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2nd International Conference Innovation in Engineering, ICIE 2022

作者： Gonçalves, A. Manuela Pereira, F. Catarina Costa, Marco Leão, Celina P. Department of Mathematics and Center of Mathematics University of Minho Braga Portugal Águeda School of Technology and Management and Center for Research and Development in Mathematics and Applications University of Aveiro Aveiro Portugal ALGORITMI Centre University of Minho Guimarães Portugal

ISBN: (纸本)9783031093593

Increasingly, reduction of water availability has been a reality, and population growth, pollution, and climate change have contributed to exacerbating this problem. Dry periods, which occur when precipitation is lower than expected in a given territory, have become more frequent and prolonged, and therefore it is crucial to efficiently manage water use in response to environmental concerns. The main challenge in this work is to present the irrigation problem as an optimal control problem along with the presentation of preliminary results based on an exploratory statistical and critical analysis of daily meteorological variables. The variables considered are: maximum air temperature, minimum air temperature, and total precipitation recorded during the last ten years (2010–2019). The methodology followed, based on state-space models, shows flexibility to allow the integration of new data, updating in real time the model, and the incorporation of covariates that are important to explain the process in analysis. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Exploratory data analysis Imputation Irrigation Meteorological variables Time series

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Light rings on stationary axisymmetric spacetimes: Blind to the topology and able to coexist

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Physical Review D 2024年第6期109卷 064050-064050页

作者： Pedro V. P. Cunha Carlos A. R. Herdeiro João P. A. Novo Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal

It has been established that black hole (BH) spacetimes obeying some general set of assumptions always possess, at least, one light ring (LR) per rotation sense [Cunha and Herdeiro, Phys. Rev. Lett. 124, 181101 (2020)]. This theorem was originally established for asymptotically flat, stationary, axial symmetric, 1+3-dimensional circular spacetimes harboring a nonextremal and topologically spherical Killing horizon. Following the mantra that a theorem is only as strong as its assumptions, in this work we extend this theorem to nontopologically spherical (toroidal) BHs and to spacetimes harboring more than one BH. As shown previously, we here show that each BH still contributes with, at least, one LR (per rotation sense).

关键词： Classical black holes General relativity formalism Spacetime topology & causal structure

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A Smart Tool to Unlock Hidden Insights in Industrial Data by Leveraging EDA, LLM, Conformal Prediction, and AutoML

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Procedia Computer Science 2025年 253卷 2615-2624页

作者： Vasco Costa Diogo Costa Eugénio M. Rocha Department of Electronics Telecommunications and Informatics University of Aveiro 3810-193 Portugal Department of Mechanical Engineering University of Aveiro 3810-193 Portugal Center for Research and Development in Mathematics and Applications (CIDMA) Aveiro 3810-193 Portugal Department of Mathematics University of Aveiro 3810-193 Portugal

Rising competitiveness and client requirements make effective use of high volume and complexity real-time industrial data crucial for faster decision-making. However, this potential is hindered by a lack of smart, user-friendly analytic tools for all collaborators. Despite the proliferation of Machine Learning (ML) tools for data scientists, non-experts struggle with converting data into actionable insights and identifying profitable data science projects. A smart tool is thus proposed, allowing non-experts to perform preliminary data evaluations through profiled analysis pathways that execute predefined sets of Exploratory Data Analysis (EDA) methods and ML operations. Further assisting users, the tool solely relies on metadata attributes and textual descriptions of datasets enhanced by interaction with a Large Language Model (LLM). This paper examines profile selection stages, replacing traditional ML methods with Conformal Prediction (CP) techniques. CP identifies multiple potential prospects with statistical confidence and recognizes when correct predictions are impossible. Trials with task-labeled metadata files (derived from publicly available datasets) showed that while classic ML methods had about 80% efficiency, CP techniques improved the selection process, keeping profiling errors below 0.06 with 99% confidence. This approach enables the correct identification (with statistical confidence) of appropriate analysis profiles for data science problems, thus paving the way for more efficient data analysis tools in industrial settings, accessible to users of all skill levels.

