4,227 research outputs found
Una respuesta metodológica para una realidad abstracta y sin sujetos : Aportes para el debate sobre abordajes metodológicos en Ciencia de la Información
En el presente trabajo se desarrolla una discusión sobre los desafíos que implica investigar en Ciencia de la Información en el marco de la modernidad contemporánea. Por una parte se discuten los desafíos teóricos, epistemológicos y metodológicos que se presentan ante una realidad conceptualizada como modernidad liquida o modernidad reflexiva, que crece en abstracción y sostiene un proceso de individualización afectando sustancialmente a los actores sociales y a las instituciones. En ese contexto, se problematiza el carácter complejo de las categorías clásicas de diferentes disciplinas, y se argumenta sobre la necesidad de mantener la distancia epistemológica con el objeto de estudio. Por último, se analiza el pasaje del paradigma positivista lógico al post positivista y su relación convergente en este proceso con el paradigma constructivista/naturalista. Esto nos permite contextualizar el uso de un enfoque metodológico multi métodos o de métodos combinados como herramienta necesaria para dar cuenta de objetos de estudio complejos que se despliegan en múltiples planos de la realidad
Es falso que la agricultura superintensiva sea sinónimo de derroche en los insumos
Artículo periodístico de una entrevista. 2 páginas.Entrevista aL investigador asegura que los trabajos científicos avalan que un olivar superintensivo consume la mitad de agua que otro tradicionalN
De la influencia literaria a la huella textual
This article considers the various reworkings which the old concept
of "influence" has undergone during the course of this century in relation
to the differing theoretical and critical tendencies that succeeded one
another from positivism onwards, especially the growth of structuralim,
deconstruction, the aesthetics of reading and the theory of multiple
systems. Its conclusion is that the relationship between texts, which was
the basis of the old concept, continues to offer guidelines and new
approaches for Comparative Literature.Este artículo tiene en cuenta numerosas reelaboraciones que el viejo concepto de “influencia” ha sufrido durante el trascurso de este siglo, en relación con las diferentes tendencias teóricas y críticas que se han ido sucediendo a raíz del positivismo (especialmente, el crecimiento del estructuralismo, la deconstrucción, la estética de la lectura y la teoría de los sistemas múltiples). Concluye que la relación entre textos (lo cual era la base del concepto antiguo) continua ofreciendo pautas y nuevos planteamientos para la Literatura Comparada
Efficient numerical schemes for viscoplastic avalanches. Part 2: the 2D case
This paper deals with the numerical resolution of a shallow water viscoplastic flow model. Viscoplastic materials are characterized by the existence of a yield stress: below a certain critical threshold in the imposed stress, there is no deformation and the material behaves like a rigid solid, but when that yield value is exceeded, the material flows like a fluid. In the context of avalanches, it means that after going down a slope, the material can stop and its free surface has a non-trivial shape, as opposed to the case of water (Newtonian fluid). The model involves variational inequalities associated with the yield threshold: finite volume schemes are used together with duality methods (namely Augmented Lagrangian and Bermúdez–Moreno) to discretize the problem. To be able to accurately simulate the stopping behavior of the avalanche, new schemes need to be designed, involving the classical notion of well-balancing. In the present context, it needs to be extended to take into account the viscoplastic nature of the material as well as general bottoms with wet/dry fronts which are encountered in geophysical geometries. Here we derive such schemes in 2D as the follow up of the companion paper treating the 1D case. Numerical tests include in particular a generalized 2D benchmark for Bingham codes (the Bingham–Couette flow with two non-zero boundary conditions on the velocity) and a simulation of the avalanche path of Taconnaz in Chamonix—Mont-Blanc to show the usability of these schemes on real topographies from digital elevation models (DEM)
Heliostat field cleaning scheduling for Solar Power Tower plants: a heuristic approach
Soiling of heliostat surfaces due to local climate has a direct impact on their
optical efficiency and therefore a direct impact on the productivity of the Solar
Power Tower plant. Cleaning techniques applied are dependent on plant construction and current schedules are normally developed considering heliostat layout patterns, providing sub-optimal results. In this paper, a method to optimise cleaning schedules is developed, with the objective of maximising energy generated by the plant. First, an algorithm finds a cleaning schedule by solving an integer program, which is then used as a starting solution in an exchange heuristic. Since the optimisation problems are of large size, a p-median type heuristic is performed to reduce the problem dimensionality by clustering heliostats into groups to be cleaned in the same period.Ministerio de Economía y Competitivida
Chemical distribution of HII regions towards the Galactic anticentre
We study the physical and chemical properties of a sample of HII regions
located at RG >11 kpc and present the radial distribution of abundances towards
the Galaxy anticentre.
