Search

This is a thesis about our basic moral equality as human beings: its meaning, its justification and its implications for our society. It offers the fundamental principles of how we are obligated to live together in a Society of Equals. Its major conclusions are as follows. First, whilst there is more than one meaning to the claim that 'we are one another's basic moral equals', the most important meaning for political philosophy is that each individual has Equal Authority. More specifically, each individual has fundamental authority over herself, and herself alone. Secondly, the justification of this fundamental authority over ourselves lies in our common limitation: we are all fallible. Further, we are not merely all fallible in the sense that any one of our beliefs could be false, but also in the sense that we have no non-circular way of judging the reliability of any of our beliefs. This aspect of our natural epistemic position justifies our equal, fundamental, practical authority over ourselves alone. Finally, the most important implication of this justification is that each individual's most basic reason for action is to promote not merely her own, but each and every individual's compliance with her fundamental authority over herself. It follows that each individual has decisive reason to constrain her own compliance with her own fundamental authority over herself, where necessary, to allow the equal promotion of someone else's compliance with her fundamental authority over herself. This principle is called 'Equal Respect'. Upon this principle of Equal Respect arises an architectonic System of Right, and correlative duties, that is called Equal Sovereignty. Under this system, our rights and duties with respect to one another are distributed in accordance with a hypothetical auction and insurance scheme to ensure that each individual is truly sovereign over their own equal share of the world.

Protected areas such as national parks provide many cultural ecosystem services, including opportunities for tourism and recreation. Understanding patterns of visitation to national parks is important socially, environmentally and economically, as is public discourse about the parks. With the rapid increase in the use of social media there is an enormous volume of publicly available spatial data about national parks posted online, but what are the benefits and limitations of this still novel source of information for research and park management? Publicly available spatial data includes global positioning system (GPS) route data posted on social media platforms by mountain bikers, walkers and runners, as well as more general geographic information embedded in texts on microblogging platforms such as Twitter. This thesis examines how both of these types of spatial social media data can be used for monitoring visitation and discourse about national parks at a range of spatial scales from single parks to global assessments. Firstly, the thesis compared how walkers, runners and mountain bikers use a series of connected urban national parks and reserves close to the city of Brisbane, Australia, using GPS route data from the social media platform MapMyFitness (Chapter 2). Route data was correlated with trail counter data, indicating that it could be used as a surrogate for monitoring within and among parks, and may, in some cases, give more reliable data particularly for mountain biking. Clear differences were found in how the parks and reserves were used for the three activities with mountain bikers travelling further and using more of the parks than walkers and runners. Also, mountain bikers and walkers preferred to visit on weekends, while runners use the parks more consistently throughout the week. The results highlighted how route data complements and expands on other visitor data including providing important spatial and temporal data to assist in managing issues such as conflict and unauthorised use. Next GPS route data for walking and running was compared among different types of parks (urban to remote) and among social media platforms in south-east Queensland, Australia (Chapter 3). The amount of route data differed among the platforms MapMyFitness, GPSies and Wikiloc. Data from the fitness focused platform MapMyFitness was the most useful for visitor monitoring in the urban park, due to large number of routes posted. However, data from the platform only showed visitation on the formal trail network. In contrast, those posting routes for the remote park, particularly on Wikiloc, often went off the formal trail network. Therefore, the best social media platform to use for monitoring depends on the questions being asked and the type of park, with the popularity of platforms also varying among countries and over time. To see if social media platforms could be used to assess the relative popularity of parks for walking, running and mountain biking, GPS route data was collected from Strava, MapMyFitness and Wikiloc for 40 national parks in south-eastern Queensland, Australia (Chapter 4). Although Strava was very popular with over 430,000 routes, the other platforms provided useful information for a wider range of activities (MapMyFitness) or a different group of walkers (Wikiloc). Distance to urban areas, and to a lesser extent, the types of trails and permitted activities, best explained the popularity of parks based on data from the two fitness-oriented platforms, Strava and MapMyFitness. For Wikiloc, however, the elevation range of the park was the best predictor of popularity with more adventurous walkers wanting to access rugged and remote areas. Understanding what makes a park popular for each activity is important when managing social and environmental issues particularly in popular urban parks. For the last results chapter, the focus changed from GPS route data within a single park or region, to using text from the microblogging platform Twitter at a global scale (Chapter 5). Twitter data collected over a 6-month period was used to assess the scale of the discourse about national parks globally and to assess spatial information in the texts, including identifying which parks are talked about and by whom. The discourse was massive, in terms of number of tweets (>2 million), number of tweeters (~750,000) and covered a wide range of parks, with 264 national parks talked about at least 100 times. The size of the discourse about parks varied among countries, but predominantly it was about North American parks, and often sent by accounts in the USA. The number of tweets was correlated with the relative popularity of parks with visitors for the 40 most talked about parks on Twitter, particularly for the most popular parks in the USA. Twitter is therefore a useful source of data for park management, particularly in countries where the platform is popular and/or there are globally renowned national parks. Overall, social media data including GPS routes, but also Twitter text, are an increasingly useful source of spatial information about parks including when assessing the movements of visitors in parks, factors influencing park popularity and what makes them noteworthy at a range of spatial scales from local urban parks to global networks. The individual results chapters, and overall results illustrated important benefits but also limitations with social media data including the range and scale of different data types as well as the ephemeral nature of social media platforms and the availability of data.

