Heriot-Watt University
ROS: The Research Output Service. Heriot-Watt University EdinburghNot a member yet
4689 research outputs found
Sort by
Additively manufactured kinematic arrays and bond analysis for compact laser diode modules
No full textAbstract unavailable. Restricted access until 31.03.2026. Please refer to PDF
An auto-ethnographic sensorial investigation through woven textiles in the creation of personal memorial to loss
No full textThe research addressed the following questions. Can visual images created through
drawing, and tactile memories from the woven translation of those drawings, connect
the bereaved to personal memories of a lost loved one and to the lived experience of
losing that person? What is the role of narrative in creating a personal memorial to loss,
and how does this differ in the creation of collective memorials to loss? A multi-method
qualitative approach was adopted, combining auto-ethnography with reflexive phases of
drawing, weaving, and writing in reflective journals and on specially designed analysis
sheets. A purposively sampled group of artists articulating loss and grief through their
practice, were compared to the author’s sensorial and experiential interpretation of
personal loss and grief. Study of sensory memory, and materiality of textiles and
garments relating to bereavement, provided contextualisation. A hand-knitted jumper
and Filofax diary belonging to a deceased parent, inspired the research practice: the
vacant jumper acting as a metaphor for the empty space left behind physically and
emotionally when a loved one dies. The first contribution to knowledge showed that the
weaving, when stimulated by the somatosensorial process of manual creation, aroused
and enhanced remembered emotions of the lived experience of losing a beloved parent,
providing greater insight and cognisance of living through loss. The second contribution
was a weave sampling and testing method that could be applied to alternative weave
practice research. A final contribution showed that specificity of individual narrative
differentiated personal memorials to loss from the shared narratives of creative collective
memorials to loss
3D printing-based microfluidics for geosciences
No full textThree-dimensional (3D) printing offers the potential to repeatably generate
porous media for the investigation of pore-scale processes such as CO2
dissolution and species transport in multiscale porous media. However, there
are concerns regarding dimensional fidelity, shape conformity and surface
quality of the 3D printed products, and therefore, the printing quality and
printer limitations must be benchmarked.
Firstly, we investigate the ability to generate porous media with our 3D
printing setup. We show that our 3D printing setup allows for cheap and fast
fabrication of micromodel devices from simple to complicated multiscale
geometries, which enable the ability to perform repeatable single-phase flow
species transport experiments. We use Particle Image Velocimetry (PIV) and
Direct Numerical simulations (DNS) to show how, with our 3D printing setup,
we can generate custom-designed micromodels accurately and repeatably
with minimum pore-throat sizes of 140 µm.
To enhance the management of subsurface engineering processes in
multiscale porous media, containing fractures and matrix, it is crucial to
comprehend the interaction between the larger-scale features (fractures) and
the smaller-scale features (matrix). While models describing fluid flow in
multiscale-porous media exists, it has not been validated experimentally due
to lack of a benchmark experimental dataset. In this work we use 3D printing
to fabricate geometries that encompass both fractures and matrix. We
conduct species transport experiments and generate a benchmark
experimental dataset for single-phase flow species transport in multiscale
geometries. Our findings demonstrate that 3D printed multiscale
micromodels allow for the visualization of species transport propagation in
such geometries, enabling the acquisition of a benchmark experimental
dataset. Subsequently, we use the acquired experimental dataset and direct
numerical simulations (DNS) to validate the multiscale species transport Darcy Brinkman Stokes (DBS) simulations in multiscale geometries
containing both fractures and matrix, which have not been previously
validated. Our research shows how DBS can accurately predict the temporal
evolution of species propagation in these multiscale geometries.
Finally, we use simple 3D printed geometries consisting of a single channel
and dead-end pores to investigate the trapping and dissolution of CO2
bubbles. Dissolution of CO2 bubbles in the pore-space is an important
trapping mechanism during CO2 storage operations, however, a benchmark
experimental dataset of dissolution of CO2 bubbles that could validate direct
numerical models does not exist. We show that repeatable experiments can
be performed in simple geometries and a benchmark experimental dataset for
multiphase flow processes can be obtained. As a result, we developed a
benchmark experimental dataset for validating DNS models describing the
dissolution of trapped CO2 bubbles which have not been before validated
against experimental data. Finally, we use DNS simulations and show that
while DNS can accurately capture dissolution of a CO2 bubble in simple
geometries, such as a dead-end pore and a throat, the current computational
requirements do not allow for simulating more complicated cases
Space-time enriched finite elements for acoustic and elastodynamic problems
Get PDFThis thesis investigates a generalised finite element method for time-dependent elastic and acoustic wave propagation, based on plane-wave enrichments of the approximation space. The enrichment allows good approximation of oscillatory solutions
even on coarse mesh grids and for large time steps. Significant reductions of the
computational cost are obtained in comparison to standard h-version finite element
methods, which are limited by the need for both fine meshes and small time-steps.
