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Hydrodynamic, acoustic, and electrical characteristics of underwater spark discharges initiated by different mechanisms
Get PDFUnderwater spark discharge is one of the most common methods to generate intense acoustic impulses in water for different purposes in practical applications. As compared with chemical explosion, the underwater spark discharges provide a number of advantages: they do not generate toxic compounds or species, no high explosives involved and they provide high degree of controllability. These features have led to a large number of studies of underwater spark discharge mechanisms and their potential practical utilisation.;This work is aimed at experimental investigation of the breakdown characteristics of underwater spark discharges with three different initiation mechanisms: free discharge, air-bubble-stimulated discharge and wire-guided discharge. Study on the electrical and acoustic parameters of the discharge process has conducted. A capacitive voltage impulse system was developed to energise three different electrode topologies.;Acoustic and electrical parameters of underwater spark discharges were obtained from experimental results, such as acoustic magnitude, period of cavity oscillation, breakdown voltage, plasma resistance and energy delivered into the plasma channel. Phenomenological scaling relations were established for these parameters, which allowed for better understanding and prediction of the acoustic performance of underwater spark discharges.;An analytical model, which describes the cavity oscillation, has been developed and comparison of the modelling and experimental results was conducted for all three types of discharges. This model allowed for accurate description of the time-dependent behaviour of different parameters during the underwater spark discharge process. The obtained results are important for optimising the circuit parameters for generation of tailored acoustic impulses for different practical applications.Underwater spark discharge is one of the most common methods to generate intense acoustic impulses in water for different purposes in practical applications. As compared with chemical explosion, the underwater spark discharges provide a number of advantages: they do not generate toxic compounds or species, no high explosives involved and they provide high degree of controllability. These features have led to a large number of studies of underwater spark discharge mechanisms and their potential practical utilisation.;This work is aimed at experimental investigation of the breakdown characteristics of underwater spark discharges with three different initiation mechanisms: free discharge, air-bubble-stimulated discharge and wire-guided discharge. Study on the electrical and acoustic parameters of the discharge process has conducted. A capacitive voltage impulse system was developed to energise three different electrode topologies.;Acoustic and electrical parameters of underwater spark discharges were obtained from experimental results, such as acoustic magnitude, period of cavity oscillation, breakdown voltage, plasma resistance and energy delivered into the plasma channel. Phenomenological scaling relations were established for these parameters, which allowed for better understanding and prediction of the acoustic performance of underwater spark discharges.;An analytical model, which describes the cavity oscillation, has been developed and comparison of the modelling and experimental results was conducted for all three types of discharges. This model allowed for accurate description of the time-dependent behaviour of different parameters during the underwater spark discharge process. The obtained results are important for optimising the circuit parameters for generation of tailored acoustic impulses for different practical applications
Adaptation and self-management after stroke: exploring the application of the Selection, Optimisation and Compensation model
Get PDFBackground: Stroke can have long-term consequences for survivors, and recovery can be acomplex process. Unfortunately, there is a lack of theory-based evidence as to how stroke survivors can be aided in coping or adjusting to their new circumstances. The Selection, Optimisation and Compensation (SOC) model describes three processes of selection, optimisation and compensation, which are suggested to allow older adults to maintain activity in areas of life that are important to them, despite loss of functional or cognitive capacity. This thesis explored the Selection, Optimisation and Compensation (SOC) model as a model for post-stroke adaptation. Method: A mixed method approach consisted of systematically reviewing previous applications of the SOC model; conducting qualitative interviews with 30 stroke survivors to determine if SOC processes could be identified within coping strategies; and using Discriminant Content Validation (DCV) methodology to further analyse stroke-specific SOC strategies. Finally, the model was operationalised in the context of stroke through the development of a SOC self-management intervention, which was piloted with five stroke survivors. Findings: One hundred and forty nine stroke-specific SOC strategies were elicited from the interviews; 78% of which were significantly classified as at least one of the theoretical constructs of SOC using DCV analysis. Such findings were used to develop a SOC