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Material and surface properties of lares satellite
Get PDFLARES (LAser RElativity Satellite) is a passive satellite put in orbit by the VEGA launcher the past 13th of February 2012. It is designed for the accurate test of the Lense-Thirring effect. This phenomenon is induced by the Earth rotation that according to Einstein General Relativity drags space-time and consequently the trajectory of orbiting objects. In order to reach the expected results of few percent accuracy in the measurement of that effect, some restrictive scientfic requirements have been imposed with regard to the material to be used for the satellite body (SB) and to the surface properties of the SB itself, giving special attention to the density of the SB (higher than 17900 kg/m3). Furthermore to reduce interaction with the magnetic field of Earth some upper limit to, the electrical conductivity of the alloy was specified. All those aspects along with some considerations on the manufacturing challenges of LARES will be reported. Finally the different methods evaluated for the finishing of the SB, so as to satisfy the scientific requirements such as the infrared emissivity (e) and the solar absorptivity (a) of the surface will be analysed. Copyright © (2012) by the International Astronautical Federation
Engineering and scientific aspects of LARES satellite
No full textLAser RElativity Satellite (LARES) is an Italian passive satellite designed for the accurate test of a phenomenon predicted by Einstein General Relativity called frame-dragging, or gravitomagnetism, i.e., the Earth angular momentum generates spacetime curvature that causes an additional perturbation of the satellite orbit, called the Lense-Thirring effect. LARES is a laser-ranged satellite of the type of the two LAGEOS satellites already orbiting the Earth. Data from these three satellites will also be used to improve the accuracy in the measurement of the Lense-Thirring effect. (C) 2011 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
COST EFFECTIVE CENTER OF MASS DETERMINATION OF LARES SATELLITE
Get PDFLAser RElativity Satellite (LARES) is a satellite designed for measuring gravitomagnetism
predicted by Einstein general relativity. One of the requirements imposed
on LARES satellite is to have the distance between the center of mass and the
geometric center of the satellite lower than 0.2 mm. The material used for LARES satellite
is a tungsten alloy. The producer provided two spheres manufactured with liquid
sintering, a process that bring the Cu and Ni present in the alloy in liquid phase. The
two spheres are among the biggest tungsten alloy items ever manufactured and the
producer could not guarantee the uniformity of the alloy. Also the center of mass could
not be predicted with a sub-millimeter level of accuracy. Balancing of satellites is
usually made by adding masses at pre-configured positions. In case the distance between
the center of mass and the geometric center is bigger than 1 mm, adding masses
on the LARES satellite would be very difficult and will increase the surface-to-mass ratio,
a very important parameter connected to the scientific objective of the mission. For
this reason a procedure for a rough measurement of the satellite center of mass has
been devised. Purpose of the paper is to show how to use a lathe machine and a homemade
system with load cells, to measure the position of the center of mass with an accuracy
of about 0.5 mm
Material and manufacturing issues of a laser ranged satellite
Get PDFThe LARES satellite is an Italian space mission funded by ASI, with CGS as prime contractor
and Salento and Sapienza Universities as subcontractors. The LARES will be put into orbit by the European
launcher VEGA during its maiden flight, foreseen in year 2011. The paper describes the general features of the
material chosen for the manufacturing of the satellite and its components. Particular interest will be devoted to
the manufacturing process and analysis of the screws
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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