O objetivo deste trabalho é demonstrar por que a cogeração não se desenvolve no Brasil, mesmo apresentando-se como alternativa para produção de eletricidade. Entretanto existem vários estímulos por parte do Estado para a implantação de grandes termoelétricas no país. Será apresentada a análise dos processos de cogeração, envolvendo: as alternativas tecnológicas, a viabilidade econômica, e as questões ambientais, chegando-se a um quadro indicando a sensibilidade aos diversos parâmetros econômicos que fazem parte dos projetos de cogeração. Serão mostrados cenários com a visão de futuro, indicando diferentes opções que permitam o crescimento do mercado de energia no Brasil, de uma forma mais segura. No momento em que o Brasil passa por profundas mudanças no setor energético, incluindo a necessidade da expansão do parque gerador e considerando que parte importante dessa expansão será através de grandes centrais termoelétricas, torna-se importante apresentar uma alternativa de produção de eletricidade, no Brasil ainda pouco explorada, que é a cogeração. Este trabalho irá mostrar que com maior incentivo aos projetos de cogeração, através de uma política energética nacional adequada, se pode produzir parcela importante da energia elétrica para o atendimento das necessidades crescentes da sociedade brasileira, com menor impacto ambiental e econômico, refletindo em menor custo final da energia produzida. / The aim of this paper is to show why the CHP does not develop in Brazil, even presenting itself as an alternative to producing electricity. However there are several incentives from the state for the deployment of large power plants in the country. You will see the analysis of cogeneration processes, involving: the technological alternatives, the economic viability and environmental issues, coming to a table showing the sensitivity to various economic parameters that are part of cogeneration projects. Scenarios are shown with the vision of the future, indicating different options that allow for growth of the energy market in Brazil, a more secure way. At the moment Brazil is going through profound changes in the energy sector, including the need for expansion of generating facilities and considering that an important part of this expansion will be through large power plants, it is important to present an alternative electricity production in Brazil still little explored, which is cogeneration. This paper will show that with greater encouragement to cogeneration projects through an adequate national energy policy, it can produce substantial amount of electricity to meet the growing needs of Brazilian society, with less environmental impact and economic development, reflecting a lesser cost final energy produced.

An Electromagnetic Pulse (EMP) resulting from, for example, the detonation of a nuclear weapon is characterised by a wave of electromagnetic activity able to couple with power lines and electro-sensitive equipment with the potential of rendering an establishment or on a greater scale, a whole city impotent. Protection against such occurrences is of paramount importance. It is now accepted that an important consideration when devising protective schemes against such phenomena is an accurate understanding of the effects on propagating waveforms such as those coupled to wires, when electrical breakdown of the dielectric material surrounding such wires occurs, otherwise known as electrical discharge. Such issues can occur around the affected wires if the electric fields generated exceed the dielectric strength of the surrounding medium, typically air or soil. Under these circumstances, the signature of the coupled waveform is known to change in characteristic ways. The form and degree of distortion needs to be understood if the harmful effects are to be prevented by protection systems put in place. The purpose of this thesis is to first describe the mechanisms that lead to the development of the Nuclear–Electromagnetic Pulse (NEMP) and the mechanisms of the discharge that can result once such pulses have coupled to a wire. Next, some of the previous corona-modelling approaches are discussed. Many of the modelling approaches have been applied to 1-D transmission-line simulations. When 3-D simulations have been performed, the Finite-Difference (Time Domain) or FD-TD approach seems to be the preferred method. At the time of writing, no 3-D Transmission Line simulations of discharge phenomena around wires were available. Hence, here, the 3-D Transmission Line Modelling Method (TLM) is described with a view to modelling such behaviour. In particular, the Embedded-Wire-Node (EWN) is used to model the discharge development around the wire. This is a fine-wire technique used to reduce computational fatigue. The node can be adapted to accept changes related to electrical discharge allowing for a real-time, self-consistent recreation of such effects. The 3-D TLM approach proves to be a decent candidate to the modelling of such behaviour. Both advantages and disadvantages of this method are discussed.

