Ageing mechanisms affect the thermal properties and creep response of polymericfoams. This research analyses the effects of gas diffusion on the mechanical responseof polymeric foams subjected to periodic loads and studies their durability.A repeat impact machine was developed to analyse changes in the mechanical responseof ethylene vinyl acetate copolymer foams used in running shoes. The equipmentshowed some advantages compared to the standard method used in runningshoes and produced reproducible results. The softening of the material with thedistance run and the reduction in the cushioning properties are mainly due to theyielding and unyielding of the cellular structure and not to a change in the air content. Midsole deterioration in running shoes was measured in controlled running tests.These confirmed the deterioration of the midsole foam, with an increase of the peakplantar pressure and structural damage in the foam after a long run.The diffusion coefficients of Ethylene-Vinyl Acetate (EVA) foams were measuredusing a microbalance where the pressure and the temperature were controlled. Theoreticalanalysis of gas diffusion in foams subjected to repeat impact was carried outand confirmed a negligible gas loss due to diffusion in foams under cyclic loads.

The development, characterisation and testing of a novel all-optical, multi-modal preclinical biomedical imaging system is presented. The system aims to provide a new way of accurately visualising the spatial distribution and activity of molecular structures and processes in small animals by combining 3D bioluminescence tomography (BLT; reconstruction-based 3D imaging of internal bioluminescent reporter distributions), diffuse optical tomography (DOT; reconstruction-based imaging of optical parameter distributions) and optical surface capture techniques. The key principle of the imaging system is to use surface capture results to enhance the accuracy of DOT image reconstruction, and to use the results of both surface capture and DOT to enhance the accuracy of BLT. Presented experiments show that the developed system can reconstruct luminescent source distributions and optical parameters accurately and that small animal imaging is feasible with the system.

The front-loading washing machine is an integral part of household life for many, with little notice given to the extensive interplay of physical, chemical and thermal phenomena taking place as the clothes inside tumble. With over 250 billion washes carried out annually in Europe alone, it has a staggering environmental impact due to its energy and water usage and also due to the chemicals that are drained to the sewage system at the end of a wash. There are two practical routes for reducing this impact; improving the design of the machine so that it requires less energy or water, or improving detergent formulations so that the required level of cleaning is achieved at lower temperatures and with a reduced input of product. The work presented in this study was initially carried out with the aim of designing better detergent formulations. Along the way, the results also enabled new tools for better washing machine design to be developed. For both routes, the basic requirement was to develop an understanding of the mechanisms which result in mechanical cleaning of textiles, which is the focus of results presented in this study.

Pervasive systems enhance a user's everyday experience. However, the use of pervasive sensing and context aware devices can result very intrusive from a privacy perspective. A familiar pervasive device is a mobile phone. Mobile telephony equipment is daily carried everywhere. Avoiding linkability of subscribers by third parties, and protecting their privacy is one of the goals of mobile telecommunication protocols. We use experimental and formal methods to model and analyse the security properties of mobile telephony protocols. We expose novel threats to the user privacy, which make it possible to trace and identify mobile telephony subscribers, and for some of the attacks we demonstrate the feasibility of a low cost implementation. We propose fixes to these privacy issues. We prove that our privacy friendly fixes satisfy the desired unlinkability and anonymity properties. Finally, we develop the first extension of the Pro Verif tool for the automatic verification of equivalence based properties of stateful protocols. This work shows how to formally verity privacy properties of pervasive systems. Moreover, we develop an automatic verification tool for the verification of equivalence based properties of stateful protocols. Further work in this direction will eventually widen the class of security protocols and security properties verifiable using automatic verification tools.

Surface engineered systems for industrial applications must be able to withstand the harsh inservice environments that they will be operated under. Localised testing on the nanoscale is a method commonly used to probe such systems at very high temperatures, varying humidity and even under liquid environments. However little or no research has been directed towards investigating their behaviour under low temperature conditions. In this study a novel sub-ambient temperature nanomechanical testing instrument has been designed and developed. It allows testing of materials under the temperature range from 20 oC to minus 30 oC. The instrument employs peltier coolers to provide vibration free measurements and a custom purging chamber has been designed to prevent condensation of water vapour on the sample surface during the sub-ambient testing. The study demonstrated the need for dual cooling of both the sample and indenter to ensure drift free measurements are obtained under sub-ambient regimes. A section of the research is dedicated to the testing of polymeric materials. A range of tests were performed from nanoindentation through to probing of time and environmental dependence parameters. In particular creep was studied at ambient temperatures on a range of engineering polymers and also on Nylon’s which were submerged in a fluid cell. The prototype was constructed and validation tests carried out to ensure its performance on standard samples. Next the mechanical properties and creep behaviour of an atacticpolypropylene through its glass transition temperature was examined. Further experiments were carried out focusing on tribological testing of surface engineered systems with the new prototype providing interesting results on DLC’s when tested under below ambient temperatures. Based on the outcomes of this research, a few papers have been published in peer-reviewed technical journals and it is envisaged that the novel sub-ambient instrumentation will be used for the design, charaterisation and optimization of novel engineered surfaces for various environmental applications.

