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Transient frequency modulation absorption spectroscopy as a probe of gas-liquid scattering
Get PDFThis thesis reports the first investigation of gas-liquid scattering dynamics via
transient frequency modulated absorption spectroscopy (TFMAS). Using this
technique in the near infrared (NIR), the inelastic scattering of gaseous CN(X
2Σ
+)
radicals from fluorinated and aliphatic liquid surfaces was found to be
predominantly impulsive. These experiments also demonstrated the first
application of a glow discharge to produce supersonically cooled CN(X) radicals in
situ. A large fraction of these incident radicals was lost on contact with the
potentially reactive hydrocarbon, most probably to hydrogen abstraction to form
HCN. Subsequently, an entirely new TFMAS probe, with the capabilities to observe
this unseen channel, was built to access the mid-infrared (MIR) region. Difference
frequency generation (DFG) of tuneable NIR and single-frequency 1064 nm lasers
was performed in periodically poled lithium niobate (PPLN) to generate the MIR.
This probe was characterised by proof-of-principle experiments, including
preliminary studies of inelastic CH4 scattering, and found to be sensitive,
narrowband and possess Gaussian mode-quality. Accompanying Monte-Carlo
simulations of both NIR- and MIR-TFMAS experiments supported the mechanistic
conclusions drawn for CN(X) scattering and indicated that modifications to the CH4
experiments, including improvements in the signal-to-noise, are required to observe
scattering in individual quantum states. On their implementation, the new MIR
probe may then be used to investigate both inelastic and reactive interactions of
innumerable interesting and relevant gas-liquid systems via the ubiquitous
fundamental vibrational modes of closed-shell species, such as C–H, N–H and O–H
stretches
The role of the audit partner in the auditor-client economic bond, auditor rotation and auditor workload
Get PDFThis thesis contains the outcome of three separate, but interrelated, empirical analyses on
the role of the individual audit partner in the auditor-client economic bond, auditor
rotation and auditor workload.
The first analysis examines the demand and supply factors associated with the
role of the audit partner in the auditor-client economic bond. Specifically, the study
examines whether (1) high fee-paying clients consider audit partner quality when
appointing an auditor and (2) audit partners compromise their independence for
economically important clients. The findings show that, while audit partners influence
audit outcomes, clients do not pay above the expected audit fees, either to select low-quality partners to enable them to manage their earnings, or high-quality partners as a
way of signalling the strength of their financial statements. The results also show no
evidence to suggest that partners compromise their independence for economically
important clients, in spite of the possible rewards attached to how much revenue they
generate. Together, the findings support the suggestions that the increased regulation of
partner activities and improved corporate governance, within the UK, has lessened
concerns regarding excessive fees and low audit quality.
The second empirical analysis examines the cost/benefit consideration of the
requirement for a mandatory partner rotation, with (without) a simultaneous firm change.
Prior research conducted on mandatory auditor rotation has been focussed either at the
partner or firm level, without recourse to the net incremental benefits (cost) associated
with the requirement for both layers of rotation over a single rotation rule. Given the
long-standing debate regarding the relative benefits of mandatory auditor rotation, this
study aims to provide key contributions that will help to advance policy formulation on
the subject. The findings of the study show that the requirement for mandatory partner
rotation, without a simultaneous firm change (single rotation), helps to control
opportunistic earnings management. In addition, the study observes that, while there
exists no evidence of audit quality improvements when mandatory partner rotation is
required concurrently with a firm change (dual rotation), there is a significant increase in
audit fees. Taken together, these findings provide evidence that the requirement for
mandatory partner rotation (but not firm rotation) is associated with increased audit
quality. Moreover, the requirement for dual rotation, while offering no improvements to
audit quality, could lead to increased audit fees - a key reason as to why dual rotation is
not practiced universally. The third and final empirical analysis of this thesis examines the role of the audit
partner workload in the audit committee’s auditor selection and retention process.
