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Mapping cross-national conceptions of essential energy to advance housing energy justice – Urban tour photos - Valencia
No full textThe project entailed qualitative research from focus groups and urban tours. The study leveraged the cross-national collaboration of the WELLBASED project. WELLBASED was a European Union Horizon 2020 project that was trialling energy poverty interventions between 2021 and 2025 across six cities: Leeds (UK), Valencia (Spain), Heerlen (Netherlands), Edirne (Turkey), Obuda (Hungary) and Jelgava (Latvia). The study captured and compared the WELLBASED professionals’ perceptions of essential energy.This dataset contains the photos of the urban tour in Valencia, Spain, in the summer of 2023.</p
A Systems Approach to Explaining the Movement of International Finance in Support of Humanitarian Action in Pakistan and Vanuatu 2007–2019
No full textHumanitarian crises are increasing in both scale and complexity. Climate change is exacerbating the frequency and intensity of natural hazards, overexploitation of resources and expanding populations are placing intense pressure on ecosystems, compounding social tensions. Despite historical global humanitarian needs, there is significant evidence that we should expect more disasters, crises, and conflicts in the coming years. To be able to provide assistance to the millions of people affected by these humanitarian crises requires substantial funds; it is this humanitarian financing that is the subject of my research project.
The research problem pertains to those countries and contexts in which finances available domestically are insufficient to provide such assistance. Actors within such contexts then turn to resources available outside the national borders. A research problem is then how to explain the provision of such international resources, or lack thereof, in these lower-middle income countries.
My research question centres on the underlying causal mechanisms that can explain who provides the relevant international finance, through which mechanisms, to whom. I have focussed my research on the contexts with greater diversity in funding instruments, providers of finance, and receivers of the same finance: the lower-middle income countries which experience multiple disasters triggered by natural hazards. Specifically, the question I have sought to address through this research project is:
What explains the movement of the international finance used to resource responses to disasters triggered by natural hazards in lower-middle income countries?
I approach the research question by first establishing philosophical and theoretical underpinnings to ground my conceptual framework. This enables me to take a specific approach to the research problem and to defend the choices I made in doing so. After weaving critical realism with social systems thinking and understandings of social power, I defend the use of case study research as an appropriate method. Subsequently, I select two relevant cases to study based on specific criteria: Pakistan and Vanuatu between 2007 and 2019. The use of archival and financial data augmented with primary data collected through semi-structured interviews was chosen to ensure alignment between the nature of the objects studied and the methods used to study them
My principal argument is that the most appropriate explanation for the movement of international finance used to resource disaster responses in the two cases studied is one centred on different yet related aspects of social power. Noting that social power is a relation, systems thinking approaches help to reveal the importance of power as a relation in the analysis of humanitarian financing. This then suggests a secondary claim in that the international humanitarian and disaster risk financing system should
be re-framed in a new concept that encompasses the novel perspectives I elucidate: ‘financing for post-disaster assistance’.
I argue how the different ‘social power’ family members can help explain different aspects of the movement of international finance intended to support humanitarian action and disaster response activities. This includes hidden, invisible, and visible power, agency power, the exercise of power - power to and over - and the possession of power. Furthermore, I demonstrate the explanatory utility of episodic, dispositional, and systemic conceptions of social power.
In my principal argument, I show how the tension between different foundational ideologies of the international humanitarian and national disaster management systems impacts the movement of relevant international finance. I reveal how the systemic power of the humanitarian system embeds dispositional power with traditional actors and how notions of resistance power can help explain the emergence of non-traditional actors. Furthermore, I illustrate how the systemic power of the international financial system enables differential dispositional power, in part explaining the newer actors and relationships in both cases. Finally, I propose the influence of the 2007-08 Global Financial Crisis as a significant disruptor of the path dependency and equilibria of the established international humanitarian and disaster risk financing system.
There is both academic and policy significance to this thesis. This research contributes to new knowledge in four domains:
• Firstly, in positioning different yet related concepts of social power as the causal mechanisms shaping the movement of finance across national borders to enable assistance to communities affected by disasters in lower-middle income countries.
• Secondly, by the development of a specific critical realist and social systems conceptual framework, demonstrating their synergies and integrating the two parallel notions of social power.
• Thirdly, uniquely applying social systems concepts to the evolution of international humanitarian action in contrast to the established trend of treating its evolution as a sector rather than as a social system.
