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Numerical study on hydrodynamics of a ship advancing in confined waterways
Get PDFThis thesis was previously held under moratorium from 22nd August 2019 to 22nd August 2021.The prediction of ship hydrodynamics in the confined waterways is challenging. It may involve both ship-bottom and ship-bank interactions. When a ship is advancing in shallow water, the hydrodynamic behaviours may vary significantly due to the hydrodynamic interaction between the bottom of the ship hull and the seabed, or so called shallow water effects. The flow velocity in the gap between the ship bottom and the seabed increases, which will lead to an increase in ship’s sinkage, trim and resistance. Also, the asymmetric flow around a ship induced by the vicinity of banks causes pressure differences between port and starboard sides, which is known as the bank effects. Therefore, an accurate prediction of shallow water and bank effects is essential to minimize the risk of the collision and the grounding for the ships. Flanders Hydraulics Research (FHR) in cooperation with the Maritime Technology Division of Ghent University has carried out shallow model tests in a towing tank equipped with surface-piercing banks and a vertical quay wall with a 1/75 scale model of the KRISO Very Large Crude carrier (KVLCC2). The forces and moments on the KVLCC2 model were obtained at various water depths, lateral distances to the banks. Additionally, the wave elevation was measured between the quay wall and the ship model. The main objective of the present paper is to simulate the complex flow around the ship and predict the hydrodynamic behaviours of a ship when advancing in the confined waterways. To simulate ship hydrodynamics in confined waterways, the CFD programme should be used to get a reliable result. In the present study, a widely used CFD programme, Star-CCM+, will be used to simulate the complex flow phenomena induced by a ship advancing in confined waterways. To evaluate the capability of the CFD software, the numerical data will be compared with the experimental data conducted by FHR. The free surface effect will be taken into account. The results will include the forces and moments acting on the ship, as well as the wave elevation between the quay wall and the ship model. The parametric study will be conducted to investigate the effects of the ship speed, the water depths and the positions in a channel. Discussions will be highlighted on the ship-bank interaction when the water depth Froude number approaches critical value.The prediction of ship hydrodynamics in the confined waterways is challenging. It may involve both ship-bottom and ship-bank interactions. When a ship is advancing in shallow water, the hydrodynamic behaviours may vary significantly due to the hydrodynamic interaction between the bottom of the ship hull and the seabed, or so called shallow water effects. The flow velocity in the gap between the ship bottom and the seabed increases, which will lead to an increase in ship’s sinkage, trim and resistance. Also, the asymmetric flow around a ship induced by the vicinity of banks causes pressure differences between port and starboard sides, which is known as the bank effects. Therefore, an accurate prediction of shallow water and bank effects is essential to minimize the risk of the collision and the grounding for the ships. Flanders Hydraulics Research (FHR) in cooperation with the Maritime Technology Division of Ghent University has carried out shallow model tests in a towing tank equipped with surface-piercing banks and a vertical quay wall with a 1/75 scale model of the KRISO Very Large Crude carrier (KVLCC2). The forces and moments on the KVLCC2 model were obtained at various water depths, lateral distances to the banks. Additionally, the wave elevation was measured between the quay wall and the ship model. The main objective of the present paper is to simulate the complex flow around the ship and predict the hydrodynamic behaviours of a ship when advancing in the confined waterways. To simulate ship hydrodynamics in confined waterways, the CFD programme should be used to get a reliable result. In the present study, a widely used CFD programme, Star-CCM+, will be used to simulate the complex flow phenomena induced by a ship advancing in confined waterways. To evaluate the capability of the CFD software, the numerical data will be compared with the experimental data conducted by FHR. The free surface effect will be taken into account. The results will include the forces and moments acting on the ship, as well as the wave elevation between the quay wall and the ship model. The parametric study will be conducted to investigate the effects of the ship speed, the water depths and the positions in a channel. Discussions will be highlighted on the ship-bank interaction when the water depth Froude number approaches critical value
A detailed investigation into the engineering properties and challenges affecting the potential introduction of a UK grown dowel-laminated timber floor panel into the domestic construction market
