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Socio-technical architectural model of collaborative engineering design
Get PDFCollaborative engineering design may be considered a socio-technical process. However, literature suggested that the fundamental constitution of the social and technical in the collaborative engineering design process and their interrelationships are unclear. Furthermore, most the identified studies tended to focus on either the social or technical collaborative engineering design with relatively little focus on their combined effects. To address these issues, the study reported in this thesis have developed an architectural model of socio-technical CED adapting the Enhanced Entity Relationship (EER) information modelling language.;The model was incrementally developed in three phases: 1). Model development, 2) model review and refinement, 3) model evaluation. Five versions of the socio-technical architectural model (STAM) of collaborative engineering design were created, each adopting methods to elicit insight from different sources. At the model development stage, the social and technical elements and their inter-relationships were induced from a literature review (i.e. resulting in STAM-1) and interviews with 28 collaborative engineering design practitioners (resulting in STAM-2).;The interviews were conducted in a UK company specialising in the design and manufacture of complex technical systems within the shipbuilding industry. The model was reviewed by a group of engineering design practitioners and academics through independent focus groups (resulting in STAM-3). To enhance the social perspective, an interview was conducted with an industrial psychology academic (yielding in STAM-4) and a review on the social collaboration literature was carried out (resulting in STAM-5).;The model was evaluated by industrial practitioners in three different companies, each with a different life phase and product focus. Preliminary evaluation was conducted in the first company using an interview method to assess the model's completeness. Findings from this interview support the completeness of the model. Learning from the evaluation approach in the first company, in the second and third company, independent focus groups and questionnaires were adopted.;In addition to completeness, the evaluation was conducted to assess the model's correctness, relevance, usefulness, ease of understanding, and achievement of purpose. Findings from the two companies generally support the correctness, relevance, and usefulness of the model. The findings showed that the model may form a basis for customisation to suite a specific company's requirement. The findings also support the general aim of the model, i.e. to provide insights into collaborative engineering design from the socio-technical perspective. Nonetheless, the findings suggest that the model was not easy to understand due to its structural complexity and terminology differences used.;Finally, the study and its findings were assessed to identify their strengths, weaknesses, and recommendations for future research.Collaborative engineering design may be considered a socio-technical process. However, literature suggested that the fundamental constitution of the social and technical in the collaborative engineering design process and their interrelationships are unclear. Furthermore, most the identified studies tended to focus on either the social or technical collaborative engineering design with relatively little focus on their combined effects. To address these issues, the study reported in this thesis have developed an architectural model of socio-technical CED adapting the Enhanced Entity Relationship (EER) information modelling language.;The model was incrementally developed in three phases: 1). Model development, 2) model review and refinement, 3) model evaluation. Five versions of the socio-technical architectural model (STAM) of collaborative engineering design were created, each adopting methods to elicit insight from different sources. At the model development stage, the social and technical elements and their inter-relationships were induced from a literature review (i.e. resulting in STAM-1) and interviews with 28 collaborative engineering design practitioners (resulting in STAM-2).;The interviews were conducted in a UK company specialising in the design and manufacture of complex technical systems within the shipbuilding industry. The model was reviewed by a group of engineering design practitioners and academics through independent focus groups (resulting in STAM-3). To enhance the social perspective, an interview was conducted with an industrial psychology academic (yielding in STAM-4) and a review on the social collaboration literature was carried out (resulting in STAM-5).;The model was evaluated by industrial practitioners in three different companies, each with a different life phase and product focus. Preliminary evaluation was conducted in the first company using an interview method to assess the model's completeness. Findings from this interview support the completeness of the model. Learning from the evaluation approach in the first company, in the second and third company, independent focus groups and questionnaires were adopted.;In addition to completeness, the evaluation was conducted to assess the model's correctness, relevance, usefulness, ease of understanding, and achievement of purpose. Findings from the two companies generally support the correctness, relevance, and usefulness of the model. The findings showed that the model may form a basis for customisation to suite a specific company's requirement. The findings also support the general aim of the model, i.e. to provide insights into collaborative engineering design from the socio-technical perspective. Nonetheless, the findings suggest that the model was not easy to understand due to its structural complexity and terminology differences used.;Finally, the study and its findings were assessed to identify their strengths, weaknesses, and recommendations for future research
Strategies for wireless networked control systems
Get PDFNetworked Control Systems (NCS) and Wireless Networked Control Systems (WNCS) are control systems where controllers, sensors and final elements of control are connected to a mutual communication network. The inclusion of the network introduces delays and dropouts, which greatly influence the stability and robustness of the controller. While there is wealth in theoretical contributions to NCS, it is still imperative to study more applications and investigate the effects of networks in a real-time operation.There are also open problems that require further study of the impact of disturbances, constraints and strong interactions in complex NCS. This thesis is concerned with the design of control strategies for WNCS mainly focused on Model-Based Predictive Control (MBPC), Proportional Integral Derivative (PID) and decentralised schemes with the aim of creating control laws suitable for compensating time-varying delays and dropouts. These strategies rely on optimisation problems which incorporate robustness and performance restrictions to compute the optimum controller. The performance and robustness of the controllers are evaluated through extensive experiments in a network simulator. A new adaptive Internal Model Control (IMC) controller has been developed to adapt to the network requirements and compute the IMC model parameters online. A new robust PID for NCS under random delays has been created by solving a new constrained optimisation problem that included constraints of maximum sensitivity to guarantee robustness. A novel optimal immune PID is developed to improve the performance of NCS under time-varying delays and dropouts. Simulation results show that the controller offers greater flexibility and improves the performance and robustness with respect to the other methods studied. Four more controllers have been tested and extensive tests have indicated stability