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Publicações

2005

Aeropalynological study of Vitis vinifera in the Braga region (1999-2003)

Autores
Ribeiro, H; Abreu, I; Cunha, M; Mota, T; Castro, R;

Publicação
AEROBIOLOGIA

Abstract
This study shows the results of Vitis vinifera pollen season in the atmosphere of the Braga region (Portugal) for the last 5 years (1999-2003). The fluctuations in the airborne pollen concentration, the synchronic rhythms in the annual pollen trends and their relationship to the main meteorological parameters were investigated. The vineyard pollen season extends from late May to early July, presenting always a bimodal pattern. During the studied period several pollen types such as Poaceae, Castanea, Olea, Urticaceae, Quercus, Plantago, Rumex, Asteraceae, Pinaceae, Ericaceae and Eucalyptus were also observed. Airborne pollen concentration is highly influenced by mean temperature, rain, number of days with rain and wind direction.

2005

CMB'05: Workshop on Computational Methods in Bioinformatics

Autores
Camacho, R; Alves, A; da Costa, JP; Azevedo, P;

Publicação
2005 Portuguese Conference on Artificial Intelligence, Proceedings

Abstract

2005

Integer vs. fractional order control of a hexapod robot

Autores
Silva, MF; Machado, JAT; Lopes, AM;

Publicação
Climbing and Walking Robots

Abstract
This paper studies the performance of integer and fractional order controllers in a hexapod robot with joints at the legs having viscous friction and flexibility. For that objective the robot prescribed motion is characterized in terms of several locomotion variables. The controller performance is analised through the Nyquist stability criterion. A set of model-based experiments reveals the influence of the different controller implementations upon the proposed metrics.

2005

Applying biological paradigms to emerge behaviour in RoboCup Rescue team

Autores
Reinaldo, F; Certo, J; Cordeiro, N; Reis, LP; Camacho, R; Lau, N;

Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE, PROCEEDINGS

Abstract
This paper presents a hybrid behaviour process for performing collaborative tasks and coordination capabilities in a rescue team. RoboCup Rescue simulator and its associated international competition are used as the testbed for our proposal. Unlike other published work in this field one of our main concerns is having good results on RoboCup Rescue championships by emerging behaviour in agents using a biological paradigm. The benefit comes from the hierarchic and parallel organisation of the mammalian brain. In our behaviour process, Artificial Neural Networks are used in order to make agents capable of learning information from the environment. This allows agents to improve several algorithms like their Path Finding Algorithm to find the shortest path between two points. Also, we aim to filter the most important messages that arise from the environment, to make the right choice on the best path planning among many alternatives, in a short time. A policy action was implemented using Kohonen's network, Dijkstra's and D* algorithm. This policy has achieved good results in our tests, getting our team classified for RoboCup Rescue Simulation League 2005.

2005

Space-time analysis of sea level in the North Atlantic from TOPEX/Poseidon satellite altimetry

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

Publicação
Gravity, Geoid and Space Missions

Abstract
Spatial and temporal sea level variability in the North Atlantic is investigated from Topex/Poseidon (T/P) altimetry data. Time series of sea level anomalies on a regular 5 degrees grid are analysed. Non-linear denoising through thresholding in the wavelet transform domain is carried out for each series in order to remove noise while preserving non-smooth features. Principal Component Analysis (PCA) is used to obtain a spatio-temporal description of the sea level field, To avoid modal mixing and improve interpretation of the principal modes, PCA is implemented separately for seasonal and trend components of the sea level field obtained from a wavelet-based multiresolution analysis. The leading pattern of the seasonal field reflects the dominance of a stable annual cycle over the study area and the change in the seasonal regime approaching the equator with contribution of the semi-annual cycle and phase-shift in the annual cycle in the tropical Atlantic. The leading pattern of the trend field is a broad spatial pattern associated with North Atlantic Oscillation (NAO), reflecting the influence of atmospheric conditions on interannual sea level variability.

2005

A new method for detecting the point of voltage collapse

Autores
Andrade, AC; Barbosa, FPM;

Publicação
UPEC 2004: 39th International Universitities Power Engineering Conference, Vols 1-3, Conference Proceedings

Abstract
This paper presents a new method for the detection of the point of collapse and a new index for the definition of the distance of the voltage collapse point. Performance index to detect and predict stability problems such as the voltage collapse have been a permanent concern for researchers and technical staff in power systems operation. This index can be used on-line or off-line to help operators determine how close the system is to a possible collapse and is a useful analysis tool for planning in power systems too. Numerical experiments using standard IEEE 14 and 57 bus systems show that the proposed method can compute the voltage collapse point using several different scenery of load increase or line outages. The methodology proposed may be easily implemented in any power flow program.

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