THREE COMPLEXITY FUNCTIONS

International audienceFor an extensive range of infinite words, and the associated symbolic dynamical systems, we compute, together with the usual language complexity function counting the finite words, the minimal and maximal complexity functions we get by replacing finite words by finite patterns, or words with holes. Given a language L on a finite alphabet A, the complexity function p L (n) counts for every n the number of factors of length n of L; this is a very useful notion, both inside word combinatorics and for the study of symbolic dynamical systems, see for example the survey [7]; of particular interest are the infinite words which are determined by the complexity of their language, those words for which p L (n) ≤ n for at least one n are ultimately periodic [15], while the Sturmian words, of complexity n + 1 for all n, are natural codings of rotations, see [6, 16], or Chapter 6 of [17], and Section 4 below. Note that the complexity is exponential when the language has positive topological entropy, and has not been widely used for that range of languages. To study further the combinatorial properties of infinite words, the notion of maximal pattern complexity, denoted by p

Etat de l'art de la segmentation de maillage 3D par patchs surfaciques

National audienceLa segmentation de maillage 3D est une composante essentielle de nombreuses applications. Elle se décline en deux familles : la segmentation en patchs surfaciques et la segmentation en parties significatives. Dans cet article, nous traitons principalement de la segmentation de maillages 3D en patchs surfaciques et en proposons un état de l'art. Nous positionnons le contexte de ce type de segmentation et discutons des contributions les plus pertinentes

A physically based trunk soft tissue modeling for scoliosis surgery planning systems

One of the major concerns of scoliotic patients undergoing spinal correction surgery is the trunk's external appearance after the surgery. This paper presents a novel incremental approach for simulating postoperative trunk shape in scoliosis surgery. Preoperative and postoperative trunk shapes data were obtained using three-dimensional medical imaging techniques for seven patients with adolescent idiopathic scoliosis. Results of qualitative and quantitative evaluations, based on the comparison of the simulated and actual postoperative trunk surfaces, showed an adequate accuracy of the method. Our approach provides a candidate simulation tool to be used in a clinical environment for the surgery planning process.IRSC / CIH

Simulation of the postoperative trunk appearance in scoliosis surgery

Persistence of external trunk asymmetry after scoliosis surgical treatment is frequent and difficult to predict by clinicians. This is a significant problem considering that correction of the apparent deformity is a major factor of satisfaction for the patients. A simulation of the correction on the external appearance would allow the clinician to illustrate to the patient the potential result of the surgery and would help in deciding on a surgical strategy that could most improve his/her appearance. We describe a method to predict the scoliotic trunk shape after a spine surgical intervention. The capability of our method was evaluated using real data of scoliotic patients. Results of the qualitative evaluation were very promising and a quantitative evaluation based on the comparison of the simulated and the actual postoperative trunk surface showed an adequate accuracy for clinical assessment. The required short simulation time also makes our approach an eligible candidate for a clinical environment demanding interactive simulations.CIHR / IRS

International Supply Chains and Trade Elasticity in Times of Global Crisis

The paper investigates the role of global supply chains in explaining the trade collapse of 2008-2009 and the long-term variations observed in trade elasticity. Building on the empirical results obtained from a subset of input-output matrices and the exploratory analysis of a large and diversified sample of countries, a formal model is specified to measure the respective short-term and long-term dynamics of trade elasticity. The model is then used to formally probe the role of vertical integration in explaining changes in trade elasticity. Aggregated results on long-term trade elasticity tend to support the hypothesis that world economy has undertaken in the late 1980s a "traverse" between two underlying economic models. During this transition, the expansion of international supply chains determined an apparent increase in trade elasticity. Two supply chains related effects (the composition and the bullwhip effects) explain also the overshooting of trade elasticity that occurred during the 2008-2009 trade collapse. But vertical specialization is unable to explain the heterogeneity observed on a country and sectoral level, indicating that other contributive factors may also have been at work to explain the diversity of the observed results

Segmentation hiérarchique de maillage 3D à partir des dynamiques de contour

La segmentation de maillage 3D est un problème fondamental en synthèse d'image et est devenu un enjeu important pour de nombreuses applications. Cet article introduit une nouvelle méthode de segmentation hiérarchique basée sur la ligne de partage des eaux (LPE), les cascades et les dynamiques de contour. La LPE génère une première partition composée de petits patchs surfaciques ; les dynamiques de contour offrent une bonne caractérisation des frontières et les cascades mettent à disposition plusieurs niveaux de segmentation pour l'utilisateur. Le procédé de fusion hiérarchique basé sur les cascades génère un arbre qui contient plusieurs schémas de segmentation ; l'utilisateur a ainsi la possibilité de parcourir facilement chacun des niveaux de segmentation contenus dans cet arbre pour sélectionner le plus adapté à son application

International Supply Chains and Trade Elasticity in Times of Global Crisis

The paper investigates the role of global supply chains in explaining the trade collapse of 2008-2009 and the long-term variations observed in trade elasticity. Building on the empirical results obtained from a subset of input-output matrices and the exploratory analysis of a large and diversified sample of countries, a formal model is specified to measure the respective short-term and long-term dynamics of trade elasticity. The model is then used to formally probe the role of vertical integration in explaining changes in trade elasticity. Aggregated results on long-term trade elasticity tend to support the hypothesis that world economy has undertaken in the late 1980s a "traverse" between two underlying economic models. During this transition, the expansion of international supply chains determined an apparent increase in trade elasticity. Two supply chains related effects (the composition and the bullwhip effects) explain also the overshooting of trade elasticity that occurred during the 2008-2009 trade collapse. But vertical specialization is unable to explain the heterogeneity observed on a country and sectoral level, indicating that other contributive factors may also have been at work to explain the diversity of the observed results