self-management intervention, which included descriptions of the SOC processes and examples of stroke-specific SOC strategies. Discussion: Overall, this thesis provided strength to the argument that the SOC model is indeed appropriate for the aim of helping stroke survivors come to terms with living with the long-term consequences of stroke. Further refinements are, however, necessary in the operationalisation of the SOC model into a post-stroke intervention. Future research should build upon these findings in order to increase the effective use of SOC strategies; with the ultimate aim of improving adaptation in stroke survivors.Background: Stroke can have long-term consequences for survivors, and recovery can be acomplex process. Unfortunately, there is a lack of theory-based evidence as to how stroke survivors can be aided in coping or adjusting to their new circumstances. The Selection, Optimisation and Compensation (SOC) model describes three processes of selection, optimisation and compensation, which are suggested to allow older adults to maintain activity in areas of life that are important to them, despite loss of functional or cognitive capacity. This thesis explored the Selection, Optimisation and Compensation (SOC) model as a model for post-stroke adaptation. Method: A mixed method approach consisted of systematically reviewing previous applications of the SOC model; conducting qualitative interviews with 30 stroke survivors to determine if SOC processes could be identified within coping strategies; and using Discriminant Content Validation (DCV) methodology to further analyse stroke-specific SOC strategies. Finally, the model was operationalised in the context of stroke through the development of a SOC self-management intervention, which was piloted with five stroke survivors. Findings: One hundred and forty nine stroke-specific SOC strategies were elicited from the interviews; 78% of which were significantly classified as at least one of the theoretical constructs of SOC using DCV analysis. Such findings were used to develop a SOC self-management intervention, which included descriptions of the SOC processes and examples of stroke-specific SOC strategies. Discussion: Overall, this thesis provided strength to the argument that the SOC model is indeed appropriate for the aim of helping stroke survivors come to terms with living with the long-term consequences of stroke. Further refinements are, however, necessary in the operationalisation of the SOC model into a post-stroke intervention. Future research should build upon these findings in order to increase the effective use of SOC strategies; with the ultimate aim of improving adaptation in stroke survivors
Investigating the protein-protein interactions of SCO3607 and SCO3608 and their role in cell morphology in Streptomyces coelicolor
Get PDFFlotillin is a protein intrinsic to cell viability in humans, where it plays a role in cell morphology and structure. In Bacillus subtilis, it is involved in sporulation. NfeD always accompanies flotillins in prokaryotes, normally as an adjacent gene, though it is not present in eukaryotes. SCO3607 and SCO3608, encoding flotillin and NfeD, respectively, are present in Streptomyces coelicolor. No previous studies have examined the role of these two proteins in S. coelicolor. Preliminary bioinformatics revealed NfeD-encoding genes in actinobacteria, which was tentatively suggested as a new group of NfeD proteins; NfeD1b-5. Tn5062 transposon insertions in SCO3607 and deletions of both genes, separately and together, displayed no macroscopic phenotype; while fluorescence microscopy revealed phenotypes related to cell polarity. SCO3607 mutants displayed shorter tip to branch and cross-wall to cross-wall distances, while SCO3608 mutants displayeda milder phenotype. A double knockout mutant displayed shorter intra cross-wall distances and enlarged spores. Bacterial two hybrid experiments were also performed, revealing SCO3607-SCO3607 interactions, though N-terminal fusions of the cya-domains to SCO3607 abolished the interaction, suggesting the N-terminus is essential for the interaction.Flotillin is a protein intrinsic to cell viability in humans, where it plays a role in cell morphology and structure. In Bacillus subtilis, it is involved in sporulation. NfeD always accompanies flotillins in prokaryotes, normally as an adjacent gene, though it is not present in eukaryotes. SCO3607 and SCO3608, encoding flotillin and NfeD, respectively, are present in Streptomyces coelicolor. No previous studies have examined the role of these two proteins in S. coelicolor. Preliminary bioinformatics revealed NfeD-encoding genes in actinobacteria, which was tentatively suggested as a new group of NfeD proteins; NfeD1b-5. Tn5062 transposon insertions in SCO3607 and deletions of both genes, separately and together, displayed no macroscopic phenotype; while fluorescence microscopy revealed phenotypes related to cell polarity. SCO3607 mutants displayed shorter tip to branch and cross-wall to cross-wall distances, while SCO3608 mutants displayeda milder phenotype. A double knockout mutant displayed shorter intra cross-wall distances and enlarged spores. Bacterial two hybrid experiments were also performed, revealing SCO3607-SCO3607 interactions, though N-terminal fusions of the cya-domains to SCO3607 abolished the interaction, suggesting the N-terminus is essential for the interaction
