Sustainable biodiesel can be produced by processing vegetable oil seeds or microalgae. The processing includes numerous processes which impact the quality and cost of the final product. Oil extraction from the feedstock is one of the most energy intensive parts of the process in the production chain. Oil extraction methods are influenced by the operational physical parameters or chemical characteristics, and their selection greatly impacts the final oil yields. This thesis investigates and compares different oil extraction methods and tries to fill the research gaps in the oil extraction processing, for example, utilising new techniques such as ultrasonic or microwave assisted solvent extraction. A detailed energy analysis for the extraction processes was conducted for each method to investigate the process feasibility to produce biodiesel more economically. Two major feedstocks were considered, flax seed and microalgae. Microwave treatment was found the most effective in terms of less time consumption and low energy requirement with higher oil yields as compared to other methods applied to flaxseed. The extracted oil fatty acid profile showed favourable properties to convert the oil into biodiesel. In-situ transesterification of flaxseed was conducted and 93 % was converted into biodiesel. The de-oiled cake and in-situ cake were torrefied (slow pyrolysis) to convert the residue into a high energy density solid bio-char, which can be used as a feedstock to produce heat energy. Microalgae can be used as a source of biofuel and food supplements, however, their exploitation is lacking due to various bottlenecks including realistic processing options at scale. Microalgae species Nannochloropsis oculata, was cultivated and harvested in the School of Engineering, University of Glasgow. The lipids were extracted to investigate their potential to produce algal biodiesel. Different techniques of cell disruption were applied prior to lipid extraction with solvent to enhance lipid yield. To assess the cell disruption viability, treatments such as: microwave, ultrasonic, water bath, blender, laser and hydraulic pressing were investigated. The microwave treatment was found the most energy efficient method with a higher percentage of cell disruption as compared the other treatments. The microwave treatment, was chosen to enhance the lipid extraction with an organic solvent extraction from dry powdered and wet algal paste. The microalgae biomass was applied with 1-5 min treatment at 50% and 100% power settings and lipids were extracted. Thermal analysis with Differential Scanning Calorimetry (DSC) was conducted to investigate the thermal behaviour of algal biomass with microwave treatment. The hydraulic pressing (10-100 bars) with and without LN2 treatment was also found with promising results with more than 90 % cell disruption. The extracted algal lipids physical and chemical properties were found in an agreement with previous workers. Powdered Chlorella vulgaris biomass was treated with hydrothermal treatment (Hydrothermal Liquefaction, HTL) in a reactor between 40-350 oC at holding times of 30 and 60 min. The vapour pressure developed in the reactor were calculated with the Clausics-Clapeyron equation and with some realistic assumptions. The bio-oil content yield was found higher at 350 oC with 30 as compared to 60 min holding times and the GC-MS analysis showed the presence of fatty acids (C14-C18). The aqueous phase contained TOC, TN and TP, which are useful nutrients for microalgae cultivation. The solid bio-char had HHV values between 17-20 MJ/kg for 30 and 60 min holding times. The protein and carbohydrates content present in the aqueous phase, after hydrothermal treatment, at 40, 60, 80 and 100 oC were measured at both holding times. Aqueous phase reforming (APR) of powdered Chlorella vulgaris biomass was done at the University of Zaragoza, Spain to produce hydrogen with or without Ni catalyst with two pressure 30 or 35 bars at 227 oC. The maximum H2 yield was 0.427 x 10-3 and 0.542 x 10-3 moles of H2 per 3 g of dry algal biomass, with Ni as catalyst at both pressure conditions. From this work, there is clearly significant benefit to using advanced processes for oil extraction such as HTL or microwave enhanced processing. Compared to other parts of the extraction process, such as energy used for drying, the use of a microwave has been shown to be economically viable. These advantages should scale with production volumes. HTL and APR offer similar advantages for processing wet feedstock’s, eliminating drying requirements altogether.

