This work represents an investigation of the corrosion behaviour of primarily high-grade alloys in marine environments. A range of marine conditions of varying severity has been considered and their effect on the electrochemical corrosion characteristics assessed. The study has utilised a range of electrochemical monitoring techniques, light and scanning electro microscopy and other surface techniques to assess the extent and morphology of corrosion attack under certain conditions. Principal components of the study include the effect of elevated temperature (up to 60oC) on corrosion initiation and propagation in static and high velocity impinging seawater. In addition, the effect of micro and macro fouling has been assessed using immersion tests and a hydrodynamic model. Continuation of the biological effects on corrosion looked at the effect of the presence and activity of Sulphate Reducing Bacteria (SRB) on corrosion mechanism. Correlations between accelerated laboratory tests and the real time behaviour of materials have been successfully made. Methods to counteract fouling often include the use of biocides and, in this study, the effect of high levels of hypochlorite dosing has been investigated. Mechanical and corrosion effects by liquid impact and by liquid-solid impact constitute a major part of this work and the use of electrochemical tests has enabled the proportions of weight loss on a given material attributed to corrosion, erosion and a synergistic factor to be elucidated. Several options exist to combat excessive deterioration due to mechanical wear. Two processes, shot-peening and laser irradiation, have been assessed primarily for corrosion resistance in a marine environment.

This thesis is concerned with the analysis, control and identification of hybrid dynamical systems. The main focus is on a particular class of hybrid systems consisting of linear subsystems. The discrete dynamic, i.e., the change between subsystems, is unknown or nondeterministic and cannot be influenced, i.e. controlled, directly. However changes in the discrete dynamic can be detected immediately, such that the current dynamic (subsystem) is known. In order to motivate the study of hybrid systems and show the merits of hybrid control theory, an example is given. It is shown that real world systems like Anti Locking Brakes (ABS) are naturally modelled by such a class of linear hybrids systems. It is shown that purely continuous feedback is not suitable since it cannot achieve maximum braking performance. A hybrid control strategy, which overcomes this problem, is presented. For this class of linear hybrid system with unknown discrete dynamic, a framework for robust control is established. The analysis methodology developed gives a robustness radius such that the stability under parameter variations can be analysed. The controller synthesis procedure is illustrated in a practical example where the control for an active suspension of a car is designed. Optimal control for this class of hybrid system is introduced. It is shows how a control law is obtained which minimises a quadratic performance index. The synthesis procedure is stated in terms of a convex optimisation problem using linear matrix inequalities (LMI). The solution of the LMI not only returns the controller but also the performance bound. Since the proposed controller structures require knowledge of the continuous state, an observer design is proposed. It is shown that the estimation error converges quadratically while minimising the covariance of the estimation error. This is similar to the Kalman filter for discrete or continuous time systems. Further, we show that the synthesis of the observer can be cast into an LMI, which conveniently solves the synthesis problem.

The golf stroke was computationally modelled using finite element analysis. Results for the impact between the club head and the ball compared well with previous research, both practical and theoretical. The results imply that for thick face club heads, such as irons, club head performance is independent of material stiffness but highly dependent on the friction of the interface and the clubhead geometry. The three ball flight predictors (speed, trajectory and spin rate) as a function of clubhead parameters are shown to be non-trivial. Acceptable models of impact could be achieved using rigid faces for thick face clubheads with the centre of mass and clubhead inertia accurately described. Results on ball construction effects imply that both the stiffness and mass distribution throughout the ball affect performance. The large deformations of the ball mean that classic rigid body mechanics cannot suffice in golf impact predictions. A model of the golf swing based on a double pendulum was constructed and shaft performance examined for various styles of golf swing. Shaft parameters thought to affect performance were quantitatively evaluated and results compared well with previous research. Increased club head speeds at impact were achieved with shafts of lighter weight or reduced bending stiffness for all styles of golf swing examined. The cause of bending forward of the shaft at impact was identified to occur from the large centrifugal forces acting on the head and the increased bending stiffness of the shaft also due to centrifugal force. On a detailed level shaft behaviour was affected by vibrations which appeared chaotic due to the changing stiffness of the system. This is expected to be less of an effect in an actual golf shot due to the damping provided by the human participant.

