Stability Analysis of Optimal Velocity Model for Traffic and Granular Flow under Open Boundary Condition

We analyzed the stability of the uniform flow solution in the optimal velocity model for traffic and granular flow under the open boundary condition. It was demonstrated that, even within the linearly unstable region, there is a parameter region where the uniform solution is stable against a localized perturbation. We also found an oscillatory solution in the linearly unstable region and its period is not commensurate with the periodicity of the car index space. The oscillatory solution has some features in common with the synchronized flow observed in real traffic.Comment: 4 pages, 6 figures. Typos removed. To appear in J. Phys. Soc. Jp

Modification de la surface d'un solide mésoporeux par l'imprégnation de liquides de polarités différentes

On étudie la modification des propriétés d'adsorption d'un polymère méso- poreux par le dépôt de deux liquides, l'un apolaire, l'autre très polaire. Les données chromatographiques relatives aux deux systèmes chromosorb 102-squalane et chromosorb 102-oxydipropionitrile ont permis de conclure à l'existence de deux zones d'adsorption différentes à la surface du solide et d'interpréter les mécanismes de rétention chromatographiques de 11 hydrocarbures et de 14 composés polaires

Closed-loop separation control using machine learning

We present the first closed-loop separation control experiment using a novel, model-free strategy based on genetic programming, which we call 'machine learning control'. The goal is to reduce the recirculation zone of backward-facing step flow at Reh = 1350 manipulated by a slotted jet and optically sensed by online particle image velocimetry. The feedback control law is optimized with respect to a cost functional based on the recirculation area and a penalization of the actuation. This optimization is performed employing genetic programming. After 12 generations comprised of 500 individuals, the algorithm converges to a feedback law which reduces the recirculation zone by 80 %. This machine learning control is benchmarked against the best periodic forcing which excites Kelvin-Helmholtz vortices. The machine learning control yields a new actuation mechanism resonating with the low-frequency flapping mode instability. This feedback control performs similarly to periodic forcing at the design condition but outperforms periodic forcing when the Reynolds number is varied by a factor two. The current study indicates that machine learning control can effectively explore and optimize new feedback actuation mechanisms in numerous experimental applications.Fil: Gautier, N.. École Supérieure de Physique et Chimie Industrielles de la ville de Paris; FranciaFil: Aider, J. L.. École Supérieure de Physique et Chimie Industrielles de la ville de Paris; FranciaFil: Duriez, Thomas Pierre Cornil. Université de Poitiers; Francia. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Mecánica. Laboratorio de Fluidodinámica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Noack, B. R.. Université de Poitiers; FranciaFil: Segond, M.. Ambrosys; AlemaniaFil: Abel, M.. Ambrosys; Alemani

Efficacy of the endoscopic management of postoperative fistulas of leakages after esophageal surgery for cancer: a retrospective series

International audienceAnastomotic leakages are severe and often lethal adverse events of surgery for esophageal cancer. The endoscopic treatment is growing up in such indications. The aim was to evaluate the efficacy and describe the strategy of the endoscopic management of anastomotic leakages/fistulas after esophageal oncologic surgery. Single-center retrospective study on 126 patients operated for esophageal carcinomas between 2010 and 2014. Thirty-five patients with postoperative fistulas/leakages (27 %) were endoscopically managed and included. The primary endpoint was the efficacy of the endoscopic treatment. The secondary endpoints were: delays between surgery, diagnosis, endoscopy and recovery; number of procedures; material used; and adverse events rate. Uni- and multivariate analyses were carried out to determine predictive factors of success. There were mostly men, with a median age of 61.7 years +/- 8.9 [43-85]. 48.6 % underwent Lewis-Santy surgery and 45.7 % Akiyama's. 71.4 % patients received neo-adjuvant chemo-radiation therapy. The primary and secondary efficacy was 48.6 and 68.6 %, respectively. The delay between surgery and endoscopy was 8.5 days [6.00-18.25]. Eighty-eight percentages of the patients were treated using double-type metallic stents, with removability and migration rates of 100 and 18 %, respectively. In the other cases, we used over-the-scope clips, naso-cystic drain or combined approach. The mean number of endoscopy was 2.6 +/- 1.57 [1-10]. The mortality rate was 17 %, none being related to procedures. No predictive factor of efficacy could be identified. The endoscopic management of leakages or fistulas after esophageal surgery reached an efficacy rate of 68.8 %, mostly using stents, without significant adverse events. The mortality rate could be decreased from 40-100 to 17 %