Many engineering structures are built from frameworks of beams, particularly lightweight structures. For the purpose of noise control from airborne and structure-borne sources, it is useful to be able to predict vibration transmission across these frameworks. This thesis investigates the potential use of Advanced Statistical Energy Analysis (ASEA) to predict structure-borne sound transmission when the beams support multiple wave types due to wave conversion at the junction. In contrast to Statistical Energy Analysis (SEA), ASEA is able to account for high propagation losses and indirect coupling through the use of ray tracing. SEA and ASEA were validated through comparison with measurements and numerical experiments with Finite Element Methods (FEM). When each beam supports at least two local modes for each wave type in the frequency band of interest and the modal overlap factor is at least 0.1, FEM and measurement data tend to have average values which form smooth curves such as those predicted by SEA and ASEA. It was shown that SEA and ASEA models could incorporate Euler-Bernoulli and Timoshenko theory by changing over from Euler-Bernoulli to Timoshenko group velocity when calculating the coupling loss factors. However, comparisons with measurements were not conclusive although there were indications that a suitable crossover frequency could be when Timoshenko and Euler-Bernoulli group velocities differ by at least 26%. Agreement between FEM and ASEA indicates that it is appropriate to ignore phase effects in the ray tracing approach used with ASEA. This was particularly noteworthy for the three-bay and five-bay truss beams as these were perfectly periodic for which phase effects could be important. Results for an L-junction, a rectangular beam frame and a five-bay truss with relatively long beams and relatively high internal loss factors demonstrated that ASEA was able to incorporate high propagation losses. This was not possible with SEA. For a three-bay truss beam with relatively short beams ASEA showed close agreement with FEM and measurements confirming that there was significant indirect coupling rather than high propagation losses. There are indications from the five-bay truss beams that ASEA may no longer be accurate in predicting the response on beams that are at least three structural junctions away from the source beam, particularly when ASEA predicts high propagation losses on the receiving beam.

The aim of this PhD work is to develop a novel and effective instrument to characterize the mechanical properties of viscoelastic material. The principle of this system is based on nanoindentation technique, which is widely used in recent years to explore the mechanical properties of various materials. However, quite a few studies demonstrated that the determination of mechanical properties of viscoelastic material by using the standard Oliver Pharr method would lead to incorrect results. Based on this issue, a new improved tribological probe microscopy (TPM) system was established to carry out the investigation of mechanical properties of viscoelastic materials. Materials including polytetrafluoroethylere (PTFE), styrene rubber and nitrile rubber were measured under quasi-static mode of nanoindentation. The inaccurate results proved that static indentation analyzed by the Oliver Pharr method is not suitable for current work. In addition, dynamic indentation was performed to measure these samples. The results demonstrated that it is a good approach to explore time-dependent properties of polymer samples. The dynamic method offers more abundant viscous information. Moreover, another measurement function was added in this facility to perform creep nanoindentation on viscoelastic samples. It enables to generate instant and infinite modulus as well as time constant. The comparison between the results obtained by dynamic and creep indentation reveals that the more physical element should be considered to bridge the gap between these two approaches. Extra works focus on the relationship between surface topography and its mechanical properties. Finite element simulation as well as actual experiments were performed to investigate the tilt effect on the results of mechanical properties. The results revealed that the standard Oliver Pharr method underestimated the contact area, which will result in overestimating the hardness and elastic modulus of engineering materials. Above all, this study proved the ability of our home made facility to further explore the viscoelastic material. More importantly, it will pave a new way for the investigation of the relationship between the surface topography and viscous property of soft matter including various biomaterials in the near future.

