997 resultados para Potencial gravitacional
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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En esta edición del Boletín se destacan partes de la investigación recientemente realizada por la Unidad de Transporte de la CEPAL para el Instituto para la Integración de América Latina (INTAL) titulada Integración Física Mercosur- Bolivia-Chile-Perú: La contribución potencial de los Ferrocarriles. En una de las conclusiones se hace hincapié a la necesidad de, previo a la construcción de proyectos significativos, existir acuerdos firmados entre las empresas ferroviarias y otras involucradas, referente a la repartición de fletes, derechos por el uso de las vías, y otros factores de los cuales dependerá la operación de los ferrocarriles cuya construcción se contempla.
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En la presente edición del Boletín FAL, se resume un análisis llevado a cabo por la CEPAL, sobre las posibilidades de un mayor intercambio por ferrocarril entre Brasil y los demás países del MercoSur ampliado, y con Asia a través de esos países.En la actualidad, ese intercambio se sitúa en niveles muy bajos, excepto en el caso del comercio con Bolivia. Sin embargo, especialmente si se lograra concretar algunos proyectos que fomentan una mayor integración de la red ferroviaria del Cono Sur, ninguno de los cuales exigiría inversiones muy elevadas, las perspectivas serían buenas en el mediano y largo plazo de aumentar sustancialmente el intercambio comercial por ferrocarril en la Región.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Agronomia (Proteção de Plantas) - FCA
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Pós-graduação em Agronomia (Proteção de Plantas) - FCA
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Pós-graduação em Psicologia - FCLAS
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Este número del Boletín FAL presenta una breve historia del canal, de su construcción y de los impactos sociales y políticos en el país, dentro del contexto del comercio internacional de la época. Se hace además una breve reseña sobre la recuperación del Canal por la República de Panamá y los principales hechos posteriores, incluyendo la decisión y el inicio de la ampliación.
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The objective of this study was to evaluate the potential of near infrared spectroscopy (NIRS) associated with multivariate statistics to distinguish coal produced from wood of planted and native forests. Timber forest species from the C errado (Cedrela sp., Aspidosperma sp., Jacaranda sp. and unknown species) and Eucalyptus clones from forestry companies (Vallourec and Cenibra) were carbonized in the final temperatures of 300, 500 and 700°C. In each heat treatment were carbonized 15 specimens of each vegetal material totaling 270 samples (3 treatments x 15 reps x 6 materials) produced in 18 carbonization (3 treatments x 6 materials). The acquisition of the spectra of coals in the near infrared using a spectrometer was performed. Principal Component Analysis (PCA) and Partial Least Squares Regression (PLS-R) were carried out in the spectra. NIR Spectroscopy associated with PCA was not able to differentiate charcoals produced from native and planted woods when utilizing all carbonized samples at different temperatures in the same analysis; The PCA of all charcoals was able to distinguish the samples depending on temperature in which they were carbonized. However, the separation of native and planted charcoal was possible when the samples were analyzed separately by final temperature. The prediction of native or planted classes by PLS-R presented better performance for samples carbonized at 300°C followed by those at 500°C, 700°C and for all together.
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Phosphate fertilizers are critical for crop production in tropical soils, which are known for having high phosphate-fixing capacity and aluminium saturation, as well as low pH and calcium contents. Fluorine is a component of many phosphate rocks used to make phosphate fertilizers, via a process that generates hexafluorosilicic acid (H2SiF6). While many treatment technologies have been proposed for removal of fluorine in industrial facilities, little attention has been given to a process of neutralizing H2SiF6 with calcium oxide aiming to find out an alternative and sustainable use of a by-product with a great potential for beneficial use in tropical agriculture. This study evaluated the effect of a by-product of phosphoric acid production (fluorite with silicon oxide, hereafter called AgroSiCa) in levels of phosphorus (P), calcium (Ca), silicon (Si), aluminum (Al) and fluorine (F) and some others parameters in soils as on growth of soybean and corn. Experiments were conducted in a greenhouse condition at the Federal University of Lavras (UFLA), Lavras, Minas Gerais, using different types of soils in tropical regions and different doses of AgroSiCa. The application of AgroSiCa resulted in a slight increase in soil pH and significant increases in calcium, phosphorus and silicon in the soil solution and the shoots of corn and soybeans. We also found very low levels of fluoride in all soil leachates. A significant reduction of labile aluminum levels found in all soils after the cultivation of corn and soybeans. In sum, AgroSiCa improved soil properties and contributed to better growth of both cultures. In sum, AgroSiCa improved soil properties and contributed to a better growth of both crops. Our results show that reacting H2SiF6 derived from the wet-process phosphoric acid production with calcium oxide leads to a by-product with potential for agricultural use, especially when applied in highly-weathered soils. Besides providing calcium and silicon to plants, the use of such by-product in soils with high phosphate-fixing capacity and high aluminium saturation delivers additional benefits, since fluoride and silicon can play an important role in improving soil conditions due to the formation of less plant-toxic forms of aluminium, as well as upon decreasing phosphate fixation, thus improving root development and making fertilizer-derived phosphate more available for plant growth.