Get PDFSatisfying the demand for more efficient and sustainable buildings presents a considerable challenge to the UK construction industry. Increasingly, the UK construction industry is looking towards prefabricated or offsite construction as a means of providing economic, sustainable and energy efficient buildings. Timber and engineered wood products (EWPs) are ideally suited to take advantage of the trend towards off site construction.;However, in the UK, planted commercial tree species, are only used in a limited fashion by the UK construction industry as it is generally perceived to be of low quality. Forestry projections indicate that within the next 10 to 15 years there will be an abundance of UK timber as large amounts of standing stock reach maturity. Subsequently, there is a need to fully utilise the available and future resource, lest large amounts of commercial timber and capital will be underutilised. This has led to more research being conducted into new or novel methods of maximising the potential of the existing and predicted UK timber stock.;Whilst the production of a variety of EWPs have been embraced on the continent by small to medium enterprises working in the timber industry similar developments in the UK have been less forthcoming. One such product that has been developed on the continent is Brettstapel, Dowellam or Dowel laminated timber (DLT). These are solid timber panels that are formed without the use of adhesive and rely on hardwood dowels to join the single laminations together to form a panel.;The creation of an engineered timber product without synthetic adhesives allows for a real reduction in the energy used to create a higher value EWP that can be produced in a variety of shapes and finishes.;Building upon the research of the Centre for Offsite Construction and Innovative Solutions (COCIS), this thesis explores the development of a DLT panel formed predominately of UK grown timber. A ground up approach to developing a DLT floor panel was undertaken; this included identifying market opportunities, locating avenues for its application and determining barriers to its implementation. One of these barriers highlighted within a market study was the lack of technical information and guidance.;The provision of technical information for the panel incorporated a staged analysis of materials and structural mechanisms within a panel that defined its structural performance. These included the determination of the pertinent mechanical properties of the softwood laminations and hardwood dowels including combined timber embedment properties to determine the most appropriate materials to be used in a panel.;An experimental investigation into the use of hardwood beech dowels in conjunction with UK Sitka spruce and larch members in double and multiple shear plane connections is also undertaken. The findings for the study are integrated into a process for the design and verification for UK DLT panels. Through a series of experimental tests conducted on UK grown and produced DLT panels the thesis demonstrates that UK grown timber could be used to create DLT panels in the future. However, the position of the dowel and the overall stiffness of the all-timber connection cannot ensure a composite panel with improved performance is created.;Finally, the thesis demonstrates the potential for the UK production of DLT panels by presenting a case study for a new build property in the Scottish Highlands that utilises UK softwood and information obtained in this study.Satisfying the demand for more efficient and sustainable buildings presents a considerable challenge to the UK construction industry. Increasingly, the UK construction industry is looking towards prefabricated or offsite construction as a means of providing economic, sustainable and energy efficient buildings. Timber and engineered wood products (EWPs) are ideally suited to take advantage of the trend towards off site construction.;However, in the UK, planted commercial tree species, are only used in a limited fashion by the UK construction industry as it is generally perceived to be of low quality. Forestry projections indicate that within the next 10 to 15 years there will be an abundance of UK timber as large amounts of standing stock reach maturity. Subsequently, there is a need to fully utilise the available and future resource, lest large amounts of commercial timber and capital will be underutilised. This has led to more research being conducted into new or novel methods of maximising the potential of the existing and predicted UK timber stock.;Whilst the production of a variety of EWPs have been embraced on the continent by small to medium enterprises working in the timber industry similar developments in the UK have been less forthcoming. One such product that has been developed on the continent is Brettstapel, Dowellam or Dowel laminated timber (DLT). These are solid timber panels that are formed without the use of adhesive and rely on hardwood dowels to join the single laminations together to form a panel.;The creation of an engineered timber product without synthetic adhesives allows for a real reduction in the energy used to create a higher value EWP that can be produced in a variety of shapes and finishes.;Building upon the research of the Centre for Offsite Construction and Innovative Solutions (COCIS), this thesis explores the development of a DLT panel formed predominately of UK grown