Thesis (M. Arch.)--University of Hong Kong, 2000. / Includes bibliographical references.

Thesis (M.Arch.)--University of Hong Kong, 2000. / Includes bibliographical references. Also available in print.

<p>For technical systems in the electricity and paper and pulpindustries, asset management is emerging as a new approachaddressing how to exploit physical assets with long operativelives in the most profitably way. An important problem forasset management staff is knowing when to carry out areplacement or renewal. This is a difficult question whichrequires taking into consideration parameters of totallydifferent natures–e.g. reliability data, operatingcosts, condition information from technical systems, theenvironment and rules and regulation. An incorrect estimate ofa residual lifetime can result in a premature renewal withaccompanying high capital costs. If, however, renewal isdelayed, a breakdown may occur which can cause major damage totechnical equipment and a loss of income due to outages.</p><p>This work presents a formal model that calculates expectedcosts of different long-term strategies when managing technicalsystems. It is shown that with relatively few inputs, which inmany cases are easy to collect or estimate, a good picture canbe developed that shows the amount of resources a company willneed in the future in terms of renewals of their technicalsystems. The foundation for this work is a case study and aliterature review; the objective was to study what methods andmodels are in use today when estimating residual lifetime oftechnical systems. Also, aspects that influence long-term assetmanagement were investigated. Lessons learned from the casestudy and literature review were then used to develop a dynamicmodel, the Dynamic Lifetime Analysis model (DLA model).</p><p>This model is based on a probabilistic and dynamic riskanalysis of a technical system, linking different aspects ofrisk management strategies to specific characteristics of thephysical system. Furthermore it is shown how this model,coupled with specific value judgments, can be used to designoptimal long-term strategies. When taking more than onetechnical system under consideration the model shows that it isnot always the most effective, from a system viewpoint, torenew it too close to a possible breakdown. If there is aperiod predicted to incur high investment, it can, at times, bebetter to do an early renewal thereby maintaining resources ata constant level. The thesis also describes how to work withlong-term strategic decisions in a structural manner in orderfor the actors on a deregulated market to stay competitive.</p><p><b>Key Words:</b>Residual lifetime estimation, Assetmanagement, Maintenance, Technical systems in power and pulp-and paper industries, Long terms renewal strategies.</p>

For technical systems in the electricity and paper and pulpindustries, asset management is emerging as a new approachaddressing how to exploit physical assets with long operativelives in the most profitably way. An important problem forasset management staff is knowing when to carry out areplacement or renewal. This is a difficult question whichrequires taking into consideration parameters of totallydifferent natures–e.g. reliability data, operatingcosts, condition information from technical systems, theenvironment and rules and regulation. An incorrect estimate ofa residual lifetime can result in a premature renewal withaccompanying high capital costs. If, however, renewal isdelayed, a breakdown may occur which can cause major damage totechnical equipment and a loss of income due to outages. This work presents a formal model that calculates expectedcosts of different long-term strategies when managing technicalsystems. It is shown that with relatively few inputs, which inmany cases are easy to collect or estimate, a good picture canbe developed that shows the amount of resources a company willneed in the future in terms of renewals of their technicalsystems. The foundation for this work is a case study and aliterature review; the objective was to study what methods andmodels are in use today when estimating residual lifetime oftechnical systems. Also, aspects that influence long-term assetmanagement were investigated. Lessons learned from the casestudy and literature review were then used to develop a dynamicmodel, the Dynamic Lifetime Analysis model (DLA model). This model is based on a probabilistic and dynamic riskanalysis of a technical system, linking different aspects ofrisk management strategies to specific characteristics of thephysical system. Furthermore it is shown how this model,coupled with specific value judgments, can be used to designoptimal long-term strategies. When taking more than onetechnical system under consideration the model shows that it isnot always the most effective, from a system viewpoint, torenew it too close to a possible breakdown. If there is aperiod predicted to incur high investment, it can, at times, bebetter to do an early renewal thereby maintaining resources ata constant level. The thesis also describes how to work withlong-term strategic decisions in a structural manner in orderfor the actors on a deregulated market to stay competitive. <b>Key Words:</b>Residual lifetime estimation, Assetmanagement, Maintenance, Technical systems in power and pulp-and paper industries, Long terms renewal strategies. / NR 20140805

