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Publications

2024

Demystifying DFT-Based Harmonic Phase Estimation, Transformation, and Synthesis

Authors
Oliveira, M; Santos, V; Saraiva, A; Ferreira, A;

Publication
SIGNALS

Abstract
Many natural signals exhibit quasi-periodic behaviors and are conveniently modeled as combinations of several harmonic sinusoids whose relative frequencies, magnitudes, and phases vary with time. The waveform shapes of those signals reflect important physical phenomena underlying their generation, requiring those parameters to be accurately estimated and modeled. In the literature, accurate phase estimation and modeling have received significantly less attention than frequency or magnitude estimation. This paper first addresses accurate DFT-based phase estimation of individual sinusoids across six scenarios involving two DFT-based filter banks and three different windows. It has been shown that bias in phase estimation is less than 0.001 radians when the SNR is equal to or larger than 2.5 dB. Using the Cram & eacute;r-Rao lower bound as a reference, it has been demonstrated that one particular window offers performance of practical interest by better approximating the CRLB under favorable signal conditions and minimizing performance deviation under adverse conditions. This paper describes the development of a shift-invariant phase-related feature that characterizes the harmonic phase structure. This feature motivates a new signal processing paradigm that greatly simplifies the parametric modeling, transformation, and synthesis of harmonic signals. It also aids in understanding and reverse engineering the phasegram. The theory and results are discussed from a reproducible perspective, with dedicated experiments supported by code, allowing for the replication of figures and results presented in this paper and facilitating further research.

2024

Estimating the Likelihood of Financial Behaviours Using Nearest Neighbors A case study on market sensitivities

Authors
Mendes Neves, T; Seca, D; Sousa, R; Ribeiro, C; Mendes Moreira, J;

Publication
COMPUTATIONAL ECONOMICS

Abstract
As many automated algorithms find their way into the IT systems of the banking sector, having a way to validate and interpret the results from these algorithms can lead to a substantial reduction in the risks associated with automation. Usually, validating these pricing mechanisms requires human resources to manually analyze and validate large quantities of data. There is a lack of effective methods that analyze the time series and understand if what is currently happening is plausible based on previous data, without information about the variables used to calculate the price of the asset. This paper describes an implementation of a process that allows us to validate many data points automatically. We explore the K-Nearest Neighbors algorithm to find coincident patterns in financial time series, allowing us to detect anomalies, outliers, and data points that do not follow normal behavior. This system allows quicker detection of defective calculations that would otherwise result in the incorrect pricing of financial assets. Furthermore, our method does not require knowledge about the variables used to calculate the time series being analyzed. Our proposal uses pattern matching and can validate more than 58% of instances, substantially improving human risk analysts' efficiency. The proposal is completely transparent, allowing analysts to understand how the algorithm made its decision, increasing the trustworthiness of the method.

2024

Comparison of Pallet Detection and Location Using COTS Sensors and AI Based Applications

Authors
Caldana, D; Carvalho, R; Rebelo, PM; Silva, MF; Costa, P; Sobreira, H; Cruz, N;

Publication
ROBOT 2023: SIXTH IBERIAN ROBOTICS CONFERENCE ADVANCES IN ROBOTICS, VOL 1

Abstract
Autonomous Mobile Robots (AMR) are seeing an increased introduction in distinct areas of daily life. Recently, their use has expanded to intralogistics, where forklift type AMR are applied in many situations handling pallets and loading/unloading them into trucks. One of the these vehicles requirements, is that they are able to correctly identify the location and status of pallets, so that the forklifts AMR can insert the forks in the right place. Recently, some commercial sensors have appeared in the market for this purpose. Given these considerations, this paper presents a comparison of the performance of two different approaches for pallet detection: using a commercial off-the-shelf (COTS) sensor and a custom developed application based on Artificial Intelligence algorithms applied to an RGB-D camera, where both the RGB and depth data are used to estimate the position of the pallet pockets.

2024

Exploring students' opinion on software testing courses

Authors
Cammaerts, F; Tramontana, P; Paiva, ACR; Flores, N; Ricós, FP; Snoeck, M;

Publication
PROCEEDINGS OF 2024 28TH INTERNATION CONFERENCE ON EVALUATION AND ASSESSMENT IN SOFTWARE ENGINEERING, EASE 2024

Abstract
Software testing is an important part of the software development lifecycle. As it is a highly sought-after skill in the industry, it is not surprising that there has been a great deal of research into the teaching of software testing in higher education. Most of this research proposes or evaluates pedagogical approaches or software testing tools to assist teachers in educating the next generation of software engineers. These evaluations are often limited to measuring teachers' opinions about the use of a novel pedagogical approach or an educational tool and students' acceptance and performance in terms of desired software testing skills. While tools and pedagogical approaches address specific aspects of a course, to date, little attention has been paid to the opinions of the students about all the individual aspects of a software testing course. This paper aims to address this missing student perspective by taking a holistic view of software testing course designs. To address this gap, an exploratory study was performed by distributing a questionnaire to 103 students from ten different courses to gauge their opinions on a software testing course they are enrolled in. The results show that students generally have a positive perception of the different aspects of their software testing course. However, several areas for improvement were suggested based on the gathered data.

2024

NAVIGATING THE SHIFTING LANDSCAPE OF TEACHER PROFESSIONALITY IN PORTUGUESE HIGHER EDUCATION: A CASE STUDY

Authors
Cruz, M; Mascarenhas, D; Queirós, R; Pinto, C;

Publication
EDULEARN Proceedings - EDULEARN24 Proceedings

Abstract

2024

Artificial Intelligence Approaches for Predictive Maintenance in the Steel Industry: A Survey

Authors
Jakubowski, J; Strzelecka, NW; Ribeiro, RP; Pashami, S; Bobek, S; Gama, J; Nalepa, GJ;

Publication
CoRR

Abstract

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