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Experimental design and mathematical modelling methods for the study of anthelmintic resistance in UK livestock populations
Get PDFThe Faecal Egg Count Reduction Test (FECRT) is the most widely used field based method for estimating anthelmintic efficacy and as an indicator of anthelmintic resistant nematodes in cattle. In this thesis, statistical aspects such as the analysis of cattle faecal egg count (FEC) data and the identification of statistically robust experimental study designs for the FECRT, are examined. Using field study cattle FECRT data, the validity of current guidelines on parameter estimates for evaluating percentage estimates and confidence intervals (CIs), were assessed. For FECs obtained using sensitive counting techniques, percentage estimates are recommended to be evaluated using arithmetic group means. For FECs obtained by less sensitive counting techniques, the maximum likelihood estimator of zero inflated distributions is recommended when evaluating percentage estimates. It would not be recommended however, to use CIs that assume FECs to be normal, and it is therefore recommended that relevant intervals for percentage estimates be obtained using a Bootstrap or Bayesian framework. A simulation study was conducted using Bootstrap methodology to assess the coverage probability of 95% percentile intervals, associated with different percentage estimates. The coverage was considered for scenarios involving various diagnostic sensitivities, treatment group sizes and classifications of pre-treatment group means. Very few scenarios consisted of 95% Bootstrapped percentile intervals with adequate coverage probabilities. A further simulation study was then carried out with Bayesian methodologies being employed. The accuracy of percentage estimates was examined under the scenarios described above. In the majority of scenarios: in order to obtain the most accurate percentage estimates, one would only need to adopt a paired study design involving a positive treatment group. The following R Shiny prototype webpage application is available to carry out the recommended analysis of cattle FECRT data, i.e. averaging over individual based egg count percentage reductions/changes based on the form of the Symmetrised Percentage Change, using our developed Bayesian methodologies: http://outreach.mathstat.strath.ac.uk/apps/FECRT.The Faecal Egg Count Reduction Test (FECRT) is the most widely used field based method for estimating anthelmintic efficacy and as an indicator of anthelmintic resistant nematodes in cattle. In this thesis, statistical aspects such as the analysis of cattle faecal egg count (FEC) data and the identification of statistically robust experimental study designs for the FECRT, are examined. Using field study cattle FECRT data, the validity of current guidelines on parameter estimates for evaluating percentage estimates and confidence intervals (CIs), were assessed. For FECs obtained using sensitive counting techniques, percentage estimates are recommended to be evaluated using arithmetic group means. For FECs obtained by less sensitive counting techniques, the maximum likelihood estimator of zero inflated distributions is recommended when evaluating percentage estimates. It would not be recommended however, to use CIs that assume FECs to be normal, and it is therefore recommended that relevant intervals for percentage estimates be obtained using a Bootstrap or Bayesian framework. A simulation study was conducted using Bootstrap methodology to assess the coverage probability of 95% percentile intervals, associated with different percentage estimates. The coverage was considered for scenarios involving various diagnostic sensitivities, treatment group sizes and classifications of pre-treatment group means. Very few scenarios consisted of 95% Bootstrapped percentile intervals with adequate coverage probabilities. A further simulation study was then carried out with Bayesian methodologies being employed. The accuracy of percentage estimates was examined under the scenarios described above. In the majority of scenarios: in order to obtain the most accurate percentage estimates, one would only need to adopt a paired study design involving a positive treatment group. The following R Shiny prototype webpage application is available to carry out the recommended analysis of cattle FECRT data, i.e. averaging over individual based egg count percentage reductions/changes based on the form of the Symmetrised Percentage Change, using our developed Bayesian methodologies: http://outreach.mathstat.strath.ac.uk/apps/FECRT
Politics and the problem of speaking for others in the work of Naomi Mitchison
