Associated natural gas is produced as a by-product from crude oil exploration and production. When perceived as a non-desirable product, it is wasted during gas flaring. Globally, about 100 Billion Cubic Meters (BCM) of gas is flared annually, leading to release of about 300 million tons of carbon dioxide yearly into the environment. Russia and Nigeria flare more than other countries to the tune of 35.5 and 18.27 BCM, respectively. The consequence of gas flaring has continued to pose significant threats to the environment as well as the economy of oil and gas producing countries. Therefore, this research is aimed at developing a sustainable framework that could enable management of flared gas in an oil and gas environment by generating energy and also minimise environmental impact that arises from gas flaring process. Three major research gaps were identified and they include lack of existing gas flare management framework in Nigeria, lack of economic evaluation of gas to wire (GTW) technology for flared gas reduction and, lack of cordial relationship and understanding between oil and gas producing/flaring companies and electricity producing sectors towards gas flare management. A qualitative research strategy was employed – utilising the single case study approach with embedded units of analysis. Three case study companies were used - one oil and gas producing company, and two electricity-generating companies. Data collection involved semi structured interviews, documentation, observation, and review of relevant literature. Data was analysed using QSR Nvivo version 10. A framework for flared gas reduction was developed based on literature review and also from information made available by experts operating in the oil and gas and electricity sectors. The framework shows inputs from various stakeholders, as well as an evaluation of volume of gas produced, utilized and flared. An economic assessment of GTW technology was carried out to determine the cost effectiveness of the framework. Findings from the study showed that GTW is a viable means of management, and could reduce the total volume of flared gas in Nigeria to 7.1%. This reduces environmental, health and safety hazards. It is also economically profitable. A total capital investment of £1.64b is required in the Nigerian context, with a net profit of £1.26b/year, and has a rate of return of investment of 16.3%. This study has demonstrated that GTW is a sustainable technology for reducing flared gas in Nigeria and other countries facing similar challenges as Nigeria; and capable of minimising adverse environmental and health impact associated with gas flaring. Therefore, the developed framework is also recommended for effective management of flared gas in such countries.

The works deals with the study of the flare stars, which is a group of stars for which sudden brightening can be observed. The work focuses on a star GJ 3236, which is a low-mass eclipsing binary and on which numerous flares have been observed. For the analysis of this system spectroscopic and photometric data were used, which were obtained at various observatories. Parameters of the binary system have been determined by analysing spectroscopic and photometric data with the program PHOEBE. A total of 241 flares have been detected in the photometric data and for 190 flares, which light curves were not affected by eclipses, released energies were estimated. The set of flares was used for the study of stellar activity of the binary. The energy distribution of observed flares is similar to the flares observed on other flare stars and also on the Sun. This suggests, that the flare mechanism is the same for these stars.

