Search results for "Fractal"
showing 10 items of 329 documents
Papel de la CX3CL1 en el incremento de los efectos reforzantes de la cocaína inducido por el estrés social
2019
La exposición al estrés social induce un incremento en los efectos reforzantes de la cocaína y del alcohol, observándose que los sujetos estresados consumen mayores cantidades de estas drogas. Se ha observado que los animales estresados consumen mayores cantidades de cocaína y de etanol (Montagud-Romero et al., 2018). Aunque hay numerosos mecanismos a través de los cuales el estrés social puede producir estos efectos, nuestro grupo ha demostrado sistemáticamente que la respuesta neuroinflamatoria media estos efectos. Hemos demostrado que la derrota social (DS), el modelo más representativo para estudiar las consecuencias del estrés social en animales, induce una activación de la microglía, …
Fingerprinting white marbles of archaeometric interest by means of combined SANS and USANS
2007
We have performed a series of USANS and SANS measurements on a selected group of marble samples characterized by similar chemical composition but wide range of known metamorphic conditions. With these samples we start the building up of a data base in an attempt to correlate metamorphism and mesoscopic structure of white marbles. Experimental data have been analysed in terms of a hierarchical model. The present data highlight the importance of the structure at meso scale in identifying the provenance of the marble samples. A remarkable simple relation between the model parameters and the metamorphic degree has been found. This curve might represent a master curve to allow fingerprinting of …
The effect of plasticity in crumpling of thin sheets
2008
Bridging the gap between theoretical and experimental work to understand the effect of plasticity on the crumpling of thin sheets into a small volume has proved difficult. A realistic numerical model now makes a distinction between elastic and elasto-plastic behaviour. Crumpling a thin sheet of material into a small volume requires energy for creating a network of deformations such as vertices and ridges1,2. Scaling properties of a single elastic vertex3,4,5 or ridge have been analysed theoretically6,7,8, and crumpling of a sheet by numerical simulations1,9,10. Real materials are however elasto-plastic11,12,13,14,15 and large local strains induce irreversible plastic deformations. Hence, a …
LA GEOMETRIE FRACTALE - UN NOUVEL OUTIL POUR EVALUER LE ROLE DE LA MORPHOLOGIE DES RESEAUX DE TRANSPORT PUBLIC DANS L'ORGANISATION SPATIALE DES AGGLO…
1998
National audience
Assessing Complexity in Physiological Systems through Biomedical Signals Analysis
2020
The idea that most physiological systems are complex has become increasingly popular in recent decades [...]
Iterative geometric modelling and new world of shapes
2010
Mes recherches ont pour cadre la modélisation géométrique pour la Conception Assistée par Ordinateur et la Synthèse d'images. Plus précisément, j'étudie les possibilités qu'offrent les procédés de construction itératifs basés sur le principe de la géométrie fractale. Partant du modèle IFS (Iterated Function System), nous avons montré qu'il est possible de modéliser des formes non conventionnelles et ainsi de donner accès à un nouvel univers de formes aux concepteurs, artistes et designers. Cette approche est notamment utilisée pour modéliser des surfaces plissées (comme pour la réalisation de coques en architecture) ou des surfaces rugueuses. Nous avons orienté nos travaux sur la notion de …
Long-term memories of developed and emerging markets: Using the scaling analysis to characterize their stage of development
2005
The scaling properties encompass in a simple analysis many of the volatility characteristics of financial markets. That is why we use them to probe the different degree of markets development. We empirically study the scaling properties of daily Foreign Exchange rates, Stock Market indices and fixed income instruments by using the generalized Hurst approach. We show that the scaling exponents are associated with characteristics of the specific markets and can be used to differentiate markets in their stage of development. The robustness of the results is tested by both Monte-Carlo studies and a computation of the scaling in the frequency-domain.
Délimitation d'ensembles morphologiques par une approche multi-échelle
2008
The paper deals with the identification of the envelope of built-up patterns that we define as the limit of a morphologically coherent set through the scales. The point of view is purely morphological; it refers to a multi-scale approach. Besides the description of the context of the research (that is the urban-rural delimitation) the paper is dedicated to the presentation of the methodological principles which allow the identification of the envelope of built-up patterns. The first step of the methodology, that is the step by step dilation of a studied built-up pattern, is briefly described. The emphasis is placed on the second step of the methodology that is the identification of a thresh…
Analyse morphologique de talwegs et comportement scalant : applications des dimensions non-entières à la géographie physique
1999
Morphological talweg analysis and scaling behaviour: applying non-integer dimension to physical geography. -- The organisation of the talweg network is fundamental to the erosion system on the silty loamy plateaux of north-western France. The morphology of the Pays de Caux is a good example of successive runoff concentration caused by the nesting of small dry valleys. These are inherited from a periglacial climate and their general direction is governed by tectonics. However the detailed pattern of these forms remains complex and without obvious explanation. Non-integer dimensions may offer a ceratin logic to this relatively chaotic pattern. This paper has therefore sought to demonstrate th…
Aménités urbaines et périurbaines dans une aire métropolitaine de forme fractale
2002
In the THÜNEN tradition, Urban Economy is a striking abstraction, giving models that keep the main features of the wide diversity of real word cities. Nevertheless, this paradigm less suits the modern urban spatial structures (polycentrism, weak centripetal forces, etc.), particularly the peri-urban form of metropolitan areas, which are an urban/rural integrated space. In this paper, we propose a classical micro-economic urban model combined with a " SIERPINSKI's carpet " geometry, a fractal form which suits for fit together urban and rural areas in a hierarchical structure. Subject to a budget constraint, a household maximises a Cobb-Douglas/CES function, where household's taste for divers…