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A study of the metallurgical and mechanical property variability in a dual phase low alloy material
Get PDFPreviously held under moratorium from 19th October 2017 until 19th October 2023.This thesis includes an author's note referring to a 7-year NDC. Please note that only a 6-year NDC was required and enforced.AISI 4161H is a low alloy material that is currently used to manufacture coil springs for the TechnipFMC portfolio of actuated gate valves. The coil springs are designed to operate in a subsea service environment for a minimum of 25 years, which can equate to conditions of a working water depth of 10,000 feet (3048metres) and pressure of 10,000 psi. As the Coil Spring is the main method of valve closure, failure of the respective material can lead to catastrophic consequences. The design has no redundancy, therefore coil spring breakages and loss of load can lead to failure in the closure of the valve gate, which is the main failsafe system, controlling the flow of oil and gas from the seabed. Throughout the initial development of the respective coil spring material, TechnipFMC has discovered that the necessary metallurgical properties requirements have not been consistently met. The initial work, which was conducted between 2012 and 2014, established that the material contained microstructural variability, which produced mechanical properties that did not meet the design intent of the coil spring. These findings were found with material procured from different mills and by two separate OEM's who hot formed the raw bar into final coil spring products. Failure to meet the design requirements, affects the functionality of the coil spring to have enough stored energy to act as failsafe mechanism to close the respective valve. To address this problem, a comprehensive design of experiment programme has been developed as a series of characterisation and validation testing, to determine the fundamental properties of the AISI 4161H material type, using different heat treatment operations and conditions. This is considered paramount, as current industry requirements do not mandate any testing or material characterization, other than a basic metallurgical assessment. These requirements and level of governance are considered inadequate by the author, as the industry controlling standards do not define the correct pass / fail criterion that ensures such a critical product will not fail in-service. The research programme contained within this thesis, addresses the reasons for the variability exhibited by the AISI 4161H material, and determines how the variation can be influenced by exposure to different hot working and heat treatment conditions. The subsequent findings from the programme will enable engineers to determine the limitations of the material, and the effect variability has on the functionality of the coil spring for subsea applications. The characterisation will also allow the industry governing bodies to align their respective test requirements and acceptance standards to that of a heterogeneous material, which contains variability throughout its cross-sectional thickness.AISI 4161H is a low alloy material that is currently used to manufacture coil springs for the TechnipFMC portfolio of actuated gate valves. The coil springs are designed to operate in a subsea service environment for a minimum of 25 years, which can equate to conditions of a working water depth of 10,000 feet (3048metres) and pressure of 10,000 psi. As the Coil Spring is the main method of valve closure, failure of the respective material can lead to catastrophic consequences. The design has no redundancy, therefore coil spring breakages and loss of load can lead to failure in the closure of the valve gate, which is the main failsafe system, controlling the flow of oil and gas from the seabed. Throughout the initial development of the respective coil spring material, TechnipFMC has discovered that the necessary metallurgical properties requirements have not been consistently met. The initial work, which was conducted between 2012 and 2014, established that the material contained microstructural variability, which produced mechanical properties that did not meet the design intent of the coil spring. These findings were found with material procured from different mills and by two separate OEM's who hot formed the raw bar into final coil spring products. Failure to meet the design requirements, affects the functionality of the coil spring to have enough stored energy to act as failsafe mechanism to close the respective valve. To address this problem, a comprehensive design of experiment programme has been developed as a series of characterisation and validation testing, to determine the fundamental properties of the AISI 4161H material type, using different heat treatment operations and conditions. This is considered paramount, as current industry requirements do not mandate any testing or material characterization, other than a basic metallurgical assessment. These requirements and level of governance are considered inadequate by the author, as the industry controlling standards do not define the correct pass / fail criterion that ensures such a critical product will not fail in-service. The research programme contained within this thesis, addresses the reasons for the variability exhibited by the AISI 4161H material, and determines how the variation can be influenced by exposure to different hot working and heat treatment conditions. The subsequent findings from the programme will enable engineers to determine the limitations of the material, and the effect variability has on the functionality of the coil spring for subsea applications. The characterisation will also allow the industry governing bodies to align their respective test requirements and acceptance standards to that of a heterogeneous material, which contains variability throughout its cross-sectional thickness
Partial discharge ageing of polymer insulation under combined AC and DC stress at elevated temperatures