for a limited percentage of process model variations and dropouts. Predictive PID controllers, with similar properties to MBPC, are developed to compensate dropouts in WNCS. A quadratic programming problem optimises a new MBPC cost function to find the optimal PID gains. The approach successfully maximises the performance by changing the controller gains at every sampling time and allowing maximum variations of system parameters and dropouts. Also, a new constrained predictive PID controller is presented to deal with input saturation. Simulation results show the superiority of the design in comparison with the control schemes studied earlier. Furthermore, a decentralised wireless networked model predictive control design for complex industrial systems has been developed. Also, the method has been applied to wind farm control. The proposed decentralised control offers an effective and innovative solution to improve the performance of large industrial applications.Networked Control Systems (NCS) and Wireless Networked Control Systems (WNCS) are control systems where controllers, sensors and final elements of control are connected to a mutual communication network. The inclusion of the network introduces delays and dropouts, which greatly influence the stability and robustness of the controller. While there is wealth in theoretical contributions to NCS, it is still imperative to study more applications and investigate the effects of networks in a real-time operation.There are also open problems that require further study of the impact of disturbances, constraints and strong interactions in complex NCS. This thesis is concerned with the design of control strategies for WNCS mainly focused on Model-Based Predictive Control (MBPC), Proportional Integral Derivative (PID) and decentralised schemes with the aim of creating control laws suitable for compensating time-varying delays and dropouts. These strategies rely on optimisation problems which incorporate robustness and performance restrictions to compute the optimum controller. The performance and robustness of the controllers are evaluated through extensive experiments in a network simulator. A new adaptive Internal Model Control (IMC) controller has been developed to adapt to the network requirements and compute the IMC model parameters online. A new robust PID for NCS under random delays has been created by solving a new constrained optimisation problem that included constraints of maximum sensitivity to guarantee robustness. A novel optimal immune PID is developed to improve the performance of NCS under time-varying delays and dropouts. Simulation results show that the controller offers greater flexibility and improves the performance and robustness with respect to the other methods studied. Four more controllers have been tested and extensive tests have indicated stability for a limited percentage of process model variations and dropouts. Predictive PID controllers, with similar properties to MBPC, are developed to compensate dropouts in WNCS. A quadratic programming problem optimises a new MBPC cost function to find the optimal PID gains. The approach successfully maximises the performance by changing the controller gains at every sampling time and allowing maximum variations of system parameters and dropouts. Also, a new constrained predictive PID controller is presented to deal with input saturation. Simulation results show the superiority of the design in comparison with the control schemes studied earlier. Furthermore, a decentralised wireless networked model predictive control design for complex industrial systems has been developed. Also, the method has been applied to wind farm control. The proposed decentralised control offers an effective and innovative solution to improve the performance of large industrial applications
Chemoselective Suzuki-Miyaura cross-coupling enabled by speciation control
Get PDFBoronic acids and esters are one of the most widely used compound classes inorganic chemistry. Recently, diboron systems have emerged as a powerful approach towards complex molecule synthesis. Selectivity in these systems is typically achieved through the use of protecting group strategies in which one boron residue is rendered unreactive under the prevailing reaction conditions, allowing selective manipulation of an unprotected unit. However, while these methods offer excellent selectivity, they do have the drawback of requiring additional synthetic manipulations, i.e., removal of the protecting group to allow subsequent functionalisation, limiting the overall efficiency of these processes. Boronic acids and esters undergo complex equilibria in solution. We have shown that control of these equilibria has been leveraged during the Suzuki-Miyaura reaction to enable the formation of a new, reactive BP in ester without the need for additional protecting group manipulations. Extensive optimisation identified that the nature of the base and quantity of water in the reaction were key in controlling the speciation events in the reaction. This allowed the generation of a broad substrate scope of formally homologated BPin esters. These newly generated reactive boron species were then reacted in situ in an iterative process, forming either terminal triaryl or contolled homologation products. The reaction was also found to have a temperature dependence, where under identical controlled basic conditions either the homologated BPin or the cross-coupled BMIDA species could be obtained based purely upon the temperature of the reaction. A series of control reactions aided in identifying the key processes in the reaction and, more importantly, the order in which these processes must occur in order to achieve the desired reaction.This work led to the development of methods to enable chemoselective reactions within non-protected diboron systems. This demonstrated how chemoselective Suzuki-Miyaura cross-coupling can be achieved within boronic acid/BPin esterdiboron systems by exploiting kinetic control of transmetallation while maintaining control of solution speciation events. This allows the selective reaction of boronic acids in the presence of BPin esters again without the need for protecting group manipulations, as either additional synthetic steps or in situ. Chemoselective transmetallation was then combined with chemoselective oxidative addition in order to establish the first complete chemoselective control over two of the three key mechanistic processes of the Suzuki-Miyaura reaction. This enables a one-pot sequential chemoselective Suzuki-Miyaura reaction without the requirement for any in situ modification of the reaction conditions (temperature change, sequential addition) or reactants (protecting group removal, boron species interconversion).Boronic acids and esters are one of the most widely used compound classes inorganic chemistry. Recently, diboron systems have emerged as a powerful approach towards complex molecule synthesis. Selectivity in these systems is typically achieved through the use of protecting group strategies in which one boron residue is rendered unreactive under the prevailing reaction conditions, allowing selective manipulation of an unprotected unit. However, while these methods offer excellent selectivity, they do have the drawback of requiring additional synthetic manipulations, i.e., removal of the protecting group to allow subsequent functionalisation, limiting the overall efficiency of these processes. Boronic acids and esters undergo complex equilibria in solution. We have shown that control of these equilibria has been leveraged during the Suzuki-Miyaura reaction to enable the formation of a new, reactive BP in ester without the need for additional protecting group manipulations. Extensive optimisation identified that the nature of the base and quantity of water in the reaction were key in controlling the speciation events in the reaction. This allowed the generation of a broad substrate scope of formally homologated BPin esters. These newly