• Finally, in proffering novel insights into the development of the disaster management and financing systems of Pakistan and Vanuatu.
In addition to the academic contributions I have made, there are significant policy implications emerging from my research. These include opportunities to further explore non-grant based financial instruments used in the international financial system to resource responses to disasters. In addition, this thesis suggests a policy shift to redraw the boundaries of the humanitarian system, acknowledging the many local and informal actors that do respond to crises but are unable to receive appropriate financial support. I conclude with suggested areas for further research, based on some of the identified limitations of this thesis as well as research areas that would extend some of the claims I make throughout the thesis.</p
Efficient Offloading in Multi-Access Edge Computing Systems
No full textThis thesis thoroughly explores Multi-Access Edge Computing (MEC) and Vehicular Networking in the evolving 5G and 6G environments. The study combines three main areas of research: surveying MEC with focuses on vehicular networks, improving energy-efficient service mobility management using Software-Defined Networking (SDN) in these networks, and proposing energy-efficient offloading policies for large-scaleMECsystems with task handover. This thesis not only addresses pivotal challenges in the field but also sets new benchmarks in network resource management for the data-intensive and dynamic conditions characteristic of modern communication networks. The first core area of this thesis presents an extensive survey on the role of MEC in vehicular networks. This part of the research highlights the critical role of MEC in supporting task offloading, resource allocation, and managing inter-server communications, all essential for low-latency, real-time applications in vehicular contexts. The survey comprehensively covers the architectural framework of MEC, its applications, and the emerging challenges in integrating MEC within vehicular networks. This section is instrumental in delineating the current landscape and future potential of MEC applications in these networks, thus bridging the gap between traditional cloud computing capabilities and the emerging demands of edge computing, and also the challenge of creating energy-efficient offloading strategies within large-scale MEC systems. This focus is pivotal given the increasing complexity brought about by the heterogeneity of mobile users and network components and their inherent mobility. The exploration extends to MEC-enabled vehicular networks, revealing the synergy between MEC and these networks. This phase also acknowledges the challenges of vehicular mobility, privacy, and security, which are paramount in this context. The second phase focuses on the proposed SDN-MEC-EE approach, a novel SDN-assisted energy-efficient MEC framework. This approach is characterized by its energy efficiency, achieving up to a 15% reduction in power consumption for compute-intensive services and an average of 20% reduction for latency-sensitive services compared to conventional SDN-MEC models. Through comprehensive simulations, the SDN-MEC-EE framework demonstrates exceptional throughput and consistently lower latency levels, validating its suitability for high-speed, real-time demands in future vehicular networks. An essential element of this approach is the strategic use of Docker containers over VMs, which significantly reduces service migration delays, enhancing network stability and user experience. The SDN-MEC-EE approach’s superiority is further confirmed in its comparative performance against Distributed Mobility Management (DMM) technologies, showcasing its ability to maintain lower latency and more stable control overheads. In this thesis, we also tackle the intricate challenge of achieving energyefficient task offloading in MEC systems with handover, particularly targeting at realistically large networks. By adopting restless-bandit-based (RBB) resource allocation techniques, we aim to meticulously minimize the long-run average power consumption, taking into account the dynamic fluctuations of channel states and network resources. We propose a novel RBB-based resource allocation scheme, referred to as HEE-ACC, with theoretically bounded performance degradation - it approaches optimality as the network system becomes sufficiently large. Within this scheme, we further delineate two nearoptimal scheduling policies, HEE-ACC-zero and HEE-ALRN, which prioritise the selection of computing and communication resources based on their marginal costs. Through analytical discussions and extensive simulations using both emulated and real-world system parameters, we demonstrate the scalability and effectiveness of our proposed policies. This comprehensive study not only advances the theoretical framework for energy-efficient computing in MEC systems but also offers practical insights for managing resource allocation in the face of task handovers, thereby contributing significantly to the field of mobile computing. This thesis focuses on improving the performance and efficiency of mobile networks, specifically in the areas of MEC in the 5G and vehicular network domains. The research outcomes not only provide an essential understanding of MEC and its applications but also propose innovative approaches like the SDN-MEC-EE approach and HEE-ACC scheme. These approaches facilitate improved network performance, energy efficiency, and user experience in the fast-changing field of mobile communications. The proposed SDN-MEC-EE approach, with its focus on energy conservation, throughput optimization, and latency reduction, sets a new promising method for future mobile networks. The HEE-ACC policies offer a scalable, near-optimal approach for tackling large-scale MEC systems in high-mobility environments. The comprehensive exploration conducted in this thesis underscores the critical role of MEC in the current networking landscape and the future potential of HEE-ACC scheduling policies and SDN-MEC-EE approach in shaping the next generation of latency-sensitive applications and services.</p
New Perspectives on Query Performance Prediction
No full textEffectively navigating the vast online data landscape is crucial in our daily
lives in the digital era. The internet serves as our primary hub for work and
personal interactions, involving the consumption and production of information.
