Elastic properties of cellular dissipative structure

Transition towards spatio-temporal chaos in one-dimensional interfacial patterns often involves two degrees of freedom: drift and out-of-phase oscillations of cells, respectively associated to parity breaking and vacillating-breathing secondary bifurcations. In this paper, the interaction between these two modes is investigated in the case of a single domain propagating along a circular array of liquid jets. As observed by Michalland and Rabaud for the printer's instability \cite{Rabaud92}, the velocity $V_g$ of a constant width domain is linked to the angular frequency $\omega$ of oscillations and to the spacing between columns $\lambda_0$ by the relationship $V_g = \alpha \lambda_0 \omega$. We show by a simple geometrical argument that $\alpha$ should be close to $1/ \pi$ instead of the initial value $\alpha = 1/2$ deduced from their analogy with phonons. This fact is in quantitative agreement with our data, with a slight deviation increasing with flow rate

Transonic liquid bells

http://www.irphe.univ-mrs.fr/~clanet/PaperFile/PHFBell.pdfThe shape of a liquid bell resulting from the overflow of a viscous liquid out of a circular dish is investigated experimentally and theoretically. The main property of this bell is its ability to sustain the presence of a ‘‘transonic point,'' where the liquid velocity equals the speed of antisymmetric—or sinuous—surface waves. Their shape and properties are thus rather different from usual ‘‘hypersonic'' water bells. We first show that the bell shape can be calculated very accurately, starting from the sonic point.We then demonstrate the extreme sensitivity of the shape of these bells to the difference of pressure across the interface, making them a perfect barometer. Finally, we discuss the oscillations of the bell which occur close to the bursting limit

A simple model for the dynamics of contact lines freezing on a cold substrate

International audienceStarting from de Gennes model of contact line dynamics, we develop a simple, analytical, description of a four phase contact line, at which a liquid advances on a cold substrate (of infinite therml conductivity) and at the same time freezes on the solid. The key idea consists in a subtle balance between thermical and hydrodynamical divergences at contact line, heat produced by dissipation in the liquid phase limitating the solid growth. We calculate the apparent liquid contact angle and its equivalent for the solid phase as a function of the contact line velocity U and the other parameters involved, in the limit of small angles. We show that the arrest condition (U=0) implies a divergence of these angles, that are presumably reaching 90°, while the liquid film thickness vanishes, which is reminiscent of previous works of Sonin et al in the 90's. Remarkably, at low contact line velocity, we show that a stick-slip behaviour is to be expected, which has been recently observed experimentally. The temperature dependance of the critical velocity differs from what is found in recent experiments, but this model is to our opinion a necessary first step to understand these complex behaviours

Caractérisation électrique et fiabilité des transistors intégrant des diélectriques High-k et des grilles métalliques pour les technologies FDSOI sub-32nm

The integration of High-k dielectrics in transistors gate stacks lead to new complex reliability issues. Furthermore new problematics appear with the use of fully depleted silicon on insulator (FDSOI) substrates for future sub-32nm planar technologies. Indeed, the integration of a buried oxide underneath the silicon film changes the electrostatic of the structure and create a new Si/SiO2 interface which may be degraded. This thesis presents different electrical characterization techniques and reliability studies on High- /metal gate FDSOI transistors. First, a complete electrostatic study of FDSOI structures is done allowing a better understanding of the effects of backgate biases. Different techniques to characterize interface traps are then presented and adapted to FDSOI devices, where traps at backgate interface, between the silicon film and the buried oxide, must be considered. Finally, different reliability studies are presented, from NBTI and PBTI issues on long channel devices to smaller dimension devices specific studies such as hot carriers degradation on ultra-thin film FDSOI devices and threshold voltage increase with gate width scaling.L'intégration de diélectriques High- k dans les empilements de grille des transistors a fait naître des problèmes de fiabilité complexes. A cela vient s'ajouter, en vue des technologies sub-32nm planaires, de nouvelles problématiques liées à l'utilisation de substrats silicium sur isolant complètement désertés FDSOI. En effet, l'intégration d'un oxyde enterré sous le film de silicium va modifier électrostatique de la structure et faire apparaître une nouvelle interface Si/SiO2 sujette à d'éventuelles dégradations. Ce manuscrit présente différentes méthodes de caractérisation électrique ainsi que différentes études de fiabilité des dispositifs FDSOI intégrants des empilements High- /grille métallique. Dans un premier temps, une étude complète du couplage électrostatique dans des structures FDSOI est réalisée, permettant de mieux appréhender l'effet d'une tension en face arrière sur les caractéristiques électriques des dispositifs. Différentes méthodes de caractérisation des pièges d'interface sont ensuite présentées et adaptées, lorsque possible, au cas spécifique du FDSOI, où les défauts entre le film de silicium et l'oxyde enterré doivent être pris en compte. Enfin, différentes études de fiabilité sont présentées, des phénomènes de PBTI et de NBTI sur des dispositifs à canaux longs aux phénomènes propres aux dispositifs de petite dimension, tels que l'impact des porteurs chauds dans des structures FDSOI à film ultra fins et les effets d'augmentation de tension de seuil lorsque les largeurs de grille diminuent

