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    Contourite cyclicity and deposition

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    Cyclic depositional features are commonly developed in deepwater sedimentary facies. Stacked sequences in varied forms is the most obvious characteristic, which is related to complex variation in depositional conditions. This study introduces several geostatistical approaches to analyse the cyclical bi-gradational sequences of contourite deposits from IODP Expedition 339 in the Contourite Depositional System (CDS) in the Gulf of Cadiz. It analysed both the vertical sequences and their cyclicity and their lateral correlation, both qualitatively and quantitatively. Additionally, similar geostatistical approaches were applied to colour sequences in turbidite and hemipelagite deposits from the Benguela Current Upwelling System, SW African continental margin. This allowed comparison of sequences and cyclicity between the different deepwater facies types. It also demonstrated the general applicability of this method to deepwater sedimentary facies. This study systematically examined contourite bi-gradational sequences deposited at IODP Sites U1386 and U1387 between mid-Pleistocene to Recent. Transition probability analysis based on the lithological logs confirmed the statistical validity of typical bi-gradational sequences composed of coarsening-upward to fining-upward contourite divisions. These typically ranged in thickness from 0.5-5m. Variations caused by minor erosion and non-deposition resulted in incomplete sequences and complex sequences with multiple gradational divisions. The cyclic patterns of contourite bi-gradational sequences varied to some extent between each studied hole. The 3-layer-sequence (C1-C2-C4-C5) dominates in this study area, and a few sequences with more than 4 divisions include the C3 (sandy) division. Autocorrelation of sequence duration in all studied holes indicates the existence of long-term cyclicity of around 350 ky. The succession can be subdivided into 4 stages (0-350 ka, 350-700 ka, 750-1000 ka and >1000 ka) with alternating occurrence of more frequent and coarser sequences and less frequent finer-grained sequences. Cross-correlation of this long-term sequence frequency as well as of individual sequences shows moderately good but not perfect correlation between holes and sites. This study suggests contourite deposition at the study sites is controlled by both bottom current strength (speed) and sediment supply, both of which can most probably be related to a complex variation in paleoclimate evolution and orbital cycles In hemipelagite and turbidite-hemipelagite hybrid deposits beneath the Benguela Upwelling System off SW Africa, two colour sequence models (Hemipelagite Dominant Sequence and Turbidite Hemipelagite Hybrid Sequence) were developed based on light-dark variation related to organic matter content. Autocorrelation of sequence duration pointed out long-term cyclicity through the past 4 My (0-1 Ma, 1-2.5 Ma, 2.5- 4 Ma and >4 Ma), which can be correlated to stages in tthe long-term evolution of the Benguela Current Upwelling System. Lateral correlation between studied sites indicated differences of sequence frequency in time and space, which further contributed to reconstruction of the upwelling system. The geostatistical study of cyclicity in contourite bi-gradational sequences and its comparison cyclic characteristics of other deepwater facies (turbidites and hemipelagites), demonstrates that such geostatistical approaches can be an important technique to evaluate the basic sedimentary character of different systems and their numerical expression. It allows for comparison between facies types and for better correlation with other time series records, such as orbital climate patterns. Cyclic signatures can be correlated between different sites and help better understand the sedimentary processes involved in their deposition

    Multi qubit gates using ZZ interactions in superconducting circuits

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    In recent years quantum computing has shown great promise and has come on in leaps and bounds. The promise of quantum computers is the speed-up over classical computers in specific areas and hence the ability to tackle even more complex problems. As quantum computers evolve the need for more complex quantum gates requiring more qubits (multi qubit gates) arises. These gates are currently broken down into their one and two qubit gates. Multi qubit gate decomposition’s involve many two qubit gates leading to the fidelity of these gates needing to be much higher in order to produce a usable multi qubit gate. A possible solution to this is to introduce a single shot method for the multi qubit gates. In this thesis we investigate the use of dispersive shifts to create these single shot methods. We examine two scenarios, first being a relatively simple three qubit gate (the iToffoli gate) to demonstrate the procedure. We then move to extend this method to a larger number of qubits examining its uses in quantum error correction and noting the potential pitfalls of this method. This thesis is organised as follows. In Chapter 1 we shall introduce the topic of superconducting circuits discussing some simple circuits such as the LC Oscillator and showing how these circuits can be modified to model superconducting qubits. We shall also introduce the topic of Quantum Computing giving an overview of the topic, discussing some quantum gates which shall be used and finally a short introduction to Quantum Error Correction. In Chapter 2 we shall show how we implemented a single shot multi qubit gate within superconducting circuits. We shall introduce some of the methods and analysis procedures we use within this thesis and show numerical evidence of this gate. In Chapter 3 we shall discuss an extension of the gate mechanism of chapter 1 to larger qubit clusters and show how it can be modified to implement parity check gates and show how they can be used to implement the stabilizer measurements used in the surface code. Finally in chapter 4 we shall discuss the future of this work, looking at some possible future directions for this research and suggesting some other more novel avenues which could be explored

