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Characterisation of advanced thermoelectric materials and devices
Get PDFPh. D. ThesisA successful method in relation to increasing the thermoelectric figure of merit is by
means of employing the lattice thermal conductivity, seeing as this one of the parameters
which is not affected by the electronic structure of the material. It can be accomplished by
employing the sol-gel method to synthesise the thermoelectric materials. The advantage of the
sol-gel method includes minimisation of the lattice vibration and consequently, lower thermal
conductivity.
In this thesis, the thermoelectric characterisation of nickel nanoparticles embedded in
silica aerogel at two different concentrations has studied and compared with pure silica
aerogel. The samples exhibit a significant increase in electrical conductivity, while the
sample’s thermal conductivity remained almost unchanged. This promising result has
motivated the nanostructuring of Zn4Sb3 and embed it in the silica aerogel using the sol-gel
method.
Thermal conductivity measurement using scanning thermal microscopy proven to be a
technique to evaluate the thermal conductivity at submicron scale. However, this technique is
limited by several important parameters in relation to extracting thermal conductivity. In this
thesis, thermal conductivity measurements using scanning thermal microscopy were studied
and all relevant parameters measured experimentally with the aim of improving the accuracy
of the thermal conductivity measurements. Likewise, a method has created that will measure
the seebeck coefficient of the material using SThM. The advantage of this technique
compared with existing methods are direct measurement, no sample preparation and no need
to fabricate seebeck coefficient test structures.
In this thesis, the thermoelectric materials are characterised using different techniques
to evaluate the performance of the material from 300K to 420K. The measurements system
used in the thesis are thermal conductivity measurements using three specific techniques:
scanning thermal conductivity, HotDisk analyser and Raman spectroscopy temperature
dependence. The electrical resistivity of the materials was studied using the Keithley 4200-
SCS four probe station. The material seebeck coefficient was measured using scanning
thermal microscopy
The Role of Non-Classical Monocytes and the CX3CL1/CX3CR1 Axis in the Immune Response to Myocardial Ischemia-Reperfusion
Get PDFPhD ThesisMyocardial Infarction is a leading cause of morbidity and mortality worldwide. Over the past decade, STEMI patient prognosis has improved in line with the increased clinical use of reperfusion therapy by primary percutaneous coronary intervention. Despite advances in treatment however, the mortality rate following STEMI remains up to 43.1%, due to a range of short and long term complications. Novel treatment options are therefore required to improve outcome following MI. In the immune response to MI, monocytes are rapidly recruited to the injured tissue where they contribute to the inflammatory milieu. While the function of classical monocytes in this response has been well described, the role of the non-classical monocyte subset is poorly defined. These cells express high levels of the fractalkine receptor, CX3CR1, which has increasingly been implicated in cardiac ischemia-reperfusion (I/R) injury. Expression of the fractalkine ligand, CX3CL1, also known as Fractalkine (FKN) is elevated in mouse models of MI, and neutralization of the ligand leads to improved survival. Similarly, in MI and heart failure patients, plasma levels of the soluble form of CX3CL1 are increased. The aim of this project was therefore to investigate non-classical monocyte behaviour and function following cardiac I/R, with relation to CX3CR1 expression, in both STEMI patients and a mouse model of cardiac I/R. The research presented in this thesis describes the distinct dynamics of CX3CR1hi non-classical monocytes in STEMI patients immediately following reperfusion. These cells show an increased depletion in patients with larger infarcts and lower left ventricular ejection fraction, thereby acting as a potential prognostic biomarker of myocardial outcome. In complementary pre-clinical mouse studies of cardiac I/R, this project established that monocyte adherence in the coronary vessel endothelium occurs over a post-reperfusion timeframe which corresponds approximately to the 90 min post-reperfusion drop in circulating non-classical monocytes in STEMI patients. Investigation of CX3CR1 function using a Cx3cr1 knockout mouse demonstrated that infarct-triggered monocyte recruitment and later decrease in myocardial function are not significantly affected by loss of the Cx3cr1 gene. Research into the signalling pathways downstream of CX3CR1 activation identified the pro-inflammatory NFkB pathway as a possible contributor to non-classical monocyte function. Based on this study, the CX3CL1/CX3CR1 axis appears to have an important role in mediating the acute post-reperfusion dynamics and function of circulating non-classical monocytes following human cardiac I/R. Unexpectedly, however, loss of Cx3cr1 in pre-clinical mouse models does not appear to compromise intra-myocardial monocyte recruitment or heart function following cardiac I/R
Exploring the role of technologies in building Syrian refugee community resilience
Get PDFPhD ThesisWe are witnessing the largest humanitarian crises occurring within the digital age. The ubiquity
of digital technologies has created a space for digital humanitarianism. Digital humanitarianism
has been tied to concepts of community resilience by critics of both fields. Humanitarian
academics call for a critical investigation of these concepts that accounts for the socio-political,
cultural and economic contexts in which they are applied. However, empirical research at the
intersection of digital humanitarianism and community resilience is lacking.
