Multiple-injection strategy can downsize the penetration and boost the atomization, causing higher IMEP and lower emissions. Multiple-injection however is complex, especially under cold condition. The injection characteristics were first studied by applying long-tube measuring instrument. Single and split injection strategies were employed. The flow rate and fuel mass were quantitatively studied. Furthermore, the interaction among splits was linked to dwell interval and injection duration of each split. The influences of temperature were also studied. A microscope and a CCD camera were then employed to study the primary breakup. The regime for the mushroom spray head was analyzed and the dispersion quality was quantified. The breakup-regime study was carried out. Flow regimes in nozzle dominate the breakup. Dwell interval, injection pressure, the number of injections and fuel temperature determined the interaction. The following is the investigation of macroscopic characteristics with high speed imaging technique. The effects of back pressure and the interaction between injections were investigated. The impact of cold fuel temperature was investigated and various correlations were employed to probe the influence of fuel temperature. The velocities and sizes of droplets were finally studied with Phase Doppler Particle Analyzer.

This thesis reports research on nanowires fabricated by FIB lithography with experiments to understand their mechanical, electrical and hydrodynamic properties. Au nanowires fabricated on Si\(_3\)N\(_4\) membranes with width below 50nm exhibit liquid like instabilities and below \(\sim\)20nm the instabilities grow destroying the nanowires due to the Rayleigh- Plateau instability. Stability is better in the case for Si substrates than for the insulators Si0\(_2\) and Si\(_3\)N\(_4\). A series of 4-terminal resistance measurements were carried out on a "platinum" nanowire grown by FIB-induced decomposition of an organometallic precursor. Such nanowires are found to be a two phase percolating system, containing up to 70% by volume carbon. They have unexpected temperature behaviour which is explained using a percolation model with Kirkpatrick conduction in the presence of temperature induced strain. Au nanowire bridges of very small diameter were probed using AFM to investigate their deformation and fracture strength. Below a diameter \(\sim\)50nm, the mechanical properties are consistent with liquid-like behaviour. After reaching the fracture, the gold molecules from the bridge retract towards the fixed ends; rebinding of the gold causing reforming of the nanowire bridge can occur. FIB fabrication was also used to form a thermal bimorph MEMS cantilever which was investigated by AFM during actuation.

Spinal fusion cages are used to aid spinal fusion where the joint between the vertebrae is fused by bone graft. The design and material of these cages are of great importance to the fusion process. Methods such as screw fixation are sometimes used to secure these cages in vivo. However, access to the cage screw holes is partially obscured by the vertebral bodies. This study aimed to evaluate the effect of side-holes on the design of a cage, assess the feasibility of a bioactive/biodegradable composite as a cage material and develop an instrument to aid screw access to the cage screw holes. Computer models of cages with between 0 and 10 side-holes were produced to model compression between adjacent vertebrae. The bioactive/biodegradable composite as a cage material was analysed using a range of Young’s modulus values for the composite. The results suggested that the number of side-holes had a negligible effect on the stress distribution within the cage and the bioactive/biodegradable composite as a cervical cage material is unlikely to fail in static compression. A cutter instrument was developed in compliance with regulatory standards. It neatly removed the targeted vertebral edge adjacent to the cage screw holes allowing screw insertion.

This work focuses on the effect of boron substitution for aluminium on the structure o£ a series of fluorine-free (4.5Si02-3A12O3-1.5P205-5Ca0) and fluorine-containing (4.5Si02-3A1203-1.5P205-3Ca0-2CaF2) glasses and the resultant glass ceramics has been studied by using a combination of analytical tools like helium pycnometer, FTIR, Raman, XRD, multinuclear MAS-NMR spectroscopy and thermal analysis by DSC and TGA. The morphology of the crystal phases was observed by ESEM, and the identification of the composition observed was achieved by EDX. The density of both boron-substituted aluminium glasses and glass ceramics decreased with increasing boron content. The glass transition temperature decreased generally with an increase of boron substitution in fluorine-free glasses. When the sintering temperature was raised to 1100°C, the calcium phosphate (C'4P20 9) phase transferred to the tricalcium phosphate [Ca3(P04)2] phase, and anorthite and aluminium phosphorus phases were crystallised. The fluorapatite phase was the first phase to be formed in the fluorine-containing glass ceramics, and with the sintering temperature raised to 1100°C, the mullite and aluminium phosphorus phases were crystallised. All the NMR results investigate the structure of boron-substituted glasses and glass-ceramics which are agree with XRD results. ESEM and EDX analysis showed changes in the composition of glass ceramics with boron substitution.

