VictorJuiz/thesis huggingface dataset:
Atomic scale characterisation of oxide dispersion strengthened steels for fusion applications
Keywords: oxide-dispersion-stregthening
atom probe
steel

Reduced-activation ferritic steels are considered as the primary candidate materials for structural applications within nuclear fusion power plants. It is known that by mechanically alloying ferritic steel powder with Y (usually in the form of Y₂O₃) then consolidating the material by hot isostatic pressing, a nanoscale dispersion of oxygen rich nanoclusters as small as ~2nm is introduced into the microstructure. This vastly improves high temperature strength and creep resistance, and the nanoclusters also act as trapping sites for helium and point defects produced under irradiation.
In this thesis, the evolution of the oxide nanoclusters in a Fe-14Cr-2W-0.3Ti & 0.3Y₂O₃ ODS alloy was investigated primarily using atom probe tomography. The microstructure was characterised at various points during processing to give an insight into the factors influencing the formation of the nanoclusters. It was found that the nanoclusters nucleated during the mechanical alloying stage, then followed near classical nucleation and growth mechanisms keeping the same composition of ~8%Y, ~12%Ti,~25%O and ~45%Cr throughout. The formation and evolution of 5-15nm grain boundary oxides was also observed, and these were shown to form first as Cr₂O₃ particles that subsequently transform into a Y-Ti-O based oxide on further processing.
The influence of mechanical alloying with 0.5wt.%Fe₂Y rather than 0.3wt.%Y₂O₃ was also investigated, and this showed that there was no difference in the final microstructure produced provided the level of Ti in the starting powder was tightly controlled. Without sufficient Ti, the nanoclusters were Y-O based and ~6nm diameter. Both the Y-O and Y-Ti-O nanoclusters were moderately stable on annealing at 1200°C for up to 100 hours, with only minimal coarsening observed. Ti was found not to influence the coarsening rate of the nanoclusters significantly.
The stability of the oxide nanoclusters under irradiation was investigated by using Fe²⁺ ion irradiation to simulate displacement cascade damage in the ODS-Eurofer material (the official European candidate material for testing in the ITER fusion test reactor). Doses up to ~6 dpa at 400°C were used, and there was no significant change to the nanocluster distribution. However segregation of Mn to dislocations was observed after irradiation.
These results indicate that ODS steels are good candidate structural materials, as the microstructure is stable at high temperature and under irradiation. The starting powders, and processing parameters need to be tightly controlled in order to produce the optimal material for use in service.
Penelope differently: feminist re-visions of myth
Keywords: classical reception
feminist
contemporary
Penelope
myth
poetry

This thesis examines feminist rewritings of the Penelope myth and the intersections between poetry, myth, and feminist theory. The theoretical framework develops from Rosi Braidotti’s theory of memory and subjectivity which has its roots in the work of Michel Foucault. In Braidotti’s understanding, subjectivity is constructed through narratives of the past including myth. In order to support new, minority, and dissident subjectivities, a re-remembering of mythical narratives needs to happen. This process is linked to Judith Butler’s recent work on narrating the self and to Adrienne Rich’s idea of “Re-vision”. What Butler’s theory adds to Braidotti’s is the notion of dispossession: that as subjects we do not own our identities. We are, instead, dependent on others for recognition. This co-dependence based notion of subjectivity has ethical implications for how we interact with one another and what kind of narratives we iterate and reiterate.
The writers discussed in this thesis, namely, Francisca Aguirre, Katerina Anghelaki-Rooke, Gail Holst-Warhaft, and Margaret Atwood, not only rewrite Penelope, but perform Re-visions of the myth. They look back at it with a critical eye and remake it. This thesis further contends that Re-vision provides contemporary feminist writers with a reading and writing strategy that allows them to engage with myth in a way that parallels feminist theory’s efforts to construct new forms of subjectivity. Chapter 1 frames feminist appropriations of myth in a contemporary context and discusses Adrienne Rich’s theory of Re- vision. The next four chapters focus on specific writers who carry out a sustained dialogue with Penelope; they each take an element of the myth and tease it out towards a modern relevance. In looking at how Penelope is revised, this thesis demonstrates that women writers are engaged in a process of remaking canonical, mythic texts in such a way that speaks to contemporary issues of ethical subjectivity and self-making.
Ground-based near-infrared remote sounding of ice giant clouds and methane
Keywords: Neptune (atmosphere)
atmospheres (composition)
atmospheres (structure)
Uranus (atmosphere)
data reduction techniques

