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Quantum transport & information geometry
Get PDFThis thesis is concerned with the modelling of energy transport processes in nanoscale
systems and the counter-intuitive quantum mechanical effects which become relevant
at such length scales. By combining standard open quantum systems techniques
for modelling these transport processes with the fascinating field of information
geometry, new insights into the efficiency and robustness of quantum transport are
presented.
The first research chapter constructs a simplified model of excitonic energy transport
as an open quantum system and investigates the information-geometric properties
of this transport model. This investigation reveals that our model belongs to an
interesting class of mathematical models, each exhibiting a striking information-geometric structure which results in a high degree of asymmetry in the relative
importance of different model parameters. Using this insight, it is then shown that
the energetic landscape of the transport network plays a dominant role in determining
transport efficiency.
The second research chapter investigates the possibility of using novel quantum effects
to enhance the efficiency of longer-range nanoscale energy transport. Specifically,
a naive transport model consisting of a chain-like system with a linear energy
gradient is first considered and shown to exhibit relatively poor efficiency. Numerical
optimization techniques are then applied to this model, revealing a surprising result:
on-site energy landscapes featuring regularly spaced energetic ‘barriers’ can lead to
significant improvements in transport efficiency.
The final research chapter extends the previously introduced chain-like model to
encompass systems consisting of multiple chains arranged in parallel. Within these
larger multi-chain systems it is shown that radiative loss processes, which often
plague nanoscale energy transport, can be effectively eliminated by modifying the
distance between the parallel chains
Taking light to the next level : harnessing high-dimensional entanglement for quantum photonic technologies
No full textThe spatial and temporal structure of photons allows us to study complex quantum systems such as high-dimensional and multipartite entangled states of light.
These serve as test beds for quantum foundations and are simultaneously powerful platforms for overcoming current limitations of quantum technologies based on
binary (qubit) encoding. This thesis presents practical demonstrations of the generation, characterisation, measurement, and transport of high-dimensional photonic
entanglement. We develop techniques for the precise measurement and efficient
certification of entangled states in the Laguerre-Gaussian and the discrete position-momentum (pixel) bases, demonstrating high-dimensional entanglement with record
quality, measurement speed, and entanglement dimensionality. Additionally, we
tackle the challenge of transporting high-dimensional entangled states by unscrambling pixel entanglement after transmission through a complex scattering channel
consisting of a commercial multi-mode fibre. Finally, we program optical circuits
inside a multi-mode fibre to observe quantum interference between two independent
photons inside a complex medium, demonstrating the potential of this platform
in the control of high-dimensional multipartite entanglement. These results bring
us closer to realising high-capacity quantum networks that operate under realistic
and noisy environments, and open a new pathway towards the control of complex
scattering processes for technologies based on multimode entanglement
Bayesian image reconstruction and adaptive scene sampling in single-photon LiDAR imaging
Get PDFThree-Dimensional multispectral Light Detection And Ranging (LiDAR) used
with time-correlated Single-Photon (SP) detection has emerged as a key imaging
modality for high-resolution depth imaging due to its high sensitivity and excellent surface-to-surface resolution. This allowed depth imaging through adversarial
conditions with a prime role in numerous applications. However, several practical
challenges currently limit the use of LiDAR in real-world conditions. Large data
volume constitutes a major challenge for multispectral SP-LiDAR imaging due to
the acquisition of millions of events per second that are usually gathered in large
histogram cubes. This challenge is more evident when the useful signal photons are
attenuated and the background noise is amplified as a result of imaging through a
scattering environment such as underwater or fog. Another limitation includes the
detection of multiple-surfaces-per pixel which usually occurs when imaging through
semi-transparent materials (e.g., windows, camouflage), or in long-range profiling.
This thesis proposes robust and fast computational solutions to improve the acquisition and processing of LiDAR data while measuring uncertainty on high-dimensional data. A smart task-based sampling framework
is proposed to improve the acquisition process and reduce data volume. In addition,
the processing was improved using a Bayesian approach to different types of inverse
problems (e.g. spectral classification, and scene reconstruction). The contributions
of this thesis enables fast and robust 3D reconstruction of complex scenes, paving
the way for the extensive use of single-photon imaging in real-world applications
Self-calibrating circuit system beamformers supporting hybrid/digital antenna phased arrays for radar applications
No full textAbstract unavailable. Please refer to PDF. Restricted access until 14.01.2033
The conceptual role of permeability contrasts within sandstone on underground hydrogen storage
Get PDFThe aim of this study is to analyse the effect of contrasting permeabilities on fluid flow
and hydrogen plume development in subsurface, porous media as this impacts upon the
efficacy of underground hydrogen storage. Reservoir-scale simulations, based upon the
Navajo sandstone, Utah in an aquifer-supported system, are generated containing
increasing levels of permeability heterogeneities. Initial investigations into the effects of
well placement on reservoir pressure, cumulative hydrogen and water production in a
homogeneous and heterogeneous model are used as baseline simulations to benchmark
the performance of scenarios containing further permeability contrasts.
