Vorticity Banding During the Lamellar-to-Onion Transition in a Lyotropic Surfactant Solution in Shear Flow

We report on the rheology of a lamellar lyotropic surfactant solution (SDS/dodecane/pentanol/water), and identify a discontinuous transition between two shear thinning regimes which correspond to the low stress lamellar phase and the more viscous shear induced multi-lamellar vesicle, or ``onion'' phase. We study in detail the flow curve, stress as a function of shear rate, during the transition region, and present evidence that the region consists of a shear banded phase where the material has macroscopically separated into bands of lamellae and onions stacked in the vorticity direction. We infer very slow and irregular transformations from lamellae to onions as the stress is increased through the two phase region, and identify distinct events consistent with the nucleation of small fractions of onions that coexist with sheared lamellae.Comment: 10 pages, 10 figure

Thermodynamics and structure of self-assembled networks

We study a generic model of self-assembling chains which can branch and form networks with branching points (junctions) of arbitrary functionality. The physical realizations include physical gels, wormlike micells, dipolar fluids and microemulsions. The model maps the partition function of a solution of branched, self-assembling, mutually avoiding clusters onto that of a Heisenberg magnet in the mathematical limit of zero spin components. The model is solved in the mean field approximation. It is found that despite the absence of any specific interaction between the chains, the entropy of the junctions induces an effective attraction between the monomers, which in the case of three-fold junctions leads to a first order reentrant phase separation between a dilute phase consisting mainly of single chains, and a dense network, or two network phases. Independent of the phase separation, we predict the percolation (connectivity) transition at which an infinite network is formed that partially overlaps with the first-order transition. The percolation transition is a continuous, non thermodynamic transition that describes a change in the topology of the system. Our treatment which predicts both the thermodynamic phase equilibria as well as the spatial correlations in the system allows us to treat both the phase separation and the percolation threshold within the same framework. The density-density correlation correlation has a usual Ornstein-Zernicke form at low monomer densities. At higher densities, a peak emerges in the structure factor, signifying an onset of medium-range order in the system. Implications of the results for different physical systems are discussed.Comment: Submitted to Phys. Rev.

Toward an automation increasingly interconnecting

Abstract—the evolution of Information and Communications Technologies ICT and their reliability in the different areas of the industry has changed completely the design of automated systems. The vision today is to manipulate the media of communication such as generic Ethernet since the connection of a sensor up to the network of workshop or for business, for this the programmable logic controllers (PLC) are become more and more of a communication through communication interfaces such as Ethernet/IP, PROFINET, PROFIBUS…,which allow you to perform a remote communication between the field level ( production tools), the workshop level ( the production service) and the local network which concepts the different service of the company. The maintenance is part of the features that can pull the advantage of interconnection of production systems.The communicative function allows you to perform the remote maintenance or at least to establish a precise diagnosis in order to reduce the time of intervention. In this paper we will explain the communication of a PLC since the Ethernet network up to the corporate network, following different policies of communications by giving some sample application in this area

Communal analysis of the tramway accidentology in France

Introduction: The purpose of this study is to assess the impact of communes size on the number and severity of tram accidents in France. Methodology: For this we calculated the average densities of accidents and serious victims of trams per line kilometer for each class of commune between 2012 and 2014. While adverting to the official data of accidentology and population. Results: The study has shown that almost one third of the municipalities served by the tram have known no accident. The study also showed that the size of the communes is proportional to the accidents density per kilometer of the tram line. The study has also concluded that the density of serious victims per line kilometer is maximum in the communes of average size. Conclusion: To carry out the modal shift toward the urban public transport, it is necessary to deepen our knowledge of the specificities of insecurity of these modes. This study is part of this framework, and made the link between the size of the communes and trams accidentology in France

Les victimes d’accidents de bus en France : quelle exposition au risque ?

