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Publications

Publications by LIAAD

2011

A simulation based decision aid tool for setting regulation of energy grids with distributed generation

Authors
Silva, S; Fidalgo, JN; Fontes, DBMM;

Publication
OPERATIONAL RESEARCH

Abstract
Energy policies in the European Union (EU) and its 27 member states respond to three main concerns namely energy security, economic development, and environmental sustainability. All the three "Es'' are pursued simultaneously with some slight differences in emphasizing the mutual importance of these, in particular the cost factors. The legislation of the EU (e. g., ETS-Emission Trading Scheme, directives) increasingly guides the member states' energy policies. However, energy policy directions are still made domestically, for example, on the support on renewable energy technologies. In this work, we look into distributed generation (DG), since it has been grown considerable in the past few years and can be used to partially fulfill renewable energy targets. The policy makers have to make decisions about regulation directives, more specifically they have to change the current regulation in order to incentive the increase in DG. However, these decisions have not only economic impacts but also technical impacts that must be accounted for. In this regard, a decision aid tool would help the policy makers in estimating producer economic impacts, as well as power network technical impacts, of various possible regulation directives. Here, we propose an interactive decision aid tool that models the aforementioned impacts and thus, can be used by policy makers to experiment with different regulation directives before deciding on the ones to set.

2011

Universality in PSI20 fluctuations

Authors
Goncalves, R; Ferreira, H; Pinto, AA;

Publication
DYNAMICS, GAMES AND SCIENCE I

Abstract
We consider the. re-scaled PSI20 daily index positive returns r(t)(alpha) and negative returns (-r(t))(alpha) called, after normalization, the. positive and negative fluctuations, respectively. We use the Kolmogorov-Smirnov statistical test as a method to find the values of alpha that optimize the data collapse of the histogram of the. fluctuations with the truncated Bramwell-Holdsworth-Pinton (BHP) probability density function (pdf) fBHP and the truncated generalized log-normal pdf fLN that best approximates the truncated BHP pdf. The optimal parameters we found are alpha(+)(BHP) = 0.48, alpha(-)(BHP) = 0.46, alpha(+)(LN) = 0.50 and alpha(-)(LN) = 0.49. Using the optimal alpha's we compute the analytical approximations of the pdf of the normalized positive and negative PSI20 index daily returns r(t). Since the BHP probability density function appears in several other dissimilar phenomena, our result reveals a universal feature of the stock exchange markets.

2011

An Overview of Optimal Life Insurance Purchase, Consumption and Investment Problems

Authors
Duarte, I; Pinheiro, D; Pinto, AA; Pliska, SR;

Publication
DYNAMICS, GAMES AND SCIENCE I

Abstract
We provide an extension to Merton's famous continuous time model of optimal consumption and investment, in the spirit of previous works by Pliska and Ye, to allow for a wage earner to have a random lifetime and to use a portion of the income to purchase life insurance in order to provide for his estate, while investing his savings in a financial market consisting of one risk-free security and an arbitrary number of risky securities whose diffusive terms are driven by a multi-dimensional Brownian motion. The wage earner's problem is to find the optimal consumption, investment, and insurance purchase decisions in order to maximize expected utility of consumption and of the size of the estate in the event of premature death, and of the size of the estate at the time of retirement. Dynamic programming methods are used to obtain explicit solutions for the case of constant relative risk aversion utility functions, and new results are presented together with the corresponding economic interpretations.

2011

Anosov and Circle Diffeomorphisms

Authors
Almeida, JP; Fisher, AM; Pinto, AA; Rand, DA;

Publication
DYNAMICS, GAMES AND SCIENCE I

Abstract
We present an infinite dimensional space of C1+ smooth conjugacy classes of circle diffeomorphisms that are C1+ fixed points of renormalization. We exhibit a one-to-one correspondence between these C1+ fixed points of renormalization and C1+ conjugacy classes of Anosov diffeomorphisms.

2011

A Tourist's Choice Model

Authors
Brida, J; Defesa, MJ; Faias, M; Pinto, AA;

Publication
DYNAMICS, GAMES AND SCIENCE I

Abstract
We present a tourism model where the choice of a resort by a tourist depends not only on the product offered in the resort, but also on the characteristics of the other tourists staying in the resort. In order to explore the effect of the types of the tourists in the allocation of tourists across resorts, we introduce a game theoretical model and describe the relevant Nash equilibria.

2011

Price-Setting Dynamical Duopoly with Incomplete Information

Authors
Ferreira, FA; Ferreira, F; Pinto, AA;

Publication
NONLINEAR SCIENCE AND COMPLEXITY

Abstract
We consider a price competition in a duopoly with substitutable goods, linear and symmetric demand. There is a firm (F-1) that chooses first the price p(1) of its good; the other firm (F-2) observes p(1) and then chooses the price p(2) of its good. The conclusions of this price-setting dynamical duopoly are substantially altered by the presence of either differentiated goods or asymmetric information about rival's production costs. In this paper, we consider asymmetric information about rival's production costs. We do ex-ante and ex-post analyses of firms' profits and market prices. We compare the ex-ante firms' expected profits with the ex-post firms' profits.

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