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Monitoring of complex nonstationary industrial processes
Get PDFThis thesis was previously held under moratorium from 4th August 2020 to 4th August 2022.Monitoring of complex manufacturing processes using multivariate statistical process control (MSPC) is becoming more important. However, classical MSPC is restricted to stationary data while most industrial processes are nonstationary. One way of addressing nonstationary data is to calculate the difference between consecutive time series data samples. However, this can cause loss of dynamic information, resulting in inadequate process monitoring or a reduced fault detection capability. Cointegration analysis has recently been adopted for process monitoring of nonstationary processes. However, the first applications considered only nonstationary variables whereas complex industrial processes contain both stationary and nonstationary variables. Furthermore, there is inefficiency in the modelling when dealing with higher level nonstationary time series. This particular issue can be solved by using common-trend residuals-based monitoring. However, the use of different models requires a number of control charts to be monitored by a data analyst. To solve these issues, a multi-level multi-factor model is proposed for the monitoring of complex continuous and batchindustrial processes. The method uses a combination of principal component analysis (PCA), and cointegration and common-trend models at the 1st level, and then a PCA model at the 2nd level to monitor the combined stationary outputs from the 1st level. The method is tested with ramp and step type fault functions on continuous and batch process simulations, and compared with conventional PCA and cointegration basedapproaches. The findings show that the multi-level multi-factor model can provide better fault detection rates compared to conventional PCA and cointegration based approaches. In addition, a parameter tuning scheme based on the big-bang big-crunch global optimisation algorithm is used to select the optimum parameters for the multilevel multi-factor model when applied to continuous and batch processes. This not only improves the model’s performance but also assists with its practical application in an industrial environment.Monitoring of complex manufacturing processes using multivariate statistical process control (MSPC) is becoming more important. However, classical MSPC is restricted to stationary data while most industrial processes are nonstationary. One way of addressing nonstationary data is to calculate the difference between consecutive time series data samples. However, this can cause loss of dynamic information, resulting in inadequate process monitoring or a reduced fault detection capability. Cointegration analysis has recently been adopted for process monitoring of nonstationary processes. However, the first applications considered only nonstationary variables whereas complex industrial processes contain both stationary and nonstationary variables. Furthermore, there is inefficiency in the modelling when dealing with higher level nonstationary time series. This particular issue can be solved by using common-trend residuals-based monitoring. However, the use of different models requires a number of control charts to be monitored by a data analyst. To solve these issues, a multi-level multi-factor model is proposed for the monitoring of complex continuous and batchindustrial processes. The method uses a combination of principal component analysis (PCA), and cointegration and common-trend models at the 1st level, and then a PCA model at the 2nd level to monitor the combined stationary outputs from the 1st level. The method is tested with ramp and step type fault functions on continuous and batch process simulations, and compared with conventional PCA and cointegration basedapproaches. The findings show that the multi-level multi-factor model can provide better fault detection rates compared to conventional PCA and cointegration based approaches. In addition, a parameter tuning scheme based on the big-bang big-crunch global optimisation algorithm is used to select the optimum parameters for the multilevel multi-factor model when applied to continuous and batch processes. This not only improves the model’s performance but also assists with its practical application in an industrial environment
Guanidinium mimetics, synthesis and application as next-generation analogues in cell penetrating peptides
No full textThis thesis was previously held under moratorium from 12th April 2021 until 12th April 2024.Cell penetrating peptides (CPPs) are short peptide sequences, usually between five and thirty amino acids long, that are able to traverse cell membranes. Since they were first discovered in 1989, CPPs have been widely used to deliver various molecular cargoes into cells, from small molecule therapeutics through to larger biologics such as oligonucleotides and proteins. A molecular hallmark of most CPPs is the incorporation of multiple arginine residues in their primary sequence (e.g. 1.1 and 1.2) [Figures in thesis text]. Although there has been extensive research and optimisation of arginine-rich CPPs, there remain multiple drawbacks in their utility as drug delivery agents. The most significant and limiting is their the toxicity in vivo, associated with the high basicity gained from multiple arginine residues within the primary sequence of these peptides. Therefore, the development of guanidine functional group analogues to mimic the arginine side-chain, while both maintaining the hydrogen bond profile and mitigating the associated toxicity could provide a new generation of delivery vehicles for valuable molecular payloads. This thesis describes the development of robust synthetic routes towards the preparation and validation of amidines as bio-isosteres of the guanidinium functional group present in arginine. Chapter one introduces the importance of the guanidinium group in the structure and function of commonly used CPPs. It will also address how they interact with the cell membrane architecture so as to be internalised into the cell. Chapter two describes the design rationale and synthesis of CPPs containing minimal arginine residues and compares their cellular permeability with common arginine-rich CPPs. The mechanism of cell uptake, viability, compartmentalisation and important regions of these peptides is also evaluated. Analysis of cell uptake of a suite of CPPs demonstrated that certain low arginine-containing peptides are more cell permeable than arginine-rich CPPs. Chapter three describes the development of mild Chan-Evans-Lam methodology to directly arylate amidines. The reaction mechanism was investigated and new off-cycle Cu-amidine species were identified. Mono N-arylation of amidines was demonstrated under mild conditions on wide variety of substrates including the