Get PDFThis thesis focuses on the political influences that shaped the life and writing of Naomi Mitchison (1897-1999). Mitchison was a polymath who published extensively in a wide range of genres, and whose left-wing political interests informed many of her works. I explore the view that in her roles as author and social activist she aimed to represent 'the people who have not spoken yet' (Calder 1997: ix), and I interrogate the potential difficulties in representing those marginal voices.;Examining texts from the 1910s through to the 1970s, this thesis traces Mitchison's political development to show how her socialist outlook emerged, shifted and directly responded to socio-historical contexts throughout the twentieth century. An evaluation of her extensive corpus, including fictional and non-fictional texts, archival material and unpublished letters, will be employed to show how she repeatedly campaigned, examined and documented the political and social issues of her time. Her role as an author not only enabled her to represent silenced groups, but also provided an opportunity to write through and explore her own, often contradictory, stance.;Drawing upon theoretical frameworks, including Linda Alcoff's 'The Problem of Speaking for Others', I contend that throughout Mitchison's career she repeatedly seeks to 'know' and explain others, and justify her right to speak for them. Mitchison's endeavours were grounded in altruism, but she was consciously aware of her paradoxical position as a privileged upper-middle-class author and socialist champion, and her writing pivots around this contradictory struggle. In representing marginal groups, she aimed to give agency to those who had been silenced, but her works also served to validate her place as spokesperson for such groups.This thesis focuses on the political influences that shaped the life and writing of Naomi Mitchison (1897-1999). Mitchison was a polymath who published extensively in a wide range of genres, and whose left-wing political interests informed many of her works. I explore the view that in her roles as author and social activist she aimed to represent 'the people who have not spoken yet' (Calder 1997: ix), and I interrogate the potential difficulties in representing those marginal voices.;Examining texts from the 1910s through to the 1970s, this thesis traces Mitchison's political development to show how her socialist outlook emerged, shifted and directly responded to socio-historical contexts throughout the twentieth century. An evaluation of her extensive corpus, including fictional and non-fictional texts, archival material and unpublished letters, will be employed to show how she repeatedly campaigned, examined and documented the political and social issues of her time. Her role as an author not only enabled her to represent silenced groups, but also provided an opportunity to write through and explore her own, often contradictory, stance.;Drawing upon theoretical frameworks, including Linda Alcoff's 'The Problem of Speaking for Others', I contend that throughout Mitchison's career she repeatedly seeks to 'know' and explain others, and justify her right to speak for them. Mitchison's endeavours were grounded in altruism, but she was consciously aware of her paradoxical position as a privileged upper-middle-class author and socialist champion, and her writing pivots around this contradictory struggle. In representing marginal groups, she aimed to give agency to those who had been silenced, but her works also served to validate her place as spokesperson for such groups
The effect of ankle-foot orthosis on gait and the procedures used to assess bi-articular muscle length and spasticity in subjects with diplegic cerebral palsy
Get PDFAnkle-foot orthoses are commonly prescribed amongst subjects with diplegic cerebral palsy as a conservative orthotic intervention. Multi-articular and bi-articular muscles are more severely involved in subjects with diplegic cerebral palsy. Appropriate clinical assessment including assessment of these muscles enables optimum ankle-foot orthosis footwear combination (AFO-FC) prescription and any required adjunct therapy.The overarching aim of this thesis was to investigate the effect of optimisation of the temporal midstance shank kinematics with the use of an AFO- FC on several variables including shank kinematics, thigh kinematics, vertical component of ground reaction force (FZ2) and ground reaction force (GRF) alignment in relation to hip and knee joint in temporal midstance to late stance. The understanding of the implication of, and the tools used to conduct assessment procedures and measurement processes were tested in the assessment of bi-articular muscles (specifically rectus femoris), to ascertain if results were predictive of presenting gait deviations and hence provide information to optimise treatment.The results of initial study suggested that a positive influence on the shank kinematics, thigh kinematics, FZ2 and GRF alignment in relation to hip and knee joint in temporal midstance to late stance was observed with the use of an AFO-FC. The results of a further study illustrated that a dominance relationship of the catch angle/length of rectus femoris (RF) measured using the Duncan-Ely with the knee or the hip joints varies at different gait points/periods. Additionally, the effect of dynamic shortness of4the RF differed on gait from the effect of true shortness. The results of series of studies testing the feasibility of using a 2-dimensional analysis system (PnO Clinical Movement Data) for hip, knee and ankle sagittal plane passive joint range of motion measurement during physical assessment confirmed the reliability and accuracy of this system.Ankle-foot orthoses are commonly prescribed amongst subjects with diplegic cerebral palsy as a conservative orthotic intervention. Multi-articular and bi-articular muscles are more severely involved in subjects with diplegic cerebral palsy. Appropriate clinical assessment including assessment of these muscles enables optimum ankle-foot orthosis footwear