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Forensic RNA analysis for estimating the age of body fluid stains
Get PDFStrathclyde theses - ask staff. Thesis no. : T15425The first appearance of ribonucleic acid (RNA) in forensic science research was in 1984 in the study of post-mortem tissues. Since then, many studies have explored the role of gene expression and its potential applications in forensic science. Some RNA types such as messenger RNA (mRNA) and microRNA (miRNA) have been subject to increasing interest in the forensic science community.It has been shown that analysis of RNA molecules can also be applied to determine the time when a biological stain was deposited at a crime scene, by analysing their stability and degradation rate. Estimating the age of a biological stain can provide essential information to an investigation. This research has analysed the expression and degradation level of different types of body fluidspecific RNA markers, including mRNA and miRNA markers, with the aim of identifying RNA markers that can be used to estimate the age of three types of body fluid (blood, saliva and semen). In this approach, reverse transcription quantitative PCR (RT-qPCR) has been utilised using appropriate primers and TaqMan® probes.;The relative expression ratio (RER) between different types of body fluid-specific RNA markers was then examined in aged body fluid samples across one-year storage interval, with the aim of developing a method to estimate the age of body fluid stains recovered at crime scenes.Each RNA marker exhibited unique degradation behaviour across ageing time points for blood, saliva and semen samples, with miRNAs showing high stability. Statistically significant correlations were found between the RERs of RNA markers and ageing time points, exhibiting a non-linear relationship.Overall, the RERs of body fluid-specific markers can be considered as apotential method for estimating the age of biological stains, and this has a widerange of applications in forensic science.The first appearance of ribonucleic acid (RNA) in forensic science research was in 1984 in the study of post-mortem tissues. Since then, many studies have explored the role of gene expression and its potential applications in forensic science. Some RNA types such as messenger RNA (mRNA) and microRNA (miRNA) have been subject to increasing interest in the forensic science community.It has been shown that analysis of RNA molecules can also be applied to determine the time when a biological stain was deposited at a crime scene, by analysing their stability and degradation rate. Estimating the age of a biological stain can provide essential information to an investigation. This research has analysed the expression and degradation level of different types of body fluidspecific RNA markers, including mRNA and miRNA markers, with the aim of identifying RNA markers that can be used to estimate the age of three types of body fluid (blood, saliva and semen). In this approach, reverse transcription quantitative PCR (RT-qPCR) has been utilised using appropriate primers and TaqMan® probes.;The relative expression ratio (RER) between different types of body fluid-specific RNA markers was then examined in aged body fluid samples across one-year storage interval, with the aim of developing a method to estimate the age of body fluid stains recovered at crime scenes.Each RNA marker exhibited unique degradation behaviour across ageing time points for blood, saliva and semen samples, with miRNAs showing high stability. Statistically significant correlations were found between the RERs of RNA markers and ageing time points, exhibiting a non-linear relationship.Overall, the RERs of body fluid-specific markers can be considered as apotential method for estimating the age of biological stains, and this has a widerange of applications in forensic science
Optimisation of GMAW via the alternating shielding gas technique
Get PDFThis thesis was previously held under moratorium from 25/11/19 to 25/11/21The use of the alternating shielding gas technique in arc welding systems has been previously studied due to advantages such as greater penetration of the weld joint, refined microstructure of the fusion zone, reduced heat input, and increased travel speeds of the welding torch. Yet, relatively little work has been carried out utilising this novel method. For instance, shielding gases employed during the arc welding procedures have been limited to Ar, CO and He, since the reactive behaviour of N within the arc plasma causes porosity development within the fusion zone. The present thesis extended the scientific knowledge regarding the alternating shielding gas technique via a systematic analysis utilising the gas metal arc welding process. It explored reductions in the shielding gas flow rate via variations in the frequency of alternation between the protective gases, investigated additions of N as a protective gas to weld DH36 grade steel plates, and examined ways to optimise the welding parameters. Measurements of the distortion of the workpiece, temperature of the weld, heat-affected zone (HAZ) and weld shape demonstrated the impact of the alternating shielding gas technique in reducing the heat input to the weldment. Microstructural characterisation coupled with analyses of the mechanical properties of the joint exhibited improved strength due to the faster welding procedures and greater formation of acicular ferrite. Additionally, mathematical modelling coupled with the genetic algorithm heuristic assisted with enhancing the efficiency of welds under the supply of N as a protective gas. The study carried out was able to diminish the shielding gas consumption even further by employing the alternating shielding gas technique. It also offered new insights in terms of shielding gas options, where the replacement of CO for N lowered the welding fume progression, eliminated the porosity development within welds, and generated a more uniform weld shape.The use of the alternating shielding gas technique in arc welding systems has been previously studied due to advantages such as greater penetration of the weld joint, refined microstructure of the fusion zone, reduced heat input, and increased travel speeds of the welding torch. Yet, relatively little work has been carried out utilising this novel method. For instance, shielding gases employed during the arc welding procedures have been limited to Ar, CO and He, since the reactive behaviour of N within the arc plasma causes porosity development within the fusion zone. The present thesis extended the scientific knowledge regarding the alternating shielding gas technique via a systematic analysis utilising the gas metal arc welding process. It explored reductions in the shielding gas flow rate via variations in the frequency of alternation between the protective gases, investigated additions of N as a protective gas to weld DH36 grade steel plates, and examined ways to optimise the welding parameters. Measurements of the distortion of the workpiece, temperature of the weld, heat-affected zone (HAZ) and weld shape demonstrated the impact of the alternating shielding gas technique in reducing the heat input to the weldment. Microstructural characterisation coupled with analyses of the mechanical properties of the joint exhibited improved strength due to the faster welding procedures and greater formation of acicular ferrite. Additionally, mathematical modelling coupled with the genetic algorithm heuristic assisted with enhancing the efficiency of welds under the supply of N as a protective gas. The study carried out was able to diminish the shielding gas consumption even further by employing the alternating shielding gas technique. It also offered new insights in terms of shielding gas options, where the replacement of CO for N lowered the welding fume progression, eliminated the porosity development within welds, and generated a more uniform weld shape
Evaluating readability as a factor in information security policies
