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Transmission congestion management and security cost optimization in deregulated electricity markets
Get PDFTwo sensitivity factors, namely the power transfer distribution factor (PTDF) and the impedance based sensitivity factor (ZS), are proposed respectively in the thesis to calculate the power flow contribution of each bus to the transmission network congestion. Generation re-dispatch and the corresponding security cost allocation are based on the calculated power flow contribution. The proposed generation re-dispatch method and the proposed security cost allocation method both with two sensitivity factors are validated respectively on four test systems including a modified IEEE-14 bus system, a modified IEEE-30 bus system, a modified IEEE-57 bus system and a modified IEEE-118 bus system.;The experimental results are obtained including the generation re-dispatch MW amount of each generator selecting different locations of slack bus, the resulted security cost and the security cost allocation to each load. The comparisons between two sensitivity-based methods on both generation re-dispatch and security cost allocation show that the PTDF-based method and the ZS-based method are both dependent on the location of slack bus selection, which increase the risks of inaccuracy and complexity.;The ZS-based method involves more generators in re-dispatch stage than the PTDF-based method, consequently results in higher security cost. Moreover, with intense level of congestion, such security cost difference between the two methods becomes larger. Compared with the ZS-based method, the PTDF-based method is more reliable on security cost allocation since in large bus system, for example, the 118-bus system, the allocation results by the ZS-based method appears unreasonable.Two sensitivity factors, namely the power transfer distribution factor (PTDF) and the impedance based sensitivity factor (ZS), are proposed respectively in the thesis to calculate the power flow contribution of each bus to the transmission network congestion. Generation re-dispatch and the corresponding security cost allocation are based on the calculated power flow contribution. The proposed generation re-dispatch method and the proposed security cost allocation method both with two sensitivity factors are validated respectively on four test systems including a modified IEEE-14 bus system, a modified IEEE-30 bus system, a modified IEEE-57 bus system and a modified IEEE-118 bus system.;The experimental results are obtained including the generation re-dispatch MW amount of each generator selecting different locations of slack bus, the resulted security cost and the security cost allocation to each load. The comparisons between two sensitivity-based methods on both generation re-dispatch and security cost allocation show that the PTDF-based method and the ZS-based method are both dependent on the location of slack bus selection, which increase the risks of inaccuracy and complexity.;The ZS-based method involves more generators in re-dispatch stage than the PTDF-based method, consequently results in higher security cost. Moreover, with intense level of congestion, such security cost difference between the two methods becomes larger. Compared with the ZS-based method, the PTDF-based method is more reliable on security cost allocation since in large bus system, for example, the 118-bus system, the allocation results by the ZS-based method appears unreasonable
Informing the next generation of auditory midbrain implants, neuronal population dynamics in the auditory cortex and midbrain, and the potentials of optogenetic stimulation
Get PDFThe performance of current generation central auditory neuroprosthetics lags behind the cochlear implant. As these new devices utilise speech processing algorithms based on the cochlea, more information may be required regarding the neuronal population activity of potential prosthetic sites, in order to optimise stimulation to mimic the area's natural inputs and achieve useful sound perception. Additionally, electrode based devices afford poor spatial resolution, which optogenetics may solve. Simultaneous silicon probe recordings were performed in the inferior colliculus (IC) and auditory cortex (AC) of awake, head-fixed mice, and repetitions of natural sound stimuli played. The two areas are different in their general cell population metrics, levels of inter-trial LFP coherence, and neuronal entrainment, with the AC favouring entrainment frequencies below 30Hz and the IC apparently entraining over a wider range of 2-200Hz.;The proportion of putative AC narrow-spiking interneurons is higher during natural sounds as opposed to spontaneous activity alone. Using linear classification analysis, a spike rate code was generally found to be sufficient for distinguishing between natural sound stimuli, in both the AC and IC. However, the IC achieved comparable performance to the AC using fewer single ormulti units. This could be due to the lower trial-trial variability (Fano factor) of the ICcell population. Dimensionality reduction revealed, qualitatively, the presence of distinct cell populations in both brain areas, responding to different aspects of the natural sound.;A viral injection protocol for expression of the Chronos opsin through the depth of themouse ICC was optimised, and light activation confirmed. A control system for a µLEDdevice was created and used in a pilot experiment, which served to highlight the importance of artefact-reducing device design. The findings indicate that IC neurons tend to fire in the same way (i.e. more reliably) to successive repetitions of natural sound when compared to the auditory cortex, and that AC narrow-spiking interneurons may have different functions between spontaneous and evoked activity. Optogenetics is a promising approach to improving auditory implant resolution, given well designed light delivery devices and accompanying software.The performance of current generation central auditory neuroprosthetics lags behind the cochlear implant. As these new devices utilise speech processing algorithms based on the cochlea, more information may be required regarding the neuronal population activity of potential prosthetic sites, in order to optimise