1,720,958 research outputs found
Peak characteristics of F2 region over Tucumán: Predictions and measurements
Full text linkIonosonde measurements obtained at Tucuman are used to check the validity of the International Reference Ionosphere model to predict the maximum electron density of F2 region (NmF2) and its height (hmF2) over this station. Data corresponding to different months and solar activity conditions are considered. CCIR and URSI options are used to model calculations. The results show that, generally, the predictions of hmF2 are better than those of NmF2. Disagreements between predicted and measured NmF2 values are observed and the consequence in the vertical total electron content modeling are stressed.Fil: Ezquer, Rodolfo Gerardo. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionósfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mosert, Marta Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Scida, Luis Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionósfera; ArgentinaFil: López, J.. Universidad Tecnológica Nacional; Argentin
IRI 2001/90 TEC predictions over a low latitude station
Full text linkTotal electron content (TEC) over Tucumán (26.9°S, 294.6°W) measured with Faraday technique during the high solar activity year 1982, is used to check IRI 2001 TEC predictions at the southern crest of the equatorial anomaly region. Comparisons with IRI 90 are also made. The results show that in general IRI overestimates TEC values around the daily minimum and underestimates it the remaining hours. Better predictions are obtained using ground ionosonde measurements as input coefficients in the IRI model. The results suggest that for hours of maximum TEC values the electron density profile is broader than that assumed by the model. The main reason for the disagreement would be the IRI shape of the electron density profile. In a previous work using TEC measurements over Tucumán, obtained from GPS satellite signals during the high solar activity year 1999, a better agreement between IRI predictions and measurements has been observed. That better agreement was produced by the fact that 1999 GPS TEC measurements are 50% lower than those obtained by Faraday rotation technique during 1982. An equator ward movement of the southern peak of the EA plus the minor ionization level in 1999 could produce this reduction in TEC values. Moreover, it can be seen that in most of cases IRI TEC values around daily minimum show an hour displacement with respect to the experimental data.Fil: Scida, Luis Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionósfera; ArgentinaFil: Ezquer, Rodolfo Gerardo. Universidad Tecnológica Nacional. Facultad Regional Tucuman; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cabrera, Miguel Angel. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionósfera; ArgentinaFil: Mosert, Marta Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin
Behavior of the equivalent slab thickness over three European stations
Full text linkThe total electron content (TEC) derived from the global positioning system (GPS) and the F2-layer peak electron density obtained from Digisonde data have been used to study the diurnal, seasonal and solar activity variations of the ionospheric equivalent slab thickness (s) over three European stations located at Pruhonice (50.0N,15.0E), Ebro (40.8N,0.5E) and El Arenosillo (37.1N,353.3E). The diurnal variation of the s is characterized by daytime values lower than nighttime ones for all seasons at low solar activity while daytime values larger than nighttime characterizes the diurnal variation for summer at high solar activity. A double peak is noticeable at dusk and at dawn, better expressed for winter at low solar activity. The seasonal variations of s depend on local time and solar activity, the daytime values of s increases from winter to summer whereas nighttime values of s show the opposite. The effect of the solar activity on s depends on local time and season, there being very sensitive for winter nighttime values of s. The results of this study are compared with those presented by other authors.Fil: Mosert, Marta Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnológico - CONICET - San Juan. Instituto de Ciencias Astronómicas de la Tierra y del Espacio; ArgentinaFil: Magdaleno, S.. Estación de Sondeos Atmosféricos “El Arenosillo”; EspañaFil: Buresova, D.. Biology Centre of the Academy of Sciences of the Czech Republic; República ChecaFil: Altadill, D.. Consejo Superior de Investigaciones Científicas; EspañaFil: Gende, Mauricio Alfredo. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Georreferenciación Satelitaria; ArgentinaFil: Gularte Scarone, Angela Erika. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Scida, Luis Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentin
Tucumán ionospheric model (TIM): Initial results for STEC predictions
