Ricardo Oliveira

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This paper analyzes the performance of two implementations of J-Flow, the flow measurement tool deployed on most Juniper routers. Our work relies on both controlled experiments and analysis of traces collected at Abilene and GEANT, which provide most of the flow traces used in the research community. We uncover two measurement artifacts in J-Flow traces: a(More)
We propose a solution to the n-frame correspondence problem under the factorization framework. During the matching process, our algorithm takes explicitly into account the geometrical constraints associated to the reconstruction process. To this end, a rank constraint is imposed on the measurement matrix. Since our method relies solely on geometric(More)
The aperture problem is one of the omnipresent issues in computer vision. Its local character constrains point matching to high textured areas, so that points in gradient-oriented regions (such as straight lines) can not be reliably matched. We propose a new method to overcome this problem by devising a global matching strategy under the factorization(More)
We report the inscription of a Bragg grating in an undoped polymethylmethacrylate based microstructured fiber in a time record. The fiber has been irradiated with a 248 nm ultraviolet radiation, through the phase mask technique using low fluence and low repetition rate. The experimental conditions were chosen to modify the core refractive index of the fiber(More)
To investigate species-specific decomposition rates of litter from native (Quercus faginea) and introduced (Eucalyptus globulus) tree species in Portugal, we monitored changes in the phenolic signature of leaf litter during decomposition as mediated by an aquatic, Proasellus coxalis (Isopoda: Asellota), and two terrestrial, Porcellio dispar and Eluma(More)
Spatio-temporal clustering is a sub field of data mining that is increasingly gaining more scientific attention due to the advances of location-based or environmental devices that register position, time and, in some cases, other semantic attributes. This process pretends to group objects based in their spatial and temporal similarity helping to discover(More)
Measuring functional activity in brain in connection with neural stimulation faces technological challenges. Our goal is to evaluate, in relative terms, the real-time variations of local cerebral blood flow in rat brain, with a convenient spatial resolution. The use of laser Doppler flowmetry (LDF) probes is a promising approach but commercially available(More)
Establishing the correct correspondence between features in an image set remains a challenging problem amongst computer vision researchers. In fact, the combinatorial nature of feature matching effectively hinders the solution of large scale problems, which have direct applications in important areas such as 3D reconstruction and tracking. The solution is(More)