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Publicações

2020

Portuguese national potential for floating photovoltaic systems: a case study

Autores
Baptista, J; Vargas, P;

Publicação
2020 20TH IEEE INTERNATIONAL CONFERENCE ON ENVIRONMENT AND ELECTRICAL ENGINEERING AND 2020 4TH IEEE INDUSTRIAL AND COMMERCIAL POWER SYSTEMS EUROPE (EEEIC/I&CPS EUROPE)

Abstract
Over the past few decades, much has been done globally to make final energy consumption more sustainable, integrating more renewable resources. In Europe, there are many directives and regulations that imposes to the states ambitious targets on the promotion of renewable energies and energetic efficiency among others. Portugal has not only fulfilled all the goals but has also exceeded them. This is the case with the integration of renew ables in electricity consumption, which is currently rated at 53 %, with the prospect of reaching 80% in 2030. In this scenario, it is important to encourage the energy production from the solar resource as the country has optimal conditions for this purpose. This research assess the existing Portuguese potential for floating photovoltaic systems and its integration in the power grid. Another aim of this study is to sizing and assesses the energetic potential of floating solar power plant in Gouvaes dam, included in the Tamega hydroelectric complex in under construction in northern Portugal belong to Iberdrola Company.

2020

Cooperative UAV-UGV Autonomous Power Pylon Inspection: An Investigation of Cooperative Outdoor Vehicle Positioning Architecture

Autores
Cantieri, A; Ferraz, M; Szekir, G; Teixeira, MA; Lima, J; Oliveira, AS; Wehrmeister, MA;

Publicação
SENSORS

Abstract
Realizing autonomous inspection, such as that of power distribution lines, through unmanned aerial vehicle (UAV) systems is a key research domain in robotics. In particular, the use of autonomous and semi-autonomous vehicles to execute the tasks of an inspection process can enhance the efficacy and safety of the operation; however, many technical problems, such as those pertaining to the precise positioning and path following of the vehicles, robust obstacle detection, and intelligent control, must be addressed. In this study, an innovative architecture involving an unmanned aircraft vehicle (UAV) and an unmanned ground vehicle (UGV) was examined for detailed inspections of power lines. In the proposed strategy, each vehicle provides its position information to the other, which ensures a safe inspection process. The results of real-world experiments indicate a satisfactory performance, thereby demonstrating the feasibility of the proposed approach.

2020

Compilation of MATLAB computations to CPU/GPU via C/OpenCL generation

Autores
Reis, L; Bispo, J; Cardoso, JMP;

Publicação
CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE

Abstract
In order to take advantage of the processing power of current computing platforms, programmers typically need to develop software versions for different target devices. This task is time-consuming and requires significant programming and computer architecture expertise. A possible and more convenient alternative is to start with a single high-level description of a program with minimum implementation details, and generate custom implementations according to the target platform. In this paper, we use MATLAB as a high-level programming language and propose a compiler that targets CPU/GPU computing platforms by generating customized implementations in C and OpenCL. We propose a number of compiler techniques to automatically generate efficient C and OpenCL code from MATLAB programs. One of such compiler techniques relies on heuristics to decide when and how to use Shared Virtual Memory (SVM). The experimental results show that our approach is able to generate code that provides significant speedups (eg, geometric mean speedup of 11x for a set of simple benchmarks) using a discrete GPU over equivalent sequential C code executing on a CPU. With more complex benchmarks, for which only some code regions can be parallelized, and are thus offloaded, the generated code achieved speedups of up to 2.2x. We also show the impact of using SVM, specifically fine-grained buffers, and the results show that the compiler is able to achieve significant speedups, both over the versions without SVM and with naive aggressive SVM use, across three CPU/GPU platforms.

2020

A measure of the size of the magnetospheric accretion region in TW Hydrae

Autores
Lopez, RG; Natta, A; Garatti, ACO; Ray, TP; Fedriani, R; Koutoulaki, M; Klarmann, L; Perraut, K; Sanchez Bermudez, J; Benisty, M; Dougados, C; Labadie, L; Brandner, W; Garcia, PJV; Henning, T; Caselli, P; Duvert, G; de Zeeuw, T; Grellmann, R; Abuter, R; Amorim, A; Baub?ck, M; Berger, JP; Bonnet, H; Buron, A; Cl?net, Y; du Foresto, VC; de Wit, W; Eckart, A; Eisenhauer, F; Filho, M; Gao, F; Dabo, CEG; Gendron, E; Genzel, R; Gillessen, S; Habibi, M; Haubois, X; Haussmann, F; Hippler, S; Hubert, Z; Horrobin, M; Rosales, AJ; Jocou, L; Kervella, P; Kolb, J; Lacour, S; Le Bouquin, JB; L?na, P; Ott, T; Paumard, T; Perrin, G; Pfuhl, O; Ramirez, A; Rau, C; Rousset, G; Scheithauer, S; Shangguan, J; Stadler, J; Straub, O; Straubmeier, C; Sturm, E; van Dishoeck, E; Vincent, F; von Fellenberg, S; Widmann, F; Wieprecht, E; Wiest, M; Wiezorrek, E; Woillez, J; Yazici, S; Zins, G;

Publicação
NATURE

Abstract
Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius(1-3). The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett gamma (Br gamma) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere(4-6)because the weak magnetic fields (some tenths of a gauss) detected in these sources(7,8)result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds(9,10)make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit). The size of the inner disk of the T Tauri star TW Hydrae is determined using optical long-baseline interferometric observations, indicating that hydrogen emission comes from a region approximately 3.5 stellar radii across.

2020

Proceedings of the 8th International Workshop on Big Data, IoT Streams and Heterogeneous Source Mining: Algorithms, Systems, Programming Models and Applications co-located with 25th ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD 2019), Anchorage, Alaska, August 4-8, 2019

Autores
Bifet, A; Berlingerio, M; Gama, J; Read, J; Nogueira, AR;

Publicação
BigMine@KDD

Abstract

2020

Backward Compatible Object Detection Using HDR Image Content

Autores
Mukherjee, R; Melo, M; Filipe, V; Chalmers, A; Bessa, M;

Publicação
IEEE ACCESS

Abstract
Convolution Neural Network (CNN)-based object detection models have achieved unprecedented accuracy in challenging detection tasks. However, existing detection models (detection heads) trained on 8-bits/pixel/channel low dynamic range (LDR) images are unable to detect relevant objects under lighting conditions where a portion of the image is either under-exposed or over-exposed. Although this issue can be addressed by introducing High Dynamic Range (HDR) content and training existing detection heads on HDR content, there are several major challenges, such as the lack of real-life annotated HDR dataset(s) and extensive computational resources required for training and the hyper-parameter search. In this paper, we introduce an alternative backwards-compatible methodology to detect objects in challenging lighting conditions using existing CNN-based detection heads. This approach facilitates the use of HDR imaging without the immediate need for creating annotated HDR datasets and the associated expensive retraining procedure. The proposed approach uses HDR imaging to capture relevant details in high contrast scenarios. Subsequently, the scene dynamic range and wider colour gamut are compressed using HDR to LDR mapping techniques such that the salient highlight, shadow, and chroma details are preserved. The mapped LDR image can then be used by existing pre-trained models to extract relevant features required to detect objects in both the under-exposed and over-exposed regions of a scene. In addition, we also conduct an evaluation to study the feasibility of using existing HDR to LDR mapping techniques with existing detection heads trained on standard detection datasets such as PASCAL VOC and MSCOCO. Results show that the images obtained from the mapping techniques are suitable for object detection, and some of them can significantly outperform traditional LDR images.

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