The ice giants, Uranus and Neptune, are the two outermost planets in our solar system. With only one satellite flyby each in the late 1980’s, the ice giants are arguably the least understood of the planets orbiting the Sun. A better understanding of these planets’ atmospheres will not only help satisfy the natural scientific curiosity we have about these distant spheres of gas, but also might provide insight into the dynamics and meteorology of our own planet’s atmosphere. Two new ground-based, near-infrared datasets of the ice giants are studied. Both datasets provide data in a portion of the electromagnetic spectrum that provides good constraint on the size of small scattering particles in the atmospheres’ clouds and haze layers. The broad extent of both telescopes’ spectral coverage allows characterisation of these small particles for a wide range of wavelengths. Both datasets also provide coverage of the 825 nm collision-induced hydrogen-absorption feature, allowing us to disentangle the latitudinal variation of CH4 abundance from the height and vertical extent of clouds in the upper troposphere. A two-cloud model is successfully fitted to IRTF SpeX Uranus data, parameterising both clouds with base altitude, fractional scale height, and total opacity. An optically thick, vertically thin cloud with a base pressure of 1.6 bar, tallest in the midlatitudes, shows strong preference for scattering particles of 1.35 μm radii. Above this cloud lies an optically thin, vertically extended haze extending upward from 1.0 bar and consistent with particles of 0.10 μm radii. An equatorial enrichment of methane abundance and a lower cloud of constant vertical thickness was shown to exist using two independent methods of analysis. Data from Palomar SWIFT of three different latitude regions (30
Discourses of mourning in Dante, Petrarch, and Proust
Keywords: Proust
Kristeva
Petrarch
mourning
Freud
Dante
melancholia
Derrida

This thesis interpolates medieval and modern authors and theorists, namely Dante, Petrarch, and Proust on the one hand, and Freud, Kristeva, and Derrida on the other. I propose that these writers are intimately connected and differentiated by their meditations on grief and loss. I compare, confront, and contrast these narratives of mourning in a discursive shuttling to and fro between medieval and modern, French and Italian, and literature and theory, in order to delineate the specificities of different forms of melancholia as legible in Dante’s Commedia, Petrarch’s Canzoniere, and Proust’s A la recherche du temps perdu, and as illuminated by Freudian melancholia, Kristeva’s Soleil noir, and Derrida’s concept of ‘demi-deuil’. I challenge the homogeny of the modern concept of melancholia and juxtapose it with the medieval sin of acedia in Dante (Inferno VII) and Petrarch (considering both the Secretum and the Canzoniere). From the examples of the treatment of the myth of Orpheus and the book of Lamentations, I argue that discourses of mourning are trapped in a fruitful tension between a desire for uniqueness or originality and a desire for legibility or the comfort of communality. In Girardian terms, I define literary representations of mourning as ‘mimetic’, that is, caught in a web of intertextual imitation and preoccupations of genre and tradition which are at odds with a quest for new forms of writing. Finally, I contend that the relationship between content and form is particularly close in grief-stricken texts, and characterise my chosen primary texts – including Dante’s Vita nuova – according to the twin poles of endlessness (which I equate with melancholia) and finitude (the teleological, closed nature of the work of mourning), with a Derridean alternative of unstable oscillation between the two (‘demi-deuil’).
Transition metal catalysis in the presence of fluorinating reagents
Keywords: oxidative coupling
fluorine
radiochemistry
gold
homogeneous catalysis

