7103 research outputs found
Sort by
Characterising mismatch negativity biomarker signatures in preclinical models relevant to schizophrenia
Get PDFMismatch negativity (MMN) has been hailed as a "break-through biomarker in predicting psychosis onset" (Naatanen 2015). This is because deficits have been found in clinical populations diagnosed with psychotic syndromes such as schizophrenia. MMN is an auditory evoked potential (AEP) difference waveform produced by subtracting standard from deviant stimuli AEPs elicited by an oddball paradigm; purportedly arising from any discriminable change in auditory stimulation.;Despite nearly four decades of basic research into MMN the underlying mechanisms are not fully understood. Although popular theories suggest that it reflects a sensory-memory trace disruption and/or differential adaptation of responses to standard and deviant/oddball stimuli, there remains considerable debate over the neural mechanism and its interpretation.;Nevertheless, associations made between N-methyl-d-aspartate (NMDA) receptors in schizophrenia and findings showing that NMDA receptor antagonists (e.g. ketamine) induce MMN deficits in healthy volunteers suggests abnormal MMNs share common traits and support its use as a biomarker from an electrophysiological perspective. However, this is still speculative and there is great impetus on developing reliable preclinical models of MMN in order to examine the underpinning neurophysiology and therefore its reliance on NMDA receptors as a test of pathology in schizophrenia.;A question this thesis aims to address is whether a mismatch response (MMR) exists in rodents which is analogous to the human MMN, and whether its modification by NMDA receptor antagonists or as a result of schizophrenia-related genetic modification sheds light on its utility as a biomarker in disease models of schizophrenia.;This thesis describes three experiments performed using mitogen activated protein kinase kinase 7 heterozygous (Map2k7+/−) mice and their wild-type littermates, incorporating NMDA receptor antagonism with ketamine (10 mg/kg i.p.). The MAP2K7 gene is associated with schizophrenia and codes for a post-synaptic intracellular signalling enzyme which is activated following glutamatergic excitation, for instance via NMDA receptors.;The MMR to stimuli duration, frequency and intensity changes in oddball paradigms are characterised in urethane-anaesthetised and conscious animals, followed by an examination of laminar auditory cortex activity in response to these physical changes. Data recorded throughout this series of experiments includes cortical electroencephalography (EEG), video footage, and intra-cortical spiking information. These data were then analysed using various time, frequency and time-frequency domain techniques; although mainly focussing on the event-related potential (ERP) approach.;Recordings demonstrated substantial differences in the AEP waveform evoked from urethane-anaesthetised and conscious animals, with the latter displaying considerably more dynamic responses, although onset and offset of auditory stimuli induced comparable waveform features in both states. Effects of varying physical properties of stimuli in oddball and control paradigms have been identified as key determinants of the AEP and correspondingly the MMR difference waveform amplitudes.;The finding that NMDA receptor disruption in conscious animals by ketamine acutely diminishes a specific AEP feature (≈20-50 ms post stimulus onset) which may impact the resulting MMR tentatively links this study in mice with findings from humans noted above. Ketamine was also found to enhance animal movement and increase EEG spectral power in the 50-70 Hz (gamma-band) frequency range, observed for approximately 10 minutes following drug administration.;Both anaesthetised and conscious cohorts of Map2k7+/− mice displayed a significantly enhanced onset response (≈0-20 ms) in the AEP. Interestingly, ketamine did not appear to have a differential effect on Map2k7+/− mice compared with the wild-type group, suggesting that NMDA receptor-mediated neurotransmission is unimpaired in this genetic model relevant to schizophrenia.;Overall, the findings suggest that the MMR in mice is fundamentally influenced by the physical properties of stimuli employed; ketamine causes an acute, specific alteration to the AEP in conscious mice in addition to other electrophysiological and behavioural changes; and Map2k7 gene disruption causes a specific and replicable change in AEP amplitude.;Overall this study indicates that mouse models are useful for exploring the effects of different pharmacological and genetic manipulations on the auditory evoked response; however, MMN data in clinical cohorts still needs to be interpreted with care. In order to address whether the rodent MMR is analogous to human MMN, it would be necessary to probe how influencing factors revealed in the rodent studies impact on the human response. Whilst the rodent MMR and human MMN show some degree of translation, their potential as schizophrenia biomarkers requires further characterisation and validation.Mismatch negativity (MMN) has been hailed as a "break-through biomarker in predicting psychosis onset" (Naatanen 2015). This is because deficits have been found in clinical populations diagnosed with psychotic syndromes such as schizophrenia. MMN is an auditory evoked potential (AEP) difference waveform produced by subtracting standard from deviant stimuli AEPs elicited by an oddball paradigm; purportedly arising from any discriminable change in auditory stimulation.;Despite nearly four decades of basic research into MMN the underlying mechanisms are not fully understood. Although popular theories suggest that it reflects a sensory-memory trace disruption and/or differential adaptation of responses to standard and deviant/oddball stimuli, there remains considerable debate over the neural mechanism and its interpretation.;Nevertheless, associations made between