In this thesis I explore how digital technologies may contribute to refugee community
resilience, using an Experience-Centred Design (ECD) research approach to engage with Syrian
refugee women residing in an informal settlement in Lebanon. Through the issue of food
security, I engage in an exploratory study using focus groups, dialogue cards and the co-creation
of an advocacy artefact to explore refugee participants’ understandings of community resilience
and how a technology designed for improving refugee food insecurity can contribute to their
community resilience. I further use paper prototypes to engage with participants to mimic
potential future experiences of technologically mediated collective purchasing. The data
collected with refugee participants is augmented by interviews with other stakeholders in the
food aid system. Additionally, I use autoethnographic methods to reflect on the value of ECD
within this context.
I highlight the potential for community-designed humanitarian technologies to increase refugee
agency, facilitate self-mobilisation and consequently contribute to refugee community
resilience. I also emphasise the need, when designing technologies for community resilience,
to account for subcommunities that form within geographically defined refugee communities.
My findings extend the concepts of community resilience and digital humanitarianism by
envisioning refugee-community-driven technology and using ECD as a methodology for
designing with refugee communities
Multi-constellation GNSS estimation of ocean tide loading displacement
Get PDFPhD ThesisFor geodetic stations in proximity to intricate coastlines and shallow seas, the ocean tide loading
(OTL) displacement, with up to decimetre level sub-daily peak-to-peak variations, is
imperfectly modelled by the procedures recommended in the International Earth Rotation and
Reference System Service (IERS) conventions. GPS Precise Point Positioning provides a
means to measure OTL displacement, and about 0.3 mm accuracy for the GPS-estimated main
lunar semidiurnal OTL displacement (M2) has been reported. Nonetheless, the GPS orbital and
satellite constellation repeat periods are identical to those of the lunisolar K2 and K1 tidal
constituents, respectively, which makes these constituents inseparable from the GPS orbit
modelling and multipath errors. To help overcome the GPS problem of estimating K2 and K1
OTL displacement, the use of GLONASS data is investigated.
After processing GPS-only, GLONASS-only and combined GPS+GLONASS observations for
49 globally-distributed stations, which are affected marginally by OTL displacement forward
modelling error, similar accuracy for the M2, N2, and O1 OTL displacement constituents
estimated by GPS-only and GLONASS-only float ambiguity PPP is demonstrated. Combined
GPS+GLONASS float ambiguity solutions show comparable precision to GPS-only fixed
ambiguity solutions, and better accuracy than GPS-only and GLONASS-only for the
aforementioned signals. The use of GLONASS data leads to about 2.0–2.5 mm accuracy
improvement for the K2 and K1 OTL displacement estimation, compared with GPS-only
estimates.
Finally, geophysical inferences of the OTL displacement in Alaska were investigated. The GPSestimated
OTL displacement at 87 stations in Alaska shows that FES2014b is the most accurate
global ocean tide model in the region. It is also shown that including asthenosphere anelastic
dispersion may improve OTL vertical displacement forward modelling in Alaska by up to 1–2
mm. Multi-GNSS OTL displacement investigation in Alaska also confirms the GLONASS data
benefits which were found at the globally-distributed stations
Using novel nanostructured materials for desulphurisation and oil clean-up
Get PDFPh. D. ThesisFuel specifications for transportation fuels have become increasingly stringent with respect to sulphur content in the past few years. The processing cost and the price of crude oil is influenced by its sulphur content. Consequently, the removal of sulphur from oil remains one of the key issues for all parts of the oil industry, including both upstream and downstream processing. The major challenge is to minimise this cost and sulphur content by using novel methods for deep desulphurisation.
Small and medium-scale Iraqi refineries need a novel, low temperature, and benign desulphurisation method especially in consideration of increasing demand for derivatives due to the decrease in capacity after the war and the lack of hydrodesulphurisation units.
The aim of this work is to develop such a technology based on adsorptive desulphurisation using a nanostructured polymerized high internal phase emulsion polymer due to its high surface area and the sorbent ability that can adsorb many times its own weight in sulphur compounds whilst rejecting hydrocarbons.
A model fuel oil was prepared from n-octane as the solvent and the main organosulphur compounds (butanethiol, di n-propyl sulphide, dimethyl disulphide, benzothiophene and dibenzothiophene) to be used as a feed to the adsorptive desulphorisation process. The basic adsorbent was prepared in different mixing time using a HIPE consisting of an oil phase of 78 wt.% monomer, 8wt. % cross-linking agent and 14 wt.% surfactant mixed with an aqueous phase containing a polymerisation initiator (potassium persulphate), then the product conducted in sulphur removal and characterised in more detail.