In the last two decades, technological progress towards the miniaturisation of products and components has increased significantly. This trend has also been driven by demands for the manufacture of devices with functional features on the nanoscale. One of the nanofabrication processes, which has been proposed by researchers to meet such needs, relies on the mechanical machining of the surface of a workpiece with the tip of an atomic force microscope (AFM) probe. In this case, the AFM probe is utilised as a cutting tool as it enables the direct contact between its sharp tip, which is fixed on a flexible micro cantilever, and the workpiece surface. A relatively large numbers of studies have been reported in the field of AFM tip-based nanomachining since the invention of the AFM instrument itself just over thirty years ago. However, such studies have typically neglected the fact that AFM probes should be considered as flexible tools when investigating this process. Thus, this shortcoming constitutes the main motivation behind this PhD research. Following a review of the literature, the work reported in this Thesis starts by a study of the bending orientation of cantilevers during AFM tip-based nanomachining operations along different processing directions. To achieve this, an advanced experimental set-up is developed first in order to monitor a number of output signals, which characterise the motions of both the fixed and the free ends of the cantilever together with the displacements of the AFM stage. A refined theoretical analysis is also presented to express the bending orientation of an AFM probe cantilever at its free end as a function of the forces acting on the tip when machining in a direction pointing away from the probe. This refined model shows that the bending orientation depends on both geometric parameters of the cantilever and on the cutting forces. Complementary experiments, which are designed to determine the quasi-static bending behaviour of cantilevers in practice, show that, contrary to assumed knowledge, both concave and convex bending orientations could take place when machining along this direction. The occurrence of a change of the cantilever deflected shape from convex to concave bending during machining can principally change the depth and width of grooves produced. For instance, the depth of grooves machined on a single crystal copper specimen may increase up to 70% following this phenomenon. iv Following this, another refined model is also developed to measure the normal force acting on the tip when the AFM stage is static by taking in account the cantilever geometry and its inclination angle with respect to the sample surface. This work leads to the introduction of a correction factor that should be applied when using the conventional equation for determining the normal load in this configuration. Results obtained when implementing this model based on the dimensions of typical commercial AFM probes show that the conventional approach always leads to an underestimation of the normal applied force. In addition, it is demonstrated, both theoretically and experimentally, that the conventional method for determining the applied normal load during AFM tip-based nanomachining, i.e. when the stage is not static, is wrong. Based on this shortcoming, a novel procedure is proposed to estimate all three force components (i.e. thrust, axial, and lateral forces) acting on the tip during AFM tip-based nanomachining. To achieve this, two novel methods are also developed to assess the actual value of normal force during machining, which in this case is referred to as the thrust force. Based on experimental data, a good agreement is found between both methods for different physical quantities evaluated. Another refined theoretical model, based on the classical beam theory, is also employed in this procedure to determine the axial force acting on the tip and subsequently, the lateral force. Using this novel procedure to estimate the cutting forces, it is also shown that even if the deflection angle at free end of probe is constant, this does not mean that the associated cantilever vertical deflection is constant between the configurations when the AFM stage is static (i.e. for nanoindentation) and when it is moving (i.e. during an actual cutting operation). Finally, in order to gain further insights into the material removal mechanisms that influence the process, a series of post-machining investigations on the topography of produced grooves is reported for different applied loads and processing directions. This particular experimental study takes advantage of the prior knowledge established in this Thesis. Indeed, the understanding of the cantilever deflected shape and the accurate assessment of cutting forces provide key inputs when the groove formation process is analysed.

