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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Influência de diferentes condições da ionosfera no posicionamento por ponto com GPS : avaliação na região brasileira /

Matsuoka, Marcelo Tomio. January 2007 (has links)
Orientador: Paulo de Oliveira Camargo / Banca: João Francisco Galera Monico / Banca: Márcio H. O. Aquino / Banca: Inez Staciarini Batista / Banca: Claudio Antonio Brunini / 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. / 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. / Doutor
42

Estudo dos efeitos de explosões solares na região D ionosférica por meio de ondas em VLF

Silva, Adriano Magno Rodrigues da 28 April 2017 (has links)
Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2017-11-13T12:52:27Z No. of bitstreams: 1 PDF - Adriano Magno Rodrigues da Silva.pdf: 16317001 bytes, checksum: 61c5d1367cca18239376cb2cc040dac2 (MD5) / Made available in DSpace on 2017-11-13T12:52:27Z (GMT). No. of bitstreams: 1 PDF - Adriano Magno Rodrigues da Silva.pdf: 16317001 bytes, checksum: 61c5d1367cca18239376cb2cc040dac2 (MD5) Previous issue date: 2017-04-28 / The D Region is the lowest portion of Ionosphere and its formation depends on the solar radiation, mainly of Lyman-α. Because of this, the D Region only exists during the day. A solar flare releases X-Rays, which are able to penetrate into the D Region and increase the ionization level, consequently inducing its lowering. Once the D Region act as a boundary of Earth-Ionosphere Waveguide, any modification produces important variations both in Very Low Frequency (VLF) radio signals amplitude and in phase. For this research was used X- Rays flow measurements obtained from the Geostationary Operational Environmental Satellite and VLF data during the period of March (2011) and July (2012), obtained by South America VLF Network. These chosen VLF signal paths correspond to the NAA Transmitter Station in Cutler, USA, and from two Receptor Stations in South America: ATI Station in Atibaia, Brazil, and the PLO Station at Punta Lobos, Peru. The VLF data allows through alterations, both in signal amplitude and in phase, alongside with X-Rays flows data to identify Ionospheric events caused by solar flares. The results of this study indicate alterations occurred in analyzed signals; this happened because of the D Region lowering caused by ionization, which came from X-Rays released through Solar Flares. One of these analyzed events started at 6:08 p.m. UTC on March 8th, 2011, and peak X-Ray release at 6:28 p.m. UTC. The signal’s amplitude increments on the pre-event state was until 11.43% to the route: NAA–ATI, and until 12.13% to the route: NAA–PLO during the mentioned Solar Flare. / A Região D é a porção mais baixa da Ionosfera e a sua formação depende da Radiação Solar, principalmente a Lyman-α. Por esse motivo, tal região existe apenas durante o dia. Sabe-se que uma explosão solar emite raios X, os quais são capazes de penetrar até a Região D e aumentar o nível de ionização, provocando o seu rebaixamento. Uma vez que a Região D comporta-se como fronteira do Guia de Onda Terra-Ionosfera, qualquer modificação nela produz variações importantes, tanto na amplitude como na fase de sinais de rádio em Very Low Frequency (VLF). Nesta Pesquisa, foram utilizadas medições dos fluxos de raios X, obtidos por meio do Satélite Geostationary Operational Environmental Satellite e dados de VLF correspondentes ao período do mês de março de 2011 e Julho de 2012, obtidos da rede South America VLF Network. Os trajetos dos sinais de VLF escolhidos correspondem à Estação Transmissora NAA em Cutler, nos Estados Unidos da América e duas Estações Receptoras na América do Sul: Estação ATI em Atibaia no Brasil e a Estação PLO em Punta Lobos, no Peru. Os dados de VLF permitem, por meio das alterações, tanto na amplitude como na fase dos sinais, juntamente com os dados de fluxo de raios X, identificar eventos ionosféricos promovidos pelas explosões solares. Os resultados deste estudo indicam que as alterações ocorridas nos sinais analisados aconteceram devido a um rebaixamento da Região D, ocasionado pela ionização advinda da emissão de raios X das Explosões Solares. Um dos eventos analisados ocorreu a partir das 18h08min UT do dia 08/03/2011 e houve por volta das 18h28min UT, o momento de maior emissão de raios X. Os incrementos nas amplitudes dos sinais, relativamente ao estado de pré-evento, foram de até 11,43% para o trajeto entre NAA– ATI e de até 12,13% para o trajeto NAA–PLO durante a Explosão Solar descrita.
43