Get PDFCable termination is the weakest part in any HV underground cable system, as defects may be left in the main insulation during the installation process. In HVDC systems, the converters produce the intended DC voltage for transmission but there may also be AC harmonics superimposed. The frequency of the AC harmonics could be in kHz range. The superimposed harmonics on the HVDC may have synergistic effects on cable insulation and may lead to further degradation in the cable insulation.;In addition, for the sake of environmental protection, XLPE is no longer the suitable choice for underground cable insulation as it cannot be recycled. Thermoplastic material may be a candidate. There is little published information on the behaviour of thermoplastic materials under combined AC and DC voltages.;In thermoplastic materials, HDPE film and PP film were selected as the target material to study in this project. As the properties of HDPE are similar to those of XLPE, the data obtained from HDPE was regarded as a bench-mark. It was decided to use the thermo-electrical stress to age the samples. For thermal stress, 90°C was chosen as the aging temperature for HDPE, while 90°C and 110°C were chosen for PP.;For the electrical stress, AC & DC combined voltage was used to age the samples. DC voltage was 6 kV. The superimposed frequency of AC voltage was 1 kHz, 1.5 kHz, 2 kHz and 2.5 kHz. The AC/DC voltage ratio is from 10%, 30% and 50%. In this project, the effect of frequency and voltage ratio on HDPE and PP degradation under superimposed stresses was studied using the following approaches:;Equivalent Phase Resolved Partial Discharge (PRPD) plots, Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR) Spectroscopy and Dielectric Spectroscopy (DS) measurements were carried out. The performance of HDPE and PP were compared.Cable termination is the weakest part in any HV underground cable system, as defects may be left in the main insulation during the installation process. In HVDC systems, the converters produce the intended DC voltage for transmission but there may also be AC harmonics superimposed. The frequency of the AC harmonics could be in kHz range. The superimposed harmonics on the HVDC may have synergistic effects on cable insulation and may lead to further degradation in the cable insulation.;In addition, for the sake of environmental protection, XLPE is no longer the suitable choice for underground cable insulation as it cannot be recycled. Thermoplastic material may be a candidate. There is little published information on the behaviour of thermoplastic materials under combined AC and DC voltages.;In thermoplastic materials, HDPE film and PP film were selected as the target material to study in this project. As the properties of HDPE are similar to those of XLPE, the data obtained from HDPE was regarded as a bench-mark. It was decided to use the thermo-electrical stress to age the samples. For thermal stress, 90°C was chosen as the aging temperature for HDPE, while 90°C and 110°C were chosen for PP.;For the electrical stress, AC & DC combined voltage was used to age the samples. DC voltage was 6 kV. The superimposed frequency of AC voltage was 1 kHz, 1.5 kHz, 2 kHz and 2.5 kHz. The AC/DC voltage ratio is from 10%, 30% and 50%. In this project, the effect of frequency and voltage ratio on HDPE and PP degradation under superimposed stresses was studied using the following approaches:;Equivalent Phase Resolved Partial Discharge (PRPD) plots, Fourier Transform Infrared - Attenuated Total Reflection (FTIR-ATR) Spectroscopy and Dielectric Spectroscopy (DS) measurements were carried out. The performance of HDPE and PP were compared
Immunomodulatory effect of the Acanthocheilonema viteae product ES-62 in arthropod extract models of asthma
No full textExcretory Secretory (ES)-62 is a product of the helminth Acanthocheilonema viteae, a member of a group of parasites known to inhibit or modulate inflammation. ES-62 has been previously shown to inhibit ovalbumin (OVA)-induced airway allergy. Additionally, the small molecule analogue 12b based on the ES product has been found to alleviate inflammation in a house dust mite extract (HDME) allergy model.;The intention of this study was to identify whether ES-62 inhibits the induction of allergy in cockroach extract (CRE) and HDME models through the analysis of several key parameters of allergy induction. ES-62 displayed some immunomodulatory activity at 1 μg/dose in the CRE allergy model. Specifically, CRE allergy-amplified Interleukin-4 (Il4), Il13 and Ifng pulmonary gene expression was reduced with ES-62 treatment.;ES-62 also decreased the level of peribronchial inflammatory infiltrate and marginally reduced the Immunoglobulin G1 (IgG1) response to CRE. Essentially no activity was seen at 2 μg/dose of ES-62 in the same model; though whether this is due to a difference in composition of CRE extract employed remains to be clarified. ES-62 is also given as a therapeutic intranasally for the first time in mice with induced airway allergy.;In the second model employed, HDME allergy, phosphorylcholine-specific IgM antibodies were produced in the presence of ES-62 in combination with HDME but not HDME alone. ES-62 lacked efficacy in this model, though further work should be undertaken to investigate dosage alterations before final conclusions are drawn.Excretory Secretory (ES)-62 is a product of the helminth Acanthocheilonema viteae, a member of a group of parasites known to inhibit or modulate inflammation. ES-62 has been previously shown to inhibit ovalbumin (OVA)-induced airway allergy. Additionally, the small molecule analogue 12b based on the ES product has been found to alleviate inflammation in a house dust mite extract (HDME) allergy model.;The intention of this study was to identify whether ES-62 inhibits the induction of allergy in cockroach extract (CRE) and HDME models through the analysis of several key parameters of allergy induction. ES-62 displayed some immunomodulatory activity at 1 μg/dose in the CRE allergy model. Specifically, CRE allergy-amplified Interleukin-4 (Il4), Il13 and Ifng pulmonary gene expression was reduced with ES-62 treatment.;ES-62 also decreased the level of peribronchial inflammatory infiltrate and marginally reduced the Immunoglobulin G1 (IgG1) response to CRE. Essentially no activity was seen at 2 μg/dose of ES-62 in the same model; though whether this is due to a difference in composition of CRE extract employed remains to be clarified. ES-62 is also given as a therapeutic intranasally for the first time in mice with induced airway allergy.;In the second model employed, HDME allergy, phosphorylcholine-specific IgM antibodies were produced in the presence of ES-62 in combination with HDME but not HDME alone. ES-62 lacked efficacy in this model, though further work should be undertaken to investigate dosage alterations before final conclusions are drawn
New approaches to real time monitoring of bio-manufacturing processes
