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Additive manufacturing of novel metal microwave components for space application
No full textThis thesis presents the design of novel waveguide components, including filters and
antennas specifically adapted to Additive Manufacturing (AM). The design freedom of
3-D printing allows passive components to have various advantages, such as enhanced
performance, reduced weight and size, integrated different functions, part consolida tion, and elimination of assembly over traditionally manufactured devices. The ben efits of metal AM are particularly important in space applications where low weight,
small size, thermal stability, and high level of robustness are always crucial considera tions. Three different filter models and one antenna model were designed for operation
within the Ku/K/Ka-bands. Namely, wideband multimode waveguide filters using de formed elliptical cavity resonators (four variations of resonators and topologies), dual band multimode waveguide filters using elliptical cylinder cavity resonators, multiband
waveguide filters using an in-band transmission zeros approach (four variations of res onators and topologies), and integrated wideband waveguide diplexer and Continuous
Transverse Stub (CTS) antenna array. The proposed models were experimentally vali dated using prototypes manufactured with Selective Laser Melting (SLM). The prototypes were manufactured in one part where possible to investigate monolithic fabrication. The printing materials included AlSi10Mg and commercially pure copper. Some
of the copper prototypes were electro-polished to examine the effect of surface post-processing on insertion loss. The measured performance and manufacturing quality
are analysed in detail, and improvements for optimising designs for AM are proposed
where appropriate.Engineering and Physical Sciences Research Council (EPSRC) fundin
Development of additively manufactured novel 3D cellular structures for protective clothing
Full text linkProtective clothing shields body parts from impact, absorbing energy to minimise or
prevent damage. Recent research has shown significant emphasis on the use of hard or a
combination of hard and soft materials. The aim of this research was to design and
manufacture novel 3D cellular structures that could provide low-velocity impact
resistance and flexibility to wearers. Six different types of 3D cellular structures were
developed using stereolithography (SLA) additive manufacturing technique with two
different types of flexible resin materials. Theoretical and experimental studies were
conducted to evaluate the low-velocity impact resistance of these flexible 3D cellular
structures. Experimental studies were carried out using a customised inhouse free fall
“impact drop test” setup, where impact forces transmitted through the impacted structures
were captured via a capacitive force sensor underneath the structure, in the form of a real-time impact force versus time plot. The results indicated that the re-entrant honeycomb
(AU) cellular structure made from Liqcreate and Prusa flexible materials experienced the
lowest peak impact force, respectively. Additionally, a static uniaxial compression test
was performed to examine the deformation behaviour of all 3D-printed cellular structures.
The results revealed that the AU cellular structure had excellent energy absorption in a
wide displacement range. To predict and validate the impact resistance response of two
novel, AU and 3D honeycomb (HC) cellular structures, finite element (FE) models were
developed using commercial FE software ABAQUS. Moreover, the predicted responses
of FE models were highly correlated to the experimental results. Overall, the research for
this study indicates that such a novel 3D AU cellular structure, made from a single flexible
material, has the potential for application as personal protective equipment (PPE) to
prevent impact injuries to knees, hips, elbows, and shoulders. This structure would ensure
wear comfort, enable body motions while offering an impact-resistant solution
Physical layer techniques for improving the performance of high-throughput satellite systems
Full text linkThe thesis proposes Physical Layer (PHY) techniques to be applied over next
generation High Throughput Satellite (HTS) systems, to optimize non-linear
links induced by High Power Amplifiers (HPAs), and mitigate inter-beam
interference in a Full Frequency Reuse (FFR) scheme. The demands for capacity increase and mission flexibility at reasonable complexity and costs for
broadband communication satellites, has led to the investigation of payload
architectures providing a large number of beams, while concurrently limiting mass, size and power consumption. This reflects in increased distortion
and inter-beam interference over the satellite channel, which constitute two
of the main challenges that arise with such designs. Computationally efficient data pre-distortion and precoding normalization techniques suitable
for practical implementation of Massive Multiple Input Multiple Output (M-MIMO) systems over satellite are introduced. The techniques were assessed
by several simulations thanks to developed transmitter and receiver models
based on DVB-S2(X) standard, and practical measurements were performed
by means of a testbed. Massive Multiple-Input Multiple-Output (M-MIMO)
performance assessment simulations were carried out in different scenarios
for Single Feed Per Beam (SFPB), Direct Radiating Array (DRA) and Array
Fed Reflector (AFR) payload architectures in Geosynchronous Orbit (GEO).
