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Publicações

Publicações por CRAS

2011

Geology and Geophysics in the assessment of contamination associated with Controlled Dumps - the Matosinhos CD case study, North Portugal [A geologia e a geofísica na avaliação da contaminação associada a vazadouros controlados - o caso do VC de Matosinhos no Norte de Portugal]

Autores
Fontoura, MJ; Moura, RMM; Dias, AG;

Publicação
Comunicacoes Geologicas

Abstract
The main goal of this study is to assess the current environmental state of the Matosinhos Controlled Dump (CD) and its surroundings. Until the end of last century the Matosinhos CD was an open area where all the wastes produced in Matosinhos were deposited. The CD lies in a granitic crystalline geological context with fissure controlled type permeability, which is not common (Mota et al., 2004) in the Portuguese context. With our set of 2D resistivity profiles was possible to detect the presence of two resistivity anomalies indicative of contamination in the Matosinhos CD surrounding, with particular emphasis in the downstream area (unsealed part). The upstream anomaly, with resistivity values lower than 30 O.m, is vertically limited by a more resistive material, a few meters from the northern boundary of the CD. The other one, more extensive, is located in the southern part of the CD, with resistivity values lower than 7 O.m. It was possible to detect that both contamination anomalies were decreasing with the increasing distance of the CD. Comparing the conductivity measurements in water samples collected from upstream piezometers with the values of downstream piezometer the presence of a strong influence of contamination downstream of the CD was found and thus confirmed and correlated with the electrical resistivity data. © 2011 LNEG - Laboratório Nacional de Geologia e Energia, IP.

2011

A methodology for assessing the impact of the use of road salt on groundwater resources in a mountain environment (Serra da Estrela, central Portugal)

Autores
Marques Espinha, J; Carvalho, A; Marques, JM; Chamine, HI; Guerner, A; Moura, R; Carreira, P; Neves, O; Samper, J; Rocha, FT;

Publicação
Cadernos do Laboratorio Xeoloxico de Laxe

Abstract
Mountain areas are the source of high quality and socioeconomic relevance water resources. The sustainable management of such regions is fundamental to maintain the water supply to populations in wide areas all over the planet. Serra da Estrela is the origin of water resources of strategic importance to Portugal. In the highest part of the mountain, especially above 1400 m a.s.l., the use of road de-icing chemicals (NaCl and, accessorily, CaCl) may affect both groundwater and surface water as well as soils and therefore is a major environmental concern that should be investigated. This article presents a multidisciplinary methodology meant to support the study of water pollution as a result of the use of road de-icing salts in a mountain environment. This methodology encompasses contributions from Hydrogeology, Hydrogeochemistry, Isotope Geochemistry, Hydrogeophysics, GIS supported geological mapping and mathematical modelling. The main purpose of the application of this methodology in Serra da Estrela is to prepare a hydrogeological conceptual model focused in the processes related to groundwater pollution by NaCl from road de-icing. Another objective is to improve the sustainability of water resources and to provide new guidelines for water exploration and exploitation in the region.

2010

Erlang Inspired Hardware

Autores
Ferreira, P; Ferreira, JC; Alves, JC;

Publicação
International Conference on Field Programmable Logic and Applications, FPL 2010, August 31 2010 - September 2, 2010, Milano, Italy

Abstract
The Erlang programming language is a concurrency oriented functional language, based on the notion of independent processes and uses message passing for communication between processes. It is specially adapted to the realization of highly reliable distributed systems. In this paper it is analyzed the use of the Erlang's computational paradigm for the design and implementation of application specific heterogeneous computational systems. The main objective is to use for the low level implementation the same computational model used in high level view of the system. This will allow an easier and faster design space exploration and optimization. © 2010 IEEE.

2010

Auto-heading controller for an autonomous sailboat

Autores
Cruz, NA; Alves, JC;

Publicação
OCEANS'10 IEEE Sydney, OCEANSSYD 2010

Abstract
This paper addresses the design and implementation of feedback controllers for the direction of autonomous robotic sailboats. In order to design such a controller, it is important to determine a model for the sailboat dynamics during turns. However, there are many uncontrollable factors that may affect the direction of the sailboat, which make it difficult to obtain an accurate model and require a lot of sensors to feed a proper controller. Instead, we assume a rather simple model relating the most important variables and concentrate on data that can easily be available with simple low-cost sensors, compensating the lack of accuracy of the model with the robustness of the controller. We describe our approach to extract the parameters of such a dynamic model using data obtained in field experiments and we show how to use this model to tune a PI controller. As a case study, we use the FASt vehicle, a 2.5 m long robotic sailing boat capable of fully autonomous navigation through a set of predefined marks. Experimental results show the performance of the designed controller. © 2010 IEEE.

2010

Adaptive Sampling of Thermoclines with Autonomous Underwater Vehicles

Autores
Cruz, NA; Matos, AC;

Publicação
OCEANS 2010

Abstract
Autonomous Underwater Vehicles (AUVs) are routinely being used to provide the scientific community with detailed ocean data at very reasonable costs. In typical operations, AUVs are programmed to follow pre-defined geo-referenced trajectories, while collecting the relevant information about the underwater environment, with a clear separation between navigation and payload sensors. Under the adaptive sampling paradigm, the AUVs are able to interpret some of the payload data in order to change the sampling pattern and concentrate measurements in the regions of interest. In this paper, we describe an implementation of such paradigm, in which a small sized AUV is able to process CTD data, in real time, and change depth in order to maintain tracking of the thermocline region. We demonstrate the developed algorithms with data from field experiments in a dam reservoir, which show a very good performance, even in very shallow waters with hardly detectable features. The implementation ensures the safety of the AUV, by resuming to standard yo-yo patterns if the thermocline is not detected.

2010

Synchronized Intelligent Buoy Network for Underwater Positioning

Autores
Almeida, R; Cruz, N; Matos, A;

Publicação
OCEANS 2010

Abstract
This paper addresses the development of a new generation of lightweight intelligent buoys. These buoys are used to support underwater acoustic positioning systems, but were also designed to be elements of portable coastal observatories for short term deployments. We will present the main features of a buoy prototype including the physical structure, the computational system and algorithms developed to support operations. The paper also shows how to take advantage of this new tool to implement different navigation algorithms for AUVs.

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