synthesis of novel analogues of the clinically approved therapeutic pentamidine.Chapter four describes the synthesis of amidine containing amino acids building blocks for solid phase synthesis and the incorporation of arginine mimetics into CPPs. The toxicity profile, cell uptake and subcellular localisation reveal replacing arginine with amidines enhances uptake of peptide within cells without any adverse toxic effects or perturbation of subcellular localisation.Finally, Chapter five summarises the work of this thesis and suggests future directions for thedevelopment of less toxic and less basic CPPs.Cell penetrating peptides (CPPs) are short peptide sequences, usually between five and thirty amino acids long, that are able to traverse cell membranes. Since they were first discovered in 1989, CPPs have been widely used to deliver various molecular cargoes into cells, from small molecule therapeutics through to larger biologics such as oligonucleotides and proteins. A molecular hallmark of most CPPs is the incorporation of multiple arginine residues in their primary sequence (e.g. 1.1 and 1.2) [Figures in thesis text]. Although there has been extensive research and optimisation of arginine-rich CPPs, there remain multiple drawbacks in their utility as drug delivery agents. The most significant and limiting is their the toxicity in vivo, associated with the high basicity gained from multiple arginine residues within the primary sequence of these peptides. Therefore, the development of guanidine functional group analogues to mimic the arginine side-chain, while both maintaining the hydrogen bond profile and mitigating the associated toxicity could provide a new generation of delivery vehicles for valuable molecular payloads. This thesis describes the development of robust synthetic routes towards the preparation and validation of amidines as bio-isosteres of the guanidinium functional group present in arginine. Chapter one introduces the importance of the guanidinium group in the structure and function of commonly used CPPs. It will also address how they interact with the cell membrane architecture so as to be internalised into the cell. Chapter two describes the design rationale and synthesis of CPPs containing minimal arginine residues and compares their cellular permeability with common arginine-rich CPPs. The mechanism of cell uptake, viability, compartmentalisation and important regions of these peptides is also evaluated. Analysis of cell uptake of a suite of CPPs demonstrated that certain low arginine-containing peptides are more cell permeable than arginine-rich CPPs. Chapter three describes the development of mild Chan-Evans-Lam methodology to directly arylate amidines. The reaction mechanism was investigated and new off-cycle Cu-amidine species were identified. Mono N-arylation of amidines was demonstrated under mild conditions on wide variety of substrates including the synthesis of novel analogues of the clinically approved therapeutic pentamidine.Chapter four describes the synthesis of amidine containing amino acids building blocks for solid phase synthesis and the incorporation of arginine mimetics into CPPs. The toxicity profile, cell uptake and subcellular localisation reveal replacing arginine with amidines enhances uptake of peptide within cells without any adverse toxic effects or perturbation of subcellular localisation.Finally, Chapter five summarises the work of this thesis and suggests future directions for thedevelopment of less toxic and less basic CPPs
Nanoelectrode lithography : : modelling, experimental validation and instrumentation
Get PDFThis thesis was previously held under moratorium from 02/11/20 to 02/11/22Continuous rapid shrinking of feature size made the authorities to seek alternative patterning methods as the conventional photolithography process is reaching its intrinsic resolution limit. In this regard, some promising techniques have been proposed as the next generation lithography (NGL) that have the potentials to achieve both high volume production and very high resolution. Among them, several methods such as Extreme Ultraviolet Lithography (EUVL), Electron Beam lithography (EBL), Nanoimprint Lithography (NIL), Directed Self Assembly (DSA) and Scanning Probe Lithography (SPL) have demonstrated excellent potentials as promising candidates for future industrial nanofabrication. -- However, all these technologies are in their development phases and still need further work to overcome some challenges in terms of flexibility, uniformity, high throughput, high resolution, high reliability, high- efficiency, defectivity, and cost of ownership. On the other hand, nanoelectrode nanolithography (NEL) has been developed in the laboratory and demonstrated as an efficient lithographic tool. It has been strengthened in recent years as one of the most promising methods due to its high reproducibility, low cost, and ability to manufacture nano-sized structures. -- -- This method is based on the spatial confinement of the anodic oxidation between a conductive stamp and the sample surface. However, the non-uniformity issue severely limits the existing nanoelectrode lithography to be applied for large area nanopatterning. Besides, other issues such as stamp lifetime and low-cost stamp fabrication method need to be addressed to make this lithography technique viable for commercial applications. -- A clear and explicit understanding of the mechanism at a molecular level helps to improve this technique. Therefore, this PhD thesis firstly aims to gain an in-depth understanding of nanoscale mechanisms involved in the anodic oxidation process and the parametric influence in nanoelectrode lithography through molecular dynamics (MD) simulations. -- To do this, three-dimensional MD models of oxidation nanocell were developed, and a reactive force field (ReaxFF) was adopted to describe the interactions between atoms. The MD simulations were implemented in LAMMPS software and were performed by using a High-Performance Computing (HPC) service, ARCHIE-WeSt. The simulation results demonstrated two forms of adsorption of water molecules: molecular adsorption and dissociative adsorption. After breaking the adsorbed hydroxyls, the oxygen atoms insert into the substrate to form the Si−O−Si bonds so as to make the surface oxidized. A linear dependency of the electric field intensity on oxidation growth was observed. The relative humidity also showed the same linear behavior after a certain value (40%). The simulation results have been compared qualitatively with the experimental results, and they show in good agreement. -- -- MD simulation results also showed that the crystallographic orientation of the substrate has a great impact on the oxidation process. It was revealed that the thickness of the oxide film and the initial oxygen diffusion rate follow an order of (100) > (110) > (111) at lower electric field intensities. It also confirmed that surfaces