Policymakers posit that the agreement and use of key audit quality indicators by auditing
stakeholders could provide insights into the principles of audit quality, whilst also
creating incentives for competition that will enhance audit quality. Highlighting the
informational value of partner workload in the audit committee’s auditor selection and
retention process, policymakers have called on researchers to examine the validity of such
indicators in relation to improving audit quality. This section represents a response to
this call, by examining the association between audit committee effectiveness (size,
independence, and expertise) and audit partner workload. The findings show that two
(size and independence) out of the three measures of audit committee effectiveness are
positively associated with partner workload. The findings from the study provide novel
evidence of the signalling ability of partner workload in the auditor selection process.
Drawing on the existing literature on partner workload, the findings suggest that a heavy
workload could be indicative of a partner's ability to manage multiple clients and to
perform high quality audits.Department of Accountancy, Economics and Finance at Heriot-Watt University Scholarshi
Improved field scale simulations of Low Salinity Waterflooding using analytical solutions, numerical analysis and upscaling
Get PDFLow Salinity Water Flooding (LSWF) is an emerging enhanced oil recovery (EOR)
process that has been increasingly studied due to its potential to reduce residual oil saturation
in oil reservoirs. This thesis focuses on modelling LSWF at the field scale. In particular, it aims
to improve the representation of flow behaviour and solute transport at the inter well scale. We
present in depth analyses of numerical issues that may appear in LSWF simulations and derive
two novel upscaling methods.
A black oil simulator was used to model this process where the research focused on the
fluid flow behaviour at the reservoir scale rather than the underlying mechanism. Two sets of
relative permeability were used to simulate the process. Switching from one set to another was
salinity dependent. The flow behaviour was first examined in 1D homogenous models. Then,
2D-layered models were studied. Also, we investigated models where permeability and
porosity were randomly distributed.
We found that an interaction between dispersion and effective salinity range led to a
retardation in the fractional flow solution of LSWF with an outcome similar to that produced
from adsorption in polymer and other cEOR models. We suggest an empirical correlation to
predict that effect which was derived later by linking the fractional flow solution with the
advection-dispersion equation. Also, we observed that salinity was transported faster than
predicted by the traditional advection-dispersion equation. We modified the advection dispersion equation to capture the advection velocity of the salinity front. We extended the
fractional flow solution of chemical flooding and the advection dispersion equation from 1D to
2D non-communicating layers where in such systems the frontal velocities vary as a function
of time. We found that dispersion induced by geological heterogeneity affects fluid flow in a
manner similar to numerical dispersion. Thus, we can use the numerical dispersion as a proxy
for the effects of physical dispersion.
In terms of the numerical issues, we found that LSWF models resulted in pulses, false
retardation and overestimated recovery factor. Pulses were apparent for stable numerical
solutions. We analysed the parameters that induce numerical error and examined the resulting
errors which were reduced by upscaling. Two upscaling methods were developed in this thesis
where these methods succeeded to control the numerical issues for coarse scale models so that
the production data matched the fine scale models. A simplified modelling process is another
outcome of this upscaling method where one can use the traditional water flooding models to
simulate LSWF
Speech dereverberation and speaker separation using microphone arrays in realistic environments
Get PDFThis thesis concentrates on comparing novel and existing dereverberation and speaker
separation techniques using multiple corpora, including a new corpus collected using
a microphone array. Many corpora currently used for these techniques are recorded
using head-mounted microphones in anechoic chambers. This novel corpus contains
recordings with noise and reverberation made in office and workshop environments.
Novel algorithms present a different way of approximating the reverberation, producing results that are competitive with existing algorithms.
Dereverberation is evaluated using seven correlation-based algorithms and applied to two different corpora. Three of these are novel algorithms (Hs NTF, Cauchy
WPE and Cauchy MIMO WPE). Both non-learning and learning algorithms are
tested, with the learning algorithms performing better.
For single and multi-channel speaker separation, unsupervised non-negative matrix factorization (NMF) algorithms are compared using three cost functions combined with sparsity, convolution and direction of arrival. The results show that the
choice of cost function is important for improving the separation result. Furthermore, six different supervised deep learning algorithms are applied to single channel
speaker separation. Historic information improves the result. When comparing
NMF to deep learning, NMF is able to converge faster to a solution and provides a
better result for the corpora used in this thesis
Understanding distribution in homelessness policy : a normative exploration of the differential treatment of homeless households in England, Scotland and Wales.
