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Publicações

Publicações por LIAAD

2025

Pycol: A Python package for dataset complexity measures

Autores
Apóstolo, D; Santos, MS; Lorena, AC; Abreu, PH;

Publicação
NEUROCOMPUTING

Abstract
Class overlap presents a significant challenge to machine learning algorithms, especially when class imbalance is present. These factors contribute substantially to the complexity of classification tasks, particularly in realworld scenarios. As a result, measuring overlap is crucial, yet it remains difficult to quantify due to its intricate nature, since it can manifest and be measured in multiple ways. To help mitigate this, recent research has conceptualized a new taxonomy of class overlap measures, divided into multiple families, which allows researchers to obtain a more complete overview of the complexity of the datasets. In line with recent research, we introduce a new Python package for class overlap measurement named pycol. This package implements 29 overlap measures, divided into four overlap families specifically designed to capture class overlap in imbalanced real-world scenarios. This makes pycol an essential tool for researchers dealing with complex classification problems, providing robust solutions to quantify the joint-effect of class overlap and class imbalance effectively.

2025

Category-wise Fine-Tuning: Resisting incorrect pseudo-labels in multi-label image classification with partial labels

Autores
Chong, CF; Fang, XY; Guo, JL; Abreu, PH; Wang, YP; Yang, X; Kea, W; Im, SK;

Publicação
NEUROCOMPUTING

Abstract
Large-scale image datasets are often partially labeled, where only a few categories' labels are known for each image. Assigning pseudo-labels to unknown labels to gain additional training signals has become prevalent for training deep classification models. However, some pseudo-labels are inevitably incorrect, leading to a notable decline in the model classification performance. In this paper, we propose a new method called Category-wise Fine-Tuning (CFT), aiming to reduce model inaccuracies caused by the wrong pseudo-labels. In particular, CFT employs known labels without pseudo-labels to fine-tune the logistic regressions of trained models individually to calibrate each category's model predictions. Genetic Algorithm, seldom used for training deep models, is also utilized in CFT to maximize the classification performance directly. CFT is applied to well-trained models, unlike most existing methods that train models from scratch. Hence, CFT is general and compatible with models trained with different methods and schemes, as demonstrated through extensive experiments. CFT requires only a few seconds for each category for calibration with consumer-grade GPUs. We achieve state-of-the-art results on three benchmarking datasets, including the CheXpert chest X-ray competition dataset (ensemble mAUC 93.33%, single model 91.82%), partially labeled MS-COCO (average mAP 83.69%), and Open Image V3 (mAP 85.31%), outperforming the previous bests by 0.28%, 2.21%, 2.50%, and 0.91%, respectively. The single model on CheXpert has been officially evaluated by the competition server, endorsing the correctness of the result. The outstanding results and generalizability indicate that CFT could be substantial and prevalent for classification model development. Code is available at: https://github.com/maxium0526/category-wise-fine-tuning.

2025

A Systematic Review and Comparison of Calibration Techniques for UWB Localization Anchors

Autores
Simoes, SA; Araújo, H; Abreu, PH;

Publicação
2025 9TH INTERNATIONAL YOUNG ENGINEERS FORUM ON ELECTRICAL AND COMPUTER ENGINEERING, YEF-ECE

Abstract
Ultra-wideband (UWB) systems are critical for indoor positioning in robotics, industrial tracking, and asset management due to their accuracy in multipath-prone environments. Like GPS satellites requiring precise orbital data, UWB systems depend on well-calibrated anchors-fixed reference points whose positional accuracy directly impacts location estimates. We systematically evaluate and compare computational calibration methods, such as Genetic Algorithms, Maximum Likelihood, and the Extended Kalman Filter, using synthetic data, assessing both efficiency and error reduction in calibration and location. Nonlinear Least Squares (NLS) outperformed other approaches from this review as well as state-of-the-art methods, reducing anchor calibration errors to 10.7cm (86.03% improvement from 1-meter initial uncertainty) and tag localization errors to 5.6cm (88.35% reduction). NLS maintained computational efficiency (mean execution time of 0.011s, proving ideal for real-world deployments where efficiency and accuracy are critical.

2025

Integrating artificial intelligence into scenario analysis: a validated framework for strategic planning under economic uncertainty

Autores
Bessa, G; Barbosa, B;

Publicação
Global Economics Research

Abstract

2025

The Impact of Brand Coolness on the Intention to Purchase Luxury Fashion Brands' NFTs

Autores
Sousa, A; Barbosa, B; Fernandes, LA;

Publicação
JOURNAL OF CONSUMER BEHAVIOUR

Abstract
The purpose of this study was to explore the influence of brand coolness on the intention to acquire NFTs within the luxury fashion market. To achieve this purpose, we developed a conceptual model offering a broader perspective regarding consumers' purchase intention of luxury brands' NFTs by including both emotional aspects related to the brand (brand love) and perceptions predominantly related to the financial nature of the investment (perceived risk). Word-of-mouth (WOM) and willingness to pay (WTP) are also analyzed as outcomes of brand coolness. The model was tested using Partial Least Squares Structural Equation Modeling (PLS-SEM) to examine the proposed relationships. The findings show that brand coolness positively impacts brand love, WOM, and WTP. Although it was not possible to observe a significant relationship between brand coolness and consumers' purchase intention of luxury brands' NFTs, it has significant indirect effects through brand love. Guided by the unexpected findings of the quantitative study, this article also includes a follow-up qualitative study, whose main aim was to further explore the influence of brand coolness on the intention to acquire NFTs within the luxury fashion market. Participants were individuals with relevant knowledge and experience with NFTs. The qualitative study revealed that brand coolness alone is insufficient to drive NFT purchases, while brand love, tied to trust and symbolic value, plays a stronger role, helping explain the quantitative results. Overall, this study contributes to the literature by shedding light on the complex interplay between brand coolness, consumer behavior, and NFTs in the luxury fashion context.

2025

The role of digital touchpoints in the five-star hospitality customer journey

Autores
Zabjesky, C; Barbosa, B; Neves, S;

Publicação
Effective Marketing and Consumer Behavior Tactics for High-End Products

Abstract
The main aim of this chapter is to study the digital touchpoints influencing customers' decisions in the five-star hospitality industry. This chapter adopted a qualitative methodology in the form of semi-structured interviews. The findings suggest the preeminent role of online travel agencies and hotel websites as the two most powerful touchpoints influencing the decision-making of the customer and serving as the principal means of making the reservation at the hotel. It also stresses the growing influence of customer-owned touchpoints, particularly user-generated content, in influencing customer perception. This research emphasizes the significance of personalized engagement in influencing customer satisfaction and loyalty. Overall, the study presents practical managerial implications for hoteliers, offering insights on how to effectively interact with customers at each stage of their journey, thereby enhancing both service delivery and overall guest experience. © 2025, IGI Global Scientific Publishing. All rights reserved.

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