Abaques virtuels pour l'optimisation géométrique de structures

Malgré le progrès constant des moyens informatiques ces dernières années, les essais expérimentaux conservent une place prépondérante lors de la conception de structures dans l’industrie, car la résolution numérique de modèles complexes de grande taille demeure encore souvent hors de portée. Et même lorsque la simulation est possible, chaque nouvelle structure conçue en bureau d’études est abordée comme un nouveau problème, traité de manière indépendante des cas déjà étudiés, ce qui conduit à un très grand nombre de simulations. Le recours à des essais expérimentaux ainsi qu’à ces multiples simulations entraîne des coûts temporels et financiers importants dont la réduction est un enjeu crucial. L’idée développée ici, consiste à regrouper les structures semblables (qui ne diffèrent que par les valeurs données à un certain jeu de paramètres) en « familles » et à précalculer la solution générale pour chacune des familles sous forme paramétrée. Les quantités d’intérêt utiles au dimensionnement sont alors stockées dans des « abaques virtuels » qui seront utilisés en quasi temps réel par l’ingénieur lors de la phase de conception en particularisant les solutions pour les valeurs de paramètres considérées. La construction de ces abaques est basée sur la méthode de réduction de modèle PGD (Proper Generalized Decomposition [1][2]) qui permet de générer la solution d’un problème paramétré pour l’ensemble des jeux de paramètres. Dans le cadre de cette étude avec ASTRIUM-ST, les abaques virtuels sont créés pour prendre en compte les variations de géométrie, qui sont un des points clés dans le processus de conception. Il s’agit alors de considérer ces variations géométriques comme des paramètres dans la méthode PGD. Cette approche a été validée dans un premier temps sur des exemples académiques bi-dimensionnels. Elle sera appliquée par la suite à des structures plus complexes afin de se rapprocher des exigences industrielles d’ASTRIUM-ST. [1] P. Ladevèze. Nonlinear Computational Structural Mechanics—New Approaches and Non-Incremental Methods of Calculation, Springer Verlag, 1999. [2] P. Ladevèze, J.C. Passieux, D. Néron. The LATIN multiscale computational method and the Proper Generalized Decomposition. Computer Methods in Applied Mechanics and Engineering, 199:1287-1296, 2010

Vocabulaire 3D - Lexique pour les Sciences Humaines et Sociales

Ce document est le résultat d’un effort continu pour permettre aux acteurs des SHS et ceux de la 3D d’interagir autour d’un vocabulaire commun. Ce lexique a pour but d’accompagner les différents livrables du consortium 3D. Il a aussi vocation à terme à aider à l’enrichissement de TaDiRAH , « Taxonomy of Digital Research Activities in the Humani-ties » du consortium européen DARIAH . Ce processus continu est illustré par le fait que ce document en est à sa deuxième versionCe document est le résultat d’un effort continu pour permettre aux acteurs des SHS et ceux de la 3D d’interagir autour d’un vocabulaire commun. Ce lexique a pour but d’accompagner les différents livrables du consortium 3D. Il a aussi vocation à terme à aider à l’enrichissement de TaDiRAH , « Taxonomy of Digital Research Activities in the Humani-ties » du consortium européen DARIAH . Ce processus continu est illustré par le fait que ce document en est à sa deuxième versio

Left atrial remodelling assessed by 2D and 3D echocardiography identifies paroxysmal atrial fibrillation