The results show, in terms of well placement, that production well placement at the top
of the reservoir was the most important factor to maximise hydrogen production, due
to the buoyancy of hydrogen. Permeabilities of 10-2 mD and below reduce hydrogen
flow and permeabilities of ≤10-4 mD provided an almost no-flow barrier. Contrasting
permeabilities can affect flow pathways, impacting upon plume integrity, or they can
compartmentalise the reservoir, reducing storage capacity and increasing pressure
fluctuations. Although the relationship between rock permeability and fluid viscosity
provides a guideline to the impact of permeability contrasts upon fluid flow, forecasts
of reservoir performance need to consider the whole system. This is because pressure,
the other variable in Darcy’s equation of flow, is also affected by factors such as,
coupling of permeabilities, compartmentalisation and impact of permeability upon
other fluid flow
Role of wettability and rock type on oil recovery by Water Alternating Gas (WAG) injection
No full textWater-Alternating-Gas (WAG) injection is a promising EOR approach to recovering more oil
than water flooding or gas injection technique and is also a relatively reasonable method
compared to other EOR techniques in terms of cost and complexity of the operation. In order
to fulfil all the objectives of this study (investigate the effect of wettability, rock type and
size/scale), a series of coreflood experiments including primary water flooding (WF), primary
gas flooding (GF), WAG starting with water injection (WAG-W), WAG starting with gas
injection (WAG-G) and simultaneous water and gas injection (SWAG) were conducted on a
2-inch Clashach sandstone core (CS), a 2-inch Indiana limestone core (IL core) and a 4-inch
IL core (whole core/WC).
The effect of wettability was investigated on the CS core under the water-wet (WW), mixed wet (MW) and oil-wet (OW) state in order to quantify the level of additional oil recovery by
WAG injection in comparison with primary water or gas flood. Furthermore, the impact of
initial wettability on oil recovery performance and fluid flow behaviour is identified for each
WAG scheme. The results show that the WF in non-WW systems has a better performance
compared to the WW state, while the oil recovery performance of GF decreases significantly
by moving towards a more Non-WW state. One of the conclusions drawn from these
comparisons is a pronounced reduction of trapped gas saturation in porous media by changing
wettability from WW towards OW state regardless of the WAG injection scheme. This finding
is attributed to the unique pore occupancy of fluids (water and gas) and displacement
mechanisms in each wettability state. It is also concluded that WAG-W in the MW state has
better efficiency compared to OW and WW states. On the other hand, when WAG started with
gas injection, more oil was recovered in the WW state than in OW and MW states. These
comparisons reveal the importance of the wettability and WAG injection order on oil recovery,
differential pressure and trapped gas saturation levels.
To address the other objective of the research, a similar series of core flood experiments were
performed on the IL core as a representative of the carbonate environment. The results of these
experiments reveal that the SWAG process is the best performer in terms of oil recovery as it
controls the gas mobility from the initiation of injection and effectively overcomes the natural
heterogeneity in the internal pore structure of this core. However, the benefit of this set of
experiments is not limited only to finding the best injection scenario in this pore network, it also allowed us to realise the effect of rock type on WAG injection performance by comparison
with experiments conducted on CS core. According to the findings, it is determined that WAG
injection (either starting with water injection or gas injection) in the CS core has a superior oil
recovery performance compared to the IL core. In contrast, the SWAG process in the IL core
outperforms the CS core in terms of oil recovery.
The other benefit of this set of experiments is to use it as the backbone to interpret the effect of
core dimension and scaling up by comparison with a similar set of experiments conducted on
the WC. Considering that the WC was subject to strong gravity force due to lack of rotation
along its axis and its large thickness, it can better show the effect of gas override and water
underride phenomena on oil recovery performance. In other words, coreflood in smaller core
plugs could misleadingly overestimate the performance of water and gas injection. Finally, it
is concluded that the gravity force ignored or not fully captured during conventional corefloods
has a pronounced effect on WAG injection performance in terms of oil recovery and fluid flow
behaviour
Theoretical study of excited molecular scattering : electronic structure, potential energy surfaces and dynamics
No full textThis thesis focuses on describing photo-excited open-shell bimolecular processes at
different levels of theory. Specifically, collisional quenching events have attracted the
interest of researchers for decades because of their importance in atmospheric and
combustion chemistry. However, only a few theoretical descriptions have been provided because of the complexity associated with modelling such phenomena. Here,
we take a step forward and lay down the steps in modelling such processes while
working on two model systems: NO A 2Σ
++ O2 and OH A2Σ
++ H2 .
