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Search Results: 1 - 10 of 199962 matches for " Farias N "
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Reducción de modelos en la presencia de parámetros de perturbación
FARIAS,RAFAEL; MORENO,GERMáN; PATRIOTA,ALEXANDRE;
Revista Colombiana de Estadística , 2009,
Abstract: in many statistical inference problems, there is interest in estimation of only some elements of the parameter vector that defines the adopted model. in general, such elements are associated to measures of location and the additional terms, known as nuisance parameters, to control the dispersion and asymmetry of the underlying distributions. to estimate all the parameters of the model and to draw inferences only on the parameters of interest. depending on the adopted model, this procedure can be both algebraically is common and computationally very costly and thus it is convenient to reduce it, so that it depends only on the parameters of interest. this article reviews estimation methods in the presence of nuisance parameters and consider some applications in models recently discussed in the literature.
REDUCTION OF MODELS IN THE PRESENCE OF NUISANCE PARAMETERS REDUCCIóN DE MODELOS EN LA PRESENCIA DE PARáMETROS DE PERTURBACIóN
Farias Rafael,Moreno Germán,Patriota Alexandre
Revista Colombiana de Estadística , 2009,
Abstract: In many statistical inference problems, there is interest in estimation of only some elements of the parameter vector that defines the adopted model. In general, such elements are associated to measures of location and the additional terms, known as nuisance parameters, to control the dispersion and asymmetry of the underlying distributions. To estimate all the parameters of the model and to draw inferences only on the parameters of interest. Depending on the adopted model, this procedure can be both algebraically is common and computationally very costly and thus it is convenient to reduce it, so that it depends only on the parameters of interest. This article reviews estimation methods in the presence of nuisance parameters and consider some applications in models recently discussed in the literature. En muchos problemas de inferencia estadística existe interés en estimar solamente algunos elementos del vector de parámetros que definen el modelo adoptado. Generalmente, esos elementos están asociados a las medidas de localización, y los parámetros adicionales -que en la mayoría de las veces están en el modelo solo para controlar la dispersión o la asimetría- son conocidos como parámetros de perturbación o de incomodidad (nuisance parameters) de las distribuciones subyacentes. Es común estimar todos los parámetros del modelo y hacer inferencias exclusivamente para los parámetros de interés. Dependiendo del modelo adoptado, este procedimiento puede ser muy costoso, tanto algebraica como computacionalmente, por lo cual conviene reducirlo para que dependa únicamente de los parámetros de interés. En este artículo, hacemos una revisión de los métodos de estimación en la presencia de parámetros de perturbación y consideramos algunas aplicaciones en modelos recientemente discutidos en la literatura.
Innovative technological capability in firms of the tourism sector: a study of the hotels in the city of Rio de Janeiro during the 1990-2008 period Capacidade tecnológica inovadora em empresas do setor turístico: um estudo dos hotéis na cidade do Rio de Janeiro durante o período 1990-2008
Paulo N. Figueiredo,Saulo Gomes,Roberto Farias
Revista de Administra??o Pública , 2010, DOI: 10.1590/s0034-76122010000500007
Abstract: This article presents the preliminary report of the research project entitled "Innovative technological capability in firms of the tourism sector: a study of the hotels in the city of Rio de Janeiro during the 1990-2008 period". The objective of this project is to apply and evaluate an analytical model of technological capability and underlying learning processes and examine the accumulation trajectory of innovative technological capability in the firms of tourism service industry, and the impact of learning processes undertaken by these firms on the technological capability levels achieved during the 1990-2008 period. Este artigo apresenta o relatório preliminar do projeto de pesquisa Capacidade Inovadora em Empresas do Setor Turístico: um Estudo dos Hotéis na Cidade do Rio de Janeiro no Período de 1990-2008, cujo objetivo é aplicar e avaliar um modelo analítico da capacidade tecnológica e dos processos de aprendizagem subjacentes, além de examinar a trajetória de acumula o de capacidades tecnológicas inovadoras nas empresas de turismo e o impacto dos processos de aprendizagem utilizados por essas empresas nos níveis de capacidade tecnológica atingidos no período.
