Noise and diffusion of particles obeying asymmetric exclusion processes

The relation between noise and Fick's diffusion coefficient in barrier limited transport associated with hopping or tunneling mechanisms of particles obeying the asymmetric simple exclusion processes (ASEP) is physically assessed by Monte Carlo simulations. For a closed ring consisting of a large number of barriers the diffusion coefficient is related explicitly to the current noise thus revealing the existence of a generalized Nyquist-Einstein relation. Both diffusion and noise are confirmed to decrease as the square root of the number of barriers as a consequence of the correlation induced by ASEP. By contrast, for an open linear chain of barriers the diffusion coefficient is found to be no longer related to current noise. Here diffusion depends on particle concentration but is independent of the number of barriers

Entropy solutions for a traffic model with phase transitions

In this paper, we consider the two phases macroscopic traffic model introduced in [P. Goatin, The Aw-Rascle vehicular traffic flow with phase transitions, Mathematical and Computer Modeling 44 (2006) 287-303]. We first apply the wave-front tracking method to prove existence and a priori bounds for weak solutions. Then, in the case the characteristic field corresponding to the free phase is linearly degenerate, we prove that the obtained weak solutions are in fact entropy solutions \`a la Kruzhkov. The case of solutions attaining values at the vacuum is considered. We also present an explicit numerical example to describe some qualitative features of the solutions

Labour market and social policy in Italy. Challenges and changes

Eight years after the outbreak of the financial crisis, Italy has still to cope with and overcome a plethora of economic and social challenges. On top of this, it faces an unfavourable demographic structure and severe disparities between its northern and southern regions. Some promising reforms have recently been enacted, specifically targeting poverty and social exclusion. However, much more remains to be done on the way towards greater economic stability and widely shared prosperity

Rigorous derivation of nonlinear scalar conservation laws from follow-the-leader type models via many particle limit

We prove that the unique entropy solution to a scalar nonlinear conservation law with strictly monotone velocity and nonnegative initial condition can be rigorously obtained as the large particle limit of a microscopic follow-the-leader type model, which is interpreted as the discrete Lagrangian approximation of the nonlinear scalar conservation law. More precisely, we prove that the empirical measure (respectively the discretised density) obtained from the follow-the-leader system converges in the 1-Wasserstein topology (respectively in $L^1_{loc}$) to the unique Kruzkov entropy solution of the conservation law. The initial data are taken in $L^1\cap L^\infty$, nonnegative, and with compact support, hence we are able to handle densities with vacuum. Our result holds for a reasonably general class of velocity maps (including all the relevant examples in the applications, e.g. in the Lighthill-Whitham-Richards model for traffic flow) with possible degenerate slope near the vacuum state. The proof of the result is based on discrete BV estimates and on a discrete version of the one-sided Oleinik-type condition. In particular, we prove that the regularizing effect $L^1\cap L^\infty \mapsto BV$ for nonlinear scalar conservation laws is intrinsic of the discrete model

CE QUE LA MULTI-ACTIVITÉ FAIT AUX SUJETS : UNE PERSPECTIVE ETHNOLOGIQUE ASSAINISSEMENT ET INTERIM

La multi-activité telle que nous l'avons observée sur nos terrains ( intérim et chantiers assainissement) s'articule aux transformations contemporaines des organisations de travail.i) Génère des couplages/découplages d’objets, par le biais des interruptions et des bifurcationsqu’elle impose. Ces couplages ont une incidence sur le "sujet-et-ses-objet" - (Warnier, 2011) y compris dans sesdimensions inconscientes. ii) Favorise des savoir-faire peu transmissibles ou tout au moins constitueun obstacle aux formes anciennes de transmission qui s'établissaient dans le temps long sur la basede collectifs de travail stabilisés. Elle a dès lors des incidences sur le sujet collectif. iii) Peut êtreenvisagée comme conduisant à une forme d'évitement de la confrontation du sujet avec le réel del'activité. Elle atteint alors le sujet réflexif. La temporalité même de la multi-activité constituant dèslors ce à quoi le sujet se confronte et qui échappe ou résiste. La question de la maîtrise du temps seposant avec acuité

Coupling conditions for isothermal gas flow and applications to valves

We consider an isothermal gas flowing through a straight pipe and study the effects of a two-way electronic valve on the flow. The valve is either open or closed according to the pressure gradient and is assumed to act without any time or reaction delay. We first give a notion of coupling solution for the corresponding Riemann problem; then, we highlight and investigate several important properties for the solver, such as coherence, consistence, continuity on initial data and invariant domains. In particular, the notion of coherence introduced here is new and related to commuting behaviors of valves. We provide explicit conditions on the initial data in order that each of these properties is satisfied. The modeling we propose can be easily extended to a very wide class of valves

Riemann problems with non--local point constraints and capacity drop

In the present note we discuss in details the Riemann problem for a one--dimensional hyperbolic conservation law subject to a point constraint. We investigate how the regularity of the constraint operator impacts the well--posedness of the problem, namely in the case, relevant for numerical applications, of a discretized exit capacity. We devote particular attention to the case in which the constraint is given by a non--local operator depending on the solution itself. We provide several explicit examples. We also give the detailed proof of some results announced in the paper [Andreainov, Donadello, Rosini, "Crowd dynamics and conservation laws with non--local point constraints and capacity drop", which is devoted to existence and stability for a more general class of Cauchy problems subject to Lipschitz continuous non--local point constraints.Comment: 19 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1304.628