1,721,104 research outputs found
Resonant radiation from Peregrine solitons
No full textWe investigate the phenomenon of resonant radiation emitted by Peregrine solitons. We show that, unlike bright or dark solitons of the nonlinear Schrödinger equation, the radiation process is affected by the intrinsic local longitudinal variation of the soliton wavenumber. We give a phase-matching condition that allows the prediction of the multiple spectral peaks of the resonant radiation
Frequency conversion based on three-wave parametric solitons
Full text linkParametric three-wave mixing in quadratic nonlinear crystals provides a versatile means of achieving widely tunable frequency conversion of laser light, thus permitting a substantial extension of the wavelength coverage of laser sources across broad wavelength regions. For mode-locked lasers, the effective parametric interaction length among short pulses at different wavelengths is limited by crystal dispersion, which leads to group velocity walk-off. Nevertheless, as well known since the 1970s, the frequency conversion of short pulses may be significantly enhanced by means of the optical soliton concept (Zakharov & Manakov, 1973). Indeed, the collision of two soliton input pulses at different frequencies, with proper durations and peak powers, leads to a time compressed pulse at the sum-frequency (Ibragimov & Struthers, 1996). However such pulse is unstable, since it rapidly decays into two, time-shifted replicas of the input pulses. On the other hand, two resonant bright pulses and a kink (or phase jump across a CW background) pulse may propagate locked together as an optical simulton, in spite of their different linear group velocities, owing to their nonlinear mutual trapping (Nozaki & Taniuti, 1973; Degasperis et al., 2006)
From regular to pseudo-stochastic recurrence of modulation instability in cascaded second-harmonic generation
No full textWe address the recurrent regime of depleted two-color modulational instability in second-harmonic generation in the cascading limit. We validate a description based on simple algebraic formulas, based on asymptotic matching, establishing quantitatively the limit of validity of this approach. In the low mismatch regime, where such description breaks down, the system is found to undergo pseudo-stochastic alternations between two types of deterministic recurrence
Sine-gordon breathers and formation of extreme waves in self-induced transparency media
Full text linkWe investigate the formation of optical extreme waves in a resonant two-level medium that entails the self-induced transparency (SIT) effect, within the framework of the sine-Gordon equation. By virtue of the exact breather solutions and numerical simulations, we reveal that the extreme waves may occur as a result of an intense interaction between individual breather components, by an optimal choice of the breathing periods and the propagation directions for each component. We expect that this work may stimulate the experimental study of the extreme wave formation in SIT media
SPECIAL TYPES OF ELASTIC RESONANT SOLITON SOLUTIONS OF THE KADOMTSEV-PETVIASHVILI II EQUATION
No full textFundamental Peregrine Solitons of Ultrastrong Amplitude Enhancement through Self-Steepening in Vector Nonlinear Systems
No full textWe report the universal emergence of anomalous fundamental Peregrine solitons, which can exhibit an unprecedentedly ultrahigh peak amplitude comparable to any higher-order rogue wave events, in the vector derivative nonlinear Schrödinger system involving the self-steepening effect. We present the exact explicit rational solutions on either a continuous-wave or a periodical-wave background, for a broad range of parameters. We numerically confirm the buildup of anomalous Peregrine solitons from strong initial harmonic perturbations, despite the onset of competing modulation instability. Our results may stimulate the experimental study of such Peregrine soliton anomaly in birefringent crystals or other similar vector systems
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
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