ENHANCEMENT OF MARGRAVE DECONVOLUTION AND Q ESTIMATION IN HIGHLY ATTENUATING MEDIA USING THE MODIFIED S-TRANSFORM

We evaluate the performance of the Margrave deconvolution and spectral ratio methods using the Gabor, S-, and modified S transforms in highly attenuating media, where the quality factor changes with depth dramatically. Our results substantiate that the modified S-transform deconvolution is more robust in terms of generating fewer artifacts and providing better estimates of reflectivities than the Gabor transform. The results also show that using the modified S-transform in the spectral ratio method produces better Q estimates than the S-transform and the Fourier transform that is conventionally used in the spectral ratio method. This improvement in the estimates of reflectivities and Q using the modified S-transform is due to the enhancement of the time-frequency decomposition obtained by substituting the frequency in the Gaussian window with a linear frequency function. The coefficients of this linear function control the time frequency localization by expanding the Gaussian window at low frequencies and tightening it at high frequencies, in turn providing a better time-frequency decomposition. We demonstrate the efficiency of the modified S-transform deconvolution and Q estimation through the analysis of both synthetic and field data

Numerical modeling of the prestressing losses in prestressed concrete beams by modal analysis method

In this paper, a numerical modal analysis method is carried out to investigate the effect of cable strain loss on the natural frequencies in prestressed concrete beams. A simply supported concrete beam is modeled using the commercial finite element code ABAQUS. The beam is composed of concrete and prestressing strands. Firstly, a general geometrically nonlinear static analysis is carried out on the beam in order to obtain the camber deflection under different prestressing magnitudes. The obtained equilibrium configuration is then used to perform a linear and nonlinear modal analysis. Thereby, a three dimensional finite element C3D8 is used for the concrete in combination with a damaged plasticity model (CDP) are considered. Whereas, the prestressing strands are modeled with an embedded T2D2 truss element. The obtained results show a good agreement with previous numerical and experimental works in literature. Furthermore, the study showed that the safety of prestressed beams depend mainly on the level of prestressing load

Structural lineament mapping using remote sensing in the aures massif (ne algeria)

The Aures massif is located in the eastern part of the Atlasic Domain and formed by Mesozoic and Cenozoic sedimentary rocks. The main objective of this study is to map the structural lineaments and geologically analyze their different geometric aspects, like orientation and distribution, using remote sensing data. Another important aim is to track the extent of lineaments, understand how they integrate into the regional structure and trace the main tectonic events responsible for the Aures' structuration. Both manual and automatic approaches were employed to achieve the study's objectives. More than twelve thousand lineaments were identified, and grouped into four direction families: NW-SE, NE-SW, E-W, and N-S. Two main factors control the orientation: density and distribution of the lineaments, and topographic and geologic factors. A good correspondence was found between literature and techniques employed in this work regarding structural lineament analysis showing that the Aures lineaments result from the succession of Alpine orogeny tectonic phases. Mainly two phases were responsible on its structuration: the major Atlasic event, which occurred during the Lutetitian stage with NW-SE trending, and the Alpine which happened in late Miocene with N-S compression