Rua Dr. Roberto Frias

Porto, Portugal

Rua Dr. Roberto Frias

Porto, Portugal
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Abreu P.,University of Porto | Barbosa M.R.,University of Porto | Lopes A.M.,Rua Dr. Roberto Frias
International Journal of Interactive Mobile Technologies | Year: 2015

This paper presents the use of a virtual lab for teaching industrial robots programming to university students. The virtual lab, that replicates the existing physical lab, is built using an industrial simulation software package, RobotStudio™. The capabilities of this tool are explored in order to complement the introduction of theoretical concepts with practical programming experience. In addition to illustrate the use of different coordinate systems in a robotic cell, a description of the tool center point calibration and examples of evaluating different moving strategies to cover a plane surface, are also presented.

Fortunato J.,University of Lisbon | Anand C.,Technical University of Delft | Braga D.F.O.,Rua Dr. Roberto Frias | Groves R.M.,Technical University of Delft | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2017

Weight reduction is an important driver of the aerospace industry, which encourages the development of lightweight joining techniques to substitute rivet joints. Friction stir welding (FSW) is a solid-state process that enables the production of lighter joints with a small performance reduction compared to the base material properties. Increasing the FSW lap joint performance is an important concern. Friction stir weld bonding is a hybrid joining technology that combines FSW and adhesive bonding in order to increase the mechanical properties of FSW lap joints. FSW and hybrid lap joints were produced, using 2-mm-thick AA6082-T6 plates and a 0.2-mm-thick adhesive layer. Defect detection using the non-destructive test, phased array ultrasonic testing (PAUT), has been made. Microscopic observations were performed in order to validate the phased array ultrasonic testing results. Lap shear strength tests were carried out to quantify the joint’s quality. PAUT inspection successfully detected non-welded specimens but was not able to distinguish specimens with major hook defects from specimens correctly weld bonded with small hook defects. © 2017 Springer-Verlag London Ltd.

Taveira-Pinto F.,Rua Dr. Roberto Frias | Santos I.,Rua Dr. Roberto Frias
Journal of Coastal Conservation | Year: 2014

The area of Cabedelo sand spit, located at the mouth of Douro River estuary (Porto, Portugal), reduced in recent decades. In order to study its evolution and also the impact of two breakwaters built to fix the river entrance, a dataset from 23 trimestral surveys using differential GPS techniques, conducted between 2001 and 2007, were considered. A time-series analysis and the estimation of relationships between Cabedelo spit area and several hydrodynamic parameters through statistical techniques were performed in order to determine which parameters have more influence in the Cabedelo spit behavior. From the time-series analysis a seasonal tendency is visible, with the lower values occurring in December and the higher values occurring in July. The estimation of a relationship between Cabedelo spit area and several independent variables reached better results when the dataset was divided in Part A (before the beginning of breakwaters construction) and Part B (during the breakwaters construction). An analysis of the morphological evolution of Cabedelo spit shoreline was also performed: (1) a simple analysis of retreat and accretion rates data with a geographical information system and (2) a more exhaustive analysis were performed using Empirical Orthogonal Functions (EOFs). The Cabedelo spit shoreline erosion occurs mostly on the West and North side, and the accretion mostly occurs in the area protected by the South breakwater. During the breakwater's construction, the Cabedelo spit shoreline presented high retreat rates, with a mean value greater than 100 m. In terms of spatial variance (EOFs analysis), when the dataset was divided in two parts, the first Principal Component (PC) represents 60.10 % and 89.86 % of the mean squared value of the data, for Part A and Part B, respectively. As proved, the breakwaters would tend to stabilize the coastline leading to a higher first PC value after breakwaters construction (Part B). © 2014 Springer Science+Business Media Dordrecht.

Cavaleiro Rufo J.,Rua Dr. Roberto Frias | Cavaleiro Rufo J.,University of Porto | Madureira J.,Rua Dr. Roberto Frias | Paciencia I.,Rua Dr. Roberto Frias | And 9 more authors.
Environmental Science and Pollution Research | Year: 2016

Extended exposure to ultrafine particles (UFPs) may lead to consequences in children due to their increased susceptibility when compared to older individuals. Since children spend in average 8 h/day in primary schools, assessing the number concentrations of UFPs in these institutions is important in order to evaluate the health risk for children in primary schools caused by indoor air pollution. Thus, the purpose of this study was to assess and determine the sources of indoor UFP number concentrations in urban and rural Portuguese primary schools. Indoor and outdoor ultrafine particle (UFP) number concentrations were measured in six urban schools (US) and two rural schools (RS) located in the north of Portugal, during the heating season. The mean number concentrations of indoor UFPs were significantly higher in urban schools than in rural ones (10.4 × 103 and 5.7 × 103 pt/cm3, respectively). Higher UFP levels were associated with higher squared meters per student, floor levels closer to the ground, chalk boards, furniture or floor covering materials made of wood and windows with double-glazing. Indoor number concentrations of ultrafine-particles were inversely correlated with indoor CO2 levels. In the present work, indoor and outdoor concentrations of UFPs in public primary schools located in urban and rural areas were assessed, and the main sources were identified for each environment. The results not only showed that UFP pollution is present in augmented concentrations in US when compared to RS but also revealed some classroom/school characteristics that influence the concentrations of UFPs in primary schools. © 2016 Springer-Verlag Berlin Heidelberg