Combining stainless steel with polyester fibres adds an attractive conductive behaviour to the yarn. Once knitted in such a manner, fabrics develop sensing properties that make them suitable for wearable applications as a consequence of the variation of their conductivity when subject to structural deformations. The use of such textiles as accurate strain/motion sensors can be considered the new frontier in wearable sensor applications, in opposition to their use as simple strain/motion detectors as mainly done until now. This thesis aims to characterise the electrical properties of knitted conductive textiles made of 20% stainless steel and 80% polyester fibres in the context of their application as fabric strain sensors. However, the use of conductive textiles as sensors is challenging and requires the combined study of their electrical and mechanical behaviours. In the first part of this thesis, the fabric resistance variation is analysed with a purposely built measurement system during a considerable number of stretch-recovery cycles performed by an Instron tensile machine. From the resulting electrical characterisation, it is possible to select the best knit pattern candidates for the second part of the study, which regards their integration into a supporting garment and further investigation of their electrical and mechanical properties in view of their application as wearable motion sensors. Two acquisition systems capture both free and constrained motions of a participant's knee and the electrical resistance variation due to combined deformation of samples and supporting leggings. In both parts of this thesis, a detailed analysis in terms of linearity, stability, sensitivity and hysteresis confirms that the overall sensing performance progressively decreases during extended use as a consequence of the short-term irreversible fabric deformation and does not significantly recover after short rest periods. For the development and use of high performance fabric-based strain sensors, it is therefore evident the importance of the long-term maintaining of a reversible stretch-recovery behaviour not only of the sensing fabrics but also of the supporting garments they are integrated in.

This thesis investigates the electron-phonon interactions in fabricated Semiconductor Devices i.e. Schottky Diodes, Quantum Well (QW) embedded p-i-n photodiodes, two dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) structures all on (311) GaAs substrates. Fast electrical measurements were performed on Schottky diodes fabricated on the (311B) GaAs surface. Optical excitation generates a compressive strain pulse in an Al film which is at the opposite side of the GaAs substrate. Two coherent acoustic phonon modes were generated in the (311B) GaAs substrate: quasi-longitudinal phonons (QLA) and quasi-transverse phonons (QTA). These two modes were detected successfully using the Schottky diode, the dependence of QLA and QTA signals on different applied bias, pump powers and temperatures were investigated. The dependence of signals on bias reveals that the temporal position of the signals for QLA and QTA moves slightly earlier times with increasing reverse bias because the width of the depletion layer increases with increasing negative bias. The first peak arrival time for QLA phonons in the measured signal moves to earlier times with increasing pump power. This was caused by the nonlinear acoustic properties of the GaAs substrate. Conversely, QTA phonons arrival time was not dependent on pump power which indicates the elastic nonlinear effects are not crucial for QTA signals. Investigation of the temperature dependence reveals that the arrival time changes to later times with increasing temperature because of the decreasing sound velocity with increasing temperature. The polarity of the experimental signals was compared to the simulated signals of electron-phonon coupling interactions concludes the predominant role of piezoelectric phonon-electric transformation mechanism over deformation potential. Detailed theoretical calculations show the dominance of the piezoelectric mechanism up to frequencies of 70GHz and 250GHz for longitudinal and transverse phonons respectively. Low dimensional structures i.e. Quantum well embedded p-i-n photodiode detector (QW-p-i-n), two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG), fabricated on the (311) GaAs surface, were also investigated as detectors for longitudinal and transverse acoustic signals. The first experimental evidence of high frequency tail in transverse signal is observed using GaAs based QW-p-i-n detector. The longitudinal signal confirms the existence of the GHz oscillations, with the most significant occurring 170 GHz, while in transverse acoustic signal we observed a high frequency tail from 300 ps to 800 ps. Fast Fourier transforms (FFT) analysis of this tail shows the existence of high frequency phonons up to 200 GHz. Photocurrent pump-probe measurements was also performed with three different Al film thicknesses (20nm, 30nm and 100nm). Experiments performed with 20nm film thickness clearly shows a weak signal at 250 GHz in the amplitude spectrum which is not observed for 30 nm and 100 nm aluminium films. This observation indicates that the thinner aluminium films can generate higher frequency phonons. The longitudinal and transverse signals were also detected by the 2DHG; for QLA predominantly the peak is negative while for QTA it is positive in contrast to the 2DEG experiments due to the reason that in 2DEG experiments the origin of the signal is due to the decrease in carrier density but for 2DHG the signal is due to the increase in carrier density. This thesis studies the interaction of subterahertz acoustic phonons with charge carriers with the aim of developing high speed acoustoelectric detectors for subterahertz compressional and shear acoustic waves, and it has been shown that the Schottky diodes are successful in this application.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy / The work presented in this thesis extends and contributes to research in the field of lightning injury mechanisms. Six mechanisms have been described in the literature about lightning injury. This thesis takes an in-depth look at the sixth injury mechanism. The sixth mechanism may be thought of as a ‘pressure-shock wave’ which is directly proportional to the current of the lightning discharge, and which is present immediately surrounding lightning’s luminous channel. A literature review, case studies and two novel experiments helped confirm the sixth mechanism’s existence. The medical data and the lightning data were then aligned. Two main questions were addressed, namely within what range is a human at risk; and what is the risk of lightning’s pressure shock wave. This ‘pressure-shock wave’ may explain some of the more curious lightning injury patterns seen on lightning-strike victims. Knowledge and insight into the sixth mechanism may have direct and indirect applications to those working in the fields of lightning injury and lightning protection. This thesis represents a contribution to the literature in both medicine and engineering.