However, the overwhelming volume of online information complicates the task of
finding accurate and relevant information. Search engines are the primary means
of accessing online information and face the critical challenge of delivering
pertinent results swiftly, especially with short and occasionally ambiguous
queries. This underscores the need to ensure the retrieval of the right
information. At the core of effective search engines lies information retrieval,
providing users with relevant information in response to queries. Traditional
methods of user feedback for evaluation prove impractical due to scalability,
time constraints, and cost. This thesis addresses these challenges by delving
into information retrieval, specifically focusing on Query Performance
Prediction (QPP). QPP estimates search result quality without relying on human
judgments, offering insights to enhance search effectiveness.
Acknowledging the flaws in even well-performing search systems, there is a
growing imperative to predict search effectiveness. QPP, as explored in this
thesis, serves as a means to anticipate potential shortcomings in meeting user
information needs. The system can adapt and pivot to alternative strategies or
alert the user, enhancing its adaptability to users' preferences and information
needs. This thesis comprehensively inspects QPP from user and system
perspectives, examining diverse evaluation methods. It deepens the understanding
of QPP, identifying critical aspects and propelling the field forward. The
introduction of two distribution-based evaluation frameworks for QPP methods
with statistical analysis enhances the evaluation process.
Initiating our exploration, we investigate the interaction between query
variations and QPP from the user's perspective, aiming to understand user
assessments and expectations. Our focus includes scrutinizing users' ability to
assess the usefulness of diverse queries for a predefined information need,
employing a crowd-sourcing user study for that purpose. Notably, our study
reveals consistent user assessments of different query variants across varying
information needs, contributing to advancing our knowledge of the user
perspective towards a more user-centric information retrieval system evaluation.
Continuing our research, we categorize different information needs into
different cognitive complexity categories, testing the efficacy of Large
Language Models (LLMs) against human experts. Our findings indicate the
comparability of LLMs to human experts in classifying cognitive complexity,
contributing to the development of more automated and scalable methods for data
annotation and classification in information retrieval.
The study then scrutinizes the dynamics of QPP, investigating factors
influencing variance in prediction quality across different information needs
and query variations. We propose a new evaluation method based on pairwise
comparisons, revealing that the variance in prediction quality is primarily due
to inherent task differences rather than the introduction of query variations.
This work enhances understanding of QPP dynamics and contributes to the
development of more accurate and robust evaluation methods across different QPP
tasks.
Introducing a distribution-based framework for QPP method evaluation, we propose
a new evaluation method to generate a distribution for the predicted and actual
search results. Using this framework, we study the variance in prediction
quality across different factors in the retrieval pipeline, advancing the
development of more accurate and robust evaluation methods for QPP models.
Finally, we present an entropy-based QPP method for neural information retrieval
models, evaluating its performance thoroughly. Our findings indicate
comparability to current unsupervised state-of-the-art QPP methods, identifying
strengths and weaknesses. This research contributes to the development of more
accurate and robust QPP methods, emphasizing the potential of simple score-based
QPP methods and the importance of thorough evaluation.
In conclusion, this thesis advances research in information retrieval,
specifically QPP, by offering insights into user assessments, cognitive
complexity evaluation, key factors affecting QPP, and improved evaluation
frameworks. These contributions enhance the development of more accurate and
adaptable information retrieval systems, opening avenues for future
investigations in addressing the evolving challenges of the digital information
landscape.</p
Always Already Translated: A Singapore Poet in Translation
No full textWhen we think of poetic translation, we think of the act of “carrying across” a poem from one language to another. We often omit that the gap we are carrying across does not just consist of the distance between languages, but also all of the complex elements that make up culture: beliefs, values hierarchies, references, systems of knowledge and more. Coming to terms with the massive gulf that we are carrying poetry across allows one to think about alternate gulfs to attempt: leaping across time instead of across language; carrying across the sound of a poem rather than a fragile idea; or examining how multiple simultaneous carryings-across change the translation of poetry.
