Includes bibliographical references. / On-line measurement of the moisture content of process streams in a mineral processing plant is vital for their efficient operation. Although many industrial moisture meters are available, most of these were designed to determine the moisture content of low density, fine grained, uniformly surfaced and low resistance materials. Consequently these meters operate poorly on mineral treatment plants as the measured material, rock, is dense, uneven and consists of mixtures of various minerals. A literature survey revealed that of the many methods available, only three techniques could be used for on-line moisture determination in mineral processing operations.These were microwave attenuation, phase and frequency techniques.

Includes bibliography. / Microwave measurement techniques have found many industrial and commercial applications. This measurement potential of microwaves, together with observations that different minerals show different microwave heating characteristics, suggests the possibility of applying microwave techniques to various forms of mineral analysis. Simple, low cost, on-line mineral analysis techniques are of interest to the mining industry. The objectives of this research project were to cover the background theory of microwave interaction with minerals and to investigate different microwave measurement techniques that could possibly be applied to mineral measurement. Measurements were then to be performed on selected minerals in order to observe any differences between them. Finally, to comment on the feasibility of using microwave measurement techniques for the differentiation, identification and analysis of minerals.

Includes bibliographical references. / The AIDS virus has been identified in breast milk which is donated by expectant and recently delivered mothers in maternity hospitals). In maternity hospitals, where the facilities exist for the treatment of pre-term infants, breast milk is collected from mothers premature even those who have not delivered premature babies) and it is used in its raw state to feed the children. The possibility of some of these mothers being infected with the AIDS virus is high in Third World countries. The premature infants have to be fed with breast milk as they are at risk of being infected if fed with commercial milk formulas. Commercially available milk sterilizers are available in Europe but they are very costly.

Bibliography: leaves 185-187. / Massflows on conveyor belts need to be measured in various process streams in mineral extraction processes to ensure good plant management. Conventional weightometers are, however, too expensive to allow a widespread installation in these processes. This study investigates more economic means to measure the massflow on horizontal conveyor belts. A deterioration of accuracy resulting from an instrument using this technique is expected, but the advantages of being able to instrument entire plants is very attractive. The study uses a model a whereby the kinetic energy of the belt system is determined during a perturbation to the system. From this the massflow can be determined.

Bibliography: leaves 115-116. / Microwave ovens have been available for domestic cooking since 1956. This method of heating is very efficient compared to conventional cooking methods. As a result many applications have arisen particularly in the field of analytical chemistry. Most routine analysis of biological and chemical samples by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) involves the time consuming operation of digesting the samples in acid on a hot plate. However, much time saving has been demonstrated by the use of microwave digestion, and successful digestions have been achieved in 10% of the time required for traditional methods. The first digestions using microwave heating were performed in open vessels. However many problems were identified.

Bibliography: leaves 155-160. / The ultimate purpose of this thesis is to compare and evaluate. South African poletop designs for 11kV and 22kV rural distribution lines. However, a frame of reference is first established from the literature and from construction practice before the analytical stage is tackled. In 1989, when the work for this thesis was started, it was quite apparent that there existed a proliferation of configuration designs for rural overhead lines at 11 kV and 22kV in South Africa. The electricity supply industry did not use a universal configuration. Eskom supplied over 97 of South Africa's electricity in 1990 (Eskom, 1990). It was also operating 160 280km of lines at 22kV and below in that year and was largely responsible for this situation. Local supply authorities or distributors S!JCh as municipalities either bought components from Eskom or used an Eskom design, or developed their own designs internally or via consultants. In any event, the designs they used are not considered to be a significant portion of the total. Historically, Eskom developed on a strongly regionalised basis, the separate Undertakings joining up (electrically) to form the national grid in 1973. Prior to 1985 there were six Regions distributing the electricity generated by the power stations. Each Region developed its own designs, independently or based on designs imported from Britain.

Bibliography: leaves 116-7. / The last decade has shown a very rapid increase in the application of digital computers to virtually all walks of life. This has resulted in a demand for better and faster digital communication links, at reasonable prices. Trellis coded modulation is a fairly recent development in the technology of digital communications that has helped to meet an aspect of this demand. The Department of Electrical Engineering at the University of Cape Town had not undertaken any research in the field of trellis coded modulation at the time this thesis was started. From what was understood of the topic at the time, it was deemed important to develop a foundation of skills and tools for working with trellis coded modulation. It was hoped that such a foundation will give current and future members of the department sufficient background to spot potential applications for the principles of trellis coded modulation.