Atomic force microscope (AFM) probe-based mechanical nanomachining has been considered as a potential low-cost alternative method for the generation of nanoscale features on the surface of components and devices. Therefore, it is important to understand the factors that influence the tip wear of AFM probes in order to achieve reliable and accurate machining operations when implementing this process. Despite the fact that the basic applicability of AFM probe-based machining has been demonstrated for many years, studies focussing on the wear of the tips as a function of processing conditions are relatively scarce. In addition, the accuracy and practical suitability of in-situ techniques to monitor the condition of AFM probes is not adequately acknowledged. To address these issues, a series of experimental studies were conducted in this PhD research when implementing the AFM probe-based machining process on a single crystal copper workpiece at selected values of applied normal loads, machining distances and for different machining directions. First, the assessment of the wear of AFM silicon probes was carried out based on two dimensional (2D) tip profile data. This particular study also presented a simple method for improving the accuracy of the tip wear assessment procedure when conducted on 2D profiles. Next, AFM silicon probes with diamond-coated tips were used as cutting tools for a different range of applied normal loads and along various processing directions. For this particular study, the AFM probes wear assessment relied on two different three dimensional (3D) in-situ measurement techniques, namely the ultra-sharp tip scan approach and the reverse imaging method. Reliability and practical suitability aspects between these two in-situ techniques were also assessed and discussed. For each set of experiments, different qualitative and quantitative ii wear metrics were observed and analysed. Particularly, from the qualitative perspective, the evolution of the AFM tip apex profiles along selected machining distances and directions was considered. As for the quantitative measurement, tip radius and tip volume loss measurements were estimated. The most important findings reached in this study are given as follows. First, it was shown that the error associated with the traditional method of assessing the tip volume from 2D profiles could be 26% in comparison with the simple method proposed here. In addition, among the 3D in-situ AFM probe characterisation methods considered, the reverse imaging approach was judged to be the most reliable technique. This study also showed that tips in silicon were very prone to initial tip fracture during the AFM probe-based nanomachining process. This phenomenon could also take place, albeit to a lesser extent, when silicon tips coated with diamond were utilised. When the nanomachining process is not in control due to such tip fracture, it is difficult to extract firm conclusions about the influence of the processing parameters on the tip wear. Besides, this rules out the application of a design of experiments approach where the minimisation of the tip wear volume may be the objective. The study also showed that the AFM probe-based nanomachining process was more likely to be in control when using silicon tips coated with polycrystalline diamond with no nitrogen doping. In this case, a much reduced likelihood of tip fracture could be achieved accompanied with negligible tip wear. In addition, the associated results suggested that the evolution of the tip wear was not equal in all machining directions investigated, with the largest wear occurring in a direction parallel and away to the cantilever long axis. The reason for this should be due to the fact that this was also the direction where the process was most likely to be conducted in the ploughing-dominated regime. Finally, when the nanomachining process was realised in iii control, the wear volume was seen to increase with the increase in the normal load for all directions considered.

Engine oil condition monitoring has attracted considerable interests from industries and general public over the years due to its critical role in maintaining the performance and longevity of cars and industrial engines. Lubricants degrade during the course of operation and can be costly or detrimental to the engine if oil change intervals are not optimised. However, on-line robust monitoring for oils has been very challenging since oil degradation process is often complicated and influenced by a number of parameters, such as the operating temperature and contamination. Due to the complexity of the oil chemistry and their degradation processes, there have not been any commercially available on-line sensors for oil chemical property monitoring reported. Oil acidity is traditionally measured through potentiometric or photometric/colorimetric titration methods. Recent attempts at miniaturising infrared (IR) and chronopotentiometric (CP) sensors based on solid-state devices for acidity/alkalinity determination of oil have not been very successful since the CP technology suffers from sensitivity and stability issues and IR sensors are still bulky and adversely susceptible to the engine‟s harsh environment. This project, sponsored by Shell Global Solutions, aims to develop robust chemical sensors that can detect oil acidity due to oil degradation. The initial comprehensive literature review has identified that thick film (TF) sensor technology offers compact and low cost mass production solutions and have been proved to be robust with good reproducibility for aqueous solutions acidity measurements. Their feasibility in detecting oil acidity was thus investigated in this study and experimental work has been carried out to fabricate TF electrodes and evaluate them in a range of oils to explain their performance in detecting acid content. Based on their performance in aqueous solutions in previous studies, this study has investigated the performance of one type of TF working electrode (Ruthenium Oxide (RuO2)) combined with various TF reference electrodes in order to develop the most suitable electrodes for oils. To simulate oil ageing, a fully formulated engine oil and a base oil were oxidised under controlled conditions. Also, different amount of nitric acid was added to a fully formulated oil to simulate the oil acidity changes. Acid number (AN) of the oil samples was obtained using conventional titration methods and viscosity and conductivity of the oil samples were measured using laboratory-based equipment in order to validate TF sensor measurements and establish a relationship between different properties of oil samples during their degradation process. Temperature effects on thick film electrodes as well as their long-term stability and repeatability were also investigated. The results show that, for the first time, TF sensors respond to the acidity changes in all oil types tested and linear correlation between the TF responses and the AN was found in the oxidised oils within certain ranges at the tested temperatures (50 °C and 80 °C). TF sensors can detect oil acidity up to AN of 28 mgKOH/g. Although oil conductivity and viscosity were affected by the oil oxidation process, but no direct relationship was found between them and the TF responses. Based on the experimental results, sensing mechanisms of the TF electrodes in oils are proposed.

