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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
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