International audienceAn approach by type of user was developed to assess the road risk exposure of victims of bus accidents in France from 2012 to 2014. The article refers to two main questions. The first concerns bus users: are they actually less likely to be a victim in a road accident than a cyclist, a motorized two-wheeler user or a motorist? Are there differences in the age and gender of the users? The second question concerns third parties involved in bus accidents. Are there differences in risk per mode by age and gender? To address these issues, two indices of exposure were used: distance traveled and time spent on a trip. Accidentology data were obtained from the BACA and travel data from the latest National Transportation and Travel Survey (ENTD). The use of distances traveled for bus passenger accidents made it possible to relativize the low risk of bus users with regard to the users of light vehicle. And the time spent by third parties involved in bus accidents has highlighted the safety issues faced by young people and pedestrians.Une approche par type d’usagers a été élaborée pour évaluer l’exposition au risque routier des victimes des accidents de bus en France de 2012 à 2014. L’article renvoie à deux questions principales. La première concerne les usagers des bus : ont-ils réellement moins de risque d’être victime dans un accident en tant qu’usager de bus qu’un cycliste, un usager de deux-roues motorisé ou un automobiliste ? Y-a-t-il des différences selon l’âge et le genre des usagers considérés ? La seconde question s’intéresse aux tiers impliqués dans des accidents de bus. Y-a-t-il des différences de risque par mode selon l’âge et le genre ? Pour traiter de ces questions, deux indices d’exposition ont été utilisés : les distances parcourues et le temps passé en voyage. Les données de l’accidentologie proviennent du Bulletin d’analyse des accidents corporels de la circulation (BAAC) et les données de déplacements de la dernière Enquête nationale transports et déplacement (ENTD). L’utilisation des distances parcourues pour les accidents de passagers de bus a permis de relativiser le faible risque des usagers de bus au regard des usagers de véhicule léger. Et les temps passés pour les tiers impliqués dans les accidents de bus ont permis de faire ressortir les enjeux de sécurité des jeunes et des piétons

Rheological behaviour of wormlike micelles : effect of salt content

We study the effect of salt content on the rheological properties of wormlike micelles formed from hexadecyltrimethylammonium bromide (CTAB) in presence of potassium bromide (KBr) and of cetylpyridinium chlorate (CPClO3) in presence of sodium chlorate (ClO3Na). Upon increasing the salt concentration, at fixed surfactant concentration, we observe for both systems a maximum of the zero-shear viscosity η0. For salt concentrations less than that corresponding to the maximum of [MATH], the variation of η0 with the surfactant concentration C can be described by a reptation model. Beyond the maximum, the scaling laws obtained for η0(C) are characterized by values of the exponent much smaller than those predicted by the existing theoretical models. The results are qualitatively interpreted by a description based on a structural evolution upon increasing salt content from a system of entangled linear micelles to a multiconnected network. Measurements of the plateau modulus of CTAB solutions, as a function of KBr, give results supporting the above hypothesis.Nous présentons une étude de l'influence de la teneur en sel sur les propriétés rhéologiques de solutions de micelles cylindriques formées à partir de bromure d'hexadecyltrimethylammonium (CTAB) en présence de bromure de potassium (KBr) et de chlorate de cetylpyridinium (CPClO3) en présence de chlorate de sodium (ClO3Na). Lorsqu'on fait varier la concentration en sel, à concentration en tensioactif constante, on observe pour les deux systèmes un maximum de la viscosité à gradient nul η0. Pour des concentrations en sel inférieures à celle correspondant au maximum de [MATH] la variation de η0 avec la concentration en tensioactif C peut être décrite par un modèle de reptation. Au-delà du maximum les lois d'échelles obtenues pour η0(C) sont caractérisées par des valeurs de l'exposant beaucoup plus faibles que celles prédites par les modèles théoriques existants. Les résultats sont interprétés qualitativement à partir d'une description fondée sur l'évolution de la structure micellaire lorsqu'on augmente la teneur en sel, d'un système de micelles linéaires enchevêtrées vers un réseau interconnecté. Les mesures du plateau du module de cisaillement en fonction de la concentration en KBr pour des solutions de CTAB donnent des résultats étayant cette hypothèse

Static and dynamic properties of a network of wormlike surfactant micelles (cetylpyridinium chlorate in sodium chlorate brine)

The structure of solutions of cetylpyridinium chlorate micelles is studied by light scattering and found to be analogous to that of polymer solutions in good solvent and in the semi dilute range. In contrast the micellar solutions are found here to be very fluid and their measured rheological properties are strikingly different from that of polymer solutions. These rheological properties are not accounted for by the recently developed model for semi dilute solutions of equilibrium polymers which described well the properties of other similar wormlike micellar systems. We suggest that the existence of crosslinks rather than entanglement points in the network of wormlike micelles could be responsible for these unexpected properties