1,216 research outputs found
Raviart Thomas Petrov-Galerkin Finite Elements
The general theory of Babu\v{s}ka ensures necessary and sufficient conditions
for a mixed problem in classical or Petrov-Galerkin form to be well posed in
the sense of Hadamard. Moreover, the mixed method of Raviart-Thomas with
low-level elements can be interpreted as a finite volume method with a
non-local gradient. In this contribution, we propose a variant of type
Petrov-Galerkin to ensure a local computation of the gradient at the interfaces
of the elements. The in-depth study of stability leads to a specific choice of
the test functions. With this choice, we show on the one hand that the mixed
Petrov-Galerkin obtained is identical to the finite volumes scheme "volumes
finis \`a 4 points" ("VF4") of Faille, Gallo\"uet and Herbin and to the
condensation of mass approach developed by Baranger, Maitre and Oudin. On the
other hand, we show the stability via an inf-sup condition and finally the
convergence with the usual methods of mixed finite elements.Comment: arXiv admin note: text overlap with arXiv:1710.0439
Local time steps for a finite volume scheme
We present a strategy for solving time-dependent problems on grids with local
refinements in time using different time steps in different regions of space.
We discuss and analyze two conservative approximations based on finite volume
with piecewise constant projections and domain decomposition techniques. Next
we present an iterative method for solving the composite-grid system that
reduces to solution of standard problems with standard time stepping on the
coarse and fine grids. At every step of the algorithm, conservativity is
ensured. Finally, numerical results illustrate the accuracy of the proposed
methods
Comparison of Demosaicking Methods for Color Information Extraction
Most digital color cameras are based on a single CCD or CMOS sensor combined with a color filter array (CFA): each pixel measures only one of the RGB colors. The most popular CFA is the Bayer CFA (Bayer, 1976) shown in fig. 1. Demosaicking algorithms interpolat
DĂ©couverte remarquable dans une grotte du sud-ouest du Maroc : Siagona taggadertensis n.sp. (Carabidae : Siagoninae)
[EN] Five species of the genus Siagona Latreille 1804 (Carabidae: Siagoninae) are known from Morocco. Siagona taggadertensis n. sp., a remarkable species of Carabidae from a Moroccan cave is described. This insect is spectacular by its large size (one of the largest species of the genus), its
external morphology, which isolates it from all the north african representant of the genus, and for the conditions of its discovery: its only known from the remains of six specimens, all of them found in the
cave of Taggadert, western Atlas. Hypotheses concerning the ecology of this species are discussed.[FR] Le genre Siagona Latreille 1804 (Carabidae: Siagoninae), compte 5 espèces au Maroc. Siagona taggadertensis n. sp., remarquable espèce collectée dans une grotte marocaine est décrite. Cet insecte est spectaculaire tant par sa grande taille, sa morphologie externe qui l’isole au premier coup d’oeil des représentants nord africains du genre Siagona, que par les conditions de sa découverte : aucun des spécimens n’ont été collectés en dehors de la grotte de Taggadert, Atlas occidental. Des hypothèses concernant l’écologie de cette espèce sont fournies.AF was supported by a postdoctoral Research
Fellowship from the Alexander von Humboldt Foundation.Peer reviewe
ANTITRUST LAW—PRICE FIXING—RULE OF REASON IN HEALTH CARE—Arizona v. Maricopa County Medical Society, [1980-1] Trade Cases (CCH) ¶ 63,239 (9th Cir. March 20, 1980)
ANTITRUST LAW—PRICE FIXING—RULE OF REASON IN HEALTH CARE—Arizona v. Maricopa County Medical Society, [1980-1] Trade Cases (CCH) ¶ 63,239 (9th Cir. March 20, 1980)
A new microphthalmic stygobitic Graptodytes Seidlitz from Morocco, with a molecular phylogeny of the genus (Coleoptera, Dytiscidae)
14 páginas, 13 figuras, 2 tablas.-- Articulo Open Access.We describe Graptodytes eremitus n.sp. (Coleoptera, Dytiscidae), a depigmented, microphthalmic stygobitic species found in a pool in the deep area of a cave in the High Atlas of Morocco. To establish its phylogenetic position we inferred a molecular phylogeny of the genus Graptodytes Seidlitz, using ca. 1.7 Kb of four mitochondrial genes for 18 of the 23 previously known species and subspecies of the genus. Graptodytes can be separated in three well supported main lineages, 1) the G. flavipes lineage (apex of median lobe narrow in ventral view), 2) the G. granularis lineage (apex of median lobe expanded and strongly asymmetrical in ventral view), and 3) the G. varius lineage (apex of median lobe expanded but symmetrical in ventral view). The G. varius lineage includes the G. aequalis and G. varius groups, the latter including G. eremitus n.sp. as sister to G. delectus Wollaston (Canary Islands) plus the G. varius complex. A molecular clock approach, using a calibration rate of 2.3% divergence/MY for the combined mitochondrial sequence, estimated the origin of the diversification within the genus at ca. 7MY (late Miocene), and the origin of G. eremitus n.sp. at ca. 2 MY (Pliocene-Pleistocene boundary).This work was partly funded with projects CGL2004-00028 and CGL2007-61665 to IR.Peer reviewe
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