Colloidal Synthesis of Silver Nanoprisms in Aqueous Medium: Influence of Chemical Compounds in UV/Vis Absorption Spectra  [PDF]
Josivandro N. Silva, Jamil Saade, Patricia M. A. Farias, Eduardo Henrique Lago Falc?o
Advances in Nanoparticles (ANP) , 2013, DOI: 10.4236/anp.2013.23030
Abstract:

In this work we explore the influence of the factors that affect the formation of silver nanoprisms (AgNPs) with distinct size and size distribution as well as the most intense absorption peak shift. Box-Behnken design analysis was applied to optimize the production of silver nanoprism via colloidal synthesis. The analysis of the responses was based on the nanoprisms plasmon peak wavelength related to in-plane dipole (tunable band) at λmax. ≥ 420 nm. The obtained results indicate that Silver ion is the main variable for the tuning of the size and the Localized Surface Plasmon Resonance (LSPR) frequency. By using the Box-Behnken design it was possible to synthesize nanoparticles with a predictable size and to establish a rigorous control of the plasmon frequency at the range of 600 up to 800 nm.

Nitrous oxide distribution and its origin in the central and eastern South Pacific Subtropical Gyre
J. Charpentier, L. Farias, N. Yoshida, N. Boontanon,P. Raimbault
Biogeosciences (BG) & Discussions (BGD) , 2007,
Abstract: The mechanisms of microbial nitrous oxide (N2O) production in the ocean have been the subject of many discussions in recent years. New isotopomeric tools can further refine our knowledge of N2O sources in natural environments. This study compares hydrographic, N2O concentration, and N2O isotopic and isotopomeric data from three stations along a coast-perpendicular transect in the South Pacific Ocean, extending from the center (Sts. GYR and EGY) of the subtropical oligotrophic gyre (~26° S; 114° W) to the upwelling zone (St. UPX) off the central Chilean coast (~34° S). Although AOU/N2O and NO3 trends support the idea that most of the N2O (mainly from intermediate water (200–600 m)) comes from nitrification, N2O isotopomeric composition (intramolecular distribution of 15N isotopes) expressed as SP (site preference of 15N) shows low values (10 to 12\permil) that could be attributed to the production through of microbial nitrifier denitrification (reduction of nitrite to N2O mediated by ammonium oxidizers). The coincidence of this SP signal with high – stability layer, where sinking organic particles can accumulate, suggests that N2O could be produced by nitrifier denitrification inside particles. It is postulated that deceleration of particles in the pycnocline can modify the advection - diffusion balance inside particles, allowing the accumulation of nitrite and O2 depletion suitable for nitrifier denitrication. As lateral advection seems to be relatively insignificant in the gyre, in situ nitrifier denitrification could account for 40–50% of the N2O produced in this layer. In contrast, coastal upwelling system is characterized by O2 deficient condition and some N deficit in a eutrophic system. Here, N2O accumulates up to 480% saturation, and isotopic and isotopomer signals show highly complex N2O production processes, which presumably reflect both the effect of nitrification and denitrification at low O2 levels on N2O production, but net N2O consumption by denitrification was not observed.
Nitrous oxide distribution and its origin in the central and eastern South Pacific Subtropical Gyre
J. Charpentier,L. Farias,N. Yoshida,N. Boontanon
Biogeosciences Discussions , 2007,
Abstract: The biogeochemical mechanism of bacterial N2O production in the ocean has been the subject of many discussions in recent years. New isotopomeric tools can help further knowledge on N2O sources in natural environments. This research shows and compares hydrographic, nitrous oxide concentration, and N2O isotopic and isotopomeric data from three stations across the South Pacific Ocean, from the center of the subtropical oligotrophic gyre (~26° S; 114° W) to the upwelling zone along the central Chilean coast (~34° S). Althought AOU/N2O and NO3 trends support the idea that most of N2O source (mainly from intermediate water (200–1000 m)) come from nitrification, N2O isotopomeric composition (intramolecular distribution of 15N isotopes in N2O) reveals an abrupt change in the mechanism of nitrous oxide production, always observed through lower SP (site preference of 15N), at a high – stability layer, where particles could act as microsites and N2O would be produced by nitrifier denitrification (reduction of nitrite to nitrous oxide mediated by primary nitrifiers). There, nitrifier denitrification can account for 40% and 50% (center and east border of the gyre, respectively) of the nitrous oxide produced in this specific layer. This process could be associated with the deceleration of sinking organic particles in highly stable layers of the water column. In constrast, coastal upwelling system is characterized by oxygen deficient condition and some N deficit in a eutrophic system. Here, nitrous oxide accumulates up to 480% saturation, and isotopic and isotopomer signal show highly complex nitrous oxide production processes, which presumably reflect both the effect of nitrification and denitrification at low oxygen levels on N2O production, but non N2O consumption by denitrification was observed.