Get PDFThis thesis was previously held under moratorium from 26/11/19 to 26/11/21Policies should be treated as rules or principles that individuals can readily comprehend and follow as a pre-requisite to any organisational requirement to obey and enact regulations. This dissertation attempts to highlight one of the important factors to consider before issuing any policy that staff members are required to follow. Presently, there is no ready mechanism for estimating the likely efficacy of such policies across an organisation. One factor that has a plausible impact upon the comprehensibility of policies is their readability. Researchers have designed a number of software readability metrics that evaluate how difficult a passage is to comprehend; yet, little is known about the impact of readability on the interpretation of information security policies and whether analysis of readability may prove to be a useful insight.This thesis describes the first study to investigate the feasibility of applying readability metrics as an indicator of policy comprehensibility through a mixed methods approach, with the formulation and implementation of a seven phase sequential exploratory fully mixed methods design. Each one was established in light of the outcomes from the previous phase. The methodological approach of this research study is one of the distinguishing characteristics reported in the thesis, which was as follows:* eight policies were selected (from a combination of academia and industry sector institutes);* specialists were requested their insights on key policy elements;* focus group interviews were conducted;* comprehension tests were developed (Cloze tests);* a pilot study of comprehension tests was organised (preceded by a small-scale test);* a main study of comprehension tests was performed with 600 participants and reduce that for validation to 396;* a comparison was made of comprehension results against readability metrics.The results reveal that the traditional readability metrics are ineffective in predicting human estimation. Nevertheless, readability, as measured using a bespoke readability metric, may yield useful insight upon the likely difficulty that end-users may face in comprehending a written text. Thereby, our study aims to provide an effective approach to enhancing the comprehensibility of information security policies and afford a facility for future research in this area.The research contributes to our understanding of readability in general and offering an optimal technique to measure the readability in particular. We recommend immediate corrective actions to enhance the ease of comprehension for information security policies. In part, this may reduce instances where users avoid fully reading the information security policies, and may also increase the likelihood of user compliance. We suggest that the application of appropriately selected readability assessment may assist policy makers to test their draft policies for ease of comprehension before policy release. Indeed, there may be grounds for a readability compliance test that future information security policies must satisfy.Policies should be treated as rules or principles that individuals can readily comprehend and follow as a pre-requisite to any organisational requirement to obey and enact regulations. This dissertation attempts to highlight one of the important factors to consider before issuing any policy that staff members are required to follow. Presently, there is no ready mechanism for estimating the likely efficacy of such policies across an organisation. One factor that has a plausible impact upon the comprehensibility of policies is their readability. Researchers have designed a number of software readability metrics that evaluate how difficult a passage is to comprehend; yet, little is known about the impact of readability on the interpretation of information security policies and whether analysis of readability may prove to be a useful insight.This thesis describes the first study to investigate the feasibility of applying readability metrics as an indicator of policy comprehensibility through a mixed methods approach, with the formulation and implementation of a seven phase sequential exploratory fully mixed methods design. Each one was established in light of the outcomes from the previous phase. The methodological approach of this research study is one of the distinguishing characteristics reported in the thesis, which was as follows:* eight policies were selected (from a combination of academia and industry sector institutes);* specialists were requested their insights on key policy elements;* focus group interviews were conducted;* comprehension tests were developed (Cloze tests);* a pilot study of comprehension tests was organised (preceded by a small-scale test);* a main study of comprehension tests was performed with 600 participants and reduce that for validation to 396;* a comparison was made of comprehension results against readability metrics.The results reveal that the traditional readability metrics are ineffective in predicting human estimation. Nevertheless, readability, as measured using a bespoke readability metric, may yield useful insight upon the likely difficulty that end-users may face in comprehending a written text. Thereby, our study aims to provide an effective approach to enhancing the comprehensibility of information security policies and afford a facility for future research in this area.The research contributes to our understanding of readability in general and offering an optimal technique to measure the readability in particular. We recommend immediate corrective actions to enhance the ease of comprehension for information security policies. In part, this may reduce instances where users avoid fully reading the information security policies, and may also increase the likelihood of user compliance. We suggest that the application of appropriately selected readability assessment may assist policy makers to test their draft policies for ease of comprehension before policy release. Indeed, there may be grounds for a readability compliance test that future information security policies must satisfy
Nucleation and growth of pharmaceutical crystals
Get PDFInvestigating nucleation, crystal growth and solid-state transformations at the nanoscale are of significant interest, as more complex routes have roused questions about the classical view of these processes. This thesis reports the characterisation of prenucleation clusters in olanzapine (OZPN) aqueous solutions, their role in non-classical heteronucleation of OZPN hydrates and during crystal growth mechanism.;Atomic force microscopy studies of the (100)OZPNI face of OZPN I crystals in contact with water show the formation, growth, and order of dense nanodroplets leading to crystallization of OZPN dihydrate on the surface of OZPN I. Dihydrate polymorphic form is driven by a templating effect of the underlying OZPN I lattice. The size and volume fraction of nanodroplets in purely aqueous and mixed ethanol and water OZPN solutions show that their radius is steady in time at ca. 35 nm and it is independent of the OZPN concentration and the solvent composition.;The OZPN fraction captured in the clusters is dictated by the solution thermodynamics. Both behaviours are consistent with the predictions of a model that assumes the formation of OZPN dimers and their decay upon exiting the clusters. Although the presence of prenucleation clusters is critical during OZPN phase transformation, it was observed that clusters do not take part in a growth mechanism and OZPN layers are generated by a spiral growth. Step velocity shows a nonlinear dependence on OZPN concentration.;The proposed growth model suggests that OZPN layers propagate by incorporation of OZPN dimers present as a minor species in OZPN solution. The growth by dimers is faster not owing to spatial or entropic factors or weakly bound solvent, but to the accumulation of dimers on crystal surfaces due to stronger binding. These findings provide guidance towards enhanced control over nucleation, molecular transitions, and the solid forms in molecular systems.Investigating nucleation, crystal growth and solid-state