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An investigation of haptic assisted robotic manipulating and planning for high accuracy control
Get PDFThis research investigation advances the understanding of force feedback with the aim to achieve better human interaction with a haptic system for a diverse range of application requirements. Human-Machine interactive systems are required in various manipulation tasks, where a higher level of precision and accuracy than normal human capabilities is necessary. These systems also require human intelligence in the control loop to manage complex challenges typically found in extreme environments such as nuclear, space, underwater and mining.;In these environments, visual information may not always be available or of substandard quality. The touch sensation, in terms of haptic perception, includes tactile and kinesthetic sensations. These sensations help the user understand an object's material properties in the environment as well as their body position and movement. Therefore, it is suggested that haptic force feedback can be introduced to provide assistance where a high level of accuracy of human manipulation is required. The knowledge gaps for the design of multitask haptic assisted systems are identified and concluded through a literature review.;A comparison table is produced to demonstrate the functionalities and inadequacies of existing systems in dealing with the required functions. There are knowledge gaps in system design, for example, regarding haptic systems in space environments. There also exists a lack of systems in manufacturing where existing robotic systems can be easily adopted for haptic control applications.;A design methodology is proposed to support the design of a haptic assisted system that integrates professional knowledge and experience with different types of haptic virtual fixtures in manipulating and planning tasks. For this design methodology, a general Haptic Assisted Robotic Manipulating and Planning system (HARMP) is proposed and investigated. This planning system provides a common haptic interface and haptic assistance for multiple applications such as for robotic planning and manipulating tasks.;A system architecture is proposed and constructed with components including hardware (Haptic user interaction system) and software (Haptic modelling environment). The system specification template is built with geometric modelling, force modelling, force rendering, environment modelling and an integrated knowledge library. The haptic virtual fixtures are classified into three categories: telepresence, virtual constraints and guidance. In three case studies, the task requirements are analysed to identify the specifications necessary along with the virtual fixtures so they can be assigned to modify the HARMP system accordingly.;A method to utilise haptic guidance in space robotic manipulation for capturing tasks is proposed. Also, a concept and implementation to enhance the HARMP design model in enabling bilateral haptic interaction is proposed and implemented as a haptic coupler which enables novel use of haptic system in both directions. This proposed HARMP is validated through three design case studies and the HARMP system has then been proven to be effective in three different types of applications namely, dental, space and manufacturing. It is anticipated that HARMP system could be equally applicable in other applications.;The contribution to knowledge reflects this wide range of activities in broad haptic interactions, including literature review, new design methodology development and validation of the proposed methodology through three case studies and finally the novel haptic systems developed through these case studies. A novel and generic design methodology, HARMP, for haptic system design is proposed, fully developed and evaluated, incorporating virtual fixtures for high accuracy manipulating and planning tasks. The HARMP methodology can be used to clarify the design process and design activity flow in order to generate necessary system specifications and components for the final haptic system for a given design problem.This research investigation advances the understanding of force feedback with the aim to achieve better human interaction with a haptic system for a diverse range of application requirements. Human-Machine interactive systems are required in various manipulation tasks, where a higher level of precision and accuracy than normal human capabilities is necessary. These systems also require human intelligence in the control loop to manage complex challenges typically found in extreme environments such as nuclear, space, underwater and mining.;In these environments, visual information may not always be available or of substandard quality. The touch sensation, in terms of haptic perception, includes tactile and kinesthetic sensations. These sensations help the user understand an object's material properties in the environment as well as their body position and movement. Therefore, it is suggested that haptic force feedback can be introduced to provide assistance where a high level of accuracy of human manipulation is required. The knowledge gaps for the design of multitask haptic assisted systems are identified and concluded through a literature review.;A comparison table is produced to demonstrate the functionalities and inadequacies of existing systems in dealing with the required functions. There are knowledge gaps in system design, for example, regarding haptic systems in space environments. There also exists a lack of systems in manufacturing where existing robotic systems can be easily adopted for haptic control applications.;A design methodology is proposed to support the design of a haptic assisted system that integrates professional knowledge and experience with different types of haptic virtual fixtures in manipulating and planning tasks. For this design methodology, a general Haptic Assisted Robotic Manipulating and Planning system (HARMP) is proposed and investigated. This planning system provides a common haptic interface and haptic assistance for multiple applications such as for robotic planning and manipulating tasks.;A system architecture is proposed and constructed with components including hardware (Haptic user interaction system) and software (Haptic modelling environment). The system specification template is built with geometric modelling, force modelling, force rendering, environment modelling and an integrated knowledge library. The haptic virtual fixtures are classified into three categories: telepresence, virtual constraints and guidance. In three case studies, the task requirements are analysed to identify the specifications necessary along with the virtual fixtures so they can be assigned to modify the HARMP system accordingly.;A method to utilise haptic guidance in space robotic manipulation for capturing tasks is proposed. Also, a concept and implementation to enhance the HARMP design model in enabling bilateral haptic interaction is proposed and implemented as a haptic coupler which enables novel use of haptic system in both directions. This proposed HARMP is validated through three design case studies and the HARMP system has then been proven to be effective in three different types of applications namely, dental, space and manufacturing. It is anticipated that HARMP system could be equally applicable in other applications.;The contribution to knowledge reflects this wide range of activities in broad haptic interactions, including literature review, new design methodology development and validation of the proposed methodology through three case studies and finally the novel haptic systems developed through these case studies. A novel and generic design methodology, HARMP, for haptic system design is proposed, fully developed and evaluated, incorporating virtual fixtures for high accuracy manipulating and planning tasks. The HARMP methodology can be used to clarify the design process and design activity flow in order to generate necessary system specifications and components for the final haptic system for a given design problem
An investigation of antecedents to social media engagement behaviours
