An advanced simulation code, LEEPS (Low Energy Electron Positron Simulation), has been adapted to simulation of electrons and positrons in liquid water for energies down to 50 eV. Different scattering parameters and results from simulations are compared with existing data in the literature.   Several programs including a subroutine package for simulation of secondary electrons created in binary like collisions have been developed in purpose of charting different characteristics of the energy deposition.   A toy model for DNA damage is presented as an example of how LEEPS possibly can be used for future investigation of cellular damage due to radiation.

No description available.

The objective of the research reported in this thesis was to develop a technique to monitor the dynamics of sediments and nutrients entering the coastal ocean with river plumes associated with high intensity low frequency events (e.g. floods), using ocean colour remote sensing. To achieve this objective, an inverse bio-optical model was developed, based on analytical and empirical relationships between concentrations of optically significant substances and remote sensing of water-leaving radiance. The model determines concentrations of water-colouring substances such as chlorophyll, suspended sediments, and coloured dissolved organic matter, as well as the values of optical parameters using water-leaving radiances derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). To solve atmospheric correction in coastal waters, the aerosol type over clear waters is transferred to adjacent turbid water pixels. The vicinity of the Herbert River, central Great Barrier Reef zone, Australia, was used as a case study for the application of the algorithm developed. The satellite ocean colour technique was successfully validated using sea-truth measurements of water-colouring constituents acquired in the area during various seasons throughout 2002-2004. A high correlation between chlorophyll and dissolved organic matter was found in the coastal waters of the region, and when the bio-optical model was constrained to make chlorophyll a function of dissolved organic matter, the relationship between in situ and satellite-derived data was substantially improved. With reliable retrieval of the major water-colouring constituents, the technique was subsequently applied to study fluxes of particulate and dissolved organic and inorganic matter following a flood event in the Herbert River during the austral summer of 1999. Extensive field observations covering a seasonal flood in the Herbert River in February 2004 revealed high sediment and nutrient exports from the river to the adjacent coastal waters during the flood event. Due to rapid settling, the bulk of the sediment-rich influx was deposited close inshore, while the majority of nutrients exported from the river were consumed by phytoplankton in a relatively small area of the coastal ocean. With the help of ocean colour remote sensing, it was demonstrated that river-borne sediments and nutrients discharged by a typical flood in the Herbert River are mostly precipitated or consumed within the first 20 km from the coast and therefore are unlikely to reach and possibly affect the midshelf coral reefs of this section of the Great Barrier Reef lagoon.

The objective of the research reported in this thesis was to develop a technique to monitor the dynamics of sediments and nutrients entering the coastal ocean with river plumes associated with high intensity low frequency events (e.g. floods), using ocean colour remote sensing. To achieve this objective, an inverse bio-optical model was developed, based on analytical and empirical relationships between concentrations of optically significant substances and remote sensing of water-leaving radiance. The model determines concentrations of water-colouring substances such as chlorophyll, suspended sediments, and coloured dissolved organic matter, as well as the values of optical parameters using water-leaving radiances derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). To solve atmospheric correction in coastal waters, the aerosol type over clear waters is transferred to adjacent turbid water pixels. The vicinity of the Herbert River, central Great Barrier Reef zone, Australia, was used as a case study for the application of the algorithm developed. The satellite ocean colour technique was successfully validated using sea-truth measurements of water-colouring constituents acquired in the area during various seasons throughout 2002-2004. A high correlation between chlorophyll and dissolved organic matter was found in the coastal waters of the region, and when the bio-optical model was constrained to make chlorophyll a function of dissolved organic matter, the relationship between in situ and satellite-derived data was substantially improved. With reliable retrieval of the major water-colouring constituents, the technique was subsequently applied to study fluxes of particulate and dissolved organic and inorganic matter following a flood event in the Herbert River during the austral summer of 1999. Extensive field observations covering a seasonal flood in the Herbert River in February 2004 revealed high sediment and nutrient exports from the river to the adjacent coastal waters during the flood event. Due to rapid settling, the bulk of the sediment-rich influx was deposited close inshore, while the majority of nutrients exported from the river were consumed by phytoplankton in a relatively small area of the coastal ocean. With the help of ocean colour remote sensing, it was demonstrated that river-borne sediments and nutrients discharged by a typical flood in the Herbert River are mostly precipitated or consumed within the first 20 km from the coast and therefore are unlikely to reach and possibly affect the midshelf coral reefs of this section of the Great Barrier Reef lagoon.

