M.Ing. (Engineering Management) / The turbo-generator unit is very important equipment for electric power production, which has a high rate of failure. As the capacity increases, condition monitoring and fault diagnostic play a crucial role to guarantee safe operation and cost efficiency. The Eskom generator fleet is fast approaching the end of the original designed life. Also in view of the recent constrained reserve margin, outage downtime, maintenance costs, resource management, and maintenance inherent problems, a systematic approach is required to optimise scheduled time-based maintenance to improve reliability and availability. The subject of turbo machine condition monitoring requires the development of new technologies to diagnose the turbo-generator problems. Condition is an underlying factor in the performance of machines. It is also an important predictor of future performance that the machine is in a good condition and will be reliable and perform better. It provides a reference for maintenance engineers on the current condition of the turbo-generator. Trends in condition monitoring can be used to determine whether turbo-generators are being maintained and that are meeting their expected service lives or whether their performance is deterioration faster than expected. In the industry, traditional maintenance philosophies have taken two approaches; the first approach is to perform fixed time interval maintenance, where the system engineers take advantage of relaxed production cycles to fully inspect all aspects of the turbo-generator. The second route is for engineers to simply react to the generator failure as and when it happens. All too many utilities operate largely in the reactive run-to-failure mode. The old phrase, “if it aren’t broken don’t fix” is perennial run to failure argument. Nonetheless, making use of today’s technology, a new scientific methodology is becoming popular to maintenance management. For the purpose of investigating the management of condition-based monitoring and diagnostic technology to optimise timed-based maintenance of large turbo-generators, Eskom Units installed with condition monitoring techniques were considered. The minidissertation culminated in the compilation of case histories based on Eskom turbo-generator fleet where the technology is being rolled out. The literature survey looked at current industry practices in areas such as total productive maintenance (TPM), technology management and support systems, return on investment (ROI) and maintenance management to compare what Eskom is doing to what in others in the field are doing. There is no research work currently that has been done that links maintenance to maintenance technology deployment enablers. The research incorporates a number of operational experiences where some Eskom turbo-generator units continue to operate with a known fault. Regular maintenance interventions introduce faults into the machine due to human error, the opening of units and the handling of components. Attention is given to the impact of two-shifting or cyclic operation on turbo-generators that were originally designed for base load condition. The time–based maintenance of these units is not taking advantage of condition monitoring information. Also, the installed condition monitoring techniques fall short of addressing twoshifting monitoring requirements. A number of lessons were learnt from the implementation of the condition-based maintenance technology on Eskom generator fleet. The theory of maintenance management underscores establishment of a good relationship between system engineers, maintenance personnel and the technology provider which is key to success of the technology. It further indicates that this relationship must go deeper than the mere technology provider and the end user of the technology service agreement. The maintenance engineers are taking key business decision for the well-being of machines and maintenance technology needs to demonstrate that it is creating value for the business. From the people perspective attention is required to staff motivation and providing balanced job satisfaction, whilst ensuring that employees feel part of an integrated organisation maintenance strategy rather than of being under thread of disempowered by the technology. A myriad of considerations have been identified to affect the effective execution of conditionbase maintenance strategy on Eskom generator fleet. There are multiple dashboards or standards indicators that can be used for maintenance management improvement. It has been established that the success of the implementation of condition-based maintenance rests in the concept of total productive maintenance approach. Within the ambit of TPM, the entire process of maintenance must be managed on the basis of maintenance programmes plan, which will have function of connecting the various maintenance programmes.

A thesis Submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, for the Degree of Master of Science. Johannesburg, December 1992. / The ethanol conversion to hydrocarbons over acidic catalysts proceeds with high activity and selectivity and has hence generated considerable interest. In this thesis an investigation of the use of a range of supports, loaded with metals as potential catalysts for the ethanol transformation reaction, is reported. In particular, Ti02 was investigated as a support and the addition of a secondary component to the catalyst was examined with respect to product selectivities. [Abbreviated Abstract. Open document to view full version] / AC2017

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg / In this thesis we investigate the evolution of viscous FRW cosmological models for two different constitutive equations for the bulk viscous pressure a, namely (Abbreviation abstract) / Andrew Chakane 2018