N-methyl-d-aspartate (NMDA) receptors in schizophrenia and findings showing that NMDA receptor antagonists (e.g. ketamine) induce MMN deficits in healthy volunteers suggests abnormal MMNs share common traits and support its use as a biomarker from an electrophysiological perspective. However, this is still speculative and there is great impetus on developing reliable preclinical models of MMN in order to examine the underpinning neurophysiology and therefore its reliance on NMDA receptors as a test of pathology in schizophrenia.;A question this thesis aims to address is whether a mismatch response (MMR) exists in rodents which is analogous to the human MMN, and whether its modification by NMDA receptor antagonists or as a result of schizophrenia-related genetic modification sheds light on its utility as a biomarker in disease models of schizophrenia.;This thesis describes three experiments performed using mitogen activated protein kinase kinase 7 heterozygous (Map2k7+/−) mice and their wild-type littermates, incorporating NMDA receptor antagonism with ketamine (10 mg/kg i.p.). The MAP2K7 gene is associated with schizophrenia and codes for a post-synaptic intracellular signalling enzyme which is activated following glutamatergic excitation, for instance via NMDA receptors.;The MMR to stimuli duration, frequency and intensity changes in oddball paradigms are characterised in urethane-anaesthetised and conscious animals, followed by an examination of laminar auditory cortex activity in response to these physical changes. Data recorded throughout this series of experiments includes cortical electroencephalography (EEG), video footage, and intra-cortical spiking information. These data were then analysed using various time, frequency and time-frequency domain techniques; although mainly focussing on the event-related potential (ERP) approach.;Recordings demonstrated substantial differences in the AEP waveform evoked from urethane-anaesthetised and conscious animals, with the latter displaying considerably more dynamic responses, although onset and offset of auditory stimuli induced comparable waveform features in both states. Effects of varying physical properties of stimuli in oddball and control paradigms have been identified as key determinants of the AEP and correspondingly the MMR difference waveform amplitudes.;The finding that NMDA receptor disruption in conscious animals by ketamine acutely diminishes a specific AEP feature (≈20-50 ms post stimulus onset) which may impact the resulting MMR tentatively links this study in mice with findings from humans noted above. Ketamine was also found to enhance animal movement and increase EEG spectral power in the 50-70 Hz (gamma-band) frequency range, observed for approximately 10 minutes following drug administration.;Both anaesthetised and conscious cohorts of Map2k7+/− mice displayed a significantly enhanced onset response (≈0-20 ms) in the AEP. Interestingly, ketamine did not appear to have a differential effect on Map2k7+/− mice compared with the wild-type group, suggesting that NMDA receptor-mediated neurotransmission is unimpaired in this genetic model relevant to schizophrenia.;Overall, the findings suggest that the MMR in mice is fundamentally influenced by the physical properties of stimuli employed; ketamine causes an acute, specific alteration to the AEP in conscious mice in addition to other electrophysiological and behavioural changes; and Map2k7 gene disruption causes a specific and replicable change in AEP amplitude.;Overall this study indicates that mouse models are useful for exploring the effects of different pharmacological and genetic manipulations on the auditory evoked response; however, MMN data in clinical cohorts still needs to be interpreted with care. In order to address whether the rodent MMR is analogous to human MMN, it would be necessary to probe how influencing factors revealed in the rodent studies impact on the human response. Whilst the rodent MMR and human MMN show some degree of translation, their potential as schizophrenia biomarkers requires further characterisation and validation
Methodologies for the analysis of value from delay-tolerant inter-satellite networking
Get PDFIn a world that is becoming increasingly connected, both in the sense of people and devices, it is of no surprise that users of the data enabled by satellites are exploring the potential brought about from a more connected Earth orbit environment. Lower data latency, higher revisit rates and higher volumes of information are the order of the day, and inter-connectivity is one of the ways in which this could be achieved. Within this dissertation, three main topics are investigated and built upon. First, the process of routing data through intermittently connected delay-tolerant networks is examined and a new routing protocol introduced, called Spae. The consideration of downstream resource limitations forms the heart of this novel approach which is shown to provide improvements in data routing that closely match that of a theoretically optimal scheme. Next, the value of inter-satellite networking is derived in such a way that removes the difficult task of costing the enabling inter-satellite link technology. Instead, value is defined as the price one should be willing to pay for the technology while retaining a mission value greater than its non-networking counterpart. This is achieved through the use of multi-attribute utility theory, trade-space analysis and system modelling, and demonstrated in two case studies. Finally, the effects of uncertainty in the form of sub-system failure are considered. Inter-satellite networking is shown to increase a system's resilience to failure through introduction of additional, partially failed states, made possible by data relay. The lifetime value of a system is then captured using a semi-analytical approach exploiting Markov chains, validated with a numerical Monte Carlo simulation approach. It is evident that while inter-satellite networking