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Developing sustainable fabrics with plant-based formulations
Get PDFSustainability is at the fore, so the textile industry is ambitiously parading towards alternative
ecological materials to refute the air and water pollution from petroleum-based contenders.
Hence the envisaged research aimed to create plant-based formulations for application on
wool and cotton fabrics. Firstly, the instigated study explored and identified eight new sources
of native flora enclosing copper and ferrous element to be implemented as biomordants and
colourants on cotton fabrics. These discoveries would assist in circumventing the depletion
of corresponding mineral ores hence sustainable. The techniques of extraction, mordanting
and colouration with natural plant materials were executed ecologically. The ATR-FTIR,
FAAS, UV-Vis Spectrophotometer and ANOVA outcomes inferred the cotton fabric
biomordanted with black cherry stems and coloured with hops flowers to be most
concentrated in the chelated form of ferrous element content of 11 mg/l and copper element
content of 6.49 mg/l, respectively hence gaining the K/S value of 7.05 and demonstrating
87.02% of protection from ultraviolet rays. The spent solution DO and ORP levels measured
8.05 and 129.2 mV, respectively hence safe to aquatic life and could be readily upscaled. The
sustainable fabrics developed with rue leaves and mugwort leaves, dandelion, nettle, and
bilberry leaves were equally promising.
Secondly, water-based inks were formulated from plant extracts distilling blue from bio
indigo leaves, red from quebracho red bark and yellow from the flame of the forest flowers
extracts. The sought-after black colour was achieved by implementing the primary colour
theory. The concocted plant-based inks were scrutinised for stoichiometry, rheology, colour
yield, inkjet print quality and coffee ring effect employing a viscometer, conductivity meter
and USB microscope. The viscosity range of 8.5 to 10 cP, the relative density of 1.06,
conductivity value of 2.51 mS/cm, the surface tension of 60 mN/m and pH of 4.9 was inferred
to be most effective in obtaining the K/S values acquired on inkjet printing of wool and cotton
fabrics. Another objective was to study the implications of plasma surface modification upon
the treated and untreated wool and cotton fabrics, subsequently inkjet printed with plant based inks. The colour values and fastness properties remarkedly improved after plasma
surface treatment. These findings were supported by data achieved from optical tensiometer,
ATR-FTIR, drop test and SEM, justifying the enhanced wettability of the modified fabrics.
The factorial experiment was designed for this segment of research, and it was further
validated with ANOVA one-way test
Robots, liquids and inference : robotic manipulation and estimation of liquids via approximate simulation
Get PDFLiquids can be found almost everywhere. They are typically observed in human
environments inside containers whose shape, form and size influence how they should
be manipulated and how they will behave. Despite their complex dynamics and
the wide range of possible objects with which they can interact, people can still
instinctively comprehend how a liquid would act in a particular circumstance and
even get insights into its characteristics through simple exploratory interactions.
On the other hand, robots have traditionally been designed to perform repetitive
tasks under predefined conditions, with minimum intuitive or adaptive capabilities.
Naturally, the following question arises: What would it take for robots to adapt
as effectively as humans do, particularly in complex scenarios where liquids are
involved?
This thesis investigates this question by employing approximate simulation mod els to learn manipulation strategies that can be transferred between simulated and
real-world contexts and used to comprehend the relevant features of such tech niques. The investigation begins by examining how a robot’s pouring strategy can
be adapted to the geometry of the containers by leveraging coarse models of liquid
behaviour to reduce spillage. The results suggest that coarse models of simulation
are helpful in some cases. Directly learning from the real world seems to work best
for simple cups. However, strategies learned in simulation significantly outperform
other solutions for challenging containers.
The thesis then analyses whether simple probing tactics such as stirring yield
relevant estimates about the properties of a liquid and analyses if such estimates
help improve the pouring results. This study considers real and simulated liquids
with viscosities ranging from water to gel. This investigation shows that stirring
estimates are indeed beneficial for spillage reduction. However, it also shows that,
due to unmodeled adhesive behaviour, the reality gap increases with liquid viscosity,
resulting in inaccurate observations and increased spillage.
