ESTG - Artigos em revistas internacionais
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- Identification of the optimal entry points at District Metered Areas and implementation of pressure managementPublication . Gomes, Ricardo; Marques, Alfeu Sá; Sousa, JoaquimNowadays, the implementation of pressure management in District Metered Areas (DMAs) is considered one of the most effective tools for leakage control, particularly in large networks and in systems with deteriorated infrastructures and with high pressure. The goal of the methodology proposed in this paper is to identify the optimal entry points at DMAs, determine the network needs in terms of reinforcement/replacement, and fix both the location and settings of different types of Pressure Reduction Valves (PRVs) for leakage control. This methodology is based on an optimisation model, which is solved by a Simulated Annealing algorithm, and the solutions obtained always fulfil the minimum pressure requirements for the network. The objective function comprises the total cost of the DMAs implementation and the economic benefits that can be achieved by pressure management. Finally, the results for two case studies are presented and discussed.
- Distributed Text Classification With an Ensemble Kernel-Based Learning ApproachPublication . Silva, Catarina; Lotric, Uros; Ribeiro, Bernardete; Dobnikar, AndrejConstructing a single text classifier that excels in any given application is a rather inviable goal. As a result, ensemble systems are becoming an important resource, since they permit the use of simpler classifiers and the integration of different knowledge in the learning process. However, many text-classification ensemble approaches have an extremely high computational burden, which poses limitations in applications in real environments. Moreover, state-of-the-art kernel-based classifiers, such as support vector machines and relevance vector machines, demand large resources when applied to large databases. Therefore, we propose the use of a new systematic distributed ensemble framework to tackle these challenges, based on a generic deployment strategy in a cluster distributed environment. We employ a combination of both task and data decomposition of the text-classification system, based on partitioning, communication, agglomeration, and mapping to define and optimize a graph of dependent tasks. Additionally, the framework includes an ensemble system where we exploit diverse patterns of errors and gain from the synergies between the ensemble classifiers. The ensemble data partitioning strategy used is shown to improve the performance of baseline state-of-the-art kernel-based machines. The experimental results show that the performance of the proposed framework outperforms standard methods both in speed and classification.
- EditorialPublication . Bártolo, Paulo; Chua, C.K.The year of 2012 is a fruitful year for Virtual & Physical Prototyping. The journal has maintained its usual publication record and published a total of twenty-three original research articles (including this issue). Similarly, total citations to this journal in Year 2012 have also maintained at a near-hundred level by the mid-October (Scopus). The stabilized publication record and total citations demonstrate a mature and healthy status of the journal. In this regard, we thank all authors who have made contributions to this journal.
- Perceptions of Organizational Virtuousness and Happiness as Predictors of Organizational Citizenship BehaviorsPublication . Rego, Arménio; Ribeiro, Neuza; Cunha, Miguel P.Moral and financial scandals emerging in recent years around the world have created the momentum for reconsidering the role of virtuousness in organizational settings. This empirical study seeks to contribute toward maintaining this momentum. We answer to researchers' suggestions that the exploratory study carried out by Cameron et al. (Am Behav Sci 47(6):766-790, 2004), which related organizational virtuousness (OV) and performance, must be pursued employing their measure of OV in other contexts and in relation to other outcomes (Wright and Goodstein, J Manage 33(6):928-958, 2007). Two hundred and sixteen employees reported their perceptions of OV and their affective well-being (AWB) at work (one of the main indicators of employees' happiness), their supervisors reporting their organizational citizenship behaviors (OCB). The main finding is that the perceptions of OV predict some OCB both directly and through the mediating role of AWB. The evidence suggests that OV is worthy of a higher status in the business and organizational psychology literatures.
- Production of glued laminated timber with copper azole treated maritime pinePublication . Gaspar, Florindo; Cruz, Helena; Gomes, Augusto; Nunes, LinaA study was conducted to evaluate the performance of glued laminated timber (glulam) of maritime pine treated with a copper azole preservative product. Shear strength of glue lines met the requirements of EN 386 (2001) with no influence of clamping pressure and cure temperature. According to the same standard, delamination was satisfactory for higher cure temperatures applied with a clamping pressure of 0.6 N/mm2. Finger joints made with treated wood gave satisfactory bending strength. The preservative treatment did not influence the modulus of elasticity of the beams. According to a Monte Carlo simulation and following the requirements of EN 1194 (2002), glulam of class GL 28c can be manufactured if visually graded maritime pine of classes E and EE (NP 4305 1995) is used in the inner and outer lamellas, respectively, and class GL 24h when using both grades in equal proportions randomly distributed through the glulam element.