transformations at the nanoscale are of significant interest, as more complex routes have roused questions about the classical view of these processes. This thesis reports the characterisation of prenucleation clusters in olanzapine (OZPN) aqueous solutions, their role in non-classical heteronucleation of OZPN hydrates and during crystal growth mechanism.;Atomic force microscopy studies of the (100)OZPNI face of OZPN I crystals in contact with water show the formation, growth, and order of dense nanodroplets leading to crystallization of OZPN dihydrate on the surface of OZPN I. Dihydrate polymorphic form is driven by a templating effect of the underlying OZPN I lattice. The size and volume fraction of nanodroplets in purely aqueous and mixed ethanol and water OZPN solutions show that their radius is steady in time at ca. 35 nm and it is independent of the OZPN concentration and the solvent composition.;The OZPN fraction captured in the clusters is dictated by the solution thermodynamics. Both behaviours are consistent with the predictions of a model that assumes the formation of OZPN dimers and their decay upon exiting the clusters. Although the presence of prenucleation clusters is critical during OZPN phase transformation, it was observed that clusters do not take part in a growth mechanism and OZPN layers are generated by a spiral growth. Step velocity shows a nonlinear dependence on OZPN concentration.;The proposed growth model suggests that OZPN layers propagate by incorporation of OZPN dimers present as a minor species in OZPN solution. The growth by dimers is faster not owing to spatial or entropic factors or weakly bound solvent, but to the accumulation of dimers on crystal surfaces due to stronger binding. These findings provide guidance towards enhanced control over nucleation, molecular transitions, and the solid forms in molecular systems
Designing efficient and contemporary ship recycling yards through discrete event simulation
Get PDFShip recycling, similar to any other recycling industry, can be considered as the most environmentally friendly option for end-of-life ships than the other alternatives. However, lack of safety, lack of environmental awareness as well as lack of a global and local regulatory framework resulted in ships being dismantled in undesirable conditions which forced international regulators to focus on developing international regulations and standards.;The International Maritime Organization's (IMO) Hong Kong Convention and the European Union's Ship Recycling Regulation are examples of the aforementioned new regulations. Both regulations require ship recycling yards to improve existing HSE standards to stay compliant. These HSE measures will negatively impact on running costs, therefore, ship recycling yards will need to increase their production efficiency to remain competitive.;Even though the industry requires support during this transition, there is no study within the current body of literature that focuses on increasing the productivity of the ship recycling facilities. Hence, there is a need to develop a framework to design contemporary and efficient ship recycling yards. Increasing production efficiency in ship recycling yards will not only decrease the costs, but it will also increase the throughput of the yards which will generate more income and positively impact on overall profitability.;Therefore, this PhD study addresses this gap through the development of a simulation framework for ship recycling industry to design and optimise the ship recycling yards. The study adopts a case-based approach where numerous design alternatives will be studied through the proposed framework. The main aim of this study is to increase the productivity of ship recycling yards and optimise their procedures towards achieving cost-efficient facilities.;Overall research conducted in this study will be significant contribution to the maritime literature as a novel framework for ship recycling yard design and optimisation is developed. The process models of this framework are developed based on real ship recycling procedures, therefore, the framework can be considered ready for practical implementation.Ship recycling, similar to any other recycling industry, can be considered as the most environmentally friendly option for end-of-life ships than the other alternatives. However, lack of safety, lack of environmental awareness as well as lack of a global and local regulatory framework resulted in ships being dismantled in undesirable conditions which forced international regulators to focus on developing international regulations and standards.;The International Maritime Organization's (IMO) Hong Kong Convention and the European Union's Ship Recycling Regulation are examples of the aforementioned new regulations. Both regulations require ship recycling yards to improve existing HSE standards to stay compliant. These HSE measures will negatively impact on running costs, therefore, ship recycling yards will need to increase their production efficiency to remain competitive.;Even though the industry requires support during this transition, there is no study within the current body of literature that focuses on increasing the productivity of the ship recycling facilities. Hence, there is a need to develop a framework to design contemporary and efficient ship recycling yards. Increasing production efficiency in ship recycling yards will not only decrease the costs, but it will also increase the throughput of the yards which will generate more income and positively impact on overall profitability.;Therefore, this PhD study addresses this gap through the development of a simulation framework for ship recycling industry to design and optimise the ship recycling yards. The study adopts a case-based approach where numerous design alternatives will be studied through the proposed framework. The main aim of this study is to increase the productivity of ship recycling yards and optimise their procedures towards achieving cost-efficient facilities.;Overall research conducted in this study will be significant contribution to the maritime literature as a novel framework for ship recycling yard design and optimisation is developed. The process models of this framework are developed based on real ship recycling procedures, therefore, the framework can be considered ready for practical implementation
Essays on the impact of changing tax rates and welfare spending
Get PDFThis thesis examines how changes in tax rates and welfare spending affect the behaviour of markets, households and individuals. In three distinct essays, we make use of appliedeconometric methods to examine both intended and unintended consequences of changes in tax and welfare policy, their impact on efficiency and equity in the economy, and the way in which they influence people’s behaviour. Our findings are intended to contribute to the wider policy debate on the optimal use of tax and spending instruments to achieve policy objectives.Chapter 1 is titled "A case study of Germany’s aviation tax using the synthetic approach". This chapter is a case study on the German Aviation Tax, a tax levied on departing passengersfrom German airports1. Aviation taxes receive considerable attention as they have been introduced recently in a number of European countries. Policy makers often motivate these taxes as environmental measures implemented to minimise negative externalities from air travel, or as tools to raise revenues from an otherwise undertaxed sector. Conversely, many experts claim that single-country aviation taxes are inefficient both as environmentalmeasures and revenue-raising tools, due to tax avoidance opportunities presented by tax-exempt airports in neighbouring countries. Critics also point to the adverse effects aviation taxes have on demand, competitiveness and connectivity at domestic air-ports.Despite their policy relevance, empirical evidence on the effects of aviation taxes is sparse.Only a few studies focus on the issue of aviation taxation, and only a handful of these studies examine the ex post effects of newly introduced aviation taxes on passenger