with higher surface energy are more reactive at lower electric field intensity. Crossovers occurred at a higher electric field intensity (7 V/nm) under which the thickness of the oxide film yields an order of T(110) > T(100) > T(111). -- -- Atomic force microscope (AFM) oxidation experiments were performed to validate these results, which showed different orders for the (100) and (111) substrates, while (110) remained the largest for the oxide thickness. A good correlation has been found between the oxide growth and the orientation-dependent parameters where the oxide growth is proportional to the areal density of the surfaces. -- The oxide growth also follows the relative order of the activation energies, which could be another controlling factor for the oxide growth. However, the differences between simulation and experimental results probably relate to the empirical potential as well as different time and spatial scales of the process. -- Another objective of this thesis is to develop a new NEL process with a brass stamp that does not require conductive layer deposition. The brass material was chosen as it has high elastic modulus and high breaking strength, which ensures higher life expectancy. Therefore, this thesis reports the feasibility of using brass materials as the conductive stamps for NEL to shorten the process steps and reduce the production cost. The fabrication of nanostructures on the brass stamp was performed on a single point diamond turning (SPDT) machine. Some burrs were formed during the machining process, that prohibit the stamps from achieving a homogeneous contact with the substrates. Oxidation experiments were carried out with a home built NEL system. The results showed that an introduction of a thin layer of polymer (PS-OH) on the silicon substrate could improve the contact uniformity so as the oxidation. -- -- Finally, a rolling nanoelectrode lithography process was proposed, for the first time, to scale up the nanoelectrode lithography technique for large-area nanofabrication. A test-bed was developed to realize uniform pressure distribution over the whole contact area so that the local oxidation process occurs uniformly over a large area of the samples. A brass roller wrapped with a fabricated polycarbonate strip has been used as a stamp to generate nanopatterns on a silicon surface. The experimental results indicated that a significant improvement in pattern uniformity compared to the other results was obtained with the conventional NEL process. -- Moreover, the impact of pattern direction has been investigated, which shows no significant variation in the oxide pattern. Lastly, the rolling speed and the applied bias voltage were identified as the primary control parameters for the oxide growth.Continuous rapid shrinking of feature size made the authorities to seek alternative patterning methods as the conventional photolithography process is reaching its intrinsic resolution limit. In this regard, some promising techniques have been proposed as the next generation lithography (NGL) that have the potentials to achieve both high volume production and very high resolution. Among them, several methods such as Extreme Ultraviolet Lithography (EUVL), Electron Beam lithography (EBL), Nanoimprint Lithography (NIL), Directed Self Assembly (DSA) and Scanning Probe Lithography (SPL) have demonstrated excellent potentials as promising candidates for future industrial nanofabrication. -- However, all these technologies are in their development phases and still need further work to overcome some challenges in terms of flexibility, uniformity, high throughput, high resolution, high reliability, high- efficiency, defectivity, and cost of ownership. On the other hand, nanoelectrode nanolithography (NEL) has been developed in the laboratory and demonstrated as an efficient lithographic tool. It has been strengthened in recent years as one of the most promising methods due to its high reproducibility, low cost, and ability to manufacture nano-sized structures. -- -- This method is based on the spatial confinement of the anodic oxidation between a conductive stamp and the sample surface. However, the non-uniformity issue severely limits the existing nanoelectrode lithography to be applied for large area nanopatterning. Besides, other issues such as stamp lifetime and low-cost stamp fabrication method need to be addressed to make this lithography technique viable for commercial applications. -- A clear and explicit understanding of the mechanism at a molecular level helps to improve this technique. Therefore, this PhD thesis firstly aims to gain an in-depth understanding of nanoscale mechanisms involved in the anodic oxidation process and the parametric influence in nanoelectrode lithography through molecular dynamics (MD) simulations. -- To do this, three-dimensional MD models of oxidation nanocell were developed, and a reactive force field (ReaxFF) was adopted to describe the interactions between atoms. The MD simulations were implemented in LAMMPS software and were performed by using a High-Performance Computing (HPC) service, ARCHIE-WeSt. The simulation results demonstrated two forms of adsorption of water molecules: molecular adsorption and dissociative adsorption. After breaking the adsorbed hydroxyls, the oxygen atoms insert into the substrate to form the Si−O−Si bonds so as to make the surface oxidized. A linear dependency of the electric field intensity on oxidation growth was observed. The relative humidity also showed the same linear behavior after a certain value (40%). The simulation results have been compared qualitatively with the experimental results, and they show in good agreement. -- -- MD simulation results also showed that the crystallographic orientation of the substrate has a great impact on the oxidation process. It was revealed that the thickness of the oxide film and the initial oxygen diffusion rate follow an order of (100) > (110) > (111) at lower electric field intensities. It also confirmed that surfaces with higher surface energy are more reactive at lower electric field intensity. Crossovers occurred at a higher electric field intensity (7 V/nm) under which the thickness of the oxide film yields an order of T(110) > T(100) > T(111). -- -- Atomic force microscope (AFM) oxidation experiments were performed to validate these results, which showed different orders for the (100) and (111) substrates, while (110) remained the largest for the oxide thickness. A good correlation has been found between the oxide growth and the orientation-dependent parameters where the oxide growth is proportional to the areal density of the surfaces. -- The oxide growth also follows the relative order of the activation energies, which could be another controlling factor for the oxide growth. However, the differences between simulation and experimental results probably relate to the empirical potential as well as different time and