Get PDFIt is becoming increasingly important for firms to encourage customer's voluntary contributions beyond the purchase transaction through customer engagement marketing efforts (Harmeling et al., 2017), particularly as these contributions, which are the behavioural dimension of customer engagement, called customer engagement behaviour (CEB), influence the customer-brand relationship. This thesis therefore seeks to investigate the antecedents of social media engagement behaviours with a focus on customer related antecedents.More specifically, this research investigates the antecedents to the specific social media engagement behaviours learning, sharing and endorsing. The research identifies the motivational drivers that influence learning, sharing and endorsing, which, according to Van Doorn et al. (2010) are required for CEBs to occur. The research then determines if the identified motivational drivers mediate the relationship between the personality-related factors and learning, sharing and endorsing. The personality-related factors investigated include, personality traits and causality orientations - an individual's characteristic behavioural patterns (Teixeira et al., 2012). Similarly, the research also determines if the identified motivational drivers mediate the relationship between brand relationship commitment and learning, sharing and endorsing.The research was undertaken using two stages of data collection and analysis which both utilised online questionnaires (N=146, and N=382, respectively). Using exploratory and confirmatory factor analysis, pleasure, self-interest, rewards and venting negative feelings were identified as the motivational drivers. Additionally, using path analysis, evidence was found of indirect relationships between the personality-related antecedents investigated and learning, sharing and endorsing through the motivational drivers identified.;Among others, it was found that pleasure positively mediated the relationship between extraverted customers and sharing and endorsing in the social media environment. Evidence was also found of indirect relationships betweenbrand relationship commitment and the behaviours through pleasure and self-interest.The findings of this research have therefore contributed to the theory around customer engagement, CEB, self-determination theory, trait theory and customer-brand relationship theory by demonstrating that specific antecedents work together with motivational drivers to influence learning, sharing and endorsing in the social media environment.These findings also indicate to managers the types of initiatives which will be effective in driving specific behaviours in the social media environment. Furthermore, based on these findings suggestions were made to managers as to what types of responses to the specific behaviours demonstrated by customers would be useful in order to maintain the customer-brand relationship. To illustrate, it was found that self-interest mediates the relationship between customers who are highly committed to a relationship with the brand and sharing and endorsing in the social media environment. It is therefore suggested that managers provide badges, ratings or personal thanks to these customers to indicate that this behaviour is valued to ensure that customers continue taking part in these behaviours.It is becoming increasingly important for firms to encourage customer's voluntary contributions beyond the purchase transaction through customer engagement marketing efforts (Harmeling et al., 2017), particularly as these contributions, which are the behavioural dimension of customer engagement, called customer engagement behaviour (CEB), influence the customer-brand relationship. This thesis therefore seeks to investigate the antecedents of social media engagement behaviours with a focus on customer related antecedents.More specifically, this research investigates the antecedents to the specific social media engagement behaviours learning, sharing and endorsing. The research identifies the motivational drivers that influence learning, sharing and endorsing, which, according to Van Doorn et al. (2010) are required for CEBs to occur. The research then determines if the identified motivational drivers mediate the relationship between the personality-related factors and learning, sharing and endorsing. The personality-related factors investigated include, personality traits and causality orientations - an individual's characteristic behavioural patterns (Teixeira et al., 2012). Similarly, the research also determines if the identified motivational drivers mediate the relationship between brand relationship commitment and learning, sharing and endorsing.The research was undertaken using two stages of data collection and analysis which both utilised online questionnaires (N=146, and N=382, respectively). Using exploratory and confirmatory factor analysis, pleasure, self-interest, rewards and venting negative feelings were identified as the motivational drivers. Additionally, using path analysis, evidence was found of indirect relationships between the personality-related antecedents investigated and learning, sharing and endorsing through the motivational drivers identified.;Among others, it was found that pleasure positively mediated the relationship between extraverted customers and sharing and endorsing in the social media environment. Evidence was also found of indirect relationships betweenbrand relationship commitment and the behaviours through pleasure and self-interest.The findings of this research have therefore contributed to the theory around customer engagement, CEB, self-determination theory, trait theory and customer-brand relationship theory by demonstrating that specific antecedents work together with motivational drivers to influence learning, sharing and endorsing in the social media environment.These findings also indicate to managers the types of initiatives which will be effective in driving specific behaviours in the social media environment. Furthermore, based on these findings suggestions were made to managers as to what types of responses to the specific behaviours demonstrated by customers would be useful in order to maintain the customer-brand relationship. To illustrate, it was found that self-interest mediates the relationship between customers who are highly committed to a relationship with the brand and sharing and endorsing in the social media environment. It is therefore suggested that managers provide badges, ratings or personal thanks to these customers to indicate that this behaviour is valued to ensure that customers continue taking part in these behaviours
Financial instruments and the governance of EU Cohesion policy : roles, responsibilities and accountability
Get PDFFrom the 2007-13 programming period, financial instruments (FI) introduced a distinct new strand to CP governance. They created new structures and delegated implementation responsibilities to new actors. This thesis explores the implications of the new modes of governance for the relationships between actors and the relationship between delegation modes and public accountability in the delivery of FI. It contributes to principal-agent, multi-level governance and public accountability theory.;First, it identifies a typical governance structure for FI implementation. This fills a gap in the study of CP governance as the focus is on the relations within the levels of governance ('intra-level' governance); second, it argues that managing authorities have strong tools to ensure accountability in policy implementation; third, it claims that rationale and the historic-economic context influence the public accountability for FI implementation.;The thesis contributes to policy studies by feeding into the debates on the future of FI and by identifying improvements in FI evaluation. The thesis uses a mixed-methods research design, in which a quantitative component (a survey) is embedded in a qualitative component (case studies). It focuses on the outcomes of 2007-13 to draw implications for the following programming periods.;The thesis identifies three delegation modes in the European Union (EU), based on the legal status of fund managers: a public mode (as in Germany); a private mode (as in the United Kingdom); and a mixed delegation mode (as in Italy). The survey data show that evaluation should expand the set of key indicators to assess FI performance and improve existing ones. The survey and case studies in Berlin, Tuscany and North East England uncover the distribution of roles, responsibilities and accountability mechanisms.;First, multiple principal-agent interactions characterize delegation in financial instrument implementation. Across all the case studies, most of the formal responsibilities were delegated by managing authorities to fund managers, via