Full text linkMost ionospheric models can calculate vertical total electron content (VTEC) predictions, but only a few are suitable for calculating slant total electron content (STEC). This ionospheric magnitude is generally measured for electron content determinations, with VTEC particularly corresponding to an elevation of 90°. This is generally obtained by applying a mapping function to STEC measurements, which leads to important calculation errors. Moreover, the equatorial region has unique characteristics, such as the fountain effect and the equatorial electrojet, which lead to significant errors in the model's calculations. In this paper, the Tucumán ionospheric model (TIM) is presented as a novel alternative for calculating the STEC in low-latitude regions (−24 to 24 dip latitude). The model is based on spatial geometry where the considered trajectory is segmented, and the corresponding electron density calculations for the resulting segment end points are determined using the semi-empirical low-latitude ionospheric model (SLIM) with reference to their corresponding magnetic coordinates and height. Finally, the electron density values are integrated along the path to obtain the STEC. This work describes the TIM and tests their STEC predictions for five ray paths around the world (totaling 16 cases under study), which are compared with experimental data from satellites and with those calculated by the NeQuick model. Moreover, the TIM performance for VTEC predictions is also checked and compared with VTEC data obtained from Global Positioning System (GPS) signals, IRI model, and NeQuick model predictions, for six GPS receiver stations during the equinox and solstice (totaling 12 cases studied). Comparisons of the TIM predictions with experimental data show that 53% of the calculation has, in general, deviations <30%. For the considered cases, TIM reproduces the experimental data better than the other models.Fil: Scida, Luis Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Ezquer, Rodolfo Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Cabrera, Miguel Angel. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Jadur, Camilo Alberto. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Matemáticas; ArgentinaFil: Sfer, Ana María. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Matemáticas; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
NeQuick 2 total electron content predictions for middle latitudes of North American region during a deep solar minimum
Full text linkThe performance of NeQuick 2 model in computing the vertical total electron content (VTEC) over a wide region placed at middle latitudes of North America during the deep solar minimum that occurred in 2008 has been checked. The long term relationship between EUV irradiance and F10.7 solar flux has changed markedly during the cycle 23/24 minimum with EUV levels decreasing more than expected from F10.7 proxy. A decrease of ionization in the ionosphere could have occurred. Thus, it could be expected that the models overestimate the value of ionospheric parameters for that deep solar minimum. For this study a high density VTEC data grid that covers the Continental United States (CONUS) has been compared with monthly median maps constructed with NeQuick 2. The results show that NeQuick 2 generally gives good predictions for the region which lies between 35°N to 50°N suggesting that nothing exceptional was happening during the 2008 minimum in terms of VTEC NeQuick 2's predictive capabilities. Taking into account that the modeled value is obtained by integration in height of the electron density profile, NeQuick2 would be assuming an inadequate profile for the few highest deviations observed, between 30°N and 35°N. Overall, the model does not give significant overestimation of VTEC as could be expected.Fil: Ezquer, Rodolfo Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentina. Universidad Tecnológica Nacional. Centro de Investigación de Atmósfera Superior y Radiopropagación; ArgentinaFil: Scida, Luis Alberto. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Física. Laboratorio de Ionosfera; Argentina. Universidad Tecnológica Nacional. Centro de Investigación de Atmósfera Superior y Radiopropagación; ArgentinaFil: Migoya Orue, Yenca Olivia. The Abdus Salam International Centre for Theoretical Physics; ItaliaFil: Lescano, G. E.. Universidad Tecnológica Nacional. Centro de Investigación de Atmósfera Superior y Radiopropagación; ArgentinaFil: Alazo Cuartas, K.. The Abdus Salam International Centre for Theoretical Physics; ItaliaFil: Cabrera, M.A.. Universidad Tecnológica Nacional. Centro de Investigación de Atmósfera Superior y Radiopropagación; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnología. Departamento de Electricidad, Electrónica y Computación. Laboratorio de Telecomunicaciones; ArgentinaFil: Radicella, Sandro María. The Abdus Salam International Centre for Theoretical Physics; Itali
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