Effect of stellar flares on the upper atmospheres of HD 189733b and HD 209458b

Chadney, J. M., Koskinen, T. T., Galand, M., Unruh, Y. C., Sanz-Forcada, J. 08 December 2017 (has links)
Stellar flares are a frequent occurrence on young low-mass stars around which many detected exoplanets orbit. Flares are energetic, impulsive events, and their impact on exoplanetary atmospheres needs to be taken into account when interpreting transit observations. We have developed a model to describe the upper atmosphere of extrasolar giant planets (EGPs) orbiting flaring stars. The model simulates thermal escape from the upper atmospheres of close-in EGPs. Ionisation by solar radiation and electron impact is included and photo-chemical and diffusive transport processes are simulated. This model is used to study the effect of stellar flares from the solar-like G star HD 209458 and the young K star HD 189733 on their respective planets, HD 209458b and HD 189733b. The Sun is used as a proxy for HD 209458, and is an element of Eridani, as a proxy for HD 189733. A hypothetical HD 209458b-like planet orbiting the very active M star AU Microscopii is also simulated. We find that the neutral upper atmosphere of EGPs is not significantly affected by typical flares on HD 209458 and HD 189733. Therefore, stellar flares alone would not cause large enough changes in planetary mass loss to explain the variations in HD 189733b transit depth seen in previous studies, although we show that it may be possible that an extreme stellar proton event could result in the required mass loss. Our simulations do however reveal an enhancement in electron number density in the ionosphere of these planets, the peak of which is located in the layer where stellar X-rays are absorbed. Electron densities are found to reach 2.2 to 3.5 times pre-flare levels and enhanced electron densities last from about 3 to 10 h after the onset of the flare, depending on the composition of the ionospheric layer. The strength of the flare and the width of its spectral energy distribution affect the range of altitudes in the ionosphere that see enhancements in ionisation. A large broadband continuum component in the XUV portion of the flaring spectrum in very young flare stars, such as AU Mic, results in a broad range of altitudes a ff ected in planets orbiting this star. Indeed, as well as the X-ray absorption layer, the layer in which EUV photons are absorbed is also strongly enhanced.
44

Avaliação dos desfechos maternos e perinatais em gestantes portadoras de Lúpus Eritematoso Sistêmico

