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Publicações

2019

Femtosecond Laser Micromachining of Fabry-Pérot Interferometers for Magnetic Field Sensing

Autores
Maia, JM; Amorim, VA; Viveiros, D; Marques, PVS;

Publicação
EPJ Web of Conferences

Abstract
Fs-laser micromachining is a high precision fabrication technique that can be used to write novel three-dimensional structures, depending on the nature of light-matter interaction. In fused silica, the material modification can lead to (i) an increase of the refractive index around the focal volume, resulting in the formation of optical circuits, or (ii) an enhancement of the etch rate of the laser-affected zones relative to the pristine material, leading to a selective and anisotropic etching reaction that enables fabrication of microfluidic systems. Here, both effects are combined to fabricate a Fabry-Pérot interferometer, where optical waveguides and microfluidic channels are integrated monolithically in a fused silica chip. By filling the channel with a magnetic fluid whose refractive index changes with an external magnetic field, the device can be used as a magnetic field sensor. A linear sensitivity of -0.12 nm/mT is obtained in the 5.0±0.5 to 33.0±0.5 mT range, with the field being applied parallel to the light propagation direction.

2019

Numerical Analysis of the Shape of Bump Solutions in a Neuronal Model of Working Memory

Autores
Wojtak, W; Ferreira, F; Bicho, E; Erlhagen, W;

Publicação
INTERNATIONAL CONFERENCE ON NUMERICAL ANALYSIS AND APPLIED MATHEMATICS (ICNAAM-2018)

Abstract
Neural field models, formalized by integro-differential equations, describe the large-scale spatio-temporal dynamics of neuronal populations [1]. They have been used in the past as a framework for modeling a wide range of brain functions, including multi-item working memory [2]. Neural field equations support spatially localized regions of high activity (or bumps) that are initially triggered by brief sensory inputs and subsequently become self-sustained by recurrent interactions within the neural population. We apply a special class of oscillatory coupling functions and analyze how the shape and spatial extension of multi-bump solutions change as the spatial ranges of excitation and inhibition within the field are varied [3]. More precisely, we use numerical continuation to find and follow solutions of neural field equations as the parameter controlling the distance between consecutive zeros of the coupling function is varied [4]. Important for a working memory application (e.g. [5]), we investigate how changes in this parameter affect the shape of bump solutions and therefore the maximum number of bumps that may exist in a given finite interval.

2019

Classification of local energy trading negotiation profiles using artificial neural networks

Autores
Pinto, A; Pinto, T; Praca, I; Vale, Z;

Publicação
IEEE Power and Energy Society General Meeting

Abstract
Electricity markets are evolving into a local trading setting, which makes it for unexperienced players to achieve good agreements and obtain profits. One of the solutions to deal with this issue is to provide players with decision support solutions capable of identifying opponents' negotiation profiles, so that negotiation strategies can be adapted to those profiles in order to reach the best possible results from negotiations. This paper presents an approach that classifies opponents' proposals during a negotiation, to determine which is the typical negotiation profile in which the opponent most relates. The classification process is performed using an artificial neural network approach, and it is able to adapt at each new proposal during the negotiation process, by re-classifying the opponents' negotiation profile according to the most recent actions. In this way, effective decision support is provided to market players, enabling them to adapt the negotiation strategy throughout the negotiations. © 2019 IEEE.

2019

A geometric distance measurement to the Galactic center black hole with 0.3% uncertainty

Autores
Abuter, R; Amorim, A; Bauboeeck, M; Berger, JP; Bonnet, H; Brandner, W; Clenet, Y; du Foresto, VC; de Zeeuw, PT; Dexter, J; Duvert, G; Eckart, A; Eisenhauer, F; Schreiber, NMF; Garcia, P; Gao, F; Gendron, E; Genzel, R; Gerhard, O; Gillessen, S; Habibi, M; Haubois, X; Henning, T; Hippler, S; Horrobin, M; Jimenez Rosales, A; Jocou, L; Kervella, P; Lacour, S; Lapeyrere, V; Le Bouquin, JB; Lena, P; Ott, T; Paumard, T; Perraut, K; Perrin, G; Pfuhl, O; Rabien, S; Coira, GR; Rousset, G; Scheithauer, S; Sternberg, A; Straub, O; Straubmeier, C; Sturm, E; Tacconi, LJ; Vincent, F; von Fellenberg, S; Waisberg, I; Widmann, F; Wieprecht, E; Wiezorrek, E; Woillez, J; Yazici, S;

Publicação
ASTRONOMY & ASTROPHYSICS

Abstract
We present a 0.16% precise and 0.27% accurate determination of R-0, the distance to the Galactic center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 mu as in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km s(-1), this yields a geometric distance estimate of R-0 = 8178 +/- 13(stat.) +/- 22(sys.) pc. This work updates our previous publication, in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20 sigma with f(redshift) = 1.04 +/- 0.05.

2019

Localization Based on Natural Features Detector for Steep Slope Vineyards

Autores
Mendes, JM; dos Santos, FN; Ferraz, NA; do Couto, PM; dos Santos, RM;

Publicação
JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS

Abstract
Placing ground robots to work in steep slope vineyards is a complex challenge. The Global Positioning System (GPS) signal is not always available and accurate. A reliable localization approach to detect natural features for this environment is required. This paper presents an improved version of a visual detector for Vineyards Trunks and Masts (ViTruDe) and, a robot able to cope pruning actions in steep slope vineyards (AgRob V16). In addition, it presents an augmented data-set for other localization and mapping algorithm benchmarks. ViTruDe accuracy is higher than 95% under our experiments. Under a simulated runtime test, the accuracy lies between 27% - 96% depending on ViTrude parametrization. This approach can feed a localization system to solve a GPS signal absence. The ViTruDe detector also considers economic constraints and allows to develop cost-effective robots. The augmented training and datasets are publicly available for future research work.

2019

Real-Time Scheduling of Demand Response Options Considering the Volatility of Wind Power Generation

Autores
Talari, S; Shafie Khah, M; Chen, Y; Wei, W; Gaspar, PD; Catalao, JP;

Publicação
IEEE TRANSACTIONS ON SUSTAINABLE ENERGY

Abstract
In this paper, a new methodology to unleash the potential of demand response (DR) in real-time is presented. Customers may tend to apply their DR potential in the real-time market in addition to their scheduled potential in the day-ahead stage. Thus, the proposed method facilitates balancing the real-time market via DR aggregators. It can be vital, once the stochastic variables of the network such as production of wind power generators do not follow the forecasted production in real-time and have some distortions. Two-stage stochastic programming is employed to schedule some DR options in both day-ahead and real-time markets. DR options in real-time are scheduled based on possible scenarios that reflect the behaviors of wind power generation and are generated through Monte-Carlo simulation method. The merits of the method are demonstrated in a 6-bus case study and in the IEEE RTS-96, which shows a notable reduction in total operation cost.

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