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Fracture analysis in marine batteries by peridynamic theory
Get PDFHybrid propulsion system (HPS) has become popular in marine industry due to increasingly strict emission control standards. Hence, as one component in the system, marine batteries become attractive in marine design. Solid Oxide Fuel Cells (SOFCs) and lithium ion battery are the most promising energy storage devices in the electric propulsion system or HPS. Since silicon particles expand around 400% in volume during lithation, the battery electrodes will experience large volumetric change during normal battery cycling.;As a result, misdistribution of stress may form inside the battery electrode. Therefore, degradation and delamination may occur in the battery electrode after many cycling process of marine battery. Many efforts have been devoted to investigate the damage in the marine battery. Majority of numerical simulation methods nowadays are based on classical continuum mechanics (CCM). Partial differential equations (PDEs) are applied in CCM to describe the motion of material structure.;However, due to the limitation of PDEs, most of numerical techniques based on this theory have difficulties in describing the motion of material body with discontinuous fields, such as cracks and kinks. In order to have a better understanding of the fracture mechanics in marine battery, the peridynamic theory is applied in this thesis. Different from classical theory, peridynamic theory has applied spatial integral equations to describe the motion of material structure.;Therefore, it has great advantage on fracture analysis of material structure. Based on the nonlocality of peridynamic theory, the peridynamic differential operator is introduced and studied in this thesis. Peridynamic differential operator has transformed the PDE into spatial integral equation under the framework of peridynamic theory. Hence, the governing equations of thermomechanical deformation and the coupled diffusive-mechanical deformation can be reformed in the framework of peridynamic theory which benefit the relative numerical simulations.;In this thesis, the electrode models of SOFC and lithium ion battery in both two and three dimensions are selected. In order to validate the peridynamic theory, some results are compared with CCM. They have shown good agreement with each other. In the fracture analysis of SOFC, we have found out that fracture formation and evolution depend on the strength of interactions between electrode and electrolyte particles. For weak connection, the cracks will propagate along the interface of electrode and electrolyte.;For uniform and strong connection, the cracks will start to propagate at regions with high geometrical singularity, such as pores or sharp corner regions. High hydrostatic stress is also located in these regions. In the fracture analysis of lithium ion battery, we have found out that facture formation and evolution depend on the hydrostatic stress and material properties. High hydrostatic stress generally reflects on high bond stretch value. Once the bond stretch value has exceed the critical value, cracks may form and propagate.;Lithiated silicon, on the other hand, has decreased the critical bond stretch value. Hence, in some situations, crack propagation may not always be led by hydrostatic stress. Besides, the high hydrostatic stress will also increase the lithium ion concentration.;Finally, peridynamic theory has shown excellent performance in the numerical estimation of damage formation and evolution in the marine batteries without pre-defined crack path or cohesive element as compared with classical techniques. It has provided an efficient and reliable tool in the design, manufacture, failure detection and life prediction of the marine battery in the real life.Hybrid propulsion system (HPS) has become popular in marine industry due to increasingly strict emission control standards. Hence, as one component in the system, marine batteries become attractive in marine design. Solid Oxide Fuel Cells (SOFCs) and lithium ion battery are the most promising energy storage devices in the electric propulsion system or HPS. Since silicon particles expand around 400% in volume during lithation, the battery electrodes will experience large volumetric change during normal battery cycling.;As a result, misdistribution of stress may form inside the battery electrode. Therefore, degradation and delamination may occur in the battery electrode after many cycling process of marine battery. Many efforts have been devoted to investigate the damage in the marine battery. Majority of numerical simulation methods nowadays are based on classical continuum mechanics (CCM). Partial differential equations (PDEs) are applied in CCM to describe the motion of material structure.;However, due to the limitation of PDEs, most of numerical techniques based on this theory have difficulties in describing the motion of material body with discontinuous fields, such as cracks and kinks. In order to have a better understanding of the fracture mechanics in marine battery, the peridynamic theory is applied in this thesis. Different from classical theory, peridynamic theory has applied spatial integral equations to describe the motion of material structure.;Therefore, it has great advantage on fracture analysis of material structure. Based on the nonlocality of peridynamic theory, the peridynamic differential operator is introduced and studied in this thesis. Peridynamic differential operator has transformed the PDE into spatial integral equation under the framework of peridynamic theory. Hence, the governing equations of thermomechanical deformation and the coupled diffusive-mechanical deformation can be reformed in the framework of peridynamic theory which benefit the relative numerical simulations.;In this thesis, the electrode models of SOFC and lithium ion battery in both two and three dimensions are selected. In order to validate the peridynamic theory, some results are compared with CCM. They have shown good agreement with each other. In the