spatial scales of the process. -- Another objective of this thesis is to develop a new NEL process with a brass stamp that does not require conductive layer deposition. The brass material was chosen as it has high elastic modulus and high breaking strength, which ensures higher life expectancy. Therefore, this thesis reports the feasibility of using brass materials as the conductive stamps for NEL to shorten the process steps and reduce the production cost. The fabrication of nanostructures on the brass stamp was performed on a single point diamond turning (SPDT) machine. Some burrs were formed during the machining process, that prohibit the stamps from achieving a homogeneous contact with the substrates. Oxidation experiments were carried out with a home built NEL system. The results showed that an introduction of a thin layer of polymer (PS-OH) on the silicon substrate could improve the contact uniformity so as the oxidation. -- -- Finally, a rolling nanoelectrode lithography process was proposed, for the first time, to scale up the nanoelectrode lithography technique for large-area nanofabrication. A test-bed was developed to realize uniform pressure distribution over the whole contact area so that the local oxidation process occurs uniformly over a large area of the samples. A brass roller wrapped with a fabricated polycarbonate strip has been used as a stamp to generate nanopatterns on a silicon surface. The experimental results indicated that a significant improvement in pattern uniformity compared to the other results was obtained with the conventional NEL process. -- Moreover, the impact of pattern direction has been investigated, which shows no significant variation in the oxide pattern. Lastly, the rolling speed and the applied bias voltage were identified as the primary control parameters for the oxide growth
Atmospheric microplastic pollution
Get PDFThis thesis was previously held under moratorium from 28th October 2020 until 28th October 2022.The following research marks the beginning of the new field of research on theatmospheric transport of microplastic and its potential terrestrial and oceanicsource. Taking atmospheric deposition samples from the French Pyrenees Iwas able to illustrate the first atmospheric transport of microplastics of at least95km using hysplit4 back trajectory modelling. Further to this I used highvolume sampling technique to show first evidence of free-troposphericmicroplastic at an altitude of 2877masl at the Pic du Midi observatory in France.I also showed the ocean to be a source of atmospheric microplastics bysampling the sea breeze in varying wind events showing first evidence of oceanto atmosphere transfer.The following research marks the beginning of the new field of research on theatmospheric transport of microplastic and its potential terrestrial and oceanicsource. Taking atmospheric deposition samples from the French Pyrenees Iwas able to illustrate the first atmospheric transport of microplastics of at least95km using hysplit4 back trajectory modelling. Further to this I used highvolume sampling technique to show first evidence of free-troposphericmicroplastic at an altitude of 2877masl at the Pic du Midi observatory in France.I also showed the ocean to be a source of atmospheric microplastics bysampling the sea breeze in varying wind events showing first evidence of oceanto atmosphere transfer
'It’s no real pleasure in life' : the grotesque in Southern Gothic and beyond
Get PDFThis PhD thesis is comprised of a collection of linked short stories 'whose characterisation and themes situation it in a modern gothic tradition that spans the anglosphere, particularly American Southern Gothic literature, and an accompanying critical reflection on the writing process and associated works.The short story cycle focuses on the blighted town of Shawkirk, a fictional area in the West of Scotland marked by woods, moorland and decay. A discovery in an abandoned church sets a ripple of unease throughout the townsfolk, and impacts their lives to varying degrees, from the mildest of rumours to the explosion of animalistic savagery. Above the escalating Gothic drama, the church sits waiting in a harsh natural landscape, a totem of the ugly past that claws into the present.The critical reflection examines the composition of the short story cycle, and the implications of taking inspiration from the Southern and other Gothic traditions – adaptation of cultural and historical context, the personal relationship to the Scottish conception of Gothic, and examinations of similar literary exchanges and evolutions in writing and folk tradition.This PhD thesis is comprised of a collection of linked short stories 'whose characterisation and themes situation it in a modern gothic tradition that spans the anglosphere, particularly American Southern Gothic literature, and an accompanying critical reflection on the writing process and associated works.The short story cycle focuses on the blighted town of Shawkirk, a fictional area in the West of Scotland marked by woods, moorland and decay. A discovery in an abandoned church sets a ripple of unease throughout the townsfolk, and impacts their lives to varying degrees, from the mildest of rumours to the explosion of animalistic savagery. Above the escalating Gothic drama, the church sits waiting in a harsh natural landscape, a totem of the ugly past that claws into the present.The critical reflection examines the composition of the short story cycle, and the implications of taking inspiration from the Southern and other Gothic traditions – adaptation of cultural and historical context, the personal relationship to the Scottish conception of Gothic, and examinations of similar literary exchanges and evolutions in writing and folk tradition
On the onset of relativistic transparency in intense laser-solid interactions
Get PDFThis thesis was previously held under moratorium from 26th May 2021 until 26th May 2023.This thesis reports on experimental and numerical investigations of the onset of relativistic transparency in initially solid density plasmas, during interactions with an ultra-intense short laser pulse and the effect this has on the resulting plasma dynamics. The research presented was conducted with the aim of increasing understanding of the complex dynamics of these interactions to accelerate the development of particle and radiation sources towards potential applications. These range from being a driver for inertially confined fusion to proton therapy for cancer treatment. To this end, control of the interaction conditions and optimisation of the particle and radiation sources generated are essential. The thesis reports results which support and deepen understanding of plasma dynamics in the relativistic transparency regime. In the first of these experiments, the onset time of transparency in initially opaque plasmas was investigated as a function of target thickness, pulse energy