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Fundamental study of printing accuracy in Fused Deposition Modelling for bioinspired micro-structured surfaces
Get PDFThe use of micro- and nanostructured surfaces has been explored as a new strategy to
enable special surface functions in a variety of areas such as wettability control, anti-biofouling, optical properties, tribology studies, and adhesion resistance. Many
manufacturing methods can be applied for producing structured surfaces, including
lithographic techniques, femtosecond laser machining or single point diamond turning.
However, the cost has often been a critical barrier for the fabrication of functional surfaces
on a mass scale.
3D printing techniques have recently emerged as a viable technology due to low material
consumption, and high energy efficiency. Among these, Fused Deposition Modelling
(FDM) provides a simpler manufacturing process and a more cost-effective method than
other prominent 3D printing techniques. Despite the constant improvements in the
resolution of this method, FDM still has the disadvantage of excessive extrudate
expansion, limiting its application in precision manufacturing of functional structured
surfaces.
This work aims to develop a novel manufacturing method based on FDM for the
fabrication of functional microstructures on thermoplastic polymers in a more cost-effective manner with high throughput on very large scales, which potentially could be
applied in the fabrication of bioinspired functional surfaces. For this purpose, the study
first assesses the manufacturing accuracy of FDM by measuring the die swell effect of
extrudate PLA filaments under varied working conditions in terms of extrusion
temperatures (170 ⁰C – 210 ⁰C), printing speeds (10 mm/s – 80 mm/s), layer heights (0.10
mm – 0.40 mm) and nozzle sizes (0.20 mm – 0.40 mm). Different cooling methods are
also applied in the printing process to suppress the die swell effect and therefore improve
the manufacturing accuracy.
By revealing the limitations of conventional theoretical models for predicting filament
die swell in FDM process, a numerical model based on the level-set technique is
developed to predict FDM extrudate die swell under different extruding conditions. This
simulation method is also applied for studying the expansion of patterned structures
during the extrusion process. The functions of structured surfaces are demonstrated by
enhancing the wettability of a variety of polymers, including polyvinyl chloride (PVC),
polyethylene 1000 (PE 1000), polypropylene copolymer (PP), and polytetrafluoroethylene (PFTE). It has been found that materials initially exhibiting
common wettability properties (θ ≈ 90°) can exhibit “superhydrophobic” behaviour (θ ˃
150°
Real estate finance in Kuwait – evaluation of the approaches of Islamic and conventional banks
Get PDFJust as shelter is one of the basic needs for human beings, it can also be said that
having the necessary finances in place to be able to live in and own a house represents
an equally critical need. Since most people are not in a financial position to pay for their
house in one transaction, the availability of a mortgage or some form of finance has
over time become an essential element in promoting and safeguarding homeownership.
Islamic finance began to emerge and received growing recognition as a new
reality in the world of international finance, particularly when the global financial crisis
occurred in 2008 providing a severe shock to the financial system and markets the world
over. While conventional and traditional banks were seriously affected, Islamic banks,
perhaps surprisingly to some within the sector, remained relatively unscathed and less
prone to the crises that followed in the aftermath. The performance of Islamic banks
through a number of key ratios has produced satisfactory results. In terms of the market
in Kuwait, Islamic banks have a history of conducting business activities within a
somewhat niche market which seeks to attract and offer products and services based on
a profit and loss sharing concept governed by the Islamic principles of Shariah. The
growth of Islamic banking during recent years in Kuwait and their superior performance
compared to the conventional system has helped to increase the relative
competitiveness of both banking systems.
This thesis seeks to provide a comparative study of conventional banks and
Islamic banks in Kuwait in terms of the challenges they face and the benefits they
provide for housing financing. It also identifies the similarities and differences between
Islamic and conventional banks. The Islamic mortgage, which is the housing finance
tool of Islamic banking and finance, offers those who desire it a home ownership
alternative that is in harmony with Islamic Shariah principles and therefore free of
interest, with engaging in interest being forbidden for Muslims. This study also aims to
explore and critically analyse the supply and demand side related to Islamic home
financing by focusing on the different propositions being offered by both Islamic and
conventional banks in Kuwait. In particular, this study explores the risks and benefits
related to Islamic banking by investigating the obstacles that effect the availability of
Islamic home finance.