fracture analysis of SOFC, we have found out that fracture formation and evolution depend on the strength of interactions between electrode and electrolyte particles. For weak connection, the cracks will propagate along the interface of electrode and electrolyte.;For uniform and strong connection, the cracks will start to propagate at regions with high geometrical singularity, such as pores or sharp corner regions. High hydrostatic stress is also located in these regions. In the fracture analysis of lithium ion battery, we have found out that facture formation and evolution depend on the hydrostatic stress and material properties. High hydrostatic stress generally reflects on high bond stretch value. Once the bond stretch value has exceed the critical value, cracks may form and propagate.;Lithiated silicon, on the other hand, has decreased the critical bond stretch value. Hence, in some situations, crack propagation may not always be led by hydrostatic stress. Besides, the high hydrostatic stress will also increase the lithium ion concentration.;Finally, peridynamic theory has shown excellent performance in the numerical estimation of damage formation and evolution in the marine batteries without pre-defined crack path or cohesive element as compared with classical techniques. It has provided an efficient and reliable tool in the design, manufacture, failure detection and life prediction of the marine battery in the real life
Governance of Offshore Freshwater Resources
Get PDFLand-based supplies of freshwater are being increasingly exploited and polluted at the same time that climate change and burgeoning human population are causing widening scarcity and rising demand. Scientists have discovered that vast quantities of fresh to slightly brackish water reserves are sequestered in continental shelves around the world. These reserves take two completely different forms: aquifers and methane hydrates. Neither of these reserves has been commercially developed, and, while current technology could be utilized for aquifers, methods for extracting freshwater from methane hydrates do not yet exist. Given the vital and unique nature of freshwater, offshore freshwater resources will become more attractive as the quality and quantity of land-based supplies dwindle.The purpose of this thesis is to fill the void in legal scholarship concerning governance of offshore freshwater resources. At least three different legal regimes are relevant: the UN Convention on the Law of the Sea, customary practices for offshore hydrocarbon development, and customary international law for land-based freshwater. All of these regimes have obligations to protect the environment and to cooperate with neighboring states, and all of them ensure sovereign rights to domestic natural resources while encouraging states sharing transboundary resources to seek equitable solutions. Similar to other natural resources, development of freshwater will have two distinct phases:access and distribution.;Under current governance structures, access to and ownership of offshore freshwater would be assigned to coastal sovereigns,either exclusively or on a shared basis where the resource is transboundary. Distribution of natural resources has thus far been viewed as a prerogative of sovereign rights to access and ownership. However, emerging principles such as the human right to water, sustainable development and ecosystem protection have begun to place limitations on unfettered distribution rights by directing that freshwater be allocated to certain beneficial purposes.Land-based supplies of freshwater are being increasingly exploited and polluted at the same time that climate change and burgeoning human population are causing widening scarcity and rising demand. Scientists have discovered that vast quantities of fresh to slightly brackish water reserves are sequestered in continental shelves around the world. These reserves take two completely different forms: aquifers and methane hydrates. Neither of these reserves has been commercially developed, and, while current technology could be utilized for aquifers, methods for extracting freshwater from methane hydrates do not yet exist. Given the vital and unique nature of freshwater, offshore freshwater resources will become more attractive as the quality and quantity of land-based supplies dwindle.The purpose of this thesis is to fill the void in legal scholarship concerning governance of offshore freshwater resources. At least three different legal regimes are relevant: the UN Convention on the Law of the Sea, customary practices for offshore hydrocarbon development, and customary international law for land-based freshwater. All of these regimes have obligations to protect the environment and to cooperate with neighboring states, and all of them ensure sovereign rights to domestic natural resources while encouraging states sharing transboundary resources to seek equitable solutions. Similar to other natural resources, development of freshwater will have two distinct phases:access and distribution.;Under current governance structures, access to and ownership of offshore freshwater would be assigned to coastal sovereigns,either exclusively or on a shared basis where the resource is transboundary. Distribution of natural resources has thus far been viewed as a prerogative of sovereign rights to access and ownership. However, emerging principles such as the human right to water, sustainable development and ecosystem protection have begun to place limitations on unfettered distribution rights by directing that freshwater be allocated to certain beneficial purposes
The effects of small molecule analogues of the anti-inflammatory parasitic worm product ES-62 on the metabolome of mouse bone marrow-derived macrophages
