1,721,729 research outputs found
Preface to the special issue on next-generation multiplexing schemes in fiber-based systems
No full textSince the beginning of optical communications in the late 70s, capacity has kept up with the exponential growth of traffic demand. This has been enabled by many technologies among which the most up-to-date wavelength multiplexing combined with coherent detection of polarized-multiplexed quadrature-amplitude-modulated signals. There is, however, a growing realization that this might no longer be sufficient and that next-generation multiplexing schemes are needed to avoid an imminent capacity crunch.Spatial multiplexing, introduced more than 3 decades ago, appears today as the last degree of freedom that can offer multiple orders of magnitude of capacity growth required to sustain the traffic demand. The potential of spatial multiplexing lies in its ability to exploit multiple cores and/or multiple modes within a single optical fiber. Since 2011 and new promising demonstrations, impressive progresses have been made. New optical fibers, components and subsystems have been developed, and record-capacity transmissions have been demonstrated. Significant efforts have also been spent to turn these research results into practical solutions.This special issue features the state-of-the-art research activities in spatial multiplexing. 13 distinguished researchers and their colleagues were invited to contribute with overviews of the latest advances in their research fields. These invited papers can be categorized into 3 groups as follows:• Optical fibers: few-mode, multi-core, and few-mode multi-core fibers.• Components and connectivity: amplifiers, (de-)multiplexers, and splicing• Systems: high-capacity transmissions, and passive optical networks.We hope that this collection will provide the readers with an in-depth overview of the most recent trends in spatial multiplexing schemes in fiber-based systems and stimulate further advances in this renewed field.Finally, we would like to thank all of the authors for their invaluable contributions, and Bertrand Desthieux, Editor-in-Chief, for encouraging and promoting this special issue
On the Changing Political Structure of the Chu State: From an Archaeological Viewpoint
No full textThe emergence of centralised power and polity has long been a crucial problem in historical studies of Eastern Zhou society, and the conclusions of researchers on whether such centralised power was achieved in the state of Chu 楚 have been divided. One reason for this disagreement is due to the differing state of source materials for the Spring and Autumn and Warring States periods, making it difficult to grasp continuity in historical phenomena. In this article, the author re-examines the changing structure of the Chu state based on archaeological evidence from bronze vessels excavated in large quantities in the middle Yangzi River region that enables us to perceive temporal changes throughout the whole Eastern Zhou period. On the basis of archaeological analysis, the author draws three major conclusions. 1) The structure of production and distribution of bronze vessels in the Chu state changed drastically from the late Spring and Autumn period to early Warring States period, and a centralised system emerged by the middle of the Warring States period. 2) In the Spring and Autumn period, the Chu state distributed bronze vessels to the neighbouring polities as a strategy of indirect control in a way similar to that of the Western Zhou dynasty, although this strategy changed to direct domination over the entire middle Yangzi River region. 3) The structure of cemeteries of upper-ranking aristocrats changed through the middle of 5ᵗʰ century BC due to the emerging middle classes, who later became the bureaucrats providing the basis of centralised polity established in the middle Warring States period. Based upon these analyses, the author concludes that the political structure of the Chu state was gradually centralised through 5th century BC, which challenges the traditional views on the centralisation of the Chu polity represented by the drastic and short-term reformation by Wu Qi 吳起. This result calls for reconsideration of the “reformations” (變法) of Eastern Zhou societies from multiple points of view including both historical texts and archaeological materials
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
No full textWe 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
Toward highly conductive n-type diamond: Incremental phosphorus-donor concentrations assisted by surface migration of admolecules
No full textThe realization of low-resistance n-type diamond is required to form novel semiconducting devices. However, heavily doping with phosphorous, the most suitable electron donor, remains challenging. Here we demonstrate that the phosphorus incorporation efficiency in deposited diamond can be maximized when using the largest possible terrace width of vicinal {111}-substrates. Given step-flow-predominant crystal growth, the greater surface migration length of phosphorus-containing admolecules compared with those of carbon-containing parent species explain this. With our findings we create a model which provides a complementary perspective to explain large fluctuations in dopant incorporation efficiencies for p-type and n-type diamond. Our model can also explain conflicting models for admolecule motion responsible for diamond crystallization.The authors thank Misa Yoshida for experimental support and Masahiko Ogura and Toshiharu Makino for valuable discussion. This work was partly supported by the Advanced Low Carbon (ALCA) Technology Research and Development Program Foundation, Japan Science and Technology Agency
Large improvement of phosphorus incorporation efficiency in n-type chemical vapor deposition of diamond
No full textMicrowave plasma enhanced chemical vapor deposition is a promising way to generate n-type, e.g., phosphorus-doped, diamond layers for the fabrication of electronic components, which can operate at extreme conditions. However, a deeper understanding of the doping process is lacking and low phosphorus incorporation efficiencies are generally observed. In this work, it is shown that systematically changing the internal design of a non-commercial chemical vapor deposition chamber, used to grow diamond layers, leads to a large increase of the phosphorus doping efficiency in diamond, produced in this device, without compromising its electronic properties. Compared to the initial reactor design, the doping efficiency is about 100 times higher, reaching 10%, and for a very broad doping range, the doping efficiency remains highly constant. It is hypothesized that redesigning the deposition chamber generates a higher flow of active phosphorus species towards the substrate, thereby increasing phosphorus incorporation in diamond and reducing deposition of phosphorus species at reactor walls, which additionally reduces undesirable memory effects.This work was partly supported by the Nuclear System Research and Development program, 120801 MEXT, and the research grant-in-aid 25-03759 JSPS, Japan
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