Abstract New Orleans in 1900 was an endangered city clinging to a narrow strip of relatively high ground along the lower Mississippi river. Frequent flooding occurred from the river in the spring and from the lake in the June to October hurricane season. No reliable source of drinking water and no systems for removal of sewerage and rain water existed. Disease mortality was very high especially from frequent outbreaks of yellow fever. The fortuitous appearance of new alternating current (AC) technologies, emerging engineering specialties, and a more progressive form of governance willing to support and finance large scale engineering projects gave New Orleans world class drainage, sewerage and potable water systems. With electric streetcars providing service to newly drained areas and greatly reduced disease mortality, New Orleans entered the twentieth century transformed into a safe and expanding city. Key Words: Electricity, New Orleans, Infrastructure

Thesis (Mathematics) -- University of Limpopo, 2010 / Forecasting electricity consumption is a challenge for most power utilities. In South Africa the anxiety posed by electricity supply disruption is a cause for concern in sustainable energy planning. Accurate forecasting of future electricity consumption has been identified as an essential input to this planning process. Forecasting electricity consumption has been widely researched and several methodologies suggested. However, various methods that have been proposed by a number of researchers are dependent on environment and market factors related to the scope of work under study making portability a challenge. The aim of this study is to investigate models to forecast short term electricity consumption for operational use and medium term electricity consumption for tactical use in the Ferrochrome sector in South Africa. An Autoregressive Moving Average method is suggested as an appropriate tool for operational planning. The Holt-Winter Linear seasonal smoothing method is suggested for tactical planning. Keywords: Forecasting, electricity consumption, operational planning, tactical planning, ARIMA, Holt-Winter Linear seasonal smoothing, Ferrochrome sector

Source: Dissertation Abstracts International, Volume: 24-01, page: 0337. / Thesis (Ph.D.)--The Florida State University, 1963.

No description available.

Thesis (Ph. D.)--Washington State University, May 2007. / Includes bibliographical references.