By employing the proposed low-complexity techniques it is demonstrated
that uniform Signal-to-Noise Ratio (SNR) and Signal-to-Noise plus Interference Ratio (SNIR) can be achieved across the users whilst satisfying the
Per-Antenna power Constraint (PAC), which ensures that the High Power
Amplifiers (HPA) are operated at the desired Input Back-Off (IBO), and
without significant impact on the payload sum rate
Navigating deaf spaces : how mobility and immobility frame the experiences of deaf people in Kakuma Refugee Camp
No full textThis doctoral thesis examines the (im)mobilities experienced by deaf refugees in their everyday
lives in a refugee camp in the global south. The study employed an ethnographic approach,
including in-depth one-to-one interviews, participant observation, fieldnotes, and drawings, during
a four-month fieldwork period at Kakuma Refugee Camp in Kenya. Safety concerns prevent
refugees from returning to their homelands, and the host country does not permit permanent
settlement outside the camp. A select few deaf refugees have been resettled in countries in the
global north. However, the majority of deaf refugees do not have the opportunity to relocate,
resulting in a protracted displacement situation.
This research into the (im)mobilities experienced by deaf refugees encompasses various scales and
temporal dimensions. The apparent isolation of the camp implies a temporal experience of
stagnation and confinement. However, it is crucial to recognise its interconnectedness with the
wider country and the world, introducing a contrasting temporal dimension of connectivity and
integration. While the camp imposes immobility on many deaf refugees, they experience a
considerable amount of mobility both within and outside its boundaries. Within the confines of the
camp, deaf refugees engage in various activities that require movement and interaction.
The transitory yet enduring nature of Kakuma Refugee Camp arises from the juxtaposition of its
intended temporary nature, and the enduring reality of waiting and uncertainty experienced by its
residents. It engenders a temporal tension wherein deaf refugees find themselves in a state of
perpetual waiting for resettlement. Simultaneously, it can be viewed as an environment that fosters
transformation, offering access to education and potential resettlement while providing
opportunities for deaf refugees to connect with others who are deaf. In this context, the camp
becomes a space where a new social formation emerges for deaf refugees, enabling them to
leverage the knowledge and skills acquired within the camp, their capital, to pursue their
aspirations. Bourdieu's theoretical concepts of field, habitus, and capital provide a powerful lens
for comprehending the unique dynamics of Kakuma Refugee Camp. Embracing the idea that
understanding social interactions necessitates an exploration of the underlying social context, this
framework unveils the complexities of “deaf space” within the camp The research also examines the language practices of deaf refugees within the camp. Deaf
individuals employ a diverse range of communication methods, including signing, writing, gesture,
and speaking. As the deaf refugee population comprises individuals from different ethnic and
national backgrounds, their communication incorporates a variety of signed and spoken languages
that are intertwined in their everyday interactions. The study investigates both formal learning
contexts, such as schools, and informal spaces where deaf individuals gather for language learning.
Some deaf refugees attribute more value to certain sign languages over others.