[pt] O presente trabalho introduz duas técnicas de medição da emissividade da superfície de três materias comumente utilizados nas plataformas offshore: cobertura de Thermal Sprayed Aluminum (TSA), cobertura de Jotatemp1000 e uma superfície crua de aço naval. Foram investigadas metodologias de medição de emissividade e os conceitos básicos de radiação e convecção natural. A partir disso, determina-se a modelagem do problema em questão para as estimativas de calor e emissividade. O primeiro experimento consistiu na medição da emissividade com o auxílio de um termógrafo, nesse foi realizada a comparação de medição sobre uma placa plana e um tubo revestido para o TSA e o Jotatemp1000. No segundo experimento, realizou-se a medição da emissividade através da medição das transferencias de calor por convecção natural e radiação em um espaço anular. As medições neste experimento foram realizadas para diferentes pressões, para que se quantifique o efeito da convecção natural. No primeiro experimento, nota-se uma discrepância significativa entre os valores medidos nos tubos e nas placas. Constatou-se também que a emissividade de todos os materiais permaneceu praticamente constante para os valores acima de 100 Graus C. Observou-se uma disparidade considerável nos valores de emissividade encontradas no primeiro experimento em comparação com o segundo para o Jotatemp e aço naval. A partir dos dados, constata-se que emissividade medida com termógrafo possui uma precisão maior, por ser uma medida direta. Dentre as medições no espaço anular, o mais confiável para pequenos intervalos de temperatura é a parametrização pela superfície dada pelo matlab. Ainda que os resultados apresentem tais discrepâncias, pode-se observar que o Jotatemp100 obteve os maiores valores de emissividade em todos os experimentos e o TSA os menores valores, mesmo com a incerteza experimental. / [en] The present work introduces two techniques for measuring the surface emissivity of three materials commonly used in offshore platforms: Thermal Sprayed Aluminum (TSA) coating, Jotatemp1000 coating and a raw marine steel surface. Emissivity measurement methodologies and the basic concepts of radiation and natural convection were investigated. From this, the modeling of the problem in question for the heat and emissivity estimates is determined. The first experiment consisted of measuring the emissivity with the aid of a thermographic camera, in which the measurement comparison was performed on a flat plate and a coated tube for TSA and Jotatemp1000. In the second experiment, emissivity was measured by gauging heat transfers by natural convection and radiation in an annular space. The measurements in this experiment were carried out for different pressures, in order to quantify the effect of natural convection. In the first experiment, there was a significant discrepancy between the values measured in the tubes and in the plates. It was also found that the emissivity of all materials remained practically constant for values above 100 C Degrees. A considerable disparity was observed in the emissivity values found in the first experiment compared to the second for Jotatemp and marine steel. From the data, is verified that emissivity measured with a thermographic camera has greater precision, as it is a direct measure. Among the measurements in the annular space, the most reliable for small temperature intervals is the surface parameterization given by matlab. Although the results show such discrepancies, it can be observed that Jotatemp100 obtained the highest emissivity values in all experiments and the TSA the lowest values, even with experimental uncertainty.

[pt] Anualmente, mais de 100 bilhões de metros cúbicos de gás são queimados mundialmente em flares nas instalações de petróleo e gás natural. Esse número era ainda maior a alguns anos atrás. No passado, o holofote estava sobre o petróleo e o gás natural era visto como uma fonte de energia não rentável. A preocupação mundial com o aquecimento global impulsionou as ações para redução das emissões de gases causadores do efeito estufa. A crescente mobilização dos órgãos reguladores de diversos países para imposição de restrições de queima e ventilação do gás natural vem contribuindo para a melhoria dos índices de aproveitamento do gás associado. Muito embora já tenha havido um avanço relevante, o montante de gás desperdiçado ainda precisa ser reduzido. Neste contexto, a necessidade de se quantificar corretamente os volumes desperdiçados de gás fica evidente. As ações para redução da queima ou ventilação de gás natural se baseiam fortemente em medições precisas. O reflexo disto são as constantes publicações de diretrizes regulatórias voltadas para as medições de vazão de gás dos sistemas de alívio/tocha. Apesar da medição de gás de flare não ser uma técnica nova, ela ainda é considerada desafiadora e bem diferente das demais aplicações de medição de vazão. A natureza imprevisível da queima de gás natural, associada a instalações inadequadas, torna a medição extremamente difícil e complexa. O presente trabalho traz uma visão geral da queima de gás natural, da regulação do tema no Brasil e no mundo e das características e desafios da medição de gás de flare. Adicionalmente, foram feitos estudos de incerteza sobre os volumes diários medidos nos pontos fiscais de gás de uma instalação típica, de forma a analisar a influência da incerteza da medição do gás de tocha sobre a incerteza da produção mensal de gás natural, que é a base de cálculo para as devidas participações governamentais. Também