We aim to develop a formal framework to reason about provenance in distributed systems. We take as our starting point an extension of the asynchronous pi-calculus where processes are explicitly assigned principal identities. We enrich this basic setting with provenance annotated data, dynamic provenance tracking and dynamically checked trust policies. We give several examples to illustrate the use of the calculus in modelling systems where principals base their trust in the quality of data on the provenance information associated with it. We consider the role of provenance in the calculus by relating the provenance tracking semantics to a plain one in which no provenance tracking or checking takes place. We further substantiate this by studying bisimulation-based behavioural equivalences for the plain and annotated versions of the calculus and contrasting the discriminating power of the equivalences obtained in each case. We also give a more denotational take on the semantics of the provenance calculus and look at notions of well-formedness and soundness for the provenance tracking semantics. We consider two different extensions of the basic calculus. The first aims to alleviate the cost of run time provenance tracking and checking by defining a static type system which guarantees that in well-typed systems principals always receive data with provenance that matches their requirements. The second extension looks at the ramifications of provenance tracking on privacy and security policies and consists of extending the calculus with a notion we call filters. This gives principals the ability to assign different views of the provenance of a given value to different principals, thus allowing for the selective disclosure of provenance information. We study behavioural equivalences for this extension of the calculus, paying particular attention to the set of principals composing the observer and its role in discriminating between systems.

This work presents the development of control systems that enable a hover-capable AUV to operate throughout a wide speed range. The Delphin2 AUV was built as part of this project and is used to experimentally verify the prototype control systems. This vehicle is over-actuated with; four throughbody tunnel thrusters, four independently-actuated control surfaces and a rear propeller. The large actuator set allows the Delphin2 to operate at low speeds, using the through-body tunnel thrusters, and at high speeds, using the rear propeller and control surfaces. There lies a region between slow and high speed where neither the control surfaces nor tunnel thrusters are operating optimally. To maintain depth stability, both actuator sets are required to operate simultaneously. The model predictive control (MPC) algorithm is used to control the vehicle given its ability to handle multiple inputs and outputs along with system uncertainties. The basis of MPC is a mathematical model of the system to be controlled. Several experiments were conducted with the Delphin2 AUV to acquire the data necessary to develop this model. Bollard pull tests were used to measure thruster performance whilst wind-tunnel and open water experiments provided a measure of the control surfaces, hull and propeller performance. Depth control is the primary focus of this Thesis, however, pitch and surge control are also addressed. Three controllers are developed in this work, of increasing complexity; a depth and pitch controller for low speed operations, a depth and surge velocity controller for medium to high speed operation, and �nally, a depth and surge velocity controller for operation from low to high speed operations. All three controllers are multi-input multi-output (MIMO) and use the MPC algorithm. Input constraints are imposed on both the absolute limits and the rate of change limits. Simulations re performed to aid in the design of each controller before it is implemented on the Delphin2 AUV and experimentally verified. The depth and pitch controller, developed for low speed operation, uses the front and rear vertical thrusters as the system inputs. This case demonstrates the implementation of the MPC algorithm and studies the effects of the various tuning parameters. A model sensitivity study is performed, showing that the controller can handle modelling errors of up to �30%. The controller is experimentally tested and shows excellent performance with zero steady-state errors although there is an undesirably large overshoot of the depth demand. The simulation and experimental results match closely. The depth and surge controller uses the control surfaces and rear propeller as system inputs. Many of the forces and moments within this system are non-linear functions of the vehicles surge velocity. Therefore the standard MPC algorithm, that utilizes just one linearised model, would not be sufficient to capture the system dynamics of the vehicle throughout the full operational envelope. A time-variant MPC (TV-MPC) algorithm is developed and shown in simulation to have excellent performance. The controller did not perform as well when tested experimentally, however, depth regulation of �0:3 m was achieved. This degradation in performance is due to inaccuracies in the estimation of the vehicles surge velocity. The final controller is also a depth and surge velocity controller, however, it is tasked with maintaining stability through-out the full speed range of the vehicle. All of the system inputs used for depth control are utilised by this controller; the two vertical through-body tunnel thrusters, horizontal control surfaces and the rear propeller. The design of the controller makes use of the TV MPC algorithm. To improve system performance a modi�cation to the controllers cost function, used within the optimisation process, was made to penalise the use of the thrusters at high speeds. This enables the controller to use the thrusters at low speeds, when performing close range inspections, but then as surge velocity increases and the thrusters are no longer required, they are switched o�. Both simulation and experimental results show excellent performance, although when the thrusters switch o�, the depth control is similar to that of the previous controller due to poor surge velocity estimation.

