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Characterisation of microglia's inflammatory response and investigation of the effect of mesenchymal stem cells-conditioned media
Get PDFStroke is the second single most common cause of death and the largest cause of disability worldwide, highlighting the urgent need for new treatments. Mesenchymal stem cell transplantation aids regeneration and repair in animal models of ischaemia, possibly, at least in part, via interaction with microglia, modulating their inflammatory response into an anti-inflammatory phenotype favouring regeneration. Evidence shows that the beneficial effects of cell therapy are due to the release of soluble factors, raising the possibility of cell-free therapeutic strategy. Our collaborators on the current project, Pischuitta et al., (2016) recently provided evidence of the comparable effects of human amniotic stem cells (hAMSC) and hAMSC-conditioned media. They found that both hAMSC and hAMSC-CM treatments induced upregulation of the microglia marker, CD11b. In order to investigate the potential for hAMSC-CM to modulate microglia, several in vitro and in vivo approaches were utilised. The aims of this thesis were to characterise the signalling and polarisation of SIM-A9cells; establish a consistent protocol for the isolation of highly pure microglia from the mouse brain; establish and optimise an in vitro microglia migration model; and to examine the effects of hAMSC-CM on SIM-A9 cells microglial cells on signalling, polarisation and migration in vitro and on polarisation in vivo. The results revealed the ability of SIM-A9 microglial cells to be polarised in to a pro-inflammatory phenotype (induced with LPS), with the expression of pro-inflammatory genes II1B and Nos2 significantly increasing; as well as an anti-inflammatory phenotype (induced with IL-4), which led to the expression of the anti-inflammatory gene, Arg1 to significantly increase. Protocols used to extract primary microglia from the neonatal and adult mouse did not produce purity, reproducibility or good survival in culture. We showed that the addition of hAMSC-CM significantly reduced mRNA expression of II1B Tnfa and CcI2 in LPS-induced microglia. Using a multi-disciplinary approach, an in vitro microglia migration model that is a better representation of the stroke environment was established, optimised and characterised. This work showed that LPS significantly inhibited glutamate-induced migration of microglial cells, while IL-4 treatment enhanced migration. Interestingly, addition of hAMSC-CM reversed the inhibitory effect of LPS on glutamate-induced migration. Translating our in vitro findings in vivo, we then investigated the effect of hAMSC-CM after stroke, using the mouse stroke model. It was concluded that hAMSC-CM, injected 3 hours after stroke, had no effect on inflammatory markers after 24 hours of recovery. In conclusion, we have shown that hAMSC-CM can modulate microglial cells from apro-inflammatory phenotype into an anti-inflammatory phenotype. Therefore, hAMSC-CM has an anti-inflammatory effect that may be beneficial after stroke.Stroke is the second single most common cause of death and the largest cause of disability worldwide, highlighting the urgent need for new treatments. Mesenchymal stem cell transplantation aids regeneration and repair in animal models of ischaemia, possibly, at least in part, via interaction with microglia, modulating their inflammatory response into an anti-inflammatory phenotype favouring regeneration. Evidence shows that the beneficial effects of cell therapy are due to the release of soluble factors, raising the possibility of cell-free therapeutic strategy. Our collaborators on the current project, Pischuitta et al., (2016) recently provided evidence of the comparable effects of human amniotic stem cells (hAMSC) and hAMSC-conditioned media. They found that both hAMSC and hAMSC-CM treatments induced upregulation of the microglia marker, CD11b. In order to investigate the potential for hAMSC-CM to modulate microglia, several in vitro and in vivo approaches were utilised. The aims of this thesis were to characterise the signalling and polarisation of SIM-A9cells; establish a consistent protocol for the isolation of highly pure microglia from the mouse brain; establish and optimise an in vitro microglia migration model; and to examine the effects of hAMSC-CM on SIM-A9 cells microglial cells on signalling, polarisation and migration in vitro and on polarisation in vivo. The results revealed the ability of SIM-A9 microglial cells to be polarised in to a pro-inflammatory phenotype (induced with LPS), with the expression of pro-inflammatory genes II1B and Nos2 significantly increasing; as well as an anti-inflammatory phenotype (induced with IL-4), which led to the expression of the anti-inflammatory gene, Arg1 to significantly increase. Protocols used to extract primary microglia from the neonatal and adult mouse did not produce purity, reproducibility or good survival in culture. We showed that the addition of hAMSC-CM significantly reduced mRNA expression of II1B Tnfa and CcI2 in LPS-induced microglia. Using a multi-disciplinary approach, an in vitro microglia migration model that is a better representation of the stroke environment was established, optimised and characterised. This work showed that LPS significantly inhibited glutamate-induced migration of microglial cells, while IL-4 treatment enhanced migration. Interestingly, addition of hAMSC-CM reversed the inhibitory effect of LPS on glutamate-induced migration. Translating our in vitro findings in vivo, we then investigated the effect of hAMSC-CM after stroke, using the mouse stroke model. It was concluded that hAMSC-CM, injected 3 hours after stroke, had no effect on inflammatory markers after 24 hours of recovery. In conclusion, we have shown that hAMSC-CM can modulate microglial cells from apro-inflammatory phenotype into an anti-inflammatory phenotype. Therefore, hAMSC-CM has an anti-inflammatory effect that may be beneficial after stroke