Unveiling of the mechanisms of acoustic streaming induced by sharp edges

Acoustic waves can generate steady streaming within a fluid owing to the generation of viscous boundary layers near walls, of typical thickness $\delta$. In microchannels, the acoustic wavelength $\lambda$ is adjusted to twice the channel width $w$ to ensure a resonance condition, which implies the use of MHz transducers. Recently though, intense acoustic streaming was generated by acoustic waves of a few kHz (hence with $\lambda \gg w$), owing to the presence of sharp-tipped structures of curvature radius at the tip $r_c$ smaller than $\delta$. The present study quantitatively investigates this sharp-edge acoustic streaming via the direct resolution of the full Navier-Stokes equation, using Finite Element Method. The influence of $\delta$, $r_c$ and viscosity $\nu$ on the acoustic streaming performance are quantified. Our results suggest choices of operating conditions and geometrical parameters, via dimensionless quantities $r_c/\delta$ and $\delta/w$ and provide guidelines on how to obtain strong, optimal sharp-edge acoustic streaming.Comment: 33 pages, 11 figure

Dynamics of Liquid Contact Line on Visco-Elastic Gels

International audienc

Drop spreading and gelation of thermoresponsive polymers

Spreading and solidification of liquid droplets are elementary processes of relevance for additive manufacturing. Here we investigate the effect of heat transfer on spreading of a thermoresponsive solution (Pluronic F127) that undergoes a sol-gel transition above a critical temperature $T_m$. By controlling the concentration of Pluronic F127 we systematically vary $T_m$, while also imposing a broad range of temperatures of the solid and the liquid. We subsequently monitor the spreading dynamics over several orders of magnitude in time and determine when solidification stops the spreading. It is found that the main parameter is the difference between the substrate temperature and $T_m$, pointing to a local mechanism for arrest near the contact line. Unexpectedly, the spreading is also found to stop below the gelation temparature, which we attribute to a local enhancement in polymer concentration due to evaporation near the contact line.Comment: 9 pages, 10 figure

Online Versus Offline NMT Quality: An In-depth Analysis on English-German and German-English

We conduct in this work an evaluation study comparing offline and online neural machine translation architectures. Two sequence-to-sequence models: convolutional Pervasive Attention (Elbayad et al. 2018) and attention-based Transformer (Vaswani et al. 2017) are considered. We investigate, for both architectures, the impact of online decoding constraints on the translation quality through a carefully designed human evaluation on English-German and German-English language pairs, the latter being particularly sensitive to latency constraints. The evaluation results allow us to identify the strengths and shortcomings of each model when we shift to the online setup.Comment: Accepted at COLING 202

Use of the pulsation to control a polydispersed particles flow in a new type of pulsed column

New internals have been designed and implemented in a semi-industrial continuous solid-liquid pulsed column. By coupling these internals with a non sinusoidal pulsation, a better control of polydispersed solid particles is achieved. The pulsation is composed of a mixing step during which only the liquid flows through the column and an impulsion step designed to transport the solid phase from stage to stage. Solid and liquid phase behaviours are characterized thanks to residence time distribution measurements. This study demonstrates the strong impact of the pulsation and of the liquid flow rate during the impulsion to reduce the particles segregation inside the pilot. The effects of operating parameters on the liquid phase are also investigated and the choice of an operating compromise is discussed to balance advantages and drawbacks on the process

The evolution of infrahissian conduction time in myotonic dystrophy patients: clinical implications

International audienc