By exploring the daily lives of deaf people in a refugee camp, this study represents an advancement
in understanding the nuanced interplay of mobility and immobility existing on a continuum. It
combines Deaf Studies and Refugee Studies, using Bourdieu’s framework to shed light on how
the habitus and capital of deaf refugees interact within the distinctive field of a refugee camp, and
how they shape their experiences. This fills a gap in existing research. My research also sheds light
on the complex interplay of languages in the linguistic marketplace of Kakuma Refugee Camp,
revealing how language ideologies impact and shape the experiences of deaf refugees. This study
not only reveals the complex realities faced by deaf refugees, but also contributes a novel
perspective to the field of Deaf Refugees Studies
Incremental multi-party conversational AI for people with dementia
Full text linkSpoken dialogue systems (SDSs, e.g. Siri and Alexa) are trained on huge corpora, helping
them accurately understand the ‘average’ user. Speech production is nuanced, however,
so some user groups fall outside the ‘average’. This thesis focuses on SDSs for people
with dementia (PwD). More naturally interactive and accessible SDSs can improve people’s autonomy at home, and in public spaces. Three challenges are tackled in this thesis,
ethical data collection, incrementality, and multi-party conversations (MPCs).
Part I details the motivations of this work, in the context of voice assistant accessibility,
with a specific focus on language technologies for people with dementia. The thesis is
then introduced in its entirety through published paper summaries, with a structure guide.
Part II focuses on data collection. An ethical framework is presented to ensure all data is
collected ethically. A data capture device is then presented to address novel challenges
introduced by COVID-19. Using the ethical framework and device, the DEICTIC corpus
was collected. It verified that, when talking to an SDS, PwD pause significantly more
often, and for significantly longer durations, than people without dementia. The corpus
also reveals that 28% of PwD’s interactions with an SDS are MPCs involving their partner. SDSs are not adapted for MPCs, so a second data collection was designed. Hospital
staff subsequently used this design with memory clinic patients and their companions.
Part III focuses on incrementality. Microsoft’s incremental speech recognition is the most
responsive, stable, accurate, and the only one that preserves disfluent material. IBM’s
services were the most suitable for MPCs. Two corpora were created and released to
explore incremental semantic parsing, together containing over 105,000 interrupted utterances paired with their underspecified meaning representation. SDSs interrupt users
if they pause too long mid-utterance, requiring them to frustratingly repeat themselves.
The use of incremental clarification requests (iCRs, e.g. “author of what?”) leads to more
naturally interactive SDSs, and improves their accessibility for PwD. Another new corpus
was created and released, containing 3,000 human elicited clarification requests. It was
used to show that some large language models (LLMs) can generate context-appropriate
iCRs, and can interpret clarification exchanges as if they were one uninterrupted turn.
Part IV tackles MPCs. The hospital corpus showed that MPCs elicit unique, complex behaviours. LLMs performed remarkably at the new task of multi-party goal tracking, when
given examples from the corpus. A multi-party SDS is required for further research, so
all the work presented in this thesis was integrated into one system, embodied by an ARI robot. It has been designed to handle MPCs with memory clinic patients and their companions, and is designed to be accessible for PwD. When PwD pause mid-utterance, the
system generates an appropriate iCR, and interprets the resulting clarification exchange.
In summary, this thesis identifies that PwD pause significantly more often, and for significantly longer durations, than people without dementia. Additionally, these interactions
are often multi-party. When mid-utterance pauses occur, interactions can be recovered
through the use of iCRs. Using the SLUICE-CR corpus, LLMs can generate effective
and human-like iCRs. They can also be used to interpret clarification exchanges, and interpret multi-party interactions. This work was integrated and deployed on a social robot
to enable conversations between the robot, memory clinic patients, and their companions
Contactless vital signs detection using radar technologies
No full textAbstract unavailable. Please refer to PDF. Restricted access until 31.12.2033
Luminescent downshifting for cadmium telluride photovoltaics
No full textThis thesis is largely based on a series of the author’s previously published work in the
field of solar photovoltaics, in particular the development of luminescent downshifting,
and the use of using fluorescent organic dye layers on cadmium-telluride cells to enhance
the absorption of shorter wavelength photons in the solar spectrum. Using such photons,
which would otherwise be refracted away from the solar cell or otherwise lost through
the cell edges, can offer substantial efficiency gains. The thesis explores the particular
characteristics of the engineering necessary to affect this, examining combinations of
dyes, substrates and types of cells, and using experimental methods, simulations and
theoretical calculations to plot the potential gains. Luminescent downshifting layers on
10 x 10 cm cadmium telluride mini-modules showed relative gains in efficiency of 5 – 10
%. For small (0.3 x 0.5 cm) flexible cadmium telluride cells gains of up to 7.6% were
measured, which translated to gains of 20% when modelled for 10 x 10 cm flexible mini-modules. It also explores the potential for using designs based on combinations of colours
to offer additional benefits in the commercial development of solar panels, and describes
the successful completion of proof-of-concept experiments on this.Engineering and Physical Sciences Research Council (EPSRC) scholarship
A critical examination of forging ‘industry-driven’ partnerships in Malaysian TVET institutions
Full text linkEspousing the sequential exploratory design, this study aims to propose industry-driven
TVET (Technical Education Vocational and Training) partnership strategies between the
local industries and TVET institutions (Higher Education Institutions) in Malaysia.