foram calculadas as diferenças obtidas entre a medição indireta (balanço volumétrico de gás) e a medição direta (medição ultrassônica) da queima de gás natural e as incertezas relacionadas à medição indireta. / [en] Annually, more than 100 billion cubic meters of gas are flared from upstream oil and gas facilities. This number was even higher a few years ago. In the past, the spotlight was on oil and natural gas was seen as a non-profitable source of energy. The worldwide concern over global warming spurred actions to reduce emissions of greenhouses effect gases, contributing to change the scenario above. The increased mobilization of regulators from many countries enforcing gas flaring and venting restrictions has contributed to the improvement of gas use. However, although some progress has been already achieved, the amount of wasted gas still needs to be reduced. In this context, the need to correctly quantify the volumes of gas flared is evident. Actions to reduce the flaring or venting of natural gas rely heavily on accurate measurements. This reflects on the rigorous flare measurement guidelines introduced by many countries to support flaring legislation. Although the flare gas measurement is not a new technique, it is still considered a challenging task and quite unique compared to other flow measurement applications. The unpredictable nature of the flaring, many times happening at inadequate facility, makes measuring it extremely difficult and complex. This work provides an overview of gas flaring, regulatory requirements in Brazil and worldwide and the characteristics and challenges of flare gas measurement. In addition, uncertainty studies were made over the daily volumes measured in the fiscal points of a typical installation, in order to analyze the influence of the uncertainty of flared gas measurement on the uncertainty of monthly gas production, which is the basis for calculating the government takes. The differences obtained between the gas flaring indirect measurement (bydifference method) and direct measurement (ultrasonic measurement) were also calculated, as well as the uncertainties related to the indirect measurement.

Após a desativação da técnica SA, a ionosfera tornou-se a principal fonte de erro no posicionamento com GPS. O erro associado à ionosfera é diretamente proporcional ao conteúdo total de elétrons (TEC – Total Electron Content) presente ao longo do caminho da trajetória percorrida pelo sinal na ionosfera e inversamente proporcional ao quadrado da freqüência do sinal. O TEC, e conseqüentemente o erro devido à ionosfera, variam no tempo e no espaço e é influenciado por diversas variáveis, tais como: ciclo solar, época do ano, hora do dia, localização geográfica, atividade geomagnética, entre outros. A região brasileira é um dos locais que apresenta os maiores valores e variações espaciais do TEC e onde estão presentes diversas particularidades da ionosfera, tais como, a anomalia equatorial e o efeito da cintilação ionosférica. Desta forma, é importante a realização de pesquisas que visam estudar o comportamento do TEC, e conseqüentemente do erro devido à ionosfera no Brasil, que é um trabalho complexo devido aos diversos fatores que influenciam a variação do TEC, além das particularidades presentes na região brasileira. Estudos desta natureza podem auxiliar a comunidade geodésica brasileira, e demais usuários do GPS, no entendimento das limitações impostas pela ionosfera nas regiões de interesse. Devido à natureza dispersiva da ionosfera, o estudo do comportamento do TEC no Brasil pode ser realizado utilizando os dados GPS de receptores de dupla freqüência pertencentes à RBMC (Rede Brasileira de Monitoramento Contínuo). Adicionalmente, para uma melhor análise, pode-se também utilizar dados das estações da rede IGS (International GNSS Service) da América do Sul. Esta pesquisa tem como principal meta o estudo do comportamento do erro devido à ionosfera na região brasileira em diferentes situações ionosféricas com base em valores de TEC advindos das estações GPS da RBMC e da rede IGS da América do Sul. Outro objetivo é avaliar a performance e as limitações do Mapa Global da Ionosfera do IGS aplicado no posicionamento por ponto na região brasileira. / In the SA absence, the ionosphere is the largest error source in GPS positioning. The error due to the ionosphere in the GPS observables depends on the signal frequency and Total Electron Content (TEC) in the ionospheric layer. The TEC varies regularly in time and space in relation to the sunspot number, the season, the local time, the geographic position, and others. The Brazilian region is one of the regions of the Earth that presents largest values and space variations of the TEC, being influenced by the equatorial anomaly of ionization and ionospheric scintillation. Therefore, it is important to study the TEC behavior in the Brazilian region. Due to the ionosphere dispersive nature, the TEC behavior in Brazil can be studied using GPS data from RBMC (Rede Brasileira de Monitoramento Contínuo – Brazilian Network for Continuous Monitoring of GPS). Additionally, GPS data from IGS (International GNSS Service) network of the South America can also be used in the experiments. The goal of this research is to study the ionospheric error behavior in the Brazilian region, considering different ionosphere situations, using TEC values computed by GPS data from RBMC and IGS network. Other goal is to evaluate the performance and limitations of Global Ionospheric Map of IGS applied in the GPS point positioning in Brazil.

