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Publicações

Publicações por CRAS

2020

Impact of Trust and Reputation Based Brokerage on the CloudAnchor Platform

Autores
Veloso, B; Malheiro, B; Burguillo, JC; Gama, J;

Publicação
Advances in Practical Applications of Agents, Multi-Agent Systems, and Trustworthiness. The PAAMS Collection - 18th International Conference, PAAMS 2020, L'Aquila, Italy, October 7-9, 2020, Proceedings

Abstract
This paper analyses the impact of trust and reputation modelling on CloudAnchor, a business-to-business brokerage platform for the transaction of single and federated resources on behalf of Small and Medium Sized Enterprises (SME). In CloudAnchor, businesses act as providers or consumers of Infrastructure as a Service (IaaS) resources. The platform adopts a multi-layered multi-agent architecture, where providers, consumers and virtual providers, representing provider coalitions, engage in trust & reputation-based provider look-up, invitation, acceptance and resource negotiations. The goal of this work is to assess the relevance of the distributed trust model and centralised fuzzified reputation service in the number of resources successfully transacted, the global turnover, brokerage fees, losses, expenses and time response. The results show that trust and reputation based brokerage has a positive impact on the CloudAnchor performance by reducing losses and the execution time for the provision of both single and federated resources and increasing considerably the number of federated resources provided. © 2020, Springer Nature Switzerland AG.

2020

Diabetes Management Guidance by a Logical Unit Supported by Data-Mining in a Mobile Application

Autores
Machado, D; Costa, VS; Dutra, I; Brandao, P;

Publicação
XV MEDITERRANEAN CONFERENCE ON MEDICAL AND BIOLOGICAL ENGINEERING AND COMPUTING - MEDICON 2019

Abstract
Diabetes type I is a chronic disease that requires strict supervision. MyDiabetes is a utility application for diabetic users. This application served as basis to develop a logical unit, composed of logical rules, translated from medical protocols and guidelines, to advise the user. The data in the application is a source of knowledge about the user's health state and diabetes intrinsic characteristics. An existing concern is the weak user adherence and consequential data absence. The implemented solutions were gamification and an interface rework. As later confirmed through a survey, users feel captivated by appealing interfaces, achievements and medals. In a near future, we will resume our work with the S. Joao's hospital, with a new trial and volunteers. User testing will be used to validate the gamification techniques.

2020

The Structure of Climate Variability Across Scales

Autores
Franzke, CLE; Barbosa, S; Blender, R; Fredriksen, HB; Laepple, T; Lambert, F; Nilsen, T; Rypdal, K; Rypdal, M; Scotto, MG; Vannitsem, S; Watkins, NW; Yang, LC; Yuan, NM;

Publicação
REVIEWS OF GEOPHYSICS

Abstract
One of the most intriguing facets of the climate system is that it exhibits variability across all temporal and spatial scales; pronounced examples are temperature and precipitation. The structure of this variability, however, is not arbitrary. Over certain spatial and temporal ranges, it can be described by scaling relationships in the form of power laws in probability density distributions and autocorrelation functions. These scaling relationships can be quantified by scaling exponents which measure how the variability changes across scales and how the intensity changes with frequency of occurrence. Scaling determines the relative magnitudes and persistence of natural climate fluctuations. Here, we review various scaling mechanisms and their relevance for the climate system. We show observational evidence of scaling and discuss the application of scaling properties and methods in trend detection, climate sensitivity analyses, and climate prediction.

2020

Ambient radioactivity and atmospheric electric field: A joint study in an urban environment

Autores
Barbosa, S;

Publicação
JOURNAL OF ENVIRONMENTAL RADIOACTIVITY

Abstract
Ambient radioactivity and atmospheric electricity are inextricably linked phenomena. In order to assess the role of ambient radioactivity in the local variability of the atmospheric electric field at an urban site, simultaneous measurements of radon concentration, gamma radiation, and atmospheric electric field are carried out in the city of Porto, Portugal. Both radon and gamma radiation display an average daily cycle peaking before sunrise, but with considerable variability from day to day, particularly in amplitude. The atmospheric electric field displays a daily cycle with a minimum at dawn and maximum in the early afternoon, as well as a secondary peak in the early morning. The temporal variation of the daily patterns is analysed by means of an empirical orthogonal function analysis, and related to local meteorological parameters. The variability of the local atmospheric electric field is mainly determined by aerosol transport and accumulation close to the surface associated with local meteorological conditions and atmospheric stability rather than by conductivity variations associated with ambient radioactivity.