intermediate-level actors, while the actual autonomy of fund managers in exercising such responsibilities varied in each case study. Second, managing authorities use a distinctive mix of control mechanisms and performance frameworks to ensure public accountability for FI implementation. This mix depends on the rationale for FI use and the policy objectives. Last, some of the variation is also explained by delegation modes.From the 2007-13 programming period, financial instruments (FI) introduced a distinct new strand to CP governance. They created new structures and delegated implementation responsibilities to new actors. This thesis explores the implications of the new modes of governance for the relationships between actors and the relationship between delegation modes and public accountability in the delivery of FI. It contributes to principal-agent, multi-level governance and public accountability theory.;First, it identifies a typical governance structure for FI implementation. This fills a gap in the study of CP governance as the focus is on the relations within the levels of governance ('intra-level' governance); second, it argues that managing authorities have strong tools to ensure accountability in policy implementation; third, it claims that rationale and the historic-economic context influence the public accountability for FI implementation.;The thesis contributes to policy studies by feeding into the debates on the future of FI and by identifying improvements in FI evaluation. The thesis uses a mixed-methods research design, in which a quantitative component (a survey) is embedded in a qualitative component (case studies). It focuses on the outcomes of 2007-13 to draw implications for the following programming periods.;The thesis identifies three delegation modes in the European Union (EU), based on the legal status of fund managers: a public mode (as in Germany); a private mode (as in the United Kingdom); and a mixed delegation mode (as in Italy). The survey data show that evaluation should expand the set of key indicators to assess FI performance and improve existing ones. The survey and case studies in Berlin, Tuscany and North East England uncover the distribution of roles, responsibilities and accountability mechanisms.;First, multiple principal-agent interactions characterize delegation in financial instrument implementation. Across all the case studies, most of the formal responsibilities were delegated by managing authorities to fund managers, via intermediate-level actors, while the actual autonomy of fund managers in exercising such responsibilities varied in each case study. Second, managing authorities use a distinctive mix of control mechanisms and performance frameworks to ensure public accountability for FI implementation. This mix depends on the rationale for FI use and the policy objectives. Last, some of the variation is also explained by delegation modes
An ethnographic investigation of information seeking in the primary classroom
Get PDFThis thesis describes a school-based study that was undertaken to investigate the information-seeking behaviour of primary school children. A review of the literature in the area of child information behaviour was undertaken. Five key areas of interest were identified for investigation: how children define success in information seeking and how this contrasts with adult perspectives on the same; the support that children require when seeking information at different ages; the influence of age on children's information channel preferences; the influence that situation or context have on child information-seeking behaviour;the effect of gender on each of these dimensions. Readings in the area revealed few studies where authentic, teacher-imposed information activities had been studied. Rather than relying on the researcher-designed tasks that were the focus of a majority of studies, existing classroom tasks derived from the national curriculum were the basis of the investigation. An ethnographic approach was taken involving data collection via observation, making extensive use of teacher-created data collection tools such as post-task evaluation forms.;Information artefacts such as posters and reports created by children during the tasks were analysed then used as a discussion point in focus groups. Teachers'perspectives were gathered by collecting and analysing their assessment feedback and also via interviews. A parallel investigation of children's leisure information seeking behaviour was undertaken using a survey and focus group approach. Two classes at either end (9-10 years and 11-12 years) of the concrete operational stage of development were studied. The findings have implications for support for children's information seeking, information task design, evaluation design and search system development. A further contribution is in the description of a method for evaluating child information-seeking behaviour via the discussion, in focus groups, of the pieces of work orartefacts produced during information tasks.This thesis describes a school-based study that was undertaken to investigate the information-seeking behaviour of primary school children. A review of the literature in the area of child information behaviour was undertaken. Five key areas of interest were identified for investigation: how children define success in information seeking and how this contrasts with adult perspectives on the same; the support that children require when seeking information at different ages; the influence of age on children's information channel preferences; the influence that situation or context have on child information-seeking behaviour;the effect of gender on each of these dimensions. Readings in the area revealed few studies where authentic, teacher-imposed information activities had been studied. Rather than relying on the researcher-designed tasks that were the focus of a majority of studies, existing classroom tasks derived from the national curriculum were the basis of the investigation. An ethnographic approach was taken involving data collection via observation, making extensive use of teacher-created data collection tools such as post-task evaluation forms.;Information artefacts such as posters and reports created by children during the tasks were analysed then used as a discussion point in focus groups. Teachers'perspectives were gathered by collecting and analysing their assessment feedback and also via interviews. A parallel investigation of children's leisure information seeking behaviour was undertaken using a survey and focus group approach. Two classes at either end (9-10 years and 11-12 years) of the concrete operational stage of development were studied. The findings have implications for support for children's information seeking, information task design, evaluation design and search system development. A further contribution is in the description of a method for evaluating child information-seeking behaviour via the discussion, in focus groups, of the pieces of work orartefacts produced during information tasks
Detection of long-chain DNA fragments and amplification products using surface enhanced raman spectroscopy and resonance raman spectroscopy
Get PDFThe aim of this research was to progress the application of surface enhanced Raman spectroscopy (SERS) and resonance Raman spectroscopy for the detection of longchain DNA fragments and amplification products.The use of SERS for the detection of DNA has significant potential in terms of sensitivity and multiplex target detection from nanoparticles. Current methods are usually performed with short chain, synthetic DNA fragments or require additional separation steps for the detection of longer chain DNA fragments. An integrated method for the rapid and sensitive detection of long-chain DNA fragments (≥ 100-base) with minimal preparation and separation steps was demonstrated. Key to this was the DNA sequence-specific assembly of silver nanoparticles labelled with a Raman tag to provide an enhanced signal from the tag and hence molecular recognition of the target DNA. Effective detection of long-chain DNA was achieved with head-to-head probes and by adding polyethylene glycol 10000 to the hybridisation buffer. This gave a 34-fold discriminatory enhancement factor when applied to a synthetic target. A structured approach toward maximising hybridisation procedures and SERS response has been described, followed by an initial demonstration of SERS detection of a single-stranded DNA target amplified by asymmetric