Thin Film Equations With van der Waals Force

We are interested in the steady states of thin films in a cylindrical container with van der Waals forces which lead to a singular elliptic equation in a bounded domain with Neumann boundary conditions. Using the prescribed volume of the thin film as a variable parameter we investigated the structure of radial solutions and their associated energies using rigorous asymptotic analysis and numerical computation. Motivated by the existence of rupture solutions for thin film equations, we considered elliptic equations with more general non linearity and obtained sufficient condition for the existence of weak rupture solutions for a class of generalized elliptic equations. Finally such results can be generalized to a class of quasi-linear elliptic partial differential equations

Service and Content Presentation in Ubiquitous Environments

The heterogeneous, dynamic nature of ubiquitous environments necessitates that all system components that form part of a personalisation framework should be context aware. Personalised service delivery requires that the system must detect and interpret device modality contexts in real time and provide automated adaptation on behalf of the user. Towards this aim, this paper presents the design and implementation of a demonstrator that offers personalised, context sensitive, service and content delivery

Persistence of frequency in gas–liquid flows across a change in pipe diameter or orientation

From a study of the characteristics of structures across a 67/38 mm sudden contraction, using air/silicone oil flows, it has been found that frequencies of the structures (mainly slugs) persist across the contraction. This is in contrast to the velocities and lengths which increase as they move into the smaller diameter pipe. These observations were found for both vertical and 5° upward orientations. A similar persistence of frequency has been found from four other sources in the literature: a vertical (gradual) contraction; a horizontal Venturi; and two cases of horizontal pipe, 90° bend and vertical riser combination. The latter were at two contrasting conditions: (i) at atmospheric pressure with air/water in small diameter (34 mm) pipes; (ii) at 20 bar in larger diameter pipes (189 mm) using nitrogen and naphtha

A lower global lung ultrasound score is associated with higher likelihood of successful extubation in invasively ventilated COVID-19 patients

Lung ultrasound (LUS) can be used to assess loss of aeration, which is associated with outcome in patients with coronavirus disease 2019 (COVID-19) presenting to the emergency department. We hypothesized that LUS scores are associated with outcome in critically ill COVID-19 patients receiving invasive ventilation. This retrospective international multicenter study evaluated patients with COVID-19-related acute respiratory distress syndrome (ARDS) with at least one LUS study within 5 days after invasive mechanical ventilation initiation. The global LUS score was calculated by summing the 12 regional scores (range 0-36). Pleural line abnormalities and subpleural consolidations were also scored. The outcomes were successful liberation from the ventilator and intensive care mortality within 28 days, analyzed with multistate, competing risk proportional hazard models. One hundred thirty-seven patients with COVID-19-related ARDS were included in our study. The global LUS score was associated with successful liberation from mechanical ventilation (hazard ratio [HR]: 0.91 95% confidence interval [CI] 0.87-0.96; P = 0.0007) independently of the ARDS severity, but not with 28 days mortality (HR: 1.03; 95% CI 0.97-1.08; P = 0.36). Subpleural consolidation and pleural line abnormalities did not add to the prognostic value of the global LUS score. Examinations within 24 hours of intubation showed no prognostic value. To conclude, a lower global LUS score 24 hours after invasive ventilation initiation is associated with increased probability of liberation from the mechanical ventilator COVID-19 ARDS patients, independently of the ARDS severity.Pathogenesis and treatment of chronic pulmonary disease

Ecoulement critique d'un liquide en vaporisation à travers une ligne de décharge comportant un orifice

Original experimental results related to the critical flashing flows through a horizontal pressure relief line involving a circular orifice are presented. On the basis of the evolution of the physical variables measured as a function of the pressure in the downstream vessel, the occurrence of the flow with the simultaneous double locations of the critical section is demonstrated and analysed experimentally. For a high enough pressure drop between the two extreme vessels, the double choking phenomenon (i.e. the simultaneous locations of a critical section at the vicinity of the orifice as well as of one other at the outlet of the line) is observed for the flow across the pressure relief Line in steady-state conditions. Depending of the value of the subcooling of the fluid at the inlet of the discharge line, the characteristics of the axial pressure profile downstream from the orifice as well as the how visualisation support the existence of several two-phase jet structures. Finally, the influence of the orifice geometry on the liquid superheat and on the critical mass flow-rate is discussed

Thermodynamique de l'écoulement diphasique compressible à deux constituants de Fanno

