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Entrepreneurial habitus and nudging at multi-generational family firms
Get PDFParent family firms engage in corporate venturing (CV) as a strategy for renewal and competitive advantage. As part of the venturing process, they provide organisational sponsorship to imbue capital and resources to their new ventures. For this study, I investigated seven parent family firms and their new ventures in order to generate a set of research questions that outline a framework for discussion and analysis. Given the exploratory nature of my research, I adopted an abductive multiple case study method at five parent family firms with family ventures and two parent family firms with non-family ventures. At each parent family firm I created case histories, data tables and event histories while also performing open coding and selective coding of data to provide within-case and cross-case analyses in order to reveal patterns in the data. Finally, I created a visual representation of the propositions in a model of a more nuanced theory of organizational sponsorship in the context of new business incubation among parent family firms.;In this study I explored paradigms of paternalism, patronage and sponsorship to show that parent family firms imbued their new ventures with dispositions and resources. I propose that over generations parent family firms imbue long-lasting, transposable and entrepreneurial dispositions while gently steering only family ventures toward available opportunities and resources. Parent family firms put opportunities and strategic resources in entrepreneurial capital within 'easy reach' and 'full view', allowing family ventures to more easily overcome a liability of newness and acquire legitimacy by choosing what is best in order to achieve power over their individual fields.Parent family firms engage in corporate venturing (CV) as a strategy for renewal and competitive advantage. As part of the venturing process, they provide organisational sponsorship to imbue capital and resources to their new ventures. For this study, I investigated seven parent family firms and their new ventures in order to generate a set of research questions that outline a framework for discussion and analysis. Given the exploratory nature of my research, I adopted an abductive multiple case study method at five parent family firms with family ventures and two parent family firms with non-family ventures. At each parent family firm I created case histories, data tables and event histories while also performing open coding and selective coding of data to provide within-case and cross-case analyses in order to reveal patterns in the data. Finally, I created a visual representation of the propositions in a model of a more nuanced theory of organizational sponsorship in the context of new business incubation among parent family firms.;In this study I explored paradigms of paternalism, patronage and sponsorship to show that parent family firms imbued their new ventures with dispositions and resources. I propose that over generations parent family firms imbue long-lasting, transposable and entrepreneurial dispositions while gently steering only family ventures toward available opportunities and resources. Parent family firms put opportunities and strategic resources in entrepreneurial capital within 'easy reach' and 'full view', allowing family ventures to more easily overcome a liability of newness and acquire legitimacy by choosing what is best in order to achieve power over their individual fields
The effect of using universal design for learning (UDL) to improve vocational programme with cognitive disability and the challenges facing this method from the point of view teachers
No full textThe purpose of this study was to investigate the effect of using universal design for learning (UDL) on the acquisition of photography profession skills in a vocational programme for students with intellectual disability (SID) in the Kingdom of Saudi Arabia (KSA). The study has also sought to discover the effectiveness of this method for integrating the SID with students of non-special educational needs (SNSEN) (or non-SEN) in the same classroom. Moreover, this study has explored the advantages, drawbacks and the challenges associated with the implementation of the UDL method in the classroom from the teachers' perspective. That this study took place in girls' secondary schools in mixed ability classrooms. that 24 numbers of students and 16 teachers took part, that data was collected by questionnaire, lists of observations, open questions, and pre- and post-testing.;The first stage was to investigate the teachers' opinions by using the questionnaire and open questions, after training the teachers in how to apply the UDL, to teach SNSEN and SID in the same classroom. This stage also sought to learn the effects of UDL on integrating the SID with SNSEN students. The second stage explored the effect of the UDL on the teaching of professional photography skills for the SID in KSA. To achieve this goal the observation lists and pre- and post-tests were used to compare the learning performance of the SID which used the UDL in experiment groups, with the performance of the SID that used the usual, traditional strategies of learning in control groups.;The results of the research were analysed using a Mann-Whitney U Test, as well as various descriptive statistics. The findings indicate that there was a statistically significant difference between the control and experimental groups in the pre- and post-tests, where the students who used UDL to learn photography developed more quickly than those in the control group. As well as this, the opinions of teachers confirmed that the use of UDL is beneficial in helping with the inclusion of the SID and SNSEN in the same classroom.;The findings further revealed the teachers' opinions on the advantages, drawbacks and obstacles to the application of UDL. The study has significantly added to our understanding of the contribution that UDL can make in developing professional skills for SID. The findings advance the current literature in the area of special education needs, particularly in respect of promoting the inclusion of students of intellectual disability within the same classroom as their non-SEN peers.The purpose of this study was to investigate the effect of using universal design for