Finite element analysis and structural optimisation of a concrete mixer
Get PDFThe UK concrete transport industry desires low weight concrete mixers in order to maximise payload. To investigate the potential for weight reduction of the mixer unit itself, three key structures of a particular mixer have been analysed using Finite Element Analysis; the front drum support structure, rear drum support structure, and the sub-frame.A full scale 'dynamic load test' has been documented. This involved recording data from 20 strain gauges and 2 accelerometers attached to a concrete mixer. The three main load cases investigated during this test were bump/pothole loads, braking loads, and 'downhill' loads. The results are presented and discussed with a view to understanding the load paths through the whole structure. The data has provided a solid foundation for future work which could focus on specific areas. A test to investigate the differences in elastic properties of holding down U-bolts versus straight bolts has also been documented as these components facilitate the main load path between the supports and the chassis. Recommended practices for implementing a Design by Analysis process are discussed.A redesign of the front drum support has allowed two sub-frame stiffening plates to be removed. This revised front support is 21% lighter than the combination of the existing front support and the stiffening plates. An optimisation study of the existing rear drum support has resulted in a reduction in the weight of this structure by 26%. The sub-frame was not lightened due to this being difficult to achieve without decreasing stiffness, which is already relatively low. However, some basic analysis has been done to examine the design of the brackets that secures the sub-frame to the chassis.This work has shown that there is scope to reduce the weight of truck-mounted concrete mixers. In this industry, applying a comprehensive Design by Analysis process would significantly increase the profits achievable by companies involved in the transport of concrete. Concrete mixer manufacturers and similar SME's should consider this approach; however it must be ensured that the capabilities of FEA are fully understood before making a business case. Furthermore, it is vital to the success of the process that the engineers using the software are suitably trained or experienced.The UK concrete transport industry desires low weight concrete mixers in order to maximise payload. To investigate the potential for weight reduction of the mixer unit itself, three key structures of a particular mixer have been analysed using Finite Element Analysis; the front drum support structure, rear drum support structure, and the sub-frame.A full scale 'dynamic load test' has been documented. This involved recording data from 20 strain gauges and 2 accelerometers attached to a concrete mixer. The three main load cases investigated during this test were bump/pothole loads, braking loads, and 'downhill' loads. The results are presented and discussed with a view to understanding the load paths through the whole structure. The data has provided a solid foundation for future work which could focus on specific areas. A test to investigate the differences in elastic properties of holding down U-bolts versus straight bolts has also been documented as these components facilitate the main load path between the supports and the chassis. Recommended practices for implementing a Design by Analysis process are discussed.A redesign of the front drum support has allowed two sub-frame stiffening plates to be removed. This revised front support is 21% lighter than the combination of the existing front support and the stiffening plates. An optimisation study of the existing rear drum support has resulted in a reduction in the weight of this structure by 26%. The sub-frame was not lightened due to this being difficult to achieve without decreasing stiffness, which is already relatively low. However, some basic analysis has been done to examine the design of the brackets that secures the sub-frame to the chassis.This work has shown that there is scope to reduce the weight of truck-mounted concrete mixers. In this industry, applying a comprehensive Design by Analysis process would significantly increase the profits achievable by companies involved in the transport of concrete. Concrete mixer manufacturers and similar SME's should consider this approach; however it must be ensured that the capabilities of FEA are fully understood before making a business case. Furthermore, it is vital to the success of the process that the engineers using the software are suitably trained or experienced
Reconsidering environmental attribution and resource costs of common pool resources : applications of environmental input-output (IO) analysis
Get PDFIn this thesis, I apply environmental input-output (IO) methods to evaluate some impacts of economic activity on the environment and the associated economy-wide implications of using the environment to meet some economic needs. The core of this thesis comprises of three independent but related chapters or papers (Chapter 2, 3 & 4). Each of these core chapters focuses on developing methods to answer key policy questions so that policy makers may be provided with a better understanding of the impacts of economic activities on the environment.;In the first core chapter (Chapter 2), the environmental IO approach is considered as a means of examining the nature of externalities via pollution generation and of attributing, as a case study, physical waste generated to production and consumption economic activity. The chapter addresses the policy-relevant question of what economic sectors may ultimately be considered responsible for waste generation and the final consumption patterns, which drive that production and in turn waste pressures in Scotland.;In the