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, / In this thesis we investigate the evolution of viscous FRW cosmological models for two different constitutive equations for the bulk viscous pressure a, namely: The truncated theory,,,,,,,,,,,,,,,, and the full (non-truncated] Israel-Stewart theory ...................We first review the relativistic theory of non-equilibrium thermodynamics developed by Eckart (1940) and the essentially equivalent formulation of the theory given by Landau and Lifshitz (1958). We give a, brief description of the relativistic second-order theories found by Israel and Stewart (1976) and subsequently developed by Pavon, Jou, and co-workers (1982, 1993). All this is done in order to develop the tools for the study of the evolution of FRW cosmological models in the context of causal thermodynamics. We find new exact and perturbative solutions of Einstein's field equations for the truncated Israel-Stewart theory of irreversible thermodynamics. We show that viscous effects speed up the expansion of the universe. We also consider a viscous fluid in the presence of a " non-interacting scalar field and show that inflationary solutions exist. The full theory of bulk viscosity is applied to dissipative FRW spacetimes. New causal viscous inflationary solutions are presented. These solutions extend the results obtained by Maartens (1995a) to cases where the coefficient of bulk viscosity e and the relaxation time r are independent. Power-law solutions for the scale factor are shown to exist. / Andrew Chakane 2018

Orientador: Ricardo Alan Verdú Ramos / Coorientador: Emanuel RochaWoiski / Banca: João Batista Aparecido / Banca: Paulo Hélio Kanayama / Resumo: O presente trabalho teve como objetivo o desenvolvimento e teste de um protótipo de um programa computacional para simulação de plantas térmica e de potência, com os principais recursos de programas comerciais existentes, com baixo custo e com interface gráfica mais amigável. O referido programa foi denominado TPPS (abreviação de Thermal Power Plant Software), tendo sido desenvolvido na linguagem object pascal, utilizando a IDE do DELPHI e a biblioteca FLUIDPROP, na qual constam os componentes para cálculo das propriedades termodinâmicas envolvidas. Para tanto, inicialmente é apresentada uma breve descrição de alguns programas computacionais disponíveis no mercado que comumente são utilizados no meio acadêmico sendo que, dentre eles, foram escolhidos três (Cycle-Tempo, EES e IPSEpro) para efeito comparativo dos resultados das simulações com o programa desenvolvido, tendo como base duas plantas básicas, uma de geração e outra de cogeração de energia. Foi utilizada uma metodologia de simulação que consiste na avaliação dos processos, dos dados e do resultado dos cálculos obtidos. Para tanto, foram consideradas as hipóteses de regime permanente; variações das energias cinéticas e potencial são desprezadas em virtude de se desejar apenas um simples comparativo de valores das propriedades termodinâmicas calculadas; processos adiabáticos em todos os equipamentos que fazem parte dos ciclos, exceto para trocadores de calor, para os quais um parâmetro de eficiência define a quantidade de calor transferida ao meio. Os resultados obtidos foram bastante satisfatórios, tendo em vista que não houve discrepâncias entre os resultados obtidos por cada um dos programas, mostrando que a ferramenta desenvolvida, em sua primeira versão, atende os requisitos a que se propôs. Por fim, são apresentados resultados de uma simulação de uma planta de cogeração mais complexa, através do TPPS / Abstract: This study aimed to develop and test a prototype of a computer program for simulation of thermal and power plants, with the main sources of existing commercial programs, with low cost and friendlier graphical interface. The program was denominated TPPS (abbreviation for Thermal Power Plant Software), and has been developed in Object Pascal language, using the Delphi IDE and FLUIDPROP library, which contains the components for calculating the thermodynamic properties involved. Therefore, initially presents a brief description of some computational programs available that are commonly utilized in the academic environment and among them, three were chosen (Cycle-Time, EES and IPSEpro) for comparison of the simulation results with the program developed, based on two basic plants, one of power generation and the other one of cogeneration. The simulation methodology consists of the evaluation of the processes, data and results obtained from the calculations. Therefore, it was considered the hypothesis of steady state and the variations of kinetic and potential energies were neglected because just a simple comparison of calculated values of thermodynamic properties; adiabatic processes in all devices of the cycles, except for heat exchangers, for which an efficiency parameter defines the amount of heat transferred to the environment. The results were quite satisfactory, considering that there were no discrepancies between the results obtained by each one of the programs, showing that the first version of the software developed meets the proposed requirements. Finally, results of simulation of a more complex cogeneration plant through the TPPS are presented / Mestre

