Planar compact array with parasitic elements for MIMO systems

A compact planar array with parasitic elements is studied to be used in MIMO systems. Classical compact arrays suffer from high coupling which makes correlation and matching efficiency to be worse. A proper matching network improves these lacks although its bandwidth is low and may increase the antenna size. The proposed antenna makes use of parasitic elements to improve both correlation and efficiency. A specific software based on MoM has been developed to analyze radiating structures with several feed points. The array is optimized through a Genetic Algorithm to determine parasitic elements position in order to fulfill different figures of merit. The proposed design provides the required correlation and matching efficiency to have a good performance over a significant bandwidth

República, 389d6

Si supusiéramos por un momento, casi como un gesto apriorístico, que la metafísica platónica sirve a la política, es decir, que su elaboración responde a la intencionalidad política platónica de instaurar una nueva forma de gobierno en la ciudad. Si supusiéramos esto -fuerte pero nada descabellado a juzgar por la pregnancia que ha tenido el pensamiento político de Platón para la posteridad, incluso, y sobre todo, cuando ha sido desprovisto de su trasfondo metafísico o cuando éste ha sido sustituido por otro más acorde con la época-, si lo supusiéramos, podríamos inferir que el relato metafísico gana cuerpo como simple relato, y que su valor ficcional se mide por la eficacia que puede tener en soportar la presentación, difusión, instauración de una propuesta paidéutica novedosa. Ahora bien, si avalamos la hipótesis de la preeminencia de la política por sobre la metafísica en Platón, es decir, si suscribimos a esta idea que -no está mal decirlo aun si nos reconocemos como platónicos- posee un cariz escéptico, o también, si no nos agrada el punto de vista maquiavélico según el cual la realidad última es una disputa por el poder y su toma y suscribimos a una hipótesis algo más débil, en donde no desdeñamos el grado de verdad del relato metafísico pero nos resistimos a ponerlo por encima de cualquier vocación política del texto, si hiciéramos todo esto, hay una operación de la República que adquiere gran relevancia. Se trata de una operación notable. Un mecanismo que abre la posibilidad misma de esto que venimos de decir.Fil: García Ponzo, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Humanidades. Universidad Nacional de Córdoba. Instituto de Humanidades; Argentin

The white dwarf cooling sequence of 47 Tucanae

47 Tucanae is one of the most interesting and well observed and theoretically studied globular clusters. This allows us to study the reliability of our understanding of white dwarf cooling sequences, to confront different methods to determine its age, and to assess other important characteristics, like its star formation history. Here we present a population synthesis study of the cooling sequence of the globular cluster 47 Tucanae. In particular, we study the distribution of effective temperatures, the shape of the color-magnitude diagram, and the corresponding magnitude and color distributions. We do so using an up-to-date population synthesis code based on Monte Carlo techniques, that incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases. We find a good agreement between our theoretical models and the observed data. Thus, our study, rules out previous claims that there are still missing physics in the white dwarf cooling models at moderately high effective temperatures. We also derive the age of the cluster using the termination of the cooling sequence, obtaining a good agreement with the age determinations using the main-sequence turn-off. Finally, we find that the star formation history of the cluster is compatible with that btained using main sequence stars, which predict the existence of two distinct populations. We conclude that a correct modeling of the white dwarf population of globular clusters, used in combination with the number counts of main sequence stars provides an unique tool to model the properties of globular clusters.Comment: 6 pages and 4 figures accepted for publication in A &

An independent constraint on the secular rate of variation of the gravitational constant from pulsating white dwarfs

A secular variation of the gravitational constant modifies the structure and evolutionary time scales of white dwarfs. Using an state-of-the-art stellar evolutionary code and an up-to-date pulsational code we compute the effects of a secularly varying $G$ on the pulsational properties of variable white dwarfs. Comparing the the theoretical results obtained taking into account the effects of a running $G$ with the observed periods and measured rates of change of the periods of two well studied pulsating white dwarfs, G117--B15A and R548, we place constraints on the rate of variation of Newton's constant. We derive an upper bound $\dot G/G\sim -1.8\times 10^{-10}$ yr$^{-1}$ using the variable white dwarf G117--B15A, and $\dot G/G\sim -1.3\times 10^{-10}$ yr$^{-1}$ using R548. Although these upper limits are currently less restrictive than those obtained using other techniques, they can be improved in a future measuring the rate of change of the period of massive white dwarfs.Comment: 13 pages, 4 tables, 3 figures. To be published in the Journal of Cosmology and Astroparticle Physic

