ABSTRACT We have been using polycrystalline thin films of anhydrous cadmium chloride (CdCI2) as an electron beam positive resist for the fabrication of features in SO2- coated silicon wafers The kinetics and mechanism of the electron-beam-induced decomposition of CdCI, which is the resist reaction, have been studied in details this work required that we know the thickness and density of the film. In the ordinary way of things, film thickness and density determination is a routine matter, but ...
Abstract Using communication signals for radar applications has been a major area of research in radar engineering. In the recent years, due to the widely available wireless signals, a new area of research called commensal radars has emerged. Commensal radars use available wireless Radio Frequency (RF) signals to detect and track targets of interest. This is achieved by placing two antennas, one towards the transmitting base station and the other towards the surveillance area. The signal rece...
ABSTRACT The main focus of this study is to evaluate whether load following operation can be performed using the existing South African nuclear power plant. Of which, knowing that will assist in determining whether the addition of load following capabilities on the planned nuclear fleet is justifiable or not. In this report the relevance of Koeberg Nuclear Power Plant to adapt to the demand is examined and the effects on plant operation simulated. The report analyses the operation of the exi...
Abstract The advent of CubeSats has provided a platform for relatively low-budget programmes to realise space missions. In South Africa, Stellenbosch University and the Cape Peninsula University of Technology have impressive space programmes and have been involved in numerous successful satellite launches. A number of CubeSat projects are currently in progress and commercial-grade Attitude Determination and Control Systems (ADCS), and communications modules, are being developed by the respect...
Abstract Active object recognition provides a mechanism for selecting informative viewpoints to complete recognition tasks as quickly and accurately as possible. One can manipulate the position of the camera or the object of interest to obtain more useful information. This approach can improve the computational efficiency of the recognition task by only processing viewpoints selected based on the amount of relevant information they contain. Active object recognition methods are based around h...
Abstract The Microsoft Kinect sensor is a low cost RGB-D sensor. In this dissertation, its calibration is fully investigated and then these parameters are compared to the parameters given by Microsoft and OpenNI. The parameters found were found to be di_erent to those given by Microsoft and OpenNI therefore, every Kinect should be fully calibrated. The transformation from the raw data to a point cloud is also investigated. Then, the Hough transform is presented in its 2-dimensional form. The ...
Abstract A 3-phase Z-source inverter has been researched, designed, simulated, built and tested. The purpose of the inverter is to deliver 3-phase 400 VAC from a DC supply that can vary over a range of 20 to 70 Vdc. This is done with a Zsource inverter topology which is a single conversion method with no additional DC to DC boost converter. A novel DSP control algorithm allows the inverter to achieve the following: · Run Space Vector Pulse Width Modulation (SV-PWM) for maximum DC bus voltag...
Abstract The characterization and classification of liquids through instrumentation is essential in many industries. As such, measuring the characteristics of liquids is not just useful as a control parameter within an industrial process; such measurements can also be used to classify the liquid. Such a sensor is especially practical if it can be connected in-line with the liquid to be measured, thus minimally influencing flow. A piezoceramic tube was studied in an attempt to produce a senso...
Abstract All real systems experience input saturation. Since the first proportional controller was implemented, systems have been susceptible to saturation. The introduction of the proportional-integral (PI) controller complicates matters further, since it reduces the steady state error to zero for zero-order setpoint tracking. This encompasses a fair portion of the implemented control strategies in the world. It is clear that saturation, by limiting the input state for the process, limits t...
Abstract Fractal image compression is a comparatively new technique which has gained considerable attention in the popular technical press, and inore recently in the research literature. The most significant advantages claimed are high reconstruction quality at low coding rates, rapid decoding, and "resolution independence" in the sense that an encoded image may be decoded at a higher resolution than the original. While many of the claims published in the popular technical press are cle...
Abstract Spread Spectrum systems are found in many flavours, used in many applications and have existed since the early days of radio communications. The properties of spread spectrum do however place restrictions on the design, and often make the implementation expensive and complex. When using spread spectrum to provide a basic communications infrastructure, many factors need to be considered. These indude supplying the appropriate technology at the right cost. To achieve this a trade-off ...
Abstract This thesis deals with the damping of electromechanical oscillations using Power System Stabilizers (PSS). The thesis focuses on three problems associated with the damping of these oscillations, namely the determination of the optimal locations of the PSS, the determination 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 two methods are based on Total Modified Coupling Factors (T...
ABSTRACT The requirements of a standard 3-phase Induction Motor driven by a Voltage Source Inverter studied. A ful I 3-phase Variable Speed Drive and its controller have been designed, constructed and tested. Gate Turn-Off Thyristors used as the main switching elements in the Inverter stage of the Drive. The drive requirements of GTO's are studied in detai 1.
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 discussed.
ABSTRACT In this thesis, a current source inverter fed squirrel cage induction motor drive at constant air gap flux is presented. The drive scheme is conceived to take advantage of the short circuit withstand capability of the current source inverter and the ruggedness (even under harsh conditions) of the squirrel cage induction motor. The variable inverter input dc link current is derivable from either a controlled ac to dc converter or a controlled dc to dc converter. The constant motor air...