During the hot-rolling of aluminium ingot into sheet, the material elongates in the rolling direction as it is reduced vertically. The spread which occurs in the lateral direction during the multiple pass schedules used in industry is minimal. However, the deformation on these edges is important. During the initial passes a concave profile develops - the material near the surfaces spreads outward while the material at the centre moves inward. The concave profile can lead to defects in the final product; these are the 'roll over' of material from the edges to the top and bottom surfaces, the fold over of material in the centre of the edge, and the formation of vertical edge cracks. To remove these the edges are trimmed at the end of the process. Research work in this area was motivated by the possibility of identifying means of reducing the amount of material that needs to be trimmed. The objectives of this thesis are to develop techniques of simulating the rolling, and to use these to investigate the deformation mechanisms which lead to the concave edge profile. Models of the rolling were developed using the general purpose, non-linear finite element code ABAQUS. To reproduce the edge profiles accurately requires large three-dimensional models, for which the explicit dynamic method was found to be the most suitable. The results of the analyses were used to investigate the mechanisms which lead to the concave edge profile. In the roll-gap the work-load arches through the ingot; and for roll passes with small reductions a stress pattern occurs which leads to the concave edge profile. In this pattern the stresses of highest magnitude at the surfaces are compressive stresses in the vertical direction, while in the centre of the ingot they are orientated in the rolling direction and are tensile. Thus deformation occurs by vertical compression near the surfaces, and by stretching in the rolling direction at the centre. At the edges the material is not constrained laterally; and due to the Poisson effect, the material spreads outward near the surfaces, and moves inward at the centre. The effect of certain variables on the edge profile were investigated with the modelling. The friction between the work-rolls and the ingot was found to have significant influence on the amount of lateral surface spread. Work hardening, strain rate and temperature effects in the material lead to variations in the yield stress through the height of the ingot. These effects were included in the modelling and were found to affect the shape of the profile, but to a lesser extent than the friction.

The novel Balanced Beam Tube Viscometer (BBTV), developed at the University of Cape Town, has been further developed and refined. Extensive work has been done in the following areas: (i) The effective length of the BBTV tubes. (ii) Interpretation of the data obtained using the BBTV in both the laminar and turbulent flow regimes. (iii) Comparison with the rotary type viscometer. Kaolin clay and uranium tailings slimes slurries of different particle size range and concentration have been successfully characterised by yield- pseudoplastic rheologies using the BBTV. The BBTV is in fact a miniature pipeline and it has been shown that it is capable of producing valid turbulent flow data and indicating the laminar/turbulent transition region in the two tube sizes .

Includes bibliographical references. / An investigation has been carried out on a dual-phase 12 % chromium steel, designated 3CR12, with the aim of developing its composition to improve its properties. By the addition of appropriate alloying elements, it was hoped to produce a fully austenitic structure in the rolling temperature range, and at the same time to enhance the kinetics of the decomposition of austenite so that a fully ferritic structure could be obtained after air cooling. The absence of delta ferrite during hot rolling would eliminate the highly anisotropic structure currently found in 3CR12, whilst accelerating the transformation to alpha ferrite might eliminate the need for an annealing treatment. Volume fraction analysis (VF A) of specimens quenched from a soaking temperature of 1000°C showed that Co, Ni and Cu stabilise austenite, whilst Si and Al have the opposite effect. These results were confirmed by finding the equilibrium transformation temperatures of the decomposition of austenite to ferrite using dilatometry, and by investigating the partition of alloying elements between delta ferrite and austenite at I 000°C using the electron microprobe. The effects of the alloying elements on the kinetics of the transformation were investigated by VF A of specimens transformed from 1000°C, and by the use of dilatometry. Dilatometry was used to find the slowest cooling rate at which the alloy was fully untransformed. It was found that Si and Al enhance the kinetics of transformation, whilst Co, Ni and Cu hinder them. The effect of each element is discussed with respect to three factors: the delta ferrite content prior to the transformation, the temperature range of transformation, and the thermodynamic effects of the element.

