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Advanced RF/microwave filtering circuits for wireless communications and radar applications.
Get PDFThe recent rapid development in modern communication systems has presented some
constraints caused by the introduced noises, as well as further requirements of low costs
and miniature designs. Such noises are overcome using efficient designs of filtering devices
which are essential components in many satellite, radar and mobile communication
systems. As a result, balanced or differential filtering components have recently received
increasing attention. A wideband microstrip balanced bandpass filter based on modified
stub line approach is presented in here. The proposed idea of extended transmission lines
(TLs) at the input and output (I/O) ports enables for very good stopband rejection and
common-mode suppression.
On the other hand, the recently introduced multilayer liquid crystal polymer (LCP) material
and fabrication technique are exclusively applied in this work for adapting the potential
solutions offered within. Therefore, a comprehensive in-house fabrication process has been
developed and extensively illustrated in this thesis starting from mask preparation covering
the entire procedure up to producing the final piece of output. As a demonstrator of the
potential capability of multilayer LCP technology, a novel miniaturized ultra-wideband
(UWB) balun with self-packaging is introduced in this study. The broadside coupled
stripline structure is adopted in this work to realize UWB performance and TEM mode
which results in excellent amplitude and phase balances.
In turn, a novel compact UWB multilayer balanced bandpass filter using LCP technology is
also presented in this thesis. The design utilizes the transversal signal-interference concept
for realizing an outstanding common-mode suppression while constructed in a stripline
configuration. All of the designs covered in this thesis are initially simulated using CAD
tools to be then validated by measurements of fabricated prototypes
Sampling, rendering, and denoising light fields for challenging environments
Get PDFLight field imaging is an important area of image-based rendering (IBR) that
is on the cusp of becoming an important area in the field of robotics. While born
into the field of graphics, light fields have evolved into and taken the form of high
resolution depth sensors that can simultaneously generate high quality views of a
subject.
Modern focused light field cameras are capable of capturing video at over 160
frames per second (FPS) and producing depth at half that rate. These modern
light field cameras have demonstrated impressively high resolution depth results,
with much of the appeal being in that it is a passive, single sensor system with the
ability to generate depth from a single shot. However, with such high framerates,
the amount of light collected decreases, affecting light field rendering and depth
estimation processes.
The objective of this thesis is to build upon existing work in light fields and
robotics. We compare methods for collecting light fields and develop a system
around focused light fields that makes them more robust to challenging conditions,
particularly in very low-light scenarios.
Our first contribution explores the usage of robotic platforms for collecting light
fields using a traditional, 2D camera and compares localization accuracy with popular visual techniques such as structure from motion (SfM) and simultaneous localization and mapping (SLAM)
We shift our focus for our second contribution to the sensor that said robot might
be equipped with, in this case a focused light field camera. We develop a method
based on deep learning that allows for enhancement of low-light light fields captured
under a time constraint. We build upon this by developing a simple algorithm that
generates smooth light field video in the absence of a reference video. To accomplish
this we also create two datasets: one containing low-light light field stills at various
shutter speeds, and another containing low-light light field videos captured at a
single shutter speed. In our third contribution we further build on the work of the previous contribution by exploiting unique aspects of the light field. In particular, we develop
a network that can learn depth from the low resolution microlens images (MLIs)
that make up the focused camera light field. As well, we develop a deep neural
network (DNN) that takes into account the light field context and angular feature
redundancies, taking inspiration from burst denoising methods for single shot light
fields.
In conclusion, we show that robot platforms are the best platforms for sensor
placement in light field acquisition and set a standard where none existed in low-light
focused light field enhancement
Photonic lantern imaging
Get PDFThe photonic lantern is an adiabatic transition from an array of single-mode waveguides
to a single multimode waveguide, which has found use historically in astrophotonics as a
reformatter of light from multimode to single mode, facilitating advanced instrumentation,
and in communication networks to allow better coupling and spatial multiplexing. The device has never before been used for imaging, but is suited to certain forms of compressive
sensing.
Light is coupled into each of the singlemode waveguides at the input to a multicore fibre
photonic lantern, producing intensity patterns at the output of that lantern which are stable
to bending, and which are used as the sampling basis for a variant of compressive imaging
related closely to ghost imaging. Improvements to such imaging modalities require a
greater number of modes to be excited simultaneously, requiring a lantern with stable
polarisation properties.
With the aid of a de novo fabricated integrated lantern custom-manufactured for such
tuned properties, more advanced techniques are explored. These include coherent combination of mode patterns to increase the possible sampling basis, as well as more complex techniques of beamshaping at the lantern output facet through holographic projection.
These proofs-of-concept of the novel imaging techniques show the previously undiscovered value of photonic lanterns in the field of imaging, and their promise for endomicroscopy systems
Understanding and improving through mobile technology users’ experience of bladder training
Get PDFIn 2018, 20.1% of the worldwide population was affected by the Overactive Bladder
(OAB) condition. Although treatable, it remains undertreated and undiagnosed. Since
mobile health applications are increasingly being used to support people during self-managed treatment, a smartphone could be the ideal technology for an OAB mobile health
application. This research aims to investigate whether a mobile health application could
be an appropriate tool to help people suffering from OAB symptoms increase their
adherence to self-managed treatment and raise awareness of symptoms.