learning (UDL) on the acquisition of photography profession skills in a vocational programme for students with intellectual disability (SID) in the Kingdom of Saudi Arabia (KSA). The study has also sought to discover the effectiveness of this method for integrating the SID with students of non-special educational needs (SNSEN) (or non-SEN) in the same classroom. Moreover, this study has explored the advantages, drawbacks and the challenges associated with the implementation of the UDL method in the classroom from the teachers' perspective. That this study took place in girls' secondary schools in mixed ability classrooms. that 24 numbers of students and 16 teachers took part, that data was collected by questionnaire, lists of observations, open questions, and pre- and post-testing.;The first stage was to investigate the teachers' opinions by using the questionnaire and open questions, after training the teachers in how to apply the UDL, to teach SNSEN and SID in the same classroom. This stage also sought to learn the effects of UDL on integrating the SID with SNSEN students. The second stage explored the effect of the UDL on the teaching of professional photography skills for the SID in KSA. To achieve this goal the observation lists and pre- and post-tests were used to compare the learning performance of the SID which used the UDL in experiment groups, with the performance of the SID that used the usual, traditional strategies of learning in control groups.;The results of the research were analysed using a Mann-Whitney U Test, as well as various descriptive statistics. The findings indicate that there was a statistically significant difference between the control and experimental groups in the pre- and post-tests, where the students who used UDL to learn photography developed more quickly than those in the control group. As well as this, the opinions of teachers confirmed that the use of UDL is beneficial in helping with the inclusion of the SID and SNSEN in the same classroom.;The findings further revealed the teachers' opinions on the advantages, drawbacks and obstacles to the application of UDL. The study has significantly added to our understanding of the contribution that UDL can make in developing professional skills for SID. The findings advance the current literature in the area of special education needs, particularly in respect of promoting the inclusion of students of intellectual disability within the same classroom as their non-SEN peers
Development of a research approach to quantify temporal variations in baseflow in the developing world, application to Malawi
Get PDFQuantification of temporal variations in baseflow is crucial for sustainable water resources management. Unfortunately, in the developing world, many countries struggle to quantify baseflow due to challenges such as lack of data, sporadic data, and limited financial resources. There is also no systematic approach to guide those on how to overcome these challenges. For this reason, this research aimed to develop an approach to quantify temporal variation in baseflow in the developing world context. Malawi in Southern Africa was selected as the study area to develop the approach. Stakeholder engagement with the Government of Malawi was conducted to verify the need for the research and ensure the practical application of the research outputs. Existing data were collected and included climate data, river flows, lake levels and groundwater levels. Four case studies were used to demonstrate and test the selected methods and approach. First, Lake Malawi was used to demonstrate how to potentially analyse the recession limb of lake levels to provide a proxy indicator of changes in baseflow over time. Second, the Bua Catchment was used to demonstrate how sporadic river data and baseflow separation could be used to determine the annual and seasonal baseflow index (BFI). The BFI represents the baseflow component of river flow and is often used as a proxy indicator for groundwater discharge to a river. Third, the approach presented in the Bua Catchment was upscaled to a larger internationally strategic catchment, the Shire River Basin. Finally, the approach was upscaled to the national scale across Malawi. The results of the Lake Malawi study showed variations occurred in the recession limb between 1900-2016 which were attributed to changes in baseflow in the lake catchment. The changes occurred in years which coincided with either extremely dry or wet conditions in Malawi (1916, 1942, 1948, 2012 and 2013). Whilst, the approach did not provide conclusive results, it highlighted the importance of baseflow to the lake in the context of sustainable water resources management for Malawi. Given the importance of the lake for water supply, further research was required outwith this thesis to quantify the volume of baseflow contribution to the lake from all inflow rivers and evaluate any variations over time. The results from the Bua Catchment, the Shire River Basin and the Malawi studies conclusively showed that the approach was successful when used on the single catchment scale up to the national scale. The approach overcame the challenges typical of the developing world by utilizing sporadic river flow data and free open source tools. Specifically, the approach allowed the determination of annual and seasonal BFI and identification of long-term trends in the BFI data for a total of 68 river gauges across Malawi. This included 6 river gauges assessed as part of the Bua Catchment study and 15 gauges assessed as part of the Shire River Basin study. The results generated new knowledge on the important role of groundwater in sustaining rivers flows across Malawi. This Malawi case study was the first national scale baseflow assessment for the country and data coverage ranged from 11-64 years. The results showed that baseflow in Malawi follows a seasonal pattern with minimal differences between the average annual and average wet season BFI (0.57 and 0.52 respectively). Generally, considerable increases were seen in the dry season BFI (0.97). This indicates that 57%, 52% and 97% of the total Malawi river flow is derived from groundwater in the annual, wet and dry season respectively. Long-term behavioural changes in BFI across all periods were also found. Annually, 10% showed an increasing trend and 16% showed a decreasing trend, which was comparable to the wet season results where 