1,721,337 research outputs found
Thermal decay of a metastable elastic string
No full textThermal nucleation of kink-antikink pairs in an elastic string subjected to a washboard potential is analyzed in the classical limit at low temperature. The nucleation rate is calculated analytically for values of the tilt up to close the instability threshold. Numerical simulation is shown to support our predictions in the diverse parameter regimes
Critical Hysteresis in a Tilted Washboard Potential
No full textThe Brownian motion in a tilted washboard potential subjected to a lowfrequency periodic drive develops large hysteresis loops, which attain their maximum at the locked-to-running transition in the underdamped regime. The dependence of such a critical phenomenon on the drive parameters and on the temperature is investigated numerically. Moreover, this hysteresis mechanism is related to the occurrence of random multiple jumps, whose length and time duration distributions appear to decay according to a universal power law with exponent alpha=1.5. This model may explain various instances of low-frequency excess damping in material science
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
Recycled noise rectification: An automated Maxwell's daemon
No full textThe one-dimensional motion of a massless Brownian particle on a symmetric periodic substrate can be rectified by reinjecting its driving noise through a realistic recycling procedure. If the recycled noise is multiplicatively coupled to the substrate, the ensuing feedback system works like a passive Maxwell's daemon, capable of inducing a net current that depends on both the delay and the autocorrelation times of the noise signals. Extensive numerical simulations show that the underlying rectification mechanism is a resonant nonlinear effect: The observed currents can be optimized for an appropriate choice of the recycling parameters with immediate application to the design of nanodevices for particle transport
Vibrational ratchets
No full textTransport in one-dimensional symmetric devices can be activated by the combination of thermal noise and
a biharmonic drive. For the study case of an overdamped Brownian particle diffusing on a periodic one-
dimensional substrate, we distinguish two apparently different biharmonic regimes: ͑i͒ Harmonic mixing,
where the two drive frequencies are commensurate and of the order of some intrinsic relaxation rate. Earlier
predictions based on perturbation expansions seem inadequate to interpret our simulation results; ͑ii͒ Vibra-
tional mixing, where one harmonic drive component is characterized by high frequency but finite amplitude-
to-frequency ratio. Its effect on the device response to either a static or a low-frequency additional input signal
is accurately reproduced by rescaling each spatial Fourier component of the substrate potential, separately.
Contrary to common wisdom, based on the linear response theory, we show that extremely high-frequency
modulations can indeed influence the response of slowly ͑or dc͒ operated devices, with potential applications
in sensor technology and cellular physiology. Finally, the mixing of two high-frequency beating signal is also
investigated both numerically and analytically
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
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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