1,721,334 research outputs found
Composition modale des roches à l'aide de l'analyse d'images sur micro-ordinateur. Modal composition of rocks using image processing on a microcomputer
No full textCOMODALE is an image processing software package which has been developed for geologists. It allows the determination of the modal analysis of rocks by digitizing video images of thin sections, each mineral been characterized by its brightness. The first program in assembly language determines the brigthness spectrum of thin sections viewed through a petrological microscope. From this spectrum, a second program (written in MS-Basic) provides the modal composition of the whole thin section and prints the results. These programs have been developed on a Victor Sirius 1 microcomputer but can be easily modified to run on any IBM compatible microcomputer. This procedure allows the rapid determination of modal composition of rocks with a better reliability than classical methods. The technique is non-destructive and analysis can be quickly performed (15 to 30 minutes according to the grain size of the rock). Finally, it uses equipment found in most geological laboratories (video-camera, microcomputer and petrological microscope). As an example, the percentage of feldspar in plagioclase lherzolites is determined using this procedure.COMODALE est un logiciel qui permet d'obtenir la composition modale de roches à partir des images vidéo de lames minces digitalisées sur 64 niveaux de gris. On distingue les phases minérales par leur luminance. Le logiciel se décompose en un programme MODALE (assembleur) qui calcule le spectre de luminance de la lame mince, et en un programme RESULT (basic) qui détermine la composition modale et édite les résultats. Ses avantages sur les méthodes classiques sont : la rapidité, la non-detruction de l'échantillon et un matériel micro-informatique et optique dont le coût n'excède pas 40 000 FF (en 1987). Ce logiciel a été utilisé de manière satisfaisante pour déterminer la composition modale de péridotites ou le pourcentage de feldspath dans une lherzolite.Allard Bruno, Sotin Christophe. Composition modale des roches à l'aide de l'analyse d'images sur micro-ordinateur. Modal composition of rocks using image processing on a microcomputer. In: Sciences Géologiques. Bulletin, tome 41, n°2, 1988. Traitements d'images et objets géologiques. pp. 135-142
Titan gravity investigation with the Oceanus mission
Full text linkOceanus is a proposed mission for NASA's New Frontiers 4 Announcement of Opportunity to study Saturn's largest moon Titan. One of the main goals of Oceanus is to examine crustal properties and determine the potential interaction of organics with the subsurface ocean, with implications for potential habitability of Titan. To this end, Oceanus could potentially characterize the thickness of the external icy shell and determine the extent of convection in the shell. The product (average ice rigidity) x (ice shell thickness) can be retrieved from the Love numbers k2 and h2, which describe Titan's gravity and shape response to Saturn's tidal field during its orbital motion around the planet, using a combined analysis of gravity and topography but also measuring Titan's physical librations from gravity data and the on-board camera surface landmarks. The gravity science experiment is crucial to accomplish the mission goals, because precise orbit determination of the spacecraft provides a direct measure of Titan's static gravitational field, the real and imaginary parts of the Love number k2, and its rotational state (obliquity and amplitude of physical librations in longitude). Moreover, a precise spacecraft orbit reconstruction throughout the entire mission is necessary to process radar altimetry data and accurately measure Titan's h2 through crossover analysis. We present the expected accuracy in the estimation of the scientific parameters of interest, obtained through numerical simulations of the orbit determination of the Oceanus spacecraft during its 2-year mission around Titan. The main observable quantities used in the analysis are two-way Doppler data obtained from the frequency shift of a highly stable microwave carrier between the spacecraft and the stations of NASA's Deep Space Network. White Gaussian noise was added to the simulated data, with a realistic standard deviation obtained from an accurate noise budget derived from the experience with Cassini Ka-band Doppler data. A covariance analysis was carried out using a multi-arc approach, comparing different observational and modeling strategies, in particular for the non-gravitational perturbations. Our results show that Oceanus will allow estimating the real and imaginary parts of Titan's k2 to an accuracy of 0.0001, the gravity field to at least degree 12 with SNR of 10, and also provide spacecraft orbit reconstruction with a radial uncertainty better than 0.5 meter during the mission
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
A Network of Geophysical Observatories for Mars
No full textFor the past 30 years there has been a strong consensus within the international scientific community in favor of sending a network of geophysical landers to Mars to characterize the near-surface weather and climate, determine the large-scale atmospheric dynamics and explore the interior structure and composition. Despite this scientific support, there has been an unbroken string of proposed missions over the past fifteen years which have failed for programmatic reasons to progress beyond the design stage (Mars Network Mission, MESUR, Marsnet, InterMarsnet, NetLander). In this presentation, we review the scientific rationale and technical requirements for such a mission, and discuss current activities aimed toward its implementation
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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