Aims Paroxysmal atrial fibrillation (PAF) is common, often silent, and can be difficult to detect. Echocardiographic parameters assessing left atrial (LA) remodelling correlated with atrial fibrosis in permanent AF, but less is known about earlier stages such as PAF. We aimed to evaluate whether 2D and 3D echocardiographic (2DE and 3DE) assessment of LA anatomy and function is able to identify patients with PAF.Methods and results This case control study included 102 patients without overt heart disease, 44 patients with PAF. Anatomical remodelling was assessed using indexed maximal, minimal, and preatrial contraction volumes. Reservoir, conduit, and pump functions were assessed by volume and strain methods. All parameters were assessed by 2DE and 3DE and were compared between the two groups. Receiver-operating characteristic curves were constructed for each parameter for PAF prediction. PAF patients had bigger LA volumes than non-PAF group. Using 3DE, all atrial functions were impaired in the PAF group, regardless of the parameters used (all P < 0.05), whereas using 2DE, conduit function did not reach significant difference. Areas under the curve (AUCs) for 3D parameters were higher than those for equivalent 2DE parameters. PAF was best predicted by LA minimal indexed volume assessed by 2DE or 3DE (AUC 0.82 and 0.86, respectively) and 3D-LA ejection fraction and area strain (AUC = 0.82 and 0.81, respectively).Conclusion Anatomical and functional LA remodelling assessed by 2DE and 3DE is independently and strongly associated with PAF, suggesting that these parameters can help identify PAF

A versatile and low-cost 3D acquisition and processing pipeline for collecting mass of archaeological findings on the field

In recent years, advances in the fields of photogrammetry and computer vision have produced several solutions for generating 3D reconstruction starting from simple images. Even if the potentialities of the image-based 3D reconstruction approach are nowadays very well-known in terms of reliability, accuracy and flexibility, there is still a lack of low-cost, open-source and automated solutions for collecting mass of archaeological findings, specially if one consider the real (and non theoretical) contextual aspects of a digitization campaign on the field (number of objects to acquire, available time, lighting conditions, equipment transport, budget, etc...) as well as the accuracy requirements for an in-depth shape analysis and classification purpose. In this paper we present a prototype system (integrating hardware and software) for the 3D acquisition, geometric reconstruction, documentation and archiving of large collections of archaeological findings. All the aspects of our approach are based on high-end image-based modeling techniques and designed basing on an accurate analysis of the typical field conditions of an archaeological campaign, as well as on the specific requirements of archaeological finding documentation and analysis. This paper presents all the aspects integrated into the prototype: - a hardware development of a transportable photobooth for the automated image acquisition consisting of a turntable and three DSLR controlled by a microcontroller; - an automatic image processing pipeline (based on Apero/Micmac) including mask generation, tie-point extraction, bundle adjustment, multi-view stereo correlation, point cloud generation, surface reconstruction; - a versatile (off-line/on-line) portable database for associating descriptive attributes (archaeological description) to the 3D digitizations on site; - a platform for data-gathering, archiving and sharing collections of 3D digitizations on the Web. The presentation and the assessment of this prototype is based on an interdisciplinary experience carried out on the study of the Tholos in Delphi within the framework of the CNRS's Eloquentia project and the EFA's archaeological program

Diastolic function deterioration in type 2 diabetes mellitus: predictive factors over a 3-year follow-up

International audienceAims Diastolic dysfunction is frequent in patients with type 2 diabetes mellitus (DM2) and associated with a poor prognosis. This study aimed to describe diastolic function changes over time in DM2 patients and to identify predictive factors of diastolic function deterioration. Methods and results Diastolic function was assessed by echocardiography according to the EACVI/ASE recommendations at baseline and 3-year follow-up in a prospective cohort of 310 DM2 patients without overt heart disease. Predictors of diastolic function deterioration were identified using logistic regression analysis. During the 3-year follow-up, prevalence of diastolic dysfunction increased from 49% to 67% (P = 0.001). Only 32% of the patients had a normal diastolic function both at baseline and 3 years and 27% of the patients presented diastolic function deterioration. At multivariable analysis, age (OR = 1.05 [1.01-1.09], P \textless 0.01), retinopathy (OR = 2.00 [1.10-3.63], P = 0.02), and increase in systolic blood pressure during follow-up (OR = 1.03 [1.01-1.04], P \textless 0.01) were predictive of diastolic function deterioration. Conclusion Age, retinopathy, and increase in blood pressure over time are associated with an increased risk of diastolic function deterioration in DM2 patients. The presence of these co-factors might help to early identify patients at risk of heart failure