Spot-welded structures contain inherent variability in location and/or stiffness due to the complexity of the manufacturing process. Therefore, an analysis that includes the uncertainty generated in the joints will provide a range of response predictions, adding more value to the design process compared to deterministic results. Finite element (FE) analysis is frequently used in conjunction with Monte Carlo simulations (MCS) to predict the variability in the vibration response of assembled structures, however this is usually computationally expensive. Small numerical spot weld models must be used since real spot welded structures usually possess many spot welds and modelling each of them in detail would lead to additional computational effort, current models provide results sensitive to the element size. In this thesis, a method to quantify the variability in the dynamic characteristics of structures due to uncertainty in the location and diameter of the spot welds is proposed and experimentally validated. Component mode synthesis (CMS) is used in combination with multipont constraint (MPC) connection models in order to improve the computational efficiency of the uncertainty analysis. However, if the number of degrees of freedom (DOFs) involved in the connection is large, then the CMS size reduction is less effective. Two techniques are proposed to overcome this problem: (i) characteristic constraint modes and (ii) application of a low rank update theory to the CMS matrices. A spot weld model based on MPCs is proposed and validated as part of the original contributions of this work. This model improves convergence and minimizes the sensitivity to the element size. The application of the new method is experimentally validated in a double hat structure. Results show that the method presented is accurate when predicting the structure’s natural frequencies and it can identify which modes are sensitive to the uncertainties in the spot welds and which modes are not.

Vibration isolators are often assumed to possess linear viscous damping which has well known consequences for their performance. However, damping may be designed to be or prove to be nonlinear. This study investigates the effect of cubic damping, as an example of damping nonlinearity, in a single degree of freedom (SDOF) vibration isolation system. The response behaviour due to two excitation types, namely harmonic and broadband excitations, was examined. For harmonic excitation, the Harmonic Balance Method (HBM) was applied to yield approximate closed form solutions and simplified analytical expressions implicitly show the influence of cubic damping for particular frequency regions. The HBM solutions were verified using direct numerical integration. The presence of cubic damping proves to be beneficial for the force excited case. It reduces response amplitude around the resonance frequency and has similar response to an undamped system in the isolation region. In contrast, for base excitation, the cubic damping is detrimental at high excitation frequencies as the base excitation and isolated mass move almost together. The effect becomes more pronounced for larger excitation amplitudes. The case of base excitation was then considered for broadband excitation. The responses using direct numerical integration were presented using power spectral densities. In contrast to harmonic excitation, the amplitude of the response does not appear to approach that of the input. Instead, a higher effective cubic damping results in a higher vibration level of the isolated mass at frequencies below the resonance frequency. It also does not reduce explicitly the response amplitude around the resonance frequency unlike the linear viscous damping. For a constant displacement amplitude random excitation, the excitation frequency bandwidth is found to be a significant factor in the level of effective cubic damping. A broader excitation bandwidth results in a higher level of cubic damping force. The theoretical and numerical results for both harmonic and broadband excitation were validated experimentally. The experimental investigation was performed using a SDOF base excited vibration isolation system possessing a simple velocity feedback control active damper to reproduce the nonlinear damping force. The predictions were shown to be in good agreement with measurements thereby verifying the effects of cubic damping on a SDOF system undergoing harmonic and broadband base excitation.