Control of cytokine production from human monocytic cells by prostaglandin 15-Deoxy-Δ-12,14-prostaglandin J2
No full textProstaglandins have several roles, but their main function is within the inflammatory process. As part of the immune response, immune cells are stimulated by lipopolysaccharide to produce pro- and anti-inflammatory cytokines including tumour necrosis factor-alpha, interleukin-1beta and interleukin-10. These cytokines can go on to stimulate the production of prostaglandins such as prostaglandin E2, prostaglandin D2 and 15-deoxy-Δ-12,14-prostaglandin J2. 15-deoxy-Δ-12,14-prostaglandin J2, is a metabolite of prostaglandin D2.;Prostaglandins have both pro- and anti-inflammatory roles. Not much is known about the pro- and anti-inflammatory effects of 15-deoxy-Δ-12,14-prostaglandin J2. As prostaglandins like prostaglandin E2, have inhibitory effects on pro-inflammatory cytokines it is an intriguing possibility that 15-deoxy-Δ-12,14-prostaglandin J2 may also share these qualities. It is also not known what cell receptor mediates these responses or what intracellular pathway is activated.;Thus, our aim was to discover what effects that 15-deoxy-Δ-12,14 -prostaglandin J2 had on the levels of pro- and anti-inflammatory cytokines, tumour necrosis factor-alpha, interleukin-1beta and interleukin-10. As well as to understand what receptor, either the prostaglandin D2 receptors DP1 or DP2, that 15-deoxy-Δ-12,14-prostaglandin J2 binds to and if cyclic adenosine monophosphate is involved in the signalling pathway.;This was achieved by stimulating the human monocytic cell line, THP-1 cells, with lipopolysaccharide and incubated for 22 hours with prostaglandins; 15-deoxy-Δ-12,14-prostaglandin J2, prostaglandin D2 and prostaglandin E2 which were used as comparisons. DP1 and DP2 antagonists BW868C and CAY10471 respectively and the cyclic adenosine monophosphate inhibitor SQ22536. The supernatants which contained the cytokines were measured by enzyme-linked immunosorbent assay. After the incubations, the cells were removed, and cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay after stimulation with lipopolysaccharide in the presence or absence of prostaglandin E2.;15-deoxy-Δ-12,14-prostaglandin J2 downregulated the levels of tumour necrosis factor-alpha by 81% and interleukin-1beta by 33% in a concentration dependent manner but had no effect on the levels of interleukin-10. As the concentration of prostaglandin E2 increased it downregulated the levels of tumour necrosis factor-alpha, interleukin-1beta and interleukin-10 by 100%, 69% and 82.6% respectively.;Surprisingly, neither of the DP antagonists had any effect on the activity of 15-deoxy-Δ-12,14-prostaglandin J2. CAY10471 (DP2), inhibited prostaglandin D2 from decreasing the level of tumour necrosis factor-alpha, but BW868C (DP1) did not have any effect. When using the cyclic adenosine monophosphate inhibitor, SQ22536, it had no effect on the levels of tumour necrosis factor-alpha, with either 15-deoxy-Δ-12,14-prostaglandin J2 or prostaglandin D2. Lipopolysaccharide and prostaglandin E2 had no effect on THP-1 cell viability confirmed by no change in the converted formazan dye.;This data indicates that 15-deoxy-Δ-12,14-prostaglandin J2 has inhibitory effects on pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin -1beta but has no effect on the anti-inflammatory cytokine interleukin-10 in human monocytic cells. The data strongly suggests that as the DP antagonists BW868C and CAY10471 do not affect the function of 15-deoxy-Δ-12,14-prostaglandin J2 then neither the DP1 or DP2 receptors are involved in the anti-inflammatory effects of 15-deoxy-Δ-12,14-prostaglandin J2.;Also, as the cyclic adenosine monophosphate inhibitor SQ22536 had no effect either on the function of 15-deoxy-Δ-12,14-prostaglandin J2, this rules out that the cyclic adenosine monophosphate pathway is involved. This is inclusive of any other receptors that follow this pathway. Further work can be carried out to understand what receptor and pathway are stimulated. As 15-deoxy-Δ-12,14-prostaglandin J2 has shown to be suppressive of tumour necrosis factor-alpha and interleukin -1beta, and as it does not alter the levels of the anti-inflammatory cytokine interleukin-10, it is propitious that it may be used successfully to modulate the inflammatory process and be developed into a therapy for inflammatory conditions.Prostaglandins have several roles, but their main function is within the inflammatory process. As part of the immune response, immune cells are stimulated by lipopolysaccharide to produce pro- and anti-inflammatory cytokines including tumour necrosis factor-alpha, interleukin-1beta and interleukin-10. These cytokines can go on to stimulate the production of prostaglandins such as prostaglandin E2, prostaglandin D2 and 15-deoxy-Δ-12,14-prostaglandin J2. 