Includes bibliographical references. / Both the declining cost and increasing capabilities of specialised computer hardware for image processing have enabled computer vision systems to become a viable alternative to human visual inspection in industrial applications. In this thesis a vision system that will analyse and classify dried fruit is investigated. In human visual inspection of dried fruit, the colour of the fruit is often the main determinant of its grade; in specific cases the presence of blemishes and geometrical fault are also incorporated in order to determine the fruit grade. A colour model that would successfully represent the colour variations within dried fruit grades, was investigated. The selected colour feature space formed the basis of a classification system which automatically allocated a sample unit of dried fruit to one specific grade. Various classification methods were investigated, and that which suited the system data and parameters was selected and evaluated using test sets of three types of dried fruit. In order to successfully grade dried fruit, a number of additional problems had to be catered for: the red/brown coloured central core area of dried peaches had to be removed from the colour analysis, and Black blemishes upon dried pears had to be isolated and sized in order to supplement the colour classifier in the final classification of the pear. The core area of a dried peach was isolated using the Morphological Top-Hat transform, and Black blemishes upon pears were isolated using colour histogram thresholding techniques. The test results indicated that although colour classification was the major determinant in the grading of dried fruit, other characteristics of the fruit had to be incorporated to achieve successful final classification results; these characteristics may be different for different types of dried fruit, but in the case of dried apricots, dried peaches and dried pears, they include the: peach core area removal, fruit geometry validation, and dried pear blemish isolation and sizing.

Bibliography: leaves 269-280. / In 1980, Bernard reported that platinum dispersed on zeolite LTL (Pt/KU had exceptionally high selectivity for the aromatization of n-hexane to benzene. The selectivity was ca. 95 at 99 conversion of n-hexane. This Pt/KL catalyst has been extensively studied to determine the reasons for the exceptional stability and benzene yields relative to platinum supported on silica (Pt/Si0₂ ) and alumina (Pt/Al₂0₃). The Pt/KL catalyst was found to be monofunctional with all the activity occurring on platinum metal clusters inside the pores of zeolite L. The catalyst exhibits excellent stability and the Aromax Process developed by Chevron Ltd., using I a barium doped Pt/KL catalyst, PtBa/KL, has been reported to operate continually for the equivalent of one year during accelerated deactivation testing at 450°C and a hydrogen partial pressure of 6 bar. However, sulphur-containing I compounds such as thiophene, result in rapid and irreversible deactivation of the catalyist due to sintering of platinum clusters. Thus the level of sulphur-containing I compounds, especially thiophene, must be kept below 50 ppb of the feed to avoid deactivation by sintering. SASOL Ltd. may be in a unique position to use Pt/KL as a catalyst for the aromatization of hexanes and heptanes to benzene and toluene respectively, as their products which are produced by the Fischer-Tropsch process are sulphur free. However, a substantial amount of oxygenates are formed in the Fischdr-Tropsch process and as yet no study has been undertaken to determine the effect of these compounds on the activity and selectivity of the catalyst.

Includes bibliographical references. / There are some common characteristics of rural communities throughout the world. They tend to lack a good economic infrastructure, essential social amenities, tourist potential, good road infrastructure, literacy, and most importantly, scarcity of sufficient energy supply to meet basic needs, and deteriorating environments due to increasing pressure on available traditional energy resources. Furthermore, rural areas in the developing countries of South and East Sub-Saharan Africa are characterised by high population ratios, low levels of income, concentration of poverty, significant socio-economic disparities relative to urban area, and a high rate rural-urban migration. The availability of adequate and convenient energy is essential in addressing these priorities of rural development. The development of energy resources for rural areas is, therefore, closely linked to the economic, social and environmental concerns of mainstream rural development. Unlike growth-driven energy development for industrialisation and urbanisation, rural energy development must consider social and environmental development. More importantly, it must be people-oriented. The result of the study has indicated that the pace of energy transition from traditional to commercial energy in the rural areas of countries in the region has lagged behind that in urban areas, a similar situation to that existing between developing countries and developed countries. Significant rural-urban inequalities in commercial energy supply and consumption exist. Rural communities still continue to rely heavily on traditional energy, mainly biomass resources.

Includes bibliographical references. / Beta alumina is a ceramic with the ability to conduct certain ions. It is conventionally formed through the high temperature solid state reaction of α-alumina with soda and lithia, which results in a mixture of β- and β"-alumina phases. To maximise the amount of β"-alumina formed, a second heat treatment step is required. Beta alumina may also be synthesised directly from the various aluminium hydroxide ( Al(OH)₃ ) and aluminium oxyhydroxide (AIOOH) polymorphs. The particular oxygen sublattice of the starting material is critical in determining which phases of beta alumina are formed. Boehmite and bayerite are known to yield pure β"-alumina. In this investigation, the differences in structure and the identification of the polymorphs is discussed. A review of the methods of synthesis and concomitant mechanisms of reaction proposed in the literature are presented. Of these, the synthesis of boehmite and bayerite are investigated experimentally. Attempts to synthesise boehmite at ambient conditions resulted in the formation of pseudoboehmite, and confirmed that boehmite can only be formed by the introduction of a hydrothermal step. However, it was possible to form bayerite at ambient conditions by sμnple chemical reaction. Control of the reaction pH and the removal of inhibiting ions were found to facilitate the formation of well crystallised bayerite. Although the factors governing the successful synthesis of bayerite need further investigation, the possibility of a direct synthesis route for β"-alumina has been demonstrated. Finally, the synthesis of β"-alumina by the solid state reaction of the hydroxide and oxyhydroxide polymorphs was successfully completed.