and pulse duration for pulses with a maximum intensity on the order of 3 × 1020 Wcm−2, on-target energies of ∼3 J and minimum pulse lengths of ∼50 fs. The fractional transmitted energy was found to match well with predictions using an established transparency model. Simultaneous frequency-resolved optical gating (FROG) measurements of the transmitted pulse profile compare favourably to particle-in-cell (PIC) code simulations. These simulations indicate that the coherent transition radiation generated by accelerated electrons interferes with the transmitted pulse in those targets which undergo transparency, resulting in fringes in the spectrum of the light measured at the target rear. This novel application of spectral interferometry is shown to be capable of high resolution measurements of the transmitted pulse spectrum and offers the potential ability to control and optimise the onset time of transparency in expanding thin foil targets. These results accelerate the development of ion acceleration in the transparency regime as the onset time greatly affects the ion beam properties, including maximum energy. In the second of these experiments, it was found that as target thickness is decreased from the micron scale to tens of nanometres that the absorption of laser energy to electrons transitions from surface to volume dominated processes. Experimentalmeasurements of the energy absorption and the population of fast electrons escaping the target show a maximum of ∼ 80% total absorption at an optimum target thickness of ∼380 nm, with a slow decrease with increasing target thickness, for incident pulses with intensities on the order 9 × 1019 Wcm−2 and pulse lengths of ∼700 fs. For thinner targets, particle-in-cell code simulations indicate that transparency occurs increasingly early, which results in a decrease in absorption. However, the experimental results suggest that with decreasing thickness more electrons escape the target, with a higher average energy, with the particle-in-cell simulations predicting similar results. This increase in “escaped” electron fraction is attributed to a direct laser acceleration of the bulk target electrons. These findings indicate a trade-off between total energycoupling to the electrons and the spectral properties of the electron beam produced. In the third of these experiments, the role of transparency in laser driven ion acceleration is investigated. This mode consists of hybrid phases of RPA, TNSA and enhancement due to the onset of transparency, with recent experimental results suggesting this mechanism can accelerate protons to maximum energies on the order of 100 MeV, for pulses with intensities on the order 3 × 1020 Wcm−2 . By comparing results from aluminium and plastic targets, it is demonstrated that the chosen target material has an effect on the maximum energy and flux of the accelerated proton beam. Plastic targets are shown to produce higher energy protons, on laser-axis, compared to thosefrom metallic targets due to the presence of hydrogen throughout the target volume rather than just in hydrocarbon surface contaminants. Particle-in-cell code simulations highlight the differing behaviour of the two target types investigated post-transparency where it is found that the peak accelerating field structures act to drive the proton population more efficiently in plastic targets. These results provide a key motivation for the choice of target material for a number of applications, where high energy, high flux proton beams are desired.The results of these investigations enable a greater understanding of the complex dynamics of initially solid density foil targets dynamically expanding to the point at which they become relativistically transparent to the intense laser light, accelerating the development of these novel ion sources towards potential applications.This thesis reports on experimental and numerical investigations of the onset of relativistic transparency in initially solid density plasmas, during interactions with an ultra-intense short laser pulse and the effect this has on the resulting plasma dynamics. The research presented was conducted with the aim of increasing understanding of the complex dynamics of these interactions to accelerate the development of particle and radiation sources towards potential applications. These range from being a driver for inertially confined fusion to proton therapy for cancer treatment. To this end, control of the interaction conditions and optimisation of the particle and radiation sources generated are essential. The thesis reports results which support and deepen understanding of plasma dynamics in the relativistic transparency regime. In the first of these experiments, the onset time of transparency in initially opaque plasmas was investigated as a function of target thickness, pulse energy and pulse duration for pulses with a maximum intensity on the order of 3 × 1020 Wcm−2, on-target energies of ∼3 J and minimum pulse lengths of ∼50 fs. The fractional transmitted energy was found to match well with predictions using an established transparency model. Simultaneous frequency-resolved optical gating (FROG) measurements of the transmitted pulse profile compare favourably to particle-in-cell (PIC) code simulations. These simulations indicate that the coherent transition radiation generated by accelerated electrons interferes with the transmitted pulse in those targets which undergo transparency, resulting in fringes in the spectrum of the light measured at the target rear. This novel application of spectral interferometry is shown to be capable of high resolution measurements of the transmitted pulse spectrum and offers the potential ability to control and optimise the onset time of transparency in expanding thin foil targets. These results accelerate the development of ion acceleration in the transparency regime as the onset time greatly affects the ion beam properties, including maximum energy. In the second of these experiments, it was found that as target thickness is decreased from the micron scale to tens of nanometres that the absorption of laser energy to electrons transitions from surface to volume dominated processes. Experimentalmeasurements of the energy absorption and the population of fast electrons escaping the target show a maximum of ∼ 80% total absorption at an optimum target thickness of ∼380 nm, with a slow decrease with increasing target thickness, for incident pulses with intensities on the order 9 × 1019 Wcm−2 and pulse lengths of ∼700 fs. For thinner targets, particle-in-cell code simulations indicate that transparency occurs increasingly early, which results in a decrease in absorption. However, the experimental results suggest that with decreasing thickness more electrons escape the target, with a higher average energy, with the particle-in-cell simulations predicting similar results. This increase in “escaped” electron fraction is attributed