stimulation to mimic the area's natural inputs and achieve useful sound perception. Additionally, electrode based devices afford poor spatial resolution, which optogenetics may solve. Simultaneous silicon probe recordings were performed in the inferior colliculus (IC) and auditory cortex (AC) of awake, head-fixed mice, and repetitions of natural sound stimuli played. The two areas are different in their general cell population metrics, levels of inter-trial LFP coherence, and neuronal entrainment, with the AC favouring entrainment frequencies below 30Hz and the IC apparently entraining over a wider range of 2-200Hz.;The proportion of putative AC narrow-spiking interneurons is higher during natural sounds as opposed to spontaneous activity alone. Using linear classification analysis, a spike rate code was generally found to be sufficient for distinguishing between natural sound stimuli, in both the AC and IC. However, the IC achieved comparable performance to the AC using fewer single ormulti units. This could be due to the lower trial-trial variability (Fano factor) of the ICcell population. Dimensionality reduction revealed, qualitatively, the presence of distinct cell populations in both brain areas, responding to different aspects of the natural sound.;A viral injection protocol for expression of the Chronos opsin through the depth of themouse ICC was optimised, and light activation confirmed. A control system for a µLEDdevice was created and used in a pilot experiment, which served to highlight the importance of artefact-reducing device design. The findings indicate that IC neurons tend to fire in the same way (i.e. more reliably) to successive repetitions of natural sound when compared to the auditory cortex, and that AC narrow-spiking interneurons may have different functions between spontaneous and evoked activity. Optogenetics is a promising approach to improving auditory implant resolution, given well designed light delivery devices and accompanying software
EMP mitigation and novel detection strategies for laser-plasma experiments
Get PDFLaser driven particle and radiation sources have the potential to become an alternative to conventional accelerators for a number of applications. Many laser-driven sources have been demonstrated, including x-rays, protons, electrons and positrons. The laser driven production of exotic particles such as muons has been theorised. Proposed applications for some of these novel particle and photon sources include a compact source of ions for cancer treatment, electrons for radar imaging, x-rays for probing high density objects, and muons to be deployed for the imaging of large dense structures including nuclear reactor cores and inspect large containers for forbidden fissile elements, to name a few. Ideally, to achieve these applications, laser-driven sources must be developed to have high conversion efficiency, high resolution and controlled directionality. Electromagnetic pulse (EMP) emission is prevalent in high power laser-plasma interactions and primarily arises due to the return current induced by the ejection of hot electrons from the target.;It is important to study these emissions at high power laser facilities as it has been shown to interfere with experimental diagnostics. Many facilities currently under development will be able to produce higher intensity laser pulses at a high repetition rate and therefore EMP may become significantly disruptive to experiments. Due to this, EMP has recently attracted considerable interest and therefore the first two experimental chapters of this thesis focus on EMP energy correlations with proton and electron measurements, and EMP control and mitigation. The first investigation reports on experimental studies into the EMP scaling with sheath accelerated protons in laser-solid interactions in the intensity region of 10 Hz, there will be a need for improved diagnostics which can operate at such repetition rates, and are also resistant to EMP. The final study presents the development of an optical based technique coupled to a fast and sensitive photon detector, able to operate at high repetition rates and is largely unaffected by EMP. It can be used to detect any relativistic charged particles, and can measure relative beam charge providing an on-shot electron beam diagnostic in electron acceleration experiments.Laser driven particle and radiation sources have the potential to become an alternative to conventional accelerators for a number of applications. Many laser-driven sources have been demonstrated, including x-rays, protons, electrons and positrons. The laser driven production of exotic particles such as muons has been theorised. Proposed applications for some of these novel particle and photon sources include a compact source of ions for cancer treatment, electrons for radar imaging, x-rays for probing high density objects, and muons to be deployed for the imaging of large dense structures including nuclear reactor cores and inspect large containers for forbidden fissile elements, to name a few. Ideally, to achieve these applications, laser-driven sources must be developed to have high conversion efficiency, high resolution and controlled directionality. Electromagnetic pulse (EMP) emission is prevalent in high power laser-plasma interactions and primarily arises due to the return current induced by the ejection of hot electrons from the target.;It is important to study these emissions at high power laser facilities as it has been shown to interfere with experimental diagnostics. Many facilities currently under development will be able to produce higher intensity laser pulses at a high repetition rate and therefore EMP may become significantly disruptive to experiments. Due to this, EMP has recently attracted considerable interest and therefore the first two experimental chapters of this thesis focus on EMP energy correlations with proton and electron measurements, and EMP control and mitigation. The first investigation reports on experimental studies into the EMP scaling with sheath accelerated protons in laser-solid interactions in the intensity region of 10 Hz, there will be a need for improved diagnostics which can operate at such repetition rates, and are also resistant to EMP. The final study presents the development of an optical based technique coupled to a fast and sensitive photon detector, able to operate at high repetition rates and is largely unaffected by EMP. It can be used to detect any relativistic charged particles, and can measure relative beam charge providing an on-shot electron beam diagnostic in electron acceleration experiments
