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A 200 Km S
No full textA molecular wind with an outflow speed in excess of 200 km s \Gamma1 has been found in the AGB carbon star V Hya. Observations of several molecular lines show that the circumstellar envelope is expanding at 15 km s \Gamma1 and is flattened and inclined to the line of sight. The fast wind appears to be expanding from the poles of the envelope, with the expansion speed increasing with distance from the star. V Hya may be in the very earliest stage of evolution beyond the AGB. 1. Introduction On the basis of its properties at optical wavelengths, V Hya is usually considered to be a normal N type carbon star on the asymptotic giant branch (AGB). Its effective temperature is 2650 K, its spectral type is C6-7,5e and it is a semiregular variable (SRa) with a period of 529 days (Kholopov et al. 1985; Lambert et al. 1986). The star has a large infrared excess and strong millimeter wavelength molecular line emission, showing that it is losing mass at a fairly high rate, several \Theta 10 \..
Reliably Analyzing the Chemical Composition of Plumes during Flybys at Velocities Exceeding 5 km/s
No full textSpacecraft flybys of planetary bodies provide an opportunity to analyze the chemical composition of their outer atmosphere by mass spectrometry. The chemical composition of the atmosphere provides key insights into the origin and evolution of an object. Additionally, sampling a plume, if present, during the flyby will provide detailed information on the complex chemistry present below the surface. At present, composition information available for many of these objects is sparse, as on one hand, the ground-based observations lack both sensitivity and spatial resolution for a detailed investigation and on the other hand recently performed flythroughs were conducted using outdated instrumentation resulting in a moderate sensitivity within a limited mass range. In contrast to the tenuous exosphere of celestial objects, plumes feature significantly increased number density of species in a spatially confined geometry. Flybys are quick events given the relative encounter velocity are easily exceeding 5 km/s, up to about 20 km/s, resulting in major design drivers for instrumentation. The tens of seconds spent in the region of interest requires instant recording of detailed data. The high flyby velocity requires sampling that prevents species from hypervelocity impact induced bond-dissociation. Such a fragmentation complicates the reliable identification of observed signals to species especially in complex mixtures, if not making it impossible. Here we present the development of a sensitive time-of-flight mass spectrometer that can analyze both the tenuous exosphere of celestial objects and plumes, if present, during hypervelocity flybys exceeding 5 km/s enabled by its novel direct open ion source. It uniquely prevents hypervelocity impact induced bond-dissociation as it directly analyzes species without contact with a wall of, for example, an antechamber or other structures in a relative encounter velocity range of 0 to 20 km/s. Using electron ionization, it is capable of analyzing even heavy species in complex mixtures. Such a capability allows for reliably analyzing plumes in a mass range of to 1000 for a relative encounter velocity of 10 km/s and a mass range of to 800 for 20 km/s, enabled by a mass resolution exceeding (full width at half maximum) for higher masses. Thanks to its sensitivity, it is able to analyze even traces of species in both the exosphere and the plumes. This novel instrument allows for detailed and rapid mass spectrometric investigations in all mission scenarios where high flyby speeds at planetary objects are foreseen, for example, Io and Enceladus. This offers the opportunity to measure these objects' exospheres at large distances and measure the plumes when in proximity to the closest approach
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
Penetration and cratering experiments of graphite by 0.5-mm diameter steel spheres at various impact velocities
Full text linkCratering experiments have been conducted with 0.5-mm diameter AISI 52100 steel spherical projectiles and 30-mm diameter, 15-mm long graphite targets. The latter were made of a commercial grade of polycrystalline and porous graphite named EDM3 whose behavior is known as macroscopically isotropic. A two-stage light-gas gun launched the steel projectiles at velocities between 1.1 and 4.5 km s 1. In most cases, post-mortem tomographies revealed that the projectile was trapped, fragmented or not, inside the target. It showed that the apparent crater size and depth increase with the impact velocity. This is also the case of the crater volume which appears to follow a power law significantly different from those constructed in previous works for similar impact conditions and materials. Meanwhile, the projectile depth of penetration starts to decrease at velocities beyond 2.2 km s 1. This is firstly because of its plastic deformation and then, beyond 3.2 km s 1, because of its fragmentation. In addition to these three regimes of penetration behavior already described by a few authors, we suggest a fourth regime in which the projectile melting plays a significant role at velocities above 4.1 km s 1. A discussion of these four regimes is provided and indicates that each phenomenon may account for the local evolution of the depth of penetration
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
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Launch capabilities to 16 km/s
No full textA systematic study is described that has led to the successful launch of thin flier-plates to velocities of 16 km/s. In this paper, the authors describe a novel technique that has been implemented to enhance the performance of the Sandia Hyper Velocity Launcher (HVL). This technique of creating an impact-generated acceleration reservoir, has allowed the launch of 0.5 mm to 1.0 mm thick titanium (Ti-6Al-4V) and aluminum (6061-T6) alloy plates to record velocities up to 15.8 km/s. These are the highest metallic projectile plate velocities ever achieved for macroscopic masses in the range of 0.1 g to 1 g
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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