may offer more value in general, it does not necessarily result in a decrease in the loss of utility over the lifetime.In a world that is becoming increasingly connected, both in the sense of people and devices, it is of no surprise that users of the data enabled by satellites are exploring the potential brought about from a more connected Earth orbit environment. Lower data latency, higher revisit rates and higher volumes of information are the order of the day, and inter-connectivity is one of the ways in which this could be achieved. Within this dissertation, three main topics are investigated and built upon. First, the process of routing data through intermittently connected delay-tolerant networks is examined and a new routing protocol introduced, called Spae. The consideration of downstream resource limitations forms the heart of this novel approach which is shown to provide improvements in data routing that closely match that of a theoretically optimal scheme. Next, the value of inter-satellite networking is derived in such a way that removes the difficult task of costing the enabling inter-satellite link technology. Instead, value is defined as the price one should be willing to pay for the technology while retaining a mission value greater than its non-networking counterpart. This is achieved through the use of multi-attribute utility theory, trade-space analysis and system modelling, and demonstrated in two case studies. Finally, the effects of uncertainty in the form of sub-system failure are considered. Inter-satellite networking is shown to increase a system's resilience to failure through introduction of additional, partially failed states, made possible by data relay. The lifetime value of a system is then captured using a semi-analytical approach exploiting Markov chains, validated with a numerical Monte Carlo simulation approach. It is evident that while inter-satellite networking may offer more value in general, it does not necessarily result in a decrease in the loss of utility over the lifetime
'Not our jobs to sell' - workforce mobilization, deindustrialisation and resistance to plant closure : Scottish female factory occupations, 1981-1982
Get PDFThis thesis was previously held under moratorium between October 2017 and October 2019.This thesis seeks to expand our understanding of widespread workplace closures and socio-economic change that occurred in Scotland in the late twentieth-century by incorporating the narratives of female workers that took resistive action to the mobility of capital. Its focus is on the early 1980s, a period of accelerated industrial contraction that saw the decline of the nation’s traditional heavy industries, and those sectors in which women dominated, such as clothing and light electronics. Three instances of previously under-researched resistance to proposed factory closure are extensively analysed in an attempt to comprehend how the workers involved perceived their work, the impacts of closure on their communities, and how their actions developed.It is argued that female manufacturing workers, while consistently occupying the lowest paid and lowest skilled jobs, extracted substantial value from their experiences of work based on the solidarities forged at the point of production. Scottish labour history has continued to neglect the narratives of the women that worked at these sites, leading to a significant degree of speculation over their perceptions of industrial work. This thesis addresses this omission by placing the testimonies and reflections of the workers at the centre of its analysis.In considering the mobilization of the workers through occupying plants to resist closure, it is argued that a multitude of factors dictate whether workers form a collective and choose to take oppositional action. The bonds of solidarity created among workers based on their position in the labour process cannot be separated from the collective actions that develop. Furthermore, it is asserted that these factory occupations were highly influenced by socio-economic developments in each of the localities where they were based, creating additional complexity to assessing why, and how, these groups of workers acted collectively, contributing to general discussions on workforce collectivism through industrial action.This thesis seeks to expand our understanding of widespread workplace closures and socio-economic change that occurred in Scotland in the late twentieth-century by incorporating the narratives of female workers that took resistive action to the mobility of capital. Its focus is on the early 1980s, a period of accelerated industrial contraction that saw the decline of the nation’s traditional heavy industries, and those sectors in which women dominated, such as clothing and light electronics. Three instances of previously under-researched resistance to proposed factory closure are extensively analysed in an attempt to comprehend how the workers involved perceived their work, the impacts of closure on their communities, and how their actions developed.It is argued that female manufacturing workers, while consistently occupying the lowest paid and lowest skilled jobs, extracted substantial value from their experiences of work based on the solidarities forged at the point of production. Scottish labour history has continued to neglect the narratives of the women that worked at these sites, leading to a significant degree of speculation over their perceptions of industrial work. This thesis addresses this omission by placing the testimonies and reflections of the workers at the centre of its analysis.In considering the mobilization of the workers through occupying plants to resist closure, it is argued that a multitude of factors dictate whether workers form a collective and choose to take oppositional action. The bonds of solidarity created among workers based on their position in the labour process cannot be separated from the collective actions that develop. Furthermore, it is asserted that these factory occupations were highly influenced by socio-economic developments in each of the localities where they were based, creating additional complexity to assessing why, and how, these groups of workers acted collectively, contributing to general discussions on workforce collectivism through industrial action
