Thesis--M. Phil., University of Hong Kong.

The notion that different ownership types may create a divergence in outcome naturally led to an appraisal of the performance of the Nigerian electricity industry and to the investigation of the influence of ownership structures upon performance as a way of explaining the disappointing state of electricity production in Nigeria. This research is primarily concerned with the factors that influence performance, the estimation of efficiency and productivity of the National Electric Power Authority (NEP A) - the integrated public utility responsible for electricity in Nigeria. The first part of the thesis is concerned with developing a conceptual framework for the performance assessment of the public enterprise focusing on transformation of inputs to outputs. The various principles and methods of measuring efficiency are considered. And consequently, an appropriate methodology for the appraisal of NEP A's performance and an examination of how NEP A's production efficiency can be improved is outlined. This provides the basis for the empirical and data analysis, which forms the second part of the thesis. The empirical analyses use the two popular approaches for measuring efficiency. These are the non-parametric (data envelopment analysis and Malmquist productivity index approach) and parametric (stochastic frontier method) approaches. The third part of the thesis investigates the issues pertaining to the reform of the electricity industry from an ownership perspective. Attention is given to privatisation and regulation. Given the state of the industry in Nigeria, and the fact that reform is imminent, a modelling approach is used to examine the impact on performance of changes in ownership type and the organisational structure of the electricity industry. The thesis concludes with a summary of the research findings and draws policy implications of the study for the reform of the electricity industry in Nigeria.

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published_or_final_version / Civil Engineering / Master / Master of Philosophy

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Floods are considered to be among of the deadliest, costliest and most common natural disasters. Rapid onset, catastrophic floods inundate the shore quickly and manifest as deep water with high velocities. The deep water and high velocities caused by these floods inflict great pressures and forces on the built and natural environments and pose a threat to human safety. Recent disasters such as Hurricane Katrina in the Southern United States and the Sumatra tsunami in the Indian Ocean have revealed that communities at risk require improved preparations for these types of dangerous events. Current building codes, design practices and disaster planning methods account for potential earthquake and wind loads on simple wood frame buildings typical of North American residential construction, however, flood impacts have not been considered in the same level of depth. The objectives of this research are to develop a theoretical model that describes flood impacts on wood frame residential buildings and relates building response to physical flood properties such as depth and velocity. This thesis provides a brief synopsis of previous approaches used to describe building response to flooding. An overview of the major loads caused by rapid onset flooding, along with a description of the structural system utilized in wood design to resist these forces is provided. The failure mechanisms considered and the model logic are described and applied to assess the response of a typical Canadian wood frame home to flood conditions that might be experienced in a rapid onset flood event like a tsunami. Building response results are discussed along with recommendations for future analysis and applications.

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High-resolution particle image velocimetry (PIV) is employed to resolve the velocity fields within a Mach 4.9 mechanically distorted turbulent boundary layer (Reθ ≈ 40,000). The goal of this study is to directly observe the mechanisms responsible for the modified turbulent stresses present in mechanically distorted boundary layers. This is achieved by measuring the effects of the mechanical distortions upon the distribution, population, size, orientation, and energy content of the turbulent structures, and how the perturbed state of these structures is manifested within the ensemble-averaged turbulent stresses. The two mechanical distortions under investigation are 1) streamline curvature-induced favorable pressure gradients (Ip = {-0.08; -0.49}), and 2) periodic arrays of diamond roughness elements (k/δ ≈ 0.07). A smooth-wall, flat-plate boundary layer is also included to establish the unperturbed state of the turbulent structures. The response of the mean turbulence statistics is investigated through ensemble-averaged profiles of Reynolds stresses, indicating the respective influences of pressure gradient effects and surface roughness upon the turbulent statistics. The distortion and reorientation of the large-scale coherent motions is quantified through the determination of the integral length scale and local structure angle from two-point correlations. Detection of individual vortices through the swirling strength criterion λci allows the population distribution of the turbulent eddies to be examined, along with the conditionally averaged hairpin structure. The baseline and rough-wall stresses showed good agreement when scaled by the smooth-wall friction velocity. Two-point correlations indicate that the reorientation of the large-scale [i.e. O(δ)] coherent structures, coupled with the modified wall-normal fluctuations, is primarily responsible for the modification of the rough-wall Reynolds stresses. The reduced Reynolds stresses observed in the favorable pressure gradients is partially due to the attenuation of the local flowfield around the near-wall hairpin structures, mitigating the mechanism for “producing” turbulence. The rotational rate of the hairpin vortices, measured through the mean prograde swirling strength, was reduced for the favorable pressure gradient models.

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No description available.