Dissertation (PhD)--University of Stellenbosch, 1995. / Bibliography. Also available via the Internet.

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by Philip N. Froelich. / Includes bibliographical references (leaves 131-133).

Thesis (M.B.A.)--University of Hong Kong, 1985.

Thesis (M. Soc. Sc.)--University of Hong Kong, 1989.

The boron isotopic ratios of three contaminated ground water samples and of leachate from four fly ash samples are shown to be significantly different than the isotopic ratio of naturally occurring boron in a selected ground water. Analysis is performed using thermal ionization mass spectrometry with a precision of less than 1 per mil. Inductively coupled plasma mass spectrometry is shown to be ineffective for this application. Boron is isolated from solution and concentrated using Amberlite IRA-743 resin with no isotopic fractionation observed. Boron desorption from fly ash is shown to be rapid. Boron isotopic analysis is shown to be a superior method to boron concentration analysis for identifying leachate in a ground water, (1) at the outer limits of a leachate plume, and, (2) when the difference between the boron concentration of the leachate and background water is small. The degree of contamination can be determined if both end members are known.

No description available.

Modern transmission systems are becoming heavily loaded. In addressing this issue Eskom has been installing series capacitors in their power transmission grids for the purposes of ensuring improved system stability, increased transmittable power, reduced transmission losses, enhanced voltage control and more flexible power flow control. Environmental concerns are also addressed at a fraction of the cost when compared to the alternative. However, with the utilization of series capacitors and their over-voltage protection devices typically the Metal Oxide Varistors and Spark Gaps when installed on transmission lines, several problems are created for the distance protection relays. This is because series capacitors when used on transmission lines can have serious effects on the performance of distance relay protection. This is because of the change of impedance seen by the distance relay since the electrical impedance measured by the relay is no longer a unique correspondence of the physical distance from the relay location to the point of fault when the protection of the series capacitors comes into play. The research results will show that, because of subsynchronous oscillations and voltage inversion phenomena as a result of series compensation, can cause distance protection’s zone 1 directional elements to operate incorrectly, more specific to internal faults which may appear as external faults and external faults which may appear as internal faults. The research will be investigating some of the challenges that are encountered by the distance protection relays when protecting a transmission line incorporating series capacitors. In answering the research question: “What are the issues associated with the utilization of series capacitors on the Eskom Transmission grid to the performance of distance protection?” the Digsilent PowerFactory software simulator package will be utilized to achieve the desired objectives. Other research projects have looked into the research question at hand utilizing the physical REL 531 relays and a real time model of the Eskom Hydra South Network, a system that supplies power to the Western Cape. In this research the author will be looking at the ability of Digsilent and its REL 531 Models to repeat and confirm the same conclusions, before considering possible alternative solutions. The Muldersvlei-Bacchus and Bacchus-Droerivier lines forming part of the Eskom Hydra South Network were selected as the area of focus. The decision to select these two particular mentioned lines as the area of focus was because the studies will be able to cover impact of external series capacitors to both the performance of the relays on lines that are series compensated and those that are not. The performance of the relays will involve analyzing the impact of series capacitors on the relays for faults before and after series capacitors. The research will also be investigating the possibility of utilizing the current supervised zone 1 configuration, which has recently been introduced on some Eskom distance protection relays as a solution, to overcome the impact of series capacitors on the performance of the distance protection relays. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

No description available.

The simple gas turbine engine Operates on the basic Joule-Brayton cycle and it is notorious for its poor thermal efficiency. Several modifications have been made to the simple cycle in order to increase its thermal efficiency but, within the thermal and mechanical stress constrains, the efficiency still ranges between 28 and 35%. However, higher values of energy utilisation efficiency have been claimed in recent years by using low grade heat from the engine exhaust either for district heating or for raising low pressure steam for chemical processes. Both applications are not very attractive in hot countries. The concept of using the low grade thermal energy from the gas turbine exhaust to raise steam in order to drive a steam turbine and generate additional electricity, i. e. the combined power and power or CPP plant would be more attractive in hot countries than the CHP plant. It was hypothesized that the operational parameters, hence the performance of the CPP plant, would depend on the allowable gas turbine entry temperature. Hence, the exhaust gas temperature could not be decided arbitrarily. This thesis deals with the performance of the gas turbine engine operating as a part of the combined power and power plant. In a CPP plant, the gas turbine does not only produce power but also the thermal energy that is required to operate the steam turbine plant at achievable thermal efficiency. The combined gas turbine-steam turbine cycles are thermodynamically analysed. A parametric study for different configurations of the combined gas-steam cycles has been carried out to show the influence of the main parameters on the CPP cycle performance. The parametric study was carried out using realistic values in view of the known constraints and taking into account any feasible future developments. The results of the parametric study show that the maximum CPP cycle efficiency would be at a point for which the gas turbine cycle would have neither its maximum efficiency nor its maximum specific work output. It has been shown that supplementary heating or gas turbine reheating would decrease the CPP cycle efficiency; hence, it could only be justified at low gas turbine inlet temperatures. Also it has been shown that although gas turbine intercooling would enhance the performance of the gas turbine cycle, it would have only a slight effect on the CPP cycle performance. A graphical method for studying operational compatibility, i.e. matching, between gas turbine components has been developed for a steady state or equilibrium operation. The author would like to submit that the graphical method offers a novel and easy to understand approach to the complex problem of component matching. It has been shown that matching conditions between the compressor and the turbine could be satisfied by superimposing the turbine performance characteristics on the compressor performance characteristics providing the axes of both were normalised. This technique can serve as a valuable tool to determine the operating range and the engine running line. Furthermore, it would decide whether the gas turbine engine was operating in a region of adequate compressor and turbine efficiencies. A computer program capable of simulating the steady state off-design conditions of the gas turbine engine as part of the CPP plant has been developed. The program was written in Visual Basic. Also, another program was developed to simulate the steady state off-design operation of the steam turbine power plant. A combination of both programs was used to simulate the combined power plant. Finally, it could be claimed that the computer simulation of the CPP plant makes significant contribution to the design of thermal power plants as it would help in investigating the effects of the performance characteristics of the components on the performance of complete engines at the design and off-design conditions. This investigation of the CPP plant performance can be carried out at the design and engineering stages and thus help to reduce the cost of manufacturing and testing the expensive prototype engines.

Thesis (M.Sc.) -- University of Adelaide, Department of Zoology, 1979.