1,720,970 research outputs found
Gauss-PSO algorithm for too short arc initial orbit determination for groud spot
No full textThe paper presents a new approach for the Initial Orbit Determination (IOD) from short observations of Resident Space Objects (RSOs). The work is in the framework of the development of the system SPOT promoted by the Italian Space Agency. The system SPOT (Star sensor image on-board Processing for orbiting Objects deTection) is composed by On-board SPOT, to detect potential RSOs from the on-board processing of star sensor images against the fixed stars, and the Ground SPOT which receives the observation data to perform the orbit determination and tracking of the RSOs. SPOT is a suitable system to detect small RSO (< 7 mm) that usually cannot be detected by ground-based observations. Due to the relative dynamics between the orbital observer and RSOs, an orbiting object appears as a streak in the star sensor image. As a result, the observation is a too short arc, which makes difficult to solve the initial orbit determination. The paper studies the IOD algorithm of Ground SPOT by devising a modified Gauss' Algorithm for space-based observer. Knowing the orbit of the observer, the measurements of the lines of sight of a RSO are used to find the state of the target orbit by the Particle Swarm Optimization (PSO) technique. The PSO is implemented in order to find the solution by minimizing a suitable cost function of the lines of sight. The developed algorithm it is able to provide a close estimate of the true state of the observer using too short arcs and it can autonomously choose a root of the Gauss' eighth grade equation
Use of the Stille coupling to label steroids with the ethynylcyclopentadienylmanganesetrocarbonyl moiety
No full text
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
The Alphasat Propagation Experiment: Interim Results from ASI and NASA Ground Stations
No full textThis contribution presents results obtained from the Italian ground stations in the frame of the Alphasat propagation experiment. Yearly statistics of the atmospheric attenuation as inferred from the received beacon signals (19.7 and 39.4 GHz) are reported and discussed for the two receiving stations installed in Spino d’Adda and Milan, whose experimental data are also combined to evaluate the advantage that would originate from a two-station diversity configuration
L-band Plasma Turnstile Antenna for GPS applications
No full textThis work presents the preliminary results of a crossed dipole antenna that works in the L-band and that exploits plasma technology to generate and receive a circularly polarized electromagnetic field. The study considered in a first stage a simplified plasma crossed dipole and successively it included a more realistic design that comprises the plasma generation equipment, more realistic glass vessels and the electrodes used to generate the plasma. The simplified design can achieve good results in terms of axial ratio (i.e., circular polarization), directivity, and input impedance if compared to its metallic counterpart. However, when the more realistic antenna is considered, a down-shift in the operation frequency can be observed. Furthermore, the influence of the plasma parameters on the antenna parameters has been analyzed. All the results have been obtained through full-wave numerical simulations in CST Microwave Studio
Design and numerical characterization of a realistic plasma dipole
No full textThis work presents the numerical results for a plasma dipole antenna that exploits plasma technology to generate and receive electromagnetic fields. Two models have been considered, namely an ideal plasma dipole, and a realistic plasma dipole. The latter comprises part of the plasma generation equipment (e.g. metal terminations, inductors). The realistic plasma dipole was realized in practice and tested for the plasma density. Moreover, a preliminary test by means of a vector network analyzer with the plasma turned off was undertaken to verify the accuracy of the simulation models. Both the models can achieve good antenna performances. However, a downshift in the operational frequency can be observed when a more realistic design is considered. All the simulated results have been obtained through full-wave numerical simulations in CST Microwave Studio
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
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