Photonic active devices exploit the interaction of light with other physical effects such as carrier, fields, power density, stress, temperature, or sound. The Stimulated Brillouin scattering (SBS) in optical waveguide is an important nonlinear effect results from the coherent interactions between optical and acoustic modes. The SBS can be considered as a primary obstacle effect in limiting the power scaling in many high power photonic devices because it normally has a lower threshold than other nonlinear effects. However, it is also well known that the interaction of light and sound can be exploited in several key applications. The guiding of acoustic wave in of optical waveguides allow interactions of light wave with the related phenomena of Brillouin Scattering (BS), Stimulated Brillouin Scattering (SBS) and Guided Acoustic Wave Brillouin Scattering (GAWBS). This thesis describes and studies the characteristics of different acoustic modes in optical waveguides by using the finite element method (FEM). A numerical approach based on the versatile FEM has been developed and employed for the analysis of acoustic modes in optical waveguides and also their interactions with optical modes. The high and low index contrast waveguides which can be designed, fabricated and optimized for different applications. The detailed spatial variations of the transverse and longitudinal displacement vectors are shown for longitudinal, bending, torsional, radial and torsional-radial modes in these waveguides. The vectorial acoustic modes in optical waveguides are shown for both the high and mlow index contrast silica waveguide along with their dispersion curves, the displacement vectors for transverse and longitudinal movements and the modal hybridness have been mdetermined and shown. Stimulated Brillouin Scattering (SBS) frequencies are also reported here for subwavelength size silica, Ge-doped rectangular and silicon slot optical waveguides. Variation of the displacement vectors, modal hybridness, and modal dispersion are also shown. A finite element based computer code is developed using a full vectorial acoustic model and combining this with another full vectorial optical model, the interaction between acoustic and optical modes are presented here and their overlap integrals have also been calculated.

The main topic of this work is detection of solid particles suspended in conductive medium and development of methodologies for determining cholesterol levels in human blood non-invasively by electrical impedance technique. The main part of this research is focused on the development of methodologies for numerical finite element (FE) modelling of simplified blood-cholesterol system, representing a real measurement system. This has been done first in 2D, to prove the concept and then in 3D, to take into account all of the effects that would only be present in 3D system as well as taking into account that there is a fully 3D problem in the heart of presented research. The proposed model has been tested in various extreme cases and theoretical and some experimental validations have been carried out to establish a degree of confidence in the modelling methodologies developed. This included novel way of model simplification by introduction of particle coagulation. This method has been proven to be successful replacement of effective conductivity method, used in the past. It has been tested against variation in physiological parameters, such as particle concentration and distribution, and material properties, such as particle ,conductivities. In 3D modelling cases the red blood cells (RBC) have been added to further increase the complexity of the system. Several case studies were used to help analyse which physical parameters of RBC would have the biggest impact on system’s impedance. Results were validated against experimental data where possible. This allowed extension of proposed methodology to non-spherical particles modelling. The other methodology adopted in this work applies to the electrode modelling. All electrodes are modelled as hollows. This tactic has been proven to work. It was validated both theoretically and by comparing computational model results with experiment results (BERG, City University London). In Conclusions, it is discussed that both methodologies can be used outside of current research in electromagnetic simulations of less conductive particles in conductive solvent and in cases where electrode material is not known. Modelling investigations of the simplified blood-cholesterol systems using the 2D and 3D FE modelling methodologies developed in this work have shown that it should be possible to measure cholesterol levels in human blood by impedance technique. Opinion sought from clinical staff highlight that this can potentially improve patient care by minimizing time needed for tests and human error (by shortening the number of people involved in testing). The work also establishes and discusses the need for further work, both theoretical and experimental for development of a measuring device for non-invasive measurement of cholesterol in human blood by impedance technique.

