1,720,974 research outputs found
<Research Report>Josephson Plasma Excitations in Intrinsic Josephson Junctions of High-Tc Superconductors
No full textStudies on excitations of electromagnetic waves inside Bi[2]Sr[2]CaCu[2]O[8+5] intrinsic Josephson junctions are described. Josephson vortices introduced between their superconductive CuO[2] layers severely couple with the excited Josephson plasma modes and result in the dominant factor for their propagating vector. Emission of the Josephson plasma was confirmed in the absence of applied magnetic field. This stimulates developments of compact superconducting THz sources in future
高温超伝導テラヘルツ光源の開発
Get PDF京都大学アカデミックデイ2015 「みんなで対話する京都大学の日」開催日時: 2015年10月4日(日)10:00-16:00会場: 京都大学百周年時計台記念館主催: 京都大学学術研究支援室, 研究推進部研究推進課, 国民との科学・技術対話ワーキンググループ京都大学の学術研究成果発信の一環として包括的に登
Terahertz-wave emission from Bi2212 intrinsic Josephson junctions: A review on recent progress
Get PDFEmission of terahertz (THz) electromagnetic (EM) waves from a high critical temperature (T c) superconductor intrinsic Josephson junction (IJJ) is a new and promising candidate for practical applications of superconducting devices. From the engineering viewpoint, the IJJ THz source is competitive against the present semiconducting THz sources such as quantum cascade lasers (QCLs) and resonance tunnelling diode oscillators because of its broad tunable frequency range and ease of the fabrication process for the device. The emitted EM waves are considered to be coherent because the emission is yielded by synchronisation of thousand stacked IJJs consisting of the mesa device. This synchronisation is peculiar: the resonant frequency of each IJJ is distributed because the cross section of the mesa device is trapezoidal in shape. One of the key features of the synchronisation mechanism is the temperature inhomogeneity of the emitting device. In this topical review, we describe the recent progress in studies of IJJ THz sources with particular emphasis on the relevance of the temperature inhomogeneity to the synchronisation and the emission intensity. This review is of specific interest because the IJJ THz source shows the rich variety of functions due to self-heating which has always been a detrimental feature in the present superconducting devices. Moreover, the thermal managements used for IJJ THz sources will be common with those of other semiconducting devices such as QCLs. In addition, this review is to invite the readers into related research through the detailed descriptions of experimental procedures
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
<Research Reports>Wide-band frequency modulated terahertz wave radiation from intrinsic Josephson junction of a high-temperature superconductor
No full textRadiation of frequency-modulated terahertz electromagnetic waves from a device made of a high-temperature superconductor is demonstrated. This is uniquely attributed to a stack of Josephson junctions included in the superconductor. The achievement stimulates implementation of superconducting terahertz technologies for lowtemperature communication systems
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Increase of superfluid density with growth of quasiparticle density of states probed by intrinsic tunneling spectroscopy in Bi_{1.9}Pb_{0.1}Sr_{2}CaCu_{2}O_{8+δ}
Get PDFInterlayer tunneling spectra, the Josephson critical current density J_{c}, and the normal tunneling resistance have been measured simultaneously for intrinsic Josephson junctions of Bi_{1.9}Pb_{0.1}Sr_{2}CaCu_{2}O_{8+δ} (BiPb2212) in the underdoped region using a small mesa structure (S=1×1 μm2) and a short-pulse technique. J_{c} was significantly enhanced when Bi was partially replaced with Pb. By comparing Jc with the value estimated by the Ambegaokar-Baratoff formula, it was found that superfluid density doubles in the Pb-containing sample. In addition, Pb raises the superconducting coherence peak without changing the value of the superconducting gap Δ. Based on a model that accounts for the inhomogeneity of Δ in k space, we argue that the superfluid density increases because Pb substitution increases the homogeneity of Δ(k)
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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