flows at tax burdened airports. A key methodological challenge in this small literature stems from the fact that the ex post effects of aviation tax changes can only be analysed in quasiexperimental settings, where airports with changes in aviation taxes (treated airports) are compared to a group of airports (controls) not affected by the same policy. Since passenger trends at airports are affected by a wide variety of factors, and are often times highly idiosyncratic, the methodological challenge is to find the appropriate group of control airports to compare treated ones to. Consequently, our main methodological contribution to the literature is to make use of a novel approach, the synthetic control method, to optimise the selection of control airports.In this chapter, we investigate the impact Germany’s aviation tax has had on passenger numbers using the synthetic control method to generate counterfactual passenger numbers for German airports, and for airports outside Germany but near the German border.Our results suggest that passengers engaged in cross-border substitution in response to the aviation tax. Most tax-exempt airports near German borders have made sizeable gains in passenger numbers since Germany introduced its aviation tax. Within Germany there appears to be a clear distinction in the impact on small/regional airports and that on larger hubs - while we find a negative impact on traffic at regional airports, passengernumbers at hubs were largely unaffected (or were even positively affected). From a policy perspective, the finding of a cross-border substitution effect implies that the aviationtax might not be effective in curbing overall emissions from air travel, whilst also leading to lost tax revenues through the displacement of passengers to neighbouring countries.Considering the dual objectives of the policy, the optimal policy outcome from the imple-mentation of AT would be 1) a reduction in overall air travel demand (to cut emissions) and 2) no cross-border substitution effect in order to avoid the loss of the tax base. Thefindings in this chapter provide evidence to the contrary: German demand, and overall air travel demand, is not reduced to a large extent, but the cross-border effect is sizeable.Chapter 2 is titled "Limiting the distortionary impacts of transaction taxes: Scottish stamp duty after the Mirrlees Review". This chapter investigates the distortionary impacts of transaction taxes through a case study of the Scottish residential property market. Tax onproperty transactions, also known as stamp duty, is a common form of property taxation but not a very popular one. Economists consider these taxes inefficient for a number of reasons. First, they reduce the incentive to engage in mutually beneficial property transactions, leading to welfare loss as properties are not owned by the individuals who assign the most value to them. Second, they increase the tax burden on those who, for whatever reason, trade housing more often. Lastly, by increasing the cost of mobility, transaction taxes make it more difficult for homeowners to relocate in search of appropriate employment In line with these efficiency concerns, recent policy changes in Scotland were aimed atreducing distortions from the transaction tax system by 1) simplifying the structure of the tax system and 2) reducing the tax burden for the majority of home buyers (and increasingit for those aiming to buy expensive properties). Although recent studies provide credible empirical evidence on the distortions created by transaction tax regimes, the key contribution of our study is that it is the first one to study policy changes aimed at reducing said distortions. From a policy perspective this is important since governments might struggle to replace transaction tax regimes for budgeting or administrative reasons, leaving sensible reform as the only feasible policy option to mitigate efficiency concerns.To study the property market impacts of transaction taxes and assess the effects of recent reform, this chapter makes use of four sources of variation in transaction tax rates present in recent Scottish tax systems: price notches, kink points, time notches and a shift to a more progressive transaction tax regime. Our analysis makes use of bunching estimator and difference-in-differences approaches to examine how variations in transaction taxrates influence transaction activity on the Scottish property market. Our results show that both kinds of notches have a distortionary impact that is sub-optimal. The Scottish Government’s recent reforms had a positive impact through replacement of price notcheswith kink points, but time notches emerged allowing other distortions to persist. Through a comparison of price ranges affected and unaffected by the policy changes, we also findthat progressive reform had a significant (and long-term) positive impact on transaction activity in the market segment where tax rates were reduced. On the other hand, the higher end of the market, where tax rates increased, was mostly unaffected by progressive reform with the exception of the market for very expensive properties, where a negative effect is identified. Implications of our findings are that if governments want to maketransaction tax regimes more efficient, progressive taxation might be a good way to limit their distortionary impact, whilst also encouraging transaction activity in the lower endof the market.Chapter 3 is titled "The impact of housing subsidy cuts on the labour market outcomes of claimants: Evidence from England". This final chapter looks at the labour market impacts of reduced housing subsidies. Housing subsidies are aimed at helping low-income individuals afford appropriate housing, but are costly to offer. Also, in the view of some experts and policy makers, housing subsidies reduce work incentives and/or work effort among claimants. Economic theory is ambiguous on the likely labour market impacts of changes in housing subsidy entitlements. To date, there is no credible empirical evidence linking housing subsidy cuts to positive changes in labour market outcomes. Nonetheless, policy makers often motivate cuts to subsidies as a way to encourage claimants to seek employment (or put in more work effort).This chapter investigates the labour market impacts of recent housing subsidy cuts in England that were justified using a similar argument to that discussed above. Our investigationmakes use of individual-level survey data from the Understanding Society survey. Using this data set allows us to track subsidy claimants over time and control for a wide range of individual and household characteristics. Our identification strategyrelies on the fact that, within the time period investigated, the subsidy cuts were only implemented for claimants renting from one segment of England’s rental sector (the private rental sector) while claimants renting from other segments (the social rental sector)were unaffected. We utilise this variation in exposure to the subsidy cuts within a difference-in-differences framework to estimate the effect of reduced housing subsidies on the labour market outcomes of claimants. We find no evidence of a change in labour market outcomes for those affected by subsidy cuts, indicating that, at least on aggregate, the reforms did not succeed in encouraging employment among claimants. These null findings should be of considerable interest to policy makers who often assume acausal link between the generosity of benefit entitlements and the work effort/incentives of claimants. More specifically, our findings suggest that as a policy instrument, cuts to housing subsidies may not be effective in generating efficiency gains through increasedlabour market participation or work effort.This thesis examines how changes in tax rates and welfare spending affect the behaviour of markets, households and individuals. In three distinct essays, we make use of appliedeconometric methods to examine both intended and unintended consequences of changes in tax and welfare policy, their impact on efficiency and equity in the economy, and the way in which they influence