Driven by the target of decarbonization through eliminating carbon emissions and developing a renewable and sustainable energy schemes, the modern power industry has been experiencing a remarkable transition. To support this, Power Hardware-in-the-Loop (PHIL) simulation, an advanced and efficient method incorporating physical power apparatus and emulated power network into a real-time testing configuration, has been leveraged for the prototyping of power components, the verification of novel control paradigms, and dynamic modelling of renewable energy systems under broad-spectrum testing scenarios. The power amplifier, sensors, and signal conversion units based power interface bridges the hardware and real-time simulation platform into PHIL closed-loop setup. However, the dynamics and non-ideal characteristics stemming from the power interface (e.g., time delay, limited bandwidth, noise perturbation, and signal distortion) pose significant challenges to the PHIL closed-loop simulation regarding its stability and accuracy. From the perspective of system performance, these challenges associated with unstable system operation, protective apparatus tripping, and accuracy deterioration issues have been intriguing many academic researchers and industrial engineers and remained to be resolved. In this thesis, research efforts have been devoted to developing novel compensation schemes to improve the stability and accuracy of PHIL simulation and thus enabling a more robust simulation environment that is extendable and re-configurable for future real-time testing of complex power systems and power apparatus. This thesis works towards the development of novel PHIL system compensation methods, designed specifically to mitigate the detrimental impact of the power interface on the stability and accuracy of PHIL closed-loop systems. Firstly, a compensation scheme comprising a Smith predictor compensator is proposed to mitigate the stability deteriorating impact stemming from the time delay. Furthermore, an online system impedance identification technique is leveraged to enhance the robustness of the proposed compensator and facilitate this compensation scheme with adaptivity to PHIL system impedance variation. Secondly, the sliding discrete Fourier transform based interfacing signal manipulation in conjunction with the phase shift addition method is proposed to compensate for the time delay on a harmonic-by-harmonic basis. Based on the proposed time delay compensation method, an optimal compensation filter is designed to compensate for the non-ideal power interface by maximising its bandwidth, maintaining its unity-gain characteristic, and compensating for its phase-shift over the frequencies of interest. This compensation scheme is crucial for improving the power signal synchronisation accuracy and the power transfer transparency. Thirdly, a novel scheme for sensitivity analysis of PHIL setups is proposed to facilitate quantitatively analysing and assessing the impact of external disturbances stemming from the sensor noise, switching harmonics, or quantization noise on the power interface. In addition, the inherent relationship between sensitivity transfer functions and stability criteria is elaborated along with theoretical and experimental validation. Based on this concept, accuracy assessment methods are employed in this scheme to quantify generic sensitivity criteria. Finally, a comprehensive assessment of the PHIL interfaces regarding their suitability, stability, and applicability for incorporating a grid-forming converter with black-start capability into PHIL closed-loop simulations is presented, and the current-type interfacing method with compensation and scaling scheme is proposed to interface a grid-forming converter with soft black-start capability into a PHIL setup.