Get PDFLipopolysaccharide (LPS) and Cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) cause macrophages to produce the proinflammatory cytokines IL-12, IL-6 and TNF-α. Pre-treatment of the macrophages with ES-62, an anti-inflammatory glycoprotein secreted by the parasitic filarial nematode Acanthocheilonema viteae suppresses the production of these cytokines.;Although able to prevent disease development in mouse models of allergy and autoimmunity, ES-62 is not suitable for drug therapy due to its potential immunogenicity. A library of small molecule analogues (SMAs) therefore was designed and tested for the previously mentioned inhibitory effects. SMAs 11a and 12b among library members were found to mimic ES-62's anti-inflammatory effects. These findings rationalised further testing in order to determine their mechanism of action based on their effects on the metabolome of primary macrophages.;From analysis of cellular extracts using hydrophilic interaction chromatography in combination with high resolution mass spectrometry it could be seen that stimulation of macrophages with either LPS or CpG produced metabolic changes in various pathways. Stimulation of macrophages with LPS or CpG in the presence of SMAs 11a and 12b revealed that many of the metabolic shifts were the same as observed with LPS and CpG alone. However, there were clear effects of the SMAs in producing downregulation in creatine metabolism/uptake and upregulation in glutathione biosynthesis.;By downregulating creatine metabolism/uptake, the SMAs may be controlling the availability of creatine for transporting high energy phosphate from the mitochondria to where it is required for biological functions including cell signalling, phagocytosis and motility. By causing an upregulation of the glutathione biosynthesis pathway the SMAs may be protecting the cells from oxidative stress and of note SMA12b has been previously linked to increased activity of the Nrf2/ARE/HO-1 anti-oxidant pathway. The SMAs may be downregulating the availability of the energy produced by oxidative phosphorylation in general without targeting the TCA cycle directly since they do not affect NADH levels in comparison with LPS or CpG stimulation alone. Finally, in the process of examining the response of the cells to LPS and CpG additional potential anti-inflammatory targets were revealed.Lipopolysaccharide (LPS) and Cytosine-phosphate-guanosine oligodeoxynucleotides (CpG ODNs) cause macrophages to produce the proinflammatory cytokines IL-12, IL-6 and TNF-α. Pre-treatment of the macrophages with ES-62, an anti-inflammatory glycoprotein secreted by the parasitic filarial nematode Acanthocheilonema viteae suppresses the production of these cytokines.;Although able to prevent disease development in mouse models of allergy and autoimmunity, ES-62 is not suitable for drug therapy due to its potential immunogenicity. A library of small molecule analogues (SMAs) therefore was designed and tested for the previously mentioned inhibitory effects. SMAs 11a and 12b among library members were found to mimic ES-62's anti-inflammatory effects. These findings rationalised further testing in order to determine their mechanism of action based on their effects on the metabolome of primary macrophages.;From analysis of cellular extracts using hydrophilic interaction chromatography in combination with high resolution mass spectrometry it could be seen that stimulation of macrophages with either LPS or CpG produced metabolic changes in various pathways. Stimulation of macrophages with LPS or CpG in the presence of SMAs 11a and 12b revealed that many of the metabolic shifts were the same as observed with LPS and CpG alone. However, there were clear effects of the SMAs in producing downregulation in creatine metabolism/uptake and upregulation in glutathione biosynthesis.;By downregulating creatine metabolism/uptake, the SMAs may be controlling the availability of creatine for transporting high energy phosphate from the mitochondria to where it is required for biological functions including cell signalling, phagocytosis and motility. By causing an upregulation of the glutathione biosynthesis pathway the SMAs may be protecting the cells from oxidative stress and of note SMA12b has been previously linked to increased activity of the Nrf2/ARE/HO-1 anti-oxidant pathway. The SMAs may be downregulating the availability of the energy produced by oxidative phosphorylation in general without targeting the TCA cycle directly since they do not affect NADH levels in comparison with LPS or CpG stimulation alone. Finally, in the process of examining the response of the cells to LPS and CpG additional potential anti-inflammatory targets were revealed
Early and effective intervention (EEI) in Scottish youth justice : benevolent principles and unintended consequences
Get PDFScotland has a distinctive youth justice system founded on the welfare ethos of Kilbrandon and the unique Children's Hearing System. The most recent addition to the youth justice landscape is the Whole System Approach and of primary concern to this research, Early and Effective Intervention (EEI). EEI a multiagency decision making process which takes a holistic, child-centred approach to offending by children and young people; views offending as a potential wellbeing concern and aims to act in a timely, effective and proportionate way. While its use in practice has increased, scrutiny of the process is scarce.;Applying a modified grounded theory methodology, this research examines how and why decisions are made at EEI and its potential impact, exploring practice in three case study locations. The research makes an original contribution to knowledge as it provides an expose of EEI decision making in practice, which then provides the opportunity to consider implications which arise from that practice.;The findings reveal inherent complexities and tensions between the intentions and practice of EEI on the ground. Applying social control theory, the potential impact of these tensions are considered in relation to outcomes for young people, practitioners and the wider youth justice system. The researcher argues that EEI represents an extension of the formal youth justice system, where the stated benevolent intentions on the part of practitioners through diversion and addressing wellbeing are met; but that net-widening, up-tariffing and boundary blurring to the detriment of rights are present