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Publications

2020

MARESye: A hybrid imaging system for underwater robotic applications

Authors
Pinto, AM; Matos, AC;

Publication
INFORMATION FUSION

Abstract
This article presents an innovative hybrid imaging system that provides dense and accurate 3D information from harsh underwater environments. The proposed system is called MARESye and captures the advantages of both active and passive imaging methods: multiple light stripe range (LSR) and a photometric stereo (PS) technique, respectively. This hybrid approach fuses information from these techniques through a data-driven formulation to extend the measurement range and to produce high density 3D estimations in dynamic underwater environments. This hybrid system is driven by a gating timing approach to reduce the impact of several photometric issues related to the underwater environments such as, diffuse reflection, water turbidity and non-uniform illumination. Moreover, MARESye synchronizes and matches the acquisition of images with sub-sea phenomena which leads to clear pictures (with a high signal-to-noise ratio). Results conducted in realistic environments showed that MARESye is able to provide reliable, high density and accurate 3D data. Moreover, the experiments demonstrated that the performance of MARESye is less affected by sub-sea conditions since the SSIM index was 0.655 in high turbidity waters. Conventional imaging techniques obtained 0.328 in similar testing conditions. Therefore, the proposed system represents a valuable contribution for the inspection of maritime structures as well as for the navigation procedures of autonomous underwater vehicles during close range operations.

2020

The Impact of Logistics Performance on Argentina, Brazil, and the US Soybean Exports from 2012 to 2018: A Gravity Model Approach

Authors
Mendes dos Reis, JGM; Amorim, PS; Sarsfield Pereira Cabral, JASP; Toloi, RC;

Publication
AGRICULTURE-BASEL

Abstract
Soybean is one of the main sources of protein directly and indirectly in human nutrition, and it is highly dependent on logistics to connect country growers and international markets. Although recent studies deal with the impact of logistics on international trade, this impact in agricultural commodities is still an open research question. Moreover, these studies usually do not consider the influence of all components of the logistics on trade. This paper, therefore, aims at identifying the role of logistics performance in soybean exports among Argentina, Brazil, the US and their trading partners from 2012 to 2018. Using an extended gravity model, we examine whether the indicators of the World Bank Logistics Performance Index (LPI), adopted as a proxy of logistics efficiency, are an important determinant of bilateral soybean trade facilitation. The results lead to the conclusion that it is necessary to analyze the LPI throughout its indicators because they may affect trade differently. The novelty of this article is to provide an analysis of the impact of different logistics aspects on commodity trade, more specifically in the soybean case. Finally, regarding the model results, logistics infrastructure has a positive and significant correlation with soybean trade as supposed in most of the literature.

2020

A Deep Learning Approach for Predicting Bus Passenger Demand Based on Weather Conditions

Authors
Fontes, T; Correia, R; Ribeiro, J; Borges, JL;

Publication
Transport and Telecommunication

Abstract
This work apply a deep learning artificial neural network model-the Multilayer Perceptron- A s a regression model to estimate the demand of bus passengers. Transit bus ridership and weather conditions were collected over a year from a medium-size European metropolitan area and linked under the assumption: Individuals choose the travel mode based on the weather conditions that are observed during (a) the departure hour, (b) the hour before or (c) two hours prior to the travel start. The transit ridership data were also labelled according to the hour of the day, day of the week, month, and whether there was a strike and/or holiday or not. The results show that the prediction error of the model decrease by ~9% when the weather conditions observed two hours before travel start is taken into account. The model sensitivity analyses reveals that the worst performance is obtained for a strike day of a weekday in spring (typically Wednesdays or Thursdays). © 2020 Tânia Fontes et al., published by Sciendo.

2020

Erratum: Using Grover's search quantum algorithm to solve Boolean satisfiability problems, part 2

Authors
Fernandes, D; Silva, C; Dutra, I;

Publication
ACM Crossroads

Abstract

2020

Assessing the Impact of Distance Functions on K-Nearest Neighbours Imputation of Biomedical Datasets

Authors
Santos, MS; Abreu, PH; Wilk, S; Santos, JAM;

Publication
Artificial Intelligence in Medicine - 18th International Conference on Artificial Intelligence in Medicine, AIME 2020, Minneapolis, MN, USA, August 25-28, 2020, Proceedings

Abstract
In healthcare domains, dealing with missing data is crucial since absent observations compromise the reliability of decision support models. K-nearest neighbours imputation has proven beneficial since it takes advantage of the similarity between patients to replace missing values. Nevertheless, its performance largely depends on the distance function used to evaluate such similarity. In the literature, k-nearest neighbours imputation frequently neglects the nature of data or performs feature transformation, whereas in this work, we study the impact of different heterogeneous distance functions on k-nearest neighbour imputation for biomedical datasets. Our results show that distance functions considerably impact the performance of classifiers learned from the imputed data, especially when data is complex. © 2020, Springer Nature Switzerland AG.

2020

Real-time issues in the ada parallel model with openmp

Authors
Pinho L.M.; Royuela S.; Quiñones E.;

Publication
Ada User Journal

Abstract
The current proposal for the next revision of the Ada language considers the possibility to map the language parallel features to an underlying OpenMP runtime. As previously presented, and discussed in previous workshops, the works on fine-grain parallelism in Ada map well to the OpenMP tasking model for parallelism. Nevertheless, and although the general model of integration, and the semantic constructs are already reflected in the proposed revision of the standard, the integration of these new features with the Real-Time Systems Annex of Ada is still not complete. This paper presents an overview of what is supported and the still open issues.

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