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Publicações

2014

Support for Refactoring an Application towards an Adaptive Object Model

Autores
Guerra, E; Aguiar, A;

Publicação
COMPUTATIONAL SCIENCE AND ITS APPLICATIONS - ICCSA 2014, PT V

Abstract
Flexibility requirements can appear in the middle of a software development, perceived by several client requests to change the application. A flexible domain model, usually implemented with using the adaptive object model (AOM) architectural style, required custom-made components to handle the current implementation of the domain entities. The problem is that by evolving an AOM model, the components need to be evolved as well, which generates constant rework. This work studied the possible AOM evolution paths, in order to provide support in the components for model changing. An evolution of the Esfinge AOM RoleMapper framework were developed to provide this functionality, allowing AOM models in different stages to be mapped to a single structure. The study was evaluated using a set of tests that were applied in each possible structure for the model.

2014

High-Level Synthesis from C vs. a DSL-based Approach

Autores
de Oliveira, CB; Marques, E; Cardoso, JMP;

Publicação
PROCEEDINGS OF 2014 IEEE INTERNATIONAL PARALLEL & DISTRIBUTED PROCESSING SYMPOSIUM WORKSHOPS (IPDPSW)

Abstract
Field-Programmable Gate Arrays (FPGAs) are able to provide hardware accelerators still maintaining the required programmability. However, the advantages of using FPGAs still depend on the expertise of developers and their knowledge of Hardware Description Languages (HDLs). Although High-level Synthesis (HLS) tools have been developed in order to minimize this problem, they commonly present solutions considered many times inefficient when compared to the ones achieved by a specialized hardware designer. Domain-specific languages (DSLs) can provide alternative solutions to program FPGAs. They can provide higher abstraction levels than HDLs and they may allow the programmer to tune implementations whenever HLS tools are unable to generate efficient designs. In this paper we compare a DSL, named LALP (Language for Aggressive Loop Pipelining), with two typical HLS approaches and show the experimental results achieved in each case. The results show that the use of LALP provides superior performance than the achieved by the HLS tools in most cases.

2014

Reduction of losses in the conductors of a sustainable street lighting as a technique for managing energy consumption and CO2 emissions

Autores
Lobão, JA; Devezas, T; Catalão, JPS;

Publicação
Renewable Energy and Power Quality Journal

Abstract
In recent years there has been a series of documents such as the European Strategy 20-20-20 to address the issue of energy efficiency in various sectors of activity. Your objective is to reduce 20% of energy consumption, 20% of GHG emissions (Greenhouse Gases) and get 20% of the energy consumed is from renewable sources [1]. The reduction of losses in the conductors of a sustainable street lighting installation as a technique for managing energy consumption, also allows the reduction of emissions of greenhouse gases, accounted for in this paper. Reduction of losses in the conductors of a sustainable street lighting, allowing a better use of the installed power, which can be an important issue, particularly allows increasing the weight of the renewable energies.

2014

Impact of Multi-Terminal HVDC grids on AC system stability and operation

Autores
Ciapessoni, E; Cirio, D; Gatti, A; Pitto, A; Denis, AM; He, L; Liu, CC; Moreira, C; Silva, B;

Publicação
CIGRE Session 45 - 45th International Conference on Large High Voltage Electric Systems 2014

Abstract
During the last years, several plans for offshore grid development in Europe have been under discussion as a result of the need for the integration of large amounts of offshore wind power, providing additional transmission capacity and building adequate conditions for the single European electricity market. From the system operation viewpoint, technical constraints justify the need for adopting High Voltage Direct Current (HVDC) technology with Voltage Source Converters (VSC) for offshore grid development rather than conventional AC connections. Additionally, reliability and flexibility of operation is pushing for the development of the Multi-Terminal DC (MTDC) grid concept, by which a set of offshore wind farms is connected to a set of onshore AC nodes via a (possibly meshed) DC grid structure. This concept is in line with the envisioned plans for the development of the pan-European Transmission System. A broad range of aspects related to MTDC grids planning, operation, and technology was dealt within the TWENTIES European research project (2009-2013). In particular, this paper presents some results regarding the impact of MTDC systems on the AC systems they are connected to: specific focus is devoted to provision of advanced ancillary services (primary frequency controls, Fault Ride Through capability to AC faults, reactive power support), to the possible contribution of the MTDC grid in enhancing the operational security of AC systems and in restarting them after partial or complete blackouts. To emphasize the advanced functionalities that can be provided for overall system operation, this MTDC grid is referred to in the paper as "DC Grid" (DCG). Simulation results illustrate the potential benefits for the AC systems deriving from the described advanced control functionalities of DCGs. The work has been carried out within TWENTIES Working Package 5.

2014

Enhancing data stream predictions with reliability estimators and explanation

Autores
Bosnic, Z; Demsar, J; Kespret, G; Rodrigues, PP; Gama, J; Kononenko, I;

Publicação
ENGINEERING APPLICATIONS OF ARTIFICIAL INTELLIGENCE

Abstract
Incremental learning from data streams is increasingly attracting research focus due to many real streaming problems (such as learning from transactions, sensors or other sequential observations) that require processing and forecasting in the real time. In this paper we deal with two issues related to incremental learning - prediction accuracy and prediction explanation - and demonstrate their applicability on several streaming problems for predicting electricity load in the future. For improving prediction accuracy we propose and evaluate the use of two reliability estimators that allow us to estimate prediction error and correct predictions. For improving interpretability of the incremental model and its predictions we propose an adaptation of the existing prediction explanation methodology, which was originally developed for batch learning from stationary data. The explanation methodology is combined with a state-of-the-art concept drift detector and a visualization technique to enhance the explanation in dynamic streaming settings. The results show that the proposed approaches can improve prediction accuracy and allow transparent insight into the modeled concept.

2014

High-sensitivity dispersive Mach -Zehnder interferometer based on a dissimilar-doping dual-core fiber for sensing applications

Autores
Martins, HF; Bierlich, J; Wondraczek, K; Unger, S; Kobelke, J; Schuster, K; Marques, MB; Gonzalez Herraez, M; Frazao, O;

Publicação
OPTICS LETTERS

Abstract
A dual-core fiber in which one of the cores is doped with germanium and the other with phosphorus is used as an in-line Mach-Zehnder dispersive interferometer. By ensuring an equal length but with different dispersion dependencies in the interferometer arms (the two cores), high-sensitivity strain and temperature sensing are achieved. Opposite sensitivities for high and low wavelength peaks were also demonstrated when strain and temperature was applied. To our knowledge this is the first time that such behavior is demonstrated using this type of in-line interferometer based on a dual-core fiber. A sensitivity of (0.102 +/- 0.0020 nm/mu epsilon, between 0 and 800 mu epsilon) and (-4.2 +/- 0.2 nm/degrees C between 47 degrees C and 62 degrees C) is demonstrated. (C) 2014 Optical Society of America

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