Convective instabilities in two superposed horizontal liquid layers heated laterally

This work is devoted to the theoretical study of the stability of two superposed horizontal liquid layers bounded by two solid planes and subjected to a horizontal temperature gradient. The liquids are supposed to be immiscible with a nondeformable interface. The forces acting on the system are buoyancy and interfacial tension. Four different flow patterns and temperature profiles are found for the basic state. A linear perturbative analysis with respect to two and three dimensional perturbations reveals the existence of three kind of patterns. Depending on the relative height of both liquids several situations are predicted: either wave propagation from cold to the hot regions, or waves propagating in the opposite direction or still stationary longitudinal rolls. The behavior of three different pairs of liquids which have been used in experiments on bilayers under vertical gradient by other authors have been examined. The instability mechanisms are discussed and a qualitative interpretation of the different behaviors exhibited by the system is provided. In some configurations it is possible to find a codimension-two point created by the interaction of two Hopf modes with different frequencies and wavenumbers. These results suggest to consider two liquid layers as an interesting prototype for the study of propagation and interaction of waves in the context of the B\'enard-Marangoni problem.Comment: 21 pages, 9 figures, 2 tables;accepted to be published in PR

Tsallis statistics generalization of non-equilibrium work relations

We use third constraint formulation of Tsallis statistics and derive the $q$-statistics generalization of non-equilibrium work relations such as the Jarzynski equality and the Crooks fluctuation theorem which relate the free energy differences between two equilibrium states and the work distribution of the non-equilibrium processes.Comment: 5 page

Nonequilibrium entropy production for open quantum systems

We consider open quantum systems weakly coupled to a heat reservoir and driven by arbitrary time-dependent parameters. We derive exact microscopic expressions for the nonequilibrium entropy production and entropy production rate, valid arbitrarily far from equilibrium. By using the two-point energy measurement statistics for system and reservoir, we further obtain a quantum generalization of the integrated fluctuation theorem put forward by Seifert [PRL 95, 040602 (2005)].Comment: 4 pages, 1 figur

Towards agent-based crowd simulation in airports using games technology

We adapt popular video games technology for an agent-based crowd simulation in an airport terminal. To achieve this, we investigate the unique traits of airports and implement a virtual crowd by exploiting a scalable layered intelligence technique in combination with physics middleware and a socialforces approach. Our experiments show that the framework runs at interactive frame-rate and evaluate the scalability with increasing number of agents demonstrating navigation behaviour

ONSAGER RELATIONS AND EXTENDED IRREVERSIBLE THERMODYNAMICS

We show that when the thermodynamic fluxes are included as independent thermodynamic state variables of a generalized entropy. the original ONSAGER formulation may be directly used in the space of the fiuxes. Therefore, the ONSAGER relations may be derived either in the space of the classical (slow) variables, by using a spatial FOURIER transformation, or in the space of the non-classical (fast) variables such as the physical fiuxes, without need of any Fourier transform. Furthermore. we analyse the question of non-linear ONSAGER relations by studying one particular set of evolution equations of the fiuxes, and considering the fluctuations of the fluxes around a non-equilibrium steady state. Comparison with kinetic theory is not completely conclusive, because of several open questions which we comment in the concluding remarks

Status of QCD

I have been asked to discuss the status of QCD. It seems to me that there are three main points to be made about the present status of QCD: $\bullet$ QCD is right, and we can do many beautiful things with it. $\bullet$ There are several important concrete problems that lie just beyond the edge of our current understanding. $\bullet$ There are some foundational issues in QCD, and some recent developments, that may point toward entirely new directions. These points will, I believe, emerge quite clearly from the following more detailed discussion. The discussion will be in three parts. I'll first discuss elementary processes, then more complicated processes, and then finally foundational issues.Comment: 28 pages, use Phyzzx, figures available by FAX or mail on request, IASSNS-HEP-93/6

HEAT CONDUCTION AT LOW TEMPERATURE: A NON-LINEAR GENERALIZATION OF THE GUYER-KRUMHANSL EQUATION

A general non-linear and non-local heat transport equation is proposed in view to study heat conduction at low temperature

Vibrational Excitons in CH-Stretching Fundamental and Overtone Vibrational Circular Dichroism Spectra

A set of vibrational circular dichroism (VCD) spectra in the CH-stretching fundamental region for about twenty compounds belonging to the class of essential oils was empirically analyzed by the use of a sort of vibrational exciton mechanism, involving three centers. Through a general formula applicable to many coupled dipole oscillators, the rotational strengths of the previously identified vibrational excitons are evaluated. The results are then critically reviewed by the use of recent ab initio methodology, as applied to selected molecules of the original set. Further insight is gained by model calculations adding up the contribution of the coupling between electric dipole moments associated with normal mode behavior and that of the polarizability from polarizable groups. The former part is responsible for the excitonic behavior of the VCD spectra. For the same selected molecules we have also investigated whether some excitonic behavior is taking place in the second overtone region, and have concluded that this is not the case

Comparison between low-order and high-order acoustic pressure solvers for bubbly media computations

Numerical modelling is a useful tool for the fundamental study of acoustic cavitation treatment in liquid metals. This treatment, also known as ultrasonic melt processing, significantly improves the properties and quality of metallic materials. However, the mechanisms leading to these observed improvements are still unclear and a fundamental study of cavitation treatment is required to understand this process. In this endeavour, this paper compares the use of high-order discretization schemes for solving acoustic pressures in cavitating liquids with its low-order counterpart. A fourth order scheme is shown to be more stable and accurate than a second order scheme when taking into account the acceleration of bubbles before their collapse, and is recommended for the full cavitation modelling of acoustic treatment of liquid metals.UK Engineering and Physical Sciences Research Council (EPSRC

Lombalgie chronique, COTOREP et reclassement professionnel en Moselle

Objectifs : Décrire les caractéristiques, la prise en charge, les résultats et le coût d\u27un reclassement professionnel concernant les assurés mosellans lombalgiques chroniques bénéficiant d’un accord de la Commission technique d\u27orientation et de reclassement professionnel (COTOREP). Méthodes : Etude descriptive menée entre août 2000 et mars 2001 dans le cadre d\u27un partenariat avec la COTOREP de Moselle intégrant 48 lombalgiques chroniques pour lesquels la COTOREP a donné en 1995 un accord de pré-orientation ou de reclassement professionnels. Résultats : Le lombalgique pris en charge était un homme jeune, de faible niveau scolaire et professionnel, en rupture avec le milieu du travail et souffrant d\u27une pathologie lombaire invalidante. Sur 32 formations suivies, 24 candidats ont réussi leur examen mais seuls dix diplômés ont trouvé un emploi. Huit diplômés ont trouvé un emploi conforme à la formation apprise. Le taux de reprise du travail était semblable pour les diplômés (10/24) et pour les autres lombalgiques (11/24). Le coût global pour l\u27assurance maladie variait de 25 000 en externat à 39 000 en internat. Conclusion : Devant la faible valeur ajoutée du reclassement professionnel que nous avons constatée, il paraît souhaitable de maintenir le lombalgique chronique dans son emploi en restaurant son rachis, en aménageant son poste de travail et, surtout, en gérant ses peurs et croyances liées au couple lombalgietravail