and unavoidable.;The system may be producing the outcomes which it aimed to avoid, particularly for groups already considered 'the usual suspects'. The research concludes that the inherent tensions in EEI, representative of wider youth justice system tensions, must be acknowledged by actors at various levels of the Scottish Youth justice system; scrutiny applied to both practice and underlying concepts; and a consideration of a truly diversionary, rights-based and inclusive system required for those involved in offending or who come into contact with the formal youth justice system.Scotland has a distinctive youth justice system founded on the welfare ethos of Kilbrandon and the unique Children's Hearing System. The most recent addition to the youth justice landscape is the Whole System Approach and of primary concern to this research, Early and Effective Intervention (EEI). EEI a multiagency decision making process which takes a holistic, child-centred approach to offending by children and young people; views offending as a potential wellbeing concern and aims to act in a timely, effective and proportionate way. While its use in practice has increased, scrutiny of the process is scarce.;Applying a modified grounded theory methodology, this research examines how and why decisions are made at EEI and its potential impact, exploring practice in three case study locations. The research makes an original contribution to knowledge as it provides an expose of EEI decision making in practice, which then provides the opportunity to consider implications which arise from that practice.;The findings reveal inherent complexities and tensions between the intentions and practice of EEI on the ground. Applying social control theory, the potential impact of these tensions are considered in relation to outcomes for young people, practitioners and the wider youth justice system. The researcher argues that EEI represents an extension of the formal youth justice system, where the stated benevolent intentions on the part of practitioners through diversion and addressing wellbeing are met; but that net-widening, up-tariffing and boundary blurring to the detriment of rights are present and unavoidable.;The system may be producing the outcomes which it aimed to avoid, particularly for groups already considered 'the usual suspects'. The research concludes that the inherent tensions in EEI, representative of wider youth justice system tensions, must be acknowledged by actors at various levels of the Scottish Youth justice system; scrutiny applied to both practice and underlying concepts; and a consideration of a truly diversionary, rights-based and inclusive system required for those involved in offending or who come into contact with the formal youth justice system
Modelling coagulation in industrial spray drying : an efficient one-dimensional population balance approach
Get PDFThis thesis examines the effects of coagulation on the droplet size distribution within the hollow cone sprays used by industrial spray dryers. A simple model is presented that incorporates the spray's conical shape, droplet transport and coagulation. Both a suitable droplet velocity profile and a coagulation success rate are selected - with the coagulation rate being dependent upon both the size and velocity of colliding droplets.;A population balance equation is used to describe how the droplet size distribution is affected by coagulation and this is combined with a conservation equation to capture the droplet transport within the spray. The resulting nonlinear partial integro-differential equation is solved numerically using the cell-average sectional method for the non-local coagulation terms and an essentially non-oscillatory scheme for droplet transport terms.;To our knowledge, this is the first time the cell average technique has been applied to the specific conical sprays found within spray drying. A key achievement of our approach is the significant reduction in computational time that it requires to simulate the droplet size distribution throughout the spray. In comparison, alternative computational fluid mechanics techniques take considerably longer to converge on a steady state solution, as they rely on tracking the trajectory of every individual droplet within the system.;Numerical results obtained from our model show that coagulation does play an important role within these sprays. Moreover, investigations into the inuence of the atomiser nozzle on the extent of coagulation reveal that an increased amount of coagulation occurs in thin, flattish sprays, whilst very little coagulation is observed in widely dispersed sprays.;The model is later extended to include the effects of droplet evaporation. In this case, an increase in the number of smaller droplets near the bottom of the spray is clearly observed in the numerical simulations. Finally, the model's predictions are validated against experimental data obtained from a series of trials conducted within an industrial-scale dryer tower. Once calibrated, the model's predictions are shown to be in very good agreement with the experimental data.This thesis examines the effects of coagulation on the droplet size distribution within the hollow cone sprays used by industrial spray dryers. A simple model is presented that incorporates the spray's conical shape, droplet transport and coagulation. Both a suitable droplet velocity profile and a coagulation success rate are selected - with the coagulation rate being dependent upon both the size and velocity of colliding droplets.;A population balance equation is used to describe how the droplet size distribution is affected by coagulation and this is combined with a conservation equation to capture the droplet transport within the spray. The resulting nonlinear partial integro-differential equation is solved numerically using the cell-average sectional method for the non-local coagulation terms and an essentially non-oscillatory scheme for droplet transport terms.;To our knowledge, this is the first time the cell average technique has been applied to the specific conical sprays