This practice-led PhD takes the form of a critical dissertation (Volume 1) alongside a folio of creative works (Volume 2). In engaging in creative poetic translative practices such as anachronistic translation, form-for-form translation, and repeated/crowd translation, I hope to envision how acts of translation can constitute a poetic practice that speaks to and from the multilingual, multicultural realities of Singapore and the Singaporean Chinese identity. I also hope to provide new opportunities for translators and poets by looking at poetry translation through the filter of other parts of my practice, which have evolved in parallel with my PRS journey of the last six years.</p
Programmable Mechanical Metamaterials based on Spinodal Architectures
No full textThe thesis explores the characteristics and properties of anisotropic metastructures produced using building blocks of spinodoids, a metamaterial known for its spatially-variant architecture and potential for diverse mechanical functionalities. The current inverse design of spinodoids employs an artificial neural networks-based framework for characterizing and reconstructing spinodoids (Kumar, Tan et al. (2020)). Nevertheless, the complex relationships between properties and structures in spinodoid elements pose challenges and inefficiencies in their simulation and analysis through computational design methods.
Consequently, a homogenisation method, which aims to represent the spinodoid metamaterial properties with a homogenised block finite element (FE) model, is proposed to address these challenges. The target mechanical properties are evaluated from the static and dynamic FE analysis of the spinodoid structures, including stiffness evaluation, coupled deformation analysis, modal analysis and wave propagation analysis.
In the static analysis, this project focuses on the stiffness evaluation, which was carried out for individual spinodoid blocks (Chapter 3) and more complex assembly models (Chapter 4). A more advanced static analysis for deformation coupling was also conducted on spinodoid assembly models. The outcomes of these analyses contribute to a deeper understanding of how spinodoid metamaterials with variant architecture can behave under various loading conditions. These static cases also investigate how spinodoid block models can be properly represented by homogenised block models in FE simulations.
Furthermore, the dynamic analyses, including modal and wave propagation analyses, were conducted for spinodoid assembly models in Chapter 4, shedding light on the dynamic characteristics of these structures assigned with different combinations of geometric parameters. These dynamic cases also prove that homogenised block models can present dynamic behaviours similar to those of the spinodoid models if they are both assigned identical material properties.
The optimized spinodoid FE models were also fabricated using Stereolithography (SLA) technique for subsequent mechanical testing. The experimental results of the spinodoid structures were then compared with corresponding FE simulation data to assess the spinodoid property evaluation framework.
This work demonstrates the feasibility and significance of employing spinodoid in architectural design through computational design, fabricating spinodoid structures with advanced manufacturing techniques, and finally experimental testing of spinodoid structures. It also characterises the mechanical performance of the spinodoid specimens and comparative evaluation with the computational models.</p
The Contribution of Neighbourhood Environmental Features to Socio-economic Inequity in Loneliness
No full textAbstract
Loneliness is a subjective feeling of unmet desired social relationships and is recognised as a primary determinant of adverse health outcomes and mortality, imposing significant economic burdens on governments worldwide. In Australia alone, the annual healthcare costs attributed to loneliness is estimated at 1,565 per person per year. Older adults are particularly vulnerable to loneliness due to the prevalence of life events such as the loss of a partner, friends, or family, along with children relocating during this stage of life. More than 30% reportedly suffering from loneliness worldwide, including in the US, England, Ireland and Australia. older adults often rely on neighbourhood opportunities for social activities, and this becomes more important over time due to declining physical functioning and limited mobility. The importance of neighbourhood features in addressing loneliness in older adults is also evident in initiatives such as ‘Ending loneliness together’ in Australia and global efforts like the ‘Campaign to End Loneliness,’ which advocate for evidence-based interventions at the neighbourhood level that seek to address loneliness and particularly target older adults.