The evolution of innovation policy in Styria : the impact of the regional innovation system concept
No full textThis study explores the concept of regional innovation systems (RIS) and its impact in practice. Taking a governance perspective at RIS, it describes how Styrian innovation policy has developed over time, how this has been shaped by the RIS concept and what challenges remain for innovation policy. Styrian policy-makers were amongst the early adopters of the RIS concept in the 1990s, explicitly referring to its terminology and assumptions. The region then went through a series of policy reforms, both in terms of strategies and innovation instruments, which allow observing how the region adjusted itself to new trends and ideas. The study shows that the RIS concept had a measurable impact on current Styrian innovation policy-making, but that the visibility of this impact changed over time. It also shows that the Styrian system of innovation policy governance is complex: many actors, many strategies and even more instruments. This complexity is partly a result of RIS-based innovation policy-making itself and brings a set of challenges discussed in the paper.This study explores the concept of regional innovation systems (RIS) and its impact in practice. Taking a governance perspective at RIS, it describes how Styrian innovation policy has developed over time, how this has been shaped by the RIS concept and what challenges remain for innovation policy. Styrian policy-makers were amongst the early adopters of the RIS concept in the 1990s, explicitly referring to its terminology and assumptions. The region then went through a series of policy reforms, both in terms of strategies and innovation instruments, which allow observing how the region adjusted itself to new trends and ideas. The study shows that the RIS concept had a measurable impact on current Styrian innovation policy-making, but that the visibility of this impact changed over time. It also shows that the Styrian system of innovation policy governance is complex: many actors, many strategies and even more instruments. This complexity is partly a result of RIS-based innovation policy-making itself and brings a set of challenges discussed in the paper
The use of terahertz spectroscopy for biomolecular analysis
Get PDFTerahertz radiation occupies part of the electromagnetic spectrum between the mid-infraredand microwave bands (approximately 0.1 - 20 THz). Within this range, spectroscopic analysis of biological molecules can detect low-frequency vibrational modes that arise from intermolecular as well as intramolecular interactions and can provide significant information regarding structure and function. For example, the spectra of small biomolecules is dominated by individual modes and hydrogen bonds that can produce a distinctive spectral 'fingerprint',whereas the spectra of macromolecules, such as protein and DNA, can reveal information regarding conformation and dynamics. However, terahertz spectroscopy has habitually been underutilised as an investigative tool in biochemistry due to lack of terahertz sources and the strong absorbance of terahertz radiation by liquid water. The aim of this study was to bridge the gap between terahertz spectroscopy and biomolecular analysis by utilising three techniques to investigate a range of biomolecules of varying complexity. The bulk of this work employed terahertz Optical Kerr Effect (OKE) Spectroscopy as a novel means to study biomolecules in solution - This Raman based technique has the advantage that it does not suffer the same water absorption as conventional terahertz spectroscopies. We analysed a variety of small biomolecules, such as amino acids and nucleotides, and identified a variety of terahertz modes that are influenced by structure and interactions with the solvent. Additionally, we have identified spectral features in proteins molecules that are indicative of conformation and also identified novel vibrational modes that mediate protein-ligand binding in solution. Analysis of DNA and its components has also lead us to identify a multitude of previously undetected modes, some of which are attributed to phonons in the double helix and also hydrogen bonded interactions. We also utilised two common methods of terahertz spectroscopy - Terahertz Time DomainSpectroscopy (THz-TDS) and Fourier Transform Infrared (FTIR) Spectroscopy - to create the first comprehensive database of small biomolecules in the terahertz range and also developed a novel membrane method for the simple and rapid analysis of biomolecules.Terahertz radiation occupies part of the electromagnetic spectrum between the mid-infraredand microwave bands (approximately 0.1 - 20 THz). Within this range, spectroscopic analysis of biological molecules can detect low-frequency vibrational modes that arise from intermolecular as well as intramolecular interactions and can provide significant information regarding structure and function. For example, the spectra of small biomolecules is dominated by individual modes and hydrogen bonds that can produce a distinctive spectral 'fingerprint',whereas the spectra of macromolecules, such as protein and DNA, can reveal information regarding conformation and dynamics. However, terahertz spectroscopy has habitually been underutilised as an investigative tool in biochemistry due to lack of terahertz sources and the strong absorbance of terahertz radiation by liquid water. The aim of this study was to bridge the gap between terahertz spectroscopy and biomolecular analysis by utilising three techniques to investigate a range of biomolecules of varying complexity. The bulk of this work employed