Education and Labor-Market Discrimination

We propose a model that combines statistical discrimination and educational sorting that explains why blacks get more education than do whites of similar cognitive ability. Our model explains the difference between blacks and whites in the relations between education and AFQT and between wages and education. It cannot easily explain why, conditional only on AFQT, blacks earn no more than do whites. It does, however, suggest, that when comparing the earnings of blacks and whites, one should control for both AFQT and education in which case a substantial black-white wage differential reemerges. We explore and reject the hypothesis that differences in school quality between blacks and whites explain the wage and education di%uFB00erentials. Our findings support the view that some of the black-white wage di%uFB00erential reflects the operation of the labor market.

RGtk2: A Graphical User Interface Toolkit for R

Graphical user interfaces (GUIs) are growing in popularity as a complement or alternative to the traditional command line interfaces to R. RGtk2 is an R package for creating GUIs in R. The package provides programmatic access to GTK+ 2.0, an open-source GUI toolkit written in C. To construct a GUI, the R programmer calls RGtk2 functions that map to functions in the underlying GTK+ library. This paper introduces the basic concepts underlying GTK+ and explains how to use RGtk2 to construct GUIs from R. The tutorial is based on simple and pratical programming examples. We also provide more complex examples illustrating the advanced features of the package. The design of the RGtk2 API and the low-level interface from R to GTK+ are discussed at length. We compare RGtk2 to alternative GUI toolkits for R.

Boolean Hedonic Games

We study hedonic games with dichotomous preferences. Hedonic games are cooperative games in which players desire to form coalitions, but only care about the makeup of the coalitions of which they are members; they are indifferent about the makeup of other coalitions. The assumption of dichotomous preferences means that, additionally, each player's preference relation partitions the set of coalitions of which that player is a member into just two equivalence classes: satisfactory and unsatisfactory. A player is indifferent between satisfactory coalitions, and is indifferent between unsatisfactory coalitions, but strictly prefers any satisfactory coalition over any unsatisfactory coalition. We develop a succinct representation for such games, in which each player's preference relation is represented by a propositional formula. We show how solution concepts for hedonic games with dichotomous preferences are characterised by propositional formulas.Comment: This paper was orally presented at the Eleventh Conference on Logic and the Foundations of Game and Decision Theory (LOFT 2014) in Bergen, Norway, July 27-30, 201

High Temperature Water Electrolysis Using Metal Supported Solid Oxide Electrolyser Cells (SOEC)

Metal supported cells as developed according to the DLR SOFC concept by applying plasma deposition technologies were investigated for use as solid oxide electrolyser cells (SOEC) for high temperature steam electrolysis. Cells consisting of a porous ferritic steel support, a diffusion barrier layer, a Ni/YSZ hydrogen electrode, a YSZ electrolyte and a LSCF oxygen electrode were electrochemically characterised by means of i-V characteristics and electrochemical impedance spectroscopy measurements including a long-term test over 2000 hours. The cell voltage during electrolysis operation at a current density of -1.0 A cm-2 was 1.28 V at an operating temperature of 850 °C and 1.4 V at 800 °C. A long-term test run over 2000 hours with a steam content of 43% at 800 °C and a current density of -0.3 A cm-2 showed a degradation rate of 3.2% per 1000 hours. The impedance spectra revealed a significantly enhanced polarisation resistance during electrolysis operation compared to fuel cell operation which was mainly attributed to the hydrogen electrode

POD model order reduction with space-adapted snapshots for incompressible flows

We consider model order reduction based on proper orthogonal decomposition (POD) for unsteady incompressible Navier-Stokes problems, assuming that the snapshots are given by spatially adapted finite element solutions. We propose two approaches of deriving stable POD-Galerkin reduced-order models for this context. In the first approach, the pressure term and the continuity equation are eliminated by imposing a weak incompressibility constraint with respect to a pressure reference space. In the second approach, we derive an inf-sup stable velocity-pressure reduced-order model by enriching the velocity reduced space with supremizers computed on a velocity reference space. For problems with inhomogeneous Dirichlet conditions, we show how suitable lifting functions can be obtained from standard adaptive finite element computations. We provide a numerical comparison of the considered methods for a regularized lid-driven cavity problem