Get PDFThe social problem of homelessness evokes strong ethical responses but the role of values in this
area has been relatively underexplored. This thesis responds to calls for more normatively engaged
work in homelessness and housing studies by using concepts from distributive justice to explore the
different entitlements of three sub-groups of homeless households (families with children, young
people, and single people) under contemporary homelessness policy in England, Scotland and
Wales. This work aims to improve conceptual clarity regarding normative principles relevant to
homelessness policy, generate empirical evidence of how these principles apply to and interact
within contemporary policy, and develop an evaluative framework through which normative
elements of homelessness policy can be critically assessed.
Underpinned by the critical realist position that ‘invisible’ social phenomena such as normative
perspectives can have a causal impact on empirically identifiable social realities, the thesis draws
upon scholarship from within moral and political philosophy to identify normative grounds for
affording different levels of support or entitlements to different types of homeless household. Six
principles in particular emerge as relevant to different positions in homelessness policy: need,
desert, vulnerability, utility, rights, and equality.
The relationship between these principles and contemporary homelessness policy in England,
Scotland and Wales is explored through primary empirical work, including analysis of key policy
documents and in-depth interviews with thirty-eight key informants. This evidence shows how these
plural values are balanced differently across the three nations, with an emphasis on responding to
acute need in England, a rights-based approach in Scotland, and a distinct split between these
‘selective’ and ‘universal’ positions in Wales. The combination of national homelessness systems and
UK-wide welfare policy produces three distinct household groups: families with children, whose
vulnerability and ‘blamelessness’ underpins strong protections; young people, conceptualised as
vulnerable but offered only ‘patchy’ support; and single adults, historically deprioritised but gaining
increasing policy attention motivated by principles of equality and concern about acute need.
The thesis develops three tools for evaluating the defensibility of these relationships in normative
terms: assessments of internal consistency, theoretical coherence, and reasonableness in the
context of pluralism. Viewing homelessness policy through these different lenses demonstrates how
a normative perspective can uncover sites of conflict, reveal policy areas ripe for change, and
indicate directions of travel that could resolve tensions between principles and practice. In
particular, the thesis highlights a shifting and perhaps diminishing role for the principle of desert in
relation to homelessness and incremental moves towards ‘universalist’ policy in this area.
The work contributes to a growing body of scholarship applying normative ideas to homelessness. It
offers novel strategies for understanding and engaging with normative issues in homelessness policy
and demonstrates how this kind of normative work can aid in mapping the policy landscape, offering
conceptual clarity that supports identification of themes and distinctions between positions. This
forms a strong position from which to evaluate different policy approaches, comparing them against
criteria such as established moral positions or consistency with the policy’s stated aims, and enables
practitioners and policymakers to take account of the moral and social context when determining
future directions.Economic and Social Research Council (ESRC) funding
Analysis and origin of characteristic aroma of whisky matured in ex-red wine casks
Get PDFTraditionally, ex-bourbon and ex-Sherry casks are used for maturation of Scotch whisky.