Get PDFOver the past decade the bioprocessing industry has embraced and led the creation of a number of initiatives to drive process development and optimisation. There has consequently been an increased demand for tools capable of meeting the requirements of these initiatives. Spectroscopic monitoring systems such as Near infrared (NIR), Mid infrared (MIR) and Raman can provide a number of substantial advantages over more conventional off-line monitoring methods, normally applied to bioprocessing. With these techniques the bioprocessing industry has means of meeting these demanding challenges. The aim of study was to determine the feasibility of using NIR, MIR and Raman spectroscopy as a combined 'toolkit' to correlate changes in metabolic profile to spectral changes, within low passage Chinese Hamster Ovary cell cultures. The target metabolites focused upon in the spectroscopic analysis for this study were glucose and lactate. Conventional off-line techniques were used to investigate any correlation between spectral changes and those in the reference data. A design of experiment (DoE) approach was used to identify the optimum preprocessing techniques of the data and to build more accurate process trajectory models. These models were subjected to both an internal and external validation to guarantee the reliability of the results. Feasibility of data fusion, to create a single 'fused' dataset from the three spectroscopic techniques was also assessed, to produce a model with lower errors of prediction that the individual parts. The other area investigated was the characterisation of low passage number cultures in various media and process formats, which was of interest to the industrial collaborators. To test this three media; CD CHO, CD OptiCHO and Dynamis were provided by Thermo Fisher Scientific. Currently there is no system which utilises this toolkit with a combined DoE and data fusion strategy, within the bioprocessing industry. This research demonstrates a gap in the industry and a novel approach as to how tackle process monitoring. The results in this project demonstrate the varying degrees of success the spectroscopic techniques across all process formats and media. The NIR proved to be the most successful at modelling the target metabolites, with MIR being unsuccessful and Raman only being able to detect but not model the metabolites. This research provides an indicator of media suitability in low passage number cell cultures, by comparing the batch culture processes. The CD CHO media proved to be the best of the three tested media, based upon the cell density, viability and mAb titre produced. Overall this study represents a valuable stage in the progression towards real time monitoring of biomanufacturing processes and development of tailored low passage number cell culture media. However there are areas of this study where further investigation could be improved.Over the past decade the bioprocessing industry has embraced and led the creation of a number of initiatives to drive process development and optimisation. There has consequently been an increased demand for tools capable of meeting the requirements of these initiatives. Spectroscopic monitoring systems such as Near infrared (NIR), Mid infrared (MIR) and Raman can provide a number of substantial advantages over more conventional off-line monitoring methods, normally applied to bioprocessing. With these techniques the bioprocessing industry has means of meeting these demanding challenges. The aim of study was to determine the feasibility of using NIR, MIR and Raman spectroscopy as a combined 'toolkit' to correlate changes in metabolic profile to spectral changes, within low passage Chinese Hamster Ovary cell cultures. The target metabolites focused upon in the spectroscopic analysis for this study were glucose and lactate. Conventional off-line techniques were used to investigate any correlation between spectral changes and those in the reference data. A design of experiment (DoE) approach was used to identify the optimum preprocessing techniques of the data and to build more accurate process trajectory models. These models were subjected to both an internal and external validation to guarantee the reliability of the results. Feasibility of data fusion, to create a single 'fused' dataset from the three spectroscopic techniques was also assessed, to produce a model with lower errors of prediction that the individual parts. The other area investigated was the characterisation of low passage number cultures in various media and process formats, which was of interest to the industrial collaborators. To test this three media; CD CHO, CD OptiCHO and Dynamis were provided by Thermo Fisher Scientific. Currently there is no system which utilises this toolkit with a combined DoE and data fusion strategy, within the bioprocessing industry. This research demonstrates a gap in the industry and a novel approach as to how tackle process monitoring. The results in this project demonstrate the varying degrees of success the spectroscopic techniques across all process formats and media. The NIR proved to be the most successful at modelling the target metabolites, with MIR being unsuccessful and Raman only being able to detect but not model the metabolites. This research provides an indicator of media suitability in low passage number cell cultures, by comparing the batch culture processes. The CD CHO media proved to be the best of the three tested media, based upon the cell density, viability and mAb titre produced. Overall this study represents a valuable stage in the progression towards real time monitoring of biomanufacturing processes and development of tailored low passage number cell culture media. However there are areas of this study where further investigation could be improved
Regulation of the autophagy pro-survival mechanism by ULK1
No full textAutophagy (from Greek to mean self‐eating) is a highly conserved pro‐survival pathway found in almost every type of eukaryotic cell. Autophagy occurs constitutively but also serves as an important stress induced cellular response in multiple contexts. Dysfunction of the autophagic pathway is strongly associated with numerous human pathologies such as cancer and neurodegeneration driving the need for better overall understanding of the fundamental mechanisms. The Uncoordinated 51‐like kinases (ULK1/2) are essential autophagy regulators that function in complex with several additional regulatory proteins. ULK complexes are critically positioned early during the signalling pathway controlling autophagosome biogenesis, receiving and integrating information from the upstream nutrient sensors mechanistic target of rapamycin (MTOR) and AMP‐activated protein kinase (AMPK).Specific roles for ULK1 as compared to its related, but less understood family member,ULK2, were unclear. However, this issue needed to be resolved to better understandhow to target this kinase pathway to block autophagy. Therefore, within this thesis, it has been investigated ULK1 and ULK2 might differentially regulate autophagic activation was investigated. Findings within this thesis support functional redundancy between ULK1 and ULK2 for nutrient-dependent initiation of autophagy. In addition, these data have indicated unexpectedly that