This thesis looks at the issue of authentication and privacy in mobile Web services. The work in this thesis builds on GSM and UMTS security framework to develop security protocols for mobile Web services environment. The thesis initially highlights some core principles of designing security protocols in such environment. The next two chapters look at the core technologies and building blocks in Web services systems and the core security features in mobile networks mainly GSM and UMTS. Registration and authentication were identified as security issues in federated systems. Proposed solutions were developed utilizing XML security mechanisms with SIM card security in GSM environment to address these issues. Also a novel system was proposed in which it is possible for a mobile user to securely authenticate and have full anonymity as far as the service providers are concerned; however it is possible for a trusted authority to reveal the identity of the user if he or she is suspected of illegal activities. The next section analyze in detail the Generic Authentication Architecture from 3GPP. Combining SAML with the Generic Authentication Architecture, we propose a novel "generic mobile Web service platform" for M-Commerce. Various solutions have been proposed to address privacy concern in distributed networks; the Platform for Privacy Preferences is one of the popular proposal, though it has many desirable features, it is not easy to enforce it. We argue that this limitation can be managed in federated system such as the Liberty Alliance framework. In the final chapter we make the case for using timestamp based authentication protocol in mobile Web service on the ground of efficiency gain.

An investigation into the feasibility of using rotating circular cylinders as the primary means of generating lift for the class of very small (0.15 m maximum dimension, 50 g weight) unmanned aircraft known as Micro Air Vehicles (MAV) has been carried out. It is hoped that such a design would be able to exploit the large lift generating properties of the rotating cylinder for the purposes of increasing the available payload weight. This would provide considerable benefits as, at present, the inability to support capable payloads significantly restricts the usefulness of MAV-sized craft. A preliminary design study was performed to investigate possible configurations for the proposed design, resulting in the selection, for reasons of simplicity, of an arrangement having two rotating cylinders about a central fuselage. Initial assessments of the practical feasibility of such a design, as well as its likely performance (in terms of lift, drag, and power requirements) were then carried out. An examination of the consequences of the presence of the cylinders on the stability and control of such a vehicle was also performed. Existing understanding of the aerodynamic characteristics of a rotating cylinder in crossflow was extended through a series of wind tunnel tests examining all aspects of rotating cylinder flow, including force and moment coefficients, behaviour at non-zero yaw angles (−30� � � 10�), power requirements for spinning the cylinder, and wake phenomena. A particular focus was the use of endplates to improve aerodynamic performance. The tests were conducted with a cylinder of aspect ratio AR = 5 across a range of Reynolds numbers (1.6 × 104 � Re � 9.5 × 104, based on cylinder diameter) and velocity ratios (4) identified as being of interest by the preliminary design study. The results were generally found to be in very good agreement with existing published data, though power requirements for spinning the cylinder were much higher than anticipated, and revealed the influence of tip vortices to be of great significance. Wind tunnel experiments with a simple prototype aircraft, based on the outcome of the preliminary design study and isolated cylinder tests, examined the overall aerodynamic performance of this type of design for a single Reynolds number of Re = 1.8×104, across a velocity ratio range of 2.5, and at various angles of attack (−10� 25�) and yaw (−10� 30�). These tests also investigated the interaction between the cylinders and the other components of the aircraft to help determine the most favourable layout. The tests revealed the effect of propeller wash over the rotors, the influence of the cylinder wake on the tail, and the design of the tail, fin, and fuselage to be of considerable importance to the aerodynamic characteristics and performance of the vehicle. Overall, the study indicated that an aircraft of the proposed configuration and suitable capability was theoretically possible at the MAV scale of flight if an appropriate rotor geometry was chosen. However, the actual construction of a vehicle able to fully provide the desired performance within the constraints placed on platform size and weight was not currently possible using commonly available materials and components. Slightly larger designs (of dimension 0.4 m and weight 250 g) were more realisable, but still lacked in performance. Successful development of this type of design is thus dependent on technological advancement, particularly improvements in power and propulsion systems.

