VictorJuiz/thesis huggingface dataset:
Development of non-linear numerical models appropriate for the analysis of jack-up units
Keywords: foundations
offshore
jack-up

Jack-up units have considerable economic significance because they are used to carry out a large proportion of the world's oil and gas exploration in water depths less than 90.0m. Due to the increase in use of jack-ups in harsher environments, analysis techniques assuming quasi-static and linear structural behaviour have had to be reassessed. This thesis is concerned with non-linear dynamic analysis methods appropriate for a jack-up assessment. Jack-up modelling requires realistic representation of the structure, the foundations and the environmental loading, together with the implementation of appropriate dynamic analysis algorithms. Techniques for each of these aspects of jack-up analysis are reviewed and the implementation of several of the methods in an advanced plane frame analysis program called JAKUP is described. Geometric non-linearity in the structure and work hardening plasticity at the foundations are accounted for in the program. Test cases are presented to verify the implementation of the methods and then some illustrative plane frame quasi-static and dynamic analyses are described. These simple models highlight the importance of accounting for dynamic motions in a jack-up analysis. For the quasi-static analyses, the assumption of pinned footing behaviour is seen to always result in the most conservative displacement and moment predictions. However, the analyses show that this is not always the case when dynamic amplification is accounted for.
Electrostatic extraction of buffer-gas-cooled beams for studying ion-molecule chemistry at low temperatures
Keywords: electrostatic velocity selection
ammonia
buffer gas cooling
Cold molecules

This thesis describes the design, construction, operation, and characterisation of an experimental apparatus that produces a source of internally cold, slow molecules that can be used for studying ion-molecule reactions at low temperatures. The apparatus combines buffer-gas cooling with a bent quadrupole velocity selector to cool both the translational and rotational degrees of freedom of the molecules.
A cold cell (6 K) is filled with a buffer gas, such as helium, that exhibits sufficiently high vapour pressure for cryogenic applications. Hot molecules (150 to 300 K) enter the cell and thermalise with the buffer gas through collisions. Molecules are subsequently loaded into an electrostatic quadrupole guide, which acts as a velocity filter; only translationally cold polar molecules are guided around the bend. Using a buffer-gas-cooled source of molecules for electrostatic velocity selection, rather than a 300 K effusive source, yields a rotationally cold sample, with J ≤ 3. This rotational selectivity will enable the dependence of reaction cross sections on the reactant rotational state to be examined.
Mass spectrometry is used to characterise cold molecular beams of ND3 and CH3F, while (2+1) REMPI spectra are recorded for the ammonia isotopologues. The peak velocity of guided ND3 is 75.86(0.70) ms-1 for standard conditions in a 6 K helium buffer gas cell (1.0 sccm ND3 flow rate, 0.6 mbar helium inlet pressure, ± 5 kV voltage). This corresponds to a peak kinetic energy of 6.92(0.13) K. (2+1) REMPI spectroscopy of the B1E''(v2'=5) ← X(1) transition enabled the rotational state distribution of guided ammonia molecules to be established. PGOPHER simulations of the experimental spectra suggest a rotational temperature of 10 K for ND3 molecules (from a 6 K helium buffer gas cell).
The extent of translational and rotational cooling can be controlled by varying the molecular and buffer gas densities within the cell, by changing the temperature of the buffer gas cell (we can operate at 6 K or 17 K), or by changing the buffer gas. The translational temperature of guided ND3 is similar in a 6 K helium and 17 K neon buffer gas cell (peak kinetic energies of 6.92(0.13) K and 5.90(0.01) K, respectively) because the heavier neon gas has a slightly lower thermal velocity at 17 K than helium does at 6 K. Despite similar translational temperatures, the rotational temperature of guided ND3 is lower for molecules exiting the 6 K helium cell compared to the 17 K neon buffer gas cell (10 K and 15 K, respectively).
The 6 K helium and 17 K neon buffer gas cells provide an excellent opportunity to investigate the effect of rotational cooling on branching ratios and reaction rates in low temperature ion-molecule reactions. The buffer gas cell and velocity guide described in this work will be combined with a linear Paul ion trap, to facilitate the study of cold ion-molecule reactions.
Three essays in dynamic macroeconomics
Keywords: zero lower bound
learnability
indeterminacy
medium frequency cycles
precautionary motives
two-country models
inequality constraints
identification
patent protection
Taylor rules
limited Information
scale effects

