Artigos Científicos - FAEST/ICEN

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4054

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Acesso aberto (Open Access)
O emprego da geoestatística na determinação do tamanho "ótimo" de amostras aleatórias com vistas à obtenção de estimativas dos volumes dos fustes de espécies florestais em Paragominas, estado do Pará
(Instituto Nacional de Pesquisas da Amazônia, 2011) SANTOS, Paulo Cerqueira dos; SANTANA, Antônio Cordeiro de; BARROS, Paulo Luiz Contente de; QUEIROZ, Joaquim Carlos Barbosa; VIEIRA, Tiago de Oliveira
The objective of this study was to determine the appropriate size sample to estimate the stem volumes stems of tree species from a population of trees to be cut in the forest management system of the timber company Cikel Brasil Verde Madeiras – Pará State, Brazil. The methodologies of systematic sampling and geostatistical kriging with sequential simulation were used, respectively, for the choice of samples and estimation of stem volumes of trees. The results showed that the methods can be used to calculate the stem volumes of trees. However, the kriging method has a smoothing effect, which resulted in an underestimation of the volumes. In such case, a correction factor was applied to minimize the effect of smoothing. The sequential simulation indicative presented more accurate results compared to kriging, since this method has certain advantages over kriging, such as not requiring samples with normal distributions and no smoothing effect characteristic of the interpolation methods.
Acesso aberto (Open Access)
Estimação volumétrica de resíduos lenhosos de madeira em uma floresta tropical através da Krigagem Ordinária, Paragominas, Estado do Pará
(2014-12) SANTOS, Paulo Cerqueira dos; SANTANA, Antônio Cordeiro de; QUEIROZ, Joaquim Carlos Barbosa; BARROS, Paulo Luiz Contente de; SANTANA, Ádamo Lima de
The objective of this paper was to test the application of geo-statistical models to estimate the volume of wood timber residues in a forest area managed in Paragominas, state of Pará. The Warren and Olsen's and Ordinary Kriging methods were used to estimate the volume of forest residues in sampled and not sampled points. The results confirm that the applied methods were appropriate, given that the estimates for the volume of wood timber residues, in the area of study, showed a small difference of 5.2%, when compared to the actual value obtained.
Acesso aberto (Open Access)
Evaluation via multivariate techniques of scale factor variability in the rietveld method applied to quantitative phase analysis with X ray powder diffraction
(2006-12) OLIVEIRA, Terezinha Ferreira de; AVILLEZ, Roberto Ribeiro de; EPPRECHT, Eugenio Kahn; QUEIROZ, Joaquim Carlos Barbosa
The present work uses multivariate statistical analysis as a form of establishing the main sources of error in the Quantitative Phase Analysis (QPA) using the Rietveld method. The quantitative determination of crystalline phases using x ray powder diffraction is a complex measurement process whose results are influenced by several factors. Ternary mixtures of Al2O3, MgO and NiO were prepared under controlled conditions and the diffractions were obtained using the Bragg-Brentano geometric arrangement. It was possible to establish four sources of critical variations: the experimental absorption and the scale factor of NiO, which is the phase with the greatest linear absorption coefficient of the ternary mixture; the instrumental characteristics represented by mechanical errors of the goniometer and sample displacement; the other two phases (Al2O3 and MgO); and the temperature and relative humidity of the air in the laboratory. The error sources excessively impair the QPA with the Rietveld method. Therefore it becomes necessary to control them during the measurement procedure.

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Navegando Artigos Científicos - FAEST/ICEN por Autor "QUEIROZ, Joaquim Carlos Barbosa"