Joaquim Teixeira de Assis

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Local perturbations around contours strongly disturb the final result of computer vision tasks. It is common to introduce a priori information in the estimation process. Improvement can be achieved via a deformable model such as the snake model. In recent works, the deformable contour is modeled by means of B-spline snakes which allows local control,(More)
This paper analyzes two variants of Principal Component Analysis (PCA) for error-concealment: blockwise PCA and clustered blockwise PCA. Realistic communication channels are not error free. Since the signals transmitted on real-world channels are highly compressed, regardless of cause, the quality of images reconstructed from any corrupted data can be very(More)
In this paper, two simple principal component regression methods for estimating the optical flow between frames of video sequences according to a pel-recursive manner are introduced. These are easy alternatives to dealing with mixtures of motion vectors in addition to the lack of prior information on spatial-temporal statistics (although they are supposed(More)
This in vivo study aimed to evaluate the influence of contact points on the approximal caries detection in primary molars, by comparing the performance of the DIAGNOdent pen and visual-tactile examination after tooth separation to bitewing radiography (BW). A total of 112 children were examined and 33 children were selected. In three periods (a, b, and c),(More)
It is well known that shot-peer&g treatment increases the fatigue resistance of metals. It is considered that this effect is caused by compressive residual stresses arising in the treated surface. Usually the mean value of residual stress is taken into consideration to explain this phenomenon but the real residual stress state must be inhomogeneous due to(More)
In this paper, a fresh procedure to handle image mixtures by means of blind signal separation relying on a combination of second order and higher order statistics techniques are introduced. The problem of blind signal separation is reassigned to the wavelet domain. The key idea behind this method is that the image mixture can be decomposed into the sum of(More)
Microtomographic (µCT) and thin section (TS) images were analyzed and compared regarding porosity and its distribution along the samples. The results show that µCT, although limited by its resolution, shows relevant information about the distribution of porosity and quantification of connected and non-connected pores. TS have no limitations concerning(More)
Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Therefore, relatively small differences in the total proton stopping power given, for example, by the different models provided by GEANT4 can lead to significant disagreements in the final proton energy spectra when integrated along lengthy proton(More)
The paper presents the implementation of a parallel version of FDK (Felkamp, David e Kress) algorithm using graphics processing units. Discussion was briefly some elements the computed tomographic scan and FDK algorithm; and some ideas about GPUs (Graphics Processing Units) and its use in general purpose computing were presented. The paper shows a(More)
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