Layer-averaged Euler and Navier-Stokes equations

In this paper we propose a strategy to approximate incompressible hydrostatic free surface Euler and Navier-Stokes models. The main advantage of the proposed models is that the water depth is a dynamical variable of the system and hence the model is formulated over a fixed domain.The proposed strategy extends previous works approximating the Euler and Navier-Stokes systems using a multilayer description. Here, the needed closure relations are obtained using an energy-based optimality criterion instead of an asymptotic expansion. Moreover, the layer-averaged description is successfully applied to the Navier-Stokes system with a general form of the Cauchy stress tensor

Interaction between the G3 and L5 proteins of the vaccinia virus entry–fusion complex

AbstractThe vaccinia virus entry–fusion complex (EFC) consists of 10 to 12 proteins that are embedded in the viral membrane and individually required for fusion with the cell and entry of the core into the cytoplasm. The architecture of the EFC is unknown except for information regarding two pair-wise interactions: A28 with H2 and A16 with G9. Here we used a technique to destabilize the EFC by repressing the expression of individual components and identified a third pair-wise interaction: G3 with L5. These two proteins remained associated under several different EFC destabilization conditions and in each case were immunopurified together as demonstrated by Western blotting. Further evidence for the specific interaction of G3 and L5 was obtained by mass spectrometry. This interaction also occurred when G3 and L5 were expressed in uninfected cells, indicating that no other viral proteins were required. Thus, the present study extends our knowledge of the protein interactions important for EFC assembly and stability

Analyse des signaux transitoires émis par les arcs électriques générés dans les panneaux photovoltaïques

National audienceDes arcs électriques aux conséquences graves peuvent parfois survenir au sein de panneaux photovoltaïques. Cet article décrit un système de détection d'arcs en utilisant deux méthodes différentes, lesquelles sont comparées au niveau des performances de détection. Une méthode de localisation est également décrite et évaluée sur la base de configurations réelles. Enfin, une description du démonstrateur opérationnel développé pour réaliser cette détection et localisation est présentée

Caractérisation des phénomènes physiques par analyse parcimonieuse des signaux transitoires

For their uniqueness, transient are really difficult to characterize. They are met everywhere and are generally the result of very complex physical phenomena that contain a lot of information such as the transient at its origin, the effect of the propagation through the medium and the effects induced by the transducers. They can correspond to communication between mammals as well as being the reflection of a fault in electrical or hydraulic networks for instance. Hence their study is of great importance even though it is quite complicated. Numerous signal processing methods have been developed in the last decades: they often rely on statistical approaches, linear projections of the signal onto dictionaries and data-driven techniques. All those methods have pros and cons since they often provide good detections, nevertheless their characterization for classification and discrimination purposes remains complicated. In this spirit, this thesis proposes new approaches to study transients. After a brief overview of the existing methods, this work first focuses on the representation of signals having tight-varying time-frequency components. Generally, general complex-time distributions present a proper framework to study them but remain limited to narrow band signals. In a first part, we propose to overcome this limitation in the case of signals with a spread time-frequency variation. This method is based on the compression of the signal's spectrum to a bandwidth that ensures the efficiency of the technique. A second part then focuses on the extraction of nonlinear modulation phase signals in the context of nonstationary noise and other coherent signals. This is performed with warping operators and compressive sensing reconstruction techniques. The third chapter then focuses on data-driven methods based on the representation of the signal in phase space. The main contribution takes advantage of the lag diversity that enables to highlight time scale transformations as well as amplitude modifications between transients. Hence, we develop different techniques enabling to highlight those properties. Finally, works presented in the first chapters are developed in applicative contexts such as: ECG segmentation, electrical transient characterization, a passive acoustic configuration and the study of acoustic signals in an immerse environment. We then end up by some conclusions and perspectives for future works.Les signaux transitoires, de par leur unicité, sont très difficiles à caractériser. Ils se rencontrent partout et sont généralement le reflet d'un phénomène physique très complexe traduisant de nombreuses informations telles que le signal à l'origine, les effets de la propagation dans le milieu considéré et aussi les effets induits par les capteurs. Ils peuvent aussi bien correspondre à un phénomène de communication entre animaux, qu'être le reflet d'un défaut dans un système électrique ou hydraulique par exemple. Tout ceci rend leur étude très difficile, mais aussi primordiale. De nombreuses techniques en traitement du signal ont été développées ces dernières années pour les étudier: elles reposent souvent sur des approches statistiques, des approches projectives sur différents dictionnaires et des techniques auto-adaptatives. Toutes ces méthodes présentent des avantages et des inconvénients, puisqu'elles permettent souvent de les détecter correctement, néanmoins leur caractérisation à des fins de classification et de discrimination reste compliquée. Cette thèse s'inscrit dans cette optique et propose de nouvelles approches d'étude des transitoires. Après un rapide descriptif des techniques d'étude des signaux transitoires, ce travail s'intéressera dans un premier temps à la représentation des signaux ayant des composantes fréquentielles variant très rapidement. De manière générale l'utilisation des distributions généralisées à temps complexe présente un cadre d'analyse adéquat, mais il est limité aux signaux possédant une bande passante étroite, nous proposons dans une première partie d'étendre cette utilisation à des signaux possédant une bande passante plus large en appliquant un changement d'échelle des signaux. Une deuxième partie s'intéressera davantage à l'extraction de signaux à modulation de phase dans le contexte d'un mélange de bruit non-stationnaire et d'autres signaux cohérents. Ceci sera effectué par des opérateurs de warping couplé à des techniques de débruitage basée sur la compression de données. Le troisième chapitre s'intéressera aux techniques guidées par les données basées sur la représentation des signaux en diagrammes de phase. La contribution principale porte sur la diversité des lags qui permet en effet de mettre en évidence les effets des opérateurs de temps-échelles, mais aussi de modification d'amplitude entre des signaux. Nous développerons donc des méthodes permettant de mettre en évidence ces propriétés. Finalement, les travaux présentés dans les premiers chapitres seront développés dans le cadre de quatre domaines applicatifs qui sont : la segmentation d'ECG, la caractérisation de transitoires électriques, un cas d'acoustique passive et l'étude de signaux acoustiques en milieu immergé. Nous terminerons enfin par une conclusion et quelques perspectives de travail

