Water trees are a major form of degradation in solid organic electrical insulation subject to high AC voltages and water. The work is aimed at developing a more rigorous approach to analysing water tree data from ageing experiments on practical insulation geometries. Such data is in the form of tree length distributions and time-increasing tree number densities. Tree inception statistics are directly accessible from the data, but the effects of growth are convolved with those of inception. An approach is developed for analysing the data to quantify aspects of both inception and growth. In particular, mean growth rates and distributions of growth times can be estimated. The distribution of inception times seems to be close to exponential. Analysis shows that the effects of varying the field on the dynamics of inception depend upon whether the voltage or the insulation thickness is being varied. Increasing the frequency or decreasing thickness increases the number of possible water tree sites but decreases the inception rate from an average site. Frequency accelerates inception in a non-linear manner. Increasing the voltage both increases the number of sites and the inception rates. At frequencies close to 1 kHz, the mean length of a tree increases with the square root of growth time. Initial tree growth rates increase in a way that is consistent with a linear dependence on frequency. It is concluded that the approach developed can be applied to real data and is useful. It is expected that application of the approach to more extensive data sets would give rise to considerable advances in the empirical knowledge of the dependence of water treeing on various physical parameters which it is not possible to obtain using existing techniques.

During the past decade, many techniques for computer-aided circuit design have been suggested and investigated, but none have been developed to the stage where the designer is redundant. The research described herein concerns the application of one technique, the method of coefficient matching, to the synthesis of lumped, linear, passive, 3-terminal networks with no mutual inductances. The author developed a program which, with further development, could perform the entire design process with no designer interaction. Further, the author considers problems where the classical synthesis methods are unsuitable, e.g. the synthesis of non-series-parallel networks with no series-parallel equivalent. The coefficient matching procedure is based on selecting a starting network which yields the correct polynomial structure and achieving a solution by component value adjustment and network evolution. The closer the starting network to a feasible topology, the more rapid the convergence to a solution. It is shown that the suitability of a starting network can be analysed on the basis of the information obtained from the different but equivalent forms of the admittance functions. The significance of common factors is discussed and the influence of various types of common factors on the network realization is investigated. For cases when the initial starting network is remote from any feasible solution, sophisticated techniques allowing substantial topological modification during network evolution are required. These techniques were developed by the author on the basis of element and node addition and elimination. A Fortran IV program has been developed by the author welding together all these aforementioned techniques for topological modification. The program makes large topological modification automatically during the design process. The effectiveness and efficiency of these techniques and the program are illustrated by a variety of synthesis examples.

The evidence for the generally accepted mechanism of the hydrolysis of acetals, ketals and glycosides is reviewed. A brief account of the proposed mechanisms for the action of the enzyme lyso-zyme is given. Some of the underlying assumptions are discussed and some criticisms are offered. Some of the more important attempts to observe "non-general" hydrolytic behavoir are discussed and the reasons for some of the failures are evaluated, Acetals with potential neighbouring nucleophiles' where in principle assistance to bond rupture in the acid catalysed hydrolysis of the acetal group is possible, have been synthesised and the kinetics of their hydrolysis investigated. It is demonstrated that catalysis is not general and in the examples studied it is necessary to lower the polarity of the hydrolytic medium in order to observe any participation Reasons for this are discussed. Steric effects in the hydrolysis of 2-methoxy methoxy benzoic acid have been investigated and it is demonstrated that substituents ortho to the formal group increase the intramolecularly catalysed rate of hydrolysis irrespective of their electronic substituent effects. A satisfactory theory is developed to explain the facts. Mixed aryl methyl acetals of benzaldehyde have been synth-esised and their hydrolysis is shown to be general acid catalysed. The facts are rationalised by a development of a previous theory. A brief section is devoted to the use of statistical methods in the calculation of rate constants and some computor programs to implement these are listed in the appendix.

An attempt is made to identify those factors associated with artificial prehension that influence the selection of prehension control laws. A study is made of the complex requirements of artificial prehension and it is proposed that these may best be satisfied by a system composed of six independent sub-control systems, defined as prehension elements. It is conjectured that complex actions, such as writing, may be realised from combinations of these prehension elements. Synthesis shows that, in general, control is a function of the modulus of the object state variables and that some prehension elements require no conscious involvement. The need to consider the object within the control loops, and in some instances the elimination of conscious effort, is a departure from traditional concepts. In an attempt to separate the problem of control from the many other factors that influence prehension device design the latter is realised by a two-dimensional calijDfci' system having a pneumatic power drive. Test objects are realised in a two-dimensional form moving in a direction normal to the caliJ)C.;system. To evaluate theability of the prehension elements to attain the required forms of object control, such as balancing, holding, etc., common tests are conducted with the prehension elements together with a simple object-open-loop pressure-feedback system representing a conventional prosthesis. A "figure of merit" associated with each test reflects the success with which the required control action is achieved by each prehension element. The range of object disturbances for the tests is limited to sinusoid, ramp and step functions. Experimental results in general confirm the need for multiple control systems, and of the importance of object position and velocity in the feedback structure, to satisfy artificial prehension. The results further indicate improved prehension control over that given by traditional systems.