combination (AFO-FC) prescription and any required adjunct therapy.The overarching aim of this thesis was to investigate the effect of optimisation of the temporal midstance shank kinematics with the use of an AFO- FC on several variables including shank kinematics, thigh kinematics, vertical component of ground reaction force (FZ2) and ground reaction force (GRF) alignment in relation to hip and knee joint in temporal midstance to late stance. The understanding of the implication of, and the tools used to conduct assessment procedures and measurement processes were tested in the assessment of bi-articular muscles (specifically rectus femoris), to ascertain if results were predictive of presenting gait deviations and hence provide information to optimise treatment.The results of initial study suggested that a positive influence on the shank kinematics, thigh kinematics, FZ2 and GRF alignment in relation to hip and knee joint in temporal midstance to late stance was observed with the use of an AFO-FC. The results of a further study illustrated that a dominance relationship of the catch angle/length of rectus femoris (RF) measured using the Duncan-Ely with the knee or the hip joints varies at different gait points/periods. Additionally, the effect of dynamic shortness of4the RF differed on gait from the effect of true shortness. The results of series of studies testing the feasibility of using a 2-dimensional analysis system (PnO Clinical Movement Data) for hip, knee and ankle sagittal plane passive joint range of motion measurement during physical assessment confirmed the reliability and accuracy of this system
Novel optical communications and imaging enabled by CMOS interfaced LED technology
No full textArrays of micron sized light-emitting diodes (micro-LEDs) allow high-frequency spatial and temporal modulation of an optical signal. Contacting micro-LED arrays to complementary metal-oxide-semiconductor (CMOS) electronics provides a mm-chip-scale device with a high level of control over the optical emission through digital input. Such devices enable novel forms of optical communication and imaging to be investigated.;This thesis first demonstrates the use of CMOS controlled micro-LEDs in multi-level intensity modulated optical communications. By generating signals in a discrete fashion with weighted groups of pixels in an array, the non-linearity issues of single LED elements can be avoided and the device functions as a digital-to-light converter. Pulse amplitude modulation and discrete orthogonal frequency division multiplexing were performed, yielding data rates up to 200 Mb/s, and spectral efficiencies up to 3.96 bits/s/Hz.;A novel form of optical communications is introduced where data is sent through modulation of the temporal correlation of a pulsed optical signal. Utilising single-photon detection at the receiver enables transmission at low received power levels, on the order of picowatts. While data rates prove to be modest, the scheme is robust to both constant and modulated background signals. Additionally, the implementation requires only simple semiconductor components, exhibits low electrical power consumption, and has been demonstrated under power from a nanosatellite simulation testbed.;The pulse correlation approach also presents opportunities in imaging. Received signals are dependent on optical power; therefore, if relative emitted power from multiple transmitters is known, information on the reectance or absorption of an intermediate material can be obtained. This potentially enables colour or hyperspectral imaging with single-photon detectors by temporally structuring light sources. Proof-of-principle experiments have been performed using commercially available LEDs of 10 different wavelengths and printed colour targets.Arrays of micron sized light-emitting diodes (micro-LEDs) allow high-frequency spatial and temporal modulation of an optical signal. Contacting micro-LED arrays to complementary metal-oxide-semiconductor (CMOS) electronics provides a mm-chip-scale device with a high level of control over the optical emission through digital input. Such devices enable novel forms of optical communication and imaging to be investigated.;This thesis first demonstrates the use of CMOS controlled micro-LEDs in multi-level intensity modulated optical communications. By generating signals in a discrete fashion with weighted groups of pixels in an array, the non-linearity issues of single LED elements can be avoided and the device functions as a digital-to-light converter. Pulse amplitude modulation and discrete orthogonal frequency division multiplexing were performed, yielding data rates up to 200 Mb/s, and spectral efficiencies up to 3.96 bits/s/Hz.;A novel form of optical communications is introduced where data is sent through modulation of the temporal correlation of a pulsed optical signal. Utilising single-photon detection at the receiver enables transmission at low received power levels, on the order of picowatts. While data rates prove to be modest, the scheme is robust to both constant and modulated background signals. Additionally, the implementation requires only simple semiconductor components, exhibits low electrical power consumption, and has been demonstrated under power from a nanosatellite simulation testbed.;The pulse correlation approach also presents opportunities in imaging. Received signals are dependent on optical power; therefore, if relative emitted power from multiple transmitters is known, information on the reectance or absorption of an intermediate material can be obtained. This potentially enables colour or hyperspectral imaging with single-photon detectors by temporally structuring light sources. Proof-of-principle experiments have been performed using commercially available LEDs of 10 different wavelengths and printed colour targets