In this thesis, the effect of fluorinating reagents on a selection of transition metal-mediated organic transformations was investigated. The first four chapters are focused on gold-catalysed nucleophilic addition processes performed in the presence of “F⁺” sources.
Chapter 1 provides a general introduction to homogeneous gold catalysis and summarises the aims and objectives of the project.
The effect of the electrophilic fluorinating reagent Selectfluor (82) on the gold-catalysed rearrangement of propargyl acetates 85 is discussed in Chapter 2. α-Fluoroenones 92 resulting from fluorodeacetylation of an allenyl acetate intermediate were delivered as the major products of these reactions (Scheme i).
[Scheme i Gold-Catalysed Rearrangement-Fluorodeacetylation of Propargyl Acetates 85.]
By contrast, performing the gold(I)-catalysed cyclisation of allenoates 102 in the presence of Selectfluor (82) led to products of oxidative coupling. The “F⁺” source in these processes most likely acts as an external oxidant in an AuI
III redox cycle. In Chapter 3, the cascade cyclisation-intramolecular arylation of benzyl-substituted substrates is discussed whilst the extension of the methodology towards intermolecular homocoupling and intermolecular alkynylation is presented in Chapter 4 (Scheme ii).
[Scheme ii Gold-Catalysed Cyclisation-Oxidative Coupling of tert-Butyl Allenoates 102.]
In Chapter 5, the feasibility of palladium-catalysed allylic [18F]radiofluorination was investigated using high-specific-activity [18F]fluoride. This study led to the development of the first transition metal-mediated C-18F bond-forming process of relevance for the preparation of radiotracers for PET imaging (Scheme iii).
[Scheme iii Palladium-Catalysed Allylic [18F]Radiofluorination of Allylic Methyl Carbonate 227b.]
Chapter 6 gives full experimental procedures and characterisation data for all compounds.
Buying influence? The international diplomacy behind donor financing of the World Bank’s International Development Association
Keywords: Development Finance
International Development Association
International Diplomacy
Power Transitions
World Bank

This thesis addresses the puzzle of why changes in relative donor contributions to the World Bank’s International Development Association (IDA) did not reflect shifts in their relative economic capabilities. It addresses the grand debates about how power transitions shape a US-led hegemonic international system by exploring one specific international organisation.
Drawing primarily on archives, elite interviews, and participant observation, I examine sixteen rounds of IDA replenishment negotiations from 1960 to 2010.
There are three puzzles a close empirical analysis throws up. The first is why the hegemon maintained its burden shares regardless of rise or fall in economic status; I call this ‘Hegemonic Lag’. The second is why ascending powers were slow to assume greater burden-shares despite economic ascents; I call this ‘Challenger Inertia.’ The third puzzle is why significant burden-shifting occurred on a much greater scale than shifts in relative economic weight; I call this ‘Accelerated Burden-Shifting.’
Two conventional explanations – donors’ relative ‘ability-to-pay’ and their ‘country-specific interests’ – offer a first-cut analysis of donors’ ability and willingness to contribute. However, they fail to uncover how bipolar geopolitics and World Bank governance shaped IDA burden-sharing dynamics.
This thesis tests whether the hegemon will maintain its shares even if its relative economic capacity wanes, if its bipolar rival poses a more intense external threat. Equally it tests whether a hegemon and/or waning powers with a desire to expand total IDA resources will cede voting rights to ascending powers in exchange for financial support to IDA. Finally, the research examines whether a hegemon violating the ‘fairness’ principle by shirking obligations but pursuing undue influence will face secondary states willing to take ‘exit/voice’ measures to restore an implicit contribution-to-influence equity line; and whether such countermeasures would be postponed if secondary states are structurally dependent upon the hegemon and/or lack viable outside options. In-depth case studies are used to test these hypotheses. Overall the thesis reveals that the US maintained or cut its burden share as the Soviet threat waxed and waned; and that as the Soviet Union collapsed the US abandoned both its leadership for IDA expansion to counter the Soviet threat and its self-restraint in controlling the World Bank, provoking the fairness concern among secondary states – the most potent factor in explaining IDA burden-sharing dynamics in the post-Cold War era.
Massively parallel computing for particle physics
Keywords: grid computing
map-reduce
virtualization
emulation
parallel computing