people’s behaviour. Our findings are intended to contribute to the wider policy debate on the optimal use of tax and spending instruments to achieve policy objectives.Chapter 1 is titled "A case study of Germany’s aviation tax using the synthetic approach". This chapter is a case study on the German Aviation Tax, a tax levied on departing passengersfrom German airports1. Aviation taxes receive considerable attention as they have been introduced recently in a number of European countries. Policy makers often motivate these taxes as environmental measures implemented to minimise negative externalities from air travel, or as tools to raise revenues from an otherwise undertaxed sector. Conversely, many experts claim that single-country aviation taxes are inefficient both as environmentalmeasures and revenue-raising tools, due to tax avoidance opportunities presented by tax-exempt airports in neighbouring countries. Critics also point to the adverse effects aviation taxes have on demand, competitiveness and connectivity at domestic air-ports.Despite their policy relevance, empirical evidence on the effects of aviation taxes is sparse.Only a few studies focus on the issue of aviation taxation, and only a handful of these studies examine the ex post effects of newly introduced aviation taxes on passenger flows at tax burdened airports. A key methodological challenge in this small literature stems from the fact that the ex post effects of aviation tax changes can only be analysed in quasiexperimental settings, where airports with changes in aviation taxes (treated airports) are compared to a group of airports (controls) not affected by the same policy. Since passenger trends at airports are affected by a wide variety of factors, and are often times highly idiosyncratic, the methodological challenge is to find the appropriate group of control airports to compare treated ones to. Consequently, our main methodological contribution to the literature is to make use of a novel approach, the synthetic control method, to optimise the selection of control airports.In this chapter, we investigate the impact Germany’s aviation tax has had on passenger numbers using the synthetic control method to generate counterfactual passenger numbers for German airports, and for airports outside Germany but near the German border.Our results suggest that passengers engaged in cross-border substitution in response to the aviation tax. Most tax-exempt airports near German borders have made sizeable gains in passenger numbers since Germany introduced its aviation tax. Within Germany there appears to be a clear distinction in the impact on small/regional airports and that on larger hubs - while we find a negative impact on traffic at regional airports, passengernumbers at hubs were largely unaffected (or were even positively affected). From a policy perspective, the finding of a cross-border substitution effect implies that the aviationtax might not be effective in curbing overall emissions from air travel, whilst also leading to lost tax revenues through the displacement of passengers to neighbouring countries.Considering the dual objectives of the policy, the optimal policy outcome from the imple-mentation of AT would be 1) a reduction in overall air travel demand (to cut emissions) and 2) no cross-border substitution effect in order to avoid the loss of the tax base. Thefindings in this chapter provide evidence to the contrary: German demand, and overall air travel demand, is not reduced to a large extent, but the cross-border effect is sizeable.Chapter 2 is titled "Limiting the distortionary impacts of transaction taxes: Scottish stamp duty after the Mirrlees Review". This chapter investigates the distortionary impacts of transaction taxes through a case study of the Scottish residential property market. Tax onproperty transactions, also known as stamp duty, is a common form of property taxation but not a very popular one. Economists consider these taxes inefficient for a number of reasons. First, they reduce the incentive to engage in mutually beneficial property transactions, leading to welfare loss as properties are not owned by the individuals who assign the most value to them. Second, they increase the tax burden on those who, for whatever reason, trade housing more often. Lastly, by increasing the cost of mobility, transaction taxes make it more difficult for homeowners to relocate in search of appropriate employment In line with these efficiency concerns, recent policy changes in Scotland were aimed atreducing distortions from the transaction tax system by 1) simplifying the structure of the tax system and 2) reducing the tax burden for the majority of home buyers (and increasingit for those aiming to buy expensive properties). Although recent studies provide credible empirical evidence on the distortions created by transaction tax regimes, the key contribution of our study is that it is the first one to study policy changes aimed at reducing said distortions. From a policy perspective this is important since governments might struggle to replace transaction tax regimes for budgeting or administrative reasons, leaving sensible reform as the only feasible policy option to mitigate efficiency concerns.To study the property market impacts of transaction taxes and assess the effects of recent reform, this chapter makes use of four sources of variation in transaction tax rates present in recent Scottish tax systems: price notches, kink points, time notches and a shift to a more progressive transaction tax regime. Our analysis makes use of bunching estimator and difference-in-differences approaches to examine how variations in transaction taxrates influence transaction activity on the Scottish property market. Our results show that both kinds of notches have a distortionary impact that is sub-optimal. The Scottish Government’s recent reforms had a positive impact through replacement of price notcheswith kink points, but time notches emerged allowing other distortions to persist. Through a comparison of price ranges affected and unaffected by the policy changes, we also findthat progressive reform had a significant (and long-term) positive impact on transaction activity in the market segment where tax rates were reduced. On the other hand, the higher end of the market, where tax rates increased, was mostly unaffected by progressive reform with the exception of the market for very expensive properties, where a negative effect is identified. Implications of our findings are that if governments want to maketransaction tax regimes more efficient, progressive taxation might be a good way to limit their distortionary impact, whilst also encouraging transaction activity in the lower endof the market.Chapter 3 is titled "The impact of housing subsidy cuts on the labour market outcomes of claimants: Evidence from England". This final chapter looks at the labour market impacts of reduced housing subsidies. Housing subsidies are aimed at helping low-income individuals afford appropriate housing, but are costly to offer. Also, in the view of some experts and policy makers, housing subsidies reduce work incentives and/or work effort among claimants. Economic theory is ambiguous on the likely labour market impacts of changes in housing subsidy entitlements. To date, there is no credible empirical evidence linking housing subsidy cuts to positive changes in labour market outcomes. Nonetheless, policy makers often motivate cuts to subsidies as a way to encourage claimants to seek employment (or put in more work effort).This chapter investigates the labour market impacts of recent housing subsidy cuts in England that were justified using a similar argument to that discussed above. Our investigationmakes use of individual-level survey data from the Understanding Society survey. Using this data set allows us to track subsidy claimants over time and control for a wide range of individual and household characteristics. Our identification strategyrelies on the fact that, within the time period investigated, the subsidy cuts were only implemented for claimants renting from one segment of England’s rental sector (the private rental sector) while claimants renting from other segments (the social rental sector)were unaffected. We utilise this variation in exposure to the subsidy cuts within a difference-in-differences framework to estimate the effect of reduced housing subsidies on the labour market outcomes of claimants. We find no evidence of a change in labour market outcomes for those affected by subsidy cuts, indicating that, at least on aggregate, the reforms did not succeed in encouraging employment among claimants. These null findings should be of considerable interest to policy makers who often assume acausal link between the generosity of benefit entitlements and the work effort/incentives of claimants. More specifically, our findings suggest that as a policy instrument, cuts to housing subsidies may not be effective in generating efficiency gains through increasedlabour market participation or work effort