Recent advancements in the development of high-efficiency multijunction solar cells have led to a renewed interest in the design and implementation of high concentration photovoltaic systems. With the emergence of novel materials and design structures, understanding the operation of multijunction solar cells has become a challenging task. Modeling and simulation hence play an important role in the analysis of such devices. In this dissertation, techniques for accurate optoelectrical modeling of concentrating photovoltaic systems, based on multijunction solar cells, are proposed. A 2-dimensional, distributed circuit model is proposed, parametrized to values obtained by numerical modeling of three multijunction cell designs, namely: a three-junction, lattice matched design, a three-junction lattice-mismatched, inverted metamorphic design, and a four-junction,lattice matched design. Cell performance for all the three designs is evaluated under both uniform and nonuniform illumination profiles at high concentrations and efficiency enhancement by optimizing finger spacing is proposed. The effect of luminescent coupling from higher bandgap subcells is also determined.Fresnel-lens based, refractive concentrating optical systems are modeled and optimized using an optical ray-tracing simulator at two different concentrations, with and without a secondary optical element. The corresponding optical efficiency, acceptance angle, and the degree of nonuniformity are determined for each optical system. An integrated approach,combining optical design with electrical modeling is proposed for optimizing the multijunction solar cell in tandem with the corresponding concentrating optics. The approach is validated by on-sun, acceptance angle measurements, using a three-junction,lattice-matched cell. Also, temperature effects are modeled and are experimentally validated for a three-junction, lattice-matched design. Experimental results with a single-junction, dilute-nitride cell, targeted for four-junction operation, are presented as well. A modified distributed circuit model is used for analysis of temperature effects in a four-junction solar cell, and the results under both uniform and nonuniform temperature profiles are presented. When implemented, the designs and their corresponding analyses, may result in new insights into the development of CPV systems, thereby enabling enhanced efficiencies at higher concentrations.

Durante a estação seca, é comum se observar um grande número de queimadas ocorrendo no Brasil. A fumaça proveniente da queima intensa é facilmente vista em imagens de satélite, principalmente na região de Cerrado e na Bacia Amazônica, e é responsável pela injeção de uma grande quantidade de partículas na atmosfera. Essas partículas de aerossol irão interagir diretamente com a radiação solar incidente, pelos processos de absorção e espalhamento, o que afetará a irradiância solar global incidente em superfície, a fração entre componente direto e difuso e a distribuição espectral. A modelagem precisa dessa interação ainda requer investigação científica. Nesse contexto, os resultados apresentados neste trabalho buscaram avaliar o desempenho de modelos ópticos para o aerossol de queimadas propostos por Rosário (2011) para a região da Reserva Biológica do Jaru (ou Rebio Jaru), Rondônia, durante a estação seca de 2007. Os modelos ópticos foram separados em intervalos de albedo simples, resultando em três grupos ou regimes: um mais absorvedor, um moderadamente absorvedor e um mais espalhador. Os dados simulados utilizando o código de transferência radiativa SBDART foram comparados com medidas feitas in situ na Rebio Jaru. Os dados foram obtidos entre os dias 24 de agosto e 31 de outubro de 2007. Foram analisados dados medidos por um Multifilter Rotating Shadowband Radiometer (MFRSR - canais de 670, 870 e 