Station-keeping and orbital transfers in the vicinity of the Moon exploiting quasi-periodic orbit dynamics
Get PDFFuture manned space exploration sets a focus on the long-term goal of landing humans on a foreign planet in particular on Mars. Translating this ambitious plan into practice is a major challenge, and beforehand several milestones have to be achieved. One major objective in the years ahead will be a return to the vicinity of the Moon with robotic exploration missions and crewed space vehicles. Not only is returning to the Moon an inspiring challenge but also and more importantly a return to the Moon opens the possibility to prove new technologies, gain scientific knowledge, and identify key requirements for further endeavours.;As a consequence it is possible that traditional mission scenarios considering the use of low lunar orbits or transfer arcs to the surface are replaced by new mission scenarios exploiting the potentialities of the collinear Earth-Moon libration point orbits. In addition, solutions considering multiple coordinated spacecraft with disaggregated payloads are becoming more and more interesting for a variety of space missions. The cooperation between spacecraft will increase redundancy and will enable new navigation and remote sensing solutions that can hardly be achieved with single monolithic spacecraft.;A key element of missions considering the collaborative interaction among groups of spacecraft is the ability to transfer them between orbits. This might include rendezvous and docking for on-orbit assembling. In this context, the vision is to have a transport system in the Earth-Moon environment that allows transferring components from the Earth to the Moon and assembling large infrastructures in the vicinity of the Moon.;This infrastructure serves as stepping stone or gateway to the exploration of the solar system. A fundamental understanding of existing orbits and transfer possibilities becomes critical for exploring and accessing the vicinity of the Moon. A transport system in this described context offers regular access to all orbits between the Earth and the Moon, which includes transfers from the Earth to the Moon, transfers among orbits in the proximity of the Moon and transfers from the Moon to interplanetary space.;From a mission design point of view it is paramount to understand the intricate interaction between the Earth's and the Moon's gravity field. Projects also benefit from the unique dynamical environment prevailing at the libration point regions enabling to choose from a huge variety of operational orbits with greatly varying parameters.;The utilisation of quasi-periodic orbits increase the flexibility in planning future missions, reduces the complexity of long-term space missions by enabling larger windows for manoeuvre execution for orbital transfers. Furthermore, properties of operational orbits might be changed by manoeuvres enabling to achieve mission objectives. Based on this assumption a variety of problems are addressed in this work. Numerical tools are presented to study and assess quasi-periodic bounded orbits in the vicinity of the Moon, in particular libration point and distant periodic orbits.;On the basis of a description of quasi-periodic orbits, mission analysis aspects studied are the identification of suitable operational orbits, transfer opportunities among those orbits, and the handling of quasi-periodic orbits in a high-fidelity dynamical model. A method is presented to systematically compute any type of transfer either for changing properties of the operational orbit or to re-phase spacecraft along the orbit. The proposed orbital transfers utilise hyperbolic invariant manifolds of orbits that exist in a three-body regime. Parameters have been identified that have a substantial impact on the existent range of orbits and figure of merits are presented for reference scenarios that comprises the elements of an exploration mission travelling to L2 libration point orbits in the proximity of the Moon.Future manned space exploration sets a focus on the long-term goal of landing humans on a foreign planet in particular on Mars. Translating this ambitious plan into practice is a major challenge, and beforehand several milestones have to be achieved. One major objective in the years ahead will be a return to the vicinity of the Moon with robotic exploration missions and crewed space vehicles. Not only is returning to the Moon an inspiring challenge but also and more importantly a return to the Moon opens the possibility to prove new technologies, gain scientific knowledge, and identify key requirements for further endeavours.;As a consequence it is possible that traditional mission scenarios considering the use of low lunar orbits or transfer arcs to the surface are replaced by new mission scenarios exploiting the potentialities of the collinear Earth-Moon libration point orbits. In addition, solutions considering multiple coordinated spacecraft with disaggregated payloads are becoming more and more interesting for a variety of space missions. The cooperation between spacecraft will increase redundancy and will enable new navigation and remote sensing solutions that can hardly be achieved with single monolithic spacecraft.;A key element of missions considering the collaborative interaction among groups of spacecraft is the ability to transfer them between orbits. This might include rendezvous and docking for on-orbit assembling. In this context, the vision is to have a transport system in the Earth-Moon environment that allows transferring components from the Earth to the Moon and assembling large infrastructures in the vicinity of the Moon.;This infrastructure serves as stepping stone or gateway to the exploration of the solar system. A fundamental understanding of existing orbits and transfer possibilities becomes critical for exploring and accessing the vicinity of the Moon. A transport system in this described context offers regular access