glucose starvation fails to induce canonical autophagy as observed in amino acid withdrawal, therefore highlighting the differential autophagy responses that arise following amino acid‐dependent MTOR vs. glucose‐dependent AMPK signalling events. Finally, this thesis aimed to understand regions of ULK1 that were critical for autophagy function, focussing on C‐terminal (early autophagy tethering "EAT") domain. The findings indicate that small helical sub‐regions of the EAT are sufficient to mediate binding to its accessory protein Atg13 and also for binding to membranes. However, more complete regions of the EAT are needed for ULK1 function in cells. Data also suggests that ULK1 interacts with specialized membrane micro‐domains known as lipid rafts.Overall, these combined approaches offered definitive evidence for ULK1/ULK2 functional redundancy in vivo, evidence of distinct MTOR and AMPK nutrient sensing pathways for autophagy; and lastly, further definition of distinct regions within the ULK1/2 EAT regulatory domain. These basic findings further support the developmentof novel inhibitors that could provide similar effects to modulate autophagy in applied settings.Autophagy (from Greek to mean self‐eating) is a highly conserved pro‐survival pathway found in almost every type of eukaryotic cell. Autophagy occurs constitutively but also serves as an important stress induced cellular response in multiple contexts. Dysfunction of the autophagic pathway is strongly associated with numerous human pathologies such as cancer and neurodegeneration driving the need for better overall understanding of the fundamental mechanisms. The Uncoordinated 51‐like kinases (ULK1/2) are essential autophagy regulators that function in complex with several additional regulatory proteins. ULK complexes are critically positioned early during the signalling pathway controlling autophagosome biogenesis, receiving and integrating information from the upstream nutrient sensors mechanistic target of rapamycin (MTOR) and AMP‐activated protein kinase (AMPK).Specific roles for ULK1 as compared to its related, but less understood family member,ULK2, were unclear. However, this issue needed to be resolved to better understandhow to target this kinase pathway to block autophagy. Therefore, within this thesis, it has been investigated ULK1 and ULK2 might differentially regulate autophagic activation was investigated. Findings within this thesis support functional redundancy between ULK1 and ULK2 for nutrient-dependent initiation of autophagy. In addition, these data have indicated unexpectedly that glucose starvation fails to induce canonical autophagy as observed in amino acid withdrawal, therefore highlighting the differential autophagy responses that arise following amino acid‐dependent MTOR vs. glucose‐dependent AMPK signalling events. Finally, this thesis aimed to understand regions of ULK1 that were critical for autophagy function, focussing on C‐terminal (early autophagy tethering "EAT") domain. The findings indicate that small helical sub‐regions of the EAT are sufficient to mediate binding to its accessory protein Atg13 and also for binding to membranes. However, more complete regions of the EAT are needed for ULK1 function in cells. Data also suggests that ULK1 interacts with specialized membrane micro‐domains known as lipid rafts.Overall, these combined approaches offered definitive evidence for ULK1/ULK2 functional redundancy in vivo, evidence of distinct MTOR and AMPK nutrient sensing pathways for autophagy; and lastly, further definition of distinct regions within the ULK1/2 EAT regulatory domain. These basic findings further support the developmentof novel inhibitors that could provide similar effects to modulate autophagy in applied settings
Numerical prediction of ship manoeuvring in regular waves by a 2.5D approach
Get PDFThis thesis intends to study the manoeuverability of a single ship advancing in regular waves which is believed to be important for ship navigation safety as the situation is much more common experienced by a seagoing ship in real seaways instead of the calm water environment for traditional manoeuverability analysis.;For this purpose, a so called two time scales model is applied to study the problem, according to the difference of the motion frequencies between the two involved sub-problems. That is to say, the total ship motions are consist of two parts, namely the wave induced motions analysed in a rapidly varying time scale system and the manoeuvring motions associated with a slowly varying time scale system. The two systems exchange data with each other at specific time intervals to reflect the interaction between two sub-motions. By this means, the analysis for an advancing ship executing a maneuver in waves can be achieved.;To make concrete analysis of the sub-problems, a boundary element method (BEM) based on the 2.5 dimensional (2.5D) potential flow theory is adopted to solve the 5 degrees of freedom (DOF) rapidly varying wave induced motions, i.e., the seakeeping problem of slender ships advancing at speeds from moderate to relatively high is determined by interactively solving the discrete boundary integrate equation, kinematic and dynamic boundary conditions on the free surface in cross sections from bow to stern in time domain. Besides, this method is also used for the estimation of the manoeuvring derivatives required by the manoeuvring analysis.;A numerical scheme called Multi-Transmitting Formula (MTF) is imposed on an artificial boundary to satisfy the radiation condition. The lift force, regarded as a consequence of the 3 dimensional (3D) flow effect which is important to manoeuvring motions but normally be neglected in the 2.5D theory, is taken into account for the evaluation of the total hydrodynamic forces acting on the ship during lateral motions. Furthermore, Non-Uniform Rational B-Spline (NURBS) is used for modelling the body plans of the ship and expressing the unknown quantities on the boundary elements to give more accurate and smoother solutions for the boundary value problems (BVP).;To validate the established numerical tool, computations are carried out on a WigleyIII hull, a Series 60 hull and a container ship S175 hull respectively. The results are compared with the available experimental data.;Regarding the manoeuvring motion simulations, the model is established based on the modular concept proposed by the Japanese Mathematical Modelling Group (MMG). The forces and moments induced by the propulsion system, the rudder system and the nonlinear viscous effect are estimated separately by empirical formulae or directly obtained from experimental measurements. The mean second order wave drift force is determined by direct pressure integration depending on the solved linear velocity