Observation and its History

Recenze: Lorraine DASTON - Elizabeth LUNBECK, E., Histories of Scientific Observation. Chicago - London: University of Chicago Press 2011, 460 pp

All-Pay Auctions with Negative Prize Externalities: Theory and Experimental Evidence

The paper characterizes the mixed-strategy equilibria in all-pay auctions with endogenous prizes that depend positively on own effort and negatively on the effort of competitors. Such auctions arise naturally in the context of investment games, lobbying games, and promotion tournaments. We also provide an experimental analysis of a special case which captures the strategic situation of a two-stage game with investment preceding homogenous Bertrand competition. We obtain overinvestment both relative to the mixed-strategy equilibrium and the social optimum.All-pay auctions, oligopoly, investment, experiment, overbidding

A thermodynamically consistent derivation of a frictional-damage cohesive-zone model with different mode i and mode II fracture energies

The present paper deals with the derivation of an interface model characterized by macroscopic fracture energies which are different in modes I and II, the macroscopic fracture energy being the total energy dissipated per unit of fracture area. It is first shown that thermo-dynamical consistency for a model governed by a single damage variable, combined with the choice of employing an equivalent relative displacement and of a linear softening in the stress-relative displacement law, leads to the coincidence of fracture energies in modes I and II. To retrieve the experimental evidence of a greater fracture energy in mode II, a micro-structured geometry is considered at the typical point of the interface where a Representative Interface Element (RIE) characterized by a periodic arrangement of distinct inclined planes is introduced. The interaction within each of these surfaces is governed by a coupled damage-friction law. A sensitivity analysis of the correlation between micromechanical parameters and the numerically computed single-point microstructural response in mode II is reported. An assessment of the capability of the model in predicting different mixed mode fracture energies is carried out both at the single microstructural interface point level and with a structural example. For the latter a double cantilever beam with uneven bending moments has been analyzed and numerical results are compared with experimental data reported in the literature for different values of mode mixity. © 2014 Elsevier Masson SAS. All rights reserved

Competition and Innovation: An Experimental Investigation

The paper analyzes the effects of competitive intensity on firms' incentives to invest in process innovations through an experiment based on two-stage games, where R&D investment choices are followed by product market competition. An increase in the intensity of competition is modeled as an increase in the number of Þrms or as a switch from Cournot to Bertrand. The theoretical prediction is that more intense competition is unfavorable to investments for both cases. In the experiment it turns out that the way of modeling the intensity of competition is essential. The theoretical prediction is confirmed for the number effects. On the other hand, the comparison of Cournot and Bertrand shows that more intense competition is beneÞcial for investments.R&D investment, intensity of competition, experiment

Solution Map Analysis of a Multiscale Drift-Diffusion Model for Organic Solar Cells

In this article we address the theoretical study of a multiscale drift-diffusion (DD) model for the description of photoconversion mechanisms in organic solar cells. The multiscale nature of the formulation is based on the co-presence of light absorption, conversion and diffusion phenomena that occur in the three-dimensional material bulk, of charge photoconversion phenomena that occur at the two-dimensional material interface separating acceptor and donor material phases, and of charge separation and subsequent charge transport in each three-dimensional material phase to device terminals that are driven by drift and diffusion electrical forces. The model accounts for the nonlinear interaction among four species: excitons, polarons, electrons and holes, and allows to quantitatively predict the electrical current collected at the device contacts of the cell. Existence and uniqueness of weak solutions of the DD system, as well as nonnegativity of all species concentrations, are proved in the stationary regime via a solution map that is a variant of the Gummel iteration commonly used in the treatment of the DD model for inorganic semiconductors. The results are established upon assuming suitable restrictions on the data and some regularity property on the mixed boundary value problem for the Poisson equation. The theoretical conclusions are numerically validated on the simulation of three-dimensional problems characterized by realistic values of the physical parameters

Institutions and Dissent: Historical Geology in the Early Royal Society

The paper aims to ques- tion the traditional view of the early Royal Society of London, the oldest scientific institution in continuous existence. According to that view, the institutional life of the Society in the early decades of activity was characterized by a strictly Baconian methodology. But the re- construction of the discussions about fossils and natural history within the Society shows that this monolithic image is far from being correct. Despite the persistent reference to the Baconian Solomon House, the Society did not impose or support a common programme of research in the field of the natural history of the Earth