Breve enunciación de los estudios hidrológicos, especialmente en lo referente a hidrogeología, en la provincia de Buenos Aires (Argentina)

En esta comunicación se hace una sucinta referencia a los estudios hidrogeológicos principales más recientes, y a los que se encuentran en ejecución dentro del ámbito de la Provincia de Buenos Aires (Argentina). Se intenta subdividir su territorio en regiones hidrogeológicas con características climáticas, geomorfológicas e hidrológicas más o menos semejantes.In his short paper, a brief reference is made to the more receno, principal hydrogeologic studies in development inside the Buenos Aires Province (Argentina). There is likewise an attempt on subdividing the area in hydrologic regions, under more or less similar climatic, geomorphologic and hydrologic characteristic

Advanced Exergy Analysis in the Dynamic Framework for Assessing Building Thermal Systems

This work applies the Dynamic Advanced Exergy Analysis (DAEA) to a heating and domestic hot water (DHW) facility supplied by a Stirling engine and a condensing boiler. For the first time, an advanced exergy analysis using dynamic conditions is applied to a building energy system. DAEA provides insights on the components’ exergy destruction (ED) by distinguishing the inefficiencies that can be prevented by improving the quality (avoidable ED) and the ones constrained because of technical limitations (unavoidable ED). ED is related to the inherent inefficiencies of the considered element (endogenous ED) and those coming from the interconnections (exogenous ED). That information cannot be obtained by any other approach. A dynamic calculation within the experimental facility has been performed after a component characterization driven by a new grey-box modelling technique, through TRNSYS and MATLAB. Novel solutions and terms of ED are assessed for the rational implementation of the DAEA in building energy installations. The influence of each component and their interconnections are valuated in terms of exergy destruction for further diagnosis and optimization purposes.BMWi, 03ET1218B, Anwendung exergiebasierter Methoden zur Verbesserung von Gebäudeenergiesysteme

Investigación hidrológica de la Cuenca del Arroyo Azul, provincia de Buenos Aires

El presente trabajo que se pudo llevar adelante mediante un subsidio de la CIC y el apoyo logístico de la Municipalidad de Azul, se originó a partir de los problemas provocados por las inundaciones en la ciudad de Azul en Abril de 1980. Por no ser las inundaciones un problema aislado dentro del ciclo hidrológico, por la importancia vital del recurso hídrico y por los efectos secundarios que pueden tener las obras, se abarca una temática más amplia que la sintética, que errónea y desprevenidamente puede suponerse como suficiente. El primer capítulo es introductorio e incluye la metodología desarrollada y las técnicas empleadas, adaptadas a las condiciones naturales y antrópicas de la región así como a la realidad de los datos antecedentes y a los logrados en las observaciones de campo en el corto tiempo disponible. En el segundo capítulo, en base a la sistematización, valoración, análisis e interpretación de la información, se efectúa una amplia caracterización hidrológica en la Cuenca del Arroyo Azul y sus aledaños, pero con las limitaciones lógicas a estos estudios, que deben ser permanentes y efectuarse en e- tapas de sucesivas aproximaciones. Por último, el tercer capítulo, fundamentado en los anteriores, abarca aspectos aplicados y se delinean en él soluciones tentativas a través del manejo del recurso hídrico, que consiste en: I) Obras de retardo y regulación de crecidas. II) Operaciones de limpieza y mantenimiento del cauce. III) Delineamiento de un sistema de pronóstico preventivo a bajo costo y relativa fácil operatividad. Como no puede ser de otra forma, tratándose problemas de los recursos hídricos, se establecen además bases generales para prevenir y regular los problemas a mediato y largo plazo. Las pautas se resumen en la complementación de una política de manejo basado en el uso conjuntivo intensivo, lo cual se sustenta en: I) Estudios de control y aproximaciones sucesivas. II) Complementación de redes de mediciones hidrométricas.Digitalizado en SEDICI-CIC Digita

The supersoft X-ray source in V5116 Sgr I. The high resolution spectra

Classical novae occur on the surface of an accreting white dwarf in a binary system. After ejection of a fraction of the envelope and when the expanding shell becomes optically thin to X-rays, a bright source of supersoft X-rays arises, powered by residual H burning on the surface of the white dwarf. While the general picture of the nova event is well established, the details and balance of accretion and ejection processes in classical novae are still full of unknowns. The long-term balance of accreted matter is of special interest for massive accreting white dwarfs, which may be promising supernova Ia progenitor candidates. V5116 Sgr was observed as a bright and variable supersoft X-ray source by XMM-Newton 610~days after outburst. The light curve showed a periodicity consistent with the orbital period. During one third of the orbit the luminosity was a factor of seven brighter than during the other two thirds of the orbital period. In the present work we aim to disentangle the X-ray spectral components of V5116 Sgr and their variability. We present the high resolution spectra obtained with XMM-Newton RGS and Chandra LETGS/HRC-S in March and August 2007. The grating spectrum during the periods of high-flux shows a typical hot white dwarf atmosphere dominated by absorption lines of N VI and N VII. During the low-flux periods, the spectrum is dominated by an atmosphere with the same temperature as during the high-flux period, but with several emission features superimposed. Some of the emission lines are well modeled with an optically thin plasma in collisional equilibrium, rich in C and N, which also explains some excess in the spectra of the high-flux period. No velocity shifts are observed in the absorption lines, with an upper limit set by the spectral resolution of 500 km/s, consistent with the expectation of a non-expanding atmosphere so late in the evolution of the post-nova.Comment: 12 pages, 15 figures, 4 tables; accepted for publication in Astronomy and Astrophysic