We carried out optical spectroscopic observations of nine HII regions with
the WHT. The sample was increased by searching the literature for optical
observations of regions towards the Galactic anticentre, re-analysing them to
obtain a single sample of 23 objects covering the Galactocentric radius from 11
kpc to 18 kpc to be processed in a homogeneous and consistent manner. Accurate
electron densities and temperatures of several ionic species were derived in 13
HII regions. These physical parameters were applied to the spectra to determine
direct total chemical abundances. For those regions without direct estimations
of temperature, chemical abundances were derived by performing tailor-made
photoionisation models and/or by using an empirical relation obtained from
radio recombination and optical temperatures.
We performed weighted least-squares fits to the distribution of the derived
abundances along the Galactocentric distances to study the radial gradients of
metallicity. The distributions O/H, N/H, S/H, and Ar/H towards the anticentre
can be represented by decreasing linear radial gradients, while in the case of
N/O abundances the radial distribution is better fitted with a two-zone model.
The He/H radial gradient is presented here for the first time; we find a slope
that is not significantly different from zero. The derived gradient for oxygen
shows a clear decrease with distance with a slope of -0.053dex/kpc. Although a
shallower slope at large Galactocentric distances is suggested by our data, the
flattening of the distribution cannot be confirmed and more objects towards the
anticentre need to be studied in order to establish the true form of the
metallicity gradient.Comment: Accepted for publication in Section 5. Galactic structure, stellar
clusters and populations of Astronomy and Astrophysics. The official date of
acceptance is 13/09/2016. 19 pages, 15 figures and 10 table
Number conserving particle-hole RPA for superfluid nuclei
TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284
Number conserving particle-hole RPA for superfluid nuclei
TheAuthor(s) - .Published by Elsevier B.V. "This is an open access article under the CCBY license (http://creativecommons.org/licenses/by/4.0/).Funded by SCOAP"We present a number conserving particle-hole RPA theory for collective excitations in the transition from normal to superfluid nuclei. The method derives from an RPA theory developed long ago in quantum chemistry using antisymmetric geminal powers, or equivalently number projected HFB states, as reference states. We show within a minimal model of pairing plus monopole interactions that the number conserving particle-hole RPA excitations evolve smoothly across the superfluid phase transition close to the exact results, contrary to particle-hole RPA in the normal phase and quasiparticle RPA in the superfluid phase that require a change of basis at the broken symmetry point. The new formalism can be applied in a straightforward manner to study particle-hole excitations on top of a number projected HFB state.Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (Spain) FQM-160 and FQM-370Fondo Europeo de Desarrollo Regional (ERDF), ref. SOMM17/6105/UGRMinisterio de Ciencia, Innovación y Universidades and the ERDF under Projects No. FIS2015-63770-P, FIS2017-88410-P and PGC2018-094180-B-I00CEAFMC and Universidad de Huelva High Performance Computer (HPC@UHU) funded by FEDER/MINECO project UNHU-15CE-284
Connection between decoherence and excited state quantum phase transitions
In this work we explore the relationship between an excited state quantum phase transition (ESQPT) and the phenomenon of quantum decoherence. For this purpose, we study how the decoherence is affected by the presence of a continuous ESQPT in the environment. This one is modeled as a two level boson system described by a Lipkin Hamiltonian. We will show that the decoherence of the system is maximal when the environment undergoes a continuous ESQPT
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