University of Alicante

About: University of Alicante is a education organization based out in Alicante, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 8681 authors who have published 22690 publications receiving 476064 citations. The organization is also known as: Universitat d'Alacant & Universidad de Alicante.

Thermal conductivity of graphite flakes–SiC particles/metal composites

Abstract: A new family of high thermal conductivity composites, produced through infiltration of a metallic alloy into preforms of mixtures of graphite flakes and either ceramic or carbon materials (in the form of particles or short fibers), has been recently developed. Composites microstructure roughly consists of alternating layers of flakes and metal-particles composite. The present work focuses on graphite flakes–SiC particles/Al–12 wt%Si composites. The effects that the relative amounts of the components, as well as the average diameter of SiC particles (varied over the range 13–170 μm), have on the thermal conductivity are investigated. The experimental results are analyzed by means of two model microstructures: (i) alternating layers of flakes and metal-particle composite, and, (ii) oriented discs (graphite flakes) randomly distributed in a metal-particle composite matrix. Fitting experimental data by means of these model microstructures leads to reasonable values of the thermal conductivity of graphite flakes along the transversal and longitudinal directions.

The population of OB supergiants in the starburst cluster Westerlund 1

Abstract: Context. After leaving the main sequence, massive stars undergo complex evolution, a process that is still poorly understood. With a population of hundreds of OB stars, the starburst cluster Westerlund 1 offers an unparallelled environment to study their evolutionary tracks. Aims. We characterise a large sample of evolved OB stars in the cluster, with the aim of determining cluster parameters and place stars in an evolutionary sequence. Methods. We used the FORS2 instrument on the VLT to obtain intermediate-resolution spectroscopy over the range 5800−9000 A of about a hundred stars selected as likely members of the cluster based on their photometry. We developed criteria for their spectral classification using only spectral features in the range observed. We discuss these criteria, useful for spectral classification of earlytype stars in the GAIA spectral region, in the appendix. Using these criteria, we obtain spectral classifications, probably accurate to one subtype, for 57 objects, most of which had no previous classification or a generic classification. Results. We identify more than 50 objects as OB supergiants. We find almost 30 luminous early-B supergiants and a number of less luminous late-O supergiants. In addition, we find a few mid B supergiants with very high luminosity, some of them displaying signs of heavy mass loss. All these stars form a sequence compatible with theoretical evolutionary tracks. In addition, two early B supergiants also show indication of heavy mass loss and may represent the evolutionary phase immediately prior to the Wolf-Rayet stage. We investigate cluster properties using the spectral types and existing photometry. We find that the reddening law to the cluster does not deviate strongly from standard, even though extinction is quite variable, with an average value AV = 10.8. Though evolutionary tracks for high-mass stars are subject to large uncertainties, our data support an age of >5 Myr and a distance d ≈ 5 kpc for Westerlund 1. Conclusions. The spectral types observed are compatible with a single burst of star formation (the age range is very unlikely to be >1 Myr). Westerlund 1 shows its potentiality as a laboratory for massive star evolution, which can be fulfilled by detailed study of the population presented here.

A model-driven goal-oriented requirement engineering approach for data warehouses

Abstract: The development of a data warehouse has been traditionally guided by an in-depth analysis of the underlying operational data sources, thus overlooking an explicit development phase in which information requirements of decision makers are addressed. This scenario has prompted that the deployed data warehouse often fails in delivering the expected support of the decision making process. To overcome this problem, we propose to use the i* modeling framework and the model driven architecture (MDA) in order to describe (i) how to model goals and information requirements for data warehouses, and (ii) how to derive a conceptual multidimensional model that provides the required information to support the decision making process.

Posidonia oceanica ‘banquettes’: a preliminary assessment of the relevance for meadow carbon and nutrients budget

Abstract: The massive supra-littoral deposit of leaf litter from the endemic Mediterranean seagrass Posidonia oceanica in Nueva Tabarca Island (Alicante, Spain), has been investigated to obtain a first assessment of its potential importance for the carbon and nutrients budget of the meadow. From approximately 18–500 kg of dry wt m −1 of shoreline P. oceanica leaves formed conspicuous wedge-shaped accumulations (‘banquettes’) all along the bay, with heights ranging from 50 to 220 cm. The materials accumulated in the banquettes represented 50.7, 71.0, 27.2, and 8.7% of the annual biomass, carbon, nitrogen, and phosphorus production of the meadow, respectively. From the proposed accretion–erosion model of the banquette, it is concluded that the only true annual sink (loss) for the meadows, would be that represented by the material of the banquettes consumed by terrestrial detritivores and/or exported further away. The majority of the accumulated material would, therefore only constitute a temporary C, N, and P sink for P. oceanica meadows, of a constant average size.