Natural fibre reinforced composites have been extensively used in non-structural components, mainly in automotive industry. For these composites to be used in structural applications, an understanding of fracture toughness behaviour is important. In this study, the influence of water absorption and hybridisation of flax and flax/basalt hybrid laminates are presented with the aim to investigating the Mode I and Mode II interlaminar fracture toughness characteristics. Four types of composite laminates namely, neat vinyl ester (neat VE), flax fibre reinforced vinyl ester (FVE), flax fibre hybridised basalt unstitched (FBVEu) and flax hybridised basalt stitched (FBVEs), were fabricated by vacuum assisted resin infusion technique. Double cantilever beam (DCB) and Three-point-end-notched flexure (3ENF) tests were performed to evaluate the critical strain energy release rates, GIC and GIIC (initiation and propagation) as well as the crack length (R-curve) in dry and wet conditions by using different data reduction methods. The morphology of delamination and the fracture shear failure of composite laminates were evaluated using scanning electron microscopy (SEM) and X-ray micro computed tomography (μCT). From the experimental results, it was found that the Mode I fracture toughness initiation GIIC init. and propagation GIIC prop. of water immersed FVE composites were decreased by an average of 27% and 10% respectively, compared to the dry specimens, whereas the fracture toughness propagation of water immersed FBVEu and FBVEs composites were increased by approximately 15% and 17% compared to dry specimens. The results of Mode II fracture toughness obtained experimentally exhibited that the fracture energy of FBVEu composites, GIIC init. and GIIC prop. were improved by 58% and 21%, respectively compared to that of FVE dry specimens. Moisture absorption behaviour caused an increase in the ductility of matrix which resultantly improved the resistance to crack initiation. However, there was a reduction in the fibre/matrix interfacial strength of FBVEu wet composites and a deterioration in the delamination resistance to crack propagation. The critical strain energy release rate of neat VE increased about 52% with reinforcement of flax fibre composites. The fracture mechanisms showed energy dissipation through matrix deformation, fibre pull-out, fibre debonding, and fibre breakage. The experimental results confirmed that basalt fibre hybridisation enhanced the durability and water repellence behaviour of flax fibre reinforced composites. Finally, this thesis provides a unique manufacturing technique to improve the interlaminar fracture toughness of flax fibre and flax/basalt hybrid composite laminates to be used in load bearing applications as an alternative to E-glass fibre reinforced composites. The outcomes of this study will be beneficial to automotive, marine and construction industries. In addition, the findings of this study will be useful for academic and researchers who are involved in the research and development of sustainable composites for light-weight structural applications.

The electricity network is undergoing significant changes to cater to environmental-deterioration and fuel-depletion issues. Consequently, an increasing number of renewable resources in the form of distributed generation (DG) are being integrated into medium-voltage distribution networks. The DG integration has created several technical and economic challenges for distribution network operators. The main challenge is basically the problem of managing network voltage profile and congestion which is caused by increasing demand and intermittent DG operations. The result of all of these changes is a paradigm shift in the way distribution networks operate (from passive to active) and are managed that is not limited only to the distribution network operator but actively engages with network users such as demand aggregators, DG owners, and transmission-system operators. This thesis expands knowledge on the active distribution system in three specific areas and attempts to fill the gaps in existing approaches. A comprehensive active network management framework in active distribution systems is developed to allow studies on (i) the flexibility of network topology using modern power flow controllers, (ii) the benefits of centralised thermal electricity storage in achieving the required levels of flexibility and resiliency in an active distribution system, and (iii) system resiliency toward fault occurrence in hybrid AC/DC distribution systems. These works are implemented within the Advanced Interactive Multidimensional Modelling Systems (AIMMS) software to carry out optimisation procedure. Results demonstrate the benefit provided by a range of active distribution system solutions and can guide future distribution-system operators in making practical decisions to operate active distribution systems in cost-effective ways.

The phase and volumetric behaviour of reservoir fluid properties, referred to as pressure-volumetemperature (PVT) properties, involve the thermodynamic studies of the fluid with respect to pressure, temperature and its volumetric compositions. PVT properties are usually determined by laboratory experiments performed on the actual samples of the reservoir fluid. Failing that, these fluid properties have been evaluated by some other methods such as equations of state, empirical correlations and recently, machine learning models. Machine learning is basically the prediction of the future with, (supervised learning), or without, (unsupervised learning), prior knowledge of the past. A common problem for the standalone machine learning technique is local minimum. In view of this, ensemble systems and hybrid techniques have been developed successfully for improvement in different fields. This work introduces two different ensemble methods based on support vector regression and regression trees where both ensemble approaches utilise a novel concept tagged "Tying Ranking" in selection of the base models. Also, a hybrid system for reservoir fluid characterisation with a novel way of grouping petroleum fluid properties using intelligent method was developed. The hybrid system uses K-Means clustering for the intuitive grouping along with functional networks for the prediction. The performance and generalisation of the developed models are compared against their standalone and selected empirical models using some statistical measures which are commonly used for performance evaluation in the petroleum industry. In the first category of experimentation, the impact and effect of training the machine learning models with more diverse and bigger data set is shown. Effects of using different functional forms to predict dead oil, saturated and undersaturated viscosity are also explored. In addition, impacts of different statistical measures on the predicted outputs and wrong interpretations of results in the literature are examined. The main statistical measures that are used for comparison are root mean squared errors, average absolute percentage relative error and maximum absolute percentage relative error. For each of the reservoir fluid properties considered in this work, at least one or more of the developed machine learning models have better overall and average performance than all the compared correlations in each category. The superiority of the three developed machine learning models is visible in the trend analysis as they show less deviations in results compared to the empirical correlations and their standalone methods in most cases for all the considered reservoir fluid properties.