The research conducted in this thesis began with a detailed literature review, followed by
requirements gathering interviews with healthcare professionals and co-design interviews
with people suffering from OAB symptoms (end-users). Based on the literature review
and requirements gathering findings, a first application prototype was designed and
developed. As part of an iterative design process, interviews were later carried out with
the same two stakeholder categories to evaluate the prototype and understand how the
user interface and the interaction with the functions can be improved. Following the
prototype interview findings and a second development phase, the application was
evaluated during a short field study of nine days with end-users. The study aimed to
understand whether using the application in a real-life context has an impact on how end-users view it and if the application contains any outstanding usability issues. Following
the short field study findings and a third development phase, a six weeks uncontrolled
field study was conducted with end-users. The aim was to determine whether the
application has the potential to raise awareness of symptoms and help people adhere to
self-managed treatment.
The research presented in this thesis is the first known attempt of investigating how a
mobile health application could actively support people suffering from a sensitive
condition such as OAB. This investigation uniquely involved people suffering from OAB
symptoms in the design and evaluation studies. This thesis provides contributions to the
Human-Computer Interaction field by showing that gender is an important factor that
needs to be considered when gathering design ideas with people suffering from a sensitive
health condition. This thesis also makes design recommendations, that could potentially
be applied to other mobile health applications for sensitive health conditions. Moreover,
it demonstrates that a mobile health application has the potential to help people adhere to
OAB self-managed treatment and raise awareness of symptoms
Vascular flow modelling for the development of ultrasound contrast imaging
Get PDFContrast Enhanced Ultrasound imaging is a safe, reliable, and inexpensive diagnostic
method that can provide information on the vascularisation of an organ and is currently
applied in a range of diagnostic protocols. This thesis combines the fields of mathematical
biology for vascular network modelling with Contrast Enhanced Ultrasound and with
Super Resolution Ultrasound to expand the range of diagnostic applications in different
conditions. The fact that microbubbles are intravascular agents allows the study of
diseases that affect organ vascularisation like obstructions and tumours. Under this scope,
vessel networks with certain blood flow conditions and dedicated, large scale organ
vascularisation models were constructed, with and without the aforementioned
pathologies, and their impact on organ perfusion was studied. Then, Contrast Enhanced
Ultrasound imaging was applied on microbubble flow through these vascular networks
and the results were compared to the readily available ground truth results. The novelty
of this approach lies on combination of the two fields: the mathematical biology models
allowed the systematic comparison of healthy organs and of disease on ground truth level,
thus allowing the investigation of ultrasound parameters that can be improve image
quality or be used as diagnostic markers. The results showed that the use of SRU provides
useful information on the structure (recovery of vessel radius) and rheological properties
of microcirculation which can be used for early detection of disease
Faunal biodiversity and food-web structure of organic falls in the deep sea
Get PDFThis thesis assesses and compares biodiversity and ecosystem functions such as trophic
structure, biological traits and production surrounding different kinds of deep-sea organic
fall, using in situ experiments and novel scientific techniques. Benthic lander technology
was used to deploy experimental substrates (wood blocks and kelp parcels) into a deep
Norwegian fjord, and fish carcasses to 4300 m in the north eastern Pacific Ocean, to
investigate benthic ecosystems. The concepts of anthropogenic disturbance are explored
such as food subsidy removal and complete habitat loss due to deep-sea mining activity.
Extensive kelp harvesting in Norway, coupled with kelp forest loss from climate change,
is likely to greatly reduce transport of this important food subsidy to deep fjord
communities. This is contrasted by success in terrestrial reforestation – the area covered
by boreal forests in Norway has tripled in the past 100 years, inevitably increasing the
amount of wood debris that makes its way to deep fjords. Strong evidence was found for
the importance of kelp detritus in deep fjord ecosystems. There was a high dietary
dependence on kelp and the potential for a multilevel trophic structure based on kelp as a
primary source of carbon. Wood falls were found to be an important habitat for a unique
community of fauna, including some specialists that completely depend of them.
However, wood does not appear to act as a like-for-like substitute for kelp detritus and an
increase afforestation will do little to mitigate the effects of kelp loss. Secondary
production for both wood and kelp falls was found to be higher than that of shallower,
soft sediment sites in European seas.
Results from a simulated fish fall experiment in the Clarion Clipperton Zone, an area
marked for deep-sea mining, revealed a relatively high diversity of benthic scavengers in
the German license area. The community of scavengers was significantly different to
those of adjacent areas, even when they were situated a short distance away (< 20 km).