This thesis presents three papers within the field of dynamic macroeconomics. The first paper, entitled “Medium-frequency cycles and the remarkable near trend-stationarity of output”, presents a dynamic stochastic general equilibrium model with endogenous growth, capable of reconciling the observed large medium-frequency fluctuations in output, with its long run (near) trend-stationarity. This requires a model in which standard business cycle shocks lead to highly persistent movements around trend, without significantly altering the trend itself. The robustness of the trend also requires that scale effects are eliminated both in the long and short runs. In an estimated version of the model, a financial-type shock to the stock of ideas emerges as the key driver of the medium frequency cycle.
The second paper, entitled “Learning from learners”, is an intervention into two long running debates: the first, on whether learnability may be used to rule out explosive paths for inflation in New Keynesian models, and the second, into whether Taylor rule parameters may be identified from observing the data. We find that in an economy populated with traditional macroeconomic learners, Taylor rule parameters can always be identified by sophisticated econometric techniques. Furthermore, when all agents in the economy use such sophisticated techniques, stationary sunspot solutions are readily learnable, and there is no guarantee of convergence to a stationary solution even in the “determinate” case. This implies that learnability cannot be used for equilibrium selection.
Finally, in the third paper, “Efficient simulation of DSGE models with inequality constraints” (joint with Michael Paetz), we present a new algorithm for the simulation of models subject to inequality constraints, such as the zero lower bound on nominal interest rates. Our algorithm is shown to deliver higher accuracy than all other non-global algorithms, and leading speed. We go on to provide a number of applications of our algorithm.
Left/Right and thinking about politics
Keywords: political narrative
political ideologies
Left/Right
Gramsci

Since its birth at the time of the French Revolution, Left/Right has been a key tool for understanding politics. This thesis investigates how we think about politics using Left/Right: how it shapes, constrains and interacts with our most deeply-held conceptions of politics, how its meaning and implications have developed historically and in the British context, and why it might warrant the attention of the student of ideologies.
After outlining the methodological underpinnings of the study and histories of Left/Right, the thesis examines uses of Left/Right in a range of contexts of actual thinking about politics. Left/Right is widely used in both the academic study of politics and popular commentary on British politics. The early New Left in Britain in the late 1950s and early 1960s is studied as a group attempting to influence the discourse around the political label “the Left”; a section of the neo-conservative New Right in Britain in the 1980s, around The Salisbury Review, is analysed as a political group with a complicated relationship to the political label “the Right”.
Left/Right emerges as an element of the contested “common sense” of politics. Further, it is argued that some elements of common sense, such as Left/Right, may be expressed through narratives. Left/Right is theorized as a political narrative, or as a story about politics. The concept of political narrative explores the possibility that Left/Right may be susceptible to “interpretation”, both in terms of the assumptions about how politics is done and how politics should be done that underlie it, and more complexly in its relationship with a master narrative of political conflict understood as class struggle. Students of ideologies can learn much about how we think about and do our politics by attending to Left/Right.
Automatic analysis of magnetic resonance images of speech articulation
Keywords: Magnetic Resonance Imaging
Automatic Image Segmentation
Acoustics
ASR
Speech Production
Articulation

Magnetic resonance imaging (MRI) technology has facilitated capturing the dynamics of speech production at fine temporal and spatial resolutions, thus generating substantial quantities of images to be analysed. Manual processing of large MRI databases is labour intensive and time consuming. Hence, to study articulation on large scale, techniques for automatic feature extraction are needed.
This thesis investigates approaches for automatic information extraction from an MRI database of dynamic articulation. We first study the articulation by observing the pixel intensity variations in image sequences. The correspondence between acoustic segments and images is established by forced alignment of speech signals recorded during the articulation. We obtain speaker-specific typical phoneme articulations that represent general articulatory configurations in running speech. Articulation dynamics are parametrised by measuring the magnitude of change in intensities over time. We demonstrate a direct correlation between the dynamics of articulation thus measured and the energy of the generated acoustic signals.
For more sophisticated applications, a parametric description of vocal tract shape is desired. We investigate different shape extraction techniques and present a framework that can automatically identify and extract the vocal tract shapes. The framework incorporates shape prior information and intensity features in recognising and delineating the shape. The new framework is a promising new tool for automatic identification of vocal tract boundaries in large MRI databases, as demonstrated through extensive assessments.
The segmentation framework proposed in this thesis is, to the best of our knowledge, novel in the field of speech production. The methods investigated in this thesis facilitate automatic information extraction from images, either for studying the dynamics of articulation or for vocal tract shape modelling. This thesis advances the state-of-the-art by bringing new perspectives to studying articulation, and introducing a segmentation framework that is automatic, does not require extensive initialisation, and reports a minimum number of failures.
Understanding journeys of transformation – Exploring new paradigms in strategic change and enterprise transformation
Keywords: top teams
leadership
transformation
change
enterprise