PCR which was used without further separation. This has implications for future developments in using SERS for DNA detection due to the new-found ability to integrate SERS with asymmetric PCR.;Furthermore, an alternative strategy for the detection of a recombinase polymerase amplification (RPA) product was demonstrated using tailed primers, an enzyme linked reporter conjugate and resonance Raman spectroscopy. The amplification ofDNA by RPA could be achieved within 20 minutes and a colorimetric change could be detected using resonance Raman spectroscopy with discriminatory value at the lowest concentration of 100 aM. This demonstrated the first application of resonance Raman spectroscopy for the detection of an RPA amplification product and indicates significant potential for the integration of resonance Raman spectroscopy with an emerging rapid isothermal nucleic acid amplification technique.The research described here has successfully demonstrated the sensitive and rapid detection of long-chain DNA fragments and amplification products using both SERS and resonance Raman spectroscopy. Furthermore, the methods presented require minimal sample preparation steps for the detection of the long-chain DNA fragments and amplification products. This indicates significant progression from current literature which commonly describes the detection of short, synthetic DNA fragments or utilises methods requiring complex physical separation or purification steps for the detection of longer DNA fragments. The findings therefore advance the potential for the application of Raman spectroscopy for the detection of biologically relevant nucleic acid target sequences, and it hoped that this will encourage further development of Raman spectroscopy for the application of DNA detection in future.The aim of this research was to progress the application of surface enhanced Raman spectroscopy (SERS) and resonance Raman spectroscopy for the detection of longchain DNA fragments and amplification products.The use of SERS for the detection of DNA has significant potential in terms of sensitivity and multiplex target detection from nanoparticles. Current methods are usually performed with short chain, synthetic DNA fragments or require additional separation steps for the detection of longer chain DNA fragments. An integrated method for the rapid and sensitive detection of long-chain DNA fragments (≥ 100-base) with minimal preparation and separation steps was demonstrated. Key to this was the DNA sequence-specific assembly of silver nanoparticles labelled with a Raman tag to provide an enhanced signal from the tag and hence molecular recognition of the target DNA. Effective detection of long-chain DNA was achieved with head-to-head probes and by adding polyethylene glycol 10000 to the hybridisation buffer. This gave a 34-fold discriminatory enhancement factor when applied to a synthetic target. A structured approach toward maximising hybridisation procedures and SERS response has been described, followed by an initial demonstration of SERS detection of a single-stranded DNA target amplified by asymmetric PCR which was used without further separation. This has implications for future developments in using SERS for DNA detection due to the new-found ability to integrate SERS with asymmetric PCR.;Furthermore, an alternative strategy for the detection of a recombinase polymerase amplification (RPA) product was demonstrated using tailed primers, an enzyme linked reporter conjugate and resonance Raman spectroscopy. The amplification ofDNA by RPA could be achieved within 20 minutes and a colorimetric change could be detected using resonance Raman spectroscopy with discriminatory value at the lowest concentration of 100 aM. This demonstrated the first application of resonance Raman spectroscopy for the detection of an RPA amplification product and indicates significant potential for the integration of resonance Raman spectroscopy with an emerging rapid isothermal nucleic acid amplification technique.The research described here has successfully demonstrated the sensitive and rapid detection of long-chain DNA fragments and amplification products using both SERS and resonance Raman spectroscopy. Furthermore, the methods presented require minimal sample preparation steps for the detection of the long-chain DNA fragments and amplification products. This indicates significant progression from current literature which commonly describes the detection of short, synthetic DNA fragments or utilises methods requiring complex physical separation or purification steps for the detection of longer DNA fragments. The findings therefore advance the potential for the application of Raman spectroscopy for the detection of biologically relevant nucleic acid target sequences, and it hoped that this will encourage further development of Raman spectroscopy for the application of DNA detection in future
Phytochemical, anticancer and antidiabetic studies on Libyan plants : Arum cyrenaicum, Pituranthos tortuosus, Teucrium zanonii, Hypochaeris radicata and Solanum sodomaeum
Get PDFThis thesis examined the in vitro anticancer and/ or antidiabetic activities of five Libyan medicinal plants which are traditionally used. They included: Arum cyrenaicum, Pituranthos tortuosus, Teucrium zanonii, Hypochaeris radicata and Solanum sodomaeum. Plants were investigated phytochemically and a range of compounds, including daucosterol ester of trans p-coumaric acid, were elucidated; one of which appears to be novel. In addition, phenolic compounds, phenolic acids, flavonoids, flavonoids glycosides, pheophytins, phenylethanoid glycoside, steroidal glycoalkaloid and fatty acid were isolated from these plants.;The work focused on the evaluation of the plant extracts and some of the isolated compounds for cytotoxicity based on metabolic activity to evaluate the potential anticancer activity against human melanoma A375, HeLa cervical, prostate LNCaP and PC-3M, pancreas PANC-1and liver HepG2 and non cancerous cells PNT2 and HEKa cells as the normal controls. Crude extracts and isolated compounds that showed weak or no inhibitory activity on the cell lines were then further investigated for hypoglycaemic activity by evaluating inhibition of carbohydrate-hydrolising enzymes protein tyrosine phosphatase 1B (PTP1B), alpha-glycosidase and alpha-amylase.;Among the A. cyrenaicum extracts, the root hexane extract showed weak activity at 250 μg/ml on cancer cells and HeLa, HepG2, HEKa and PNT2 cells with an IC50 of 181.3, 128.3, 136.6, and 140.7 μg/ml, respectively, while A. cyrenaicum fruit showed toxicity on normal cells. The hexane extract of P. tortuosus showed no selective toxicity toward cancers cells, as it killed normal and cancer cells (A375, PANC-1 and PNT2) at the lowest concentration with IC50 values of 76.97, 86.57 and 80.30 μg/ml, respectively and this extract was toxic to LNCaP, PC-3M and HepG2 at 250 μg/ml. However, PTH-6-7 from hexane extract, showed selective activity on A375, PC-3M and PANC-1 cells with an IC50 of 70.11, 72.20 and 75.88 μg/ml, respectively. The ethyl acetate extract of P. tortuosus showed weak activity at 250 μg/ml against A375, PANC-1 and PNT2 cells, but the methanol extract of P. tortuosus showed no toxicity on cancer cells.;The ethyl acetate extract of T. zanonii showed selective activity against A375 and LNCaP cancer cells, while the methanol extract showed selective activity against PANC-1 cells with an IC50 of 62.02 μg/ml and this effect was linked in part to the extracts' contents of phenylethanoid glycoside types. However, the hexane extract of T. zanonii showed weak activity on PANC-1 cells with an IC50 of 132.9 μg/ml; this could be due to the presence of salvigenin.;The hexane extract of H. radicata showed no selective activity against cancer cells, but the ethyl acetate extract of H. radicata showed selective activity against hepatoma cells with an IC50 of 63.43 μg/ml and this effect was linked in part to the extracts' flavonoids. The methanol extract of H. radicata did not exhibit activity on cancer cells.;S.sodomaeum methanol crude extract (SSM) and chlorogenic acid (SSM-56) were the most active against cancer cells. SSM showed toxicity against LNCaP, PC-3M, A375, HeLa, PANC-1 and HepG2 cells at different concentrations with different IC50 values 18.95 μg/ml, 18.37 μg/ml, 93.58 μg/ml, 29.20 μg/ml, 8.72 μg/ml and 18.98 μg/ml, respectively. Compound SSM-56 was toxic to LNCaP, PC-3M and HepG2 with IC50 values of 371.90 μM, 266.97 μM and 337.83 μM, respectively. However, both SSM and