Image processing for the analysis of TI-6AL-4V microstructures
Get PDFThe primary aim of the work presented in this thesis is to develop new and improved methods for analysing the microstructure of titanium alloys, specifically Ti-6Al-4V. This is achieved through the introduction of a software tool which incorporates novel image processing techniques to automate the measurement of a wide range of microstructural features in microscopic images of Ti-6Al-4V. It is shown that these measurements are performed in a faster, more repeatable way, with minimal input from expert materials scientists, when compared with existing methods.The microstructure of a material consists of individual grains of different shapes and sizes. Precise analysis of these provides information about the properties of the material and thus is valuable for quality assurance and development of new materials, models or manufacturing processes. However, performing this analysis usually depends manual analysis techniques, requiring extensive input from expert materials scientists. Attempts at more efficient automated methods have so far had limited success, largely due to the wide variations that can occur in microstructural images.;In this thesis, a robust set of image processing techniques are proposed to automatically identify and measure key features of microstructural images. Due to the unique challenges posed by different microstructure types, two separate techniques are proposed; one aimed at measuring globular grains within microstructures and another aimed at measuring elongated grains, known as platelets. Measurements of globular grains are obtained using a novel segmentation algorithm that partitions the image such that each grain is individually labelled. Once identified in this way, the size and shape of each grain can then be measured, allowing both individual and aggregated measurements to be reported. The algorithm includes a variety of pre- and post- processing steps that dramatically reduce measurement errors, common in other segmentation methods. However, it was found that this method could not be reliably applied to segment and measure platelets. Measurements of these are instead determined by shape fitting techniques. Similar approaches are already used for analysing this type of elongated object in similar datasets. However, several limitations exist that negatively affect both the accuracy and usefulness of these methods when applied to the dataset in this study. This thesis proposes novel adaptations to such techniques to improve reliability and extend the range of properties that can be measured.;The resulting technique can be applied to measure platelet width, orientation, and morphology. A separate algorithm is also proposed that uses this data to identify and measure colonies of platelets. A software tool is designed to allow these tools to be deployed by material's scientists. This tool provides simple, intuitive feedback to the user to allow the proposed algorithms to be properly parameterised without image processing experience, or a good understanding of their operation.This work is validated through a range of trials conducted on real world datasets of Ti-6Al-4V microstructural images. The dataset uses images from different microscopy technologies as well as different morphological types of microstructure. Results are validated through comparison with measurements performed by expert materials scientists using the most reliable procedures currently available, and demonstrate accurate results can be achieved automatically, significantly faster than before. The techniques proposed in this thesis also have general value in the wider domain of image processing, due to their robustness in challenging datasets. This is demonstrated by a detailed comparison with existing image processing tools, never before testing on microstructural data.The primary aim of the work presented in this thesis is to develop new and improved methods for analysing the microstructure of titanium alloys, specifically Ti-6Al-4V. This is achieved through the introduction of a software tool which incorporates novel image processing techniques to automate the measurement of a wide range of microstructural features in microscopic images of Ti-6Al-4V. It is shown that these measurements are performed in a faster, more repeatable way, with minimal input from expert materials scientists, when compared with existing methods.The microstructure of a material consists of individual grains of different shapes and sizes. Precise analysis of these provides information about the properties of the material and thus is valuable for quality assurance and development of new materials, models or manufacturing processes. However, performing this analysis usually depends manual analysis techniques, requiring extensive input from expert materials scientists. Attempts at more efficient automated methods have so far had limited success, largely due to the wide variations that can occur in microstructural images.;In this thesis, a robust set of image processing techniques are proposed to automatically identify and measure key features of microstructural images. Due to the unique challenges posed by different microstructure types, two separate techniques are proposed; one aimed at measuring globular grains within microstructures and another aimed at measuring elongated grains, known as platelets. Measurements of globular grains are obtained using a novel segmentation algorithm that partitions the image such that each grain is individually labelled. Once identified in this way, the size and shape of each grain can then be measured, allowing both individual and aggregated measurements to be reported. The algorithm includes a variety of pre- and post- processing steps that dramatically reduce measurement errors, common in other segmentation methods. However, it was found that this method could not be reliably applied to segment and measure platelets. Measurements of these are instead determined by shape fitting techniques. Similar approaches are already used for analysing this type of elongated object in similar datasets. However, several limitations exist that negatively affect both the accuracy and usefulness of these methods when applied to the dataset in this study. This thesis proposes novel adaptations to such techniques to improve reliability and extend the range of properties that can be measured.;The resulting technique can be applied to measure platelet width, orientation, and morphology. A separate algorithm is also proposed that uses this data to identify and measure colonies of platelets. A software tool is designed to allow these tools to be deployed by material's scientists. This tool provides simple, intuitive feedback to the user to allow the proposed algorithms to be properly parameterised without image processing experience, or a good understanding of their operation.This work is validated through a range of trials conducted on real world datasets of Ti-6Al-4V microstructural images. The dataset uses images from different microscopy technologies as well as different morphological types of microstructure. Results are validated through comparison with measurements performed by expert materials scientists using the most reliable procedures currently available, and demonstrate accurate results can be achieved automatically, significantly faster than before. The techniques proposed in this thesis also have general value in the wider domain of image processing, due to their robustness in challenging datasets. This is demonstrated by a detailed comparison with existing image processing tools, never before testing on microstructural data