Biozones of Patagonia (Argentina)

We present a classification of Patagonian ecosystems based on functional attributes derived from the seasonal curves of Normalized Difference Vegetation Index (NDVI), calculated from spectral data provided by the NOAA/AVHRR satellites. The attributes used were the annual integral, the relative range of NDVI, and the date of maximum NOW. These attributes capture critical aspects of the seasonal dynamics of carbon gains and allow for a good description of the spatial heterogeneity of ecosystem function in temperate areas. Our analysis defined 12 biozones that capture current ecosystem functioning. The units defined showed a good agreement with previously defined phytogeographical provinces. Mapping biozones based on attributes derived from satellite data does not require assumptions on the relationship between vegetation units and environmental features. This reduces the errors associated to the lack of correlation between the vegetation and environmental features

Asymptotic Expansions of Jacobi Polynomials for Large Values of Beta

Asymptotic approximations of Jacobi polynomials are given for large values of the Beta-parameter and of their zeros. The expansions are given in terms of Laguerre polynomials and of their zeros. The levels of accuracy of the approximations are verified by numerical examples.This work was supported by Ministerio de Econom a y Competitividad, project MTM2015-67142-P (MINECO/FEDER, UE). NMT thanks CWI, Amsterdam, for scienti c support

On the computation and inversion of the cumulative noncentral beta distribution function

The computation and inversion of the noncentral beta distribution Bp,q(x, y) (or the noncentral F-distribution, a particular case of Bp,q(x, y)) play an important role in different applications. In this paper we study the stability of recursions satisfied by Bp,q(x, y) and its complementary function and describe asymptotic expansions useful for computing the function when the parameters are large. We also consider the inversion problem of finding x or y when a value of Bp,q(x, y) is given. We provide approximations to x and y which can be used as starting values of methods for solving nonlinear equations (such as Newton) if higher accuracy is needed

Fast, reliable and unrestricted iterative computation of Gauss-Hermite and Gauss-Laguerre quadratures

Methods for the computation of classical Gaussian quadrature rules are described which are effective both for small and large degree. These methods are reliable because the iterative computation of the nodes has guaranteed convergence, and they are fast due to their fourth-order convergence and its asymptotic exactness for an appropriate selection of the variables. For Gauss?Hermite and Gauss?Laguerre quadratures, local Taylor series can be used for computing efficiently the orthogonal polynomials involved, with exact initial values for the Hermite case and first values computed with a continued fraction for the Laguerre case. The resulting algorithms have almost unrestricted validity with respect to the parameters. Full relative precision is reached for the Hermite nodes, without any accuracy loss and for any degree, and a mild accuracy loss occurs for the Hermite and Laguerre weights as well as for the Laguerre nodes. These fast methods are exclusively based on convergent processes, which, together with the high order of convergence of the underlying iterative method, makes them particularly useful for high accuracy computations. We show examples of very high accuracy computations (of up to 1000 digits of accuracy)

Asymptotic inversion of the binomial and negative binomial cumulative distribution functions

ABSTRACT: The computation and inversion of the binomial and negative binomial cumulative distribution functions play a key role in many applications. In this paper, we explain how methods used for the central beta distribution function (described in Gil, Segura, and Temme, [Numer. Algorithms, 74 (2017), pp. 77?91]) can be utilized to obtain asymptotic representations of these functions and also for their inversion. The performance of the asymptotic inversion methods is illustrated with numerical examples.Acknowledgments. The authors thank the anonymous referees for their constructive comments and suggestions. This work was supported by Ministerio de Ciencia e Innovación, Spain, projects MTM2015-67142-P (MINECO/FEDER, UE) and PGC2018-098279-B-I00 (MCIU/AEI/FEDER, UE). NMT thanks CWI, Amsterdam, for scientific support

The recurrent nova RS Oph: A possible scenario for type Ia supernovae

The recurrent nova RS Oph experienced an outburst in 2006, 21 years after its previous explosion in 1985, as expected. It was observed at almost all wavelengths, and important information about its properties is still being extracted. We present theoretical models of the explosion of this fascinating object, which indicate that the mass of the accreting white dwarf should be very close to the Chandrasekhar mass, to allow for such a short recurrence period. In addition, since models suggest that this nova ejects less mass than it accretes, it is an excellent candidate for a thermonuclear supernova explosion, in about $10^5-10^7$ years from now. We also analyze the emission of soft gamma-rays by RS Oph detected with the BAT instrument onboard Swift, and with the PCA onboard RXTE. We rule out that this emission has its origin in radioactive decays in the expanding nova envelope.Comment: 10 pages, 2 figures, to be published in New Astronomy Review