Two novel pump/probe techniques have been developed for measuring the recombination lifetime in crystalline silicon wafers. The first technique, single-beam pump/probe, uses one laser as both pump and probe. The second technique, quasi-steady state free-carrier absorption, measures lifetime under quasi-steady state conditions. These techniques are supported by a general mathematical model that predicts the experimental signal accounting for the 3D charge-carrier transport and recombination within the semiconductor. The predictions of the model are validated experimentally, and quantitative agreement is found between the model and experimental results for both techniques. The recombination lifetime measured by these techniques is verified independently using a standard pump/probe method, and the results are in agreement with this work. Single-beam pump/probe is a first-time demonstration of a technique capable of measuring lifetime in silicon using a single laser beam. It dramatically simplifies traditional pump/probe measurements by completely eliminating the second laser beam. QSS-FCA is the first quasi-steady state technique that can be calibrated in situ without the requirement of a calibrated reference wafer. The calibration constant is the free-carrier absorption cross section of silicon, which is a material constant. QSS-FCA is able to measure this cross section to a higher precision than what has been reported in the literature. Precise measurement of this constant opens up the possibility of studying more fundamental physics of silicon using QSS-FCA. / Thesis / Doctor of Philosophy (PhD)

At the moment, when energy and environmental issues are of concerned in our society, photovoltaic technology has received tremendous development and demand. Because carrier lifetime and diffusion coefficient are the important indicators to determine the recombination level, which influences the efficiency of solar cells to a large extent, they are regarded as key in choosing solar cell materials. A technique for effective lifetime measurement, modulated free-carrier absorption (FCA), can extract lifetime and diffusion coefficient simultaneously, which is supported by a general mathematical model that predicts the experimental signal accounting for the 3-dimensional (3D) charge-carrier transport and recombination within the semiconductor. A single mode 1064 nm laser modulated by an EO modulator is used as the pump and a 2050 nm modulated LED is used as probe in this experiment as the pump/probe parts. An IR camera detects the frequency-domain diffusion image from the tested silicon sample at the tested frequency range between 1 kHz to 200 kHz and the lifetime can be extracted by frequency-domain free-carrier concentration equation, which is a Lorentzian model. By simulating the diffusion data from the camera with the 3D free-carrier absorption model, we can extract lifetime and diffusion coefficient simultaneously. The fitted lifetime from frequency-domain free-carrier absorption equation is 33.5 ± 1.3 μs, and the fitted lifetime from this 3D FCA model is 32.8 ± 1.5 μs, which match to within the error bars. The fitted diffusion coefficient from this 3D FCA model is 15.6 ± 0.7 cm2/s, which agrees with the theoretical value of 16 cm2/s for silicon. Good quantitative agreement is found among the model, experimental data, and theory. / Thesis / Master of Applied Science (MASc)

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All animals, including insect herbivores, eat to acquire nutrients that are essential for fueling physiological processes associated with growth, development, and reproduction. Protein and digestible carbohydrates are two nutrients required in large quantities by insect herbivores, but the amounts in which they occur in plants can be highly variable. In this thesis, I explore how the amounts and ratios of protein and digestible carbohydrate in an insect herbivore's food affect lifetime performance and body elemental composition. I do this by confining a generalist caterpillar, Heliothis virescens, to semi-synthetic foods with fixed protein-carbohydrate amounts and ratios. I show that foods with protein-carbohydrate ratios that match the self-selected protein-carbohydrate intake of final instar caterpillars correlate strongly with best performance, and that small deviations away from this optimal protein-carbohydrate ratio can result in large drop-offs in overall performance, particularly for males. I also show the importance of protein-carbohydrate balance over total macronutrient content. Finally, my results demonstrate that H. virescens caterpillars do not practice strict elemental homeostasis. My result, when contrasted with earlier work on caterpillars, suggests that hemimetabolous and holometabolous insect herbivores practice different degrees of elemental homeostasis.