Departamento de Física
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/785
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2 resultados
Resultados da Pesquisa
- Portable X-ray fluorescence system to measure Th and U concentrations(2018) Guazzelli da Silveira M.A.; Pereira B.R.; Medina N.H.; Rizzutto M.A.© 2018 Elsevier LtdThis study reports the results obtained in the analysis of waste material samples generated by the industries of phosphate fertilizers, in particular, the use of specific filters in a portable X-ray fluorescence system, a simple equipment allowing the characterization, identification and quantification of low concentrations of Th and U (ppm). The industrial byproduct is classified as a Technologically-Enhanced, Naturally-Occurring Radioactive Material - TENORM, and therefore requires monitoring for its radio-toxic activity due to the presence of radioactive thorium and uranium families. From the results obtained, it is concluded that this technique is able to determine the contents of these elements to concentrations of tens of ppm in measurements of about 300 s, and a small sample amount (∼0.1 g).
- Dynamic distribution of potassium in sugarcane(2013) Medina N.H.; Branco M.L.T.; Silveira M.A.G.D.; Santos R.B.B.In this work the distribution of potassium in sugarcane has been studied during its growth. The soil was prepared with natural fertilizers prepared with sugarcane bagasse. For the measurement of potassium concentration in each part of the plant, gamma-ray spectrometry was used to measure gamma-rays emitted from the radioisotope 40K. The concentrations of potassium in roots, stems and leaves were measured every two to three months beginning about five months after planting the sugarcane. The results show a higher concentration of potassium at the beginning of plant development and over time, there is an oscillatory behavior in this concentration in each part of the plant, reaching a lower concentration in the adult plant. To describe the evolution of potassium distribution in sugarcane we proposed a phenomenological model assuming that the potassium incorporation rate is proportional to the difference between the element concentration in the plant and a very long term equilibrium value and it is coupled to a resource-limited growth model. The proposed model succeeded in interpreting the results for the potassium distribution in stems and leaves during the sugarcane growth. © 2013 Elsevier Ltd.