second core chapter (Chapter 3), the environmental IO model is applied to model and incorporate the resource implications of negative externalities from waste generation into economic processes. It builds on a previous but inconclusive study on this issue, here using improved data.;The chapter addresses a key policy issue regarding identifying the implications if the direct polluter pays or does not pay for waste management implied by their waste generation and, in either case, who ultimately bears the cost for the provision of waste management services within the economy;In the third core chapter (Chapter 4), the environmental IO model is applied in a novel way to consider the case of supplying a physical resource like water (as opposed to providing a clean environment as in the event of pollution or waste generation). The chapter addresses key policy issues regarding the causes and implications of the deviation between actual expenditure for the output of the water sector and actual physical water use.;More generally, this thesis makes empirical and analytical improvements to the application of the Leontief, (1970) environmental IO model, a seminal theoretical contribution in terms of the resource cost of environmental protection and provision of common pool resources.In this thesis, I apply environmental input-output (IO) methods to evaluate some impacts of economic activity on the environment and the associated economy-wide implications of using the environment to meet some economic needs. The core of this thesis comprises of three independent but related chapters or papers (Chapter 2, 3 & 4). Each of these core chapters focuses on developing methods to answer key policy questions so that policy makers may be provided with a better understanding of the impacts of economic activities on the environment.;In the first core chapter (Chapter 2), the environmental IO approach is considered as a means of examining the nature of externalities via pollution generation and of attributing, as a case study, physical waste generated to production and consumption economic activity. The chapter addresses the policy-relevant question of what economic sectors may ultimately be considered responsible for waste generation and the final consumption patterns, which drive that production and in turn waste pressures in Scotland.;In the second core chapter (Chapter 3), the environmental IO model is applied to model and incorporate the resource implications of negative externalities from waste generation into economic processes. It builds on a previous but inconclusive study on this issue, here using improved data.;The chapter addresses a key policy issue regarding identifying the implications if the direct polluter pays or does not pay for waste management implied by their waste generation and, in either case, who ultimately bears the cost for the provision of waste management services within the economy;In the third core chapter (Chapter 4), the environmental IO model is applied in a novel way to consider the case of supplying a physical resource like water (as opposed to providing a clean environment as in the event of pollution or waste generation). The chapter addresses key policy issues regarding the causes and implications of the deviation between actual expenditure for the output of the water sector and actual physical water use.;More generally, this thesis makes empirical and analytical improvements to the application of the Leontief, (1970) environmental IO model, a seminal theoretical contribution in terms of the resource cost of environmental protection and provision of common pool resources
Harmonic analysis in power network with renewable power generator
Get PDFConsidering the rapidly rising cost of primary fuel for electricity generation and the extensive concern of the international community for global warning, electricity generation with renewable sources has been actively developed all over the world. A large number of renewable energy generators, more highly sensitive electronic equipment and more electronics or microprocessor controllers are used in the power system. It has brought new challenges to supply quality, and thus the study of Power Quality (PQ) has become obviously important. Harmonic analysis plays an important role in PQ study because harmonic has great influence on the power system equipment as well as on their operation. Harmonics can lead to operation failure of electrical and electronic components, overheating of neutral wires and transformer, failure of power factor correction capacitors, loss in power generation and transmission, and interference with protection, control and communication networks as well as customer loads. Therefore, developing an advanced PQ disturbances classification system and a more accurate harmonic analysis method is the key of this thesis. It is necessary to determine the sources and causes of such disturbances to solve PQ problems. When the type of disturbance has been classified accurately, PQ engineers can define the major effects at the load and analyse the source of the disturbances. Many approaches based on Fourier Transform (FT) and neural network for the classification of PQ disturbance have been developed in the last few years. The key factor of these methods is that the correct rate for the actual event is not high enough and thus there is still space to improve accuracy. In this thesis, a fuzzy-expert system based on Wavelet Transforms (WT) to classify power supply waveforms into different groups or categories for PQ classification is proposed with the aim which is to classify the disturbance type with higher accuracy. A new approach for the evaluation of harmonic contents of power system waveforms is also proposed in [sic] thesis. The conventional harmonic analysis method is Fourier analysis. However, Fourier analysis provides signals which are mainly localised in the frequency domain and it gives limited information of the signals in the time