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Améliorer l’efficacité du service public pour l’emploi
No full textInternational audienceLe service public pour l’emploi a connu depuis 2008 de profondes réformes. Malgré leur ampleur, la période récente a montré le besoin de poursuivre la réflexion autour de leur approfondissement. Nous proposons ici, à la lumière des expériences passées, françaises comme étrangères, et des travaux d’évaluations, quelques pistes de réflexion. Nous abordons la question du financement de l’assurance chômage et celle de l’accompagnement des demandeurs d’emploi. Nous montrons à la fois le besoin de renforcer et de repenser les modalités de l’accompagnement
Cluster algebras of type : pseudotriangulations approach
No full textInternational audienceWe present a combinatorial model for cluster algebras of type in terms of centrally symmetric pseudotriangulations of a regular -gon with a small disk in the centre. This model provides convenient and uniform interpretations for clusters, cluster variables and their exchange relations, as well as for quivers and their mutations. We also present a new combinatorial interpretation of cluster variables in terms of perfect matchings of a graph after deleting two of its vertices. This interpretation differs from known interpretations in the literature. Its main feature, in contrast with other interpretations, is that for a fixed initial cluster seed, one or two graphs serve for the computation of all cluster variables. Finally, we discuss applications of our model to polytopal realizations of type associahedra and connections to subword complexes and c-cluster complexes
Solving Problems with Unknown Solution Length at (Almost) No Extra Cost
No full textInternational audienceMost research in the theory of evolutionary computation assumes that the problem at hand has a fixed problem size. This assumption does not always apply to real-world optimization challenges, where the length of an optimal solution may be unknown a priori. Following up on previous work of Cathabard, Lehre, and Yao [FOGA 2011] we analyze variants of the (1+1) evolutionary algorithm for problems with unknown solution length. For their setting, in which the solution length is sampled from a geometric distribution, we provide mutation rates that yield an expected optimization time that is of the same order as that of the (1+1) EA knowing the solution length.We then show that almost the same run times can be achieved even if no a priori information on the solution length is available.Finally, we provide mutation rates suitable for settings in which neither the solution length nor the positions of the relevant bits are known. Again we obtain almost optimal run times for the OneMax and LeadingOnes test functions, thus solving an open problem from Cathabard et al
Quantifying molecular oxygen isotope variations during a Heinrich stadial
No full textInternational audienceδ 18 O of atmospheric oxygen (δ 18 O atm) undergoes millennial-scale variations during the last glacial period, and systematically increases during Heinrich stadials (HSs). Changes in δ 18 O atm combine variations in biospheric and water cycle processes. The identification of the main driver of the millennial variability in δ 18 O atm is thus not straightforward. Here, we quantify the response of δ 18 O atm to such millennial events using a freshwater hosing simulation performed under glacial boundary conditions. Our global approach takes into account the latest estimates of isotope frac-tionation factor for respiratory and photosynthetic processes and make use of atmospheric water isotope and vegetation changes. Our modeling approach allows to reproduce the main observed features of a HS in terms of climatic conditions , vegetation distribution and δ 18 O of precipitation. We use it to decipher the relative importance of the different processes behind the observed changes in δ 18 O atm. The results highlight the dominant role of hydrology on δ 18 O atm and confirm that δ 18 O atm can be seen as a global integrator of hydrological changes over vegetated areas
Parallelising the Computation of Minimal Absent Words
No full textInternational audienceAn absent word of a word y of length n is a word that does not occur in y. It is a minimal absent word if all its proper factors occur in y. Minimal absent words have been computed in genomes of organisms from all domains of life; their computation also provides a fast alternative for measuring approximation in sequence comparison. There exists an O(n)-time and O(n)-space algorithm for computing all minimal absent words on a fixed-sized alphabet based on the construction of suffix array (Barton et al., 2014). An implementation of this algorithm was also provided by the authors and is currently the fastest available. In this article, we present a new O(n)-time and O(n)-space algorithm for computing all minimal absent words; it has the desirable property that, given the indexing data structure at hand, the computation of minimal absent words can be executed in parallel. Experimental results show that a mul-tiprocessing implementation of this algorithm can accelerate the overall computation by more than a factor of two compared to state-of-the-art approaches. By excluding the indexing data structure construction time, we show that the implementation achieves near-optimal speed-ups
