Redes neurais e análise estatística para classificação de mapas topográficos da córnea baseados em coeficientes de Zernike: uma comparação quantitativa

PURPOSE: The main goal of this study was to develop and compare two different techniques for classification of specific types of corneal shapes when Zernike coefficients are used as inputs. A feed-forward artificial Neural Network (NN) and discriminant analysis (DA) techniques were used. METHODS: The inputs both for the NN and DA were the first 15 standard Zernike coefficients for 80 previously classified corneal elevation data files from an Eyesys System 2000 Videokeratograph (VK), installed at the Departamento de Oftalmologia of the Escola Paulista de Medicina, São Paulo. The NN had 5 output neurons which were associated with 5 typical corneal shapes: keratoconus, with-the-rule astigmatism, against-the-rule astigmatism, "regular" or "normal" shape and post-PRK. RESULTS: The NN and DA responses were statistically analyzed in terms of precision ([true positive+true negative]/total number of cases). Mean overall results for all cases for the NN and DA techniques were, respectively, 94% and 84.8%. CONCLUSION: Although we used a relatively small database, results obtained in the present study indicate that Zernike polynomials as descriptors of corneal shape may be a reliable parameter as input data for diagnostic automation of VK maps, using either NN or DA.OBJETIVOS: Nosso principal objetivo neste trabalho foi de desenvolver e comparar duas técnicas diferentes para classificação de superfícies corneanas. Uma rede neural artificial alimentada adiante e análise descriminante foram as técnicas de classificação comparadas neste trabalho. MÉTODOS: As entradas para ambos os métodos de classificação foram os primeiros 15 coeficientes de Zernike para 80 córneas mensuradas anteriormente em um topógrafo Eyesys instalado no Departamento de Oftalmologia da Escola Paulista de Medicina - UNIFESP. A rede neural tem 5 saídas que foram associados aos cinco casos típicos contidos na base de dados: ceratocone, astigmatismo a favor da regra, astigmatismo contra a regra, formato "regular" ou "normal" e pós-PRK. RESULTADOS: Os resultados de ambos os métodos foram estatisticamente analisados em termos de precisão. Os resultados gerais para ambos os métodos de redes neurais e análise discriminante foram 94% e 84,8%, respectivamente. CONCLUSÃO: Embora tenha-se utilizado uma base de dados relativamente pequena, os resultados obtidos aqui indicam que os polinômios de Zernike podem ser um parâmetro de entrada para classificação de diferentes formatos de córnea, tanto para uso com redes neurais ou análise discriminante

Teses equivocadas no debate sobre desindustrialização e perda de competitividade da indústria brasileira

O presente artigo tem por objetivo apresentar as teses da ortodoxia sobre a desindustrialização da economia brasileira, apontando a razão pela qual as mesmas são equivocadas. Como iremos argumentar ao longo deste artigo, a desindustrialização brasileira não é uma decorrência natural do processo de desenvolvimento, sendo de natureza precoce e causada, sobretudo, pela apreciação cambial decorrente da valorização dos termos de troca observada nos últimos anos. Além disso, a desindustrialização não é um fenômeno irrelevante sobre o desenvolvimento da economia brasileira no médio e longo-prazo, uma vez que a indústria não é um setor como outro qualquer, mas é o setor onde se observam os maiores níveis da produtividade do trabalho

Gaia's Cepheids and RR Lyrae Stars and Luminosity Calibrations Based on Tycho-Gaia Astrometric Solution

Gaia Data Release 1 contains parallaxes for more than 700 Galactic Cepheids and RR Lyrae stars, computed as part of the Tycho-Gaia Astrometric Solution (TGAS). We have used TGAS parallaxes, along with literature ($V, I, J, {K_\mathrm{s}}, W_1$) photometry and spectroscopy, to calibrate the zero point of the Period-Luminosity and Period-Wesenheit relations of classical and type II Cepheids, and the near-infrared Period-Luminosity, Period-Luminosity-Metallicity and optical Luminosity-Metallicity relations of RR Lyrae stars. In this contribution we briefly summarise results obtained by fitting these basic relations adopting different techniques that operate either in parallax or distance (absolute magnitude) space.Comment: 5 pages, 4 figures, proceedings for the 22nd Los Alamos Stellar Pulsation Conference Series Meeting "Wide field variability surveys: a 21st-century perspective", held in San Pedro de Atacama, Chile, Nov. 28 - Dec. 2, 201

Episodic Random Accretion and the Cosmological Evolution of Supermassive Black Hole Spins

The growth of supermassive black holes (BHs) located at the centers of their host galaxies comes mainly from accretion of gas, but how to fuel them remains an outstanding unsolved problem in quasar evolution. This issue can be elucidated by quantifying the radiative efficiency parameter ($\eta$) as a function of redshift, which also provides constraints on the average spin of the BHs and its possible evolution with time. We derive a formalism to link $\eta$ with the luminosity density, BH mass density, and duty cycle of quasars, quantities we can estimate from existing quasar and galaxy survey data. We find that $\eta$ has a strong cosmological evolution: at z~2, $\eta \approx 0.3$, and by $z\approx 0$ it has decreased by an order of magnitude, to $\eta\approx 0.03$. We interpret this trend as evolution in BH spin, and we appeal to episodic, random accretion as the mechanism for reducing the spin. The observation that the fraction of radio-loud quasars decreases with increasing redshift is inconsistent with the popular notion that BH spin is a critical factor for generating strong radio jets. In agreement with previous studies, we show that the derived history of BH accretion closely follows the cosmic history of star formation, consistent with other evidence that BHs and their host galaxies coevolve.Comment: 4 page, 2 color figures. Accepted by ApJ