Orientador: Celso Eduardo Tuna / Coorientador: José Alexandre Matelli / Banca: Pedro Magalhães Sobrinho / Banca: Diovana Aparecida dos Santos Napoleão / Resumo: As indústrias queimam combustíveis para produzir energia térmica para um processo. Em alguns casos, uma fração dessa energia não é completamente utilizada. Com o intuito melhorar a eficiência do sistema, essa fração de energia térmica não utilizada pode ser usada para acionar um Sistema de Refrigeração por Absorção (SRA). Nas últimas décadas, o interesse em usar SRA aumentou consideravelmente por conta da possibilidade de se utilizar vapor, água quente e gases de exaustão de sistemas de potência. Além disso, melhorias tecnológicas permitiram uma melhor eficiência do SRA. Uma modelagem termodinâmica do SRA foi realizada para analisar o desempenho de uma máquina em termos energéticos e exergéticos para obter água gelada a 5, 7, 9, 11 e 15 oC com uma fonte de água quente a 80, 90, 100, 110, 120 e 130 oC . A primeira e segunda lei da termodinâmica, tabelas e equações das propriedades da solução aquosa de brometo de lítio e água foram utilizadas para modelar o ciclo e efetuar os cálculos. As hipóteses básicas consideradas foram regime permanente, água pura, bomba isentrópica e processos adiabáticos. Através da análise dos resultados, que essa metodologia pode ser aplicada para determinar o comportamento da variação do COP e eficiência exergética em função da temperatura da água quente que alimenta o gerador e da água gelada obtida no evaporador. Realizou-se análise energética e exergética em cada componente do sistema. Com base nesses dados, pode-se verificar que a faixa de temper... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Industries burn fuels to produce thermal energy for a process. In some cases, a fraction of this energy is not fully utilized. In order to improve the efficiency of the system, this waste of energy can be used to drive an Absorption Refrigeration System (ARS). On the last decades, the interest in using ARS increased considerably because of the possibility of using steam, hot water or exhaust gases from thermal engines. Furthermore, technological improvements increased efficiency of this cycle. A thermodynamic model of an ARS was developed to calculate the required energy to generate cold water at 5, 7, 9, 11 e 15 oC from a heat source at 80, 90, 100, 110, 120, 130 oC. First law of thermodynamic, tables and equations of property of aqueous solution of lithium bromide and water were used to model the cycle. The basic hypothesis considered was steady state, pure water, isentropic pump and adiabatic processes. Analysis of the results revealed that this methodology can be applied to study the relationship between COP and exergetic efficiency as a function of the inlet hot water temperature and outlet cold water . Energetic and exergetic analysis were performed for each component. The results show that the highest COP and exergetic efficiency were obtained for hotwater temperature range between 90 to 100 oC. The distribution in terms of exergy in main components were studied and revealed that the high losses of exergy occurred in evaporator and absorber / Mestre