Machining of thin wall structures is a challenging area due to the problems such as chatter and forced vibrations that arise due to low stiffness of such structures. Up to now, most of the research was driven by need to improve productivity in manufacturing of aircraft components such as airframe panels; hence, straight thin walls such as cantilever structures were considered for research in machining dynamics. However, thin wall casings and particularly thin wall assemblies that are encountered in jet engine casings are not well studied. Not only their dynamics is quite different from that of straight thin walls, they present a different set of challenges for fixturing to minimise machining vibrations. Hence, there is a two-fold need of research: (i) to understand the effect of dynamics of thin wall casings on interaction of tool and workpiece and (ii) to design and validate damping solutions to minimise machining vibrations in such structures. In this work, both the above objectives are addressed. Initially a coupled dynamic interaction of tool and workpiece is studied through experimental analysis of machining vibration signal. This study was carried out both on a straight thin wall cantilever and on a thin wall casing to present the effect of variation of dynamics on dynamic coupling between tool and workpiece. The machining vibration signal was analysed in frequency and time-frequency domain to see which of the elements (tool or workpiece) are dominant during machining. For providing fixturing solutions to minimise machining vibrations, initially tuned mass dampers were studied. Tuned dampers with increased mass ratio were studied to see their effect in minimising vibrations. Subsequently, two novel surface damping solutions - viscoelastic based surface damper and torsion spring fixture - were proposed and validated experimentally. The design philosophy behind both these solutions is to improve mass and stiffness of the casing in addition to imparting damping. Finite element modelling was carried out to predict the dynamic response without and with proposed solutions.

Aviation is a pastime enjoyed by many amateur pilots. Of the 21 000 aircraft registered in the UK [1], 96% are engaged in general aviation activities (non-commercial flying). The UK Civil Aviation Authority (UK CAA) classifies microlights, gliders and autogyros as recreational sports aircraft. Of the 21 000 UK-registered general aviation aircraft, only 306 are autogyros, compared to over 4300 microlights and almost 2600 gliders. Despite this fact, the autogyro has been seen to exhibit a fatal accident rate up to 100 times higher than those of the microlight or glider. In response to the identification of this high accident rate amongst autogyro type vehicles, the CAA commissioned a programme of research intended to understand the cause. This research, undertaken in the UK by the University of Glasgow, consisted of analytical, wind tunnel and flight test activities. These studies concluded that the autogyro displayed “conventional lateral and directional dynamic stability characteristics”, and that both the static and dynamic stability (in particular, a lightly damped phugoid mode) was highly sensitive to the vertical position of the centre of gravity (c.g.) relative to the propeller thrust line. The lack of provision within the autogyro community to collect meaningful data in relation to the airworthiness requirements was also highlighted. Outside of the work performed as part of the research programme that generated this report, there is still considered to be “little indication that rigorous scientific or engineering investigation of airworthiness has occurred”. Therefore, there remains significant scope for further research into just what makes autogyros so unsafe to fly and how to improve their airworthiness. Prior research into the autogyro and its aerodynamic characteristics can be broadly divided into two phases, the first being from its inception in 1923 to the beginning of World War II and the period between 1996 and the present day, when a resurgence of interest in the autogyro began to occur. Much of the early works concentrate on characterising the autogyro’s aerodynamic characteristics, relying heavily upon wind tunnel testing, flight testing and analytical investigation to establish an understanding of the fundamental flight dynamics of the autogyro. With the first flight of the first functional helicopter, the outbreak of World War II and the death of the inventor of the autogyro, research interest in this aircraft type was critically diminished. Only three papers on the subject of autogyros were published between 1939 and 1996. The Air Accident Investigation Branch (AAIB) review of the airworthiness of the grounded Air Command autogyro, conducted after the occurrence of 5 fatal accidents between 1989 and 1991, recommended the commissioning of a programme of research into both the airworthiness and aerodynamic characteristics of light autogyros. As a result of this recommendation, the autogyro experienced a resurgence in research interest, culminating in the publication of a CAA Paper which presented 4 recommendations intended to improve the airworthiness of the autogyro: 1. It is recommended that the vertical location of the centre of gravity (c.g.) should lie within a ± 2 inch envelope of the propeller thrust line. 2. Horizontal tailplanes are largely ineffective in improving the long term pitch dynamic stability (phugoid mode). 