1,720,967 research outputs found
Efficient conversion to radial polarization in the two-micron band using a continuously space-variant half-waveplate
No full textWe demonstrate efficient conversion of a linearly-polarized Gaussian beam to a radially-polarised doughnut beam in the two-micron band using a continuously space-variant half-waveplate created by femtosecond writing of subwavelength gratings. The low scattering loss (<0.07) of this device indicates that it would be suitable for use with high power lasers
Integrated disruptive components for 2 µm fiber Lasers (ISLA): project overview and passive component development
No full textIn this paper, an overview of the EU FP7 project ISLA (Integrated disruptive componentS for 2 µm fibre Lasers) is given. The aim of ISLA was to develop a set of “building block” components and a “tool-kit” of processes to define an integrated modular common platform for two micron fibre lasers consisting of compatible and self-consistent active and passive fibres, fused fibre couplers and combiners, fibre-coupled isolators, modulators and high power pump laser diodes. We also present results from our work on developing passive components for 2 µm fibre lasers. This includes high power pump combiners that have been tested up to 0.5 kW and combiners for in-band pumping of holmium lasers. Couplers for use as splitters, power monitors and wavelength division multiplexers have also been demonstrated. Wideband couplers, with a coupling ratio that only varies ± 12% over 400 nm, have also been developed to exploit the wide tuning range possible with thulium fibre lasers. Research into different isolator materials was also conducted to find materials with large Verdet constants to be used in 2 µm isolators. Fibre-coupled isolators were then manufactured using a selection of these materials. Isolators that had insertion losses of <1 dB and isolation of > 35 dB were demonstrated using PM and non-PM fibres. In the PM isolators, PER > 23 dB was achieved
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
Generation of radially-polarized and azimuthally-polarized beams in the two-micron band using a space-variant half-wave plate
No full textRadially and azimuthally polarized beams have attracted growing interest for use in a variety of applications. The most popular way to obtain these beams at relatively low power levels is to transform a linearly-polarized TEM00 beam into a radially or azimuthally-polarised beam using an external polarisation mode converter. Traditionally, these converters were constructed from an arrangement of half-wave plates bonded together to form a segmented spatially-variant retardation plate and, as a consequence, they generally suffered from low polarization purity and low transformation efficiency. However, recent work on femtosecond laser writing of nanostructure gratings in silica glass has allowed the realization of a new type of polarization converter with improved performance. In these converters the grating structures induce birefringence with slow and fast axes aligned parallel and perpendicular to the grating direction respectively, allowing the construction of a continuously space-variant half-wave plate (S-waveplate). S-waveplate provides dramatically improved polarization purity compared to segmented retardation plates. Here we report on an S-waveplate designed for use in ~2µm wavelength band for use with Tm-doped and Ho-doped solid-state lasers and fiber laser. The S-waveplate was tested with a relatively low power (~1.5 W) tunable Tm fiber laser yielding a donut-shaped radially-polarized (or azimuthally-polarized) beam with a polarization extinction ratio (PER) of 18dB and a transmission efficiency of ~86%. The beam propagation factor (M2) was measured to be ~2.1 and hence in close agreement with the theory. The prospects for further scaling output power and improving efficiency will be discussed
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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