timber. A ground up approach to developing a DLT floor panel was undertaken; this included identifying market opportunities, locating avenues for its application and determining barriers to its implementation. One of these barriers highlighted within a market study was the lack of technical information and guidance.;The provision of technical information for the panel incorporated a staged analysis of materials and structural mechanisms within a panel that defined its structural performance. These included the determination of the pertinent mechanical properties of the softwood laminations and hardwood dowels including combined timber embedment properties to determine the most appropriate materials to be used in a panel.;An experimental investigation into the use of hardwood beech dowels in conjunction with UK Sitka spruce and larch members in double and multiple shear plane connections is also undertaken. The findings for the study are integrated into a process for the design and verification for UK DLT panels. Through a series of experimental tests conducted on UK grown and produced DLT panels the thesis demonstrates that UK grown timber could be used to create DLT panels in the future. However, the position of the dowel and the overall stiffness of the all-timber connection cannot ensure a composite panel with improved performance is created.;Finally, the thesis demonstrates the potential for the UK production of DLT panels by presenting a case study for a new build property in the Scottish Highlands that utilises UK softwood and information obtained in this study
Inductive interconnecting solutions for airworthiness standards and power-quality requirements compliance for more-electric aircraft/engine power networks
Get PDFDriven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions.Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions
Negatively-valenced influencing behaviour: forms, triggers and impacts
No full textThis thesis was previously held under moratorium from 3rd October 2018 until 3rd October 2020.Influencing behaviour, as a form of Customer Engagement Behaviour (CEB), has the potential to impact other actors within a network and likewise the value and performance of firms in different ways, depending on its valence. However, despite its potentially detrimental effect, negatively-valenced influencing behaviour (NVIB) remains relatively poorly studied in terms of empirical work, specifically regarding its forms, triggers and impact. This thesis adopts mixed methods research, specifically, a sequential exploratory design so that the qualitative study provides findings that inform the quantitative study. The first study which is qualitative used netnography to explore how customers engage in NVIB and what triggers customers to engage in NVIB on review sites. The findings include six forms of NVIB classified as direct and indirect, based on the way customers use each form in their online reviews. The findings also contain five triggers of NVIB and indicate relationships between forms and triggers of NVIB.;The second study which is quantitative used three experiments to measure the impact of NVIB on other actors' attitude and behavioural intentions towards service providers using the forms conceptualised in the first study. The results from the three experiments showed the negative impact of NVIB on other actors' attitudes and behavioural intentions, with a relative strength of direct over indirect NVIB displayed. The thesis contributes to understanding NVIB by providing a typology of six distinct forms of NVIB and five triggers and also by showing that customers may directly or indirectly address other actors when engaging in NVIB; however, both direct and indirect forms of NVIB negatively impact other actors' attitudes and behavioural intentions. Finally, this thesis contributes to studies in this area with empirical results that show the impact of specific forms of NVIB on other actors' attitude and behavioural intentions towards service providers.Influencing behaviour, as a form of Customer Engagement Behaviour (CEB), has the potential to impact other actors within a network and likewise the value and performance of firms in different ways, depending on its valence. However, despite its potentially detrimental effect, negatively-valenced influencing behaviour (NVIB) remains relatively poorly studied in terms of empirical work, specifically regarding its forms, triggers and impact. This thesis adopts mixed methods research, specifically, a sequential exploratory design so that the qualitative study provides findings that inform the quantitative study. The first study which is qualitative used netnography to explore how customers engage in NVIB and what triggers customers to engage in NVIB on review sites. The findings include six forms of NVIB classified as direct and indirect, based on the way customers use each form in their online reviews. The findings also contain five triggers of NVIB and indicate relationships between forms and triggers of NVIB.;The second study which is quantitative used three experiments to measure the impact of NVIB on other actors' attitude and behavioural intentions towards service providers using the forms conceptualised in the first study. The results from the three experiments showed the negative impact of NVIB on other actors' attitudes and behavioural intentions, with a relative strength of direct over indirect NVIB displayed. The thesis contributes to understanding NVIB by providing a typology of six distinct forms of NVIB and five triggers and also by showing that customers may directly or indirectly address other actors when engaging in NVIB; however, both direct and indirect forms of NVIB negatively impact other actors' attitudes and behavioural intentions. Finally, this thesis contributes to studies in this area with empirical results that show the impact of specific forms of NVIB on other actors' attitude and behavioural intentions towards service providers