generated reactive boron species were then reacted in situ in an iterative process, forming either terminal triaryl or contolled homologation products. The reaction was also found to have a temperature dependence, where under identical controlled basic conditions either the homologated BPin or the cross-coupled BMIDA species could be obtained based purely upon the temperature of the reaction. A series of control reactions aided in identifying the key processes in the reaction and, more importantly, the order in which these processes must occur in order to achieve the desired reaction.This work led to the development of methods to enable chemoselective reactions within non-protected diboron systems. This demonstrated how chemoselective Suzuki-Miyaura cross-coupling can be achieved within boronic acid/BPin esterdiboron systems by exploiting kinetic control of transmetallation while maintaining control of solution speciation events. This allows the selective reaction of boronic acids in the presence of BPin esters again without the need for protecting group manipulations, as either additional synthetic steps or in situ. Chemoselective transmetallation was then combined with chemoselective oxidative addition in order to establish the first complete chemoselective control over two of the three key mechanistic processes of the Suzuki-Miyaura reaction. This enables a one-pot sequential chemoselective Suzuki-Miyaura reaction without the requirement for any in situ modification of the reaction conditions (temperature change, sequential addition) or reactants (protecting group removal, boron species interconversion)
Impact of network relational and structural embeddedness on firm's innovation : a study at the Saudi firm's level
Get PDFFirms are facing great challenges in the rapidly changing economy of today's world. Therefore, firms have begun searching for new means and ways to innovate in order to stay alive, compete and grow. However, many firms have yet to discover that their embedded network of relations and structures can play a crucial role in their innovation outcomes. As a result, there is growing consensus among innovation scholars that networking and inter-firm collaboration are key strategies in stimulating innovation within firms. This has resulted in a growing body of literature focused on studying the link between innovation performance and firm participation and position in networks. However, there is still disagreement and fragmented results among scholars regarding the optimum firm's network embeddedness configuration for both product and process innovation. Moreover, firms should be aware of the type of network embeddedness configurations that could constrain their innovation performance. This remains unresolved academic and practitioner challenges that require detailed investigation. Furthermore, a limited number of studies have theoretically discussed and empirically tested this research area in the context of emerging economies.This research study addresses the aforementioned challenges and aims to shed light on the relationship between firms' network embeddedness characteristics (i.e. relational embeddedness and structural embeddedness) and their innovation output (i.e. product and process innovation).;This study draws primarily on three complimentary perspectives-social capital, social network and network embeddedness-in order to shed more light on the effect that network embeddedness characteristics have on firms' product and process innovation. Furthermore, the thesis aims to both conceptually and empirically reveal the influence that network embeddedness aspects have on innovation outcomes in the context of emerging economies, with particular reference to medium and high (M&H) technology sectors in Saudi Arabia.The study draws on the significance of network embeddedness characteristics in influencing firms' innovation performance with the principle aim of unravelling key network relational and structural embeddedness characteristics at the firm's level. This research is primarily based on new empirical evidence from the primary source data of 121 firms in M&H technology sectors in Saudi Arabia, using social network analysis and logistic regression modelling to investigate the effect of various configurations of firms' network, relational and structural embeddedness characteristics on the types of innovation (i.e. product and process innovation). The results of this study indicate that firms' innovation outcomes largely depend on their various network relational and structural embeddedness configurations. As a result, in order to fully capture the impact of network embeddedness characteristics on firms' innovation outcomes, network relational and structural embeddedness characteristics should be jointly considered (i.e. the interaction effect among different network embeddedness settings).;The evidence reveals that, by analysing the combination of firms' relational and structural network embeddedness characteristics, firms can recognise the potential, associated effects in product and process innovation outputs. This is indicated by the interaction effect between network embeddedness relational aspects (i.e. strong/weak ties) and structural properties (i.e. dense/sparse network and peripheral/central position). For instance, the findings suggest that, for high-density and central network embeddedness, strong ties type of relations will have a positive impact on firms' product and process innovation. In contrast, the empirical analysis suggests that firms that are sparsely and peripherally embedded in a network will become better product and process innovators if they develop relationships with other organisations in terms of weak ties type of relations.The outcome of this research has both theoretical and practical implications. These implications are theoretical in the sense that they provide new insights into innovation networks area from the social capital, social network and network embeddedness perspectives, jointly considering firms' network relational and structural embeddedness characteristics, as well as the direct, and the interaction effect on firm's innovation outcome. Regarding managerial implications, this study highlights the primary network structural properties, specifically addressing their direct, interaction effect on firms' product and process innovation. This could guide professional managers aiming for high innovation performance to re-evaluate their firms' network embeddedness configurations. Furthermore, in light of this study's limitations, directions for future research are outlined.Firms are facing great challenges in the rapidly changing economy of today's world. Therefore, firms have begun searching for new means and ways to innovate in order to stay alive, compete and grow. However, many firms have yet to discover that their embedded network of relations and structures can play a crucial role in their innovation outcomes. As a result, there is growing consensus among innovation scholars that networking and inter-firm collaboration are key strategies in stimulating innovation within firms. This has resulted in a growing body of literature focused on studying the link between innovation performance and firm participation and position in networks. However, there is still disagreement and fragmented results among scholars regarding the optimum firm's network embeddedness configuration for both product and process innovation. Moreover, firms should be aware of the type of network embeddedness configurations that could constrain their innovation performance. This remains unresolved academic and practitioner challenges that require detailed investigation. Furthermore, a limited number of studies have theoretically discussed and empirically tested this research area in the context of emerging economies.This research study addresses the aforementioned challenges and aims to shed light on the relationship between firms' network embeddedness characteristics (i.e. relational embeddedness and