Persistent whole-plant disturbances can have an especially large impact on product quality and running costs. There is thus a motivation for the automated detection of a plant-wide disturbance and for the isolation of its sources. Oscillations increase variability and can prevent a plant from operating close to optimal constraints. They can also camouflage other behaviour that may need attention such as upsets due to external disturbances. A large petrochemical plant may have a 1000 or more control loops and indicators, so a key requirement of an industrial control engineer is for an automated means to detect and isolate the root cause of these oscillations so that maintenance effort can be directed efficiently. The propagation model that is proposed is represented by a log-ratio plot, which is shown to be ‘bell’ shaped in most industrial situations. Theoretical and practical issues are addressed to derive guidelines for determining the cut-off frequencies of the ‘bell’ from data sets requiring little knowledge of the plant schematic and controller settings. The alternative method for isolation is based on the bispectrum and makes explicit use of this model representation. A comparison is then made with other techniques. These techniques include nonlinear time series analysis tools like Correlation dimension and maximal Lyapunov Exponent and a new interpretation of the Spectral ICA method, which is proposed to accommodate our revised understanding of harmonic propagation. Both simulated and real plant data are used to test the proposed approaches. Results demonstrate and compare their ability to detect and isolate the root cause of whole plant oscillations. Being based on higher order statistics (HOS), the bispectrum also provides a means to detect nonlinearity when oscillatory measurement records exist in process systems. Its comparison with previous HOS based nonlinearity detection method is made and the bispectrum-based is preferred.

The erosion-corrosion characteristics of a WC-Co-Cr coating were assessed under an impinging jet of 3.5% NaCl solution at a velocity of 12 ms-1 both free from solids and containing solids up to 2500 mg/l at a range of impingement angles. The total weight loss increased with increasing solids in the liquid stream and maximum material loss occurred in the area directly under the jet where high impact angles occurred. The material loss tended to reduce as the impingement angle reduced. The mechanism and contribution to the overall material loss in erosions-corrosion processes were studied. Surface profiling revealed the erosions mechanism to be that of solid particles causing craters on the surface of the coating, not associated with any specific microstructural aspect of the coating. The total contribution to overall material loss from corrosion processes was substantial (up to 30%). While the impinging jet increased the corrosion rate, in the absence and presence of solids, these corrosive effects could be inhibited, particularly in the presence of solids, by the application of cathodic protection which reduced overall material loss by up to 50%. The synergistic component of material loss can be referred to as an indirect corrosion effect, and in this work, the synergistic effect was significant (up to 40%). However, more complex direct corrosion effects were found in the form of galvanic currents between the area directly under the impinging jet and the outer area which significantly increase the corrosion rate on the impinged area. This study, which focuses on the interactions between corrosion and erosion, has improved the understanding of erosion-corrosion processes on complex composite materials.

The thesis includes a literature survey of small hydraulic turbines, incorporating a historical review. The possible role of "micro hydros" in generating power in various parts of the world, and particularly in Iran, is discussed. The theory of turbo machinery, particularly with regard to axial flow turbines, is presented next. This is followed by some details on the design of guide vanes, runner blades and draft tube of axial flow turbines, these components being usually regarded as areas which have major impact on the performance of hydraulic turbines. The next chapter gives the details of the test circuit that was constructed. This could provide water volume flow rates of up to 0.15 m3/s at heads of up 25m. The two dynamometers that were used could adsorb pores to up to 25 kw and 50 kw respectively. An existing micro-turbine, the Agnew turbine, was selected for examination and possible improvement. The first possible improvement was the introduction of guide vanes upstream of the turbine runner (this inclusion necessitated a second support for the main shaft). It was found that this gave significant improvements - efficiency raised by over 20% in some cases. The domain of high efficiency working was considerably extended. It was observed that instability (with fall in power output) could occur after a period of running. This seemed to be associated with an accumulation of air bubbles at the highest point in the casing of the machine. Introduction of a vent from this point was found to relieve this problem and ensure stable operation.

Stab wounds are an increasingly common cause of death or series injury and the high-risk groups in society are growing both in size and number. These facts make the study of mechanics of knife penetration more relevant than ever. The aim was to quantify the penetration force needed to inflict a certain stab wound by modelling knife penetration via the Finite Element Method. Case studies of stabbing incidents were carried out to give some insight into the nature and type of problem to be modelled. It was decided to work with an idealised stab-penetration model including a section of target tissue simulants. This stab-penetration test could yield repeatable and comparable results both experimentally and computationally. Suitable target simulants were identified by the stab-penetration test and also by uniaxial tensile tests. Pig skin was found to roughly match the mechanical properties of human skin with gelatine as a realistic flesh simulant. Computational modelling of knife penetration was attempted by use of Abaqus/Explicit, a nonlinear FEA package which features modelling of contact-impact problems. A true to scale finite element model of the stab-penetration test set-up was built including a material model of the target simulant. The computed penetration force was found highly mesh dependent for sharp blades and too high forces were predicted. Blunt penetrators were also tested both by experiments and computationally. By refining the constitutive model for skin computed values were obtained in reasonable agreement with the experiments for blunt penetrators. Mesh dependency was minimal in the computational model with blunt penetrators. It was concluded that modelling of knife penetration via finite element method is possible but analysis is time consuming due to the high mesh refinement required. Accuracy of the predicted penetration force is still too low for typical blade sharpnesses to be of practical use.