found within spray drying. A key achievement of our approach is the significant reduction in computational time that it requires to simulate the droplet size distribution throughout the spray. In comparison, alternative computational fluid mechanics techniques take considerably longer to converge on a steady state solution, as they rely on tracking the trajectory of every individual droplet within the system.;Numerical results obtained from our model show that coagulation does play an important role within these sprays. Moreover, investigations into the inuence of the atomiser nozzle on the extent of coagulation reveal that an increased amount of coagulation occurs in thin, flattish sprays, whilst very little coagulation is observed in widely dispersed sprays.;The model is later extended to include the effects of droplet evaporation. In this case, an increase in the number of smaller droplets near the bottom of the spray is clearly observed in the numerical simulations. Finally, the model's predictions are validated against experimental data obtained from a series of trials conducted within an industrial-scale dryer tower. Once calibrated, the model's predictions are shown to be in very good agreement with the experimental data
A novel role for CaMKIIδ in modulating vascular inflammation in young and aged aortae
Get PDFAgeing presents as the greatest risk factor for development of cardiovascular disease. Calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) is well established as playing a fundamental role in normal cardiac function, as well contributing to the pathophysiology of heart disease. A similar role for CaMKIIδ in the vasculature remains elusive. Furthermore, very little is known of whether this enzyme contributes to cardiovascular pathology associated with ageing.;Oxidative stress and chronic inflammation are both key features of the ageing process and are underpinned predominantly by the development of vascular endothelial dysfunction. Nuclear Factor kappa B (NF-κB) pro-inflammatory signalling is a key modulator of endothelial dysfunction and in recent years has been shown in the heart to be regulated by CaMKIIδ. The precise mechanisms by which CaMKIIδ exerts these effects on NF-κB signalling remain poorly understood and a comparable link has yet to be recognised between both pathways in the vascular endothelium.;This study has used a combination of in vitro and in vivo techniques to focus on (i) identifying a link between CaMKII and NF-κB signalling in vascular endothelial cells, (ii) characterising a chronic inflammatory and stressed phenotype in parallel with cardiovascular dysfunction in aged rats, and (iii) assessing alterations in both CaMKII and NF-κB signalling during ageing. Importantly the study has focused on vascular endothelial cells, providing novel insight into the role of CaMKIIδ in these cells during their dysfunction with ageing.;A novel direct interaction between CaMKII and NF-κB signalling has been demonstrated at the level of inhibitory-κB kinase β (IKKβ) using proximity ligation assay (PLA) technology. Aged animals displayed visible signs of both cardiac and vascular dysfunction and this correlated with enhanced inflammation and oxidative stress. Interestingly, both CaMKIIδ and NF-κB signalling were both altered specifically at the level of the endothelium with ageing and therefore may both contribute to endothelial dysfunction.;Future work should be performed to investigate the interaction between CaMKIIδ and NF-κB in the endothelium in more detail. By specifically targeting the protein-protein interaction between CaMKII and IKKβ, inflammation associated with endothelial dysfunction may be reduced and restoring the balance in activity of both pathways could also reduce or prevent the progression of other age-related conditions.Ageing presents as the greatest risk factor for development of cardiovascular disease. Calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) is well established as playing a fundamental role in normal cardiac function, as well contributing to the pathophysiology of heart disease. A similar role for CaMKIIδ in the vasculature remains elusive. Furthermore, very little is known of whether this enzyme contributes to cardiovascular pathology associated with ageing.;Oxidative stress and chronic inflammation are both key features of the ageing process and are underpinned predominantly by the development of vascular endothelial dysfunction. Nuclear Factor kappa B (NF-κB) pro-inflammatory signalling is a key modulator of endothelial dysfunction and in recent years has been shown in the heart to be regulated by CaMKIIδ. The precise mechanisms by which CaMKIIδ exerts these effects on NF-κB signalling remain poorly understood and a comparable link has yet to be recognised between both pathways in the vascular endothelium.;This study has used a combination of in vitro and in vivo techniques to focus on (i) identifying a link between CaMKII and NF-κB signalling in vascular endothelial cells, (ii) characterising a chronic inflammatory and stressed phenotype in parallel with cardiovascular dysfunction in aged rats, and (iii) assessing alterations in both CaMKII and NF-κB signalling during ageing. Importantly the study has focused on vascular endothelial cells, providing novel insight into the role of CaMKIIδ in these cells during their dysfunction with ageing.;A novel direct interaction between CaMKII and NF-κB signalling has been demonstrated at the level of inhibitory-κB kinase β (IKKβ) using proximity ligation assay (PLA) technology. Aged animals displayed visible signs of both cardiac and vascular dysfunction and this correlated with enhanced inflammation and oxidative stress. Interestingly, both CaMKIIδ and NF-κB signalling were both altered specifically at the level of the endothelium with ageing and therefore may both contribute to endothelial dysfunction.;Future work should be performed to investigate the interaction between CaMKIIδ and NF-κB in the endothelium in more detail. By specifically targeting the protein-protein interaction between CaMKII and IKKβ, inflammation associated with endothelial dysfunction may be reduced and restoring the balance in activity of both pathways could also reduce or prevent the progression of other age-related conditions