In order to achieve its principal aim, this study has employed a mixed method
approach whereby data and information was obtained from questionnaire surveys,
interviews and case studies.
The interviews and case study findings have revealed several challenges such as
cancellation of mortgage products, default on payments, remaining interest, lack of
products within the traditional banks and a lack of supply. All of these factors are
collectively believed to be hindering the growth and potential of housing finance in
Kuwait. The study has also noted the problems that arose for the bank, such as central
bank decision and government rules.
The findings of the questionnaire survey have revealed that customer awareness
of Islamic mortgage products is still somewhat low vis-à-vis products offered by their
conventional counterparts. This was particularly the case for Islamic home finance. In
addition, it has been noted that clients opted for Islamic finance mainly due to religious
reasons; and the reason for non-take-up was mainly due to financial costs. However, it
is interesting to note that the majority of the respondents expected the Islamic mortgage
to be capable of safeguarding their interests.
Many of the respondents believed that the Islamic mortgage could achieve the
inherent advantages linked to it, which provides the capability of assisting not only the
individual, but also wider societal interests. This factor is crucial to Islamic banks, as
this situation was broadly agreed upon and expected by a number of respondents.
Going forward, based on the study’s findings, a road map has been developed
to promote a greater understanding of Islamic home finance. It consists of five parts
comprising regulation and policies, challenges and risks, benefits, availability and
obstacles, and comparative criteria. A great deal of modern processing and analysis
techniques have been used to determine the differences between Islamic and
conventional banks. This study asserts that these techniques can help revive the soul of
Islamic Shariah, which will ultimately help to highlight the efficiency and effectiveness
of Islamic finance, particularly home financing, which can benefit all key stakeholders
Flow diagnostics for naturally fractured reservoirs
No full textAbstract unavailable please refer to PDF.Engineering and Physical Sciences Research Council (EPSRC
Penny for your thoughts : understanding metacognition in autism
Get PDFMetacognition (the understanding of one’s own thinking processes) has a positive
relationship with academic achievement, is important in mental health, and is positively
related to social skills in autism. Research in metacognition and autism has found equivocal
results, possibly due to methodological differences, varying taxonomies of metacognition, or
the presence of co-occurring conditions. This thesis aimed to define a taxonomy and
determine the best methodology for evaluating metacognition in autism (studies 1 and 2),
evaluate the relationships between autistic traits and academic achievement, social skills, and
health and well-being (studies 3-5). Study 1 confirmed a two-factor taxonomy with statistical
and theoretical support for 3 components relating to each factor. Study 2 suggests co-occurring conditions may influence autistic metacognition. Research should screen or control
for co-occurring conditions. Those with more autistic traits and accurate metacognitive skills
have better numeracy and literacy achievement and social skills (studies 3-5). In contrast,
those who had positive beliefs about their own metacognitive skills who also had increased
autistic traits had elevated levels of anxiety and depression. Professionals need to be aware
that an expression of confidence in one’s metacognitive abilities may not indicate good health
and well-being; autistic individuals may be camouflaging. It is important to explore these
relationships to best inform practice
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
New times in the Faroe Islands, new speakers of Faroese and the sociolinguistics of labour market inclusion : challenges and opportunities
Get PDFThis thesis presents a critical sociolinguistic ethnography of the role of language in
gaining access to resources and how new speakers can be delegitimated as part of that
process. It focuses on newcomers to the Faroe Islands and the situated ways in which the
Faroese and Danish languages are linked to career advancement, labour market mobility
and processes of inclusion and exclusion. The ethnographic research focuses on migrants
of non-Nordic origin working in fish-processing and cleaning. The research includes
participant observation in fish factories, interviews with 29 participants and follow-up
interviews with focal participants. These data are analysed drawing on recent theory-building in New Speaker studies (e.g. O’Rourke et al. 2019), research into global
mobilities, labour migration and linguistic inequalities (e.g. Duchêne et al. 2013), and a
new framework for research into investment in language learning (Darvin & Norton
2015). The thesis makes a distinctive contribution to the sociolinguistics of the periphery
(e.g. Pietikäinen et al. 2016), revealing specific challenges involved in acquiring small
languages in a bilingual context; the conditions for learning Faroese, the limited language
learning opportunities in blue-collar workplaces, the barriers for newcomers in finding
jobs commensurate with their qualifications, and the role of language ideologies in this
respect.James Watt Scholarshi
Predictive and reactive reinforcement learning from images
Get PDFDeep Reinforcement Learning (DRL) is a general purpose approach for solving se quential tasks. It is based on decades of research in control theory combined with the
relatively recent field of Deep Learning (DL), which takes advantage of hierarchical
trainable models with millions, and more recently billions, of parameters. These
together enable successful control policies in high dimensional unstructured data
settings from zero domain knowledge. Currently, game-like environments, where
agents perceive worlds through images and receive scores, serve as reliable scientific
benchmarks. Thus, we refer to sequential problems from this category frequently.
