Using Resonances to Control Chaotic Mixing within a Translating and Rotating Droplet

Enhancing and controlling chaotic advection or chaotic mixing within liquid droplets is crucial for a variety of applications including digital microfluidic devices which use microscopic ``discrete'' fluid volumes (droplets) as microreactors. In this work, we consider the Stokes flow of a translating spherical liquid droplet which we perturb by imposing a time-periodic rigid-body rotation. Using the tools of dynamical systems, we have shown in previous work that the rotation not only leads to one or more three-dimensional chaotic mixing regions, in which mixing occurs through the stretching and folding of material lines, but also offers the possibility of controlling both the size and the location of chaotic mixing within the drop. Such a control was achieved through appropriate tuning of the amplitude and frequency of the rotation in order to use resonances between the natural frequencies of the system and those of the external forcing. In this paper, we study the influence of the orientation of the rotation axis on the chaotic mixing zones as a third parameter, as well as propose an experimental set up to implement the techniques discussed.Comment: 15 pages, 6 figure

Composants Passifs Intégrés en Technologie CMOS pour la Miniaturisation des Circuits RF

Une démarche originale pour le développement de composants passifs dans une filière industrielle consiste à effectuer un report des contraintes en performances sur les caractéristiques électriques des matériaux utilisés en couches minces. Nous présentons dans cet article la démarche adoptée à travers trois phases clés du développement d’une technologie faibles coûts de composants passifs intégrés en filière CMOS. Le développement et la caractérisation de films minces d’oxyde de titane et de tantale. L’intégration de films résistifs d’oxynitrure de titane en filière industrielle et la modélisation électrique d’inductances spirales intégrées en CMOS

Dingoes at the doorstep: home range sizes and activity patterns of dingoes and other wild dogs around urban areas of north-eastern Australia

Top-predators around the world are becoming increasingly intertwined with humans, sometimes causing conflict and increasing safety risks in urban areas. In Australia, dingoes and dingo x domestic dog hybrids are common in many urban areas, and pose a variety of human health and safety risks. However, data on urban dingo ecology is scant. We GPS-collared 37 dingoes in north-eastern Australia and continuously monitored them each 30 min for 11–394 days. Most dingoes were nocturnal, with an overall mean home range size of 17.47 km2. Overall mean daily distance travelled was 6.86 km/day. At all times dingoes were within 1000 m of houses and buildings. Home ranges appeared to be constrained to patches of suitable vegetation fragments within and around human habitation. These data can be used to reallocate dingo management effort towards mitigating actual conflicts between humans and dingoes in urban areas

Cyclostationnarités d'ordre 1 et 2 : application à des signaux vibratoires d'engrenages

Le diagnostic précoce des pannes des engrenages fait, en particulier, appel aux caractéristiques cyclostationnaires du signal vibratoire. La cyclostationarité d'un signal se manifeste sur les propriétés moyennes (ordre 1) et sur les propriétés énergétiques (ordre 2) du signal. Nous montrons l'importance de la prise en compte de ces 2 ordres de cyclostationarité pour l'analyse du signal et pour l'estimation de la corrélation spectrale. Nous appliquons cette nouvelle méthode de caractérisation à un signal vibratoire d'engrenage. L'exploitation complète des propriétés cyclostationnaires d'ordre 1 et 2 apporte de nouveaux moyens de diagnostic

Diet of dingoes and other wild dogs in peri-urban areas of north-eastern Australia

Knowledge of the resource requirements of urban predators can improve our understanding of their ecology and assist town planners and wildlife management agencies in developing management approaches that alleviate human-wildlife conflicts. Here we examine food and dietary items identified in scats of dingoes in peri-urban areas of north-eastern Australia to better understand their resource requirements and the potential for dingoes to threaten locally fragmented populations of native fauna. Our primary aim was to determine what peri-urban dingoes eat, and whether or not this differs between regions. We identified over 40 different food items in dingo scats, almost all of which were mammals. Individual species commonly observed in dingo scats included agile wallabies, northern brown bandicoots and swamp wallabies. Birds were relatively common in some areas but not others, as were invertebrates. Dingoes were identified as a significant potential threat to fragmented populations of koalas. Dietary overlap was typically very high or near-identical between regions, indicating that peri-urban dingoes ate the same types or sizes of prey in different areas. Future studies should seek to quantify actual and perceived impacts of, and human attitudes towards, peri-urban dingoes, and to develop management strategies with a greater chance of reducing human-wildlife conflicts

Démarche d'analyse spectrale en vue d'une interprétation automatique, application à un signal d'engrenages

Cet article décrit une démarche complète d'analyse spectrale commune à des experts du signal et du domaine concerné (acoustique, mécanique vibratoire) dans le but d'estimer un contenu spectral. L'originalité réside dans le processus de décision qui est fondé sur une confrontation de méthodes (Fourier, Maximum de Vraisemblance, paramétriques, déflation) couplée à une interprétation spectrale. Une pré-analyse consiste à évaluer certaines propriétés du signal (stationnarité, hypothèse gaussienne) et à étudier son autocorrélation. Ensuite, une démarche est construite à partir d'une succession d'analyses spectrales, aboutissant à la détection et à l'identification des différents motifs spectraux. L'interprétation de chaque étape est facilitée par la mise en place de critères objectifs. Enfin des analyses complémentaires sont envisagées (cyclostationnarité, recherche d'harmoniques)

Review on computational methods for Lyapunov functions

Lyapunov functions are an essential tool in the stability analysis of dynamical systems, both in theory and applications. They provide sufficient conditions for the stability of equilibria or more general invariant sets, as well as for their basin of attraction. The necessity, i.e. the existence of Lyapunov functions, has been studied in converse theorems, however, they do not provide a general method to compute them. Because of their importance in stability analysis, numerous computational construction methods have been developed within the Engineering, Informatics, and Mathematics community. They cover different types of systems such as ordinary differential equations, switched systems, non-smooth systems, discrete-time systems etc., and employ di_erent methods such as series expansion, linear programming, linear matrix inequalities, collocation methods, algebraic methods, set-theoretic methods, and many others. This review brings these different methods together. First, the different types of systems, where Lyapunov functions are used, are briefly discussed. In the main part, the computational methods are presented, ordered by the type of method used to construct a Lyapunov function