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Publications

2015

Predicting Grapevine Water Status Based on Hyperspectral Reflectance Vegetation Indices

Authors
Pocas, I; Rodrigues, A; Goncalves, S; Costa, PM; Goncalves, I; Pereira, LS; Cunha, M;

Publication
REMOTE SENSING

Abstract
Several vegetation indices (VI) derived from handheld spectroradiometer reflectance data in the visible spectral region were tested for modelling grapevine water status estimated by the predawn leaf water potential ((pd)). The experimental trial was carried out in a vineyard in Douro wine region, Portugal. A statistical approach was used to evaluate which VI and which combination of wavelengths per VI allows the best correlation between VIs and (pd). A linear regression was defined using a parameterization dataset. The correlation analysis between (pd) and the VIs computed with the standard formulation showed relatively poor results, with values for squared Pearson correlation coefficient (r(2)) smaller than 0.67. However, the results of r(2) highly improved for all VIs when computed with the selected best combination of wavelengths (optimal VIs). The optimal Visible Atmospherically Resistant Index (VARI) and Normalized Difference Greenness Vegetation Index (NDGI) showed the higher r(2) and stability index results. The equations obtained through the regression between measured (pd) ((pd_obs)) and optimal VARI and between (pd_obs) and optimal NDGI when using the parameterization dataset were adopted for predicting (pd) using a testing dataset. The comparison of (pd_obs) with (pd) predicted based on VARI led to R-2 = 0.79 and a regression coefficient b = 0.96. Similar R-2 was achieved for the prediction based on NDGI, but b was smaller (b = 0.93). Results obtained allow the future use of optimal VARI and NDGI for estimating (pd), supporting vineyards irrigation management.

2015

An overview on the exploitation of time in collaborative filtering

Authors
Vinagre, J; Jorge, AM; Gama, J;

Publication
WILEY INTERDISCIPLINARY REVIEWS-DATA MINING AND KNOWLEDGE DISCOVERY

Abstract
Classic Collaborative Filtering (CF) algorithms rely on the assumption that data are static and we usually disregard the temporal effects in natural user-generated data. These temporal effects include user preference drifts and shifts, seasonal effects, inclusion of new users, and items entering the systemand old ones leavinguser and item activity rate fluctuations and other similar time-related phenomena. These phenomena continuously change the underlying relations between users and items that recommendation algorithms essentially try to capture. In the past few years, a new generation of CF algorithms has emerged, using the time dimension as a key factor to improve recommendation models. In this overview, we present a comprehensive analysis of these algorithms and identify important challenges to be faced in the near future.(C) 2015 John Wiley & Sons, Ltd.

2015

Incorporating regulator requirements in reliability analysis of smart grids. Part 2: Scenarios and results

Authors
Ridzuan M.I.M.; Hernando-Gil I.; Djokic S.; Langella R.; Testa A.;

Publication
IEEE PES Innovative Smart Grid Technologies Conference Europe

Abstract
This is the second paper in a two-part series discussing how Regulator requirements for continuity of supply could be incorporated in the reliability analysis of existing electricity networks and future 'smart grids'. Part 1 paper presents input data, parameters and models required for a comprehensive assessment of system reliability performance, including an overview of the overall and guaranteed standards of performance in the UK and Italy. This paper presents scenarios and results of both analytical and probabilistic reliability assessment procedures for the test network introduced in Part 1 paper.

2015

Information architecture as an enabler for business development: A case study

Authors
Mamede, HS;

Publication
Handbook of Research on Information Architecture and Management in Modern Organizations

Abstract
Intelligence involves knowing information about some competitive factors like competitors' profitability and turnover rate. Information technology can help organizations to seize the information available. In this chapter we will present the solution architected and developed for a Portuguese company with a starting scenario that showed characteristics like dispersed information, concentration of knowledge in a single individual, no defined architecture for data or information, simple changes involving huge efforts and lack of agility. We found that business decision makers had problems of relying on the results, as the system was like a black box and often provided not accurate data. We will describe how we solved the problem, designing and implementing a business intelligence solution and the impact of having an information architecture.

2015

Rail vehicle localization exploiting rail track georeferenced coordinates

Authors
Ferreira, AJ; Almeida, JM; Silva, E;

Publication
U.Porto Journal of Engineering

Abstract
A novel dead reckoning algorithm conceived for localization of small inspection rail vehicles in Global Navigation Satellite System (GNSS) denied environments is presented. This work focus on simplifying the rail vehicle localization task, taking into account restrictions on movement imposed by the railroad tracks. Considering that dead reckoning techniques accumulate errors over time, leading to increasing global uncertainty, a method was designed to correct the estimates and also smooth trajectory errors backwards in time, through visualization of global landmarks. Results show the effectiveness of this approach in reducing long-term position errors. The current document reports real railroad experiments, featuring a specially designed non-motorized mobile modeling vehicle.

2015

Message from general and program co-chairs

Authors
Silvano, C; Agosta, G; Cardoso, JMP; Huebner, M;

Publication
ACM International Conference Proceeding Series

Abstract

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