The former is the most challenging because it is an open-shell Rydberg state that
can exist across several spin-multiplicities, and it can decay through different types
of quenching channels, including the formation of ion-pair states. The collisional
quenching of the OH A2Σ
++ H2 system has already been studied both by computing the potential energy surfaces, and using them to run semi-classical trajectories.
Here, we use it more as a development tool to extend the possibilities of modelling
the dynamics of bimolecular processes.
Firstly, we described the long-range interactions between NO A 2Σ
+ and O2 X 3Σ
−
g
using customized basis sets and the coupled-cluster method. The van der Waals
region of the excited potential energy surface allows one to understand how two
molecules will orientate when approaching each other in cold molecular collisions.
This is important as the induced orientation will condition the subsequent quenching event.
Next, we explored the full dimensionality of the short-range region of the NO +
O2 system by computing up to 29 adiabatic states at the CASSCF and CASPT2
levels of theory. We find two main quenching pathways for NO A 2Σ
++ O2 X 3Σ
−
g
.
Both can produce the overall system in its ground state, as well as excited O2 .
Alternatively, reactive quenching can break the dioxygen molecule to create either
NO2 + O or NO X 2Π+ 2 O3
(P).
Finally, a series of scripts was developed to produce initial conditions and analyse
surface-hopping trajectories for a scattering problem of two diatomic molecules.
The preparation of initial conditions includes the setup of the initial orientation,
the initial rotational and translational velocities, depending on the initial rotational
level, the collision energy, and the impact parameter. The analysis script can sort
the trajectories depending on their final products, and compute the translational,
rotational, and vibrational energies redistributed in each diatomic. These codes were
used to study OH A2Σ
++ H2 molecular scattering with on-the-fly surface hopping
dynamics.James-Watt scholarshi
Accountability relationships and populism in the Greek National Health System. Evidence from the 1980s
Get PDFThe aim of this thesis is to examine accountability in the Greek National Health system
in regard to the emerging managerialism that prevailed in the Western countries since the
1980s. The distinction between political and managerial accountability has been utilised
for the conceptualisation of empirical data. The theory of populism was used in order to
interpret accountability relationships and explain the impact of the political environment
on accountability. Parliamentary debate and the press of the period were examined, and
they demonstrated that populism was a dominant force in the public debate. Populism
was expressed as fierce polarisation on behalf of the government towards the opposition
and it constituted a major way of political accountability. In this context, accounting was
not a part of the legitimation scheme and there was direct clash between populism and
the discourses of accounting. We also examined how this context was transfused into
organisational practices. For this reason, we conducted interviews with people who were
involved in the System. Analysis has shown that populism also had significant impact on
organisations, as it was translated to severe partisanism and created clientelistic networks
which monopolised power. Political accountability infiltrated in organisations through
populism, dominated all aspects of accountability and it was turned to partisan
accountability. As a result, managerial accountability was overshadowed, and it was
never allowed to operate as a system for more efficient control. In fact, managerialism
was victimised as a potential threat to the existing status. This thesis contributes to the
examination of accountability beyond the Anglo-Saxon context, which dominates
scientific literature. Additionally, it provides insights regarding the impact of politicians
on accountability and accounting. Moreover, it proposes populism as a new theoretical
framework for accountability, because it can have significant impact in a specific setting.
Consequently, this thesis aims at further improving the understanding of accounting
within the context in which it operates
Enabling pro-active robotic assistance in activities of daily living
No full textAssistive robots have the potential to support individuals in their daily life and with
their Activities of Daily Living (ADLs) at home. Rather than simply responding to user
commands, proactive robots are able to anticipate, plan, and act to autonomously provide
appropriate support when needed.
This thesis focuses on incorporating Human-in-the-Loop (HITL) techniques for Ambient
Intelligence (AmI) systems with proactive robot assistants. In particular, by: (i) exploiting
the potential of direct and indirect interaction with the system for the purposes of end-user control and to gather feedback; and (ii) learning while online, rather than relying on
a priori data.