With the advancing technology of jet engines and more stringent specifications about fast transients, complex questions are having to be answered at an early stage of development. To make some headway in answering these questions various one dimensional models of a multistage axial flow compressor have been developed. These are based on the principles of conservation of mass, linear momentum and energy, and use the steady state stage characteristics to introduce the effects of the blading. The compressor speed has been assumed to be constant since the transients considered were faster than the response of the control systems normally controlling them. It has been shown both by applying a stability test to the linearised system equations and by digitally simulating the full non-linear differential equations, that models entered a region of dynamic instability in the region of compressor surge but that increasing the complexity of models does not necessarily improve surge prediction. An investigation of the dynamic response of some of the models has indicated that their stability depended on the operation of stages over some finite time interval, and that when the models were subjected to sinusoidal fluctuations in either inlet total pressure or temperature there was a change in time meaned stage matching which resulted in stages being matched nearer stage stall; the overall time meaned effects being a reduction in both surge pressure ratio and equivalent inlet flow. This same investigation indicated that as frequency increased the complexity of the models required did also, and that exponential decreases in inlet total pressure could produce quasi-steady operation above the steady state surge line. It has been concluded that the investigation has shown encouraging results and that there were many possible uses of similar models where the transient operation of compressors was important.

This study investigated the premise that ceramics might sometimes profitably be shaped using techniques more traditionally associated with metals and plastics, particularly forging of solids and extrusion of liquids. This firstly required that the high temperature formability of ceramics be known. Existing forming and associated testing techniques were therefore surveyed, establishing short-comings and pointing to areas requiring new techniques. Plastic deformation mechanisms of principal simple ceramics were reviewed to determine the scope of novel techniques required, and to show evidence of suitability for forming. Emphasis was given to the deformation behaviour of alumina, the ceramic chosen for experimental investigation. Five rigs were constructed for an experimental schedule in three phases: (I) two furnaces and one press were used to study the compatibility of alumina with graphite, tantalum, tungsten and molybdenum under forming conditions. Some original microhardness values for carbides were measured. Observations were made of graphite's spectral emissivity. Sensitive temperature control was achieved. ii) a special melting unit was developed for inflating molten alumina to form hollow spheres, resembling blow-moulding of glass and plastics. Thermal endurances of tungsten heaters in vacuo, in argon and in molten alumina were studied. Heat transfer through sintered and powder alumina was measured. The spectral emissivity of sintered alumina was found. The freezing contraction of molten alumina, and the contact angle with tungsten were found accurately using a novel technique with possible wide application. iii) a multipurpose rig with tungsten tooling was constructed for tests of alternating drivedown - stress relaxation, compressive creep, and forging on recrystallised alumina. The experiments gave information on forgeability, ductility above 1150C, crack healing, tertiary creep rate, pore distribution effect on steady state creep rate, and pore closing contribution to deformation. It was concluded that forging and liquid extrusion of alumina is feasible and is sometimes preferable to traditional shaping methods.

This thesis is concerned with intelligent computer-based instrumentation which can be easily adapted for measurement, modelling and control in a range of application domains. The particular application area selected for study and used to illustrate the main features of the scheme was in anaesthesia for measurement and control of high-frequency jet ventilation (HFJV). The analytical methods and experimental procedures required for this area are also applicable to many other areas throughout engineering and biomedicine. A prototype general-purpose signal processing computer (SPC) encompassing many new design concepts was built to provide a flexible and user-friendly system for performing dedicated measurement and control tasks - as specified by the application program interface. The other objective of this study was to develop a new measurement and control environment for investigating the underlying respiratory dynamics of patient airways during HFJV - to facilitate a study of the efficacy of this mode of ventilation. Drawing on past experience with the SPC, a new computer-system was designed which overcame the bandwidth limitations of the original SPC. Based around powerful, modem and cost- effective commercial system hardware it is shown that this second-generation SPC can perform real-time measurement, modelling and control in HFJV as required. Modifications were carried out on an existing high-frequency jet ventilator to allow new modes of respiratory excitation. The signal processing system described together with these modifications to the jet ventilator coupled with the development of a new non- invasive fibre-optic chest-wall displacement transducer forms a complete environment which permits systematic identification of respiratory dynamics with extremely high precision in a fraction of the time taken by previous workers in this field. This is achieved with only minor changes to existing jet ventilation equipment and procedures. The system is intended to cope with the volume of information that needs to be considered during HFJV and the level of complexity that this method of ventilation entails. The measurement environment has undergone clinical trials on a small population of patients. The study clearly validated the hypothesis that the respiratory airways exhibit characteristics similar to an acoustic resonant circuit over the range of frequencies covered by HFJV. Based on this study, a Lyapunov model-reference adaptive control (MRAC) system has been designed and simulated for performing automatic control of HFJV and tested for stability and convergence over a wide range of operating conditions. The thesis concludes with a consideration of how the presented approach can be extended to take account of new hardware and software developments.

