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Publications

Publications by HumanISE

2004

Accelerated epipolar geometry computation for 3D reconstruction using projective texturing

Authors
Rodrigues, R; Fernandes, AR;

Publication
Proceedings of the 20th Spring Conference on Computer Graphics, SCCG '04, Budmerice, Slovakia, April 22-24, 2004

Abstract
The process of 3D reconstruction, or depth estimation, is a complex one, and many methods often have several parameters that may require fine tunning to adapt to the scene and improve reconstruction results. Usability of these methods is directly related to their response time. Epipolar geometry, a fundamental tool used in 3D reconstruction, is commonly computed on the CPU. We propose to take advantage of the advances of graphic cards, to accelerate this process. Projective texturing will be used to transfer a significant part of the computational load from the CPU into the GPU. The new approach will be illustrated in the context of a previously published work for 3D point reconstruction from a set of static images. Test results show that gains of up to two orders of magnitude in terms of computation times can be achieved, when comparing current CPU's and CPU's. We conclude that this leads to an increase in usability of 3D reconstruction methods. Copyright © 2004 by the Association for Computing Machinery, Inc.

2004

From spatiotemporal curves to reconstructed depth

Authors
Rodrigues, R; Fernandes, A; van Overveld, K; Ernst, F;

Publication
IMAGE AND VISION COMPUTING

Abstract
We present a novel approach for 3D reconstruction based on a set of images taken from a static scene. Our solution is inspired by the spatiotemporal analysis of video sequences. The method is based on a best fitting scheme for spatiotemporal curves that allows us to compute 3D world coordinates of points within the scene. As opposed to a large number of current methods, our technique deals with random camera movements in a transparent way, and even performs better in these cases than with restrained motion such as pure translation. Robustness against occlusion and aliasing is inherent to the method as well.

2004

Methods for the experimental functional assessment of rat sciatic nerve regeneration

Authors
Varejao, ASP; Melo Pinto, P; Meek, MF; Filipe, VA; Bulas Cruz, J;

Publication
NEUROLOGICAL RESEARCH

Abstract
In experimental peripheral nerve studies, the rat sciatic nerve model is widely used to examine functional changes after different surgical repairs or pharmacological treatments, following nerve injury. The number and diversity of tests which have been used to assess functional recovery after experimental interventions often makes it difficult to recommend any particular indicator of nerve regeneration. Functional assessment after sciatic nerve lesion has long been focused on walking track analysis, therefore, this article describes in more detail the method to obtain and measure the walking tracks in order to calculate the sciatic functional index (SFI). However, it is important to note that the validity of the SFI has been questioned by several researchers. In addition, the present review includes other traditional tests described in the experimental peripheral nerve literature regarding the rate of return of motor function and sensation, such as the extensor postural thrust (EPT), nociceptive function, and the gastrocnemius-soleus weight parameters. In the last decade, several authors have designed a series of sensitive quantitative methods to assess the recovery of hind limb locomotor function using computerized rat gait analysis. This study aims to review kinematic measures that can be gathered with this technology, including calculation of sciatic functional index, gait-stance duration, ankle kinematics and toe out angle (TOA). A combination of tests, each examining particular components of recovered sensorimotor function is recommended for an overall assessment of rat sciatic nerve regeneration.

2004

A surrogate indicator of criticality for stochastic project networks

Authors
Tavares, LV; Ferreira, JA; Coelho, JS;

Publication
Int Trans Operational Res - International Transactions in Operational Research

Abstract

2004

Nonlinear sea level trends from European tide gauge records

Authors
Barbosa, SM; Fernandes, MJ; Silva, ME;

Publication
ANNALES GEOPHYSICAE

Abstract
Mean sea level is a variable of considerable interest in meteorological and oceanographic studies, particularly long-term sea level variation and its relation to climate changes. This study concerns the analysis of monthly mean sea level data from tide gauge stations in the Northeast Atlantic with long and continuous records. Much research effort on mean sea level studies has been focused on identifying long-term linear trends, usually estimated through least-squares fitting of a deterministic function. Here, we estimate nonparametric and robust trends using lowess, a robust smoothing procedure based on locally weighted regression. This approach is more flexible than a linear trend to describe the deterministic part of the variation in tide gauge records, which has a complex structure. A common trend pattern of reduced sea levels around 1975 is found in all the analysed records and interpreted as the result of hydrological and atmospheric forcing associated with drought conditions at the tide gauge sites. This feature is overlooked by a linear regression model. Moreover, nonlinear deterministic behaviour in the time series, such as the one identified, introduces a bias in linear trends determined from short and noisy records.

2004

Visual knowledge discovery

Authors
Marcos, AF; Muller, W; Schumann, H;

Publication
COMPUTERS & GRAPHICS-UK

Abstract

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