16% showed an increasing trend and 18% showed a decreasing trend. In contrast, in the dry season only 1% showed an increasing trend and 6% showed a decreasing trend. These distinct patterns were also reflected in results of the Bua Catchment and Shire River Basin studies. This thesis has important implications on the sustainable management of water resources. The developed approach is practical, flexible and can be used as an independent assessment tool, or to complement an existing practice or framework. It fills an important gap in the literature by facilitating quantification of temporal variations in baseflow by environmental practitioners in a methodical manner using minimal data and resources. The research outputs also have specific implications for the management of Malawi's water resources. They offer crucial baseline data to support national policy and investment decisions, Integrated Water Resources Management (IWRM) and planning towards Sustainable Development Goal 6.Quantification of temporal variations in baseflow is crucial for sustainable water resources management. Unfortunately, in the developing world, many countries struggle to quantify baseflow due to challenges such as lack of data, sporadic data, and limited financial resources. There is also no systematic approach to guide those on how to overcome these challenges. For this reason, this research aimed to develop an approach to quantify temporal variation in baseflow in the developing world context. Malawi in Southern Africa was selected as the study area to develop the approach. Stakeholder engagement with the Government of Malawi was conducted to verify the need for the research and ensure the practical application of the research outputs. Existing data were collected and included climate data, river flows, lake levels and groundwater levels. Four case studies were used to demonstrate and test the selected methods and approach. First, Lake Malawi was used to demonstrate how to potentially analyse the recession limb of lake levels to provide a proxy indicator of changes in baseflow over time. Second, the Bua Catchment was used to demonstrate how sporadic river data and baseflow separation could be used to determine the annual and seasonal baseflow index (BFI). The BFI represents the baseflow component of river flow and is often used as a proxy indicator for groundwater discharge to a river. Third, the approach presented in the Bua Catchment was upscaled to a larger internationally strategic catchment, the Shire River Basin. Finally, the approach was upscaled to the national scale across Malawi. The results of the Lake Malawi study showed variations occurred in the recession limb between 1900-2016 which were attributed to changes in baseflow in the lake catchment. The changes occurred in years which coincided with either extremely dry or wet conditions in Malawi (1916, 1942, 1948, 2012 and 2013). Whilst, the approach did not provide conclusive results, it highlighted the importance of baseflow to the lake in the context of sustainable water resources management for Malawi. Given the importance of the lake for water supply, further research was required outwith this thesis to quantify the volume of baseflow contribution to the lake from all inflow rivers and evaluate any variations over time. The results from the Bua Catchment, the Shire River Basin and the Malawi studies conclusively showed that the approach was successful when used on the single catchment scale up to the national scale. The approach overcame the challenges typical of the developing world by utilizing sporadic river flow data and free open source tools. Specifically, the approach allowed the determination of annual and seasonal BFI and identification of long-term trends in the BFI data for a total of 68 river gauges across Malawi. This included 6 river gauges assessed as part of the Bua Catchment study and 15 gauges assessed as part of the Shire River Basin study. The results generated new knowledge on the important role of groundwater in sustaining rivers flows across Malawi. This Malawi case study was the first national scale baseflow assessment for the country and data coverage ranged from 11-64 years. The results showed that baseflow in Malawi follows a seasonal pattern with minimal differences between the average annual and average wet season BFI (0.57 and 0.52 respectively). Generally, considerable increases were seen in the dry season BFI (0.97). This indicates that 57%, 52% and 97% of the total Malawi river flow is derived from groundwater in the annual, wet and dry season respectively. Long-term behavioural changes in BFI across all periods were also found. Annually, 10% showed an increasing trend and 16% showed a decreasing trend, which was comparable to the wet season results where 16% showed an increasing trend and 18% showed a decreasing trend. In contrast, in the dry season only 1% showed an increasing trend and 6% showed a decreasing trend. These distinct patterns were also reflected in results of the Bua Catchment and Shire River Basin studies. This thesis has important implications on the sustainable management of water resources. The developed approach is practical, flexible and can be used as an independent assessment tool, or to complement an existing practice or framework. It fills an important gap in the literature by facilitating quantification of temporal variations in baseflow by environmental practitioners in a methodical manner using minimal data and resources. The research outputs also have specific implications for the management of Malawi's water resources. They offer crucial baseline data to support national policy and investment decisions, Integrated Water Resources Management (IWRM) and planning towards Sustainable Development Goal 6
Characteristics of partial discharge under high voltage AC & DC conditions
