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Within the aircraft industry, a large number of the aluminium components are milled entirely from single solid billets of metal. Current practice is to machine at conservative and constant feed-rates. This avoids damage to the workpiece and therefore reduces costly scrap. On-board monitoring systems on milling machines within the aerospace industry have introduced the possibility of continuously and adaptively varying the feed-rate online. It is proposed that this variation could be based on cutting power. Machining parameters, such as depth and width of cut, and tool efficiency, can vary considerably during the manufacture of a single component. It is therefore likely that an adaptive controller should be used. NICS is an adaptive controller algorithm that has been under development since 1990 Stoten et al. It is known to have good properties with respect to robustness and controller performance and is therefore being investigated for use on the milling machines for aluminium components. Substructuring is a dynamic testing technique that combines numerical models and physical tests into a single hybrid experiment. Briefly, it allows the engineer to "glue" a real component (in a lab) and a virtual component (implemented on a computer) together. These real and virtual components can then be tested dynamically and in real-time as if they were a single, complete component. Hence, substructuring provides the engineer with a framework to allow testing of individual components from entire structures at full scale without requiring the complete structure to be physically present. Accurate, hi-fidelity control is essential to the successful reproduction of structures using this technique. Hence, the goal of the work presented in this thesis is the development and implementation of control strategies for use in the field of metal machining. A scheme that the controls the cutting force transmitted to aluminium workpieces by varying the feed-rate is developed. A requirement of this scheme is that it be simple to set up and implement whilst, at the same time, regulate the cutting power in the face of process para peter variations. The ability of the adaptive controller to meet these requirements is demonstrated both in simulation and on a pilot rig developed in the work. A model that relates peak cutting force to measured cutting power is developed for use with the aforementioned control scherne along with high-level control software implementing this scheme. Rirther, controllers both fixed-gain and adaptive, are developed and tailored for use in the substructuring technique. The performance of the developed controllers is investigated both in simulation and in the laboratory on a linear large-scale hydraulic system. The advantages of using the adaptive controller scheme over a fixed-gain linear equivalent are presented. An example demonstrating the use of the substructuring technique in the field of machining is discussed, including a specific application.

This thesis describes an investigation into the application and performance of direct sequence spread spectrum techniques for land mobile radio systems. There is a brief description of the basic principles of operation of direct sequence systems. The multiple user facility is analysed and values obtained for the maximum number of simultaneous system users in terms of system parameters. This clearly illustrates the need for power control. A possible method of providing power control is described. Comparison of user density is made against conventional narrowband modulation methods. There is some discussion of the effect of sequence cross-correlations on the number of system users. The system organisation is mentioned, showing possible application of a calling channel. Consideration is given to the possibilities of bandsharing with narrowband modulation systems. Figures are derived for the resulting interference to existing systems which would be caused by such an arrangement. A brief resume of the pertinent features of the land mobile radio channel is given. The effects of shadowing on the output quality and spectral efficiency of direct sequence systems is discussed. There is an analysis of the effects of shadowing on the user density in small cell schemes. An analysis shows the effects of multipath propagation on direct sequence performance by reference to a simple two path channel. Details are given of a simple experimental direct sequence spread spectrum transmitter and receiver constructed. The measured results for the performance of the system against various forms of interference and channel degredation are compared with their theoretical values. Finally ideas for future work are discussed.

