Produção Científica



Apresentação
29/11/2011

Design of all-pass operators using a genetic algorithm for mixed phase deconvolution
Dorian Caraballo L. CPGG/UFBA and Milton J. Porsani, CPGG/IGEO/UFBA and INCT-GP/CNPQ

SUMMARY
This paper present a new approach for mixed phase deconvolution. We investigate the use of arbitrary subsets of roots, distributed outside of the unit circle, to estimated mixed-phase inverse filter and wavelets. All pass filters are used to change the phase of the minimum phase filter. The influence of numbers of roots and its distributions was studied in order the obtain a optimum inverse mixed-phase filter. The optimization process to obtain the best inverse filter is performed by using a genetic algorithm. We have used the varimax norm as the object function to measure the simplicity of the deconvolved seismic trace. The method was tested using synthetic and real seismic data.
Apresentação
29/11/2011

Numerical integration in the Calculation of the 2.5-D Response of a Very Large Loop
Valdelírio da Silva e Silva, Cícero Régis, Allen Q. Howard Jr.,
Universidade Federal do Pará and National Institute of Science and Technology of Petroleum Geophysics

SUMMARY
This work presents the details of a procedure for the numerical integration of Hankel transforms in the calculation of the electromagnetic fields generated by a large horizontal loop over a 2D earth. The method performs the integration by deforming the integration path into the complex plane and applying Cauchy’s theorem on a modified version of the integrand. The modification is the replacement of the Bessel functions J0 and J1 by the Hankel functions H(1) 0 and H(1) 1 . The integration on a path going up the complex plane allows us to take advantage of the vanishing properties of the Hankel functions, so that we can calculate on very small segments, instead of the infinite line of the original improper integrals. We have applied the method to calculate the fields of very large loops, at distances and depths which are prohibitive for the traditional numerical integration methods.
Apresentação
29/11/2011

Separate P- and SV-wave equations for VTI media
Reynam C. Pestana, CPGG/UFBA and INCT-GP/CNPQ, Bjørn Ursin, Norwegian University of Science and Technology (NTNU) and Paul L. Stoffa, University of Texas at Austin, Institute for Geophysics

SUMMARY
In isotropic media we use the scalar acoustic wave equation to perform reverse time migration (RTM) of the recorded pressure wavefield data. In anisotropic media P- and SV-waves are coupled and the elastic wave equation should be used for RTM. However, an acoustic anisotropic wave equation is often used instead. This results in significant shear wave energy in both modeling and RTM. To avoid this undesired SV-wave energy, we propose a different approach to separate P- and SV-wave components for vertical transversely isotropic (VTI) media. We derive independent pseudo-differential wave equations for each mode. The derived equations for P- and SV-waves are stable and reduce to the isotropic case. The equations presented here can be effectively used to model and migrate seismic data in VTI media where |e −d| is small. The SV-wave equation we develop is now well-posed and triplications in the SV wavefront are removed resulting in stable wave propagation. We show modeling and RTM results using the derived pure P-wave mode in complex VTI media and use the rapid expansion method (REM) to propagate the wavefields in time.
Apresentação
05/09/2011

A experiência nos programas pioneiros de pesquisa e formação de mestres e doutores em geofísica para exploração de petróleo em parceria com a PETROBRAS, o CNPq e a FINEP, na UFBA e na UFPA
Conferência apresentada no 1º Workshop do INCT-GP pelo Prof. Carlos Alberto Dias (PhD - LENEP / UENF).
Apresentação
01/01/2011

Ground-roll attenuation based on SVD filtering
We present a singular value decomposition (SVD) filtering method for attenuation of the ground roll. Before the SVD computation, the normal move-out (NMO) correction is applied to the seismograms, with the purpose of flattening the reflections. SVD is performed on a small number of traces in a sliding window. The output trace is the central trace of the first few eigenimages. These contains mostly horizontally aligned signals, and other noise in the data will be suppressed. The new method preserves the character and frequency content of the horizontal reflections and attenuates all other type of events. We illustrate the method using land seismic data of the Tacutu basin, located in the north-east part of Brazil. The results show that the proposed method is effective and is able to reveal reflections masked by the ground-roll. ©2009 Society of Exploration Geophysicists
Apresentação
12/10/2010

An adaptive local-slope SVD filtering approach to enhance events on seismic sections
We present an adaptive singular value decomposition (SVD) filtering method for enhancement of the spacial coherence of the reflections and for the attenuation of the uncorrelated noise. The SVD filtering is performed on a small number of traces and a small number of samples collected around each data component. The method uses the local slope of the reflections to re-sample the data set surrounding each data component and the SVD filtering is locally applied to compute the filtered data.
Apresentação
09/10/2010

The use of discrete wavelet transform in road loads signals.
ANDRADE, G. S.; DUARTE, A. A.; SCHNITMAN, L.. In: CONGRESSO SAE BRASIL, 2009, São Paulo. Anais do Congresso SAE Brasil 2009, 2009.
Apresentação
09/10/2010

Aplicação de Redes Neurais Artificiais no Reconhecimento de Padrões de Cartas Dinamométricas de Sistemas de Bombeio Mecânico de Petróleo.
BEZERRA, Marco A.D.; BARRETO FILHO, Manoel de A.; SCHNITMAN, L.. In: IX Simpósio Brasileiro de Automação Inteligente, 2009, Brasília. Anais do IX Simpósio Brasileiro de Automação Inteligente, 2009. v. 9.
Apresentação
09/10/2010

Alternative concepts for the high precision bearings in torque standard machines.
BITENCOURT, Antônio Carlos Peixoto; THESKA, R.; Wagner, A.; LEPIKSON, H. A.; WEINGAERTNER, W.. In: 10th Int Conf of the European Society for Precision Engineering & Nanotechnology, 2010, Delft. Proceedings of 10th Int Conf of the European Society for Precision Engineering & Nanotechnology. Cranfield, England : Euspen - European Society for Precision Engineering & Nanotechnology, 2010. v. 1. p. 474-477.
Apresentação
09/10/2010

UM SISTEMA CAM PARÁ MÁQUINAS DE PROTOTIPAGEM RÁPIDA DE BAIXO CUSTO.
MARTINS, S.R.M.; LEPIKSON, H. A.; COSTA, B.L.S.. In: VI CONEM - Congresso Nacional de Engenharia Mecânica, 2010, Campina Grande, PB. Anais do VI CONEM - Congresso Nacional de Engenharia Mecânica. Rio de Janeiro, RJ : ABCM - Associação Brasileira de Ciências e Engenharia Mecânica, 2010. v. 1. p. 1-9.
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