The thesis begins by presenting the wider case for deployment of CCS at the global level and the UK level. It is shown that from a policy perspective, the deployment of coal with CCS is necessary to ensure emissions targets can be met, as apart from nuclear, it is the only technology that will allow existing fossil fuel reserves to be used- something that will certainly happen. However, questions remain over the technical feasibility and the commercial case for the adoption of CCS technology. Therefore, the remainder of the thesis presents a detailed technology assessment and financial analysis to derive the market case for deploying coal with CCS. The technology assessment extends previous work in this area by comparing sub system performance across all capture technologies in detail. The combination of current and future technical developments for CCS along with the use of technology and system readiness levels is a novel approach to technology assessment and extends previous work in the area by presenting a systems framework under which CCS technology can be evaluated. The conclusion of the technology assessment is that pulverised-coal plant with post combustion capture is the closest CCS technology to deployment. The second part of this thesis concerns the investment case for CCS. The analysis involves a derivation of costs for carbon capture technologies. The financial characteristics of CCS are identified using sensitivity analysis to compare to both the original plant and incumbent choice for new generation (gas fired CCGT), and implications for policy and investors are drawn out. Investment in a CCS plant is then valued as a perpetual American call option, while the expected time to investment is evaluated using mean time to absorption calculus. This approach of combining the American call option with the mean time to absorption method is a novel way to assess the expected timeframe over which investment in CCS could take place and extends previous work in this area. Recently, real options analysis has been used in engineering systems analysis. Although not as advanced as in business and economic investigations, real options analysis has begun to be used to recognise the value of flexibility in system design. The intellectual and practical contribution of this thesis to the field of engineering systems lies in the derivation of a framework for the consistent analysis of current and future power generation technologies, coupled with real options analysis of an American call option with the mean time to absorption to evaluate the investment case for coal CCS. The relevance of adopting a systems approach for real world application of this research has been proved by the project commissioned during the course of this research for ATCO Power (Canada) Ltd concerning evaluation of the most promising options for carbon capture and storage and technology and investment case for future business strategy, which included material from Chapters 4 and 5 of the thesis.

The research covered in this thesis is concerned with the effects of the behaviour and load carrying capacities of classes of steel beam structures with various shapes of web openings. A comprehensive investigation on non-composite and partially concrete encased perforated steel Isections with large web openings positioned along the centre-line of the beams was undertaken. This thesis enhances the current knowledge on these classes of perforated beams, as previous research has shown that these beams are susceptible to various failure modes, due to the existence of large web openings. Currently, perforated steel beams with large web openings are utilised in most engineering applications such as infrastructure, ship building and aeronautical engineering. The most significant benefits of using such beams are the achievement of reductions in weight and accommodation of services within their structural depth of floor systems. Specifically, in building applications, service integration eliminates the internal columns and supports, produces lighter structures which leading to reduced construction and installation time and results in cost effective structural forms and uses. However, many uncertainties are associated with perforated beams as well as non-standard methodology is used for their assessment. Perforated beams with standard circular, hexagonal and elongated web openings are most widely used nowadays, whilst various non-standard web opening shapes, such as `elliptical', are introduced through this thesis for first time. These new pioneering web opening shapes improve the structural performance of the perforated beams when examined under two critical failure modes (i. e. shear-'Vierendeel' mechanism and web-post buckling). Moreover, the manufacturing procedure of the `elliptical' web openings show great advantage in comparison with the manufacturing way of the more popular perforated beams with circular web openings (i. e. cellular beams). Also, other web opening shapes are reported and examined in this thesis. Furthermore, the novelty of the work seems to consist of the treatment of web openings of somewhat greater web opening depth than those usually considered and the introduction of a new class of composite concrete-steel beam. Despite the abundant experimental work on perforated steel beams that has been conducted by researchers throughout the years, the results are not comprehensive, due to the complexity of the beam configuration and the large number of variable parameters. Therefore, using commercially available finite element (FE) software, numerical analyses were verified by comparison to a new experimental programme designed to test each of the new structural forms. The numerical programme was then used to undertake extensive parametric studies to isolate some of the geometric and material properties that influence the failure modes associated with each of the new forms of structural systems. The main parameters under consideration are the web opening depth (noted usually as diameter), the critical opening length of the top and bottom tee-sections, the web opening spacing, the steel flange and web thicknesses, the concrete strength and contact properties between the steel and concrete of the newly formed composite beams. Detailed study of plastic hinges formation (i. e. high stress concentrations) was also employed in the vicinity of the web openings, by conducting both experimental and finite element (FE) investigation. This research study should now lead to better management of the use of perforated beams with large web openings as the profound difference between the novel and the conventional perforated beams is demonstrated. Useful practical applications of the so-called structural forms would be of particular interest in the general engineering, not just because of their superior structural performance, but also because of their low cost in manufacturing and usage. Another contribution is the investigation of the partial steel encasement with the concrete in-fill, on the percentage of enhancement of the steel perforated beams with web openings under high shear forces as well as on the distinction which is drawn between the conventional and the new composite beams. Finally, a further indirect outcome of this research thesis is the excellent agreement between the experimental and FE analyses as well as the data that can be used by future researchers to widen the above research to various engineering applications.