关键词： Exploratory Data Analysis Machine Learning Conformal Prediction Large Language Models Industry 4.0

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Exact multiblack hole spacetimes in Einstein-ModMax theory

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Physical Review D 2025年第6期111卷 064046-064046页

作者： Ana Bokulić Carlos A. R. Herdeiro Department of Physics Faculty of Science University of Zagreb Bijenička cesta 32 10000 Zagreb Croatia and Departamento de Matemática Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-193 Aveiro Portugal Departamento de Matemática Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-193 Aveiro Portugal

Exact solutions describing multiple, electrically charged black holes (BHs) in a model of nonlinear electrodynamics (NLE) minimally coupled to Einstein’s gravity are presented. The NLE model is ModMax theory, that has attracted much attention due to its duality and conformal invariance, features shared with standard (linear) electrodynamics. In the nonextremal case, the solution has conical singularities, similarly to the multi Reissner-Nordström solution in Einstein-Maxwell theory. In the extremal case the solution is regular on and outside the event horizon; it is isometric to the Majumdar-Papapetrou solution, although the individual BHs have a nonunitary charge to mass ratio, due to screening effects. Using the ModMax electromagnetic duality invariance, magnetically charged and dyonic generalizations are also obtained. Finally, we construct multi-BH solutions with a positive cosmological constant.

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Evaluating Student Behaviour on the MathE Platform-Clustering Algorithms Approaches 16th

Evaluating Student Behaviour on the MathE Platform-Clusterin...

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16th International Conference on Learning and Intelligent Optimization, LION 16 2022

作者： Azevedo, Beatriz Flamia Rocha, Ana Maria A. C. Fernandes, Florbela P. Pacheco, Maria F. Pereira, Ana I. Instituto Politécnico de Bragança Bragança5300-253 Portugal Algoritmi Research Centre University of Minho Campus Azurém Guimarães4800-058 Portugal Center for Research and Development in Mathematics and Applications CIDMA University of Aveiro Aveiro Portugal

ISBN: (纸本)9783031248658

The MathE platform is an online educational platform that aims to help students who struggle to learn college mathematics as well as students who wish to deepen their knowledge on subjects that rely on a strong mathematical background, at their own pace. The MathE platform is currently being used by a significant number of users, from all over the world, as a tool to support and engage students, ensuring new and creative ways to encourage them to improve their mathematical skills. This paper is addressed to evaluate the students’ performance on the Linear Algebra topic, which is a specific topic of the MathE platform. In order to achieve this goal, four clustering algorithms were considered;three of them based on different bio-inspired techniques and the k-means algorithm. The results showed that most students choose to answer only basic level questions, and even within that subset, they make a lot of mistakes. When students take the risk of answering advanced questions, they make even more mistakes, which causes them to return to the basic level questions. Considering these results, it is now necessary to carry out an in-depth study to reorganize the available questions according to other levels of difficulty, and not just between basic and advanced levels as it is.

关键词： Students

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Unlocking Tourism Diversity in Winter: Clusters of Tourists in Lisbon Based on Motivations, Profiles, and Behaviour 19

Unlocking Tourism Diversity in Winter: Clusters of Tourists ...

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19th European Conference on Innovation and Entrepreneurship, ECIE 2024

作者： Teresa Machado, Ana Raposo Santos, Zélia Nunes, Sandra Rosário, João Belo, Miguel Costa, Teresa Segurado Severino, Filipe de Lurdes Calisto, Maria Gláucia Roque, Ana Cristina, Margarida Lisbon Portugal Setúbal Portugal Estoril Portugal CiTUR - Center for Tourism Research Development and Innovation Estoril Portugal NovaMath - Center for Mathematics and Applications Nova University Lisbon Almada Portugal RESILIENCE - Center for Regional Resilience and Sustainability Setúbal Portugal

