ESTG - Artigos em revistas internacionais
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- Seismic behavior of strengthened RC columns under biaxial loading: An experimental characterizationPublication . Pinheiro Rodrigues, Hugo Filipe; Arêde, António; Furtado, André; Rocha, PatrícioAbstract The main purpose of this work it to present an experimental campaign of different strengthening strategies of RC columns, and evaluating benefits concerning their structural behavior for cyclic loading. 9 RC columns were tested, two of them without strengthening and seven composed by strengthened columns by CFRP or steel plates jacketing. The aim is, therefore, to contribute for developing and calibration a procedure that enables the evaluation of the efficiency of the strengthening strategies, their possibilities and application. It was also an objective of this work to explore the possibility of using this techniques on the improvement of existing buildings performance.
- Carbon nanotubes in electrospun polyethylene oxide nanofibres: A potential route to conducting nanofibresPublication . Nazhipkyzy, M; Mohan, S D; Davis, F J; Mitchell, GeoffreyPolyethylene oxide solution containing multi-walled carbon nanotubes have been electrospun onto a rotating collector to produce highly aligned arrays of electrospun nanofibers ranging in diameters from (200 - 360) nanometres. The addition of a surfactant (Triton X-100) is highly effective in dispersing carbon nanotube within an aqueous solution of polyethylene oxide and the resulting mixture can be electrospun without excessive clumping to produce nanofibers containing high loadings of nanotubes; in this case up to 5% wt thereby providing an effective route to electrically conductive nanofibres.
- Edge detection based on Krawtchouk polynomialsPublication . Rivero-Castillo, Daniel; Pijeira, Héctor; Assunção, PedroAbstract Discrete orthogonal polynomials are useful tools in digital image processing to extract visual object contours in different application contexts. This paper proposes an alternative method that extends beyond classic first-order differential operators, by using the properties of Krawtchouk orthogonal polynomials to achieve a first order differential operator. Therefore, smoothing of the image with a 2-D Gaussian filter is not necessary to regularize the ill-posed nature of differentiation. Experimentally, we provide simulation results which show that the proposed method achieves good performance in comparison with commonly used algorithms.
- Proposal for selection of mental health indicators in the management of health networks: from heuristic to process modelingPublication . Lima, Inacia Bezerra de; Yamada, Diego Bettiol; Yoshiura, Vinicius Tohoru; Lance, Rogério Cortecioni; Rodrigues, Lidia Maria Lourençön; Vinci, Andre Luiz Teixeira; Martinho, Ricardo; Pádua, Silvia Dallavalle de; Rijo, Rui Pedro Charters Lopes; Rijo, Rui, Rui Pedro Charters Lopes; Furegato, Antonia Regina Ferreira; Alves, DomingosIn 2011, Brazil instituted the Psychosocial Care Network (RAPS) for people suffering from mental disorders and needs arising from the use of alcohol and other drugs within the Unified Health System an electronic information system that supports the planning, regulation, control and evaluation of mental health actions. Several studies have been done to select a complete set of indicators for mental health in Brazil; however, these studies do not describe how these principles are transposed into indicators. In this work we will use Business Process Management Notation (BPMN) to analyze the process of patient care in a mental health unit and to search through this analysis to select and map those that apply to the specific RAPS institutions. We propose a method, using process modeling along the Thornicroft and Tansella matrix, to select the relevant indicators and their mapping along the network. The method was effective allowing the application of indicators to the concrete reality of a psychiatric hospital in Brazil.
- Effects of Shot-Peening and Stress Ratio on the Fatigue Crack Propagation of AL 7475-T7351 SpecimensPublication . Ferreira, Natália; Antunes, Pedro; Ferreira, José; Costa, José D. M.; Capela, CarlosShot peening is an attractive technique for fatigue enhanced performance of metallic components, because it increases fatigue crack initiation life prevention and retards early crack growth. Engineering design based on fatigue crack propagation predictions applying the principles of fracture mechanics is commonly used in aluminum structures for aerospace engineering. The main purpose of present work was to analyze the effect of shot peening on the fatigue crack propagation of the 7475 aluminum alloy, under both constant amplitude loading and periodical overload blocks. The tests were performed on 4 and 8 mm thickness specimens with stress ratios of 0.05 and 0.4. The analysis of the shot-peened surface showed a small increase of the micro-hardness values due to the plastic deformations imposed by shot peening. The surface peening beneficial effect on fatigue crack growth is very limited; its main effect is more noticeable near the threshold. The specimen’s thickness only has marginal influence on the crack propagation, in opposite to the stress ratio. Periodic overload blocks of 300 cycles promotes a reduction of the fatigue crack growth rate for both intervals of 7500 and 15,000 cycles.