Our aim is to investigate the critical behaviour of lattice spin models such as the three-dimensional Ising model in the thermodynamic limit. The exact partition functions (typically summed over the order of 1075 states) for finite simple cubic Ising lattices are computed using a transfer matrix approach. Q-state Potts model partition functions on two- and three-dimensional lattices are also computed and analysed. Our results are analysed as distributions of zeros of the partition function in the complex-temperature plane. We then look at sequences of such distributions for sequences of lattices approaching the thermodynamic limit. For a controlled comparison, we show how a sequence of zero distributions for finite 2d Ising lattices tends to Onsager’s thermodynamic solution. Via such comparisons, we find evidence to suggest, for example, a thermodynamic limit singular point in the behaviour of the specific heat of the 3d Ising model.

Groups of piles are commonly used as high capacity foundations. It is recognised that the load distribution among piles in a group will vary and it is thought that the inner piles are likely to make a relatively small contribution to the total load carried. The essence of the research undertaken is to establish the relative effectiveness of pile groups with either no inner piles (perimeter group) or a single central pile (target group) when compared to the more commonly used grid group arrangement. Pile groups in which the central piles were omitted were used for the Cannon Place redevelopment in london and provided the impetus for the research project. The main research technique used is geotechnical centrifuge modelling. Samples of overconsolidated kaolin clay were prepared and tested on the centrifuge at City University london. This provided a firm clay into which pile groups could be installed in a wide variety of arrangements. Three or four different pile groups were located in each centrifuge model and loaded to failure using a strain-rate controlled load actuator. The individual model piles were made of 5 mm diameter aluminium rod placed in holes pre-drilled in the consolidated kaolin prior to the centrifuge test. All piles extended to a depth 250 mm in the clay giving an lId ratio of 50. The ranges of pile groups tested are linear, circular and square perimeter, circular and square target and square grid. Single pile tests provided the reference pile capacities used to normalise the data from the 23 centrifuge models tested. The experimental work was complemented by a parametric numerical modelling study using the finite element programme Abaqus. This gave insight into the pile-soil interaction and permitted a more meticulous analysis of the soil stresses and displacements. In addition, the numerical modelling enabled extension to the original variables tested as part of the centrifuge experiments and the soil shear strength and lId ratio were varied. The pile groups failed in one of two ways: either as individual piles with the piles settling into the ground with no noticeable settlement of the soil surrounding a pile, or as a block with the soil contained within the outer ring of piles settling by the same or xxiv similar amount as the piles. The change from block failure to individual pile failure often occurred at a pile centre-to-centre spacing of about two pile diameters though variables such as number of piles, the presence of a target pile and the strength of the soil all had an effect. The efficiency of a pile group is defined as the load capacity of a pile group expressed as a ratio of the number of the piles in the group multiplied by the load capacity of a single isolated pile. It was demonstrated that a grid group arrangement was the least efficient of the groups tested, whereas a perimeter group arrangement could achieve higher efficiencies of greater than unity and the inclusion of a target pile could further enhance the group efficiency. It has been shown that a target group comprised of 17 piles (16 piles plus one central pile) has a significantly higher efficiency than a 5x5 grid group comprised of 25 piles, such that the capacity at lower settlements is the same for both groups.

This thesis considers the problem of supporting traffic with elastic bandwidth requirements and hard end-to-end delay constraints in multi-hop wireless networks, with focus on source transmission rates and link data rates as the key resource allocation decisions. Specifically, the research objective is to develop a source rate control and scheduling strategy that guarantees bounded average end-to-end queueing delay and maximises the overall utility of all incoming traffic, using network utility maximisation framework. The network utility maximisation based approaches to support delay-sensitive traffic have been predominantly based on either reducing link utilisation, or approximation of links as M/D/1 queues. Both approaches lead to unpredictable transient behaviour of packet delays, and inefficient link utilisation under optimal resource allocation. On the contrary, in this thesis an approach is proposed where instead of hard delay constraints based on inaccurate M/D/1 delay estimates, traffic end-to-end delay requirements are guaranteed by proper forms of concave and increasing utility functions of their transmission rates. Specifically, an alternative formulation is presented where the delay constraint is omitted and sources’ utility functions are multiplied by a weight factor. The alternative optimisation problem is solved by a distributed scheduling algorithm incorporating a duality-based rate control algorithm at its inner layer, where optimal link prices correlate with their average queueing delays. The proposed approach is then realised by a scheduling algorithm that runs jointly with an integral controller whereby each source regulates the queueing delay on its paths at the desired level, using its utility weight coefficient as the control variable. Since the proposed algorithms are based on solving the alternative concave optimisation problem, they are simple, distributed and lead to maximal link utilisation. Hence, they avoid the limitations of the previous approaches. The proposed algorithms are shown, using both theoretical analysis and simulation, to achieve asymptotic regulation of end-to-end delay given the step size of the proposed integral controller is within a specified range.

