Search results for "normal"
showing 10 items of 2571 documents
Timing and patterns of the ENSO signal in Africa over the last 30 years: insights from normalized difference vegetation index data.
2014
Abstract A more complete picture of the timing and patterns of the ENSO signal during the seasonal cycle for the whole of Africa over the three last decades is provided using the normalized difference vegetation index (NDVI). Indeed, NDVI has a higher spatial resolution and is more frequently updated than in situ climate databases, and highlights the impact of ENSO on vegetation dynamics as a combined result of ENSO on rainfall, solar radiation, and temperature. The month-by-month NDVI–Niño-3.4 correlation patterns evolve as follows. From July to September, negative correlations are observed over the Sahel, the Gulf of Guinea coast, and regions from the northern Democratic Republic of Congo…
Finite-size scaling in Ising-like systems with quenched random fields: Evidence of hyperscaling violation
2010
In systems belonging to the universality class of the random field Ising model, the standard hyperscaling relation between critical exponents does not hold, but is replaced by a modified hyperscaling relation. As a result, standard formulations of finite size scaling near critical points break down. In this work, the consequences of modified hyperscaling are analyzed in detail. The most striking outcome is that the free energy cost \Delta F of interface formation at the critical point is no longer a universal constant, but instead increases as a power law with system size, \Delta F proportional to $L^\theta$, with $\theta$ the violation of hyperscaling critical exponent, and L the linear ex…
Identification of Precious Artefacts: The Sonic Imprint for Small Artefacts
2010
Identification of artworks is mainly based on a few characteristics which can be observed using non-invasive tools (sight, touch, simple instruments), the investigated properties being geometry, weight, colours, texture, etc. Nowadays, technology allows reproducing all these characteristics to such an extent that even expert conservators can be deceived: in particular at the present time even the geometry of an artwork can be easily reproduced with the help of laser scanner analysis and with a rapid prototyping machine or a computer numerical control (CNC) milling machine. We propose a new tool, the Sonic Imprint, producing a code capable of identifying a rigid artefact from its vibrational…
Arqueología del futuro en el barrio El Raval de Barcelona: a propósito de tres inercias del urbanismo tecnocrático y sus efectos indeseables
2021
Este artículo es el resultado de nuestro esfuerzo analítico para comprender cómo se han pensado y practicado intervenciones urbanísticas, extremadamente drásticas, contra el barrio El Raval de Barcelona en períodos formalmente democráticos. Lo que consideramos original de nuestra propuesta analítica es la identificación de una suerte de doxa tecnocrática que habría impregnado el urbanismo –también el barcelonés- desde sus inicios, y que acabará caracterizando el aclamado tanto como discutido “Modelo Barcelona”. La metodología utilizada proviene de la antropología histórica y de la sociología urbana. Nuestro prisma teórico entrecruza perspectivas historiográficas como la biopolítica, socioló…
Étudiantes à l'ENS Cachan : sur-dotées et sous-représentées
2013
Le département Sciences du sport et éducation physique (2SEP) de l'École normale supérieure Cachan, antenne de Bretagne, vient de fêter ses dix ans d'existence. Occasion d'un bilan sur son recrutement.
PARETO OR LOG-NORMAL? BEST FIT AND TRUNCATION IN THE DISTRIBUTION OF ALL CITIES*
2015
In the literature, the distribution of city size is a controversial issue with two common contenders: the Pareto and the log-normal. While the first is most accredited when the distribution is truncated above a certain threshold, the latter is usually considered a better representation for the untruncated distribution of all cities. In this paper, we reassess the empirical evidence on the best-fitting distribution in relation to the truncation point issue. Specifically, we provide a comparison among four recently proposed approaches and alternative definitions of U.S. cities. Our results highlight the importance to look at issue of the best-fitting distribution together with the truncation …
Rutas cognitivas de futuros maestros ante una situación comparativa de razones desiguales
2019
En esta investigación se analizan las rutas cognitivas que subyacen a las resoluciones de un grupo de futuros maestros ante una tarea de comparación de razones desiguales en el contexto de las ofertas comerciales. La revisión de la literatura y el análisis en profundidad de las componentes críticas de la tarea nos han permitido definir las dimensiones de análisis de las resoluciones. A partir de ellas hemos realizado un análisis cualitativo de corte interpretativo del cual se desprende que los participantes poseen un escaso desarrollo del pensamiento relativo. Un número importante de ellos presenta dificultades con la comparación de las cantidades relativas desiguales cuando estas se les pr…
A New Analysis of the Three-Body Problem
2022
In the recent papers [5, 18], respectively, the existence of motions where the perihelions afford periodic oscillations about certain equilibria and the onset of a topological horseshoe have been proved. Such results have been obtained using, as neighbouring integrable system, the so-called two-centre (or Euler) problem and a suitable canonical setting proposed in [16, 17]. Here we review such results.
Chen’s iterated integral represents the operator product expansion
1999
The recently discovered formalism underlying renormalization theory, the Hopf algebra of rooted trees, allows to generalize Chen’s lemma. In its generalized form it describes the change of a scale in Green functions, and hence relates to the operator product expansion. Hand in hand with this generalization goes the generalization of the ordinary factorial n! to the tree factorial t. Various identities on tree-factorials are derived which clarify the relation between Connes-Moscovici weights and Quantum Field Theory.
A Positive Definite Advection Scheme Obtained by Nonlinear Renormalization of the Advective Fluxes
1989
Abstract A new method is developed to obtain a conservative and positive definite advection scheme that produces only small numerical diffusion. Advective fluxes are computed utilizing the integrated flux form of Tremback et al. These fluxes are normalized and then limited by upper and lower values. The resulting advection equation is numerically solved by means of the usual upstream procedure. The proposed treatment is not restricted to the integrated flux form but may also be applied to other known advection algorithms which are formulated in terms of advective fluxes. Different numerical tests are presented illustrating that the proposed scheme strongly reduces numerical and diffusion an…