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Publicações

Publicações por CRAS

2017

Phase-interrogated SPR sensing structures based on tapered and tip optrode optical fiber configurations with bimetallic layers

Autores
Moayyed, H; Leite, IT; Coelho, L; Santos, JL; Viegas, D;

Publicação
MEASUREMENT SCIENCE AND TECHNOLOGY

Abstract
This work reports the theoretical investigation of optical fiber surface plasmon resonance sensors incorporating bimetallic layer combinations. Different metals like silver, gold, copper, and aluminum are considered to investigate the refractometric sensing properties of tapered and tip optrode phase-interrogated optical fiber plasmonic sensor structures. It is shown that the gold-silver combination, coupled to a tip optrode layout, is capable of maximizing the resolution and operation range of these sensing structures for environmental refractive index measurement.

2017

Adapting bobbert-vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

Autores
Viegas, D; Fernandes, E; Queirós, R; Petrovykh, DY; De Beule, P;

Publicação
Biomedical Optics Express

Abstract
We investigate spectroscopic imaging ellipsometry for monitoring biomolecules at surfaces of nanoparticles. For the modeling of polarimetric light scattering off surface-adsorbed core-shell nanoparticles, we employ an extension of the exact solution for the scattering by particles near a substrate presented by Bobbert and Vlieger, which offers insight beyond that of the Maxwell-Garnett effective medium approximation. Varying thickness and refractive index of a model bio-organic shell results in systematic and characteristic changes in spectroscopic parameters ? and ?. The salient features and trends in modeled spectra are in qualitative agreement with experimental data for antibody immobilization and fibronectin biorecognition at surfaces of gold nanoparticles on a silicon substrate, but achieving a full quantitative agreement will require including additional effects, such as nanoparticle-substrate interactions, into the model. © 2017 Optical Society of America.

2017

Functionalities and Requirements of an Autonomous Shopping Vehicle for People with Reduced Mobility

Autores
Neves, A; Campos, D; Duarte, F; Domingues, I; Santos, J; Leao, J; Xavier, J; de Matos, L; Camarneiro, M; Penas, M; Miranda, M; Silva, R; Esteves, T;

Publicação
VEHITS: PROCEEDINGS OF THE 3RD INTERNATIONAL CONFERENCE ON VEHICLE TECHNOLOGY AND INTELLIGENT TRANSPORT SYSTEMS

Abstract
This paper concerns a robot to assist people in retail shopping scenarios, called the wGO. The robot's behaviour is based in a vision-guided approach based on user-following. The wGO brings numerous advantages and a higher level of comfort, since the user does not need to worry about controlling the shopping cart. In addition, this paper introduces the wGOs functionalities and requirements to enable the robot to successfully perform personal assistance while the user is shopping in a safe way. A user satisfaction survey is also presented. Based on the highly encouraging results, some conclusions and guidelines towards the future full deployment of the wGO in commercial environments are drawn. Copyright

2017

LPV system identification using the matchable observable linear identification approach

Autores
dos Santos, PL; Romano, R; Azevedo Perdicoulis, TP; Rivera, DE; Ramos, JA;

Publicação
2017 IEEE 56TH ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC)

Abstract
This article presents an optimal estimator for discrete-time systems disturbed by output white noise, where the proposed algorithm identifies the parameters of a Multiple Input Single Output LPV State Space model. This is an LPV version of a class of algorithms proposed elsewhere for identifying LTI systems. These algorithms use the matchable observable linear identification parameterization that leads to an LTI predictor in a linear regression form, where the ouput prediction is a linear function of the unknown parameters. With a proper choice of the predictor parameters, the optimal prediction error estimator can be approximated. In a previous work, an LPV version of this method, that also used an LTI predictor, was proposed; this LTI predictor was in a linear regression form enablin, in this way, the model estimation to be handled by a Least-Squares Support Vector Machine approach, where the kernel functions had to be filtered by an LTI 2D-system with the predictor dynamics. As a result, it can never approximate an optimal LPV predictor which is essential for an optimal prediction error LPV estimator. In this work, both the unknown parameters and the state-matrix of the output predictor are described as a linear combination of a finite number of basis functions of the scheduling signal; the LPV predictor is derived and it is shown to be also in the regression form, allowing the unknown parameters to be estimated by a simple linear least squares method. Due to the LPV nature of the predictor, a proper choice of its parameters can lead to the formulation of an optimal prediction error LPV estimator. Simulated examples are used to assess the effectiveness of the algorithm. In future work, optimal prediction error estimators will be derived for more general disturbances and the LPV predictor will be used in the Least-Squares Support Vector Machine approach.

2017

Transmission gas pipelines: 2D models simulation

Autores
Azevedo Perdicoulis, TPA; dos Santos, PL;

Publicação
2017 10TH INTERNATIONAL WORKSHOP ON MULTIDIMENSIONAL (ND) SYSTEMS (NDS)

Abstract
This article presents four state-space models for high pressure gas pipelines, departing from a system of nonlinear partial differential equations. The models were derived taking advantage of an electrical analogy and are very accurate and simple, therefore suitable for network simulation and analysis. The models' simulation is compared with the data obtained with Simone (R), a commercial simulator of gas transport and distribution networks used by many european companies, and exhibit similar accuracy.

2017

Obtaining Multivariable Continuous-Time Models From Sampled Data

Autores
Romano, RA; Pait, F; dos Santos, PL;

Publicação
2017 AMERICAN CONTROL CONFERENCE (ACC)

Abstract
While most physical systems or phenomena occur in continuous-time, identification methods based on discrete-time models are more widespread among practitioners and academic community, possibly due to the discrete-time nature of the data records. There has been a growing interest in estimating continuous-time (CT) models in the last decade. This work develops algorithms to estimate the parameters of multivariable state-space CT models from input-output samples using a method based on the recently developed MOLI-ZOFT approach. The performance of the algorithm is evaluated using real data from an industrial winding process.

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