potential from the seakeeping module.;Simulations of the standard free running maneuvers, namely turning circle motion and Zig-zag motion, are carried out on the S175 ship in calm water and different regular waves successively. The results are compared with experimental measurements for validation which demonstrates that the present numerical tool can reasonably predict the manoeuvring motions of a slender ship in regular waves.This thesis intends to study the manoeuverability of a single ship advancing in regular waves which is believed to be important for ship navigation safety as the situation is much more common experienced by a seagoing ship in real seaways instead of the calm water environment for traditional manoeuverability analysis.;For this purpose, a so called two time scales model is applied to study the problem, according to the difference of the motion frequencies between the two involved sub-problems. That is to say, the total ship motions are consist of two parts, namely the wave induced motions analysed in a rapidly varying time scale system and the manoeuvring motions associated with a slowly varying time scale system. The two systems exchange data with each other at specific time intervals to reflect the interaction between two sub-motions. By this means, the analysis for an advancing ship executing a maneuver in waves can be achieved.;To make concrete analysis of the sub-problems, a boundary element method (BEM) based on the 2.5 dimensional (2.5D) potential flow theory is adopted to solve the 5 degrees of freedom (DOF) rapidly varying wave induced motions, i.e., the seakeeping problem of slender ships advancing at speeds from moderate to relatively high is determined by interactively solving the discrete boundary integrate equation, kinematic and dynamic boundary conditions on the free surface in cross sections from bow to stern in time domain. Besides, this method is also used for the estimation of the manoeuvring derivatives required by the manoeuvring analysis.;A numerical scheme called Multi-Transmitting Formula (MTF) is imposed on an artificial boundary to satisfy the radiation condition. The lift force, regarded as a consequence of the 3 dimensional (3D) flow effect which is important to manoeuvring motions but normally be neglected in the 2.5D theory, is taken into account for the evaluation of the total hydrodynamic forces acting on the ship during lateral motions. Furthermore, Non-Uniform Rational B-Spline (NURBS) is used for modelling the body plans of the ship and expressing the unknown quantities on the boundary elements to give more accurate and smoother solutions for the boundary value problems (BVP).;To validate the established numerical tool, computations are carried out on a WigleyIII hull, a Series 60 hull and a container ship S175 hull respectively. The results are compared with the available experimental data.;Regarding the manoeuvring motion simulations, the model is established based on the modular concept proposed by the Japanese Mathematical Modelling Group (MMG). The forces and moments induced by the propulsion system, the rudder system and the nonlinear viscous effect are estimated separately by empirical formulae or directly obtained from experimental measurements. The mean second order wave drift force is determined by direct pressure integration depending on the solved linear velocity potential from the seakeeping module.;Simulations of the standard free running maneuvers, namely turning circle motion and Zig-zag motion, are carried out on the S175 ship in calm water and different regular waves successively. The results are compared with experimental measurements for validation which demonstrates that the present numerical tool can reasonably predict the manoeuvring motions of a slender ship in regular waves
A critical evaluation of wind turbine technology, leading to the development of 20mw multi rotor systems
Get PDFThe development of the conventional wind turbine from conception to modern day has been based on evolutionary and incremental design changes. Current existing commercial horizontal axis machines have yet to breach the 6MW power rating without significant cost penalties. The reason for this is primarily due to the negative effects of the square cubed law which shows that any increase in turbine diameter will lead to a cubic increase in turbine mass for only a square increase in power output.;Unfortunately, this universal truth can only be delayed and not ignored by advances in wind energy systems and it is therefore probable that conventional machines are nearing their power rating limits.;This project is focused firstly on a concerted review and evaluation of the wind energy design space followed by a more detailed study of those systems which theoretically should scale well with size and which may allow the wind industry to move to individual ratings of 10MW and beyond. Multi rotor systems with ratings of 20MW and above have been identified as serious contenders when considering cost of energy - the reduction of which, is a primary objective of the wind industry.;Detailed cost analysis, conducted after extensive development of the multi rotor concept has found that multi rotors can provide cost of energy at around 85% of conventional 10MW single rotor machines and around 82% of a conventional 20MW machine in a far-offshore environment.;More specifically, this thesis details the development of the multi rotor system from initial concept, considering all the main engineering points and presenting them in a useful way to alleviate concerns and pioneer the way for future research into the concept.The development of the conventional wind turbine from conception to modern day has been based on evolutionary and incremental design changes. Current existing commercial horizontal axis machines have yet to breach the 6MW power rating without significant cost penalties. The reason for this is primarily due to the negative effects of the square cubed law which shows that any increase in turbine diameter will lead to a cubic increase in turbine mass for only a square increase in power output.;Unfortunately, this universal truth can only be delayed and not ignored by advances in wind energy systems and it is therefore probable that conventional machines are nearing their power rating limits.;This project is focused firstly on a concerted review and evaluation of the wind energy design space followed by a more detailed study of those systems which theoretically should scale well with size and which may allow the wind industry to move to individual ratings of 10MW and beyond. Multi rotor systems with ratings of 20MW and above have been identified as serious contenders when considering cost of energy - the reduction of which, is a primary objective of the wind industry.;Detailed cost analysis, conducted after extensive development of the multi rotor concept has found that multi rotors can provide cost of energy at around 85% of conventional 10MW single rotor machines and around 82% of a conventional 20MW machine in a far-offshore environment.;More specifically, this thesis details the development of the multi rotor system from initial concept, considering all the main engineering points and presenting them in a useful way to alleviate concerns and pioneer the way for future research into the concept