1036 nm e da irradiância solar total), por um sensor PAR (irradiância fotossinteticamente ativa) e dados de um pirânometro (irradiância solar total). A irradiância fotossinteticamente ativa compreende o intervalo entre 400 e 700 nm e corresponde à energia solar utilizada na fotossíntese realizada pelas plantas. Ela foi utilizada para avaliar o desempenho dos modelos propostos por Rosário (2011). Para esse intervalo espectral, o modelo óptico mais espalhador é o que melhor representou o período analisado. Estudos de caso foram feitos para avaliar o comportamento dos demais dados para dias com valores distintos da profundidade óptica do aerossol em 550nm. Os resultados obtidos pela análise das medidas feitas pelo MFRSR divergiram com relação ao do sensor PAR e do Piranômetro. As divergências observadas podem estar associadas à degradação instrumental. Sugere-se que sejam realizados estudos mais detalhados levando em consideração o conteúdo integrado de vapor dágua, entre outras variáveis meteorológicas, com a finalidade de definir um método eficiente para determinar o melhor modelo óptico para o aerossol de queimadas e para diferentes regiões da Bacia Amazônica, como efetuado por Rosário (2011) na região de Alta Floresta. / During the dry season biomass burning activities are frequent in Brazil. The smoke from these intense fires can easily be seen with satellite imaging, mostly in the centermost region of Brazil and the Amazon, and it is responsible for the input of large amounts of particles to the atmosphere. These aerosol particles interact directly with the incoming solar radiation, through absorption and scattering processes, which will affect the incoming global solar irradiation reaching the surface, the fraction between the direct and diffuse components and the spectral distribution. The accurate modeling of these interactions requires further scientific investigation. In this context, the present work evaluated the performance of biomass burning aerosol optical models proposed by Rosario (2011) for the southern Amazon, in the Jaru Biological Reserve, Rondônia, during the dry season of 2007. The proposed models were classified according to single scattering albedo intervals, and three distinct groups or regimes were identified: one for more absorbing particles, one for moderately absorbing particles and one for more scattering particles. Simulated data using the Radiative Transfer code SBDART were compared with in situ measurements performed at Rebio Jaru. The data were collected between August 24th and October 31st 2007. Data measured by a Multifilter Shadowband Rotating Radiometer (MFRSR - channels 670, 870 and 1036 nm and the total solar irradiance) from a PAR sensor (photosynthetically active radiation) and from a pyranometer (total solar irradiance) were included in the analysis. Photosynthetically active irradiance spectral interval spans between 400 and 700 nm, and corresponds to the solar energy used on the vegetation photosynthesis. This spectral region was chosen to evaluate the performance of the optical models. For this spectral interval, the more scattering optical model better represented the measured values. Case studies were conducted to evaluate the performance of the radiative transfer code and the optical models on days with distinct values of the aerosol optical depth at 550nm. The results showed that simulations for MFRSR channels diverged from the PAR sensor and the pyranometer. These divergences could be associated to instrumental degradation. It is suggested that further studies be conducted taking into account water vapor content variability, and other meteorological variables, in order to define an efficient method to determine the best optical model for the smoke aerosol and for different regions in the Amazon Basin, as performed by Rosario (2011) for Alta Floresta.