terahertz Optical Kerr Effect (OKE) Spectroscopy as a novel means to study biomolecules in solution - This Raman based technique has the advantage that it does not suffer the same water absorption as conventional terahertz spectroscopies. We analysed a variety of small biomolecules, such as amino acids and nucleotides, and identified a variety of terahertz modes that are influenced by structure and interactions with the solvent. Additionally, we have identified spectral features in proteins molecules that are indicative of conformation and also identified novel vibrational modes that mediate protein-ligand binding in solution. Analysis of DNA and its components has also lead us to identify a multitude of previously undetected modes, some of which are attributed to phonons in the double helix and also hydrogen bonded interactions. We also utilised two common methods of terahertz spectroscopy - Terahertz Time DomainSpectroscopy (THz-TDS) and Fourier Transform Infrared (FTIR) Spectroscopy - to create the first comprehensive database of small biomolecules in the terahertz range and also developed a novel membrane method for the simple and rapid analysis of biomolecules
A vessel crew scheduling problem : formulations and solution methods
Get PDFCrew scheduling problems have been well studied in a variety of areas within transportation and logistics; however, the application of mathematical modelling techniques within a specifically maritime setting has received relatively little attention in the literature. This research focusses on the crew scheduling problem faced by a large, global company providing support services in the offshore oil industry.Starting with an introduction to crew scheduling and the maritime industry, this thesis goes on to review literature in related areas before giving details of the broader business context and the specific crew scheduling problem in which we are interested. With the company currently using a manual method to update their crew schedules weekly on a rolling basis, often under time pressure, we argue that there is scope for a decision support tool to be introduced which will help the crew planners to find feasible, and potentially good quality, schedules.Two main formulations are presented - a Task-Based model, which makes simplifying assumptions about crew contracts and working patterns, and a more realistic but more complex Time-Windows model. Both of these models can be likened to the crew recovery problems seen in other transportation scheduling literature, and can be solved with the objective of minimizing either the number of changes from the existing schedule or the cost of these changes.While the Task-Based model proved relatively easy to solve, a number of solution methods had to be considered for the Time-Windows problem. Ultimately, a heuristic method was proposed to underpin the scheduling tool. This heuristic method finds an initial solution with a low number of changes, before performing a neighbourhood search which seeks to reduce the solution cost. Results however show there is still much room for improvement, and the thesis concludes with ideas for further extending this research.Crew scheduling problems have been well studied in a variety of areas within transportation and logistics; however, the application of mathematical modelling techniques within a specifically maritime setting has received relatively little attention in the literature. This research focusses on the crew scheduling problem faced by a large, global company providing support services in the offshore oil industry.Starting with an introduction to crew scheduling and the maritime industry, this thesis goes on to review literature in related areas before giving details of the broader business context and the specific crew scheduling problem in which we are interested. With the company currently using a manual method to update their crew schedules weekly on a rolling basis, often under time pressure, we argue that there is scope for a decision support tool to be introduced which will help the crew planners to find feasible, and potentially good quality, schedules.Two main formulations are presented - a Task-Based model, which makes simplifying assumptions about crew contracts and working patterns, and a more realistic but more complex Time-Windows model. Both of these models can be likened to the crew recovery problems seen in other transportation scheduling literature, and can be solved with the objective of minimizing either the number of changes from the existing schedule or the cost of these changes.While the Task-Based model proved relatively easy to solve, a number of solution methods had to be considered for the Time-Windows problem. Ultimately, a heuristic method was proposed to underpin the scheduling tool. This heuristic method finds an initial solution with a low number of changes, before performing a neighbourhood search which seeks to reduce the solution cost. Results however show there is still much room for improvement, and the thesis concludes with ideas for further extending this research
Data-based vibration structural health monitoring methodology for composite laminated structures