Get PDFHigh voltage AC has been the technology of choice for electricity transmission since the creation of electric grids throughout the world. However due to a wide range of factors, including the availability of new AC-DC and DC-AC converter designs, an increasing requirement for subsea interconnections for off-shore wind and continental super-grids, a greater emphasis on efficient operation for cost and environmental reasons, and a desire for ever-increasing transmission distances, high voltage DC is increasingly seen as an attractive and viable choice. While HVDC technologies have existed for as long as HVAC, their lack of significant use until recently mean that several gaps in knowledge exist, including in the area of condition monitoring of assets. One such condition monitoring technology is partial discharge monitoring, which, while it is a mature technology that is frequently used in AC systems, it has had limited deployment under DC conditions. As such it still lacks the field experience, well-developed standards, technical expertise, and overall knowledge base for DC that exists for AC. This thesis presents research into the characteristics of partial discharge under both AC and DC conditions. A review of relevant literature is presented, followed by the research methodology, including the use of thin film polymer samples, and a 'coring' method for introducing an artificial void into a cable sample. Data and analysis are then presented which compare the presentation of PD in different materials, the impact of multiple void configurations on PD, and statistical analysis of the PD pulses themselves. These analyses demonstrate clear differences between the behaviour of PD, and the characteristics of the PD pulses themselves, under the different voltage types, void configurations, and materials investigated, with potential reasons for these differences discussed, and suggestions made for how knowledge of these differences should affect the detection of PD, and, therefore improve condition monitoring of both AC and DC equipment.High voltage AC has been the technology of choice for electricity transmission since the creation of electric grids throughout the world. However due to a wide range of factors, including the availability of new AC-DC and DC-AC converter designs, an increasing requirement for subsea interconnections for off-shore wind and continental super-grids, a greater emphasis on efficient operation for cost and environmental reasons, and a desire for ever-increasing transmission distances, high voltage DC is increasingly seen as an attractive and viable choice. While HVDC technologies have existed for as long as HVAC, their lack of significant use until recently mean that several gaps in knowledge exist, including in the area of condition monitoring of assets. One such condition monitoring technology is partial discharge monitoring, which, while it is a mature technology that is frequently used in AC systems, it has had limited deployment under DC conditions. As such it still lacks the field experience, well-developed standards, technical expertise, and overall knowledge base for DC that exists for AC. This thesis presents research into the characteristics of partial discharge under both AC and DC conditions. A review of relevant literature is presented, followed by the research methodology, including the use of thin film polymer samples, and a 'coring' method for introducing an artificial void into a cable sample. Data and analysis are then presented which compare the presentation of PD in different materials, the impact of multiple void configurations on PD, and statistical analysis of the PD pulses themselves. These analyses demonstrate clear differences between the behaviour of PD, and the characteristics of the PD pulses themselves, under the different voltage types, void configurations, and materials investigated, with potential reasons for these differences discussed, and suggestions made for how knowledge of these differences should affect the detection of PD, and, therefore improve condition monitoring of both AC and DC equipment
Structure-guided discovery of a novel steroid-derived family of autotaxin inhibitors based on endogenous allosteric modulators
No full textAutotaxin (ATX) facilitates the hydrolysis of lysophosphatidyl choline to lysophosphatidic acid, a bioactive signalling lipid, which acts on its cognate receptors to facilitate a diverse range of cellular effects in multiple tissues. Abnormal LPA expression can lead to the progression of diseases such as cancer and fibrosis. Modulation of ATX has been predominantly based around the generation of orthosteric or “Type I” inhibitors, which structurally mimic the natural substrate, LPA (Figure 1). However, despite being active, their therapeutic development has been limited. Progress in inhibitor diversification has recently led to the evolution of potent hybrid inhibitors binding in both the tunnel and pocket of ATX, which fall into the class of “Type IV” inhibitors. Collaboration between Netherlands Cancer Institute and University of Strathclyde has facilitated the development of a novel class of inhibitors which can be confidently designated as first-in-class “Type V” inhibitors (Figure 2), the design, synthesis and biological evaluation of which will be described in this thesis. Amalgamation of key structural features from two comprehensive historical design hypotheses, based on both endogenous allosteric modulators and competitive orthosteric inhibitors, has led to the discovery of steroid-derived inhibitors armed with a key warhead pharmacophore, capable of interacting with the tunnel and active site of ATX. Our binding hypothesis has been corroborated with three crystallographic structures of potent exemplar compounds bound to ATX, one of which we additionally disclose as a novel zinc binder with comparable potency to our lead analogue. Further confirmatory studies have been undertaken through ATX kinetics, cell-based analysis and phenotypic studies in order to ascertain the fate of these novel compounds in the downstream signalling cascade and also in a disease-relevant context. Our lead compounds act through competitive inhibition of ATX and achieve modulation of LPA mediated ATX allostery and inhibition of LPA-dependent signalling pathways in cells, which we believe serves as a solid baseline for further investigation into the impact of ATX in debilitating diseases, such as fibrosis and cancer (Figure 3). [See thesis pp. v-vii for figures]Autotaxin (ATX) facilitates the hydrolysis of lysophosphatidyl choline to lysophosphatidic acid, a bioactive signalling lipid, which acts on its cognate receptors to facilitate a diverse range of cellular effects in multiple tissues. Abnormal LPA expression can lead to the progression of diseases such as cancer and fibrosis. Modulation of ATX has been predominantly based around the generation of orthosteric or “Type I” inhibitors, which structurally mimic