Analysis of the factors influencing higher education participation
Get PDFThis thesis contributes to the theory of the demand for higher education through an empirical analysis of higher education participation in Great Britain (with particular reference to Scotland). Three dimensions of higher education participation are empirically assessed using Higher Education Statistics Agency data: the effects of tuition fees, differences in participation by gender and student mobility. These research themes are pertinent to policy in the provision of higher education.;The chapter 'Tuition Fees and Higher Education Participation' examines the impact of the abolition of tuition fees on higher education enrolment in Scotland. Employing a difference-in-differences methodology, this study shows the effects of abolishing tuition fees on Age Participation Indices in higher education in Scotland. From a policy perspective, the results show that participation rates in higher education are price sensitive and participation is increased by the abolition of tuition fees.;The chapter 'Higher Education Enrolment by Gender' analyses female and male enrolments in higher education in Scotland. Female participation in higher education has become significantly higher than male participation in Scotland. This study analyses factors contributing to differences in participation by gender. The graduate employment rate and the population positively influence female enrolments in higher education. Female price response models are developed to analyse the introduction of the Graduate Endowment Fee on female participation. For the majority of institutions, the Fee did not impact the female share of participation.;The chapter 'Geographical Mobility in Higher Education' explores factors influencing cross country migration in Great Britain for higher education. Using logistic regressions for British micro data from 1998/99 to 2015/16, this study finds age, socio-economic background, institution classification, subject area and regional location contribute to the probability of individuals moving country for higher education. The largest mobility differences across males and females occur by subject area.This thesis contributes to the theory of the demand for higher education through an empirical analysis of higher education participation in Great Britain (with particular reference to Scotland). Three dimensions of higher education participation are empirically assessed using Higher Education Statistics Agency data: the effects of tuition fees, differences in participation by gender and student mobility. These research themes are pertinent to policy in the provision of higher education.;The chapter 'Tuition Fees and Higher Education Participation' examines the impact of the abolition of tuition fees on higher education enrolment in Scotland. Employing a difference-in-differences methodology, this study shows the effects of abolishing tuition fees on Age Participation Indices in higher education in Scotland. From a policy perspective, the results show that participation rates in higher education are price sensitive and participation is increased by the abolition of tuition fees.;The chapter 'Higher Education Enrolment by Gender' analyses female and male enrolments in higher education in Scotland. Female participation in higher education has become significantly higher than male participation in Scotland. This study analyses factors contributing to differences in participation by gender. The graduate employment rate and the population positively influence female enrolments in higher education. Female price response models are developed to analyse the introduction of the Graduate Endowment Fee on female participation. For the majority of institutions, the Fee did not impact the female share of participation.;The chapter 'Geographical Mobility in Higher Education' explores factors influencing cross country migration in Great Britain for higher education. Using logistic regressions for British micro data from 1998/99 to 2015/16, this study finds age, socio-economic background, institution classification, subject area and regional location contribute to the probability of individuals moving country for higher education. The largest mobility differences across males and females occur by subject area
Multi-objective inversion-based control of building integrated energy systems