Análisis de concentración del mercado de seguros en Costa Rica del año 2010 al 2014

Proyecto de graduación (Licenciatura en Administración de Empresas. Enfasis en Finanzas) Instituto Tecnológico de Costa Rica, Escuela de Administración de Empresas, 2015Aborda el tema de análisis de concentración del mercado de seguros en Costa Rica del año 2010 al 2014, tratando de medir la concentración de participación del mercado de empresas aseguradoras por parte de la Superintendencia General de Seguros en Costa Rica, para así conocer el estado real del mercado. Para dicho análisis se realiza el estudio de cada una de las aseguradoras presentes en el mercado costarricense y de la teoría sobre seguros y su mercado. El tipo de investigación desarrollado es exploratorio ya que se desea examinar el grado de concentración del mercado de seguros costarricense, él cual está teniendo un cambio debido a que los consumidores además de asegurar casas y autos, están asegurando la salud y ponen más atención a la responsabilidad civil, demostrando una mayor madurez en el mercado local

Estimating Black Hole Masses in Active Galactic Nuclei Using the MgII 2800 Emission Line

We investigate the relationship between the linewidths of broad Mg II \lambda2800 and Hbeta in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archival ultraviolet spectra for nearby sources monitored with reverberation mapping. Careful attention is devoted to accurate spectral decomposition, especially in the treatment of narrow-line blending and Fe II contamination. We show that, contrary to popular belief, the velocity width of Mg II tends to be smaller than that of Hbeta, suggesting that the two species are not cospatial in the broad-line region. Using these findings and recently updated BH mass measurements from reverberation mapping, we present a new calibration of the empirical prescriptions for estimating virial BH masses for AGNs using the broad Mg II and Hbeta lines. We show that the BH masses derived from our new formalisms show subtle but important differences compared to some of the mass estimators currently used in the literature.Comment: Matches version to appear in ApJ, preliminarily 706:1-13, 2009; a minor error corrected (in Table 2 only

Herramientas para la implementación del SIG en organización del sector productivo primario dedicada a la Conservación Ambiental y Forestal

El documento describe el posible diseño de un Sistema Integrado de Gestión (SIG) bajo los requerimientos de las Normas Técnicas NTC ISO 9001:2015, NTC ISO 14001:2015 y NTC ISO 45001:2018., para ser implementados en la compañía prestadora de servicios ambientales y forestales de carácter privado en el sector económico primario. Sus servicios se relacionan con la gestión y asesorías para tramitar estudios de impacto ambientales y licencias ambientales solicitada por nuestros clientes potenciales en proyectos de construcción y comercialización de bienes y servicios, requeridos por la autoridad ambiental municipales y departamentales en valle del cauca DAGMA y CVC. Este diseño se desarrolló mediante el análisis de los documentos aportados por la compañía que posee en la actualidad para ejecutar sus actividades en los diferentes puntos de trabajo internos y externos, se inició con un primer diagnóstico de la situación empresarial en cuanto a organización, riesgos y demás requerimientos según la norma vigente, con esta información obtenida se estructuro este diseño para aplicarlo y aceptado. La propuesta generada, de manera resumida, aporta acciones para mejorar en el cumplimiento delas actividades y las necesidades de la compañía bajo las normas integradas de calidad, medio ambiente, salud y seguridad en el trabajo que incluyen los modelos de análisis PESTEL, mapa de riesgos VESTEL, Ciclo PHVA, Mapa de jerarquías y de procesos, entre otros, que buscan avanzar en la mejora continua de la compañía para la satisfacción de los clientes de manera objetiva y eficaz.The document describes the possible design of an Integrated Management System (SIG) under the requirements of the Technical Standards NTC ISO 9001:2015, NTC ISO 14001:2015 and NTC ISO 45001:2018, to be implemented in the service provider company. environmental and forestry activities of a private nature in the primary economic sector. Its services are related to the management and advice to process environmental impact studies and environmental licenses requested by our potential clients in construction projects and marketing of goods and services, required by the municipal and departmental environmental authority in Valle del Cauca DAGMA and CVC. This design was developed through the analysis of the documents provided by the company that it currently has to carry out its activities in the different internal and external work points, it began with a first diagnosis of the business situation in terms of organization, risks and Other requirements according to the current standard, with this information obtained, this design was structured to apply it and accepted. The generated proposal, in summary, provides actions to improve compliance with the activities and needs of the company under the integrated standards of quality, environment, health and safety at work that include the PESTEL analysis models, risk map VESTEL, PHVA Cycle, Map of hierarchies and processes, among others, which seek to advance in the continuous improvement of the company for customer satisfaction in an objective and effective manner