to all orbits between the Earth and the Moon, which includes transfers from the Earth to the Moon, transfers among orbits in the proximity of the Moon and transfers from the Moon to interplanetary space.;From a mission design point of view it is paramount to understand the intricate interaction between the Earth's and the Moon's gravity field. Projects also benefit from the unique dynamical environment prevailing at the libration point regions enabling to choose from a huge variety of operational orbits with greatly varying parameters.;The utilisation of quasi-periodic orbits increase the flexibility in planning future missions, reduces the complexity of long-term space missions by enabling larger windows for manoeuvre execution for orbital transfers. Furthermore, properties of operational orbits might be changed by manoeuvres enabling to achieve mission objectives. Based on this assumption a variety of problems are addressed in this work. Numerical tools are presented to study and assess quasi-periodic bounded orbits in the vicinity of the Moon, in particular libration point and distant periodic orbits.;On the basis of a description of quasi-periodic orbits, mission analysis aspects studied are the identification of suitable operational orbits, transfer opportunities among those orbits, and the handling of quasi-periodic orbits in a high-fidelity dynamical model. A method is presented to systematically compute any type of transfer either for changing properties of the operational orbit or to re-phase spacecraft along the orbit. The proposed orbital transfers utilise hyperbolic invariant manifolds of orbits that exist in a three-body regime. Parameters have been identified that have a substantial impact on the existent range of orbits and figure of merits are presented for reference scenarios that comprises the elements of an exploration mission travelling to L2 libration point orbits in the proximity of the Moon
Artifact removal in digital retinal images
Get PDFGlobally 2.2 million people are visually impaired and, of these, approximately 1 million present forms of visual impairment that could be addressed or prevented. Retinal imaging is a key step in the diagnosis and follow-up of major causes of visual impairment. As much as 20% of retinal images collected in the population are affected by artifacts, that render them ungradable both by expert graders and by the more recent automatic grading systems.;This work aims to develop an artifact removal strategy able to improve the effectiveness of retinal image grading, in particular for retinal feature segmentation. First, a large group of statistical parameters designed to measure image quality have been selected from the literature. A new ophthalmic database was then collected (CORD - the Comprehensive Ophthalmic Research Database), which includes retinal images with and without artifacts.;A mathematical model describing artifacts on the basis of the interaction of the light with the eye during eye photography was then developed. CORD and the mathematical model were then used to train a binary classifier to distinguish pixels affected by distortions within the image without the need for interpretive knowledge of the image itself and, on the basis of this, to establish a validation criterion for quality improvement in retinal images. Finally, an algorithm was developed to isolate in retinal images the regions affected by artifacts, and to subtract from the images the additive contributions to the distortion.;The artifact clean-up has been shown to increase the textural information of the retinal images, by improving vessel segmentation by more than 10%. By avoiding the use of interpretative elements of the image, this improvement in the quality of retinal images is agnostic to specific disease processes, and thus potentially applicable to population screening. Further work is necessary to improve the cosmetic quality of the images, to optimise the artifact removal strategy, and to relate the feature extraction improvement to clinical performance.Globally 2.2 million people are visually impaired and, of these, approximately 1 million present forms of visual impairment that could be addressed or prevented. Retinal imaging is a key step in the diagnosis and follow-up of major causes of visual impairment. As much as 20% of retinal images collected in the population are affected by artifacts, that render them ungradable both by expert graders and by the more recent automatic grading systems.;This work aims to develop an artifact removal strategy able to improve the effectiveness of retinal image grading, in particular for retinal feature segmentation. First, a large group of statistical parameters designed to measure image quality have been selected from the literature. A new ophthalmic database was then collected (CORD - the Comprehensive Ophthalmic Research Database), which includes retinal images with and without artifacts.;A mathematical model describing artifacts on the basis of the interaction of the light with the eye during eye photography was then developed. CORD and the mathematical model were then used to train a binary classifier to distinguish pixels affected by distortions within the image without the need for interpretive knowledge of the image itself and, on the basis of this, to establish a validation criterion for quality improvement in retinal images. Finally, an algorithm was developed to isolate in retinal images the regions affected by artifacts, and to subtract from the images the additive contributions to the distortion.;The artifact clean-up has been shown to increase the textural information of the retinal images, by improving vessel segmentation by more than 10%. By avoiding the use of interpretative elements of the image, this improvement in the quality of retinal images is agnostic to specific disease processes, and thus potentially applicable to population screening. Further work is necessary to improve the cosmetic quality of the images, to optimise the artifact removal strategy, and to relate the feature extraction improvement to clinical performance
Learning how to learn in the Chinese policy making process