Após a desativação da técnica SA, a ionosfera tornou-se a principal fonte de erro no posicionamento com GPS. O erro associado à ionosfera é diretamente proporcional ao conteúdo total de elétrons (TEC – Total Electron Content) presente ao longo do caminho da trajetória percorrida pelo sinal na ionosfera e inversamente proporcional ao quadrado da freqüência do sinal. O TEC, e conseqüentemente o erro devido à ionosfera, variam no tempo e no espaço e é influenciado por diversas variáveis, tais como: ciclo solar, época do ano, hora do dia, localização geográfica, atividade geomagnética, entre outros. A região brasileira é um dos locais que apresenta os maiores valores e variações espaciais do TEC e onde estão presentes diversas particularidades da ionosfera, tais como, a anomalia equatorial e o efeito da cintilação ionosférica. Desta forma, é importante a realização de pesquisas que visam estudar o comportamento do TEC, e conseqüentemente do erro devido à ionosfera no Brasil, que é um trabalho complexo devido aos diversos fatores que influenciam a variação do TEC, além das particularidades presentes na região brasileira. Estudos desta natureza podem auxiliar a comunidade geodésica brasileira, e demais usuários do GPS, no entendimento das limitações impostas pela ionosfera nas regiões de interesse. Devido à natureza dispersiva da ionosfera, o estudo do comportamento do TEC no Brasil pode ser realizado utilizando os dados GPS de receptores de dupla freqüência pertencentes à RBMC (Rede Brasileira de Monitoramento Contínuo). Adicionalmente, para uma melhor análise, pode-se também utilizar dados das estações da rede IGS (International GNSS Service) da América do Sul. Esta pesquisa tem como principal meta o estudo do comportamento do erro devido à ionosfera na região brasileira em diferentes situações ionosféricas com base em valores de TEC advindos das estações GPS da RBMC e da rede IGS da América do Sul. Outro objetivo é avaliar a performance e as limitações do Mapa Global da Ionosfera do IGS aplicado no posicionamento por ponto na região brasileira. / In the SA absence, the ionosphere is the largest error source in GPS positioning. The error due to the ionosphere in the GPS observables depends on the signal frequency and Total Electron Content (TEC) in the ionospheric layer. The TEC varies regularly in time and space in relation to the sunspot number, the season, the local time, the geographic position, and others. The Brazilian region is one of the regions of the Earth that presents largest values and space variations of the TEC, being influenced by the equatorial anomaly of ionization and ionospheric scintillation. Therefore, it is important to study the TEC behavior in the Brazilian region. Due to the ionosphere dispersive nature, the TEC behavior in Brazil can be studied using GPS data from RBMC (Rede Brasileira de Monitoramento Contínuo – Brazilian Network for Continuous Monitoring of GPS). Additionally, GPS data from IGS (International GNSS Service) network of the South America can also be used in the experiments. The goal of this research is to study the ionospheric error behavior in the Brazilian region, considering different ionosphere situations, using TEC values computed by GPS data from RBMC and IGS network. Other goal is to evaluate the performance and limitations of Global Ionospheric Map of IGS applied in the GPS point positioning in Brazil.