Get PDFBuildings are a key target for energy efficiency measures and the integration of renewable technologies. However, a high penetration of intermittent renewable energy in the electrical grid and in the buildings themselves will result in a reduction of the grid's ability to absorb excess generation freely.One method for improving the efficiency of buildings and addressing the intermittent availability of renewables is to make them more energy autonomous i.e. creating and consuming the majority of their own energy. The needs of a building cannot usually be met by a single energy resource alone, but requires the adoption and coordinated operation of a multitude of energy sources such as combined heat and power (chp) units, thermal energy storage (tes), electrical energy storage (ees) and photovoltaics (pv). Making these systems work together presents a control challenge for their efficient use, especially since they can have a simultaneous effect on both the thermal and electrical energy networks.This research addresses the design of a robust multi-input multi-output (mimo) controller applicable to any configuration of the aforementioned systems, with the control goal of minimising the electrical grid utilisation of a building while fulfilling the thermal demands of the building. The controller employs the inverse dynamics of the building, mechanical/servicing systems, and energy storage with a robust control methodology. This inverse dynamics provides the controller with knowledge of the complex cause and effect relationships between the system, the controlled inputs, and the external disturbances, while an outer-loop control ensures robust, stable control in the presence of modelling deficiencies/uncertainty and unknown disturbances. The physical limitations of the systems are also accounted for via variable structure control whereby the control strategy employed switches depending on the current utilisation and availability of the energy supplies.Results indicate that the control strategy is effective in minimising the electrical grid use and maximising the utilisation of the available energy when compared to conventional system operation.Buildings are a key target for energy efficiency measures and the integration of renewable technologies. However, a high penetration of intermittent renewable energy in the electrical grid and in the buildings themselves will result in a reduction of the grid's ability to absorb excess generation freely.One method for improving the efficiency of buildings and addressing the intermittent availability of renewables is to make them more energy autonomous i.e. creating and consuming the majority of their own energy. The needs of a building cannot usually be met by a single energy resource alone, but requires the adoption and coordinated operation of a multitude of energy sources such as combined heat and power (chp) units, thermal energy storage (tes), electrical energy storage (ees) and photovoltaics (pv). Making these systems work together presents a control challenge for their efficient use, especially since they can have a simultaneous effect on both the thermal and electrical energy networks.This research addresses the design of a robust multi-input multi-output (mimo) controller applicable to any configuration of the aforementioned systems, with the control goal of minimising the electrical grid utilisation of a building while fulfilling the thermal demands of the building. The controller employs the inverse dynamics of the building, mechanical/servicing systems, and energy storage with a robust control methodology. This inverse dynamics provides the controller with knowledge of the complex cause and effect relationships between the system, the controlled inputs, and the external disturbances, while an outer-loop control ensures robust, stable control in the presence of modelling deficiencies/uncertainty and unknown disturbances. The physical limitations of the systems are also accounted for via variable structure control whereby the control strategy employed switches depending on the current utilisation and availability of the energy supplies.Results indicate that the control strategy is effective in minimising the electrical grid use and maximising the utilisation of the available energy when compared to conventional system operation
Development of a novel SERS assay for the detection of MiRNA and the synthesis and use of lipid soluble nanoparticles for the application to cardiovascular disease
Get PDFCardiovascular disease (CVD) encompasses a wide range of clinical conditions including atherosclerosis. This progressive inflammatory disease can develop and present no symptoms for along period of time before classifying as clinical. Current detection methods include the non-invasive technique of x-rays and the invasive technique of angiography. Both of these have several limitations including the delayed timeframe from which they can detect the disease. It is desirable for a technique to be able to detect early (sub-clinical) stages, to allow early treatment and the best possible chances patient recovery.;Small endogenous RNA species (microRNA's) play an important role in cardiac homeostasis, therefore lending themselves as potential biomarkers. This research demonstrates the use of nanoparticle-oligonucleotide conjugates, together with surface-enhanced Raman scattering (SERS) to detect and identify CVD specific microRNA sequences. The use of a Raman reporter functionalised to the nanoparticle surface allows a signal to be obtained and thus an attribute by which the presence, or lack of, a target microRNA sequence can be concluded.;In order for such species to be used for clinical purposes, they must be capable of passing through the cell membrane. This research shows the synthesis of cholesterol covered particles and their ability to penetrate the phospholipid bilayer, thus demonstrating their potential to act as a biomarker detector.Cardiovascular