The dynamics of soliton pulses for use in nonlinear optical devices is mathematically modelled by Maxwell-Bloch systems of equations for the interaction of light with a uniform distribution of quantum-mechanical atoms. We study the Reduced Maxwell-Bloch (RMB) equations occurring when an ensemble of rotationally symmetric 3-level atoms is assumed. The model applies for on and off-resonance conditions and is completely integrable using Inverse Scattering theory, since it arises as the compatibility condition of a 3 x 3 AKNS-system. Furthermore this integrability remains valid for all timescales of the optical field because only the “one-way wave approximation” is required during the derivation. Solutions are constructed in two ways: 1. Darboux-Bäcklund transforms are applied, generating single soliton pulses of ultrashort (< 1ps) duration, and families of elliptically polarised 2-solitons not possible in lower dimensional problems. 2. A general Inverse Scattering scheme is developed and tested. The Direct Scattering Problem is dealt with first to obtain a complete set of scattering data. Subsequently the Inverse Problem is solved both formally and then in explicit closed form for the special case that the reflection coefficients vanish for real values of the spectral parameter. In this case the main result is a determined system of n linear algebraic equations which yield the n-soliton of our RMB-system. It is confirmed that the 1-solitons found by means of Darboux transform are precisely the same as those given by the full mechanism of Inverse Scattering. Finally we calculate the invariants of the motion for the RMB-equations, and derive an evolution equation giving the variation with propagation distance of the invariant functionals when the original RMB-system is modified by an arbitrary perturbing term. As an application dissipative effects on 1-solitons are considered.

This thesis provides an account of an investigation into possible dynamic interactions between two coupled nonlinear sub-systems, each possessing opposing nonlinear overhang characteristics in the frequency domain in terms of positive and negative cubic stiffnesses. This system is a two degree-of-freedom Duffing oscillator coupled in series in which certain nonlinear effects can be advantageously neutralised under specific conditions. This theoretical vehicle has been used as a preliminary methodology for understanding the interactive behaviour within typical industrial ultrasonic cutting components. Ultrasonic energy is generated within a piezoelectric exciter, which is inherently nonlinear, and which is coupled to a bar-horn or block-horn to one, or more, material cutting blades, for example. The horn/blade configurations are also nonlinear, and within the whole system there are response features which are strongly reminiscent of positive and negative cubic stiffness effects. The two degree-of-freedom model is analysed and it is shown that a practically useful mitigating effect on the overall nonlinear response of the system can be created under certain conditions when one of the cubic stiffnesses is varied. It has also bfeen shown experimentally that coupling of ultrasonic components with different nonlinear characteristics can strongly influence the performance of the system and that the general behaviour of the hypothetical theoretical model is indeed borne out in practice.

Three fundamental tether motions were considered for payload orbital transfer with tethers: hanging, prograde libration and prograde motorised spin. The symmetrical double-ended motorised spinning tether performed best and was most efficient, improving by two orders of magnitude on the librating tether which in turn improved on the hanging tether by roughly a factor of two. An upper payload using long tethers with a motorised tether on a circular orbit can be transferred from a low to a geostationary Earth orbit by employing relatively high motor torque and a safety factor on the tether strength close to unity. Two common literature results, the constant efficiency index of seven for a hanging tether upper payload release and the maximum efficiency index of fourteen for an upper payload released from a prograde librating tether, were found to be a lower bound and quite readily breached, respectively. Orbit circularisation through tether release was found to be feasible with retrograde librating tethers. When the point of release does not occur along the local vertical then a non-optimum release of the payload was found to severely reduce the performance of payload transfer with tethers. Consequently, a very precise and accurately timed release is important for the success of payload orbital transfer with tethers since missing the point of release by a single degree with a spinning tether, say, can cause the payload to miss its required target. The best design for the outrigger system to provide the necessary resistive torque is to utilise the gravity gradient and tap the outrigger system within the gravitational potential well. In this manner the outrigger tether length can be significantly reduced and the outrigger end masses can be minimised, thus saving valuable launch mass and cost, as well as exposing less tether surface area to the space environment. With current materials the maximum ?V to be expected with a motorised tether is between 600-1400 m/s depending on the tether length and payload mass. The duration of the spin-up lasts approximately between half and a full Earth day but may vary by an hour, say, depending on the initial conditions and orbit eccentricity. Ensuring the motor torque axis remains perpendicular to the orbital plane was found to be vital otherwise the spin-up time is greatly increased. The motorised tether has the ability to shift the datum of a hanging tether, which may have useful applications in Earth monitoring or tethered Interferometry. Out-of-plane initial angular displacements or the motor torque axis not remaining perpendicular to the orbital plane caused the motorised tether to precess. Furthermore, the motion of the motorised tether with a constant motor torque was found to be regular, but quasi-periodic, which implies that the payload cannot be reliably delivered at perigee along the local vertical.