    Optical ground receivers for satellite based quantum communications

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    Cryptography has always been a key technology in security, privacy and defence. From ancient Roman times, where messages were sent cyphered with simple encoding techniques, to modern times and the complex security protocols of the Internet. During the last decades, security of information has been assumed, since classical computers do not have the power to break the passwords used every day (if they are generated properly). However, in 1984, a new threat emerged when Peter Shor presented the Shor’s algorithm, an algorithm that could be used in quantum computers to break many of the secure communication protocols nowadays. Current quantum computers are still in their early stages, with not enough qubits to perform this algorithm in reasonable times. However, the threat is present, not future, since the messages that are being sent by important institutions can be stored, and decoded in the future once quantum computers are available. Quantum key distribution (QKD) is one of the solutions proposed for this threat, and the only one mathematically proven to be secure with no assumptions on the eavesdropper power. This optical technology has recently gained interest to be performed with satellite communications, the main reason being the relative ease to deploy a global network in this way. In satellite QKD, the parameter space and available technology to optimise are very big, so there is still a lot of work to be done to understand which is the optimal way to exploit this technology. This dissertation investigates one of these parameters, the encoding scheme. Most satellite QKD systems use polarisation schemes nowadays. This thesis presents for the first time an experimental work of a time-bin encoding scheme for free-space receivers within a full QKD system in the second chapter. The third and fourth chapter explore the advantages of having multi-protocol free-space receivers that can boost the interoperability between systems, polarisation filtering techniques to reduce background. Finally, the last chapter presents a new technology that can help increase communications rates

    Developing an implementation framework for Lean Six Sigma in high-value and low-volume industries

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    High-value low-volume (HVLV) industries hold a strong relevance in Germany, with a focus on complex engineering and large projects conducted at low frequencies. Methodologies for continuous improvement (CI), such as Lean Six Sigma (LSS), have been used in mass production industries, such as automotive, to promote operational excellence and are now relevant in HVLV industries to survive amid growing international competition. The implementation of LSS in the HVLV industries has not yet been studied to much extent. Therefore the purpose of the present study is to develop an implementation framework for Lean Six Sigma in the wind power industry in Germany. To develop the conceptual framework, a systematic literature review of critical success factors (CSFs) and critical failure factors (CFFs) was conducted. The review identified similarities between the CSFs and CFFs which often reflected opposite conditions of the same variable. The present study connects the success and failure factors as critical influencing factors (CIFs), which include reasons for both failure and success. An analysis of five relevant implementation frameworks of LSS shows that none of the frameworks fully includes all CIFs and do not provide a complete answer concerning LSS implementation in terms of what should be done to secure success and avoid failure in the process. The chosen research paradigm was critical realism and the research method was action case in combination with action learning. The outcome of the study was an implementation framework for LSS, the 3D framework house, as the essential result of the research, which was validated by LSS experts. The present study contributes to scholarship with the 3D framework house and a cycle approach in 18 steps, as well as with the detailed description of the newly defined CIFs with the focus dimensions and with the HVLV-specific focus dimensions. It contributes to practice with the improved situation in the research organisation and with the clear guideline for practitioners, giving answers to the questions “what needs to be done” to improve the situation of the CIFs of LSS, “how this can be implemented” and “who is responsible” in the HVLV industry context

    Sequential assimilation of crowdsourced social media data into a simplified flood inundation model

