title: Design of SCALDO based high-current DC power supply

authors: Ariyarathna, Thilanga

subjects: Supercapacitor

abstract: Supercapacitor assisted (SCA) techniques are primarily based on supercapacitors having in the order of one million times more capacitance, together with one to two orders of magnitude smaller equivalent series resistance (ESR), compared with conventional capacitors. In the first successful SCA technique, the supercapacitor-assisted low dropout regulator (SCALDO) combined a linear regulator in series with a supercapacitor to act as a lossless voltage dropper. SCALDO created the opportunity to develop an entirely new family of highly efficient, interference-free, very-low-frequency DC-DC converters, which have evolved further into several branches over the last 6 years.

Leading data centre operators such as Google have announced their intention to move toward 48 V server rack architecture to minimise power losses in distribution lines and to improve overall operating efficiency. This thesis investigated the potential of the SCALDO technique to develop a high-current DC power supply suitable for Google server racks, meeting requirements such as electrical isolation, fast transient response, high efficiency and DC-UPS capability within the converter.

Work related to this thesis proved that by creatively extending the SCALDO technique to achieve higher current at high voltage and further developing a bulk DC-rail from AC input by extending the previously proven fast supercapacitor charger technique, a SCALDO-assisted high-current DC power supply can be achieved. As a proof-of-concept project with a DC output of 12 V (one fourth scale) at 10 A load current capability, several key circuit blocks were developed including: (i) high current discrete LDO of 10 A; (ii) four switch implementation of a SCALDO stage; and (iii) a transformer-isolated input DC stage to feed the output SCALDO stage based on a hybrid-type medium frequency switch mode. This overall implementation is expected to overcome the limitations of a direct-SCALDO stage, maintaining high end-to-end efficiency. Matlab and LTspice simulation models were developed to observe the behaviour of these new power converter techniques.

The thesis discusses the significance of this work, related techniques, the loss-circumventing principle in the RC charging loop, which is the theoretical basis of SCALDO, and the design and simulation details of a novel power conversion technology. It also presents the implementation details of the prototypes built to verify this approach.

text: Design of SCALDO based high-current DC power supply Supercapacitor assisted (SCA) techniques are primarily based on supercapacitors having in the order of one million times more capacitance, together with one to two orders of magnitude smaller equivalent series resistance (ESR), compared with conventional capacitors. In the first successful SCA technique, the supercapacitor-assisted low dropout regulator (SCALDO) combined a linear regulator in series with a supercapacitor to act as a lossless voltage dropper. SCALDO created the opportunity to develop an entirely new family of highly efficient, interference-free, very-low-frequency DC-DC converters, which have evolved further into several branches over the last 6 years.

Leading data centre operators such as Google have announced their intention to move toward 48 V server rack architecture to minimise power losses in distribution lines and to improve overall operating efficiency. This thesis investigated the potential of the SCALDO technique to develop a high-current DC power supply suitable for Google server racks, meeting requirements such as electrical isolation, fast transient response, high efficiency and DC-UPS capability within the converter.

Work related to this thesis proved that by creatively extending the SCALDO technique to achieve higher current at high voltage and further developing a bulk DC-rail from AC input by extending the previously proven fast supercapacitor charger technique, a SCALDO-assisted high-current DC power supply can be achieved. As a proof-of-concept project with a DC output of 12 V (one fourth scale) at 10 A load current capability, several key circuit blocks were developed including: (i) high current discrete LDO of 10 A; (ii) four switch implementation of a SCALDO stage; and (iii) a transformer-isolated input DC stage to feed the output SCALDO stage based on a hybrid-type medium frequency switch mode. This overall implementation is expected to overcome the limitations of a direct-SCALDO stage, maintaining high end-to-end efficiency. Matlab and LTspice simulation models were developed to observe the behaviour of these new power converter techniques.