One of the most commonly utilised methods of diagnosing surface wave plasmas in recent years has involved the measurement of the electric fields surrounding the plasma column. However, such work has almost exclusively been confined to plasmas with generating frequencies typically greater than 200 MHz. The research reported in this thesis represents the first systematic diagnostic investigation of low frequency surface wave plasmas. Three distinct diagnostic methods are employed which have been developed specifically to facilitate the diagnosis of low frequency surface wave plasmas. Each diagnostic technique is comprised of a two-stage process. The first stage involves the measurement of the electric fields surrounding the plasma, from which point determinations of the surface wave wave number are obtained. In the second stage, an axial plasma density gradient is inferred from the wave number values using a theoretical surface wave model. The thesis begins with a general introduction to the characteristics of surface wave plasmas and details the principle research objectives in the present investigation. Previous work in related areas is reviewed and its relevance to the present study highlighted. The equipment employed for the experimental part of the research programme is discussed in detail. The theoretical surface wave model is then developed which serves to interpret the experimental measurements. The design of the Axial and FRD diagnostic techniques is described together with their application for diagnosing the low frequency surface wave plasmas. A new diagnostic tool; the parasitic test-wave technique; has been developed and the results from which serve to validate the data from the Axial and FRD techniques. The thesis concludes with a summary of what has gone before and suggests topics for future research.

Small battery charging wind turbines are used to provide electric power in locations where grid connection would not be feasible. However, existing controllers for such small wind turbines are often inefficient and unreliable. This work therefore examines the application of the little used Cuk converter to charge efficiently a battery bank from a 2kW permanent magnet generator. This circuit was chosen because the buck:boost action allows battery charging over a wide range of windspeeds, and neither the input or output currents are discontinuous. A controlled resistive dump load both safely loads the wind turbine when the batteiy bank is unable to accept all the power available from the generator, and also provides a low grade source of heat. A development of the basic circuit is to consider the use of self-regulating blades, which through safely limiting the maximum available generator power and controller input voltage, allows the significant simplification of the control electronics. The final stage of the work is the development of a PC-based simulator for rapidly evaluating the effect of different turbine designs or control strategies under a range of actual recorded wind conditions. A test bed is described on which a motor, controlled by the PC, mimics the effect of the wind turbine driving an actual small generator.

A statically-scheduled time-triggered (TT) software architecture demonstrates very predictable patterns of temporal behaviour and is – therefore – widely considered to be an appropriate platform for many high integrity and safety-critical embedded applications. However, there remains an important class of highly dynamic control systems for which it is considered that TT architectures are not a good match and for which the use of ―event triggered‖ (ET) designs is usually preferred. These applications include the control systems for internal combustion engines, brushless DC motors and synchronous AC motors. The aim of the research project presented in this thesis was to explore ways in which a static TT architecture could be adapted in order to better meet the requirements of such highly-dynamic control systems. The project had three main outcomes. The first project outcome was that a novel ―flexible TT architecture was developed. This architecture differs significantly from conventional TT designs in that – during the system operation – only the timing of the next system interrupt is known in advance (that is, the timing of subsequent interrupts is unknown). This allows for considerable flexibility in the task scheduling while retaining most of the features that make static TT approaches attractive. The second project outcome was that two novel schedulers were designed and implemented, in order to demonstrate (by means of an ―existence proof‖) that it was possible to construct a practical implementation of the flexible TT architecture. The third outcome from this project was that a comprehensive evaluation of the flexible TT architecture and the associated scheduler implementations was carried by means of two representative case studies. The case studies involved engine synchronisation and control of a brushless DC motor (BLDCM). In the engine synchronisation case study, the flexible TT architecture was shown to be a viable alternative to ET in conditions where a static TT was unable to cope with the system demands. In the BLDCM case study, while both static TT and flexible TT were viable alternatives, the flexible TT was able to provide similar levels of performance to the static TT solution at a fraction of the resource usage.