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Publications

2023

Pocket Labs as a STEM Learning Tool and for Engineering Motivation

Authors
Cardoso, A; Oliveira, PM; Sa, J;

Publication
LEARNING IN THE AGE OF DIGITAL AND GREEN TRANSITION, ICL2022, VOL 1

Abstract
Teaching and learning are processes that must accompany the digital transition, which is one of the biggest challenges we currently face, along with the green transition. The digital transition in education is a process with several challenges that must count on the involvement and collaboration of all stakeholders, contributing to the schools of the future. For this, technology plays a decisive role, and must be integrated into classes as a relevant tool to develop and implement different types of experiments, motivating the students towards STEM areas. In this context, a project financed by IFAC made it possible to use pocket laboratories in different high schools, encouraging teachers to prepare activities supported by this equipment, stimulating students to be interested in engineering topics. This article presents the approach followed in one high school and discusses the results obtained, highlighting the usefulness and opportunity of using pocket labs, and low-cost equipment in general, in school activities, which can promote the STEM areas and, in particular, the engineering courses.

2023

MRVs: Enforcing Numeric Invariants in Parallel Updates to Hotspots with Randomized Splitting

Authors
Faria, N; Pereira, J;

Publication
Proc. ACM Manag. Data

Abstract
Performance of transactional systems is degraded by update hotspots as conflicts lead to waiting and wasted work. This is particularly challenging in emerging large-scale database systems, as latency increases the probability of conflicts, state-of-the-art lock-based mitigations are not available, and most alternatives provide only weak consistency and cannot enforce lower bound invariants. We address this challenge with Multi-Record Values (MRVs), a technique that can be layered on existing database systems and that uses randomization to split and access numeric values in multiple records such that the probability of conflict can be made arbitrarily small. The only coordination needed is the underlying transactional system, meaning it retains existing isolation guarantees. The proposal is tested on five different systems ranging from DBx1000 (scale-up) to MySQL GR and a cloud-native NewSQL system (scale-out). The experiments explore design and configuration trade-offs and, with the TPC-C and STAMP Vacation benchmarks, demonstrate improved throughput and reduced abort rates when compared to alternatives.

2023

Novelty detection for multi-label stream classification under extreme verification latency

Authors
Costa, JD; Júnior; Faria, ER; Silva, JA; Gama, J; Cerri, R;

Publication
Appl. Soft Comput.

Abstract
Multi-Label Stream Classification (MLSC) is the classification streaming examples into multiple classes simultaneously. Since new classes may emerge during the streaming process (concept evolution) and known classes may change over time (concept drift) it is challenging task. In real situations, concept drift and concept evolution occur in scenarios where the actual labels of arriving examples are never available; hence it is impractical to update decision models in a supervised fashion. This is known as Extreme Verification Latency, a topic that has not been well investigated in MLSC literature. This paper proposes a new method called MultI-label learNing Algorithm for Data Streams with Binary Relevance transformation (MINAS-BR), integrated with a Novelty Detection (ND) procedure for detecting concept evolution and concept drift, updating the model in an unsupervised fashion. Furthermore, since the label space is not static, we propose a new evaluation methodology for MLSC under extreme verification latency. Experiments over synthetic and real-world data sets with different concept drift and concept evolution scenarios confirmed the strategies employed in the MINAS-BR and presented relevant advances for handling streaming multi-label data. © 2023 Elsevier B.V.

2023

Prototyping with the IVY Workbench: Bridging Formal Methods and User-Centred Design

Authors
da Costa, RB; Campos, JC;

Publication
HUMAN-COMPUTER INTERACTION - INTERACT 2023, PT II

Abstract
The IVY workbench is a model-based tool for the formal modelling and verification of interactive systems. The tool uses model checking to carry out the verification step. The goal is not to replace, but to complement more exploratory and iterative user-centred design approaches. However, the need for formal and rigorous modelling and reasoning raises challenges for the integration of both approaches. This paper presents a new plugin that aims to provide support for the integration of the formal methods based analysis supported by the tool, with user-centred design. The plugin is described, and an initial validation of its functionalities presented.

2023

Designing a Skilled Soccer Team for RoboCup: Exploring Skill-Set-Primitives through Reinforcement Learning

Authors
Abreu, M; Reis, LP; Lau, N;

Publication
CoRR

Abstract

2023

Calibration for an Ensemble of Grapevine Phenology Models under Different Optimization Algorithms

Authors
Yang, CY; Menz, C; Reis, S; Machado, N; Santos, JA; Torres-Matallana, JA;

Publication
AGRONOMY-BASEL

Abstract
Vine phenology modelling is increasingly important for winegrowers and viticulturists. Model calibration is often required before practical applications. However, when multiple models and optimization methods are applied for different varieties, it is rarely known which factor tends to mostly affect the calibration results. We mainly aim to investigate the main source of the variability in the modelling errors for the flowering timings of two important varieties of vine in the Douro Demarcated Region (DDR) of Portugal; this is based on five phenology model simulations that use optimal parameters and that are estimated by three optimization algorithms (MLE, SA and SCE-UA). Our results indicate that the main source of the variability in calibration can be affected by the initially assumed parameter boundary. Restricting the initial parameter distribution to a narrow range impedes the algorithm from exploring the full parameter space and searching for optimal parameters. This can lead to the largest variation in different models. At an identified appropriate boundary, the difference between the two varieties represents the largest source of uncertainty, while the choice of algorithm for calibration contributes least to the overall uncertainty. The smaller variability among different models or algorithms (tools for analysis) compared to between different varieties could indicate the overall reliability of the calibration. All optimization algorithms show similar results in terms of the obtained goodness-of-fit: the RMSE (MAE) is 5-6 (4-5) days with a negligible mean bias and moderately good R-2 (0.5-0.6) for the ensemble median predictor. Nevertheless, a similar predictive performance can result from differently estimated parameter values, due to the equifinality or multi-modal issue in which different parameter combinations give similar results. This mainly occurs for models with a non-linear structure compared to those with a near-linear one. Yet, the former models are found to outperform the latter ones in predicting the flowering timing of the two varieties in the DDR. Overall, our findings highlight the importance of carefully defining the initial parameter boundary and decomposing the total variance of prediction errors. This study is expected to bring new insights that will help to better inform users about the importance of choice when these factors are involved in calibration. Nonetheless, the importance of each factor can change depending on the specific situation. Details of how the optimization methods are applied and of the continuous model improvement are important.

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