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

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

Optimisation of microscopic techniques to assess isolated islet characteristics

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

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

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

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

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

Protecting the online safety, security and privacy of autistic children and young people

The aim of this PhD thesis was to investigate how autistic children and young people experience online safety risks and what could help them to navigate such risks in the future. In Study 1, two groups of parents (autistic children, n = 63; non-autistic children, n = 41) completed an online survey about their child’s online safety behaviours and wellbeing. Study 2 involved semi-structured interviews with 14 autistic young people aged 11-17 years investigating their first-hand accounts of their online safety experiences. Study 3 piloted two low-fidelity prototype solutions to common online safety scenarios with 11 autistic young people aged 11-18 years, who fed back how these could be improved to help keep themselves safe in the future. Results indicated that autistic children experienced significantly more online safety risks than non-autistic children and poorer wellbeing than autistic children who did not experience online safety risks.. Secondly, autistic young people reported being victims of cyberbullying and online sexual harassment and a desire for more design support to block online comments and/or individuals. Thirdly, autistic young people fed back that visual cues in low-fidelity prototypes of online safety solutions were beneficial in informing their online safety risk management. To conclude, this PhD thesis highlights that autistic children and young people are at risk pertaining to certain online safety risks. The findings will benefit designers looking to develop online safety interventions in ways that autistic children will both accept and can actively benefit from. This research will shape the direction of future interventions and policy for this population and thus will help to protect autistic children and young people online

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

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

Algebraic and geometric aspects of two-dimensional Artin groups

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

A study of unskilled migrant construction workers in developing countries

Over the past twenty years, migrants have become essential to the construction industry’s workforce in developing countries. This thesis is a labour migration study and investigates the involvement of migrant workers and their issues in the wider labour market with a particular focus on the construction sector. Although there is research on the living and working conditions of migrant workers and growing acknowledgement of the construction industry being hazardous for low skilled workers in particular, there has been little research on employment conditions given the new requirements that have put considerable pressure on the industry. This study takes a qualitative approach, with in-depth interviews with both employers and employees in the construction industry. In-depth telephone interviews were conducted with 12 managers from the UAE (n=5), and the KSA (n=7). In addition, data was collected from the fieldwork in Thailand, which includes face-to face in-depth interviews with managers (n=10) and with migrant workers (n=22). The experiences of the 44 participants in this study provide the basis for understanding the situation of migrant construction workers. The aim is to find ways for improving the conditions of migrant construction workers in developing countries. Based on the experiences of the participants, this study positions migrant workers within the construction industry by examining the factors that have the greatest impact on the lived reality of work. It considers how they could enjoy positive migration and work experiences in the sector that would allow them to both contribute to and benefit from the new developments within the construction industry. The conceptual models were designed based on the fundamentals of system thinking for a system of several elements under the key catalysers migration and employment. It is vital that knowledge be gathered about factors acting as force to changes within the construction industry to ensure that policies and practices relating to migration, employment, Occupational Health and Safety, and wellbeing are well evidenced. This thesis contributes to existing knowledge by shaping the linkages that reveal the opinions, requirements, and experiences of migrant construction workers. The study outlines recommendations for improving conditions for migrant workers in construction sector

Novel image processing strategies for probing photoelectron dichroism effects in chiral molecules

The phenomenon of photoelectron circular dichroism (PECD) has revolutionised the study of chiral molecules in the gas-phase. PECD presents itself as an asymmetry in the photoelectron angular distribution (PAD) of chiral molecules upon photoionization with circularly polarized light, with measurable dichroism signals typically of order ±10%. To study and extract the subtle features (including those due to PECD effects) present in PADs, advanced experimental techniques, such as velocity map imaging (VMI), and complementary sophisticated data-processing techniques are required. The use of elliptically polarized laser pulses, or mixing together linear and circular polarizations for creating the PADs further complicates the analysis of experimental data, and often requires the use of comparatively time-consuming tomographic imaging techniques. This thesis investigates and develops a number of novel image processing approaches for tackling some of the challenges common to VMI experiments. This includes exploring applications of machine learning and artificial neural networks for solving ill-posed problems that frequently arise during the analysis of experimental data. New tomographic reconstruction approaches are also investigated for the first time within the context of VMI experiments. It is found that the Hankel Transform Reconstruction (HTR) approach, in particular, has significant advantages over other reconstruction options, and allows for PADs to be determined tomographically with the minimum possible volume of imaging data. These novel image processing strategies are tested by accurately reconstructing the full three-dimensional PADs in a study of the photoelectron elliptical dichroism (PEELD) of (R)-camphor following three photon ionization with elliptically polarized 400 nm light. This measurement revealed clear features in the PADs of chiral molecules that have previously been thought to be negligible in other related experiments. Finally, the first experimental photoelectron images recorded using a laser-based desorption source (LBD) coupled directly into a VMI spectrometer are presented. LBD sources permit the vaporization of highly non-volatile molecules that would otherwise be too challenging to study with gas-phase spectroscopy techniques. As an initial test system, the multiphoton PECD of the amino-acid phenylalanine is measured at 400 nm and shown to have a G-value of around ±7%. Overall, the utility of photoelectron imaging experiments as a whole is anticipated to be expanded significantly as a result of the work presented here; with the novel image processing strategies simplifying the use of more complex polarization geometries in experiments, and the LBD technique allowing for a much wider range of interesting molecules to be accessed in gas-phase spectroscopy measurements

Robust high dynamic range transducers for surface form and finish

Abstract and full text unavailable. Restricted access until 01.04.2025. Please refer to PDF