1,720,976 research outputs found
From UNISAT-3 to UNISAT-4
No full textThe microsatellite UNISAT-3, completely designed, manufactured and operated in orbit by a team of students, researchers and professors of Gruppo di Astrodinamica dell’Università degli Studi “La Sapienza” (GAUSS) at the Scuola di Ingegneria Aerospaziale of the University of Roma “La Sapienza”, is the third microsatellite of the UNISAT program, which has the main goal of providing “hands-on education”, where the students can complete their instruction by practicing on a real, even if small, space program. UNISAT-3 was launched on June 29th 2004.
This paper describes the microsatellite UNISAT-3, its main subsystems, the building procedures set up using mainly industrial, not space qualified, materials. Moreover ground test campaign carried out on UNISAT-3, in particular tests concerning the structure and photovoltaic subsystems, are described.
The fourth satellite of the UNISAT program, UNISAT-4, has been designed and almost ready for final integration, with launch scheduled on December 2005.
The lessons learned and preliminary results from operation in orbit suggested some improvements to be implemented on the satellite bus. In particular it has been realized that significant enhancement could be achieved concerning the photovoltaic system. UNISAT-4 photovoltaic system is based on monocrystalline terrestrial grade silicon solar arrays extensively tested on previous satellites and triple junction solar cells which required the development of a custom assembling technology deeply discussed in the paper
The unisat program: Lessons learned and achieved results
No full textThe Group of Astrodynamics of University of Roma "La Sapienza" (GAUSS) established the UNISAT program at the Scuola di Ingegneria Aerospaziale of the University of Roma "La Sapienza". It is an educational project for designing, manufacturing and operating in orbit small microsatellites. The main goal of the UNISAT program is the education, with the aim of the participation of the students in all the phases of a real space program, from the initial mission concept to the operations in orbit. There is a strict time constraint on the mission development, which must fit in the two years didactical plan of the students. In the framework of this project four microsatellite have already been launched from Baikonour cosmodrome using the DNEPR launch vehicle, and UNISAT-4 is scheduled to be launched on May 2006. The program has now achieved an experience of several years, in which the methods of hands-on education have been employed, along with traditional class teaching, to improve the students skills. Many program organization issues have been faced in these years, to improve and verify the didactical effectiveness of the teaching method followed. The paper describes briefly the program, focussing on the didactical aspects and describing the direct experience of some students, involved in the design of the satellite subsystems. Other goal of the UNISAT program is testing in orbit and space qualifying the terrestrial off the shelf commercial and industrial components and technologies, yielding a direct technological interest for the industries and contributing to keep low the program cost and affordable for the University research budget. The main microsatellite subsystems are described in this paper, showing the students contribution to the program and their involvement in the decision process of the design, manufacturing and testing. The design process includes the realization of a virtual "digital mock-up" of the satellite, in which all the parts are simulated to verify dimensions, fitting conflicts, and weight distributions. The electronic boards have been completely designed by the students. A significant effort has been devoted to the ground station automation, including remote operation by accredited users. In particular high school students are involved in an education program for space culture diffusion among young people
UNISAT-3 power system
No full textAn overview of the UNISAT-3 microsatellite power subsystem is given. This is an educational, low weight and low cost microsatellite designed, built, launched and operated in space by students and professors of Scuola di Ingegneria Aerospaziale, at University of Rome "La Sapienza". The satellite power system is based on terrestrial technology solar arrays and NiCd batteries. The microsatellite hosts other solar arrays, including multi-junction solar cells and mono-crystalline silicon high efficiency solar cells, in order to compare their behaviour in orbit. Moreover a MPPT (Maximum Power Point Tracking ) system has been designed and tested, and it is a technological payload of UNISAT-3. The MPPT design follows the studies performed in the field of solar powered racing cars, with modifications to make the system suitable for use in space. The system design, numerical simulation and hardware ground testing are described in the paper. The experiment and the performance evaluation criterion are described, together with the preliminary results of the first eight months of operation in orbit
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
Unisat-3 Mission: Preliminary Results
No full textThe research and education program UNISAT was established at Scuola di Ingegneria Aerospaziale of Università di Roma “La Sapienza” by GAUSS (Gruppo di Astrodinamica dell’Università degli Studi “la Sapienza”) research group. The main goal of the program is to provide “hands-on education”, where the students can complete their education by practicing on a real, even if small, space program.
The paper describes the UNISAT program, focussing on the design, manufacturing, test and launch of the microsatellite UNISAT-3, launched on June 29th 2004. The satellite has been designed realized, integrated, tested and currently operated in orbit by the students, assisted by University staff. Preliminary results of the experiments in orbit are discussed
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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