While DRL is responsible for achieving many recent AI milestones, such as su perhuman competence at Go, Starcraft, Dota and Atari, the ambitions are greater.
In the future, reinforcement learners are likely to control cars, robots and stock
trading. The majority of successful learners so far have been model-free learners -
agents that discover reflex-like responses to stimuli by relying on expressive deep
neural architectures and high volumes of data (up to hundreds of years of experi ence). Recently there have been attempts to enable predictive behaviour - where
agents learn models of their environments and generate plans. While there are suc cessful examples that fit this description, the problem proves more challenging than
initially anticipated.
This thesis comprehensively presents and examines building parts of predictive
agents, expected challenges in transitioning from reactive approaches and the trade offs between the two classes of agents.
The early part of the thesis provides the theoretical background necessary for
the exploration of predictive agents. This includes reviews of deep learning and
reinforcement learning as well as probabilistic state estimation and prediction. We
then introduce a novel approach for learning the physics of a stochastic process solely
through observation of images. The method is based on a deep recurrent neural
architecture. It exemplifies how agents with no domain knowledge can build forward
models of environments which can then serve for planning and other purposes. In the same section we review approaches that followed ours and reflect on their importance
for building predictive agents.
The second part of the thesis pools insights, advantages and shortcomings of
the many variants of reactive and predictive reinforcement learners proposed to
date. We distil the fundamental differences and generalise to finally offer a novel
categorisation of agents. Through this, we identify the key trade-offs and provide
recommendations of suitability for different classes of environments. We identify a
particular category, termed implicitly predictive agents, as especially promising for
the complex benchmarks that involve large complexity and partial observability.
The last part of the thesis presents an evaluation of reinforcement learners on
a task that is normally solved through recursive search (maze navigation). Here,
we experimentally confirm our hypotheses about implicitly predictive agents and
provide novel agent designs. We find that agents relying on recurrent neural architectures may implicitly learn to use recursive computation to solve search problems.
Finally, we explore the implications of our findings for the future of predictive
agents and recommend promising research avenues
Flavour extraction during gin production using different distillation methods
Get PDFGin distillation is a flavouring process through extraction of flavour compounds from
essential oils in plant materials (botanicals) by the usage of a neutral alcohol-water
solution. There are two principal distillation methods used: steep and vapour infusion.