15-deoxy-Δ-12,14-prostaglandin J2, is a metabolite of prostaglandin D2.;Prostaglandins have both pro- and anti-inflammatory roles. Not much is known about the pro- and anti-inflammatory effects of 15-deoxy-Δ-12,14-prostaglandin J2. As prostaglandins like prostaglandin E2, have inhibitory effects on pro-inflammatory cytokines it is an intriguing possibility that 15-deoxy-Δ-12,14-prostaglandin J2 may also share these qualities. It is also not known what cell receptor mediates these responses or what intracellular pathway is activated.;Thus, our aim was to discover what effects that 15-deoxy-Δ-12,14 -prostaglandin J2 had on the levels of pro- and anti-inflammatory cytokines, tumour necrosis factor-alpha, interleukin-1beta and interleukin-10. As well as to understand what receptor, either the prostaglandin D2 receptors DP1 or DP2, that 15-deoxy-Δ-12,14-prostaglandin J2 binds to and if cyclic adenosine monophosphate is involved in the signalling pathway.;This was achieved by stimulating the human monocytic cell line, THP-1 cells, with lipopolysaccharide and incubated for 22 hours with prostaglandins; 15-deoxy-Δ-12,14-prostaglandin J2, prostaglandin D2 and prostaglandin E2 which were used as comparisons. DP1 and DP2 antagonists BW868C and CAY10471 respectively and the cyclic adenosine monophosphate inhibitor SQ22536. The supernatants which contained the cytokines were measured by enzyme-linked immunosorbent assay. After the incubations, the cells were removed, and cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay after stimulation with lipopolysaccharide in the presence or absence of prostaglandin E2.;15-deoxy-Δ-12,14-prostaglandin J2 downregulated the levels of tumour necrosis factor-alpha by 81% and interleukin-1beta by 33% in a concentration dependent manner but had no effect on the levels of interleukin-10. As the concentration of prostaglandin E2 increased it downregulated the levels of tumour necrosis factor-alpha, interleukin-1beta and interleukin-10 by 100%, 69% and 82.6% respectively.;Surprisingly, neither of the DP antagonists had any effect on the activity of 15-deoxy-Δ-12,14-prostaglandin J2. CAY10471 (DP2), inhibited prostaglandin D2 from decreasing the level of tumour necrosis factor-alpha, but BW868C (DP1) did not have any effect. When using the cyclic adenosine monophosphate inhibitor, SQ22536, it had no effect on the levels of tumour necrosis factor-alpha, with either 15-deoxy-Δ-12,14-prostaglandin J2 or prostaglandin D2. Lipopolysaccharide and prostaglandin E2 had no effect on THP-1 cell viability confirmed by no change in the converted formazan dye.;This data indicates that 15-deoxy-Δ-12,14-prostaglandin J2 has inhibitory effects on pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin -1beta but has no effect on the anti-inflammatory cytokine interleukin-10 in human monocytic cells. The data strongly suggests that as the DP antagonists BW868C and CAY10471 do not affect the function of 15-deoxy-Δ-12,14-prostaglandin J2 then neither the DP1 or DP2 receptors are involved in the anti-inflammatory effects of 15-deoxy-Δ-12,14-prostaglandin J2.;Also, as the cyclic adenosine monophosphate inhibitor SQ22536 had no effect either on the function of 15-deoxy-Δ-12,14-prostaglandin J2, this rules out that the cyclic adenosine monophosphate pathway is involved. This is inclusive of any other receptors that follow this pathway. Further work can be carried out to understand what receptor and pathway are stimulated. As 15-deoxy-Δ-12,14-prostaglandin J2 has shown to be suppressive of tumour necrosis factor-alpha and interleukin -1beta, and as it does not alter the levels of the anti-inflammatory cytokine interleukin-10, it is propitious that it may be used successfully to modulate the inflammatory process and be developed into a therapy for inflammatory conditions
Explicating natural-resource-based view capabilities : a dynamic framework for innovative sustainable supply chain management in UK agri-food
Get PDFThe natural-resource-based view resonates with significance some twenty years after its conception. The theory features prominently in modern literature where it enjoys links with enhanced competitiveness, and responds to the need for innovative sustainable operations in modern business. However, literature argues that a lack of practical guidance has resulted in a theory-practice gap, which to some extent is typical of resource-based theory research. This study resolves this via definition of dynamic natural-resource-based view capabilities. Exploration of links between natural-resource-based view, sustainable supply chain management and innovation literature identifies implications for capabilities. Categorizing these capabilities according to the four natural-resource-based view resources of pollution prevention, product stewardship, clean technologies and base of the pyramid, dynamic capabilities activities of sensing, seizing and transforming and an internal versus external focus facilitates the creation of a conceptual framework of dynamic capabilities. Employing the UK agri-food sector as a contextual setting, an empirical study comprising of two phases is undertaken. Phase 1 involves seven in-depth interviews with agri-food experts to empirically validate links between the natural-resource-based view, sustainable supply chain management and innovation. Phase 2 involves twenty semi-structured interviews and six observations with UK agri-food companies to empirically define and explain dynamic natural-resource-based view capabilities. In its completion, this study demonstrates the existence of pollution prevention, product stewardship and clean technologies in UK agri-food, confirms their synergies with sustainable supply chain management and innovation and explicates and elucidates their dynamic capabilities. Whilst base of the pyramid did not feature in the empirical study, the resource is not falsified and further investigation is recommended. This study concluded with five contributions: empirical definition of dynamic natural-resource-based view capabilities; dynamic capability and internal-external