Get PDFWhile it is widely accepted that a decentralised system can enhance policy learning and the spread of best practices, an under-researched question is where that learning process takes place, and another more important and intriguing question is what supports and sustains that learning. As a highly decentralised country, China has experienced a transition from a command to a social market economy and rapid socio-economic development in the past four decades. Last year the communist country celebrated its 70th birthday. How did the communist country achieve high-speed development whilst maintaining long term stability? With recent political enthusiasm in summarizing experiences since the opening up and reform period in late 1970s, learning has become a hot word both in policy document and in research papers in China. It is seen as the main capability of both the rank-and-file communist party member and policy maker.;A national strategy on improving learning capabilities has been released recently, defining learning contents, methods, and the role of the thinktank. All these raise the interest in another question concerning the policy learning: is there a high-level of learning that sustains policy learning and making in China? Considered as a main avenue for improving the people's livelihood through government action, the health sector has undergone radical reforms and development to adapt to disease and demographic changes brought by the rapid socio-economic transitions. With its highly decentralised mode of service provision, the health system has managed to provide equal and universal access to essential medical care and public health services, in a hope of achieving Universal Health Coverage (UHC). One important strategy for achieving this has been to encourage implementation units (local governments or other organizations) to experiment and then incorporate lessons from successful interventions into national plans and policies. The thinktank and research institutions have played an important role in supporting learning and diffusion of best practices.;With latest central policy on improving the policy learning capabilities and thinktank development, China is purposefully targeting to improve governance and the learning ability of the government with assistance of thinktanks. Using case studies in the health sector, the thesis identifies the underlying methodologies supporting learning in China and how learning capability has been enhanced in order to manage changes and seek innovations in supporting UHC. The results show that a meta learning approach has developed with the support of the national thinktank, for supporting and sustaining the distinctive policy learning process. The story of the thesis closes at the time of the COVID-19 pandemic crisis. China has impressed the world with its quick and determined actions and successful containment of an unknown disease within 3 months. This further shows the relevance of the topic to the other countries, especially low- and middle-income countries (LMICs) which need to learn and innovate local health service in the complex environment.While it is widely accepted that a decentralised system can enhance policy learning and the spread of best practices, an under-researched question is where that learning process takes place, and another more important and intriguing question is what supports and sustains that learning. As a highly decentralised country, China has experienced a transition from a command to a social market economy and rapid socio-economic development in the past four decades. Last year the communist country celebrated its 70th birthday. How did the communist country achieve high-speed development whilst maintaining long term stability? With recent political enthusiasm in summarizing experiences since the opening up and reform period in late 1970s, learning has become a hot word both in policy document and in research papers in China. It is seen as the main capability of both the rank-and-file communist party member and policy maker.;A national strategy on improving learning capabilities has been released recently, defining learning contents, methods, and the role of the thinktank. All these raise the interest in another question concerning the policy learning: is there a high-level of learning that sustains policy learning and making in China? Considered as a main avenue for improving the people's livelihood through government action, the health sector has undergone radical reforms and development to adapt to disease and demographic changes brought by the rapid socio-economic transitions. With its highly decentralised mode of service provision, the health system has managed to provide equal and universal access to essential medical care and public health services, in a hope of achieving Universal Health Coverage (UHC). One important strategy for achieving this has been to encourage implementation units (local governments or other organizations) to experiment and then incorporate lessons from successful interventions into national plans and policies. The thinktank and research institutions have played an important role in supporting learning and diffusion of best practices.;With latest central policy on improving the policy learning capabilities and thinktank development, China is purposefully targeting to improve governance and the learning ability of the government with assistance of thinktanks. Using case studies in the health sector, the thesis identifies the underlying methodologies supporting learning in China and how learning capability has been enhanced in order to manage changes and seek innovations in supporting UHC. The results show that a meta learning approach has developed with the support of the national thinktank, for supporting and sustaining the distinctive policy learning process. The story of the thesis closes at the time of the COVID-19 pandemic crisis. China has impressed the world with its quick and determined actions and successful containment of an unknown disease within 3 months. This further shows the relevance of the topic to the other countries, especially low- and middle-income countries (LMICs) which need to learn and innovate local health service in the complex environment
Design and implementation of high linearity FPGA-TDCs and an integrated large scale TCSPC system for time-resolved applications