A Lagrangian particle multiphase model based on the Meshless Local Petrov-Galerkin method with Rankine source solution (MLPG_R) is proposed to simulate 2D flows of two immiscible fluids. The model is applicable to fluids with a wide range of density ratio from 1.01 to 1000, capable of dealing with violent flow situations (e.g. breaking waves) and maintaining the sharp discontinuity of properties of the fluids at the interface. In order to extend the MLPG_R method to model multiphase flows, an innovative phase coupling is proposed using an equation for pressure at the interface particle through two stages. In the first stage, the formulation is based on ensuring the continuity of the pressure and the ratio of the pressure derivative in the normal direction of the interface to the fluid density across the interface. Gravity current, natural sloshing of two layered liquids and air-water violent sloshing are successfully simulated and compared with either experimental data or analytical solution demonstrating a second order convergent rate. The second stage involves the extension of the method to account for interface tension and large viscosity. This is achieved by adding additional terms in the original pressure formulation considering jumps for both the pressure and the ratio of pressure derivatives in either the normal or tangential direction to fluid density at the interface. The method ensures both velocity continuity even with highly viscous fluids and interface stress balance in the presence of interface tension. Simulation of square-droplet deformation illustrates sharp pressure drop at the interface and relieved spurious currents that are known to be associated with predictions by other existing models. The capillary wave case also demonstrates the necessity of maintaining the jump in the ratio of pressure gradient to fluid density and the bubble rising case further validates the model as compared with the benchmark numerical results. Apart from being the first application of the MLPG_R method to multiphase flows the proposed model also contains two highly effective and robust techniques whose applicability is not restricted to the MLPG_R method. One is based on use of the absolute density gradient for identifying the interface and isolated particles which is essential to ensure that interface conditions are applied at the correct locations in violent flows. The effectiveness of the technique has been examined by a number of particle configurations, including those with different levels of randomness of particle distribution. The other is about solving the discretised pressure equation, by splitting the one set equations into two sets corresponding to two phases and solving them separately but coupled by the interface particles. This technique efficiently gives reasonable solutions not only for the cases with low density ratio but also for the ones with very high density ratio.

As far as is known, this is the first study to concentrate on the microstructural deformation of clay is undrained shear. The material was naturally dispersed; and it had been expected that during pre-peak deformation the platy clay particles would slip and turn to form large domains (i.e. groups of sub-parallel particles) inclined at 45o or more, although other hypotheses were also under consideration. Both optical microscopy and electron microscopy showed that the preferred orientation, which was originally horizontal, definitely remained horizontal whilst the shear strain increased, until the failure plane cut through the orientated structure. It was expected that when strongly anisotropic clay samples are deformed, the shear strain will disrupt the structure, so that the strength of anisotropy decreases. Conversely, when isotropic clay samples are deformed, it was expected that slippage of the particles will cause the strength of anisotropy to increase. The present samples started at a moderate strength of anisotropy, and the subsequent changes were small. This observation supports the above hypothesis and suggests that the examples were on the borderline between the two types of behaviour. There were, however, some changes of the microstructure. The strength of anisotropy at first appeared to increase and later to decrease as strain increased. The deviations of the orientations of the individual structural elements appeared to decrease at first and later to increase, this being the complementary trend. In addition, post-peak, the between-samples standard deviations increased with strain, suggesting that different samples were deforming in different ways. These results suggest that in normally consolidated undrained shear there may be three mechanisms acting within these samples, i.e. they were bedding down at first, and later being disrupted by the shear strains; but the failure plane cut through all pre-existing structure non-conformably. Further, there may have been an element of instability in the microstructural response to strain. The results available for the outer series of tests led to broadly similar conclusions.