According to The Star (2023), the Malaysian TVET enrolment rate was at 6.1% compared to
Singapore (23.8%), Indonesia (12.8) and South Korea (14.2%) and cannot be perceived as a
convincing rate. The dip in student enrolment rates, archaic teaching and learning
pedagogical approaches, and hesitance from the industrial sector to participate in TVET
partnerships pose impediments to the growth of the Malaysian TVET program. Via these
partnership strategies, it is anticipated that TVET students will be able to hone their
capabilities to respond to the skills requirements required by the industry to boost
productivity and profitability. Anchored on the Triple Helix Model of Innovation, the study
began inductively to explore the viewpoints of seventeen respondents using the semi-structured interview technique to discover emerging TVET partnership strategies applying
the reflexive thematic analysis approach. Consequently, five themes, (1) curriculum design
and delivery collaboration, (2) mentor-mentee relationship, (3) research and development
collaboration, (4) infrastructural collaboration and (5) joint promotional activities were
identified. These five themes and self-determined pedagogical approach were then
quantitatively validated and generalized using structured questionnaires distributed to
medium and large industries in Malaysia. The collected data was statistically assessed using
the Structural Equation Modelling (SEM) technique to evaluate the path significance and the
moderating effect of self-determined learning (heutagogy). All direct paths were found to be
significant. However, heutagogy was found to significantly moderate the relationship
between mentor-mentee relationship and the successful fulfilment of industry skills
requirements. In theory, this research highlights the pertinent role of the Triple Helix Model
in proportioning the function of the industries, institutes and the government, while also
accentuating the viability of heutagogy in the Malaysian context. In practice, the study
provides an impetus to the government to vigorously implement an ‘industry-driven TVET’
strategy to successfully achieve the Malaysian TVET agenda
The customer journey in the German automotive industry : a model of practice to identify and implement new touchpoints
Full text linkDriven by evolving customer preferences, technological advancements, environmental
requirements to reduce CO-2 emissions and other external factors such as the recent
COVID-19 pandemic, the automotive industry is undergoing significant changes in
customer buying behaviour. Over the past decade, researchers and practitioners have been
debating these developments including the understanding, improvement, and
management of customer journeys. Traditional touchpoints are deemed less relevant,
while new touchpoints emerge rapidly due to innovative technologies, novel market
entrants, and new marketing approaches. However, selecting and developing the most
valuable touchpoints is challenging from a company’s perspective. Research has focused
on customer journey management but lacks practical guidance for organisations to
pinpoint and implement new touchpoints effectively. This gap is being addressed using
mixed-methods research to explore customer journey management in the context of a
Japanese automotive brand operating in Germany. The customer perspective is
investigated by directly exchanging with customers of the brand using questionnaires and
focus group interviews. Firstly, the customer journey in the awareness, research and
purchase phase is analysed based on questionnaires, taking online and offline touchpoints
from the brand, its dealer network and third parties into account. Insights are generated
to identify different behaviour patterns between groups of customers, which are evaluated
and assessed using hypothesis testing. Secondly, focus group interviews are conducted in
