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Intended and actual outcomes of hostel accommodation use for single homeless people : a critical realist explanation
Get PDFDespite an expanding body of research documenting the harms associated with hostel
accommodation, it continues to play a central role in response to homelessness across the
United Kingdom and Ireland. While few would deny the existence of harmful hostels,
many continue to extol the impact of ‘good’ hostels, arguing that they play a unique and
important role in resolving homelessness and associated support needs; a role that some
argue cannot be replicated in Housing First, housing led, or rapid rehousing models,
despite a growing consensus regarding the efficacy of these approaches. This study takes
as its starting point this contested terrain, with a particular focus on identifying and
understanding the outcomes of hostel accommodation. Utilising a conceptual framework
rooted in critical realism, the study seeks, first, to bring conceptual clarity to bear on what
is signified by the term ‘hostel accommodation’. It aims to do so by setting out the
constituent components of hostels, both necessary and contingent, with a view to
understanding what it is about these components that sets a hostel apart from other
responses.
The thesis continues to draw on critical realism to distinguish between three ontological
domains of reality – the real, the actual, and the empirical - with this stratified ontology
then allowing for a close exploration of the divergence between the intended and actual
outcomes of hostel accommodation. Drawing on the testimony of national key
informants – spanning hostel providers, commissioners, academics, and hostel sector
representatives - the thesis identifies four ‘tensions’ arising between that which is
intended and that which is actualised in hostel accommodation. These are the safety-harm tension, the independence-dependence tension, and the inclusion-exclusion tension,
with these three tensions then functioning collectively as a fourth (meta)tension, namely
the progress-entrenchment tension. The thesis is structured around these tensions which
are expressed as hypotheses and then interrogated through a qualitative multiple case
study design. The study design pursued cases of maximum difference across a range of
hostel components – such as hostel size, support model, and target group – allowing for
the perspective of hostel managers, staff, and residents to be explored across a broad
gamut of hostel types.
The thesis concludes that the intended outcomes of hostel accommodation - safety,
independence, and social inclusion – are vital to human wellbeing and that living
environments that enable the actualisation of these outcome ought to be valued. The necessary tendencies of hostel accommodation are, however, strongly oriented against
the actualisation of these outcomes, toward their anthesis (in the form of harm,
dependence, and exclusion). While hostels can (sometimes) generate intended outcomes,
doing so requires purposeful and resource intensive efforts. Even with clear intent,
consistent effort, and optimal conditions, hostels often actualise outcomes that are not
only contrary to those intended but are (at least in part) generative of the need and demand
that informs the basis of that intention. This means that hostel accommodation is not only
ill-suited to generating its intended outcomes but is also generative of illusory and
contingent versions of the need it seeks to address
3D printing of electrically conductive soft multi-material composites for strain and pressure sensors
Get PDF3D printing on flexible microelectronics design and manufacturing is an emerging and
burgeoning field. However, the existing platforms cannot meet the requirements for processing
complex 3D flexible electronic circuit models. This project aims to establish a full-scale
framework for 3D printing and its applications.
The combination of stretchable polymers with conductive carbon-based fillers has attracted
attention in the multifunctional sensing materials field. Upon dynamic loading, these polymer
composites exhibit piezoresistive behaviour that can be utilised for strain and tactile pressuresensing applications. This project investigates the piezoresistive behaviour of stretchable
thermoplastic conductive polymers and their strain and pressure-sensing capabilities.
Modification of the conductive composites has led to the development of fully 3D printed strain
sensors. A 3D printer with a dual material extrusion system was employed to fabricate the
conductive composites embedded in a stretchable elastomer substrate to create highly sensitive
and linear strain sensors. Pre-straining of the 3D printed strain sensors caused crack formations;
higher pre-straining values resulted in higher sensitivity. The sensors’ sensitivity reached a
gauge factor (GF) value of 163. Highly sensitive and tuneable pressure sensors were also
realised by utilising multi-material 3D printing techniques. Combining conductive flexible
polymers and scaffold materials allowed the fabrication of novel pressure sensors with
enhanced compressibility and a wide sensing range. The physical properties of the materials
were tested, and the electromechanical properties of the 3D printed sensors were investigated.