Porous ceramics have been widely used in many fields. Among the fabrication techniques for porous ceramic, freeze casting has recently attracted much attention as being a versatile, low cost and environmental friendly process. In this study, alumina and Al\(_2\)O\(_3\)-ZrO\(_2\) were utilized as model materials to investigate the preparation technique of freeze casting. Basic factors such as initial solids loading, cooling rate, and sintering temperature that would affect the final morphologies and the effect of additives have been studied. Porous alumina ceramics with lamellar microstructure exhibited compressive strengths up to 123 MPa for 33% porosity and 55 MPa for 42% porosity, making them suitable to be considered for potential load-bearing applications. In a two-phase system (Al\(_2\)O\(_3\)-ZrO\(_2\)), the choice of particle size of the ceramic powder was of great significance, which can lead to engulfment and phase segregation. BaTiO\(_3\) and Lead zirconate titanate (PZT) were employed to demonstrate the application of the freeze casting technique. BaTiO\(_3\)-epoxy composites exhibited modest piezoelectric constant but the dielectric constant was 1 order of magnitude higher than conventional composites with randomly distributed ceramic particles. For the 2-2 PZT-epoxy composites, with an increase of initial solids loading from 11 vol.% to 25 vol.%, the volume of ceramic phase in the composite gradually increased from about 30 vol.% to 50 vol.%, the piezoelectric constant \(d_{33}\) increased from about 103 pC/N to 203 pC/N, demonstrating the potential applications of this technique for the fabrication of 2-2 piezocomposites.

When a computer program requires legitimate access to confidential data, the question arises whether such a program may reveal sensitive information to an unauthorised observer. There is therefore a need to ensure that a program, which processes confidential data, is free of unwanted information flow. This thesis presents a formal framework for the analysis and enforcement of secure information flow in computational systems such as computer programs. An important aspect of the problem of secure information flow is the development of policies by which we can express intended information release. For this reason information lattices and maps on these lattices are presented as models, which capture intuitive notions about information and information flow. A definition of security is given, based on the lattice formalisation of information and information flow, that exploits the partial order of the information lattice. The lattice formalisation gives us a uniform way to enforce information security policies under various qualitative and quantitative representations of information. An input-output relational model, which describes how a system transforms its input to publicly observable outputs with respect to a given attacker model, is presented as a primitive for the study of secure information flow. By using the relational model, various representations of information, which are shown to fit into the lattice model of information, are derived for the analysis of information flow under deterministic and nondeterministic system models. A systematic technique to derive the relational model of a system, under a given attacker model, from the operational semantics in a language-based setting, is also presented. This allows the development of information flow analyses parametrised by chosen attacker models. A flow-sensitive and termination-sensitive static analysis calculus is presented for the analysis of information flow in programs written in a deterministic While language with outputs. The analysis is shown to be correct with respect to an attacker model that is able to observe all program outputs and which can determine the termination or nontermination of program execution. The static analysis also detects certain disjunctive information release. A termination-sensitive dependency analysis is developed which demonstrates how, by employing abstract interpretation techniques, other less precise but possibly more efficient information flow analysis may be obtained. The thesis concludes with further examples to highlight various aspects of the information flow analysis and enforcement framework developed.

