Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

Publications by CRAS

2014

Coastal Geo-Engineering Techniques for the Assessment of Rock Armour Structures

Authors
Pires, A; Chamine, HI; Piqueiro, F; Rocha, F;

Publication
MARINE GEORESOURCES & GEOTECHNOLOGY

Abstract
This work deals with the problem of assessing armourstone structures focusing on strengthening the combination of geo-marine techniques and geotechnical properties. The research has two main purposes: (i) to establish an integrative coastal geo-engineering approach for better assessment of the hydraulic structures; and (ii) to draw attention to the importance of quarry evaluation in order to improve armourstone quality and durability. Several studies have demonstrated the relevance of a holistic approach to coastal design issues. The suggested approach couples GIS-based mapping with geo-engineering techniques assessment along five pilot sectors of the Espinho coastal system in Northwestern Portugal. This investigation allowed us to propose zoning a coastal structure according to its degree of deterioration, geomechanical properties and geomaterial status. Replacement of the primary armour layer in only selected sections or components of the structure will reduce the cost of maintenance, repair and reinforcement work. All the gathered data about the preservation status of the armour layer and the quarry inventory have been compiled in a powerful GIS geo-database. The paper argues for the wider use of combination of coastal geo-engineering and GIS analysis in planning the monitoring and/or maintenance of marine works using armourstone.

2014

LPV system identification using a separable least squares support vector machines approach

Authors
dos Santos, PL; Azevedo Perdicoulis, TP; Ramos, JA; Deshpande, S; Rivera, DE; de Carvalho, JLM;

Publication
2014 IEEE 53RD ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC)

Abstract
In this article, an algorithm to identify LPV State Space models for both continuous-time and discrete-time systems is proposed. The LPV state space system is in the Companion Reachable Canonical Form. The output vector coefficients are linear combinations of a set of a possibly infinite number of nonlinear basis functions dependent on the scheduling signal, the state matrix is either time invariant or a linear combination of a finite number of basis functions of the scheduling signal and the input vector is time invariant. This model structure, although simple, can describe accurately the behaviour of many nonlinear SISO systems by an adequate choice of the scheduling signal. It also partially solves the problems of structural bias caused by inaccurate selection of the basis functions and high variance of the estimates due to over-parameterisation. The use of an infinite number of basis functions in the output vector increases the flexibility to describe complex functions and makes it possible to learn the underlying dependencies of these coefficients from the data. A Least Squares Support Vector Machine (LS-SVM) approach is used to address the infinite dimension of the output coefficients. Since there is a linear dependence of the output on the output vector coefficients and, on the other hand, the LS-SVM solution is a nonlinear function of the state and input matrix coefficients, the LPV system is identified by minimising a quadratic function of the output function in a reduced parameter space; the minimisation of the error is performed by a separable approach where the parameters of the fixed matrices are calculated using a gradient method. The derivatives required by this algorithm are the output of either an LTI or an LPV (in the case of a time-varying SS matrix) system, that need to be simulated at every iteration. The effectiveness of the algorithm is assessed on several simulated examples.

2014

NUCLEAR SEISMOLOGY: THE CASE OF THE PORTO (PTO) WORLD-WIDE STANDARD SEISMOGRAPHIC NETWORK WWSSN STATION

Authors
Moura, R; Sant'Ovaia, H; Simoes, B; dos Santos, CA; Teixeira, L; Marieta Soares, JFM; Ferreira, R;

Publication
GEOCONFERENCE ON SCIENCE AND TECHNOLOGIES IN GEOLOGY, EXPLORATION AND MINING, VOL I

Abstract
The Geophysical Institute of the University of Porto (IGUP) constitutes an important pillar in the scientific and technological culture, developed over more than a century in the city of Porto. A strategic plan for its recovery has been recently developed. In terms of instruments there are currently some instruments related to seismology, meteorology and radiation, which are directly related to the measurement of variables involved in the estimation of seismic hazard and risk, meteorological hazards and radiological hazards. Thus IGUP has the potential to become a center for research in the field of Natural Hazards that in turn may contribute to studies, data and parameters for civil society and the scientific community. The Recovery that is already underway in seismic station, previously included as PTO in the world network known as Worldwide Standardized seismographic Network (WWSSN), can help achieve the implementation of a complex research in seismology and simultaneously acknowledging the geopolitical importance of this stations records. With the current work we intend to show a brief analysis of a few previously unknown seismic records, relating to Soviet nuclear explosions, as well as a few aspects of the the digital signal conversion adaptation of the previous 1960s analogue equipment.