disease (CVD) encompasses a wide range of clinical conditions including atherosclerosis. This progressive inflammatory disease can develop and present no symptoms for along period of time before classifying as clinical. Current detection methods include the non-invasive technique of x-rays and the invasive technique of angiography. Both of these have several limitations including the delayed timeframe from which they can detect the disease. It is desirable for a technique to be able to detect early (sub-clinical) stages, to allow early treatment and the best possible chances patient recovery.;Small endogenous RNA species (microRNA's) play an important role in cardiac homeostasis, therefore lending themselves as potential biomarkers. This research demonstrates the use of nanoparticle-oligonucleotide conjugates, together with surface-enhanced Raman scattering (SERS) to detect and identify CVD specific microRNA sequences. The use of a Raman reporter functionalised to the nanoparticle surface allows a signal to be obtained and thus an attribute by which the presence, or lack of, a target microRNA sequence can be concluded.;In order for such species to be used for clinical purposes, they must be capable of passing through the cell membrane. This research shows the synthesis of cholesterol covered particles and their ability to penetrate the phospholipid bilayer, thus demonstrating their potential to act as a biomarker detector
A numerical study on the maneuverability of the DTMB 5415 using CFD
Get PDFThe International Maritime Organization (IMO) has proposed various safety standards which ship engineers are required to follow. It is therefore necessary to consider a ship's safety during its initial design stages. The larger ships such as large cargo carriers require strict safety standards. With larger vessels such as these, the IMO safety standards stipulate the need for a vessel to demonstrate high maneuverability - this may be achieved with a twin-screw ship. Demand for twin-screw ships will therefore increase in near future. Thus, when it comes to the maneuverability of a twin-screw ship, the existing research leaves a lot to be desired as it primarily focuses on container ships. For these reasons, it is crucial that thorough research is performed on the maneuverability of other styles of twin-screw ships, such as naval combatants.Most studies on the manoeuvrability of twin-screw ships have focused on container ships as there is an abundance of existing data available for them. However, container ships tend to have less manoeuvring problems compared to other types of ships. Thus, when it comes to the manoeuvrability of a twin-screw ship, the existing research leaves a lot to be desired as it primarily focuses on container ships. For these reasons, it is crucial that thorough research is performed on the manoeuvrability of other types of twin-screw ships, such as naval combatants.The main goal of this research is to assess the manoeuvrability of the twin-screw naval combatant ship the DTMB 5415 using Computational Fluid Dynamics (CFD) and MATLAB.In this research, Star-CCM+ is used as a RANS solver to measure the hydrodynamic forces and moments on the twin-screw and derive the hydrodynamic derivatives. To validate the simulated results, a comparison is made against the existing experimental data from the published literature. Following this, MATLAB will be used to predict the manoeuvrability of the vessel in question such as its turning ability and course changing ability. A Mathematical Modelling Group (MMG) model is then used to predict the individual hydrodynamic forcesof the propeller and hull.The International Maritime Organization (IMO) has proposed various safety standards which ship engineers are required to follow. It is therefore necessary to consider a ship's safety during its initial design stages. The larger ships such as large cargo carriers require strict safety standards. With larger vessels such as these, the IMO safety standards stipulate the need for a vessel to demonstrate high maneuverability - this may be achieved with a twin-screw ship. Demand for twin-screw ships will therefore increase in near future. Thus, when it comes to the maneuverability of a twin-screw ship, the existing research leaves a lot to be desired as it primarily focuses on container ships. For these reasons, it is crucial that thorough research is performed on the maneuverability of other styles of twin-screw ships, such as naval combatants.Most studies on the manoeuvrability of twin-screw ships have focused on container ships as there is an abundance of existing data available for them. However, container ships tend to have less manoeuvring problems compared to other types of ships. Thus, when it comes to the manoeuvrability of a twin-screw ship, the existing research leaves a lot to be desired as it primarily focuses on container ships. For these reasons, it is crucial that thorough research is performed on the manoeuvrability of other types of twin-screw ships, such as naval combatants.The main goal of this research is to assess the manoeuvrability of the twin-screw naval combatant ship the DTMB 5415 using Computational Fluid Dynamics (CFD) and MATLAB.In this research, Star-CCM+ is used as a RANS solver to measure the hydrodynamic forces and moments on the twin-screw and derive the hydrodynamic derivatives. To validate the simulated results, a comparison is made against the existing experimental data from the published literature. Following this, MATLAB will be used to predict the manoeuvrability of the vessel in question such as its turning ability and course changing ability. A Mathematical Modelling Group (MMG) model is then used to predict the individual hydrodynamic forcesof the propeller and hull
