1,721,032 research outputs found
Calibration of the VIR/Dawn hyperspectral imager spare model and spectroscopy of HED meteorites
No full textDawn è una missione in fase di svolgimento che esplora la Fascia Principale degli asteroidi per chiarire importanti questioni sulla formazione e l'evoluzione del Sistema Solare.
Dawn è stata lanciata il 27 settembre 2007 da Cape Canaveral ed è la prima sonda ad orbitare intorno a due corpi durante lo stesso viaggio; ha, infatti, raggiunto Vesta nel luglio del 2011 e raggiungerà Cerere nel Febbraio del 2015.
Il suo obiettivo è acquisire dati relativi a Vesta e Cerere, due asteroidi complementari che si sono formati ai primordi del Sistema Solare. Il programma di ricerca Dawn è volto a dare un significativo incremento alle conoscenze sulle condizioni e sui processi all'epoca della formazione del nostro Sistema Planetario, esaminando le proprietà geofisiche dei due asteroidi con immagini multispettrali e pancromatiche; per acquisire questi dati la navicella orbiterà intorno ai due corpi.
Fra gli obiettivi della missione c’è la caratterizzazione degli asteroidi osservati in termini di forma e proprietà fisiche (dimensioni, forma, massa, periodo e asse di rotazione), l’individuazione di caratteristiche morfologiche (strutture locali, distribuzione dei crateri, presenza o meno di regolite), della natura geologica e mineralogica della superficie e della presenza di polveri e/o gas.
Per raggiungere gli obiettivi prefissati, la missione è supportata da attività di analisi da Terra.
In laboratorio, si studiano campioni di meteoriti di cui Vesta è il progenitore; si crea un database spettrale per l'interpretazione dei dati acquisiti in volo.
L'attività svolta ha riguardato anche la misura dei parametri strumentali fondamentali dello spettrometro ad immagine, 'gemello' di quello in volo
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
Optimization of the principal eigenvalue under mixed boundary conditions
No full textWe investigate minimization and maximization of the principal
eigenvalue of the Laplacian under mixed boundary conditions in case the
weight has indefinite sign and varies in a class of rearrangements. Biologically,
these optimization problems are motivated by the question of determining the
most convenient spatial arrangement of favorable and unfavorable resources
for a species to survive or to decline. We prove existence and uniqueness re-
sults, and present some features of the optimizers. In special cases, we prove
results of symmetry and results of symmetry breaking for the minimizer
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
A brief note on the coarea formula
No full textIn this note we consider a special case of the famous Coarea Formula whose initial proof (for functions from any Riemannian manifold of dimension 2 into R) is due to Kronrod (Uspechi Matem Nauk 5(1):24–134, 1950) and whose general proof (for Lipschitz maps between two Riemannian manifolds of dimensions n and p) is due to Federer (Am Math Soc 93:418–491, 1959). See also Maly et al. (Trans Am Math Soc 355(2):477–492, 2002), Fleming and Rishel (Arch Math 11(1):218–222, 1960) and references therein for further generalizations to Sobolev mappings and BV functions respectively. We propose two counterexamples which prove that the coarea formula that we can find in many references (for example Bérard (Spectral geometry: direct and inverse problems, Springer, 1987), Berger et al. (Le Spectre d’une Variété Riemannienne, Springer, 1971) and Gallot (Astérisque 163(164):31–91, 1988), is not valid when applied to C∞ functions. The gap appears only for the non generic set of non Morse functions
A short note on the mean exit time of the Brownian motion
No full textWe investigate the functional (Formula presented.) where (Formula presented.) runs through the set of compact domains of fixed volume (Formula presented.) in any Riemannian manifold (Formula presented.) and where (Formula presented.) is the mean exit time from (Formula presented.) of the Brownian motion. We give an alternative analytical proof of a well-known fact on its critical points proved by McDonald: the critical points of (Formula presented.) are harmonic domains
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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