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Effect Of Noise And Pump Depletion On The Plasma Beat Wave Accelerator
Full text linkPhysic
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Emittance Control In Laser Wakefield Accelerator
Full text linkIn this paper we summarize our recent effort and results in theoretical study of the emittance issues of multistaged Laser Wakefield Accelerator (LWFA) in TeV energy range, In such an energy regime the luminosity and therefore the emittance requirements become very stringent and tantamount to the success or failure of such an accelerator. The system of such a machine is very sensitive to jitters due to misalignment between the beam and the wakefield. In particular, the effect of jitters in the presence of a strong focusing wakefield and initial longitudinal phase space spread of the beam leads to severe transverse emittance degradation of the beam. To improve the emittance we introduce several methods: a mitigated wakefield focusing by working with a plasma channel, an approximately synchronous acceleration in a superunit setup, the >horn> model based on exactly synchronous acceleration achieved through plasma density variation and lastly an algorithm based on minimization of the final beam emittance to actively control the stage displacement of such an accelerator.Physic
Particle simulation of Lyapunov exponents in one-component strongly coupled plasmas
Full text linkThe Lyapunov exponents and instantaneous expansion rates in a phase space of Coulomb many-body systems are measured with the use of a three-dimensional particle code SCOPE [K. Nishihara, Kakuyugo Kenkyu 66, 253 (1991)]. The code calculates particle dynamics determined by Coulomb forces among individual particles. The Lyapunov exponents normalized by plasma frequency are found to be proportional to Gamma(-25) in the range of 1 less than or equal to Gamma less than or equal to 160, where Gamma is the Coulomb coupling constant of the ion one-component plasma. There is a large jump of the Lyapunov exponent near Gamma similar to 170, which corresponds to the phase transition from the liquid to the solid state in the one-component plasma. In the solid state, the normalized Lyapunov exponents are proportional to Gamma(-6/5) for 170<Gamma<300. The observed dependence is discussed in analogy to a rigid-body particle system and a weakly nonlinear lattice system for liquid and solid states, respectively. Diffusion coefficients are found to be proportional to the third power of the Lyapunov exponent in the liquid state, that is, for 1 less than or equal to Gamma less than or equal to 160. These results imply that the Lyapunov exponent is in close relation to the transport processes. The instantaneous expansion rate starts from a small value and increases rapidly to a large peak value before declining slowly towards an asymptotic value. This stage is called the Lyapunov transient stage. Products of the transient time and the Lyapunov exponent are found to be 1.5-2. Information of the initial state is lost after-the transient time. The chaotic behavior of the instantaneous expansion rate is also shown.Institute for Fusion Studie
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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