This work presents a comparison among seventeen different proposals for estimating the hourly diffuse fraction of irradiance. Twelve of them are polynomial correlations of different orders, two are based on a logistic function and the three last ones consider the diffuse irradiance values in the...

At the 2000 Lisbon summit, the European Union formulated the ambition to transform itself into "the most competitive and dynamic knowledge-based economy in the world capable of sustainable economic growth with more and better jobs and greater social cohesion'. It is remarkable that, until...

This paper uses statistical data from the annual R&D survey of financial flows received or spent by the firm for R&D activities. To describe R&D networks, attention is focused on the construction of four synthetic proxies from empirical literature on social networks: variety of partners,...