1,720,958 research outputs found
Nonlinear optics in novel periodic media.
Full text linkThe major focus of the work in this thesis is on the solution of the electromagnetic wave equations in novel structures that exhibit nonlinearity in their response to the incident field. These structures are further characterized by the presence of a spatial periodicity in their dielectric permittivity. The presence of spatial periodicity results in a number of coherent scattering phenomena when the light wavelength is
comparable to the period of this spatial perturbation. Here we use a combination of
analytical and numerical methods to gain insight into these phenomena. Two problems each involving a different nonlinear phenomenon have been considered.
First, we take the classical problem of hysteretic switching response exhibited by a nonlinear periodic structure. This problem is reexamined in the context of the presence of a negative refractive index (left-handed electromagnetic structure). We theoretically predict an exotic behavior that involves an omnidirectional response
quite distinct from the well known behavior. We examine the field distribution in detail and propose the existence of a spatial soliton called the zero-n gap soliton. Next, we investigate the practical problem of output power scaling in fiber lasers. Self scattering nonlinearities currently set the limit on power scalability. In particular, for narrow linewidth systems, Stimulated Brillouin scattering (SBS) is known to be the limiting nonlinearity. This scattering phenomenon is a result of Bragg reflection from a periodic index modulation induced by an acoustic wave. Several novel schemes are proposed and analyzed in terms of their ability to suppress SBS and enhance power
scalability.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/61585/1/rhegde_1.pd
Fractal Plasmonic Nanoantennae
No full textThe ability to precisely tailor lineshapes, operational bandwidth and localized electromagnetic field enhancements (“hot spots”) in nanostructures is currently of interest in advancing the performance of plasmonics based chemical and biological sensing techniques as well as in plasmonics based energy harvesting applications. Fractal geometries are an intriguing alternative in the design of plasmonic nanostructures as they offer tunable multi-band response spanning the visible and infrared spectral regions. This chapter reviews the recent developments concerning the incorporation of fractal geometries into plasmonic nanostructures. The scope is restricted to the review of fractal shaped antenna elements as opposed to fractal based array placement methods. Beginning with a brief overview of fractals and fractal based radio-frequency antenna engineering, the review focuses on two canonical geometries: the Sierpinski carpet and the fractal tree. Fractal geometries are promising for improving the performance of plasmonics based optical applications like ultrasensing and energy harvesting
Bilayered nanoantenna design improves the performance of silicon metasurfaces in the visible-wavelength region
No full text
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
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