Browsing Facultad de Ciencias Exactas y Naturales by Title
Now showing items 17-36 of 2533
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A mixed virtual element method for the boussinesq problem on polygonal meshes
(Global Science Press, 2021)In this work we introduce and analyze a mixed virtual element method (mixed-VEM) for the two-dimensional stationary Boussinesq problem. The continuous formulation is based on the introduction of a pseudostress tensor ... -
A mixed virtual element method for the Brinkman problem
(Mathematical Models and Methods in Applied Sciences vol.27 no.4 707-743 2017, 2017)In this paper, we introduce and analyze a mixed virtual element method (mixed-VEM) for the two-dimensional Brinkman model of porous media flow with non-homogeneous Dirichlet boundary conditions. More precisely, we employ ... -
A Monte Carlo Study of the Photon Spectrum due to the Different Materials Used in the Construction of Flattening Filters of LINAC
(Hindawi, 2017-07-10)Different types the spectrum of photons were studied; they were emitted from the flattening filter of a LINAC Varian 2100 C/D that operates at 15 MV. The simplified geometry of the LINAC head was calculated using the MCNPX ... -
A new Costa Rican species of Drosophila visiting inflorescences of the hemi-epiphytic climber Monstera lentii (Araceae)
(Universidad Nacional, Costa Rica, 2018-09)Drosophila monsterae sp. nov. is described from 11 males and 13 females collected from the inside of closed inflorescences of Monstera lentii (Araceae) at 1810 m altitude in the Forest Reserve of Cerro de La Carpintera, ... -
A new giant species of placented worm and the mechanism by which onychophorans weave their nets (Onychophora: Peripatidae)
(Universidad de Costa Rica, 2010)Onychophorans, or velvet worms, are poorly known and rare animals. Here we report the discovery of a new species that is also the largest onychophoran found so far, a 22cm long female from the Caribbean coastal forest of ... -
A new giant velvet worm from Costa Rica suggests absence of the genus Peripatus (Onychophora: Peripatidae) in Central Americ
(Universidad de Costa Rica, 2020-02-03)Introduction: Neotropical onychophoran taxonomy and diversity has been poorly investigated. Recent studies have discovered problems in species classification: they have questioned the accepted genera and the actual number ... -
A New Hybrid of Serpocaulon (Polypodiaceae) from Costa Rica
(Bio One Research Evolved, 2013)A new hybrid Serpocaulon 3 sessilipinnum A. Rojas & J.M. Chaves is described. The new taxon has characters intermediate between S. fraxinifolium (Jacq.) A.R. Sm. and S. ptilorhizon (Christ) A.R. Sm., which are related ... -
A new species of Elaphoglossum Schott ex J. Sm. (Dryopteridaceae) from Costa Rica
(Universidad Nacional (Costa Rica), 2017-12)Una especie nueva de Elaphoglossum Schott ex J.Sm. Dryopteridaceae) para Costa Rica.Una especie nueva de ElaphoglossumSchott ex J. Smde la sección UndulataChrist es descrita aquí: Elaphoglossum pallidosquamum A. Rojas & ... -
A new species of Seticeros from Costa Rica (Coleoptera, Cerambycidae, Prioninae)
(Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), 2011)A new species of Seticeros Perger & Santos-Silva, 2010 (Prioninae: Callipogonini) from San Isidro del General, San José, Costa Rica is described and illustrated. A key to the species of Seticeros is added. -
A new vanilla species from Costa Rica closely related to V. planifolia (Orchidaceae)
(European Journal of Taxonomy, 2017-02-22)We describe a new vanilla species growing in sympatry with Vanilla planifolia Jacks. ex Andrews (Orchidaceae) in the province of Limón, Caribbean coast of Costa Rica. The morphology of the reproductive and vegetative organs ... -
A novel host-adapted strain of SalmonellaTyphimurium causes renal disease in olive ridley turtles (Lepidochelys olivacea) in the Pacifc
(Springer Nature, 2019-06)Salmonella spp. are frequently shed by wildlife including turtles, but S. enterica subsp. enterica serovar Typhimurium or lesions associated with Salmonella are rare in turtles. Between 1996 and 2016, we necropsied 127 ... -
A posteriori error analysis of a mixed virtual element method for a nonlinear Brinkman model of porous media flow
(Elsevier Ltd, 2020-06-25)In this paper we present an a posteriori error analysis of a mixed-VEM discretization for a nonlinear Brinkman model of porous media flow, which has been proposed by the authors in a previous work. Therein, the system ... -
A preliminary isotope-based evapotranspiration partitioningapproach for tropical Costa Rica
(John Wiley and Sons Ltd, 2021-07)Spatially and seasonally distributed information on transpiration (T) fluxes is limited in the tropics. Here, we applied a coupled isotope mass balance model to separate water fluxes of T and evapotranspiration (ET) from ... -
A preliminary market research about tambaqui (Colossoma macropomum) in Costa Rica
(Universidad Nacional (Costa Rica), 1996)En los meses de enero a julio de 1995 se desarrolló una prueba de mercado con el pez de agua dulce “Tambaqui” (Colossoma macropomum) en Costa Rica. Unos 1200 peces de aproximadamente 800g peso promedio se obtuvieron de la ... -
A priori and a posteriori error analyses of a pseudostress-based mixed formulation for linear elasticity
(Computers and Mathematics with Applications vol.71 no.2 585-614 2016, 2016-01-02)In this paper we present the a priori and a posteriori error analyses of a non-standard mixed finite element method for the linear elasticity problem with non-homogeneous Dirichlet boundary conditions. More precisely, the ... -
A Priori and a Posteriori Error Analyses of an Augmented HDG Method for a Class of Quasi-Newtonian Stokes Flows
(Springer, 2016-12)In a recent work we developed a new hybridizable discontinuous Galerkin (HDG) method for a class of nonlinear Stokes models arising in quasi-Newtonian fluids. The approach there uses the incompressibility condition to ... -
A priori and a posteriori error analyses of an HDG method for the Brinkman problem
(Elsevier, 2018-01-15)In this paper we introduce and analyze a hybridizable discontinuous Galerkin (HDG) method for the linear Brinkman model of porous media flow in two and three dimensions and with non-homogeneous Dirichlet boundary conditions. ... -
A proposal for implementing PBL in programming courses
(XL Latin American Computing Conference, CLEI 2014, 2014)In the search of teaching strategies more consistent with the current needs of the industry and with the new university pedagogical model, an action research project was carried in the programming courses of the study ... -
A proposed solution to the species problem in velvet worm conservation (Onychophora)
(Universidad Estatal a Distancia, 2018)Onychophorans or velvet worm are the only phylum without extant marine species and the only invertebrates with a true placenta, but most species are rare and thus more likely to become extinct. A key obstacle for ... -
A RTk - P-k approximation for linear elasticity yielding a broken H(div) convergent postprocessed stress
(Universidad Nacional, Costa Rica, 2015)We present a non-standard mixed finite element method for the linear elasticity problem in R-n with non-homogeneous Dirichlet boundary conditions. More precisely, our approach is based on a simplified interpretation of the ...