The aim of this PhD project is to develop a fuzzy knowledge-based approach in support of risk analysis in the Customs domain. Focusing upon risk management and risk analysis in the Customs domain, this thesis explores the relationship of risk with uncertainty, fuzziness, vagueness, and imprecise knowledge and it analyses state of the art detection techniques for fraud and risk. Special focus is given to fuzzy logic, ontological engineering, and semantic modelling considering aspects such as the importance of human knowledge and semantic knowledge in the context of risk analysis for the Customs domain. An approach is presented combining the fuzzy modelling and reasoning with semantic modelling and ontologies. Fuzzy modelling and reasoning is explored in the context of risk analysis and detection in order to examine approximate human reasoning based on human knowledge. Ontologies and semantic modelling are explored as an approach to represent domain knowledge and concepts. The purpose is to enable easier communication and understanding as well as interoperability. Risk management is broader, multi-dimensional process involving a number of task, activities, and practises. The presented approach is focused on examining the analysis and detection of the risk, based on the outputs of the risk management process with the use of ontologies and fuzzy rule-based reasoning. An ontological architecture is developed in the context of the presented approach. It is considered that such architecture is possible to enable modularity, maintainability, re-usability, and extensibility and can also be extended or integrated with other ontologies. In addition, examples are discussed to illustrate representation of concepts at various levels (generic or specific) and the modelling of various semantics. Furthermore, fuzzy modelling and reasoning are investigated. This investigation consists of literature research and the use of a generic research prototype (examination of Mamdani and Sugeno model types). From theoretical research, fuzzy logic enables the expression of human knowledge with linguistic terms and it could simulate human reasoning in the context of risk analysis and detection. In addition, Hierarchical Fuzzy Systems (HFS) or Hybrid Hierarchical Fuzzy Controllers (HHFC) approaches can be used to manage complexity especially for complex domains. Linguistic fuzzy modelling (LFM) is an aspect that should be considered during fuzzy modelling. From the generic research prototype, fuzzy modelling with the use of ontologies is demonstrated together with their integration in the context of fuzzy rule-based reasoning. It is also considered that Mamdani type of fuzzy models is easier to express human knowledge since the output can be expressed with linguistic terms. However, Sugeno type of fuzzy model could be used from adaptive techniques for optimisation purposes.

An advanced laboratory facility has been designed, developed and commissioned which offers an extensive capability for detailed study of various aspects of geoenergy problems in fractured rocks. It comprises i) a high pressure manometric sorption apparatus, ii) a high pressure triaxial core flooding system and iii) an ancillary system including pure and mixed gas supply and analysing units. The manometric sorption apparatus is capable of measuring adsorption/desorption isotherms of various gas species on powdered and intact samples. The triaxial core flooding system is capable of measuring the gas flow properties and deformation behaviour of coal samples, up to 0.1m diameter and 0.2m length. Deep underground conditions in terms of pore pressure and confining pressure can be replicated using the high pressure triaxial cell for depths up to 2000m. The laboratory facility has been designed and developed to produce high resolution data for a broad range of gas injection pressures (up to 20MPa) and temperature values (up to 338K). Appropriate pressure transducers and flow meters were selected and have been incorporated into the system following a series of detailed and thorough analyses performed to define and optimise the specifications of the measurement devices. Anthracite coal samples from the South Wales coalfield (6-ft seam measure) have been characterised and tested. Equilibrium and kinetic phenomena of the adsorption and desorption of different gases, i.e. nitrogen (N2), methane (CH4) and carbon dioxide (CO2), at injection pressures up to 7MPa have been studied. A series of core flooding experiments have been carried out on samples of 0.07m diameter and 0.12m length, at gas injection pressures up to 5.5MPa and confining pressures up to 6MPa. The absolute and relative permeability of the samples, to different gases and the permeability evolution with changes in the gas pressure and confining stress condition have been studied. The fate of adsorbed CO2 was studied via a sequential series of N2 and CH4 flooding experiments. The storage and displacement of N2 and CO2 in a sample saturated with CH4 at 5MPa pressure was investigated via another series of flooding tests. During the injection of the gases, the composition of the outflow gas was analysed. Modelling work has been carried out to further investigate the experimental results and processes involved in gas transport and reactions. The numerical model used, includes a theoretical approach for modelling the permeability evolution in coal. The results of the gas adsorption tests indicated a higher adsorption capacity to CO2 compared to CH4 and N2, i.e. 1.3 and 2.5 times higher, respectively. Also, different hysteresis behaviours were observed during the adsorption and desorption measurements, for the different gases studied. An improved understanding of the controlling mechanisms of gas adsorption rate and the kinetics of the processes has thus been achieved. From the results of the core flooding experiments, it was found that the permeability evolution of the coal sample to CO2, due to an increase in gas pressure, exhibited a different pattern compared to the other gases. A considerable reduction above a certain gas pressure value was observed. This was found to be related to coal matrix swelling induced by CO2 adsorption. The results of following N2 and CH4 flooding experiments showed a partial restoration of the initial permeability of the coal sample, indicating the stability of the adsorbed CO2 in the coal matrix during the period of analysis. The results of N2 and CO2 storage and displacement in coal showed that CO2 injection into coal was more efficient in terms of total CH4 recovery, gas displacement ratio, breakthrough time and amount of the gas storage than achieved through N2 displacements. The effect of swelling on the coal permeability however was found to be considerable. The application of the experimental results in the adopted theoretical model led to the identification of the major mechanisms controlling the behaviour of coal during gas displacement, together with the influential factors on flow behaviour. The results also highlighted coupled physico-chemical effects during carbon dioxide sequestration in coal. It is claimed that the work presented in this thesis has provided a new and comprehensive set of high resolution data. Various aspects related to high pressure flow and reaction of various gas species in coal have been studied. A detailed set of benchmarks have been produced that can be used for the development and validation of theoretical models. New insights into several phenomena related to carbon sequestration in coal are thus claimed to have been achieved.