Characterisation through scanning electron microscopy (SEM) and optical microscopic
imaging was conducted throughout this research. The 3D printed strain and pressure sensors
demonstrated cyclic behaviour with linear, repeatable, and reproducible responses suggesting
great potential for many applications
Performance of FRP-strengthened reinforced concrete columns under impact loading
Get PDFThe work presented herein focuses on studying experimentally and numerically the
behaviour of RC columns under the combined action of axial and lateral static or impact
loading, in particular when these members are strengthened with external sheets of
Carbon Fiber Reinforced Polymers (CFRP). In total, twenty-five RC column specimens
(un-strengthened and CFRP-strengthened) with identical dimensions have been tested.
Each specimen was first axially loaded to a predefined level and then subject to a three point bending test during which a lateral concentrated load was applied at mid-span.
The lateral load was applied either quasi-statically in the form of small increments up to
the specimen’s failure or dynamically by dropping a steel mass from a predefined
height. In the case of the un-strengthened specimens, the study mainly focused on
examining the effect of axial loading on the behaviour of the RC columns under lateral
impact. In the case of the strengthened specimens, the effect of different configurations
of CFRP sheets used for strengthening on the response of RC columns under static and
lateral impact loading was also investigated.
The experimental results have shown that the CFRP wrapping provides confinement to
the concrete which, in turn, reduces the sustained damage and increases the energy
absorbed by the strengthened specimens. The ultimate and residual mid-span deflections
decrease compared to those of the un-strengthened specimens indicating that the CFRP
sheets increase the stiffness of RC columns. Furthermore, as a consequence of the
smaller damage sustained by the strengthened specimens, the number of impact drops,
which these specimens can sustain before failure, increases.
In the numerical studies, a 3-dimensional finite element (FE) model has been developed
using commercial software ABAQUS to simulate the static and impact behaviour of RC
columns and validated using the experimental results. The Concrete Damage Plasticity
(CDP) model has been adopted to describe the concrete properties. The numerical
results have shown that the CDP model can predict reasonably well the response of RC
columns, including the crack pattern, under static and impact loading
Hydrogenated micro-/nano-crystalline silicon thin films for thermoelectrics
Get PDFHydrogenated microcrystalline silicon thin films (µc-Si: H) deposited by plasma-enhanced chemical vapour deposition represent a relatively low cost material to process
at commercial scale in mature sectors, i.e. photovoltaics and thin film transistors. This,
accompanied by low intrinsic thermal conductivity (k) (~ 1W/m K) [1] and the ability
to control the microstructure and doping, make µc-Si: H a promising candidate for
thermoelectric (TE) applications. Hence, this study reports on a comprehensive
evaluation and optimisation via thermal annealing of the TE properties of p- and n-doped
films deposited on rigid and flexible substrates (glass and Kapton).
The initial focus is on the behaviour of TE properties with annealing of n-doped
films. An increase of the thermoelectric power factor (PF) up to 2.08 × 10-4 W/m K2
at
500 °C for rigid, and up to 8.6 × 10-5 W/m K2
at 200 °C for flexible samples was achieved,
along with a reduction of the thermal conductivity (k) down to 2.9 ±0.4 W/m K in rigid
samples. Then, the same study was performed for p-doped samples finding an increase in
PF up to ~3 × 10-4 W/m K2
at 500 °C for rigid, and up to 1.2 × 10-4 W/m K2
at 350 °C for
flexible samples, with a decrease of k to 1.5 ±0.4 W/mK in rigid samples. Irrespective of
the doping type, samples deposited on Kapton substrates demonstrated to have a lower
thermal stability.
Subsequently and for the first time, the behaviour of µc-Si: H’s TE properties as
a function of uniaxial mechanical strain, and its combined effect with temperature are
presented. Due to compensation effects between the electrical conductivity and the
Seebeck coefficient, the PF was not enhanced, but overall was largely preserved.
Finally, a thermoelectric generator design was proposed to illustrate the suitability
of the deposition method for direct translation into practical device. It consists of twelve
thermocouples with dimensions (n: 20 x 10; p: 20 x 9)mm, electrically connected in series
in a lateral/lateral configuration to provide a power output of 1.04 µW, and a voltage ~
0.15 V under a temperature difference of 60 °C. These findings demonstrate a means of
optimising thermoelectric performance, provide an insight into the physics at work, and
underline the clear potential for application of µc-Si: H thin films in thermoelectric
generators
Photoluminescence quantum yield optimization techniques, influential effects involving upconversion materials, and investigation for nanothermometry
Get PDFPhotoluminescent materials, which possess the ability to emit optical radiation after a
photon absorption event, have garnered high levels of attention for applications such as
sensing. Initially, this thesis examines the latest generation of photoluminescent probes,
including various organic dyes, quantum dots (QDs), and upconversion (UC) materials,
to establish the compositions and synthesis routes that yield optimal performance to
increase their application potential. Characterising the photoluminescent quantum yield
(PLQY) is particularly important as it determines the efficiency of their
photoluminescence mechanism. Due to the low efficiency of UC materials, an aim of this
thesis is to explore new PLQY optimisation techniques. This was carried out by
investigating effects such as excitation beam scattering, which proved to be advantageous
to the UC mechanism due to its non-linear dependence on the excitation power. However,
limitations also arose as the scattering limited the excitation beam penetration depth.