domain. Furthermore, the FT cannot obtain accurate values of amplitude and phases from harmonics with frequencies different from that of the window function frequency. In order to overcome the limitations of Fourier analysis and obtain better results, wavelet analysis has been proposed. A novel harmonic analysis method using Discrete Wavelet Packet Transform (DWPT) filter bank decomposition and Continuous Wavelet Transform (CWT) identification has been proposed. In order to evaluate the performance and result of the proposed analysis method, another two conventional methods, i.e. Fast Fourier Transform (FFT) and the combination method of Discrete Wavelet Transform (DWT) filter bank and CWT calculation, are compared through a large number of identical applications. Based on the harmonic analysis, the harmonic penetration is considered and its effects to power networks with increasing of renewable power generations are investigated. With increasing of renewable generators in power networks, it creates PQ problems caused by harmonic injections with a large frequency range, such as integer-harmonics, inter-harmonics and sub-harmonics. Therefore, the steady state harmonic power flow in power system with discrete frequencies is calculated with Root Mean Square (RMS) values of bus current and voltage magnitudes and Total Harmonic Voltage Distortion (THDv) values. Variable of tests are designed to investigate the effects to the harmonic penetration with multiple types of harmonic sources in power networks.Considering the rapidly rising cost of primary fuel for electricity generation and the extensive concern of the international community for global warning, electricity generation with renewable sources has been actively developed all over the world. A large number of renewable energy generators, more highly sensitive electronic equipment and more electronics or microprocessor controllers are used in the power system. It has brought new challenges to supply quality, and thus the study of Power Quality (PQ) has become obviously important. Harmonic analysis plays an important role in PQ study because harmonic has great influence on the power system equipment as well as on their operation. Harmonics can lead to operation failure of electrical and electronic components, overheating of neutral wires and transformer, failure of power factor correction capacitors, loss in power generation and transmission, and interference with protection, control and communication networks as well as customer loads. Therefore, developing an advanced PQ disturbances classification system and a more accurate harmonic analysis method is the key of this thesis. It is necessary to determine the sources and causes of such disturbances to solve PQ problems. When the type of disturbance has been classified accurately, PQ engineers can define the major effects at the load and analyse the source of the disturbances. Many approaches based on Fourier Transform (FT) and neural network for the classification of PQ disturbance have been developed in the last few years. The key factor of these methods is that the correct rate for the actual event is not high enough and thus there is still space to improve accuracy. In this thesis, a fuzzy-expert system based on Wavelet Transforms (WT) to classify power supply waveforms into different groups or categories for PQ classification is proposed with the aim which is to classify the disturbance type with higher accuracy. A new approach for the evaluation of harmonic contents of power system waveforms is also proposed in [sic] thesis. The conventional harmonic analysis method is Fourier analysis. However, Fourier analysis provides signals which are mainly localised in the frequency domain and it gives limited information of the signals in the time domain. Furthermore, the FT cannot obtain accurate values of amplitude and phases from harmonics with frequencies different from that of the window function frequency. In order to overcome the limitations of Fourier analysis and obtain better results, wavelet analysis has been proposed. A novel harmonic analysis method using Discrete Wavelet Packet Transform (DWPT) filter bank decomposition and Continuous Wavelet Transform (CWT) identification has been proposed. In order to evaluate the performance and result of the proposed analysis method, another two conventional methods, i.e. Fast Fourier Transform (FFT) and the combination method of Discrete Wavelet Transform (DWT) filter bank and CWT calculation, are compared through a large number of identical applications. Based on the harmonic analysis, the harmonic penetration is considered and its effects to power networks with increasing of renewable power generations are investigated. With increasing of renewable generators in power networks, it creates PQ problems caused by harmonic injections with a large frequency range, such as integer-harmonics, inter-harmonics and sub-harmonics. Therefore, the steady state harmonic power flow in power system with discrete frequencies is calculated with Root Mean Square (RMS) values of bus current and voltage magnitudes and Total Harmonic Voltage Distortion (THDv) values. Variable of tests are designed to investigate the effects to the harmonic penetration with multiple types of harmonic sources in power networks
Probabilistic modelling of the process of evacuation for ship crises management