the natural substrate, LPA (Figure 1). However, despite being active, their therapeutic development has been limited. Progress in inhibitor diversification has recently led to the evolution of potent hybrid inhibitors binding in both the tunnel and pocket of ATX, which fall into the class of “Type IV” inhibitors. Collaboration between Netherlands Cancer Institute and University of Strathclyde has facilitated the development of a novel class of inhibitors which can be confidently designated as first-in-class “Type V” inhibitors (Figure 2), the design, synthesis and biological evaluation of which will be described in this thesis. Amalgamation of key structural features from two comprehensive historical design hypotheses, based on both endogenous allosteric modulators and competitive orthosteric inhibitors, has led to the discovery of steroid-derived inhibitors armed with a key warhead pharmacophore, capable of interacting with the tunnel and active site of ATX. Our binding hypothesis has been corroborated with three crystallographic structures of potent exemplar compounds bound to ATX, one of which we additionally disclose as a novel zinc binder with comparable potency to our lead analogue. Further confirmatory studies have been undertaken through ATX kinetics, cell-based analysis and phenotypic studies in order to ascertain the fate of these novel compounds in the downstream signalling cascade and also in a disease-relevant context. Our lead compounds act through competitive inhibition of ATX and achieve modulation of LPA mediated ATX allostery and inhibition of LPA-dependent signalling pathways in cells, which we believe serves as a solid baseline for further investigation into the impact of ATX in debilitating diseases, such as fibrosis and cancer (Figure 3). [See thesis pp. v-vii for figures
Development of novel combination strategies for the treatment of pancreatic cancer
Get PDFPancreatic cancer represents the seventh leading cause of cancer mortality globally, and despite the advances in cancer therapy over the last two decades, its prognosis is still poor with the survival rate among patients with pancreatic cancer for five years being less than 5%. This can be attributed to late-stage diagnosis, tumour heterogeneity, early metastasis, high local recurrence risk and resistance to conventional chemotherapy.The current single agent or combination-based therapy approaches for pancreatic cancer have either failed to improve the overall survival or offered a marginal improvement as well as increasing the accompanied adverse events. Therefore, this project investigated, for the first time, novel triple combinations treatment schedules utilising the gold standard current treatment of gemcitabine plus the repurposed tyrosine kinase inhibitors (sunitinib or pazopanib) plus external beam radiation in pancreatic cancer cell lines in vitro and in vivo. We hypothesised that these novel combination strategies would improve anti-tumour efficacy in pancreatic cancer models compared to single or double combination therapies.Our novel combination strategies with lower doses of gemcitabine, sunitinib, and XBR, resulted in greater anticancer efficacy than either treatment alone. The concurrent administration of gemcitabine with sunitinib when administered after radiation (three-treatment schedule 2 combination), showed a synergistic effect and was found to be the most effective combination strategy in our models.Furthermore, our three-treatment combination in an in vivo pancreatic cancer nude mouse xenograft model, was the only combination approach able to shrink the tumours while other treatment strategies only delayed the xenografted pancreatic cancer tumour growth. Of note, all mice in this treatment group were euthanised two days before the end of the experiment (day 18) because of 20% weight loss relative to the initial body weight.Altogether, our findings in this project offer a promising approach for treating pancreatic ductal adenocarcinoma in the clinic. Furthermore, lowering doses of all three agents is warranted to decrease the unfavourable side effects while maintaining anti-tumour activity.Pancreatic cancer represents the seventh leading cause of cancer mortality globally, and despite the advances in cancer therapy over the last two decades, its prognosis is still poor with the survival rate among patients with pancreatic cancer for five years being less than 5%. This can be attributed to late-stage diagnosis, tumour heterogeneity, early metastasis, high local recurrence risk and resistance to conventional chemotherapy.The current single agent or combination-based therapy approaches for pancreatic cancer have either failed to improve the overall survival or offered a marginal improvement as well as increasing the accompanied adverse events. Therefore, this project investigated, for the first time, novel triple combinations treatment schedules utilising the gold standard current treatment of gemcitabine plus the repurposed tyrosine kinase inhibitors (sunitinib or pazopanib) plus external beam radiation in pancreatic cancer cell lines in vitro and in vivo. We hypothesised that these novel combination strategies would improve anti-tumour efficacy in pancreatic cancer models compared to single or double combination therapies.Our novel combination strategies with lower doses of gemcitabine, sunitinib, and XBR, resulted in greater anticancer efficacy than either treatment alone. The concurrent administration of gemcitabine with sunitinib when administered after radiation (three-treatment schedule 2 combination), showed a synergistic effect and was found to be the most effective combination strategy in our models.Furthermore, our three-treatment combination in an in vivo pancreatic cancer nude mouse xenograft model, was the only combination approach able to shrink the tumours while other treatment strategies only delayed the xenografted pancreatic cancer tumour growth. Of note, all mice in this treatment group were euthanised two days before the end of the experiment (day 18) because of 20% weight loss relative to the initial body weight.Altogether, our findings in this project offer a promising approach for treating pancreatic ductal adenocarcinoma in the clinic. Furthermore, lowering doses of all three agents is warranted to decrease the unfavourable side effects while maintaining anti-tumour activity