Profiling of propolis samples from UK, Indonesia and sub-Saharan Africa and isolation of some pure components
Get PDFPropolis is a resinous material collected by bees as part of the defensive system of the bee hive. It has a wide range of biological activities including anti-protozoal and [sic] and microbial activity. Samples of propolis from different parts of the UK, Africa and Indonesia were extracted and profiled by liquid chromatography-high resolution mass spectrometry. The data were aligned and features were extracted into 0.02 amu windows. In order to establish a platform for comparison of the samples the top features by peak intensity, after excluding abundant dimer peaks, were further characterized by MS2. Putative identities were deduced from accurate masses which were within 3 ppm deviations from the exact mass of the proposed elemental compositions. For the UK propolis samples, over 90% of the peaks could be assigned identities with some level of confidence. The compounds identified fell into the major categories: flavonoid esters and possibly some ethers, phenyl propanoid esters, glycerol esters, flavonoid glycosides and hydroxylated fatty acids. Pinobanksin was the most abundant compound in the samples. The flavonoids pinocembrin, pinobanksin, galangin and chrysin showed a relatively low degree of variation across the nine samples whereas flavonoid esters and glycerol esters were more variable in their response across the nine samples. The propolis samples from hives in three different areas of Scotland yielded hundreds of components, many of which were not identified. In the Aberdeenshire samples principal components analysis (PCA) followed by hierarchical cluster analysis (HCA) grouped nine samples into six groups according to the abundance of their components. The Aberdeenshire samples were abundant in glycerol esters. Five samples from Fort William could be divided into four groups. These samples had quite a different composition from the Aberdeenshire samples containing an abundance of compounds putatively identified as being sesquiterpene acids. Three samples from Dunblane were different again but had more similarity in composition to the Aberdeenshire samples than the Fort William samples. The propolis sample from Indonesia yielded predominantly phenolic compounds. Although standards were not available to determine the identities and actual amounts of the compounds in the samples, preparative chromatographic separation enabled the identification of some of the compounds by NMR spectroscopy (1D and 2D) and mass spectra as pinobanksin, apigenin, lupeol, gallic acid and quercetin. The role of propolis in warding off infections in the bee hive which is yet established was addressed in this study and the approach provides a potential method for correlating hive health with the composition of the propolis gathered by the bees. Thus this study also confirms local and regional variations in propolis composition over a relatively small areas and over wide geographical regions.Propolis is a resinous material collected by bees as part of the defensive system of the bee hive. It has a wide range of biological activities including anti-protozoal and [sic] and microbial activity. Samples of propolis from different parts of the UK, Africa and Indonesia were extracted and profiled by liquid chromatography-high resolution mass spectrometry. The data were aligned and features were extracted into 0.02 amu windows. In order to establish a platform for comparison of the samples the top features by peak intensity, after excluding abundant dimer peaks, were further characterized by MS2. Putative identities were deduced from accurate masses which were within 3 ppm deviations from the exact mass of the proposed elemental compositions. For the UK propolis samples, over 90% of the peaks could be assigned identities with some level of confidence. The compounds identified fell into the major categories: flavonoid esters and possibly some ethers, phenyl propanoid esters, glycerol esters, flavonoid glycosides and hydroxylated fatty acids. Pinobanksin was the most abundant compound in the samples. The flavonoids pinocembrin, pinobanksin, galangin and chrysin showed a relatively low degree of variation across the nine samples whereas flavonoid esters and glycerol esters were more variable in their response across the nine samples. The propolis samples from hives in three different areas of Scotland yielded hundreds of components, many of which were not identified. In the Aberdeenshire samples principal components analysis (PCA) followed by hierarchical cluster analysis (HCA) grouped nine samples into six groups according to the abundance of their components. The Aberdeenshire samples were abundant in glycerol esters. Five samples from Fort William could be divided into four groups. These samples had quite a different composition from the Aberdeenshire samples containing an abundance of compounds putatively identified as being sesquiterpene acids. Three samples from Dunblane were different again but had more similarity in composition to the Aberdeenshire samples than the Fort William samples. The propolis sample from Indonesia yielded predominantly phenolic compounds. Although standards were not available to determine the identities and actual amounts of the compounds in the samples, preparative chromatographic separation enabled the identification of some of the compounds by NMR spectroscopy (1D and 2D) and mass spectra as pinobanksin, apigenin, lupeol, gallic acid and quercetin. The role of propolis in warding off infections in the bee hive which is yet established was addressed in this study and the approach provides a potential method for correlating hive health with the composition of the propolis gathered by the bees. Thus this study also confirms local and regional variations in propolis composition over a relatively small areas and over wide geographical regions
The nature and extent of sentence discounting for guilty pleas : in Scottish Sheriff Court summary cases
No full textThis thesis was previously held under moratorium from 28th November 2019 until 28th November 2024.The thesis starts from a position whereby almost nothing is known about Sentence
Discounting in practice. This research addresses this knowledge gap by observing two courts and conducting interviews with seven sheriffs, eight defence lawyers, two
prosecutors, and twelve accused persons. Firstly, the thesis argues that while practitioners believe the formal law is authoritative, in both statute and case-law the position is ambivalent and occasionally somewhat contradictory. The thesis shows that the formal law is radically indeterminate with regard to Sentence Discounting. Secondly, the thesis shows that case disposal via Guilty Pleas depends upon social relationships between legal practitioners (judges, prosecutors, and defence lawyers). These social relationships result in an element of predictability regarding the stated Sentence Discount. The importance of social relationships also means that formalistic innovations intended to yield greater efficiency may have been counter-productive. Thirdly, the thesis documents how individual courts generate unique norms. The thesis demonstrates this by analysing differences between two neighbouring courts of comparable size. Court 1 took significantly longer than the national average to reach a Guilty Plea while Court 2 was considerably faster. The research shows that different intra-court cultures partly explain the differences between the two courts. Fourthly, the thesis reveals that Sentence Discounting contributes to accused persons’ feelings of disconnection with the criminal process. While accused persons believed in some idea of the majesty of the law, they lamented that this did not materialise in their cases. Accused persons felt Sentence Discounting trivialised their experiences and introduced inappropriate elements of gamesmanship.The thesis starts from a position whereby almost nothing is known about Sentence
Discounting in practice. This research addresses this knowledge gap by observing two courts and conducting interviews with seven sheriffs, eight defence lawyers, two
prosecutors, and twelve accused persons. Firstly, the thesis argues that while practitioners believe the formal law is authoritative, in both statute and case-law the position is ambivalent and occasionally somewhat contradictory. The thesis shows that the formal law is radically indeterminate with regard to Sentence Discounting. Secondly, the thesis shows that case disposal via Guilty Pleas depends upon social relationships between legal practitioners (judges, prosecutors, and defence lawyers). These social relationships result in an element of predictability regarding the stated Sentence Discount. The importance of social relationships also means that formalistic innovations intended to yield greater efficiency may have been counter-productive. Thirdly, the thesis documents how individual courts generate unique norms. The thesis demonstrates this by analysing differences between two neighbouring courts of comparable size. Court 1 took significantly longer than the national average to reach a Guilty Plea while Court 2 was considerably faster. The research shows that different intra-court cultures partly explain the differences between the two courts. Fourthly, the thesis reveals that Sentence Discounting contributes to accused persons’ feelings of disconnection with the criminal process. While accused persons believed in some idea of the majesty of the law, they lamented that this did not materialise in their cases. Accused persons felt Sentence Discounting trivialised their experiences and introduced inappropriate elements of gamesmanship
Passive Q-switching of 1 micron Nd:YAG lasers for military target designator applications