Other factors such as UC emission self-absorption, inner-filter effects, and thermal
effects, were then explored and found to limit the maximum PLQY of these materials as
well as reduce the measurements’ reliability. Overall, an in-depth summary of all the
effects that influence these characterisations was produced as a steppingstone towards
acquiring PLQY standards and improving comparability in the UC field. Finally, due to
the growing interest of using photoluminescent materials for temperature sensing, this
thesis also aimed to advance characterisation methods in this sub-field. This was achieved
through modifying the experimental setup to acquire novel PLQY measurements in
relation to photoluminescent probe’s temperature.Engineering and Physical Sciences Research Council (EPSRC) funding
Applications of biomolecules and isotopes to infer ancient human subsistence activities : Olduvai Gorge, northern Tanzania (early Pleistocene) and Valdocarros, Spain (mid-Pleistocene)
Get PDFAn ongoing debate in human evolution research is whether there are connections
between eco(hydro)logic changes, and the essential resources (food, water, shade) used
by early humans (hominins) that lived in a highly competitive and biodiverse
environment. Water and its accessibility provide a direct link between climate,
landscape, and large-mammal behaviors, and therefore exerted direct influence as well
on early human activities. Additionally, in human evolution, the use of fire is
considered a technological landmark; in particular its implications as widening diets and
calories intake, defensive tool, and heat source. However, the early development of
pyro-technology remains controversial because its remains are easily reworked and their
identification in the archaeological record can be impeded.
Biomarkers are chemical ‘fossils’ that function as a foundation of high-resolution
sedimentary (paleo)climate and (paleo)environmental reconstructions, as well as
preservation of plant tissues. Such ‘fossils’ include a wide range of diagnostic organic
compounds with known origins, which – due to their relative stability during geologic
and biochemistry processes – offer uniquely quantitative insights into ancient landscape
conditions across space and through time. Furthermore, stable (lipid) biomarkers
derived from vegetation, such as leaf-waxes (i.e., n-alkyl lipids) are commonly
preserved in soils and lake sediments associated with hominin archaeological localities.
Since plant biomarkers comprise repeated hydrocarbon (–CH2–) sub-units, which differ
in atomic composition (13C/12C [δ
13C]; 2H/1H [δD]) among plant types, it is possible to
reconstruct the composition of vegetation communities using plant biomarker-specific
isotopic signatures. As such, the combination of sedimentary plant biomarker δ
13C
measurements offers remarkable insights into vegetation and hydroclimate conditions
during geologic history.
The environmental factors that drove differences in apparent behavioral development
(i.e., evolution) between hominin species during the last 2 million years remain a matter
of heated debate. This research focuses on novel biomarker-specific isotope data
acquisition to (1) resolve the importance of different dietary options and water resources
among past hominin species, and (2) improve upon our current knowledge of how
ancient humans adapted to dramatic climate change regarding their (pyro-)technological
advancements.Funded by Heriot-Watt Universit
Coherent light-matter interaction in semiconductor quantum dots
No full textCoherent light-matter interaction allows for population control of a single quantum emitter. Detection of the photons emitted immediately after the interaction
is equivalent to reading out the state of the emitter. Frequency and time-domain
measurements on these photons reveal the information about the coherence of the
emitter, typically imprinted as the indistinguishability of the scattered photons.
This thesis focuses on the optical spectroscopy of semiconductor quantum dots at
cryogenic temperature (4 K) under coherent driving. By analyzing the coherence and
the statistics of the scattered photons, the population inversion, the fundamental
dephasing mechanisms, and the coherent coupling amongst emitters can be probed.