Get PDFEvacuation analysis of passenger ships is mandatory since June 2016 for all passenger ships as prescribed by the International Maritime Organisation (IMO) in the revised guidelines for evacuation analysis (MSC.Circ.1533). The advanced evacuation analysis defined in the IMO guidelines, relies on the usage of computer models to simulate the movement of people and their interactions with the environment and the other evacuees. These models are powerful tools which allow for a detailed representation of theEnvironment and the people specific characteristics and behaviour. Setting up and running simulations is a very time consuming process and the bigger and more complex the ship or building is, the longer it takes. In situations when time is critical such as during emergencies and when a fast assessment of theevacuation time is needed, then relying on evacuation simulation tools might not be an option. Having a simplified model that can capture the different factors influencing the evacuation process and predict the total evacuation time would be a real advantage. In the research presented here, an attempt to develop such a simplified model has been made. The work undertaken during this research focused on investigating the possibility to derive a parametric model that could be simple enough to produce fast estimates of evacuation times but also capture the different elements of the evacuation process to satisfactory accuracy. Different parametric models were investigated. The nature of the problem led to investigate arrival processes, which were a good candidate for the underlying model explaining the evacuation of passengers. A close analysis showed that a Batch Non-Homogeneous Poisson Process (Batch NHPP) was needed to model the problem at hand. The batch arrivals and the NHPP are independent of each other so they were modelled and studied separately. The data used in this research came from a number of simulations (8 000 individual runs) performed with the Evacuation simulation software Evi as well as from the validation dataset produced by the EU-funded project SAFEGUARD and its associated Evi simulation runs (about 200 runs). The work was split between the fitting of the batch sizes of the arrivals and the NHPP. A complete analysis of the data was performed. The fitting of the batch sizes as well as the arrivals with the selected models produced very good results. Then, using the fitted models, new data was generated and analysed. The results were compared to the original data for both the batch sizes and the NHPP.Evacuation analysis of passenger ships is mandatory since June 2016 for all passenger ships as prescribed by the International Maritime Organisation (IMO) in the revised guidelines for evacuation analysis (MSC.Circ.1533). The advanced evacuation analysis defined in the IMO guidelines, relies on the usage of computer models to simulate the movement of people and their interactions with the environment and the other evacuees. These models are powerful tools which allow for a detailed representation of theEnvironment and the people specific characteristics and behaviour. Setting up and running simulations is a very time consuming process and the bigger and more complex the ship or building is, the longer it takes. In situations when time is critical such as during emergencies and when a fast assessment of theevacuation time is needed, then relying on evacuation simulation tools might not be an option. Having a simplified model that can capture the different factors influencing the evacuation process and predict the total evacuation time would be a real advantage. In the research presented here, an attempt to develop such a simplified model has been made. The work undertaken during this research focused on investigating the possibility to derive a parametric model that could be simple enough to produce fast estimates of evacuation times but also capture the different elements of the evacuation process to satisfactory accuracy. Different parametric models were investigated. The nature of the problem led to investigate arrival processes, which were a good candidate for the underlying model explaining the evacuation of passengers. A close analysis showed that a Batch Non-Homogeneous Poisson Process (Batch NHPP) was needed to model the problem at hand. The batch arrivals and the NHPP are independent of each other so they were modelled and studied separately. The data used in this research came from a number of simulations (8 000 individual runs) performed with the Evacuation simulation software Evi as well as from the validation dataset produced by the EU-funded project SAFEGUARD and its associated Evi simulation runs (about 200 runs). The work was split between the fitting of the batch sizes of the arrivals and the NHPP. A complete analysis of the data was performed. The fitting of the batch sizes as well as the arrivals with the selected models produced very good results. Then, using the fitted models, new data was generated and analysed. The results were compared to the original data for both the batch sizes and the NHPP
Solving crew scheduling problem in offshore supply vessels : heuristics and decomposition methods
Get PDFFor the efficient utilisation of resources in various transportation settings, scheduling is a significant area of research. Having crew as the main resource for operation maintenance, scheduling crew have been a powerful decision making tool for optimisation studies. This research provides a detailed real case study analysis regarding the difficulties in planning crew in maritime industry. As a special case study, this thesis researches crew scheduling in offshore supply vessels which are used for specific operations of a global scaled company in oil and gas industry deeply with modified formulations, heuristics and decomposition methods.An extended version of computational study for a simple formulation approach (Task Based Model) is applied as deeper analysis to Leggate (2016). Afterwards, more realistic approach to the same problem is revised. Following the revision, a customized and thorough computational study on the heuristic method with various settings is designed and implemented in C++. After elaborated analysis completed on the suggested models firstly, a modification on Time Windows model is presented to increase the efficacy. This modification provides a sharp decrease in upper bounds within a short time compared to the previously suggested models. Through this suggestion, more economic schedules within a short period of time are