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    Flooding is the most common natural hazard worldwide. Severe floods can cause significant damage and sometimes loss of life. During a flood event, hydraulic models play an important role in forecasting and identifying potential inundated areas, where emergency responses should be deployed. Nevertheless, hydraulic models are not able to capture all of the processes in flood propagation because flood behaviour is highly dynamic and complex. Thus, there are always uncertainties associated with model simulations. As a result, near-real time observations are required to incorporate with hydraulic models to improve model forecasting skills. Crowdsourced (CS) social media data presents an opportunity for supporting urban flood management as it can provide insightful information collected by individuals in near real-time. In this thesis, approachesto maximise the impact of CS social media data (Twitter) to reduce uncertainty in flood inundation modelling (LISFLOOD-FP) through data assimilation were investigated. The developed methodologies were tested and evaluated using a real flooding case study of Phetchaburi city, Thailand. Firstly, two approaches (binary logistic regression and fuzzy logic) were developed based on Twitter metadata and spatiotemporal analysis to assess the quality of CS social media data. Both methods produced good results, but the binary logistic model was preferred as it involved less subjectivity. Next, the generalized likelihood uncertainty estimation methodology was applied to estimate model uncertainty and identify behavioural parameter ranges. Particle swarm optimisation was also carried out to calibrate for an optimum model parameter set. Following this, an ensemble Kalman filter was applied to assimilate the flood depth information extracted from the CS data into the LISFLOOD-FP simulations using various updating strategies. The findings show that the global state update suffers from inconsistency of predicted water levels due to overestimating the impact of the CS data, whereas a topography based local state update provides encouraging results as the uncertainty in model forecasts narrows, albeit for a short time period. To extend the improvement time span, a combination of state and boundary updating was further investigated to correct both water levels and model inputs, and was found to produce longer lasting improvements in terms of uncertainty reduction. Overall, the results indicate the feasibility of applying CS social media data to reduce model uncertainty in flood forecasting

    An assessment of the assisted seismic history matching workflow, practical innovations and solutions

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    In hydrocarbon reservoir monitoring, assisted seismic history matching (ASHM) remains a large and intractable problem. Despite advances in optimisation algorithms, quantification of uncertainty, data quality, data processing, computational resources and general subsurface knowledge, practical implementations of assisted/automated seismic history matching (ASHM) remain boutique and inflexible. Consideration of recent research on ASHM problems highlights a single-minded focus on algorithmic solutions, that ignore the broader perspective of ASHM as a multidisciplinary framework for improving subsurface models. This thesis expands the consideration of ASHM beyond the optimisation, to propose a novel three-phase approach. ASHM is posed as a larger workflow that includes acquiring, evaluating and establishing an ASHM model (Phase 1), history matching (Phase 2) and model evaluation and improvement (Phase 3). By taking a big picture perspective with respect to ASHM, additional value and patterns to workflows emerge that will improve the adoption of ASHM within the subsurface industry, by offering pragmatic and targeted guidance to development, evaluation and improvement around subsurface models via ASHM

    Optimisation of microscopic techniques to assess isolated islet characteristics

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    Islets of Langerhans or pancreatic islets constitute ~2% of the mass of the human pancreas and present on isolation as spheroids of 100-200 µm diameter. The 3D cellular organisation of islets is specific to each species, and important for islet viability and functionality. Isolated donor islets are used in transplantation for ameliorating Type I diabetes in humans, however current techniques to assess islet viability are highly specialised and not easily accessible in a non-clinical set up. The research in this thesis aimed to create and optimise methodologies for multiple microscopic techniques and analysis for isolated pancreatic islets. I found that live imaging of 3D intact pancreatic islets has multiple challenges, one of the most important being techniques to efficiently immobilise these organoid structures while retaining high-quality imaging and flexibility in the experimental set-up. I developed a tailor-made hydrogel for pancreatic islets and validated its use in live intact islets. The hydrogel was combined with experimental and commercially available chemical dyes and enabled optimisation of the analysis. Limitations in the labelling and imaging are discussed. Alternative dyes were tested to label different structures as steps towards automated viability assessment of isolated islets. New applications for an experimental dye to label alpha and beta cells were tested in human islets. In pursuit of a better understanding of the insulin metabolic pathways for its synthesis, maturation and release, a fluorescence timer tag was designed and validated for its use in beta cell lines and pancreatic islets. This validation was a multiple optimisation processes consisting of immunostaining and histology, imaging analysis and characterisation in live beta cells. The thesis offers insight into the complexities, opportunities and limitations offered by microscopic techniques in islet assessment with the aim of enabling assessment of islet health before transplantation and for research purposes

    What does this notation mean anyway? Interpreting BNF-style notation as it is used in practice

