Recursos de colección

Universidad Nacional de La Plata (75.687 recursos)

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Mostrando recursos 1 - 20 de 92

  1. Arreglo de antenas orientable electrónicamente: software de control

    Fontana, Mauro
    Se desarrolla en FCAG-UNLP un arreglo de antenas con haz orientable electrónicamente que se empleará como radar de dispersión incoherente para el estudio de la ionósfera. Cada antena cuenta con un desplazador de fase configurable digitalmente, permitiendo obtener un patrón de interferencia que otorga un máximo de ganancia en la dirección deseada. Este trabajo trata sobre el software de control. Los objetivos de este trabajo son -obtener un software de control que, configurando las fases, permita apuntar el sistema utilizando acimut y altura como valores de entrada. Este software deberá, además, dejar sentadas las bases de desarrollo para futuras posibilidades...

  2. Boletín de Noticias de Astronomía, Geofísica y Meteorología

    Facultad de Ciencias Astronómicas y Geofísicas
    Boletín de noticias de la Facultad de Ciencias Astronómicas y Geofísicas de la UNLP. Edición especial por el 132 aniversario del Observatorio de La Plata. Contiene declaraciones de distintas personalidades vinculadas a la facultad y el observatorio, así como una recopilación de noticias en los medios locales.

  3. Ondas gravitacionales de choque

    Ranea Sandoval, Ignacio Francisco
    En este trabajo monográfico se presenta un breve resumen relacionado con las ondas gravitacionales y con la teoría general de la relatividad. Realizado esto se presenta una adaptación de trabajos científicos asociados con un fenómeno conocido como ondas gravitacionales de choque.

  4. La objetividad entre paréntesis en el aula de Física

    Knopoff, Patricia A.
    En el presente trabajo pretendemos hacer una pequeña reseña del pensar del epistemólogo y gnoseólogo chileno Humberto Maturana (1986, 1995, 2002, 2010, 2011) y a partir de ella, y mediante la adscripción a la propuesta didáctica para la enseñanza de la ciencia de Otero (2006), intentaremos realizar una reflexión respecto de la posibilidad de instaurar el camino explicativo de la objetividad entre paréntesis en el aula de Física de la Escuela Media. Haremos una reflexión también a partir del estado de situación actual del trabajo en las aulas de las escuelas públicas de la Provincia, en función de analizar los inconvenientes...

  5. Do crustal deformations observed by GPS in Tierra del Fuego (Argentina) reflect glacial-isostatic adjustment?

    Mendoza, Luciano; Richter, Andreas; Hormaechea, José Luis; Perdomo, Raúl; Del Cogliano, Daniel; Dietrich, Reinhard; Fritsche, Mathias
    Vertical site velocities determined by geodetic GPS observations in the Lago Fagnano area, Tierra del Fuego main island, are interpreted with respect to their potential relation with the glacial-isostatic crustal response to ice mass changes. The spatial pattern of the uplift rates, in combination with the horizontal crustal deformation pattern, point towards a fault-tectonic rather than glacial-isostatic origin of the determined vertical crustal deformations. This implies rather small GIA effects pointing towards relatively small Holocene ice-mass changes in Tierra del Fuego. However, these findings are considered to be preliminary. They should be confirmed by additional observations covering an extended area...

  6. Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

    Sahai, Y.; Becker Guedes, F.; Fagundes, P. R.; Abreu, A. J. de; Jesus, R. de; Pillat, V. G.; Abalde, J. R.; Martinis, C. R.; Brunini, Claudio Antonio; Gende, Mauricio; Huang, C. S.; Pi, X.; Lima, W. L. C.; Bittencourt, J. A.; Otsuka, Y.
    The response of the ionospheric F-region in the South American sector during the super geomagnetic storms on 29 and 30 October 2003 is studied in the present investigation. In this paper, we present ionospheric sounding observations during the period 29-31 October 2003 obtained at Palmas (a near equatorial location) and Sao Jose dos Campos (a location under the southern crest of the equatorial ionospheric anomaly), Brazil, along with observations during the period 27-31 October 2003 from a chain of GPS stations covering the South American sector from Imperatriz, Brazil, to Rio Grande, Argentina. Also, complementary observations that include sequences of...

