Search results for "Abilities"

3D YSO accretion shock simulations: a study of the magnetic, chromospheric and stochastic flow effects

2013

AbstractThe structure and dynamics of young stellar object (YSO) accretion shocks depend strongly on the local magnetic field strength and configuration, as well as on the radiative transfer effects responsible for the energy losses. We present the first 3D YSO shock simulations of the interior of the stream, assuming a uniform background magnetic field, a clumpy infalling gas, and an acoustic energy flux flowing at the base of the chromosphere. We study the dynamical evolution and the post-shock structure as a function of the plasma-beta (thermal pressure over magnetic pressure). We find that a strong magnetic field (~hundreds of Gauss) leads to the formation of fibrils in the shocked gas …

Nonlinear Multimode Fiber Optics

2018

We overview recent advances in the nonlinear optics of multimode optical fibers, including ultrabroadband sideband and supercontinuum generation, Kerr and Raman beam cleanup, modal modulation instabilities, four wave mixing, and second harmonic beam cleaning.

Limitation of the ECRIS performance by kinetic plasma instabilities (invited).

2016

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropic electron velocity distribution. The instabilities are associated with strong microwave emission and periodic bursts of energetic electrons escaping the magnetic confinement. The instabilities explain the periodic ms-scale oscillation of the extracted beam current observed with several high performance ECRISs and restrict the parameter space available for the optimization of extracted beam currents of highly charged ions. Experiments with the JYFL 14 GHz ECRIS have demonstrated that due to the instabilities the optimum Bmin-field is less than 0.8BECR, which is the value suggested by …

Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities.

2015

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space avail…

The Fluorescence Detector of the Pierre Auger Observatory

2010

The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detecto…

Condensation and thermalization of classsical optical waves in a waveguide

2011

http://pra.aps.org/; International audience; We consider the long-term evolution of a random nonlinear wave that propagates in a multimode optical waveguide. The optical wave exhibits a thermalization process characterized by an irreversible evolution toward an equilibrium state. The tails of the equilibrium distribution satisfy the property of energy equipartition among the modes of the waveguide. As a consequence of this thermalization, the optical field undergoes a process of classical wave condensation, which is characterized by a macroscopic occupation of the fundamental mode of the waveguide. Considering the nonlinear Schrödinger equation with a confining potential, we formulate a wav…

Dialogue sur le handicap : réciprocité et altérité

2017

This dialogue is not one between a lecturer in philosophy (Pierre Ancet) questioning a person in a situation of physical dependency (Marcel Nuss), but a dialogue between two full-fledged authors. In this exchange the organic deficiency constitutes only the specific character of an individual’s experience, which is to be described without making it a pathology. Disability is considered in its organic, psychological and social dimension, as an incapacitating constraint, but also as a potential vector to discover nonstandard capacities. Among these capacities, the authors stress the consciousness of time and of the body, particularly unexpected as this consciousness is examined by an entirely …

Mode-particle Interactions as Sources of Gamma-ray Bubbles in the Galaxy

A plasma outflow coming from the center of Our Galaxy is simulated by an ion beam reaching a nearly stationary magnetic field that can excite lower hybrid waves efficiently in the rarefied plasma (10-2-10-4 cm-3) surrounding the whole galaxy. The electrostatic lower hybrid waves are driven to instability via Cerenkov interaction. In this work we derive (by using a fluid model) the relevant dispersion relation and the expression for the growth rate by solving the dispersion relation both analytically and numerically. Parametric studies show that the growth rate of the instability increases with the beam density. The instability is found to have the maximum growth rate when the perpendicular …

Estudiantes universitarios en riesgo de exclusión social: una aproximación a una realidad social oculta

2017

La reciente recesión y la crisis económica en España han supuesto un duro impacto en las condiciones de vida de la población. En el presente estudio se profundiza en el impacto de la crisis sobre el acceso a los estudios superiores, así como en los comportamientos relacionados con la exclusión social que los estudiantes universitarios han realizado o serían capaces de realizar con el único propósito de costearse su educación. Para ello, 96 estudiantes contestaron voluntariamente una encuesta cuyo objetivo era evaluar su situación sociolaboral y detectar posibles situaciones de riesgo social. La mayor parte de participantes percibía su situación económica como media o baja a pesar de que muc…

Porti e automazione: spunti in materia di responsabilità delle imprese di sbarco

2019

Lo studio si incentra sull'automazione delle operazioni portuali di imbarco e di sbarco, con particolare riferimento all'incidenza della tecnologia sul sistema di responsabilità degli attori del trasporto marittimo. Sarà trattata la normativa portuale, la governance, il sistema di protezione sociale dei lavoratori portuali e il regime giuridico dei terminal operator. La relazione tra attività totalmente automatizzata e infrastrutture marittime è analizzata nel contesto del diritto internazionale marittimo. The article focuses on the automatization of loading, stowing and unloading ports operations, from the point of view of the impact of the technologies on the system of liabilities of the …