There has been much interest in the optical and mechanical properties of metal nanostructures and the possibility to use them as very high frequency opto-acoustic transducers. This interest stems from the ability of such devices to work as sources of ultrasound when a short optical pulse is used to thermally excite them producing GHz acoustic waves. This vibrational response can be detected in the time domain (with other short optical pulse) by measuring the changes in the scattered light using a technique called time-resolved pump-probe spectroscopy. In particular, these devices may allow the generation of ultrasound with very high spatial frequencies (short wavelengths and oblique directions) that will enable very high resolution imaging. In this thesis, the use of spherical metal nanoparticles as nano-sized opto-acoustic transducers will be explored by time-resolved pump-probe spectroscopy measurements using solid and core-shell nanoparticles made by a single metal layer and dielectric-metal layers, respectively. Firstly, the study of the optical and mechanical responses of these devices will be studied by analytical and finite element models. This allows one to obtain the absorption/scattering coefficients and vibrational modes of metal nanostructures by solving Mie and Lamb theory, respectively. Then, time-resolved experimental data will be compared with the modelling achieving two main results. Firstly, the possibility of ``turning off'' the detection mechanism of these devices by tuning the probe wavelength without affecting the generation mechanism. Secondly, the development of a size characterisation technique which can obtain the size of individual particles, their size distribution and also, may be able to obtain information about the surrounding medium. Finally, the main novelty of this work will be described showing a new super-resolution imaging/localisation technique. Here, the optical diffraction limit is overcome by resolving several particles inside the optical point spread function by centroiding and differentiating their vibrational frequencies.

The unique electronic structure - partial electron delocalisation (PED) -has been for the first time correlated with pseudocapacitance in graphene-based electrode materials in this study. Pseudocapacitive charge storage was observed on electrodes fabricated from graphene and related materials with different degrees of electron delocalisation (DED%), including graphene oxide (GO), partially oxidised graphene (POG) and polycrystalline monolayer graphene (PMG). GO working electrodes were electrochemically reduced (ECR) via different potential cycling controls to prepare POGs with different DED%. Raman spectroscopy and X-ray photoelectrons spectroscopy (XPS) were used to qualitatively correlate the DED% with the state of oxidation of GOs. It was found that when the ECR was increased from 0 to 1000 potential cycles, the DED% of GO improved from 12.5% to 60.4%. Electrochemical characterisations were used to monitor the charge storage of ECR-treated GOs, i.e. POGs, in 3.0 M KCl and 1.0 M H2SO4, respectively. Cyclic voltammetry (CV) results showed that as the DED of GO was improved, the specific capacitance (Cm) increased from 0.1 to 38.0 F/g in 3.0 M KCl and 0.2 to 62.0 F/g in 1.0 M H2SO4. Electrochemical impedance spectroscopy (EIS) indicated that the improvement of charge storage could be mainly attributed to pseudocapacitance. In the case of PMG, the CV results showed that the value of Cm was ca. 28.0 F/g in 3.0 M KCl and ca. 64.0 F/g in 3.0 M HCl, respectively, although the DED% of PMG was almost 95.0% as derived from the XPS results. The EIS analyses again indicated that the pseudocapacitive contribution predominated the total charge storage. The electronic structures of representative GO models with DED% varying from 0 to 100% were established based on the density functional theory (DFT) modelling. The results showed that extra electronic states only emerged around the Fermi level of POG species (0% < DED% < 100%), but not in fully oxidised graphene (DED% = 0%), nor in pure graphene (DED% = 100%). These states should have originated from the partially delocalised valence electrons rather than those localised electrons. A non-linear relationship between the charge storage capacity and the DED% was found with a peak at between 65.0 and 75.0% of the DED. Finally, by sorting the specific capacitance of the above mentioned graphene species in the order of their DED%, a non-linear relationship has been found again with a peak between 65.0 to 75.0% of the DED. Both the experimental observations and theoretical predictions have revealed a consistent correlation between the pseudocapacitance and the DED% in graphene oxide electrode materials.