This thesis seeks to study the phenomenon of transformational journeys in major organisations, defined as a process of radical change delivering dramatic and sustained improvement in market competitive performance within an aggressive timescale. This is characterised by strategic repositioning, alongside shifts in both strategic and organisational architecture, and is observable as periodic in the life of an organisation.
A research framework for observation and explanation is taken from theories and research in strategic change, strategic intent and competitive advantage, strategic and organisational architecture, management process in transformation and typologies of transformational journeys. The primary research question, “how do top managers in different organisations lead and manage transformational change?” was addressed with an overall qualitative dual approach: firstly a pilot cross-company study with executives from 23 organisations to develop a high level typology and compare and contrast aspects of process; secondly longitudinally to examine in detail the complex interrelationships and aspects of emergent process. The prime empirical work was a main case study of Thames Water Utilities on a 7 year journey. Limited or secondary data was used from around 7 other longitudinal cases.
The thesis conclusions make a number of specific propositions: around effective use of the descriptive framework and metaphor of a journey; on dependencies between aspects of context, content and process of change in transformation; on typologies of different journey management styles; on perceived conditions for success; and on practical applicability. Specifically, the adoption of “navigational leadership” capability, defined by a number of dimensions and characteristics, is explored as a new and emergent style appropriate in future business circumstances of increasing change and uncertainty. The research also concludes that such styles can be learnt and adopted by top teams.
A study of interferometric distance measurement systems on a prototype rapid tunnel reference surveyor and the effects of reference network errors at the International Linear Collider
Keywords: Particle Accelerator Alignment

The International Linear Collider (ILC) aims to collide electrons and positrons with a centre of mass energy of 500GeV and a luminosity of 2×1034 cm−2 s−1. To achieve this luminosity, the nominal final emittance of the electron and positron beams have to be below 10μm.rad horizontally and 0.04μm.rad vertically. To prevent the emittance from becoming too large, the main linacs will require alignment at an unprecedented level. The ILC main linacs will be aligned with respect to a reference network which runs along the entire length of the tunnel. The Linear Collider Alignment and Survey (LiCAS) Rapid Tunnel Reference Surveyor (RTRS) is the prototype of a device proposed to survey the ILC reference network. The LiCAS RTRS has several measurement systems; its Frequency Scanning Interferometry (FSI) measurement system is studied in this thesis. The FSI system has three distinct sub-systems: the reference interferometers, the external FSI measurement system and the internal FSI measurement system. The errors on the length of the reference interferometers are shown to be of the order of 1.1μm (0.3ppm). The external FSI measurement system is shown to measure distances close to 0.42m with errors of &pm;1.9μm stat &pm;0.16μm syst and the internal FSI measurement system is shown to measure distances close to 4.2m with errors of &pm;0.24μm stat &pm;1.6μm syst.
A survey of the ILC reference network using laser trackers is simulated without taking account of systematic measurement errors from refraction in the tunnel air. The simulated networks are used to misalign the simulated accelerators in Dispersion Matched Steering (DMS) simulations. The DMS simulations show that only 30% of the simulated accelerators produce an acceptable final corrected vertical emittance. It is further shown that the introduction of long range distance measurements between primary reference markers (PRMs) using GPS, reduces the long range error growth in the network, and that 95% of simulated accelerators give acceptable performance. A simplified network simulation model, which is capable of simulating reference networks surveyed by conventional and novel devices, is produced and compares favorably to full simulations.
Social change along the Middle Yangzi river: re-configurations of late Neolithic society
Keywords: Neolithic
Archaeology
Yangzi River
China