ISBN: (纸本)9781917204149

Recent trends in Lisbon's winter tourism indicate a shift towards off-peak travel, attracting diverse visitors with its rich cultural heritage, sustainable initiatives, and extended stay options for digital nomads. The city's culinary scene, arts, wellness activities, and tech-driven tourism options enhance its appeal. Aligned with these recent trends, tourism in Lisbon's region during the winter season presents a unique and dynamic landscape influenced by a wide range of motivations, tourist profiles, and travel behaviours. This study aims to define distinctive clusters of winter tourists in Lisbon by analysing these key variables, providing valuable insights specific to the winter travel context. Based on a compiled dataset from the winter season in Lisbon, this study delves into examining the factors driving tourist visits, encompassing socio-economic backgrounds, travel frequency, and age demographics. We aim to reveal the distinctive subgroups that define Lisbon's winter tourist population, employing data analysis techniques such as cluster analysis. From an academic perspective, this study offers a novel tourist segmentation model based on motivations, profiles, and behaviour. This model enriches the existing body of knowledge in tourism studies, providing a valuable reference for future research. For tourism agents in Lisbon, this study provides actionable insights to enhance strategic decision-making. By segmenting winter tourists, they can tailor marketing strategies and product development to cater to diverse tourist segments. Moreover, this approach can lead to economic benefits, optimising resource allocation, and revenue generation. © 2024 Academic Conferences and Publishing International Limited. All rights reserved.

关键词： Leisure

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Bottleneck prediction and data-driven discrete-event simulation for a balanced manufacturing line

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Procedia Computer Science 2022年 200卷 1145-1154页

作者： Eugénio M. Rocha Maria J. Lopes Department of Mathematics University of Aveiro 3810 Portugal Center for Research and Development in Mathematics and Applications (CIDMA) Aveiro 3810 Portugal Bosch Termotecnologia S.A. 3800 Portugal

Bottleneck identification is a relevant tool for continuous optimization of production lines. In this work, we implement a data-driven discrete-event simulator (DDS) based on experimental distributions, obtained from real historical data. The DDS allows to analyse the behavior of a balanced manufacturing line at Bosch Thermotechnology, under different hypotheses. It shows that some scenarios perceived as likely to increase output may actually decrease production metrics, reveals the importance of line injection rates, and leads to the need for adequate real time bottleneck forecasting tools, which allow shift managers intervention in a useful time frame. Eleven prediction models are tested, where a random forest and a multi-layer perceptron attain the best performances (above 95% in all metrics). This data flow is operationalized through a micro-services pipeline which is briefly discussed.

关键词： data-driven discrete-event simulation bottleneck prediction machine learning manufacturing lines

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EMRIs around j = 1 black holes with synchronised hair

arXiv

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arXiv 2023年

作者： Delgado, Jorge F.M. Herdeiro, Carlos A.R. Radu, Eugen Departamento de Matemática Universidade de Aveiro Center for Research and Development in Mathematics and Applications CIDMA Campus de Santiago Aveiro3810-183 Portugal

We study extreme mass ratio inspirals (EMRIs) due to an infalling Light Compact Object (LCO) onto a generic class of stationary and axi-symmetric massive compact objects (MCO - with or without a horizon). Using the quadrupole hybrid formalism we obtain a master formula for the evolution of the radius of the LCO and find qualitatively different behaviours depending on the geodesic structure of the MCO. We then specialize the MCO to a black hole with synchronised scalar hair (BHsSH). To allow a comparison with a highly spinning Kerr BH, we consider BHsSH with dimensionless spin, j = 1. This yields two distinct sequences of solutions. The first harbours Kerr-like solutions with maximal hairiness of ∼ 10%. The corresponding EMRIs are Kerr-like, but the cut-off frequency can be a few times smaller than in Kerr, yielding waveforms with quantitatively significant non-Kerrness. The second sequence links the extremal Kerr black hole to a mini-boson star with j = 1. Here we observe qualitative non-Kerrness, such as the non-monotonically increase of the angular velocity and stagnation endpoints, reflecting Kerr-unlike geodesic structures. Copyright © 2023, The Authors. All rights reserved.