Get PDFThis thesis was previously held under moratorium from 2nd April 2019 until 5th May 2021.In this research project we assess the potential for a passively Q-switched, diode end pumped 1064 nm Nd:YAG system to be implemented in future generations of military target designators. The main challenges were to achieve a pulse energy above 50 mJ, timing jitter below ± 5 μs, and ensuring operation over a temperature range of -40 to +70 °C. We have addressed these challenges and established a framework for future research into passively Q-switched designators. We found that the limited pulse energy was due largely to a non-uniform pump beam, which was corrected with an engineered diffuser. This enabled us to achieve a single pulse energy of 53.4 mJ, which is the highest reported energy for a diode end pumped, passively Q-switched 1064 nm Nd:YAG laser. Secondly, we identified, through experiment and modelling, that the main causes of timing jitter in our system were mechanical vibrations and pump power fluctuations. We also investigated the presence of satellite pulses, which we experimentally attribute to longitudinal mode competition. We also provide a summary of the Q-switching performance of V:YAG, Cr:YAG and BDN (bis[4-dimethylaminodithiobenzil] nickel) dye saturable absorbers, through experiment and rate equation modelling. From this we can confirm that Cr:YAG is the only commercially viable material suitable for high energy passive Q-switching at 1064 nm. Finally we evaluated the thermal performance of a mechanically robust Nd:YAG laser passively Q-switched with Cr:YAG. The pulse energy, duration, jitter and threshold were measured over the temperature range -40 to +70 °C. Through modelling we propose that the experimentally observed changes in the laser parameters are driven by the temperature dependence of the effective emission cross section (Nd:YAG), pump power and laser mode size.In this research project we assess the potential for a passively Q-switched, diode end pumped 1064 nm Nd:YAG system to be implemented in future generations of military target designators. The main challenges were to achieve a pulse energy above 50 mJ, timing jitter below ± 5 μs, and ensuring operation over a temperature range of -40 to +70 °C. We have addressed these challenges and established a framework for future research into passively Q-switched designators. We found that the limited pulse energy was due largely to a non-uniform pump beam, which was corrected with an engineered diffuser. This enabled us to achieve a single pulse energy of 53.4 mJ, which is the highest reported energy for a diode end pumped, passively Q-switched 1064 nm Nd:YAG laser. Secondly, we identified, through experiment and modelling, that the main causes of timing jitter in our system were mechanical vibrations and pump power fluctuations. We also investigated the presence of satellite pulses, which we experimentally attribute to longitudinal mode competition. We also provide a summary of the Q-switching performance of V:YAG, Cr:YAG and BDN (bis[4-dimethylaminodithiobenzil] nickel) dye saturable absorbers, through experiment and rate equation modelling. From this we can confirm that Cr:YAG is the only commercially viable material suitable for high energy passive Q-switching at 1064 nm. Finally we evaluated the thermal performance of a mechanically robust Nd:YAG laser passively Q-switched with Cr:YAG. The pulse energy, duration, jitter and threshold were measured over the temperature range -40 to +70 °C. Through modelling we propose that the experimentally observed changes in the laser parameters are driven by the temperature dependence of the effective emission cross section (Nd:YAG), pump power and laser mode size
Suction drain as a novel low-carbon ground improvement technique
Get PDFThis thesis was previously held under moratorium from 17th November 2019 until 1st April 2021.No abstract available.No abstract available
Applications of the operator Schmidt decomposition in the quantification and exploitation of correlations
Get PDFIn this thesis we analyse a particular decomposition of the density matrix into tensor product terms - known as the operator Schmidt decomposition (OSD) - showing how it can be used in order to measure and exploit correlations in bipartite quantum systems. Correlations rest at the heart of Quantum Information theory for both their foundational significance and their irreplaceable role in quantum computation and communication. However, because of their difficult characterisation, detecting and measuring correlations are usually believed arduous tasks. This is particularly true in the mixed-state domain, where the diversity of potential correlations represents a further complication.;For these reasons, it would be advisable to define a common framework for examining and quantifying correlations of all kinds and degrees, both for pure and mixed states. Here we argue that the OSD is a powerful tool for this purpose, in that it can be used to devise measures of correlations, whether classical or quantum. In turn, these measures can be exploited in order to detect the presence of entanglement and steering, for example. The first part of this work is devoted to the definitions of such measures and the analysis of their properties. In