Get PDFThe time-correlated single-photon counting (TCSPC) technology is a vital, advanced measurement and analytical tool for time-resolved biomedical, physics research and many industry areas because of its high temporal resolution and sensitivity. Analogue-based conventional TCSPC systems have been commercialised and applied in scientific experiments widely. However, the complicated system of conventional TCSPC equipment causes the bulky size, high cost, low conversion rate and limited channel number. With the recent rapid development of semiconductor technology, Field Programmable Gate Arrays (FPGA) become the promising platforms for high-performance digital TCSPC systems.;The time-to-digital converter (TDC) is the core component of a TCSPC system as it provides the temporal measurements with extremely high-resolution. For the scientific experiments, prototyping and high-end instruments, FPGA-based TDCs or TCSPC systems can provide excellent flexibility and compatibility with the much lower design and implementation costs. However, compared with ASIC and analogue implementations, the reported FPGA-TDCs have poor linearity performances with severe non-linearity problems such as missing-codes, ultra-wide bins and the bubbles problems. As a result, this study focuses on to improve the linearity performance by exploring the sources of non-linearity in the tapped delay line (TDL)-based FPGA-TDCs;This thesis proposes two novel FPGA-TDC designs to address the linearity drawbacks. The first TDC design proposes a combination architecture innovatively to restrain the differential non-linearity (DNL) to 24K independent TCSPC channels with both photon counting and time-correlated imaging mode and a tunable temporal resolution. For verification, this study applied the system in a typical fluorescence lifetime measurement. According to the CMM calculated results base on the measured data, the proposed system demonstrated the accurate and reliable measurement performances.The time-correlated single-photon counting (TCSPC) technology is a vital, advanced measurement and analytical tool for time-resolved biomedical, physics research and many industry areas because of its high temporal resolution and sensitivity. Analogue-based conventional TCSPC systems have been commercialised and applied in scientific experiments widely. However, the complicated system of conventional TCSPC equipment causes the bulky size, high cost, low conversion rate and limited channel number. With the recent rapid development of semiconductor technology, Field Programmable Gate Arrays (FPGA) become the promising platforms for high-performance digital TCSPC systems.;The time-to-digital converter (TDC) is the core component of a TCSPC system as it provides the temporal measurements with extremely high-resolution. For the scientific experiments, prototyping and high-end instruments, FPGA-based TDCs or TCSPC systems can provide excellent flexibility and compatibility with the much lower design and implementation costs. However, compared with ASIC and analogue implementations, the reported FPGA-TDCs have poor linearity performances with severe non-linearity problems such as missing-codes, ultra-wide bins and the bubbles problems. As a result, this study focuses on to improve the linearity performance by exploring the sources of non-linearity in the tapped delay line (TDL)-based FPGA-TDCs;This thesis proposes two novel FPGA-TDC designs to address the linearity drawbacks. The first TDC design proposes a combination architecture innovatively to restrain the differential non-linearity (DNL) to 24K independent TCSPC channels with both photon counting and time-correlated imaging mode and a tunable temporal resolution. For verification, this study applied the system in a typical fluorescence lifetime measurement. According to the CMM calculated results base on the measured data, the proposed system demonstrated the accurate and reliable measurement performances
Multiprotocol label switching network optimization by metaheuristic algorithms
Get PDFFrom the network management approach, the term network efficiency signifies the effective utilization of network resources. The critical aspect of managing the Multi-Protocol Label Switch (MPLS) networks is to compute the best routes across the network that guarantees the cohesive traffic flow with the effective use of network resources. Considering the optimal routes in multiple switching based MPLS networks, comprised of multiple domains, serves as a complex and challenging task. Technically, the computation of optimal routes that can be depending on multiple objectives along with constraints introduces the concept of multi-objective subject to multiple constraints (MCOP) optimization problem in the field of optimization, which is considered as a computationally complex optimization problem.;Metaheuristic optimization algorithms have raised as a mainstream approach for solving MCOP based complex optimization problems. However, metaheuristic algorithms can generate sub-optimal solutions because rooted problems within algorithms that badly disturbs the algorithm`s performance. Therefore, extensive research on the improvement of algorithms has become necessary. This thesis investigates the particle swarm optimization (PSO), bat, and dolphin echolocation (DEA) algorithms, highlights the problems in the algorithms and offers novel versions of these algorithms as a proposed methodology for the MPLS optimization problem.;For MPLS optimization, the offers the MCOP based optimization models which consist of multiple objective functions and are mathematically formulated for experimental setups. For the considered optimization problems, the new metaheuristic algorithms are suggested as the modified and hybrid versions of PSO, Bat, and DEA algorithms. The numbers of experiments are conducted along with extensive results analysis, which demonstrates the performance of presented algorithms for MPLS optimization, and to validate these algorithm performances, an exclusive comparative analysis is established with other familiar metaheuristic algorithms.From the network management approach, the term network efficiency signifies the effective utilization of network resources. The critical aspect of managing the Multi-Protocol Label Switch (MPLS) networks is to compute the best routes across the network that