For time-independent problems in the frequency domain, such enriched methods
have been shown since the late 1990s to significantly reduce the computational cost
of the numerical approximation of emission and scattering problems.
The proposed method is illustrated for both the acoustic wave equation and
linear elastodynamics and compared with conventional finite element methods. It is
based on a discontinuous Galerkin approach in time and a continuous finite elements
in space. Numerical experiments study the stability and accuracy of the proposed
method and confirm the reduction of the computational effort required to achieve
engineering accuracy.Engineering and Physical Sciences Research Council (EPSRC)
grant EP/L016508/0
Multi qubit gates using ZZ interactions in superconducting circuits
Get PDFIn 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
Capturing the future : modelling CO2 and H2O co-adsorption, processes, and techno-economics for solid sorbent direct air capture
Get PDFDirect air capture will be required to offset hard-to-abate sectors and reduce the overall
CO2 concentration in our atmosphere, as a response to Earth’s rapid warming. However,
direct air capture is especially challenging due CO2’s ultra-low concentrations in air.
Temperature vacuum swing adsorption processes using amine-functionalised adsorbents
is one of the most promising approaches. The synthesis of these materials is well
understood, but the underlying adsorption, in particular the multicomponent CO2 and H2O
interactions, is not. As a result, process modelling of solid sorbent direct air capture is
inadequate. Consequently, the state-of-the-art performance and cost is not understood.
Neither is there a clear path to optimise materials and processes going forwards. This
thesis presents four peer-reviewed published articles that attempt to address these major
challenges for direct air capture using amine-functionalised adsorbents. These include:
1. Comprehensive measurements of CO2 and H2O co-adsorption data.
2. Mechanistic models to predict CO2 and H2O co-adsorption and process
optimisation of a state-of-the-art temperature vacuum swing adsorption
process.
3. Global sensitivity analysis to fully understand where these processes and
materials can be improved going forwards.
4. Techno-economic evaluation of a state-of-the-art benchmark and comparison
to other promising direct air capture technologies.Engineering and Physical Sciences Research Council (EPSRC) fundin
Tracking medical devices using time-correlated single photon counting imaging
Get PDFThe presence of time-correlated diffuse light imaging technologies is growing within the
healthcare space and beyond. Such devices offer desirable light capture ability for application within diffuse light imaging scenarios (characteristic of biological applications)
and their performance is ever-improving, enabled by relentless development in sensor
technology and computational processing techniques. Within this thesis an optical imaging system incorporating time-resolved single photon detector technology has been developed. This system is applied to solve an outstanding clinical challenge, that being, the
misplacement of in-vivo feeding tube devices. Within the context of this clinical need,
this thesis outlines a method of providing spatial information regarding the location of
such in-vivo devices in a non-ionising modality through time-resolved imaging of NIR
light emitted from within the device itself. This thesis describes the development of several unique devices created to enable this medical device location mechanism including
a scanning imaging system offering high resolution time-resolved imaging capability.
This system was deployed within a portable configuration designed for use within clinical settings. Another major piece of hardware development within this work involved
the creation of custom fibre optic probes designed to provide controllable in-vivo light
emission. These two devices were applied in tandem to provide spatial information of
otherwise obscured fibre optic probes within a simple model with a view to providing
evidence for the clinical relevance of such a technique. Subsequently a series of clinically relevant models, including a porcine cadaver model, were used to better constrain
the clinical utility of such a device location technique in the context of the outlined clinical need. Fibre optic probes were packaged within standard medical feeding devices and
used to provide the in-vivo light emission necessary to gain spatial information regarding
the location of the feeding tube within the patient. This testing provided a clear indication of the direct clinical usefulness of the devices and the technique outlined within this
thesis. In a wider sense, the developed hardware could prove beneficial in a number of
non-clinical applications, including within remote sensing, communications and imaging.Science and Technologies Facilities Council (STFC) funded PhD studentship
Developing the next generation of Sediment profile imaging camera system
Get PDFThe Sediment profiling imaging (SPI) camera can be a convenient tool to assess
marine benthic environments. It is possible to study the sediment-animal-water
relationship according to chemical, biological and physical properties on a small
scale of the seafloor. Further, the SPI is and has been used to inform stakeholders in
academia and industry about benthic health, however, potentially associated
artefacts with inserting the camera into the sediment have not been studied yet.