structural embeddedness) and their innovation output (i.e. product and process innovation).;This study draws primarily on three complimentary perspectives-social capital, social network and network embeddedness-in order to shed more light on the effect that network embeddedness characteristics have on firms' product and process innovation. Furthermore, the thesis aims to both conceptually and empirically reveal the influence that network embeddedness aspects have on innovation outcomes in the context of emerging economies, with particular reference to medium and high (M&H) technology sectors in Saudi Arabia.The study draws on the significance of network embeddedness characteristics in influencing firms' innovation performance with the principle aim of unravelling key network relational and structural embeddedness characteristics at the firm's level. This research is primarily based on new empirical evidence from the primary source data of 121 firms in M&H technology sectors in Saudi Arabia, using social network analysis and logistic regression modelling to investigate the effect of various configurations of firms' network, relational and structural embeddedness characteristics on the types of innovation (i.e. product and process innovation). The results of this study indicate that firms' innovation outcomes largely depend on their various network relational and structural embeddedness configurations. As a result, in order to fully capture the impact of network embeddedness characteristics on firms' innovation outcomes, network relational and structural embeddedness characteristics should be jointly considered (i.e. the interaction effect among different network embeddedness settings).;The evidence reveals that, by analysing the combination of firms' relational and structural network embeddedness characteristics, firms can recognise the potential, associated effects in product and process innovation outputs. This is indicated by the interaction effect between network embeddedness relational aspects (i.e. strong/weak ties) and structural properties (i.e. dense/sparse network and peripheral/central position). For instance, the findings suggest that, for high-density and central network embeddedness, strong ties type of relations will have a positive impact on firms' product and process innovation. In contrast, the empirical analysis suggests that firms that are sparsely and peripherally embedded in a network will become better product and process innovators if they develop relationships with other organisations in terms of weak ties type of relations.The outcome of this research has both theoretical and practical implications. These implications are theoretical in the sense that they provide new insights into innovation networks area from the social capital, social network and network embeddedness perspectives, jointly considering firms' network relational and structural embeddedness characteristics, as well as the direct, and the interaction effect on firm's innovation outcome. Regarding managerial implications, this study highlights the primary network structural properties, specifically addressing their direct, interaction effect on firms' product and process innovation. This could guide professional managers aiming for high innovation performance to re-evaluate their firms' network embeddedness configurations. Furthermore, in light of this study's limitations, directions for future research are outlined
Towards a space/nature syntax : the influence of spatial configuration and a view of nature on social interaction, with Arcosanti, Arizona, USA, as case study
Get PDFIn 1984 E.O. Wilson proposed the Biophilia Hypothesis, an evolutionary theory which holds that there is a connection between humans and non-human Nature which is innate: that when this connection is provided the human mind performs at its best, and when this connection is absent the human mind is in a state of deterioration. Increasingly, research in the field of environmental psychology supports the Biophilia Hypothesis; studies show that connection to Nature provides psychological, physical, and emotional benefits. Concurrently, the world's urban population is rapidly growing and is expected to reach 70% of the world's total by 2050. Thus a dichotomy emerges: how do we maintain this essential and beneficial human connection to Nature in an increasingly urbanising world? The research has developed the Space/Nature Syntax, a novel, cross-disciplinary methodology which attempts to understand how maintaining an instinctive bond with Nature, through visual connectivity, can enhance social interactions and inform future design choices within built environments. Arcosanti, an "urban laboratory" in the Arizona desert which is built to the design principles of Paolo Soleri's Arcology (ARChitecture + ecOLOGY) theory, serves as a site for both development and application of the Space/Nature Syntax methodology. The Space/Nature Syntax was applied to 15 public spaces at Arcosanti and both qualitative and quantitative relationships between spatial configuration, visual connectivity to Nature and observed social Interactions were produced. The main findings support a relationship between spatial configuration and both Passive Interaction with Space and Spontaneous Use of Space, echoing existing established patterns in spatial analysis research. Additionally, the research finds a relationship between visual connectivity to Nature and Intimate Interaction with Others, and between Visual Interaction with the Natural Environment and Personal Interaction with Others, suggesting that a view of Nature encourages a social connection between people of a certain emotional closeness. Finally, the thesis presents the viability of the Space/Nature Syntax methodology as a design tool, projecting where social interactions within built spaces at Arcosanti could be influenced by alterations to spatial configuration and visual connectivity to Nature following future stages of construction; demonstrating where informed design can allow for the essential human/Nature connection to thrive, and taking steps towards understanding how cities can be built in harmony with Nature.In 1984 E.O. Wilson proposed the Biophilia Hypothesis, an evolutionary theory which holds that there is a connection between humans and non-human Nature which is innate: that when this connection is provided the human mind performs at its best, and when this connection is absent the human mind is in a state of deterioration. Increasingly, research in the field of environmental psychology supports the Biophilia Hypothesis; studies show that connection to Nature provides psychological, physical, and emotional benefits. Concurrently, the world's urban population is rapidly growing and is expected to reach 70% of the world's total by 2050. Thus a dichotomy emerges: how do we maintain this essential and beneficial human connection to Nature in an increasingly urbanising world? The research has developed the Space/Nature Syntax, a novel, cross-disciplinary methodology which attempts to understand how maintaining an instinctive bond with Nature, through visual connectivity, can enhance social interactions and inform future design choices within built environments. Arcosanti, an "urban laboratory" in the Arizona desert which is built to the design principles of Paolo Soleri's Arcology (ARChitecture + ecOLOGY) theory, serves as a site for both development and application of the Space/Nature Syntax methodology. The Space/Nature Syntax was applied to 15 public spaces at Arcosanti and both qualitative and quantitative relationships between spatial configuration, visual connectivity to Nature and observed social Interactions were produced. The main findings support a relationship between spatial configuration and both Passive Interaction with Space and Spontaneous Use of Space, echoing existing established patterns in spatial analysis research. Additionally, the research finds a relationship between visual connectivity to Nature and Intimate Interaction with Others, and between Visual Interaction with the Natural Environment and Personal Interaction with Others, suggesting that a view of Nature encourages a social connection between people of a certain emotional closeness. Finally, the thesis presents the viability of the Space/Nature Syntax methodology as a design tool, projecting where social interactions within built spaces at Arcosanti could be influenced by alterations to spatial configuration and visual connectivity to Nature following future stages of construction; demonstrating where informed design can allow for the essential human/Nature connection to thrive, and taking steps towards understanding how cities can be built in harmony with Nature