Includes bibliography. / The increasing high standards of fruit quality expected by the agricultural export market of South Africa has reached a stage that fruit must be accurately graded in a short a time as possible. This thesis describes colour systems and methods to grade the fruit automatically via the clustering and classification methods. After investigating several approaches to automatically sort fruit based on colour, an image processing approach was taken. The colours on the fruit (specifically apples) were analyzed, by capturing a colour image of the fruit and analyzing the pixels in the image. Several colour representation systems were investigated and they are: colours represented by spectral power distributions and spectral reflectance curves; the CIE 1931 XYZ tristimulus values; the CIE 1931 x ,y ,z chromaticity coordinates; the CIE 1960 L, u, v uniform chromaticity scale (UCS); the Munsell colour wheel of hue, value and chroma (HVC); the L*u*v* system; the L *a*b* system; the Red, Green and Blue (RGB) system; and the hue, saturation and intensity (HSI) perceptual colour representations. In addition, several clustering and classification techniques were investigated and they are: the supervised methods of Parametric Bayesian classification and minimum Euclidean distance classification; and the unsupervised methods of the K-means algorithm and the ISODATA classification approach. The ICS Texicon computer spectrophotometer (ICS Texicon Spectraflash Manual (1991)) was used to check the performance of most of the colour systems described by analyzing apple sample colours

Bibliography: leaves 136-145. / This thesis is concerned with the application of a method for control system design based on Youla(Q)-Parametrization. The fundamental concepts of the parametrization method have been used by Newton et al, Franklin and Raggazzini [Maciejewski, 1989] as early as 1957. The importance of its implications were not noticed during those years, but Youla and Kucera renewed it in the seventies [Maciejewski, 1989]. For the special case of an open loop stable plant, the implementation can be realized in the Internal Model Control(IMC)-Structure [Morari, 1987]. The IMC-Structure is essentially a open loop design method for closed loop controllers, thereby simplifying the design procedure. A Multivariable controller design method is proposed that unifies the advantages offered by three design approaches/techniques, namely, The Q-Parametrization, The IMC-Structure and The Characteristic Loci Technique. The proposed method is based on controller parametrization. In addition, it retains the engineering insight and simplicity of the IMC-Structure. This is particularly useful in solving complex multivariable problems. The design method was evaluated by its application to the design of a control law for a FLOTATION PROCESS SIMULATOR RIG(FLOTRIG) built by Mr Fisher[Fisher, 1988]. The design of the Multivariable controller was based on a Transfer Function Matrix, G(s), which is a Linear Time Invariant(LTI) model of the FLOTRIG.

The aim of the dissertation is to explore a method of enhancing learning in the Electrical Engineering curriculum, which effectively exploits the computer. The different modes used in computer-based learning are discussed and compared, and the conclusion reached that simulation provides the best basis for a learning enhancement system. It has the ability to facilitate demonstration of basic concepts, learning of estimation, modular system design, and the use of models in engineering, and group work. It is a useful complement to laboratory work. It also enhances motivation and interest. A system is motivated loosely based on the architecture of the analogue computer, but tailored for an educational environment by being interactive, simple-to-use, adaptable and extendable by the tutor, and carrying a wide variety of educationally valuable inbuilt functions. The system proposed, SOFTWIRE, consists of a software package, a hardware laboratory interface as well as a broad approach to strategy, based on basic Learning Theory. Design issues relating to the hardware, software, and implementation of pedagogic strategy are discussed. Some examples of the use of the system are given. Thus both the broad and specific approach are covered. Some of the modes of useage discussed are demonstrations, design problems involving the construction of simulations in SOFTWIRE's language, interacting with simulations to experience them and to see the effects of parameter and structure changes, and learning about modelling and its relation to the real world. Evaluation is discussed, especially in relation to SOFTWIRE. Conclusions are drawn, and suggestions made about future development of the SOFTWIRE system, as well as relevant trends in computer education.