Methodologies for scalable and responsive swarms and networked systems
No full textCurrently, engineers can only aspire to match nature's capabilities where the same control mechanism can scale from one hundred starlings to five thousand whilst maintaining properties such as cohesion and rapid response to predation. These aspirations have led to engineered swarms that rely on remote or human control to assemble formations, which therefore do not require leaders within the network that can communicate using inter-agent connections. As a consequence, it is primarily in theory where network leadership is considered, usually through the exploitation of a standard set of centrality metrics - such as PageRank, degree centrality or betweenness - ubiquitous across network science.This dissertation attempts to lay the foundations for large, mobile, multiagents warms through a scalable control approach. This mechanism can achieve similar capabilities to that of a starling flock but with greater control over the swarm's movement. These criteria are met by defining control rules for the environment, using artificial kinematic fields, rather than for the individual; enabling agents to join or leave the swarm without a breakdown in cohesion or responsiveness - just like starlings. The functionality of this method, and the potential for swarm based applications, is demonstrated through a remote inspection case study. This control approach contributes to our rapidly increasing ability to create networked systems, but our understanding of how to control such complexity is not advancing as fast.The identification of optimal network leaders is a significant step towards achieving a responsive, controllable, swarm. By not constraining the problem to a set number of leaders, the solution space - for anything other than small networks - is too vast to attempt an exhaustive search. The remedy for this leader selection problem has, so far, eluded researchers. Eigenvectors are presented here as key to solving this problem for determining optimal leadership when considering fast convergence to consensus. The semi-analytical algorithms, developed herein, have O(n3) time complexity and are found to perform as well as numerical optimisers with significantly greater complexity, O(n4). Eigenvectors map the dynamic response of a network where they are found to expose the most responsive communities that form in the wake of external perturbations. Comparisons, of eigenvector-based methods, with information flow simulations illustrate that analytical models can, in a computationally efficient manner, cast light on the interplay between leadership and topology. Whilst providing a greater understanding of the effectiveness and function of nature's networked systems, including the vastly complicated and responsive network of the human brain.Currently, engineers can only aspire to match nature's capabilities where the same control mechanism can scale from one hundred starlings to five thousand whilst maintaining properties such as cohesion and rapid response to predation. These aspirations have led to engineered swarms that rely on remote or human control to assemble formations, which therefore do not require leaders within the network that can communicate using inter-agent connections. As a consequence, it is primarily in theory where network leadership is considered, usually through the exploitation of a standard set of centrality metrics - such as PageRank, degree centrality or betweenness - ubiquitous across network science.This dissertation attempts to lay the foundations for large, mobile, multiagents warms through a scalable control approach. This mechanism can achieve similar capabilities to that of a starling flock but with greater control over the swarm's movement. These criteria are met by defining control rules for the environment, using artificial kinematic fields, rather than for the individual; enabling agents to join or leave the swarm without a breakdown in cohesion or responsiveness - just like starlings. The functionality of this method, and the potential for swarm based applications, is demonstrated through a remote inspection case study. This control approach contributes to our rapidly increasing ability to create networked systems, but our understanding of how to control such complexity is not advancing as fast.The identification of optimal network leaders is a significant step towards achieving a responsive, controllable, swarm. By not constraining the problem to a set number of leaders, the solution space - for anything other than small networks - is too vast to attempt an exhaustive search. The remedy for this leader selection problem has, so far, eluded researchers. Eigenvectors are presented here as key to solving this problem for determining optimal leadership when considering fast convergence to consensus. The semi-analytical algorithms, developed herein, have O(n3) time complexity and are found to perform as well as numerical optimisers with significantly greater complexity, O(n4). Eigenvectors map the dynamic response of a network where they are found to expose the most responsive communities that form in the wake of external perturbations. Comparisons, of eigenvector-based methods, with information flow simulations illustrate that analytical models can, in a computationally efficient manner, cast light on the interplay between leadership and topology. Whilst providing a greater understanding of the effectiveness and function of nature's networked systems, including the vastly complicated and responsive network of the human brain
High-skilled migrant workers, transnational networks, equality and voice : civil society organisations as new regulatory actors in work and employment