França, Maria Laura Marconi January 2020 (has links)
Orientador: Leandro Gustavo de Oliveira / Resumo: Introdução: O Lúpus Eritematoso Sistêmico (LES) é uma doença sistêmica de caráter autoimune, que acomete mulheres em idade reprodutiva, sendo que a inter-relação entre a doença e a gestação determina importantes desfechos maternos e perinatais. Objetivos: Descrever os desfechos maternos e perinatais em gestações de pacientes portadoras de LES e avaliar o impacto da nefrite lúpica sobre os resultados encontrados. Métodos: Este é um estudo observacional descritivo desenvolvido para avaliar as inter-relações entre gestação e lúpus eritematoso sistêmico em pacientes atendidas na Maternidade do Hospital das Clínicas da Faculdade de Medicina de Botucatu – HCFMB. O período de estudo foi de janeiro de 2010 a agosto de 2019. Resultados: Foram avaliadas 38 gestações em 31 pacientes com LES. A média das idades foi de 27,4 + 6 anos. A média das idades gestacionais ao nascimento foi de 36 + 3 semanas. As principais intercorrências observadas foram: anemia (39,4%), nefrite lúpica (29%) e hipertensão arterial crônica (10,5%). Hidroxicloroquina foi utilizada em 47,4% das gestações. Em 51,4% das pacientes houve necessidade de antecipação do parto e em 13,1% houve piora da função renal. A incidência de pré-eclâmpsia foi de 19,4%. Prematuridade ocorreu em 20% dos casos e restrição de crescimento fetal, em 19,4%. Nefrite lúpica determinou maior ocorrência de flare (p<0,05) e maior necessidade de antecipação do parto (p< 0,05). Conclusão: O presente estudo permitiu avaliar a inter-relação entre L... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Introduction: Systemic Lupus Erythematosus is an autoimmune systemic disease that affects women of reproductive age, and the interrelation between disease and pregnancy determines important maternal and perinatal outcomes. Objectives: To describe maternal and perinatal outcomes in pregnancies of patients with SLE and to evaluate the impact of lupus nephritis on the results found. Methods: Descriptive observational study developed to assess the interrelation between pregnancy and systemic lupus erythematosus in patients attended at the Maternity of the Clinics Hospital from Botucatu Medical School – HCFMB. The study period corresponded to January 2010 until August 2019. Results: Thirty-eight pregnancies were evaluated in 31 patients with SLE. Their average age was 27.4 + 6.0 years. The average gestational age at birth was 36 + 3 weeks. The main clinical complications observed were anemia (39.4%), lupus nephritis (29%) and chronic hypertension (10.5%). In 51,4% of the patients, it was necessary to anticipate delivery and in 13.1%, there was worsening of the renal function. Prematurity occurred in 20% of cases and FGR in 19,4%. Hydroxicloroquine was used in 47,4% of the pregnancies. Lupus nephritis determined a higher occurrence of flare (p<0.05) and a greater need to anticipate delivery (p<0.05). Conclusion: The present study made it possible to relate the main clinical characteristics and the maternal and perinatal outcomes from the pregnant women with SLE treated at the prena... (Complete abstract click electronic access below) / Mestre
45

Physically-based Real-time Glare

Delavennat, Julien January 2021 (has links)
The theme of this master’s thesis is the real-time rendering of glare as seen through human eyes, as a post-processing effect applied to a first-person view in a 3D application. Several techniques already exist, and the basis for this project is a paper from 2009 titled Temporal Glare: Real-Time Dynamic Simulation of the Scattering in the Human Eye, by Ritschel et al. The goal of my project was initially to implement that paper as part of a larger project, but it turned out that there might be some opportunities to build upon aspects of the techniques described in Temporal Glare; in consequence these various opportunities have been explored and constitute the main substance of this project. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>
46

Enhanced flare prediction by advanced feature extraction from solar images : developing automated imaging and machine learning techniques for processing solar images and extracting features from active regions to enable the efficient prediction of solar flares.

Ahmed, Omar W. January 2011 (has links)
Space weather has become an international issue due to the catastrophic impact it can have on modern societies. Solar flares are one of the major solar activities that drive space weather and yet their occurrence is not fully understood. Research is required to yield a better understanding of flare occurrence and enable the development of an accurate flare prediction system, which can warn industries most at risk to take preventative measures to mitigate or avoid the effects of space weather. This thesis introduces novel technologies developed by combining advances in statistical physics, image processing, machine learning, and feature selection algorithms, with advances in solar physics in order to extract valuable knowledge from historical solar data, related to active regions and flares. The aim of this thesis is to achieve the followings: i) The design of a new measurement, inspired by the physical Ising model, to estimate the magnetic complexity in active regions using solar images and an investigation of this measurement in relation to flare occurrence. The proposed name of the measurement is the Ising Magnetic Complexity (IMC). ii) Determination of the flare prediction capability of active region properties generated by the new active region detection system SMART (Solar Monitor Active Region Tracking) to enable the design of a new flare prediction system. iii) Determination of the active region properties that are most related to flare occurrence in order to enhance understanding of the underlying physics behind flare occurrence. The achieved results can be summarised as follows: i) The new active region measurement (IMC) appears to be related to flare occurrence and it has a potential use in predicting flare occurrence and location. ii) Combining machine learning with SMART¿s active region properties has the potential to provide more accurate flare predictions than the current flare prediction systems i.e. ASAP (Automated Solar Activity Prediction). iii) Reduced set of 6 active region properties seems to be the most significant properties related to flare occurrence and they can achieve similar degree of flare prediction accuracy as the full 21 SMART active region properties. The developed technologies and the findings achieved in this thesis will work as a corner stone to enhance the accuracy of flare prediction; develop efficient flare prediction systems; and enhance our understanding of flare occurrence. The algorithms, implementation, results, and future work are explained in this thesis.
47

