Browsing by Issue Date, starting with "2016-04"
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- ODAC-based traffic lights for intelligent transport systemsPublication . Dobesch, Ales; Alves, Luis Nero; Wilfert, Otakar; Ribeiro, Carlos GasparThe optical digital to analog converter (ODAC) concept is introduced to be used in an intelligent transportation system (ITS). The paper explores the performance of ODAC adapted into a traffic light head in order to enable transferring information from the infrastructure to the vehicle (I2V). The performance of such a scenario is shown by reconstructing error as a function of emitter placement, LED’s half power angle (HPA) and receiver’s field of view (FOV). The obtained results reveal that ODAC performance strictly depends on geometrical deployment. Moreover, increasing signal frequency additionally introduces noticeable signal distortion.
- MarinEye - A tool for marine monitoringPublication . Martins, Alfredo; Dias, André; Silva, Eduardo; Ferreira, Hugo; Dias, Ireneu; Almeida, José Miguel; Torgo, Luis; Gonçalves, Marco; Guedes, Maurício; Dias, Nuno; Jorge, Pedro; Mucha, Ana Paula; Magalhães, Catarina; Carvalho, Maria de Fátima; Ribeiro, Hugo; Almeida, C. Marisa R.; Azevedo, Isabel; Ramos, Sandra; Borges, Teresa; Leandro, Sérgio Miguel; Maranhão, Paulo; Mouga, Teresa; Gamboa, Roberto; Lemos, Marco; Santos, Antonina dos; Silva, Alexandra; Frazão e Teixeira, Bárbara; Bartilotti, Cátia; Marques, Raquel; Cotrim, SóniaThis work presents an autonomous system for marine integrated physical-chemical and biological monitoring – the MarinEye system. It comprises a set of sensors providing diverse and relevant information for oceanic environment characterization and marine biology studies. It is constituted by a physicalchemical water properties sensor suite, a water filtration and sampling system for DNA collection, a plankton imaging system and biomass assessment acoustic system. The MarinEye system has onboard computational and logging capabilities allowing it either for autonomous operation or for integration in other marine observing systems (such as Observatories or robotic vehicles. It was designed in order to collect integrated multi-trophic monitoring data. The validation in operational environment on 3 marine observatories: RAIA, BerlengasWatch and Cascais on the coast of Portugal is also discussed.
- O espólio literário de Afonso Lopes Vieira na Biblioteca Municipal de LeiriaPublication . Nobre, CristinaQuais os elementos inéditos presentes no espólio de Afonso Lopes Vieira guardado na Biblioteca Municipal de Leiria e como podem ser imprescindíveis na descoberta da modernidade do escritor.
- Predictive models for physical and mechanical properties of Ti6Al4V produced by Selective Laser MeltingPublication . Bartolomeu, F.; Faria, S.; Carvalho, O.; Pinto, E.; Alves, Nuno; Silva, F.S.; Miranda, G.The properties of parts produced by Selective Laser Melting (SLM) are highly influenced by the processing parameters. The calculation of the energy density is not enough for justifying the mechanical and physical properties, and understand the microstructures of Ti6Al4V samples produced by SLM. In fact, samples produced with the same energy density, but with different processing parameters, present distinct properties. In this sense, it is necessary to assess the influence of processing parameters on SLM fabrication, as isolated parameters but also their interactions. This work presents a study on the influence of several SLM processing parameters (laser power, scan speed and scan spacing) on density, hardness and shear strength of Ti6Al4V samples. The influence of these processing parameters on the final properties of SLM parts was obtained by using statistical analysis. Additionality, with the drive of finding the significant main factors and their interactions, analysis of variance (ANOVA) was performed. The influence of the above mentioned processing parameters on shear strength, hardness and density resulted in three models that can be used as predictive design tools for Ti6Al4V parts produced by SLM technology. Moreover, a study on the microstructures of the Ti6Al4V samples was performed and correlated with the obtained models.
- Entrepreneurial orientation pathways to performance: A fuzzy-set analysisPublication . Lisboa, Ana; Skarmeas, Dionysis; Saridakis, CharalamposMost prior research on entrepreneurial orientation (EO) aggregates its features into a gestalt construct to investigate its influence on firm performance. This study deconstructs EO into innovativeness, proactiveness, and risktaking dimensions and focuses on the causalmechanisms bywhich those factors collectively affect performance. By drawing on the resource-based view of the firm and its dynamic capabilities extension, the study identifies multiple paths of complex causal recipes that can lead to certain organizational capabilities, competitive advantages, and performance. To do that, the study uses fuzzy-set qualitative comparative analysis (fsQCA), a technique that provides a holistic view of the examined interrelationships, compared to traditional net effect approaches that assumesymmetric and linear relationships among variables. The study provides key conclusions and insightful implications for managers and researchers.
