Connection between type B (or C) and F factorizations and construction of algebras

In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33 4059), we started a systematic study of the connections among different factorization types, suggested by Infeld and Hull, and of their consequences for the construction of algebras. We devised a general procedure for constructing satellite algebras for all the Hamiltonians admitting a type E factorization by using the relationship between type A and E factorizations. Here we complete our analysis by showing that for Hamiltonians admitting a type F factorization, a similar method, starting from either type B or type C ones, leads to other types of algebras. We therefore conclude that the existence of satellite algebras is a characteristic property of type E factorizable Hamiltonians. Our results are illustrated with the detailed discussion of the Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in JP

Tool-path effect on the geometric deviations in the machining of UNS A92024 aeronautic skins

Traditionally, aeronautics skins are being machined by chemical milling, a high-pollutant process. An efficient alternative to this technology is conventional machining. However, to ensure the parts machined with this process keeps the industrial quality controls, the effect of tool-path might be characterized, specially analyzing final thickness and roughness. In this paper, five different tool-paths have been applied under the same machining parameters in the dry milling of Al-Cu UNS A92024 thin plates. Machining time, final thickness and roughness have been evaluated. Most roughness and thickness results are under the industrial quality limits stablished for this type of parts.This work has received financial support from Spanish Goverment (Project DPI2015-71448-R), TECNALIA Research & Innovation and the University of Cadiz (University training plan UCA/REC01VI/2016)

Tourism and urban transport : holding demand pressure under supply constraints

Scholars and local planners are increasingly interested in tourism contribution to economic and social development. To this regard, several European cities lead the world rankings on tourist arrivals, and their governments have promoted tourism activity. Mobility is an essential service for tourists visiting large cities, since it is a crucial factor for their comfort. In addition, it facilitates the spread of benefits across the city. The aim of this study is to determine whether city planners respond to this additional urban transport demand pressure by extending supply services. We use an international database of European cities. Our results confirm that tourism intensity is a demand enhancing factor on urban transport. Contrarily, cities do not seem to address this pressure by increasing service supply. This suggests that tourism exerts a positive externality on public transport since it provides additional funding for these services, but it imposes as well external costs on resident users because of congestion given supply constraints

L'evaporació podria moure el món

Forma part de la col·lecció: Càpsules de sostenibilita

El verd renova l'aire de l'oficina

Forma part de la col·lecció: Càpsules de sostenibilita

Les dones pateixen més els efectes del canvi climàtic

Forma part de la col·lecció: Càpsules de sostenibilita

La publicitat indueix al consumisme

Forma part de la col·lecció: Càpsules de sostenibilita

Is it redistribution or centralization? On the determinants of government investment in infrastructure

The dilemma efficiency versus equity, together with political partisan interests, has received increasing attention to explain the territorial allocation of investments. However, centralization intended to introduce or reinforce hierarchization in the political system has not been object as of now of empirical analysis. Our main contribution to the literature is providing evidence that meta-political objectives related to the ordering of political power and administration influence regional investment. In this way, we find evidence that network mode's (roads and railways) investment programs are influenced by the centralization strategy of investing near to the political capital, while investment effort in no-network modes (airports and ports) appears to be positively related to distance. Since investment in surface transportation infrastructures is much higher than that in airports and ports, and taken into account that regions surrounding the political capital are poorer than the average, we suggest that centralization rather than redistribution has been the driver for the concentration of public investment on these regions

Carrega't d'energia

Forma part de la col·lecció: Càpsules de sostenibilita

Satellite potentials for hypergeometric Natanzon potentials

As a result of the so(2,1) of the hypergeometric Natanzon potential a set of potentials related to the given one is determined. The set arises as a result of the action of the so(2,1) generators.Comment: 9 page