This project is focused on accelerating fatigue tests and constant strain rate (CSR) creep tests for composites which are widely used in aircraft due to a higher strength-to-weight ratio. To achieve this ultimate objective, research will be conducted to establish a damage model for linear viscoelastic materials and combine this model with time temperature superposition principle (TTSP). Since the mechanical behaviour of polymer resins exhibits linear viscoelastic properties which are time and temperature dependent, we wish to accelerate fatigue test by using the TTSP which is empirical and phenomenological. Then a damage model needs to be built for these linear viscoelastic materials to provide a physically-based interpretation for TTSP. To understand the properties of viscoelastic materials, a complete damage model was constructed for linear viscoelastic UD composites. Firstly, the damage representation for the corresponding elastic UD composites with an array of dispersed matrix cracks was derived from Li's work based on continuum damage mechanics (CDM). The elastic-viscoelastic correspondence principle was used to obtain the damage representation for corresponding linear viscoelastic UD composites in the Laplace domain. Secondly, a damage evolution law for the transverse direction of the UD composites was derived by making using of the Weibull distribution of defects, and by assuming that damage is driven by strain. To explain the time and temperature effects on the strength of the UD composites, a long-term creep strength prediction model was built by taking advantage of conventional strength prediction models, known as the global load sharing (GLS) model and simultaneous fibre failure (SFF) model. Finally, a rational test acceleration method was proposed by modelling the behaviour of the UD composites during deformation.

Micro-Electro-Mechanical Systems (MEMS) inertial sensors are used to measure acceleration and rate of angular rotation based on the deformation of a small sensitive structure, and are widely used from low-cost commercial to high-performance space and defence applications. Packaging processes can induce thermo-mechanical stresses and curvature within the MEMS die, leading to stressing and deformation of the sensitive MEMS element, which change over time and temperature. These effects cause performance changes over time and temperature, including zero-g offsets and bias and scale factor changes in MEMS accelerometers and quadrature bias changes in MEMS gyroscopes. The die bond, a small adhesive bond attaching the die to the package, can induce significant stresses and deformation in the die that have potential to cause these effects. This thesis focuses on the die curvature induced by the die bonding process, the mechanical properties of bonds, and investigates the changes in properties over temperature and time. The effects of bond design parameters are investigated to evaluate the performance of 4-dot and 9-dot bond shapes to reduce stress and reduce changes in curvature and mechanical properties over temperature and time. The behaviour of these bond shapes and the traditional square full coverage bond with thickness reductions is also investigated. Methods to characterise the mechanical properties of bonds are developed based on vibration testing of plain bonded dies, in bounce and shear directions, and using a single degree of freedom Kelvin-Voigt model with hysteretic damping. These methods are used to characterise different bond designs over the typical operating temperature range of a MEMS inertial sensor, in terms of apparent modulus and loss factor, as well as over time caused by thermal cycling and high temperature storage. White light interferometry is used to assess the die deformation induced by bonding and changes over time. The influence of imperfection effects on the dynamic response of the die is investigated, including coupling between translational and rotational coordinates and the resulting errors induced in the characterised properties. Finite Element models are developed to investigate the bond design parameters and their effect on bond induced curvature and translational die mode frequencies, along with their change over temperature. The results indicate the bond design parameters that are expected to reduce die curvature and property changes over temperature, as well as beneficial bond material properties. It was found that a bond material with a reduced thermal expansion coefficient provided the most significant reduction in die curvature from varying the bond material properties, and greatly reduced the percentage change in bond properties over temperature. It is thought that minimisation of performance effects would be achieved through matching of the bond and adherends thermal expansion rates. The 9-Dot bond was observed to induce the lowest die curvature of the bond shapes investigated and it was indicated that further discretisation would lead to further improvements. To reduce the temperature dependency of the bond properties, the bond should be designed such that it does not experience significant slenderness stiffening effects. To achieve the small thicknesses used in MEMS devices a very low shape factor is required, this can be achieved through a high perimeter to cross-sectional area ratio of the bond shape. Improvements and future works are proposed to allow full assessment of bond design effects experimentally and using finite element modelling. It is recommended for future investigations into die bond designs, to use larger-scale bonded samples, but maintaining slenderness ratios, to reduce the effects of imperfections and noise observed in the experiments, through reduced coupling and increased vibration response and die curvature.