Recently however, maturation in other types of cask such as ex-red wine casks or rum
casks has become popular as a method to extend the flavour profile. For example,
whisky matured in ex-red wine casks has a characteristic, strawberry-like, sweet and sour
aroma. We have investigated the key components of the characteristic sweet aroma
imparted during ex-red wine cask maturation using fractionation techniques and mass
spectrometry-olfactometry (GC/MS-O). The results of fractionation experiments
showed that the sweet aroma was found in the neutral and mid-polar fraction. The
results of GC/MS-O analysis of the neutral and mid-polar fraction showed that
2-heptanone, 2-nonanone, 1,1-diethoxyethane, diethyl succinate, γ-nonalactone and
trans-oak lactone provided sweet, fruity and green aromas and were present at higher
concentrations in ex-red wine cask matured whisky compared to remade hogshead cask
matured whisky. In addition, spiking tests revealed that whilst each of these compounds
individually contributed to the sweet character, it was the combination of all these
compounds that gave more complexity and was closer to the target ex-red wine cask
character. Furthermore, whilst acidic compounds such as acetic acid, propionic acid,
ethyl lactate and 3-hydroxy-2-butanone did not have a sweet aroma, they did enhance this
aroma and the ex-red wine cask maturation character. Therefore, these results suggest
that the characteristic aroma of whisky matured in ex-red wine casks is complex and
attributable to several different compounds
Novel structural details to mitigate progressive collapse in steel nominally-pinned joints
Get PDFSteel structures are frequently used worldwide. The beam-column connections play a vital
role in those structures. In a case of column removal due to blast, fire or vehicle impact,
the disproportionate collapse can occur if the robustness of the joint is not enough and the
failure propagates to other members. Current design practices require that the beam-column joints shall withstand a minimum tie force to prevent progressive collapse.
However, several pieces of research have shown that nominally pinned joints which are
commonly used in steel frames cannot provide the required tie force while undergoing
significant rotations imposed by a column removal event. The present thesis proposes a
set of novel structural detail to be added to the steel nominally pinned joints to arrest
progressive collapse by enhancing both their tensile resistance and rotation capacity. The
proposed structural details exploit the exceptional strength and ductility of Duplex
stainless steel pins (SSPs) under bending which allows them to withstand excessive
deformation prior to their fracture. First, the monotonic fracture capacity of SSPs was
experimentally evaluated followed by the calibration of numerical models with the
capability of predicting fracture of SSPs. Employing the calibrated numerical models, a
set of parametric study was carried out on various geometry properties of SSPs to develop
a design procedure to reliably achieve the required levels of tie force and rotation in a
joint. An experimental programme including static and dynamic tests on the proposed
joint was presented, discussed, and simulated in Abaqus. In addition, more analyses were
conducted to determine the Dynamic Increase Factor (DIF). Finally, the proposed joint
was modelled as a 3D connection including the primary and secondary directions. It was
observed that the proposed joint significantly increases the joint rotation while providing
appreciable tie force compared to standard fin plate connection.Heriot-Watt University scholarshi
Development of a novel bio-ink for 3D bioprinting liver tissue models
Get PDFGiven the essential biological role the liver plays, reliable and reproducible in vitro models are
vital for furthering research in many fields. The current in vitro liver models have limitations,
most often that they are two-dimensional and lack critical architectural features of the endogenous
liver. The goal of this research project was to utilise stem cell-derived hepatocytes, and the cancer
cell-line HepaRG, to develop a 3D tissue model that can be bioprinted in a high throughput
manner.
Initial experiments with human embryonic stem cells (hESCs) resulted in high levels of cell death.
Robust viability of encapsulated hESCs was achieved by first generating hESCs before
encapsulation. Preliminary differentiation of hESCs within the alginate was inefficient soit was
necessary to adapt the differentiation protocol for stem cell-derived hepatocytes. This was
achieved by preloading the alginate with growth factors andelongating the initial differentiation
step.
Identification of porous hydrogels was essential for permeation of crucial growth factors
throughout the bioprinted structures to control differentiation. Carboxymethyl cellulose was
identified as producing the most porous hydrogels in combination with alginate, determined
through the leaching of fluorescent proteins from the gel.
The previous results were translated to the liver cell line, HepaRG cells. The carboxymethyl
cellulose and alginate composite supported the highest function from the HepaRG cells. This
bioink of encapsulated HepaRGs was then bioprinted in a high throughput manner into 96 well
plates using a custom designed 3D model. These HepaRG-laden structures were subsequently
used for a hepatotoxicity drug assay. The structures showed expected levels of hepatotoxicity in
response to these molecules.
This work demonstrated the feasibility of generating reproducible and reliable liver tissue in vitro,
which could be used for mid to high throughput research
The future of plug-in hybrid passenger cars in Europe
Get PDFThis research study establishes the most likely scenarios for which plug-in hybrid
passenger vehicles will be used as company cars within the European Union by 2035.
