older individuals and older couples may retain control and pursue their own happiness in ways that suit their idiosyncratic needs and desires. As such, housing-with-care has always seemed a promising way to addressing the longstanding strategic problem of spiralling care costs. However, the problem is that there has been no conceptualisation of an integrated public/private policy nor strategy to procure these clusters of care. My thesis aims to contribute to filling that void.Problem Statement : If each of us knew that we had only 1,000 days left to live, I wonder how we might like to spend such time? The chances are that we might like to spend our time along with our families and engaged, should we so choose, with pursuits that we may find fulfilling. If this is the case, then perhaps a public strategy for the social care for older people might configure the resources that may be to hand in order to best enable these outcomes for us. My thesis examines how a strategy can be configured as to achieve these outcomes better.;That people are living longer worldwide is to be celebrated, but along with this success comes significant challenges for individuals, families and society. To illustrate the scale of this challenge, consider that in the UK, one person in six born today are expected to live to be 100 years old, some 10 million people,rising from some 13,000 today. Such rapid growth has been evident in Northern Ireland where the Northern Ireland Statistics and Research Agency found that between 2007 and 2017, the number of people aged between 90 and 98 grew by 55% from 1,956 to 3,029 (NISRA, 2019).;In this cohort, a great many find themselves at the 'interface' between care-at-home and care home, torn between their deep-seated desire to maintain their quality of life through remaining in control, and their capability to do so. Many are forced to trade in their independence in return for the security and standardised interventions of institutional care.;Regrettably, such care is not well suited to maximise the individuals' quality of life. Nor is it financially sustainable. Mean care costs for 65-year-olds are £2,000 per year, whereas costs for 85-year-olds are closer to £12,000 per year (Bengoa et al., 2016). Such expense is partially due to unplanned acute care events by older people living at home at this interface, as well as the costs relating to the number living their last 1,000 days in institutional care.;Demographics, costs of institutional care, plus non-elective and extended stays in acute care are significant reasons behind the health and social care system finding itself on an unsustainable trajectory. The resulting pressures on the acute care system mean that a different strategy is sorely needed. Such a strategy may well be an approach that enables older people's autonomy, but with security. It may likely take the form of a housing-with-care environment that enables the well-being contributions of the home, autonomy and relationships.;Accordingly, it has been long recognised that for those older people at the interface between care-at-home and care home, enabling them to remain in control via housing with care both maximises their quality of life and constitutes cost-effective care. Indeed, as I detail within Section 1 of my enclosures companion document, in Northern Ireland, there have been successive policy initiatives for over 30 years that have advocated creating more clusters of housing-with-care.;Therein, it has been long recognised that older individuals and older couples may retain control and pursue their own happiness in ways that suit their idiosyncratic needs and desires. As such, housing-with-care has always seemed a promising way to addressing the longstanding strategic problem of spiralling care costs. However, the problem is that there has been no conceptualisation of an integrated public/private policy nor strategy to procure these clusters of care. My thesis aims to contribute to filling that void
Non-intrusive load monitoring solutions for low- and very low-rate granularity
Get PDFStrathclyde theses - ask staff. Thesis no. : T15573Large-scale smart energy metering deployment worldwide and the integration of smart meters within the smart grid are enabling two-way communication between the consumer and energy network, thus ensuring an improved response to demand. Energy disaggregation or non-intrusive load monitoring (NILM), namely disaggregation of the total metered electricity consumption down to individual appliances using purely algorithmic tools, is gaining popularity as an added-value that makes the most of meter data.In this thesis, the first contribution tackles low-rate NILM problem by proposing an approach based on graph signal processing (GSP) that does not require any training.Note that Low-rate NILM refers to NILM of active power measurements only, at rates from 1 second to 1 minute. Adaptive thresholding, signal clustering and pattern matching are implemented via GSP concepts and applied to the NILM problem. Then for further demonstration of GSP potential, GSP concepts are applied at both, physical signal level via graph-based filtering and data level, via effective semi-supervised GSP-based feature matching. The proposed GSP-based NILM-improving methods are generic and can be used to improve the results of various event-based NILM approaches. NILM solutions for very low data rates (15-60 min) cannot leverage on low to highrates NILM approaches. Therefore, the third contribution of this thesis comprises three very low-rate load disaggregation solutions, based on supervised (i) K-nearest neighbours relying on features such as statistical measures of the energy signal, time usage profile of appliances and reactive power consumption (if available); unsupervised(ii) optimisation performing minimisation of error between aggregate and the sum of estimated individual loads, where energy consumed by always-on load is heuristically estimated prior to further disaggregation and appliance models are built only by manufacturer information; and (iii) GSP as a variant of aforementioned GSP-based solution proposed for low-rate load disaggregation, with an additional graph of time-of-day information.Large-scale smart energy metering deployment worldwide and the integration of smart meters within the smart grid are enabling two-way communication between the consumer and energy network, thus ensuring an improved response to demand. Energy disaggregation or non-intrusive load monitoring (NILM), namely disaggregation of the total metered electricity consumption down to individual appliances using purely algorithmic tools, is gaining popularity as an added-value that makes the most of meter data.In this thesis, the first contribution tackles low-rate NILM problem by proposing an approach based on graph signal processing (GSP) that does not require any training.Note that Low-rate NILM refers to NILM of active power measurements only, at rates from 1 second to 1 minute. Adaptive thresholding, signal clustering and pattern matching are implemented via GSP concepts and applied to the NILM problem. Then for further demonstration of GSP potential, GSP concepts are applied at both, physical signal level via graph-based filtering and data level, via effective semi-supervised GSP-based feature matching. The proposed GSP-based NILM-improving methods are generic and can be used to improve the results of various event-based NILM approaches. NILM solutions for very low data rates (15-60 min) cannot leverage on low to highrates NILM approaches. Therefore, the third contribution of this thesis comprises three very low-rate load disaggregation solutions, based on supervised (i) K-nearest neighbours relying on features such as statistical measures of the energy signal, time usage profile of appliances and reactive power consumption (if available); unsupervised(ii) optimisation performing minimisation of error between aggregate and the sum of estimated individual loads, where energy consumed by always-on load is heuristically estimated prior to further disaggregation and appliance models are built only by manufacturer information; and (iii) GSP as a variant of aforementioned GSP-based solution proposed for low-rate load disaggregation, with an additional graph of time-of-day information
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!