Therefore, it is important to assess the potential artefacts and if necessary, develop
a new generation of SPI cameras or a correction factor for SPI camera use.
This thesis covers two main components, the first part evaluated the impact of
particle displacement of the Sediment profiling imaging (SPI) camera, and other SPI-like devices when inserted into the sediment and potentially associated artefacts.
The second part focuses on overcoming the particle displacement artefacts by
developing new optical sensors that are able to distinguish oxic from anoxic
sediment.
Previous research has shown that inserting SPI-like devices into the sediment can
have an impact on particle displacement by pushing oxygenated surface sediments
to deeper sediment depths, so-called smearing, and subsequently making
anthropogenically-disturbed sediment appear healthier than it may actually be.
The potential particle displacement has been first investigated with two SPI-like
devices in Chapters 2 and 3. First, a laboratory-based testing device, termed the SPI
purpose-built sediment chamber (SPI-PUSH) and second an intertidal field-based
device termed the Dummy SPI. In chapter 4, a real SPI was used to perform in-situ
experiments to assess the potential artefact associated with the SPI system. The SPI-PUSH differed structurally the most from the real SPI system as a flat plate was
lowered in an enclosed space within a laboratory environment. Whereas the
intertidal Dummy SPI was structurally and dimensionally similar to the real SPI and
can be easily deployed in intertidal flats and gather valuable data. The structural
differences between the three systems were taken into account when comparing the
results.
Inert-dyed sediment particles, so-called luminophores were used to demonstrate
the extent of particle displacement caused by the SPI and SPI-like devices being
pushed into the sediment. Pictures of potential particle smearing were taken and
analysed for all three devices. Three different approaches have been used to analyse the particle smearing on the pictures taken: the point measurement, the grid
measurement, and the luminophore coverage (%) per depth row.
Using three different methods to analyse the particle smearing helped to explore
how the analysing method has an impact on the results. In chapters 2 and 3, the
analysing methods used did not differ from each other whereas in chapter 4 the
results differed, therefore, the luminophore coverage per depth row method was
established. Analysing the luminophore coverage for each row parallel to the
sediment surface was the most robust method trialled. The point and the grid
measurement are potentially less accurate. For example, the point measurement
does not account for most of the imaged area, whereas in the grid method any
amount of luminophores in each 0.7 x 0.7 cm grid counted, might overestimate the
particle smearing.
The mean particle smearing measured with the SPI-PUSH directly behind the
inserted plate was 2.9 ± 1.5 cm (mean ± SD, n = 5) for mud sediments with sand-like
luminophores, 4.3 ± 2.5 cm (mean ± SD, n = 5) for fine sand sediments with sand-like luminophores and 1.9 ± 1.1 cm (mean ± SD, n = 5) for medium sand sediments
with mud-like luminophores. The mean particle smearing during the Dummy SPI
experiments was 5.5± 2.2 cm (mean ± SD, n = 12) and 3.7 ± 2.3 cm (mean ± SD, n = 4)
for the real SPI system using sand-like luminophores in sandy sediments.
The data in this thesis shows that future studies using the SPI camera, or any other
periscope-like device, need to acknowledge that smearing may be significant.
Particle displacement of surface sediment could lead to overestimating the apparent
redox potential discontinuity (aRPD) layer. The aRPD is used in environmental
indices like the Benthic Habitat Quality (BHQ) index and could therefore
overestimate the health of the marine environment.
In this thesis, the intertidal Dummy SPI was not only used as a proxy for the real SPI
system. The intertidal SPI was successfully tested to be used as a stand-alone system
to assess intertidal soft sediment environments.
The second part of the thesis focused on developing the next generation of the SPI
camera system (Chapter 5). Chapter 5, therefore explores if a miniaturised optical
sensor can detect oxic and anoxic sediment based on the sediment colour. If an
optical sensor would be able to assess the aRPD reliably the size of the probe would
simultaneously reduce the smearing artefacts. Three different devices were trialled:
the chip, the Tiny SPI and the coupler end. The chip was used with two optical fibres, one to send light into the sediment and one to detect the reflected light. The Tiny SPI
is simpler built using only one fibre and a coupler to send light into the sediment
and detect the light reflected. The coupler end is an even simpler professionally
manufactured version sending light the sediment with one fibre and a coupler as
well as detecting the reflected signal.
The development of an optical sensor that could reliably measure the sediment
colour was more difficult than anticipated. During the development of the sensor,
the original prototype of a chip-based device was simplified to the Tiny SPI and
eventually to the coupler end, to aim for repeatable and reliable data output.
Unfortunately, it was not possible to gain consistent and reliable results. Although
the approach was conceptually valid, the development was not straightforward and
would have required a greater investment of time which lies beyond the scope of
this thesis.
