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Publicações

2025

Capacity Planning in Maintenance Repair and Overhaul Operations: Evaluating Uncertainty with Discrete Event Simulation

Autores
Teles, ,; Santos, F; Guardao, L; Figueira, G;

Publicação
Procedia Computer Science

Abstract
The Maintenance, Repair and Overhaul (MRO) activities in the aviation industry face constant challenges due to the uncertainty and variability of their operations. Aircraft engine maintenance, which is fundamental to the safety of aircraft operations, is particularly challenging due to its job-shop nature. Each engine requires a specific intervention process, based on its condition and the needs identified. The inherent uncertainty in task duration, resource availability, and the scope of required repairs adds complexity to capacity planning. Traditional capacity planning methods often fall short in accounting for these uncertainties, leading to potential inefficiencies and bottlenecks. Discrete Event Simulation (DES) emerges as a powerful tool to address these challenges. By modelling the entire MRO process, DES can consider various scenarios, incorporating the stochastic nature of task times, machine downtimes, and labour availability. This study explores the application of DES to evaluate capacity planning and quantify the impact of uncertainty on operational efficiency. The proposed methodology enables the anticipation of delays and enhances resource management. The primary contribution of this work is the ability to predict delays and quantify their impact. The future application of this tool in real-world MRO operations has the potential to enhance operational efficiency and reliability. © 2025 Elsevier B.V., All rights reserved.

2025

A Computer-Aided Approach to Canine Hip Dysplasia Assessment: Measuring Femoral Head-Acetabulum Distance with Deep Learning

Autores
Franco-Gonçalo, P; Leite, P; Alves-Pimenta, S; Colaço, B; Gonçalves, L; Filipe, V; McEvoy, F; Ferreira, M; Ginja, M;

Publicação
APPLIED SCIENCES-BASEL

Abstract
Canine hip dysplasia (CHD) screening relies on radiographic assessment, but traditional scoring methods often lack consistency due to inter-rater variability. This study presents an AI-driven system for automated measurement of the femoral head center to dorsal acetabular edge (FHC/DAE) distance, a key metric in CHD evaluation. Unlike most AI models that directly classify CHD severity using convolutional neural networks, this system provides an interpretable, measurement-based output to support a more transparent evaluation. The system combines a keypoint regression model for femoral head center localization with a U-Net-based segmentation model for acetabular edge delineation. It was trained on 7967 images for hip joint detection, 571 for keypoints, and 624 for acetabulum segmentation, all from ventrodorsal hip-extended radiographs. On a test set of 70 images, the keypoint model achieved high precision (Euclidean Distance = 0.055 mm; Mean Absolute Error = 0.0034 mm; Mean Squared Error = 2.52 x 10-5 mm2), while the segmentation model showed strong performance (Dice Score = 0.96; Intersection over Union = 0.92). Comparison with expert annotations demonstrated strong agreement (Intraclass Correlation Coefficients = 0.97 and 0.93; Weighted Kappa = 0.86 and 0.79; Standard Error of Measurement = 0.92 to 1.34 mm). By automating anatomical landmark detection, the system enhances standardization, reproducibility, and interpretability in CHD radiographic assessment. Its strong alignment with expert evaluations supports its integration into CHD screening workflows for more objective and efficient diagnosis and CHD scoring.

2025

Exploring multimodal learning applications in marketing: A critical perspective

Autores
César, I; Pereira, I; Rodrigues, F; Miguéis, VL; Nicola, S; Madureira, A;

Publicação
Int. J. Hybrid Intell. Syst.

Abstract
This review discusses the integration of intelligent technologies into customer interactions in organizations and highlights the benefits of using artificial intelligence systems based on a multimodal approach. Multimodal learning in marketing is explored, focusing on understanding trends and preferences by analyzing behavior patterns expressed in different modalities. The study suggests that research in multimodality is scarce but reveals that it is as a promising field for overcoming decision-making complexity and developing innovative marketing strategies. The article introduces a methodology for accurately representing multimodal elements and discusses the theoretical foundations and practical impact of multimodal learning. It also examines the use of embeddings, fusion techniques, and explores model performance evaluation. The review acknowledges the limitations of current multimodal approaches in marketing and encourages more guidelines for future research. Overall, this work emphasizes the importance of integrating intelligent technology in marketing to personalize customer experiences and improve decision-making processes.