Antimicrobial 405 nm light for clinical decontamination : investigation of the antiviral efficacy and potential for bacterial tolerance
Get PDFHospital associated infections result in longer patient stays, increased treatment costs and morbidity and mortality. Novel technologies utilising UV light, hydrogen peroxide vapour and ozone have been designed to provide high-level environmental decontamination, in an attempt to prevent patient acquisition of nosocomial pathogens. However due to safety concerns, these technologies are only suitable for intermittent terminal cleaning, and surfaces can become quickly re-contaminated. Recently developed systems which utilise antimicrobial 405 nm violet-blue visible light have been successfully used for continuous decontamination of surfaces and air, in the presence of patients. This study investigated some fundamental questions surrounding the use of antimicrobial 405 nm light for clinical decontamination.Initial investigations studied the antiviral efficacy of 405 nm light on a model for the nosocomial pathogen, Norovirus. Studies showed positive antiviral effects in suspension and on clinically-relevant surfaces when virions were exposed in minimal media (DPBS), however this inactivation efficacy was significantly improved (85% lower dose) when the virus was suspended in organically-rich, biologically-relevant media (such as saliva and blood plasma). This enhanced inactivation is likely due to photoexcitation of the suspending media, and was demonstrated using fluorescence spectrophotometry, with excitation peaks seen for all suspending media except minimal media. A systematised review also compared 405 nm light inactivation of viruses with other clinical pathogens (bacteria, fungi), and found that viruses (exposed in minimal media) are more resilient structures, requiring higher doses for equivalent reductions, likely due to differing inactivation mechanisms.Further studies also investigated the potential for proliferating and non-proliferating bacteria, Staphylococcus aureus, to become tolerant to 405 nm light. Results demonstrated that exposure to 405 nm light during cultivation resulted in higher dose requirements for complete inactivation and increased stress tolerance, however the process was unlikely to be selective. Results also demonstrated that repeated sub-lethal exposure of antibiotic sensitive and resistant vegetative cells did not give rise to tolerance or alter antibiotic susceptibility.This study has provided significant fundamental information about antimicrobial violet-blue light. The results demonstrate proof-of-concept evidence of the virucidal efficacy of 405 nm light, as well as demonstrating that bacterial tolerance is unlikely. These results further support the clinical use of antimicrobial 405 nm light for continuous environmental decontamination, with implementation likely to aid infection control and reduce hospital associated infections.Hospital associated infections result in longer patient stays, increased treatment costs and morbidity and mortality. Novel technologies utilising UV light, hydrogen peroxide vapour and ozone have been designed to provide high-level environmental decontamination, in an attempt to prevent patient acquisition of nosocomial pathogens. However due to safety concerns, these technologies are only suitable for intermittent terminal cleaning, and surfaces can become quickly re-contaminated. Recently developed systems which utilise antimicrobial 405 nm violet-blue visible light have been successfully used for continuous decontamination of surfaces and air, in the presence of patients. This study investigated some fundamental questions surrounding the use of antimicrobial 405 nm light for clinical decontamination.Initial investigations studied the antiviral efficacy of 405 nm light on a model for the nosocomial pathogen, Norovirus. Studies showed positive antiviral effects in suspension and on clinically-relevant surfaces when virions were exposed in minimal media (DPBS), however this inactivation efficacy was significantly improved (85% lower dose) when the virus was suspended in organically-rich, biologically-relevant media (such as saliva and blood plasma). This enhanced inactivation is likely due to photoexcitation of the suspending media, and was demonstrated using fluorescence spectrophotometry, with excitation peaks seen for all suspending media except minimal media. A systematised review also compared 405 nm light inactivation of viruses with other clinical pathogens (bacteria, fungi), and found that viruses (exposed in minimal media) are more resilient structures, requiring higher doses for equivalent reductions, likely due to differing inactivation mechanisms.Further studies also investigated the potential for proliferating and non-proliferating bacteria, Staphylococcus aureus, to become tolerant to 405 nm light. Results demonstrated that exposure to 405 nm light during cultivation resulted in higher dose requirements for complete inactivation and increased stress tolerance, however the process was unlikely to be selective. Results also demonstrated that repeated sub-lethal exposure of antibiotic sensitive and resistant vegetative cells did not give rise to tolerance or alter antibiotic susceptibility.This study has provided significant fundamental information about antimicrobial violet-blue light. The results demonstrate proof-of-concept evidence of the virucidal efficacy of 405 nm light, as well as demonstrating that bacterial tolerance is unlikely. These results further support the clinical use of antimicrobial 405 nm light for continuous environmental decontamination, with implementation likely to aid infection control and reduce hospital associated infections
Uncertainty quantification and state estimation for complex nonlinear problems in space flight mechanics
Get PDFThe complex dynamics which describe the motion of a spacecraft far from a massive planetary body or in a highly perturbed environment close to minor celestial objects raises two fundamental but related problems. The first is represented by the difficulty to accurately predict the evolution of its orbit even over short period when its initial conditions are known with a small degree of confidence. The second is given by the need for precise real time estimation of the trajectory when the spacecraft orbits near the asteroid's surface to avoid impacting on it. The main example of the first problem is the perturbed four body problem for the Earth-Sun-Moon system. Earth-Sun Lagrangian Point Orbits (LPOs) are often selected for astrophysics and solar terrestrial missions while low cost missions aim at exploiting the so called Weak Stability Boundaries (WSB) to move at low propellant expense within the Earth sphere of influence. As current and future missions are planned to be placed on LPOs, it is a critical aspect to clear these regions at the end of operations to avoid damages to other spacecraft. For the second problem, we have a great number of asteroids and comets orbiting the inner solar system; they represent the so-called minor celestial objects which are very interesting for science since they preserve the remnants of the early formation of the planets and could shed light on the origins of life. At the same time they are very appealing for