Após a desativação da técnica SA, a ionosfera tornou-se a principal fonte de erro no posicionamento com GPS. O erro associado à ionosfera é diretamente proporcional ao conteúdo total de elétrons (TEC – Total Electron Content) presente ao longo do caminho da trajetória percorrida pelo sinal na ionosfera e inversamente proporcional ao quadrado da freqüência do sinal. O TEC, e conseqüentemente o erro devido à ionosfera, variam no tempo e no espaço e é influenciado por diversas variáveis, tais como: ciclo solar, época do ano, hora do dia, localização geográfica, atividade geomagnética, entre outros. A região brasileira é um dos locais que apresenta os maiores valores e variações espaciais do TEC e onde estão presentes diversas particularidades da ionosfera, tais como, a anomalia equatorial e o efeito da cintilação ionosférica. Desta forma, é importante a realização de pesquisas que visam estudar o comportamento do TEC, e conseqüentemente do erro devido à ionosfera no Brasil, que é um trabalho complexo devido aos diversos fatores que influenciam a variação do TEC, além das particularidades presentes na região brasileira. Estudos desta natureza podem auxiliar a comunidade geodésica brasileira, e demais usuários do GPS, no entendimento das limitações impostas pela ionosfera nas regiões de interesse. Devido à natureza dispersiva da ionosfera, o estudo do comportamento do TEC no Brasil pode ser realizado utilizando os dados GPS de receptores de dupla freqüência pertencentes à RBMC (Rede Brasileira de Monitoramento Contínuo). Adicionalmente, para uma melhor análise, pode-se também utilizar dados das estações da rede IGS (International GNSS Service) da América do Sul. Esta pesquisa tem como principal meta o estudo do comportamento do erro devido à ionosfera na região brasileira em diferentes situações ionosféricas com base em valores de TEC advindos das estações GPS da RBMC e da rede IGS da América do Sul. Outro objetivo é avaliar a performance e as limitações do Mapa Global da Ionosfera do IGS aplicado no posicionamento por ponto na região brasileira. / In the SA absence, the ionosphere is the largest error source in GPS positioning. The error due to the ionosphere in the GPS observables depends on the signal frequency and Total Electron Content (TEC) in the ionospheric layer. The TEC varies regularly in time and space in relation to the sunspot number, the season, the local time, the geographic position, and others. The Brazilian region is one of the regions of the Earth that presents largest values and space variations of the TEC, being influenced by the equatorial anomaly of ionization and ionospheric scintillation. Therefore, it is important to study the TEC behavior in the Brazilian region. Due to the ionosphere dispersive nature, the TEC behavior in Brazil can be studied using GPS data from RBMC (Rede Brasileira de Monitoramento Contínuo – Brazilian Network for Continuous Monitoring of GPS). Additionally, GPS data from IGS (International GNSS Service) network of the South America can also be used in the experiments. The goal of this research is to study the ionospheric error behavior in the Brazilian region, considering different ionosphere situations, using TEC values computed by GPS data from RBMC and IGS network. Other goal is to evaluate the performance and limitations of Global Ionospheric Map of IGS applied in the GPS point positioning in Brazil.