Studies have revealed that older adults residing in disadvantaged neighbourhoods, experience higher levels of loneliness and live in areas characterized by inequalities in social determinants of health such as higher walkability, poor quality and quantity of greenspace, and higher crime rates compared to advantaged neighbourhoods. This emphasises the presence of socio-spatial inequality in the distribution of neighbourhood features and neighbourhood socio-economic inequity in loneliness. Inequity represents avoidable and unfair inequality, while inequality explains the unequal or disproportionate distribution of goods, wealth, education, opportunities, rewards, and punishments, which is not necessarily unjust.
Few studies have investigated how inequality in modifiable neighbourhood features, such as walkability, quality and quantity of green space, and crime, are associated with inequity in loneliness, especially in the Australian context in middle-aged to older aged adults. This thesis aimed to understand the contribution of socio-spatial inequality in the distribution of modifiable neighbourhood features related to social determinants of health equity (walkability, green space, and crime) to neighbourhood socio-economic inequity in loneliness. Three empirical cross-sectional studies investigated the contribution of socio-spatial inequities in walkability and its components (Chapter 4), greenspace quality and quantity (Chapter 5), and objective and perceived crime (Chapter 6) to neighbourhood socio-economic inequity in loneliness. All three studies utilised 2016 data from HABITAT (How Areas in Brisbane Influence HealTh and AcTivity) dataset, a multilevel longitudinal study of middle-aged adults living in the Brisbane Local Government Area (LGA) in Queensland, Australia, spanning 2007 to 2016.
This research identified several key findings that contribute new knowledge to neighbourhood socio-economic inequity in loneliness. Firstly, loneliness was higher in disadvantaged neighbourhoods compared to advantaged neighbourhoods. Socio-spatial inequalities were observed between advantaged and disadvantaged neighbourhoods, with disadvantaged neighbourhoods having higher walkability, street connectivity, land use mix, residential density, poorer quality and quantity of green spaces. and higher objective and perceived crime rates.
This research revealed that higher residential density, higher objective and perceived crime contributed to higher levels of loneliness. However, only socio-spatial inequalities in residential density and perceived crime contributed to neighbourhood socio-economic inequity in loneliness. Other neighbourhood features showed no significant contribution in explaining loneliness or inequity in loneliness. Interestingly, while objective crime appeared to explain loneliness, it did not contribute to inequity in loneliness. The results highlight the impact of neighbourhood context as a potential influence on the relationship between inequality in opportunities and health inequities.
Findings from this research emphasise the significance of prioritising certain neighbourhood features as interventions aimed at improving specific health outcomes. This includes prioritising factors such as residential density, and objective and perceived crime, over others like walkability or green space, particularly in middle aged and older adults within the specific context of Brisbane, to efficiently combat loneliness. The thesis supported the idea that the mechanisms of neighbourhood effects on health are dynamic and not uniform, necessitating attention and prioritising of certain features based on a specific health outcome, target population, and local context.
Findings from the research suggest that loneliness among middle aged and older adults could possibly worsen if inequalities in residential density and perceived crime widen between disadvantaged and advantaged neighbourhoods. This requires a move to more detailed longitudinal investigations to understand if these trends change over time and deepen our understanding of the dynamics involved.
Importantly, the evidence produced in this thesis suggests great potential for the application of neighbourhood-level interventions to reduce loneliness among middle-aged to older adults and supporting national and international initiatives aimed at combating loneliness. Policy changes and new evidence-informed initiatives based on these findings could play a crucial role in helping Australia fulfill its commitment to Sustainable Development Goals (SDGs), creating age-friendly neighbourhoods areas promoting healthy aging and improved quality of life for older adults into the future.</p
Biodegradable Poly (Butylene Adipate-co-terephthalate) (PBAT)/ Polylactic Acid (PLA)/ Tetrapod-ZnO Whisker Composite Film with Improved Properties
No full textThe environmental issue posed by the non-biodegradable polymer blend film underscores the necessity for identifying alternatives to mitigate their impact. Substituting non-biodegradable films with biodegradable polymer films emerges as a promising solution to address environmental concerns. Considering these environmental issues, degradable poly-mers particularly biodegradable polymers have gained prominence as substitutes for these non-degradable polymer materials. Polylactic acid (PLA), among these biodegradable poly-mers, stands out due to its widespread applications resulting from available ingredients and optimised properties. However, the brittleness and other limitations have impeded its further development.