future commercial applications for the high content of precious ore. Among these celestial objects, the family of Near Earth Objects (NEOs) follows trajectories which lie close to, and sometimes cross, the Earth's orbit. The impact hazard with the Earth has started to become considered as serious threat. Over the last three decades a number of missions have flown to and explored asteroids and comets, relying heavily on ground support with limited autonomy. In order to perform either asteroid's exploration or collision hazard protection, autonomous navigation is needed, also to deal with the uncertain environment. Then the manipulation of asteroids' orbit and attitude for deflection purposes is therefore required and an interesting problem to be studied.The aim of the research presented in this dissertation is to identify and develop methodologies for uncertainty propagation for spacecraft orbit and the application to orbit determination for complex nonlinear space mechanics problems, with particular care paid to the case of close proximity operations which are required when performing missions to minor celestial objects. The results are not limited only to this kind of problem but can be applied also to different scenarios.;A first set of results focuses on the prediction of the trajectory evolution under initial condition uncertainties. The accuracy of the propagation of uncertainties is intimately related to the process of trajectory estimation, which relies on the use of the covariance matrix. The covariance matrix gives an idea of the dispersion of the spacecraft in terms of position and velocity. Different techniques to propagate the covariance matrix are used to predict the evolution of the trajectory when the initial conditions are known only to a certain degree of accuracy. They are compared under a highly nonlinear scenario where a spacecraft is injected into a disposal orbit towards an impacting trajectory with the Moon from a Lagrangian Point Orbit. A second set of results focuses on the identification of the estimation techniques applied to a single spacecraft. The estimation process performs well depending on the capability to propagate the covariance matrix and to incorporate the new information. A number of filtering techniques based on the Kalman and H∞ filters, employing different methods to handle the propagation of the covariance matrix, are presented and tested in typical nonlinear environments, i.e. a WSB transferan asteroid proximity, to draw precious information on their performance. The analyses demonstrate that only a hybrid Kalman- H∞ filter can enable the spacecraft to estimate its trajectory with a good balance between accuracy and computational costs. Then this method is applied to the navigation of spacecraft formation about a NEO showing that the navigation performance is significantly improved by sharing relative information among the spacecraft and the overall system is shown to be fault-tolerant.Finally the orbit's and attitude manipulation of a small asteroid using a laser ablation system is analysed. An on-board state estimation and control algorithm is presented that simultaneously provides an optimal proximity control and control of the rotational motion of the asteroid. During the deflection, the proximity motion of the spacecraft is coupled with the orbital and rotational motion of the asteroid. The combination of the deflection acceleration, solar radiation pressure, and gravity field and plume impingement will force the spacecraft to drift away from the asteroid. In turn, a variation of the motion of the spacecraft produces a change in the modulus and direction of the deflection action which modifies the rotational and orbital motion of the asteroid.The complex dynamics which describe the motion of a spacecraft far from a massive planetary body or in a highly perturbed environment close to minor celestial objects raises two fundamental but related problems. The first is represented by the difficulty to accurately predict the evolution of its orbit even over short period when its initial conditions are known with a small degree of confidence. The second is given by the need for precise real time estimation of the trajectory when the spacecraft orbits near the asteroid's surface to avoid impacting on it. The main example of the first problem is the perturbed four body problem for the Earth-Sun-Moon system. Earth-Sun Lagrangian Point Orbits (LPOs) are often selected for astrophysics and solar terrestrial missions while low cost missions aim at exploiting the so called Weak Stability Boundaries (WSB) to move at low propellant expense within the Earth sphere of influence. As current and future missions are planned to be placed on LPOs, it is a critical aspect to clear these regions at the end of operations to avoid damages to other spacecraft. For the second problem, we have a great number of asteroids and comets orbiting the inner solar system; they represent the so-called minor celestial objects which are very interesting for science since they preserve the remnants of the early formation of the planets and could shed light on the origins of life. At the same time they are very appealing for future commercial applications for the high content of precious ore. Among these celestial objects, the family of Near Earth Objects (NEOs) follows trajectories which lie close to, and sometimes cross, the Earth's orbit. The impact hazard with the Earth has started to become considered as serious threat. Over the last three decades a number of missions have flown to and explored asteroids and comets, relying heavily on ground support with limited autonomy. In order to perform either asteroid's exploration or collision hazard protection, autonomous navigation is needed, also to deal with the uncertain environment. Then the manipulation of asteroids' orbit and attitude for deflection purposes is therefore required and an interesting problem to be studied.The aim of the research presented in this dissertation is to identify and develop methodologies for uncertainty propagation for spacecraft orbit and the application to orbit determination for complex nonlinear space mechanics problems, with particular care paid to the case of close proximity operations which are required when performing missions to minor celestial objects. The results are not limited only to this kind of problem but can be applied also to different scenarios.;A first set of results focuses on the prediction of the trajectory evolution under initial condition uncertainties. The accuracy of the propagation of uncertainties is intimately related to the process of trajectory estimation, which relies on the use of the covariance matrix. The covariance matrix gives an idea of the dispersion of the spacecraft in terms of position and velocity. Different techniques to propagate the covariance matrix are used to predict the evolution of the trajectory when the initial conditions are known only to a certain degree of accuracy. They are compared under a highly nonlinear scenario where a spacecraft is injected into a disposal orbit towards an impacting trajectory with the Moon from a Lagrangian Point Orbit. A second set of results focuses on the identification of the estimation techniques applied to a single spacecraft. The estimation process performs well depending on the capability to propagate the covariance matrix and to incorporate the new information. A number of filtering techniques based on the Kalman and H∞ filters, employing different methods to handle the propagation of the covariance matrix, are presented and tested in typical nonlinear environments, i.e. a WSB transferan asteroid proximity, to draw precious information on their performance. The analyses demonstrate that only a hybrid Kalman- H∞ filter can enable the spacecraft to estimate its trajectory with a good balance between accuracy and computational costs. Then this method is applied to the navigation of spacecraft formation about a NEO showing that the navigation performance is significantly improved by sharing relative information among the spacecraft and the overall system is shown to be fault-tolerant.Finally the orbit's and attitude manipulation of a small asteroid using a laser ablation system is analysed. An on-board state estimation and control algorithm is presented that simultaneously provides an optimal proximity control and control of the rotational motion of the asteroid. During the deflection, the proximity motion of the spacecraft is coupled with the orbital and rotational motion of the asteroid. The combination of the deflection acceleration, solar radiation pressure, and gravity field and plume impingement will force the spacecraft to drift away from the asteroid. In turn, a variation of the motion of the spacecraft produces a change in the modulus and direction of the deflection action which modifies the rotational and orbital motion of the asteroid
