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Publicações

2025

High-Birefringence and Quarter-Wave Plates at 1550 nm Using Azopolymers

Autores
Soares, B; Silva, S; Ribeiro, P; Frazao, O;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
Azobenzenes are a class of compounds which allow the writing and erasure of linear birefringence along any desired direction, through their ability to photoisomerize. This property enables applications requiring polarization control, which, despite extensive exploration in the visible spectrum, have yet to be fully capitalized in the infrared region. This study aims to systematically characterize the creation and relaxation of induced linear birefringence dynamics in azopolymers thin films for the 1550 nm region. Maximum birefringence values as high as 6.02 x 10(-2) were attained during the recording phase with a 445 nm pump laser, that stabilized at 5.40 x 10(-2) during the relaxation phase, achieved for a 2.4 mu m sample. In addition, a maximum phase shift of Delta Phi = 0.54 pi stabilizing at Delta Phi = 0.50 pi, was observed for a 9.7 mu m sample with a 532 nm writing laser. Accordingly, this shows the promising potential of azopolymers for many applications.

2025

An Over-Actuated Hexacopter Tilt-Rotor UAV Prototype for Agriculture of Precision: Modeling and Control

Autores
Pimentel, GO; dos Santos, MF; Lima, J; Mercorelli, P; Fernandes, FM;

Publicação
SENSORS

Abstract
This paper focuses on the modeling, control, and simulation of an over-actuated hexacopter tilt-rotor (HTR). This configuration implies that two of the six actuators are independently tilted using servomotors, which provide high maneuverability and reliability. This approach is predicted to maintain zero pitch throughout the trajectory and is expected to improve the aircraft's steering accuracy. This arrangement is particularly beneficial for precision agriculture (PA) applications where accurate monitoring and management of crops are critical. The enhanced maneuverability allows for precise navigation in complex vineyard environments, enabling the unmanned aerial vehicle (UAV) to perform tasks such as aerial imaging and crop health monitoring. The employed control architecture consists of cascaded proportional (P)-proportional, integral and derivative (PID) controllers using the successive loop closure (SLC) method on the five controlled degrees of freedom (DoFs). Simulated results using Gazebo demonstrate that the HTR achieves stability and maneuverability throughout the flight path, significantly improving precision agriculture practices. Furthermore, a comparison of the HTR with a traditional hexacopter validates the proposed approach.

2025

Jazzline: Composable CryptoLine Functional Correctness Proofs for Jasmin Programs

Autores
Almeida, JB; Barbosa, M; Barthe, G; Blatter, L; Marinho Alves, GXD; Duarte, JD; Grégoire, B; Oliveira, T; Quaresma, M; Strub, PY; Tsai, MH; Wang, BY; Yang, BY;

Publicação
CCS

Abstract

2025

Integration of Online Communication Channels and Online Consumer Behavior

Autores
Pires, PB; Santos, JD; de Brito, PQ;

Publicação
Smart Innovation, Systems and Technologies

Abstract
Establishing the relationship between online communication channels and the stages of the consumer decision-making process was the aim of this research. A review of online communication channels and consumer behavior models was conducted for this purpose. Subsequently, three experiments (car glass repair, retail of clothing and sports equipment, and retail of books and technological products) were carried out that consisted of questionnaires that were applied in companies belonging to different industries. The questionnaires were used to measure the expectations and preferences of consumers at each stage for each channel. The results showed that there is no relationship between online communication channels and the stages of the decision-making process. They also revealed a gap between expectations and preferences for each channel in each phase. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.

2025

Unified concepts: a review and proposal for virtual reality terminology

Autores
Gonçalves, G; Peixoto, B; Miguel, M; Bessa, M;

Publicação
VIRTUAL REALITY

Abstract
Throughout the Virtual Reality (VR) literature, we find different terms to define the same concepts as well as the same terms addressing different concepts. This issue can easily cause misinterpretations and difficulty in the analysis of papers from different authors. This work addresses this terminology confusion through a detailed analysis of current key concepts, how they have been employed, comparing them to other concepts, and proposing adaptations to their definitions to reduce conceptual overlap while preserving the original terms. In this work, we reviewed widely used terms in VR: Fidelity, Realism, Immersion, Presence, and Coherence. We also identified and discussed derivative terms, such as Place Illusion, Plausibility Illusion, Sensorimotor Contingencies, Multisensory, Virtual Content, Objective and Subjective Realism, and Objective and Subjective Internal Coherence. We proposed how these distinct concepts can be separated, merged, and linked, providing a clearer terminology for future use and discussing the implications of this terminology.

2025

Sustainability practices for software development in Scrum environment

Autores
Almeida, F;

Publicação
International Journal of Agile Systems and Management

Abstract
This paper aims to characterise the relevance of sustainability practices in the context of software companies that adopt the Scrum methodology. In the first phase, a multidimensional framework for software sustainability was built, based on the individual, technical, environmental, and social dimensions. Subsequently, a quantitative study was carried out using a survey answered by 397 Scrum professionals working in software companies registered in Portugal. The results reveal significant asymmetries in the implementation of sustainable practices, in which micro companies experience the greatest difficulties in their implementation. The findings also indicate that the practices most adopted by organisations are in the technical and individual dimensions, where a proactive level of maturity is evident. On the other hand, environmental and social practices are still poorly implemented and appear mainly at a reactive level due to the needs of the projects or their teams. © 2025 Elsevier B.V., All rights reserved.

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