关键词： Black holes

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Analyzing the MathE Platform Through Clustering Algorithms 22nd

Analyzing the MathE Platform Through Clustering Algorithms

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22nd International Conference on Computational Science and Its applications , ICCSA 2022

作者： Azevedo, Beatriz Flamia Amoura, Yahia Rocha, Ana Maria A. C. Fernandes, Florbela P. Pacheco, Maria F. Pereira, Ana I. Instituto Politécnico de Bragança Bragança5300-253 Portugal ALGORITMI Center University of Minho Campus de Azurém Guimarães4800-058 Portugal Center for Research and Development in Mathematics and Applications CIDMA University of Aveiro Aveiro Portugal

ISBN: (纸本)9783031105616

University lecturers have been encouraged to adopt innovative methodologies and teaching tools in order to implement an interactive and appealing educational environment. The MathE platform was created with the main goal of providing students and teachers with a new perspective on mathematical teaching and learning in a dynamic and appealing way, relying on digital interactive technologies that enable customized study. The MathE platform has been online since 2019, having since been used by many students and professors around the world. However, the necessity for some improvements on the platform has been identified, in order to make it more interactive and able to meet the needs of students in a customized way. Based on previous studies, it is known that one of the urgent needs is the reorganization of the available resources into more than two levels (basic and advanced), as it currently is. Thus, this paper investigates, through the application of two clustering methodologies, the optimal number of levels of difficulty to reorganize the resources in the MathE platform. Hierarchical Clustering and three Bio-inspired Automatic Clustering Algorithms were applied to the database, which is composed of questions answered by the students on the platform. The results of both methodologies point out six as the optimal number of levels of difficulty to group the resources offered by the platform. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Students

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The Volume-Viscosity Swallowing Test – Portuguese Version: Validation and prevalence of safety and efficacy clinical signs in acute stroke patients

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Revista de Logopedia, Foniatria y Audiologia 2022年第4期42卷 227-237页

作者： Camões, Catarina Matos, Assunção Sa-Couto, Pedro Dourado, Marília Faculty of Medicine of the University of Coimbra Coimbra Portugal Center for Research in Health Technologies and Services (CINTESIS @RISE) Porto Portugal School of Health Sciences University of Aveiro (ESSUA) Aveiro Portugal Centre for Research and Development in Mathematics and Applications (CIDMA) Department of Mathematics University of Aveiro (DMAT) Portugal Center for the Study and Development of Continuing and Palliative Care Faculty of Medicine of the University of Coimbra Coimbra Portugal Centre for Health Studies and Research of the University of Coimbra – Faculty of Economics of University of Coimbra Portugal

Purpose: The early identification of oropharyngeal dysphagia (OD) in patients after an acute stroke using non-invasive and easily administered instruments can minimize its consequences and reduce comorbidity and mortality. The Volume-Viscosity Swallow Test (V-VST) is a screening test that makes it possible. The goal of this study is to contribute to the validation of the V-VST European Portuguese (V-VST: EP) version and study the prevalence of safety and efficacy signs in acute stroke patients. Method: The V-VST: EP, its instructions manual and algorithm, was presented to a panel of experts, to assess its content validity. It was applied to 33 acute stroke patients, with signs of OD, to analyze its psychometric properties. Finally, the prevalence of impaired signs of safety and efficacy was analyzed. Results: The V-VST: EP and its instruction manual (content) demonstrate very good agreement values. Most of the results for inter and intra-evaluator reliability presented Cohen's kappa values higher than 0.60 or 0.80 (75.0%). The concurrent validity (against the 3 OZ wst) presented a sensitivity of 100% and a specificity of 57.1%. For evaluator 1, the results presented are for the nectar, liquid and pudding consistencies, the prevalence values for the 5 ml, 10 ml and 20 ml volume capacity was: impaired lip closure (36%, 39%, 18%), piecemeal deglutition (50%, 50%, 50%), oral residue (7%, 0%, 9%), pharyngeal residue (25%, 17%, 9%) and safe swallowing (89%, 33%, 94%), respectively. © 2022 Elsevier España, S.L.U. y Asociación Española de Logopedia, Foniatría y Audiología e Iberoamericana de Fonoaudiología

关键词： Acute stroke Dysphagia screening Swallowing disorders V-VST

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