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Publications

2025

A comparative analysis of unsupervised machine-learning methods in PSG-related phenotyping

Authors
Ghorvei, M; Karhu, T; Hietakoste, S; Ferreira Santos, D; Hrubos Strom, H; Islind, AS; Biedebach, L; Nikkonen, S; Leppaenen, T; Rusanen, M;

Publication
JOURNAL OF SLEEP RESEARCH

Abstract
Obstructive sleep apnea is a heterogeneous sleep disorder with varying phenotypes. Several studies have already performed cluster analyses to discover various obstructive sleep apnea phenotypic clusters. However, the selection of the clustering method might affect the outputs. Consequently, it is unclear whether similar obstructive sleep apnea clusters can be reproduced using different clustering methods. In this study, we applied four well-known clustering methods: Agglomerative Hierarchical Clustering; K-means; Fuzzy C-means; and Gaussian Mixture Model to a population of 865 suspected obstructive sleep apnea patients. By creating five clusters with each method, we examined the effect of clustering methods on forming obstructive sleep apnea clusters and the differences in their physiological characteristics. We utilized a visualization technique to indicate the cluster formations, Cohen's kappa statistics to find the similarity and agreement between clustering methods, and performance evaluation to compare the clustering performance. As a result, two out of five clusters were distinctly different with all four methods, while three other clusters exhibited overlapping features across all methods. In terms of agreement, Fuzzy C-means and K-means had the strongest (kappa = 0.87), and Agglomerative hierarchical clustering and Gaussian Mixture Model had the weakest agreement (kappa = 0.51) between each other. The K-means showed the best clustering performance, followed by the Fuzzy C-means in most evaluation criteria. Moreover, Fuzzy C-means showed the greatest potential in handling overlapping clusters compared with other methods. In conclusion, we revealed a direct impact of clustering method selection on the formation and physiological characteristics of obstructive sleep apnea clusters. In addition, we highlighted the capability of soft clustering methods, particularly Fuzzy C-means, in the application of obstructive sleep apnea phenotyping.

2025

Toilet-Seat ECG as a Gateway to Stress Monitoring: Non-Invasive Stress Index Extraction in Subjects with and Without Cardiovascular Disease

Authors
Aline dos Santos Silva; Miguel Velhote Correia; Andreia Gonçalves da Costa; Hugo Plácido da Silva;

Publication
2025 IEEE 8th Portuguese Meeting on Bioengineering (ENBENG)

Abstract

2025

Converge: towards an efficient multi-modal sensing research infrastructure for next-generation 6 G networks

Authors
Filipe B. Teixeira; Manuel Ricardo; André Coelho; Hélder P. Oliveira; Paula Viana; Nuno Paulino; Helder Fontes; Paulo Marques; Rui Campos; Luís Pessoa;

Publication
EURASIP Journal on Wireless Communications and Networking

Abstract

2025

From data to action: How AI and learning analytics are shaping the future of distance education

Authors
Dias, JT; Santos, A; Mamede, HS;

Publication
AI and Learning Analytics in Distance Learning

Abstract
This chapter examines how Artificial Intelligence (AI) and Learning Analytics (LA) are transformingdistanceeducation, accelerated by the COVID-19 shift toe-learning. By using data from Learning Management Systems (LMS), these technologies can personalize learning, improve student retention, and automate tasks. AI, particularly machine learning, enables dynamic adaptation to student needs, while LA provides valuable insights for informed instructional decisions. However, ethical concerns, including data privacy and algorithmic bias, must be addressed to ensure equitable access and fair learning outcomes. The future of distance learning lies in responsible integration of AI and LA, creating immersive and inclusive educational experiences. © 2025 by IGI Global Scientific Publishing. All rights reserved.

2025

Logic and Calculi for All on the occasion of Luis Barbosa's 60th birthday

Authors
Madeira, A; Oliveira, JN; Proença, J; Neves, R;

Publication
JOURNAL OF LOGICAL AND ALGEBRAIC METHODS IN PROGRAMMING

Abstract
[No abstract available]

2025

Towards Non-Intrusive Blood Pressure Estimation Using Thigh ECG and PPG Signals Acquired from a Smart Toilet Seat

Authors
Aline dos Santos Silva; Miguel Velhote Correia; Andreia Gonçalves da Costa; Hugo Plácido da Silva;

Publication
2025 IEEE 8th Portuguese Meeting on Bioengineering (ENBENG)

Abstract

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