generated.Achieving high performances from the modified model, an application of a decomposition algorithm is provided. We implemented a hybrid solution of Benders Decomposition with a customized heuristic for the modified model. Although this hybrid solution does not provide high quality solutions, it evaluates the performance of possible decomposed models with potential improvements for future research. An introduction to robust crew scheduling in maritime context is also given with a description of resources of uncertainty in this concept and initial robust formulations are suggested.For the efficient utilisation of resources in various transportation settings, scheduling is a significant area of research. Having crew as the main resource for operation maintenance, scheduling crew have been a powerful decision making tool for optimisation studies. This research provides a detailed real case study analysis regarding the difficulties in planning crew in maritime industry. As a special case study, this thesis researches crew scheduling in offshore supply vessels which are used for specific operations of a global scaled company in oil and gas industry deeply with modified formulations, heuristics and decomposition methods.An extended version of computational study for a simple formulation approach (Task Based Model) is applied as deeper analysis to Leggate (2016). Afterwards, more realistic approach to the same problem is revised. Following the revision, a customized and thorough computational study on the heuristic method with various settings is designed and implemented in C++. After elaborated analysis completed on the suggested models firstly, a modification on Time Windows model is presented to increase the efficacy. This modification provides a sharp decrease in upper bounds within a short time compared to the previously suggested models. Through this suggestion, more economic schedules within a short period of time are generated.Achieving high performances from the modified model, an application of a decomposition algorithm is provided. We implemented a hybrid solution of Benders Decomposition with a customized heuristic for the modified model. Although this hybrid solution does not provide high quality solutions, it evaluates the performance of possible decomposed models with potential improvements for future research. An introduction to robust crew scheduling in maritime context is also given with a description of resources of uncertainty in this concept and initial robust formulations are suggested
Governing in authoritarian regimes : a study of speeches, ministerial portfolios and budget allocations during Qadhafi's rule in Libya
No full textFeeder reconfiguration on distribution network considering harmonics
Get PDFOne of the most important measures that can be employed to enhance the supply reliability and quality of electrical energy in a distribution network is feeder reconfiguration. Many studies have been conducted in this area, but only a minor proportion have considered the concept of system harmonics in feeder reconfiguration. In recent years, an increasing number of invertor/converter-based renewable generators are being connected to the distribution network, and given that these generators are harmonic sources, it is important to consider the impacts of the system harmonics in the feeder reconfiguration. Load flow analysis is used to determine a suitable network structure for specific purposes in the feeder reconfiguration problem. In this thesis, a new load flow method is proposed based on the backward/forward sweep method. This method can analyse distribution network load flow under both fundamental and harmonic conditions with distributed generators. Following this, a hybrid optimization method is proposed based on the salient features of the ant colony system and particle swarm optimization. This hybrid method has a higher searching accuracy performance for feeder reconfiguration when compared, on test system, with the ant colony system and particle swarm optimization. Finally, a 118 mid-voltage level distribution system is used to investigate the impacts of renewable generators and system harmonics. The test results verify that system harmonics will have a significant influence on feeder reconfiguration and, consequently, cannot be ignored. Furthermore, other factors including the different capacities of renewable generators, fluctuations in load demands over 24 hours, and the variable output of the renewable generators in different seasons are also investigated in the feeder reconfiguration problem.One of the most important measures that can be employed to enhance the supply reliability and quality of electrical energy in a distribution network is feeder reconfiguration. Many studies have been conducted in this area, but only a minor proportion have considered the concept of system harmonics in feeder reconfiguration. In recent years, an increasing number of invertor/converter-based renewable generators are being connected to the distribution network, and given that these generators are harmonic sources, it is important to consider the impacts of the system harmonics in the feeder reconfiguration. Load flow analysis is used to determine a suitable network structure for specific purposes in the feeder reconfiguration problem. In this thesis, a new load flow method is proposed based on the backward/forward sweep method. This method can analyse distribution network load flow under both fundamental and harmonic conditions with distributed generators. Following this, a hybrid optimization method is proposed based on the salient features of the ant colony system and particle swarm optimization. This hybrid method has a higher searching accuracy performance for feeder reconfiguration when compared, on test system, with the ant colony system and particle swarm optimization. Finally, a 118 mid-voltage level distribution system is used to investigate the impacts of renewable generators and system harmonics. The test results verify that system harmonics will have a significant influence on feeder reconfiguration and, consequently, cannot be ignored. Furthermore, other factors including the different capacities of renewable generators, fluctuations in load demands over 24 hours, and the variable output of the renewable generators in different seasons are also investigated in the feeder reconfiguration problem