Development of an automated plasmapheresis system for the treatment of sepsis
Get PDFThis thesis was previously held under moratorium from 10/02/2020 to 10/02/2022Background: Sepsis is one of the leading cause of death in ICU. The causes of sepsis could be viral, bacterial, fungal infection, also, and in some instances trauma. When a local response to the infection becomes a systemic response, the immune system becomes chaotic. Cytokines are produced in an uncontrolled way, resulting in a cytokines storm. The immune system enters a hyperactivation status that leads to multiple organ failures. Despite advances in the medical treatment and clinical experience, there is currently no single medication approved for treating sepsis. Thus, removal of the plasma that contains the inflammatory mediators is a potential solution to reduce their effect in the body. Objectives: The aim of this project is to develop a device that is able to separate plasma from whole blood. The device should be able to generate secondary flow to enhance the performance by reducing the formation of cake layer. In addition, the device should be fully automated in order to simplify the technology for the end user. Approach: Design using computer aided design employing different methods for producing secondary flow, investigate the impact of these techniques on formed blood element, by assessment of shear stress. The design was 3D printed to investigate the performance in term of plasma filtration using different membranes with different effective pore area. The next step was to increase the dimension of the rig and test the increase in surface area on flux rate. In addition, an automation system was designed and assembled in order to control the transmembrane pressure, blood pump and plasma replacement pump through feedback from sensors read by a microcontroller.Results: The device was able to separate the plasma from the blood. The polyethersulfone membrane that has higher effective pore size had higher filtration rate. By increasing the size of the rig, the filtration volume increased. Also, the methods used to increase the flux were able to improve the flux rate. The automation system was tested and functioned well. Different flow rates were tested to investigate the performance of the system, and the results demonstrated the relationship between the flow rate and flux rate. In the TMP range 40-50 mmHg, at 260 ml/min flow rate, was the optimum flux rate. The device had the ability to run for 12 hours with a constant flux rate. The device achieved this with little haemolysis (pfHb <4 mg/L).Background: Sepsis is one of the leading cause of death in ICU. The causes of sepsis could be viral, bacterial, fungal infection, also, and in some instances trauma. When a local response to the infection becomes a systemic response, the immune system becomes chaotic. Cytokines are produced in an uncontrolled way, resulting in a cytokines storm. The immune system enters a hyperactivation status that leads to multiple organ failures. Despite advances in the medical treatment and clinical experience, there is currently no single medication approved for treating sepsis. Thus, removal of the plasma that contains the inflammatory mediators is a potential solution to reduce their effect in the body. Objectives: The aim of this project is to develop a device that is able to separate plasma from whole blood. The device should be able to generate secondary flow to enhance the performance by reducing the formation of cake layer. In addition, the device should be fully automated in order to simplify the technology for the end user. Approach: Design using computer aided design employing different methods for producing secondary flow, investigate the impact of these techniques on formed blood element, by assessment of shear stress. The design was 3D printed to investigate the performance in term of plasma filtration using different membranes with different effective pore area. The next step was to increase the dimension of the rig and test the increase in surface area on flux rate. In addition, an automation system was designed and assembled in order to control the transmembrane pressure, blood pump and plasma replacement pump through feedback from sensors read by a microcontroller.Results: The device was able to separate the plasma from the blood. The polyethersulfone membrane that has higher effective pore size had higher filtration rate. By increasing the size of the rig, the filtration volume increased. Also, the methods used to increase the flux were able to improve the flux rate. The automation system was tested and functioned well. Different flow rates were tested to investigate the performance of the system, and the results demonstrated the relationship between the flow rate and flux rate. In the TMP range 40-50 mmHg, at 260 ml/min flow rate, was the optimum flux rate. The device had the ability to run for 12 hours with a constant flux rate. The device achieved this with little haemolysis (pfHb <4 mg/L)
Computational generation of wear maps for H13 tool steel in open die hot forging
Get PDFForging tools are associated with as much as 40% of the costs any forging operation and consequently understanding the causes of their failure is key to improving productivity. The literature suggests that wear is responsible for 70%of failures in hot forging with abrasive and adhesive wear being the main failure modes in open die forging.Understanding the modes and mechanisms with which wear occurs on worn surfaces and contact faces is essential to minimise or eliminate the product defects and improve the quality. Tool wear phenomena can be understood and represented by wear maps for different materials (generated using a lab-based pin on disc).Such maps illustrate the wear mechanisms and wear progress from mild to transition and severe.However, some researchers prefer to explain wear behavior using analytical methods instead of empirical wear map. This thesis argues that, firstly, the pin on disc method, often used to generate wear maps, is not reliable, and produces many errors and is not representative of the industrial process. Secondly, wear maps created from a mathematical model alone (i.e. without physical trial cannot truly capture the wear characteristic of the material. As an alternative, this thesispresents a series of abrasive and adhesive wear maps created using modifiedArchard mathematical model that is validated with a series of physical forging trials.;The Archard mathematical model subroutine was embedded in the DEFORM FE simulation software. A series of FE simulations implemented a full factorial design of experiment with furnace temperature and energy in the screw press as the main variables. The FEA results were validated with a series of physical trials. A similar experiment was repeated after nitriding the tool by 0.1mm case depth. The comparison between the FE simulations and physical trials showed a good correlation of 80-90% for abrasive wear on un-nitrided tools and 70-84% on nitrided tools. While the correlation of 80-85% for adhesive wear on un-nitrided tools and 70-85% on nitrided tools was achieved. These comparisons then were used to produce a series of wear maps.This novel method of wear map generation can be used to optimise H13 tool steel performance and make the manufacturing process more cost effective. The optimised and predicted wear conditions help to minimise tool wear and improve the quality of obtained parts. Designer by having all the information using FE simulation alongside the wear maps can make the right decision in design and material selection. Potentially this