The final study focuses on understanding the interplay between initial conditions
and parameters of a pouring policy. In this case, simulation-based models are used
to learn a distribution over the set of conditions or environmental parameters under
which the pouring policy is most likely to be effective. Evidence shows that the
proposed method can capture complex relations like multi-modality and sharp edges
in moderate dimensional spaces
Mutual fund performance : uncertainty, sustainability and data envelopment analysis
Get PDFThis thesis contributes to three aspects of the rich literature on mutual fund performance evaluation and portfolio selection. In the first study, we examine the effects of
uncertainty on the distribution of mutual fund returns. We find a widening return dispersion in response to high uncertainty while the average return is unaffected. Examining
fund flow data, we show that investors do not react to changes in uncertainty. We also
demonstrate that a strategy that invests in momentum during stable periods yet takes a
contrasting position during volatile periods generates outstanding returns. In the second
part of our study, we investigate how uncertainty affects the impact of environmental,
social and governance (ESG) ratings on mutual fund performance and flow. We construct
fund-level ESG scores based on their stock holdings and show a significant U-shaped effect of ESG score on risk-adjusted returns (value at risk), which changes during times of
peak uncertainty. In addition, we identify a drastic shift in investors’ ESG preferences in
response to uncertainty levels. In the final chapter, we empirically examine whether the
data envelopment analysis (DEA) can be used as a tool to generate investment plans.
We identify a significant positive impact of the current DEA score on subsequent fund
returns. Constructing DEA-sorted fund portfolios, we demonstrate significant practical
value of the DEA method in fund selection and propose the DEA-momentum strategy
that can deliver superior performance compared with traditional strategies and can be
used by both retail and institutional investors.Funded by Edinburgh Business Schoo
Laser polishing of additively manufactured metal parts with application to medical implants
Get PDFThis thesis explores using laser polishing as a surface finishing method for additively
manufactured metal parts. Providing the advantage of increased repeatability, automation and
selectivity of processing, laser polishing offers clear benefits over currently employed
mechanical and electrochemical polishing techniques. The research focus has mainly been on
optimisation of the laser processing parameters for a variety of materials, where there is less
work published on the application of the technique to complex geometries. Publications on the
impact of the polishing process on the mechanical performance of parts is also limited and in
some cases contradictory.
The laser polishing process was optimised for both continuous wave and pulsed lasers on
selective laser melted Ti6Al4V components to obtain the lowest roughness. An alternative
optical system was designed and built to increase flexibility by increasing the depth of focus to
accommodate height variation across the surface. Additionally, a rotational system was
developed to provide continuous laser scanning for cylindrical samples. This system was also
used to showcase laser polishing of the internal surface of a cylinder using a prism to redirect
the light. To demonstrate the laser polishing process, example cranial and dental implants were
showcased. A roughness of the dental implant was reduced from an initial value of 5.6 µm to
0.45 µm with a processing time of 60 s (approximately 1.5 mm2
s
-1
).
The impact of the laser polishing process on the material is also investigated within this work.
Using a custom designed system, the fatigue performance of parts was found to significantly
improve after laser polishing. This is likely due to an improvement in the porosity and reduction
in surface roughness, both of which increase the likelihood of crack formation. The tensile
strength was proven to be the same for both surface conditions, however, the elongation was
slightly less for the laser polished compared with the as-built surface. The hardness within the
re-melted layer after laser polishing was shown to increase.
The adhesion of bacteria Staphylococcus Aureus on the surface of laser polished surfaces was
compared with mechanical polished and bead blasted samples. It was found that the surface
finish did not significantly affect the growth of the bacteria.Engineering and Physical Sciences Research Council (EPSRC) fundin
Physical layer security (PLS) solutions for passive eavesdropping in wireless communication
Get PDFAn absolute secured wireless communication is unattainable. Nevertheless, communication models must be secure and unique across each layer of the model. The
physical layer is the easiest layer through which information leaks, due to its broadcast nature. The security in the physical layer, measured as secrecy capacity, is
subdivided into keyed and keyless security models. In practice, the eavesdropper’s
evasive and obscure random wireless channel model makes it difficult to optimise
keyless security measure at the physical layer. Considering this practical challenge,
the objective of this work is to use novel keyless approaches to reduce the ability of
an illegitimate user to access the transmitted message via the physical layer. Physical layer security (PLS) was achieved through the deployment of unmanned aerial
vehicles (UAV), intelligent reflecting surfaces (IRS), and communication sensing as
security enablers in this thesis. The UAV operates with interfering signals while the
IRS and sensing techniques optimise respective inherent properties leading to higher
PLS performance. The thesis presents solutions to the parametric design of UAV,
IRS, and wireless sensing technologies for PLS functionality. Designs and analysis
herein follow from analytical derivations and numerical simulations. Specifically, the
thesis presents a novel average secrecy rate formulation for passive eavesdropping
with a reception rate upper bound by that of the legitimate receiver. The keyless
PLS assessed from the formulations guaranteed positive rates with the design of a
broadcast interfering signal delivered from a UAV. Based on the verification of the
positive secrecy rate with passive eavesdropping, a swarm of UAVs improved the
PLS of the communication system delivering more interfering signals. Furthermore,
the functionalities of the interference driven UAV swarm were miniaturised with a
system of aerial IRS. By harnessing inherent channel dynamics, a novel non-iterative
design of the aerial IRS system was presented as a panacea to PLS requirements.