No full textComposite materials are steadily replacing traditional materials in a wide range of industry sectors thanks to their remarkable properties. Damage in composite materials exhibits complex failure modes which are difficult to identify by conventional techniques. Composite materials demonstrate complex nonlinear vibration behaviour where conventional vibration-based structural health monitoring (VSHM) methods might not give adequate information for damage identification. This thesis investigates the capabilities of singular spectrum analysis (SSA) as a technique for developing a completely data-based VSHM methodology. The methodology decomposes the vibration responses in a certain number of principal components having in consideration all rotational patterns at any frequency including the nonlinear oscillations. This thesis develops two approaches to use SSA in the time and frequency domain. The methodology has been validated using a numerical system and an experiment with delaminated beams.The results demonstrate the methodology capability for assessing damages at different locations and with different sizes. The progression of damage can also be tracked. Delamination was successfully assessed in composite laminated plates with different delamination locations, in-plane and through different layers. Damage in wind turbine blades was assessed by the damage assessment methodology with a statistical hypothesis inspection phase based on probability distribution functions. Different damage locations and sizes were assessed as well as damage progression. This thesis explores the use of smart materials which enable self-sensing and self-diagnosing of its structural integrity coupled with the data-based VSHM. The results demonstrate the substantial potential of this approach. Overall, the data-based VSHM methodology presented in this thesis is proven to give adequate information about the presence, location and extent of delamination and other defects in different composite laminated structures.Composite materials are steadily replacing traditional materials in a wide range of industry sectors thanks to their remarkable properties. Damage in composite materials exhibits complex failure modes which are difficult to identify by conventional techniques. Composite materials demonstrate complex nonlinear vibration behaviour where conventional vibration-based structural health monitoring (VSHM) methods might not give adequate information for damage identification. This thesis investigates the capabilities of singular spectrum analysis (SSA) as a technique for developing a completely data-based VSHM methodology. The methodology decomposes the vibration responses in a certain number of principal components having in consideration all rotational patterns at any frequency including the nonlinear oscillations. This thesis develops two approaches to use SSA in the time and frequency domain. The methodology has been validated using a numerical system and an experiment with delaminated beams.The results demonstrate the methodology capability for assessing damages at different locations and with different sizes. The progression of damage can also be tracked. Delamination was successfully assessed in composite laminated plates with different delamination locations, in-plane and through different layers. Damage in wind turbine blades was assessed by the damage assessment methodology with a statistical hypothesis inspection phase based on probability distribution functions. Different damage locations and sizes were assessed as well as damage progression. This thesis explores the use of smart materials which enable self-sensing and self-diagnosing of its structural integrity coupled with the data-based VSHM. The results demonstrate the substantial potential of this approach. Overall, the data-based VSHM methodology presented in this thesis is proven to give adequate information about the presence, location and extent of delamination and other defects in different composite laminated structures
A novel zonal adaptive DG anti-islanding protection scheme to enhance future system stability using real-time inertia estimates
Get PDFEmerging power system designs are driven towards supporting the diversity of generation supply through increased flexibility and progressive employment of renewable resources, in order to fulfil sustainable and low carbon energy development strategies. The resulting impact on system response, especially during and following disturbances, can incur negative power system stability issues. With particular attention given to the anticipated reduction and variation of system inertia, concerns are growing with respect to power system frequency stability following large disturbances. This is attributed to the potential involvement of acceleration and magnification in frequency excursions due to reduced inertia and differences in generator (particularly converter-interfaced source) control and responses to disturbances.Despite the fact that new techniques, such as those that produce "synthetic" inertial responses, are evolving to compensate for the absence of inherent inertia from renewable resources, their practical integration into the existing grid is limited at the present stage. This is attributed to the uncertainties underlying when and how these techniques should be applied, with a major barrier to their deployment being a lack of prevailing system inertia information. As the exact amount of real-time response required cannot be known with a high degree of confidence, a risk of "over-responding" would be incurred if inertial responses are deployed widely throughout the system. Moreover, the suitability of adopting present-day frequency-based protection settings in conjunction with aforementioned techniques in future power networks has not been fully investigated, where frequency stability margins, necessitating active regulation, could dynamically vary. As such, the work reported in this thesis focuses on evaluating the impact of variable inertia on the performance of existing frequency-based protections and the feasibility of introducing adaptive solutions as a flexible and reliable approach to improve the performance of affected frequency protection schemes, thereby enhancing future system frequency performance. There are two major contributions in this thesis. Firstly, a Switching Markov Gaussian Model (SMGM) has been proposed with which the real-time inertia estimates can be profiled from observed frequency variations during normal system operation. An optimised error of lower than 10% (taken for a system of an overall inertia equal to 3 seconds) was produced for 95% of the daily estimation if being calibrated with the equivalent inertia derived from generation dispatch data on a half-hourly basis and its robustness