As ferramentas computacionais utilizadas em diferentes áreas de pesquisa têm como vantagem sobre análises e ensaios reais a possibilidade de analisar sistemas em diferentes condições de forma mais ágil e com menor consumo de tempo e recursos. A modelagem óptica de dispositivos fotovoltaicos é bastante difundida. Existem diferentes trabalhos na área, com diferentes escopos e graus de detalhamento, que permitem a análise e melhor compreensão das diferentes etapas da conversão da radiação em energia elétrica, expandindo as possibilidades de otimização. No presente trabalho foi desenvolvida, em uma etapa inicial, uma metodologia computacional para análise óptica de módulos fotovoltaicos, para então, em uma segunda etapa, serem realizados estudos do desempenho de diferentes materiais inseridos no conjunto de camadas que compõe os módulos, através da metodologia. O modelo óptico que embasa o método tem como foco os módulos de silício monocristalino. Esses módulos agregam de três a quatro camadas transparentes sobre as células fotovoltaicas. Ao incidir nesse conjunto de camadas radiação é submetida a diferentes eventos de extinção, como função do comprimento de onda da radiação e ângulo de incidência, que devem ser previstos em um modelo de forma a obter-se resultados válidos de transmissividade. A metodologia propõe a realização de uma análise aprofundada dos fenômenos ópticos que ocorrem mediante a incidência de radiação em um módulo fotovoltaico de modo a auxiliar na análise da adequação e desempenho de diferentes materiais ao sistema óptico formado. A otimização da transmissão de radiação em um módulo fotovoltaico tem uma influência direta e significativa sobre a eficiência de tais dispositivos, justificando sua importância. A validação do modelo foi realizada através da literatura, em partes, e apresentou coerência com os resultados de referência. Foram produzidos na segunda etapa estudos de desempenho de materiais ou propriedades isoladamente. No primeiro estudo foram analisados três materiais para aplicação como filme de passivação sobre a célula, sendo eles Si3N4, SiO2, e TiO2; o filme de Si3N4 apresentou o melhor desempenho. O segundo estudo, de avaliação da influência do índice de refração do encapsulante na transmissividade do sistema, demonstrou que a variação desse parâmetro tem muito pouca influência. No terceiro estudo foi analisado o potencial dos materiais PDMS e TiO2 como filmes anti-reflexo sobre vidro. O PDMS gerou melhores resultados de transmissividade. Por fim um estudo de desempenho de um conjunto de materiais frente à mudança do espectro incidente foi realizado. Foi utilizado até então o espectro de referência, que foi então comparado a um espectro médio de um dia de equinócio da cidade de Porto Alegre. O desempenho do sistema foi em torno de 3% inferior em incidência normal. / Computational tools raise the possibility of studying and understanding systems under different conditions in a faster and less resource and time consuming way. The optical modeling of photovoltaic devices is a very developed issue, and paperworks and projects in different scopes e levels of detail were produced, providing a better understanding of the different steps of converting light into electricity, expanding optimization possibilities. For this project a computational methodology was developed, as an initial step, for the optical assessment of the transmission of radiation in photovoltaic modules. In a second step, studies were performed using the method as a tool for analyzing the system formed by the layers covering the cells embedded in modules. The optical model describes monocristalline silicon modules, which are constituted by three to four layers covering the cell. Once it penetrates the set of layers, incident light suffers different extinction phenomena, which are predicted in this model in order to generate valid results. It’s a function of wavelength and incidence angle of the incoming radiation. The model presented aims to deeply analyse and understand the optical phenomena light undergoes through its way from the external environment to the interior of the cell, supporting the process of observing the performance and adequacy of different materials as the referred layers. Optimizing transmission of radiation in a photovoltaic device plays a main role in increasing the efficiency of the energy conversion process, which is why it’s so important. The model was validated by literature in parts, and showed coherence within reference results. Studies were produced in a second step of this work, using the method, concerning optical issues, for the thin film on top of the cell, the refractive index of the encapsulating material, and the optical effect of coating the outer glass surface. In the first study Si3N4, SiO2 and TiO2 were analyzed; the Si3N4 film produced the best results. The second study, concerning encapsulant’s refractive index, demonstrates this parameter has a very weak influence in the system’s transmission. The third one observed the performance of two materials, PDMS and TiO2, as AR coating,. The PDMS film produced a better effect. At last, the best performance set of layers was analyzed under a representative spectral distribution of an equinox day of the city of Porto Alegre, considering so far it was used the standard. The transmission suffered a slight decrease, around 3%.