Multi-Lag Phase Space Representations for Transient Signals Characterization

International audienceTransient signals are very difficult to characterize due to their short duration and their wide frequency content. Various methods such as spectrogram and wavelet decomposition have already been extensively used in the literature to detect them, but show limits when it comes to near similar transients discrimination. In this paper, we propose the multi-lag phase space analysis as a way to characterize them. This data-driven method enables the comparison between features extracted from two different signals. In an example, we compare the multi-lag phase space representations of three similar transients and show that common features can be found to discriminate them. Finally the results are compared with a wavelet decomposition

Focus groups and critical social IS research: How the choice of method can promote emancipation of respondents and researchers

Critical social research in information systems has been gaining prominence for some time and is increasingly viewed as a valid research approach. One problem of the critical tradition is that there is a lack of empirical research. A contributing factor to this gap in the literature is the lack of agreement on what constitutes appropriate methodologies for critical research. The present paper contributes to this debate by outlining the role that focus group research can play in the critical approach. The paper outlines the main characteristics of critical research with an emphasis on its emancipatory faculties. It then goes on to review the focus group method in general and gives an account of two research projects that used focus groups as a method of data collection. It is argued that focus groups can contribute to emancipation of researchers as well as respondents. This argument is built upon the critical theories of the two most prominent theorists currently relied upon in critical social IS research, namely Jürgen Habermas and Michel Foucault. Focus groups can improve communication and move real discourses closer to the Habermas\u27s ideas speech situation. At the same time, they can contribute to the challenging of prevailing orthodoxy and thereby overcome established regimes of truth in the Foucauldian tradition. The paper ends with a critical reflection of the shortcomings of focus groups as a critical method and of the specific approach chosen in this paper

Sparse representation of channel's impulse response for underwater inhomogeneities tracking

International audienceIn this paper, we propose a method for underwater inhomogeneities characterization using sparse representation of channel's impulse response. We consider the case of moving vortices created naturally or artificially that do not conserve their physical properties when observed at two distinct positions in space. Existing amplitude-based techniques fail to provide an accurate representation when the physical properties of the dynamic inhomogeneity are altered, but it can be achieved using the decomposition of the inhomogeneity's impulse response, based on a physically driven decomposition basis. Tests carried out in a reduced scale experimental facility show, on real data, the efficiency of the inhomogeneities tracking

ATA Practice Guidelines for Live, On-Demand Primary and Urgent Care

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140286/1/tmj.2015.0008.pd