can be maintained for a period of up to two hours when losing frequency observations. Secondly, a zonal adaptive Distributed Generation (DG) anti-islanding protection scheme has been developed and demonstrated with protection settings being adjusted in response to estimated levels of system inertia. Enhancement of the performance of DG anti-islanding protection has been tested and demonstrated on a reduced GB power network model. Validity and robustness have been analysed, along with discussions of configuration adjustments and practicalities of adopting reliable adaptive protection schemes.Emerging power system designs are driven towards supporting the diversity of generation supply through increased flexibility and progressive employment of renewable resources, in order to fulfil sustainable and low carbon energy development strategies. The resulting impact on system response, especially during and following disturbances, can incur negative power system stability issues. With particular attention given to the anticipated reduction and variation of system inertia, concerns are growing with respect to power system frequency stability following large disturbances. This is attributed to the potential involvement of acceleration and magnification in frequency excursions due to reduced inertia and differences in generator (particularly converter-interfaced source) control and responses to disturbances.Despite the fact that new techniques, such as those that produce "synthetic" inertial responses, are evolving to compensate for the absence of inherent inertia from renewable resources, their practical integration into the existing grid is limited at the present stage. This is attributed to the uncertainties underlying when and how these techniques should be applied, with a major barrier to their deployment being a lack of prevailing system inertia information. As the exact amount of real-time response required cannot be known with a high degree of confidence, a risk of "over-responding" would be incurred if inertial responses are deployed widely throughout the system. Moreover, the suitability of adopting present-day frequency-based protection settings in conjunction with aforementioned techniques in future power networks has not been fully investigated, where frequency stability margins, necessitating active regulation, could dynamically vary. As such, the work reported in this thesis focuses on evaluating the impact of variable inertia on the performance of existing frequency-based protections and the feasibility of introducing adaptive solutions as a flexible and reliable approach to improve the performance of affected frequency protection schemes, thereby enhancing future system frequency performance. There are two major contributions in this thesis. Firstly, a Switching Markov Gaussian Model (SMGM) has been proposed with which the real-time inertia estimates can be profiled from observed frequency variations during normal system operation. An optimised error of lower than 10% (taken for a system of an overall inertia equal to 3 seconds) was produced for 95% of the daily estimation if being calibrated with the equivalent inertia derived from generation dispatch data on a half-hourly basis and its robustness can be maintained for a period of up to two hours when losing frequency observations. Secondly, a zonal adaptive Distributed Generation (DG) anti-islanding protection scheme has been developed and demonstrated with protection settings being adjusted in response to estimated levels of system inertia. Enhancement of the performance of DG anti-islanding protection has been tested and demonstrated on a reduced GB power network model. Validity and robustness have been analysed, along with discussions of configuration adjustments and practicalities of adopting reliable adaptive protection schemes
Technological innovation and resource management in the fisheries of the British Isles, ca. 1400-1900
Get PDFThis thesis represents the first in-depth study of interactions between fishermen, fisheries managers and fishery resources in British waters before the industrial age. In particular, it investigates those interactions during periods of technological innovation and intensified fishing activity in the period between 1400 and 1900, and seeks to explain the responses of both fishermen and managers to those changes. By bringing together methodological tools from social history, environmental history and modern fisheries science it demonstrates that fishermen have always had a sophisticated understanding of the potential impact of their activities on the marine environment, and of the overall health of the fisheries in which they were engaged. Moreover, it makes clear that keen resistance to what were perceived as destructive fishing practices (particularly in relation to growth overfishing) has an unbroken history stretching back to the Plantagenets, and that fishermen's complaints about such practices were very often met with sympathy and protective legislation for the majority of that time. What follows also demonstrates that, contrary to the conventional historical view, the most consistently reviled of all marine fishing practices, beam trawling, also has an unbroken history of usage reaching back to at least the fourteenth century. Finally, it goes on to show that the majority view of fishermen, who remained largely in favour of protection for inshore fisheries and the inshore marine environment, was sidelined in debates about fisheries management at some point in the mid- to late-nineteenth century. This shift in perspective heralded the abandonment of at least six hundred years of protectionism in the management of Britain and Ireland's fisheries and ushered in a new era of fish production at any cost.This thesis represents the first in-depth study of interactions between fishermen, fisheries managers and fishery resources in British waters before the industrial age. In particular, it investigates those interactions during