SSM-56 were most toxic to PANC-1 cells with IC50 values of 15.6 μg/ml and 20.19 μg/ml, respectively. On PNT2, the SSM extract showed toxic effects at concentrations above 125 μg/ml while SSM-56 did not show toxicity on normal cells. Therefore SSM extract and SSM-56 showed selective activity on PANC-1 cells. On further analysis, both SSM and SSM-56 had an inhibitory effect on adhesion, migration and invasion of PANC-1 cells. The effect of SSM and SSM-56 inhibited adhesion of PANC-1 cells to fibronectin and collagen IV. Therefore, SSM and SSM-56 have the potential to treat pancreatic cancer by inhibition of cell migration and invasion as a result of reduced or inhibited attachment to ECM proteins (collagen IV and fibronectin).;In terms of antidiabetic assessment, protein tyrosine phosphatase inhibition was observed for the hexane extract of T. zanonii (Ki 1.18±0.006 μg/ml), hexane and ethyl acetate extracts of H. radicata (Ki 1.207 ± 0.008 and 1.301± 0.006 μg/ml) and the hexane root and aerial part extracts of A. cyrenaicum (Ki 1.902± 1.51 μg/ml and 1.65± 1.37 μg/ml). The extract of H. radicata displayed alpha-glucosidase inhibition (Ki value of 2.160±1.007 μg/ml) and no activity for alpha-amylase. Results obtained indicated that all four plant extracts tested had the potential to lower blood glucose levels to some extent and therefore in part corroborates the ethnomedicinal use of these four species in the treatment of diabetes.;In conclusion, traditional Libyan plants can provide an excellent source of natural raw material to isolate anticancer or antidiabetic's agents, in addition, to phytochemicals, preliminary data showed the possibility from these plants having an anti-cancer or anti-diabetic role to play.This thesis examined the in vitro anticancer and/ or antidiabetic activities of five Libyan medicinal plants which are traditionally used. They included: Arum cyrenaicum, Pituranthos tortuosus, Teucrium zanonii, Hypochaeris radicata and Solanum sodomaeum. Plants were investigated phytochemically and a range of compounds, including daucosterol ester of trans p-coumaric acid, were elucidated; one of which appears to be novel. In addition, phenolic compounds, phenolic acids, flavonoids, flavonoids glycosides, pheophytins, phenylethanoid glycoside, steroidal glycoalkaloid and fatty acid were isolated from these plants.;The work focused on the evaluation of the plant extracts and some of the isolated compounds for cytotoxicity based on metabolic activity to evaluate the potential anticancer activity against human melanoma A375, HeLa cervical, prostate LNCaP and PC-3M, pancreas PANC-1and liver HepG2 and non cancerous cells PNT2 and HEKa cells as the normal controls. Crude extracts and isolated compounds that showed weak or no inhibitory activity on the cell lines were then further investigated for hypoglycaemic activity by evaluating inhibition of carbohydrate-hydrolising enzymes protein tyrosine phosphatase 1B (PTP1B), alpha-glycosidase and alpha-amylase.;Among the A. cyrenaicum extracts, the root hexane extract showed weak activity at 250 μg/ml on cancer cells and HeLa, HepG2, HEKa and PNT2 cells with an IC50 of 181.3, 128.3, 136.6, and 140.7 μg/ml, respectively, while A. cyrenaicum fruit showed toxicity on normal cells. The hexane extract of P. tortuosus showed no selective toxicity toward cancers cells, as it killed normal and cancer cells (A375, PANC-1 and PNT2) at the lowest concentration with IC50 values of 76.97, 86.57 and 80.30 μg/ml, respectively and this extract was toxic to LNCaP, PC-3M and HepG2 at 250 μg/ml. However, PTH-6-7 from hexane extract, showed selective activity on A375, PC-3M and PANC-1 cells with an IC50 of 70.11, 72.20 and 75.88 μg/ml, respectively. The ethyl acetate extract of P. tortuosus showed weak activity at 250 μg/ml against A375, PANC-1 and PNT2 cells, but the methanol extract of P. tortuosus showed no toxicity on cancer cells.;The ethyl acetate extract of T. zanonii showed selective activity against A375 and LNCaP cancer cells, while the methanol extract showed selective activity against PANC-1 cells with an IC50 of 62.02 μg/ml and this effect was linked in part to the extracts' contents of phenylethanoid glycoside types. However, the hexane extract of T. zanonii showed weak activity on PANC-1 cells with an IC50 of 132.9 μg/ml; this could be due to the presence of salvigenin.;The hexane extract of H. radicata showed no selective activity against cancer cells, but the ethyl acetate extract of H. radicata showed selective activity against hepatoma cells with an IC50 of 63.43 μg/ml and this effect was linked in part to the extracts' flavonoids. The methanol extract of H. radicata did not exhibit activity on cancer cells.;S.sodomaeum methanol crude extract (SSM) and chlorogenic acid (SSM-56) were the most active against cancer cells. SSM showed toxicity against LNCaP, PC-3M, A375, HeLa, PANC-1 and HepG2 cells at different concentrations with different IC50 values 18.95 μg/ml, 18.37 μg/ml, 93.58 μg/ml, 29.20 μg/ml, 8.72 μg/ml and 18.98 μg/ml, respectively. Compound SSM-56 was toxic to LNCaP, PC-3M and HepG2 with IC50 values of 371.90 μM, 266.97 μM and 337.83 μM, respectively. However, both SSM and SSM-56 were most toxic to PANC-1 cells with IC50 values of 15.6 μg/ml and 20.19 μg/ml, respectively. On PNT2, the SSM extract showed toxic effects at concentrations above 125 μg/ml while SSM-56 did not show toxicity on normal cells. Therefore SSM extract and SSM-56 showed selective activity on PANC-1 cells. On further analysis, both SSM and SSM-56 had an inhibitory effect on adhesion, migration and invasion of PANC-1 cells. The effect of SSM and SSM-56 inhibited adhesion of PANC-1 cells to fibronectin and collagen IV. Therefore, SSM and SSM-56 have the potential to treat pancreatic cancer by inhibition of cell migration and invasion as a result of reduced or inhibited attachment to ECM proteins (collagen IV and fibronectin).;In terms of antidiabetic assessment, protein tyrosine phosphatase inhibition was observed for the hexane extract of T. zanonii (Ki 1.18±0.006 μg/ml), hexane and ethyl acetate extracts of H. radicata (Ki 1.207 ± 0.008 and 1.301± 0.006 μg/ml) and the hexane root and aerial part extracts of A. cyrenaicum (Ki 1.902± 1.51 μg/ml and 1.65± 1.37 μg/ml). The extract of H. radicata displayed alpha-glucosidase inhibition (Ki value of 2.160±1.007 μg/ml) and no activity for alpha-amylase. Results obtained indicated that all four plant extracts tested had the potential to lower blood glucose levels to some extent and therefore in part corroborates the ethnomedicinal use of these four species in the treatment of diabetes.;In conclusion, traditional Libyan plants can provide an excellent source of natural raw material to isolate anticancer or antidiabetic's agents, in addition, to phytochemicals, preliminary data showed the possibility from these plants having an anti-cancer or anti-diabetic role to play
A metabolomics approach for targeted isolation and production of bioactive secondary metabolites in microbial isolates from extreme environments
Get PDFThis thesis was previously held under moratorium from 22/08/2019 to 22/08/2021.Marine microorganisms produce unique secondary metabolites, which are responsible for a variety of biologically active molecules with a wide range of pharmaceutical properties. There is a lack of novel effective drugs for metabolic diseases, cancer and parasite infections as well as TNF-alpha inhibitors hence; underexplored marine bacteria could be an important source for new bioactive molecules.Two strains of Muricauda ruestringensis (SBT531 and SBT587) were isolated from geothermal intertidal pools in Iceland and two strains of Micromonospora sp. N17 and N74 (SBT 687 and SBT692) were isolated from the Mediterranean sponge Phorbas tenacior from the Santorini volcanic complex of Crete. Bioactive metabolites production in thermophile strains of M. ruestringensis (SBT531 and SBT587) and Micromonospora sp. (SBT687 and SBT692) were identified and isolated, by using a metabolomics approach to analyse the liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) data sets. The LC HRMS data was processed by using the modified version of Mzmine 2.10 software, dereplicated with an in-house EXCEL macro coupled to the AntiMarin and Dictionaryof Natural Products (DNP) database to be statistically evaluated by multivariate analysis in SIMCA v15.02. Orthogonal partial least squares discriminant analysis (OPLS-DA) in SIMCA was used to predict and pinpoint the biologically active secondary