No description available.

This thesis presents the research carried out on the integration of filters and antennas for wireless transceivers. Filters and antennas are parts of wireless transceivers of all wireless communication systems. Filters and antennas, albeit connected, are separate circuits which take up their own individual space in wireless transceivers. Moreover, since they are individual circuits, the cost to manufacture them is also separate. Hence, to effectively combine them together in the form of a single component has a number of advantages. The overall size of the wireless transceivers with such a single component will reduce. There will be a decrease in the manufacturing cost as well. In addition, the single component will use a single feed network and may also utilise a common ground plane. The research is driven by the goal of achieving a successful and efficient integration of filters and antennas for wireless transceivers of various wireless communication systems. The research further aims to show that the integration of filters and antennas can address issues pertaining to broadband and narrowband antennas and achieve their solutions. These include the integration of bandstop filters with ultra-wideband bandpass filters and within broadband antennas in order to reject some specific interfering frequency bands and the integration of bandpass filters with narrowband antennas in order to suppress frequency harmonics and noise. In order to achieve the goal of the research, a methodical approach was adopted. Initially, individual components were designed and electromagnetically simulated. These included bandstop and bandpass filters and broadband and narrowband antennas. After that, bandstop filters were integrated with broadband antennas — forming “broadband filtennas” — and bandpass filters were integrated with narrowband antennas — forming “narrowband filtennas”. Furthermore, the ability to switch off or switch on the bandstop filters in broadband filtennas was incorporated by making the broadband filtennas reconfigurable using standard PIN diodes and novel Graphene based switches. Both sets of filtennas were designed, electromagnetically simulated and their prototypes fabricated. The prototypes were fabricated using the conventional printed circuit board technology and the newly emerging inkjet-printing technology. Hence, both rigid and flexible filtennas were constructed. The fabricated prototypes were then measured. The simulated and the measured results include S-parameters, current density, distribution of surface currents, radiation patterns, gain and efficiency. Satisfactory and desired results have been obtained for all the developed filtennas; with a reasonable agreement between the simulated and the measured results. With such results, it can be concluded that the research presented in this thesis reached the intended target and made a significant contribution to knowledge.

No description available.

This research aims to analyse inter-organisational collaboration activities and mechanisms in general and also those specific to the nanotechnology field with the purpose of identifying their effectiveness and efficiency in innovation processes. This research proposes and adapts two new frameworks to be used in its analyses and also in future studies. Following these frameworks, this study investigates the nanotechnology patent network to identify many important aspects of it, such as: key actors, network structures and national differences. Some of the research objectives are: 1) to examine the key determinants of collaborative innovation mechanisms that encourage or hinder organisations to involve themselves in collaborative innovation activities; 2) to discover how the collaboration mechanism impacts the innovation process in the nanotechnology field; and 3) to analyse what kind of collaboration mechanisms exist at different stages of the innovation process. This comprehensive study applies a mixed-method approach that combines both patent and interview data analyses, and draws upon an extensive data sample. The patent data covers almost fifty thousand patent documents that are well-optimised for this study, and the interview sample covers the key experts across different regions. The main contributions of this research are theoretical, empirical and practical as well as methodological contributions to the field. The results of patent data analyses identify many key issues in this field, such as collaboration activities for key organisations, nations' competitiveness and innovation networks in the nanotechnology field. The results of interview analyses present a comparative study on the collaboration structures across the UK, the US, Germany and China. In addition, this research provides case studies of where inter-organisational collaborations resulted in innovations to illustrate successful scenarios for the nanotechnology field. The analysis of the nanotechnology innovation networks demonstrates that the proposed network model is a useful means of differentiating types of network structures such as mono-linkages, central-linkages and distributed network. With regard to the various stages of collaboration, new funding systems are found to be a mechanism for encouraging organisations to work together from the initial stage of collaboration. To enhance the collaboration mechanism, nanotechnology centres appear to be an effective place to overcome difficulties related to the multi-disciplinarity of nanotechnology. The results show that large organisations are currently the key organizations for the commercialisation process, especially in the electronics industry where high investments are required. SMEs appear to be the key organisations at the incremental level of innovations, and are essential to the expansion and up-scaling of the number of collaborations within the innovation network. The findings of this study are not only applicable to the nanotechnology field; this study could be beneficial within a wider range of social domains (academia, industry, government, intermediaries, fund providers and policy makers) where active and potential organisations are involved in technological collaboration. Moreover, this study differentiates its findings across the selected regions to show national factors, making this study even more valuable.