3. Extreme manoeuvring can lead to excessive rotor teeter angles during certain phases of flight, potentially resulting in the rotor blades striking the prop or empennage. 4. The chordwise centre of gravity of the rotor blades should always lie at or ahead of the 25% chord position to prevent rotor blade instability. One of the primary aims of this Thesis was to assess the validity and applicability of these recommendations; in order to do so, a simulation model of an autogyro was created. The model was based on the G-UNIV research autogyro owned by Glasgow University and validated against flight test data in order to ensure the required level of fidelity was achieved. Upon re-assessing the recommendations, in some cases, different conclusions were drawn. The first recommendation, while accepted as a sensible design aim, was found to be overly restrictive. BCAR Section T, the airworthiness specification for autogyros, specifies requirements on the period and time to half amplitude of any longitudinal oscillations present in the aircraft. Limiting the vertical position of the centre of gravity to within ±2 inches of the propeller thrustline resulted in forcing a design which is compliant with the requirements of BCAR Section T outside the specified range, to become non-compliant when the centre of gravity lies within the range. Recommendation 2 suggests that the removal of the tailplane of the aircraft has little impact on the longitudinal trim control positions and the characteristics of the phugoid mode. It was found that the results from the simulation model disagreed with this conclusion; the removal of the tailplane changed the characteristics of the phugoid model and the trimmed control positions significantly. The third recommendation highlighted the potential for a rotor blade to strike the propeller or the empennage under extreme manoeuvring. The simulation environment provided a safe environment in which to test this recommendation; it was found under the loading of an extreme manoeuvre it was possible for the main rotor to strike the tail, supporting the conclusion drawn in CAA Report 2009/02. It was not possible to assess the fourth and final recommendation, relating the positioning of the chord-wise position of the blade centre of gravity, due to the limitations of the simulation model developed. Another focus of the recent work surrounding the autogyro has been on quantifying and assessing the handling qualities of such vehicles. This presents many challenges, including the fact that no autogyro-specific handling qualities specifications currently exist. One of the main themes of this Thesis was to progress towards the creation of such a specification, either through development of a new methodology or development of existing specifications, such as ADS-33E-PRF. The first steps in this field have been taken by Glasgow University using ADS-33; the primary specification used in the assessment of military rotorcraft. Assessment of the autogyro was previously carried out in a real-world flight trial using existing Mission Task Elements (MTEs) taken from ADS-33, the Slalom and the Acceleration-Deceleration. The results from this trial were then used to derive proposed Level 1, 2 and 3 boundaries for quickness and pilot attack. This Thesis replicated this trial using real-time piloted simulation, and the method described in the work carried out by Glasgow University was also utilised to derive a set of predicted handling qualities Levels for both quickness and pilot attack. It was found that the predicted Level boundaries generated from the simulation trial did not agree well with those predicted in the original flight trial. There were several reasons for this; in the original flight trial the pilot used a non-standard technique to fly the Slalom manoeuvre, using sideslip to complete the test course. Additionally, both the original flight trial and the simulated flight trial used data from several different course geometries. This resulted in the ordering of the Level boundaries being reversed for the Levels predicted by the simulated flight trial, as those test points carried out on the more aggressive course geometries received lower handling qualities ratings, whilst using the most aggressive control inputs, compared to those on easier courses which used lower magnitude and aggression inputs, and thus a lower quickness, while receiving better handling qualities. Recommendations were made to address these issues in future iterations of this work.

