Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 129-135). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948026.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 65-68). Also available in electronic version.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xiii, 105 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 97-98).

Made available in DSpace on 2014-10-09T12:53:11Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:02Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:53:11Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:02Z (GMT). No. of bitstreams: 0 / A avaliação metrológica da incerteza da medição, apesar de estar normalizada internacionalmente (ISO-GUM, 1995) desde a metade dos anos 90, só agora está se popularizando nas indústrias, nas escolas técnicas e de engenharia. Em algumas áreas, como na metrologia dimensional, está avançada e em outras, como na medição de variáveis de processos industriais tais como vazão, pressão e temperatura, ainda está numa fase intermediara. Um dos principais entraves para essa popularização é a falta de padronização da nomenclatura nas especificações técnicas dos instrumentos de medição, onde se declara a incerteza, por exemplo, de 1% de ?acurácia? sem definir se é percentual da leitura, da faixa calibrada ou da faixa máxima. Ou ainda, sem definir se a probabilidade de abrangência é 68, 95 ou 99,7%. Esse trabalho entra nesse cenário com a pretensão de clarificar e simplificar esses conceitos, começando pelo histórico da evolução do pensamento que transformou a incerteza numa variável quantitativa com sua avaliação efetuada de uma maneira padronizada e internacionalmente aceita. Em seguida é feita uma descrição conceitual sucinta do método ISO-GUM e também é desvendado o intrincado jogo de palavras e fórmulas das declarações de incertezas dos fabricantes de instrumentos de medição. Com o domínio desses conceitos, partimos para efetuar dois exemplos numéricos de avaliação metrológica de incertezas na medição de vazão, usando um conjuntos de fórmulas semelhantes Ás publicadas por renomados fabricantes de instrumentos de medição. No primeiro exemplo usando a medição de vazão por pressão diferencial com placa de orifício e no segundo usando um medidor volumétrico, nos quais são identificadas e quantificadas todas as potenciais fontes de incerteza. A visualização e a analise é feita através de gráficos e planilhas em Excel. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

M.Ing. / This thesis describes a full design project of a processor based sophisticated measurement instrument - the datalogger. It covers the theoretical approach to the design project followed with hardware and software design. Many nonstandard solutions in hardware and software parts are used to approach a target, and they are fully described. The world that surrounds us today is full of products based on science and technology knowledge. These products are part of everyday life. The development of science and technology is very much depend upon a parallel development of measurement techniques and instruments. Measurement and the technology of measurement called instrumentation, serves not only science but all branches of engineering, medicine and almost every sphere of human life. Measuring instruments are used in the monitoring and control of processes and operations, too. Most specialised instruments, such as the datalogger, are used in experimental, research and develop science and engineering work. This thesis is organised into six chapters. The dataloger position in the measurement instruments tree is shown in the first chapter. The electronics design philosophy follows in the next chapter. It covers the most common problems found when the new design project starts. The global design strategy with brief description of all steps follows. The second chapter contains the datalogger project history, the reasons for going into the project, and the requests of the new device, too. At the end of this chapter the basic work principle of the datalogger is described to allow an easily following applied solutions. The third chapter covers all datalogger design specialities that make the datalogger design different from the design of other measurement instruments. It starts with remote sensors problems and problems commonly connected to the input stage of similar systems. The second half of this chapter analyses the instrument precision and error sources. There are several different methods that precision can be increased. Two methods applied here, reducing measurement range and oversampling with noise, are briefly described. The forth chapter interpretates the design of the processor board. It starts with a general microcontroller overview, describing the reasons for selecting the Hitachi microcontroller H8/532. The most important microcontroller characteristics are shown, too. The second part of this chapter contains the organisation, connections and contents of other electronics blocks in the processor board. At the end of this chapter the processor board schematic and full characteristics are given. The datalogger's hardware is described in the fifth chapter. The basic work principles of the various hardware parts are given in the beginning. The hardware is broken down and described in the following way: power electronics, digital control, signal processing part, and interface cards. All parts are covered with detailed descriptions of design circuit and the following calculation. The last chapter shows the software for the datalogger. It starts with the mathematical calculation principle developed and used in the datalogger. The customer part which follows covers software and hardware part relation between user and datalogger. One of the datalogger's software speciality is organisation of RAM space which allows high software flexibility of the datalogger as a measurement instrument. At the end the full datalogger program organisation is given on a global level.

This thesis addresses one of the major limiting factors in the performance of photomultipliers, that is that the photocathodes employed often only absorb a small fraction, typically less than 25%, of the power in the incident light. Current photocathodes are almost exclusively planar and the starting point of the thesis is the mathematical modelling of both, semitransparent and reflective planar photocathodes. The analysis shows that the absorptance of semitransparent photocathodes increases for light incident beyond the critical angle needed for Attenuated Total Internal Reflection (ATIR). Reflective type planar photocathodes could certainly have their absorptance enhanced by use of silver rather than nickel substrates, as increases in absorptance of 2-3 times are possible for red light. The proposed method for remedying the inherent loss in sensitivity of photomultipliers caused by the non-total absorption of light in the photocathode was to employ a ridged substrate in the photocathode. The ridged substrate, glass or metal for semitransparent and reflective type photocathodes respectively, allows the light multiple interactions with the photoemissive layer. In the case of semitransparent photocathodes ATIR would mean no power is transmitted for those interactions that take place beyond the critical angle of incidence. The mathematical modelling and subsequent analysis of ridged photocathodes show enhanced absorptance (20-30 fold improvements are certainly achievable), especially for light in the red end of the operating spectral range. Further gains in quantum efficiency can follow by the reduction of the optimum photocathode thickness, resulting from the structure, while maintaining high absorptance. Some subwavelength structures are also modelled and analysed to ascertain whether this route could be used to improve the absorptance of photocathodes, the results are inconclusive but generally indicate anti-reflective, rather than absorbing properties. Finally the extremely sparse nature of published permitivity data has been rectified by our own measurements for the permitivities of certain photocathodes over a wide wavelength range.

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