Composition and Inversion of Schema Mappings

In the recent years, a lot of attention has been paid to the development of solid foundations for the composition and inversion of schema mappings. In this paper, we review the proposals for the semantics of these crucial operators. For each of these proposals, we concentrate on the three following problems: the definition of the semantics of the operator, the language needed to express the operator, and the algorithmic issues associated to the problem of computing the operator. It should be pointed out that we primarily consider the formalization of schema mappings introduced in the work on data exchange. In particular, when studying the problem of computing the composition and inverse of a schema mapping, we will be mostly interested in computing these operators for mappings specified by source-to-target tuple-generating dependencies

Policy implications of suboptimal choice: theory and evidence: misperceptions about tax audits

For some entities, such as self-employed individuals reporting income taxes or firms reporting value-added taxes, the optimal evasion rate depends substantially on audit features like audit probabilities and penalty rates (Allingham and Sandmo 1972). Whereas it is easy for firms to find other important information such as inflation rates or exchange rates, it is difficult to find information about the probability of being audited and penalty rates. Indeed, Bérgolo et al. (2017) show evidence that firms have large misperceptions about these audit features.1 In this paper, we expand their analysis to explore the sources of these misperceptions.Fil: Bérgolo, Marcelo. Universidad de la República; UruguayFil: Ceni, Rodrigo. Universidad de la República; UruguayFil: Cruces, Guillermo Antonio. Universidad Nacional de La Plata. Facultad de Ciencias Económicas. Departamento de Ciencias Económicas. Centro de Estudios Distributivos Laborales y Sociales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Giaccobasso, Matias. University of California at Los Angeles; Estados UnidosFil: Perez Truglia, Ricardo. University of California at Los Angeles; Estados Unido

A Defense of Moderate Language Pluralism in Scholarly Production in the Humanities

In this paper we argue in favor of a moderate language plurilingualism in scholarly production in the humanities. We start by proposing some desiderata that a good policy regarding language use in the humanities should meet. We then survey institutional/policy options regarding the use of languages in the humanities and argue that different versions of monolingualism fall short of satisfying the desiderata. As a result, we consider different alternatives supporting plurilingualism and we defend that one of the options, that we call Moderate Language Pluralism or Moderate Plurilingualism, does better than the others vis-à-vis the desiderata. Finally, we suggest some policies that would help to implement Moderate Plurilingualism.Fil: Perez, Diana Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Filosóficas. - Sociedad Argentina de Análisis Filosófico. Instituto de Investigaciones Filosóficas; ArgentinaFil: Sabatés, Marcelo. Columbia College; Estados Unido

2MASS J18082002-5104378: The brightest (V=11.9) ultra metal-poor star

Context. The most primitive metal-poor stars are important for studying the conditions of the early galaxy and are also relevant to big bang nucleosynthesis. Aims. Our objective is to find the brightest (V<14) most metal-poor stars. Methods. Candidates were selected using a new method, which is based on the mismatch between spectral types derived from colors and observed spectral types. They were observed first at low resolution with EFOSC2 at the NTT/ESO to obtain an initial set of stellar parameters. The most promising candidate, 2MASS J18082002-5104378 (V=11.9), was observed at high resolution (R=50 000) with UVES at the VLT/ESO, and a standard abundance analysis was performed. Results. We found that 2MASS J18082002-5104378 is an ultra metal-poor star with stellar parameters Teff = 5440 K, log g = 3.0 dex, vt = 1.5 km/s, [Fe/H] = -4.1 dex. The star has [C/Fe]<+0.9 in a 1D analysis, or [C/Fe]<=+0.5 if 3D effects are considered; its abundance pattern is typical of normal (non-CEMP) ultra metal-poor stars. Interestingly, the star has a binary companion. Conclusions. 2MASS J1808-5104 is the brightest (V=11.9) metal-poor star of its category, and it could be studied further with even higher S/N spectroscopy to determine additional chemical abundances, thus providing important constraints to the early chemical evolution of our Galaxy.Comment: A&A Letter

Control and grid integration of MW-range wind and solar energy conversion systems

Solar-based energy generation has increased by more than ten times over the same period. In total, worldwide electrical energy consumption increased by approximately 6340 TWh from 2003 to 2013. To meet the challenges created by intermittent energy generation sources, grid operators have increasingly demanded more stringent technical requirements for the connection and operation of grid-connected intermittent energy systems, for instance concerning fault ride through capability, voltage and frequency support, and inertia emulation. Ongoing developments include new or improved high-voltage converters, power converters with higher power density, control systems to provide ride-through capability, implementation of redundancy schemes to provide more reliable generation systems, and the use of high-voltage direct current (HVdc) links for the connection of large off-shore intermittent energy systems