to a direct laser acceleration of the bulk target electrons. These findings indicate a trade-off between total energycoupling to the electrons and the spectral properties of the electron beam produced. In the third of these experiments, the role of transparency in laser driven ion acceleration is investigated. This mode consists of hybrid phases of RPA, TNSA and enhancement due to the onset of transparency, with recent experimental results suggesting this mechanism can accelerate protons to maximum energies on the order of 100 MeV, for pulses with intensities on the order 3 × 1020 Wcm−2 . By comparing results from aluminium and plastic targets, it is demonstrated that the chosen target material has an effect on the maximum energy and flux of the accelerated proton beam. Plastic targets are shown to produce higher energy protons, on laser-axis, compared to thosefrom metallic targets due to the presence of hydrogen throughout the target volume rather than just in hydrocarbon surface contaminants. Particle-in-cell code simulations highlight the differing behaviour of the two target types investigated post-transparency where it is found that the peak accelerating field structures act to drive the proton population more efficiently in plastic targets. These results provide a key motivation for the choice of target material for a number of applications, where high energy, high flux proton beams are desired.The results of these investigations enable a greater understanding of the complex dynamics of initially solid density foil targets dynamically expanding to the point at which they become relativistically transparent to the intense laser light, accelerating the development of these novel ion sources towards potential applications
An empirical investigation into the motivations for and consequences of China's aid to developing countries
Get PDFThis thesis consists of three distinct, yet interrelated, chapters titled 'Assessing the Impact of China's Aid on the World Bank Conditionality', 'A Study on the Role of Human Rights in the Aid Allocations of China and the United States.', and 'The Impact of China's Aid on the Trading Behaviour of Developing Countries'.;The first chapter investigates whether the stringency of conditions attached to the World Bank aid projects are influenced by the additional supply of aid from China. The World Bank's conditionality has been disaggregated into prior actions and benchmarks. Prior actions are the legal conditions that determine aid disbursement, while benchmarks describe the contents and progress of an aid project.;We find that, in particular, China is challenging the way the World Bank is providing aid to African countries, and its impact appears evident from the World Bank's response; it has reduced the number of prior actions. However, providing an alternate source to China's aid for other regions seems rather difficult, as no statistically significant association between China's aid and prior actions can be found.;The second chapter considers whether there is substance to claims that, relative to the US, China disregards human rights considerations when allocating aid. Bivariate analysis demonstrates that a significant share of China's aid flows to countries that have a poor human rights record. At the same time, the policy of the US in providing aid to those countries seems little different. The empirical results also provided some support for the general pessimism regarding China's provision of aid to countries with poor human rights records yet challenge the optimists who expect better targeted aid from the US.;The impact of China's aid on the trading behaviour of developing countries is evaluated in the third chapter. The wider implications of China's aid on developing countries' exports and imports from the rest of the world are analysed, and there is also focus on the bilateral effects of China's aid by evaluating recipients' exports and imports from China.;The key results indicate that China's aid is effective in promoting the overall exports and imports of developing countries from the rest of the world. As far as the bilateral effects of China's aid on recipients' exports and imports from China are concerned, no strong evidence is found that aid recipients significantly increase their exports and imports from China as a result of receiving aid.This thesis consists of three distinct, yet interrelated, chapters titled 'Assessing the Impact of China's Aid on the World Bank Conditionality', 'A Study on the Role of Human Rights in the Aid Allocations of China and the United States.', and 'The Impact of China's Aid on the Trading Behaviour of Developing Countries'.;The first chapter investigates whether the stringency of conditions attached to the World Bank aid projects are influenced by the additional supply of aid from China. The World Bank's conditionality has been disaggregated into prior actions and benchmarks. Prior actions are the legal conditions that determine aid disbursement, while benchmarks describe the contents and progress of an aid project.;We find that, in particular, China is challenging the way the World Bank is providing aid to African countries, and its impact appears evident from the World Bank's response; it has reduced the number of prior actions. However, providing an alternate source to China's aid for other regions seems rather difficult, as no statistically significant association between China's aid and prior actions can be found.;The second chapter considers whether there is substance to claims that, relative to the US, China disregards human rights considerations when allocating aid. Bivariate analysis demonstrates that a significant share of China's aid flows to countries that have a poor human rights record. At the same time, the policy of the US in providing aid to those countries seems little different. The empirical results also provided some support for the general pessimism regarding China's provision of aid to countries with poor human rights records yet challenge the optimists who expect better targeted aid from the US.;The impact of China's aid on the trading behaviour of developing countries is evaluated in the third chapter. The wider implications of China's aid on developing countries' exports and imports from the rest of the world are analysed, and there is also focus on the bilateral effects of China's aid by evaluating recipients' exports and imports from China.;The key results indicate that China's aid is effective in promoting the overall exports and imports of developing countries from the rest of the world. As far as the bilateral effects of China's aid on recipients' exports and imports from China are concerned, no strong evidence is found that aid recipients significantly increase their exports and imports from China as a result of receiving aid
A structured, systemic methodology to improve maritime fire safety in machinery spaces