The data of Chapters 2, 3 and 4, successfully showed that particle subduction from
the surface can be significant, with a smearing of up to 3.7 ± 1.2 cm (n = 5) for all
SPI-like devices in varying soft sediments. The results in chapter 4 indicate that the
particle smearing might differ with the sediment grain size. However, the
relationship between sediment grain size and smearing depth needs further
investigation. This could be investigated by utilising the intertidal Dummy SPI
(Chapter 3).
In chapter 5, the attempt to miniaturise the SPI camera for the next generation has
proven to not be as straightforward as expected, however, it provided valuable
information on potential suitable starting points for future research. All three SPI-like devices, the laboratory-based SPI-PUSH, the intertidal Dummy SPI and the real
SPI camera were representative of the actual smearing that takes place when using
real SPI system. Therefore, improving the current existing systems might be more
beneficial than developing a new generation of SPI. Future research should account
for particle smearing when using SPI and SPI-like devices this would additionally
improve the data quality.
Data gathered with any SPI system, if uncorrected for smearing, may lead to
incorrect assumptions regarding benthic health, which could ultimately lead to
inappropriate management decisions
Adaptive Milstein methods for stochastic differential equations
Get PDFIt was shown in [27] that the Euler-Maruyama (EM) method fails to converge with
equidistant timesteps in the strong sense to the solutions of stochastic differential
equations (SDEs) when either of the drift or diffusion coefficients is not globally
Lipschitz continuous. Higher-order methods or schemes that are developed based
on EM, e.g. Milstein method or EM with jumps, inherit the problem.
We introduce an explicit adaptive Milstein method for SDEs with no commutativity condition. The drift and diffusion are separately locally Lipschitz and together
satisfy a monotone condition. This method relies on a class of path-bounded time-stepping strategies which work by reducing the stepsize as solutions approach the
boundary of a sphere, invoking a backstop method in the event that the timestep
becomes too small. We prove that such schemes are strongly L2 convergent of order
one. This order is inherited by an explicit adaptive EM scheme in the additive noise
case. Moreover, we show that the probability of using the backstop method at any
step can be made arbitrarily small. We compare our method to other fixed-step
Milstein variants on a range of test problems.
Secondly, we introduce a jump-adapted adaptive Milstein (JAAM) method for
SDEs driven by Poisson random measure. With the conditions of drift and diffusion
coefficients remaining the same as for the adaptive Milstein method, and the jump
coefficient is globally Lipschitz continuous. The corresponding time-stepping strategies that we propose are hence path-bounded and also jump-adapted. We prove
the L2 strong convergence of order one for JAAM and compare its computational
efficiency with jump-adapted and fixed-step methods on test models
Heterogeneous photocatalysis in flow : technologies for accelerating sustainable synthesis
Get PDFThe global climate crisis has driven society to strive for sustainability across all
industries in order to combat anthropogenic greenhouse gas emissions and pollution. For
over a century, utilisation of solar irradiation has been an attractive but challenging
solution to providing sustainable energy, leading to significant academic and industrial
research and development of a wide range of light harvesting technologies, such as
photovoltaics and, more recently, photocatalysis.
Simultaneously, society is progressing rapidly towards a fourth industrial
revolution, with automation, robotics, artificial intelligence, and machine learning being
broadly adopted throughout industry and academic research. Within chemistry, these
technologies are driving the development of automated synthesis platforms that can
rapidly perform and analyse chemical reactions, quickly exploring a vast chemical space
to find optimised conditions. Enabling technologies for synthesis, such as flow chemistry
and in-line process analytical tools, are critical to these efforts as they provide the physical
means to automate altering reaction conditions and data collection which enable machine
learning algorithms to search chemical space and self-optimise.
The combination of heterogeneous photocatalysis and enabling technologies is a
promising strategy to provide sustainable and continuous photosynthetic processes for the
chemical industry. However, the efficiency of heterogeneous photocatalysts remains a
significant challenge that must be overcome through material design and reactor
engineering. Within this thesis, we discuss our recent contributions to this field, including
the development of new polymer-supported photocatalyst materials which share
advantages of both homogeneous and heterogeneous photocatalysts. Additionally, we
demonstrate enabling technologies such as flow chemistry, additive manufacturing, and
in-line analysis as powerful tools for enhancing heterogeneous photocatalysis.
Furthermore, we present the development of an entirely new technology for automated
flow (photo)synthesis and purification: in-line flash chromatography
Access Repository Dashboard
Do you manage ROS: The Research Output Service. Heriot-Watt University Edinburgh ? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!