The thesis discusses the significance of this work, related techniques, the loss-circumventing principle in the RC charging loop, which is the theoretical basis of SCALDO, and the design and simulation details of a novel power conversion technology. It also presents the implementation details of the prototypes built to verify this approach.

year: 2021

title: Exploring and analysing the notion of worst case scenario in professional rugby union

authors: Haakma, Morgan Louise

subjects: Worst case scenario

abstract: Rugby union is an interval-based contact sport, demanding intermittent bursts of high-intensity running, collisions and impacts. Players need to be conditioned in a way that best prepares them for the demands of the game, and to perform repeated bouts of high-intensity workloads. Understanding the peak periods of ‘play’ and the ‘worst case scenario’ (WCS) in rugby union is essential to inform effective training interventions. Through a review of current literature around the notion of WCS and peak periods of play, limitations in existing research methods were identified. Specifically, limitations within the ability of global positioning system (GPS) units to quantify contact and collision workloads, and the error of data recorded over short distances and durations. Limitations within the methodology of fixed-time epochs and rolling-average epochs as a way of quantifying WCS were also explored.
After reviewing the current literature, this thesis encloses an original and innovative study. This research aims to determine a potentially more accurate representation of WCS by quantifying the maximal intensity locomotive demands during ‘ball in play’ (BIP) for a single play, and across a series of consecutive plays through an innovative rolling-MultiPlay epoch analysis (5 min, 10 min, 15 min, 20 min epochs). This study will also give a contextual indication by identifying the segment of the game in which these maximal workload demands occur.
Data was collected for 51 professional rugby union players over the 2019-2020 seasons. All players wore GPS units (Apex Pro Pod, STATSport, Newry, NIR). All games were filmed and coded through the Sportscode software (Sportscode V8.9, Sportstec, Australia) which was then combined with GPS data from which drills were created for each BIP period. This data was then analysed through a bespoke software where the maximum BIP (MaxBIP) values for a range of GPS metrics were determined for each positional subgroup. A WCS BIP analysis was completed as well as a WCS MultiPlay analysis. Each half of the game was divided into 4 equal segments, and the segments where the MaxBIP values occurred were identified. 
Practical applications for indicative training drills for WCS BIP, WCS 5 minute drill, and WCS 20 minute drill are provided. In conclusion, there were no distinct patterns found within the data that suggests the WCS MaxBIP demand could occur in any segment of the game. Therefore, we believe it would be beneficial for players to be conditioned for these peak demands to occur at any stage of the game.

text: Exploring and analysing the notion of worst case scenario in professional rugby union Rugby union is an interval-based contact sport, demanding intermittent bursts of high-intensity running, collisions and impacts. Players need to be conditioned in a way that best prepares them for the demands of the game, and to perform repeated bouts of high-intensity workloads. Understanding the peak periods of ‘play’ and the ‘worst case scenario’ (WCS) in rugby union is essential to inform effective training interventions. Through a review of current literature around the notion of WCS and peak periods of play, limitations in existing research methods were identified. Specifically, limitations within the ability of global positioning system (GPS) units to quantify contact and collision workloads, and the error of data recorded over short distances and durations. Limitations within the methodology of fixed-time epochs and rolling-average epochs as a way of quantifying WCS were also explored.
After reviewing the current literature, this thesis encloses an original and innovative study. This research aims to determine a potentially more accurate representation of WCS by quantifying the maximal intensity locomotive demands during ‘ball in play’ (BIP) for a single play, and across a series of consecutive plays through an innovative rolling-MultiPlay epoch analysis (5 min, 10 min, 15 min, 20 min epochs). This study will also give a contextual indication by identifying the segment of the game in which these maximal workload demands occur.
Data was collected for 51 professional rugby union players over the 2019-2020 seasons. All players wore GPS units (Apex Pro Pod, STATSport, Newry, NIR). All games were filmed and coded through the Sportscode software (Sportscode V8.9, Sportstec, Australia) which was then combined with GPS data from which drills were created for each BIP period. This data was then analysed through a bespoke software where the maximum BIP (MaxBIP) values for a range of GPS metrics were determined for each positional subgroup. A WCS BIP analysis was completed as well as a WCS MultiPlay analysis. Each half of the game was divided into 4 equal segments, and the segments where the MaxBIP values occurred were identified. 
Practical applications for indicative training drills for WCS BIP, WCS 5 minute drill, and WCS 20 minute drill are provided. In conclusion, there were no distinct patterns found within the data that suggests the WCS MaxBIP demand could occur in any segment of the game. Therefore, we believe it would be beneficial for players to be conditioned for these peak demands to occur at any stage of the game.

year: 2021

title: A trans-national analysis of equitable utilisation and minimisation of environmental harm under environmental laws at international, federal and national levels

authors: Hasan, Qaraman

subjects: International Environmental Law

abstract: Due to increasing demand for various human needs and climate change issues, rivers are now under enormous pressure. With increasing pressure on these valuable natural resources, responses among state and non-state actors are insufficient in the Anthropocene. To fill the gap, International Environmental Law (IEL) provides several principles for better management of these resources. Equitable utilisation and minimisation of environmental harm are among the most important principles of the IEL. From a theoretical perspective, these principles should lead to the sustainability of these resources and promote cooperation among relevant actors.