After the identification of the role that the connections between people and information can play in supporting personal information tasks, some means of exploiting these connections to support information re-finding and sharing were considered. Some past research has examined the use of people in relation to information to perform information tasks, primarily applied to information re-finding and sharing. This small body of work, however, has not explored in depth a basis for how best to design interfaces focused on people, to support users in performing personal information tasks in this manner. Two further studies were therefore conducted to explore how to design interfaces that support a greater focus on people -- interfaces that are 'person-centric' in nature. The first of these studies provided a basis for how to design interfaces focused on the use of people for personal information tasks, and the second evaluated a 'person-centric' design based on the findings of the prior study. Designing interfaces that provide a means of accessing or sharing information through interaction with personal contacts requires a means of organising and representing those contacts. Just as the diary study revealed some of the prominent dimensions that information is recalled and ordered by, the design of 'person-centric' interfaces requires a similar understanding of what dimensions influence how to structure and order contacts. In order to design an interface based on supporting information tasks using people as a central component of the interface, how people think about relationships between their contacts and how people would choose to represent their contacts was examined. This was approached in two ways. First, through use of a modified repertory grid method, whereby participants made comparisons between many combinations of their own personal contacts to elicit constructs which described the different forms of relationships they perceived between their contacts. Second, through participants making free-hand drawings that illustrated how they would choose to represent all of their contacts. From analysing this data a categorisation of the different forms of contact groups people perceived was generated. Applying this to the data revealed which forms of expressing relationships were most prevalent, which at the highest level were those related to organisations, locations, relationship types and events. Different forms of representations of contacts, which each structured the contacts in different ways, were also identified from the data. These representations each emphasised different aspects such as overlaps between groups of contacts, the relative importance of contacts, the location of contacts, and the links between contacts. A prototype 'person-centric' system was then developed to evaluate a range of 'person-centric' design concepts for supporting people in performing information sharing and re-finding tasks. This incorporated design ideas based on examination of the re-finding behaviours from the diary study and the examination of contact relationships and representations. The prototype system extracted contacts with whom the user had reciprocated contact from their email and Facebook accounts, as well as related messages, files and links. The user was then able to use the system to create groups of contacts, which could then later be used to aid performing information sharing and re-finding tasks through a series of different 'person-centric' interface presentations. The structure of these presentations could be changed, re-ordered, and filtered based on the results of the repertory grid and free-hand diagramming, which provided a basis for understanding different ways people may wish to order or filter contacts, and the different ways to structure contacts in an interface. The prototype was evaluated in two parts. In the first part the process of contact grouping was studied, and in the second part the design ideas and the use of people as a primary unit of interaction was evaluated. In both parts of the evaluation participants performed think-aloud protocol while interacting with the interfaces to perform the tasks, which was recorded using audio and video capture. In the evaluation of the contact grouping two grouping interface designs were used. The participant's task with the interfaces was to group all of their contacts in each interface condition. The aim of this was to explore what constituted a meaningful contact group and to understand what role interface design played in this. In the re-finding and information sharing interface evaluation participants were questioned about their personal data in order to generate tasks to re-find information, or items to share from their personal data using the prototype system. Using the identified information items, tasks were set using four different representations that supported information sharing and re-finding. These tasks aimed to evaluate the utility of the different 'person-centric' design concepts that had been identified. Following both parts of the evaluation interviews were conducted to understand the experiences and preferences of the participants in using the different interfaces. From the two part evaluation, the decision-making processes of constructing groups and the factors that influence that process were outlined, as well as preferences and behaviour regarding different features of the interfaces that supported performing the information tasks. Evaluation of design ideas from the previous two studies through the prototype confirmed the value of utilising connections made between people and information when re-finding information, and allowed factors that have implications for 'person-centric' interface design to be identified in relation to how contacts and groups should be represented. Through its examination of the use of connections that are made between people and information when performing personal information tasks and the representation of people in interface design, this thesis provides a greater degree of understanding of typical information re-finding behaviours, the representation and relationships of people in interfaces for performing information tasks, the process of constructing contact groups and what constitutes a meaningful contact grouping. It contributes guidelines that inform how to design 'person-centric' interfaces in relation to the structure of representations, ordering and filtering of contacts, and the linking of information to contacts. An improved understanding of the processes involved in contact group creation and factors that influence it with implications for supporting for manual, semi-automated, and automated group creation and identification. As well as a more complete picture of what information re-finding entails through analytical frameworks that describe the how, what, and why of re-finding tasks.

