Search results for "Divergence"
showing 10 items of 257 documents
Toward a Phylogenetic Classification of the Lauraceae: Evidence from matK Sequences
2000
Abstract The larger part of the matK gene and the (3′−) adjacent spacer have been sequenced and used for phylogenetic analyses in 48 species of Lauraceae from all parts of their geographical range, and in three outgroup taxa. Except for the aberrant genera Hypodaphnis and Cassytha, the genetic divergence within the family is surprisingly low. In spite of this, several clades receive sufficient support to change our current concepts of relationships within the family. Particularly well supported is a Beilschmiedia–Cryptocarya clade that had been recognized by wood anatomy, but not in most of the recent morphological systems. The separation between taxa with involucrate and non-involucrate in…
Overland flow generation on hillslopes of complex topography: analytical Solutions
2007
The analytical solution of the overland flow equations developed by Agnese et al. (2001; Hydrological Processes15: 3225–3238) for rectangular straight hillslopes was extended to convergent and divergent surfaces and to concave and convex profiles. Towards this aim, the conical convergent and divergent surfaces are approximated by a trapezoidal shape, and the overland flow is assumed to be always one-dimensional. A simple ‘shape factor’ accounting for both planform geometry and profile shape was introduced: for each planform geometry, a brachistochrone profile was obtained by minimizing a functional containing a slope function of the profile. Minima shape factors are associated with brachist…
Reduced Reference Mesh Visual Quality Assessment Based on Convolutional Neural Network
2018
3D meshes are usually affected by various visual distortions during their transmission and geometric processing. In this paper we propose a reduced reference method for mesh visual quality assessment. The method compares features extracted from the distorted mesh and the original one using a convolutional neural network in order to estimate the visual quality score. The perceptual distance between two meshes is computed as the Kullback-Leibler divergence between the two sets of feature vectors. Experimental results from two subjective databases (LIRIS masking database and LIRIS/EPFL general purpose database) and comparisons with seven objective metrics cited in the state-of-the-art demonstr…
A statistical model for magnitudes and angles of wavelet frame coefficients and its application to texture retrieval
2014
Abstract This paper presents a texture descriptor based on wavelet frame transforms. At each position in the image, and for each resolution level, we consider both vertical and horizontal wavelet detail coefficients as the components of a bivariate random vector. The magnitudes and angles of these vectors are computed. At each level the empirical histogram of magnitudes is modeled by a Generalized Gamma distribution, and the empirical histogram of angles is modeled by a different version of the von Mises distribution that accounts for histograms with 2 modes. Each texture is characterized by few parameters. A new distance is presented (based on the Kullback–Leibler divergence) that allows g…
Computable majorants of the limit load in Hencky’s plasticity problems
2018
Abstract We propose a new method for analyzing the limit (safe) load of elastoplastic media governed by the Hencky plasticity law and deduce fully computable bounds of this load. The main idea of the method is based on a combination of kinematic approach and new estimates of the distance to the set of divergence free fields. We show that two sided bounds of the limit load are sharp and the computational efficiency of the method is confirmed by numerical experiments.
Probabilistic Logic under Coherence: Complexity and Algorithms
2005
In previous work [V. Biazzo, A. Gilio, T. Lukasiewicz and G. Sanfilippo, Probabilistic logic under coherence, model-theoretic probabilistic logic, and default reasoning in System P, Journal of Applied Non-Classical Logics 12(2) (2002) 189---213.], we have explored the relationship between probabilistic reasoning under coherence and model-theoretic probabilistic reasoning. In particular, we have shown that the notions of g-coherence and of g-coherent entailment in probabilistic reasoning under coherence can be expressed by combining notions in model-theoretic probabilistic reasoning with concepts from default reasoning. In this paper, we continue this line of research. Based on the above sem…
A new look at global growth convergence and divergence
2014
A key question in economics is whether poor countries will automatically close the income gap with rich countries. However, different empirical methods yield different answers – growth regressions suggest convergence, whereas tests of distribution dynamics suggest divergence. This column discusses recent research that reconciles these two strands of the literature. It extends the benchmark growth regression model to include a parameter that determines the share of new technologies a country can adopt each year. The result is that, although each country converges to a growth path, the growth paths themselves may diverge
La citoyenneté à l’épreuve des divergences sociales et spatiales
2017
International audience
Evolution of Complex Acoustic Signals in Drosophila Species
2009
species produce complex acous-tic cues, so-called courtship songs, while pursuing a female.In most of the over 100 species studied so far (see thelist of these species in Hoikkala, 2005), such cues areproduced by wing vibration. Other mechanisms of songproduction include abdomen purring (Hoy, Hoikkala, &Kaneshiro, 1988) and rapid vibrations of the whole body(Ritchie & Gleason, 1995). The carrier frequency of songsproduced through any of these actions ranges from 150 to500Hz. A hitherto unknown mechanism enables males ofsome Hawaiian species to generate songs of up to 15,000Hz(Hoikkala, Hoy, & Kaneshiro, 1989).The structure of the courtship songs of closely relatedspecies often reflects phylo…
Allozyme variation in populations of scallops, Pecten jacobaeus (L.) and P. maximus (L.) (Bivalvia: Pectinidae), across the Almeria–Oran front
2002
Abstract The scallops Pecten jacobaeus and P. maximus have been traditionally considered as different species which shared a common ancestor some 5 Ma ago. This view has been challenged by recent reports of genetic distances based on allozymes and mitochondrial DNA which are incompatible with such a long period of isolation and are more typical of conspecific populations. To explain the slight allozyme differentiation opposed to a clear morphological distinctiveness, two main hypotheses have been proposed. One hypothesis views interpopulation allozyme differentiation as an outcome of simple population genetic processes such isolation by distance. The other considers that the intertaxa alloz…