Phase-sensitive optical spectroscopy of a laser-cooled, microwave atomic clock
Get PDFThis thesis reports on the experimental characterisation of an optically interrogated microwave frequency reference based on a compact source of cold atoms. The work addresses a method of reducing the complexity of cold-atom systems, plus the phase-sensitive optical interrogation of a microwave transition in rubidium.Laser-cooling has provided the means for many significant developments in precision metrology, but the optical apparatus required is often large and bulky.;The grating magneto-optical trap is a promising candidate for the realisation of a field-grade platform, from which we could build a portable atomic clock. The grating-MOT provided 107 rubidium atoms, cooled to sub-Doppler temperatures, as a test-bed for the characterisation of a microwave clock. The microwave interrogation of the ground state frequency splitting was applied optically using Ramsey-like interferometry and coherent population trapping technique in the Lin perpendicular to Lin polarisation scheme. The theory and experimental techniques that were applied in the development of this system are described, and the short-term stability of the unlocked CPT apparatus is presented.This thesis reports on the experimental characterisation of an optically interrogated microwave frequency reference based on a compact source of cold atoms. The work addresses a method of reducing the complexity of cold-atom systems, plus the phase-sensitive optical interrogation of a microwave transition in rubidium.Laser-cooling has provided the means for many significant developments in precision metrology, but the optical apparatus required is often large and bulky.;The grating magneto-optical trap is a promising candidate for the realisation of a field-grade platform, from which we could build a portable atomic clock. The grating-MOT provided 107 rubidium atoms, cooled to sub-Doppler temperatures, as a test-bed for the characterisation of a microwave clock. The microwave interrogation of the ground state frequency splitting was applied optically using Ramsey-like interferometry and coherent population trapping technique in the Lin perpendicular to Lin polarisation scheme. The theory and experimental techniques that were applied in the development of this system are described, and the short-term stability of the unlocked CPT apparatus is presented
Small signal impedance modelling and stability assessment of HVDC systems
No full textWith high penetration of converter interfaced renewable energy and distributed generation, and increased use of HVDC interconnections, the characteristics of power systems is undergoing significantly changes. Interaction between grid-connected converters and networks is likely to increase, which may lead to stability and resonance problems, and in particular, when the grid is "weak" as the relatively high system impedance. Therefore, that is important adequate method is developed for assessing system stability. This thesis presents the small signal impedance modelling of grid-connected 2-level voltage source converters (VSC) and modular multilevel converter (MMC) for system stability assessment.;In the case of 2-level VSC connected to weak grid system, the VSC impedance is mapped into the positive-negative (pn) sequence-frame for ease of analysis, and the stability problem associated with the coupling admittance is studied. It is found that traditional outer-loop controllers (e.g., active/reactive power and AC voltage controllers) create high coupling admittance that has negative impact on system stability. Improved outer-loop controllers are proposed and to improve the system stability which add compensation terms into the d and q-axis at the potential resonance frequency range. Small signal analysis and time domain simulation confirm the effectiveness of the proposed method. Large number of MMC based HVDC systems for interconnection or offshore wind farm integration are already in operation and many more will be installed in the coming years.;MMC has multiple internal harmonics, which causes complex internal dynamics and multifrequency response. To accurately model the multiple frequency response and include all internal harmonics dynamics with MMC, the harmonic state-space (HSS) modeling approach is adopted. A detailed procedure for deriving the small-signal model of single-phase MMC system using HSS modelling approach is presented first. To address the issues related to single-phase MMC modelling including the existence of zero-sequence current and the use of controllers in abc frame, which are not in accordance with practical 3-phase system, impedance modelling and validation of the three-phase MMC based on HSS are conducted. In order to simplify the analysis on the coupling characteristics between different frequencies in MMCs, the proposed model is developed in pn frame, where the zero-sequence current in three-phase three wire system is modelled in a simple way.;A simplified 2 by 2 admittance matrix in pn frame is extracted from the MMC small-signal model for ease of system stability analysis. Different outer-loop controllers, operating points and working mode are adopted and compared in the analysis to illustrate the effects system stability. It is found that for AC grid with single MMC, high PLL bandwidth leads to a less stable system. Compared with inverter mode, MMC in rectifier mode is more likely to induce system instability. Using the developed impedance model, the multi-infeed interaction factor (MIIF) measure is adopted to analyze the interactions for multi-infeed converter systems. Detailed studied are carried out for an AC network with two MMCs considering different MIIIF. Analytical studies and time-domain simulation results show that system with high MIIF where strong couplings between the two MMCs exist may lead to instability.With high penetration of converter interfaced renewable energy and distributed generation, and increased use of HVDC interconnections, the characteristics of power systems is undergoing significantly changes. Interaction between grid-connected converters and networks is likely to increase, which may lead to stability and resonance problems, and in particular, when the grid is "weak" as the relatively high system impedance. Therefore, that is important adequate method is developed for assessing system stability. This thesis presents the small signal impedance