Multi-Junction (MJ) solar cells are new generation of Photovoltaic (PV) technology with high efficiency, better response to high solar concentration and lower temperature coefficients. MJ cells are integrated with high concentrating optical systems to maximise their power output. However, high concentration of solar radiation can lead to significant increase in the cells temperature thus cooling is essential which offers potential for heat recovery leading to the development of High Concentrator PV/Thermal (HCPV/T) systems. This thesis presents a detailed investigation of the MJ based HCPV/T optical, electrical and thermal performance. The performance analysis of HCPV/T integrating 0.25x0.25 m\(^2\) Fresnel lens under concentration ratios of 425X (X=1000 W/m\(^2\)) was carried out to estimate the maximum power output that can be collected. It was found that the yearly total power yield can be up to 191.25 kWh. Therefore, 184 units of HCPV/T, which occupy only 11.5 m\(^2\), can generate 35,190 kWh. Also, in comparison to the flat plate Silicon PV module with electrical efficiency of 20% and 1.2x0.8 m\(^2\) area, HCPV/T system can save about 76% of the area needed to meet this demand. On the other hand, in terms of pollution these units can displace about 23 tons of CO\(_2\) every year.

This PhD project sets out to investigate the potential of colloidal lithography and explore its application for the creation of highly accurate periodic nanostructures. This research can be classified into three main sections based on the materials used in fabrication. In the first section, fabrication of high precision nanopatterns on a photoresist surface was studied using the inherent potential of polystyrene spheres as lenses. The experiments were conducted to obtain uniform arrays of single and dual nanoholes on a surface of AZ 5214-E photoresist via monolayer and bilayer colloidal lithography, respectively. In the second section, the research intention was to produce uniform arrays of nanostructures by using colloidal lithography, soft lithography and metal deposition. In this section, two different strategies were proposed. The first strategy was mainly devoted to fabricated ordered arrays of periodic nanostructures on the basis of PDMS/PDMS replica moulding. In the third section, nickel electroforming was developed to produce periodic nanostructures through a highly accurate approach. The proposed nanofabrication methods within this research facilitate production of multi-material periodic nanostructures with a high precision and tuneable size.

Designing automotive catalysts for the effective control of NOx, HC (Hydrocarbon) and CO (Carbon Monoxide) emissions under both lean and stoichiometric engine operation is a challenging task. The research presented in this thesis assesses the performance efficiency of a three-zone prototype catalytic converter in reducing exhaust emissions from a gasoline engine, operating in HCCI (Homogeneous Charge Compression Ignition) and SI (Spark Ignition) mode under lean and stoichiometric conditions. The research was carried out using Jaguar V6 engine operating in SI and HCCI mode using commercial unleaded gasoline fuel. The catalyst efficiency in reducing the three pollutant emissions is closely related to the exhaust gas conditions (e.g. temperature and space velocity), oxygen content and composition i.e. NOx, CO and HC concentrations. As part of this study a quantitative and qualitative analysis of C1-C11 hydrocarbon compounds achieved before and after the catalytic converter. The results show that hydrocarbon species formation in the combustion process and destruction over the catalyst is primarily dependent on the engine operation and combustion mode (i.e. HCCI or SI). Alkane concentrations were found to be higher in the HCCI mode, while alkene species were mainly found in the engine exhaust under SI mode. The analysis showed that the HCCI exhaust contained heavier hydrocarbon species (e.g. toluene, p-exylene, naphthalene and methylnaphthalene) compared to the exhaust from the SI engine operation. Methane, Naphthalene and methylnaphthalene were the most resistant compounds while toluene was the most degradable compound over the catalyst.