Gallium nitride light-emitting diode enabled visible light communications
Get PDFThis thesis focuses on the development, measurement and application of novel micrometre-sized light emitting diodes (micro-LEDs) based on Gallium Nitride (GaN) for visible light communications (VLC) in both free-space and guided wave configurations. The goal is to set benchmarks for LED-based wireless optical communications. An overview of the field integrating research, industry and standards is presented.A top-down approach is taken with application requirements driving development of new micro-LEDs with simultaneously increased optical power and modulation bandwidth. This was achieved by mitigating two limitations, namely current crowding and mutual device heating.Two novel techniques were developed to access pixel performance: spatially-resolved mapping of modulation bandwidth and spectral characteristics, and thermal imaging. On this basis, broad-area LEDs were used to understand the independent benefits, providing insight for the design of novel micro-LEDs. Circular segmented micro-LEDs emitting at 450nm achieved modulation bandwidths in excess of 800MHz, the highest reported for LEDs, while maintaining optical power above 2mW. In data transmission using systems with 1.8GHz bandwidth,the devices achieved 8Gbps in free-space and guided-wave operation at wavelengths of 400nm, 450nm and 520nm. Ring and half-ring micro-LEDs introduced here have shown modulation bandwidths that scale with the increase of active area and consequently optical power. Bandwidths in excess of of 600MHz were achieved at optical powers over 5mW. In data transmission using a system limited to 1GHz bandwidth, these devices achieved 7Gbps in free-space operation.This thesis focuses on the development, measurement and application of novel micrometre-sized light emitting diodes (micro-LEDs) based on Gallium Nitride (GaN) for visible light communications (VLC) in both free-space and guided wave configurations. The goal is to set benchmarks for LED-based wireless optical communications. An overview of the field integrating research, industry and standards is presented.A top-down approach is taken with application requirements driving development of new micro-LEDs with simultaneously increased optical power and modulation bandwidth. This was achieved by mitigating two limitations, namely current crowding and mutual device heating.Two novel techniques were developed to access pixel performance: spatially-resolved mapping of modulation bandwidth and spectral characteristics, and thermal imaging. On this basis, broad-area LEDs were used to understand the independent benefits, providing insight for the design of novel micro-LEDs. Circular segmented micro-LEDs emitting at 450nm achieved modulation bandwidths in excess of 800MHz, the highest reported for LEDs, while maintaining optical power above 2mW. In data transmission using systems with 1.8GHz bandwidth,the devices achieved 8Gbps in free-space and guided-wave operation at wavelengths of 400nm, 450nm and 520nm. Ring and half-ring micro-LEDs introduced here have shown modulation bandwidths that scale with the increase of active area and consequently optical power. Bandwidths in excess of of 600MHz were achieved at optical powers over 5mW. In data transmission using a system limited to 1GHz bandwidth, these devices achieved 7Gbps in free-space operation
Contribution of biomechanical measurements to detection of toxicity in vitro : an atomic force microscope study
Get PDFThe liver has a wide range of capabilities and is the key organ for drug metabolism, detoxification and elimination. Molecules are absorbed from the GI tract into the bloodstream and transported to the liver through the portal vein circulation system. Most of the metabolic functions within the liver are processed by hepatocytes. The project aim was to test two drugs (5-Fluorouracil (5-FU) and diclofenac) with different metabolic pathways, interpret their toxic effects in hepatocytes and relate these to mechanical and morphological alterations in the cells. The findings of this project thereby allow development of a cell mechanics model for toxicity profiling and drug efficacy at a subcellular level.;Hepatocellular carcinoma (HCC) is the second most common cancer in the world and the most frequent type of liver cancer. Therefore, a great amount of effort has been aimed at the discovery of anticancer compounds to treat it. The majority of conventional chemotherapeutic drugs work on the principle of halting DNA synthesis, and 5-FU follows this principle. This drug is also commonly used for treatment for most gastrointestinal tract cancers. When 5-FU is administered, the toxic adverse effects need to be considered as there is a possibility of severe side effects.;To characterise toxic changes in hepatocytes, an Atomic Force Microscope (AFM) was used, which can produce high-resolution images by probing the surface of the cell, to provide information on the cell's mechanical properties (such as Young's modulus). However, with the complexity of this technique it has proved to be challenging to measure relative Young's modulus values that minimise artefacts which affected the image quality of the cells.;Using 5-FU as a model drug, apoptosis was detected by relating surface morphology and mechanical measurements. The surface morphology of HepG2 cells was examined with AFM, and the images produced showed cells exhibiting networking lines of a fibrous nature on the cell surface and protrusions from the cell membrane after the application of 5-FU. This is thought to be related to apoptotic behaviour occurring within the cell but this is not conclusive and further investigations need to be conducted.;Mitochondria are the main source of adenosine triphosphate (ATP), which is vital for energy, and therefore control all active processes within the cell. Mitochondrial injury often occurs due to drug toxicity, causing altered metabolic function within the cells. Diclofenac is a widely prescribed NSAID, which may cause serious hepatotoxicity, and is thought to be a mitochondrial toxicant.;When altering the physiological conditions from glucose containing medium to galactose containing medium, it was shown that