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Publications

2004

Topological navigation in configuration space applied to soccer robots

Authors
Neto, G; Costelha, H; Lima, P;

Publication
ROBOCUP 2003: ROBOT SOCCER WORLD CUP VII

Abstract
This paper describes a topological navigation system, based on the description of key-places by a reduced number of parameters that represent images associated to specific locations in configuration space, and the application of the developed system to robotic soccer, through the implementation of the developed algorithms to RoboCup Middle-Size League (MSL) robots, under the scope of the SocRob project (Soccer Robots or Society of Robots). A topological map is associated with a graph, where each node corresponds to a key-place. Using this approach, navigation is reduced to a graph path search. Principal Components Analysis was used to represent key-places from pre-acquired images and to recognize them at navigation time. The method revealed a promising performance navigating between key-places and proved to adapt to different graphs. Furthermore, it leads to a robot programming language based on qualitative descriptions of the target locations in configuration space (e.g., Near Blue Coal with the Goal on its Left). Simulation results of the method application are presented, using a realistic simulator.

2004

Parallel computation of optical flow

Authors
Dopico, AG; Correia, MV; Santos, JA; Nunes, LM;

Publication
IMAGE ANALYSIS AND RECOGNITION, PT 2, PROCEEDINGS

Abstract
This paper describes a new parallel algorithm to compute the optical flow of a video sequence. A previous sequential algorithm has been distributed over a cluster. It has been implemented in a cluster with 8 nodes connected by means of a Gigabit Ethernet. On this architecture, the algorithm, that computes the optical flow of every image on the sequence, is able of processing 10 images of 720 x 576 pixels per second.

2004

Scheduling under conditions of uncertainty: A Bayesian approach

Authors
Santos, LP; Proenca, A;

Publication
EURO-PAR 2004 PARALLEL PROCESSING, PROCEEDINGS

Abstract
The efficient execution of irregular parallel applications on shared distributed systems requires novel approaches to scheduling, since both the application requirements and the system resources exhibit an unpredictable behavior. This paper proposes Bayesian decision networks as the paradigm to handle the uncertainty a scheduler has about the environment's current and future states. Experiments performed with a parallel ray tracer show promising performance improvements over a deterministic approach of identical complexity. These improvements grow as the level of system sharing and the application's workload irregularity increase, suggesting that the effectiveness of decision network based schedulers grows with the complexity of the environment being managed.

2004

Distributed computation of optical flow

Authors
Dopico, AG; Correia, MV; Santos, JA; Nunes, LM;

Publication
COMPUTATIONAL SCIENCE - ICCS 2004, PT 2, PROCEEDINGS

Abstract
This paper describes a new parallel algorithm to compute the optical flow of a video sequence. A previous sequential algorithm has been distributed over a cluster. It has been implemented in a cluster with 8 nodes connected by means of a Gigabit Ethernet. On this architecture, the algorithm, that computes the optical flow of every image on the sequence, is able of processing 10 images of 720x576 pixels per second.

2004

Structural, Syntactic, and Statistical Pattern Recognition

Authors
Fred, A; Caelli, TM; Duin, RPW; Campilho, AC; de Ridder, D;

Publication
Lecture Notes in Computer Science

Abstract

2004

Voltage stability evaluation using the relation between impedances

Authors
Santos, JL; Barbosa, FPM;

Publication
MELECON 2004: PROCEEDINGS OF THE 12TH IEEE MEDITERRANEAN ELECTROTECHNICAL CONFERENCE, VOLS 1-3

Abstract
The increasing loads, the great distances between the production and consumption centers as well as the state of the transport and distribution networks turns the Electrical Power System operating near its stability limit. When the system gets instable a blackout situation may occur, which is critical to the system operator and consumers. We have recent examples in United States and Italy where the system was without power for several hours, causing serious problems in hospitals and public transportations. One of the causes of a blackout may be the Voltage Instability, which turns this subject widely discussed and studied. The speed of evolution of the Voltage Stability phenomenon allows us to analyze the problem as a static problem rather than a transitory one [1]. This article will show one way to "measure" locally the proximity of the system to the Voltage Stability Limit.

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