2014

STUDENTS' MENTAL MODELS ABOUT THE EFFECTS OF EARTHQUAKES ON SOILS AND BUILDINGS

Authors
Moutinho, S; Moura, R; Vasconcelos, C;

Publication
GEOCONFERENCE ON ECOLOGY, ECONOMICS, EDUCATION AND LEGISLATION, SGEM 2014, VOL III

Abstract
Mental models are students' representations of the real world based on their knowledge and understanding. In a meaningful learning it is essential to analyse students' mental models and promote a reconstruction of scientific knowledge, by allowing them to become consistent with the scientific models. Having this in mind, we aimed to analyse undergraduate students' mental models concerning the seismic effects on soils and buildings, before they learn these contents at the university. To collect the data we applied a questionnaire with several items. The questionnaire was answered by a convenient sample of 31 freshmen from an undergraduate degree in Geology, in a northern Portuguese university. The results show that, in the majority of the items, students recognized the seismic effects on soils and buildings. However, some of their mental models were inconsistent with the scientific model, highlighting the importance of diagnosing students' mental models and their restructuring to promote a meaningful learning and scientific literacy.

2014

Geoscience modelling in opens days to schools [Modelação em geociências nos dias abertos às escolas]

Authors
Moutinho, S; Moura, R; Vasconcelos, C;

Publication
Comunicacoes Geologicas

Abstract
Faculty of Sciences of University of Porto annually organizes the Open Days to Schools, which allow the contact of high school students with researchers from different scientific areas. By recognizing a high potential to modelling, which promotes the construction of students’ knowledge through models that recreate geological phenomena, participants contacted with some models that simulated the effect of earthquakes on soils and buildings. We tried to understand if the use of models in the dissemination of Geology helps students to build their scientific knowledge, concerning seismology contents. A seismology model evaluation scale was applied to 126 high school students from schools of northern Portugal, which participated in the activities at Open Days to Schools. The results shown that students consider that models help to clarify and to restructure their knowledge about geological phenomena, highlighting the importance of modeling in the promotion of a meaningful learning. © 2014 LNEG - Laboratório Nacional de Geologia e Energia IP.

2014

IGUP and nuclear seismology in Portugal [O IGUP e a sismologia nuclear em Portugal]

Authors
Moura, R; Sant'Ovaia, H; Simao, B; Santos, C; Freitas, JM; Teixeira, L; Ferreira, R;

Publication
Comunicacoes Geologicas

Abstract
The Geophysical Institute of the University of Porto (IGUP) is an important marker in the scientific and technological culture developed over more than a century in the city of Porto, thus a strategy is being planned out for its recovery. This mission aims to take advantage of all the activities in the history of this institution, taking into account several components such as research in areas of natural hazards, seismology, weather and radiometry, support for graduate and post-graduate education at the University of Porto, scientific dissemination, training addressed to students of the 2nd and 3rd cycles of basic education and in the context of extracurricular activities that are currently the responsibility of the municipality of Vila Nova de Gaia as well as the installation of a pole of the Science Museum of the University of Porto. This infrastructure has some instruments related to seismology, meteorology and radiation, which are directly related to the measurement of variables involved in the estimation of seismic, meteorological and radiological hazards and can thus relate to risk estimation. As such, it has the potential to become a center for research in Natural Hazards, which may contribute with studies, data and parameters for civil society and the scientific community. The recovery that is now underway in the previously integrated PTO seismic station - Worldwide Standardized Seismographic Network (WWSSN), can help to achieve the implementation of a center of research in seismology and simultaneously acknowledge the geopolitical importance of this station. As such, in the present work we intend to show part of the analysis of seismic records relating to previously unknown Soviet nuclear explosions as well as bringing back to life inactive equipment that was switched off since the 1990s and thus enabling the recording of more modern digital seismic records. © 2014 LNEG – Laboratório Nacional de Geologia e Energia IP.

  • 106
  • 167