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Publicações

2025

In-context learning of evolving data streams with tabular foundational models

Autores
Lourenço, A; Gama, J; Xing, EP; Marreiros, G;

Publicação
CoRR

Abstract

2025

From waste to resource: LIBS methodology development for rapid quality assessment of recycled wood

Autores
Capela, D; Pessanha, S; Lopes, T; Cavaco, R; Teixeira, J; Ferreira, MFS; Magalhaes, P; Jorge, PAS; Silva, NA; Guimaraes, D;

Publicação
JOURNAL OF HAZARDOUS MATERIALS

Abstract
Management and reuse of wood waste can be a challenging process due to the frequent presence of hazardous contaminants. Conventional detection methods are often limited by the need for excessive sample preparation and lengthy and expensive analysis. Laser-induced Breakdown Spectroscopy (LIBS) is a rapid and micro- destructive technique that can be a promising alternative, providing in-situ and real-time analysis, with minimal to no sample preparation required. In this study, LIBS imaging was used to analyze wood waste samples to determine the presence of contaminants such as As, Ba, Cd, Cr, Cu, Hg, Pb, Sb, and Ti. For this analysis, a methodology based on detecting three lines per element was developed, offering a screening method that can be easily adapted to perform qualitative analysis in industrial contexts with high throughput operations. For the LIBS experimental lines selection, control and reference samples, and a pilot set of 10 wood wastes were analysed. Results were validated by two different X-ray Fluorescence (XRF) systems, an imaging XRF and a handheld XRF, that provided spatial elemental information and spectral information, respectively. The results obtained highlighted LIBS ability to detect highly contaminated samples and the importance of using a 3-line criteria to mitigate spectral interferences and discard outliers. To increase the dataset, a LIBS large-scale study was performed using 100 samples. These results were only corroborated by the XRF-handheld system, as it provides a faster alternative. In particular cases, ICP-MS analysis was also performed. The success rates achieved, mostly above 88 %, confirm the capability of LIBS to perform this analysis, contributing to more sustainable waste management practices and facilitating the quick identifi- cation and remediation of contaminated materials.

2025

Early Failure Detection for Air Production Unit in Metro Trains

Autores
Zafra, A; Veloso, B; Gama, J;

Publicação
HYBRID ARTIFICIAL INTELLIGENT SYSTEM, PT I, HAIS 2024

Abstract
Early identification of failures is a critical task in predictive maintenance, preventing potential problems before they manifest and resulting in substantial time and cost savings for industries. We propose an approach that predicts failures in the near future. First, a deep learning model combining long short-term memory and convolutional neural network architectures predicts signals for a future time horizon using real-time data. In the second step, an autoencoder based on convolutional neural networks detects anomalies in these predicted signals. Finally, a verification step ensures that a fault is considered reliable only if it is corroborated by anomalies in multiple signals simultaneously. We validate our approach using publicly available Air Production Unit (APU) data from Porto metro trains. Two significant conclusions emerge from our study. Firstly, experimental results confirm the effectiveness of our approach, demonstrating a high fault detection rate and a reduced number of false positives. Secondly, the adaptability of this proposal allows for the customization of configuration of different time horizons and relationship between the signals to meet specific detection requirements.

2025

Multilayer quantile graph for multivariate time series analysis and dimensionality reduction

Autores
Silva, VF; Silva, ME; Ribeiro, P; Silva, F;

Publicação
INTERNATIONAL JOURNAL OF DATA SCIENCE AND ANALYTICS

Abstract
In recent years, there has been a surge in the prevalence of high- and multidimensional temporal data across various scientific disciplines. These datasets are characterized by their vast size and challenging potential for analysis. Such data typically exhibit serial and cross-dependency and possess high dimensionality, thereby introducing additional complexities to conventional time series analysis methods. To address these challenges, a recent and complementary approach has emerged, known as network-based analysis methods for multivariate time series. In univariate settings, quantile graphs have been employed to capture temporal transition properties and reduce data dimensionality by mapping observations to a smaller set of sample quantiles. To confront the increasingly prominent issue of high dimensionality, we propose an extension of quantile graphs into a multivariate variant, which we term Multilayer Quantile Graphs. In this innovative mapping, each time series is transformed into a quantile graph, and inter-layer connections are established to link contemporaneous quantiles of pairwise series. This enables the analysis of dynamic transitions across multiple dimensions. In this study, we demonstrate the effectiveness of this new mapping using synthetic and benchmark multivariate time series datasets. We delve into the resulting network's topological structures, extract network features, and employ these features for original dataset analysis. Furthermore, we compare our results with a recent method from the literature. The resulting multilayer network offers a significant reduction in the dimensionality of the original data while capturing serial and cross-dimensional transitions. This approach facilitates the characterization and analysis of large multivariate time series datasets through network analysis techniques.

2025

Pre- and post-deployment recommendations for single-point current meters and Acoustic Doppler Current Profilers

Autores
Tomasi, B; Ursella, L; Heyndrickx, CL; Le Menn, M; Lefevre, D; Malley, CO; Ferreira, HA; Martins, A; Cusi, S;

Publicação
OCEANS 2025 BREST

Abstract
In this paper, we propose pre-and post-deployment guidelines for both single point current-meters and Acoustic Doppler Current Profilers (ADCPs) to improve awareness of the quality, in terms of accuracy, of the data collected by these instruments among their user community. In the realm of oceanographic instrumentation, single-point current meters and ADCPs are considered to be a well understood and mature technology, however, to ensure that the measurements are not affected by biases due to magnetic anomalies or sensor drifts before and after their deployment, it is necessary to have an understanding of how the velocity vectors are derived from the measurements. Tests performed on three ADCP instruments show that heading errors of up to 10 degrees can be caused by instruments being deployed in the vicinity of the ADCP. In this paper, we will also investigate the consequences of not compensating for these biases in two oceanographic examples, one of them revealing 16% horizontal velocity errors in the worst case.

2025

IMPROVED ADMS WITH AN OPERATOR FRIENDLY INTERFACE

Autores
Pereira, JC; Gouveia, CS; Portelinha, RK; Viegas, P; Simões, J; Silva, P; Dias, S; Rodrigues, A; Pereira, A; Faria, J; Pino, G;

Publicação
IET Conference Proceedings

Abstract
The purpose of an Advanced Distribution Management System (ADMS) is to consolidate the key operational functions of a SCADA system, Outage management System (OMS) and Distribution Management System (DMS) into a unified platform. This includes several key functions: SCADA operation, incidents and outages management, teams and field works management including switching operations and advanced applications for network analysis and optimization. The new generation of ADMS also implements a predictive operation strategy to enhance real-time operator responsiveness. The innovative aspects related to the new generation of ADMS built on top of an open architecture will be presented in this paper. © The Institution of Engineering & Technology 2025.

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