D Viegas C.M.,Rua Dr. Roberto Frias | Vasques F.,Rua Dr. Roberto Frias | Portugal P.,Rua Dr. Roberto Frias | Moraes R.,Federal University of Santa Catarina
Eurasip Journal on Wireless Communications and Networking | Year: 2014

With the widespread deployment of wireless mesh networks (WMNs) in industrial environments, real-time (RT) communication may benefit from the multi-hop relaying infrastructure provided by WMNs. However, RT communication must be able to coexist with non-RT traffic sources that will interfere with RT communication. Within this context, this paper assesses the impact of interferences caused by non-RT traffic sources upon RT traffic in IEEE 802.11s mesh networks. Through an extensive set of simulations, we assess the impact of external traffic sources upon a set of RT message streams in different communication scenarios. According to the simulation results, we infer that RT traffic in 802.11s networks may be highly affected by external interferences, and therefore, such interferences must be taken into account when setting-up 802.11s networks. By varying the network load imposed by external interferences, we provide some useful hints about utilization thresholds above which the network can no longer reliably support RT traffic. We also present insights about the setting-up of some network parameters in order to optimize the RT communication performance. © 2014, Viegas et al.; licensee Springer.

Alves M.A.,CEFT | Baptista A.,Rua Dr. Roberto Frias | Coelho P.M.,CEFT
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2015

This work completes a previous study (Cruz et al., in J Heat Transf 134:091703, 2012) by evaluating the performance of the simplified method proposed therein for calculating the Nusselt number for laminar flow of non-Newtonian fluids in pipes with constant wall temperature. The methodology was tested using the Herschel-Bulkley, Bingham, Casson and Carreau-Yasuda generalized Newtonian models, and also the simplified form of the Phan-Thien–Tanner viscoelastic model. The error of the approximate methodology is below 3 %, except for yield stress fluids, for which the maximum error increases to 7.4 % for the cases analyzed, which cover a wide range of shear viscosity curves. An explicit expression of Nusselt number for Casson fluids is also presented. © 2015, Springer-Verlag Berlin Heidelberg.

Madaleno M.,University of Aveiro | Pinho C.,University of Aveiro | Ribeiro C.,Rua Dr. Roberto Frias
Lecture Notes in Energy | Year: 2014

This work anlyses the relationship between the returns for carbon, electricity and fossil fuel price (coal, oil and natural gas), focusing on the impacts of emissions trading via a Vector Error Autoregressive Correction Model (VECM) for both German and French markets. Results show that the effect of carbon depends on the energy mix of the country under analysis but that it is not the only factor. Less carbon coercion takes place in the European Energy Exchange (EEX) and innovations in carbon are not strongly reflected in electricity prices. Also, market power affects the correct transfer of prices, thus limiting cost increases. © Springer-Verlag Berlin Heidelberg 2014.

Khoshrou S.,INESC Porto | Cardoso J.S.,INESC Porto | Teixeira L.F.,Rua Dr. Roberto Frias
Machine Learning | Year: 2015

Nowadays, video surveillance systems are taking the first steps toward automation, in order to ease the burden on human resources as well as to avoid human error. As the underlying data distribution and the number of concepts change over time, the conventional learning algorithms fail to provide reliable solutions for this setting. In this paper, we formalize a learning concept suitable for multi-camera video surveillance and propose a learning methodology adapted to that new paradigm. The proposed framework resorts to the universal background model to robustly learn individual object models from small samples and to more effectively detect novel classes. The individual models are incrementally updated in an ensemble-based approach, with older models being progressively forgotten. The framework is designed to detect and label new concepts automatically. The system is also designed to exploit active learning strategies, in order to interact wisely with operator, requesting assistance in the most ambiguous to classify observations. The experimental results obtained both on real and synthetic data sets verify the usefulness of the proposed approach. © 2015, The Author(s).

Topa Gomes A.,Rua Dr. Roberto Frias | Viana Da Fonseca A.,Rua Dr. Roberto Frias | Silva Cardoso A.,Rua Dr. Roberto Frias
Defect and Diffusion Forum | Year: 2011

The seepage analysis in geotechnical problems, namely in excavations, was typically performed assuming saturated conditions in the ground. It is now know that the flow in the non saturated part of the ground assumes also relevant importance and hence it is vital to characterize its behaviour. The Soil Water Characteristic Curve (SWCC) of the soil is probably the most important parameter in defining this behaviour and particularly for estimating the permeability of the soil. This paper presents the definition of the SWCC for a granite residual soil using pressure plates and the filter paper method. Based on experimental data some equations are adjusted and the results obtained are discussed. At the end of the paper some predictions of the non saturated permeability of the ground are also performed. © (2011) Trans Tech Publications.

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