With the aim to achieve a better understanding of the time- and rate-dependent behaviour of unsaturated clays, particularly stiff natural clays, a critical review of the literature and a program of laboratory testing were carried out as part of this research. With emphasis on examining the effect of suction on viscous response, mainly primary and secondary consolidation (creep), stress-relaxation, and rate-dependency, a series of conventional multi-stage loading (MSL) oedometer tests, long-term single-stage loading (SSL) oedometer tests, and advanced constant-rate-of-strain (CRS) oedometer tests were carried out on natural and corresponding reconstituted specimens of a stiff clay namely, London Clay, retrieved from a site in the Isle of Sheppey, UK. The results obtained provide a significant contribution to the existing database and address important knowledge gaps highlighted from the literature review. The experimental studies performed included; a) An investigation of the effect of water reservoir surface roughness on the cavitation mechanism and performance of a newly designed high-capacity tensiometer (HCT), with regard maximum sustainable suction (smax) and maximum duration of measurements (tmax). b) An examination of the influence of soil suction on the primary and secondary consolidation of natural and reconstituted London Clay from a set of MSL and SSL oedometer tests. c) Characterisation of the stress-relaxation behaviour of the reconstituted London Clay subjected to suction and strain-rate variations from a set of CRS oedometer tests in an in-house designed suction-monitored cell. d) An examination of the coupled effects of suction and strain-rate on one-dimensional (1D) stress-strain response of reconstituted London Clay. Based on the experimental findings, the validity of the empirical relationships proposed in the literature for correlating time- and rate-dependency coefficients was examined and necessary modifications were proposed. The main experimental findings can be outlined as: - The mechanism of cavitation in tensiometers is indeed influenced by the surface roughness of the water reservoir. The new approach for expanding the range and duration of suction measurements for a newly designed HCT, based on hydrophilic coating of the reservoir walls, sounds promising. - The compression index (Cc) and creep index (Cαe) and the ratio α = Cαe/Cc for Sheppey London Clay are stress- and suction-dependent. The hypothesis of constant α for natural clays, as suggested by Mesri et al. (1994), is therefore rejected. - The volumetric creep deformations of unsaturated stiff clays appear to be relatively simply modelled by a creep law based on a power function. - A coupled effect of suction and strain-rate on 1D compression response was identified. At a constant suction, the higher the strain-rate, the higher the apparent preconsolidation pressure (σ'p). Similarly, at a constant strain-rate, the higher the suction, the higher the σ'p. - The values of relaxation coefficient (Rα) differ in saturated and unsaturated states. However, a clear relationship between Rα and suction was not found. The Rα = Cαe/Cc relationship, suggested by Yin et al. (2014) for saturated soft clays, appears, with an approximation, to be valid for the unsaturated stiff London Clay in the range of applied vertical stresses and soil suctions in this study. - The process of stress-relaxation in unsaturated clays is highly influenced by factors such as soil suction, pre-relaxation strain, stress, and strain-rate.