metabolites. Up-scaling was optimised to increase the production yield of the target metabolites. Additionally, specific bioassay screening determined the activity, if any, from the crude extracts, fractions and isolated compounds.The total ethyl acetate organic extracts of SBT531 and SBT587 were active inhibitors in target-based functional assays: alpha-glucosidase and protein-tyrosine phosphatase 1B (PTP1B) that are a therapeutic target for the treatment of diabetes and other metabolic syndromes. The fractionation of SBT531 afforded a series of bioactive alpha and beta-hydroxy acid derivatives and allowed the definition of a preliminary structure-activity relationship based on their relative potency. Aseanostatin P6 (13-methyltetradecanoic acid) was the major compound identified, followed by two derivatives, 3-hydroxy-13-methyltetradecanoic acid and 2-hydroxy-14-methylhexadecanoic acid.On the other hand, the initial organic crude extracts of SBT687 and SBT692 showed inhibition activity against sea lice and inhibition of TNF alpha respectively, however after further fermentation scale-up the fractions were missing the inhibition activity.Marine microorganisms produce unique secondary metabolites, which are responsible for a variety of biologically active molecules with a wide range of pharmaceutical properties. There is a lack of novel effective drugs for metabolic diseases, cancer and parasite infections as well as TNF-alpha inhibitors hence; underexplored marine bacteria could be an important source for new bioactive molecules.Two strains of Muricauda ruestringensis (SBT531 and SBT587) were isolated from geothermal intertidal pools in Iceland and two strains of Micromonospora sp. N17 and N74 (SBT 687 and SBT692) were isolated from the Mediterranean sponge Phorbas tenacior from the Santorini volcanic complex of Crete. Bioactive metabolites production in thermophile strains of M. ruestringensis (SBT531 and SBT587) and Micromonospora sp. (SBT687 and SBT692) were identified and isolated, by using a metabolomics approach to analyse the liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) data sets. The LC HRMS data was processed by using the modified version of Mzmine 2.10 software, dereplicated with an in-house EXCEL macro coupled to the AntiMarin and Dictionaryof Natural Products (DNP) database to be statistically evaluated by multivariate analysis in SIMCA v15.02. Orthogonal partial least squares discriminant analysis (OPLS-DA) in SIMCA was used to predict and pinpoint the biologically active secondary metabolites. Up-scaling was optimised to increase the production yield of the target metabolites. Additionally, specific bioassay screening determined the activity, if any, from the crude extracts, fractions and isolated compounds.The total ethyl acetate organic extracts of SBT531 and SBT587 were active inhibitors in target-based functional assays: alpha-glucosidase and protein-tyrosine phosphatase 1B (PTP1B) that are a therapeutic target for the treatment of diabetes and other metabolic syndromes. The fractionation of SBT531 afforded a series of bioactive alpha and beta-hydroxy acid derivatives and allowed the definition of a preliminary structure-activity relationship based on their relative potency. Aseanostatin P6 (13-methyltetradecanoic acid) was the major compound identified, followed by two derivatives, 3-hydroxy-13-methyltetradecanoic acid and 2-hydroxy-14-methylhexadecanoic acid.On the other hand, the initial organic crude extracts of SBT687 and SBT692 showed inhibition activity against sea lice and inhibition of TNF alpha respectively, however after further fermentation scale-up the fractions were missing the inhibition activity
Autonomous unmanned aerial vehicle for non-destructive testing
Get PDFUnmanned Aerial Vehicles (UAVs) are receiving increasing attention for use in Non-Destructive Testing / Evaluation (NDT / NDE), due to affordability, safety, and the ability to access areas where manned inspection is not practical. The mobility and size of UAVs offer the flexibility to quickly deploy remote inspections of large-scale assets and targets with complex geometry, such as wind turbine blades. The platform also provides airborne approaches to inspect high-risk sites, such as areas within nuclear facilities, which conventionally require inspectors to work at high altitude or in the presence of safety risks. Although ground crawler vehicles have been seen in such applications, UAVs offers true three-dimensional (3D) inspections and solve many challenging access problems. Commercial UAV-deployed NDT inspections typically rely on a high-resolution camera that is manually piloted with a relatively large standoff distance, due to collision concerns and aerodynamic challenges. Close-range and contact-based inspections grant more detailed and accurate evaluations, whilst demanding an advanced UAV flight control system. This thesis evaluates two approaches to automated remote NDT, namely 3D photogrammetric and ultrasonic inspection. 3D photogrammetric inspection is a visual NDT method used to quantify surface integrity and detect discontinuities in a structure's coating. Compared with traditional inspections from offline images, a 3D photogrammetric inspection provides results with intrinsic position and location information, which is essential to meaningful surface condition evaluations. Structural health conditions, such as internal support material corrosion and fatigue crack formation beneath an outersurface coating, require contact-based measurement technologies. Contact-based ultrasonic measurements grant the opportunity to remotely monitor the structural health of an industrial asset with enhanced internal integrity information. This thesis has investigated and evaluated photogrammetric and contact-based inspections deployed by an aerial vehicle. The novel contribution of the research is to investigate the connection between the inspection accuracy and parameters in UAV-deployed inspections. Additionally, a novel, airborne, ultrasonic measurement system for the contact inspection of non-magnetic facilities was established. As far as the author aware, this is the first time such an inspection has been implemented and evaluated. The implementation and modification of the autonomous flight controller on an AscTec Firefly UAV for indoor inspections are detailed within. A miniature planar laser scanner with a curve fitting was integrated into the system to map the UAV surroundings, measuring the displacement and alignment error against the inspection target. Brightness conditions, motion blur, and focal blur parameters influenced the accuracy of the photogrammetric inspections and were quantified and discussed. The inspection accuracy was improved from 0.3853 mm to 0.3098mm using more detailed features on the mesh while the photogrammetric inspection was undertaken with a laser-based flight trajectory. The negative influences of these parameters were mitigated with an active flight path and an appropriate experimental setup, improving the reconstruction error by a factor of 13 versus the poorest scenario. An autonomous UAV-deployed ultrasonic measurement system was developed for the inspection of vertical structures. The inspection constraints, such as transducer alignment and UAV positional accuracy, impacted the measurement error during the ultrasonic inspections. The influences of these constraints were evaluated and analysed. An additional contribution was presented on the improved inspection accuracy while applying a coded excitation to the ultrasonic measurement system to increase Signal-to-Noise Ratio. The maximum error was reduced from 0.83 mmto 0.66 mm in scenarios where the transducer was sub-optimally aligned.Unmanned Aerial Vehicles (UAVs) are receiving increasing attention for use in Non-Destructive Testing / Evaluation (NDT / NDE), due to affordability, safety, and the ability to access areas where manned inspection is not practical. The mobility and size of UAVs offer the flexibility to quickly deploy remote inspections of large-scale assets and targets with complex geometry, such as wind turbine blades. The platform also provides airborne approaches to inspect high-risk sites, such as areas within nuclear facilities, which conventionally require inspectors to work at high altitude or in the presence of safety risks. Although ground crawler vehicles have been seen in such applications, UAVs offers true three-dimensional (3D) inspections and solve many challenging access problems. Commercial UAV-deployed NDT inspections typically rely on a high-resolution camera that is manually piloted with a relatively large standoff distance, due to collision concerns and aerodynamic challenges. Close-range and contact-based inspections grant more detailed and accurate evaluations, whilst demanding an advanced UAV flight control system. This thesis evaluates two approaches to automated remote NDT, namely 3D photogrammetric and ultrasonic inspection. 