Power analysis revealed that as few as 10 baited-camera deployments are required to gain
a good understanding of the communities living within an area. When attempting to
mitigate the effects of deep-sea mining, careful consideration must be given to the scale
over which baseline and monitoring studies are carried out
Limit properties of stochastic multiple access networks
Get PDFStochastic multiple-access networks are systems in which services are randomly requested by multiple users, and often simultaneously. We analyse such a system, where
we assume that each node of the network receives a random number of new packets
within each time slot and transmits them according to the centralised slotted Aloha protocol. We construct a new model for the workload in the system, while taking into account the one-way spatial interactions that occur at nodes that are simultaneously in activity at a relatively small distance apart. Our new model is a time-homogeneous and
irreducible Markov chain on a countable state space. We investigate the stochastic stability, the instability, and the partial stability properties of the network and obtain appropriate conditions on the mean number of new packets. For the latter two properties,
we consider single-node and two-node networks and make some conjecture for a higher
number of nodes. Our proofs are mainly based on the drift analysis approach. We also
study the large deviations asymptotics for the stationary workload in a single-node network and obtain new results. Besides, we obtain the stationary distribution for single-node and two-node networks in particular cases
Development of mid-infrared laser sources with atmospheric turbulence resistance
No full textAbstract and full text not available - restricted until 01.12.2025. Please refer to PDF
Development of new organic synthetic methods using photoredox catalysis, gold catalysis and metal-free reactions
Get PDFThis thesis describes the work undertaken on three projects throughout the period of
study. Due to the diverse nature of the topics covered, the traditional introductory chapter
has been forgone in favour of a longer introductory section at the beginning of each
chapter outlining the research carried out by the author.
Chapter 1 outlines the successful development of a dual copper- and photoredox-catalysed C(sp2
)-C(sp3
) cross-coupling between benzyl bromides and aryl boronic acids.
Under the developed conditions, this challenging transformation is achieved under mild
conditions using a cheap copper catalyst, which is less toxic than the commonly used
nickel alternatives.
Chapter 2 details efforts to synthesise biologically relevant unsymmetrical 3,3′-
bis(indoloyl)methanes through control of the selectivity of Au(I)-catalysed
hydroarylation of alkynes with indoles. This resulted in the first reported Au(I)-catalysed
hydroarylation of alkynes with indoles which is selective for the monoarylated vinyl
indole product. Following this success, the reaction was also developed into an efficient
telescoped protocol for the synthesis of unsymmetrical 3,3′-bis(indoloyl)methanes, which
provided these difficult to access compounds in good yields with no intermediate
purification.
Chapter 3 describes the development of a metal- and light-free protocol for the
hydrodecarboxylation of alkyl carboxylic acids. The reaction benefits from using cheap
reagents, having fast reaction times and mild conditions. It also circumvents the need for
the addition of an exogenous hydrogen atom donor in the case of most substrates. The
transformation was also shown to be compatible with visible-light photocatalysis,
providing a complementary method to promote the reaction.Engineering and Physical Sciences Research Council (EPSRC
Vibrationally-assisted collective quantum optical effects
Get PDFThis thesis considers a variety of systems which are designed to take advantage of
collective optical effects in the presence of a vibrational environment; a necessary
condition for such systems to exist on a quantum platform outside of superconducting qubits. The first research chapter considers the effect of superabsorption, the
time-reversed process of Dicke superradiance. A series of conditions for a guide-slide superabsorber are proposed, which allow a system to sacrifice some optical
coupling for the benefit of still operating when coupled to a phonon bath. We suggest a system geometry which meets these properties, and then use this as a case
study to show such a system does indeed display the hallmarks of superabsorbing
behaviour. This remains when disorder is introduced to the system, as well as with
a strongly-coupled vibrational environment in the polaron frame, amongst several
other model extensions. The second research chapter looks at optical ratcheting,
a process whereby an artificial light-harvester with an extraction bottleneck can
improve performance by relaxing to a state which is dark with respect to optical
relaxation, while still being able to absorb more photons. We examine how the
performance scales with system size before looking at how the phenomena performs
in the polaron frame. While strong vibrational coupling can be the undoing of collective optical effects, we find that it is still possible to observe ratcheting in the
strong-coupling regime. We use the model as a platform to investigate more accurate means of incorporating extraction via a trap, by treating it as an additional
dipole in the system. This change means one needs to consider both the optical
and geometric properties of the trap to achieve optimal performance. The third
research chapter stems from collaborative work with quantum biologists. We study
the recently resolved structure of a photosynthetic complex, iron stress-induced protein A (IsiA), to establish if the structure allows the complex to utilise vibrational
relaxation into a collectively dark delocalised state to reduce the likelihood of loss.
By distorting different components, we establish which parts of the structure this
effect is susceptible to changes in, providing insight into the function of the complex.
Finally, the fourth research chapter investigates the feasibility of using a molecular
aggregate of two identical absorbers as a gain medium in a laser. With adequate
control of the geometry, we show that the combination of collective optical coupling
and rapid vibrational relaxation make population inversion possible. By coupling a
disordered collection of such systems to a resonant cavity, we demonstrate that a
stable laser field can be generated. The results of this work support an approach
derived by our collaborators, allowing larger, more complex aggregates to be used
instead, which require less fine control over the molecular geometry to achieve lasing
behaviour.Scottish
Condensed Matter Centre for Doctoral Training (EPSRC grant no. EP/L015110/1
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