To reduce the environmental impact, there is a trend for the thermal power generation industry to increase the usage of the biomass fuel. However, the severe corrosion of boiler materials that is brought about by the high chlorine and alkaline content in the biomass limits the application of biomass fuel and the operation temperature of the biomass boiler. NiCr based alloys that have high Cr content are an ideal solution to combat this problem; they can protect the boiler steel substrate from the chlorine-induced corrosion. There are quite a lot of coating deposition techniques, but the most suitable one for the deposition of Ni50Cr alloy on the boiler material and thereby provides satisfactory protection is still in debate. The major aims of this research included: determining the most suitable coating deposition technique for high temperature oxidation/corrosion applications of NiCr alloys in four candidates (high velocity oxygen liquid/gas fuel (HVOLF/HVOGF) thermal, cold spray and laser cladding); describing and explaining the high temperature oxidation/corrosion performance of coatings deposited using shortlisted deposition routine. The key objectives of this research were: a literature review that can identify the knowledge gap existing in the current research of high temperature oxidation/corrosion NiCr-based coatings; successful deposition of NiCr-based coatings using techniques include in this study, and the deposition product should be of satisfactory quality; high temperature oxidation/corrosion exposure of deposited coatings in test rigs; comprehensive summary of the oxidation/corrosion behaviours of coatings and identification of possible mechanism to explain these behaviours; direction for the future development of high temperature NiCr-based corrosion resistance coatings. To achieve abovementioned objectives, following work were conducted. Short-term air thermogravimetric analysis (TGA) results of as-sprayed HVOF coatings were used to determine the air oxidation resistance of the five HVOF thermal sprayed coatings. The HVOLF and HVOGF coatings that had better air oxidation resistance were hypothesized to have better steam oxidation and fireside corrosion performance and shortlisted for the subsequent high temperature test in various atmospheres. There was no recommended process parameter sets for the laser cladding of the Ni50Cr powder. Therefore, a process window was built to help decide the most suitable parameter set. Laser cladded coating that had satisfactory metallurgical quality, acceptable thickness, maximum width and minimum dilution was selected as the candidate for subsequent high temperature exposure. The optimization process of the laser cladding parameter had been published and was not included in this thesis. The cold sprayed coating was deposited by using the Xi'an Jiaotong University's custom-made cold spray set-up. The microstructure of the deposited cold sprayed coating was acceptable after grinding several top layers of the coating (~ 500 μm), and the coating was placed into the high temperature test rigs for the further investigation of the high temperature oxidation/performance of cold sprayed coating. Longer-term air oxidation (compared with the TGA dwell time), steam oxidation and chlorine-induced fireside corrosion tests of four coatings were conducted in the simulation test rigs built in our laboratory. Following procedures were adopted to investigate the oxidation/corrosion behaviour. In the case of the air oxidation test, three samples of each coating were placed into the high temperature box furnace and was removed from the furnace after 1 h, 10 h and 100 h of exposure time, in succession. In the case of the steam oxidation test, four samples of each coating were sent into the test rig and collected after 250 h, 500 h, 750 h and 1000 h of exposure time one after another. While in the case of the chlorine-induced fireside corrosion test, two samples, with KCl and without KCl deposit on the surface of coating, were the candidates of the 250 h high temperature corrosion exposure. Adopting a relative short exposure time in the chlorine-induced corrosion test was owing to the severe attack ability of chlorine and alkali metal on material. Specimens, after the high temperature oxidation/corrosion and collected at the specific time points, can provide valuable information about the evolution of the air oxidation, steam oxidation and fireside corrosion behaviour of four coatings. Several material characterisation methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were used to obtain the said information. By conducting the abovementioned experiments and analysing the obtained results, the rank of the oxidation/ corrosion resistance of four coatings in various atmospheres at high temperature can be asserted. The mechanism behind the different oxidation/corrosion behaviour for various coatings can be investigated and several possible mechanisms that can explain the observed results are adopted. Finally, a promising Ni50Cr coating deposition method - HOVLF and laser cladding is recommended.

The main purpose of this thesis is on one hand to enhance the current predictive capabilities of the stability of soil slopes and on the other hand, to improve the design practice to stabilise natural slopes showing signs of distress and make the design of engineered slopes more affordable. To achieve the first objective an analytical method achieved by the upper bound theorem of limit analysis and the pseudo-static approach is derived for the assessment of the stability of slopes manifesting vertical cracks and subject to seismic action. The method is validated by numerical limit analyses and displacement-based finite-element analyses with strength reduction technique. Employing this method slope stability charts to assess the stability factor for fissured slopes subject to both horizontal and vertical accelerations for any combination of c, φ, and slope inclination are produced. To achieve the second objective limit analysis was employed to derive a semi-analytical method to extend the applicability of current method to design the slope reinforcement for frictional backfills to cohesive frictional backfills. Design charts providing the amount of reinforcement needed as a function of cohesion, tensile strength, angle of shearing resistance and slope inclination are obtained. From the results, it emerges that accounting for the presence of cohesion allows significant savings to be made, and that cracks are often significantly detrimental to slope stability so they cannot be overlooked in the design calculations of the reinforcement. Also, a new numerical method to determine multi-linear profiles of optimal shapes for reinforced slopes in frictional backfills is presented. The method is based on the limit analysis upper bound method together with genetic algorithms and provides an optimal profile for a prescribed average slope inclination, backfill strength properties and desired number of layers to be used. Several stability charts illustrating the savings on the required amount of reinforcement are provided for the benefit of designers.