modelling of grid-connected 2-level voltage source converters (VSC) and modular multilevel converter (MMC) for system stability assessment.;In the case of 2-level VSC connected to weak grid system, the VSC impedance is mapped into the positive-negative (pn) sequence-frame for ease of analysis, and the stability problem associated with the coupling admittance is studied. It is found that traditional outer-loop controllers (e.g., active/reactive power and AC voltage controllers) create high coupling admittance that has negative impact on system stability. Improved outer-loop controllers are proposed and to improve the system stability which add compensation terms into the d and q-axis at the potential resonance frequency range. Small signal analysis and time domain simulation confirm the effectiveness of the proposed method. Large number of MMC based HVDC systems for interconnection or offshore wind farm integration are already in operation and many more will be installed in the coming years.;MMC has multiple internal harmonics, which causes complex internal dynamics and multifrequency response. To accurately model the multiple frequency response and include all internal harmonics dynamics with MMC, the harmonic state-space (HSS) modeling approach is adopted. A detailed procedure for deriving the small-signal model of single-phase MMC system using HSS modelling approach is presented first. To address the issues related to single-phase MMC modelling including the existence of zero-sequence current and the use of controllers in abc frame, which are not in accordance with practical 3-phase system, impedance modelling and validation of the three-phase MMC based on HSS are conducted. In order to simplify the analysis on the coupling characteristics between different frequencies in MMCs, the proposed model is developed in pn frame, where the zero-sequence current in three-phase three wire system is modelled in a simple way.;A simplified 2 by 2 admittance matrix in pn frame is extracted from the MMC small-signal model for ease of system stability analysis. Different outer-loop controllers, operating points and working mode are adopted and compared in the analysis to illustrate the effects system stability. It is found that for AC grid with single MMC, high PLL bandwidth leads to a less stable system. Compared with inverter mode, MMC in rectifier mode is more likely to induce system instability. Using the developed impedance model, the multi-infeed interaction factor (MIIF) measure is adopted to analyze the interactions for multi-infeed converter systems. Detailed studied are carried out for an AC network with two MMCs considering different MIIIF. Analytical studies and time-domain simulation results show that system with high MIIF where strong couplings between the two MMCs exist may lead to instability
Signal processing and methods for advanced acoustic applications
Get PDFFrom a loudspeaker manufacturer perspective, the intelligibility of sound can be significantly affected on both downstream and upstream side of a loudspeaker production chain, differently. On the downstream side, the sound intelligibility can be affected by characteristics of typical acoustic environments: sound waves are partially reflected by the physical boundaries of the environment leading to reverberation, echo and feedback problems. On the upstream side, the quality of the sound is directly correlated to the quality of the speaker: inspections and quality control protocols are conducted during pre-production, production, and pre-shipment stage to reduce the amount of damaged drivers.;The research presented in this thesis deals with signal processing algorithms in order to develop both robust downstream and upstream solutions of a loudspeaker production chain, providing increased performance and sound quality for advanced acoustic systems in realistic conditions.;On the downstream side of a loudspeaker production chain, the acoustic feedback problem is considered and a novel algorithm for the adaptive feedback cancellation in a single acoustic MIMO array is proposed. When a microphone is too close to the loudspeaker or the amplification is too large, acoustic feedback can occur where acoustic effects are perceived as howling and ringing, degrading sound intelligibility and sound quality.;While the canonical methods (automatic gain control, notch filtering, phase modulation) provide a reactive solution with limited performance, gain and high computational complexity, the new framework namely, Partitioned Block Frequency Domain (PBFD) based Adaptive Feedback Cancellation (AFC) method, is able to tackle the acoustic feedback problem in large acoustic spaces. The results of the proposed framework is compared with the state of the art using real acoustic data showing superior performance with up to 18dB of Maximum Stable Gain (MSG) and 30 seconds less convergence time.;On the upstream side of a loudspeaker production chain, the use of radar micro-Doppler for loudspeaker analysis is introduced for the first time. This approach offers the potential benefits to characterize the mechanical motion of a loudspeaker and identify defects. Increasing quality checks at various stages of production (with limited costs) can provide substantial benefits to loudspeaker manufacturers. Compared with acoustic based approaches, the use of a radar allows reliable measurements in an acoustically noisy end of production line. In addition, when compared to a laser vibrometric approach the use of radar micro-Doppler reduces the number of measurements required and provides direct access to the information of the metallic components of the loudspeaker.;Following the modelling of the radar return from the loudspeaker, a procedure to extract mechanically impaired features of the loudspeaker motion is introduced. Results show the ability to detect the linear and harmonic frequency responses of both good and defected speakers. These are used as features of a Bidirectional Long Short-Term Memory (BiLSTM) Recurrent Neural Network (RNN) classifier, leading to classification accuracy above the 98% on real data.From a loudspeaker manufacturer perspective, the intelligibility of sound can be significantly affected on both downstream and upstream side of a loudspeaker production chain, differently. On the downstream side, the sound intelligibility can be affected by characteristics of typical acoustic