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coimbra, Portugal

Soares S.,University of Coimbra | Antunes C.H.,INESC Coimbra | Araujo R.,University of Coimbra

In the last decades ensemble learning has established itself as a valuable strategy within the computational intelligence modeling and machine learning community. Ensemble learning is a paradigm where multiple models combine in some way their decisions, or their learning algorithms, or different data to improve the prediction performance. Ensemble learning aims at improving the generalization ability and the reliability of the system. Key factors of ensemble systems are diversity, training and combining ensemble members to improve the ensemble system performance. Since there is no unified procedure to address all these issues, this work proposes and compares Genetic Algorithm and Simulated Annealing based approaches for the automatic development of Neural Network Ensembles for regression problems. The main contribution of this work is the development of optimization techniques that selects the best subset of models to be aggregated taking into account all the key factors of ensemble systems (e.g., diversity, training ensemble members and combination strategy). Experiments on two well-known data sets are reported to evaluate the effectiveness of the proposed methodologies. Results show that these outperform other approaches including Simple Bagging, Negative Correlation Learning (NCL), AdaBoost and GASEN in terms of generalization ability. © 2013 Elsevier B.V. Source

Branco F.G.,INESC Coimbra | Godinho L.,University of Coimbra
Construction and Building Materials

Most recent European acoustic design codes and regulations establish a maximum value for impact sound insulation on pavement slabs. These requirements demand the implementation of technical solutions such as floating floors, with the introduction of a resilient layer under the finishing pavement layer. Technical solutions such as floating concrete slabs (placed over synthetic foam or natural fibers layers), or floating pavements (like wooden floors built over synthetic foam layers) became quite common on recently built constructions. A possible alternative solution to floating pavements is the use of lightweight soft layers, applied over the structural concrete slab. These lightweight materials may present high quality results on the reduction of impact sound transmission. In the present work, lightweight mortar slabs were tested, and the impact sound insulation for different materials was quantified. Different types of cement mortar containing expanded polystyrene, expanded cork and expanded clay granulates were compared. The acoustical performance of these solutions was evaluated through laboratory tests, using an acoustic chamber with small dimensions, which allows comparing several solutions, on similar test conditions, in an expedite way. The influence of the type floor covering used over the lightweight mortar layer was also analysed. Different types of materials were tested. © 2013 Elsevier Ltd. All rights reserved. Source

The current financial crisis has reinforced the need for transparency and accountability in the context of open government. As such, governments have promoted transparency initiatives by developing portals where a huge number of datasets is made available. But simply to disclose datasets in a centralized web portal might not address the variety of citizens' and other stakeholders' information seeking scenarios. To characterize such scenarios we considered the role of scientists and researchers as 'information brokers' and analysed transparency assessment literature and the way information was being searched for in those exercises. Based on this analysis, we propose an overall data disclosure strategy which contemplates several different types of information sources (other than just one centralized web portal) and lay out a set of desired characteristics for those sources. We then use the proposed strategy as a framework to assess the Portuguese panorama with respect to information disclosure, and also to practically illustrate the strategy and its components. The assessment exercise showed that the proposed strategy could indeed be used not only as an open government policy guideline, but also as an open government (transparency) assessment framework. © 2013 - IOS Press and the authors. All rights reserved. Source

Jose Oliveira M.,University of Algarve | Ribeiro A.B.,National Laboratory for Civil Engineering | Branco F.G.,INESC Coimbra
Construction and Building Materials

Self-compacting concrete possesses special properties that recommend its application in many repair jobs. However, in some practical cases, inappropriate performance of the repair material has been observed in the early stages of hydration, including cracks or delamination due to shrinkage. This study presents laboratory test results on the autogenous shrinkage of self-compacting concrete. Taking into account the typically high autogenous shrinkage of concrete mixtures with low W/C, associated with this type of concrete, the efficiency of different shrinkage-compensating products was evaluated. Two shrinkage reducing admixtures and one expansive binder have been studied. The results show the efficiency of the individual use of each product and put in evidence a synergistic effect on the autogenous shrinkage reduction when shrinkage reducing admixture and expansive agent were combined. The results also show a potential for achieving a predefined shrinkage range, by using the combined effect of a set retarder and an expansive admixture. © 2013 Elsevier Ltd. All rights reserved. Source

Girao Coelho A.M.,Technical University of Delft | Girao Coelho A.M.,INESC Coimbra
Computers and Structures

This paper presents a finite element analysis of partial strength steel joints. The joint configurations are drawn from a previous experimental study, with good prediction shown by the finite element model. Failure of the joint is confined to the end plate and is predicted by means of micromechanical models based on void growth mechanisms and coalescence, which are practical to apply to finite element analyses without additional modelling effort. Parametric studies are carried out to investigate the structural behaviour with variations in beam depth and thickness of the end plate. Quantitative assessments of resistance and rotation capacity are undertaken. © 2012 Elsevier Ltd. All rights reserved. Source

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