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Publicações

2009

Manoeuvre Based Mission Control System for Autonomous Surface Vehicle

Autores
Dias, N; Almeida, C; Ferreira, H; Almeida, J; Martins, A; Dias, A; Silva, E;

Publicação
OCEANS 2009 - EUROPE, VOLS 1 AND 2

Abstract
In this work the mission control and supervision system developed for the ROAZ Autonomous Surface Vehicle is presented. Complexity in mission requirements coupled with flexibility lead to the design of a modular hierarchical mission control system based on hybrid systems control. Monitoring and supervision control for a vehicle such as ROAZ mission is not an easy task using tools with low complexity and yet powerful enough. A set of tools were developed to perform both on board mission control and remote planning and supervision. "ROAZ- Mission Control" was developed to be used in support to bathymetric and security missions performed in river and at seas.

2009

Line Indices for Voltage Stability Assessment

Autores
Reis, C; Maciel Barbosa, FPM;

Publicação
2009 IEEE BUCHAREST POWERTECH, VOLS 1-5

Abstract
Voltage stability has become one of the most important issues in electrical power systems. The power system ability to maintain acceptable bus voltage is a very important characteristic of a network. This paper analyzes the performance of line stability indices. These indices were tested in IEEE 14 and IEEE 57 busbar test systems, with satisfactory results. Simulation results show that using line stability indices the most critical line and the weakest bus of the system can be correctly identified.

2009

IDENTIFYING CANCER REGIONS IN VITAL-STAINED MAGNIFICATION ENDOSCOPY IMAGES USING ADAPTED COLOR HISTOGRAMS

Autores
Sousa, A; Dinis Ribeiro, M; Areia, M; Coimbra, M;

Publicação
2009 16TH IEEE INTERNATIONAL CONFERENCE ON IMAGE PROCESSING, VOLS 1-6

Abstract
In-body imaging technologies such as vital-stained magnification endoscopy pose novel image processing challenges to computer-assisted decision systems given their unique visual characteristics such as reduced color spaces and natural textures. In this paper we will show the potential of using adapted color features combined with local binary patterns, a texture descriptor that has exhibited good adaptation to natural images, for classifying gastric regions into three groups: normal, pre-cancer and cancer lesions. Results exhibit 91% accuracy, confirming that specific research for in-body imaging could be the key for future computer assisted decision systems for medicine.

2009

Entropy and Correntropy Against Minimum Square Error in Offline and Online Three-Day Ahead Wind Power Forecasting

Autores
Bessa, RJ; Miranda, V; Gama, J;

Publicação
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
This paper reports new results in adopting entropy concepts to the training of neural networks to perform wind power prediction as a function of wind characteristics (speed and direction) in wind parks connected to a power grid. Renyi's entropy is combined with a Parzen windows estimation of the error pdf to form the basis of two criteria (minimum entropy and maximum correntropy) under which neural networks are trained. The results are favorably compared in online and offline training with the traditional minimum square error (MSE) criterion. Real case examples for two distinct wind parks are presented.

2009

Pluggable parallelisation

Autores
Gonçalves, RC; Sobral, JL;

Publicação
Proc. 18th ACM International Symposium on High Performance Distributed Computing, HPDC 09, Co-located with the 2009 International Symposium on High Performance Distributed Computing Conf., HPDC'09

Abstract
This paper presents the concept of pluggable parallelisation that allows scientists to develop "sequential like" codes that can take advantage of multi-core, cluster and grid systems. In this approach parallel applications are developed by plugging parallelisation patterns/idioms into scientific codes (e.g., "sequential like" codes), softening the move from sequential to parallel programming and promoting the separation between domain specific code and parallelisation issues. Pluggable parallelisation combines three characteristics: 1) parallelisation is performed from "outside to inside", localising parallelisation concerns into well defined modules, reducing changes required to the domain specific code and avoiding invasive parallelisation of base code; 2) control view is separated from data view promoting a stronger separation of concerns which improves reuse of parallelisation concerns across platforms and enables fine-grained refinements; and 3) abstractions can be composed, supporting the development of more complex patterns based on fine-grained features. This paper presents the concept of pluggable parallelisation and shows how some well-known parallelisation strategies can be implemented in this approach. Results show that this is a feasible approach and performance is competitive with traditional parallel programming. Copyright 2009 ACM.

2009

Viability-based computation of spatially constrained minimum time trajectories for an autonomous underwater vehicle: implementation and experiments

Autores
Tinka, A; Diemer, S; Madureira, L; Marques, EB; de Sousa, JB; Martins, R; Pinto, J; da Silva, JE; Sousa, A; Saint Pierre, P; Bayen, AM;

Publicação
2009 AMERICAN CONTROL CONFERENCE, VOLS 1-9

Abstract
A viability algorithm is developed to compute the constrained minimum time function for general dynamical systems. The algorithm is instantiated for a specific dynamics (Dubin's vehicle forced by a flow field) in order to numerically solve the minimum time problem. With the specific dynamics considered, the framework of hybrid systems enables us to solve the problem efficiently. The algorithm is implemented in C using epigraphical techniques to reduce the dimension of the problem. The feasibility of this optimal trajectory algorithm is tested in an experiment with a Light Autonomous Underwater Vehicle (LAUV) system. The hydrodynamics of the LAUV are analyzed in order to develop a low-dimension vehicle model. Deployment results from experiments performed in the Sacramento River in California are presented, which show good performance of the algorithm.

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