Investigating influencing parameters for extraction of terpenes during the vapour infusion
process showed that the botanical ratio had the greatest effect on the extraction, but the
ethanol concentration of the charge had a significant influence on the extraction levels of
oxygenated monoterpenes. By fractioning and measuring the distillate at different time
points a kinetic study was carried out to investigate the extraction dynamics of flavour
constituents during gin distillation, where steep infusion was best described with a first-order rate equation and vapour infusion by using a logistic function. A comparison of the
behaviour of three classes of terpenes solubilized in an ethanol solution, distilled in a
batch still with two modes of reflux and with or without a packed column and two
pressures (atmospheric and partial vacuum) was carried out. The results showed a clear
difference in behaviour between monoterpenes, with highest concentration in the
distillate in the beginning, and oxygenated terpenes and sesquiterpenes, with an increase
of the concentration towards the end of the distillation. Simulation of two different
distillation settings were carried out with a heterogeneous approach using the non-random
two liquid (NRTL) activity coefficient model to represent the interactions within the
liquid between terpenes and water and ethanol
Understanding the cost overrun causation in construction megaprojects – a grounded systems thinking approach
Get PDFResearch background: The problem of cost overruns in construction megaprojects is a
‘complex problem’. Although a considerable amount of research has been conducted to
identify the isolated factors causing cost overruns in megaprojects, there is a lack of
holistic understanding of the complex causal interrelationships between the causes of cost
overruns. Therefore, to fulfil this research gap, adding a novel contribution to the existing
body of knowledge, adopting systems thinking approach, this thesis aims to holistically
examine and understand the cost overrun causation in construction megaprojects and
develop a model/substantive theory that represents the complex problem of cost overruns
in construction megaprojects.
Research methodology and design: The thesis adopted a qualitative research
methodology based on a case study research design. California High-Speed Rail project
was selected as the case study and data were collected from a range of sources. Data were
analysed using grounded theory method and systems thinking approach was used to
develop the model (systems map). Seven (07) theoretical propositions that emerged from
the data analysis were developed to explain the drivers of each systems map and their
cause and effect relationships. The developed model/substantive theory and the
underpinning propositions were validated using a two-round modified Delphi survey.
Important research findings: The holistic examination of the complex problem of cost
overruns revealed that the project cost overruns were an emergent ‘symptom’ caused by
multiple interrelated causes and events occurring at different levels and phases of the
project thus cannot be attributed to one single cause. Further to the current academic
explanations on cost overruns in the project management literature, findings of the
research revealed that that ignorance, impulsive decision-making, immature project
organisation, and political pressures collectively led to initiating the project with
unrealistic cost and schedule estimates and an undefined scope. Scope creep, inflation,
community pressure, lawsuits, and multiple delays were collectively responsible for cost
overruns during the execution phase.
Contribution to knowledge: Using systems thinking approach, this thesis holistically
examined the cause and effect relationships between the drivers of cost overruns in
megaprojects by developing a model/substantive theory (systems map) of cost overrun
causation. The developed systems map could be used as a tool for strategic decision-making in megaprojects to understand how cost overruns emerge as a result of multiple
interrelated causes and events occurring at different levels and phases of the project.James Watt Scholarshi
The use of multidimensional interpolation with thermal dynamic simulation and adaptive thermal comfort
Get PDFThe research work presented in this thesis is concerned with the development of a more
economical and efficient method of designing near zero energy, thermally comfortable,
resilient buildings for the future by reducing the number of onerous inputs necessary for
building thermal analysis. Existing building design methods either do not evaluate thermal
comfort of the designed building or are too complex to be widely applicable, in the case of
simulation approaches. It is proposed that a surrogate model, using multidimensional
interpolation analysis, of a dynamic simulation engine is the most appropriate model to
develop. Thermal comfort evaluation methods, the means of passive thermal storage to increase
resilience of the designed building, currently employed building design tools and
multidimensional interpolation analysis are investigated. It is determined that Kriging is the
most appropriate surrogate model to examine. Ordinary Kriging is then selected for testing
using dynamic simulation results as known points. The output of the surrogate model is
compared against the results of IES VE and EnergyPlus simulations to determine its validity.
It is found that the surrogate model matches the simulation results closely in 50% of test cases
but performs poorly when limited known results are in close proximity to the unknown point
or more than 4 alterations from the baseline model are made. Utilising interpolation allows
designers to understand the impact of each input and, therefore, highlights which parameters
need to be closely monitored during the construction phase to ensure actual performance is in
line with simulated. As we aim to design resilient buildings in response to extreme weather
events due to climate change, the use of the KTool (a simplified input surrogate model based
on Ordinary Kriging) can contribute to the global effort to improve energy efficiency in
buildings and meet the building needs of future generations in a thermally comfortable, low
energy and low carbon manner
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