Oxide dispersion strengthened (ODS) steels contain a fine dispersion of nano-sized, typically Y based, oxide particles which result in the material displaying significantly better creep, irradiation and oxidation resistance when compared to conventional alloys. Thus, such materials are considered as candidate structural materials for a number of applications in the fossil and nuclear energy sectors and in other high-temperature applications. ODS steels are currently produced by powder metallurgy which includes mechanical alloying (MA) of master alloys or elemental powder, hot extrusion or hot isostatic pressing (HIP) followed by a final heat treatment. Recent studies revealed that Y added during MA in the form of yttria (Y2O3) breaks down and the elements go into supersaturated solution in the Fe matrix; and Y based dispersoids form during fabrication of the alloy. In this work, an additive manufacturing method, selective laser melting (SLM), was applied to as-MA ODS-PM2000 (Fe-19.0wt.%Cr-5.5Al-0.5Ti-0.5Y2O3) powder. SLM produces almost fully dense solid freeform components by successively melting thin layers of metal powder. In order to investigate the feasibility of SLM in an ODS alloy environment, a number of builds were fabricated. These included a complex thin walled structure, coatings on Inconel IN939 (Ni-22.5wt.%Cr-19.0Co-3.7Ti-2W-1.9Al-1.0Nb-1.4Ta-0.15C), a nickel based superalloy, and optimised wall and solid builds. A wide range of microstructural and mechanical characterisation techniques were carried out on these builds with the focus to study the fundamentals of SLM in ODS environment. The most important finding of this work was that a fine homogeneous dispersion of globular shaped nanoscopic particulates could be retained in the SLM build configurations investigated. Indications were found that there is a very low number of dispersoids in the deposited layer after it was put down. Repeated heating cycles during SLM deposition of further slices resulted in coarsening and growth of existing precipitates, but probably also in nucleation and growth of new dispersoids in the α-Fe matrix. Such heating cycles and post-build annealing trials resulted in modification of initially multiphased dispersoid compounds including originally a number of elements, such as O, Al, Si, Ti, Cr, Fe and Y, into structures having significantly increased concentrations of Al and Y. After post-build annealing, the particles were most frequently of the compound type yttrium aluminium monoclinic, Y4Al2O9. SLM processing parameters were developed leading to a relative density of >99.5 % for wall builds having different thicknesses and of >98.5 % for solid builds. Electron backscatter diffraction (EBSD) was conducted and revealed a strong [001] fibre texture along the growth direction of a wall build. For annealed walls, values of the 0.2% offset yield strength YS0.2 up to those of recrystallized conventional produced PM2000 could be achieved. Fracture behaviour and the individual key parameters determined, YS0.2 and Young's modulus were anisotropic due to this texture. In coatings, Y-rich dispersoids could be retained. When oxidised isothermally in laboratory air at 1100°, the SLM deposit PM2000 formed a mainly α-Al2O3 (alumina) scale, which was similar to conventionally fabricated PM2000. Oxidation at 870°C, however, resulted in different scale morphologies between both variants. Those were Al-rich equiaxed structures and nodules and Ti-rich needles for conventional PM2000. On the other hand, the SLM material exhibited Al-rich platelet structures and Al-rich equiaxed crystals in pores. The observations of this work confirmed the feasibility of SLM in ODS alloy environment, which may motivate further studies in this field.