- Firm growth and R&D: Evidence from the Portuguese manufacturing industryPublication . Oliveira, Blandina; Fortunato, AdelinoThis work studies the effects of R&D activities and investment, both phys ical and R&D, on the growth of firms by considering a dynamic firm growth model with serial correlation. The main hypotheses maintain that firms with a strong com mitment to R&D have a higher growth rate, and investment has a positive effect on firm growth. We investigate such relations with reference to an unbalanced panel data set of Portuguese manufacturing firms over the period of 1990 to 2001. We find that a systematic tendency for smaller firms to grow more quickly is the main reason why firm growth is not entirely stochastic.
- An observation on n-permutabilityPublication . Martins-Ferreira, Nelson; Rodelo, Diana; Van der Linden, TimWe prove that in a regular category all reflexive and transitive relations are symmetric if and only if every internal category is an internal groupoid. In particular, these conditions hold when the category is n-permutable for some n.
- Performance Analysis of 8-bit ODACs for VLC ApplicationsPublication . Dobesch, A.; Figueiredo, Mónica; Alves, L. N.; Wilfert, O.A discrete optical power level stepping technique in visible light communication (VLC), also known, as an optical digital to analog conversion (ODAC) has been proposed. This is an alternative concept for VLC front-end design, able to mitigate the LED intrinsic non-linearity. Additionally, it removes the need of an electrical digital to analog conversion (EDAC) in the driver stage. This paper provides an experimental evaluation of two different ODAC front-ends. The results investigate the spatial relation between the optical front-end and the optical receiver. In addition, the performance evaluation employs dynamic test metrics rather than conventional static metrics previously reported in the literature.
- 3D fast convex-hull-based evolutionary multiobjective optimization algorithmPublication . Zhao, Jiaqi; Jiao, Licheng; Liu, Fang; Basto-Fernandes, Vitor; Yevseyeva, Iryna; Xia, Shixiong; Emmerich, Michael T.M.The receiver operating characteristic (ROC) and detection error tradeoff (DET) curves have been widely used in the machine learning community to analyze the performance of classifiers. The area (or volume) under the convex hull has been used as a scalar indicator for the performance of a set of classifiers in ROC and DET space. Recently, 3D convex-hull-based evolutionary multiobjective optimization algorithm (3DCH-EMOA) has been proposed to maximize the volume of convex hull for binary classification combined with parsimony and three-way classification problems. However, 3DCH-EMOA revealed high consumption of computational resources due to redundant convex hull calculations and a frequent execution of nondominated sorting. In this paper, we introduce incremental convex hull calculation and a fast replacement for non-dominated sorting. While achieving the same high quality results, the computational effort of 3DCH-EMOA can be reduced by orders of magnitude. The average time complexity of 3DCH-EMOA in each generation is reduced from to per iteration, where n is the population size. Six test function problems are used to test the performance of the newly proposed method, and the algorithms are compared to several state-of-the-art algorithms, including NSGA-III, RVEA, etc., which were not compared to 3DCH-EMOA before. Experimental results show that the new version of the algorithm (3DFCH-EMOA) can speed up 3DCH-EMOA for about 30 times for a typical population size of 300 without reducing the performance of the method. Besides, the proposed algorithm is applied for neural networks pruning, and several UCI datasets are used to test the performance.
- Estimation of Energy Savings Potential in Higher Education Buildings Supported by Energy Performance Benchmarking: A Case StudyPublication . Bernardo, Hermano; Oliveira, Filipe TadeuThis paper presents results of work developed in the field of building energy benchmarking applied to the building stock of the Polytechnic Institute of Leiria, Portugal, based on a thorough energy performance characterisation of each of its buildings. To address the benchmarking of the case study buildings, an energy efficiency ranking system was applied. Following an energy audit of each building, they were grouped in different typologies according to the main end-use activities developed: Pedagogic buildings, canteens, residential buildings and office buildings. Then, an energy usage indicator was used to establish a metric to rank the buildings of each typology according to their energy efficiency. The energy savings potential was also estimated, based on the reference building energy usage indicator for each typology, and considering two different scenarios, yielding potential savings between 10% and 34% in final energy consumption.