guarantees the cohesive traffic flow with the effective use of network resources. Considering the optimal routes in multiple switching based MPLS networks, comprised of multiple domains, serves as a complex and challenging task. Technically, the computation of optimal routes that can be depending on multiple objectives along with constraints introduces the concept of multi-objective subject to multiple constraints (MCOP) optimization problem in the field of optimization, which is considered as a computationally complex optimization problem.;Metaheuristic optimization algorithms have raised as a mainstream approach for solving MCOP based complex optimization problems. However, metaheuristic algorithms can generate sub-optimal solutions because rooted problems within algorithms that badly disturbs the algorithm`s performance. Therefore, extensive research on the improvement of algorithms has become necessary. This thesis investigates the particle swarm optimization (PSO), bat, and dolphin echolocation (DEA) algorithms, highlights the problems in the algorithms and offers novel versions of these algorithms as a proposed methodology for the MPLS optimization problem.;For MPLS optimization, the offers the MCOP based optimization models which consist of multiple objective functions and are mathematically formulated for experimental setups. For the considered optimization problems, the new metaheuristic algorithms are suggested as the modified and hybrid versions of PSO, Bat, and DEA algorithms. The numbers of experiments are conducted along with extensive results analysis, which demonstrates the performance of presented algorithms for MPLS optimization, and to validate these algorithm performances, an exclusive comparative analysis is established with other familiar metaheuristic algorithms
Governments in the spotlight? : on the use and impacts of freedom of information laws and proactive publication of government data
Get PDFIn election times, political parties promise in their manifestos to pass reforms increasing access to government information to root out corruption and improve public service delivery. Scholars have already offered several fascinating explanations of why governments adopt policies that constrain their choices. However, knowledge of their impacts is limited. Does greater access to information deliver on its promises as an anti-corruption policy? While some research has already addressed this question concerning freedom of information (FOI) laws, the emergence of new digital technologies enabled new policies, such as open government data. Its effect on corruption and government accountability remains empirically underexplored due to its novelty and a lack of measurements. The following pages aim to fill this gap. I propose a theoretical framework which specifies conditions necessary for FOI laws and open government data to affect corruption, and I test it on a novel cross-country dataset collated for this thesis. The results suggest that the effect of both FOI laws and open government data on corruption is conditional upon the quality of media freedom. Moreover, other factors, such as free and fair elections, independent and accountable judiciary or economic development, are far more critical for tackling corruption than increasing access to information. These findings have important policy implications. In particular, digital transparency reforms will unlikely yield results in the anti-corruption fight unless robust provisions safeguarding media freedom complement them. While a cross-country approach has revealed the importance of the media's role as an information intermediary, it does not enable for an in-depth understanding of how media engage with government information. Therefore, in addition to comparative cross-country analysis, two empirical chapters focus on the UK case study. I combine various methods: survey of investigative journalists, qualitative interviews with civic activists and civil servants and quantitative text analysis of FOI requests sent to the UK central government from 2008 to 2017 to investigate how different groups engage with FOI laws and open government data and what their demand for government information is. I find that the use of FOI laws is very heterogeneous. By no means, the proactive publication of open government data could address such a diverse demand, and thus it could not substitute FOI laws. A substantial proportion of topics, which occur in FOI requests covers information in the public interest. However, some FOI uses for private ends could also be linked to the concept of accountability, as they often point to the failure of other government communication channels and poor explanation of newly introduced policies. My work also shows the potential of applying computational social science methods to FOI requests to study the impact of major changes in government policies on people, and rights infringements.In election times, political parties promise in their manifestos to pass reforms increasing access to government information to root out corruption and improve public service delivery. Scholars have already offered several fascinating explanations of why governments adopt policies that constrain their choices. However, knowledge of their impacts is limited. Does greater access to information deliver on its promises as an anti-corruption policy? While some research has already addressed this question concerning freedom of information (FOI) laws, the emergence of new digital technologies enabled new policies, such as open government data. Its effect on corruption and government accountability remains empirically underexplored due to its novelty and a lack of measurements. The following pages aim to fill this gap. I propose a theoretical framework which specifies conditions necessary for FOI laws and open government data to affect corruption, and I test it on a novel cross-country dataset collated for this thesis. The results suggest that the effect of both FOI laws and open government data on corruption is conditional upon the quality of media freedom. Moreover, other factors, such as free and fair elections, independent and accountable judiciary or economic development, are far more critical for tackling corruption than increasing access to information. These findings