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Barranquilla, Colombia

Hernandez J.,University of Caldas | Hernandez J.,National University of Colombia | Gordillo G.,National University of Colombia | Vallejo W.,University of the Atlantic
Applied Energy | Year: 2013

This paper presents a methodology to predict in a statistically reliable way the behavior of a grid-connected photovoltaic system. The methodology developed can be implemented either in common programming software or through an off-the-shelf simulation of electrical systems. Initially, the atmospheric parameters that influence the behavior of PV generators (radiation and temperature) are characterized in a probabilistic manner. In parallel, a model compound by various PV generator components is defined: the modules (and their electrical and physical characteristics), their connection to form the generator, and the inverter type. This model was verified for comparing their behavior with output measured on a real installed system of 3.6. kWp. The solar resource characterized and the photovoltaic system model are integrated in a non-deterministic approach using the stochastic Monte Carlo method, developed in the programming language DPL of the electrical-systems simulation software DIGSILENT®. It is done to estimate the steady-state electrical parameters describing the influence of the grid-connected photovoltaic system. Specifically, we estimated the nominal peak power of the PV generator to minimize network losses, subject to constraints on nodes voltages and conductor currents. © 2012 Elsevier Ltd.

Vega Monroy R.,University of the Atlantic
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

In this paper we point out the possible observation of the Bose-Einstein condensation for a gas of paired photon-dressed electrons in a graphene monolayer. At T=0 the condensation presents a strong crossover from the BCS state to the Bose-Einstein condensate. In an explicit way we calculated the fraction of condensed photon-dressed electron pairs as a function of the photon-electron bound energy and the temperature. The range of coherence of condensed quasiparticles is circumscribed to local bound states, where the Off-diagonal long-range order is guaranteed via the BCS state. © 2014 Elsevier B.V.

In conflicts between primate groups, the resource-holding potential (RHP) of competitors is frequently related to group size or male group size, which can remain relatively constant for long periods of time, promoting stable intergroup dominance relationships. Demographic changes in neighboring groups, however, could introduce uncertainty into existing relationships. Among tufted capuchin monkeys (Cebus apella nigritus), dominant male replacement is a relatively infrequent demographic event that can have a profound effect on both the composition and size of the social group. Here, we report such a case and the consequences for home range use and intergroup aggression. Between June 2008 and August 2010, we periodically followed two neighboring groups (Macuco and Rita) in Iguazú National Park, recording daily paths (N = 143) and encounters between the groups (N = 28). We describe the events leading to a change in the male dominance hierarchy in the larger group (Macuco), which resulted in the death or dispersal of all adult males, followed by the succession of a young adult male to the dominant position. This takeover event reduced the numerical advantage in number of males between the two groups, although the ratio of total group sizes remained nearly constant. Following this shift in numerical asymmetry, the degree of escalation of intergroup aggression increased, and we observed reversals in the former intergroup dominance relationship. These changes in behavior during intergroup encounters were associated with changes in the use of overlapping areas. In the 6 months following the takeover, the area of home range overlap doubled, and the formerly dominant group's area of exclusive access was reduced by half. These results suggest that RHPin tufted capuchin monkeys is related to male group size. Furthermore, they highlight the importance of considering rare demographic events in attempts to understand the dynamics of aggression between primate groups. © 2012 Wiley Periodicals, Inc.

Rangel-Buitrago N.,University of the Atlantic
International Journal of Climatology | Year: 2015

The present work deals with the characterization and classification of storm events affecting Cadiz Gulf, i.e. the coast including Southern Portugal, SW Spain and Northern Morocco. The general morphology of the gulf and its location determine the exposition and trajectory of storms affecting the zone, producing significant energy gradients alongshore. This study focuses on the frequency and distribution of the different types of storms, in order to estimate their probability of occurrence. Storm classification was obtained by using wave data records from the HIPOCAS (Hindcast of dynamic Processes of the Ocean and Coastal Areas of Europe) network. The Storm Power Index was used to classify coastal storms. The investigated data sets covered 44years, between 1958 and 2001. A significant gradient in energy (Storm Power and storm class frequency), approaching direction and storm duration was observed along the gulf, from the most exposed points (Cape San Vicente-Portimão) to the inner, more sheltered ones (Faro-Huelva-Cadiz) and to the southern moderately exposed ones (Bolonia-Tangier). The monthly distribution of number of storms, duration and sum of Storm Power were compared by means of multiple and independent regression analysis with values of different climatic and meteorological indexes. Multiple linear regression analysis between storminess indices and the teleconnection patterns points out that 45% of the change in monthly storminess indices calculated along the Cadiz Gulf are related to changes in the teleconnection patterns, especially North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and East Atlantic (EA). Negative NAO and AO phases and positive EA phases correlate with storminess in the zone. Furthermore, when neutral to strong negative NAO-AO and positive EA phases occurred at the same time and/or when an abrupt change of theses indices occurred, then a greater number of storms with longer duration and higher Storm Power Index were recorded. © 2015 Royal Meteorological Society.

Reslen J.,University of the Atlantic
Revista Mexicana de Fisica | Year: 2013

A protocol to obtain the matrix product state representation of a class of boson states is introduced. The proposal is presented in the context of linear systems and is tested by performing simulations of a reference model. The method can be applied regardless of the details of the coupling among modes and can be used to extract the most significant contribution of the tensorial representation. Characteristic issues as well as potential variants of the proposed protocol are discussed.

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