This thesis presents methods to run scientific code safely on a global-scale desktop grid. Current attempts to harness the world’s idle desktop computers face obstacles such as donor security, portability of code and privilege requirements. Nereus, a Java-based architecture, is a novel framework that overcomes these obstacles and allows the creation of a globally-scalable desktop grid capable of executing Java bytecode. However, most scientific code is written for the x86 architecture. To enable the safe execution of unmodified scientific code, we created JPC, a pure Java x86 PC emulator.
The Nereus framework is applied to two tasks, a trivially parallel data generation task, BlackMax, and a parallelization and fault tolerance framework, Mycelia. Mycelia is an implementation of the Map-Reduce parallel programming paradigm. BlackMax is a microscopic blackhole event generator, of direct relevance for the Large Hadron Collider (LHC). The Nereus based BlackMax adaptation dramatically speeds up the production of data, limited only by the number of desktop machines available.
Large–scale urban localisation with a pushbroom LIDAR
Keywords: Robotics
Localisation

Truly autonomous operation for any field robot relies on a well-defined pyramid of technical competencies. Consider the case of an autonomous car – we require the vehicle to be able to perceive its environment through noisy sensors, robustly fuse this information into an accurate representation of the world, and use this representation to plan and execute complex tasks – all the while dealing with the uncertainties inherent in real world operation.
Of fundamental importance to all these capabilities is localisation – we always need to know where we are, if we are to be able to plan where we are going (or how to get there). As road vehicles make the push towards becoming truly autonomous, the system’s ability to stay accurately localised over its operating lifetime is of crucial importance – this is the core issue of lifelong localisation.
The goals in this thesis are threefold – to develop the hardware needed to reliably acquire data over large scales, to build a localisation framework that is robust enough to be used over the long–term, and to establish a method of adapting our framework when necessary such that we can accommodate the inevitable difficulties present when operating over city-scales.
We begin by developing the physical means to make large-scale localisation achievable, and affordable. This takes the form of a stand-alone, rugged sensor payload – incorporating a number of sensing modalities – that can be deployed in either a mapping or localisation role.
We then present a new technique for localisation in a prior map using an information theoretic framework. The core idea is to build a dense retrospective sensor history, which is then matched statistically within a prior map. The underlying idea is to leverage the persistent structure in the environment, and we show that by doing so, it is possible to stay localised over the course of many months and kilometres.
The developed system relies on orthogonally-oriented ranging sensors, to infer both velocity and pose. However, operating in a complex, dynamic, setting (like a town centre) can often induce velocity errors, distorting our sensor history and resulting in localisation failure. The insight into dealing with this failure is to learn from sensor context – we learn a place-dependent sensor model and show that doing so is vital to prevent such failures.
The integration of these three competencies gives us the means to make inex- pensive, lifelong localisation an achievable goal.
Ice-stream dynamics: the coupled flow of ice sheets and subglacial meltwater
Keywords: ice sheets
ice streams
subglacial hydrology
Antarctica

Ice sheets are among the key controls on global climate and sea level. A detailed understanding of their dynamics is crucial to make accurate predictions of their future mass balance. Ice streams are the dominant negative component in this balance, accounting for up to 90% of the Antarctic ice flux into ice shelves and ultimately into the sea. Despite their importance, our understanding of ice-stream dynamics is far from complete.
A range of observations associate ice streams with meltwater. Meltwater lubricates the ice at its bed, allowing it to slide with less internal deformation. It is believed that ice streams may appear due to a localisation feedback between ice flow, basal melting and water pressure in the underlying sediments.
This thesis aims to address the instability of ice-stream formation by considering potential feedbacks between the basal boundary and ice flow. Chapter 2 considers ice-flow models, formulating a model that is capable of capturing the leading-order dynamics of both a slow-moving ice sheet and rapidly flowing ice streams. Chapter 3 investigates the consequences of applying different phenomenological sliding laws as the basal boundary condition in this ice-flow model. Chapter 4 presents a model of subglacial water flow below ice sheets, and particularly below ice streams. This provides a more physical representation of processes occurring at the bed. Chapter 5 then investigates the coupled behaviour of the water with the sediment, and Chapter 6 the coupled behaviour of the water with the ice flow. Under some conditions this coupled system gives rise to ice streams due to instability of the internal dynamics.
Ontology module extraction and applications to ontology classification
Keywords: description logics
OWL 2
ontologies
classification
semantic web
modules

