A two-stage stochastic transportation problem with fixed handling costs and a priori selection of the distribution channels

In this paper, a transportation problem comprising stochastic demands, fixed handling costs at the origins, and fixed costs associated with the links is addressed. It is assumed that uncertainty is adequately captured via a finite set of scenarios. The problem is formulated as a two-stage stochastic program. The goal is to minimize the total cost associated with the selected links plus the expected transportation and fixed handling costs. A prototype problem is initially presented which is then progressively extended to accommodate capacities at the origins and multiple commodities. The results of an extensive set of computational tests are reported and discussed

OPTIMAL INTERNATIONAL RESERVES HOLDINGS IN EMERGING MARKETS ECONOMIES: THE BRAZILIAN CASE

This paper discusses the optimal international reserves holding for Brazilian economy. The optimal is determined with the buffer stock (inventory) model, using a time series approach. This paper differs from traditional approaches that run cross-section analysis. We evaluate Brazilian's reserves holdings with the model and discuss the role of IMF accord in the reserves holdings. The paper also presents evidence to support the idea of fewer needs to hold international reserves in a floating foreign exchange rate regime than in a fixed one. Conclusions highlight that Brazilians' foreign reserves are slightly above the optimal level and the model may allow the country to evaluate the needs of IMF accord renew.

Has core inflation been doing a good job in Brazil?

This paper assesses the performance of the core inflation measures calculated by the Brazilian Central Bank (BCB). The evidence shows that they do not meet some key statistical criteria that a good core inflation should have: unbiasedness and the ability to forecast inflation. That performance stems, to a large extent, from the lack of a well-grounded statistical and economical basis behind them. Three new measures are built and assessed using the same criteria. The evidence shows that their behaviour is more in accordance to what the theory claims. However, they still lack the ability to help forecasting inflation. Hence both the BCB and the market should use core inflation cautiously.Core inflation; inflation; supply shocks; relative prices; volatility

Border trees of complex networks

The comprehensive characterization of the structure of complex networks is essential to understand the dynamical processes which guide their evolution. The discovery of the scale-free distribution and the small world property of real networks were fundamental to stimulate more realistic models and to understand some dynamical processes such as network growth. However, properties related to the network borders (nodes with degree equal to one), one of its most fragile parts, remain little investigated and understood. The border nodes may be involved in the evolution of structures such as geographical networks. Here we analyze complex networks by looking for border trees, which are defined as the subgraphs without cycles connected to the remainder of the network (containing cycles) and terminating into border nodes. In addition to describing an algorithm for identification of such tree subgraphs, we also consider a series of their measurements, including their number of vertices, number of leaves, and depth. We investigate the properties of border trees for several theoretical models as well as real-world networks.Comment: 5 pages, 1 figure, 2 tables. A working manuscript, comments and suggestions welcome

Stability of a two-sublattice spin-glass model

We study the stability of the replica-symmetric solution of a two-sublattice infinite-range spin-glass model, which can describe the transition from antiferromagnetic to spin glass state. The eigenvalues associated with replica-symmetric perturbations are in general complex. The natural generalization of the usual stability condition is to require the real part of these eigenvalues to be positive. The necessary and sufficient conditions for all the roots of the secular equation to have positive real parts is given by the Hurwitz criterion. The generalized stability condition allows a consistent analysis of the phase diagram within the replica-symmetric approximation.Comment: 21 pages, 5 figure

Portugal e o desafio europeu

O texto analisa os grandes desafios com que se confronta o actual processo europeu, na perspectiva da intervenção portuguesa. São ponderados os resultados do Tratado de Amsterdão, a integração de Portugal na 3" fase da União Económica e Monetária, as grandes linhas das negociações em curso sobre o financiamento futuro da União ("Agenda 2000"), o próximo processo de alargamento da UE, bem como eventuais reformas institucionais que possam vir a ser necessárias nesse contexto. É feita igualmente uma referência aos efeitos da globalização sobre o quadro económico português e adiantados elementos relativamente à presidência portuguesa da UE no ano 200

Geopatrimónio ligado à água: o caso do património industrial na bacia hidrográfica do rio Ave

Pretende-se com este artigo dar um contributo sobre o património que resultou da relação entre o recurso água e a indústria e as potencialidades que decorreram da sua integração territorial na bacia hidrográfica do rio Ave