3D photogrammetric inspection is a visual NDT method used to quantify surface integrity and detect discontinuities in a structure's coating. Compared with traditional inspections from offline images, a 3D photogrammetric inspection provides results with intrinsic position and location information, which is essential to meaningful surface condition evaluations. Structural health conditions, such as internal support material corrosion and fatigue crack formation beneath an outersurface coating, require contact-based measurement technologies. Contact-based ultrasonic measurements grant the opportunity to remotely monitor the structural health of an industrial asset with enhanced internal integrity information. This thesis has investigated and evaluated photogrammetric and contact-based inspections deployed by an aerial vehicle. The novel contribution of the research is to investigate the connection between the inspection accuracy and parameters in UAV-deployed inspections. Additionally, a novel, airborne, ultrasonic measurement system for the contact inspection of non-magnetic facilities was established. As far as the author aware, this is the first time such an inspection has been implemented and evaluated. The implementation and modification of the autonomous flight controller on an AscTec Firefly UAV for indoor inspections are detailed within. A miniature planar laser scanner with a curve fitting was integrated into the system to map the UAV surroundings, measuring the displacement and alignment error against the inspection target. Brightness conditions, motion blur, and focal blur parameters influenced the accuracy of the photogrammetric inspections and were quantified and discussed. The inspection accuracy was improved from 0.3853 mm to 0.3098mm using more detailed features on the mesh while the photogrammetric inspection was undertaken with a laser-based flight trajectory. The negative influences of these parameters were mitigated with an active flight path and an appropriate experimental setup, improving the reconstruction error by a factor of 13 versus the poorest scenario. An autonomous UAV-deployed ultrasonic measurement system was developed for the inspection of vertical structures. The inspection constraints, such as transducer alignment and UAV positional accuracy, impacted the measurement error during the ultrasonic inspections. The influences of these constraints were evaluated and analysed. An additional contribution was presented on the improved inspection accuracy while applying a coded excitation to the ultrasonic measurement system to increase Signal-to-Noise Ratio. The maximum error was reduced from 0.83 mmto 0.66 mm in scenarios where the transducer was sub-optimally aligned
An occupant-centric assessment of the building performance gap in low utilisation, higher education facilities
Get PDFSeminal literature advocates that the occupants of buildings are the real consumers ofenergy, not the buildings. While this is a helpful philosophy for design and retrofit analysis, it is not entirely accommodating of operational building energy demand. An optimistic amendment would suggest that it is the needs of people that consume energy rather than buildings, for nondomestic buildings at least. However, needs in operation are not guaranteed to correlate with simulation, and servicing of needs is not bound to the real occupant presence. The presence of the people, whose needs exist in a given discrete space is not a prerequisite of energy consumption. In broader terms of occupancy, the observation is absent from the nature of consuming services' relationships with occupants and the activities that drive the second-order interests. That is, what constitutes as needs of one occupant is not necessarily equivalent of identical needs of another. These factors cause great concern for retrofit decision-making and invariably make a significant contribution to the building performance gap. Given the presumption of needs' role in building energy consumption, it appears that the industry must revise its current definitions of what constitutes as an occupant and how efficiency is measured. After all, an ideal system is still inefficient, if its operation has no utility. Further and higher education facilities are notably sensitive to these concerns. Where the assumption that needs exist in design models is known typically to deviate by 73% in teaching spaces, in the United Kingdom. However, they are also uniquely equipped for stabilising their utilisation through strict class allocation planning. The difference in utilisation when mapped to zones in EnergyPlus can profoundly affect how a simulated building behaves. These changes to simulated behaviour can redefine the retrofit solution space. Without strict heating management through registration of periods of nonzero density presence to a building management system, over two-thirds of needs do not exist. This study aims to demonstrate the severity of the presence simulation gap and provide a case for heat management as a precursor for conventional retrofit analysis. It also aims to determine whether gaps exist in the current occupant ontologies. A registration system-led occupancy modelling tool for EnergyPlus is developed to explore divergence from standardised and real utilisation to simulated behaviours under known conditions. The tool is tested through two virtual cases under different building states by assessing real-world utilisation of the teaching spaces for two years' weather data and six Schedule-Climate scenarios. Three retrofit options encompassing heating management, lighting and boiler replacement are simulated and presented under each Schedule-Climate scenario. All results form building energy modelling are considered in terms of emissions, net energy and operation costs. Retrofit results are assessed using discounted cash flow analysis at the Green Book suggested discount rate. The entire solution space is procedurally generated by a bespoke library which integrates EnergyPlus and data analytics tools. The experimentation results show the severity of the presence and presence-bound scheduling simulations gaps. It is shown simulated heating energy demand is dependent on latent gains to the extent that when heating schedules are decoupled from presence as per the real world, retrofitting lighting will have an adverse effect on building energy performance. The results proceed to explore the underlying relationship between heating and lighting energy demand, occupancy and net building energy demand. This is demonstrated through presentation of disaggregated internal gains and determining the ratio of energy consumption to net energy demand for combined lighting and heating. The experimentation results are concluded by presentation of result from constant-efficacy lighting retrofits from eighty Schedule-Climate scenarios. Referencing the low utilisation from the registration system and out-of-design presence, the discussion proposes how measuring efficiency in terms of met needs has merit in the higher education sector. Findings from the literature review and consideration of the heterogeneous utilisation is used to explore several new ontologies which bridge the gap between virtual and real occupants.The thesis which is themed on a previous publication proposes a philosophical framing of energy consumption in low-utilisation buildings. It makes several suggestions for future research ultimately concluding that retrofit analysis should focus on robust mediocrity over simulated optimality of proposals.Seminal literature advocates that the occupants of buildings are the real consumers ofenergy, not the buildings. While this is a helpful philosophy for design and retrofit analysis, it is not entirely accommodating of operational building energy demand. An optimistic amendment would suggest that it is the needs of people that consume energy rather than buildings, for nondomestic buildings at least. However, needs in operation are not guaranteed to correlate with simulation, and servicing of needs is not bound to the real occupant presence. The presence of the