Environmental pollutants pose great risks and adverse effects to humans and therefore arouse global environmental concern. Bacterial sensors capable of assessing the bioavailability and toxicity of pollutants show great advantages in environmental sensing. This project aims at developing a bioluminescent bacteria-based microfluidic sensor for online monitoring of environmental contaminants and toxicity. Microfluidic devices immobilised with Acinetobacter sp. ADP1_lux cells as a model strain have been developed for quantitative bioassays. Three microfluidic devices were developed and tested in order to trap and culture a monolayer of bacterial cells. The terrace device is capable of trapping a monolayer of cells in a chamber for tracking single-cell growth and response. This device utilises a barrier channel lower than the cell diameter. Two flow channels can be used to load bacterial cells, deliver fresh media and inducers and wash away overgrown cells. The device was used to measure the bioluminescence induction of ADP1_lux cells and its capability to track individual cell growth was demonstrated with E.coli cells. Since bioluminescence signals from a monolayer of ADP1_lux cells were too weak to be detected after 2 h induction by 200 µM salicylate, a microwell device was developed to concentrate cells in individual microwells for population-based analysis. Cell loading procedures, dimensions of wells, carbon sources and on-chip cultures that affect bioluminescence light intensities were investigated. This device succeeded in detecting 200 µM salicylate within 1 h. However, long-term cell culture revealed that ADP1_lux cells tend to form biofilms. Cell populations in individual wells varied greatly, making quantification impossible. Therefore, this device is only suitable for rapid detection of high concentrations of contaminants if biofilm forming bacteria cells are used as biosensors. In contrast, in the case of non-adherent cells such as E.coli, a uniform population distribution in each well was achieved after 2-day culture, suggesting this method is applicable to perform long term, quantitative bioassays using suitable, non-adherent cells. To be able to detect low concentrations of contaminants and overcome potential biofilm formation, a new population array device was developed as a proof of concept to control and isolate cell populations. It consists of a network of microfluidic channels and an array of microchambers. The device was characterised with fluorescent dyes and its capability to perform quantitative bioluminescence assays was evaluated by detecting a range of concentrations of salicylate solutions (from 10 µM to 50 µM salicylate) using ADP1_lux cells. A linear correlation between bioluminescence intensities and salicylate concentrations was successfully established within 90 min induction. It is worth noting that the population array device is the first demonstration of bioluminescence detection at the length scale of microns. Therefore, it has potential to perform multiplex detection within a small footprint where different types of whole cell biosensors can be employed simultaneously. To this end, a logarithmic serial dilution device was also developed to enable quantitative, multiplex bioassays to be conducted in the same device. This integrated dilution and population device provides a powerful tool for rapid quantification of multiple contaminants simultaneously in a sample.

Multilayer metallic/composite stacks are increasingly being used in wing and tail plane sections of modern commercial aircraft, with component assembly primarily through mechanical joining, hence the requirement for fixation holes. Currently, the individual material sections (titanium, aluminium and CFRP) are machined independently prior to assembly however; there is growing demand within the industry to produce holes through the stack in a single operation. The research detailed in the thesis involves evaluating the effect of operating parameters, drill geometry, tool materials/coatings and cutting strategy when single shot drilling three-layer Ti/CFRP/Al stacks. Performance was assessed against various process measures including thrust forces/torque, hole accuracy/quality, tool wear/life, burr formation and hole surface integrity (microhardness and microstructure). Statistical design of experiments and associated analysis techniques (main effects plots, ANOVA etc.) were employed to identify the significance of variable factors and preferred operating levels with respect to different responses. Based on the experimental results, a bespoke drill design was formulated, which was validated against current commercially available drills recommended for the drilling of multilayer stacks. Finally, the influence of cutting fluid pressure on temperature and hole quality was investigated.

Microorganisms, such as bacteria, fungi, viruses and protozoa, colonise the inner surfaces of drinking water pipes and form biofilms. Drinking water biofilms act to protect the microorganisms that they house from the harsh conditions that we impose such as disinfection. Biofilms are generally thought of as being detrimental in drinking water distribution systems; they can harbour pathogens that intermittently emerge at the tap and they can affect the aesthetics of drinking water. The formation and dissolution of biofilms are intricately linked with the flow conditions and therefore, if we are to manage biofilms in drinking water systems, then it is imperative that we understand the crucial role that hydrodynamics play. Thus, my thesis focuses on the growth of biofilms in drinking water under three distinct flow regimes: turbulent, transition and laminar, and under stagnant conditions, and reveals the role that hydrodynamics play in shaping biofilms in drinking water distribution systems. Not all bacteria are merely passive tracers in flow whose fate is governed by the physical flow alone. This thesis presents evidence that there might be key bacteria in aggregation in drinking water, whose biology acts to enhance the formation of multi-species biofilms. I explored that by testing the role that the Methylobacterium strain DSM 18358 played in the formation of biofilms on surfaces that starts with the formation of aggregates in the bulk water. I also explored whether the ability of this Methylobacterium strain to form aggregates was influenced by the flow regime. Ultimately, this research reveals whether the formation and structure of those aggregates in drinking water is influenced by the subtle interplay between biological and physical processes. Given that they are bacteria that can degrade various dangerous chlorine disinfection by-products I explored the role of the Methylobacterium strain DSM 18358 in the concentration of trihalomethanes in drinking water as these chlorine disinfection by-products can cause serious problems to human health when they occur at high concentrations in drinking water. Overall, I identified whether the presence of this Methylobacterium strain in drinking water can actually deliver a service that contributes to better drinking water quality.