No description available.

No description available.

No description available.

No description available.

No description available.

This research project is primarily concerned with the development of a new generation of power transmission lines for both non-real-time and real-time electromagnetic transient studies. The method proposed is entirely formulated in phase co-ordinates, avoiding the use of modal transformation matrices at every stage in the analysis. In comparison, the phase domain models presented thus far in the open literature have all incorporated the concept of modal decomposition in the initial frequency domain formulation of the problem. Only the time domain analysis is conducted in the phase domain. These models can therefore be regarded as a hybrid between the phase and modal methodologies. Algorithms are presented which allow accurate and efficient determination of the characteristic admittance matrix, Yc(), and wave propagation matrix, H(), directly in phase co-ordinates. A Padé iteration scheme is used for evaluating the characteristic admittance matrix, derived by exploiting a relationship between the matrix sign function and the matrix square root. Padé techniques have also been used to approximate the matrix exponential in order to evaluate the wave propagation function. By evaluating Yc() and H() directly in phase co-ordinates, any imbalances naturally present in the line will intrinsically be taken into account in these functions. Both methods have been extensively tested using line configurations of different size and complexity and both algorithms are shown to be very robust, accurate and efficient in all cases. One of the main difficulties in formulating the analysis entirely in phase co-ordinates for multiconductor systems concerns the unwinding of the wave propagation matrix. This is addressed in this research by evaluating a matrix phase shift function in phase co-ordinates. Since the method inherently takes into account the coupled time delays of the line, the elements of H() can be successfully unwound, irrespective of the configuration of the line, e.g. single-circuit, multi-circuit or asymmetrical.

Retentate obtained from ultrafiltration was used as a substitute for skim milk powder, in the manufacture of ice cream and cajeta (Mexican dairy spread). The products were assessed by chemical, physical, sensory and structural analysis. Ice creams made using ultrafiltered retentate had increased ash, protein, calcium, phosphorus and magnesium, but reduced lactose, potassium and sodium contents. Physical evaluation showed that UF-products were harder, more viscous and had better melting resistance, but had lower overrun and extrusion temperature than control ice cream. In Sensory analysis UF-products scored better for iciness, sandiness and fluffiness, and resisted heat shock treatment better. No consumer preference for UF-based ice cream or control ice cream was found. The UF-ice cream took longer to soften to eating consistency. Structural examination of ice cream products by various microscopy techniques revealed air cell, ice crystal and fat droplet structures within a sugar and protein matrix. Freeze substitution was applied to ice cream for Transmission Electron Microscopy to produce unique thin sectioned samples. This showed a more agglomerated casein structure than UF-based ice cream. Heat shock changed ice cream structure. Ice crystal size increased and crystals fused into a network. Air cells could be distorted into a modified channel shape. Chemical, physical, microbiological and sensorial analysis of cajeta were carried out. UF-cajeta had slightly higher protein calcium and phosphorous contents and lower lactose, potassium and sodium contents. UF-cajeta showed better sensory attributes after storage than the control, however as shelf life was extended yeast and mould growth was possible. Structural examination of cajeta showed ultrafiltered retentate in cajeta manufacture prevented the formation of larger crystals and prevented sandiness that developed in the control product.

This thesis addresses the improvement in quality of decision making in design through the use of decomposed design evaluation. The research reported in this thesis is supported by the Design Research Methodology. To perform decomposed decision making, it is necessary to identify criteria that are deemed important for this activity. Questionnaire surveys, literature review and interviews with industry helped to identify these criteria. Reliability and realizability are two criteria that are selected for research in this thesis. The questionnaire surveys are discussed in chapter 2. A review of literature on decision making, reliability and realizability is reported in chapters 3 and 4. Methodologies for evaluating reliability and physical realizability are discussed in chapter 5. Relative reliability risk assessment methodology is applied to various examples consisting of university and industry projects in chapter 6. The application helps to reveal the strengths of the methodology and is termed ‘Verification of the methodology’. Validation issues of both the methodologies are dealt with in chapter 7 using the controlled experimental design. It is found that both the methodologies help to improve the quality of decision making during design evaluation. Relative reliability risk evaluation methodology helps to improve the quality of decision making to a substantial extent but physical realizability evaluation methodology shows only a little improvement in quality of decision making. Finally, it is suggested that the decomposed design evaluation methodology helps to improve the quality of decision making and is therefore proposed to be used by both novice and experienced designers.