First, the experimental data indicates that the coupling of the atom-like transitions to the vibronic transitions of the crystal lattice is independent of the driving
strength, even for detuned excitation using the spin-Λ configuration. This imposes
a fundamental limit to the coherence of the photons emitted from solid-state emitters. Next, the coherent dynamics of a two-level quantum emitter driven by a pair
of symmetrically detuned phase-locked pulses is studied. The spectroscopic results
of a solid-state two-level system show that coherent population control and a large
amount of population inversion are possible using asymmetric dichromatic excitation, which is achieved by adjusting the relative weighting between the red- and bluedetuned pulses. Furthermore, this technique can be extended to multi-level systems
like the biexciton-exciton cascade, such that a pair of suitably detuned laser pulses,
each resonant to the biexciton-exciton or the exciton-ground state transition, can be
used to achieve population inversion from the ground state to the excited (biexciton)
state. In addition, coherent control of cooperative emission arising from two distant
but indistinguishable solid-state emitters due to path erasure is demonstrated via
the results from the photon correlations, measured with Hanbury Brown-Twiss and
Hong-Ou-Mandel interferometers. Finally, applications of these single-photon emitters integrated in deterministically-positioned nanowires and micropillar cavities are
discussed. The former allows for the demonstration of the parallel spectroscopy of
up to 7 emitters using a multi-core-fiber-based confocal microscope. In the latter case, the coherence, indistinguishability as well as photon-number distribution of the
scattered photons from a neutral exciton resonantly coupled to the cavity resonance
are characterized, before they are converted to the telecommunication C-band via
quantum frequency conversion. With these photons, the single-photon BB84 protocol is implemented and a secure key rate of ∼ 1 kHz after propagating through
150 km of optical fiber is observed. This constitutes a key step towards integration
of this single-photon source for fiber-based quantum networking
Use of semi-empirical modelling to design and control the electronic properties of Half-Heusler thermoelectrics
Get PDFWith increasing energy demand and a move away from non-renewable power generation,
the development of more efficient renewable energy sources is important. Thermoelectric
generators (TEGs) can convert heat directly into electricity, which can be used to increase
the overall efficiency of heat-based processes or operate independently in extreme
conditions. Half-Heusler materials are of interest due to their good electronic and
structural properties.
Chapters 3 and 4 examine the thermoelectric properties of n-type XNiCuySn
(X = Ti, Zr and Hf) materials, using the Single Parabolic Band (SPB) and Callaway
models to rationalise the change in properties with Cu doping and X-site alloying. An
effective synthetic protocol using arc-melting is established to maximise the
thermoelectric performance, which yielded zT = 0.83 for TiNiCu0.03Sn based material and
zT = 1 for the alloyed composition Ti0.7Zr0.3NiCu0.025Sn.
Chapter 5 covers the behaviour of interstitial Ni in the XNi1+xSn (X = Ti, Zr and Hf)
materials, which is responsible for increased scattering of electrons and phonons. Neutron
and X-ray powder diffraction reveal that interstitial Ni is trapped after arc-melting and a
large concentration can remain trapped in ZrNi1+xSn and HfNi1+xSn if not annealed above
700 °C. This knowledge is used to prepare a HfNi1.1Sn sample with an out of equilibrium
excess interstitial Ni concentration and measure its electronic properties.
In Chapter 6, band engineering to increase S is attempted in [Ti1-xVx][FeyCo1-y]Sb
materials. X-ray powder diffraction and SEM reveal the samples to be phase segregated
with preferential formation of TiCoSb. p-type samples are insulating despite high nominal
doping, while n-type samples are metallic, although neither show promising
thermoelectric properties. p-type samples show positive Lorentz magnetoresistance
below 100 K, which becomes negative at 2 K, potentially due to magnetic ordering
Development of a well placement strategy for the Bowland Shale, UK, considering complex basin structure, wireline-derived petrophysical and rock properties, geomechanical models and the impacts of fracture stimulations
Get PDFThe aim of this thesis is to assess the quality of shale intervals for gas production and to
consider where horizontal wells could be drilled with respect to geological faults. The
Bowland Shale, located in a region of NW England, is investigated where it is a potential
shale gas play. The shale is situated within a complex geological setting, which
necessitates an integrated analysis of fault patterns, reservoir and geomechanical
properties, and hydraulic fracture characteristics to realise these aims.
We ask to what extent the structural geology places limitations on where horizontal wells
can be drilled. Mapping of key stratigraphic surfaces and structures using a high-fidelity
3D seismic dataset allows the geological history to be reconstructed, and the detrimental
effects of Variscan compression realised. The results suggest that faulting does restrict
the available sites where horizontal wells can be drilled. Short, vertically stacked wells
may therefore be required to avoid major faults whilst ensuring gas can be extracted
commercially. We investigate if there is an opportunity for this in the Bowland Shale by
assessing both reservoir and geomechanical properties over the entire stratigraphic
section at a single well. From this, we find that the upper section exhibits particularly
good reservoir properties. These intervals of good reservoir properties also exhibit a
distinctive rock physics response that can be modelled and visualised using templates.
