ESTiG - Artigos em Revistas Indexados à WoS/Scopus
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- A split and merge strategy for multi-objective clustering algorithmsPublication . Azevedo, Beatriz Flamia; Rocha, Ana Maria A.C.; Pereira, Ana I.Complex real-world problems require advanced models for large datasets; combining optimization and machine learning methods can enhance solution effectiveness and efficiency. This work presents an automatic bio-inspired clustering algorithm named Multi-objective Clustering Algorithm II. Through an optimization process, the algorithm autonomously determines the number of clusters, their centroids, and the optimal distribution of their elements. Furthermore, the paper also presents a split and merge strategy for clustering algorithms, with a special focus on multi-objective ones. The proposed algorithms were executed on 10 benchmark datasets, yielding satisfactory results by accurately estimating the optimal number of clusters and providing appropriate dataset partitions. These results outstand the k-means and DBSCAN algorithms results, which were used as a comparison.
- Stock market reaction to the recurring incidents at boeing: an event study analysisPublication . Cró, Susana; Moutinho, Nuno; Martins, António MiguelThis paper examines the short‐term market reaction of aircraft commercial manufacturers and airline industry for eight Boeing aircraft incidents occurred in the first semester of 2024. Using an event study, we observe a negative and statistically significant stock price reaction for Boeing around the dates of the aircraft incidents and positive statistically significant abnormal returns to its rivals Airbus and Embraer. The competitive effect explains this result. As for the airline industry, the results do not show the existence of statistically significant effects on share prices. The absence of fatalities associated with these events helps to explain the lack of statistical significance for airline industry. However, a more detailed analysis of the sample reveals different patterns of behaviour of airline share prices—a negative and statistically significant abnormal return for airline firms with a fleet with a high weight of Boeing aircraft, for low‐cost carriers and for airlines with a poor safety record. Since all of these airlines use Boeing aircrafts, it seems there is a ‘guilt by association’ effect. These reactions are also reinforced or mitigated by airline‐specific characteristics such as size, leverage, and firm age. Practical implications of our findings are provided.
- A thematic literature review on politicians’ use of financial and non-financial information: Insights and future directionsPublication . Jorge, Susana; Silva, Adriana; Nogueira, Sónia P.This article provides a qualitative overview of literature on politicians’ use of financial and non-financial information over recent decades. Key themes include performance management, accountability, usability, and political decision-making and governance. While research has advanced in understanding how politicians use such data, gaps remain. Under-explored areas include trust in information, financial literacy among politicians, the impact of information design and presentation, and the growing influence of digital technologies and real-time data access on financial and non-financial information use by politicians. © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
- Insights from a five-year academic analytics observatory: challenges and achievementsPublication . Franco, Tiago; Alves, Paulo; Rufino, José; Pacheco, Maria F.; Ribeiro, Nuno A.This paper presents a five-year case study of the development and operation of the Academic Success Observatory, an institutional platform designed to support data-driven academic management in higher education. The system combines automated data extraction modules, interactive dashboards, and a machine learning-based dropout prediction model. Drawing from three institutional databases, updated weekly, the platform enables continuous monitoring of academic indicators, report generation, and targeted support actions. The article discusses key technical and institutional challenges faced, as well as the benefits of integrating the platform into the academic decisionmaking process. The results highlight the system’s potential to enhance decision-making, enable faster interventions, and foster a data-informed institutional culture.
- An ICT-enhanced methodology for the characterization of vernacular built heritage at a regional scalePublication . Tapiero, Juan; Graus, Sandra; Khei, Soon; Silva, Dener; Conde, Otavio; Ferreira, Tiago Manuel; Ortega, Javier; Luso, Eduarda; Rodrigues, Hugo; Vasconçelos, GraçaThe characterization of vernacular buildings is crucial for understanding the historical, social, and cultural significance of a community. These buildings reflect a collective memory and result from a long adaptation process to the local environment. Documenting them facilitates better decision-making regarding the preservation of their intrinsic values and long-term conservation. Unfortunately, depopulation processes in many areas threaten this invaluable heritage. Furthermore, this heritage is often overlooked due to a lack of awareness and appreciation by local authorities and residents. This paper presents a methodology for documenting and inventorying vernacular built heritage, with the main goal of contributing to promoting its valorization. The methodology integrates Information and Communication Technologies (ICT) with GIS tools to create large-scale inventories. Using the Montesinho Natural Park (Portugal) as a case study, the methodology facilitated the collection of data from over 2,000 buildings in 13 villages. The collected data was then used to characterize the vernacular built heritage of selected villages in terms of authenticity, conservation state, materials, construction systems, past interventions, present use, and occupancy. The findings of this study can serve as a valuable resource for developing inventories of vernacular buildings in rural areas, contributing to the protection of this distinctive architectural heritage
- Optimization approaches in electric machine design: insights from a bibliometric analysisPublication . Nascimento, Cecilia Pagnozzi do; Silvério, Ana Cristina; Baptista, Bruno; Carvalho, José Augusto; Bazzo, Thiago; Ferreira, Ângela P.Optimizing the design of electric machines is a complex task due to the large number of interrelated geometric and physical parameters that influence performance, efficiency, cost, and sustainability. Numerous deterministic and stochastic optimization techniques have been developed to address these challenges, each presenting distinct advantages and limitations. Deterministic approaches, though computationally efficient, often converge to local minima, while stochastic methods provide broader search capabilities at the expense of higher computational effort. Despite the growing application of optimization in electric machine design, a comprehensive bibliometric overview of this research area is lacking. This study aims to fill that gap by conducting a bibliometric analysis of optimization methods applied to electric machine design. Using data retrieved from the Web of Science (WoS) and analyzed through co-citation mapping with VOSviewer, 246 relevant articles were examined, resulting in a focused sample of 73 key studies. The analysis identifies the most frequently optimized machine types, the main optimization objectives, and the predominant methodologies employed in recent years. By addressing these dimensions, this work provides a conceptual reference framework to guide both academic researchers and industry professionals in selecting appropriate optimization strategies. The results also highlight emerging trends and future research opportunities, contributing to a deeper understanding of the evolution and intellectual structure of optimization in electric machine design.