Many Public-Private Partnership Projects (PPPs) have failed because of risks occurring during operation and earlier studies have demonstrated a need for risk assessment and allocation methods for PPPs. Although researchers have been working in this area for years, the amount of empirical work is limited, especially when applied to developing countries, particularly to Vietnamese PPPs. This research attempts to design a framework using quantitative methods. Besides, qualitative methods are also used as supportive methods. The framework is proposed to identify risks, allocate risks, evaluate the project’s riskiness and return, and optimize concession parameters. The proposed framework is based on two fundamental theories which are Analytical Hierarchy Process (AHP) and Risk Adjusted Decoupled Net Present Value (Risk Adjusted DNPV). In AHP, the subjective evaluations are converted into numerical values and analysed to rank each alternative on a numerical scale. A pairwise comparison is then applied to the alternatives regarding specific criteria. Mathematical analysis is then used to create a comprehensive comparison of alternatives. Therefore, in this framework, first, critical risks are identified and evaluated based on their probability of occurrence and the degree of impact. After that, AHP is used to evaluate alternatives’ (projects) riskiness. In addition, AHP is used to allocate critical identified risks with regards to the ability criteria of each party. Risk adjusted DNPV in this framework is used to evaluate returns of the projects and to optimize the concession parameters. Currently, Net Present Value method (NPV) is being widely used to evaluate projects’ returns because of its simplicity to investors. In the NPV method, risks are accounted for by adjusting a “risk-free rate” to form a risk-adjusted discount rate (RADR), and then the RADR is used to devalue cash flow with time. However, it has been argued that time and risk are different variables, and they should be separated in evaluating projects, otherwise evaluation errors can be generated, especially for projects which require long-term investment. PPPs typically demand long-term investments. Consequently, PPPs should be an environment in which the limitations of NPV are exposed. To minimize the limitations of NPV, Risk Adjusted Decoupled Net Present Value method (Risk Adjusted DNVP) has been developed as a new tool to assess projects. In Risk Adjusted DNVP, risks are decoupled from the time value, and they are quantified and treated as a cost to the project. Nevertheless, Risk Adjusted DNVP has not been applied to the area of PPPs. Therefore, this research attempts to use DNPV to evaluate projects’ returns, and to optimize concession parameters. This research also clarifies how the public and private sector can use the proposed framework. Case studies from five Vietnamese PPPs will be shown in the thesis to demonstrate the proposed framework.

The Internet has become the dominant means of communication in modern society. Increased use of and dependence on such things as email and the web has speeded up communication and allowed for a wide range of new ways in which we can communicate. The use of social media and Internet based shopping are amongst the most common forms of this development. Images are particularly common in such media. They are used for all sorts of purposes – from displaying products or pictures of individuals to decorations of all sorts. Blind people have the same rights and needs to use these modern technologies and so making sure that they can gain benefit from the images contained on these media is vital. The World Wide Web Consortium has drawn up specifications for the ways in which such images should be adaptable for best value by blind users. However, a large proportion of authors of web content do nothing to annotate the images they use in a way that would be of value to blind users. A number of attempts have been made to create adaptation processes in which descriptions can be added to images after the page has been created. All of these methods use information and activity outside of the process of loading the pages – often involving large amounts of human effort. The work for this research has identified that it is possible to take the information that is already available inside the web pages themselves to enable valuable descriptions to be added to all image elements within pages in such a way that the usefulness of the images is improved for blind users. The software developed has made use of an algorithm which can define image purpose. In addition the algorithm uses mining of local data on the web pages to determine the relationship between the images and the text on the page to create an annotation of the images which is meaningful. An ethnographic study has revealed that the image descriptions should be clear, precise and meaningful and this has been the major aim of the software that has been developed. The mechanism was tested with two groups of blind users under different conditions. The first test revealed inadequacies in the software. These were tackled and the second test showed that the software enabled all users to gain better access to images in web pages that were adapted by the software than they were able to achieve for non-adapted web pages. A number of possible extensions to the work have been established.