However, many river basins are still not allocated equitably and suffer from environmental damage. By using comparative, doctrinal, and empirical research methods, this thesis evaluates the two principles at the international level in Tigris and Euphrates River Basin, the federal level in Murray Darling Basin and at the local level in the Waikato River catchment. The research discovered major challenges for implementing the two principles. One major challenge is sovereignty, another is a lack or weakness of local voices and transparency. As the nature and status of all basins are different, the challenges are not exactly the same. For example, hearing local voices and better information transparency have significantly improved in the Waikato River.

As the challenges for implementing the two principles are not purely legal, the responses should blend legal solutions with political and socio-economic solutions. Therefore, this thesis strongly supports shared sovereignty among states at the international level as well as shared sovereignty with indigenous and minority groups at the national level. Cooperation among national and international actors in the river basins is also crucial for implementing the two principles effectively. Finally, there is the opportunity to establish basin institutions or organisations to manage river basins integrated and sustainable. This is vital in the case of TE-RB because the basin still lacks an institution. Furthermore, the basin institution in the MDB requires more robust compliance and monitoring power because the provisions of the Water Act 2007 and the basin plan still have not been implemented effectively.

Finally, the thesis concludes with two common lessons in comparing these cases. The first lesson is that equitable utilisation cannot be implemented effectively if it is not accepted by the local community in a broad and deep meaning. It means that the equitable allocation should be extended from only the riparian states to equitable allocation among the people within each state. The second lesson is that the minimisation of environmental harm cannot be implemented without determining the minimum flow of rivers, particularly transboundary rivers. Determining an environmental impact assessment for water projects and taking advantage of available solutions of nature contributes significantly in implementing the two principles and sustainable management of our rivers.

text: A trans-national analysis of equitable utilisation and minimisation of environmental harm under environmental laws at international, federal and national levels Due to increasing demand for various human needs and climate change issues, rivers are now under enormous pressure. With increasing pressure on these valuable natural resources, responses among state and non-state actors are insufficient in the Anthropocene. To fill the gap, International Environmental Law (IEL) provides several principles for better management of these resources. Equitable utilisation and minimisation of environmental harm are among the most important principles of the IEL. From a theoretical perspective, these principles should lead to the sustainability of these resources and promote cooperation among relevant actors.

However, many river basins are still not allocated equitably and suffer from environmental damage. By using comparative, doctrinal, and empirical research methods, this thesis evaluates the two principles at the international level in Tigris and Euphrates River Basin, the federal level in Murray Darling Basin and at the local level in the Waikato River catchment. The research discovered major challenges for implementing the two principles. One major challenge is sovereignty, another is a lack or weakness of local voices and transparency. As the nature and status of all basins are different, the challenges are not exactly the same. For example, hearing local voices and better information transparency have significantly improved in the Waikato River.

As the challenges for implementing the two principles are not purely legal, the responses should blend legal solutions with political and socio-economic solutions. Therefore, this thesis strongly supports shared sovereignty among states at the international level as well as shared sovereignty with indigenous and minority groups at the national level. Cooperation among national and international actors in the river basins is also crucial for implementing the two principles effectively. Finally, there is the opportunity to establish basin institutions or organisations to manage river basins integrated and sustainable. This is vital in the case of TE-RB because the basin still lacks an institution. Furthermore, the basin institution in the MDB requires more robust compliance and monitoring power because the provisions of the Water Act 2007 and the basin plan still have not been implemented effectively.

Finally, the thesis concludes with two common lessons in comparing these cases. The first lesson is that equitable utilisation cannot be implemented effectively if it is not accepted by the local community in a broad and deep meaning. It means that the equitable allocation should be extended from only the riparian states to equitable allocation among the people within each state. The second lesson is that the minimisation of environmental harm cannot be implemented without determining the minimum flow of rivers, particularly transboundary rivers. Determining an environmental impact assessment for water projects and taking advantage of available solutions of nature contributes significantly in implementing the two principles and sustainable management of our rivers.

year: 2023