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Publications

Publications by João Gama

2012

Predicting Ramp Events with a Stream-Based HMM Framework

Authors
Ferreira, CA; Gama, J; Costa, VS; Miranda, V; Botterud, A;

Publication
Discovery Science - 15th International Conference, DS 2012, Lyon, France, October 29-31, 2012. Proceedings

Abstract
The motivation for this work is the study and prediction of wind ramp events occurring in a large-scale wind farm located in the US Midwest. In this paper we introduce the SHRED framework, a stream-based model that continuously learns a discrete HMM model from wind power and wind speed measurements. We use a supervised learning algorithm to learn HMM parameters from discretized data, where ramp events are HMM states and discretized wind speed data are HMM observations. The discretization of the historical data is obtained by running the SAX algorithm over the first order variations in the original signal. SHRED updates the HMM using the most recent historical data and includes a forgetting mechanism to model natural time dependence in wind patterns. To forecast ramp events we use recent wind speed forecasts and the Viterbi algorithm, that incrementally finds the most probable ramp event to occur. We compare SHRED framework against Persistence baseline in predicting ramp events occurring in short-time horizons, ranging from 30 minutes to 90 minutes. SHRED consistently exhibits more accurate and cost-effective results than the baseline. © 2012 Springer-Verlag Berlin Heidelberg.

2008

Wind Power Forecasting With Entropy-Based Criteria Algorithms

Authors
Bessa, R; Miranda, V; Gama, J;

Publication
2008 10TH INTERNATIONAL CONFERENCE ON PROBABILISTIC METHODS APPLIED TO POWER SYSTEMS

Abstract
This paper reports new results in adopting entropy concepts to the training of mappers such as neural networks to perform wind power prediction as a function of wind characteristics (mainly 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 three criteria (MEE, MCC and MEEF) under which neural networks are trained. The results are favourably compared with the traditional minimum square error (MSE) criterion. Real case examples for two distinct wind parks are presented.

2023

Explainable Predictive Maintenance

Authors
Pashami, S; Nowaczyk, S; Fan, Y; Jakubowski, J; Paiva, N; Davari, N; Bobek, S; Jamshidi, S; Sarmadi, H; Alabdallah, A; Ribeiro, RP; Veloso, B; Mouchaweh, MS; Rajaoarisoa, LH; Nalepa, GJ; Gama, J;

Publication
CoRR

Abstract

2023

Modeling Events and Interactions through Temporal Processes - A Survey

Authors
Liguori, A; Caroprese, L; Minici, M; Veloso, B; Spinnato, F; Nanni, M; Manco, G; Gama, J;

Publication
CoRR

Abstract

2023

Towards federated learning: An overview of methods and applications

Authors
Silva, PR; Vinagre, J; Gama, J;

Publication
WILEY INTERDISCIPLINARY REVIEWS-DATA MINING AND KNOWLEDGE DISCOVERY

Abstract
Federated learning (FL) is a collaborative, decentralized privacy-preserving method to attach the challenges of storing data and data privacy. Artificial intelligence, machine learning, smart devices, and deep learning have strongly marked the last years. Two challenges arose in data science as a result. First, the regulation protected the data by creating the General Data Protection Regulation, in which organizations are not allowed to keep or transfer data without the owner's authorization. Another challenge is the large volume of data generated in the era of big data, and keeping that data in one only server becomes increasingly tricky. Therefore, the data is allocated into different locations or generated by devices, creating the need to build models or perform calculations without transferring data to a single location. The new term FL emerged as a sub-area of machine learning that aims to solve the challenge of making distributed models with privacy considerations. This survey starts by describing relevant concepts, definitions, and methods, followed by an in-depth investigation of federated model evaluation. Finally, we discuss three promising applications for further research: anomaly detection, distributed data streams, and graph representation.This article is categorized under:Technologies > Machine LearningTechnologies > Artificial Intelligence

2022

Contextualization for the Organization of Text Documents Streams

Authors
Sarmento, RP; Cardoso, DdO; Gama, J; Brazdil, P;

Publication
CoRR

Abstract

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