Environmental incentives to combat climate change are providing the motivation to improve the energy efficiency of power distribution systems and integrate state-of-the-art renewable technologies. DC distribution networks are receiving considerable attention in the literature because they offer a simple and flexible interface between these modern resources and consumers. However, many technical challenges relating to the design and standardisation of DC protection devices still exist that must be overcome prior to widespread adoption. Since DC fault current develops rapidly, many high-speed protection schemes tailored for DC networks have been proposed. However, few of them have considered the difficulties in practical implementation. This thesis will present the implementation challenges and propose corresponding protection schemes to address the issues. In seeking to achieve this aim, the work presented within this thesis makes three main contributions. This thesis has fi�rstly improved the reliability of the high-speed DC differential protection scheme. The main implementation challenge of this scheme is that a short time synchronisation error may cause a signi�ficant current difference error, resulting in a false-trip problem when a fault occurs outside the protected zone. This thesis has proposed a "multi-sample differential (MSD) protection scheme" to ensure the protection stability for external zone faults (i.e., the relays must not operate) whilst maintaining sensitivity for internal zone faults (i.e., the relays must operate) by examining multiples measurement samples. Secondly, the difficulty in realising high-speed DC distance protection is that measurement of rate-of-change of current can be severely affected by even low-level noise, resulting in a failure in fault detection. This thesis has presented the methodology for selecting the appropriate sampling time of the numerical derivative as well as the cut-off frequency of low-pass current measurement �lfiters. Although high-speed protection schemes can effectively isolate faults quickly, their implementation requires many advanced devices, which may not be economical for lowpower and low-cost DC networks. Finally, this thesis has proposed a "modulated low fault-energy (MLE) protection scheme" that employs fault current limiters (FCL) at the grid energy sources and mechanical circuit breakers (MCB) elsewhere throughout the distributed network. This deployment can constrain the fault current to a lowenergy level that enables a longer time window for the downstream MCBs to realise protection with a lower total implementation cost. Drawing conclusions from this PhD research, the author advocates that more consideration should be given to implementation challenges when designing protection schemes in DC distribution networks. Excessive pursuit of ultrafast fault isolation speeds can lead to over-cost and protection instability issues in practice. A prospective protection scheme must compromise between the high-speed protection requirements in theory and the reliable but economical requirements in practice, to accelerate the realisation of large-scale DC grids in future.

Electrical propulsion aircraft (EPA) have been cited as the future of aviation, enabling greener, quieter, more efficient aircraft. However, due to the stringent requirements surrounding aircraft certification, these novel EPA concepts will need to demonstrate high levels of safety and reliability if electrified flight is ever to become a mainstream mode of passenger transportation. Therefore, robust electrical fault management (FM) is necessary to maintain critical levels of aircraft thrust and to enable high confidence in the reliability and safety of future EPA designs. To date, electrical FM for EPA has been done at a first-pass, minimal level or not at all. For electrical FM to be effective, it must be integrated into the aircraft design from an early stage. This dictates that a novel approach to the design of electrical architectures for EPA is required which addresses the current uncertainty in the availability of suitable FM technologies for future EPA electrical architectures. Therefore, a first-of-kind FM strategy map is presented which identifies projections on the progression of key areas of future EPA-specific FM technology development and acts as a pre-cursor to future FM technology roadmaps. Furthermore, the FM orientated early-stage electrical architecture design methodology presented in this thesis derives feasible, FM-capable electrical architectures for a given EPA concept and captures significant assumptions which impact the down selection process. Since any novel EPA electrical architecture will require some form of testing in hardware, a novel framework for strategic FM demonstrator development is then proposed and the FM test goals for different levels of demonstrator are identified. This strategic development of critical aspects of FM and early integration of FM requires a portfolio of FM demonstrators and test beds for EPA and is crucial if unproven, future EPA electrical architectures are to reach high confidence.

Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight. This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings. However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements. It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures. Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions.