3,141 research outputs found
Non-mean-field effects in systems with long-range forces in competition
We investigate the canonical equilibrium of systems with long-range forces in
competition. These forces create a modulation in the interaction potential and
modulated phases appear at the system scale. The structure of these phases
differentiate this system from monotonic potentials, where only the mean-field
and disordered phases exist. With increasing temperature, the system switches
from one ordered phase to another through a first-order phase transition. Both
mean-field and modulated phases may be stable, even at zero temperature, and
the long-range nature of the interaction will lead to metastability
characterized by extremely long time scales
Le fleuve dans la ville nord-méditerranéenne : de la friche urbaine à l'infrastructure paysagÚre
Les paysages fluviaux sont devenus l\u27un des éléments phares du marketing urbain. Certaines villes nord méditerranéennes, qui se sont historiquement distanciées de leur cours d\u27eau, s\u27appuient désormais sur celui-ci pour élaborer leurs stratégies de développement. à Montpellier et Perpignan, la continuité du fleuve est un argument majeur des politiques publiques actuelles : il fait figure de matérialité végétale et de repÚre géographique pour la construction de la ville. Cependant, les choix motivés par ces nouvelles valeurs de l\u27aménagement reposent sur une image de continuité, et contredisent parfois les impératifs des spécificités physiques et hydraulogiques de ces riviÚres
Southern France riverbank projects in Montpellier and Perpignan: from designed space to interpreted space
This examination of recent landscape architecture interventions along two rivers in southern Franceâthe River Lez in Montpellier and the River TĂȘt in Perpignanâquestions the popular notion of âintervening in spaceâ. Observing the features of the interventions and their consequences, the author investigates whether a change of paradigm occurs with regard to the approach employed. The results of this analysis demonstrate an evolution in the role of the landscape professional, who now seeks to translate or interpret a space rather than to act upon it materially. Pertinent tasks comprise not only installation in the sense of designing or bringing order to space, but also producing communications about the site. The landscape architect aims, at at a local scale, to persuade the community to accept the existing space (notably using a discourse on the values of natural and cultural heritage); and at a territorial scale, to use the riverbanks, and more generally the idea of the river, to restructure or give coherence to the city. Finally, this river intervention approach produces either conceptual pieces (such as reports, maps, films, animation) or minimal changes for ambitious infrastructural projects
Construire lâespace public : du diagnostic au projet
Cet exposĂ© vise Ă relater, dans ses grandes lignes, les coulisses du travail de celui qui va concevoir un projet sur l\u27espace public. MĂȘme sans ĂȘtre concepteur, il est important pour un maĂźtre d\u27ouvrage de bien connaĂźtre cette dĂ©marche de conception, non seulement pour pouvoir Ă©valuer la qualitĂ© du projet, mais aussi pour pouvoir ĂȘtre cohĂ©rent dans les choix successifs qui s\u27imposent Ă une commune (cohĂ©rent sâentend ici comme : reprendre la mĂȘme logique, la mĂȘme dĂ©marche dâun projet Ă lâautre, ou savoir les articuler).
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La structure de cette communication suit la logique dâun diagnostic multiscalaire qui conduit Ă formuler un projet :
âąÂ   RĂ©aliser un diagnostic Ă lâĂ©chelle de lâespace Ă transformer, pour comprendre ce qui fait sa spĂ©cificitĂ©Â : analyser les caractĂ©ristiques matĂ©rielles dâun espace public pour en connaĂźtre la singularitĂ©Â (lâanalyse in situ)
âąÂ   RĂ©aliser un diagnostic Ă une Ă©chelle plus globale pour Ă©valuer les enjeux de l\u27amĂ©nagement : mettre en Ă©vidence les enjeux sociaux et environnementaux qui sous-tendent lâamĂ©nagement (lâanalyse contextuelle)Â
âąÂ DĂ©finir un projet pour lâespace public : le schĂ©ma d\u27intention : faire le choix dâun type de rapport Ă lâespace au travers dâun schĂ©ma dâintentionÂ
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Lâobjectif des trois temps de cette dĂ©marche est de produire un espace public adaptĂ© Ă son environnement : un espace spĂ©cifique, non uniformisĂ©, non banalisĂ©, et non aveugle aux problĂ©matiques quâil soulĂšve
La construction des paysages fluviaux urbains : comparaison de l'Ă©volution du statut du fleuve Ă Perpignan et Montpellier
National audienc
Le développement durable à l'oeuvre : Corridors verts et parcs sur les rives de la Thur, Cernay et Wesserling - Compte-rendu des 4Úmes Assises Européennes du Paysage de Strasbourg
Aux questions sur le développement durable posées au conseil de l\u27Europe lors des deux premiÚres journées des Assises Européennes du Paysage, les ateliers mobiles du troisiÚme jour ont apporté des illustrations concrÚtes. Voici ici retracées les grandes lignes de l\u27atelier mobile n°5, qui présentait deux démarches de projet de parcs le long des rives de la Thur, à Cernay et Wesserling, dans le département du Haut Rhin
Differential interferometry of QSO broad line regions I: improving the reverberation mapping model fits and black hole mass estimates
Reverberation mapping estimates the size and kinematics of broad line regions
(BLR) in Quasars and type I AGNs. It yields size-luminosity relation, to make
QSOs standard cosmological candles, and mass-luminosity relation to study the
evolution of black holes and galaxies. The accuracy of these relations is
limited by the unknown geometry of the BLR clouds distribution and velocities.
We analyze the independent BLR structure constraints given by super-resolving
differential interferometry. We developed a three-dimensional BLR model to
compute all differential interferometry and reverberation mapping signals. We
extrapolate realistic noises from our successful observations of the QSO 3C273
with AMBER on the VLTI. These signals and noises quantify the differential
interferometry capacity to discriminate and measure BLR parameters including
angular size, thickness, spatial distribution of clouds, local-to-global and
radial-to-rotation velocity ratios, and finally central black hole mass and BLR
distance. A Markov Chain Monte Carlo model-fit, of data simulated for various
VLTI instruments, gives mass accuracies between 0.06 and 0.13 dex, to be
compared to 0.44 dex for reverberation mapping mass-luminosity fits. We
evaluate the number of QSOs accessible to measures with current (AMBER),
upcoming (GRAVITY) and possible (OASIS with new generation fringe trackers)
VLTI instruments. With available technology, the VLTI could resolve more than
60 BLRs, with a luminosity range larger than four decades, sufficient for a
good calibration of RM mass-luminosity laws, from an analysis of the variation
of BLR parameters with luminosity.Comment: 19 pages, 14 figures, accepted by MNRAS on December 5, 201
A constitutive model for simple shear of dense frictional suspensions
Discrete particle simulations are used to study the shear rheology of dense,
stabilized, frictional particulate suspensions in a viscous liquid, toward
development of a constitutive model for steady shear flows at arbitrary stress.
These suspensions undergo increasingly strong continuous shear thickening (CST)
as solid volume fraction increases above a critical volume fraction, and
discontinuous shear thickening (DST) is observed for a range of . When
studied at controlled stress, the DST behavior is associated with non-monotonic
flow curves of the steady-state stress as a function of shear rate. Recent
studies have related shear thickening to a transition between mostly lubricated
to predominantly frictional contacts with the increase in stress. In this
study, the behavior is simulated over a wide range of the dimensionless
parameters , and , with the dimensionless shear stress and the coefficient of
interparticle friction: the dimensional stress is , and , where is the magnitude of repulsive force at contact
and is the particle radius. The data have been used to populate the model
of the lubricated-to-frictional rheology of Wyart and Cates [Phys. Rev.
Lett.{\bf 112}, 098302 (2014)], which is based on the concept of two viscosity
divergences or \textquotedblleft jamming\textquotedblright\ points at volume
fraction (random close packing) for the
low-stress lubricated state, and at for
any nonzero in the frictional state; a generalization provides the normal
stress response as well as the shear stress. A flow state map of this material
is developed based on the simulation results.Comment: 12 pages, 10 figure
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