Methodology to investigate the energy and indoor environmental performance of typical Egyptian offices
Get PDFBuildings are a contributor to increasing electricity demand in Egypt, straining the existing supply network causing economic and social impacts. Current initiatives that aim to improve building performance include the adoption of international standards. Existing Egyptian buildings performance is not understood making the impact of current initiatives uncertain.;The main aim of this thesis is to better understand current energy performance and Indoor Environmental Quality (IEQ) for Egyptian office buildings and capture this knowledge in methods to inform new Egyptian policy.;Performance of current Egyptian office buildings was assessed through a 59 office energy survey and a more detailed energy and indoor environmental investigation for a case study office. The case study office was representative of the most common type found in the survey which has natural ventilation and locally controlled cooling systems. Naturally ventilated offices with local cooling were found to use less than 50% of the energy of fully centrally serviced offices.;A two-step process to capture the observed performance in a representative model and input parameter set is elaborated based on first creating a calibrated model for the case study office; then adjusting this model to be more representative of the broader survey data. The representative model uses the appropriate thermal comfort standard selected by comparing observations against various pre-existing comfort standards. Uncertainties are captured in the formulation of the model input parameter sets.;The representative model is then used to investigate the impacts of parameters including location, weather, building envelope, occupancy, behaviour, and installed systems including Heating, Ventilation, & Air Conditioning (HVAC) strategy. HVAC strategy installed system efficiencies and occupant behaviour was identified as the three most influential parameters.;Possible policy measures to promote system energy efficiencies and encourage adoption of energy conscious behaviour are proposed. Together these can reduce the energy used in the naturally ventilated and locally cooled offices by 50%. Trade-offs between energy use and IEQ are discussed.;In summary, this research gives new insight into energy, indoor environmental conditions and behaviour in Egyptian office buildings. A new method for defining a representative model capturing uncertainties in input data sets is elaborated. The representative model's use to identify the impacts of various parameters for the Egyptian context is illustrated through a combinatorial parametric study. Insights useful to inform future Egyptian policy were proposed. The methodology developed in this work has applicability to other contexts and building categories.Buildings are a contributor to increasing electricity demand in Egypt, straining the existing supply network causing economic and social impacts. Current initiatives that aim to improve building performance include the adoption of international standards. Existing Egyptian buildings performance is not understood making the impact of current initiatives uncertain.;The main aim of this thesis is to better understand current energy performance and Indoor Environmental Quality (IEQ) for Egyptian office buildings and capture this knowledge in methods to inform new Egyptian policy.;Performance of current Egyptian office buildings was assessed through a 59 office energy survey and a more detailed energy and indoor environmental investigation for a case study office. The case study office was representative of the most common type found in the survey which has natural ventilation and locally controlled cooling systems. Naturally ventilated offices with local cooling were found to use less than 50% of the energy of fully centrally serviced offices.;A two-step process to capture the observed performance in a representative model and input parameter set is elaborated based on first creating a calibrated model for the case study office; then adjusting this model to be more representative of the broader survey data. The representative model uses the appropriate thermal comfort standard selected by comparing observations against various pre-existing comfort standards. Uncertainties are captured in the formulation of the model input parameter sets.;The representative model is then used to investigate the impacts of parameters including location, weather, building envelope, occupancy, behaviour, and installed systems including Heating, Ventilation, & Air Conditioning (HVAC) strategy. HVAC strategy installed system efficiencies and occupant behaviour was identified as the three most influential parameters.;Possible policy measures to promote system energy efficiencies and encourage adoption of energy conscious behaviour are proposed. Together these can reduce the energy used in the naturally ventilated and locally cooled offices by 50%. Trade-offs between energy use and IEQ are discussed.;In summary, this research gives new insight into energy, indoor environmental conditions and behaviour in Egyptian office buildings. A new method for defining a representative model capturing uncertainties in input data sets is elaborated. The representative model's use to identify the impacts of various parameters for the Egyptian context is illustrated through a combinatorial parametric study. Insights useful to inform future Egyptian policy were proposed. The methodology developed in this work has applicability to other contexts and building categories
Characterisation of plasma closing switches filled with different gases
Get PDFSulphur Hexafluoride (SF6) is one of the most commonly used gases within switching applications for pulsed power applications due to a large number of desirable properties, however, it is a greenhouse gas and global concerns over the emission of this gas into the atmosphere have led to an increase in research into potential environmentally friendly alternatives.;This study focused on an experimental investigation into the breakdown characteristics of two commonly used plasma closing switch topologies when filled with different gasses and gas mixtures not previously considered in as much depth for switching purposes (air, N2, 60%/40% N2/O2, 90%/10% Ar/O2, and CO2) as compared to the characteristics of the switches when filled with SF6.;A self-breakdown switch and a field-distortion triggered switch topology with varying inter-electrode gap lengths up to 9mm, filled with gasses at pressures in the range 0.1MPa-0.5MPa were studied and some key operational characteristics and switching parameters such as the self-breakdown voltage of the gases, the spread in self-breakdown voltage, time to breakdown and jitter of the switches were investigated and compared.;Temperature of the plasma that forms during breakdown and the conductivity of plasma was extracted for each gas and in addition to this, analysis of post-breakdown waveforms allowed for obtaining values of inductance and resistance of the switches.;Experimental results