Get PDFThis thesis examines the role of migrant civil society organisations (CSOs) in the regulation of work and employment. The perspective of social regulation is adopted which conceptualises regulation as constituting the incorporation, allocation, control and reproduction of labour within labour markets through processes that transfer, utilise and convert social, cultural and economic capital of migrant workers. Migrant CSOs are conceptualised as resisting or reproducing social inequality. The major empirical contribution of this thesis is its empirical focus on CSOs in the UK representing skilled migrant workers originating from outside the European Economic Area, which has hitherto been under-researched. Data was collected from 38 key respondent and elite interviews drawn from a purposive sample of nine skilled migrant CSOs. The key conceptual contribution of this thesis is the development of a multi-disciplinary conceptual framework to investigate skilled migrant CSOs. It synthesizes the concepts of regulatory space, civil society, migrant capital, equality, diversity and 'new' actors in work and employment. The findings indicate that skilled migrant CSOs socially regulate migrants and labour market actors, processes and outcomes as diaspora organisations. CSOs use migrant capital through a range of formal and informal processes to support international mobility, recruitment, career mentoring, training and skills development. This study makes specific theoretical contributions by providing evidence of migrant collective action within and outside organisational workplaces in contrast to the International HRM literature which portrays skilled migrants as individualised and passive. The ways in which skilled migrant CSOs 'occupy' regulatory spaces by exploiting loopholes and occupying gaps expands our understanding of regulatory spaces. Skilled migrant CSOs articulate the voices of their constituencies in two broad ways: through political engagement such as public campaigns and lobbying; and through subtler apolitical forms of influence such as knowledge transfer, policy advice and diffusion of 'best practices' across transnational borders.This thesis examines the role of migrant civil society organisations (CSOs) in the regulation of work and employment. The perspective of social regulation is adopted which conceptualises regulation as constituting the incorporation, allocation, control and reproduction of labour within labour markets through processes that transfer, utilise and convert social, cultural and economic capital of migrant workers. Migrant CSOs are conceptualised as resisting or reproducing social inequality. The major empirical contribution of this thesis is its empirical focus on CSOs in the UK representing skilled migrant workers originating from outside the European Economic Area, which has hitherto been under-researched. Data was collected from 38 key respondent and elite interviews drawn from a purposive sample of nine skilled migrant CSOs. The key conceptual contribution of this thesis is the development of a multi-disciplinary conceptual framework to investigate skilled migrant CSOs. It synthesizes the concepts of regulatory space, civil society, migrant capital, equality, diversity and 'new' actors in work and employment. The findings indicate that skilled migrant CSOs socially regulate migrants and labour market actors, processes and outcomes as diaspora organisations. CSOs use migrant capital through a range of formal and informal processes to support international mobility, recruitment, career mentoring, training and skills development. This study makes specific theoretical contributions by providing evidence of migrant collective action within and outside organisational workplaces in contrast to the International HRM literature which portrays skilled migrants as individualised and passive. The ways in which skilled migrant CSOs 'occupy' regulatory spaces by exploiting loopholes and occupying gaps expands our understanding of regulatory spaces. Skilled migrant CSOs articulate the voices of their constituencies in two broad ways: through political engagement such as public campaigns and lobbying; and through subtler apolitical forms of influence such as knowledge transfer, policy advice and diffusion of 'best practices' across transnational borders
A study of a coordinated path planning strategy for a fleet of unmanned surface ships in the presence of static obstacles
Get PDFThis thesis addressed the problem of path planning for a fleet of unmanned surface ships in the presence of static obstacles. The aim of this study is to propose a new strategy to avoid potential collisions with static obstacles and each ship. In addition, the objective of the proposed strategy is to enable the fleet to autonomously change an initial formation shape into a safer formation shape when the fleet of the ships faces with static obstacles. A core idea adopted for the proposed strategy was motivated by behaviours of school of fish in the ocean.;We assumed that the behaviours of school of fish follow three rules. These assumptions were extended to main methodology of this study: 1) Path planning for a leader ship (Potential Field Method), 2) Formation control for a fleet (Consensus algorithm) and 3) Path planning strategy for follower ships of a fleet. In addition, Potential Field Method and Consensus algorithm were integrated to develop the new path planning strategy, which imitates the motion of school of fish when obstacles are encountered.;Repulsive force vectors obtained from results of Potential Field Method were used as parameters of proposed mathematical equations to change formation shapes of the fleet. In order to validate the proposed strategy, simulations have been carried out for five unmanned surface ships modelled as point mass models with full actuation under MATLAB/Simulink environment. Simulation results illustrated that the fleet of the five ships changed their formation shape into a safer formation shape in the presence of user-designed static obstacles and the fleet of ships successfully passed through the static obstacles without collisions with each ship.;From these simulation results, this study has demonstrated that this proposed strategy will contribute to safety and