This thesis details the necessary evolutions to Cardiff University's HF measurement system and current CAD model implementation to allow for input second harmonic and mixing models to be measured, generated, and simulated. A coherent carrier distribution system was built to allow four Agilent PSGs to be trigger linked, thus enabling for the first time three harmonic active source- and load-pull measurements at X-band. Outdated CAD implementations of the Cardiff Model were made dynamic with the use of ADS' AEL. The move to a program controlled schematic population for the model allows for any type of model to be generated and input into ADS for simulation. The investigations into isolated input second harmonic models have yielded an optimal formulation augmentation that describes a quadratic magnitude and phase dependency. Furthermore, augmentations to the model formulation have to comprise of a model coefficient and its complex conjugate in order to maintain real port DC components. Any additional terms that describe higher than a cubic phase dependency are not recommended as average model accuracy plateaus, at 0.89%, from the quartic terms onwards. Further model investigations into input and output harmonic mixing of coefficients has been detailed and shows that model coefficient mixing achieves better model accuracy, however, coefficient filtering is suggested to minimize model file sizes. Finally, exercising the modelling process from measurement to design, a generated source- and load-pull mixing model was used to simulate an extrinsic input second harmonic short circuit, an intrinsic input second harmonic short circuit, and input second harmonic impedance that half-rectified the input voltage waveform with Class-B output impedances. The tests were set up to see the impact of input second harmonic tuning on drain efficiency. Efficiencies of 77.31%, 78.72%, and 73.35% were observed for the respective cases, which are approximately a 10% efficiency improvement from measurements with no input second harmonic tuning. These results indicate that to obtain performances at X-band close to theory or comparable to performance at lower frequencies input waveform engineering is required.

The purpose of this thesis is to critically highlight the development of solar absorption refrigeration technologies through time. The factors that have prompted the urgent need to reconsider this area of engineering will also be analyzed in depth. The relevant research in the area of solar absorption to date will be shown with specific emphasis on its contribution to industrial and domestic cooling systems. The Middle East may be awash with oil in the present circumstances with 48% of the known oil reserves in the world but challenges exist owing to fossil fuel being a finite resource and its exploitation fraught with environmental problems. Therefore developing solar cooling systems appears to be an essential and inevitable requisite for harnessing solar energy in order to make a lasting contribution to the development of the region, as well as the world Targeting the coefficient of performance (COP) of the solar absorption refrigeration systems was considered to be the fundamental part of this research. By investigating the absorber chamber in an absorption refrigeration system, it was found that enhancing the quality of the spray of the absorber fluid could raise the COP. Using a Phase Doppler Anemometry (PDA), a detailed analysis of the spray characteristics was achievable; this helped in targeting parameters which will have influence on the spray characteristics. These include the nozzle geometry, for instance, the size of orifice, as well as the internal forces of the liquid such as viscosity and surface tension. Operating parameters were also considered to influence the spray quality. The main operating parameter is to create a partial vacuum to simulate the absorber chamber working condition. Results revealed that high viscosity of the fluid and the vacuum had negative effects towards spray quality. But when combining these with a surfactant such as 2-ethyl-1-hexanol, the spray quality increases in terms of droplet diameter, which in turn decreases and thereby causes an increase in the surface area to volume ratio, resulting in the enhancement of COP.

