DM - Capítulos/Artigos em Livros Internacionais / Chapters in International Works
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- Production and management of sugarcane biomass: process optimizationPublication . Florentino, Helenice de Oliveira; Pato, Margarida Vaz; Jones, Dylan; Cantane, Daniela RenataThese studies have the purposes of providing a management procedure at a lower economic cost and improving the quality and quantity of the cane produced. These objectives can be attained through optimized cane cultivation planning because the planning brings about several benefits, principally enhanced quality, and yield, and thus an increase in the bio-energy to be generated. However, crop planning is a complex process that requires considerable care by sector managers as it involves social, economic, political, and environmental factors. These convert the decision-making processes into issues of a multiobjective nature with significant consequences. In this case, the need arises for mathematical and computational techniques, which may assist managers in setting up the planning process for cultivation and handling of the cane.
- The European survey on OR/MS Education : statistical analysis addressing the lecturing modulesPublication . Teixeira, Ana Paula; Miranda, João Luís deThis work addresses the European survey conducted with the aim of learning from the most recent developments in the Higher Education (HE) area concerning the Operational Research/Management Science (OR/MS) field. This regards, in particular: (i) the enrolment; (ii) the reduction in first year students’ failure rates; (iii) the perceived value of OR/MS courses; (iv) the OR/MS teaching practices; and (v) the transition onto the Labour Market. A statistical analysis is performed to understand if there is a relation of the respondents’ perceptions (“Positive” and “Negative”) and the types of OR/MS modules that were lectured at their institutions (type-A, bachelor/master programmes; type-B, separate majors/minors, and type-C, courses). The results analysis of independence tests are presented; most of the queries concerning the restructuring procedures are weakly related with the lecturing modules and the same occurs with half of the queries regarding the first year students; the opposite occurs with the labour market responses, as all of them are independent of the lecturing modules; and, both for the students enrolment and the OR/MS teaching practices, although weakly one-third of the responses are related with the lectured modules. Finally, further developments within the evidence-based approach are discussed too.
- Mathematical models in financePublication . Grossinho, Maria do RosárioIn this paper we illustrate the interplay between Mathematics and Finance, pointing out the relevance of stochastic calculus and mathematical modelling in some important aspects of modern finance. We present two types of mathematical models: the binomial asset pricing model and continuous-time models. We point out some sensitive points of research.
- An overview of some mathematical models of blood rheologyPublication . Sequeira, Adélia; Janela, JoãoExperimental investigations over many years reveal that blood flow exhibits non-Newtonian characteristics such as shear-thinning, viscoelasticity and thixotropic behaviour. The complex rheology of blood is influenced by numerous factors including plasma viscosity, rate of shear, hematocrit, level of erythrocytes aggregation and deformability. Hemodynamic analysis of blood flow in vascular beds and prosthetic devices requires the rheological behaviour of blood to be characterized through appropriate constitutive equations relating the stress to deformation and rate of deformation. The objective of this paper is to present a short overview of some macroscopic constitutive models that can mathematically characterize the rheology of blood and describe its known phenomenological properties. Some numerical simulations obtained in geometrically reconstructed real vessels will be also presented to illustrate the hemodynamic behaviour using Newtonian and non-Newtonian inelastic models under a given set of physiological flow conditions.
- Financial econometric modelPublication . Nicolau, JoãoFour recent financial econometric models are discussed. The first aims to capture the volatility created by “chartists”; the second intends to model bounded random walks; the third involves a mechanism where the stationarity is volatility-induced, and the last one accommodates nonstationary diffusion integrated stochastic processes that can be made stationary by differencing.
- KAM theory as a limit of renormalizationPublication . Dias, João LopesThis is a brief survey of recent results on the KAM stability of quasiperiodic dynamics using renormalization of vector field
- Generic Hamiltonian dynamical systems : an overviewPublication . Bessa, Mário; Dias, João LopesWe present for a general audience the state of the art on the generic properties of C² Hamiltonian dynamical systems.
- From ice to penguins : the role of mathematics in Antarctic researchPublication . Xavier, José C.; Hill, S. L.; Belchier, M.; Lopes, João DiasMathematics underpins all modern Antarctic science as illustrated by numerous activities carried out during the international year “Mathematics for Planet Earth”. Here, we provide examples of some ongoing applications of mathematics in a wide range of Antarctic science disciplines: (1) Feeding and foraging of marine predators; (2) Fisheries management and ecosystem modelling; and (3) Climate change research. Mathematics has allowed the development of diverse models of physical and ecological processes in the Antarctic. It has provided insights into the past dynamics of these systems and allows projections of potential future conditions, which are essential for understanding and managing the effects of fishing and climate change. Highly specific methods and models have been developed to address particular questions in each discipline, from the detailed analyses of remote-sensed predator tracking data to the assessment of the outputs from multiple global climate models. A key issue, that is common to all disciplines, is how to deal with the inherent uncertainty that arises from limited data availability and the assumptions or simplifications that are necessary in the analysis and modeling of interacting processes. With the continued rapid development of satellite-based and remote observation systems (e.g. ocean drifters and automatic weather stations), and of new methods for genetic analyses of biological systems, a step-change is occurring in the magnitude of data available on all components of Antarctic systems. These changes in data availability have already led to the development of new methods and algorithms for their efficient collection, validation, storage and analysis. Further progress will require the development of a wide range of new and innovative mathematical approaches, continuing the trend of world science becoming increasingly international and interdisciplinary.
- Polygonal billiards with a contractive reflection law: a review of some hyperbolic propertiesPublication . Del Magno, Gianluigi; Dias, João Lopes; Duarte, Pedro; Gaivão, José Pedro; Pinheiro, DiogoWe provide an overview of recent results concerning the dynamics of polygonal billiards with a contractive reflection law.
- Periodic solutions of parabolic and telegraph equations with asymmetric nonlinearitiesPublication . Grossinho, Maria do Rosário; Nkashama, M. N.This paper is organized as follows: Introduction, In Section 2, we collect the notation and basic assumptions that we shall suppose fulfilled throughout this paper. Section 3 is devoted to second order nonlinear one-dimensional parabolic and (linearly) damped hyperbolic equations. We compare, in some sense, the nonlinearity g(x, u) with the Fuçik spectrum of the corresponding piecewise linear differential equations with homogeneous Dirichlet boundary conditions, and a resonance condition of Landesman-Lazer type with respect to the forcing term h(x, t). More specifically, we assume that (the asymptotic behavior of) u - ¹ g ( x , u) lies in a rectangle located in what we should call the Fucik -Landesman-Lazer "resolvent" set. In Section 4, we take up the case of second-order multi-dimensional equations, and we prove results on crossing at not necessarily simple (higher) eigenvalues. Finally, in Section 5 we indicate the conditions under which one can extend our results to higher-order multi-dimensional equations.