Evaluating the impact of pro environmental energy policy in Scotland and the UK : the case of increased efficiency in household energy use
Get PDFIn this thesis, I use multi-sectoral computable general equilibrium techniques to investigate the system wide impacts of improvements in households' energy efficiency use, and technical progress in delivering households' energy services, in Scotland and the UK. The thesis consists of three main, self-contained but correlated essays.The first essay looks the system wide impacts of an illustrative 5% energy efficiency improvement in households' energy use in Scotland and highlights the economic implications of increasing energy efficiency in a regional economy. I find that this results in a small economic stimulus, accompanied by a reduction in energy use that is less than the expected energy savings from the pure energy efficiency increase- the rebound effect. The stimulus is higher when migration of workers is allowed between Scotland and the rest of the UK. However, the higher expansion also delivers a higher rebound in energy use. The stimulus from the higher efficiency in energy use if further enhanced when I consider the impact of greater fiscal autonomy in Scotland, and allow for endogenous government expenditure or tax rates. The second essay analyses the distributional impacts of households' energy efficiency improvements in the UK, focussing the attention on efficiency improvements in lower income households. I discuss whether there is an argument for the Government to fund household energy efficiency programmes via a temporary reallocation of current government expenditure or an increase in the income tax rate. While reallocating public spending has short-term negative impacts on demand over the period of the payment, the efficiency improvement delivers a net long-run stimulus. However, an increase in income tax adversely affects the real take home wage and delivers a long-term reduction in GDP. In all scenarios, lower income households are able to increase their energy consumption and their income by approximately the same amount. The third essay looks at the consumption of energy intensive services using the example of private transport. Here I argue that private transport should be modelled as a household self-produced commodity, composed of refined fuels and motor vehicles. By using a simple partial equilibrium model, I show that technical improvement in motor vehicles can reduce refined fuels use, when there is enough substitutability between the two inputs, and depending on the price elasticity of demand for private transport. By taking the case of the UK, and using a CGE model, I find that technical progress in motor vehicles delivers a small expansionary improvement if the consumer price index is adjusted to account for the implicit price of private transport.In this thesis, I use multi-sectoral computable general equilibrium techniques to investigate the system wide impacts of improvements in households' energy efficiency use, and technical progress in delivering households' energy services, in Scotland and the UK. The thesis consists of three main, self-contained but correlated essays.The first essay looks the system wide impacts of an illustrative 5% energy efficiency improvement in households' energy use in Scotland and highlights the economic implications of increasing energy efficiency in a regional economy. I find that this results in a small economic stimulus, accompanied by a reduction in energy use that is less than the expected energy savings from the pure energy efficiency increase- the rebound effect. The stimulus is higher when migration of workers is allowed between Scotland and the rest of the UK. However, the higher expansion also delivers a higher rebound in energy use. The stimulus from the higher efficiency in energy use if further enhanced when I consider the impact of greater fiscal autonomy in Scotland, and allow for endogenous government expenditure or tax rates. The second essay analyses the distributional impacts of households' energy efficiency improvements in the UK, focussing the attention on efficiency improvements in lower income households. I discuss whether there is an argument for the Government to fund household energy efficiency programmes via a temporary reallocation of current government expenditure or an increase in the income tax rate. While reallocating public spending has short-term negative impacts on demand over the period of the payment, the efficiency improvement delivers a net long-run stimulus. However, an increase in income tax adversely affects the real take home wage and delivers a long-term reduction in GDP. In all scenarios, lower income households are able to increase their energy consumption and their income by approximately the same amount. The third essay looks at the consumption of energy intensive services using the example of private transport. Here I argue that private transport should be modelled as a household self-produced commodity, composed of refined fuels and motor vehicles. By using a simple partial equilibrium model, I show that technical improvement in motor vehicles can reduce refined fuels use, when there is enough substitutability between the two inputs, and depending on the price elasticity of demand for private transport. By taking the case of the UK, and using a CGE model, I find that technical progress in motor vehicles delivers a small expansionary improvement if the consumer price index is adjusted to account for the implicit price of private transport