categorization; the four-resource perspective of the natural-resource-based view; linking the natural-resource-based view, sustainable supply chain management and innovation; and conceptualisation of local philanthropy and proposal of the natural-resource-based view cycle.The natural-resource-based view resonates with significance some twenty years after its conception. The theory features prominently in modern literature where it enjoys links with enhanced competitiveness, and responds to the need for innovative sustainable operations in modern business. However, literature argues that a lack of practical guidance has resulted in a theory-practice gap, which to some extent is typical of resource-based theory research. This study resolves this via definition of dynamic natural-resource-based view capabilities. Exploration of links between natural-resource-based view, sustainable supply chain management and innovation literature identifies implications for capabilities. Categorizing these capabilities according to the four natural-resource-based view resources of pollution prevention, product stewardship, clean technologies and base of the pyramid, dynamic capabilities activities of sensing, seizing and transforming and an internal versus external focus facilitates the creation of a conceptual framework of dynamic capabilities. Employing the UK agri-food sector as a contextual setting, an empirical study comprising of two phases is undertaken. Phase 1 involves seven in-depth interviews with agri-food experts to empirically validate links between the natural-resource-based view, sustainable supply chain management and innovation. Phase 2 involves twenty semi-structured interviews and six observations with UK agri-food companies to empirically define and explain dynamic natural-resource-based view capabilities. In its completion, this study demonstrates the existence of pollution prevention, product stewardship and clean technologies in UK agri-food, confirms their synergies with sustainable supply chain management and innovation and explicates and elucidates their dynamic capabilities. Whilst base of the pyramid did not feature in the empirical study, the resource is not falsified and further investigation is recommended. This study concluded with five contributions: empirical definition of dynamic natural-resource-based view capabilities; dynamic capability and internal-external categorization; the four-resource perspective of the natural-resource-based view; linking the natural-resource-based view, sustainable supply chain management and innovation; and conceptualisation of local philanthropy and proposal of the natural-resource-based view cycle
Development of a ship weather routing system towards energy efficient shipping
Get PDFThe energy consumption and the Greenhouse Gas (GHG) emissions from shipping field are vast and very important which cannot be ignored for both economic and environmental reasons. Improving energy efficiency of the ship through the technical and operational means has become a pressing issue faced by the shipping industry. In this context, ship weather routing technique, as one of the effective energy efficiency improvement methods has attracted more and more interests from technical staff. A ship weather routing system towards energy efficiency is developed in this study. This system consists of six modules which are ship performance calculation module, grids system design module, weather data module, ship safety module, weather routing module and post-processing module. These modules basically cover the essential elements of a ship weather routing system. Among them, the calculation methods of various ship performances are utilised in ship performance module; The design principle of grids system and an intelligent land avoidance function are developed in grids system design module; The acquisition and decoding of weather data files are introduced in weather data module; A ship safety guidance is selected and followed in ship safety module; A combination of global and local optimization algorithm is adopted in weather routing module; A backward iteration algorithm is developed and the visualization of result routes is implemented in the post-processing module. The role of each module and the data transfer relationship between these modules are described in detail. Next, seven effective methods are introduced to upgrade the system. These methods which can greatly improve the working efficiency of the system are respectively: create ship performance database, redefine ship travel principle and adjust the grids system scale, merge ship safety module to ship performance prediction module, delete results in every waypoint which cannot meet the time schedule, set the speed control parameter, delete results in every waypoint which cannot meet expected fuel consumption and optimise programming codes. With these methods introduced, the structure and operation logic of the system also becomes more effective. A series of representative case studies are carried out to verify the proposed methodology and the tool. Finally, the approach is implemented on a container ship in both purely motorised and Flettner rotor assisted propulsion conditions, to see the energy efficiency gained through Flettner rotor technology. Case studies in various shipping routes, departure times and ship speeds are carried out based on this system and finally a framework for assessing the performance