  7. Ionospheric biases correction for coordinates derived from GPS single point positioning

    Gende, Mauricio; Mohíno Harris, Elsa; Brunini, Claudio Antonio; Radicella, Sandro M.; Herraiz, Miguel
    Most GPS users employ low cost receivers. These receivers do not allow users to record the pseudorange that they observe, but the computed coordinates. This work presents an original and simple method to correct ionospheric biases introduced in GPS signals. The originality of this method is based on the fact that no pseudorange is needed to correct the biases, only the calculated coordinates are used. This distinguishes this method from other classic alternatives. This paper evaluates the efficiency of the method with the use of real data.

  8. Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

    Natali, María Paula; Meza, Amalia
    Annual, semiannual and seasonal variations of the Vertical Total Electron Content (VTEC) have been investigated during high solar activity in 2000. In this work we use Global IGS VTEC maps and Principal Component Analysis to study spatial and temporal ionospheric variability. The behavior of VTEC variations at two-hour periods, at noon and at night is analyzed. Particular characteristics associated with each period and the geomagnetic regions are highlighted. The variations at night are smaller than those obtained at noon. At noon it is possible to see patterns of the seasonal variation at high latitude, and patterns of the semiannual anomaly...

  9. A model assisted ionospheric electron density reconstruction method based on vertical TEC data ingestion

    Nava, Bruno; Coïsson, Pierdavide; Miró Amarante, Gloria; Azpilicueta, Francisco; Radicella, Sandro M.
    A technique to reconstruct the electron density of the ionosphere starting from total electron content values has been developed using the NeQuick ionospheric electron density model driven by its effective ionization parameter Az. The technique is based on the computation of Az values for a suitable worldwide grid of points. A simple way to obtain relevant Az grids is to use global vertical Total Electron Content (TEC) maps to define for each grid point as Az value, the one that minimizes the difference between the experimental and the modeled vertical TEC. Having a global grid of Az values it is...

  10. Lake-level variations of Lago Fagnano, Tierra del Fuego: observations, modelling and interpretation

    Richter, Andreas; Hormaechea, José Luis; Dietrich, Reinhard; Perdomo, Raúl; Fritsche, Mathias; Del Cogliano, Daniel; Liebsch, Gunter; Mendoza, Luciano
    The lake-level variations of Lago Fagnano, the largest lake in Tierra del Fuego, southernmost South America, on time scales from a few minutes to three years are investigated using a geodetic approach and applying the tools of time series analysis. Based on pressure tide gauge records at three locations in the lake precise lake-level time series are derived. The analysis of the observed variations in space, time and frequency domain leads to the separation of the principal force-response mechanisms. We show that the lake-level variations in Lago Fagnano can be described essentially as a combination of lake-level shift and tilt...

  11. Numerical modeling of actual evapotranspiration of a coffee crop

    Cesanelli, Andrés; Guarracino, Luis
    The evapotranspiration estimation has great importance to crop productivity and agricultural water management. In this study, evapotranspiration is analyzed in a coffee (Coffea arabica L.) crop located in Piracicaba, state of São Paulo (Brazil) using a numerical method based on the simulation of both water flow and crop activity in the unsaturated zone of the soil. Actual evapotranspiration is estimated from potential evapotranspiration using water stress functions, meteorological data, soil hydraulic parameters, crop coefficients and leaf area index values. Crop transpiration and soil evaporation are individually quantified improving the analysis of the evapotranspiration process. The numerical procedure can predict periods...

  12. Informe técnico para usuarios de tdaGEOBA

    Perdomo, Raúl; Del Cogliano, Daniel; Mendoza, L.; Gomez, María Eugenia; Bagú, Diego
    Informe técnico sobre los conceptos y herramientas utilizados para la construcción del modelo de transformación de alturas en la Provincia de Buenos Aires, que permite convertir alturas elipsoidales en cotas sobre el nivel medio del mar. Este modelo denominado tdaGEOBA cuenta con una aplicación en forma de calculador en la página geoweb.fcaglp.unlp.edu.ar/tdaGEOBA. A partir de la metodología descripta en el informe y el empleo del calculador de la página es posible obtener cotas sobre el nivel medio del mar a partir de alturas geoidales determinadas con GPS en el marco de la red geodésica GEOBA.

  13. Constraints to Uranus' Great Collision III: The Origin of the Outer Satellites

    Brunini, Adrián; Parisi, M. Gabriela; Tancredi, G.
    The theory of satellite loss resulting from a giant impact on Uranus (Parisi and Brunini 1997, Planet. Space Sci. 45, 181–187) is revisited, in the light of the discovery of its five outer moons (Gladman et al. 1998, Nature 392, 897–899; Gladman et al. 2000, Icarus 147, 320–324; erratum 148, 320). Physical conditions and dynamical constraints in the great collision scenario and restrictions in the possible mechanisms for the origin of the outer uranian satellites are obtained from the knowledge of their actual orbital properties. We conclude that the existence of these moons implies that their origin must be connected...

