AbstractFractal image compression is a comparatively new technique which has gained considerableattention in the popular technical press, and inore recently in the research literature.The most significant advantages claimed are high reconstruction quality at low codingrates, rapid decoding, and "resolution independence" in the sense that an encoded imagemay be decoded at a higher resolution than the original. While many of the claims publishedin the popular technical press are clearly ...
AbstractSpread Spectrum systems are found in many flavours, used in many applications and haveexisted since the early days of radio communications. The properties of spread spectrum dohowever place restrictions on the design, and often make the implementation expensive andcomplex. When using spread spectrum to provide a basic communications infrastructure,many factors need to be considered. These indude supplying the appropriate technologyat the right cost. To achieve this a trade-off a...
AbstractThis thesis deals with the damping of electromechanical oscillations using Power SystemStabilizers (PSS). The thesis focuses on three problems associated with the damping ofthese oscillations, namely the determination of the optimal locations of the PSS, thedetermination of the best control structure of the PSS and the design of robust PSS.We develop two new methods for determining the optimal locations of the PSS. These twomethods are based on Total Modified Coupling Factors (T...
AbstractAn anisotropic damage model is proposed for the constitutive description of microcracking processesin brittle rock under a general loading path. Experimental data and micromechanicalmodels are reviewed to quantify the effect of microcracking on the material stiffness and themechanisms of microcrack formation in brittle rocks under compression are discussed. Thesliding crack concept is adopted as the micromechanical basis of the anisotropic damage model.Undamaged material is repre...
ABSTRACTContinuum and finite element formulations ofthe static and dynamic initial-boundaryvalueevolution (elastoplastic) problems are considered in terms of both the classicaland internal variable frameworks. The latter framework is employed to developalgorithms in the form of convex mathematical programming and Newton-Raphsonschemes. This latter scheme is shown to be linked to the former in the sense that itexpresses the conditions under which the convex non-linear function can be min...
ABSTRACTMATHEMATICAL SIMULATION OF DYNAMIC BEHAVIOUROF SECONDARY SETTLING TANKSThe main objective of this thesis was to briiig the theoretical and practical aspects ofsecondary settling tank developments closer together. This was achieved firstly, byevaluating and developing empirical relationships from which the flux theory constantsmay be derived from simpler sludge settleability measures; and secondly, bydeveloping a computer model for the simulation of dynamic behaviour of full scal...
ABSTRACTSeveral theories of creep and creep rupture are reviewed.Specific attention is devoted to the brittle damage theoryproposed by Kachanov. Creep, damage and life predictions forrectangular or circular cross section beams under bendingand tensile loads are presented. Comparison with data for aNi Superalloy showed life predictions could be 30X in excessof experimental values. This beam model also revealed thatit is imperative that no bending moments be inadvertentlyapplied during ...
ABSTRACTCoal is one of the most importa~t energy resources in South Africa.It covers 80% of the country's energy needs and provides valuableforeign exchange and employment. The purpose of this thesis is toprovide an analytical framework for the examination of the demandfor coal for the generation of electricity where more than 50%of the coal produced in the country is consumed.More specifically, the aim of the thesis is to identify the factorsinfluencing the demand for steam-coal, dise...
ABSTRACTThe requirements of a standard 3-phase InductionMotor driven by a Voltage Source Inverter
Abstract Selection of optimum machining parameters is an essential factor in process planning for efficient metal cutting operations. In this study, an artificial neural network- based tool wear predictive model and a genetic algorithm-based optimization model were developed to determine the optimum cutting parameters for turning NST 37.2 steel with uncoated carbide cutting inserts. Multi-layer, feed-forare, back -propagation network was used in predictive model, while maximum metal ...
ABSTRACTCrop production is influenced by on-site soil moisture availability and application of waterconservation methods for dry areas. This research explored the interactive effects of spateirrigation as an application method and the soil moisture conservation techniques. The objectiveof this research was to analyze the effectiveness of soil moisture conservation techniques and itscorrelation to water productivity for sorghum production under spate irrigation. The soil waterholding capa...
ABSTRACT The e-beam stimulated reaction, CdCI2(s) ---> Cd (s) + CI(g), has been studied in casmium chloride thin films between 303 and 483 K using 2-keV electrons. The dose required to make 90-nm-deep holes at 483 K is 3x10-3 C cm -2. Extrapolated dosing levels of 6x10-5 C cm -2 are expected. The use of CdCI2 as a positive-type electron resist in a new scheme is proposed. A working model, useful for considering the e-beam stimulated decomposition energetics and mechanism is briefly ...
Abstract Several procedures have been proposed to overcome various challenges of product-content analysis after manufacturing and downstream automatad recycling pmcesws. These procedures have been restricted by factors such as the inabiiity to determine exactly the physical state of the hidden pm of End-of-Life products. This inhibition among others has rresldted into an explosion of solutions by researchers. This paper presents the initial investigations in the development of imagi...
ABSTRACT Tool wear measurement is of great concern in machining industry, as it affects the surface qualities, dimensional accuracy and production costs of the machined components. The orthodox methods of measuring tool wear are time consuming and limited in accuracy and application. In this study, machine vision system based on digital image processing was developed for measurement of tool wear. The basic components of the system are: a charge coupled device (CCD) camera, PC, Micro...
ABSTRACTEngineering structures subjected to dynamic loading exhibit vibration motions.These vibrations induce accelerations on the structures and their componentparts. The accelerations in turn generate inertia forces that propagate thevibrations and significantly affect the response of the structures and theircomponents parts to external loading. This cyclic cause and effect situation resultin randomly oriented and time-dependent displacements as the basic responsecriteria of structure...