people, whose needs exist in a given discrete space is not a prerequisite of energy consumption. In broader terms of occupancy, the observation is absent from the nature of consuming services' relationships with occupants and the activities that drive the second-order interests. That is, what constitutes as needs of one occupant is not necessarily equivalent of identical needs of another. These factors cause great concern for retrofit decision-making and invariably make a significant contribution to the building performance gap. Given the presumption of needs' role in building energy consumption, it appears that the industry must revise its current definitions of what constitutes as an occupant and how efficiency is measured. After all, an ideal system is still inefficient, if its operation has no utility. Further and higher education facilities are notably sensitive to these concerns. Where the assumption that needs exist in design models is known typically to deviate by 73% in teaching spaces, in the United Kingdom. However, they are also uniquely equipped for stabilising their utilisation through strict class allocation planning. The difference in utilisation when mapped to zones in EnergyPlus can profoundly affect how a simulated building behaves. These changes to simulated behaviour can redefine the retrofit solution space. Without strict heating management through registration of periods of nonzero density presence to a building management system, over two-thirds of needs do not exist. This study aims to demonstrate the severity of the presence simulation gap and provide a case for heat management as a precursor for conventional retrofit analysis. It also aims to determine whether gaps exist in the current occupant ontologies. A registration system-led occupancy modelling tool for EnergyPlus is developed to explore divergence from standardised and real utilisation to simulated behaviours under known conditions. The tool is tested through two virtual cases under different building states by assessing real-world utilisation of the teaching spaces for two years' weather data and six Schedule-Climate scenarios. Three retrofit options encompassing heating management, lighting and boiler replacement are simulated and presented under each Schedule-Climate scenario. All results form building energy modelling are considered in terms of emissions, net energy and operation costs. Retrofit results are assessed using discounted cash flow analysis at the Green Book suggested discount rate. The entire solution space is procedurally generated by a bespoke library which integrates EnergyPlus and data analytics tools. The experimentation results show the severity of the presence and presence-bound scheduling simulations gaps. It is shown simulated heating energy demand is dependent on latent gains to the extent that when heating schedules are decoupled from presence as per the real world, retrofitting lighting will have an adverse effect on building energy performance. The results proceed to explore the underlying relationship between heating and lighting energy demand, occupancy and net building energy demand. This is demonstrated through presentation of disaggregated internal gains and determining the ratio of energy consumption to net energy demand for combined lighting and heating. The experimentation results are concluded by presentation of result from constant-efficacy lighting retrofits from eighty Schedule-Climate scenarios. Referencing the low utilisation from the registration system and out-of-design presence, the discussion proposes how measuring efficiency in terms of met needs has merit in the higher education sector. Findings from the literature review and consideration of the heterogeneous utilisation is used to explore several new ontologies which bridge the gap between virtual and real occupants.The thesis which is themed on a previous publication proposes a philosophical framing of energy consumption in low-utilisation buildings. It makes several suggestions for future research ultimately concluding that retrofit analysis should focus on robust mediocrity over simulated optimality of proposals
Modular multilevel converter designs for medium-voltage machine drives
No full textVarious industry sectors are now adopting high-power applications that involve power electronics on a large scale. This increases the power level requirement of the adjustable-speed drives utilized in such applications to scores of megawatts, triggering the need for high-power driving at the medium-voltage (MV) level. Thus, this thesis addresses the modular multilevel converter (MMC) as a promising topology for MV machine drives.;A special focus is given to the variable-speed operation of MMC-fed three-phase machines, where the MMC experiences a serious challenge when operating at low frequencies. The MMC's unique operation principles imply its floating submodule (SM) capacitors experience voltage fluctuation at the fundamental operating frequency. At lower operating frequencies, MMC capacitor voltage fluctuations can reach extreme levels, inversely proportional to the operating frequency, where increasing the SM capacitance for voltage ripple compensation is not viable.;In this context, this thesis proposes an approach for SM capacitor voltage ripple compensation, which employs magnetic chain links involving dual half-bridges (DHBs) to interface the SMs, for ripple power decoupling. The approach is able to transfer the ripple power of one SM to another in a bidirectional fashion, countering the energy fluctuation. This allows for an even capacitive energy distribution across MMC SMs, independent of the operating frequency, resulting in a significant reduction in SM capacitance. A class of different DHB modules allocations relevant to the MMC SMs is investigated.;Also, this thesis addresses MMC application for multiphase machine drives, where reduced topological designs derived from the standard MMC are presented for six-phase machine drives. The topologies are enhanced to realize a more-economic six-phase machine drive without any performance compromise.;Analytical investigations are derived for the different approaches presented in this thesis, while necessary control algorithms are analyzed. The viability of proposed concepts and approaches are substantiated through both simulation and experimentation.Various industry sectors are now adopting high-power applications that involve power electronics on a large scale. This increases the power level requirement of the adjustable-speed drives utilized in such applications to scores of megawatts, triggering the need for high-power driving at the medium-voltage (MV) level. Thus, this thesis addresses the modular multilevel converter (MMC) as a promising topology for MV machine drives.;A special focus is given to the variable-speed operation of MMC-fed three-phase machines, where the MMC experiences a serious challenge when operating at low frequencies. The MMC's unique operation principles imply its floating submodule (SM) capacitors experience voltage fluctuation at the fundamental operating frequency. At lower operating frequencies, MMC capacitor voltage fluctuations can reach extreme levels, inversely proportional to the operating frequency, where increasing the SM capacitance for voltage ripple compensation is not viable.;In this context, this thesis proposes an approach for SM capacitor voltage ripple compensation, which employs magnetic chain links involving dual half-bridges (DHBs) to interface the SMs, for ripple power decoupling. The approach is able to transfer the ripple power of one SM to another in a bidirectional fashion, countering the energy fluctuation. This allows for an even capacitive energy distribution across MMC SMs, independent of the operating frequency, resulting in a significant reduction in SM capacitance. A class of different DHB modules allocations relevant to the MMC SMs is investigated.;Also, this thesis addresses MMC application for multiphase machine drives, where reduced topological designs derived from the standard MMC are presented for six-phase machine drives. The topologies are enhanced to realize a more-economic six-phase machine drive without any performance compromise.;Analytical investigations are derived for the different approaches presented in this thesis, while necessary control algorithms are analyzed. The viability of proposed concepts and approaches are substantiated through both simulation and experimentation
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