Decreased Radial Function is Associated With Subtle Left Ventricular Remodeling in Type 2 Diabetes Mellitus

Background: Previous studies have suggested that reduced longitudinal myocardial function might be compensated by increased radial contractility in patients with type 2 diabetes mellitus (DM). Aim: To evaluate left ventricular (LV) remodeling in type 2 DM according to radial function assessed by STI. Methods: 234 asymptomatic type 2 DM patients with no sign or history of heart disease and normal conventional echo parameters were included. Mean radial strain (SR) was assessed by STI from short-axis view at the midventricular level. Mean longitudinal strain (SL) was calculated from the apical 2- and 4-chamber views. The population was divided into 3 groups according to SR value: group I = SR 60% (n = 57). Differences between groups were tested by ANOVA. Results: Clinical, biological and echographic data are shown in table. Age, body mass index (BMI), duration and severity of DM, systolic (sBP) and diastolic (dBP) blood pressure and LV mass index (LVMi) were similar between groups. Conventional systolic parameters (LVEF: LV ejection fraction and FS: fractional shortening) were also similar. However, a lower SR was associated with a significant increase in LV end-diastolic (LVEDD) and end-systolic (LVESD) diameters and a decreased SL. Conclusion: These data suggest that an altered radial function might be an indicator of more advanced diabetic cardiomyopathy with altered systolic function and beginning of eccentric LV remodelling

Impaired myocardial radial function in asymptomatic patients with type 2 diabetes mellitus: a speckle-tracking imaging study

Background: Diabetic cardiomyopathy has been characterized by an early impairment of left ventricular (LV) longitudinal function as opposed to preserved LV radial function. Methods: Conventional echocardiography and longitudinal (eL) and radial (eR) systolic strain assessed by speckle-tracking imaging were obtained in 114 type 2 diabetic patients and 88 age-matched controls. Results: LV ejection fraction was similar in diabetic patients and controls. The presence of subclinical LV systolic dysfunction in diabetic patients was demonstrated by lower values of midwall fractional shortening (18% 6 3% vs 20% 6 3%, P = .006), eL (-19% 6 3% vs –22% 6 2%, P < .001), and eR (50% 6 16% vs 56% 6 12%, P = .003) compared with controls. On multivariate analysis, factors predicting strain values were diabetes (P = .001) and gender (P = .001) for eL and diabetes (P = .003) for eR. Conclusion: Diabetic patients without overt heart disease display subclinical alteration of both radial and longitudinal LV systolic function even after adjustment for blood pressure, age, and body mass index

Vocabulaire 3D - Lexique pour les Sciences Humaines et Sociales

Ce document est le résultat d’un effort continu pour permettre aux acteurs des SHS et ceux de la 3D d’interagir autour d’un vocabulaire commun. Ce lexique a pour but d’accompagner les différents livrables du consortium 3D. Il a aussi vocation à terme à aider à l’enrichissement de TaDiRAH , « Taxonomy of Digital Research Activities in the Humani-ties » du consortium européen DARIAH . Ce processus continu est illustré par le fait que ce document en est à sa deuxième versionCe document est le résultat d’un effort continu pour permettre aux acteurs des SHS et ceux de la 3D d’interagir autour d’un vocabulaire commun. Ce lexique a pour but d’accompagner les différents livrables du consortium 3D. Il a aussi vocation à terme à aider à l’enrichissement de TaDiRAH , « Taxonomy of Digital Research Activities in the Humani-ties » du consortium européen DARIAH . Ce processus continu est illustré par le fait que ce document en est à sa deuxième versio

Diastolic Dysfunction in Patients with Type 2 Diabetes Mellitus: Is It Really the First Marker of Diabetic Cardiomyopathy?

International audienc