A Drift-Kinetic Analytical Model for SOL Plasma Dynamics at Arbitrary Collisionality

A drift-kinetic model to describe the plasma dynamics in the scrape-off layer region of tokamak devices at arbitrary collisionality is derived. Our formulation is based on a gyroaveraged Lagrangian description of the charged particle motion, and the corresponding drift-kinetic Boltzmann equation that includes a full Coulomb collision operator. Using a Hermite-Laguerre velocity space decomposition of the gyroaveraged distribution function, a set of equations to evolve the coefficients of the expansion is presented. By evaluating explicitly the moments of the Coulomb collision operator, distribution functions arbitrarily far from equilibrium can be studied at arbitrary collisionalities. A fluid closure in the high-collisionality limit is presented, and the corresponding fluid equations are compared with previously-derived fluid models

Curvature-driven coarsening in the two dimensional Potts model

We study the geometric properties of polymixtures after a sudden quench in temperature. We mimic these systems with the $q$-states Potts model on a square lattice with and without weak quenched disorder, and their evolution with Monte Carlo simulations with non-conserved order parameter. We analyze the distribution of hull enclosed areas for different initial conditions and compare our results with recent exact and numerical findings for $q=2$ (Ising) case. Our results demonstrate the memory of the presence or absence of long-range correlations in the initial state during the coarsening regime and exhibit super-universality properties.Comment: 12 pages, 16 figure

Global city: the occupational layer

Nowadays discussion on global cities concept is being addressed on European level. The concept is a consequence of multiplicities of globalization processes adding different layers according to social, economic and environmental requirements. Cities must also be seen as working systems, with the same needs and requirements in terms of safety and well-being that are considered for other systems. In this paper Authors address the evidences that support the importance of this additional layer. Different sources were used in order to obtain the data related to working systems and their relation to the global cities concept. The conducted systematic review indicate that the search words: sustainability, occupational and global city were not crossed for research. Furthermore, challenges that cities are facing must be understood as additional source of motivation and innovation towards a global city. Cities must also be seen as working systems, with the same needs and requirements in terms of safety and well-being that are considered for other systems

Theory of the Drift-Wave Instability at Arbitrary Collisionality

A numerically efficient framework that takes into account the effect of the Coulomb collision operator at arbitrary collisionalities is introduced. Such model is based on the expansion of the distribution function on a Hermite-Laguerre polynomial basis, to study the effects of collisions on magnetized plasma instabilities at arbitrary mean-free path. Focusing on the drift-wave instability, we show that our framework allows retrieving established collisional and collisionless limits. At the intermediate collisionalities relevant for present and future magnetic nuclear fusion devices, deviations with respect to collision operators used in state-of-the-art turbulence simulation codes show the need for retaining the full Coulomb operator in order to obtain both the correct instability growth rate and eigenmode spectrum, which, for example, may significantly impact quantitative predictions of transport. The exponential convergence of the spectral representation that we propose makes the representation of the velocity space dependence, including the full collision operator, more efficient than standard finite difference methods.Comment: 7 pages, 3 figures, accepted for publication on Physical Review Letter

Weighting table : a broader view for the ergonomic intervention

The use of the Ergonomics Tridimensional Analysis (ETdA) methodology to perform the assessment of risk situations on areas commonly used by workers and clients allows a broader understanding of a system ergonomic approach. The final task of the ETdA is the establishment of a Weighting Table to support the analyst on the ergonomic intervention decisions. The decision-making process is based on a 3-point colored scale, identifying the situations requiring a short-term intervention, a mediumterm intervention or non-critical situations. In order to study the influence of the weights in decision making process a comparative study on results obtained from the Weighting Tables was done. The Ergonomic factors affected by the clients’ weight were assessed and each type of changes separately studied. Obtained results showed that increasing weights given to clients dimension can lead to different decision-makings regarding the ergonomic intervention

Fast magnetic reconnection in the plasmoid-dominated regime

A conceptual model of resistive magnetic reconnection via a stochastic plasmoid chain is proposed. The global reconnection rate is shown to be independent of the Lundquist number. The distribution of fluxes in the plasmoids is shown to be an inverse square law. It is argued that there is a finite probability of emergence of abnormally large plasmoids, which can disrupt the chain (and may be responsible for observable large abrupt events in solar flares and sawtooth crashes). A criterion for the transition from magnetohydrodynamic to collisionless regime is provided.Comment: 4 pages, 1 figur

Unique positive solution for an alternative discrete Painlevé I equation

We show that the alternative discrete Painleve I equation has a unique solution which remains positive for all n >0. Furthermore, we identify this positive solution in terms of a special solution of the second Painleve equation involving the Airy function Ai(t). The special-function solutions of the second Painleve equation involving only the Airy function Ai(t) therefore have the property that they remain positive for all n>0 and all t>0, which is a new characterization of these special solutions of the second Painlevé equation and the alternative discrete Painlevé I equation