the second part instead we consider the possibility of taking advantage of the OSD in the context of quantum process discrimination and tomography.;These tasks are central to the implementation of quantum technologies, since the actual realisation of any application based upon quantum phenomena largely relies on the determination of quantum processes.We provide a set of tools - based on the OSD - that could serve as a means by which enabling or improving certain specific protocols of ancilla-assisted quantum process discrimination (AAPD) and tomography (AAPT). First, we present a quantifier for the performance of bipartite input states in AAPD.;We show that the possibility to improve the discrimination power of this protocol - or to enable it altogether - is imprinted in the OSD of the input state. For what AAPT is concerned, we demonstrate how the OSD of the input state can be exploited in order to allow a characterization of an unknown local channel via a relatively small number of local transformations of the input state. More in general, we provide several results which show a sharp connection between the tasks of channel discrimination and tomography, the OSD of the input state, and the degree of correlations carried by the latter.;We conclude the thesis with a collection of results of a seemingly different nature, but that were actually inspired by the examination of the previously mentioned ancilla-assisted tasks. In short, we define a family of state-dependent metrics on the space of quantum channels and show that they are deeply connected to the OSD of the state defining them. As a byproduct, the latest results entail a possible generalisation of the Choi-Jamio lkowski isomorphism, thus providing an interesting motivation to the extension of this research project.In this thesis we analyse a particular decomposition of the density matrix into tensor product terms - known as the operator Schmidt decomposition (OSD) - showing how it can be used in order to measure and exploit correlations in bipartite quantum systems. Correlations rest at the heart of Quantum Information theory for both their foundational significance and their irreplaceable role in quantum computation and communication. However, because of their difficult characterisation, detecting and measuring correlations are usually believed arduous tasks. This is particularly true in the mixed-state domain, where the diversity of potential correlations represents a further complication.;For these reasons, it would be advisable to define a common framework for examining and quantifying correlations of all kinds and degrees, both for pure and mixed states. Here we argue that the OSD is a powerful tool for this purpose, in that it can be used to devise measures of correlations, whether classical or quantum. In turn, these measures can be exploited in order to detect the presence of entanglement and steering, for example. The first part of this work is devoted to the definitions of such measures and the analysis of their properties. In the second part instead we consider the possibility of taking advantage of the OSD in the context of quantum process discrimination and tomography.;These tasks are central to the implementation of quantum technologies, since the actual realisation of any application based upon quantum phenomena largely relies on the determination of quantum processes.We provide a set of tools - based on the OSD - that could serve as a means by which enabling or improving certain specific protocols of ancilla-assisted quantum process discrimination (AAPD) and tomography (AAPT). First, we present a quantifier for the performance of bipartite input states in AAPD.;We show that the possibility to improve the discrimination power of this protocol - or to enable it altogether - is imprinted in the OSD of the input state. For what AAPT is concerned, we demonstrate how the OSD of the input state can be exploited in order to allow a characterization of an unknown local channel via a relatively small number of local transformations of the input state. More in general, we provide several results which show a sharp connection between the tasks of channel discrimination and tomography, the OSD of the input state, and the degree of correlations carried by the latter.;We conclude the thesis with a collection of results of a seemingly different nature, but that were actually inspired by the examination of the previously mentioned ancilla-assisted tasks. In short, we define a family of state-dependent metrics on the space of quantum channels and show that they are deeply connected to the OSD of the state defining them. As a byproduct, the latest results entail a possible generalisation of the Choi-Jamio lkowski isomorphism, thus providing an interesting motivation to the extension of this research project
Droplet behaviour in microfluidic devices
