After the brief review on adaptive array processing, three fairly separate topics on the power inversion adaptive array are treated in this thesis. The first topic is the behaviour of a narrowband array using the stochastic gradient descent algorithm, with the environment assumed to rotate at constant velocity in the sine domain. Conditions for steady state weight deviations and output power deterioration from optimal values due to the nonstationary environment are derived and are then used to determine the maximum scan rate of a radar side-lobe canceller. The second topic is the jamming rejection capability of a broadband array using tapped delay line processing. The results obtained are used for designing the tap spacing and number of taps of the delay lines as well as assessing, in terms of the number of variable weights, the relative advantage of the alternative broadband processing method using several narrowband array processors. The frequency distortions at various directions introduced by rejecting the jammers are also studied qualitatively. The third topic is the convergence behaviour of the broadband array when the stochastic gradient descent algorithm is employed. Comparison with the alternative broadband processing method is again given. A simple transformation pre-processor, independent of the external environment and capable of improving the convergence behaviour of using tapped delay line processing, is also derived.

The purpose of this work was to investigate the production of a large volume electric discharge with particular reference to the superposition of DC and high frequency discharges. The principle objective was to enable a reduction in the operating frequency of the high frequency power source to values more amenable to industrial application. This has been achieved.

Over the last few years, radio frequency, also known as dielectric heating has become well established in a number of process industr1es because of its unique heat transfer characteristics which make it a fourth category, volumetric heating, alongside the well established mechanisms of radiation, conduction and convection. RF has become widely accepted in the textile, food, woodworking and paper converting industries amongst others, even though a fully integrated theory, which brings together heat and mass transfer, electrical theory, material characteristics, and process parameters has yet to be established.

The aim of the work described in this thesis was to examine the starting characteristics of Trapatt (Trapped Plasma Avalanche Triggered Transit) oscillators capable of producing high (peak) power at high efficiencies, normally in L and S bands. General approach was aimed to be mainly experimental using deep diffused silicon devices suitable for operation in S band. To perform the experiments an oscillator circuit, in 7 mm coaxial line was constructed, suitable for using a device in S-4 package. The overall arrangement of the experimental setup was similar to one described by various other researchers for observing the dynamic current and voltage waveforms. The C-V profiling experiment produced a characteristic which suggested that the depletion layer capacitance of the device does not really saturate for increasing voltage even upto its breakdown voltage. A detailed analysis of the C-V plot and related features was carried out and it was concluded that the actual doping distribution appears to be favouring a graded junction. Experimentally it was established that the device has negative resistance at VHF and also at d.c. It has also been shown that the device has small signal negative resistance at the operating frequency of the oscillator. Detailed investigations into the starting characteristics indicated that the oscillations start from the beginning at the final fundamental frequency of the oscillator. For the device and the circuit reported in this thesis no evidence could be found to suggest that Impatt type oscillations trigger the Trapatt oscillations. As a result of our experiments it has been possible to establish that the rate of growth and the time taken for the oscillations to start depend upon the d.c.drive. There are strong indications that in future Trapatt devices could successfully be employed in various systems as a microwave generator.

The control of a modem power generating station is a complex task involving the acquisition and processing of a large amount of data. This involves the processing of data from transducers or other inputs which then produce the desired outputs for actuators and displays etc. The advent of small cheap digital data processing systems has made it economically desirable and indeed feasible to implement distributed computer control schemes. The overall control of the station can be achieved by an interconnected set of such computer systems, each computer being at the node of a communications network. The actual control functions are implemented as a number of co-operating modular programs resident in each of the control nodes. It is assumed that the computers will be functionally similar ( hardware and software ) and that the characteristics of each module (task) such as the CPU loading and the inter-task communication requirements are known a priori. This work investigates the assignment of these tasks such that the distributed computer network uses the minimum number of computers and that the overall inter-computer communication is minimised. However, this overall objective is influenced by a number of technical and operational constraints which are used to formulate a series of mathematical models that progressively include more aspects of the problem. The application of various linear and non-linear optimisation techniques to the solution of these models is investigated. Three independant methods of optimisation are investigated to solve the computer control network problem. In each case, the aim is to construct a simple model based on certain aspects of the problem and then extend the model to include all other aspects. A complete mathematical model which applies the standard methods of optimisation is presented. It is claimed that these formulations are original. It is shown that the complete network design problem is difficult to solve efficiently using standard methods of optimisation, because of the size and the complexity of a practical problem. Hence, the central component of this research has been the development of an algorithm to solve practical network design problems. This algorithm is claimed to be original and is computationally more efficient than the standard methods of optimisation for this type of problems. The basic steps of this algorithm are to decompose the problem and then interactively solve the less complex subproblems. It is shown that this algorithm used interactively will provide a feasible solution. This work contributes to the research into the design of distributed computing systems for process control applications, undertaken by the Central Electricity Research Laboratory (C.E.R.L., Leatherhead, Surrey). In particular it makes a major contribution to the objective of producing a design aid for such computing systems.

Capturing user preferences is a problematic task. Simply asking the users what they want is too intrusive and prone to error, yet monitoring behaviour unobtrusively and finding meaningful patterns is both difficult and computationally time consuming. Capturing accurate user preferences is, however, an essential task if the information systems of tomorrow are to respond dynamically to the changing needs of their users. This thesis tests the hypothesis that using an ontology to represent user profiles offers advantages over traditional profile representations in the context of recommender systems. A novel ontology-based approach to recommendation is applied to a real world problem and empirically evaluated. Synergy between recommender systems and ontologies is then explored to help overcome both the recommender system cold-start problem and the ontology interest-acquisition problem. Finally, the visualization of profiles in ontological terms is examined in a real world situation and empirically evaluated.

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In a synchronous serial data-transmission system using iterative detection process, the received signal is sampled and each signal element is detected by means of an iterative process that uses some or all sample values dependent on that element. The intersymbol interference of the signal element in the following elements is then cancelled, before the detection of the next element, and so on.