2007
Autores
Berti, E; Cardoso, J; Cardoso, V; Cavaglia, M;
Publicação
PHYSICAL REVIEW D
Abstract
Using recent results from numerical relativity simulations of nonspinning binary black hole mergers, we revisit the problem of detecting ringdown waveforms and of estimating the source parameters, considering both LISA and Earth-based interferometers. We find that Advanced LIGO and EGO could detect intermediate-mass black holes of mass up to similar to 10(3)M(circle dot) out to a luminosity distance of a few Gpc. For typical multipolar energy distributions, we show that the single-mode ringdown templates presently used for ringdown searches in the LIGO data stream can produce a significant event loss (> 10% for all detectors in a large interval of black hole masses) and very large parameter estimation errors on the black hole's mass and spin. We estimate that more than similar to 10(6) templates would be needed for a single-stage multimode search. Therefore, we recommend a "two-stage" search to save on computational costs: single-mode templates can be used for detection, but multimode templates or Prony methods should be used to estimate parameters once a detection has been made. We update estimates of the critical signal-to-noise ratio required to test the hypothesis that two or more modes are present in the signal and to resolve their frequencies, showing that second-generation Earth-based detectors and LISA have the potential to perform no-hair tests.
2007
Autores
Cardoso, MJ; Cardoso, J; Amaral, N; Azevedo, I; Barreau, L; Bernardo, M; Christie, D; Costa, S; Fitzal, F; Fougo, JL; Johansen, J; Macmillan, D; Mano, MP; Regolo, L; Rosa, J; Teixeira, L; Vrieling, C;
Publicação
BREAST
Abstract
Twelve expert observers from nine different countries convened in a workshop to evaluate the validity of the Breast Cancer Conservative Treatment. Cosmetic results (BCCT.core) software, an objective method for the aesthetic evaluation of breast cancer conservative treatment. Experts were initially asked to subjectively classify the aesthetic results of 30 photographed cases submitted to breast cancer conservative treatment according to the four-point Harris scale. It was pre-established that if at least two-thirds [Cardoso MJ, Cardoso J, Santos AC, Barros H, Oliveira MC. Interobserver agreement and consensus over the esthetic evaluation of conservative treatment for breast cancer. Breast 2005] of participants provided the same classification this would be considered a consensual evaluation for that case. For cases where such agreement was not reached, consensus was obtained using a nominal group technique. Experts then individually performed objective evaluation of the same set of photographs using the BCCT.core software. This provides an automatic rating of aesthetic results, once scale and reference points in the photograph have been chosen. Agreement between observers, between each observer and the consensus, for computer evaluation obtained by the different participants and between software and consensus was calculated using multiple kappa (k) and weighted kappa (wk) statistics. In the subjective assessment, first-round consensus was achived in 17 (57%) cases. Overall interobserver agreement was fair to moderate (k = 0.40, wk = 0.57). In the objective assessment there was a higher level of concordance between participants (k = 0.86, wk = 0.90). Agreement between software and consensus classification was fair (k = 0.34, wk = 0.53), but was higher in the 17 cases that reached first-round consensus (k = 0.60, wk = 0.73). Merging the two middle classes of the Harris scale, to form a three-point scale, led to an improvement of all non-weighted measures of agreement. These results show that the BCCT.core software provides consistent evaluation of cosmesis. It has the potential to become a gold standard method for assessment of breast cosmesis in clinical trials, as it can be used simultaneously by a panel of observers from different parts of the world to provide more reliable assessments than has been possible previously.
2007
Autores
Cardoso, JS; Cardoso, MJ;
Publicação
Advances in Soft Computing
Abstract
Cosmetic assessment of breast cancer conservative treatment (BCCT) plays a major role in the evaluation of this form of treatment. Objective assessment methods are being preferred to overcome the drawbacks of subjective evaluation. A recent computer-aided medical system was developed to objectively and automatically perform the aesthetic evaluation of the result of BCCT. In order to extract relevant features from the image, the detection of the breast contour is necessary. In this paper an algorithm based on the shortest path on a graph is proposed to detect the breast contour. The proposed method was applied to 300 breast images with an accuracy of 98%. © 2007 Springer-Verlag Berlin Heidelberg.
2007
Autores
Teixeira, LF; Cardoso, JS; Corte Real, L;
Publicação
Journal of Multimedia
Abstract
The automatic extraction and analysis of visual information is becoming generalised. The first step in this processing chain is usually separating or segmenting the captured visual scene in individual objects. Obtaining a perceptually correct segmentation is however a cumber some task. Moreover, typical applications relying on object segmentation, such as visual surveillance, introduce two additional requirements: (1) it should represent only a small fraction of the total amount of processing time and (2) realtime overall processing. We propose a technique that tackles these problems using a cascade of change detection tests, including noise-induced, illumination variation and structural changes. An objective comparison of common pixelwise modelling methods is first done. A cost-based partition- distance between segmentation masks is introduced and used to evaluate the methods. Both the mixture of Gaussians and the kernel density estimation are used as a base to detect structural changes in the proposed algorithm. Experimental results show that the cascade technique consistently outperforms the base methods, without additional post-processing and without additional processing overheads. © 2007 ACADEMY PUBLISHER.
2007
Autores
Cardoso, JS; Cardoso, JCS; Corte Real, L;
Publicação
2007 IEEE Workshop on Motion and Video Computing, WMVC 2007
Abstract
Automatic spatial video segmentation is a problem without a general solution at the current state-of-the-art. Most of the difficulties arise from the process of capturing images, which remain a very limited sample of the scene they represent. The capture of additional information, in the form of depth data, is a step forward to address this problem. We start by investigating the use of depth data for better image segmentation; a novel segmentation framework is proposed, with depth being mainly used to guide a segmentation algorithm on the colour information. Then, we extend the method to also incorporate motion information in the segmentation process. The effectiveness and simplicity of the proposed method is documented with results on a selected set of images sequences. The achieved quality raises the expectation for a significant improvement on operations relying on spatial video segmentation as a pre-process. ©2007 IEEE.
2007
Autores
Lagrange, M; Martins, LG; Teixeira, LF; Tzanetakis, G;
Publicação
2007 INTERNATIONAL WORKSHOP ON CONTENT-BASED MULTIMEDIA INDEXING, PROCEEDINGS
Abstract
In this paper, we study the use of audio and visual cues to perform speaker segmentation of audiovisual recordings of formal meetings such as interviews, lectures, or courtroom sessions. The sole use of audio cues for such recordings can be ineffective due to low recording quality and high level of background noise. We propose to use additional cues from the video stream by exploiting the relative static locations of speakers among the scene. The experiments show that the combination of those multiple cues helps to identify more robustly the transitions arriong speakers.
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