Due to increasing oil costs and environmental unpopularity of the normal diesel or petrol
engine car, it is expected that the electric car will eventually take over. However, electric
cars still have major challenges to overcome with limited mileage range between charging
intervals and sparsely located charge points from which to recharge the car battery. For
this reason, the plug-in hybrids, which have both electric and petrol/diesel power options,
have the potential to begin replacing the normal combustion engine car while providing
some of the cost and environmental benefits of the electric car not yet sufficiently
developed.
Using the Delphi method and the expert knowledge of stakeholders in the automotive and
company car fleet sectors; this study has obtained their privileged viewpoints on various
future scenarios for plug-in hybrids. These viewpoints, following some statistical
analysis, were shared anonymously among an expert panel to facilitate further discussion.
The results were then reviewed and used to create an interview guide in order to carry out
semi-structured interviews with fifteen ‘subject matter experts’. Interview transcripts
were subject to thematic analysis from which themes were derived and final scenarios
concluded the future of plug-in hybrid cars in the European company car fleet. Results
indicated a mixed model of passenger cars power chains by 2035, with plug-in hybrids in
a declining market. Fully electric cars dominate, with a minority, but growing share of
the market, going to hydrogen vehicles. Cars powered by hydrogen fuel cells will
eventually disrupt the entire European car market in the 2040s, as hydrogen gas becomes
more efficiently produced.
Understanding the potential for plug-in hybrid technology as the next market innovation
disrupter in the car industry and developing a methodology from which to research this,
makes an important theoretical contribution to research on emerging car technologies. It
also fulfils the current knowledge gap that exists regarding diffusion of this technology
platform in the automotive and financial leasing markets. It provides valuable direction
to passenger car fleet providers and car manufacturers alike, as they struggle with new
technology innovations in the automotive sector and with investment strategies required
to make the proposed transition to electric vehicles
Robust dense visual SLAM using sensor fusion and motion segmentation
Get PDFVisual simultaneous localisation and mapping (SLAM) is an important technique for
enabling mobile robots to navigate autonomously within their environments. Using
cameras, robots reconstruct a representation of their environment and simultaneously
localise themselves within it. A dense visual SLAM system produces a high-resolution
and detailed reconstruction of the environment which can be used for obstacle avoidance or semantic reasoning.
State-of-the-art dense visual SLAM systems demonstrate robust performance and
impressive accuracy in ideal conditions. However, these techniques are based on requirements which limit the extent to which they can be deployed in real applications.
Fundamentally, they require constant scene illumination, smooth camera motion and
no moving objects being present in the scene. Overcoming these requirements is not
trivial and significant effort is needed to make dense visual SLAM approaches more
robust to real-world conditions.
The objective of this thesis is to develop dense visual SLAM systems which are
more robust to real-world visually challenging conditions. For this, we leverage sensor
fusion and motion segmentation for situations where camera data is unsuitable.
The first contribution is a visual SLAM system for the NASA Valkyrie humanoid
robot which is robust to the robot’s operation. It is based on a sensor fusion approach
which combines visual SLAM and leg odometry to demonstrate increased robustness
to illumination changes and fast camera motion.
Second, we research methods for robust visual odometry in the presence of moving
objects. We propose a formulation for joint visual odometry and motion segmentation
that demonstrates increased robustness in scenes with moving objects compared to
state-of-the-art approaches.
We then extend this method using inertial information from a gyroscope to compare the contributions of motion segmentation and motion prior integration for robustness to scene dynamics. As part of this study we provide a dataset recorded in
scenes with different numbers of moving objects.
In conclusion, we find that both motion segmentation and motion prior integration
are necessary for achieving significantly better results in real-world conditions. While
motion priors increase robustness, motion segmentation increases the accuracy of the
reconstruction results through filtering of moving objects.Edinburgh Centre for RoboticsEngineering and Physical Sciences Research Council (EPSRC
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