of wind assist technology is proposed. The proposed weather routing system has significant practical application and can provide an effective reference for related research in the shipping industry.The energy consumption and the Greenhouse Gas (GHG) emissions from shipping field are vast and very important which cannot be ignored for both economic and environmental reasons. Improving energy efficiency of the ship through the technical and operational means has become a pressing issue faced by the shipping industry. In this context, ship weather routing technique, as one of the effective energy efficiency improvement methods has attracted more and more interests from technical staff. A ship weather routing system towards energy efficiency is developed in this study. This system consists of six modules which are ship performance calculation module, grids system design module, weather data module, ship safety module, weather routing module and post-processing module. These modules basically cover the essential elements of a ship weather routing system. Among them, the calculation methods of various ship performances are utilised in ship performance module; The design principle of grids system and an intelligent land avoidance function are developed in grids system design module; The acquisition and decoding of weather data files are introduced in weather data module; A ship safety guidance is selected and followed in ship safety module; A combination of global and local optimization algorithm is adopted in weather routing module; A backward iteration algorithm is developed and the visualization of result routes is implemented in the post-processing module. The role of each module and the data transfer relationship between these modules are described in detail. Next, seven effective methods are introduced to upgrade the system. These methods which can greatly improve the working efficiency of the system are respectively: create ship performance database, redefine ship travel principle and adjust the grids system scale, merge ship safety module to ship performance prediction module, delete results in every waypoint which cannot meet the time schedule, set the speed control parameter, delete results in every waypoint which cannot meet expected fuel consumption and optimise programming codes. With these methods introduced, the structure and operation logic of the system also becomes more effective. A series of representative case studies are carried out to verify the proposed methodology and the tool. Finally, the approach is implemented on a container ship in both purely motorised and Flettner rotor assisted propulsion conditions, to see the energy efficiency gained through Flettner rotor technology. Case studies in various shipping routes, departure times and ship speeds are carried out based on this system and finally a framework for assessing the performance of wind assist technology is proposed. The proposed weather routing system has significant practical application and can provide an effective reference for related research in the shipping industry
A multilevel approach for approximating the inverse Hessian in four-dimensional variational data assimilation
No full textData assimilation methods are routinely employed in many scientific and technological fields. The inverse Hessian, and inverse square root Hessian, are of importance in various aspects of these procedures. The Hessian vector product is usually defined in the context of geophysical and engineering applications by the sequential solution of a tangent linear and adjoint problem. However, there are no readily available routines for computing the inverse Hessian, and inverse square root Hessian, vector products.;It is generally necessary, when solving high-dimensional data assimilation problems, to operate in a matrix-free environment. A suitable method for generating a compact representation of the inverse Hessian, and inverse square root Hessian, is required in such cases.;A multilevel eigenvalue decomposition algorithm for constructing a limited-memory approximation to the inverse (and inverse square root) of any given symmetric positive definite matrix with eigenvalues clustered around unity is presented in this thesis. This algorithm is applied to the Hessian in the framework of incremental four-dimensional variational data assimilation (4D-Var), with the standard control variable transform implemented, in order to construct an approximation to the inverse Hessian. A novel decomposition of the Hessian as the sum of a set of local Hessians is introduced in this setting.;Two practical variants of the multilevel eigenvalue decomposition algorithm for constructing a limited-memory approximation to the inverse (and inverse square root) of this Hessian are also presented. The accuracy of approximations to the inverse Hessian generated by applying the three algorithms proposed is investigated. The application considered in this thesis focuses on preconditioning the system of linear equations in the inner step of a Gauss-Newton procedure in incremental 4D-Var with an approximation to the inverse Hessian generated using the three algorithms proposed.Data assimilation methods are routinely employed in many scientific and technological fields. The inverse Hessian, and inverse square root Hessian, are of importance in various aspects of these procedures. The Hessian vector product is usually defined in the context of geophysical