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    BNF (Backus Naur Form) notation, as introduced in the Algol 60 report, was followed by numerous notational variants (EBNF ISO (1996), ABNF Crocker et al. (2008), etc.), and later by a new metalanguage which is used for discussing structured objects in Computer Science and Mathematical Logic. We call this latter offspring of BNF MBNF (Math BNF). MBNF is sometimes called “abstract syntax”. MBNF can express structured objects that cannot be serialised as finite strings. What MBNF and other BNF variants share is the use of production rules, whose form is given below, which state that “every instance of ◦i for i ∈ {1, . . . , n} is also an instance of •”. • ::= ◦1 | · · · | ◦n This thesis studies BNF and its variant forms and contrasts them with MBNF production rules. We show via a series of detailed examples and lemmas that MBNF, differs substantially from BNF and its variants in how it is written, the operations it allows, and the sets of entities it defines. We demonstrate with an example and a proof that MBNF has features that, when combined, could make MBNF rule sets inconsistent. Readers do not have a document which tells them how to read MBNF and have to learn MBNF through a process of cultural initiation. We propose a framework, MathSyn, that handles most uses of MBNF one might encounter in the wild

    Algebraic and geometric aspects of two-dimensional Artin groups

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    In this thesis we study the algebra and the geometry of two-dimensional Artin groups under various aspects. First, we solve the problem of acylindrical hyperbolicity, by proving that all the two-dimensional Artin groups that are not trivially non-acylindrically-hyperbolic are acylindrically hyperbolic. In particular, we prove that every non-spherical Artin group of dimension 2 has trivial centre. Then, we study the structure of parabolic subgroups of large-type Artin groups, and prove various results about their combinatorial structure. We notably show that any intersection of parabolic subgroups is again a parabolic subgroup. Finally, we study the isomorphisms between Artin groups of large-type, and we prove that the family of large-type free-of-infnity Artin groups is rigid. We also fully describe the automorphism groups of these Artin groups

    Assessing the impact of new woodland creation on catchment hydrology and flood risk

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    Woodland creation is a known broad measure used as part of nature-based solutions for different catchments. Previous research studies have established the multiple benefits of woodland creation related to more comprehensive catchment research. However, those benefits have been researched on a broader catchment scale rather than on the small scales that include cultivation practices. This created a lack of evidence for studies related to the hydrology of cultivation techniques. This case study added unique values to researching different cultivated areas (plough, excavation mounding and hand-screefing cultivation) in Menstrie catchment, Scotland. For this study, the cultivation techniques were monitored for two years regarding runoff and sediment delivery at the field scale. Seven different plots (one unplanted plot, one hand-screefing plot, three plough plots and two excavation mounding plots -P6, P7) were monitored on microscale level (< 0.5 km2 ). Furthermore, monitoring included surface water level monitoring from two streams (Inch 1 and Inch 2) of the main water course in the Menstrie catchment. For better understanding of hydrological behaviour data has been analysed from dry (API30 ≤ 20 mm) and wet (API30 > 20 mm) weather perspective. However, according to monitored data, the study distinguished differences between runoff and sediment delivery from different cultivation plots and their effectiveness. On sub-catchment level main findings highlighted forest cover importance. This clearly showed that Inch 1 sub-catchment had lower values of runoff water than Inch 2 subcatchment for any weather conditions. Inch 2 sub-catchment had 25 % more grassland cover than Inch 1 sub-catchment. On another hand, monitored cultivations plot and unplanted plot discovered hydrology on microscale for dry and wet weather conditions. Analysed data showed that runoff water will first in unplanted plot area, followed by peaty based plough plot, hand-screefing plot, brown soil-based plough plots and excavation mounding plots during dry weather conditions. On the other hand, the fastest response for wet weather conditions will occur in unplanted plot area, plough plots, lowland excavation mounding plot, followed by hand-screefing plot and upland excavation mounding plot. Then, the highest amount of runoff for dry weather conditions occurred in the case of unplanted plot, peaty soil-based plough plot and lowland excavation mounding plot, since wet weather conditions had unplanted plot, handscreefing plot and lowland excavation mounding plot. However, those finding was associated with cultivation design, slope of catchment area, slope of channel, soil type etc. However, the highest amount of sediment delivery refers to plough plots since hand screefing plot and excavation mounding plots monitoring plots have experienced significantly less sediment delivery. Those data have been analysed in connection with precipitation, runoff peak and runoff volume. Overall, this research defined hydrology and sedimentology of different cultivated areas depending on main properties of monitored plots. Those findings can be improved by further research in the same area

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