- Water quality in Lis river, PortugalPublication . vieira, judite; Fonseca, André; Vilar, Vítor J. P.; Boaventura, Rui A. R.; Botelho, Cidália M. S.In the past 30 years, the Lis river basin has been subjected to constant ecological disasters mainly due to piggery untreated wastewater discharges. The aim of this study was to evaluate the effect of existing domestic, agricultural, and industrial activities on the water quality, and to propose a watershed plan to protect and manage surface water resources within the Lis river basin. For this purpose, 16 monitoring stations have been strategically selected along the Lis river stretch and its main tributaries to evaluate the water quality in six different sampling periods (2003- 2006). All samples were characterized in terms of organic material, nutrients, chlorophyll, and pathogenic bacteria. Generally, the Lis river presents poor water quality, according to environmental quality standards for surface water, principally in terms of dissolved oxygen, biochemical oxygen demand, total nitrogen, and fecal coliform, which can be associated mainly with the contamination source from pig-breeding farms. © Springer Science+Business Media B.V. 2012.
- EditorialPublication . Bártolo, Paulo; Chua, C. K.In this issue, we invited five winners of the ‘Best Paper Awards’ at the 4th International Conference on Advanced Research in Virtual and Rapid Prototyping, Leiria, Portugal, 6-10 October 2009, to enhance their conference papers to the standard of an international journal. One paper each from ‘Materials’ track, ‘Biomanufacturing’ track and ‘Virtual Environment & Simulation’ track and two papers from ‘Advanced Rapid Prototyping Technologies and Nanofabrication’ track.
- Evaluation of in vitro degradation of PCL scaffolds fabricated via BioExtrusion. Part 1: Influence of the degradation environmentPublication . Domingos, M.; Chiellini, F.; Cometa, S.; De Giglio, E.; Grillo-Fernandes, E.; Bártolo, P.; Chiellini, E.One of the most promising approaches in tissue engineering (TE) comprises the development of 3D porous scaffolds which are able to promote tissue regeneration. Biocompatible and biodegradable poly(e-caprolactone) (PCL) structures are increasingly used as temporary extra-cellular matrices for bone tissue engineering. To ensure an appropriate bone restoration over the long term, the selected material must have a degradation rate that match the in-growth of new bone. The in vivo process, by which the scaffold degrades and is resorbed transferring the load and function back to the host tissue, is complex. Consequently, an appropriate preliminary in vitro study is required. A novel extrusion-based technology called BioExtruder was used to produce PCL porous scaffolds made with layers of directionally aligned microfilaments. The in vitro degradation behaviour in both simulated body fluid (SBF) and phosphate buffer solution (PBS) were investigated over 6 months. The characterization of the degradation behaviour of the structures was performed at specific times by evaluating changes in the average molecular weight, the weight loss and its thermal properties. Morphological and surface chemical analyses were also performed using a Scanning Electron Microscopy (SEM) and an X-ray Photoelectron Spectroscopy (XPS), respectively.
- Particle swarm optimization with fractional-order velocityPublication . Pires, E. J. Solteiro; Machado, J. A. Tenreiro; Oliveira, P. B. de Moura; Cunha, J. Boaventura; Mendes, LuísThis paper proposes a novel method for controlling the convergence rate of a particle swarm optimization algorithm using fractional calculus (FC) concepts. The optimization is tested for several wellknown functions and the relationship between the fractional order velocity and the convergence of the algorithm is observed. The FC demonstrates a potential for interpreting evolution of the algorithm and to control its convergence.
- Performance and Computational Complexity Assessment of High-Efficiency Video EncodersPublication . Correa, Guilherme; Assunção, Pedro; Agostini, Luciano; Cruz, Luis A. da SilvaThis paper presents a performance evaluation study of coding efficiency versus computational complexity for the forthcoming High Efficiency Video Coding (HEVC) standard. A thorough experimental investigation was carried out to identify the tools that most affect the encoding efficiency and computational complexity of the HEVC encoder. A set of 16 different encoding configurations was created to investigate the impact of each tool, varying the encoding parameter set and comparing the results with a baseline encoder. This paper shows that, even though the computational complexity increases monotonically from the baseline to the most complex configuration, the encoding efficiency saturates at some point. Moreover, the results of this paper provide relevant information for implementation of complexity-constrained encoders by taking into account the tradeoff between complexity and coding efficiency. It is shown that low-complexity encoding configurations, defined by careful selection of coding tools, achieve coding efficiency comparable to that of high-complexity configurations.