Of the 36 diurnal raptor species in North America, 31 (~86%) are either complete or partial migrants. During fall and spring, raptors use "leading lines" or topographic features, such as mountain ranges, rivers, and coastlines that help guide them during their migration, and sometimes are redirected by diversion lines, or barriers that they are hesitant to cross (e.g., large bodies of water). Our objective was to assess the use of mountain ranges and rivers in central and southeastern Arizona by migrating raptors and to determine physical and ecological factors that are important to raptor migration across the United States. We counted migrating raptors in the spring and fall for two years at ten paired count stations in central and southeastern Arizona. Arizona counts were incorporated with counts from across the United States to determine physical and ecological features that influence migration rates. Raptor counts for central and southeastern Arizona averaged 2.0 raptors/hour, and were similar to what is observed at most other counting stations in the Central and Pacific Flyways. Stepwise regression models for the United States indicated counts were negatively related to distance from a diversion barrier and positively related to continuity of elevation. Understanding the factors that influence migrating raptors will inform decisions about environmental modifications and their potential influence on raptor populations. The following appendices are written and formatted to be submitted to journals. Although part of a thesis, they are written in plural to reflect the necessary authorship for journal submission. The first appendix, titled "Assessment of raptor migration corridors in central and southeastern Arizona", will be submitted to the Southwestern Naturalist. The second appendix, title "Assessment of raptor migration corridors in the United States", will be submitted to the Journal of Raptor Research.

Numerical modeling of electromagnetic fields is becoming an important topic in such diverse areas as microwave and RF engineering, antenna design, bio-electromagnetics, and electromagnetic compatibility and interference (EMC/EMI). Among several techniques, time-domain schemes are of particular interest, due to their high flexibility and ease of implementation. This thesis is focused on the Transmission Line Matrix (TLM) method, based on a space and time discrete formulation of Maxwell's equations. The objective of this thesis is to develop, implement and test a number of techniques aimed to the enhancement of the accuracy of the method without increasing the computational load. The link between the electromagnetic theory and the TLM updating equations is first investigated, creating a solid background for the implementation of hybrid schemes characterized by better accuracy. The problem of coarseness error is in particular addressed. Two methods are proposed and analyzed. In the first approach the knowledge of the relationship between field equations and TLM equations is exploited to incorporate the static field behavior in the vicinity of singularities into the three-dimensional TLM mesh. Secondly, the field distribution around a corner is represented in terms of an equivalent circuit derived from a quasi-static approximation of the Green's functions for an infinite conductive wedge. As a result, relatively coarse TLM meshes, in combination with hybrid schemes, can be used to obtain highly accurate results, within the dispersion error margin, across a wide frequency range. By taking advantage of these techniques it is possible to incorporate more information of the structure under study into the TLM solution, thus creating an accurate and efficient CAD tool. / Graduate

The gas kinetic temperature (T-K) of various interstellar environments is often inferred from observations that can deduce level populations of atoms, ions, or molecules using spectral line observations; H I 21 cm is perhaps the most widely used, and has a long history. Usually the H I 21 cm line is assumed to be in thermal equilibrium. and the populations are given by the Boltzmann distribution. A variety of processes, many involving Ly alpha, can affect the 21 cm line. Here we show how this is treated in the spectral simulation code Cloudy, and present numerical simulations of environments where this temperature indicator is used, with a detailed treatment of the physical processes that determine level populations within H-0. We discuss situations where this temperature indicator traces TK, cases where it fails, as well as the effects of Lya pumping on the 21 cm spin temperature. We also show that the Lya excitation temperature rarely traces the gas kinetic temperature.

M.A. / Emergence of informal settlements on vacant lands in urban areas results from intuition and political decisions, and sometimes cultural background. So any available vacant land is used for settlement development and dwelling sites. An informal settlement named after Elias Motsoaledi, a political activist of the African National Congress (ANC), was developed in the south-western part of the city of Johannesburg in 1993. Motsoaledi informal settlement was established on a vacant piece of land where there are overhead power lines. Motsoaledi community members that have their dwellings in close proximity and even underneath overhead power lines are exposed to an environment that is surrounded by electrical magnetic fields (EMFs). There are no reported cases of biological and health consequences that have been caused by EMFs as yet. This study aims to focus on the health aspect of persons who have their dwelling in the vicinity of the overhead power lines in Motsoaledi. The high levels of EMFs around Motsoaledi is further excelerated by the zinc structures that are conductive to electricity and may result in electrocution for dwellers that are in the direct vicinity of overhead power lines. Longer exposure to athermal conditions may result in bio-effects and lead to changes in human health. Furthermore, effects from EMFs are possible electrocution, often causing immediate death of persons and destruction of property. Due to the lack of proper planning of informal settlements, such settlements become vulnerable to potential environmental hazards such as the destruction of structures. This study hopes to identify the plight of a particular informal settlement, namely, Motsoaledi as an isolated case to reflect dire conditions of most of the informal settlements around the country.

M.Ing. (Electrical and Electronic Engineering) / This research project sets out to investigate passive L-C coupling circuits as an alternative to transformer-capacitor couplers, with the prime intention to reduce the cost of coupling in power-line communications, hence the title “Compact, Economical Coupling Circuits for Low-Voltage Power-line Communications”. This chapter first presents a short introduction to Power-Line Communications, and then briefly reviews relevant topics surrounding this project. Also discussed, in general, are the standards and regulations for power-line communications i.e. the CENELEC EN50065.1 Standard and the IEEE 1901.2 Standard. This information intends to give the reader guidelines and relevant protocols and/or rules when designing and building communication devices for PLC. This information will also help us in our designs and experimental set-ups as we proceed with this project. The reader will also be introduced to the concept of filtering and impedance matching in communication systems. Emphasis will be laid on the required output signal frequency profile of a coupling band-pass filter. The chapter will define filtering in terms of communications and also discuss the more significant and important parameters in filter circuits. The last section of this chapter will touch on impedance matching and the concept of maximum power transfer, so as to attain maximum signal transfer to the receiver-end.