- Three-dimensional modelling of in-isolation tensile response of geogrids using hyperbolic constitutive modelsPublication . Paiva, Lucas; Pinho-Lopes, Margarida; Valente, Robertt; Paula, António MiguelNumerical modelling of geogrids is a challenging task, with extruded geogrids often presenting complex geometries and nonlinear tensile response even at low strain rates. In this study, threedimensional (3D) models were developed in ABAQUS to investigate the in-isolation tensile response of extruded geogrids, accounting for a detailed geometric discretization. Hyperbolic constitutive models were used to represent the nonlinear tensile response, including fracture simulation. A benchmarking exercise was initially performed using the literature data to assess the main numerical modelling parameters for a precise and time efficient simulation. Then, a case study composed of three extruded geogrids were used to validate the model. Particular emphasis was given on the data treatment of the case study, namely with the development of a data-driven model to obtain the most representative load strain curve from experimental specimens. The modelling approach proposed in this study was capable of capturing the inisolation tensile response of extruded geogrids with good accuracy, and accounting for softening and fracture responses.
- Tensile behavior of weathered thermally bonded polypropylene geotextiles: analysis using constitutive modelsPublication . Carneiro, Jose Ricardo; Paula, António Miguel; Pinho-Lopes, MargaridaWeathering agents can significantly affect the mechanical response of geotextiles, particularly when long exposure periods are involved. Usually, in design, changes in the mechanical behavior of geotextiles are represented by reduction factors for their tensile strength. However, their full tensile force versus elongation response can be affected. The main aim of this work was to contribute to defining simple procedures to estimate tensile force versus elongation curves for weathered samples of geotextiles. The tensile response of two thermally bonded polypropylene geotextiles, before and after natural and artificial weathering, was assessed experimentally and analyzed using different constitutive models: polynomial (Orders 4 and 6) and hyperbolic. The influence of weathering on the mechanical response of the geotextiles was analyzed, polynomial and hyperbolic models for representing the tensile force versus elongation response were adopted and their parameters derived, and simple relations were implemented to estimate model parameters for weathered samples. Results revealed the occurrence of changes in the tensile behavior of the geotextiles, both under natural and artificial weathering conditions. Both groups of models fitted the experimental data properly. The Order 4 and 6 polynomial models are shown to have limited application, as the model parameters had no link to the tensile properties of the geotextiles. By contrast, the parameters of the hyperbolic model were linked to the tensile properties, particularly if affected by correction factors. The hyperbolic model parameters of the weathered samples were estimated using the model parameters of the reference samples and the reduction factors to allow for weathering (initial stiffness and tensile strength). These estimates proved to be adequate for representing the tensile response of weathered samples, particularly for low ranges of elongation. Finally, a simple procedure to represent the tensile response of weathered geotextiles was proposed. This procedure has shown promise in generating realistic tensile versus elongation curves.
- A constitutive model for describing the tensile response of woven polyethylene terephthalate geogrids after damagePublication . Lombardi, Giovani; Pinho-Lopes, Margarida; Paula, António Miguel; Pereira, AntónioA constitutive model was used to describe the tensile response of two woven Polyethylene Terephthalate (PET) geogrids, before and after mechanical damage. The model parameters of undamaged and damaged specimens were estimated via numerical regressions of test results. For each sample, the experimental and fitted tensile strengths were statistically compared using hypothesis tests. For each geogrid, tensile load-strain curves of damaged samples were drawn by applying scaling factors to the plot of the undamaged sample. The curve fittings resulted in high R-2 values for undamaged and damaged specimens of the geogrids. For most samples, there was no significant mean difference between the experimental and fitted tensile strength. The model allowed us to describe the load-strain curve of a geogrid from its tensile properties: & epsilon;(max), T-max and J(i). Regardless of the type of damage (in laboratory or in situ), the model was able to describe the load-strain curves of damaged samples using data from undamaged samples and scaling factors.
- 3D Numerical modeling of geosynthetics for soil reinforcement: a bibliometric analysis and literature reviewPublication . Paiva, Lucas; Pinho-Lopes, Margarida; Paula, António Miguel; Valente, RoberttSoil reinforcement using geosynthetics is an efficient and cost-effective solution for a variety of geotechnical structures. Along with the increasing use of geosynthetics, there is a need to expand and enhance the design methodologies for these elements, which are still frequently based on conservative limit equilibrium approaches. In this paper, a bibliometric analysis was conducted on geosynthetic-reinforced soil structures (GRS), identifying the state of the art, research trends, and other indicators. The data were obtained from the Scopus platform and processed by VOSViewer v1.6 software. The initial search comprised 552 papers and the screening process selected 516 relevant papers from 1992 to October 2023. The study analyzed the occurrence of publications by year, keyword trends, authors, citations/co-citations, and bibliographic coupling. Then, a focus was given to 3D modeling research on geosynthetics, highlighting the dominant modeling techniques, material properties, and design challenges in GRS. The bibliometric analysis provided a crucial guideline in the identification of relevant papers and research trends, and a series of conclusions were presented regarding the 3D modeling techniques, choice of material properties, and boundary conditions.