With increasingly tighter regulations on noise exposure during flight, aircraft designers have been compelled to innovate structures that minimise noise transmission into the cabin space. Porous material is widely used as a passive noise control medium because of their light weight, low cost, and broad band sound abatement effectiveness. The present work, inspired by the need to be able to predict noise transmission characteristics for commonly used constructions, incorporates the effect of flow into the calculations. Three types of sandwich configurations {bonded-bonded, bonded-unbonded and unbonded-unbonded{ are considered. Biot's theory is used to simulate the poroelastic material. The sound transmission though a double-walled panel lined with porous material in the presence of external mean flow is considered, first. The transmission loss is found to increase with increasing Mach number of the external mean flow. This is then explained on the basis that external mean flow increases the impedance of the panel. Mismatch in the characteristic acoustic impedances of the exterior and the interior results in the change of transmission loss. Transmission loss increases gradually when the pressure difference between air gap and that in the exterior decreases. A bi-objective optimization study is carried out to simultaneously minimize the sound transmission and the structural weight. The effect of laminated composite face plate in the structure is also brought out. Sound transmission through a system of double shells, lined with poroelastic material in the presence of external mean flow, is studied next. The transmission characteristics of the sandwich construction are presented for different incidence angles and Mach numbers over a wide frequency range. It is noted that the transmission loss exhibits three dips on the frequency axis as opposed to flat panels where there are only two such frequencies. Results are discussed in the light of these observations. Flow is shown to decrease the transmission loss below the ring frequency, but to increase this above the ring frequency due to the reduction of stiffness and the damping effect added by the flow. Finally, sound transmission through double-walled cylindrical shell lined with poroelastic material in the core excited by the exterior pressure fluctuation due to the turbulent boundary layer is investigated. The peaks of power spectral density of the inner shell kinetic energy due to shell resonance, hydrodynamic coincidence and acoustic coincidence are discussed. The results show that if the high frequency is interested, an air gap, even if very thin, between the two face shells provide superior sound insulation.

In this thesis, I investigate fibre optical parametric amplifiers (OPA) and oscillators (OPO), in terms of their potential for efficient large frequency-shift wavelength conversion. The underlying physical mechanism of fibre four wave mixing (FWM) offers simultaneous up-conversion and down-conversion in frequency to arbitrary wavelengths, determined by the pump wavelength and chromatic dispersion of the fibre. Using optical pulses from an ytterbium-doped fibre master-oscillator power-amplifier (MOPA), at a wavelength of 1080 nm, I experimentally and numerically evaluate the suitability of various fibres for frequency up-conversion towards the visible spectrum. The use of an Yb-doped fibre source allows for all-fibre integration with fibre optical parametric devices, potentially making it a viable alternative to expensive bulk sources currently employed in the sub-1-μm spectral region. To accommodate an all-fibre configuration, the first part of the thesis numerically investigates polarization maintaining (PM) as well as higher-order mode fibres for phase-matched FWM at relatively modest pump peak powers (< 1 kW). Experiments using the PM fibre in an OPA configuration, and employing multiple seeding arrangements, are subsequently presented. Here, it is found that the influence of fibre inhomogeneity, coupled with a relatively small parametric bandwidth and competing nonlinear processes, severely impairs the conversion efficiency from the 1080 nm pump wave to the anti-Stokes wave at 840 nm. The work in the second part of the thesis reports on the use of higher-order dispersion phase-matching in a photonic crystal fibre (PCF). In the OPA configuration, this approach proves more efficient and demonstrates parametric conversion over 142 THz to an anti-Stokes wave at 715 nm. The PCF is also reconfigured into an all-fibre uni-directional ring-cavity OPO, for which the dependence on nonlinear converter length, out-coupling ratio, pump pulse duration and intra-cavity filtering are studied. Using a PCF length of 18 m and 800 ps pump pulses with sub-kW peak powers, this all-fibre OPO demonstrates, what is believed to be, a record in-fibre pump-to-anti-Stokes conversion efficiency in excess of 10% over 142 THz. Finally, computer simulations, aimed at realising a dispersion engineered PCF for an enhanced parametric gain bandwidth, is carried out for a pump wavelength around 1 μm. PCF designs of this type, using GeO2-doped core regions, are identified for arbitrary frequency-shift FWM. It is demonstrated that these fibres can enhance the parametric bandwidth by up to three orders of magnitude, which can lead to a significant reduction in the sensitivity of FWM to fibre inhomogeneities. An increased parametric bandwidth should furthermore enable the use of pump sources that are not currently considered to be viable. The fibres are finally also considered in terms of fabrication tolerances.