Control strategy for variable-speed wind turbine in below rated wind speed
Get PDFGenerating electrical power from renewable sources has increased substantially over the past decades and one of the most capable is wind power. From this energy source, the electrical power is directly generated using wind turbines. The type of the wind turbine used for this project is a variable-speed horizontal-axis wind turbine. Comparing variable speed wind turbines with constant speed wind turbines, variable speed machines have several advantages over constant speed machines, which outweigh the substantial cost of the power electronics necessary to obtain variable speed operations.;The major advantage in below rated wind speed is additional energy capture and in above rated wind speed the frequent mentioned advantage is additional power-train compliance and associated load alleviation.;In variable speed wind turbines, the operational strategy is regularly selected to maximise the energy capture. For this purpose, the operating state of the wind turbine is caused to track the Cpmax curve, which is the maximum aerodynamic efficiency curve. The accuracy of this tracking depends on the controller designed for the wind turbine and the control strategy used. The purpose of this project is to investigate a control strategy for a variable-speed wind turbine in below rated wind speed to improve the power capture. To achieve the objective of this thesis, a controller to track the Cpmax curve is designed in this project.;The controller is validated using a Simulink model developed to the wind turbine. The Simulink model tested for different wind speeds from 4 m/s to 12 m/s with different turbulences from 5% to 20%.Generating electrical power from renewable sources has increased substantially over the past decades and one of the most capable is wind power. From this energy source, the electrical power is directly generated using wind turbines. The type of the wind turbine used for this project is a variable-speed horizontal-axis wind turbine. Comparing variable speed wind turbines with constant speed wind turbines, variable speed machines have several advantages over constant speed machines, which outweigh the substantial cost of the power electronics necessary to obtain variable speed operations.;The major advantage in below rated wind speed is additional energy capture and in above rated wind speed the frequent mentioned advantage is additional power-train compliance and associated load alleviation.;In variable speed wind turbines, the operational strategy is regularly selected to maximise the energy capture. For this purpose, the operating state of the wind turbine is caused to track the Cpmax curve, which is the maximum aerodynamic efficiency curve. The accuracy of this tracking depends on the controller designed for the wind turbine and the control strategy used. The purpose of this project is to investigate a control strategy for a variable-speed wind turbine in below rated wind speed to improve the power capture. To achieve the objective of this thesis, a controller to track the Cpmax curve is designed in this project.;The controller is validated using a Simulink model developed to the wind turbine. The Simulink model tested for different wind speeds from 4 m/s to 12 m/s with different turbulences from 5% to 20%
Factors influencing citizens' adoption of e-government in Saudi Arabia
Get PDFE-government adoption is one of the key factors for E-government success. The adoption of E-government is necessary to reap its benefits. The conducted literature review on citizens' adoption of E-government revealed that although there are studies on this subject conducted in the developed countries, only few studies examined E-government adoption in the developing countries, including Saudi Arabia.;Moreover, the literature review revealed that the existing literature on citizens' adoption of E-government in Saudi Arabia failed to examine the effect of several constructs and associations which were considered crucial in many IS/IT adoption studies. This research aims to investigate the factors affecting citizens' adoption of E-government in Saudi Arabia.;To achieve this aim, a primary objective was set, which is to propose and validate a model in order to find the salient factors in citizens' adoption of E-government in Saudi Arabia. This objective was fulfilled by proposing a model that integrates three well-known IS/IT adoption models and a cultural theory: Technology Adoption Model (TAM), Information System Success Model (ISSM), Trust and Risk Model, and Hofstede's national culture values.;A deductive approach was followed throughout this study. The proposed model was validated quantitatively and the data was collected through online questionnaire which was developed using adapted measuring items. The sample was collected using a self-selection convenience sampling technique. The collected data consisted of 527 usable questionnaires, which was then analysed using PLS-SEM through using SmartPLS