Get PDFThe primary cause of machinery space fires is cited as the release of flammable oil mist contacting unprotected hot surfaces. With this being common knowledge why do we continue to see this type of incident reoccurring on ships carrying thousands of passengers to precarious destinations? Anecdotal evidence suggests that the prime focus of maritime fire safety falls on risk mitigation, as opposed to its prevention. It also appears technological safety barriers are placed in an 'install and forget' mentality through lack of appreciation of the overall system of safety control.;This belief is explained by referring to risk reduction of adding a 'layer of protection' or by supposedly higher cost-effectiveness of accident mitigation measures. The significance of this belief goes beyond the accurate understanding of the state-of-the-art of maritime safety. If it turns to be wrong, at best it can misplace precious resources aimed at safety improvements, at worst it can result in an almost inevitable drift towards a machinery space fire with neglect of the control of fire free operation.;The current approach to fires in machinery spaces is hypothesised to be reactive in nature, primarily focusing on detection of already materialised hazards with little or no regard to the systemic nature of hazard occurrence. My research analyses the focus to verify the hypothesis. I then determine if an alternative method can be applied to improve fire safety.;With the initial hypothesis proven correct, the societal implication could be significant. Everyday life in the 21st century involves the interactions between humans, machines and the environment, and this trend is only increasing. If safety fails to account for such factors adequately, safety related accidents may continue to occur at a consistent, if not increased, rate. Conversely with the application of the methodology developed in this research, which accounts for systemic factors using established state of the art hazard analysis techniques to a new application and in a novel manner (directly incorporating design and operation), society may see the elimination of accidents it has grown to accept as unavoidable.;This thesis adopts an alternative method and process (STPA) to apply a structured approach to systemic fire hazard identification and analysis, as an input to safety barrier identification and improvement techniques (e.g. Dynamic Barrier Management [DBM], real time risk representation, etc.). Barrier identification and improvement techniques are only useful if relevant hazards and causal factors are being evaluated alongside the interactions between humans, technology, and the environment.;The approach also only has success if applied into the facility lifecycle during the operational phase. The novelty of applying a structured systemic approach to achieving fire safety during HAZID with a direct link to safety auditing is therefore fundamental to the impact of this thesis.;Within the research I apply this technique in a case study and audit on an operational cruise ship where it is demonstrated that the approach has unearthed otherwise dormant safety concerns. These gaps would have been difficult to discover through the application of an unstructured/ traditional approach to fire safety design and auditing. The findings from the case study provide a critical input to the improvement of the leak prevention barrier of fire safety and demonstrate the novelty and usefulness of such an approach in striving for fire free operations.;Where safety barriers are required or can be improved (i.e. if the same events occur at a consistent frequency from seemingly the same causal factors), the research introduces the Systemic HAZID and Operational Risk Evaluation (SHORE) methodology which presents an easy to follow process (for those not familiar with STPA) leading to the informed selection of specific sensor inputs, for example, which are safety critical and either not installed, or ineffective where they have been installed. The methodology also allows for easy and direct incorporation into the Safety Management System (SMS) of the ship through auditing for continued operational safety evaluation.The primary cause of machinery space fires is cited as the release of flammable oil mist contacting unprotected hot surfaces. With this being common knowledge why do we continue to see this type of incident reoccurring on ships carrying thousands of passengers to precarious destinations? Anecdotal evidence suggests that the prime focus of maritime fire safety falls on risk mitigation, as opposed to its prevention. It also appears technological safety barriers are placed in an 'install and forget' mentality through lack of appreciation of the overall system of safety control.;This belief is explained by referring to risk reduction of adding a 'layer of protection' or by supposedly higher cost-effectiveness of accident mitigation measures. The significance of this belief goes beyond the accurate understanding of the state-of-the-art of maritime safety. If it turns to be wrong, at best it can misplace precious resources aimed at safety improvements, at worst it can result in an almost inevitable drift towards a machinery space fire with neglect of the control of fire free operation.;The current approach to fires in machinery spaces is hypothesised to be reactive in nature, primarily focusing on detection of already materialised hazards with little or no regard to the systemic nature of hazard occurrence. My research analyses the focus to verify the hypothesis. I then determine if an alternative method can be applied to improve fire safety.;With the initial hypothesis proven correct, the societal implication could be significant. Everyday life in the 21st century involves the interactions between humans, machines and the environment, and this trend is only increasing. If safety fails to account for such factors adequately, safety related accidents may continue to occur at a consistent, if not increased, rate. Conversely with the application of the methodology developed in this research, which accounts for systemic factors using established state of the art hazard analysis techniques to a new application and in a novel manner (directly incorporating design and operation), society may see the elimination of accidents it has grown to accept as unavoidable.;This thesis adopts an alternative method and process (STPA) to apply a structured approach to systemic fire hazard identification and analysis, as an input to safety barrier identification and improvement techniques (e.g. Dynamic Barrier Management [DBM], real time risk representation, etc.). Barrier identification and improvement techniques are only useful if relevant hazards and causal factors are being evaluated alongside the interactions between humans, technology, and the environment.;The approach also only has success if applied into the facility lifecycle during the operational phase. The