8,579 research outputs found
De l'interactivité du récit au récit interactif
À ses origines, la théorie du récit, notamment la narratologie d'inspiration formaliste et structuraliste, s'est développée dans le creuset des études littéraires. De ce fait, le point focal de cette discipline a longtemps été constitué par le récit verbal, généralement sous la forme d'un texte écrit et planifié par un auteur, laissant de côté les formes narratives émergentes, participatives ou interactives. On observe cependant, depuis une vingtaine d'année, une accélération dans le processus d'élargissement des objets d'étude de la narratologie, accompagnée par une mutation épistémologique. Retraçant cette évolution, Jan Christoph Meister observe ainsi un changement d'orientation faisant passer la théorie du récit de l'étude de phénomènes textuels à l'analyse « des fonctions cognitives de récits oraux et non littéraires, ouvrant ainsi un nouveau chapitre dans le projet narratologique » (2009 : 340). Si l'intrigue peut être décrite - en adoptant un point de vue fonctionnaliste et cognitiviste - comme une matrice de possibilités ontologiquement instable, comme un dispositif dont la fonction première est d'ouvrir des virtualités narratives et d'engendrer de la curiosité ou du suspense (Baroni 2007 ; 2009), alors il n'y a pas de raison de la considérer comme un obstacle à l'analyse de récits émergents et participatifs, voire de simulations ou de pratiques ludiques hautement interactives
Relativistic Hydrodynamic Flows Using Spatial and Temporal Adaptive Structured Mesh Refinement
Astrophysical relativistic flow problems require high resolution
three-dimensional numerical simulations. In this paper, we describe a new
parallel three-dimensional code for simulations of special relativistic
hydrodynamics (SRHD) using both spatially and temporally structured adaptive
mesh refinement (AMR). We used the method of lines to discretize the SRHD
equations spatially and a total variation diminishing (TVD) Runge-Kutta scheme
for time integration. For spatial reconstruction, we have implemented piecewise
linear method (PLM), piecewise parabolic method (PPM), third order convex
essentially non-oscillatory (CENO) and third and fifth order weighted
essentially non-oscillatory (WENO) schemes. Flux is computed using either
direct flux reconstruction or approximate Riemann solvers including HLL,
modified Marquina flux, local Lax-Friedrichs flux formulas and HLLC. The AMR
part of the code is built on top of the cosmological Eulerian AMR code {\sl
enzo}. We discuss the coupling of the AMR framework with the relativistic
solvers. Via various test problems, we emphasize the importance of resolution
studies in relativistic flow simulations because extremely high resolution is
required especially when shear flows are present in the problem. We also
present the results of two 3d simulations of astrophysical jets: AGN jets and
GRB jets. Resolution study of those two cases further highlights the need of
high resolutions to calculate accurately relativistic flow problems.Comment: 14 pages, 23 figures. A section on 3D GRB jet simulation added.
Accepted by ApJ
Radio detection of the young binary HD 160934
Precise determination of dynamical masses of pre-main-sequence (PMS) stars is
essential to calibrate stellar evolution models that are widely used to derive
theoretical masses of young low-mass objects. Binary stars in young, nearby
loose associations are particularly good candidates for this calibration since
all members share a common age. Interestingly, some of these young binaries
present a persistent and compact radio emission, which makes them excellent
targets for astrometric VLBI studies. We aim to monitor the orbital motion of
the binary system HD 160934, a member of the AB Doradus moving group. We
observed HD 160934 with the Very Large Array and the European VLBI Network at
8.4 and 5 GHz, respectively. The orbital information derived from these
observations was analyzed along with previously reported orbital measurements.
We show that the two components of the binary, HD 160934 A and HD 160934 c,
display compact radio emission at VLBI scales, providing precise information on
the relative orbit. Revised orbital elements were estimated. Future VLBI
monitoring of this pair should determine precise model-independent mass
estimates for the A and c components, which will serve as calibration tests for
PMS evolutionary models.Comment: 5 pages, 5 figures, accepted for publication in A&
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