<p>The reaction cross section gives the probability that a particle will undergo a nonelastic process when passing through a nuclear medium. Therefore reaction cross section data are of importance both for theoretical studies and for applications in such diverse fields as medicine, biology, astrophysics and accelerator-driven transmutation of nuclear waste.</p><p>There exist many data sets with angular distributions of elastic scattering, but very few measurements of the complementary reaction cross section have been performed. The measurement is in principle simple but has in practice proved to be very difficult to perform, and the relatively limited amount of experimental data displays some serious inconsistencies.</p><p>Results from measurements of reaction cross sections are presented for:</p><p>• ³He on ⁹Be, ¹²C, ¹⁶O, ²⁸Si, ⁴⁰Ca, ^58,60Ni, ^{112,116,118,120,124}Sn and ²⁰⁸Pb at 96, 138 and 167 MeV</p><p>• protons on ¹²C, ⁴⁰Ca, ⁹⁰Zr and ²⁰⁸Pb at six energies in the energy range 80-180 MeV, and on </p><p>⁵⁸Ni at 81 MeV. </p><p>Experimental uncertainties were 3-9% for ³He and 1.5-8% for protons.</p><p>The apparatus and the experimental method used for the measurements of reaction cross sections, using a modified attenuation technique, is described. The detection method enables simultaneous measurements of reaction cross sections for five different sizes of the solid angles in steps from 99.0 to 99.8% of the total solid angle. The final results are obtained by extrapolation to the full solid angle.</p><p>Experimental results are compared with predictions from optical model calculations using phenomenological global optical potentials.</p><p>Phenomenological parametrizations of reaction cross sections for scattering of projectiles on targets are presented. The parametrizations show that reaction cross sections are very sensitive to matter distributions at very large radii of both the projectile and the target. For protons the derived relations makes it possible to predict the reaction cross sections on targets for which no experimental data exist.</p>

The reaction cross section gives the probability that a particle will undergo a nonelastic process when passing through a nuclear medium. Therefore reaction cross section data are of importance both for theoretical studies and for applications in such diverse fields as medicine, biology, astrophysics and accelerator-driven transmutation of nuclear waste. There exist many data sets with angular distributions of elastic scattering, but very few measurements of the complementary reaction cross section have been performed. The measurement is in principle simple but has in practice proved to be very difficult to perform, and the relatively limited amount of experimental data displays some serious inconsistencies. Results from measurements of reaction cross sections are presented for: • 3He on 9Be, 12C, 16O, 28Si, 40Ca, 58,60Ni, 112,116,118,120,124Sn and 208Pb at 96, 138 and 167 MeV • protons on 12C, 40Ca, 90Zr and 208Pb at six energies in the energy range 80-180 MeV, and on 58Ni at 81 MeV. Experimental uncertainties were 3-9% for 3He and 1.5-8% for protons. The apparatus and the experimental method used for the measurements of reaction cross sections, using a modified attenuation technique, is described. The detection method enables simultaneous measurements of reaction cross sections for five different sizes of the solid angles in steps from 99.0 to 99.8% of the total solid angle. The final results are obtained by extrapolation to the full solid angle. Experimental results are compared with predictions from optical model calculations using phenomenological global optical potentials. Phenomenological parametrizations of reaction cross sections for scattering of projectiles on targets are presented. The parametrizations show that reaction cross sections are very sensitive to matter distributions at very large radii of both the projectile and the target. For protons the derived relations makes it possible to predict the reaction cross sections on targets for which no experimental data exist.