Finite element and experimental evaluation of injection forging for the forming of automotive fasteners
Get PDFWith the increasing global competition, it is important for the automotive fasteners industries to reduce the cost and improve the production efficiency against other competitors. To achieve it, the author intends to introduce injection forging as an alternative method to conventional forming for automotive fastener production. This study investigates the characteristics of injection forging by finite element (FE) analysis and physical experiment. For the comparison of the conventional forming process with injection forging, ABAQUS and DEFORM were used to conduct FE simulations of the forming of a wheel bolt. Axisymmetric models were developed with both FE codes to analyse forging force, forging energy, forming form-error, tool stress, etc. of conventional multistep forging and injection forging (single step forging). A ring test was also conducted to determine the coefficient of friction between the workpiece and the tools in order to define the contact conditions in the FE models. Subsequently, tests on injection forging were carried out in Ritai Auto Standard Component Co. Ltd. The trials included forging force measurement, evaluation of lubricants, critical dimension measurement, macroetch testing micro-hardness tests and a manufacturing try-out. FE simulation results and experimental results were then compared. Behaviour of the lubricants was also examined for injection forging. Through the comparison, FE models were verified. Some improvements, regarding the influence of forging speed, thermal issues, meshing plan and the limitation of axis-symmetric model, were proposed. By using improved FE models, effects of critical aspects such as process parameters (forging speed and coefficient of friction), tool parameters (tool structure, tool geometry and tool materials), and workpiece parameters (workpiece material and workpiece geometry), were investigated in detail. With the improved FE models, influences of these parameters on fatigue life of the die, die wear, form-errors, and grain flow-lines, were examined. Based on the sensitivity analysis of forging parameters, optimisation was carried out on the tool parameters, and a new tool structure has been proposed for injection forging of the fastener. The tool design was assessed through FE simulations. As results of FE simulations and experiments, the main findings included the merits and drawbacks of injection forging compared with traditional forging process, the precision of FE models, the optimal lubricant for injection forging, the behaviour of injection forging in manufacture trials, the influence of process factors on tool life, forming accuracy and grain flow line. These findings supported the further tool optimization. After optimization, the tool life and forming accuracy had an increase. Based on the research work, the contributions were defined and recommendations of the further work were proposed.With the increasing global competition, it is important for the automotive fasteners industries to reduce the cost and improve the production efficiency against other competitors. To achieve it, the author intends to introduce injection forging as an alternative method to conventional forming for automotive fastener production. This study investigates the characteristics of injection forging by finite element (FE) analysis and physical experiment. For the comparison of the conventional forming process with injection forging, ABAQUS and DEFORM were used to conduct FE simulations of the forming of a wheel bolt. Axisymmetric models were developed with both FE codes to analyse forging force, forging energy, forming form-error, tool stress, etc. of conventional multistep forging and injection forging (single step forging). A ring test was also conducted to determine the coefficient of friction between the workpiece and the tools in order to define the contact conditions in the FE models. Subsequently, tests on injection forging were carried out in Ritai Auto Standard Component Co. Ltd. The trials included forging force measurement, evaluation of lubricants, critical dimension measurement, macroetch testing micro-hardness tests and a manufacturing try-out. FE simulation results and experimental results were then compared. Behaviour of the lubricants was also examined for injection forging. Through the comparison, FE models were verified. Some improvements, regarding the influence of forging speed, thermal issues, meshing plan and the limitation of axis-symmetric model, were proposed. By using improved FE models, effects of critical aspects such as process parameters (forging speed and coefficient of friction), tool parameters (tool structure, tool geometry and tool materials), and workpiece parameters (workpiece material and workpiece geometry), were investigated in detail. With the improved FE models, influences of these parameters on fatigue life of the die, die wear, form-errors, and grain flow-lines, were examined. Based on the sensitivity analysis of forging parameters, optimisation was carried out on the tool parameters, and a new tool structure has been proposed for injection forging of the fastener. The tool design was assessed through FE simulations. As results of FE simulations and experiments, the main findings included the merits and drawbacks of injection forging compared with traditional forging process, the precision of FE models, the optimal lubricant for injection forging, the behaviour of injection forging in manufacture trials, the influence of process factors on tool life, forming accuracy and grain flow line. These findings supported the further tool optimization. After optimization, the tool life and forming accuracy had an increase. Based on the research work, the contributions were defined and recommendations of the further work were proposed
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