Modern technologies for seismic hazard mitigation in building structures, such as passive dampers, make it possible to design economically viable buildings that (a) experience significantly less damage than conventional buildings designed according to seismic codes; and (b) return to service within an acceptable short, if not immediate, time after a strong earthquake. The latter is of significant importance as recent strong earthquakes resulted in high socio-economic losses due to long disruption of the use or occupation of a large number of buildings. Among the different types of passive dampers available in the market, fluid viscous dampers are known for their major advantages including large capacity of energy dissipation and peak forces that are out of phase with the peak drifts of elastic or mildly inelastic structures. Steel moment-resisting frames (MRFs) with viscous dampers are prone to plastic mechanisms that involve hinges in columns because of the large column axial forces due to the large damper forces and have less collapse resistance than conventional steel MRFs designed for the same drift performance under the design earthquake. In this research, a seismic design procedure for steel MRFs with viscous dampers within the framework of Eurocode 8 is developed, addressing the issues of (a) the satisfaction of a sway plastic mechanism with plastic hinges in beams and column bases and (b) collapse resistance of steel MRFs with viscous dampers at least equal with that of conventional steel MRFs. A conservative design rule is proposed for the capacity design of the columns in the force path of viscous dampers. More specifically, the column axial force used to perform the capacity design is the envelope of the axial force from the peak drift state and the axial force from the peak velocity state. The capacity design rule becomes stricter for buildings with more than 10 storeys to address that linear elastic analysis methods for structures with dampers underestimate the peak damper forces in the lower storeys of yielding tall steel MRFs. Appropriate limit values for the storey drift sensitivity coefficient θ are recommended to guarantee for steel MRFs with viscous dampers collapse resistance at least equal with that of conventional steel MRFs.

Sprayed concrete lining (SCL) is an important part of soft ground tunnelling. It provides immediate ground support and maintains tunnel stability. A quick set and rapid strength development of freshly sprayed concrete are crucial for maintaining SCL integrity. An inadequate strength development leads to the SCL failure and tunnel instability. This poses serious health and safety risks to construction workers and nearby structures. Therefore, early age strength development monitoring forms a crucial aspect of SCL construction. Currently used testing methods, namely needle penetrometer, stud-driving and uniaxial compressive testing of cored samples, are of destructive nature. To avoid damage to the freshly sprayed lining and to mitigate safety hazards to testing operatives, testing is performed on test panels. Current test methods, however, test a very small part of the sprayed concrete. Since the temperature histories of the lining section are different from the test panels, the outcomes are local in nature and provide an incomplete picture of the SCL strength gain. Thus, there remains a need for a test method with a capability of testing large volumes of the sprayed concrete works remotely, holistically and non- destructively. The maturity method is well established for normal concretes and allows maturity and hence strength to be calculated from a temperature history. A new method called Strength Monitoring Using Thermal Imaging seeks to apply this principle to accelerated sprayed concrete using an Arrhenius equation based maturity function, but there are significant challenges to overcome to obtain the input parameters. This research establishes a thermo-chemo-mechanical evaluation methodology for obtaining the input parameters and verifies its reliability through two detailed case studies on live tunnelling projects. The two-staged methodology involved thermo-chemical evaluation of a total of twelve cement pastes, through isothermal calorimetry and thermogravimetry, and thermo-mechanical evaluation of two sprayed concrete mixes, through strength testing and thermal imaging of more than fifty test panels. The thermo-chemical evaluation revealed that the sprayed concrete has very different hydration kinetics at different temperatures and the reference temperature approach is not valid for the maturity assessments. The maturity modelling procedure was modified to account for kinetics variability. The thermo-mechanical evaluation revealed that sprayed concrete holds a multilinear strength – maturity relationship as against a single linear relationship for plain concrete.