1,720,978 research outputs found
Manipulate light propagation based on gradient-phase meta-interfaces
No full text超穎材料(plasmonic metamaterials)由次波長(sub-wavelength)尺寸的侷域共振結構組成，這些共振結構隨電磁波激發產生電偶(electric dipole)及磁偶極矩(magnetic dipole)共振，並展現一些特殊的電磁波特性如負折射(negative refraction)、完美成像(perfect imaging)等。近年來藉由一種介面梯度超穎材料(graded metamaterial systems)，實現許多新穎的現象如影形斗篷(invisibility cloaking)及侷域彩虹(trapped rainbow)等。近年來N. Yu等人根據Generalized Snell’s law的理論基礎設計了尺寸漸變的奈米天線(optical antenna)振列，並在近紅外光(8微米)波段實現異常(anomalous)穿透與反射的調控效果。X. Ni等人以類似的結構將尺寸縮小使之於波長2微米工作，並具有寬頻(broadband)工作的特性。 Sun 等人透過一種反射式的結構於微波(microwave)波段將入射的傳遞波近乎100%轉為表面波。這系列研究主要是透過不同尺寸的超穎材料在介面上不同位置產生漸變的電磁波相位(phase)，並在遠場干涉(interference)後建構出特定指向的平面波前(wave front)。
在此研究中透過模擬設計介面結構，使結構將正向入射平面波高效率(78%)調控到異常反射角度，並在850nm光頻段工作下具有200nm的寬頻調控效果。此設計結構的調控特性可應用於分光元件(beam splitter)、表面電漿波耦合器(SPP coupler)及光吸收元件(light absorber)等。Plasmonic metamaterials are artificial composites made by sub-wavelength local resonance structures of electric and/or magnetic type(s) exhibiting novel electromagnetic properties, such as negative refraction, perfect imaging, etc. In last several years, various graded metamaterial systems have brought us new fascinating phenomena such as invisibility cloaking [1], trapped rainbow [2], etc. Recently, N. Yu et. al. showed that a graded optical antenna array could realize anomalous reflection and refraction for light at infra-red (8 micrometer), following a generalized Snell’s law [3], and X. Ni et. al. soon pushed the idea to 2-micrometer wavelength with a relative broad operation bandwidth [4]. Sun et. al. further proved that a particular gradient-index meta-surface can convert a propagating wave to a surface wave with nearly 100% efficiency [5], and demonstrated the idea in microwave frequency regime. The key idea behind this set of works is to utilize the local reflection/refraction phase properties of a gradient metamaterial, so that coherent beams can be formed by constructive interference.
In this work, we push the idea to visible frequencies. We designed and fabricated a graded meta-surface working around 850 nm, and demonstrated that an incident beam can be redirected to a non-specular channel after reflection by our system. The measured conversion efficiency from the incident beam to the anomalous reflection one is quite high (up to 78%), and the working bandwidth is very broad (about 200 nm). We believe that our systems can have broad applications including beam splitter, SPP coupler, light absorber, etc
Design of high birefringence and low confinement loss photonic crystal fibers with five rings hexagonal and octagonal symmetry air-holes in fiber cladding
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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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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