The project involved producing further adsorbents by using monoethanolamine and activated carbon that assessing improving the adsorption capacity and regeneration ability. This followed by testing the sulphur removal capacity of the material using real industrial oils. Characterisation and analysis of all materials will be undertaken before and after testing by SEM, then FTIR, BET, mechanical compression, and oil uptake tests to assess material handleability.BP British petroleu
Software package applications for designing rail freight interchanges
Get PDFPh.D. ThesisRail freight transport has a crucial role to play in the economy,
delivering significant reductions in logistics costs, pollution, and congestion.
Typically, the conventional architecture and layout of the rail freight
interchange constrain the capacity and performance of the whole railway
system. A well-designed rail freight interchange can enhance the system
performance by maximizing vehicle usage and minimizing last mile
distribution cost. Therefore, the study of rail freight interchange operation is
considered crucial to understand how to increase and improve the
attractiveness for rail freight transport.
This thesis uses game engines to develop software packages that are
used for the design of new rail freight interchanges, considering multistakeholder decisions drivers. A novel and modular approach has been
applied with the purpose of developing and deploying simulation tools that can
be used by multiple stakeholders to:
-Understand the impact of multiple-criteria decision analysis on rail
freight interchange layouts;
-Use a genetic algorithm to identify the most suitable components of
the future interchange to be designed, considering the multi-stakeholders’
priorities;
- Quickly enable the design of a wide variety of rail freight interchanges
from the information selected by a decision maker in a computer-based userfriendly interface.
This research has proposed a framework for software development.
Three case studies are used to illustrate adaptability of a number of
applications for different scenarios. The findings of the research contribute to
a better understanding of the impacts of the multiple stakeholder’s decisions
on rail freight interchange designs.
Key words: Rail Freight Interchanges, Multi stakeholders decision,
genetic algorith
Investigation of Tx-Rx mutual inductance eddy current system for high lift-off inspection
Get PDFPhD ThesisEddy current (EC) testing is a popular inspection technique due to its harsh environment tolerance and cost-effectiveness. Despite the immense research in EC inspection, defect detection at high lift-off still poses a challenge. The weakening mutual coupling of EC probe and sample due to the increase in lift-off degrades signal strength and thus reduces the detection sensitivity. Although signal processing can be used to mitigate lift-off influence, it is laborious and time consuming. Therefore, in this study, a Tx-Rx probe system is proposed to deal with high lift-off inspection.
The parts of the study of the Tx-Rx EC system includes optimisation of probe configuration, improvement of signal conditioning circuit and comparative study of excitation modes. In optimisation of probe configuration, lift-off and coil gap are optimized to mitigate the offset caused by the direct coupling of Tx-Rx coils. The optimum coil gaps of Tx-Rx probe for different lift-offs are found by observing the highest signal strength. The optimisation of coil gap against lift-off extends the detection sensitivity of the EC system to a lift-off of about 30 mm which is by far higher than 5 mm lift-off limit of a single-coil EC probe. In signal conditioning aspect, a modified Maxwell bridge circuit is designed to remove the offset due to self- impedance of the Rx coil. The proposed circuit mitigates the influence of the self-impedance of Rx coil and improves signal-to- noise ratio SNR. In the excitation mode, pulse and sweep frequency signals are compared to study detection sensitivity, SNR and crack quantification capability. The result of the comparative study reveals that pulse excitation is good for crack sizing while sweep frequency excitation is better for crack detection. Simulations and experimental studies are carried out to show the efficacy of the Tx-Rx EC system in high lift-off crack detection
Bioprinting of skin equivalents for immunotoxicity testing
Get PDFPh. D. (Integrated) ThesisThe aim of this project was to develop bioprinted 3D full-thickness human skin equivalents (HSEs) which could be exploited for safety testing of biologics in-vitro. In this study, handmade 3D HSEs in a 24-well format were first optimised, and the structure of the 24-well HSEs were shown to be comparable to physiological healthy human skin. To improve the feasibility of bioprinting 3D HSEs the overall size of the equivalents was reduced by scaling the HSEs to a 96-well plate format using prototype 96-well Alvetex® inserts. Histological analysis of the optimised 96-well skin equivalents showed these to be similar to both the 24-well HSEs and physiological human skin.
