Human Capital Convergence: A Joint Estimation Approach

In the growth literature, evidence on convergence of per capita incomes is mixed. In the development literature, health and education indicators are often used to measure countries' development progress. This study examines whether average stocks of health and education are converging across countries and calculates the speed of their convergence using data from 84 countries for 1970-90. A three-stage least-squares (3SLS) procedure is used in a joint analysis of human capital convergence. The results confirm that investments in education and health are closely linked. The study finds unconditional convergence for life expectancy and infant survival, and for the stock of education as measured by average levels of total and secondary schooling in the adult population. Copyright 2002, International Monetary Fund

The Impact of Oil Prices on the Real Exchange Rate of the Dirham: a Case Study of the United Arab Emirates

This study investigated the impact of oil shocks on the real exchange rate of the United Arab Emirates (UAE) dirham. Time series data were used for the period 1977 to 2007 covering four important oil shocks. Five variables have been used in this study, with the real exchange rate of the dirham as the dependent variable and the gross domestic product per capita, oil price, trade balance, and foreign direct investment inflows as the independent variables. In this study we used the Johansen-Juselius cointegration procedure, and conducted the Granger causality tests based on the VECM. Through this research, we found that a fixed exchange rate to the U.S. dollar is not an appropriate exchange rate regime for the UAE. This is because when the price of oil increases, and with a fixed exchange rate regime, this would lead to rapid growth in GDP and liquidity in the UAE economy. This in turn causes domestic prices to increase, which results in high levels of inflation.oil Prices, real exchange rate, UAE, VAR

Homogenization of a space frame as a thick plate: Application of the Bending-Gradient theory to a beam lattice

International audienceThe Bending-Gradient theory for thick plates is the extension to heterogeneous plates of Reissner-Mindlin theory originally designed for homogeneous plates. In this paper the Bending-Gradient theory is extended to in-plane periodic structures made of connected beams (space frames) which can be considered macroscopically as a plate. Its application to a square beam lattice reveals that classical Reissner-Mindlin theory cannot properly model such microstructures. Comparisons with exact solutions show that only the Bending-Gradient theory captures second order effects in both deflection and local stress fields

A bending-gradient model for thick plates, I : theory

International audienceThis is the first part of a two-part paper dedicated to a new plate theory for out-of-plane loaded thick plates where the static unknowns are those of the Kirchhoff-Love theory (3 in-plane stresses and 3 bending moments), to which six components are added representing the gradient of the bending moment. The new theory, called the Bending-Gradient plate theory is described in the present paper. It is an extension to arbitrarily layered plates of the Reissner-Mindlin plate theory which appears as a special case of the Bending-Gradient plate theory when the plate is homogeneous. However, we demonstrate also that, in the general case, the Bending-Gradient model cannot be reduced to a Reissner-Mindlin model. In part two (Lebee and Sab, 2010a), the Bending-Gradient theory is applied to multilayered plates and its predictions are compared to those of the Reissner-Mindlin theory and to full 3D Pagano's exact solutions. The main conclusion of the second part is that the Bending-Gradient gives good predictions of both deflection and shear stress distributions in any material configuration. Moreover, under some symmetry conditions, the Bending-Gradient model coincides with the second-order approximation of the exact solution as the slenderness ratio L/h goes to infinity

Quelques exemples d'application aux composites stratitfiés de la théorie Bending-Gradient pour les plaques

International audienceCe travail présente l'application aux composites fibrés d'une nouvelle théorie de plaque. Ce modèle destiné aux plaques épaisses et anisotropes utilise les six inconnues statiques de la theorie de Kirchhoff-Love auxquelles sont ajoutées six nouvelles inconnues représentant le gradient dumoment de flexion. Nommé théorie Bending-Gradient, ce nouveaumodèle peut être considéré comme une extension aux plaques hétérogènes dans l'épaisseurs du modèle de Reissner-Mindlin ; ce dernier étant un cas particulier lorsque la plaque est homogène. La théorie Bending-Gradient est appliquée aux plaques stratifiées et comparée à la solution exacte de Pagano [1] ainsi qu'à d'autres approches. Elle donne de bonnes prédictions pour la flèche, pour la distribution des contraintes de cisaillement transverse ainsi que pour les déplacements plans dans de nombreuses configurations matérielles