Engineering problems are very often characterised by a large ratio between the scale of the structure and the scale at which the phenomena of interest need to be described. In fracture mechanics, the initiation and propagation of cracks is the result of localised microscopic phenomena. This local nature of fracture leads to large numerical models. Projection-based reduced order modelling is an increasingly popular technique for the fast solution of parametrised problems. However, traditional model order reduction methods are unable to reliably deal with either the initiation or the propagation of a crack or a local zone with high damage concentration. In this thesis, we look at the general problem of applying model order reduction to fracture/ damage mechanics, in the pursuit of rationalising the computational time involved in these kind of simulations. The �rst contribution of this thesis is the development of a reduced-order modelling for computational homogenisation, which is a general multiscale method used to take microscopic data into account when deriving an engineeringscale model. A speci�c strategy is used to reduce the cost of solving the representative element volume (RVE) boundary value problem traditionally formulated in this method. The second contribution was made by developing a partitioned reduced-order procedure for the case of parametrised nonlinear material deformations involving a local lack of correlation, which typically happens with fracture. The method allows to reduce the regions undergoing little non-linearities whilst computational work can be concentrated on regions of high non-linearity.

Particulate matter (PM) emissions from combustion processes are of concern as evidence increasingly shows the negative impact that airborne concentrations of ultra-fine particulates can have on human health, environmental damage and global climate change. Aviation gas turbine and automotive engine exhaust contain a polydisperse mixture of solid and liquid, volatile and non-volatile particles in a hot, highly turbulent flow. In recent years it is the potential health implications of these combustion generated particulates which has become the driving force for more stringent PM emission regulations and improved sampling methodologies. This Thesis explores the characterisation of PM produced by current fleet aviation gas turbines and direct injection gasoline (GDI) automotive engines. Both the automotive Particle Measurement Programme (PMP) which dictates the European regulatory sampling system and the system currently being developed for international aviation industry regulation only consider non-volatile PM in recorded measurements to increase both reliability and repeatability of results. Experiments were performed to evaluate the performance differences between a volatile particle remover (VPR) which adheres to the specifications within the automotive PMP sampling methodology and that of a system which does not. Two sample aerosols were considered; these consisted of an aerosol containing solely volatile particles and another which consisted of solid core volatile coated particles. Mono-disperse size distributions (100, 50, 30 and 15nm) of each aerosol were employed as ‘challenge’ aerosols during VPR testing where particle size distributions and number concentrations were performed upstream and downstream of the VPR. GDI engine technology is becoming more prominent in the automotive market primarily due to the potential for increased operation flexibility and fuel reduction benefits. Regulations governing the output of PM from light duty GDI engines will come into force in 2014 resulting in a new phase of research into GDI engine PM vii emission and potential reduction or mitigation methodologies. This Thesis examined how PM emissions varied in response to changes to key engine operational parameters at homogeneous and stratified charge combustion modes and multiple engine loadings. PM produced by aviation gas turbines is currently regulated using SAE Smoke Number (SN). The main shortfall of SAE SN is that it gives little or no indication of PM size, number or mass; particle parameters which would greatly improve the sensitivity and understanding of an exhaust emission assessment. In order to address these inadequacies the International Civil Aviation Organisation (ICAO) plans to implement a new regulatory standard for the sampling and measurement of non-volatile PM in 2016 through the Committee on Aviation Environmental Protection (CAEP). Appointed with the development of this new methodology is the SAE E-31 Committee, a broad consortium which includes academic institutions, aircraft manufactures, aircraft operators, engine manufactures and Government agencies. During the development of the new standard, multiple large scale PM emission sampling tests have been and are continuing to be performed in order to validate the performance of the sample transfer mechanism and the measurement apparatus being considered as replacements for SAE SN. Analysis of PM emissions gathered during European Aviation Safety Agency (EASA) funded research projects (SAMPLE projects) is presented in this Thesis with a focus on how PM varies as a result of sample conditioning (i.e. dilution, line temperature and length), sample line loses, and the emission source. Gas turbine designers and manufactures are continually researching new combustion technologies as they strive for a competitive advantage in the industry. The introduction of lean-burn combustion regimes into engine combustor design is one such advancement which can provide a significant reduction in pollutant emission formation. In this Thesis analysis of PM emissions generated from the combustor sections of a modern large civil aviation gas turbine, operating in rich and lean burning combustion modes was performed. The use of a traversing sample probe system to acquire exhaust emissions at the exit of the combustor allowed fully annular sample measurements to be made.