1,721,092 research outputs found
Evidence of thermal pressurization in high-velocity friction experiments on smectite-rich gouges
No full textThermal pressurization of pore fluid is one of the possible mechanisms responsible for dynamic weakening in landslides and earthquakes, but, to date, has not been reproduced in the laboratory. Here, we report high-velocity experiments performed in a rotary shear friction apparatus on smectite-rich gouges from the 1963 Vaiont landslide (Italy). The gouges were slid under 1 MPa normal stress, for displacements up to 30 m and a slip rate of 1.31 m s-1 under room-humidity and water-saturated conditions. Sample dilatancy was observed in room-humidity runs after similar to 3-4 m of slip, concomitant with an increase in normal stress and a decrease in shear stress. Mineralogical and microstructural investigations suggest that dilatancy resulted from expansion of the H(2)O released by the collapse of the smectite structure due to frictional heating of the slipping zone at T > 200 degrees C. We conclude that sample dilatancy is due to thermal pressurization of the clay-rich gouge
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
Relating high-velocity rock friction experiments to coseismic slip in the presence of melts
No full textThe dynamic strength (tau_f) of faults during coseismic slip is a major unknown
in earthquake mechanics, though it has crucial influence on rupture properties,
dynamic stress drop, radiated energy and heat produced during slip. In order to
provide constraints on tau_f, High-Velocity Rock Friction Experiments (HVRFE) are
conducted on natural rocks with rotary shear apparatuses, reproducing slip (several
meters) and slip rate (0.1–3 m s-1) typical of large earthquakes. Among the various
weakening mechanisms possibly activated during seismic slip, we focus on melt
lubrication. Solidified, friction-induced melts (pseudotachylytes) decorate some
exhumed seismic faults, showing that melt can occur on natural faults, though its
frequency is still a matter of debate. In the presence of melt, tau_f undergoes an initial
strengthening stage, followed by a dramatic weakening stage (thermal runaway).
Field estimates based on pseudotachylyte thickness and experimental measures of
tau_f suggest large stress drops once thermal runaway is achieved. These estimates of
tau_f are compatible with large dynamic stress drops and high radiation efficiency, as
observed for some earthquakes. Moreover, the threshold for the onset of thermal
runaway might explain differences between the mechanics of small (M < 4) and
large earthquakes. A simple mathematical model coupling melting, extrusion and
thermal diffusion reproduces some observed experimental features such as the
duration of the weakening stage and the convergence to a steady-state
High magnetic susceptibility produced in high-velocity frictional tests on core samples from the Chelungpu fault in Taiwan
No full textDispelling 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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