2014
Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Guerreiro, A; Viegas, D;
Publication
Latin America Optics and Photonics Conference, LAOP 2014
Abstract
The recent burst of R&D activity in Plasmonics, associated with the possibility of materials nanostructuring which enables the access to metamaterials, has been strongly impacting many branches of optics such as imaging, data recording and sensing. This talk details the factors that turned the combination Plasmonics and Metamaterials a huge opportunity to optical sensing.© OSA 2014.
2014
Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;
Publication
IEEE SENSORS JOURNAL
Abstract
An effective analytical model combining geometrical optics with the transfer-matrix theory for stratified optical media is applied to investigate the sensing properties of tapered optical fiber surface plasmon resonance (SPR) sensors incorporating Ag-Au bimetallic layers, particularly in the context of phase interrogation. The performance of the sensing structures is studied as a function of the tapering parameters and thickness of the metallic layers. It is shown that the Ag-Au bimetallic combination is capable of improving the resolution and tuning working region of SPR fiber-optic sensors and that by tapering the sensing structures enhanced sensitivity can be achieved when phase interrogation is considered.
2014
Authors
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Guerreiro, A; Viegas, D;
Publication
SECOND INTERNATIONAL CONFERENCE ON APPLICATIONS OF OPTICS AND PHOTONICS
Abstract
Optical fiber sensors based on the phenomenon of plasmonic resonance can be interrogated applying different methods, the most common one being the spectral approach where the measurand information is derived from the reading of the wavelength resonance dip. In principle, a far better performance can be achieved considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This approach is investigated in this work for surface plasmon based fiber optic sensors with overlays which are combinations of bimetallic layers, permitting not only to tune the wavelength of the plasmon resonance but also the sensitivity associated with the phase interrogation of the sensors. The metals considered for the present analysis are silver, gold, copper, and aluminum.
2014
Authors
Pires, A; Chamine, HI; Perez Alberti, A; Gomes, A; Rocha, F;
Publication
ROCK ENGINEERING AND ROCK MECHANICS: STRUCTURES IN AND ON ROCK MASSES
Abstract
This work addresses the rock matrix strength comparative analysis on rocky coasts. A coastal geoengineering integrated system for rocky coast assessment was proposed and applied in two fissured granitic key-sites in NW Iberia (NW Portugal, and Galicia). The main stages of the study comprise six steps: (i) high-resolution aerial imagery survey; (ii) visual inspection and systematic monitoring; (iii) applied field datasheet; (iv) in situ evaluation; (v) scanline survey; (vi) coastal geosciences engineering GIS based mapping. The Schmidt Hammer and Equotip tester were applied to measure the rebound and hardness, respectively, in rocky platforms, geoforms and coastal boulders. Moreover a detailed description of discontinuities and a geologic-geotechnical evaluation in the rocky platforms was performed. The current rock project is of great interest especially to highly dynamic coastal areas. This approach evolving geomorphic processes, geoengineering issues and geomechanical testing assessment contributes to support coastal management/planning.
2014
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
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.
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