Get PDFThis work is a study to understand the various aspects of a microfluidic device. In the first half we take the role of an end user, experimenting to learn how best to use the device efficiently. In the second half we are the manufacturer, trying to fabricate a user friendly, and fully functioning microfluidic device. As the end user, we have three different T-junction droplet generator devices, with similar geometries. We start investigating by generating water droplets in an oil medium. They self-organise into various flow patterns: single-profile, double-helix profile and triple-helix profile. We document how, with increasing flow rate ratio and capillary number, we observe more densely packed droplet flow patterns. The device with the deeper expansion channel provides more space for the droplets and they self-organise the triple-helix pattern in 3-dimension. We then use the same devices to generate droplets for which we can calculate the volume. The fluid flow in a microchannel happens in four different regimes: ballooning, squeezing, dripping and jetting regimes. In single-cell and single-molecule analysis devices, the ability to create droplets on demand and of a certain volume is a desired capability. This can be achieved by understanding and learning how to use the fluid flow characteristics accurately. We experiment with the three different sized microfluidic devices, to measure the droplet volume throughout the squeezing to dripping regimes. This is achieved by manipulating the capillary number and the flow rate ratio. We observe a similar result as with the flow patterns: that the capillary number has an impact on the droplet volume. As the capillary number increases the droplet diameter decreases. Further, for a set capillary number we can fine tune the droplet diameter by changing the flow rate ratio. As the flow rate ratio increases the volume of water droplets increases, despite the fact the capillary number is set. These coincide with our flow pattern results. Our results fit to the scaling law to predict the droplet size introduced by Tanet al. in 2008 [51]. Unlike some other authors in the literature, we did not observe a critical capillary number where the droplet volume changes suddenly. However, we did observe a transition area where we cannot define the regime of the fluid flow. As the manufacturer we designed and fabricated our own planar free standing microfluidic devices using a polymer called SU-8. After looking into the weaknesses and the strengths of using SU-8, we describe how we successfully fabricated working devices and developeda new procedure in adhesive low temperature bonding. We finish by considering the challenges of connecting micro sized structures to a macro sized syringe pump, and fabricated a chip-holder inspired by applications in industry.This work is a study to understand the various aspects of a microfluidic device. In the first half we take the role of an end user, experimenting to learn how best to use the device efficiently. In the second half we are the manufacturer, trying to fabricate a user friendly, and fully functioning microfluidic device. As the end user, we have three different T-junction droplet generator devices, with similar geometries. We start investigating by generating water droplets in an oil medium. They self-organise into various flow patterns: single-profile, double-helix profile and triple-helix profile. We document how, with increasing flow rate ratio and capillary number, we observe more densely packed droplet flow patterns. The device with the deeper expansion channel provides more space for the droplets and they self-organise the triple-helix pattern in 3-dimension. We then use the same devices to generate droplets for which we can calculate the volume. The fluid flow in a microchannel happens in four different regimes: ballooning, squeezing, dripping and jetting regimes. In single-cell and single-molecule analysis devices, the ability to create droplets on demand and of a certain volume is a desired capability. This can be achieved by understanding and learning how to use the fluid flow characteristics accurately. We experiment with the three different sized microfluidic devices, to measure the droplet volume throughout the squeezing to dripping regimes. This is achieved by manipulating the capillary number and the flow rate ratio. We observe a similar result as with the flow patterns: that the capillary number has an impact on the droplet volume. As the capillary number increases the droplet diameter decreases. Further, for a set capillary number we can fine tune the droplet diameter by changing the flow rate ratio. As the flow rate ratio increases the volume of water droplets increases, despite the fact the capillary number is set. These coincide with our flow pattern results. Our results fit to the scaling law to predict the droplet size introduced by Tanet al. in 2008 [51]. Unlike some other authors in the literature, we did not observe a critical capillary number where the droplet volume changes suddenly. However, we did observe a transition area where we cannot define the regime of the fluid flow. As the manufacturer we designed and fabricated our own planar free standing microfluidic devices using a polymer called SU-8. After looking into the weaknesses and the strengths of using SU-8, we describe how we successfully fabricated working devices and developeda new procedure in adhesive low temperature bonding. We finish by considering the challenges of connecting micro sized structures to a macro sized syringe pump, and fabricated a chip-holder inspired by applications in industry
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