In the recent development of the gasoline combustion engine, direct injection (DI) technology has been widely used to improve fuel economy and reduce exhaust emissions. Because of the limitation of experimental techniques, the transportation of fuel within the GDI injector nozzle hole and near-field spray is not well understood. In this study, computational fluid dynamics (CFD) modelling and direct coupling of the Euler in-nozzle flow model with the Lagrangian spray model are employed to investigate the effect of different nozzle geometrical designs on the GDI spray characteristics. Euler modelling of the inside-nozzle flow reveals that a round nozzle inlet significantly increases the mass flow rate and nozzle exit velocity. A longer internal nozzle wall length results in a decrease in mass flow rate and larger droplet distribution in the nozzle near-field. At the nozzle exit, the nozzle flow parameters obtained from the Euler-based study are implemented as initial conditions for the subsequent Lagrangian-based spray model. The direct coupled Euler–Lagrangian approach is then compared with the Kelvin-Helmholtz-aerodynamic cavitation–turbulence (KH-ACT) model and the Max Planck Institute (MPI) model. The effects of injection and ambient pressure on spray characteristics are separately investigated by experimental and numerical approaches. Three different fuels, iso-octane, DMF and ethanol, are investigated using the MPI-CAB model and experimental approaches in order to gain comprehensive insight into the effect of fuel properties on spray characteristics.

This work focuses on the improvements of the Bees Algorithm in order to enhance the algorithm’s performance especially in terms of convergence rate. For the first enhancement, a pseudo-gradient Bees Algorithm (PG-BA) compares the fitness as well as the position of previous and current bees so that the best bees in each patch are appropriately guided towards a better search direction after each consecutive cycle. This method eliminates the need to differentiate the objective function which is unlike the typical gradient search method. The improved algorithm is subjected to several numerical benchmark test functions as well as the training of neural network. The results from the experiments are then compared to the standard variant of the Bees Algorithm and other swarm intelligence procedures. The data analysis generally confirmed that the PG-BA is effective at speeding up the convergence time to optimum. Next, an approach to avoid the formation of overlapping patches is proposed. The Patch Overlap Avoidance Bees Algorithm (POA-BA) is designed to avoid redundancy in search area especially if the site is deemed unprofitable. This method is quite similar to Tabu Search (TS) with the POA-BA forbids the exact exploitation of previously visited solutions along with their corresponding neighbourhood. Patches are not allowed to intersect not just in the next generation but also in the current cycle. This reduces the number of patches materialise in the same peak (maximisation) or valley (minimisation) which ensures a thorough search of the problem landscape as bees are distributed around the scaled down area. The same benchmark problems as PG-BA were applied against this modified strategy to a reasonable success. Finally, the Bees Algorithm is revised to have the capability of locating all of the global optimum as well as the substantial local peaks in a single run. These multi-solutions of comparable fitness offers some alternatives for the decision makers to choose from. The patches are formed only if the bees are the fittest from different peaks by using a hill-valley mechanism in this so called Extended Bees Algorithm (EBA). This permits the maintenance of diversified solutions throughout the search process in addition to minimising the chances of getting trap. This version is proven beneficial when tested with numerous multimodal optimisation problems.

With increasing number of degrees of freedom for engine operations, traditional mapping based engine calibration methods are reaching their limits. To take their place, automated, multi-objective engine optimisation approaches are desirable. In this thesis, the author presents a model-based multi-objective engine optimisation algorithm using the Strength Pareto Evolutionary Algorithm (SPEA2). The author demonstrates the performance of his approach using a model of a Homogenous Charge Compression Ignition (HCCI) and Spark Ignition (SI) engine. The HCCI combustion model has been developed based on the Apparent Fuel Burning Rate formulations (AFBR) method. The model has been validated from 1500 rpm to 2250 rpm with different engine loads. For the experiments reported here, the calibration objective is the optimisation of valve timing (IVO, EVC) and λ with respect to indicated specific fuel consumption (ISFC) and indicated specific hydrocarbon (ISHC) for HCCI cases, and optimise throttle position, spark timing, injection timing, IVO and EVC for ISHC, ISPMM and ISPMN for SI cases, while achieving a predefined power output at a given engine speed. The method is able to find optimal engine parameters with good accuracy and calculation speed. The initial model calibration requires 90 and 108 engine test bed experiments for SI and HCCI cases respectively, after that the run time for any set of operating conditions is around 3hours and 20mins.