methodology could also be used to compare different die materials, lubricants, and coatings.Forging tools are associated with as much as 40% of the costs any forging operation and consequently understanding the causes of their failure is key to improving productivity. The literature suggests that wear is responsible for 70%of failures in hot forging with abrasive and adhesive wear being the main failure modes in open die forging.Understanding the modes and mechanisms with which wear occurs on worn surfaces and contact faces is essential to minimise or eliminate the product defects and improve the quality. Tool wear phenomena can be understood and represented by wear maps for different materials (generated using a lab-based pin on disc).Such maps illustrate the wear mechanisms and wear progress from mild to transition and severe.However, some researchers prefer to explain wear behavior using analytical methods instead of empirical wear map. This thesis argues that, firstly, the pin on disc method, often used to generate wear maps, is not reliable, and produces many errors and is not representative of the industrial process. Secondly, wear maps created from a mathematical model alone (i.e. without physical trial cannot truly capture the wear characteristic of the material. As an alternative, this thesispresents a series of abrasive and adhesive wear maps created using modifiedArchard mathematical model that is validated with a series of physical forging trials.;The Archard mathematical model subroutine was embedded in the DEFORM FE simulation software. A series of FE simulations implemented a full factorial design of experiment with furnace temperature and energy in the screw press as the main variables. The FEA results were validated with a series of physical trials. A similar experiment was repeated after nitriding the tool by 0.1mm case depth. The comparison between the FE simulations and physical trials showed a good correlation of 80-90% for abrasive wear on un-nitrided tools and 70-84% on nitrided tools. While the correlation of 80-85% for adhesive wear on un-nitrided tools and 70-85% on nitrided tools was achieved. These comparisons then were used to produce a series of wear maps.This novel method of wear map generation can be used to optimise H13 tool steel performance and make the manufacturing process more cost effective. The optimised and predicted wear conditions help to minimise tool wear and improve the quality of obtained parts. Designer by having all the information using FE simulation alongside the wear maps can make the right decision in design and material selection. Potentially this methodology could also be used to compare different die materials, lubricants, and coatings
Control and operation of offshore wind farms connected with diode rectifier HVDC systems
Get PDFDue to the advantage of abundant space and more consistent wind speed, interest in offshore wind energy has significantly increased. To reduce the cost related to offshore wind power integration, this thesis investigates the control, modelling and operation of offshore wind farms connected with diode rectifier HVDC (DR-HVDC) systems, where a diode rectifier is used offshore and a modular multilevel converter (MMC) is used onshore. Compared to MMC based HVDC systems, the main benefits of DR-HVDC are lower investment, lower space requirement, higher efficiency and improved robustness. However, as the diode rectifier is unable to control offshore frequency and voltage as the MMC counterpart does, permanent magnet synchronous generator based wind turbines (WTs) have to perform more control functions including the establishment of the offshore AC network.In order to ensure that each WT converter autonomously contributes to the regulation of the overall offshore voltage and frequency, a distributed phase locked loop-based control for WT converters connected with DR-HVDC is proposed. A small-signal state-space model of the DR-HVDC system is developed to justify the use of active power and voltage (P-V) control, and reactive power and frequency (Q-f) control. The WT level analysis is implemented and to reveal the coupling between WT active power and reactive power with such control scheme. An angle compensation control is further proposed to reduce the coupling during WT active power change. Small-signal analysis is also carried out to investigate the impact of the angle compensation control parameters, active power control parameters and reactive power control parameters on system stability.;To ride-through onshore faults, an active MMC DC voltage control combined with a WT overvoltage limiting control is proposed. With this control scheme, active power re-balance between the offshore and onshore side is achieved faster and thus, the MMC submodule capacitor overvoltage is alleviated. During offshore AC faults, a current limiting method is proposed to ensure the safe operation of WTs and an effective offshore overcurrent protection solution is proposed for fault detection and isolation. In addition, the system response during permanent DC pole-to-pole faults is analysed. Finally, the operation of offshore wind farms connected with two parallel transmission links, i.e. a DR-HVDC and a HVAC link, is investigated. A hierarchical control structure which contains primary, secondary and tertiary controls, is proposed to ensure reliable operation and smooth transition between DR-HVDC mode, HVAC mode and parallel mode.Due to the advantage of abundant space and more consistent wind speed, interest in offshore wind energy has significantly increased. To reduce the cost related to offshore wind power integration, this thesis investigates the control, modelling and operation of offshore wind farms connected with diode rectifier HVDC (DR-HVDC) systems, where a diode rectifier is used offshore and a modular multilevel converter (MMC) is used onshore. Compared to MMC based HVDC systems, the main benefits of DR-HVDC are lower investment, lower space requirement, higher efficiency and improved robustness. However, as the diode rectifier is unable to control offshore frequency and voltage as the MMC counterpart does, permanent magnet synchronous generator based wind turbines (WTs) have to perform more control functions including the establishment of the offshore AC network.In order to ensure that each WT converter autonomously contributes to the regulation of the overall offshore voltage and frequency, a distributed phase locked loop-based control for WT converters connected with DR-HVDC is proposed. A small-signal state-space model of the DR-HVDC system is developed to justify the use of active power and voltage (P-V) control, and reactive power and frequency (Q-f) control. The WT level analysis is implemented and to reveal the coupling between WT active power and reactive power with such control scheme. An angle compensation control is further proposed to reduce the coupling during WT active power change. Small-signal analysis is also carried out to investigate the impact of the angle compensation control parameters, active power control parameters and reactive power control parameters on system stability.;To ride-through onshore faults, an active MMC DC voltage control combined with a WT overvoltage limiting control is proposed. With this control scheme, active power re-balance between the offshore and onshore side is achieved faster and thus, the MMC submodule capacitor overvoltage is alleviated. During offshore AC faults, a current limiting method is proposed to ensure the safe operation of WTs and an effective offshore overcurrent protection solution is proposed for fault detection and isolation. In addition, the system response during permanent DC pole-to-pole faults is analysed. Finally, the operation of offshore wind farms connected with two parallel transmission links, i.e. a DR-HVDC and a HVAC link, is investigated. A hierarchical control structure which contains primary, secondary and tertiary controls, is proposed to ensure reliable operation and smooth transition between DR-HVDC mode, HVAC mode and parallel mode
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