As ferramentas computacionais utilizadas em diferentes áreas de pesquisa têm como vantagem sobre análises e ensaios reais a possibilidade de analisar sistemas em diferentes condições de forma mais ágil e com menor consumo de tempo e recursos. A modelagem óptica de dispositivos fotovoltaicos é bastante difundida. Existem diferentes trabalhos na área, com diferentes escopos e graus de detalhamento, que permitem a análise e melhor compreensão das diferentes etapas da conversão da radiação em energia elétrica, expandindo as possibilidades de otimização. No presente trabalho foi desenvolvida, em uma etapa inicial, uma metodologia computacional para análise óptica de módulos fotovoltaicos, para então, em uma segunda etapa, serem realizados estudos do desempenho de diferentes materiais inseridos no conjunto de camadas que compõe os módulos, através da metodologia. O modelo óptico que embasa o método tem como foco os módulos de silício monocristalino. Esses módulos agregam de três a quatro camadas transparentes sobre as células fotovoltaicas. Ao incidir nesse conjunto de camadas radiação é submetida a diferentes eventos de extinção, como função do comprimento de onda da radiação e ângulo de incidência, que devem ser previstos em um modelo de forma a obter-se resultados válidos de transmissividade. A metodologia propõe a realização de uma análise aprofundada dos fenômenos ópticos que ocorrem mediante a incidência de radiação em um módulo fotovoltaico de modo a auxiliar na análise da adequação e desempenho de diferentes materiais ao sistema óptico formado. A otimização da transmissão de radiação em um módulo fotovoltaico tem uma influência direta e significativa sobre a eficiência de tais dispositivos, justificando sua importância. A validação do modelo foi realizada através da literatura, em partes, e apresentou coerência com os resultados de referência. Foram produzidos na segunda etapa estudos de desempenho de materiais ou propriedades isoladamente. No primeiro estudo foram analisados três materiais para aplicação como filme de passivação sobre a célula, sendo eles Si3N4, SiO2, e TiO2; o filme de Si3N4 apresentou o melhor desempenho. O segundo estudo, de avaliação da influência do índice de refração do encapsulante na transmissividade do sistema, demonstrou que a variação desse parâmetro tem muito pouca influência. No terceiro estudo foi analisado o potencial dos materiais PDMS e TiO2 como filmes anti-reflexo sobre vidro. O PDMS gerou melhores resultados de transmissividade. Por fim um estudo de desempenho de um conjunto de materiais frente à mudança do espectro incidente foi realizado. Foi utilizado até então o espectro de referência, que foi então comparado a um espectro médio de um dia de equinócio da cidade de Porto Alegre. O desempenho do sistema foi em torno de 3% inferior em incidência normal. / Computational tools raise the possibility of studying and understanding systems under different conditions in a faster and less resource and time consuming way. The optical modeling of photovoltaic devices is a very developed issue, and paperworks and projects in different scopes e levels of detail were produced, providing a better understanding of the different steps of converting light into electricity, expanding optimization possibilities. For this project a computational methodology was developed, as an initial step, for the optical assessment of the transmission of radiation in photovoltaic modules. In a second step, studies were performed using the method as a tool for analyzing the system formed by the layers covering the cells embedded in modules. The optical model describes monocristalline silicon modules, which are constituted by three to four layers covering the cell. Once it penetrates the set of layers, incident light suffers different extinction phenomena, which are predicted in this model in order to generate valid results. It’s a function of wavelength and incidence angle of the incoming radiation. The model presented aims to deeply analyse and understand the optical phenomena light undergoes through its way from the external environment to the interior of the cell, supporting the process of observing the performance and adequacy of different materials as the referred layers. Optimizing transmission of radiation in a photovoltaic device plays a main role in increasing the efficiency of the energy conversion process, which is why it’s so important. The model was validated by literature in parts, and showed coherence within reference results. Studies were produced in a second step of this work, using the method, concerning optical issues, for the thin film on top of the cell, the refractive index of the encapsulating material, and the optical effect of coating the outer glass surface. In the first study Si3N4, SiO2 and TiO2 were analyzed; the Si3N4 film produced the best results. The second study, concerning encapsulant’s refractive index, demonstrates this parameter has a very weak influence in the system’s transmission. The third one observed the performance of two materials, PDMS and TiO2, as AR coating,. The PDMS film produced a better effect. At last, the best performance set of layers was analyzed under a representative spectral distribution of an equinox day of the city of Porto Alegre, considering so far it was used the standard. The transmission suffered a slight decrease, around 3%.