and engineering applications by the sequential solution of a tangent linear and adjoint problem. However, there are no readily available routines for computing the inverse Hessian, and inverse square root Hessian, vector products.;It is generally necessary, when solving high-dimensional data assimilation problems, to operate in a matrix-free environment. A suitable method for generating a compact representation of the inverse Hessian, and inverse square root Hessian, is required in such cases.;A multilevel eigenvalue decomposition algorithm for constructing a limited-memory approximation to the inverse (and inverse square root) of any given symmetric positive definite matrix with eigenvalues clustered around unity is presented in this thesis. This algorithm is applied to the Hessian in the framework of incremental four-dimensional variational data assimilation (4D-Var), with the standard control variable transform implemented, in order to construct an approximation to the inverse Hessian. A novel decomposition of the Hessian as the sum of a set of local Hessians is introduced in this setting.;Two practical variants of the multilevel eigenvalue decomposition algorithm for constructing a limited-memory approximation to the inverse (and inverse square root) of this Hessian are also presented. The accuracy of approximations to the inverse Hessian generated by applying the three algorithms proposed is investigated. The application considered in this thesis focuses on preconditioning the system of linear equations in the inner step of a Gauss-Newton procedure in incremental 4D-Var with an approximation to the inverse Hessian generated using the three algorithms proposed
Life extension for wind turbine structures and foundations
No full textThis thesis explores economic and technical lifetime extension considerations of wind turbine generators. The research unveils that onshore support structures will likely have suffcient fatigue reserves left, beyond the initial design life, to support an extended operation. However, suitability is strongly dependent on the difference between the designand encountered load profile, asset maintenance activities, operational knowledge, and the policy environment. A lifetime extension decision model is developed and input parameters are scrutinised revealing the feasibility to replace the entire drive train of a wind turbine and yet, be profitable when exposed to a non-subsidised environment. The designed decision modelis further applied based on operational data of two wind farms in the UK to derive anasset specific lifetime extension strategy. In addition, a methodology and field trial is presented to monitor operational foundationstresses based on optical sensor networks aimed at reducing conservative designassumptions, enabling the reuse of foundations for greater rated turbines as well as tosupport the lifetime extension decision-making. Furthermore, this thesis provides guidance on how to evaluate and obtain the strategic lifetime extension decision-making at an early stage (year 10-14) by means of a fatigue analysis of tower strain measurements. Fatigue tower findings in conjunction with operational data of an asset are subsequently assessed to define the turbine's/wind farm'sunique economic lifetime extension boundaries.This thesis explores economic and technical lifetime extension considerations of wind turbine generators. The research unveils that onshore support structures will likely have suffcient fatigue reserves left, beyond the initial design life, to support an extended operation. However, suitability is strongly dependent on the difference between the designand encountered load profile, asset maintenance activities, operational knowledge, and the policy environment. A lifetime extension decision model is developed and input parameters are scrutinised revealing the feasibility to replace the entire drive train of a wind turbine and yet, be profitable when exposed to a non-subsidised environment. The designed decision modelis further applied based on operational data of two wind farms in the UK to derive anasset specific lifetime extension strategy. In addition, a methodology and field trial is presented to monitor operational foundationstresses based on optical sensor networks aimed at reducing conservative designassumptions, enabling the reuse of foundations for greater rated turbines as well as tosupport the lifetime extension decision-making. Furthermore, this thesis provides guidance on how to evaluate and obtain the strategic lifetime extension decision-making at an early stage (year 10-14) by means of a fatigue analysis of tower strain measurements. Fatigue tower findings in conjunction with operational data of an asset are subsequently assessed to define the turbine's/wind farm'sunique economic lifetime extension boundaries
Three applications using panel data