Analysis of passive cardiac constitutive laws for parameter estimation using 3D tagged MRI
No full textInternational audienceAn unresolved issue in patient-specific models of cardiac mechanics is the choice of an appropriate constitutive law, able to accurately capture the passive behavior of the myocardium, while still having uniquely identifiable parameters tunable from available clinical data. In this paper, we aim to facilitate this choice by examining the practical identifiability and model fidelity of constitutive laws often used in cardiac mechanics. Our analysis focuses on the use of novel 3D tagged MRI, providing detailed displacement information in three dimensions. The practical identifiability of each law is examined by generating synthetic 3D tags from in silico simulations, allowing mapping of the objective function landscape over parameter space and comparison of minimizing parameter values with original ground truth values. Model fidelity was tested by comparing these laws with the more complex transversely isotropic Guccione law, by characterizing their passive end-diastolic pressure–volume relation behavior, as well as by considering the in vivo case of a healthy volunteer. These results show that a reduced form of the Holzapfel–Ogden law provides the best balance between identifiability and model fidelity across the tests considered
On pseudo-inverses of matrices and their characteristic polynomials in supertropical algebra
No full textInternational audienceThe only invertible matrices in tropical algebra are diagonal matrices, permutation matrices and their products. However, the pseudo-inverse A ∇ , defined as 1 det(A) adj(A), with det(A) being the tropical permanent (also called the tropical determinant) of a matrix A, inherits some classical algebraic properties and has some surprising new ones. Defining B and B to be tropically similar if B = A ∇ BA, we examine the characteristic (max-)polynomials of tropically similar matrices as well as those of pseudo-inverses. Other miscellaneous results include a new proof of the identity for det(AB) and a connection to stabilization of the powers of definite matrices
Technical Change Biased Toward the Traded Sector and Labor Market Frictions
No full textThis paper investigates the relative wage and the relative price effects of higher productivity growth in tradables relative to non tradables in a two-sector open economy model with search unemployment. Applying cointegration methods to a panel of eighteen OECD countries over the period 1970-2007, our estimates reveal that a 1 percentage point increase in the productivity differential between tradables and non tradables lowers the non traded wage relative to the traded wage (relative wage) by 0.22% and appreciates the relative price of non tradables by 0.64%. While the decline in the relative wage reveals the presence of mobility costs preventing from the wage equalization across sectors, the relative wage responses to a productivity differentialdisplay a large dispersion across countries, thus suggesting that labor market frictions vary substantially across OECD economies. Using a set of indicators capturing the heterogeneity of labor market frictions across economies, we find that the relative wage significantly declines more in countries where labor market regulation is more pronounced. These empirical findings can be rationalized in a two-sector open economy model with search in the labor market and an endogenous labor force participation. In line with our estimates, our quantitative analysis reveals that the relative wage falls more in countries where unemployment benefits are more generous, firing cost is high, the worker bargaining power is large, and/or the labor force is less responsive at the extensive margin. When calibrating the model to each OECD economy, our numerical results reveal that the model predicts the relative wage response fairly well, and to a lesser extent the relative price response
Computation in Focused Intuitionistic Logic
No full textInternational audienceWe investigate the control of evaluation strategies in a variant of the λ-calculus derived through the Curry-Howard correspondence from LJF, a sequent calculus for intuitionistic logic implementing the focusing technique. The proof theory of focused intuitionistic logic yields a single calculus in which a number of known λ-calculi appear as subsystems obtained by restricting types to a certain fragment of LJF. In particular, standard λ-calculi as well as the call-by-push-value calculus are analysed using this framework, and we relate cut elimination for LJF to a new abstract machine subsuming well-known machines for these different strategies