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Publications

2011

Indirect continuous-time LPV system identification through a downsampled subspace approach

Authors
Santos, PL; Perdicoúlis, TPA; Ramos, JA; Carvalho, JLM;

Publication
Linear Parameter-varying System Identification: New Developments And Trends

Abstract
The successive approximation Linear Parameter Varying systems subspace identification algorithm for discrete-time systems is based on a convergent sequence of linear time invariant deterministic-stochastic state-space approximations. In this chapter, this method is modified to cope with continuous-time LPV state-space models. To do this, the LPV system is discretised, the discrete-time model is identified by the successive approximations algorithm and then converted to a continuous-time model. Since affine dependence is preserved only for fast sampling, a subspace downsampling approach is used to estimate the linear time invariant deterministic-stochastic state-space approximations. A second order simulation example, with complex poles, illustrates the effectiveness of the new algorithm. © 2012 by World Scientific Publishing Co. Pte. Ltd.

2011

Variability modelling in the ABS language

Authors
Clarke, D; Muschevici, R; Proenca, J; Schaefer, I; Schlatte, R;

Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
The HATS project aims at developing a model-centric methodology for the design, implementation and verification of highly configurable systems, such as software product lines, centred around the Abstract Behavioural Specification (ABS) modelling Language. This article describes the variability modelling features of the ABS Modelling framework. It consists of four languages, namely, µTVL for describing feature models at a high level of abstraction, the Delta Modelling Language DML for describing variability of the 'code' base in terms of delta modules, the Product Line Configuration Language CL for linking feature models and delta modules together and the Product Selection Language PSL for describing a specific product to extract from a product line. Both formal semantics and examples of each language are presented. © 2011 Springer-Verlag Berlin Heidelberg.

2011

Relationship between cooking habits and skills and Mediterranean diet in a sample of Portuguese adolescents

Authors
da Rocha Leal, FMD; Paz Mendes de Oliveira, BMPM; Pereira Rodrigues, SSP;

Publication
PERSPECTIVES IN PUBLIC HEALTH

Abstract
Aims: To assess the cooking habits and skills of adolescents and its relation to Mediterranean diet adherence. Methods: Adolescents (N = 390) from the seventh, eighth and ninth grades in a school from a semi-urban region in northern Portugal were asked to fill in a questionnaire. The questionnaire assessed self-reported cooking habits and skills, for example enjoying and knowing how to cook and wanting to cook and learn more. Answers were taken on a scale from 0 to 5, 0 being 'no' and 5 being 'very much'. Learning sources, cooking frequency, and confidence in cooking ten particular foods were also assessed using the following answers: 'no, never', 'yes, with help from family/friends', 'yes, all by myself'. Adherence to Mediterranean diet was evaluated using the KIDMED index. Results: Adolescents who said that they cooked, did so usually between one and four times a month (56.2%). A high proportion of respondents had never cooked vegetables (57%), fish (51%) and soup (49%). Girls were more likely to have cooked foods listed in the questionnaire (p <= .002). Adolescents who did not know how to cook (8.7%) stated that the main reasons were that they had someone to cook for them (47%) and had no interest (35%). Those who knew how to cook mainly stated that they had learnt from their family (87.9%) and by themselves (7.9%). Most of our sample wanted 'to learn how to cook better' (M = 3.8, SD = 1.5), preferably with family/friends (82%) or by taking culinary courses (10%). The KIDMED index was poor for 7.2% of the sample, average for 50.8% and good for 42.1%. Adolescents with higher KIDMED scores were younger (p = .025), knew how to cook better (p < .001), cooked more often (p < .001), enjoyed cooking (p < .001), would like to cook more frequently (p < .001), and would like to learn how to cook better (p < .001). Conclusion: Almost one in every ten adolescents did not know how to cook. Vegetables, fish and soup were found to be foods that nearly half of the adolescents had never cooked. Female adolescents were more involved in cooking than males. Better cooking habits and skills were positively related with adolescents' adherence to the Mediterranean diet, which reinforces the idea that teaching cooking skills may have a positive impact in future food choice.

2011

Bayesian-Nash equilibria in theory of planned behaviour

Authors
Almeida, L; Cruz, J; Ferreira, H; Pinto, AA;

Publication
JOURNAL OF DIFFERENCE EQUATIONS AND APPLICATIONS

Abstract
The theory of planned behaviour studies the decision-making mechanisms of individuals. We propose the Bayesian-Nash equilibria as one, of many, possible mechanisms of transforming human intentions in behaviour. This process corresponds to the best strategic individual decision taking in account the collective response. We show that saturation, boredom and frustration can lead to splitted strategies, in opposition to no saturation that leads to a constant strategy.

2011

Hybrid Specification of Reactive Systems: An Institutional Approach

Authors
Madeira, A; Faria, JM; Martins, MA; Barbosa, LS;

Publication
SOFTWARE ENGINEERING AND FORMAL METHODS

Abstract
This paper introduces a rigorous methodology for requirements specification of systems that react to external stimulus by evolving through different operational modes. In each mode different functionalities are provided. Starting from a classical state-machine specification, the envisaged methodology interprets each state as a different mode of operation endowed with an algebraic specification of the corresponding functionality. Specifications are given in an expressive variant of hybrid logic which is, at a later stage, translated into first-order logic to bring into scene suitable tool support. The paper's main contribution is to provide rigorous foundations for the method, framing specification logics as institutions and the translation process as a comorphism between them.

2011

Importance of the relative delay of glottal source harmonics

Authors
Soiisa, R; Ferreira, A;

Publication
Proceedings of the AES International Conference

Abstract
In this paper we focus on the real-time frequency domain analysis of speech signals, and on the extraction of suitable and perceptually meaningful features that are related to the glottal source and that may pave the way for robust speaker identification and voice register classification. We take advantage of an analysis-synthesis framework derived from an audio coding algorithm in order to estimate and model the relative delays between the different harmonics reflecting the contribution of the glottal source and the group delay of the vocal tract filter. We show in this paper that this approach effectively captures the shape invariance of a periodic signal and may be suited to monitor and extract in real-time perceptually important features correlating well with specific voice registers or with a speaker unique sound signature. A first validation study is described that confirms the competitive performance of the proposed approach in the automatic classification of the breathy, normal and pressed voice phonation types.

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