2011
Autores
Batista, NC; Melicio, R; Matias, JCO; Catalao, JPS;
Publicação
IET Conference Publications
Abstract
The wind power generation is experiencing a rapid growth, achieving the highest number of European installations in 2010 comparing to other renewable sources. The need for a smarter grid capable of integrating several decentralized sources of energy and the increasing need for energy in urban areas, has led to an increase interest in wind turbines for the urban areas. In these environments, vertical axis wind turbines (VAWT) have several advantages over horizontal axis wind turbines (HAWT), namely: their ability to operate closer to the ground; their insensitivity to yaw wind directions; the smaller number of components; the operation at low sound emissions; the ability to generate energy from wind in skew flow. One problem with the lift-type VAWT (Darrieus wind turbines) is their natural inability to self-start at low wind speeds without extra components. Hence, a new blade profile for Darrieus type VAWT is presented in this paper, capable to self-start at low wind speeds. A methodology is developed to compare the new blade profile with other known airfoils. Finally, conclusions are duly drawn.
2011
Autores
Agra, A; Cerveira, A; Requejo, C; Santos, E;
Publicação
NETWORK OPTIMIZATION
Abstract
We consider the weight-constrained minimum spanning tree problem which has important applications in telecommunication networks design. We discuss and compare several formulations. In order to strengthen these formulations, new classes of valid inequalities are introduced. They adapt the well-known cover, extended cover and lifted cover inequalities. They incorporate information from the two subsets: the set of spanning trees and the knapsack set. We report computational experiments where the best performance of a standard optimization package was obtained when using a formulation based on the well-known Miller-Tucker-Zemlin variables combined with separation of cut-set inequalities.
2011
Autores
Ribeiro, DMD; Colunas, MFM; Ferreira Marques, FAF; Fernandes, JM; Silva Cunha, JPS;
Publicação
2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC)
Abstract
The study of stress and fatigue among First Responders is a major step in mitigating this public health problem. Blood pressure, heart rate variability and fatigue related arrhythmia are three of the main "windows" to study stress and fatigue. In this paper we present a wearable medical device, capable of acquiring an electrocardiogram and estimating blood pressure in real time, through a pulse wave transit time approach. The system is based on an existent certified wearable medical device called "Vital Jacket" and is aimed to become a tool to allow cardiologists in studying stress and fatigue among first response professionals.
2011
Autores
Gama, J; Kosina, P;
Publicação
IJCAI International Joint Conference on Artificial Intelligence
Abstract
Decision rules, which can provide good interpretability and flexibility for data mining tasks, have received very little attention in the stream mining community so far. In this work we introduce a new algorithm to learn rule sets, designed for open-ended data streams. The proposed algorithm is able to continuously learn compact ordered and unordered rule sets. The experimental evaluation shows competitive results in comparison with VFDT and C4.5rules.
2011
Autores
Statkiewicz Barabach, G; Carvalho, JP; Frazao, O; Olszewski, J; Mergo, P; Santos, JL; Urbanczyk, W;
Publicação
INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
Microstructured optical fibers (MOFs) have been widely studied owing to their potential for obtaining novel transmission, nonlinear and sensing characteristics. Sensing applications of MOFs cover various types of devices for measurements of different physical and specific chemical compounds in gases and liquids employing evanescent field techniques. Such fibers can also be used as active and passive elements in fiber-optic polarimetric and interferometric sensors. We present an in-line fiber modal interferometer fabricated in boron-doped highly birefringent microstructured fiber. The boron-doped region located in the middle of the core decreases the effective index of the fundamental mode and facilitates coupling between the fundamental and the first order mode. The coupling regions have the form of fiber narrowings fabricated using CO2 laser and are distant by a few millimeters. The spectral intensity at the sensor output is modulated only by intermodal interference produced by a short piece of fiber between the two coupling points. Moreover, as the fiber is highly birefringence, each pair of polarization modes produces its own intermodal fringes, which results in the contrast modulation of the overall interference signal observed at the fiber output, and provides an additional degree of freedom to measure simultaneously a pair of measurands.
2011
Autores
Pousinho, HMI; Mendes, VMF; Catalao, JPS;
Publicação
IET Conference Publications
Abstract
This paper develops a computational tool, based on two-stage stochastic programming, for a wind power producer bidding in the electricity market. The uncertainty related to electricity market prices and wind power production is taken into account. A hybrid intelligent technique, combining wavelet transform, particle swarm optimization and adaptive-networkbased fuzzy inference system, enables the generation of scenarios. Besides, risk aversion is considered using the conditional value-at-risk methodology. Computer simulation results are provided and analyzed. Finally, conclusions are duly drawn.
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