A platform for online learning of ADLs is created, allowing the user to manually
‘teach’ samples of relevant ADLs. This is based on a hybrid Markov Logic Network (MLN)
approach to modelling. Following on from this, the issue of long-term learning is
addressed by introducing a novel approach to active learning using conversation and
dialogue. Using semantic similarity measures, a general purpose end-user labelling tool
for ADLs is introduced.
This leads to work on proactive assistance, initially working to understand use
preferences in relation to robot autonomy and interaction during Human-Robot Collaboration (HRC) on ADLs. Findings highlight the importance of human control, and reveal a
divide in opinion over prioritising efficiency versus trust and safety.
A framework for modelling and estimation of Human-Robot Collaboration (HRC)
during ADLs is then introduced. Activity Collaboration Markov Model (AC-MM)s can be
used to represent Human-Robot Interaction (HRI) during ADL and the assistance provided
by the robot relative to the state of the environment. Super AC-MM are probabilistic
representations of learned ADLs with multiple samples, which can be used to estimate
Activity of Daily Living (ADL) state and what help the robot can offer. Practical evaluation
of the system applied to a real-world use case highlights the importance of having the
user ‘in-the-loop’ and highlights the potential of end-user programming
Integration of circular economy strategy as an innovative approach of waste management, within the oil and gas construction projects
Get PDFWaste management within oil and gas construction projects is confronted with significant challenges
due to the industry's complex and large-scale nature, that necessitating a nuanced exploration. The
sector's complexities, characterized by extensive excavation, drilling, and construction undertakings,
contribute to a substantial volume of waste generation. Notably, the presence of hazardous materials
further amplifies the intricacies associated with waste handling and disposal within this industry. The
regulatory landscape adds another layer of complexity, with stringent environmental standards
imposing specific criteria for waste treatment and disposal. Moreover, logistical challenges stemming
from remote project locations and challenging terrains underscore the need for meticulous planning
and resource allocation in waste transportation and disposal. Current linear project delivery methods
deployed in the oil and gas sector predominantly embrace end-of-pipe solutions. These linear
approaches contribute to a heavy reliance on new materials, overlooking opportunities for reusing
construction materials or incorporating sustainable design principles. The lack of integration across
project stages hampers the adoption of circular economy practices, constraining the industry's ability
to shift towards more sustainable and environmentally conscious waste management strategies.
Traditional approaches, including waste sorting, recycling, and landfill disposal, persist despite efforts
to minimize environmental impact.
To provide a contextual background, validate and enhance the research, an assessment of the existing
literature on sustainable construction, waste management strategies was conducted. 15 preliminary
interviews were performed with oil and gas construction project clients, architects, and contractors in
order to identify the construction waste generation challenges related to oil and gas construction
projects. The findings revealed that oil and gas construction projects generate significantly more
waste than other building projects throughout the project lifecycle, identified complex features that
influence waste generation, and identified specific causes of construction waste in oil and gas
construction projects. Similarly, the study discovered various characteristics that shed insight on the
existing practice of the waste management strategy. A deeper investigation was conducted based on
multiple case studies, direct observation, and project documentation analysis to understand the impact
of waste generation due to waste causes, the relationship between complex features in oil and gas
construction projects and waste causes, and best waste minimisation practices to be implemented
throughout the oil and gas construction projects lifecycle to address construction waste causes. During
the data gathering stage, 65 interviews with stakeholders from various case studies were conducted.
The Circular Economy Process Model was then developed based on the findings of the literature
review, the preliminary interview analysis, and the multiple case studies, project documentation,
direct observation, which integrates circular economy principles into the project delivery /
management process. This model is designed to enable the application of the circular economy
concept from the beginning to the end of a construction project and throughout its lifecycle. The
process model was evaluated by 11 industry experts by adopting semi – structured interview to assess its feasibility, functionality, coverage and practicality. The feedback received from the evaluation
demonstrated that the process model is effective in promoting certain aspects of sustainable principles
such as designing for zero waste and encouraging the reuse of project materials and components.
Additionally, the evaluation revealed numerous benefits and potentials of the process model.
In this study, it has been determined that the integration of circular economy principles into the
construction project delivery process can facilitate the reuse of project components and promote a
zero-waste, sustainable environment. The practical outcome of this research is a process model that
can be implemented at all stages of the project management process, enabling the construction
industry to incorporate circular economy principles into their activities. The implementation of this
process model is expected to have a positive impact on the construction industry, as it offers a
solution to reduce the environmental impact of construction activities
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