FCT: DM - Capítulos de livros internacionais
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- Recent Advances in Complex Fluids ModelingPublication . Rebelo, Magda; Ferrás, Luis; Morgado, Maria Luísa; Afonso, Alexandre M.; McKinley, Gareth Huw; Castelo, Antonio; Leiva, Rosalía; DM - Departamento de Matemática; CMA - Centro de Matemática e AplicaçõesIn this chapter, we present a brief description of existing viscoelastic models, starting with the classical differential and integral models, and then focusing our attention on new models that take advantage of the enhanced properties of the Mittag-Leffler function (a generalization of the exponential function). The generalized models considered in this work are the fractional Kaye-Bernstein, Kearsley, Zapas (K-BKZ) integral model and the differential generalized exponential Phan-Thien and Tanner (PTT) model recently proposed by our research group. The integral model makes use of the relaxation function obtained from a step-strain applied to the fractional Maxwell model, and the differential model generalizes the familiar exponential Phan-Thien and Tanner constitutive equation by substituting the exponential function of the trace of the stress tensor by the MittagLeffler function. Since the differential model is based on local operators, it reduces the computational time needed to predict the flow behavior, and, it also allows a simpler description of complex fluids. Therefore, we explore the rheometric properties of this model and its ability (or limitations) in describing complex flows.
- Multivariate Analysis - A Great Tool for a Multivariate WorldPublication . Coelho, Carlos A.; DM - Departamento de MatemáticaIn this short report the author tries to introduce in simple terms some Multivariate Analysis techniques and show their usefulness in the analysis of econometric data, namely in studies which aim at studying and comparing different regions inside a given country.
- Comparison of two Meta-Heuristics for the Bi-Objective Flexible Job Shop Scheduling Problem with Sequence Dependent Setup TimesPublication . Sacramento, João; Pedrosa, João; Chibeles-Martins, Nelson; Pinto-Varela, Tânia; DM - Departamento de Matemática; CMA - Centro de Matemática e AplicaçõesThe increasingly competitivity in the plastic container market is driving companies toward a greater focus on efficiency, and mass production customisation, which triggers the increase of productivity by implementing more efficient and faster IT solutions. This work is based on a Portuguese case study, to develop a scheduling model considering the specific characteristics of this type of facilities and increase its competitiveness. To this end, two different approaches, the Tabu Search and Genetic Algorithm, were developed to solve a flexible job shop scheduling problem under a make-to-order production strategy. Each approach was validated using the case study, and the model's applicability were testes trough five instances. The results have shown that Tabu Search has a better efficacy and the Genetic Algorithm shows better efficiency.
- Preliminary results on confidence intervals for open bonus malusPublication . Guerreiro, Gracinda R.; Mexia, João T.; Miguens, Maria F.; DM - Departamento de MatemáticaConsidering open portfolios, we analyze bonus–malus systems (BMS) under a realistic approach, as we already did in Guerreiro and Mexia (Discuss. Math. Probab. Stat. 24(2):197–213, 2004). Using stochastic vortices model we are now able to predict long-run distribution through confidence intervals.
- Fitting johnson’s sB distribution to forest tree diameterPublication . Mateus, Ayana; Tomé, Margarida; CMA - Centro de Matemática e Aplicações; DM - Departamento de MatemáticaThe simulation of diameter distributions is an essential aid for a more efficient planning of the harvesting operations which usually represents a high percentage in costs associated with production of pulp. In this chapter Johnson’s SB probability density function has been used to model diameter distribution of Eucalyptus globulus Labill. in Portugal.
- Μηδεὶς ἀγεωμέτρητοϛ εἰσίτωPublication . Kahle, Reinhard; DM - Departamento de Matemática; CMA - Centro de Matemática e AplicaçõesThis paper provides a discussion to which extent the Mathematician David Hilbert could or should be considered as a Philosopher, too. In the first part, we discuss some aspects of the relation of Mathematicians and Philosophers. In the second part we give an analysis of David Hilbert as Philosopher.
- Eigenvalues, multiplicities and graphsPublication . Johnson, Charles R.; Leal-Duarte, António; Saiago, Carlos Manuel; Sher, David A.; DM - Departamento de Matemática; CMA - Centro de Matemática e AplicaçõesFor a given graph, there is a natural question of the possible lists of multiplicities for the eigenvalues among the spectra of Hermitian matrices with that graph (no constraint is placed upon the diagonal entries of the matrices by the graph). Here, we survey some of what is known about this question and include some new information about it. There is a natural focus upon the case in which the graph is a tree. In this event, there is remarkable structure to the possible lists. Both the general theory and a summary of specific results is given. At the end, this allows to give, in compact tabular form, all lists for trees on fewer than 11 vertices (a potentially valuable tool for further work). There is a brief discussion of non-trees.