which the findings from the questionnaires are confirmed, and additional qualitative
insights are generated. By generating and analysing this customer feedback, a deeper
understanding of customer behaviour and touchpoint usage in the automotive industry
and beyond is generated, and a customer journey model is proposed. Moreover, a model
of practice is developed to identify upcoming touchpoints and evaluate their potential
future benefits from a company’s standpoint. This eight-step model is intended to serve
as a guiding framework for practitioners, enabling them to capitalise on customer
interactions by strategically investing in the most relevant and valuable touchpoints,
including new ones. Practically, being able to identify new and existing touchpoints, as
well as critical success factors, offers opportunities to implement and enhance the
touchpoints of the organisation. Investing in these touchpoints can improve customer
experiences and increase customer satisfaction and loyalty. Understanding customer
behaviour throughout the automotive purchase process enables businesses to tailor marketing efforts, product offerings, and customer interactions according to customer
needs and expectations
Synthesis, phase behaviour and thermoelectric properties of half-Heusler materials
Full text linkWith increasing worldwide demand for energy and an over reliance on non-renewable
fossil fuels, the development of more sustainable power generation is paramount. One
emergent technology for this is Thermoelectric Generators (TEGs), which can convert
thermal energy into electricity. In TEGs, half-Heusler (HH) materials have drawn
attention as power generating components due to their tunable electronic properties and
abundant precursors. This thesis is focused on further exploring known HH systems and
developing new ones, investigating the impact of excess Cu in the XNiSn (X = Ti, Zr)
compositions and the properties of novel Zn1-xTixNiSb.
The impact of excess Cu on the phase behaviour and thermoelectric properties of the
Ti0.5Zr0.5NiCuySn (y = 0.025, 0.1) HH system is examined in Chapter 3. Structural
characterization shows minimal impact on phase behavior by 2.5 at% Cu. In contrast, 10
at% Cu enables the formation of single phase Ti0.5Zr0.5NiCu0.1Sn, with low
κlat, 793 K = 1.25 W.m-1
.K-1
. However, excess Cu leads to over doping and a lower
zTmax ~ 0.5 in the 10 at% Cu samples, whilst Ti0.5Zr0.5NiCu0.025Sn achieves zTmax = 0.7.
Chapter 4 explores the impact of excess Cu on the formation pathway of
Ti0.5Zr0.5NiCuySn (y = 0.025, 0.1). From in-situ neutron diffraction, different reaction
mechanisms are proposed for the two systems, with single phase Ti0.5Zr0.5NiCu0.1Sn
observed again at 1373 K. Investigation of the HH phase stability reveals expected
multiphase behavior in the 2.5 at% Cu system, whilst Ti0.5Zr0.5NiCu0.1Sn remains single
phase and is stable towards X-site segregation on cooling. The Cu occupancy was found
to be under thermodynamic control in both systems, with temperature dependent
solubility limits established from Rietveld refinement.
Chapter 5 discusses the implementation of inert atmosphere shaker milling protocols to
improve sample densification and reduce oxidation. The addition of Cu compromised
initial routes developed for ZrNiSn, with a modified protocol achieving zTmax = 0.7 in
ZrNiCu0.03Sn and zTmax = 0.9 in Ti0.7Zr0.3NiCu0.025Sn. Efforts for high performance
TiNiCu0.03Sn was stymied by sample instability, only achieving zTmax = 0.6.
Finally, the complex Zn1-xTixNiSb HH system is investigated in Chapter 6. Diffraction
and microscopy confirm phase formation, with a solubility range of 0.4 ≤ x ≤ 0.65 and no
evidence of local ordering. With low κlat, 340 K = 2.5 W.m-1
.K-1
found in all compositions,
optimization of electronic transport properties by manipulation of x leads to zTmax = 0.18
and 0.33 for p-type Zn0.6Ti0.4NiSb and n-type Zn0.4Ti0.6NiSb respectively
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