New boundary conditions for the computation of the apparent stiffness of statistical volume elements

International audienceWe present a new auxiliary problem for the determination of the apparent stiffness of a Statistical Volume Element (SVE). The SVE is embedded in an infinite, homogeneous reference medium, subjected to a uniform strain at infinity, while tractions are applied to the boundary of the SVE to ensure that the imposed strain at infinity coincides with the average strain over the SVE. The main asset of this new auxiliary problem resides in the fact that the associated Lippmann-Schwinger equation involves without approximation the Green operator for strains of the infinite body, which is translation-invariant and has very simple, closed-form expressions. Besides, an energy principle of the Hashin and Shtrikman type can be derived from this modified Lippmann-Schwinger equation, allowing for the computation of rigorous bounds on the apparent stiffness. The new auxiliary problem requires a cautious mathematical analysis, because it is formulated in an unbounded domain. Observing that the displacement is irrelevant for homogenization purposes, we show that selecting the strain as main unknown greatly eases this analysis. Finally, it is shown that the apparent stiffness defined through these new boundary conditions "interpolates" between the apparent stiffnesses defined through static and kinematic uniform boundary conditions, which casts a new light on these two types of boundary conditions

A Bending-Gradient theory for thick laminated plates homogenization

This work presents a new plate theory for out-of-plane loaded thick plates where the static unknowns are those of the Love-Kirchhoff theory, to which six components are added representing the gradient of the bending moment. The Bending-Gradient theory is an extension to arbitrary multilayered plates of the Reissner-Mindlin theory which appears as a special case when the plate is homogeneous. The new theory is applied to multilayered plates and its predictions are compared to full 3D Pagano's exact solutions and other approaches. It gives good predictions of both deflection and shear stress distributions in any material configuration. Moreover, under some symmetry conditions, the Bending-Gradient model coincides with the second-order approximation of the exact solution as the slenderness ratio L/h goes to infinity

Raideur en cisaillement transverse du module à chevrons utilisé comme âme de panneaux sandwich = Transverse Shear Stiffness of a Chevron Folded Core Used in Sandwich Construction

National audienceEn se basant sur la méthode proposée par Kelsey et al. [1], les bornes supérieures et inférieures de la raideur en cisaillement transverse d'une âme pliée en module à chevrons sont déterminées analytiquement et comparées au calcul par éléments finis. On observe que ces bornes sont généralement assez larges et qu'il existe des configurations géométriques pour lesquelles le module à chevrons peut être jusqu'à 40% plus raide que les nids d'abeille

Analysis of the mechanical behaviour of soft rockfall barriers

International audienceSoft rockfall barriers are complex structures that generally consist of a metallic net supported by steel posts and cables with brake elements. Several experimental and numerical studies have been carried out to evaluate their behaviour and a technical agreement in EU was recently established to certify these barriers based on experimental tests. Actually, manufacturers develop rockfall kits with their own technical specificities. The objective of the present paper is to determine the intrinsic properties of most common nets technologies and to investigate their influence on the overall mechanical behaviour of the structure. To this end, a comprehensive comparison between the local behaviours of the different nets is first presented using equivalent homogeneous membranes. Results derived for square nets under static concentrated loading illustrate the influence of the manufacturing technology on the deflection and stresses distribution. Then, a numerical and analytical model for the so-called "curtain effect" is developed and validated. In the conclusion, it is focused on the capacity of the pro-posed methodology to study and evaluate the response of the whole barrier

Dynamique Harmonique d'un Couplage Discret/Continu : Application à un Modèle Unidimensionnel de Voies Ferrées

International audienceDans ce papier, on propose d'étudier un modèle simple de voies ferrées en 1D, à l'aide d'une méthode de couplage entre les milieux discrets et continus. Cette méthode de couplage repose sur une partition de la structure en sous domaines. Un domaine modélisé par une approche continue capable de reproduire le même comportement du matériau que celui produit par une approche discrète. Un second domaine est modélisé par une approche discrète où la structure est endommagée. Entre les deux domaines existe un domaine de transition où un raffinement de l'approche continue sera exigé