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Publications

2011

On the series expansion of the spatial SIS evolution operator

Authors
Martins, J; Aguiar, M; Pinto, A; Stollenwerk, N;

Publication
JOURNAL OF DIFFERENCE EQUATIONS AND APPLICATIONS

Abstract
For the spatial stochastic susceptible-infected-susceptible model, we consider the perturbative series expansion of the gap between the dominant and subdominant eigenvalues of the evolution operator. We compute explicitly the first terms of the series expansion of the gap with difference equations for the calculation of states.

2011

Hybridization of Institutions

Authors
Martins, MA; Madeira, A; Diaconescu, R; Barbosa, LS;

Publication
Algebra and Coalgebra in Computer Science - 4th International Conference, CALCO 2011, Winchester, UK, August 30 - September 2, 2011. Proceedings

Abstract
Modal logics are successfully used as specification logics for reactive systems. However, they are not expressive enough to refer to individual states and reason about the local behaviour of such systems. This limitation is overcome in hybrid logics which introduce special symbols for naming states in models. Actually, hybrid logics have recently regained interest, resulting in a number of new results and techniques as well as applications to software specification. In this context, the first contribution of this paper is an attempt to 'universalize' the hybridization idea. Following the lines of [15], where a method to modalize arbitrary institutions is presented, the paper introduces a method to hybridize logics at the same institution-independent level. The method extends arbitrary institutions with Kripke semantics (for multi-modalities with arbitrary arities) and hybrid features. This paves the ground for a general result: any encoding (expressed as comorphism) from an arbitrary institution to first order logic (FOL ) determines a comorphism from its hybridization to FOL. This second contribution opens the possibility of effective tool support to specification languages based upon logics with hybrid features. © 2011 Springer-Verlag.

2011

Event cube: Another perspective on business processes

Authors
Ribeiro, JTS; Weijters, AJMM;

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

Abstract
In this paper the so-called Event Cube is introduced, a multidimensional data structure that can hold information about all business dimensions. Like the data cubes of online analytic processing (OLAP) systems, the Event Cube can be used to improve the business analysis quality by providing immediate results under different levels of abstraction. An exploratory analysis of the application of process mining on multidimensional process data is the focus of this paper. The feasibility and potential of this approach is demonstrated through some practical examples. © 2011 Springer-Verlag.

2011

A transcritical bifurcation in an immune response model

Authors
Burroughs, NJ; Ferreira, M; Oliveira, BMPM; Pinto, AA;

Publication
JOURNAL OF DIFFERENCE EQUATIONS AND APPLICATIONS

Abstract
The consequences of regulatory T cell (Treg) inhibition of interleukine 2 secretion are examined by mathematical modelling. We find a transcritical bifurcation that might explain two alternative scenarios: in one case the appearance of autoimmune responses and in another the suppression of the immune response.

2011

Uniformly hyperbolic diffeomorphisms in every surfaces

Authors
Pinto, AA; Rand, DA;

Publication
JOURNAL OF DIFFERENCE EQUATIONS AND APPLICATIONS

Abstract
We present the construction of new pseudo-smooth structures, near the singularities, such that the pseudo-Anosov maps are diffeomorphisms, in this pseudo-smooth structures, and have the property that the stable and unstable foliations are uniformly contracted and expanded by the pseudo-Anosov dynamics. We construct the C(1+) orthogonal charts of such pseudo-Anosov diffeomoprhisms.

2011

Reasoning about the Learning Process

Authors
Gama, J;

Publication
Extraction et gestion des connaissances (EGC'2011), Actes, 25 au 29 janvier 2011, Brest, France

Abstract

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