the growth and metabolic function of HepG2 cells decreased. Diclofenac caused a depletion of ATP within the cells. When imaging the cell with AFM, after treatment with diclofenac, there were alterations at surface of HepG2 cells. When the cantilever was separated from the cell surface, the retraction curves showed intermolecular interactions occurring, after treatment with diclofenac which were not observed if the cells were untreated. Microscopic evidence suggested apoptosis may have occurred and it is proposed that the changes in the cell surface reflect this.;Liposomes consisting of lipid bilayers can encapsulate a wide range of drugs, and their behaviour can be controlled by modifying their surface properties. This research also studied the production of liposomes in order to understand their interaction with cells. Liposomal delivery systems are used to improve the bioavailability of drugs and can reduce toxic effects. The liposomes were shown to engage with the cell surface by use of AFM but did not influence the cells viability, suggesting that they had potential as a non-toxic delivery system.;This thesis has produced initial data to suggest that changes in cell mechanical properties can be used to detect changes in cell behaviour, such as apoptosis, but the method is still fraught with complexity.The liver has a wide range of capabilities and is the key organ for drug metabolism, detoxification and elimination. Molecules are absorbed from the GI tract into the bloodstream and transported to the liver through the portal vein circulation system. Most of the metabolic functions within the liver are processed by hepatocytes. The project aim was to test two drugs (5-Fluorouracil (5-FU) and diclofenac) with different metabolic pathways, interpret their toxic effects in hepatocytes and relate these to mechanical and morphological alterations in the cells. The findings of this project thereby allow development of a cell mechanics model for toxicity profiling and drug efficacy at a subcellular level.;Hepatocellular carcinoma (HCC) is the second most common cancer in the world and the most frequent type of liver cancer. Therefore, a great amount of effort has been aimed at the discovery of anticancer compounds to treat it. The majority of conventional chemotherapeutic drugs work on the principle of halting DNA synthesis, and 5-FU follows this principle. This drug is also commonly used for treatment for most gastrointestinal tract cancers. When 5-FU is administered, the toxic adverse effects need to be considered as there is a possibility of severe side effects.;To characterise toxic changes in hepatocytes, an Atomic Force Microscope (AFM) was used, which can produce high-resolution images by probing the surface of the cell, to provide information on the cell's mechanical properties (such as Young's modulus). However, with the complexity of this technique it has proved to be challenging to measure relative Young's modulus values that minimise artefacts which affected the image quality of the cells.;Using 5-FU as a model drug, apoptosis was detected by relating surface morphology and mechanical measurements. The surface morphology of HepG2 cells was examined with AFM, and the images produced showed cells exhibiting networking lines of a fibrous nature on the cell surface and protrusions from the cell membrane after the application of 5-FU. This is thought to be related to apoptotic behaviour occurring within the cell but this is not conclusive and further investigations need to be conducted.;Mitochondria are the main source of adenosine triphosphate (ATP), which is vital for energy, and therefore control all active processes within the cell. Mitochondrial injury often occurs due to drug toxicity, causing altered metabolic function within the cells. Diclofenac is a widely prescribed NSAID, which may cause serious hepatotoxicity, and is thought to be a mitochondrial toxicant.;When altering the physiological conditions from glucose containing medium to galactose containing medium, it was shown that the growth and metabolic function of HepG2 cells decreased. Diclofenac caused a depletion of ATP within the cells. When imaging the cell with AFM, after treatment with diclofenac, there were alterations at surface of HepG2 cells. When the cantilever was separated from the cell surface, the retraction curves showed intermolecular interactions occurring, after treatment with diclofenac which were not observed if the cells were untreated. Microscopic evidence suggested apoptosis may have occurred and it is proposed that the changes in the cell surface reflect this.;Liposomes consisting of lipid bilayers can encapsulate a wide range of drugs, and their behaviour can be controlled by modifying their surface properties. This research also studied the production of liposomes in order to understand their interaction with cells. Liposomal delivery systems are used to improve the bioavailability of drugs and can reduce toxic effects. The liposomes were shown to engage with the cell surface by use of AFM but did not influence the cells viability, suggesting that they had potential as a non-toxic delivery system.;This thesis has produced initial data to suggest that changes in cell mechanical properties can be used to detect changes in cell behaviour, such as apoptosis, but the method is still fraught with complexity
Reconfiguring smart structures using approximate heteroclinic connections
Get PDFThe term smart structures is commonly used to describe structures which have the ability to actively change their geometry or mechanical properties. Potential applications can be found in the aerospace, energy and marine sectors, e.g. use of MEMS-type devices which require frequent switching of compliant components and morphing of advanced aerofoils to generate additional lift. Traditional reconfigurable smart structures are designed with multi-stable characteristics.;In particular, such structures can use stored strain energy to enable motion from one stable position to another stable position. However, the means of reconfiguring smart structures between stable con-figurations requires the input of, and then dissipation of energy to cross the potential barrier separating the stable configurations. Therefore, the accumulated work done for frequently actuated devices in reconfiguring between stable states can be significant.;Considering reconfigurable smart structures for power and energy constrained applications, this thesis investigates a novel concept of reconfiguring smart structures between unstable states. The vision is to take advantage of modern dynamical system theory to develop entirely new devices that use the instability of mechanical systems to deliver energy-efficient shape-changing structures.;This thesis indicates