Navegando por Autor "QUEIROZ, Joaquim Carlos Barbosa"

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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)
Estudo de anomalias eletromagnéticas de um condutor tabular vertical sob camadas parcialmente condutiva em multifrequência e multiseparação através de modelamento analógico
(Universidade Federal do Pará, 1986-05-09) QUEIROZ, Joaquim Carlos Barbosa; VERMA, Om Prakash; http://lattes.cnpq.br/2723609019309173
Partially conducting environment surrouding an one body highly affect its electromagnetic response. Conducting host rock, overburden and disseminated sulphide halo, for example, affect the electromagnetic response in different ways depending upon their electrical properties, areal and geometrical relation with the target, and in particular to the EM system used for prospecting. In the thesis, EM anomalies due to vertical tabular conducting bodies under am overburden, obtained through reduced scale models, are analised for different ground EM systems - horizontal coplanar, vertical coplanar and vertical coaxial - in 8 frequencies between 250 Hz to 35 kHz and the coil separation 0,15; 0,20 and 0,25m. Overburden was simulated by horizontally placed thin stainless steel sheet and the main conducting target by thin aluminium shets placed vertically below the former. The dimensions of these sheets were determined according to the modelling conditions for a plane and half-plane. Various geological situations were represented in modelling using the combinations of the three metallic sheets of varying thicknesses and conductivities to simulate the ore body and another three sheets to simulated the overburden. Set of diagrams are plotted using peak-to-peak in phase and quadrature anomalies for analyzing the results. However, another set of diagrams show that the maximum in phase anomaly occurs when the quadrature countpart is zero at relatively low frequencies when the ore-body together with the overburden is studied. On the other hand, the maximum amplitude in quadrature is obtained at relatively high frequencies when the in phase component attains the minimum, almost zero. With this type of analysis, it was to known the band of frequencies, for each of prospecting systems studied, in wich the EM response of the ore body is least affected by the overburden. Highest response was obtained with the horizontal coplanar system and the least with the vertical coplanar coils. An increase in the separation between the transmitter-receiver resulted in dislocating the peaks to lower frequencies. Widest band of frequencies, in wich the EM response of the body is least affected by the overburden, is obtained in case of vertical coaxial system and narrowest for the horizontal coplanar coils. These results helps us in planning the EM prospecting systems by knowing the position and the band with of frequencies to be used along with otimum transmitter-receiver separation such that the EM response remains free from undesired signals, for example those caused by to overburden.
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.
Acesso aberto (Open Access)
Modelagem Hidrológica Estocástica Aplicada ao Rio Tocantins para a Cidade de Marabá-PA
(Universidade Federal do Pará, 2016-03) CÂMARA, Renata Kelen Cardoso; ROCHA, Edson José Paulino da; PROTÁZIO, João Marcelo Brazão; QUEIROZ, Joaquim Carlos Barbosa; RIBEIRO, Wanda Maria do Nascimento; SIQUEIRA, Ionara Santos; LIMA, Aline Maria Meiguins de
Hydrology studies show that it is possible to avoid natural disasters through the proper use of hydrological forecasts. In this work we used the Box-Jenkins Methodology (Time Series Analysis) to model the daily level of the Tocantins river in the city of Maraba - PA, in order to predict floods caused by its regular increase, an event that usually puts the resident population of risk areas in vulnerable situations. For the study, we used the daily levels of data observed in gauged stations of Maraba and Carolina and Conceição do Araguaia National Water Agency (ANA), the period of 01/12/2008 to 31/03/2011. It was evident that the adjusted model was able to capture the dynamics of time series with good prognosis for a period of seven days with a maximum absolute error of 0.08 m and with precision in forecasting over 99%. The forecasting model showed good results and can then be used as support tools for Civil Defense, assisting in the planning and preparation of preventive actions for the city of Maraba.