In this master project, the properties of PLA are modified by blending with another biode-gradable polymer poly (butylene adipate-co-terephthalate) (PBAT), known for its superior ductile properties. Additionally, these blends are further reinforced with Tetrapod-Zinc Ox-ide whiskers (t-ZnOw) fillers. In this project, the ratio of PLA and PBAT was fixed at 30/70 due to the content of approximately 65%~70% having the best properties in impact and ten-sile suitable for film blowing. The content of t-ZnOw varies at 0%, 1%, 3%, and 7%. The primary objective of this research project is to elucidate how the content of t-ZnOw impacts the properties of the PBAT/PLA blends and investigate the content of t-ZnOw that could im-pact the PBAT/PLA blends to have the optimised properties in crystalline, rheological, me-chanical and some functional properties and be used as a potential packaging film. The study also delves into the impact of a chain extender on polymer compatibility and the use of a silane coupling agent to modify t-ZnOw.
The thesis also focuses on the blend melt flow properties of the PBAT/PLA/t-ZnOw blends encompassing the crystallisation properties and the rheological properties of the PBAT/PLA/t-ZnOw blends. The primary objective is to identify the optimal processing con-ditions for PBAT/PLA blends. In the crystallinity analysis, a quantitative methodology has been employed to scrutinize the crystallisation kinetic of the cooling. The objective is to discern the dimension of the crystal growth in the isothermal and non-isothermal way and the optimum temperature or heating rate for the PLA/PBAT/t-ZnOw with the highest crys-talline rate and achieve the best mechanical and optical properties. The melt flow rheologi-cal investigations using the isothermal frequency scan and the temperature range frequency scan of the samples to identify the impact of t-ZnOw on the properties of the PBAT/PLA, determine the polymer blends are incompatible and the blends do not follow the time-temperature superposition principle due to thermogeological complexity.
The next section addresses the composite film properties of the PBAT/PLA/t-ZnOw. This section focuses on the method of producing the PBAT/PLA/t-ZnOw film and the perfor-mance related to the practical application of PBAT/PLA/t-ZnOw film such as the optical, mechanical, barrier and anti-bacterial properties. The processing method for the PBAT/PLA film preparation emphasizes the formulations, processing equipment, processibility condi-tions and most importantly the usage of a silane coupling agent for the filler. Due to the strong polarity of the t-ZnOw, which poses challenges for direct filling into the PBAT/PLA matrix, the surface modification was performed through the coupling agent to alter the po-larity of the t-ZnOw and better integrate into the PBAT/PLA matrix. The practical properties of the polymer film are evaluated through various tests including mechanical, optical, mor-phology, barrier, and anti-bacterial assessments. The chapter identified how the properties are impacted by the t-ZnOw and determined the optimised ratio of t-ZnOw in enhancing the properties in comparison to some commonly used non-biodegradable film as a potential an-ti-bacterial packaging film material.
The last section addresses the degradation of the sample film. As a fully degradable film ma-terial, the enzymatic degradation of the PBAT/PLA/t-ZnOw sample film is an area of lim-ited exploration. In this part, the protease is introduced to facilitate the degradation of the sample film over varying time periods. Subsequent to the degradation process, the related evaluation has been carried out on the degraded film including the weight loss, morphology change, alterations in functional groups and modifications in crystalline properties. The analysis compared the properties of the sample before and after enzyme degradation, allow-ing for a further study on the impact of t-ZnOw on the degradation process.
In summary, this research contributes to the understanding of the enhanced performance of the fully degraded PBAT/PLA film properties through t-ZnOw addition and their potential applications. The findings are anticipated to play a pivotal role in developing the degrada-ble polymer material film and identifying alternatives to the non-biodegradable polymer film to mitigate environmental concerns.</p
Numerical Modelling of the Hydraulic Performance and Clogging Development of Porous Asphalt Mixes Using CFD and DEM
No full textThe hydraulic performance of porous asphalt (PA) pavements is significantly affected
by pores connectivity, shape, content, and distribution. The variety of pore patterns has
been proven to impact the porous structure significantly. However, for any type of
permeable pavement, clogging is a challenge and a potential issue that cannot be
perfectly addressed. The accumulated clogging materials, such as debris, sediments,
and organic matter, can enter the pores, progressively blocking the water flow path and
affecting the infiltration capacity negatively. The functionality of porous asphalt will
be eventually lost once the pavement is fully clogged. It is necessary to systematically
analyse the relationship between pore characteristics and hydraulic performance, and
evaluate the magnitude of the clogging mechanism inside the pore structure.