2020

Morphological controls and statistical modelling of boulder transport by extreme storms

Autores
Oliveira, MA; Scotto, MG; Barbosa, S; de Andrade, CF; Freitas, MD;

Publicação
MARINE GEOLOGY

Abstract
The study of coastal boulder accumulations generated by extreme marine events, and of the energy and frequency involved in boulder transport, is of paramount importance in understanding the risk associated with extreme marine inundations. One of the frequently asked questions is whether the deposits are storm or tsunami-related, both events being characterized by different return periods. Boulder transport by storms was monitored on the west coast of Portugal. Significant changes were detected in boulders' position as a result of extreme inundation by the 2013/2014 winter storms. Results presented in this work indicate that the wave power associated with the "Christina" and "Nadja" storms occur once every three years. However, this interval is not supported by field observations of boulder displacement, which suggests that wave power over-predicts boulder movement in the study area. Furthermore, wave parameters from the "Christina" and "Nadja" storms were very similar, but have generated different impacts in the boulder accumulation described herein. Differences include the magnitude and direction of boulder movement, and are most likely associated with distinct tidal levels during the events. Higher tide levels generated an increase in the sea surface level and thus in the reach of waves, which generated displacement of larger boulders and consequent cross-shore contribution in boulder transport. Regardless, the combination of monitoring campaigns, wave data, and statistical modelling of extreme values indicate that boulder transport by storms is more frequent than initially expected. Based on recorded boulder movements, we present a conceptual model for boulder ridge formation and development and identify significant control of incoming flow by local geomorphological/topographical features. Storm events, not less frequent tsunamis, are identified as the events responsible for modulating this rocky coastline. These results question a direct attribution of coastal boulder deposits to tsunamis in coastal regions with a high risk of tsunami inundation.

2020

Vertical land motion in the Iberian Atlantic coast and its implications for sea level change evaluation

Autores
Mendes, VB; Barbosa, SM; Carinhas, D;

Publicação
JOURNAL OF APPLIED GEODESY

Abstract
In this study, we estimate vertical land motion for 35 stations primarily located along the coastline of Portugal and Spain, using GPS time series with at least eight years of observations. Based on this set of GPS stations, our results show that vertical land motion along the Iberian coastline is characterized, in general, by a low to moderate subsidence, ranging from -2.2 mm yr(-1) to 0.4 mm yr(-1), partially explained by the glacial isostatic adjustment geophysical signal. The estimates of vertical land motion are subsequently applied in the analysis of tide gauge records and compared with geocentric estimates of sea level change. Geocentric sea level for the Iberian Atlantic coast determined from satellite altimetry for the last three decades has a mean of 2.5 +/- 0.6 mm yr(-1), with a significant range, as seen for a subset of grid points located in the vicinity of tide gauge stations, which present trends varying from 1.5 mm yr(-1) to 3.2 mm yr(-1). Relative sea level determined from tide gauges for this region shows a high degree of spatial variability, that can be partially explained not only by the difference in length and quality of the time series, but also for possible undocumented datum shifts, turning some trends unreliable. In general, tide gauges corrected for vertical land motion produce smaller trends than satellite altimetry. Tide gauge trends for the last three decades not corrected for vertical land motion range from 0.3 mm yr(-1) to 5.0 mm yr(-1) with a mean of 2.6 +/- 1.4 mm yr(-1), similar to that obtained from satellite altimetry. When corrected for vertical land motion, we observe a reduction of the mean to E1.9 +/- 1.4 mm yr(-1). Actions to improve our knowledge of vertical land motion using space geodesy, such as establishing stations in co-location with tide gauges, will contribute to better evaluate sea level change and its impacts on coastal regions.

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