Issues on the Measurement of the Solow Residual and the Testing of its Exogeneity: a Tale of Two Countries

Using aggregate US and Canadian data, this paper examines the implications for the empirical assessment of market structure and exogeneity of productivity shocks of correcting the Solow residual for variation in capacity utilization. In contrast to most studies, not accounting for capacity utilization, our results suggest that the US and Canadian market structures are well described by constant returns to scale and perfect competition. They also suggest that Canadian productivity shocks are exogenous to real and monetary variables, while US productivity shocks become exogenous to narrowly-defined monetary aggregates and monetary policy innovations when the capital stock is adjusted for variations in utilization rates. À l'aide de données agrégées américaines et canadiennes, nous examinons les implications empiriques quant à la structure de marché et à l'exogénéité des chocs de productivité, suite à la correction de la mesure du résidu de Solow lorsqu'il y a utilisation variable du capital. Comparativement, à la plupart des études qui ont ignoré cette considération, nos résultats suggèrent qu'en agrégé, les structures de marché canadienne et américaine sont convenablement caractérisées par des rendements constants à l'échelle et la concurrence parfaite. Nous trouvons aussi qu'après ajustement pour un taux variable d'utilisation du stock de capital, la mesure corrigée des chocs de productivité canadiens est exogène aux variables monétaires et réelles, alors que celle des chocs de productivité américains devient exogène aux agrégats monétaires étroits et aux innovations monétaires.Solow residuals; exogeneity; productivity shocks; market structure; varying capacity utilization

Vitreous silica distends in helium gas: acoustic vs. static compressibilities

Sound velocities of vitreous silica are measured under He compression in the pressure range 0-6 GPa by Brillouin light scattering. It is found that the well-known anomalous maximum in the pressure dependence of the compressibility is suppressed by He incorporation into the silica network. This shows that the elastic anomaly relates to the collapse of the largest interstitial voids in the structure. The huge difference between the static and the acoustic compressibilities indicates that the amount of incorporated helium still increases at 6 GPa.Comment: 5 pages, 4 figure

Modeling Modeling Modeling

International audienceModel-driven engineering and model-based approaches have permeated all branches of software engineering to the point that it seems that we are using models, as Molière's Monsieur Jourdain was using prose, without knowing it. At the heart of modeling, there is a relation that we establish to represent something by something else. In this paper we review various definitions of models and relations between them. Then, we define a canonical set of relations that can be used to express various kinds of representation relations and we propose a graphical concrete syntax to represent these relations. We also define a structural definition for this language in the form of a metamodel and a formal interpretation using Prolog. Hence, this paper is a contribution towards a theory of modeling

Branch and Price for a Reliability Oriented DARP Model

Version 1 - Présentation à ISCO 2014We deal here with a static decisional model related to the monitoring of a DARP (Dial and Ride) model which involves, on a closed industrial site, small electrical autonomous vehicles. Because of technological issues, we focus on reliability, and propose a model which assign requests to vehicles while minimizing Load/Unload transactions. We study this model through both a Branch/Price approach, which provides us with benchmarks, and insertion based heuristics, well-fitted to dynamic contexts

CLIC Detector Main Solenoid Design & Status Report

The magnet system for the CLIC Detector concepts is composed of the central solenoid in combination with the two forward anti-solenoids and the ancillary systems necessary for their operation, including the so-called push-pull scenario, allowing the quick exchange of the two detectors on the beam line. An overview of the design parameters of the detector main solenoids is presented hereafter.Comment: LCWS2011, Granada, Spai

Snow stratigraphic heterogeneity within ground-based passive microwave radiometer footprints: implications for emission modeling

Two-dimensional measurements of snowpack properties (stratigraphic layering, density, grain size and temperature) were used as inputs to the multi-layer Helsinki University of Technology (HUT) microwave emission model at a centimeter-scale horizontal resolution, across a 4.5 m transect of ground-based passive microwave radiometer footprints near Churchill, Manitoba, Canada. Snowpack stratigraphy was complex (between six and eight layers) with only three layers extending continuously throughout the length of the transect. Distributions of one-dimensional simulations, accurately representing complex stratigraphic layering, were evaluated using measured brightness temperatures. Large biases (36 to 68 K) between simulated and measured brightness temperatures were minimized (-0.5 to 0.6 K), within measurement accuracy, through application of grain scaling factors (2.6 to 5.3) at different combinations of frequencies, polarizations and model extinction coefficients. Grain scaling factors compensated for uncertainty relating optical SSA to HUT effective grain size inputs and quantified relative differences in scattering and absorption properties of various extinction coefficients. The HUT model required accurate representation of ice lenses, particularly at horizontal polarization, and large grain scaling factors highlighted the need to consider microstructure beyond the size of individual grains. As variability of extinction coefficients was strongly influenced by the proportion of large (hoar) grains in a vertical profile, it is important to consider simulations from distributions of one-dimensional profiles rather than single profiles, especially in sub-Arctic snowpacks where stratigraphic variability can be high. Model sensitivity experiments suggested the level of error in field measurements and the new methodological framework used to apply them in a snow emission model were satisfactory. Layer amalgamation showed a three-layer representation of snowpack stratigraphy reduced the bias of a one-layer representation by about 50%