Module extraction is the task of computing a (preferably small) fragment M of an ontology O that preserves a class of entailments over a signature of interest ∑. Existing practical approaches ensure that M preserves all second-order entailments of O over ∑, which is a stronger condition than is required in many applications. In the first part of this thesis, we propose a novel approach to module extraction which, based on a reduction to a datalog reasoning problem, makes it possible to compute modules that are tailored to preserve only specific kinds of entailments. This leads to obtaining modules that are often significantly smaller than those produced by other practical approaches, as shown in an empirical evaluation.
In the second part of this thesis, we consider the application of module extraction to the optimisation of ontology classification. Classification is a fundamental reasoning task in ontology design, and there is currently a wide range of reasoners that provide this service. Reasoners aimed at so-called lightweight ontology languages are much more efficient than those aimed at more expressive ones, but they do not offer completeness guarantees for ontologies containing axioms outside the relevant language. We propose an original approach to classification based on exploiting module extraction techniques to divide the workload between a general purpose reasoner and a more efficient reasoner for a lightweight language in such a way that the bulk of the workload is assigned to the latter. We show how the proposed approach can be realised using two particular module extraction techniques, including the one presented in the first part of the thesis. Furthermore, we present the results of an empirical evaluation that shows that this approach can lead to a significant performance improvement in many cases.
The role of aquatic systems and the re-occupation and settlement of the North European Plain during the Lateglacial
Keywords: Cladocera
Tephra
Hamburgian
Lateglacial

The Lateglacial between &Tilde;14,600 - 11,500 cal yr BP is characterised by the rapid fluctuation of climatic conditions following the termination of the Last Glacial Maximum. During this period, the North European Plain (NEP) was re-occupied and settled by hunter-gather groups utilising a succession of lithic technocomplexes. Contrasting models of population expansion exist to explain the re-occupation of the NEP by &Tilde;14,600 cal yr BP. Both rapid climatic amelioration and increased food resource availability on the NEP are suggested as possible stimuli. Studies of food resource availability as a stimulus for re-occupation and settlement of the NEP have long been dominated by the prevailing view that large mammal hunting was the dominant subsistence strategy. A number of archaeological finds across the NEP however, suggest that the exploitation of aquatic resources such as fish may have played a role in a more varied subsistence strategy during the period &Tilde;14,600 - 11,500 cal yr BP.
This thesis sets out to examine the development of palaeolake systems and examine their potential as a resource base for Lateglacial hunter-gatherers. This is achieved through the analysis of sedimentary organic matter and cladoceran records from five Lateglacial sites in northern Germany and southern Denmark, providing important information on basin development and the presence or absence of fish. The results suggest that significant variability existed in the development and resource availability of the basins over a local scale. Observed variability in the organic matter and cladoceran records within chronozone boundaries suggests that the Lateglacial – Holocene development of aquatic systems across the NEP cannot be solely explained by external climate change, and that local environmental and ecological factors are likely to have played a major part in their development.
This thesis demonstrates that the local variance in aquatic conditions and fish populations would have offered, at best, limited and ephemeral resource availability and were therefore unlikely to have formed a major resource base for hunter-gatherer groups across the NEP. It is more likely that lakes were exploited opportunistically and as such formed only a minor component of a subsistence strategy more focussed on large mammal hunting.