The thesis is concerned with the design, analysis, fabrication am evaluation of integrated optic lenses which are inhomogeneous either in physical shape or in refractive index profile. The thesis has nine chapters. Chapter one, the introduction, illustrates the importance of these lenses within the domain of integrated optiCS, where the complicated mathematical functions required to describe the lens profiles are most easily realised. Connections are made between the study of these lenses and the exciting new field of optical computing. A special class of non-uniform lenses which are conceptually perfect optical instruments forms the main area of interest in the present study. Historically, the development of these lenses has followed two distinct lines, related to two possible methods of physically obtaining the required variation in path of light rays passing through the lens. In one method the optical path is made to vary directly, whilst the other method involves controlling the fi'lysical path, and thus the optical path, through the principle of equivalence. The dual development has been continued in the field of integrated optiCS, where lenses based on direct control of the optical path are termed variable-index lenses and those based on physical path control are termed geodesic lenses. The perfect variable-index lens studied in this work was the well-known Luneburg lens. Perfect geodesic lens designs have also been published. The design formulae for both types of lens are presented in chapter two. A simpler lens, of spherical geometry, is also presented which is easily analyzed and characterised and which serves as an archetypal model against which the performance of the more sophisticated lenses can be assessed. Chapter three investigates the problems involved in modelling fabrication conditions in a thermal-evaporation-invacuum environment so that lens profiles can actually be constructed. Chapter four goes into methods of tracing rays through these lenses in some detail. Ray-tracing has long been the classical tool of optical designers, providing a useful guide to optical performance. Ray methods, which effectively provide image error evaluations, are not entirely-appropriate for those lenses which are conceptually perfect within the geometrical optics approximation. Diffraction effects prevent the lenses from attaining true perfection. In such cases the wave-field produced by the lenses in the image space is the important quantity. In chapter five, the beam-propagation method (BPM) is used to study diffraction arrl associated effects in inhomogeneous lenses. '!he method allows the propagation of complicated waveshapes in lnhomogeneous media, normally a difficult task. Furthermore, anlsotropic effects and the interaction between acoustic waves aoo optical waves can be studied with the method. Negative focal shifts are reported which are not predicted by geometrical optics or the usual approximate diffraction theories. The fabrication of lenses is considered in chapter six. Planar waveguide measurements car r ied out on the var ious materials used in the study are presented. A major problem in the fabrication of geodesic lenses, that of obtaining a uniform wavegulde layer over the complete lens area, is dealt with in some detail in chapter seven. In chapter eight, extensive tests on the experimental performance of several lenses are reported. Near diffraction-limited performance is reported for geodesic lenses. More limited performance figures are obtained for Luneburg lenses though the possibility of high performance is lndicated if profile resolution can be improved. The themes of the thesls are pulled together for discussion in chapter nine and conclusions are drawn as to the relative merits of the various lenses. Possible means of improving fabrication procedures, thus driving lenses closer to ultimate resolution limits, are presented. The greatest problem faced is that of scatter ing in the waveguide, which appears to be accentuated as the waveguide traverses the lens surface. If the scattering problem can be successfully dealt with it is concluded that integrated optical lenses could be important and viable components in addresslng the problem of fast, high-throughput data processing.

Allpass filters are commonly employed in many applications to perform group delay equalisation in the passband. They are non-minimum phase by definition and are characterised by poles and zeros in mirror-image symmetry. SI allpass filters of both cascade biquad and bilinear-LDI ladder types have been in existence. These were implemented using Euler based integrators. Cascade biquads are known to have highly sensitive amplitude responses and Euler integrators suffer from excess phase. The equalisers that are proposed here are based on bilinear integrators instead of Euler ones. Derivation of these equalisers can proceed from either the s-domain, or directly from the z-domain, where a prototype is synthesised using the respective continued-fractions expansions, and simulated using standard matrix methods. The amplitude response of the bilinear allpass filter is shown to be completely insensitive to deviations in the reactive ladder section. Simulations of sensitivities and non-ideal responses reveal the advantages and disadvantages of the various structures. Existing DI multirate filters have to date been implemented as direct-form FIR and IIR polyphase structures, or as simple cascade biquad or ladder structures with non-optimum settling times. FIR structures require a large number of impulse coefficients to realise highly selective responses. Even in the case of linear phase response with symmetric impulse coefficients, when the number of coefficients can be halved, significant overheads can be incurred by additional multiplexing circuitry. Direct-form IIR structures are simple but are known to be sensitive to coefficient deviations and structures with non-optimum settling times operate entirely at the higher clock frequency. The novel SI decimators and interpolators proposed are based on low sensitivity ladder structures coupled with FIR polyphase networks. They operate entirely at the lower clock frequency which maximises the time available for the memory cells to settle. Two different coupling architectures with different advantages and disadvantages are studied.