Astrostatistics: Statistical Analysis of Solar Activity from 1939 to 2008

Yousef, Mohammed A. 10 April 2014 (has links)
No description available.
48

Modelling of Traffic Performance for Swedish Roads and Motorways

Strömgren, Per January 2016 (has links)
This thesis consists of five scientific articles oriented towards capacity. Managing capacity constraints with associated delays is a big issue at new design as well as at trimming existing traffic facilities. In larger Swedish cities these challenges have become more and more important as a result of growing traffic demand due to rapid population increase.Models for estimating capacity and delay are available, but not many are calibrated for Swedish conditions due to the high effort required. This thesis documents development and calibration of new models for motorway links, entry and exit lanes and weaving areas and an developed space-time model with the ability to calculate queue length, delay, etc.The first article is focused on identifying weaknesses in the former Swedish capacity method for motorways, and development of new models overcoming these shortcomings. The development includes new models for jam density at queue, capacity in weaving areas and fundamental flow-density relationships for 15 different highway types for inclusion in the new Swedish capacity manual.The second article describes the development of a Swedish motorway space-time model to estimate travel times and queues in oversaturated conditions based on the American FREEVAL model in Highway Capacity Manual 2010 (HCM 2010). Calibration and validation of the model has been performed with data from the Motorway Control System (MCS) in Stockholm. A good correspondence was obtained for most cases, but further calibration and validation efforts are required for entry and exit lanes.The third article describes further development of the intersection model in the Swedish microscopic model “Rural Traffic Simulator (RuTSim). This is a continuation of the work documented in the author’s licentiate thesis published in 2002. The development focused on simulation of intersections using a new concept on lane use not included in the old RuTSim model. The model describes Swedish rural intersections with flared approaches providing a non-discreet lane use due to vehicle types in queue. New data for calibration and validation data was also generated. The validation results showed good correspondence between simulated and empirical delay results. The new intersection model is now implemented in RuTSim, providing new tools for estimation of capacity, delay and queue length already included in Swedish guidelines and capacity manuals/software (Capcal).The fourth article describes the development of a new capacity model for roadwork zones. Focus is on the resulting capacity of one lane due to several reduction factors. These factors include impacts of closed road shoulders, reduction of number of lanes, diversion of traffic to the opposite carriageway, commuting traffic, length of work zone, lane width and type of road work. The first two correction factors were successfully validated in a full-scale test on the E6 motorway in Gothenburg.The fifth article describes development and implementation of a new harmonization algorithm for MCS systems on motorways designed to increase bottleneck capacity and throughput. Two different models were developed, one of which was implemented in the existing MCS system on E4 Södertäljevägen south of Stockholm. Full-scale trials were carried out with a model based on trigger levels in terms of flow. The second model based on the difference in the variance of speed during two following time periods was tested offline also with very good results. / <p>QC 20160429</p>
49

Enhanced flare prediction by advanced feature extraction from solar images : developing automated imaging and machine learning techniques for processing solar images and extracting features from active regions to enable the efficient prediction of solar flares

Ahmed, Omar Wahab January 2011 (has links)
Space weather has become an international issue due to the catastrophic impact it can have on modern societies. Solar flares are one of the major solar activities that drive space weather and yet their occurrence is not fully understood. Research is required to yield a better understanding of flare occurrence and enable the development of an accurate flare prediction system, which can warn industries most at risk to take preventative measures to mitigate or avoid the effects of space weather. This thesis introduces novel technologies developed by combining advances in statistical physics, image processing, machine learning, and feature selection algorithms, with advances in solar physics in order to extract valuable knowledge from historical solar data, related to active regions and flares. The aim of this thesis is to achieve the followings: i) The design of a new measurement, inspired by the physical Ising model, to estimate the magnetic complexity in active regions using solar images and an investigation of this measurement in relation to flare occurrence. The proposed name of the measurement is the Ising Magnetic Complexity (IMC). ii) Determination of the flare prediction capability of active region properties generated by the new active region detection system SMART (Solar Monitor Active Region Tracking) to enable the design of a new flare prediction system. iii) Determination of the active region properties that are most related to flare occurrence in order to enhance understanding of the underlying physics behind flare occurrence. The achieved results can be summarised as follows: i) The new active region measurement (IMC) appears to be related to flare occurrence and it has a potential use in predicting flare occurrence and location. ii) Combining machine learning with SMART's active region properties has the potential to provide more accurate flare predictions than the current flare prediction systems i.e. ASAP (Automated Solar Activity Prediction). iii) Reduced set of 6 active region properties seems to be the most significant properties related to flare occurrence and they can achieve similar degree of flare prediction accuracy as the full 21 SMART active region properties. The developed technologies and the findings achieved in this thesis will work as a corner stone to enhance the accuracy of flare prediction; develop efficient flare prediction systems; and enhance our understanding of flare occurrence. The algorithms, implementation, results, and future work are explained in this thesis.
50