novelty of applying a structured systemic approach to achieving fire safety during HAZID with a direct link to safety auditing is therefore fundamental to the impact of this thesis.;Within the research I apply this technique in a case study and audit on an operational cruise ship where it is demonstrated that the approach has unearthed otherwise dormant safety concerns. These gaps would have been difficult to discover through the application of an unstructured/ traditional approach to fire safety design and auditing. The findings from the case study provide a critical input to the improvement of the leak prevention barrier of fire safety and demonstrate the novelty and usefulness of such an approach in striving for fire free operations.;Where safety barriers are required or can be improved (i.e. if the same events occur at a consistent frequency from seemingly the same causal factors), the research introduces the Systemic HAZID and Operational Risk Evaluation (SHORE) methodology which presents an easy to follow process (for those not familiar with STPA) leading to the informed selection of specific sensor inputs, for example, which are safety critical and either not installed, or ineffective where they have been installed. The methodology also allows for easy and direct incorporation into the Safety Management System (SMS) of the ship through auditing for continued operational safety evaluation
Global claims in engineering and construction contracts
No full textIn the UK over the last 50 years or so, legal developments in relation to extensions of time and/or monetary compensation for delays in construction projects, have been both cautious and incremental. In order to contend with the practical difficulties inherent in the construction industry, the courts have established various legal concepts and principles, not least those pertaining to claims which, given the often complex nature of construction projects, are evidentially difficult to prove; and where a myriad of events,which are both the employer and contractor responsibility, may have caused a composite loss and/or delay. The foregoing claims are commonly understood by the construction industry as being global in nature, the legal determination and assessment of which remains, to a degree intractable.;In the last 20 years or so, there has been a growing perception in the construction industry that the UK courts are becoming more sympathetic towards global claims. This perception is evidenced in a revision made between the 1st and 2nd Editions of the Society of Construction Law's Delay and Disruption Protocol, which has moved from global claims being 'rarely accepted by the courts' to 'an apparent trend for the courts to take a more lenient approach towards global claims'.;This thesis examines the foregoing proposition by adopting an exhaustive, historical case based analysis of the UK case law relevant to global claims from its origins in the1960's, until the present day. The doctrinal approach, including an in-depth analysis of authoritative literature on the subject, reveals that aside from a softening of judicial language and certain clarifications; the UK courts are not, in fact, taking a more lenient approach to global claims. The thesis also provides an updated and fresh perspective on various legal principles germane to the phenomena of global claims, such as the burden of proof, causation, contributory negligence, the dominant cause and apportionment.;The research also identifies and explains certain jurisprudential disparities between the English and Scottish courts, in particular how causation is applied differently to global claims where competing causes are evident. In consequence, it is submitted that despite creative application of the law, the disparity in the judgements, north and south of the border may have inadvertently tightened the Gordian knot, the courts set out to untangle.In light of this complexity, the thesis also includes a framework with support diagrams,in order to assist a claimant in navigating its way around the preconditions required in order to maximise its chances of successfully pleading a claim which may include an element of globality.In the UK over the last 50 years or so, legal developments in relation to extensions of time and/or monetary compensation for delays in construction projects, have been both cautious and incremental. In order to contend with the practical difficulties inherent in the construction industry, the courts have established various legal concepts and principles, not least those pertaining to claims which, given the often complex nature of construction projects, are evidentially difficult to prove; and where a myriad of events,which are both the employer and contractor responsibility, may have caused a composite loss and/or delay. The foregoing claims are commonly understood by the construction industry as being global in nature, the legal determination and assessment of which remains, to a degree intractable.;In the last 20 years or so, there has been a growing perception in the construction industry that the UK courts are becoming more sympathetic towards global claims. This perception is evidenced in a revision made between the 1st and 2nd Editions of the Society of Construction Law's Delay and Disruption Protocol, which has moved from global claims being 'rarely accepted by the courts' to 'an apparent trend for the courts to take a more lenient approach towards global claims'.;This thesis examines the foregoing proposition by adopting an exhaustive, historical case based analysis of the UK case law relevant to global claims from its origins in the1960's, until the present day. The doctrinal approach, including an in-depth analysis of authoritative literature on the subject, reveals that aside from a softening of judicial language and certain clarifications; the UK courts are not, in fact, taking a more lenient approach to global claims. The thesis also provides an updated and fresh perspective on various legal principles germane to the phenomena of global claims, such as the burden of proof, causation, contributory negligence, the dominant cause and apportionment.;The research also identifies and explains certain jurisprudential disparities between the English and Scottish courts, in particular how causation is applied differently to global claims where competing causes are evident. In consequence, it is submitted that despite creative application of the law, the disparity in the judgements, north and south of the border may have inadvertently tightened the Gordian knot, the courts set out to untangle.In light of this complexity, the thesis also includes a framework with support diagrams,in order to assist a claimant in navigating its way around the preconditions required in order to maximise its chances of successfully pleading a claim which may include an element of globality
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