Determination of the Antiretroviral Drug Zidovudine in Diluted Alkaline Electrolyte by Adsorptive Stripping Voltammetry at the Mercury Film Electrode  [PDF]
Arnaldo Aguiar Castro, Ricardo Queiroz Aucélio, Nicolás Adrián Rey, Eliane Monsores Miguel, Percio Augusto Mardini Farias
American Journal of Analytical Chemistry (AJAC) , 2011, DOI: 10.4236/ajac.2011.22027
Abstract: This paper describes a stripping method for the determination of zidovudine at the submicromolar concentration levels. This method is based on the controlled adsorptive accumulation of zidovudine at the thin-film mercury electrode, followed by a linear-sweep stripping voltammetry measurement of the surface species. Optimal experimental conditions include a NaOH solution of 2.0 × 10–3 mol●L–1 (sup-porting electrolyte), an accumulation potential of –0.30 V and a scan rate of 100 mV?s–1. The response of zidovudine is linear over the concentration range 0.01 - 0.08 ppm. After an accumulation time of 5 minutes, the detection limit was found to be 0.67 ppb (2.5 × 10–9 mol●L–1). More convenient methods to measure zidovudine concentration in the presence of the didanosine, acyclovir, nevirapine, lamivudine, and efavirenz, were also investigated. The presence of zidovudine together with ATP or ssDNA demonstrates the utility of this method.
ELABORACIóN DE una tabla predictiva de diámetro DE MANZANAS cv. gRANNY sMITH USANDO LOS GRADOS DíAS ACUMULADOS
Ortega-Farias,Samuel; Flores,Luis; Lorenzo,León;
Agricultura Técnica , 2002, DOI: 10.4067/S0365-28072002000400014
Abstract: a study was performed in three orchards of san fernando, vi region, chile, in order to develop a predictive table of apple size (malus domestica borkh.) using a logistical equation, whose main variable was accumulated degree days (gda). to this end, data were collected on fruit equatorial diameter and air temperature for the 1989/90 and 1992/93 seasons in three apple orchards cv. granny smith. sampling was carried out from 80 gda until harvest, selecting 5 trees in each orchard, in which 40 fruit/tree were chosen, covering all the size ranges, at a height approximately 1.0 to 2.0 meters about the soil. at harvest, the evaluated fruit was grouped according to four ranges of diameter (63-68, 69-74, 75-80, and 81-86 mm), to develop the logistic growth models as a function of gda. the results of this study indicated that the implemented models were able to estimate apple sizes with a coefficient of determination (r2), absolute error (ea) and standard error of estimate (see) ranging from 0.91 to 0.94; 5.8 and 6.7%; and 3.0 to 3.6 mm, respectively. based on these statistical results a predictive table able to predict apple size as a function of gda was constructed, which presented an ea of 5% starting at 600 gda.
Mielopatias: considera??es clínicas e aspectos etiológicos
Brito, José Correia de Farias;Nóbrega, Paulo Virgolino da;
Arquivos de Neuro-Psiquiatria , 2003, DOI: 10.1590/S0004-282X2003000500021
Abstract: we studied 97 inpatients with myelopathy at the university hospital lauro wanderley from 1985 to 2002. ages ranged from 10 to 78 years and average age was 39.8 years. all patients were examined by neurologist. cerebrospinal fluid (csf) was analysed in 44 (45.3%) cases and immunofluorescence reactions and/or elisa in csf were made in 32 (32.9%) cases. radiologic investigation of the vertebral spine and spinal cord of the 32 (32.9%) cases consisted of 8 radiographies, 10 computed tomography and 14 magnetic resonance image. in 41 (42.2%) cases the lesions were situated in the lower dorsal and lumbar level and complete transverse lesion were registred in 61 (62.8%) cases. there was predominance of transverse myelitis (43.2%) and spinal cord compression (15.46%). spinal cord schistosomiasis was the form more often of the transverse myelitis (13.4%).
Mass transport in spheroids using the Galerkin method
Lima, D. R.;Farias, S. N.;Lima, A. G. B.;
Brazilian Journal of Chemical Engineering , 2004, DOI: 10.1590/S0104-66322004000400016
Abstract: this work presents an analytical modelling of mass transfer in spheroidal solids using a liquid diffusion model. the diffusion equation, written in cylindrical coordinates, is solved using the galerkin method with a constant diffusion coefficient and an equilibrium boundary condition at the surface of the solid. results on the drying kinetics, and moisture content distribution in the solids are presented and analysed. the iso-concentration lines for moisture content show that the drying process is faster in sharp areas,. it was verified that solids with a larger area/volume ratio dry faster. the results obtained are consistent so the model presented can be used to solve diffusion problems such as drying, wetting, heating and cooling of solids with a shape that varies from a circular disk to an infinite cylinder, including a sphere and ellipsoids.
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