M.Ing. / Please refer to full text to view abstract

Fault location for series compensated lines cannot be addressed sufficiently by conventional solutions developed for traditional uncompensated lines. Line-parameters vary with loading and weather conditions, and therefore settings used for fault location are often erroneous. Line-parameter free solutions for fault location are therefore more reliable and accurate than conventional solutions that require such settings. Hence, line-parameter free fault location algorithms for single-circuit and double-circuit series compensated transmission lines were developed during the research project. Single-circuit lines and double-circuit lines both present unique challenges for fault location. They also vary in the number of available measurements that can be used to arrive at a solution for distance to fault. A third algorithm is presented that allows the extension of existing short line algorithms to the case of long lines. This is done by providing a method for incorporating the line shunt admittance into these existing algorithms. The aforementioned three bodies of research work, form the focus of this thesis. The algorithms are derived using two-terminal synchronised current and voltage sampled measurements. Of these, the algorithms for series compensated lines are also derived for asynchronous measurements. Phasors are obtained by carrying out a Fast Fourier Transform, and then appropriate calculations are performed for distance to fault. The thesis covers the mathematical derivations of the algorithms, involving the algebraic reduction of non-linear equations in numerous variables into a single expression for distance to fault. The results for a variety of simulation tests are shown subsequently and discussed. Various fault resistances, fault types, degrees of series compensation, line lengths, fault levels are considered in the tests carried out. The algorithms are largely found to be highly accurate under these various conditions, and where the algorithms perform to a lesser degree of accuracy are highlighted and discussed. Lastly, a detailed chapter discussing future work is also included in the thesis.

The use of electrical networks for telecommunications has a long history. It has been known since the beginning of the twentieth century [Ahola03]. The idea of using electrical networks for broadband communications arose in the 1990s [Hrasnica et al 04]. Recent and growing research interest has indicated that PowerLine Communications (PLC) is the threshold for achieving broadband delivery particularly in very dispersed and low teledensity areas. Currently, there are numerous PLC trials and commercial deployments underway inside and outside South Africa. Nevertheless, these PLC deployments are very isolated, done without clear methodology and performance remains bound to the physical layout of the electrical network. Because of that high bandwidth broadband PLC systems are prone to poor performance and this in turn limits the acceptance and deployment of this emerging alternative broadband technology. Though, PLC technical challenges are being addressed, there has been little analysis and research work that is focused on the “Development of Methodologies for Deploying and Implementing Local & Medium Area Broadband Power Line in Residential and Office Electric Grids” that would lead to broadband PLC being adopted and be of greater use to non-broadband communities of South Africa. PLC is a term describing several different systems using electrical grid distribution wires for simultaneous distribution of data by superimposing an analog signal [Hrasnica et al 04]. The research proposed and presented broadband PLC methodologies for typical medium voltage and local voltage PLC networks. These methodologieswere implemented and experimented with in configurations which closely mirrored residential and office settings through laboratory and multibuilding experiments using commercial 2nd Generation Mitsubishi Electric PLC technology. Research results presented not only serve to provide insight into broadband PLC but also how it handled broadband applications (communications), competed and compared with other technologies such as Ethernet LAN. In combination with networking communication theories, the research explored and analyzed the extent of PLC in providing broadband communication to residential and office electric grids at the University Fort Hare, Computer Science Department.

In this thesis, the finite element method (FEM) is applied to the calculation of frequency-dependent series impedances and shunt capacitances of underground power cables. The principal equations describing the quasi-magnetic fields and static electric fields are solved with FEM based on the Galerkin technique. The Js method and the loss-energy method are derived to calculate the impedances of a multiconductor system from its field solution, and the energy method and the surface charge method are derived to calculate the capacitances. With a single-core (SC) coaxial cable, the suitability of quadratic isoparametric elements and high-order simplex elements are studied, and a suitable division scheme is suggested for the auto-mesh program. The conventional FEM with a field truncation boundary is applied to the impedance calculation of buried SC cables. Suitable locations for the field truncation boundary and division schemes in the earth are studied. The results show that rb ≥ 12[symbol omitted] is required to obtain accurate impedances of shallowly buried cables with the conventional FEM. This requires a large solution region in the earth at low frequencies. A new technique based on the perturbation concept is proposed to reduce the solution region in the earth. Comparisons between the results from the conventional FEM and from the proposed technique with a significantly reduced solution region in the earth show good agreement. In the case studies, the FEM is applied to the parameter calculation of multiphase SC cables, PT cables, sector-shaped cables, and stranded conductors. The numerical results are compared with those from analytical formulas. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Geomagnetically Induced Currents (GIC's) in B. C. Hydro's 500 kV transmission system have in the past been responsible for the generation of harmonics of 60 Hz, system voltage drops, and misoperation of relay units. Characterization of the associated magnetic storms' spatial scales would further the understanding of GIC generation in the area, and allow advanced warning of potential problems in future power transmission projects. Data collected in 1984 at four substations were analysed to determine lateral variations in geomagnetically induced earth surface electric fields. Inversion techniques were employed to find a variety of solutions that would reproduce the data. Results suggested that the magnetic storms were larger than the area monitored, and that resultant electric fields seen by a large portion of the transmission grid were uniform. Departures from this uniformity in other portions of the electric field models were felt either to be due to earth induction effects, or in some cases, to be artifacts of the data analysis techniques. An experiment designed to determine the controlling factors behind GIC's is outlined. Considerable effort would be required to explicitly determine all electric fields affecting the transmission system / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate