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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.
1

Uso da energia radiativa do fogo para estimativa do coeficiente de consumo de biomassa por queima de vegetação campestre

Costa, Bibiana Salvador Cabral da January 2012 (has links)
No Rio Grande do Sul (RS), a prática de queimadas está relacionada principalmente com a renovação do pasto e agricultura. Embora o RS não seja o Estado com maior incidência de queimadas no Brasil, centenas de focos são identificados por dados de satélites anualmente. O uso de dados de sensores remotos para identificar focos de queimadas vem sendo utilizado há décadas, com o desenvolvimento de novos algoritmos. Uma técnica que vem sendo utilizada consiste na obtenção da Potência Radiativa do Fogo (PRF), a partir de dados de sensores remotos. A PRF é uma medida da energia radiante liberada no processo de queima de biomassa. Estudos demonstram que a PRF possui uma relação linear positiva com a biomassa em processo de combustão, permitindo gerar valores de coeficientes de consumo de biomassa. O conhecimento dos valores destes coeficientes pode determinar o total de biomassa queimada quando multiplicados pela PRF obtida por sensores remotos, no momento da passagem do satélite, em tempo quase real. A determinação dos coeficientes de consumo, por sua vez, depende da tipologia vegetal submetida à queima. Devido à pequena quantidade de dados sobre as queimadas no RS, o objetivo deste trabalho consiste em estimar o coeficiente de consumo de biomassa por queima de vegetação campestre no RS, através da utilização da Potência Radiativa do Fogo (PRF), obtida a partir de dados do sensor MODIS e dados de campo de biomassa. A área de estudo escolhida foi o município de André da Rocha, por possuir focos de queimadas identificados pelo MODIS (pelo produto MYD14 - Thermal Anomalies/Fire products), e dados sobre a quantidade de biomassa em áreas frequentemente queimadas. Também foram obtidos dados de experimentos in situ do comportamento do fogo em área campestre no RS. Foi identificada e quantificada a área queimada, a partir do uso de uma cena do satélite Landsat. A obtenção de dados de experimentos de campo e da cicatriz da área queimada permitiu a obtenção da taxa média de consumo de biomassa e a obtenção dos valores de PRF pelo produto MYD14 permitiu obter o valor da PRF média na área de estudo. Pela relação linear existente entre esses dois parâmetros, foi obtido o coeficiente médio de consumo de biomassa. O valor do coeficiente de consumo foi de 0,24 kg/MJ, resultado esse próximo do encontrado por outros autores. A metodologia utilizada neste trabalho difere da metodologia utilizada em trabalhos anteriores para a obtenção do coeficiente de consumo de biomassa. De qualquer maneira, o dado obtido é uma estimativa preliminar para novos estudos e experimentos em campo. / In Rio Grande do Sul (RS), the practice of burning is mainly related to the renewal of pasture and agriculture. Although the RS is not the state with the highest incidence of fires in Brazil, hundreds of fire focuses are identified by satellite data annually. The use of remote sensing data to identify burning areas has been used for decades with the development of new algorithms. One technique that has been used consists in obtaining the Fire Radiative Power (FRP) from remote sensing data. The FRP is a measure of the radiant energy released in the process of burning biomass. Studies have shown that the FRP has a positive linear relationship with the biomass in the combustion process, allowing to generate coefficient values biomass consumption.The knowledge of the values of these coefficients can determine the total biomass burned when multiplied by FRP obtained by remote sensors at the time of passage of the satellite, in near real time. The determination of the coefficients of consumption, in turn, depends on the type of plant subject to burning. Due to the small amount of data on fires in the RS, the objective of this study is to estimate the coefficient of biomass consumption by burning Campos grassland in RS, by using the FRP obtained from MODIS (from the product MYD14 - Thermal Anomalies / Fire products) and field biomass data. The chosen study area was André da Rocha, for having fires focus identified by MODIS and data from biomass often burned. Experiment data in situ of the fire behavior in campos grassland in RS were also been obtained. The scar burned area was identified and quantified from the use of a Landsat scene. Data of the field and the burned scar area allowed to obtain the average rate of consumption of biomass, and FRP values from MODIS allowed to obtain the average value of the FRP in the study area. The coefficient value was calculated from the linear relationship between these two parameters. The coefficient of consumption obtained was 0.24 kg/MJ, a result close to that found by other authors. The methodology used in this study differs from the method used in previous studies. Anyway the data is a preliminary estimate for new studies and field experiments.
2

Uso da energia radiativa do fogo para estimativa do coeficiente de consumo de biomassa por queima de vegetação campestre

Costa, Bibiana Salvador Cabral da January 2012 (has links)
No Rio Grande do Sul (RS), a prática de queimadas está relacionada principalmente com a renovação do pasto e agricultura. Embora o RS não seja o Estado com maior incidência de queimadas no Brasil, centenas de focos são identificados por dados de satélites anualmente. O uso de dados de sensores remotos para identificar focos de queimadas vem sendo utilizado há décadas, com o desenvolvimento de novos algoritmos. Uma técnica que vem sendo utilizada consiste na obtenção da Potência Radiativa do Fogo (PRF), a partir de dados de sensores remotos. A PRF é uma medida da energia radiante liberada no processo de queima de biomassa. Estudos demonstram que a PRF possui uma relação linear positiva com a biomassa em processo de combustão, permitindo gerar valores de coeficientes de consumo de biomassa. O conhecimento dos valores destes coeficientes pode determinar o total de biomassa queimada quando multiplicados pela PRF obtida por sensores remotos, no momento da passagem do satélite, em tempo quase real. A determinação dos coeficientes de consumo, por sua vez, depende da tipologia vegetal submetida à queima. Devido à pequena quantidade de dados sobre as queimadas no RS, o objetivo deste trabalho consiste em estimar o coeficiente de consumo de biomassa por queima de vegetação campestre no RS, através da utilização da Potência Radiativa do Fogo (PRF), obtida a partir de dados do sensor MODIS e dados de campo de biomassa. A área de estudo escolhida foi o município de André da Rocha, por possuir focos de queimadas identificados pelo MODIS (pelo produto MYD14 - Thermal Anomalies/Fire products), e dados sobre a quantidade de biomassa em áreas frequentemente queimadas. Também foram obtidos dados de experimentos in situ do comportamento do fogo em área campestre no RS. Foi identificada e quantificada a área queimada, a partir do uso de uma cena do satélite Landsat. A obtenção de dados de experimentos de campo e da cicatriz da área queimada permitiu a obtenção da taxa média de consumo de biomassa e a obtenção dos valores de PRF pelo produto MYD14 permitiu obter o valor da PRF média na área de estudo. Pela relação linear existente entre esses dois parâmetros, foi obtido o coeficiente médio de consumo de biomassa. O valor do coeficiente de consumo foi de 0,24 kg/MJ, resultado esse próximo do encontrado por outros autores. A metodologia utilizada neste trabalho difere da metodologia utilizada em trabalhos anteriores para a obtenção do coeficiente de consumo de biomassa. De qualquer maneira, o dado obtido é uma estimativa preliminar para novos estudos e experimentos em campo. / In Rio Grande do Sul (RS), the practice of burning is mainly related to the renewal of pasture and agriculture. Although the RS is not the state with the highest incidence of fires in Brazil, hundreds of fire focuses are identified by satellite data annually. The use of remote sensing data to identify burning areas has been used for decades with the development of new algorithms. One technique that has been used consists in obtaining the Fire Radiative Power (FRP) from remote sensing data. The FRP is a measure of the radiant energy released in the process of burning biomass. Studies have shown that the FRP has a positive linear relationship with the biomass in the combustion process, allowing to generate coefficient values biomass consumption.The knowledge of the values of these coefficients can determine the total biomass burned when multiplied by FRP obtained by remote sensors at the time of passage of the satellite, in near real time. The determination of the coefficients of consumption, in turn, depends on the type of plant subject to burning. Due to the small amount of data on fires in the RS, the objective of this study is to estimate the coefficient of biomass consumption by burning Campos grassland in RS, by using the FRP obtained from MODIS (from the product MYD14 - Thermal Anomalies / Fire products) and field biomass data. The chosen study area was André da Rocha, for having fires focus identified by MODIS and data from biomass often burned. Experiment data in situ of the fire behavior in campos grassland in RS were also been obtained. The scar burned area was identified and quantified from the use of a Landsat scene. Data of the field and the burned scar area allowed to obtain the average rate of consumption of biomass, and FRP values from MODIS allowed to obtain the average value of the FRP in the study area. The coefficient value was calculated from the linear relationship between these two parameters. The coefficient of consumption obtained was 0.24 kg/MJ, a result close to that found by other authors. The methodology used in this study differs from the method used in previous studies. Anyway the data is a preliminary estimate for new studies and field experiments.
3

Uso da energia radiativa do fogo para estimativa do coeficiente de consumo de biomassa por queima de vegetação campestre

Costa, Bibiana Salvador Cabral da January 2012 (has links)
No Rio Grande do Sul (RS), a prática de queimadas está relacionada principalmente com a renovação do pasto e agricultura. Embora o RS não seja o Estado com maior incidência de queimadas no Brasil, centenas de focos são identificados por dados de satélites anualmente. O uso de dados de sensores remotos para identificar focos de queimadas vem sendo utilizado há décadas, com o desenvolvimento de novos algoritmos. Uma técnica que vem sendo utilizada consiste na obtenção da Potência Radiativa do Fogo (PRF), a partir de dados de sensores remotos. A PRF é uma medida da energia radiante liberada no processo de queima de biomassa. Estudos demonstram que a PRF possui uma relação linear positiva com a biomassa em processo de combustão, permitindo gerar valores de coeficientes de consumo de biomassa. O conhecimento dos valores destes coeficientes pode determinar o total de biomassa queimada quando multiplicados pela PRF obtida por sensores remotos, no momento da passagem do satélite, em tempo quase real. A determinação dos coeficientes de consumo, por sua vez, depende da tipologia vegetal submetida à queima. Devido à pequena quantidade de dados sobre as queimadas no RS, o objetivo deste trabalho consiste em estimar o coeficiente de consumo de biomassa por queima de vegetação campestre no RS, através da utilização da Potência Radiativa do Fogo (PRF), obtida a partir de dados do sensor MODIS e dados de campo de biomassa. A área de estudo escolhida foi o município de André da Rocha, por possuir focos de queimadas identificados pelo MODIS (pelo produto MYD14 - Thermal Anomalies/Fire products), e dados sobre a quantidade de biomassa em áreas frequentemente queimadas. Também foram obtidos dados de experimentos in situ do comportamento do fogo em área campestre no RS. Foi identificada e quantificada a área queimada, a partir do uso de uma cena do satélite Landsat. A obtenção de dados de experimentos de campo e da cicatriz da área queimada permitiu a obtenção da taxa média de consumo de biomassa e a obtenção dos valores de PRF pelo produto MYD14 permitiu obter o valor da PRF média na área de estudo. Pela relação linear existente entre esses dois parâmetros, foi obtido o coeficiente médio de consumo de biomassa. O valor do coeficiente de consumo foi de 0,24 kg/MJ, resultado esse próximo do encontrado por outros autores. A metodologia utilizada neste trabalho difere da metodologia utilizada em trabalhos anteriores para a obtenção do coeficiente de consumo de biomassa. De qualquer maneira, o dado obtido é uma estimativa preliminar para novos estudos e experimentos em campo. / In Rio Grande do Sul (RS), the practice of burning is mainly related to the renewal of pasture and agriculture. Although the RS is not the state with the highest incidence of fires in Brazil, hundreds of fire focuses are identified by satellite data annually. The use of remote sensing data to identify burning areas has been used for decades with the development of new algorithms. One technique that has been used consists in obtaining the Fire Radiative Power (FRP) from remote sensing data. The FRP is a measure of the radiant energy released in the process of burning biomass. Studies have shown that the FRP has a positive linear relationship with the biomass in the combustion process, allowing to generate coefficient values biomass consumption.The knowledge of the values of these coefficients can determine the total biomass burned when multiplied by FRP obtained by remote sensors at the time of passage of the satellite, in near real time. The determination of the coefficients of consumption, in turn, depends on the type of plant subject to burning. Due to the small amount of data on fires in the RS, the objective of this study is to estimate the coefficient of biomass consumption by burning Campos grassland in RS, by using the FRP obtained from MODIS (from the product MYD14 - Thermal Anomalies / Fire products) and field biomass data. The chosen study area was André da Rocha, for having fires focus identified by MODIS and data from biomass often burned. Experiment data in situ of the fire behavior in campos grassland in RS were also been obtained. The scar burned area was identified and quantified from the use of a Landsat scene. Data of the field and the burned scar area allowed to obtain the average rate of consumption of biomass, and FRP values from MODIS allowed to obtain the average value of the FRP in the study area. The coefficient value was calculated from the linear relationship between these two parameters. The coefficient of consumption obtained was 0.24 kg/MJ, a result close to that found by other authors. The methodology used in this study differs from the method used in previous studies. Anyway the data is a preliminary estimate for new studies and field experiments.
4

Modélisation du bord d'un plasma de fusion en vue d'ITER et validation expérimentale sur JET / Modelling of the edge of a fusion plasma towards ITER and experimental validation on JET

Guillemaut, Christophe 24 October 2013 (has links)
Les conditions pour la fusion DT peuvent-être obtenues dans les tokamaks. Dans ces machines, l'interaction plasma-paroi et l'extraction de puissance sont gérées dans une cavité appelée divertor. Toutefois, les hautes puissances impliquées et les limitations des composants face au plasma (CFP) sont problématiques. Ce domaine fait l'objet de nombreuses recherches dans le contexte de ITER qui doit démontrer 500 MW de puissance fusion durant 400 s. Ces opérations nécessitent sur la réduction des flux de chaleur sur les CFP à un niveau gérable et repose sur le détachement du plasma dans le divertor qui implique la décroissance des flux de particules et de chaleur. Malheureusement, ce processus demeure difficile à modéliser. Le but the ce doctorat est d'utiliser la modélisation d'expériences de JET avec EDGE2D-EIRENE pour faire des progrès dans la compréhension du détachement. Les simulations reproduisent le détachement observé en environnement C comme Be/W. La distribution du rayonnement est reproduite par le code en C mais des écarts subsistent en Be/W. La comparaison entre différents processus de physique atomique montre que les collisions élastiques ion-molécule sont responsables du détachement. Ce processus permet le confinement des neutres dans le divertor ainsi que des pertes de moments significatives à basse température lorsque le plasma est recombinant. La comparaison entre EDGE2D-EIRENE et SOLPS4.3 montre des tendances similaires pour le détachement. Les deux codes suggèrent que tout processus capable d'améliorer le confinement des neutres dans le divertor devrait faciliter la modélisation du détachement. / The conditions required for fusion can be obtained in tokamaks. In most of these machines, the plasma wall-interaction and the exhaust of heating power are handled in a cavity called divertor. However, the high heat flux involved and the limitations of the materials of the plasma facing components (PFC) are problematic. Many researches are done this field in the context of ITER which should demonstrate 500 MW of DT fusion power during ~ 400 s. Such operations could bring the heat flux on the PFC too high to be handled. Its reduction to manageable levels relies on the divertor detachment involving the reduction of the particle and heat fluxes on the PFC. Unfortunately, this phenomenon is still difficult to model. The aim of this PhD is to use the modelling of JET experiments with EDGE2D-EIRENE to make some progress in the understanding of the detachment. The simulations reproduce the observed detachment in C and Be/W environments. The distribution of the radiation is well reproduced by the code for C but with some discrepancies in Be/W. The comparison between different sets of atomic physics processes shows that ion-molecule elastic collisions are responsible for the detachment seen in EDGE2D-EIRENE. This process provides good neutral confinement in the divertor and significant momentum losses at low temperature, when the plasma is recombining. Comparison between EDGE2D-EIRENE and SOLPS4.3 shows similar detachment trends but the importance of the ion-molecule elastic collisions is reduced in SOLPS4.3. Both codes suggest that any process capable of improving the neutral confinement in the divertor should help to improve the modelling of the detachment.
5

Spektroskopische Untersuchungen hochgeladener Krypton-Ionen im Röntgen-Bereich

Fuchs, Tino 23 June 2000 (has links)
Diese Dissertation widmet sich der spektroskopischen Untersuchung verschiedener Aspekte der Strahlungsemis\-sion hochgeladener Krypton-Ionen mit Relevanz für die Fusionsforschung. Die Experimente hierzu erfolgten an der Berliner Elektronenstrahl-Ionenfalle (EBIT). Der erste Teil der Arbeit hat die Messung kanalspezifischer Wirkungsquerschnitte für die dielektronische Rekombination (DR) der KL$n$-Resonanzserie ($n$=2, \ldots, 5) von Helium- bis Kohlenstoff-ähnlichen Kr-Ionen ($\mbox{Kr}^{(34\, \ldots\,30)+}$) zum Inhalt, die relativ zum Wirkungsquerschnitt der nichtresonanten strahlenden Rekombination (RR) bestimmt wurden. Die Anpassung der Anregungskurven durch eine Modellfunktion aus berechneten Resonanzst ärken ermöglichte den Vergleich mit theoretischen DR-Wirkungsquerschnitten. Es zeigt sich, dass Vorhersagen des HULLAC-Atomstrukturcodes für die Resonanz\-st"ar\-ken der Kr-Ionen durch das Experiment innerhalb der Me"sunsicherheiten best"a\-tigt werden. Darüber hinaus wurde auch die Relaxation der einfach angeregten Ionen nach erfolgtem DR-Stabilisierungsübergang analysiert. Die zur Auswertung der DR-Anre\-gungs\-kurven angewandte Technik eröffnet gleichzeitig eine spektroskopische Methode für die Bestimmung der relativen Konzentration hochgeladener Ionen in EBIT. Die Messung der Strahlungskühlungsrate von Krypton, die den zweiten inhaltlichen Schwerpunkt der Dissertation darstellt, wäre ohne diese in situ Diagnostik der Ladungbilanz nicht möglich gewesen. Hier wurde die Ionenfalle so eingestellt, dass sich eine Ladungsverteilung herausbildet, die dem Ionisationsgleichgewicht eines Plasmas bei einer Temperatur von etwa $5\;\mbox{keV}$ entspricht. Die Bestimmung der Strahlungsk"uhlungsrate profitierte von dem Potential einer EBIT, die gefangenen Ionen mit Elektronenenergien aus einem weiten Bereich abzutasten und einzelne Strahlunsprozesse selektiv anzuregen. Die Röntgenemission verschiedener Strahlungskanäle, wie Bremsstrahlung, strahlende Rekombination, dielektronische Rekombination und Linienstrahlung nach direkter Anregung wurde separat erfaßt. Hieraus konnten erstmals kanalspezifische Strahlungskühlungsraten bestimmt werden. Es stellte sich heraus, dass der dominante Beitrag zur Strahlungskühlungsrate durch die direkt angeregte Linienstr ahlung des L-Schalen-Spektrums zustande kommt, die etwa 75\% der gesamten Verlustleistung ausmacht. Beim Vergleich der totalen Strahlungsverlustleistung mit Vorhersagen der Theorie sind Abweichungen festzustellen. Die berechneten Werte sind je nach Modell um einen Faktor 1.5 - 2.0 kleiner als das Ergebnis der Messung. Dieser Unterschied liegt außerhalb der experimentellen Unsicherheit von maximal 30\%. / This thesis deals with the spectroscopic investigation of various aspects of the x-ray emission of highly charged krypton ions with relevance for fusion research. The experiments have been performed at the Berlin electron beam ion trap (EBIT). One part of the work was devoted to the measurement of channel-specific cross sections for dielectronic recombination (DR) via the KL$n$ ($n$=2, \ldots, 5) resonance series of He- to C-like krypton ions ($\mbox{Kr}^{(34\, \ldots\,30)+}$). The DR cross sections were determined relative to the cross section for non-resonant radiative recombination (RR). A fit procedure was used to compare the measured data with theoretical calculations. Predictions of the HULLAC atomic structure code are confirmed within the experimental uncertainties. Additionally, the radiative relaxation mechanism following the stabilizing transition in the DR process was analyzed. The approach used to obtain the DR excitation function opens up a spectroscopic method to determine the relative abundance of the highly charged ions in the trap. This in situ diagnostic of the charge state balance allowed for the measurement of the radiative cooling rates of krypton being the second focus of the thesis. For this purpose EBIT was tuned to a charge state distribution approaching the ionization balance of a plasma at a temperature of about $5\;\mbox{keV}$. EBIT's capability to sample a wide range of electron-beam energies and distinguish between different radiation channels was utilized to determine the cooling rate. The x-ray emission from the various plasma radiation channels, like bremsstrahlung, radiative recombination, dielectronic recombination, and line radiation following electron-impact excitation was analyzed. For the first time, channel-specific cooling rates could be obtained from these data. It was found, that the dominant contribution to the cooling rate is made up by the directly excited x-rays of the L-shell spectra of krypton, producing more than 75\% of the total radiation loss. A difference with theoretical calculations is noted for the total cooling rate. The predicted values are lower by a factor of 1.5 - 2.0, depending on the theoretical model. This discrepancy is clearly beyond the experimental uncertainty of 30\% at maximum.

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