39 research outputs found
Tropical Fourier-Motzkin elimination, with an application to real-time verification
We introduce a generalization of tropical polyhedra able to express both
strict and non-strict inequalities. Such inequalities are handled by means of a
semiring of germs (encoding infinitesimal perturbations). We develop a tropical
analogue of Fourier-Motzkin elimination from which we derive geometrical
properties of these polyhedra. In particular, we show that they coincide with
the tropically convex union of (non-necessarily closed) cells that are convex
both classically and tropically. We also prove that the redundant inequalities
produced when performing successive elimination steps can be dynamically
deleted by reduction to mean payoff game problems. As a complement, we provide
a coarser (polynomial time) deletion procedure which is enough to arrive at a
simply exponential bound for the total execution time. These algorithms are
illustrated by an application to real-time systems (reachability analysis of
timed automata).Comment: 29 pages, 8 figure
Enhancement of Heat Transfer by Ultrasound: Review and Recent Advances
This paper summarizes some applications of ultrasonic vibrations regarding heat transfer enhancement techniques. Research literature is reviewed, with special attention to examples for which ultrasonic technology was used alongside a conventional heat transfer process in order to enhance it. In several industrial applications, the use of ultrasound is often a way to increase productivity in the process itself, but also to take advantage of various subsequent phenomena. The relevant example brought forward here concerns heat exchangers, where it was found that ultrasound not only increases heat transfer rates, but might also be a solution to fouling reduction
Environmental characterisation of retification process by-products (liquid and gaseous wastes)
6th International Symposium âEnvironment and Wood Preservationâ Cannes-Mandelieu, France 7-8 February 2005 14 pagesIn order to reduce environmental risks during the service life of the treated wood and to find new alternative developments on the durability of wood, some research and technology development have been made on thermal treatment. The retification process is one of these processes. The retification process induces chemical modification of the lignin and cellulosic components and modifies the intrinsic properties of wood : efficient increases the durability against fungi and insects, increases of the dimensional stability, decrease of the mechanical properties. The interest of this process is to reduce the environmental impact during the service life. In order to confirm the high interest of this process for the reduction of the environmental impact, an environmental characterisation of wastes on pilot plant have been carried out. Chemical analysis on gaseous and liquid effluents have been performed. An energetic assessment has been realised. The results indicate the high interest of this process in terms of possible biodegradable wastes and chemical valorisation interest, interest on energetic consumption in comparison with other wood processing treatment, interest on using retification treated wood in flooring according to indoor air quality requirements
Enriched finite elements and level sets for damage tolerance assessment of complex structures
A hybrid smoothed extended finite element/level set method for modeling equilibrium shapes of nano-inhomogeneities
Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.
RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 â„60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Les données spatiales au service du suivi des ressources en eau
Les donnĂ©es satellitaires peuvent enrichir le suivi des ressources en eau, quels que soient les objectifs de ce suivi (gestion stratĂ©gique des ressources en eau, gestion des ouvrages, prĂ©vision des crues et Ă©tiagesâŠ). Ces donnĂ©es prĂ©sentent lâavantage de couvrir Ă pas-de-temps rĂ©gulier le monde entier, y compris des territoires difficiles dâaccĂšs. Lâusage de ces donnĂ©es soulĂšve plusieurs questions : comment Ă©valuer leur qualitĂ© ? Comment les corriger ? Quelle pertinence au regard des donnĂ©es au sol dont on dispose ? Comment les utiliser pour optimiser le rĂ©seau de mesures hydrologiques ? Ă travers plusieurs projets et avec des partenaires scientifiques et industriels variĂ©s (IRD, CNES, CLS, CNRS, CENEAUâŠ) BRL IngĂ©nierie contribue Ă Ă©valuer et Ă valoriser lâusage des donnĂ©es satellitaires pour la gestion des ressources en eau Ă lâĂ©chelle dâun bassinversant (e.g. lâAmazone) ou dâun territoire (lâOuganda). Lâobjectif est de dĂ©livrer des indicateurs hydrologiques issus de lâassociation de modĂšles hydrologiques, de donnĂ©es in-situ et de donnĂ©es satellitaires, intĂ©grĂ©s en temps rĂ©el dans un systĂšme dâinformation sur lâeau. Cet article prĂ©sente les possibilitĂ©s et les limites actuelles de lâutilisation des donnĂ©es satellitaires afin dâoptimiser le suivi des ressources en eau
Les Nocturnes du Plan de Rome : Corinne Bonnet - Nommer les dieux en Méditerranée
Le 2 fĂ©vrier 2022, dans le cadre du sĂ©minaire de l'ERLIS Les Nocturnes du Plan de Rome, a Ă©tĂ© donnĂ©e Ă l'UniversitĂ© de Caen la confĂ©rence intitulĂ©e : Nommer les dieux en MĂ©diterranĂ©e. RĂ©sumĂ© de la confĂ©rence : Dans un monde antique plein de dieux, comme lâaffirmait dĂ©jĂ ThalĂšs de Milet, repris par Aristote, les sociĂ©tĂ©s oscillent, dans la façon de les dĂ©signer, entre un attachement Ă la tradition et une crĂ©ativitĂ© foisonnante, signe dâun imaginaire protĂ©iforme et dâun souci dâefficacitĂ©. Car les noms servent avant tout Ă communiquer avec les puissances divines dans le cadre de pratiques cultuelles variĂ©es : offrandes, imprĂ©cations, commĂ©morations, vĆux, oracles, etc. Cet ocĂ©an de noms divins constitue un rĂ©servoir extraordinaire dâinformations sur les modes de reprĂ©sentation des dieux : les espaces quâils occupent, les compĂ©tences quâon leur attribue, les modes dâaction quâon leur impute, mais aussi les relations quâils entretiennent entre eux au sein de ce que nous appelons commodĂ©ment des « panthĂ©ons », qui ne regroupent cependant jamais la totalitĂ© des dieux. Nous partirons donc sur les traces des dieux, sur tout le pourtour de la MĂ©diterranĂ©e, de JĂ©rusalem Ă Gibraltar, dâAthĂšnes Ă CyrĂšne en utilisant leurs noms comme boussoles. Nous mobiliserons des noms grecs, phĂ©niciens, hĂ©breux, aramĂ©ens, des noms simples et connus, dâautres rares et Ă©tranges, Ă travers la longue durĂ©e de toute lâAntiquitĂ©. Nous tenterons dâesquisser des portraits et des rĂ©seaux onomastiques et nous scruterons les intentions de celles et ceux qui adressent leurs priĂšres Ă un dieu, Ă un couple, Ă une triade, Ă une liste de puissances, bref Ă mille et une configurations chargĂ©es de sens