Thesis advisor: Susanto Basu / My dissertation consists of three independent chapters analyzing parameter estimation and structural change in applied macroeconomics. A first theme linking these papers is structural change, especially as it relates to the monetary policy transmission mechanism through the Phillips curve. A second theme is an assessment of small-sample statistical inference for impulse response functions after estimating macroeconomic models. Two of my chapters provide simulation studies of statistical coverage of standard test statistics after estimating impulse response functions in both atheoretical (local projection) and highly structural (dynamic stochastic general equilibrium) models. The first chapter of my dissertation, ``Using Survey Expectations to Estimate the New Keynesian Phillips Curve,'' provides new estimates of the parameters in the New Keynesian Phillips Curve, exploiting survey based expectations data provided by the Survey of Professional Forecasters and the Michigan Survey of Consumers. I find that the use of survey expectations in US data improves the fit of the textbook Phillips Curve model to the data and provides economically sensible estimates of its coefficients. The estimated model provides stable parameter estimates until the Great Recession, after which inflation becomes less dependent on marginal cost. Household and professional forecasts each contribute to the forward-looking component of inflation expectations, with household forecasts given more weight. The second chapter of my dissertation, ``Estimating Structural Breaks in Impulse Response Functions via the Local Projection Estimator,'' proposes an estimator for parameter instability in impulse response functions that are estimated by local projections. I use the estimator to investigate the presence of parameter instability in the Romer--Romer monetary policy shocks. I find evidence of a structural break in the impulse response coefficients in the late 1970s. In the early period, there is strong evidence that monetary policy shocks have real effects. There is little evidence that monetary policy shocks have real effects in the later period. Tax and oil price shocks exhibit little change in their effects on output throughout the postwar period. The third chapter of my dissertation, ``Standard Errors for Impulse Response Functions of Estimated DSGE Models,'' provides a method for constructing appropriate asymptotic standard errors for impulse responses of estimated dynamic stochastic general equilibrium models. The method requires only the matrices characterizing the model solution, the derivatives of those matrices with respect to the underlying structural parameters, and the covariance estimate of the structural parameters themselves. I provide simulation evidence on the small-sample properties of these standard errors. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Includes bibliography. / The governing equations for interactions between surface gravity wavetrains and slowly-varying water currents are derived and the incorporation of Vocoidal water wave theory into this framework is discussed. The emphasis throughout is on the derivation of the general form of the governing equations plus a detailed discussion of the qualitative physical behaviour implied by the equations. Particular solutions are usually given only where they serve to clarify the general method or some physical feature of the analysis. The thesis proper is introduced by a derivation of wave kinematics on still water. A review of the kinematics and dynamics of an inviscid and irrotational fluid follows. The wave and fluid properties are then combined via the definition of wave integral properties. A derivation of the Airy and Stokes O(a2) wave theories is given and used to illustrate a number of points. Water currents (following or opposing the waves) are introduced via their influence on the wave-kinematics. The wave/current dynamics are then presented in two ways: firstly using a wave energy approach and secondly by introducing the wave action concept. Wave action is more convenient because it is a conserved quantity unlike wave energy. The general equations for two dimensional wave/current interactions are derived and discussed. At this point three topics are reconsidered: group velocity, momentum density in wave motion and Lagrangian mean forms of averaging. The general equations for wave/current interaction are shown to be compatible with the Vocoidal water wave theory and applications of the theory to wave/current problems are discussed.

Includes bibliographical references. / The fundamental degrees of freedom in string theory are extended objects. Solving their equations of motion can be difficult unless they are considered in very constrained situations. We investigate the dynamics of gravitational D-brane radiation. Results of others are reviewed which show that in the static case the string prole of Newtonian and relativistic strings are the same. We show that for slow moving strings the relativistic solution agrees with the classical one.