Paris West University Nanterre La Défense

About: Paris West University Nanterre La Défense is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Finite element method. The organization has 895 authors who have published 1430 publications receiving 21712 citations.

An operator approach to zero-sum repeated games

Abstract: We consider two person zero-sum stochastic games. The recursive formula for the valuesvλ (resp.v n) of the discounted (resp. finitely repeated) version can be written in terms of a single basic operator Φ(α,f) where α is the weight on the present payoff andf the future payoff. We give sufficient conditions in terms of Φ(α,f) and its derivative at 0 for limv n and limvλ to exist and to be equal. We apply these results to obtain such convergence properties for absorbing games with compact action spaces and incomplete information games.

Profiling fetal cardiac function in twin–twin transfusion syndrome

Abstract: Objectives Cardiomyopathy in the recipient twin is a marker of severity in twin–twin transfusion syndrome (TTTS), making it a potentially valuable tool for staging the disease. This study aimed to provide a quantitative description of cardiac function in the recipient twin. Methods Consecutive monochorionic pregnancies complicated with TTTS and treated by percutaneous laser coagulation underwent fetal echocardiography before surgery. An unsupervised classification analysis was conducted to identify groups of twins with similar cardiac profiles. The predictive value of the recipient twin's preoperative cardiac function based on these profiles was assessed, using perinatal death of at least one twin as the main outcome. The cardiac function profiles that we identified were compared with the current Quintero staging. Results A total of 107 pregnancies were included, with six of these lost to follow-up; 63/107 complete cases were available for multivariate description of the recipient's cardiac function. Three different preoperative cardiac profiles were identified with increasing right and left myocardial performance index, decreasing right and left shortening fraction, and increasing ductus venosus pulsatility index. Although the three groups represented progressive stages of the syndrome-related cardiomyopathy, no correlation was found with pregnancy outcome. Of Quintero Stage 1 cases, 55% showed significant alterations of cardiac function in the recipient twin. Conclusions Progressive cardiomyopathy can be assessed quantitatively in the recipient twin and does not influence pregnancy outcome when fetoscopic laser coagulation is the first-line treatment. Compared with the current staging, cardiac profiling allows discrimination of cases with significant myocardial dysfunction. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.

Equilibrium with a Market of Permits

Abstract: In this paper we present the main results of three original studies on the equilibrium with a market of tradeable permits in a static framework. In first study, we have considered an international equilibrium of two countries which depend on the quantity of permits to each country. The allocation is efficient if and only if it is proportional to efficient labor. A redistribution in favor of the less developed country implies a redistribution to this country but leads to a dilemma with efficiency. In the second study, we analyze the consequences of the choice between giving free permits to firms and other possibilities. We show that for equalizing incomes of production factors with there marginal productivities, each factor should receive a quantity of free permits proportional to its contribution to production. In the third study, we consider the partial equilibrium of an industry where each firm is characterized by a parameter combining production efficiency and pollution effect. We define a theoretical indicator of environmental efficiency and we analyze its properties.

Slider block friction model for landslides: Application to Vaiont and La Clapière landslides

Abstract: [1] Accelerating displacements preceding some catastrophic landslides have been found to display a finite time singularity of the velocity v ∼1/(tc − t) [Voight, 1988a, 1988b]. Here we provide a physical basis for this phenomenological law based on a slider block model using a state- and velocity-dependent friction law established in the laboratory. This physical model accounts for and generalizes Voight's observation: Depending on the ratio B/A of two parameters of the rate and state friction law and on the initial frictional state of the sliding surfaces characterized by a reduced parameter Xi, four possible regimes are found. Two regimes can account for an acceleration of the displacement. For B/A > 1 (velocity weakening) and Xi 1. In this case, the acceleration of the displacement evolves toward a stable sliding with a constant sliding velocity. The two other cases (B/A 1 and Xi > 1) give a deceleration of the displacement. We use the slider block friction model to analyze quantitatively the displacement and velocity data preceding two landslides, Vaiont and La Clapiere. The Vaiont landslide was the catastrophic culmination of an accelerated slope velocity. La Clapiere landslide was characterized by a peak of slope acceleration that followed decades of ongoing accelerating displacements succeeded by a restabilization. Our inversion of the slider block model in these data sets shows good fits and suggests a classification of the Vaiont landslide as belonging to the unstable velocity-weakening sliding regime and La Clapiere landslide as belonging to the stable velocity-strengthening regime.

On the identification of de facto currency pegs

Abstract: We describe an exchange rate peg on a dollar/euro/yen basket as an orthogonality condition for bilateral exchange rates vis-a-vis these currencies. This approach avoids the choice of a numeraire and allows simple testing on the composition of the peg. GMM estimation is performed before and after the 1997–1998 crises for up to 139 currencies. We find that the number of pegs has not diminished after the crises. Intermediate regimes, defined as de facto pegs which are not reported as hard pegs to the IMF, have been replaced by hard pegs (primarily as a consequence of the launch of the euro) while the proportion of free floats has not increased. The dollar remains the main anchor currency. J. Japanese Int. Economies 20 (1) (2006) 112–127.