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Publicações

Publicações por Alexandre Valle

2021

A Comparative Study on the Performance of the IB+ Tree and the I2B+ Tree

Autores
Carneiro, E; de Carvalho, AV; Oliveira, MA;

Publicação
Journal of Information Systems Engineering and Management

Abstract
Index structures were often used to optimise fetch operations to external storage devices (secondary memory). Nowadays, this also holds for increasingly large amounts of data residing in main-memory (primary memory). Within this scope, this work focuses on index structures that efficiently insert, query and delete valid-time data from very large datasets. This work performs a comparative study on the performance of the Interval B+ tree (IB+ tree) and the Improved Interval B+ tree (I2B+ tree): a variant that improves the time-efficiency of the deletion operation by reducing the number of traversed nodes to access siblings. We performed an extensive analysis of the performance of two operations: insertions and deletions, on both index structures, using multiple datasets with growing volumes of data, distinct temporal distributions and tree parameters (time-split alpha and node order). Results confirm that the I2B+ tree globally outperforms the IB+ tree, since, on average, deletion operations are 7% faster, despite insertions requiring 2% more time. Furthermore, results also allowed to determine the key factors that augment the performance difference on deletions between both trees. Copyright © 2021 by Author/s and Licensed by Veritas Publications Ltd., UK.

2021

Computer Graphics teaching challenges: Guidelines for balancing depth, complexity and mentoring in a confinement context

Autores
Rodrigues, R; Matos, T; de Carvalho, AV; Barbosa, JG; Assaf, R; Nóbrega, R; Coelho, A; de Sousa, AA;

Publicação
Graph. Vis. Comput.

Abstract

2025

Multiplatform Ecosystem for Visualizing Ocean Dynamic Formations with Virtual Choreographies: Oil Spill Case

Autores
Lacet, D; Cassola, F; Valle, A; Oliveira, M; Morgado, L;

Publicação
2025 IEEE CONFERENCE ON VIRTUAL REALITY AND 3D USER INTERFACES ABSTRACTS AND WORKSHOPS, VRW

Abstract
This paper presents a solution for visualizing oil spills at sea by combining satellite data with virtual choreographies. The system enables dynamic, interactive visualization of oil slicks, reflecting their shape, movement, and interaction with environmental factors like currents and wind. High resolution geospatial data supports a multiplatform experience with aerial and underwater perspectives. This approach promotes independence, interoperability, and multiplatform compatibility in environmental disaster monitoring. The results validate virtual choreographies as effective tools for immersive exploration and analysis, offering structured data narratives beyond passive visualization especially valuable for mixed reality applications.

2025

Image-Based Video Game Asset Generation and Evaluation Using Deep Learning: A Systematic Review of Methods and Applications

Autores
Ribeiro, R; de Carvalho, AV; Rodrigues, NB;

Publicação
IEEE TRANSACTIONS ON GAMES

Abstract
Creating content for digital video game is an expensive segment of the development process, and many techniques have been explored to automate it. Much of the generated content is graphical, ranging from textures and sprites to typographical elements and user interfaces. Numerous techniques have been explored to automate the generation of these assets, with recent advancements incorporating artificial intelligence methodologies, such as deep learning generative models. This study comprehensively surveys the literature from 2016 onward, focusing on using machine learning to generate image-based assets for video game development, reviewing the deep learning approaches employed, and analyzing the specific challenges found. Specifically, the deep learning approaches employed, the problems addressed within the domain, and the metrics used for evaluating the results. The study demonstrates a knowledge gap in generative methods for some types of video game assets. In addition, applicability and effectiveness of the most used evaluation metrics in the literature are studied. As future research prospects, with the increase in popularity of generative AI, the adoption of such techniques will be seen in automation processes.

2023

BEYOND FRONT AND BACK OFFICE: VISUALIZATIONS, REPRESENTATIONS AND ACCESS THROUGH POSTCOLONIAL LENSES BETWEEN A RESEARCH PLATFORM AND AN ARTS EDUCATION ARCHIVE

Autores
Assis, T; Martins, C; Valle, A; Santos, A; Castro, J; Osório, L; Silva, P;

Publicação
ICERI2023 Proceedings - ICERI Proceedings

Abstract

2023

A Comparison of Point Set Registration Algorithms for Quantification of Change in Spatiotemporal Data

Autores
Gomes M.; De Carvalho A.V.; Oliveira M.A.; Carneiro E.;

Publicação
Iberian Conference on Information Systems and Technologies, CISTI

Abstract
Point Set Registration (PSR) algorithms have very different underlying theoretical models to define a process that calculates the alignment solution between two point clouds. The selection of a particular PSR algorithm can be based on the efficiency (time to compute the alignment) and accuracy (a measure of error using the estimated alignment). In our specific context, previous work used a CPD algorithm to detect and quantify change in spatiotemporal datasets composed of moving and shape-changing objects represented by a sequence of time stamped 2D polygon boundaries. Though the results were promising, we question if the selection of a particular PSR algorithm influences the results of detection and quantification of change. In this work we review and compare several PSR algorithms, characterize test datasets and used metrics, and perform tests for the selected datasets. The results show pyCPD and cyCPD implementations of CPD to be good alternatives and that BCPD can have potential to be yet another alternative. The results also show that detection and quantification accuracy change for some of the tested PSR implementations.

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