have been used in the development of two computational models of Marx Generators which are used in the voltage erection stage of pulsed power systems. The models developed describe the switches as either having constant resistance or taking into account the transient plasma resistance which allows for a more accurate representation of the voltage and current behavior across the output load over the first quarter of the current oscillation after switch closure occurs.Sulphur Hexafluoride (SF6) is one of the most commonly used gases within switching applications for pulsed power applications due to a large number of desirable properties, however, it is a greenhouse gas and global concerns over the emission of this gas into the atmosphere have led to an increase in research into potential environmentally friendly alternatives.;This study focused on an experimental investigation into the breakdown characteristics of two commonly used plasma closing switch topologies when filled with different gasses and gas mixtures not previously considered in as much depth for switching purposes (air, N2, 60%/40% N2/O2, 90%/10% Ar/O2, and CO2) as compared to the characteristics of the switches when filled with SF6.;A self-breakdown switch and a field-distortion triggered switch topology with varying inter-electrode gap lengths up to 9mm, filled with gasses at pressures in the range 0.1MPa-0.5MPa were studied and some key operational characteristics and switching parameters such as the self-breakdown voltage of the gases, the spread in self-breakdown voltage, time to breakdown and jitter of the switches were investigated and compared.;Temperature of the plasma that forms during breakdown and the conductivity of plasma was extracted for each gas and in addition to this, analysis of post-breakdown waveforms allowed for obtaining values of inductance and resistance of the switches.;Experimental results have been used in the development of two computational models of Marx Generators which are used in the voltage erection stage of pulsed power systems. The models developed describe the switches as either having constant resistance or taking into account the transient plasma resistance which allows for a more accurate representation of the voltage and current behavior across the output load over the first quarter of the current oscillation after switch closure occurs
Studies of the structure and ultrafast dynamics of DNA using 2D-IR spectroscopy
Get PDFIn this thesis, two-dimensional infrared spectroscopy (2D-IR) spectroscopy is used to study changes in structure and dynamics in deoxyribonucleic acid (DNA) containing only Adenine-Thymine (AT) base pairs. The aims of the studies in this thesis are to demonstrate the ability of 2D-IR spectroscopy to extract unique dynamic information, not accessible via established experimental methods from nucleic acid systems, as it has for protein- and peptide-based systems. The underlying theory of both linear and nonlinear 2D-IR spectroscopies is described in the initial Chapter, following this the details of the types of information already obtained using these methods from DNA in the current literature is presented.;Chapter (2) describes the experimental setups and methodologies used to acquire the data in this thesis. A description of FTIR spectroscopy as well as the two laser systems used to acquire 2D-IR data (ULTRA and LIFEtime) are presented. In Chapter (3), the thermal denaturation of an AT DNA sequence 15 base pairs in length is studied with 2D-IR in the spectral region where vibrational modes of the DNA bases are observed. Changes in the unique features observed in these spectra that are sensitive to DNA conformation are described along with the suitability of 2D-IR for accurately following the transition from double- to single stranded DNA compared to established methods. Changes in solvation dynamics experienced by functional groups of the DNA bases are also discussed.;Chapter (4) demonstrates the ability of 2D-IR to explore multiple spectral regions simultaneously using a two-colour 2D-IR method. This allowed examination of communication between the vibrational modes of the DNA bases and those of the DNA backbone in the same DNA sequence used in the previous Chapter. Dynamics extracted from the features linking these two spectral regions present evidence for an energy transfer pathway through DNA that could be responsible for allowing dissipation of excess energy absorbed by DNA, preventing photo-damage of sequences. Chapter (5) expands on the studies in the previous Chapter by employing the same experimental methodology to AT DNA sequences of lengths varying from 15 bases pairs to a single base mononucleotide. The changes in observed features that link the base and backbone regions for the different sequences is presented along with the effects varying the sequence length has on the timescales of the energy transfer mechanism described in the previous Chapter.In Chapter (6) the conclusions presented in the Chapters prior to this point are drawn together to highlight progress made in gaining new insights into structure and dynamics of DNA and also presents possible future directions for studying nucleic acid systems with 2D-IR.In this thesis, two-dimensional infrared spectroscopy (2D-IR) spectroscopy is used to study changes in structure and dynamics in deoxyribonucleic acid (DNA) containing only Adenine-Thymine (AT) base pairs. The aims of the studies in this thesis are to demonstrate the ability of 2D-IR spectroscopy to extract unique dynamic information, not accessible via established experimental methods from nucleic acid systems, as it has for protein- and peptide-based systems. The underlying theory of both linear and nonlinear 2D-IR spectroscopies is described in the initial Chapter, following this the details of the types of information already obtained using these methods from DNA in the current literature is presented.;Chapter (2) describes the experimental setups and methodologies used to acquire the data in this thesis. A description of FTIR spectroscopy as well as the two laser systems used to acquire 2D-IR data (ULTRA and LIFEtime) are presented. In Chapter (3), the thermal denaturation of an AT DNA sequence 15 base pairs in length is studied with 2D-IR in the spectral region where vibrational modes of the DNA bases are observed. Changes in the unique features observed in these spectra that are sensitive to DNA conformation are described along with the suitability of 2D-IR for accurately following the transition from double- to single stranded DNA compared to established methods. Changes in solvation dynamics experienced by functional groups of the DNA bases are also discussed.;Chapter (4) demonstrates the ability of 2D-IR to explore multiple spectral regions simultaneously using a two-colour 2D-IR method. This allowed examination of communication between the vibrational modes of the DNA bases and those of the DNA backbone in the same DNA sequence used in the previous Chapter. Dynamics extracted from the features linking these two spectral regions present evidence for an energy transfer pathway through DNA that could be responsible for allowing dissipation of excess energy absorbed by DNA, preventing photo-damage of sequences. Chapter (5) expands on the studies in the previous Chapter by employing the same experimental methodology to AT DNA sequences of lengths varying from 15 bases pairs to a single base mononucleotide. The changes in observed features that link the base and backbone regions for the different sequences is presented along with the effects varying the sequence length has on the timescales of the energy transfer mechanism described in the previous Chapter.In Chapter (6) the conclusions presented in the Chapters prior to this point are drawn together to highlight progress made in gaining new insights into structure and dynamics of DNA and also presents possible future directions for studying nucleic acid systems with 2D-IR
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