No description available.

Conservativeness (or conservatism), in general, is a measure of the lack of confidence in any activity that we do in the spheres of life. It is a reflection of our apprehension for the consequences of failure, and hence we instinctively tend to be conservative in order to be safe. Engineering design involves incorporation of various physical characteristics of the materials and systems through various mathematical models and design criteria. These models and criteria are developed based on empirically observed, experimentally measured, logically anticipated, analytically testified and/or hybrid behaviours and responses of materials and systems. All these processes invariably involve uncertainties arising from the deficiency in terms of knowledge, data and time-testimony. Uncertainties also arise from the lack of precision in expressing a phenomenon or mechanics, or from the inherent variability associated with them. All these factors lead to lack of confidence in the use of materials and systems, and compels our designs to be conservative. Comprehending uncertainties in engineering design, and refining their design treatment can pay big dividends. Design of fibre reinforced polymer (FRP) based structural strengthening systems involves an interesting interplay of uncertainties between those inherent in the existing structure being strengthened and those arising from the lack of complete knowledge and time-testimony of using FRP composites for structural strengthening. Most strengthening design guidelines tend to be more conservative than the conventional structural design norms in order to meet the safety targets. A popular approach for achieving this requirement is through prescribing a set of safety factors within the strengthening design, which are substantially higher compared to those used in structural design using conventional materials like concrete and steel. However, FRP composites in general, and their use as externally bonded reinforcement in particular, involve considerable peculiarities compared to the conventional structural materials. Also, the type and form of post-strengthening failure modes exhibit substantial qualitative distinctions compared to the pre-strengthening failure modes. Therefore, the design processes for strength (for new constructions) and additional strength (for strengthening existing structures) can have conflicting design requirements and objectives. A strategy of prescribing quantitatively higher safety factors, under this condition, could be ineffective in producing required conservativeness for some design scenarios, and can instigate undesirable side-effects. This thesis aims at assessing performance of flexural and shear strengthening design processes under the identified contradictory and contrasting features of the safety format used in strengthening design. It also provides a deeper interpretation of conservativeness in strengthening design by identifying implications of the means employed for producing conservativeness on the course of strengthening design process and on the quality of the resultant strengthening design solutions. An exhaustive review of literature, spanning over past three decades, on the design for structural strengthening using externally bonded FRP reinforcement has been carried out. This review has identified various sources of uncertainties, gap in knowledge and design conflicts associated with the mechanics of FRP-based structural strengthening systems. Detailed taxonomies of uncertainties and safety parameters concerning FRP-based structural strengthening systems have been proposed. The uncertainties are classified into constitutive and behavioural uncertainties. The former are attributed to the variability in constitutive material properties of FRP, while the latter are due deviations between the ideally expected or real behaviours of FRP composites and that predicted within the design process. It is suggested that the utility of this study can further be increased by developing an expert system based on the directions and knowledge-based presented within this study. The applicability of this study can be expanded by converting it into probability-based reliability format that can inform us on the fragility and risk profiling. It is also shown that the concept of conservativeness can also be extended to cover issues related to structural robustness and resiliency.

Building on the historic work of Huffman (Demaine et al. 2011), there has been increasing recent interest in the digital design and architectural application of curved-crease folded (CCF) geometries. This is particularly timely, given the new possibilities of producing curved surfaces from flat sheet material afforded by developments in robotic technology. However there are difficulties in interactively modelling such geometries, which stem from the lack of both appropriate geometric descriptions and constructive tools available in commercial CAD software. The author’s initial survey of methods included both the iterative optimization-based methods and simple constructive methods. Most methods presented difficulties for incorporation within an intuitive, real-time, edit-and-observe exploratory method. This research overcomes attempts to overcome these difficulties through the use of Dynamic Relaxation (DR) (Day 1965) for the interactive modelling of CCF geometries. It applies discrete differential operators and their gradients(Meyer et al. 2003), within a DR framework, to perturb meshes to satisfy the geometric criteria of CCF geometries outlined in Kilian et al. (2008). This research also outlines procedural strategies for generating appropriate topologies of an initial mesh, and a novel method for applying boundary conditions. The dissertation also includes a broad overview of existing methods to model developable surfaces, simulate elasto-plastic behaviour of thin (inextensible) shells and 2D parameterization of 3D meshes.