Senecio is the largest angiosperm genus, taking in about 1/7 of all Compositae and exhibiting nearly the whole range of vegetative diversity encompassed by the family. There is satisfactory definition of the genus, and the oft-quoted 'diagnostic' features are commonly lacking, especially among extra-european species. In fact, in the Genera Plantarum of Bentham and Hooker, the diagnosis of Senecio is essentially the same as that of the tribe Senecionideae. It is a commentary on taxonomic progress that the only comprehensive account is that of De Candolle (1837), although since his time the number of named Senecio species has increased fourfold. Clearly a reappraisal of the taxonomy of Senecio and of its relationships with other Compositae is long overdue. Regarding the classification of Compositae, one finds that despite nama changes the tribes have altered very little since their delimitation and establishment by Cassini (1816-34). This is remarkable because the largest angiosperm family, taking in about 1/10 of the flowering plants, would seem to provide plenty of scope for discordant taxonomic opinion. Nevertheless Table 1 shows that of the 13 tribes recognised by Bentham (I873A), seven (i.e. 2, 3, 6, 7, 9, 10 and I3) are identical with or practically the same as Cassini's; and four (i.e. 5, 8, 11 and 12) incorporate or are merely fusion products of short sequences of Cassini's tribes with his groups adopted as subtribes. Only 2 of Cassini's tribes (i.e. 12 and 20) had suffered significant changes.

The thesis that follows this abstract describes the development of a high bandwidth active gate driving testbed and the investigation of effects that multi-GHz bandwidth gate signals have on the switching of 650 V GaN HEMT power devices. It covers the development of the support hardware required to drive a proto-type active gate driver capable of updating its output impedance every 100 ps to deliver between ±10 A of gate current. The challenges caused by 150 V/ns and 10 A/ns slew rates on the support circuitry are investigated to select DC-DC converters and digital signal isolators which allow the testbed to be self-immune to the transitions it can produce. Measurement techniques suitable for GaN HEMT devices and optimised power circuits are explored and evaluated. Considerations on the impact of a measurement technique on circuit layout and the parasitic inductance present are explored as this impacts the viability of power circuit current measurement methods. High bandwidth active gate driving is used to demonstrate beneficial control via the gate of < 5 KW scale transitions during double pulse tests with 650 V normally off GaN HEMTs. Reductions in drain oscillation of up to 10% and switch node voltage spectra by 9 dB above 125 MHz were observed depending on the load configuration. The impact of environmental and electrical operating parameters on the robustness of demonstrated improvements is investigated and discussed. For load current variations of ±3 A a resistance sequence is shown to keep drain current peak spectral content within 10 dB of the minimum achieved with a fixed gate resistance sequence. Finally, a method is proposed that allows the established resistance sequence to be compensated for changing load current and keep peak spectral content within 5 dB of minimum for a new optimised point.

The continuous drive towards more electric technologies and the subsequent need for high-performance electric machines calls for a more accurate and reliable thermal design-analysis, where various design, manufacture and assembly factors are accounted for at the initial stage of the design process. The wide ranges of built factors have a significant impact on the overall thermal behaviour of the machine, and frequently require empirical techniques to validate the initial design assumptions. The conventional approach employed in empirical validation of thermal models of electrical machines makes use of thermal testing on a complete machine prototype. This is usually performed at the end of the machine manufacturing process to assess the measured thermal characteristics against the design targets and theoretical predictions. Thermal model validation from a complete machine assembly is frequently effective for experienced-based designs, where a designer has confidence in the pre-existing machine thermal design. In such a case, the initial machine assembly should closely match the specifications. However, for novel machine topologies, a designer typically needs to evaluate several design variants to realise an optimal solution. The machine fabrication for all design iterations would not be feasible due to the cost and time constraints. For these reasons, a method providing reliable loss and thermal predictions would significantly reduce the number of prototype iterations required for the development of a new machine. Therefore, time and cost associated with the new design would be substantially reduced. This thesis presents an experimentally-informed methodology for the high-fidelity thermal design of electrical machines. The methodology focuses on the stator-winding region, which is frequently attributed with the dominant power loss component within the machine body. The developed approach accounts for a variety of permanent magnet machine designs, where the majority of the heat produced in the machine is evacuated by conduction into the machine periphery. Three machine sub-assemblies have been selected to form the foundation of the proposed methodology, based on their complementarity and their capability to incrementally inform the machine thermal design. Efficacy of the proposed methodology is illustrated on a number of machine demonstrators with different build attributes. The proposed methodology aims to be a systematic and reliable tool for machine designers, guiding empirical calibration depending on available hardware, required fidelity and machine design focus.