La transition géonumérique

Desbois, Henri

doi:10.4000/books.pressesenssib.1957

Cited by 3 publications

(4 citation statements)

References 57 publications

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“…Remark : Brownian path/random walk.-We have shown that the distribution of the number n ∈ Z of cells enclosed by a Brownian path in the square lattice is very close from the Levy law describing the distribution of the algebraic area enclosed by a planar Brownian motion (continuum limit) already for n 2. It is interesting to point out that this remark also holds for the number of cells enclosed by a discrete random walk jumping between the different nodes of the square lattice 76,77 .…”

Section: A Model Amentioning

confidence: 79%

“…This behaviour was observed experimentally for thin metallic film 81 and two-dimensional electron gas 82 . We recall that 2d magnetoconductance is given by 2,13,83 : (91) where τ B = φ 0 /(8πDB) and ψ(z) is the Digamma function 84 (the additional factor 1/2 in the Digamma function, compared to (77), is explained in appendix G 2). We may simply write ∆σ − 2e 2 h 1 2πb ln[min τ film N , τ B /τ e ]+cste.…”

Section: The Two-dimensional Limitmentioning

confidence: 99%

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Quantum oscillations and decoherence due to electron-electron interaction in metallic networks and hollow cylinders

2009

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We have studied the quantum oscillations of the conductance for arrays of connected mesoscopic metallic rings, in the presence of an external magnetic field. Several geometries have been considered: a linear array of rings connected with short or long wires compared to the phase coherence length, square networks, and hollow cylinders. Compared to the well-known case of the isolated ring, we show that for connected rings, the winding of the Brownian trajectories around the rings is modified, leading to a different harmonics content of the quantum oscillations. We relate this harmonics content to the distribution of winding numbers. We consider the limits where coherence length L is small or large compared to the perimeter L of each ring constituting the network. In the latter case, the coherent diffusive trajectories explore a region larger than L, whence a networkdependent harmonics content. Our analysis is based on the calculation of the spectral determinant of the diffusion equation for which we have a simple expression on any network. It is also based on the hypothesis that the time dependence of the dephasing between diffusive trajectories can be described by an exponential decay with a single characteristic time ͑model A͒. At low temperature, decoherence is limited by electronelectron interaction, and can be modeled in a one-electron picture by the fluctuating electric field created by other electrons ͑model B͒. It is described by a functional of the trajectories and thus the dependence on geometry is crucial. Expressions for the magnetoconductance oscillations are derived within this model and compared to the results of model A. It is shown that they involve several temperature-dependent length scales.

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Section: A Model Amentioning

confidence: 79%

Section: The Two-dimensional Limitmentioning

confidence: 99%

Quantum oscillations and decoherence due to electron-electron interaction in metallic networks and hollow cylinders

2009

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“…This is when the storms have reached maturity. Isolated, short-lived storms, or events initiated by topographic forcing, will also be modulated by the diurnal cycle (Desbois et al 1989). The timing and relative importance of these short-lived storms depends strongly on location.…”

Section: Introductionmentioning

confidence: 99%

The diurnal cycle and African easterly waves: A land surface perspective

Taylor

CLARK

2001

Quarterly Journal of the Royal Meteorological Society

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S u MM ARYFluxes from the land surface into the atmosphere exhibit strong variability on diurnal and daily time-scales during the Sahelian wet season. The influence of this variability on the atmosphere is examined here using a general circulation model. A land-surface scheme with an improved description of the sparse vegetation which characterizes the Sahel is introduced, and compared with simulations using existing parameters. With smaller evaporation rates, the sparse vegetation results in a warmer and deeper planetary boundary layer (PBL) in better agreement with observations. The diurnal cycle in simulated rainfall is much weaker, due to less frequent triggering of daytime convection. The damping of diurnal variability is accompanied by enhanced daily variability, with a deep moist PBL developing over several days. Above the sparsely vegetated surface, there is also greater African easterly wave (AEW) activity, and more long-lived rain events associated with it.A mechanism is proposed to explain the increased frequency of AEWs above sparser vegetation, based on wave composites in the model. Surface heating of the lower atmosphere is modulated strongly by AEWs. This occurs via a surfacexonvection-radiation feedback. Estimates of the boundary-layer heat budget indicate that variations in surface heating can, to a large extent, account for the low-level temperature signal characteristic of AEWs. By reinforcing the low-level temperature anomalies, the surface may influence the meridional wind signature of the wave above the PBL. Further evidence of the close coupling between the land surface and atmosphere is found by examining the modulation of precipitation by AEWs. Surface heat and moisture fluxes influence the build-up of convective available potential energy ahead of the wave trough. In this way, the properties of the surface can affect the timing and intensity of rainfall associated with, an AEW.

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“…Aucun système d'écriture ni de représentation n'échappe ainsi à une profonde transformation. Il en va ainsi des représentations cartographiques (Desbois, 2012). Le numérique agit en redéfinissant ce qu'est une carte.…”

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Tracer la route. Les cartes d’itinéraire du papier à l’écran, usages et représentations : contribution pour une étude diachronique comparée (France/États-Unis)

Morcrette

2020

mappemonde

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La transition géonumérique

Abstract: Écritures : sur les traces de Jack Goody [texte imprimé] / sous la direction d'Éric Guichard. -Villeurbanne : Presses de l'enssib, cop. 2012. -1 vol. (237 p.) ; 23 cm. -(collection Papiers).

Cited by 3 publications

References 57 publications

Quantum oscillations and decoherence due to electron-electron interaction in metallic networks and hollow cylinders

Quantum oscillations and decoherence due to electron-electron interaction in metallic networks and hollow cylinders

The diurnal cycle and African easterly waves: A land surface perspective

Tracer la route. Les cartes d’itinéraire du papier à l’écran, usages et représentations : contribution pour une étude diachronique comparée (France/États-Unis)

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