Through the case study of the Shijiahe site, Tianmen, Hubei, this thesis investigates the dynamics of enclosures along the Middle Yangzi River during the third millennium BC. During the early third millennium over a dozen of enclosures were constructed in this region, earlier than elsewhere in China during this millennium. All were abandoned and some re-settled around 2000 BC, followed by another episode of abandonment. The major theoretical paradigms dominating the field are culture history and social complexity. The thesis argues that these are insufficient to fully appreciate the actual details and dynamics of the developments at the Middle Yangzi sites. As an alternative, this thesis employs a combination of approaches. A detailed practice-based analysis of the biography of Shijiahe reveals dynamics of identity formation and changes to tradition not observed before. The techniques of enclosure construction, reasons for their construction and abandonment will also be discussed.
The thesis acknowledges the central importance of religion and interaction as two essential underlying currents of prehistoric lives that, in the case of China, have largely been ignored. From this angle a series of objects, such as red pottery cups, pottery pointed-bottom vessels and jade ornaments, from Shijiahe are investigated and their religious significance established. They and the practices they were used in are also mapped according to their find spots, which show the connection of Shijiahe with regions even beyond the Middle Yangzi, such as the Yellow and Huai river regions. These interactions were probably also stimulated by religious practices. The northward connections are of particular importance, as they confirm that the Yangzi, and the giant swamp of the Yunmengze in the Jianghan Plain, were formidable barriers southwards. The usually posited direction of movements from the Yellow River into the south must be challenged on the basis of this thesis, which argues for multiple directions of interaction and transmission of objects and ideas.
Silicon isotopes and the development of the Earth
Keywords: terrestrial
continental crust
silicon isotopes

Silicon (Si) isotopes have been extensively studied in low temperature environments but the science of Si isotopes in igneous material has been comparatively ignored. This is because the degree of isotopic fractionation at high temperatures is relatively small, making the accurate measurement of these variations extremely challenging. Using state-of-the-art analytical techniques and instrumentation, which deliver high levels of precision, the objective of this research is to rectify this omission. Specifically, this study aims to investigate whether there are systematic Si isotope variations within, and provide robust Si isotopic compositions for, the major silicate reservoirs on Earth. To this end, a broad range of mantle and crustal lithologies, sourced globally and from various tectonic regimes, have been analysed using high resolution MC-ICP-MS.
Analyses indicate that the Si isotopic compositions of mantle-derived mafic and ultramafic material are extremely homogeneous. These data are used to calculate a Bulk Silicate Earth (BSE) average of δ30Si = -0.29 ± 0.08 ‰ (2 s.d.). The degree of Si isotopic fractionation as a result of magmatic differentiation has also been assessed, and found to be small but resolvable between basalt and rhyolitic end-members. Finally, this research shows that, although igneous rocks and sediments derived from the continental crust can be relatively heterogeneous with respect to Si isotopes, bulk averages calculated for the upper, middle and lower continental crust are all very similar to that of BSE. Providing robust estimates for these reservoirs has greatly improved our knowledge of the behaviour of Si isotopes in silicate lithologies and provides a framework for further Si isotopic investigations of such material.
High fidelity readout of trapped ion qubits
Keywords: measurement
trapped ions
qubit
readout
quantum computing
quantum computation
quantum information
ion trap

This thesis describes experimental demonstrations of high-fidelity readout of trapped ion quantum bits ("qubits") for quantum information processing. We present direct single-shot measurement of an "optical" qubit stored in a single calcium-40 ion by the process of resonance fluorescence with a fidelity of 99.991(1)% (surpassing the level necessary for fault-tolerant quantum computation). A time-resolved maximum likelihood method is used to discriminate efficiently between the two qubit states based on photon-counting information, even in the presence of qubit decay from one state to the other. It also screens out errors due to cosmic ray events in the detector, a phenomenon investigated in this work. An adaptive method allows the 99.99% level to be reached in 145us average detection time. The readout fidelity is asymmetric: 99.9998% is possible for the "bright" qubit state, while retaining 99.98% for the "dark" state. This asymmetry could be exploited in quantum error correction (by encoding the "no-error" syndrome of the ancilla qubits in the "bright" state), as could the likelihood values computed (which quantify confidence in the measurement outcome). We then extend the work to parallel readout of a four-ion string using a CCD camera and achieve the same 99.99% net fidelity, limited by qubit decay in the 400us exposure time. The behaviour of the camera is characterised by fitting experimental data with a model. The additional readout error due to cross-talk between ion images on the CCD is measured in an experiment designed to remove the effect of qubit decay; a spatial maximum likelihood technique is used to reduce this error to only 0.2(1)x10^{-4} per qubit, despite the presence of ~4% optical cross-talk between neighbouring qubits. Studies of the cross-talk indicate that the readout method would scale with negligible loss of fidelity to parallel readout of ~10,000 qubits with a readout time of ~3us per qubit. Monte-Carlo simulations of the readout process are presented for comparison with experimental data; these are also used to explore the parameter space associated with fluorescence detection and to optimise experimental and analysis parameters. Applications of the analysis methods to readout of other atomic and solid-state qubits are discussed.