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Publications

2014

Untitled

Authors
Lukovic, I; Budimac, Z; Leal, JP; Janousek, J; Rocha, A; Burdescu, DD; Dragan, D;

Publication
COMPUTER SCIENCE AND INFORMATION SYSTEMS

Abstract

2014

Two, three, four or six telescopes with phase referencing or closure phase relations: the best tactics for interferometric image reconstruction

Authors
Gomes, N; Garcia, PJV; Thiebaut, E;

Publication
OPTICAL AND INFRARED INTERFEROMETRY IV

Abstract
Two simulated astronomical objects (a star cluster, and a young stellar object) were mock observed with the VLTI for different array configurations and instruments, and their images reconstructed and compared. The aim of the work is to infer when/if phase referencing with less telescopes is a better choice over closure phases with more telescopes. Three scenarios were put under scrutiny: Phase Referencing (PhR) with 2 telescopes vs Closure Phase (CPh) with 3 telescopes, PhR with 3 telescopes vs CPh with 4 telescopes, and PhR with 4 telescopes vs CPh with 6 telescopes. The number of nights is kept fixed for a given PhR vs CPh configuration. The UV-coverage was improved for the PhR case, by uniformly paving the (u, v) plane while keeping fixed the total number of sampled spatial frequencies. For the majority of the configurations, the results point to comparable performances of phase referencing and closure phases, when the UV-space is judiciously chosen.

2014

Optimal Self-Scheduling of a Wind Power Producer in Energy and Ancillary Services Markets using a Multi-Stage Stochastic Programming

Authors
Shafie khah, M; de la Nieta, AAS; Catalao, JPS; Heydarian Forushani, E;

Publication
2014 SMART GRID CONFERENCE (SGC)

Abstract
Wind power is expected to deliver a significant part of power generation in future smart grid. However, many economic challenges have arisen from the intermittent nature of wind power. In this paper, a multi-stage stochastic model is proposed for self-scheduling problem of Wind Power Producers (WPPs) in competitive electricity markets. The proposed model includes three trading levels namely; forward, day-ahead, and balancing sessions. The problem uncertainties, such as wind power, market prices and quantity of activated reserve by ISO are considered by the Monte Carlo method. Moreover, Conditional Value-at-Risk (CVaR) is employed in the model as an appropriate risk measuring technique. The proposed model yields the optimal behavior of WPPs to participate in day-ahead energy and ancillary services markets (i.e. spinning reserve and regulation). Simulation results indicate that simultaneous participation of the WPPs in the mentioned markets not only augments their profit but also can significantly decrease the associated risks.

2014

Renormalization of circle diffeomorphism sequences and markov sequences

Authors
Almeida, JP; Pinto, AA; Rand, DA;

Publication
Springer Proceedings in Mathematics and Statistics

Abstract
We show a one-to-one correspondence between circle diffeomorphism sequences that are C1+ n-periodic points of renormalization and smooth Markov sequences. © Springer Science+Business Media New York 2014.

2014

Artificial Neural Networks Applied to an Earthwork Construction Database

Authors
Parente, M; Correia, AG; Cortez, P;

Publication
INFORMATION TECHNOLOGY IN GEO-ENGINEERING

Abstract
This paper presents a study based on the application of cascade ANN prediction models to an earthwork construction database. Results show not only a good adjustment to the data, but also the influence of each earthwork construction process on the work rate of the global production line. Furthermore, the obtained results emphasize the importance of optimal resource allocation and management throughout earthwork construction phases. Following this framework, the study concludes with a demonstration of how the developed models can be integrated into a more complex system in order to pursue that purpose.

2014

Rapid fabrication of polymeric micro lenses for optical fiber trapping and beam shaping

Authors
Ribeiro, RSR; Queiros, RB; Ecoffet, C; Soppera, O; Oliva, A; Guerreiro, A; Jorge, PAS;

Publication
OPTICAL TRAPPING AND OPTICAL MICROMANIPULATION XI

Abstract
This work reports a new type of optical fiber tweezers based on polymeric micro-lenses. The lenses are achieved by means of an economical and fast fabrication process, using an in-fiber photo-polymerization technique. The polymerization radiation is guided towards the fiber tip creating a polymeric waveguide. The method allows tailoring the geometry of the tip by adjusting the fabrication parameters. Furthermore, more complex shapes can be fabricated by exploring modal effects at the polymerization/trapping wavelengths, which can be used for different applications such as trapping, beam shaping and patterned illumination.

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