periods of technological innovation and intensified fishing activity in the period between 1400 and 1900, and seeks to explain the responses of both fishermen and managers to those changes. By bringing together methodological tools from social history, environmental history and modern fisheries science it demonstrates that fishermen have always had a sophisticated understanding of the potential impact of their activities on the marine environment, and of the overall health of the fisheries in which they were engaged. Moreover, it makes clear that keen resistance to what were perceived as destructive fishing practices (particularly in relation to growth overfishing) has an unbroken history stretching back to the Plantagenets, and that fishermen's complaints about such practices were very often met with sympathy and protective legislation for the majority of that time. What follows also demonstrates that, contrary to the conventional historical view, the most consistently reviled of all marine fishing practices, beam trawling, also has an unbroken history of usage reaching back to at least the fourteenth century. Finally, it goes on to show that the majority view of fishermen, who remained largely in favour of protection for inshore fisheries and the inshore marine environment, was sidelined in debates about fisheries management at some point in the mid- to late-nineteenth century. This shift in perspective heralded the abandonment of at least six hundred years of protectionism in the management of Britain and Ireland's fisheries and ushered in a new era of fish production at any cost
Migration, structures of feeling and pathways to inclusion and exclusion : migrant workers in Northern Ireland, Scotland, and Poland
Get PDFDrawing on a concept well-established in social theory, but not yet applied by scholars of migration, namely, the concept of Structures of Feeling, the thesis develops a novel perspective on the role of the context of departure and destination in shaping migration experiences, especially the experience of inclusion and exclusion. The main argument of the thesis is that migration involves a continuous process of migrants interpreting and reinterpreting a country of departure and destination, a process driven by ethics relevant to migrants. The experience of these ethics, largely shaped by the employment trajectories of migrants, can vary depending on a country or locality within it and, therefore, results in different experiences and interpretations of, or simply, different Structures of Feeling in connection with different places. In this process people also interpret and reinterpret themselves and their relationship with different places involved in migration. In this way, Structures of Feeling can affect people's sense of belonging and their migration decisions, especially decisions regarding settlement. By exploring this phenomenon, the study reveals complex subjective processes involved in migration.This conceptual framework emerged from the qualitative analysis of data from nearly 100 interviews with 50 migrant workers in Northern Ireland, Scotland, and Poland. The thesis shows that interviewees experienced work and life abroad through the prism of three ethics connected with neoliberalism. Differences in the experiences of these ethics in the country of departure and destination mediated their sense of inclusion and exclusion and gave rise to the dual-idealisations of a place of departure and arrival which, in turn, affected their settlement decisions. Moreover, it is demonstrated that, while these experiences may not seem straightforwardly different across the three destinations taken into account in this study, certain context-specific variations can be identified, too. These are accounted for by the notion of Local Structures of Feeling.Drawing on a concept well-established in social theory, but not yet applied by scholars of migration, namely, the concept of Structures of Feeling, the thesis develops a novel perspective on the role of the context of departure and destination in shaping migration experiences, especially the experience of inclusion and exclusion. The main argument of the thesis is that migration involves a continuous process of migrants interpreting and reinterpreting a country of departure and destination, a process driven by ethics relevant to migrants. The experience of these ethics, largely shaped by the employment trajectories of migrants, can vary depending on a country or locality within it and, therefore, results in different experiences and interpretations of, or simply, different Structures of Feeling in connection with different places. In this process people also interpret and reinterpret themselves and their relationship with different places involved in migration. In this way, Structures of Feeling can affect people's sense of belonging and their migration decisions, especially decisions regarding settlement. By exploring this phenomenon, the study reveals complex subjective processes involved in migration.This conceptual framework emerged from the qualitative analysis of data from nearly 100 interviews with 50 migrant workers in Northern Ireland, Scotland, and Poland. The thesis shows that interviewees experienced work and life abroad through the prism of three ethics connected with neoliberalism. Differences in the experiences of these ethics in the country of departure and destination mediated their sense of inclusion and exclusion and gave rise to the dual-idealisations of a place of departure and arrival which, in turn, affected their settlement decisions. Moreover, it is demonstrated that, while these experiences may not seem straightforwardly different across the three destinations taken into account in this study, certain context-specific variations can be identified, too. These are accounted for by the notion of Local Structures of Feeling
Access Repository Dashboard
Do you manage STAX (Strathclyde Repository)? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!