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Publicações

2019

Gemini north adaptive optics (GNAO): An MCAO system for Gemini North towards conceptual design

Autores
Sivo G.; Palmer D.; Scharwächter J.; Andersen M.; Provost N.; Marin E.; Van Dam M.; Chinn B.; Chirre E.; Cavedoni C.; Schneider T.; Kang S.; Hirst P.; Rambold W.; Ebbers A.; Gigoux P.; Catala L.; Hayward T.; Blakeslee J.; Roe H.; Lotz J.; Kleinman S.; Lazo M.; Blain C.; Sivanandam S.; Feldmeier-Krause A.; Ammons M.; Trujillo C.; Packham C.; Marchis F.; Christou J.; Jee J.; Bally J.; Pierce M.; Puzia T.; Turri P.; Kim H.; Schwamb M.; Dupuy T.; Diaz R.; Carrasco R.; Neichel B.; Correia C.; Steinbring E.; Rigaut F.; Véran J.P.; Chun M.; Lamb M.; Chapman S.; Esposito S.; Fusco T.;

Publicação
AO4ELT 2019 - Proceedings 6th Adaptive Optics for Extremely Large Telescopes

Abstract
Gemini Observatory has been awarded from the National Science Foundation a major fund to build a new state-of-the-art Multi Conjugate Adaptive Optics facility for Gemini North on Maunakea called GNAO. The current baseline system will use two lasers each split in two to create an artificial constellation of four laser guide star to measure the distortions caused by the atmosphere. At least two deformable mirror conjugated to 0km and the main altitude layer above Maunakea will be used to correct these distortions. The facility will be designed to feed future instrumentation, initially a near infrared imager and potentially a visiting 4-arm multi object adaptive optics IFU spectrograph.1 In this paper I will present the main characteristics of this exciting facility, its promises and its challenges. I will also present its conceptual design and results of trade studies conducted within the team and the Gemini Adaptive Optics Working Group. The expected first light is for October 2024.

2019

What Will the Future Bring? The Impact of Automation on Skills and (Un)employment

Autores
Au Yong Oliveira, M; Almeida, AC; Arromba, AR; Fernandes, C; Cardoso, I;

Publicação
Advances in Intelligent Systems and Computing

Abstract
A big concern in seeking to understand the evolution of the future of jobs and the demand for skills with the increase of automation is shown by the wide range of existing literature regarding the subject. This study gathers relevant information about the topics of: automation, the future of employment, advantages and disadvantages of technological changes, changes in the range of skills and if people are ready for the future changes or not. Firstly, the authors give an overview on the main topics that will be discussed later on in the article and construct a theoretical framework based on the current literature. Secondly, the methodology is presented namely the field work involving 21 interviews. After that, the interview results are analyzed, discussed and compared with what was shown in the literature review. The results revealed that people in general are not aware of the impact that automation will have on their working environment. Additionally, the authors concluded that existing education systems should be reformulated since the portfolio of skills will change in the future. © 2019, Springer Nature Switzerland AG.

2019

Digital Piracy: Factors that Influence the Intention to Pirate - A Structural Equation Model Approach

Autores
Meireles, R; Campos, P;

Publicação
INTERNATIONAL JOURNAL OF HUMAN-COMPUTER INTERACTION

Abstract
Faster Internet connections are breaking most of the geographic barriers. At the same time, the huge digital content that have been generated in last years is motivating new forms of digital piracy. We know that piracy of copyrighted digital material has a huge impact on countries' economy, being a major issue for the whole society and not only for content creators. The purpose of this paper is to investigate digital piracy intention. For that purpose, we have expanded the framework of the theory of planned behavior using the utility theory, the deterrence theory and other relevant constructs. Using data from students of a Portuguese university and high school, a sample of 590 questionnaires has been collected. Two models were developed and analyzed using structural equation modeling. The first considers the full sample (Full Model), while the second considers only those who had pirated (Pirate Model). The pirate model confirmed the existence of a significant and strong relation between past behavior and intention toward digital piracy.

2019

Deep Vesselness Measure from Scale-Space Analysis of Hessian Matrix Eigenvalues

Autores
Araújo, RJ; Cardoso, JS; Oliveira, HP;

Publicação
PATTERN RECOGNITION AND IMAGE ANALYSIS, IBPRIA 2019, PT II

Abstract
The enhancement of tubular structures such as vessels in medical images has been addressed in the past, aiming for easier extraction and or visualization of such structures by professionals. Some literature methodologies propose vesselness measures whose design is motivated by local properties of vascular networks and how these influence the eigenvalues of the Hessian matrix. However, past work fails to combine properly the scale-space and neighborhood information, thus leading to the proposal of suboptimal vesselness measures. In this paper, we show that a shallow convolutional neural network is able to learn more optimal embedding spaces from the eigenvalue analysis at different scales, thus leading to a stronger vessel enhancement. Additionally, we also show that such a system maintains one of the biggest advantages of Hessian-based vesselness measures, which is the robustness to data with varying statistics. © 2019, Springer Nature Switzerland AG.

2019

Memory Reclamation Methods for Lock-Free Hash Tries

Autores
Moreno, P; Areias, M; Rocha, R;

Publicação
2019 31ST INTERNATIONAL SYMPOSIUM ON COMPUTER ARCHITECTURE AND HIGH PERFORMANCE COMPUTING (SBAC-PAD 2019)

Abstract
Hash tries are a trie-based data structure with nearly ideal characteristics for the implementation of hash maps. Starting from a particular lock-free hash map data structure, named Lock-Free Hash Tries (LFHT), we focus on solving the problem of memory reclamation without losing the lock-freedom property. We propose an approach that explores the characteristics of the LFHT structure in order to achieve efficient memory reclamation with low and well-defined memory bounds. Experimental results show that our approach obtains better results when compared with other state-of-the-art memory reclamation methods and provides a competitive and scalable hash map implementation, if compared to lock-based implementations.

2019

Co-optimization of Transmission Switching and Variable Reactance Devices Control under Worst-Case Wind Uncertainty

Autores
Nikoobakht, A; Aghaei, J; Lotfi, M; Osorio, GJ; Shafie Khah, M; Catalao, JPS;

Publicação
2019 3RD IEEE CONFERENCE ON CONTROL TECHNOLOGY AND APPLICATIONS (IEEE CCTA 2019)

Abstract
The work reported in this paper jointly addresses two major challenges in modern power systems: 1) systematically maximizing wind power generation (WPG) utilization under worst-case uncertainty and 2) employing mixed integer-nonlinear programming (MINLP) in the co-optimization of variable reactance devices (VRD) and transmission switching (TS) in an AC optimal power flow problem (ACOPF). The first challenge is solved by proposing an interval based robust approach to identify the worst-case WPG uncertainty. Similarly, to overcome the second challenge, a tri-level decomposition algorithm is used to decompose the MINLP representation into one consisting of one mixed-integer linear programming (MILP) and two nonlinear programming (NLPs) problems. Finally, the effectiveness and efficiency of the proposed model is shown by analysing results from testing on the modified RTS-96 system.

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