Within these rock types, three sections are highlighted that present the ideal combination
of good reservoir and completion properties. Importantly, they are also separated by
highly stressed intervals that may also mitigate risk of vertical fracture interference
between stacked wells.
However, to assess the risk of stimulated fractures propagating near major faults, further
study is required of the Bowland Shale’s typical hydraulic fracture characteristics. While
this is typically performed whilst stimulations are ongoing through analysis of
microseismic events; prior to stimulation, a model is required to attempt to predict
fracture geometries for a formation of specified rock properties and a specified treatment
schedule. Using a simulation model, we ask how far the fractures propagate laterally,
what their geometries are and if there is a risk of vertical interference between each
proposed landing zone.
It is determined that there is minimal risk of vertical fracture interference and potential
fracture barriers behave effectively. Within the pre-defined landing zones, the fractures
observed are relatively simple in geometry and propagate laterally over large distances
between 500 m and 1000 m. This latter observation does further limit the areas where completion stages could be placed without risk of fractures interfering with the faults
mapped from seismic data. Bringing together the results of the mapping and hydraulic
fracture modelling, we can map a maximum of 13 well locations in the study area where
horizontals could be drilled, but some of these wells are very short (~ 500 m). There
remains excellent production potential in the area however, and by combing our results
with production rates using an analogue play, we estimate ~ 300 Bcf of gas production
could potentially be achieved
Gas phase catalytic tandem processes for sustainable chemical production
Get PDFThis PhD thesis has investigated a series of alternative sustainable routes for the
production of commercially important chemicals (i.e. multifunctional ketones/aldehydes,
alkene, alcohols and chalcones) via continuous gas phase (P = 1 atm; 453 K ≤ T ≤ 623 K)
selective tandem (dehydrogenation-hydrogenation and dehydrogenation-hydrogenation-condensation) processes over unsupported (SiO2, ZnO, ZrO2, CeO2 and MgO) and
supported mono- (Au, Cu) and bi-metallic (Au-Cu) catalysts. The role of copper oxidation
state was considered in the case of benzyl alcohol dehydrogenation coupled with
phenylacetylene hydrogenation over a series of CeO2 supported catalysts. Cu+
/Cu0 molar
ratio (confirmed by XPS analysis) is shown to impact on catalytic activity, selectivity and
hydrogen utilisation efficiency. The continuous hydrogenation of biomass-derived
furaldehydes (e.g. furfural and 5-hydroxymethyl-2-furaldehyde) coupled with alcohol
(e.g. 2-butanol and cyclohexanol) dehydrogenation was investigated over oxide
supported gold/copper catalysts. Physical mixtures of Au/CeO2 + Cu supported on a range
of oxides (Al2O3, ZrO2, SiO2, TiO2 and CeO2) served to prove a correlation between
support basicity and H2 generation where hydrogen transfer was favoured by coke. The
use of a bimetallic Au-Cu/CeO2 (based on XPS and HRSTEM-EDX) was adopted as a
strategy to improve hydrogen transfer. The feasibility of continuous gas phase catalytic
condensation of ketones and aldehydes to valuable chalcones was also examined. Under
explicit catalytic control, it was demonstrated that conversion of
acetophenone + benzaldehyde → benzylidenacetophenone over commercial MgO obeys
a Langmuir-Hinshelwood type model where the catalyst shows long term stability.
Benzylidenacetophenone production rate exhibits a positive dependence on Lewis
basicity (quantified by CO2 chemisorption/TPD) for a series of thermally and chemically
(Li- and Cs-promoted) magnesium oxide catalysts, where the caesium-promoted system
delivered the highest activity. The potential of tandem dehydrogenation-hydrogenation condensation of benzyl alcohol + 2ˈ-nitroacetophenone → 2ˈ-aminochalcone over
physical mixtures of supported gold (Au/CeO2, Au/MgO and Au/TiO2) and copper
catalysts (Cu/CeO2 and Cu/MgO) was demonstrated, where product selectivity is
sensitive to the Au oxidation state. The results gathered in this thesis demonstrate feasible
innovative tandem processes with enhanced activity/selectivity and orders of magnitude
improved H2 utilisation efficiency relative to standard catalytic routes.Engineering and Physical Sciences Research Counci
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