Icing testing in the large Modane wind-tunnel on full-scale and reduced scale models

Icing tests on full scale models of parts of aircraft (wings, tailplanes, radome) equipped with actual de-icing systems were carried out in the large Modane wind tunnel of ONERA. For studying icing on the Concorde, it was necessary to use a 1/6 scale half model. The equations governing the relevant parameter ratios to obtain reasonably good similitude water catching and ice accretion are recalled. Despite the inherent limitations of this particular kind of testing, i.e., the impossibility of duplicating both the Mach and Reynolds conditions for the main flow pattern, it is possible to obtain on a reduced scale model a reasonably good representation of icing cloud catching and of the shape of resulting ice accretion

Modelling the temperature, maturity and moisture content in a drying concrete block

In this paper we continue work from a previous Study Group in developing a model for the maturation of concrete. The model requires equations describing the temperature, moisture content and maturity (or amount of cement that has reacted with the water). Non-dimensionalisation is used to simplify the model and provide simple analytical solutions which are valid for early time maturation. A numerical scheme is also developed and simulations carried out for maturation over one day and then two months. For the longer simulation we also investigate the effect of building the block in a single pour or two stages

Weather hazard simulation in the Modane wind-tunnels

Specially designed wind tunnel setups make it possible to simulate various weather hazards, in an imperfect but systematic manner. Systems installed in the Modane wind tunnels for rain and icing tests are described. A qust simulator being developed is also discussed

Réévaluation des modèles d’estimation précoce de la croissance

Dans le n˚ 108 de la Revue de l’OFCE, des modèles d’estimation précoce de la croissance française ont été proposés et évalués en pseudo temps réel sur la période 2001-2007. La crise financière a quelque peu dégradé leur performance. Le changement de base des comptes trimestriels en mai 2011 modifie aussi sensiblement les résultats car il affecte la croissance du PIB sur toute la période d’estimation des modèles. Ainsi le moment est venu de faire le point sur les outils de prévision à court terme présentés dans l’article de F. Charpin (2009). C’est aussi l’occasion de les confronter à d’autres modèles et d’évaluer l’ensemble de nos outils en pseudo temps réel sur la période allant du 1er trimestre 2001 au 1er trimestre 2011.In the number 108 of the OFCE review, nowcasting factor models of French growth were proposed and assessed in pseudo real time over the period 2001-2007. The financial crisis has reduced their accuracy. The new basis of the French quarterly accounts published mid-may 2011 modifies also the results noticeably because it concerns GDP growth over the whole estimation period. Thus, it is the opportunity to reassess these models presented in Charpin (2009). It is also the occasion to confront them to other models by comparing their performance in pseudo real time over the period 2001 Q1 – 2011 Q1

Construction of coincident indicators for euro area key macroeconomic variables. 28th International Symposium on Forecasting, Nice, June 23 2008.

The availability of timely and reliable information on main macroeconomic variables is considered both by policy makers and analysts crucial for an effective process of decision making. Unfortunately official statistics cannot always meet adequately users' needs, especially concerning their timely availability. This is the reason why, using econometric techniques, analysts try to anticipate or estimate in real time short-term movements of main macroeconomic variables. In this paper we propose a strategy simple and easily replicable in production processes for the estimation of the period on period growth rates of the euro area Industrial Production Index and Gross Domestic Product (GDP). Our strategy is based on the classical multivariate regression model on growth rates with autoregressive error term which is widely used in anticipating economic movements. Concerning GDP three different equations were identified, while for Industrial Production Index we have identified only two suitable representations. Furthermore for both variables we also use a purely autoregressive representation as a benchmark.

Transportation of water-based slurry in an open furrow, launder or stream

The transport of large boulders in a furrow from a mining area to a nearby pond was considered. The furrow is filled with a mixture of water and soil particles flowing down to the pond at a very high velocity. Due to operating constraints, the slope of the furrow is reduced progressively. A formula is derived, relating the slope of the furrow and the composition of the fluid to the maximum size and shape of the transported boulders. The characteristics of the boulders carried all the way down to the pond may then be determined

Definition et Caracterisation d'une Dimension Minimale pour les Codes Principaux Nilpotents d'une Algebre Modulaire de p-Groupe Abelien Elementaire

L'ensemble des idéaux de L'algèbre est partitionné en sous-ensembles déterminés a partir de la situation d'un idéal dans la suite décroissante d'idéaux que forment les codes de Reed et Muller Généralisés (GRM-codes). Dans chaque sous-ensemble, la dimension des idéaux est bornée inférieurement. Nous caractérisons les idéaux de dimension minimale; nous en déduisons une nouvelle représentation des éléments du GRM-code d'ordre 1.The set of the ideals belonging to the algebra is divided into subsets; they are determined by the place of an ideal in the decreasing series of ideals composed by the Generalized Reed and Muller codes (GRM-codes). A lower bound is obtained for the dimension of the ideals in each subset. We characterize the minimal dimension ideals and such investigation permits us to represent elements of the first order GRM-code