Compared with laboratory test, numerical modelling can provide more details, visualise
motions, and reveal the movement at any flow time inside a porous structure, which is
hard to observe during laboratory experiments. The discrete element method (DEM)
has been widely used to reconstruct the granular structure in the geomechanical field;
commonly, soil granules have been represented by spheres. However, there is a
substantial difference between spherical particles and actual aggregate in terms of
shapes, which might lead to inaccurate structure reconstruction, especially affecting the
prediction of hydraulic conductivity. Based on the literature review, limited
investigation has been conducted into the hydraulic performance of asphalt pavements
considering a more realistic, thus complex, structure of the asphalt concrete. In most
cases, the porous structure is created using the DEM approach; however, in those
studies, spherical balls representing the aggregate are used to virtually reconstruct a PA
pavement specimens.
In addition to using simple spheres, previous studies had limitations in reconstructing
realistic particle size distributions (PSD). Due to the characteristics of the spherical
balls used in past models, compaction of the asphalt sample proved difficult, especially
when the size difference between the largest and smallest particle diameters is large.
Due to the sphere pattern and PSD, the analysis of virtual PA samples made by DEM
using spheres has significant limitations. Two different particle arrangements, cubic
and hexagonal arrangements, can also be incorporated in a DEM model. The results
from past studies showed that the minimum porosity of spherical aggregates can reach
47.64% for cubic arrangement and 25.95% for the hexagonal arrangement. The design
used in this study for the virtual reconstruction of PA specimens follows the guidelines
of the Victorian Department of Transport and Planning, Australia (Section 417 - Open
Graded Asphalt, 2018) for open-graded asphalt mixes (OGA). According to the
specification, OGA's porosity shall be in the range of 18% to 25%, which is outside of
the porosity tolerance range for PA samples made by spherical aggregates. To control
the air voids content, aggregates in a DEM model would need to be more realistic (i.e.
shape and size) so that the compaction process can be similar to the experiments
conducted in the laboratory.
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This thesis aims to investigate the relationship between the hydraulic performance of
PA mixes and their porous structure through numerical simulation using the DEM and
computational fluid dynamics (CFD). This advanced numerical model combining DEM
with CFD method is developed to mitigate the adverse effects brought by spherical
shape aggregate and deeply understand the relationship between the volumetric
properties of the pore structure of PA pavements and the infiltration capacity. To solve
the issue caused by spherical aggregates, a photogrammetry approach is applied to
capture the realistic aggregate shape as scanned in the laboratory via a simple mobile
phone. The 3D model so reconstructed follows the PSD of the OGA mix, as specified
by the Victorian standard. Firstly, the investigation is carried out in 2D to understand
the foundations of combining the processes of DEM and CFD . Experimental PA slices
were prepared and reconstructed computationally using image morphology for
calibration and validation purposes. The result shows that, in a 2D simulation, DEM
can perfectly reconstruct the pore structure similarly to the structure captured from the
laboratory-made slices. However, it also pointed out that limitations still exist under 2D
analysis and a single-phase CFD simulation in pore structure calculations of hydraulic
conductivity.
To investigate the effects of the volumetric properties and the pore structure of PA
pavements on the infiltration performance and run-off potential, a 3D numerical model
using DEM for sample generation and CFD for hydraulic simulation is developed. This
study scans various aggregates at different gradations to build a comprehensive 3D
shape template database. Then, DEM software is applied to randomly generate non
spherical particles and compact the asphalt mix to the design porosity of 20% and 25%.
To provide a higher-quality and accurate calculation for the water motion inside
connected pores, a multi-phase with volume of fluid (VOF) model is applied to replace
the single-phase CFD simulation. With the VOF model support, the multi-phase CFD
simulation provides detailed information about the water infiltration inside the pore
structure dynamically. The effect of the volumetric properties of pore structure on
hydraulic conductivity can be further evaluated via the voids distribution curve of pore
location over depth. Moreover, the relationship between general air voids and effective
voids can also be analysed via VOF-CFD simulation, which builds the fundamental
understanding of the effect of air voids on the hydrology behaviour of PA pavements.
