1,720,995 research outputs found
Non-equilibrium Thermodynamics of Piecewise Deterministic Markov Processes
No full textWe consider a class of stochastic dynamical systems, called piecewise deterministic Markov processes, with states (x, sigma) is an element of Omega x Gamma, Omega being a region in R(d) or the d-dimensional torus, Gamma being a finite set. The continuous variable x follows a piecewise deterministic dynamics, the discrete variable sigma evolves by a stochastic jump dynamics and the two resulting evolutions are fully-coupled. We study stationarity, reversibility and time-reversal symmetries of the process. Increasing the frequency of the sigma-jumps, the system behaves asymptotically as deterministic and we investigate the structure of its fluctuations (i.e. deviations from the asymptotic behavior), recovering in a non Markovian frame results obtained by Bertini et al. (Phys. Rev. Lett. 87(4): 040601, 2001; J. Stat. Phys. 107(3-4): 635-675, 2002; J. Stat. Mech. P07014, 2007; Preprint available online at http://www.arxiv.org/abs/0807.4457, 2008), in the context of Markovian stochastic interacting particle systems. Finally, we discuss a Gallavotti-Cohen-type symmetry relation with involution map different from time-reversal
Polarization Shift Keying for High Bit-Rate Multilevel Soliton Transmissions
No full textA novel scheme for high-capacity optical transmission is studied. The proposed system is based on a multilevel modulation technique that uses solitons. The basic idea relies on the property of solitons that the evolution of the state of polarization during propagation can be represented with a good degree of approximation with a rigid rotation of the Poincaré sphere. Therefore, besides the rigid rotation that can be compensated for at the receiver, the state of polarization of the signal can be used to carry information. Here the limits of the rigid rotation that are due to polarization mode dispersion and amplified spontaneous emission noise are envisaged. Results show how this scheme permits the transmission-distance limit to be overcome for single-channel intensity-modulated direct-detection soliton systems. As an example we show how a 2.5-Gsymbol/s system with 24 polarization levels leads to a total capacity of 10 Gbits/s over distances up to 3000 km in links encompassing standard dispersion fibers
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
Circuit Based Quantification: Back to State Set Manipulation within Unbounded Model Checking
No full textIn this paper a non-canonical circuit-based state set representation is used to efficiently perform quantifier elimination. The novelty of this approach lies in adapting equivalence checking and logic synthesis techniques, to the goal of compacting circuit based state set representations resulting from existential quantification. The method can be efficiently combined with other verification approaches such as inductive and SAT-based pre-image verifications
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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