Le comportement d'un fluide diphasique gaz-liquide lors d'un écoulement adiabatique à travers une conduite de section constante est étudié, dans cet article, du point de vue thermodynamique. En admettant le mélange diphasique homogène, le traitement des lois physiques de conservation permet de déduire analytiquement l'équation d'évolution du fluide et la manière dont celle-ci s'écarte de l'évolution isotherme. Sur les bases de la forme différentielle de cette équation et du second principe de la thermodynamique, les propriétés de cet écoulement sont discutées. La détermination de la limite de Fanno a permis de mettre en évidence l'existence d'une longueur maximale de conduite au-delà de laquelle l'écoulement considéré n'est plus possible. Cette longueur maximale est fonction du titre massique et des conditions initiales, c'est-à-dire les variables d'état et la vitesse à l'entrée. La cohérence des résultats est vérifiée en appliquant systématiquement ceux-ci à l'écoulement d'un gaz parfait. Cette théorie permet de comprendre et de justifier l'existence d'états d'écoulement dits multicritiques pour lesquels un formalisme physique est proposé. Elle est appliquée à des écoulements diphasiques à travers les circuits de décharge comportant des singularités géométriques telles que des élargissements brusques. Le présent modèle, basé sur le formalisme proposé pour la multicriticité, est validé au moyen de données expérimentales obtenues pour des relâchements quasi stationnaires d'azote pur et de mélange eau-azote à travers une ligne de décharge complexe comportant plusieurs élargissements brusques en cascade. Prédites par le modèle, la configuration critique et les valeurs du débit maximum et des variables de l'écoulement (pression et température) à travers la ligne de décharge s'accordent avec succès avec les résultats expérimentaux

Thermodynamique de l'écoulement diphasique compressible à deux constituants de Fanno

International audienceLe comportement d'un fluide diphasique gaz-liquide lors d'un écoulement adiabatique à travers une conduite de section constante est étudié, dans cet article, du point de vue thermodynamique. En admettant le mélange diphasique homogène, le traitement des lois physiques de conservation permet de déduire analytiquement l'équation d'évolution du fluide et la manière dont celle-ci s'écarte de l'évolution isotherme. Sur les bases de la forme différentielle de cette équation et du second principe de la thermodynamique, les propriétés de cet écoulement sont discutées. La détermination de la limite de Fanno a permis de mettre en évidence l'existence d'une longueur maximale de conduite au-delà de laquelle l'écoulement considéré n'est plus possible. Cette longueur maximale est fonction du titre massique et des conditions initiales, c'est-à-dire les variables d'état et la vitesse à l'entrée. La cohérence des résultats est vérifiée en appliquant systématiquement ceux-ci à l'écoulement d'un gaz parfait. Cette théorie permet de comprendre et de justifier l'existence d'états d'écoulement dits multicritiques pour lesquels un formalisme physique est proposé. Elle est appliquée à des écoulements diphasiques à travers les circuits de décharge comportant des singularités géométriques telles que des élargissements brusques. Le présent modèle, basé sur le formalisme proposé pour la multicriticité, est validé au moyen de données expérimentales obtenues pour des relâchements quasi stationnaires d'azote pur et de mélange eau-azote à travers une ligne de décharge complexe comportant plusieurs élargissements brusques en cascade. Prédites par le modèle, la configuration critique et les valeurs du débit maximum et des variables de l'écoulement (pression et température) à travers la ligne de décharge s'accordent avec succès avec les résultats expérimentaux

[Thermodynamic of two-phase two component compressible Fanno type flow]

The behaviour of an adiabatic two-phase gas-liquid Row through a duct with a constant cross-sectional area is studied from a thermodynamics point of view. By assuming the two-phase mixture as homogeneous, the treatment of the physical conservation laws makes it possible to obtain an analytical equation of the fluid evolution which expresses the difference between the Fanno and the isothermal evolutions. On the basis of its differential form and the second principle of thermodynamic, the properties of this flow are discussed. The determination of the Fanno limit shows the existence of a maximum length of the duct, For a length greater than this maximum one, the flow is no more possible. One shows that this maximum length is a function of the mass quality as well as the initial conditions, i.e. the inlet state variables and the inlet velocity. The results are systematically verified by considering the limit of a single phase ideal gas flow. The theory allows to understand and to justify the existence of the so-called multichoked flow, It is applied to the two-phase flow through discharge lines involving geometrical singularities (sudden enlargement for example). The proposed model is validated on the basis of experimental data obtained for quasi steady-state discharges of pure nitrogen and water-nitrogen mixture through a complex pressure relief line involving several abrupt enlargements. The critical configuration and the maximum mass flowrate as well as the variables of the flow (pressure and temperature) predicted from the model are in good agreement with the experimental results