To investigate the clogging mechanism in pore structure and its impact on the hydraulic
performance, the study on the short-term hydraulic conductivity using DEM and CFD
approach is conducted. The clogging potential at different porosities is different.
Various gradations of sediments are applied to test the clogging potential at 20% and
25% porosity. To better understand the clogging mechanism, pre-tests about clogging
simulation with sediment gradations from 0.25 mm to 1.0 mm in PA samples with 20%
and 25% porosity are applied. The research shows that it is harder for particles larger
than 0.6 mm to travel inside the pores and move deeper into the asphalt layer when the
porosity is less than 25% (i.e. surface accumulation). Based on the finding and balance
of computing power, the mixed sediments gradation of 80% 0.5 mm and 20% 0.75 mm
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particles is used for the analysis of the clogging mechanism and reduction in hydraulic
conductivity.
Lastly, it should be noted that the study of 2D modelling with single-phase simulation
(Chapter 4) is published in the Journal of Hydrology in April 2023. The study of 3D
modelling with multi-phase CFD simulations (Chapter 5) has been submitted to
Construction and Building Materials in October 2023, and it is currently under review.
The study “Investigation for the effect of sediment clogging development on the short
term hydraulic conductivity using CFD and DEM method” (Chapter 6) prepared in
December 2023 is currently under review.</p
Alternative View on Governance in Developing Countries: An Integrative Analysis of Governance for Sustainable Development in Somaliland
No full textGovernance is a crucial factor for achieving sustainable development, especially in less developed economies. While the state has traditionally been seen as the primary actor in the governance process, alternative forms of governance have emerged in less developed countries, where private actors and societal groups have taken on a more significant role. This thesis unpacks the concept of governance and its related definitions in the literature, while exploring the ways in which Somaliland has utilised governance to affect the development outcomes of its society.
This thesis endeavours to understand the impact of governance on development outcomes by delving deeper into the various actors involved in governance and evaluating how their interactions, both formal and informal, influence governance outcomes for sustainable development. The analytical approach adopted in this study was guided by the concept of governance for sustainable development, which refers to sociopolitical governance processes specifically oriented towards attaining sustainable development objectives. To achieve this objective, Somaliland was used as a case study to examine the diverse actors involved in governance and their related interactions. The unique hybrid of traditional and modern governance structures in Somaliland provides a fascinating context for exploring the impact of governance on sustainable development outcomes. In this context, governance is defined as the entirety of interactions in which both public and private actors participate, with the goal of addressing societal challenges or creating opportunities. This definition reflects the flexible and adaptable nature of governance, which can take on various forms and involve different actors, depending on the specific context. Additionally, this thesis explores the concept of sustainable development and defines it as a process that involves meeting the current needs of society without compromising the ability of future generations to meet their own needs.
The outcomes of this case study have the potential to inform policy and practice in other contexts that aim to promote sustainable development through effective governance. The study delves into the distinctive governance arrangements employed by the Somaliland government to accomplish Sustainable Development Goal 16, which focuses on building peace and stability and strengthening core institutions without relying on external donors or interventions. Furthermore, the study aimed to identify the various actors, factors, influences and motivations that have facilitated and fostered social and economic development in Somaliland, to enable it to make greater progress towards sustainable development than its neighbouring country, Somalia. Through an in-depth exploration of the unique context of Somaliland, this study aimed to provide valuable insight into how effective governance can promote sustainable development outcomes and identify key success factors that can inform similar endeavours in other regions.
The case study of Somaliland provides critical lessons for other postcolonial African states because it showcases how alternative forms of governance can be effective in achieving Sustainable Development Goals. Specifically, the governance system of the Somaliland government, which has enabled the attainment of peace and stability and the establishment of functional institutions without external intervention, serves as a valuable example. By contributing to the literature on governance for sustainable development, this research can inform policymaking processes by providing empirical insights into the interactions of policy actors and identifying areas where the governance process can be made more effective for addressing political and sustainable development challenges in developing societies. Consequently, this study has the potential to enhance the knowledge base of policymakers, scholars and practitioners working to achieve Sustainable Development Goals in other regions of the world.
Overall, the thesis contributes to the literature on governance for sustainable development and multilevel governance theory, while providing insight into the governance challenges facing Somaliland and how they can be addressed.</p