Finally, the thesis presents the analysis of a legitimate receiver with a novel noise
and interference filter as a sensing mitigation technique. The filter enhanced PLS
by enabling the legitimate receiver to effectively extract desired information
The impacts of the developmental state model on competition, efficiency and performance : the case of the Ethiopian banking industry
Get PDFInspired by the East Asian growth experience of the second half of the 20th century, the
government of Ethiopia implemented a developmental state model in the middle of the
2000s. The model embedded a state-directed financial system to support industrialization.
This financial system defined by directed credit schemes, interest rates control, the NBE
advance to the government and sale of treasury bills to a captive market, financial
restrictions, and state ownership of banks. These policy instruments may have impacts on
the banking sector in Ethiopia.
A large number of empirical studies on banking have been conducted in the context of
financial sector liberalization. The opportunity for studying banking in the presence of a
state-directed financial system is few. This thesis makes novel contribution by filling this
gap. Hence, the aim of this thesis is to investigate the impacts of the Ethiopian
developmental state model on the competition, efficiency, and performance of banks.
The thesis focuses on annual panel data for 2001-2019, separated into two periods, 2001-
2005 and 2006-2019. The reason for the two-period analysis is that the developmental
state emerged as the economic model of the Ethiopian Government in 2005. Including the
period before 2006 in this research gives a comparative perspective on the situation of the
banking industry in the absence of highly interventionist economic policies.
The thesis adopts a positivist paradigm and quantitative methods as it deals with the
measurement of quantitative variables, relationships between them and testing theoretical
predictions via directional hypotheses. The Panzar Rosse method is used to measure
competition, Data Envelopment Analysis to estimate efficiency and financial ratios are
used to measure the performance of the Ethiopian banks. Regression methods are applied
to establish the direction and strength of association between the developmental state
model as implemented in Ethiopia and the competition, efficiency, and performance of the
country’s banks. In doing so, bank-specific, market structure and macroeconomic factors
are identified and controlled for their impacts.
The study discovers robust results. Directed credit schemes, interest rates control, and lack
of financial freedom reduce the competition and efficiency of banks. The NBE advance to
the government and sale of treasury bills to a captive market enhance the competition of banks while negatively affecting banking efficiency. In similar vein, interest rates control
and lack of financial freedom lower banking performance. Unexpectedly, directed credit
schemes improve banking performance. The impact of bank ownership is mixed.
Although the state banks are less competitive, they are more efficient than their private
counterparts. When it comes to performance, the two state banks have a highly divergent
result. The CBE is highest performer, the DBE is the lowest performer, and the private
banks are in the middle.
When the relationship between competition, efficiency, and performance of the Ethiopian
banks is examined, a result that supports the “efficiency hypothesis” emerges. The
efficient banks produce more output for given input prices, have a larger market share and
achieve a higher performance.