have important policy implications. In particular, digital transparency reforms will unlikely yield results in the anti-corruption fight unless robust provisions safeguarding media freedom complement them. While a cross-country approach has revealed the importance of the media's role as an information intermediary, it does not enable for an in-depth understanding of how media engage with government information. Therefore, in addition to comparative cross-country analysis, two empirical chapters focus on the UK case study. I combine various methods: survey of investigative journalists, qualitative interviews with civic activists and civil servants and quantitative text analysis of FOI requests sent to the UK central government from 2008 to 2017 to investigate how different groups engage with FOI laws and open government data and what their demand for government information is. I find that the use of FOI laws is very heterogeneous. By no means, the proactive publication of open government data could address such a diverse demand, and thus it could not substitute FOI laws. A substantial proportion of topics, which occur in FOI requests covers information in the public interest. However, some FOI uses for private ends could also be linked to the concept of accountability, as they often point to the failure of other government communication channels and poor explanation of newly introduced policies. My work also shows the potential of applying computational social science methods to FOI requests to study the impact of major changes in government policies on people, and rights infringements
Signal information processing tools for healthcare diagnostics
Get PDFThe smart healthcare monitoring service has been given more attention in recent decades. With rising healthcare demand and progress in image processing, video-based gait assessment becomes a good alternative solution to assess the physical recovery progress for post-stroke survivors. However, most video-based assessment systems, commercially and in the literature, usually requires large laboratory space, are of high cost, and not portable, thus are impractical for in-home use. Accurate, low-cost, portable motion capture systems are growing in popularity, especially those that do not require expert knowledge to operate. This research proposes an alternative single depth camera based OPTIcal Kinematics Analysis system (named 'OPTIKA'). Novel signal processing and computer vision algorithms are proposed to determine motion patterns of interest from infrared and depth data, and enable real-time simultaneous tracking of joints based on attached retroreflective ball markers. Specifically, an accurate trajectory-based gait phase classification system is proposed to facilitate the diagnostics of muscle activities during gait, using readings from low-cost motion capture systems 'OPTIKA'. Feature selection/extraction methods are proposed to enable an automatic segmentation of motion records into individual gait cycles with nine gait phases slice, which provides a more intuitive diagnostics experience for clinical therapists to analyze the rehabilitation progress associated to the kinematics in particular gait periods. This research also analyzes the sensitivity of feature selection/extraction methods against the classification performance in two healthcare monitoring applications. To overcome the limitations of high-cost training data labeling work and when parts of the training labels are noisy, a robust semi-supervised binary classifier is proposed to combine deep learning and graph based signal processing methods. The experiments demonstrate that given an acceptable proportion of noisy training labels, the proposed classifier outperforms several state-of-the-art classifiers. The overall concepts and systems presented in this thesis form an underlying approach for further video-based healthcare monitoring service that assists the diagnostics of physical rehabilitation.The smart healthcare monitoring service has been given more attention in recent decades. With rising healthcare demand and progress in image processing, video-based gait assessment becomes a good alternative solution to assess the physical recovery progress for post-stroke survivors. However, most video-based assessment systems, commercially and in the literature, usually requires large laboratory space, are of high cost, and not portable, thus are impractical for in-home use. Accurate, low-cost, portable motion capture systems are growing in popularity, especially those that do not require expert knowledge to operate. This research proposes an alternative single depth camera based OPTIcal Kinematics Analysis system (named 'OPTIKA'). Novel signal processing and computer vision algorithms are proposed to determine motion patterns of interest from infrared and depth data, and enable real-time simultaneous tracking of joints based on attached retroreflective ball markers. Specifically, an accurate trajectory-based gait phase classification system is proposed to facilitate the diagnostics of muscle activities during gait, using readings from low-cost motion capture systems 'OPTIKA'. Feature selection/extraction methods are proposed to enable an automatic segmentation of motion records into individual gait cycles with nine gait phases slice, which provides a more intuitive diagnostics experience for clinical therapists to analyze the rehabilitation progress associated to the kinematics in particular gait periods. This research also analyzes the sensitivity of feature selection/extraction methods against the classification performance in two healthcare monitoring applications. To overcome the limitations of high-cost training data labeling work and when parts of the training labels are noisy, a robust semi-supervised binary classifier is proposed to combine deep learning and graph based signal processing methods. The experiments demonstrate that given an acceptable proportion of noisy training labels, the proposed classifier outperforms several state-of-the-art classifiers. The overall concepts and systems presented in this thesis form an underlying approach for further video-based healthcare monitoring service that assists the diagnostics of physical rehabilitation
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