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Publicações

Publicações por LIAAD

2012

Fostering microgeneration in power systems: The effect of legislative limitations

Autores
Fidalgo, JN; Fontes, DBMM;

Publicação
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
The large-scale integration of microgeneration (MG) can bring several technical benefits, such as: improving the voltage profile, reducing power losses and allowing for network capacity investment deferral. Furthermore, it is now widely accepted that introducing new renewable MG, such as wind turbines, photovoltaic panels or biomass can help control carbon emissions, reduce our dependence on oil and contribute to a sustainable energy growth. This paper presents an empirical analysis of the benefits of MG on avoided losses, voltage profiles and branch congestion. The main goal is to clarify whether the current regulatory framework allows for obtaining all the MG potential gains. The main conclusion is that some legal constraints should be removed, or at least relaxed, in order to promote the growth of distributed power generation, particularly, for domestic MG.

2012

GOLDEN TILINGS

Autores
Pinto, AA; Almeida, JP; Portela, A;

Publicação
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY

Abstract
We introduce the notion of golden tilings, and we prove a one-to-one correspondence between (i) smooth conjugacy classes of Anosov diffeomorphisms, with an invariant measure absolutely continuous with respect to the Lebesgue measure, (ii) affine classes of golden tilings and (iii) solenoid functions. The solenoid functions give a parametrization of the infinite dimensional space consisting of the mathematical objects described in the above equivalences.

2012

Strategic optimization in R&D investment

Autores
Ferreira, M; Figueiredo, IP; Oliveira, BMPM; Pinto, AA;

Publicação
OPTIMIZATION

Abstract
We use d'Aspremont and Jacquemin's strategic optimal R&D investment in a duopoly Cournot competition model to construct myopic optimal discrete and continuous R&D dynamics. We show that for some high initial production costs, the success or failure of a firm is very sensitive to small variations in its initial R&D investment strategies.

2012

Stationarity in moment closure and quasi-stationarity of the SIS model

Autores
Martins, J; Pinto, A; Stollenwerk, N;

Publicação
MATHEMATICAL BIOSCIENCES

Abstract
Previous epidemiological studies on SIS model have only considered the dynamic evolution of the mean value and the variance of the infected individuals. In this paper, through cumulant neglection, we use the dynamic equations of all the moments of infected individuals to develop a recursive method to compute the equilibria manifold of the moment closure ODE's. Specifically, we use the stable equilibria of the moment closure ODE's to obtain good approximations of the quasi-stationary states of the SIS model. This is a crucial step when the quasi-stationary distribution is highly skewed.

2012

On the convergence to Walrasian prices in random matching Edgeworthian economies

Autores
Pinto, AA; Ferreira, M; Finkenstaedt, BF; Oliveira, B; Yannacopoulos, AN;

Publicação
CENTRAL EUROPEAN JOURNAL OF OPERATIONS RESEARCH

Abstract
We show that for a specific class of random matching Edgeworthian economies, the expectation of the limiting equilibrium price coincides with the equilibrium price of the related Walrasian economies. This result extends to the study of economies in the presence of uncertainty within the multi-period Arrow-Debreu model, allowing to understand the dynamics of how beliefs survive and propagate through the market.

2012

Goodness-of-fit for a concentrated von Mises-Fisher distribution

Autores
Sousa Figueiredo, AMS;

Publicação
COMPUTATIONAL STATISTICS

Abstract
The von Mises-Fisher distribution is widely used for modelling directional data. In this paper we propose goodness-of-fit methods for a concentrated von Mises-Fisher distribution and we analyse by simulation some questions concerning the application of these tests. We analyse the empirical power of the Kolmogorov-Smirnov test for several dimensions of the sphere, supposing as alternative hypothesis a mixture of two von Mises-Fisher distributions with known parameters. We also compare the empirical power of the Kolmogorov-Smirnov test with the Rao's score test for data on the sphere, supposing as alternative hypothesis, a mixture of two Fisher distributions with unknown parameters replaced by their maximum likelihood estimates or a 5-parameter Fisher-Bingham distribution. Finally, we give an example with real spherical data.

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