Get PDFThis Thesis comprises three applied studies related to labour economics that utilise different Panel Datasets, assembled by the Author from public sources. The common Aim in all three studies is to determine whether the conclusions drawn from regression-based modelling would have been significantly different had standard estimators, as opposed to Panel-based ones, been applied. The stance taken, is that of the policymaker wishing to either evaluate the effectiveness of an established policy, or to quantify an established trend in Society, with a view to designing and implementing Policy in the future. In so doing, they wish to adopt an evidence-based approach to this exercise, using historic data. While the three studies are related to labour economics, the have been deliberately chosen to differ from each other, both in the scenario being studied, the variables involved, and the estimators applied. The first study is related to gendered policing and arrests made for gender-based violence in England and Wales; the second, estimates the returns to qualifications in the UK Labour market, evaluated at the quantiles of males' and females' wage-rate distributions and the third, the technical efficiency of a panel of US Airlines. The overall conclusions from the studies are that Panel-based estimators can lead to significantly different conclusions being drawn from regression-based evaluations but this need not always be the case. Nevertheless, where data are available as a Panel, or can be rendered as such, the Policy-maker should apply both Pooled- and Panel based estimators before drawing their conclusions from the exercise.This Thesis comprises three applied studies related to labour economics that utilise different Panel Datasets, assembled by the Author from public sources. The common Aim in all three studies is to determine whether the conclusions drawn from regression-based modelling would have been significantly different had standard estimators, as opposed to Panel-based ones, been applied. The stance taken, is that of the policymaker wishing to either evaluate the effectiveness of an established policy, or to quantify an established trend in Society, with a view to designing and implementing Policy in the future. In so doing, they wish to adopt an evidence-based approach to this exercise, using historic data. While the three studies are related to labour economics, the have been deliberately chosen to differ from each other, both in the scenario being studied, the variables involved, and the estimators applied. The first study is related to gendered policing and arrests made for gender-based violence in England and Wales; the second, estimates the returns to qualifications in the UK Labour market, evaluated at the quantiles of males' and females' wage-rate distributions and the third, the technical efficiency of a panel of US Airlines. The overall conclusions from the studies are that Panel-based estimators can lead to significantly different conclusions being drawn from regression-based evaluations but this need not always be the case. Nevertheless, where data are available as a Panel, or can be rendered as such, the Policy-maker should apply both Pooled- and Panel based estimators before drawing their conclusions from the exercise
Reading and writing confessional poetry
No full textThis dissertation is comprised of a creative component and a critical component. The creative component is presented in the form of a sequence of twenty-seven confessional poems. This sequence of poems is composed under the formative influence of the works of various confessional poets, which include but are not limited to, Robert Lowell, Anne Sexton and Sylvia Plath.;The critical component is presented in the form of an examination of the genre and original school of confessional poetry. This paper seeks to investigate and confirm the various traits of the genre of confessional poetry through an examination of both the works of Lowell, Sexton and Plath, as well as relevant literary criticism. This literary criticism includes, but is not limited to, the influential study of the original school of confessional poets, written by the critic, Robert Phillips.;In his study, Phillips develops a criteria which can be applied to confessional poetry. This paper also seeks highlight an omission in Phillips' criteria by proving the existence of the shared theme of physical disassociation between the subject or speaker of the poem and the surrounding environment through the genre of confessional poetry by referral to the works of the aforementioned poets as well as referral back to the creative element of this dissertation.This dissertation is comprised of a creative component and a critical component. The creative component is presented in the form of a sequence of twenty-seven confessional poems. This sequence of poems is composed under the formative influence of the works of various confessional poets, which include but are not limited to, Robert Lowell, Anne Sexton and Sylvia Plath.;The critical component is presented in the form of an examination of the genre and original school of confessional poetry. This paper seeks to investigate and confirm the various traits of the genre of confessional poetry through an examination of both the works of Lowell, Sexton and Plath, as well as relevant literary criticism. This literary criticism includes, but is not limited to, the influential study of the original school of confessional poets, written by the critic, Robert Phillips.;In his study, Phillips develops a criteria which can be applied to confessional poetry. This paper also seeks highlight an omission in Phillips' criteria by proving the existence of the shared theme of physical disassociation between the subject or speaker of the poem and the surrounding environment through the genre of confessional poetry by referral to the works of the aforementioned poets as well as referral back to the creative element of this dissertation
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