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CDI Versus invers?o: aplica??o a dados reais
Huelsen, M?nica Giannoccaro Von;Moraes, Roberto Alexandre Vitória de;
Revista Brasileira de Geofísica , 2008, DOI: 10.1590/S0102-261X2008000300004
Abstract: the aim of this paper is to carry out a comparison between two types of 2d electromagnetic modeled sections normally used on aem data quantitative interpretation especially on those obtained from atdem measurements (atdem). one is obtained from fast modeling of the secondary magnetic flux decay and is the most common quantitative interpretation tool. the other is of more restrict usage and use 1d inversion techniques. in the first case, the technique transforms the atdem responses on a conductivity depth image (cdi) and a glimpse of the subsurface conductivity distribution can be obtained with a fast processing approach. in the second case, the use of a 1d inversion, based on the nlstci computational algorithm (short for nonlinear least-squares inversion of transient soundings for a central induction loop) allows to get a similar result but now relying on a wave equation development. it is a mathematically and computationally complex, and more time consuming technique. the two approaches were applied to airborne geotemtm system real data, collected on a survey at san pedro valley (southeast arizona) in 1997.the available data from this region were made available by the usgs and were used in this quantitative analysis. as such, 2d sections were obtained, and from these, maps were generated. the results from 2d sections - conductivity spatial distribution obtained from cdis and 1d inversions - were volumetrically interpolated (voxels) allowing a 3d representation of the conductivity spatial distribution for the surveyed area.
Imageamento da subsuperfície baseado na condutividade: obten??o de CDIs para o Sistema Geotem
Huelsen, M?nica Giannoccaro Von;Moraes, Roberto Alexandre Vitória de;Carvalho, Thiago Silva de;
Revista Brasileira de Geofísica , 2008, DOI: 10.1590/S0102-261X2008000300010
Abstract: the objective of subsurface imaging is to transform responses measured by atdem methods in an image of the electrical conductivity versus depth (cdi) and with this, to get information on target geometry and conductivity (geoelectrical model). this work presents a methodology to get cdis over the measurement profile (2-d) used subsequently to visualize the geoelectrical model in 3-d, which would help to integrate and to understand the local geology. to accomplish this, a layered geoelectrical model is used (1-d) together with the depth attained by the maximum electrical induced current concept. the conductivity and the layer characterization are based on a simplified modeling algorithm (early and late asymptote approximations). resultant software (sandberg, 1986) was adapted to calculate the depth and to processes geotem data.
Influence of the substrate lattice structure on the formation of Quantum Well States in thin In and Pb films on silicon
J H Dil,B Huelsen,T U Kampen,P Kratzer,K Horn
Physics , 2008, DOI: 10.1088/0953-8984/22/13/135008
Abstract: The substrate lattice structure may have a considerable influence on the formation of quantum well states in a metal overlayer material. Here we study three model systems using angle resolved photoemission and low energy electron diffraction: indium films on Si(111) and indium and lead on Si(100). Data are compared with theoretical predictions based on density functional theory. We find that the interaction between the substrate and the overlayer strongly influences the formation of quantum well states; indium layers only exhibit well defined quantum well states when the layer relaxes from an initial face-centered cubic to the bulk body-centered tetragonal lattice structure. For Pb layers on Si(100) a change in growth orientation inhibits the formations of quantum well states in films thicker than 2 ML.
Seismicity patterns and focal mechanisms in southeastern Brazil
Assump??o, M.;Barbosa, J. R.;Berrocal, J.;Bassini, A. M.;Veloso, J. A. V.;Marza, V. I.;Huelsen, M. G.;Ribotta, L. C.;
Revista Brasileira de Geofísica , 1997, DOI: 10.1590/S0102-261X1997000200002
Abstract: the seismicity of se brazil is studied with a recent deployment of additional temporary digital and analog seismographic stations. regional and local stations have allowed the determination of three new composite focal mechanisms for the earthquake series of betim in 1992/93, formiga in 1993, and the reservoir-induced events of nova ponte in 1995, all in minas gerais state. the focal mechanism data in the southern part of the s?o francisco craton and adjacent brasília fold belt indicate both normal and reverse faulting with a common e-w to ne-sw orientation of the maximum horizontal stress. far from the continental margin, the focal mechanisms are consistent with theoretical estimates of stress directions from finite-element modelings of the forces driving the south american plate. near the serra do mar coastal range, the stress pattern seems more complex. a selection of the earthquake catalog, using threshold magnitudes varying in time to yield a data set with spatially uniform coverage, indicates two main seismic areas: 1) the offshore continental shelf , and 2) the southern part of the brasília fold belt and the s?o francisco craton. the high topography areas of the serra do mar and serra da mantiqueira (in the ribeira fold belt) and the paraná basin are much less seismically active.
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