[en] METROLOGICAL EVALUATION OF THE INFLUENCE OF THE COMPOSITION OF THE NATURAL GAS ON FLOW RATE MEASUREMENTS IN PRESSURE RELIEF FLARE SYSTEMS / [pt] AVALIAÇÃO METROLÓGICA DA INFLUÊNCIA DA COMPOSIÇÃO DO GÁS NATURAL NA MEDIÇÃO DE VAZÃO EM SISTEMAS DE ALÍVIO DE PRESSÃO TIPO TOCHA

FAGNER GEOVANI DE SÁ 25 March 2015 (has links)
[pt] Esta dissertação de mestrado teve por objetivo avaliar a influência da composição do gás natural na medição de vazão pela técnica de ultrassom em sistemas de alívio de pressão tipo tocha. A inclusão da composição do gás na correção da medição da vazão do gás em sistemas de tocha constitui uma exigência legal imposta pelo regulador brasileiro do setor de petróleo, gás natural e biocombustíveis. A histórica dificuldade técnica associada à coleta de amostras de gás em sistemas de tocha e os constantes questionamentos sobre a representatividade das amostras coletadas são as principais motivações para a realização deste estudo. A metodologia utilizada fundamentou-se em pesquisa bibliográfica, documental e de campo. Por meio de pesquisa bibliográfica, documental e normativa realizou-se o embasamento técnico e teórico do estudo. A pesquisa de campo teve por finalidade coletar informações de estações de medição de gás em sistemas de tocha de uma unidade marítima de produção de petróleo e gás. A partir do tratamento das informações coletadas, os resultados da pesquisa permitiram quantificar que o erro máximo na medição de vazão de gás por ultrassom devido ao desconhecimento de sua real composição é 0,04 porcento. Dentre as conclusões, (i) as amostras de gás coletadas em sistemas de tocha não representam de forma adequada o volume de gás medido e (ii) o erro máximo estimado associado à totalização do volume de gás mostrou-se desprezível quando comparado ao volume total de gás documentado nos históricos de medição e aos erros aleatórios aceitáveis para o tipo de estação de medição considerado. / [en] The objective of this dissertation is to evaluate the influence of the composition of the natural gas on the flow rate measurements in pressure relief flare systems. The consideration of the gas composition in the correction of the gas flow rate measurements in the flare system is a legal requirement imposed by the Brazilian regulating agency for oil, natural gas and biofuels. The historical technical difficulties associated with collecting gas samples from flare systems and the constant questions about the representativeness of the collected samples are the main motivations for this study. The methodology used was based on literature, documental and field research. Through literature, documental and normative research was conducted at the technical and theoretical foundation of the study. The field research aimed at collecting information of measurement systems of gas flare in a maritime unit of oil and gas production. From the treatment of collected information, the research results allowed to quantify that the maximum error in the measurement of gas flow rate by ultrasonic meters due to the lack of knowledge of its actual composition is 0.04 percent. Among the conclusions, (i) the collected gas samples in flare systems do not adequately represent the volume of measured gas and (ii) the estimated maximum error associated with the totalization of the gas volume was found to be negligible compared to the documented total volume gas on historical measurements and to acceptable random errors for the type of the considered measurement system.

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