- Evolution from 3D video to light-field coding and transmission over future media networksPublication . Assunção, PedroThree-dimensional (3D) images and video have been around for decades in a variety of formats and supported by different technologies. In the recent past, these technologies have been given increasing attention from both academia and industry mainly due to advances in capture, coding, transmission and display technologies. 3D video has evolved from stereoscopic towards multi-view video plus depth, enabling immersive and interactive experiences. One of the last important advances in 3D content acquisition is the Plenoptic or Light Field technology, which has the capability of capturing a dense set of light rays coming from the 3D scene. This is foreseen as a promising technology for 3D multimedia applications and services, which is driving research and technological developments not only due to the huge amount of data required for Light Field representation, but also due to the limited performance of current technology. In this technological context, COST Action IC1105 3D Content Creation, Coding and Transmission over Future Media Networks (3D-ConTourNet), is intended to bring together researchers from all the spectrum of the 3D multimedia technology chain to research problems of common interest. In its activities, 3DConTourNet has dealt with 3D video, from stereoscopic to Light Field, from content representation and coding to transmission, display and quality measurement involving human factors. This article describes the research context of 3D-ConTourNet, mostly covering recent advances in 3D video communications.
- Detection of plasmid mediated colistin resistance (MCR-1) in Escherichia coli and Salmonella enterica isolated from poultry and swine in SpainPublication . Quesada, Alberto; Ugarte-Ruiz, María; Iglesias, M. Rocío; Porrero, M. Concepción; Martínez, Remigio; Florez-Cuadrado, Diego; Campos, Maria J.; García, María; Píriz, Segundo; Sáez, José Luis; Domínguez, LucasRecent findings suggest that use of colistin as a last resort antibiotic is seriously threatened by the rise of a new plasmid mediated mechanism of resistance (MCR-1). This work identifies, for the first time in Southern Europe, the gene mcr-1 in nine strains from farm animals (poultry and swine) corresponding to five Escherichia coli and four Salmonella enterica, amongwhich three belong to serovar Typhimuriumand one to Rissen. TheMCR-1 was found encoded by a plasmid highly mobilizable by conjugation to the E. coli J53 strain. Two E. coli strains carried two determinants, mcr-1 plus pmrA or pmrB mutations, known to confer colistin resistance.
- Effect of explosive mixture on quality of explosive welds of copper to aluminiumPublication . Loureiro, A.; Mendes, R.; Ribeiro, J.B.; Leal, Rui; Galvão, I.The aim of this research is to investigate the influence of explosive ratio and type of sensitizer on the quality of explosive welds between copper and aluminium alloy plates. The welds were performed on a partially overlapping joint configuration using an emulsion explosive (EE) with two different sensitizers, hollow glass microspheres (HGMS) and expanded polystyrene spheres (EPS). Welds with an improved surface were achieved by using the HGMS sensitizer. A higher wave amplitude was registered in welds produced with the EPS sensitizer. In turn, the dimension of the molten pockets was influenced by the explosive ratio, increasing in size with increases in the values of this parameter. The intermetallic content of these zones varied according to the sensitizer type.Unlike the CuAl2 phase, the Cu-richer phases CuAl and Cu9Al4were only identified inwelds performed using the EPS sensitizer. An increase in hardness was observed at the interface of all welds, which resulted from both the presence of intermetallic phases and the plastic deformation of the materials promoted by the impact. This effect was most evident on the aluminium alloy side. All the welds had a greater strength than copper, i.e. the weakest material of the joint.
- A dual-band sine-square FSS designPublication . Ferreira, David; Cuinas, Inigo; Caldeirinha, Rafael; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.This paper proposes a new frequency selective surface (FSS) based on the combination of four sinusoidal-waveform like shapes, each formed by the combination of two semi-circles, for an overall arrangement similar to a square shape. The proposed design was simulated and evaluated through a commercial electromagnetic (EM) simulation software. The sine-square FSS has a relatively simple design, yet provides a dual band frequency response, with narrow bandwidths compared to classical designs, and with a relatively stable angular behavior of up to at least 45◦. It was shown that the second resonance frequency can, within a limited range, be independently controlled from the first resonance frequency band. Both band reject and band pass variants, as well as possible active/tunable implementations of this FSS design, were evaluated and are discussed in this paper.
- Improving occupational health by modelling indoor pollutant distributionPublication . Pitarma, Rui; Lourenço, Miguel; Ramos, JoaoPurpose Indoor environments are characterized by several pollutant sources. Some of these can be sufficiently characterized through the prediction of the airflow and pollutant distribution patterns. The purpose of this study was to simulate, analyze and compare different locations of known pollutant source inside a ventilated room. Design/methodology/approach Computational fluid dynamics modelling approach was used to analyze the prediction of the airflow and pollutant distribution patterns for different locations of known pollutant source inside a ventilated room by mixing ventilation. Findings Distinct areas of poor air quality, perfectly identified by concentration fields, were given. The indoor air quality obtained by the different simulated conditions was analyzed and compared. Research limitations/implications Pollutant concentration was not measured in the validation experiments (qualitative validation based on the velocity fields). Practical implications Once the contaminant concentration fields are calculated based on the source location, the model is very useful to choose the best place to install any pollutant indoor equipment to preserve breathing zones. Originality/value Providing an effective indoor air quality assessment to prevent exposure risk. The results would be useful for making decisions to optimize the design procedure, such as establish the best location to install polluting equipment, occupied areas and their interdependence with ventilation systems. In addition, this tool also helps to choose the best location and correct set point adjustment for the pollutant sensors.