that theoretically in a simple model, transitioning between unstable states (so-called heteroclinic connections) can be more energy-efficient than traditional structures which transition between stable states and so need to cross a potential barrier. However, further experimental work will be required to verify this initial finding for real engineering systems. Clearly, energy is required to stabilize the unstable configurations, but if the energy required for active control of the instability is sufficiently small, or devices need to be frequently switched between different states, this concept is likely to be of benefit.;The concept of using instability for reconfiguration is demonstrated first by controlling a mass-spring chain model through a simple cubic nonlinearity, which is sufficient to provide the required qualitative behaviour of the system. A sufficiently smooth set of functions is then used to generate a path to approximate the heteroclinic connection, which is then used as reference trajectory for reconfiguring between different unstable configurations.;Moreover, the model is extended to a smart surface as a two-dimensional spring-mass array without dissipation. It is shown that the activere configuration scheme can be used to connect equal-energy unstable (but actively controlled) configurations for the purpose of energy-efficient morphing of the smart surface. However, in consideration of the difference between the cubic and real spring model, a spring-mass model with fully geometric non-linearity is also developed to verify the possibility of using heteroclinic connections to reconfigure future real smart structures.;Furthermore, by considering a compliant mechanism, the concept of reconfiguration of a four-bar mechanism using heteroclinic connections is also investigated. Different models varying from fully rigid to purely elastic are employed to be controlled for reconfiguring between different unstable configurations. In addition, a continuous buckled beam model has been investigated with its characteristics based on the Euler-Bernoulli beam theory. An experimental beam was fabricated with shape memory alloy actuators for active control. Although the shape memory alloy was a slow response to time, it illustrates the possibility of reconfiguration of smart structures by using heteroclinic connections.;In summary, this thesis demonstrates the potential of using heteroclinic connection to reconfigure smart structures with both numerical investigation and experimental validation.This entirely new approach to smart structures offers potentially significant benefits for power and energy constrained applications which require frequent reconfiguration.The term smart structures is commonly used to describe structures which have the ability to actively change their geometry or mechanical properties. Potential applications can be found in the aerospace, energy and marine sectors, e.g. use of MEMS-type devices which require frequent switching of compliant components and morphing of advanced aerofoils to generate additional lift. Traditional reconfigurable smart structures are designed with multi-stable characteristics.;In particular, such structures can use stored strain energy to enable motion from one stable position to another stable position. However, the means of reconfiguring smart structures between stable con-figurations requires the input of, and then dissipation of energy to cross the potential barrier separating the stable configurations. Therefore, the accumulated work done for frequently actuated devices in reconfiguring between stable states can be significant.;Considering reconfigurable smart structures for power and energy constrained applications, this thesis investigates a novel concept of reconfiguring smart structures between unstable states. The vision is to take advantage of modern dynamical system theory to develop entirely new devices that use the instability of mechanical systems to deliver energy-efficient shape-changing structures.;This thesis indicates that theoretically in a simple model, transitioning between unstable states (so-called heteroclinic connections) can be more energy-efficient than traditional structures which transition between stable states and so need to cross a potential barrier. However, further experimental work will be required to verify this initial finding for real engineering systems. Clearly, energy is required to stabilize the unstable configurations, but if the energy required for active control of the instability is sufficiently small, or devices need to be frequently switched between different states, this concept is likely to be of benefit.;The concept of using instability for reconfiguration is demonstrated first by controlling a mass-spring chain model through a simple cubic nonlinearity, which is sufficient to provide the required qualitative behaviour of the system. A sufficiently smooth set of functions is then used to generate a path to approximate the heteroclinic connection, which is then used as reference trajectory for reconfiguring between different unstable configurations.;Moreover, the model is extended to a smart surface as a two-dimensional spring-mass array without dissipation. It is shown that the activere configuration scheme can be used to connect equal-energy unstable (but actively controlled) configurations for the purpose of energy-efficient morphing of the smart surface. However, in consideration of the difference between the cubic and real spring model, a spring-mass model with fully geometric non-linearity is also developed to verify the possibility of using heteroclinic connections to reconfigure future real smart structures.;Furthermore, by considering a compliant mechanism, the concept of reconfiguration of a four-bar mechanism using heteroclinic connections is also investigated. Different models varying from fully rigid to purely elastic are employed to be controlled for reconfiguring between different unstable configurations. In addition, a continuous buckled beam model has been investigated with its characteristics based on the Euler-Bernoulli beam theory. An experimental beam was fabricated with shape memory alloy actuators for active control. Although the shape memory alloy was a slow response to time, it illustrates the possibility of reconfiguration of smart structures by using heteroclinic connections.;In summary, this thesis demonstrates the potential of using heteroclinic connection to reconfigure smart structures with both numerical investigation and experimental validation.This entirely new approach to smart structures offers potentially significant benefits for power and energy constrained applications which require frequent reconfiguration
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