The thesis looks at approaches to the detection and tracking of potential objects of interest in surveillance video. The aim was to investigate and develop methods that might be suitable for eventual application through embedded software, running on a fixed-point processor, in analytics capable cameras. The work considers common approaches to object detection and representation, seeking out those that offer the necessary computational economy and the potential to be able to cope with constraints such as low frame rate due to possible limited processor time, or weak chromatic content that can occur in some typical surveillance contexts. The aim is for probabilistic tracking of objects rather than simple concatenation of frame by frame detections. This involves using recursive Bayesian estimation. The particle filter is a technique for implementing such a recursion and so it is examined in the context of both single target and combined multi-target tracking. A detailed examination of the operation of the single target tracking particle filter shows that objects can be tracked successfully using a relatively simple structured grey-scale histogram representation. It is shown that basic components of the particle filter can be simplified without loss in tracking quality. An analysis brings out the relationships between commonly used target representation distance measures and shows that in the context of the particle filter there is little to choose between them. With the correct choice of parameters, the simplest and computationally economic distance measure performs well. The work shows how to make that correct choice. Similarly, it is shown that a simple measurement likelihood function can be used in place of the more ubiquitous Gaussian. The important step of target state estimation is examined. The standard weighted mean approach is rejected, a recently proposed maximum a posteriori approach is shown to be not suitable in the context of the work, and a practical alternative is developed. Two methods are presented for tracker initialization. One of them is a simplification of an existing published method, the other is a novel approach. The aim is to detect trackable objects as they enter the scene, extract trackable features, then actively follow those features through subsequent frames. The multi-target tracking problem is then posed as one of management of multiple independent trackers.

This thesis presents an experimental and numerical investigation undertaken in order to develop the understanding of the behaviour of orthogonal 3D woven composites under quasi-static tension/compression, out-of-plane bending and dynamic soft and multi-hit ballistic impact load cases. Focus is given to the deformed configuration of samples, and to the initiation and propagation of damage within the material. The damage mitigation properties of the through-the-thickness (TTT) reinforcement are highlighted throughout. A pressurised gas gun test system was developed at the University of Nottingham in order to undertake the soft and ballistic impact tests upon 3D woven composite samples. Experimental and numerical comparisons are made to similar UD-laminate composite materials. An established continuum damage mechanics framework is employed for numerical modelling of the quasi-static and soft impact load cases, allowing for further insights into the experimental results. A review of the efficacy of the numerical modelling strategy is presented, alongside a study on the influence of the TTT reinforcement on the out-of-plane static and dynamic response of the material. The numerical modelling strategy is then adapted for ballistic impact events. A numerical study is conducted on the multi-hit ballistic impact properties of orthogonal 3D woven composites, the first of its kind. Comparisons are made between experimental ballistic impact experiments and numerical calculations.

This thesis is focused on the investigation and implementation of novel techniques for the design of X band (8 - 12GHz) power amplifiers. One of the main topics is the expansion and novel implementation of continuous mode theory, with the intention of improving the bandwidth and efficiency of X band power amplifiers. This work builds upon the Class B/J continuous mode theory to incorporate cases where <[ZF0] 6= RL, not described by the original Class B/J theory, with a tool called the “clipping contour”. The clipping contour tool shows a graphical representation on the Smith chart of the boundary between impedances generating a voltage waveform which will modulate or “clip” the current waveform, and a voltage waveform which will leave the current waveform unaltered. This non-clipping space is shown, with measured load pull and amplifier data, to represent the maximum efficiency case for a given ZF0, thus the clipping contour tool thus gives designers the ability to predict the areas of highest efficiency and power given any ZF0, without the need to use costly, time consuming multi harmonic load pull techniques. Push pull amplifiers using quarter wave coupled line baluns are proposed as an ideal matching topology to exploit this new tool. Various balun topologies are studied using a novel extended transmission line model. This model is shown to predict accurately and explain the “trace separation” effect seen in planar baluns and not their 3D coaxial cable equivalents. It also forms the basis of analysis which results in a powerful new equation capable of guaranteeing the elimination of trace separation completely, without compromising performance. This equation is used to design an optimal balun which possesses the largest fractional bandwidth (130%) of any balun ever published on single layer thin film Alumina, whilst simultaneously eliminating trace separation. The optimised Alumina baluns are used to construct push pull output demonstrator circuits which show efficiencies of 40% over greater than an octave bandwidth, a significant advancement of any other comparable published work. These techniques demonstrate the potential to exceed double octave bandwidths with efficiencies greater than 40% once optimised. Initial investigations on MMIC and 2.5D processes show the potential to replicate the Alumina performance over octave and decade bandwidths respectively.