automation of multiple unmanned surface ships in the presence of static obstacles.This thesis addressed the problem of path planning for a fleet of unmanned surface ships in the presence of static obstacles. The aim of this study is to propose a new strategy to avoid potential collisions with static obstacles and each ship. In addition, the objective of the proposed strategy is to enable the fleet to autonomously change an initial formation shape into a safer formation shape when the fleet of the ships faces with static obstacles. A core idea adopted for the proposed strategy was motivated by behaviours of school of fish in the ocean.;We assumed that the behaviours of school of fish follow three rules. These assumptions were extended to main methodology of this study: 1) Path planning for a leader ship (Potential Field Method), 2) Formation control for a fleet (Consensus algorithm) and 3) Path planning strategy for follower ships of a fleet. In addition, Potential Field Method and Consensus algorithm were integrated to develop the new path planning strategy, which imitates the motion of school of fish when obstacles are encountered.;Repulsive force vectors obtained from results of Potential Field Method were used as parameters of proposed mathematical equations to change formation shapes of the fleet. In order to validate the proposed strategy, simulations have been carried out for five unmanned surface ships modelled as point mass models with full actuation under MATLAB/Simulink environment. Simulation results illustrated that the fleet of the five ships changed their formation shape into a safer formation shape in the presence of user-designed static obstacles and the fleet of ships successfully passed through the static obstacles without collisions with each ship.;From these simulation results, this study has demonstrated that this proposed strategy will contribute to safety and automation of multiple unmanned surface ships in the presence of static obstacles
The use of metabolomics tools to assess the therapeutic natural products of honey and propolis from Malaysia and New Zealand
Get PDFThe bee products including honey, propolis, pollen, and bee venom have been reported to have therapeutic benefits in traditional and conventional medicine. Honey is collected from nectar which appeared as caramelised sugar, while propolis is mainly composed of plant resins and exudates that bees gather. Many studies demonstrated anti-inflammatory, anti-bacterial, anti-oxidant and anti-proliferative properties of honey and propolis extract.;However the chemical profiling of Malaysian honey and propolis has not been well studied. The composition of honey and propolis depends on its geographical origin and also on its botanical source. Furthermore, the extraction of secondary metabolites from propolis is very crucial because its bioavailability is only 2% in raw form. Metabolomics tools have been applied employing liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) to afford an intensive chemical profile of the propolis samples to target the bioactive metabolites.;The obtained HRLCMS data was processed with MZmine 2.10 and was dereplicated using an in-house Excel Macro to couple the MS data with the Dictionary of Natural Products 2016 database. A supervised multivariate analysis was done by orthogonal partial least squares discriminant analysis (OPLS-DA) in SIMCA-P 14.0 to predict and pinpoint the plausible bioactive components against respective cancer cell lines. The chemical profiling of honey from Malaysia and New Zealand were also obtained using the same metabolomics approach.;However, isolation work was only done for propolis due to their potent bioactivities. Ten compounds have been isolated from Malaysia and New Zealand propolis, which consisted mainly of triterpenoid and flavonoid derivatives, respectively. Several compounds revealed anticancer properties on several cancer cell lines (lung, breast and ovary), as well as phenotypic alteration on zebrafish embryo that can be related with activation of Notch signalling for anticancer study.The bee products including honey, propolis, pollen, and bee venom have been reported to have therapeutic benefits in traditional and conventional medicine. Honey is collected from nectar which appeared as caramelised sugar, while propolis is mainly composed of plant resins and exudates that bees gather. Many studies demonstrated anti-inflammatory, anti-bacterial, anti-oxidant and anti-proliferative properties of honey and propolis extract.;However the chemical profiling of Malaysian honey and propolis has not been well studied. The composition of honey and propolis depends on its geographical origin and also on its botanical source. Furthermore, the extraction of secondary metabolites from propolis is very crucial because its bioavailability is only 2% in raw form. Metabolomics tools have been applied employing liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) to afford an intensive chemical profile of the propolis samples to target the bioactive metabolites.;The obtained HRLCMS data was processed with MZmine 2.10 and was dereplicated using an in-house Excel Macro to couple the MS data with the Dictionary of Natural Products 2016 database. A supervised multivariate analysis was done by orthogonal partial least squares discriminant analysis (OPLS-DA) in SIMCA-P 14.0 to predict and pinpoint the plausible bioactive components against respective cancer cell lines. The chemical profiling of honey from Malaysia and New Zealand were also obtained using the same metabolomics approach.;However, isolation work was only done for propolis due to their potent bioactivities. Ten compounds have been isolated from Malaysia and New Zealand propolis, which consisted mainly of triterpenoid and flavonoid derivatives, respectively. Several compounds revealed anticancer properties on several cancer cell lines (lung, breast and ovary), as well as phenotypic alteration on zebrafish embryo that can be related with activation of Notch signalling for anticancer study
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