2025

Air Quality Data Analysis with Symbolic Principal Components

Autores
Loureiro, P; Oliveira, M; Brito, P; Oliveira, L;

Publicação
Springer Proceedings in Mathematics and Statistics

Abstract
Air pollution is a global challenge with deep implications in public health and environment. We examine air quality data from a monitoring station in Entrecampos, Lisbon, Portugal, using Symbolic Data Analysis. The dataset consists of hourly concentrations of nine pollutants during three years, which are logarithmically transformed and aggregated in intervals, taking the daily minimum and maximum values. The symbolic mean and variance are estimated for each variable through the method of moments, and the pairwise dependencies are captured using a bivariate copula. Symbolic principal component scores are obtained from the estimated covariance matrix and used to fit generalized extreme value distributions. Outlier maps, based on these distributions’ quantiles, are used to identify outlying observations. A comparative analysis with daily average-based outlier detection methods is conducted. The results show the relevance of Symbolic Data Analysis in revealing new insights into air quality. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.

2025

Automated optical system for quality inspection on reflective parts

Autores
Nascimento, R; Rocha, CD; Gonzalez, DG; Silva, T; Moreira, R; Silva, MF; Filipe, V; Rocha, LF;

Publicação
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY

Abstract
The growing demand for high-quality components in various industries, particularly in the automotive sector, requires advanced and reliable inspection methods to maintain competitive standards and support innovation. Manual quality inspection tasks are often inefficient and prone to errors due to their repetitive nature and subjectivity, which can lead to attention lapses and operator fatigue. The inspection of reflective aluminum parts presents additional challenges, as uncontrolled reflections and glare can obscure defects and reduce the reliability of conventional vision-based methods. Addressing these challenges requires optimized illumination strategies and robust image processing techniques to enhance defect visibility. This work presents the development of an automated optical inspection system for reflective parts, focusing on components made of high-pressure diecast aluminum used in the automotive industry. The reflective nature of these parts introduces challenges for defect detection, requiring optimized illumination and imaging methods. The system applies deep learning algorithms and uses dome light to achieve uniform illumination, enabling the detection of small defects on reflective surfaces. A collaborative robotic manipulator equipped with a gripper handles the parts during inspection, ensuring precise positioning and repeatability, which improves both the efficiency and effectiveness of the inspection process. A flow execution-based software platform integrates all system components, enabling seamless operation. The system was evaluated with Schmidt Light Metal Group using three custom datasets to detect surface porosities and inner wall defects post-machining. For surface porosity detection, YOLOv8-Mosaic, trained with cropped images to reduce background noise, achieved a recall value of 84.71% and was selected for implementation. Additionally, an endoscopic camera was used in a preliminary study to detect defects within the inner walls of holes. The industrial trials produced promising results, demonstrating the feasibility of implementing a vision-based automated inspection system in various industries. The system improves inspection accuracy and efficiency while reducing material waste and operator fatigue.

2025

Collaborative fault tolerance for cyber-physical systems: The detection stage

Autores
Piardi, L; de Oliveira, AS; Costa, P; Leitao, P;

Publicação
COMPUTERS IN INDUSTRY

Abstract
In the era of Industry 4.0, fault tolerance is essential for maintaining the robustness and resilience of industrial systems facing unforeseen or undesirable disturbances. Current methodologies for fault tolerance stages namely, detection, diagnosis, and recovery, do not correspond with the accelerated technological evolution pace over the past two decades. Driven by the advent of digital technologies such as Internet of Things, cloud and edge computing, and artificial intelligence, associated with enhanced computational processing and communication capabilities, local or monolithic centralized fault tolerance methodologies are out of sync with contemporary and future systems. Consequently, these methodologies are limited in achieving the maximum benefits enabled by the integration of these technologies, such as accuracy and performance improvements. Accordingly, in this paper, a collaborative fault tolerance methodology for cyber-physical systems, named Collaborative Fault * (CF*), is proposed. The proposed methodology takes advantage of the inherent data analysis and communication capabilities of cyber-physical components. The proposed methodology is based on multi-agent system principles, where key components are self-fault tolerant, and adopts collaborative and distributed intelligence behavior when necessary to improve its fault tolerance capabilities. Experiments were conducted focusing on the fault detection stage for temperature and humidity sensors in warehouse racks. The experimental results confirmed the accuracy and performance improvements under CF* compared with the local methodology and competitiveness when compared with a centralized approach.

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