1,721,065 research outputs found
A 10-µs-tuning MEMS-actuated Gires-Tournois filter for use as a tunable wavelength demultiplexer and a tunable OCDMA encoder/decoder
No full textEightfold 40-320 Gbit/s phase-coherent multiplexing and 320-40 Gbit/s demultiplexing using highly nonlinear fibers
No full textWe experimentally demonstrate 40-320 Gbit/s phase-coherent multiplexing based on cross-phase modulation and subsequent 320-40 Gbit/s demultiplexing using cross-phase-modulation-induced frequency shift in highly nonlinear fibers. An average penalty of approximately 7 dB at a 10~-9 bit-error rate is observed after the nonlinear processes. We also show the generation of a phase-coherent 320 GHz optical pulse train. A delay-line interferometer based on differential group delay is used to verify the phase coherence characteristic of the multiplexed 320 Gbit/s signal and the generated 320 GHz pulses. © 2010 Optical Society of America
Visible-light communications and light fidelity
No full textThis chapter starts by explaining the significantly increased interest in visible-light communications (VLC) and light fidelity (LiFi) during the last 10 years. Next, a taxonomy of the various optical wireless communications technologies is provided, and we discuss their key discriminating features. Typical applications for each technology are presented. The important element of the optical wireless propagation channel is discussed in detail. The essential differences to radio-frequency-based wireless communications are highlighted, and we discuss what these differences mean in terms of designing VLC and LiFi systems. The detailed knowledge of the channel allows for an efficient design of the analog optical front ends; thus, various source and receiver technologies are introduced including micro-light-emitting diodes as transmitters, and single-photon avalanche diodes and photovoltaic cells as data receivers. Next, a review of recent advances in digital modulation techniques for intensity modulation/direct detection for single-input single-output channels is provided. The chapter then discusses multichannel data transmission by considering spatial and wavelength domains. The ability to serve randomly moving mobile terminals is a key property of LiFi. The last two sections, therefore, introduce key functions that will enable this. In this context, the latest advancements in multiple access such as nonorthogonal multiuser access are reviewed. The methods to mitigate cochannel interference when multiple closely located light sources transmit different signals to different users are reviewed, along with methods to enable seamless services when users roam through a room or inside a building. The last section summarizes this chapter
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
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
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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