Approved for public release; distribution is unlimited / The Linearly Tapered Slot Antenna (LTSA) had been investigated and developed experimentally; its applications have primarily been based on empirical designs. An accurate theoretical model based on Moment Methods (MM) is developed here to study the radiation characteristics of the LTSA. Using the MM solutions to the reaction integral equation, this thesis presents an analysis to model and explain the LTSA behavior. The effects of variable design parameters on radiation patterns are studied. Discussion is augmented by relating predicted radiation patterns to calculated current distributions on the antenna surface. Conclusions are made regarding optimum designs for the LTSA. Relevant observations are made concerning the extensive computational tasks and the computer resources required for the MM model. / http://archive.org/details/modelingbehavior00kell / Major, United States Army

<p>The high power, broadband very low frequency (VLF, 3--30 kHz) and extremely low frequency (ELF, 3--3000 Hz) electromagnetic waves generated by lightning discharges and propagating in the Earth-ionosphere waveguide can be used to measure the average electron density profile of the lower ionosphere (<italic>D</italic> region) across the wave propagation path due to several reflections by the upper boundary (lower ionosphere) of the waveguide. This capability makes it possible to frequently and even continuously monitor the <italic>D</italic> region electron density profile variations over geographically large regions, which are measurements that are essentially impossible by other means. These guided waves, usually called atmospherics (or sferics for short), are recorded by our sensors located near Duke University. The purpose of this work is to develop and implement algorithms to derive the variations of <italic>D</italic> region electron density profile which is modeled by two parameters (one is height and another is sharpness), by comparing the recorded sferic spectra to a series of model simulated sferic spectra from using a finite difference time domain (FDTD) code.</p><p>In order to understand the time scales, magnitudes and sources for the midlatitude nighttime <italic>D</italic> region variations, we analyzed the sferic data of July and August 2005, and extracted both the height and sharpness of the <italic>D</italic> region electron density profile. The heights show large temporal variations of several kilometers on some nights and the relatively stable behavior on others. Statistical calculations indicate that the hourly average heights during the two months range between 82.0 km and 87.2 km with a mean value of 84.9 km and a standard deviation of 1.1 km. We also observed spatial variations of height as large as 2.0 km over 5 degrees latitudes on some nights, and no spatial variation on others. In addition, the measured height variations exhibited close correlations with local lightning occurrence rate on some nights but no correlation with local lightning or displaced lightning on others. The nighttime profile sharpness during 2.5 hours in two different nights was calculated, and the results were compared to the equivalent sharpness derived from International Reference Ionosphere (IRI) models. Both the absolute values and variation trends in IRI models are different from those in broadband measurements.</p><p>Based on sferic data similar to those for nighttime, we also measured the daytime <italic>D</italic> region electron density profile variations in July and August 2005 near Duke University. As expected, the solar radiation is the dominant but not the only determinant source for the daytime <italic>D</italic> region profile height temporal variations. The observed quiet time heights showed close correlations with solar zenith angle changes but unexpected spatial variations not linked to the solar zenith angle were also observed on some days, with 15% of days exhibiting regional differences larger than 0.5 km. During the solar flare, the induced height change was approximately proportional to the logarithm of the X-ray fluxes. During the rising and decaying phases of the solar flare, the height changes correlated more consistently with the short (wavelength 0.5-4 &Aring), rather than the long (wavelength 1-8 &Aring) X-ray flux changes. The daytime profile sharpness during morning, noontime and afternoon periods in three different days and for the solar zenith angle range 20 to 75 degrees was calculated. These broadband measured results were compared to narrowband VLF measurements, IRI models and Faraday rotation base IRI models (called FIRI). The estimated sharpness from all these sources was more consistent when the solar zenith angle was small than when it was large.</p><p>By applying the nighttime and daytime measurement techniques, we also derived the <italic>D</italic> region variations during sunrise and sunset periods. The measurements showed that both the electron density profile height and sharpness decrease during the sunrise period while increase during the sunset period.</p> / Dissertation

Guided missiles are among the most effective threats against air platforms. Aircraft and helicopter losses in the last decades were mostly due to guided missiles, 70% of which were infrared guided missiles. Today, there are as many as 500,000 shoulder-fired missiles in military arsenals around the world, whose guidance algorithms enable them to track the desired trajectories very precisely. In this thesis, main focus is on defining infrared missile guidance and control algorithms in order to study on various target-missile scenarios for the effectiveness of these algorithms. First, a mathematical model of a generic missile is given. Then the flight control system of the missile is created by using LQR and PID controllers. Different kinds of PNG algorithms applied to an infrared missile are presented. The seeker part of the infrared missile is also discussed. The effectiveness of guidance algorithms are studied based on different target &ndash / missile scenarios and the responses of them to IR countermeasures are also observed. This study shows that different guidance algorithms can be used for different scenarios. If suitable algorithms are combined and suitable constants are applied, the guided missile can track the target very precisely. In addition, the seeker part has to be improved with tracking algorithms in order to recognize IR-countermeasures and not to follow them.