An industry case study: a mobile-based business strategy to improve the customer care service in a major retail company

Customer service is a key factor that influences customer loyalty and overall satisfaction during the buying experience. With the growth of ecommerce, many companies have detect several issues in the performance of their customer service departments. Customer dissatisfaction may represent significant losses in sales and reputation. In this context, this report describes a success experience in the industry of retail, in which a mobile-based solution was applied to improve the customer service performance and reduce overall costs of one of the major retailers of the US. We present preliminary results indicating the potential benefits of our solution to the company.Sociedad Argentina de Informática e Investigación Operativa (SADIO

An industry case study: a mobile-based business strategy to improve the customer care service in a major retail company

Customer service is a key factor that influences customer loyalty and overall satisfaction during the buying experience. With the growth of ecommerce, many companies have detect several issues in the performance of their customer service departments. Customer dissatisfaction may represent significant losses in sales and reputation. In this context, this report describes a success experience in the industry of retail, in which a mobile-based solution was applied to improve the customer service performance and reduce overall costs of one of the major retailers of the US. We present preliminary results indicating the potential benefits of our solution to the company.Sociedad Argentina de Informática e Investigación Operativa (SADIO

Sobre la traducción y edición de literatura griega moderna y contemporánea en España (1993-2005)

In order to study the development of the Spanish reception of Modern and Contemporary Greek literature in the second half of the twentieth century and approach more fully the present-day state of the question, it is necessary to avoid a consideration of these five decades as if they constituted a homogeneous period. For the objectives of our study it is posible to distinguish three phases. The first covers the period from the first Spanish editions of the work of Casantsakis (1959) and the poetry of C.P. Cavafis (1962) to the death of the dictator and the beginning of the Spanish transition to democracy (1975). The second one covers the years from 1976 (first publication of Cavafy’s 154 canon poems a few months after Franco´s death) to 1992, an emblematic year in the recent history of Spain. The third phase goes from 1993 to 2005, year in which Liber, the International Book Fair in Madrid, was dedicated to Greece

Análisis de los factores determinantes de los flujos de IDE de los países comunitarios a América Latina.

Este trabajo permite constatar la importancia de los flujos de IDE desde la UE hacia América Latina. El objetivo es el análisis de los determinantes de dichos flujos a partir de la síntesis entre el paradigma OLI y la teoría de la integración regional, desde la perspectiva de los países emisores, mediante una estimación con datos de panel y efectos fijos. Los resultados muestran la similitud para Argentina, Brasil y México del papel del comercio, la ventaja tecnológica y el efecto paí[email protected]; [email protected]

White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up

We present new white dwarf evolutionary sequences for low-metallicity progenitors. White dwarf sequences have been derived from full evolutionary calculations that take into account the entire history of progenitor stars, including the thermally-pulsing and the post-asymptotic giant branch phases. We show that for progenitor metallicities in the range 0.00003--0.001, and in the absence of carbon enrichment due to the occurrence of a third dredge-up episode, the resulting H envelope of the low-mass white dwarfs is thick enough to make stable H burning the most important energy source even at low luminosities. This has a significant impact on white dwarf cooling times. This result is independent of the adopted mass-loss rate during the thermally-pulsing and post-AGB phases, and the planetary nebulae stage. We conclude that in the absence of third dredge-up episodes, a significant part of the evolution of low-mass white dwarfs resulting from low-metallicity progenitors is dominated by stable H burning. Our study opens the possibility of using the observed white dwarf luminosity function of low-metallicity globular clusters to constrain the efficiency of third dredge up episodes during the thermally-pulsing AGB phase of low-metallicity progenitors.Comment: To be published in Astronomy and Astrophysics. 12 pages, 11 figure

Constraining the neutrino magnetic dipole moment from white dwarf pulsations

Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. By comparing the theoretical rate of change of period expected for this star with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment. Our upper limit for the neutrino magnetic dipole moment is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.Comment: 18 pages, 10 figures, 3 tables. Accepted for publication in Journal of Cosmology and Astroparticle Physic