  14. Testing theories that predict time variation of fundamental constants

    Landau, Susana J.; Vucetich, Héctor
    We consider astronomical and local bounds on the time variation of fundamental constants to test some generic Kaluza-Klein–like models and some particular cases of Beckenstein theory. Bounds on the free parameters of the different theories are obtained. Furthermore, we find that none of the proposed models is able to explain recent results (as from Webb and coworkers in 1999 and 2001) claiming an observed variation of the fine-structure constant from quasar absorption systems at redshifts 0:5 < z < 3.

  15. Supernovae, CMB, and gravitational leakage into extra dimensions

    Deffayet, Cedric; Landau, Susana J.; Raux, Julien; Zaldarriaga, Matías; Astier, Pierre
    We discuss observational constraints coming from CMB and type Ia supernovae, for the model of accelerated universe produced by gravitational leakage into extra dimensions. Our fits indicate that the model is currently in agreement with the data. We also give the equations governing the evolution of cosmological perturbations. Future observations will be able to severely constrain the model.

  16. Revealing the parameters of the open cluster Ruprecht 58

    Giorgi, E.; Vázquez, R. A.; Solivella, G. R.; Orellana, Rosa Beatriz; Núñez, J.
    We present results of a study that combines UBV I photometry, MK spectral classification and proper motions in the area of the, up to now unknown, open cluster Ruprecht 58 at the Puppis region. Star counts from the 2MASS data catalog to- gether with the analysis of CCD UBV I photometry demonstrate that it is a real open cluster with 9' size approximately. The cluster is placed at a distance of 3.9 kpc and is about 250 Myr old with mean reddening E(B-V ) = 0:33 mag. Proper motions con¯rm Ruprecht 58 is a real cluster with mean absolute proper...

  17. On some aspects of the stirring rate of planetesimal velocities by a protoplanet

    Brunini, Adrián; Santamaría, Pablo Javier
    We discuss some aspects of the evolution of the relative velocities of a swarm of planetesimals stirred by a protoplanet. We show that the prescriptions most commonly used in semi-analytical `oligarchic growth' models overestimate the relative velocities of planetesimals by a non-negligible factor. We discuss the probable origin of this discrepancy, proposing a correction factor that provides good agreement between these prescriptions and the results of numerical experiments. The proposed correction factor can be easily implemented in semi-analytical accretion models.

  18. On the number of particles in N-body simulations of planet disk interaction

    Brunini, Adrián; Santamaría, Pablo Javier; Viturro, Héctor; Cionco, Rodolfo Gustavo
    In this paper we present a new mixed-variables symplectic tree code for planetesimal dynamics, which allows to use a very large number of particles in numerical simulations of planet disk interaction. Furthermore, we discuss how a wrong election of the number of particles to model a planetesimal disk, in order to carry out realistic numerical simulations, can cause spurious result. If the particle number is not enough, the close encounter between the planet and unrealistic massive particles will introduce a stochastic component of planet migration. This has an impact on the migration rate and it can even change its sign....

  19. On the number of particles in N-body simulations of planet disk interaction

    Brunini, Adrián; Santamaría, Pablo Javier; Viturro, Héctor; Cionco, Rodolfo Gustavo
    In this paper we present a new mixed-variables symplectic tree code for planetesimal dynamics, which allows to use a very large number of particles in numerical simulations of planet disk interaction. Furthermore, we discuss how a wrong election of the number of particles to model a planetesimal disk, in order to carry out realistic numerical simulations, can cause spurious result. If the particle number is not enough, the close encounter between the planet and unrealistic massive particles will introduce a stochastic component of planet migration. This has an impact on the migration rate and it can even change its sign....

  20. Surface composition of Hilda asteroids from the analysis of the Sloan Digital Sky Survey colors

    Gil-Hutton, R.; Brunini, Adrián
    In this paper we search for photometric data of asteroids in the Hilda region in the Moving Object Catalogue of the Sloan Digital Sky Survey to find the spectral characteristics of small members of this group. We found that the correlation between size and spectral slope previously suggested for Hilda asteroids is correct only for large objects (H<12) but it is not supported by data obtained for the small ones. The best possibility to explain this behavior is that a space weathering process affecting the surface properties of these primitive objects is operating, modulated by a collisional resurfacing process affected...

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