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Publicações

2025

A Systematic Review of Cyber Threat Intelligence: The Effectiveness of Technologies, Strategies, and Collaborations in Combating Modern Threats

Autores
Santos, P; Abreu, R; Reis, MJCS; Serôdio, C; Branco, F;

Publicação
SENSORS

Abstract
Cyber threat intelligence (CTI) has become critical in enhancing cybersecurity measures across various sectors. This systematic review aims to synthesize the current literature on the effectiveness of CTI strategies in mitigating cyber attacks, identify the most effective tools and methodologies for threat detection and prevention, and highlight the limitations of current approaches. An extensive search of academic databases was conducted following the PRISMA guidelines, including 43 relevant studies. This number reflects a rigorous selection process based on defined inclusion, exclusion, and quality criteria and is consistent with the scope of similar systematic reviews in the field of cyber threat intelligence. This review concludes that while CTI significantly improves the ability to predict and prevent cyber threats, challenges such as data standardization, privacy concerns, and trust between organizations persist. It also underscores the necessity of continuously improving CTI practices by leveraging the integration of advanced technologies and creating enhanced collaboration frameworks. These advancements are essential for developing a robust and adaptive cybersecurity posture capable of responding to an evolving threat landscape, ultimately contributing to a more secure digital environment for all sectors. Overall, the review provides practical reflections on the current state of CTI and suggests future research directions to strengthen and improve CTI's effectiveness.

2025

Synthetic Data Generation for Time Series Imputation: Comparing the Foundation Model Chronos with Established Methods

Autores
Lessa, SS; Lucas, A;

Publicação
2025 IEEE KIEL POWERTECH

Abstract
Accurately imputing missing data is critical in time series analysis. The present work compares Foundation Model Chronos against Linear Interpolation, K-Nearest Neighbor Imputer, and Gaussian Mixture Model Imputer with three types of missing data patterns: random, short sequential chunks, and a long sequential chunk. These results confirm that for random missing values, KNN and interpolation yield the highest performance, while Chronos outperforms these on sequences. Indeed, however, for longer sequences of missing values, Chronos starts suffering from cascading errors which eventually allow the simpler imputation methods to outrank it. Another test with limited quantities of training data showed different trade-offs for the different methods. Unlike KNN and interpolation, which smooth out the gaps, Chronos generates variable synthetic data. This can be beneficial in tasks which require control or simulation. The results highlight the strengths and weaknesses of the imputers and, therefore, offer practical insights into trade-offs between computational complexities, accuracy, and suitability for time series imputation scenarios.

2025

A New Design for an Electrolyzer Power Converter Architecture Capable of Fault Ride Through

Autores
Elhawash, AM; Araújo, RE; Lopes, JAP;

Publicação
2025 IEEE KIEL POWERTECH

Abstract
This paper presents a new power chain and its control scheme that provides highly flexible low voltage ride through (LVRT) capabilities for power converters that feed the stack of Polymer Electrolyte Membrane (PEM) hydrogen electrolyzers. It introduces an intermediate power stage with a new adaptive feedforward controller, that isolates the electrolyzer stack from grid-side disturbances. An RMS model of the whole solution is developed and validated. The system was developed in MATLAB/SIMULINK and PLECS environments. Furthermore, the system was tested in DC and AC grids by subjecting it to a fault reducing the input voltage magnitude down to 0.2 pu. The system demonstrated its ability to ride through the fault whilst maintaining the power set-points and supply quality at the electrolyzer stack connection point.

2025

“Counting zzz’s” exploring and evaluating sleep apps across mobile platforms: scoping review (Preprint)

Autores
Araújo, MI; Ferreira-Santos, D;

Publicação

Abstract
BACKGROUND

Good sleep is crucial for human life. Research has shown that poor-quality sleep is related to several cardiovascular and metabolic disorders. Sleep disorders are well categorized, and most of them have defined diagnostic criteria, with level 1 polysomnography being the gold standard. With the increasing use of technology, specifically smartphones, in people’s everyday lives, the search for alternative ways of monitoring sleep disorders or certain sleep parameters has been gaining relevance.

OBJECTIVE

This scoping review aims to understand which mobile applications (apps) are available and might be useful in the Portuguese reality and explore their features.

METHODS

A search was performed in Google Play and Apple App Store for mobile applications that monitored sleep cycles, sleep movements, or sound recording and that were available in Portuguese until February 2025. Afterward, a search for scientific evidence of the selected apps was conducted.

RESULTS

Out of the 981 search results obtained, 34 applications met the study’s inclusion criteria. These were then divided into 5 categories according to their main functions: sleep cycle monitoring (SCM), sound recording (SR), SCM&SR, SCM and movement monitoring (MM), and SCM&SR&MM. 23 apps were available in both stores. Almost half of the selected apps (n=15) functioned better or needed wearable devices associated with a more thorough sleep analysis. To be fully operational, none of the mobile apps is entirely free for the user. Most of the applications did not have scientific evidence substantiating their features.

CONCLUSIONS

The mobile applications market is volatile, with little regulation and a lack of scientific evidence available to sustain the accuracy of its products. Even though mobile applications cannot substitute polysomnography in diagnosing sleep disorders, they might be relevant in monitoring sleep since they are easily available and do not require highly specific circumstances to be used. More studies are needed to validate apps, specifically in Portuguese.

2025

AI-mediated Collaborative Crowdsourcing for Social News Curation: The Case of Acropolis

Autores
Schneider, D; Chaves, R; Pimentel, AP; de Almeida, MA; de Souza, JM; Correia, A;

Publicação
IMX

Abstract

2025

A GRASP-based multi-objective approach for the tuna purse seine fishing fleet routing problem

Autores
Granado, I; Silva, E; Carravilla, MA; Oliveira, JF; Hernando, L; Fernandes Salvador, JA;

Publicação
COMPUTERS & OPERATIONS RESEARCH

Abstract
Nowadays, the world's fishing fleet uses 20% more fuel to catch the same amount offish compared to 30 years ago. Addressing this negative environmental and economic performance is crucial due to stricter emission regulations, rising fuel costs, and predicted declines in fish biomass and body sizes due to climate change. Investment in more efficient engines, larger ships and better fuel has been the main response, but this is only feasible in the long term at high infrastructure cost. An alternative is to optimize operations such as the routing of a fleet, which is an extremely complex problem due to its dynamic (time-dependent) moving target characteristics. To date, no other scientific work has approached this problem in its full complexity, i.e., as a dynamic vehicle routing problem with multiple time windows and moving targets. In this paper, two bi-objective mixed linear integer programming (MIP) models are presented, one for the static variant and another for the time-dependent variant. The bi-objective approaches allow to trade off the economic (e.g., probability of high catches) and environmental (e.g., fuel consumption) objectives. To overcome the limitations of exact solutions of the MIP models, a greedy randomized adaptive search procedure for the multi-objective problem (MO-GRASP) is proposed. The computational experiments demonstrate the good performance of the MO-GRASP algorithm with clearly different results when the importance of each objective is varied. In addition, computational experiments conducted on historical data prove the feasibility of applying the MO-GRASP algorithm in a real context and explore the benefits of joint planning (collaborative approach) compared to a non-collaborative strategy. Collaborative approaches enable the definition of better routes that may select slightly worse fishing and planting areas (2.9%), but in exchange fora significant reduction in fuel consumption (17.3%) and time at sea (10.1%) compared to non-collaborative strategies. The final experiment examines the importance of the collaborative approach when the number of available drifting fishing aggregation devices (dFADs) per vessel is reduced.

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