This thesis contributes to academic study and professional practice as it increases our
understanding of the impacts of developmental state model policies as implemented in
Ethiopia on the competition, efficiency, and performance of the country’s banks. It
provides inputs for reforming the part of the financial sector which is not covered by the
Ethiopian government current economic reform package. Furthermore, it offers insights
to the banks pertaining the factors that affect the industry
Cultural transmission : exploring the role of language and transmission pathways in social networks
Get PDFThis thesis investigates previously underexamined or unexplored aspects of the cultural
transmission process with the overall aim of advancing cultural evolutionary theory. The first
study implements the linear transmission chains experimental design to systematically compare
language versus demonstration as social transmission modes in adult and child chains. Despite
its importance in social learning, language is extremely underexamined as a distinct mode of
transmission. The results, however, illustrate that it supports the type of high-fidelity social
transmission that is required for cumulative cultural evolution, especially in children. The
second study examines social learning from a multi-generational perspective. By using a novel
design, it investigates how the context of acquisition of a cultural trait affects the onward
transmission of that trait. This is the first experimental instance in which onward transmission
is examined. The findings suggest that a context-congruence bias impacts cultural transmission
and it even modulates model-based biases. The context-congruence bias is the first factor found
to link acquisition and onward transmission. The third study uses qualitative data to explore
how cultural information flows in a real-world social network. It explains how the previously
proposed transmission biases may impact acquisition and onward transmission, and how
vertical congruence – the result of our proposed context-congruence bias – can lead to
increased longevity and stability. By exploring cultural transmission at the level of the
individual, we uncover new questions and present new hypotheses. As different social learning
and teaching mechanisms are documented, their connection with trait longevity is also
considered. In the final chapter, the implications of the studies are discussed, as are their
possible limitations and the avenues for future research that arise from the findings
Single-photon avalanche diodes for short-wave infrared detection
Get PDFSingle-photon detection is an exciting and rapidly advancing field with numerous emerging
applications areas. There is a demand for highly efficient low noise single-photon detectors.
1310 and 1550 nm are particularly desirable detection wavelengths for use in time-of-flight
imaging, light detection and ranging in automobiles, and low loss optical fibre transmission
in quantum key distribution networks. Silicon based single-photon detectors dominate in the
visible and near-infrared spectral ranges, but this report investigates the design and
characterisation of planar Germanium-on-Silicon Single-Photon Avalanche Diodes (SPADs)
as an efficient short-wave infrared detector. A single-photon detection efficiency of up to 30
% at a temperature of 125 K was achieved at a wavelength of 1310 nm, with dark count rates
in the order of a few thousand counts per second, a low noise equivalent power of 4 x10 -17
WHz-1/2 and timing jitter as low as 126 ps at 150 K. These results represent the highest
sensitivity and lowest jitter Ge-on-Si SPAD detectors demonstrated. These planar geometry
Ge-on-Si SPADs show potential for operation at Peltier cooled temperatures and easy
integration into readily available Si SPAD circuitry as well as high efficiency single-photon
detection. Further investigation was performed into altering the thickness of the germanium
absorption layer within the Ge-on-Si devices and the results showed potential to improve the
single-photon detection efficiency with a refined fabrication process by growing thicker Ge
layers to increase the absorption of SWIR photons. A selection of avalanche photodiodes
fabricated in the alternative material system of InGaAsSb/GaSb and AlGaAsSb/GaSb were
also investigated for operation in the short-wave infrared region
The interplay between circular economy and productivity : multiple case studies in remanufacturing companies
Get PDFThe circular economy (CE) refers to a cluster of strategies which are necessary to create
more sustainable production-consumption systems. Although remanufacturing is a key
principle of CE, there is limited empirical research investigating its relationships with the
productivity of firms, supply chains, or nations. This study therefore aimed to investigate
the interplay between CE (with a focus on remanufacturing) and productivity.
Underpinned by a critical realist philosophy, eight qualitative case studies were conducted
in remanufacturing firms in the UK. Data was collected through semi-structured
interviews and triangulated with financial statements and publicly available information.
As a key result, this research demonstrated that the relationship between remanufacturing
and firm productivity is moderated by the firm’s chosen value proposition. Specifically,
it found that remanufacturers offering specialised and quick solutions can be productive,
whilst competing through price might reduce the productivity of remanufacturers over
time. Supply chains can benefit from speedy remanufacturing which prevents disruption
in their operations. The productivity of the studied remanufacturing firms was found to
be somewhat in between the productivity of the services and the manufacturing sectors.
This study contributes to develop the literature in CE and management through the
development of eight propositions to guide future research, and highlights implications
for managers and policymakers.Heriot-Watt University fundin
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