To demonstrate that skin cells could be bioprinted in the high densities required to create 3D HSEs, cells were printed using a Jetlab 4 Tabletop printer and solenoid microvalves. Fibroblasts were printed at concentrations of 1x106 cells/mL, 10x106 cells/mL, 20x106 cells/mL and 40x106 cells/mL. Cell count and viability immediately post printing demonstrated that microvalves could be used to reliably dispense a high density of cells over 1 hour with minimal cell death. 96-well HSEs were then bioprinted and compared to handmade 24-well and 96-well HSEs in addition to human skin using histological techniques. Fully autologous 96-well HSEs were then bioprinted and co-cultured in-vitro with autologous peripheral blood mononuclear cells (PBMCs) in the presence and absence of biologics known to cause (OKT3) or not to cause (Natalizumab) immunotoxicity. Investigation of supernatants revealed significant proinflammatory cytokine responses (interferon gamma (IFN-γ)) in co-cultures treated with OKT3 when compared to negative controls.
This research developed a 96-well format bioprinted HSE and demonstrated the feasibility of using bioprinted 3D tissue equivalents for in-vitro immunotoxicity testing of biologics. In conclusion, microvalve based bioprinting technology can be used to fabricate HSEs suitable for application of in-vitro screening of biologics.Engineering and Physical Sciences Research Council, the Centre for Doctoral Training in Additive Manufacturing and 3D Printing, and Alcyomics Lt
Fracture mechanics based offshore mooring fatigue assessment
Get PDFPhD ThesisSafety is crucially important for permanent offshore floating structures. However, over the past
few decades, mooring accidents of permanent floating structures occurred at a high rate, and
accident reports show that fatigue failure has become one of the most critical failure modes of
mooring systems. There is thus a need to develop rational fatigue assessment approaches for
offshore permanent mooring systems during the design phase.
In this thesis, a fracture mechanics (FM) based approach for offshore mooring fatigue
assessment is developed, in which a mooring chain link is treated as a round bar, an initial
surface crack is assumed to propagate at the surface of the chain link. Stress ranges are
calculated based on the tension ranges of a mooring line subjected to the combined loading
process induced by the motions of low-frequency (LF) and wave-frequency (WF). A
comparison between T-N & S-N curves based fatigue assessment approaches and the developed
FM based mooring fatigue assessment approach is made, and the results show that fatigue lives
predicted by the three approaches are well comparable if the safety factors suggested by API
and DNVGL are applied to T-N & S-N curves based approaches.
The developed FM based mooring fatigue assessment approach is then applied for mechanism
investigation on mooring chain links subjected to out-of-plane bending (OPB), mooring chain
links subjected to torque, and mooring chain links tensioned over a curved surface. The results
show that the fatigue lives of mooring chain links are in general decreased significantly due to
the effects of OPB and curved surfaces. In contrast, the effects of torque induced by the chain
twist on fatigue lives of mooring chain links are not evident.
Finally, an investigation on the effects of load combination methods on fatigue lives of mooring
chain links predicted by the FM based mooring fatigue assessment approach is also conducted.
The results show that the FM based approach based on the narrow-band method generally offers
the most conservative fatigue life prediction and the differences of fatigue lives of mooring
chains estimated based on general wide-band methods and dual narrow-band methods are not
obvious
Magnetic polymethylmethacrylate cements for hyperthermic cancer treatment
Get PDFPhD ThesisPolymethyl methacrylate (PMMA) bone cements have been used for stabilizing bone prostheses and filling cavities due to their suitable mechanical properties. PMMA bone cements, with and without addition of magnetic glass-ceramic (MGC), have been recently investigated for the treatment of bone cancer. The addition of MGC to PMMA bone cements allows for the treatment of cancer via magnetic induction hyperthermia.This PhD thesis focused on the potential of MGC addition to commercial dental and orthopaedic PMMA cements for bone cancer treatment. MGC was prepared by melt-quenching technique at 1550°C. It contained a crystalline magnetic phase embedded in the glass matrix. MGC was mixed with dental and orthopaedic PMMA cements in amounts up to 40%. A method for production of magnetic PMMA cements (MPCs) with high reproducibility and dimensional accuracy was developed. The mechanical properties, in vitro bioactivity, cytotoxicity and heat generation of the resulted MPCswere evaluated.Compressive strength and four-point bending tests on MPCs were performed using the ISO 5833:2002 standard. The magnetic cements containing up to 30% MGC met the ISO 5833:2002 standard requirements.In vitro bioactivity was tested in a simulated body fluid (SBF). Apatite crystals started to form on the surface of MPCs after 2 weeks of immersion in SBF, showing the bioactive properties of these MPCs. Although cytotoxicity test results were found inconclusive, there was a decrease in the cell viability with addition of MGC in the bone cement. Preliminary induction heating tests showed that all MPC samples could be heated to a similar temperature range in 5 minutes using magnetic fields compatible with operating rooms in hospitals. The thermal, mechanical and biological properties of MPCs, analysed during this PhD thesis, showed that MPCs are promising biomaterials for the treatment of bone cancer using magnetic induction hyperthermia