by Lee Siu-keung. / Parallel title in Chinese. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 162-164). / Chapter Chapter 1 --- Introduction --- p.5 / Chapter Chapter 2 --- Path Integrals / Chapter 2.1 --- Path´ؤIntegral Approach to Quantum Mechanics --- p.8 / Chapter 2.2 --- Path´ؤIntegral Approach to Statistical Mechanics --- p.14 / Chapter 2.3 --- Variational Principle --- p.18 / Chapter 2.4 --- "Variational Method Proposed by Giachetti and Tognetti, and by Feynman and Kleinert" / Chapter 2.4.1 --- Effective Classical Partition Function --- p.24 / Chapter 2.4.2 --- Particle Distribution Function From Effective Classical Potential --- p.34 / Chapter Chapter 3 --- Systematic Perturbation Corrections to the Variational Approximation Proposed in Section2.4 / Chapter 3.1 --- Formalism / Chapter 3.1.1 --- Free Energy --- p.38 / Chapter 3.1.2 --- Particle Distribution Function --- p.49 / Chapter 3.2 --- Second Order Correction to Free Energy --- p.53 / Chapter 3.3 --- First Order Correction to Particle Distribution Function --- p.60 / Chapter Chapter 4 --- Examples and Results / Chapter 4.1 --- Quartic Anharmonic Oscillator / Chapter 4.1.1 --- "Free Energy, Internal Energy and Specific Heat" --- p.69 / Chapter 4.1.2 --- Particle Distribution Function --- p.87 / Chapter 4.2 --- Symmetric Double-well Potential / Chapter 4.2.1 --- "Free Energy, Internal Energy and Specific Heat" --- p.88 / Chapter 4.2.2 --- Particle Distribution Function --- p.106 / Chapter 4.3 --- Quartic-cubic Anharmonic Potential / Chapter 4.3.1 --- Free Energy --- p.108 / Chapter 4.3.2 --- Particle Distribution Function --- p.115 / Chapter Chapter 5 --- Application to the One-dimensional Ginzburg-Landau Model / Chapter 5.1 --- Introduction --- p.120 / Chapter 5.2 --- Exact Partition Function and Free Energy Per Unit Length --- p.123 / Chapter 5.3 --- Zeroth Order Approximation to Free Energy Per Unit Length --- p.126 / Chapter 5.4 --- Exact Specific Heat --- p.133 / Chapter 5.5 --- Zeroth Order Approximation to Specific Heat --- p.139 / Chapter Chapter 6 --- Conclusion --- p.141 / Chapter Appendix I --- Functional Calculus - Differentiation --- p.145 / Chapter Appendix II --- Evaluation of Feynman Propagator Δf(τ) --- p.147 / Chapter Appendix III --- Vanishing of the First Order Correction-βf1 --- p.150 / Chapter Appendix IV --- Numerical Method for the Energy Eigenvalues and Eigenfunctions of the One-dimensional Schroedinger Equation with ax2 + bx4 Potential --- p.153 / Chapter Appendix V --- Numerical Integrations with imaginary Ω --- p.158 / References --- p.162 / Figures --- p.165

Coarse-graining and multi-scale approaches are rapidly becoming important tools for computer simulations of large complex molecular systems. Such theoretical models are powerful tools because they allow one to probe the essential features of a complex, many-bodied system on length and time scales over which emergent phenomena may occur. Because of the computational advantages and fundamental insight made available through coarse-grained methods, a vast array of various phenomenological potentials to describe coarse-grained interactions have been developed; nonetheless, the ability of these potentials to provide quantitative information about several different properties of the same system is not evident. On a theoretical level, it is not well-understood how small correlations in the long-range structure propagate through the coarse-graining procedure into the effective potential and lead to incorrect thermodynamics. Taking an alternative approach, this dissertation will discuss an analytical coarse-graining method for synthetic polymer chains of specific chemical structure, where a group of atoms on a polymer chain are represented by a variable number of soft interacting effective sites. The approach is based in liquid-state theory, providing a theoretical framework to address questions of thermodynamic consistency. It will be shown that the proposed method of coarse-graining maintains thermodynamic consistency for a variety of polymer models. In a multi-scale modeling scheme simulations of the same system represented by several different levels of detail may be joined to provide a complete description of the system at all length and time scales of interest. This dissertation includes previously published and unpublished co-authored material.

Vita. / Digitized by Kansas Correctional Industries

Este trabalho consiste basicamente em dois experimentos: Determinação da equação de estado de um gás frio aprisionado, e na comparação das temperaturas de uma amostra de átomos confinadas em dois tipos de armadilhas magneto-ópticas. No primeiro experimento utilizamos a generalização do conceito de pressão e volume que foram redefinidos de maneira apropriada para alcançamos uma equação de estado. Experimentalmente nossa amostra apresentou um desvio do esperado para um gás ideal, dessa forma utilizamos uma expansão virial com as novas definições de pressão e volume para investigar as interações entre os átomos. Já no segundo experimento utilizamos uma técnica que mede transiente temporal da absorção do feixe pelos átomos através de um fotodetector para a obtenção da temperatura. Neste experimento obtemos temperaturas equivalentes para as duas armadilhas. / This work consists of two experiments: Determination of the state equation a trapped cold gas, and the comparison of the temperatures of confined atoms in two types of magneto-optical traps. For the first experiment we generalized and defined a new pressure and volume concept and we reached a state equation. Experimentally our sample presented a deviation of the ideal gas, in that way we used a virial expansion with the new pressure and volume definitions to investigate the interactions among the atoms. In the second experiment we used a technique that measures temporal variation of the absorption of a probe beam that crosses the atoms by a photodetector, witch gives us the information about the temperature. We have found equivalent temperatures for the two traps.