Dispersion of inert particles in a rough fracture.

International audienceThis paper aims to show a transport model of either smooth or rough fractures. These are numerically generated by means of a fractal surface method. In order to study dispersion processes, a 3D transport model is used. This model is based on a random walk that takes into account both the sizes of the particles and the size exclusion effect of particles on the fracture walls. Simulations are carried out to study dispersion processes in which transport cases in either smooth or rough fractures and transport of several sizes particles are involved. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS

Changement climatique

Dans son ouvrage l’auteur nous propose un nouveau regard sur la modélisation des processus du changement climatique : l’identification. La théorie de l’identification des systèmes dynamiques est éprouvée depuis plusieurs décennies mais principalement dans le domaine industriel. Or, l’auteur nous démontre qu’elle a toute sa place dans la modélisation climatique planétaire. Pourtant, aucun article scientifique n’y fait référence ! En quoi consiste l’identification et qu’est-ce que cette méthode..

A model of cockpit karst landscape, Jamaica

International audienceThis paper deals with a landscape evolution model to compute cockpit karsts landforms. The CHILD model is used to model geomorphic processes at regional scale. After examining briefly CHILD's principles and equations of limestone dissolution processes, the denudation model is detailed. The relation between subcutaneous dissolution and denudation of the topography is introduced by means of an empirical equation associated with epikarst processes: the denudation is taken to be proportional to the dissolution in the subcutaneous zone. The model takes into account an anisotropic dissolution in space according to what is observed in reality or described by scenarios of cockpit karst landscape evolution. Simulated cockpit karst terrains are compared with real landscapes by means of several morphometric criteria: slope, relative relief and scaling properties. Results confirm the importance of anisotropic dissolution processes and could provide a numerical validation of the epikarst processes to describe cockpit karst genesis

Modelling cockpit karst landforms

International audienceThe purpose of this article is to present a model of the formation processes of cockpit karst landscapes. The CHILD software was used to simulate landscape evolution including dissolution processes of carbonate rocks. After examining briefly how the CHILD model operates, two applications of this model involving dissolution of carbonate rocks are presented. The simulated landscapes are compared with real landscapes of the Cockpit Country, Jamaica, using morphometric criteria. The first application is based on the hypothesis that dissolution of carbonate rocks is isotropic over time and space. In this case, dissolution is constant throughout the whole area studied and for each time step. The simulated landscapes based oil this hypothesis have morphometric features which are quite different from those of real landscapes. The second application considers that dissolution of carbonate rocks is anisotropic over time and space. In this case, it is necessary to take into account subsurface and under.-round processes, by Coupling surface runoff and water infiltration into the fractured carbonates

Modèle d'évolution de paysages, application aux karsts en cockpit de Jamaïque

International audienceCet article présente les résultats d'un modèle géomorphologique d'évolution des karsts en cockpit (Jamaïque). Dans un premier temps, nous expliquons comment les processus de dissolution des carbonates ont été implémentés dans le logiciel d'évolution géomorphologique CHILD. Puis nous donnons les détails de notre modèle d'érosion, basé sur les principes de la théorie de l'épikarst. Le modèle prend en compte l'anisotropie spatio-temporelle conformément à ce qui est observé empiriquement ou encore décrit par des scénarii de l'évolution des karsts en cockpit. Ce modèle nécessite d'abord d'introduire un réseau de fractures afin de prendre en compte les écoulements de sub-surface. Ensuite, la dissolution et donc l'ouverture des fractures sont calculées ce qui participe à un processus de feed-back positif entre dissolution et écoulement. La relation entre la dissolution des carbonates fracturés et l'évolution de la topographie est introduit

Inverse box-counting method: A fractal-based procedure to create biospheric landscape patterns

1st WSEAS International Conference on Landscape Architecture (LA 2008), Univ Algarve, Algarve, PORTUGAL, JUN 11-13, 2008International audiencePlanners and designers are interested in replicating biospheric landscape patterns to reclaim surface mines to match existing natural landscape patterns. One approach that shows promise is the use of fractal geometry to generate biospheric landscape patterns. While the measurement of the actual fractal dimension of a landscape can be difficult, a box-counting method was developed at INHP, Angers, France which approximates the spatial patterns of biospheric landscapes. Essentially the procedure entails covering a natural object/pattern with a regular grid of size r and then one simply counts the number of grid boxes, N(r), that contain some part of the object. The boxes are subdivided and the value of r is progressively reduced and N(r) is similarly re-measured until some of the boxes become empty (containing no landscape objects of interest). Then the fractal dimension of the object is approximated to be the log(N(r))/Iog(l/r). We illustrate this procedure by measuring and replicating a stand of trees in the Upper Peninsula of Michigan. Our study revealed a fractal number of 1.0 17 (p < 0.01), with a mean of 77.4 trees per 100 in by 100 in stand, and a standard deviation of 34.87 trees per stand

Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS, ISS and RADAR data and comparison with the Etosha Pan (Namibia)

International audienceOntario Lacus is the largest lake of the whole southern hemisphere of Titan, Saturn's major moon. It has been imaged twice by each of the Cassini imaging systems (Imaging Science Subsystem (ISS) in 2004 and 2005, Visual and Infrared Mapping Spectrometer (VIMS) in 2007 and 2009 and Radar in 2009 and 2010). In this study, we take advantage of each imaging dataset to establish a global survey of Ontario Lacus' environment from 2005 to 2010. We perform a geomorphological mapping and interpretation of Ontario Lacus, mainly based on a joint analysis of VIMS and Radar SAR datasets, along with the T49 altimetric profile acquired in December 2008. The morphologies observed on Ontario Lacus are compared to landforms of a semi-arid terrestrial analog, which closely resembles Titan's lakes: the pans of the Etosha Basin, located in Namibia. From this comparison, we infer that Ontario Lacus is an extremely flat depression where liquids, only located in the darkest areas in the Radar data, cover topographic lows where the "alkanofer" would raise above the depression floor. The rest of the depression appears rather as a muddy flat surface likely composed of a thick coating of photon-absorbing materials, explaining its still rather dark appearance in the infrared and radar data. We also determined whether surface changes occurred during the 5 years time interval between 2005 and 2010. We found that the depression contour is constant at the resolution of ISS and VIMS data, both being consistent with the depression contour derived from the Radar data. Our interpretation, in which the liquids are located only in some parts of Ontario Lacus, agrees with the lack of significant change of the depression contour between 2007 (and 2005 with more uncertainties) and 2010

Mathematics for Earth Science and Geography

This undergraduate textbook presents a unique comprehensive overview on Mathematics in Earth Sciences and Geography. It deals with fundamental theoretical and applied mathematics, needed by bachelor students in a wide range of subjects.The book is illustrated with many examples and over a hundred practical exercises, with solutions included in the book. In addition, this textbook highlights numerical resources by using two free software packages (R and Xcas) and introducing their use.</p

Bases de mathématiques pour la géologie et la géographie

International audienc