and SPSS. The analysis revealed that trust of the Internet does not have a significant influence on intention to use.;Also, surprisingly, service quality was found to have significant positive influence on perceived risk, which is the opposite of the proposed hypothesis. Moreover, none of the espoused national culture values have significant moderating effect on the relationship between perceived usefulness and intention to use. On the other hand, perceived usefulness was confirmed having a significant positive effect on intention to use, while intention to use showed significant positive influence on usage behaviour.;As for the three quality factors adopted from ISSM, system quality, information quality, and service quality proved to have significant positive effect on perceived usefulness, while system quality and information quality were confirmed to have significant negative impact on perceived risk. When it came to the trust factors, both trust of the government and trust of the Internet had significant negative effect on perceived risk. In addition, trust of the government was found to have significant positive effect on intention to use.;Finally, the data analysis confirmed that perceived risk has a significant negative influence on intention to use. The findings of this research provided theoretical contribution through developing and validating an integrated model for E-government adoption, investigating the effects of information quality, system quality, and service quality on perceived risk, and examining the moderating effect of the espoused national culture values.;Moreover, this research proposed several guidelines for E-government managers based on the findings of this study to enhance and promote E-government in Saudi Arabia. Finally, several implications for future research were proposed based on the limitations of this study.E-government adoption is one of the key factors for E-government success. The adoption of E-government is necessary to reap its benefits. The conducted literature review on citizens' adoption of E-government revealed that although there are studies on this subject conducted in the developed countries, only few studies examined E-government adoption in the developing countries, including Saudi Arabia.;Moreover, the literature review revealed that the existing literature on citizens' adoption of E-government in Saudi Arabia failed to examine the effect of several constructs and associations which were considered crucial in many IS/IT adoption studies. This research aims to investigate the factors affecting citizens' adoption of E-government in Saudi Arabia.;To achieve this aim, a primary objective was set, which is to propose and validate a model in order to find the salient factors in citizens' adoption of E-government in Saudi Arabia. This objective was fulfilled by proposing a model that integrates three well-known IS/IT adoption models and a cultural theory: Technology Adoption Model (TAM), Information System Success Model (ISSM), Trust and Risk Model, and Hofstede's national culture values.;A deductive approach was followed throughout this study. The proposed model was validated quantitatively and the data was collected through online questionnaire which was developed using adapted measuring items. The sample was collected using a self-selection convenience sampling technique. The collected data consisted of 527 usable questionnaires, which was then analysed using PLS-SEM through using SmartPLS and SPSS. The analysis revealed that trust of the Internet does not have a significant influence on intention to use.;Also, surprisingly, service quality was found to have significant positive influence on perceived risk, which is the opposite of the proposed hypothesis. Moreover, none of the espoused national culture values have significant moderating effect on the relationship between perceived usefulness and intention to use. On the other hand, perceived usefulness was confirmed having a significant positive effect on intention to use, while intention to use showed significant positive influence on usage behaviour.;As for the three quality factors adopted from ISSM, system quality, information quality, and service quality proved to have significant positive effect on perceived usefulness, while system quality and information quality were confirmed to have significant negative impact on perceived risk. When it came to the trust factors, both trust of the government and trust of the Internet had significant negative effect on perceived risk. In addition, trust of the government was found to have significant positive effect on intention to use.;Finally, the data analysis confirmed that perceived risk has a significant negative influence on intention to use. The findings of this research provided theoretical contribution through developing and validating an integrated model for E-government adoption, investigating the effects of information quality, system quality, and service quality on perceived risk, and examining the moderating effect of the espoused national culture values.;Moreover, this research proposed several guidelines for E-government managers based on the findings of this study to enhance and promote E-government in Saudi Arabia. Finally, several implications for future research were proposed based on the limitations of this study
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