Four types of WC-Co cermet powders (conventional WC-12 wt% Co, two different types of conventional WC-17 wt% Co and nanoscale WC-12 wt% Co powders), which have differences in terms of Co content, powder manufacturing process and WC grain size, have been sprayed to form coatings with both the high velocity oxygen-gas fuel (HVOGF) and the high velocity oxygen-liquid fuel (HVOLF) processes. The carbide grain size, powder particle size distribution and phase volume fraction of the starting powders were measured. The as-sprayed coatings were characterised by optical microscopy (OM), scanning electron microscopy (SEM), xray diffraction (XRD), transmission electron microscopy (TEM) and microhardness and surface roughness measurements. The HVOGF coatings all displayed a lamellar splat structure characteristic of thermal spraying. HVOLF coatings had less well defined splat structures which suggested lower degrees of particle melting. A number of phases (WC, W2C. W and amorphous) were observed in the coatings by XRD, SEM and TEM analysis indicating phase decomposition and oxidation during spraying. The degree of decomposition was increased by higher gas temperatures, longer particle residence times in the jet, small carbide grain size in the powder particles and an open powder structure. By suitable selection of the spraying system, spraying parameters and powder feedstock, particle decomposition during spraying could be minimised. All coatings obtained were subjected to sliding wear against an alumina ball; a sintered WC-11 wt% Co solid disc was also tested for comparison. The decomposition of the original WC-Co powder structure in the coatings was found to be deleterious to wear resistance since the tungsten rich binder phase that now existed was significantly more brittle than the pure cobalt binder in the feedstock powder from which it was derived. However, optimisation of the conditions to reduce decomposition did not result in an increase in wear resistance. Instead, deposition of powder particles that had a significant portion of solid phase resulted in fragmentation and debonding of the carbides resulting from deformation during impact and causing increased wear. The sintered WC-Co exhibited the highest wear resistance of all materials examined, whilst the HVOGF sprayed WC-12 wt% Co coating, which exhibited significant decomposition, was the most wear resistant of all the coatings examined.

The work is concerned with the application of the hybrid finite element method to thin plate and cylindrical shell structures. One plate bending element and three shell elements are studied. The plate element is the same as one already appearing in the literature but it is also used here to form the basis of a flat triangular element for the analysis of shells. The main effort, however, has been devoted to the development of two new hybrid cylindrical shell elements. One is rectangular and the other of triangular planform. The aim has been to use fully compatible edge displacement assumptions (with exact representations of rigid body motions) together with stress assumptions consisting of complete polynomials. In assessing the performance of these elements the primary concern has been the quality of stress predictions. The two elements are tested separately on a variety of problems and found to give good results which compare well, in some cases, with those obtained using more complicated displacement assumption elements. They are the used together to analyse a cylinder intersection problem – that of a mitred bend in a pipe subjected to an in-plane bending moment. Results comparing well with some available strain gauge readings are obtained. As a result of the work some general conclusions on the hybrid method are drawn. More specific conclusions relating to these elements are also noted and suggestions for further work are made.

Bitumens are used as a binder in roadway pavements largely because they are relatively inexpensive and generally provide good adhesion and waterproofing characteristics. They are generally rather resistant to the detrimental effects of the environment and usually remain pliant for many years. In other words, bitumens are relatively inexpensive binders that generally provide good durability (or longevity of service) in pavement mixtures. Bitumens are no panacea, however. Many factors affect the durability of bitumens and, thus, bituminous mixtures. However, assuming that a pavement layer is constructed according to specifications (which attempt to account for durability), it is generally agreed that the two primary factors affecting the durability of bituminous paving mixtures are damage due to water and embrittlement of the bitumen due to age hardening. Much effort has been afforded to the study of age hardening and water damage and much has been learned. However, the exact mechanisms of ageing and water damage in bituminous mixtures remains an enigma. This thesis attempts to provide an improved understanding of these mechanisms through a comprehensive literature review, development of performance tests to assess mixture durability and investigation of the rheological characteristics of bitumens aged and tested whilst in contact with mineral aggregate.