environments: sound waves are partially reflected by the physical boundaries of the environment leading to reverberation, echo and feedback problems. On the upstream side, the quality of the sound is directly correlated to the quality of the speaker: inspections and quality control protocols are conducted during pre-production, production, and pre-shipment stage to reduce the amount of damaged drivers.;The research presented in this thesis deals with signal processing algorithms in order to develop both robust downstream and upstream solutions of a loudspeaker production chain, providing increased performance and sound quality for advanced acoustic systems in realistic conditions.;On the downstream side of a loudspeaker production chain, the acoustic feedback problem is considered and a novel algorithm for the adaptive feedback cancellation in a single acoustic MIMO array is proposed. When a microphone is too close to the loudspeaker or the amplification is too large, acoustic feedback can occur where acoustic effects are perceived as howling and ringing, degrading sound intelligibility and sound quality.;While the canonical methods (automatic gain control, notch filtering, phase modulation) provide a reactive solution with limited performance, gain and high computational complexity, the new framework namely, Partitioned Block Frequency Domain (PBFD) based Adaptive Feedback Cancellation (AFC) method, is able to tackle the acoustic feedback problem in large acoustic spaces. The results of the proposed framework is compared with the state of the art using real acoustic data showing superior performance with up to 18dB of Maximum Stable Gain (MSG) and 30 seconds less convergence time.;On the upstream side of a loudspeaker production chain, the use of radar micro-Doppler for loudspeaker analysis is introduced for the first time. This approach offers the potential benefits to characterize the mechanical motion of a loudspeaker and identify defects. Increasing quality checks at various stages of production (with limited costs) can provide substantial benefits to loudspeaker manufacturers. Compared with acoustic based approaches, the use of a radar allows reliable measurements in an acoustically noisy end of production line. In addition, when compared to a laser vibrometric approach the use of radar micro-Doppler reduces the number of measurements required and provides direct access to the information of the metallic components of the loudspeaker.;Following the modelling of the radar return from the loudspeaker, a procedure to extract mechanically impaired features of the loudspeaker motion is introduced. Results show the ability to detect the linear and harmonic frequency responses of both good and defected speakers. These are used as features of a Bidirectional Long Short-Term Memory (BiLSTM) Recurrent Neural Network (RNN) classifier, leading to classification accuracy above the 98% on real data
HRM and performance in the public sector : the role of line managers and employee perception in HRM implementation
Get PDFThe New Public Management (NPM) movement emphasises performance, efficiency and effectiveness based on the principle that public organisations perform better when private sector management practices are implemented. The adoption of the NPM model in the public sector has led to the application of a more strategic approach to managing the workforce. There has been growing research on the positive impact of HRM on performance in the public sector. However, the majority of public sector HRM performance research focuses on HRM practices as a mechanism for improving performance. Little is known about the implementation of HRM practices and employees' perception of them. This thesis aims to fill this gap by focusing on the role of line managers in HRM implementation and employee perceptions of HRM systems of practices in the Malaysian public sector. In a multilevel study of 86 line managers and 453 employees obtained from various working units of two Malaysian public sector organisations, this study tested hypotheses about the relationships between line managers' ability, motivation and opportunity to implement HRM practices, employee perceptions of HRM, and perceived effectiveness of HRM implementation and unit performance. The moderating effects of employee perception of the HRM system, examining the dimensions of distinctiveness, consistency and consensus around HRM practices, was also examined. The study contributes to a better understanding of the implementation of strategic HRM in the public sector specifically on the importance of line manager ability, motivation and opportunity and the applicability of NPM in a non-western cultural context.The New Public Management (NPM) movement emphasises performance, efficiency and effectiveness based on the principle that public organisations perform better when private sector management practices are implemented. The adoption of the NPM model in the public sector has led to the application of a more strategic approach to managing the workforce. There has been growing research on the positive impact of HRM on performance in the public sector. However, the majority of public sector HRM performance research focuses on HRM practices as a mechanism for improving performance. Little is known about the implementation of HRM practices and employees' perception of them. This thesis aims to fill this gap by focusing on the role of line managers in HRM implementation and employee perceptions of HRM systems of practices in the Malaysian public sector. In a multilevel study of 86 line managers and 453 employees obtained from various working units of two Malaysian public sector organisations, this study tested hypotheses about the relationships between line managers' ability, motivation and opportunity to implement HRM practices, employee perceptions of HRM, and perceived effectiveness of HRM implementation and unit performance. The moderating effects of employee perception of the HRM system, examining the dimensions of distinctiveness, consistency and consensus around HRM practices, was also examined. The study contributes to a better understanding of the implementation of strategic HRM in the public sector specifically on the importance of line manager ability, motivation and opportunity and the applicability of NPM in a non-western cultural context
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