1,721,233 research outputs found
An investigation of laser oscillators and amplifiers using high intensity diode-pumping
No full textThe work presented in this thesis is split into two related areas. The first area of research was the construction of high gain, high power, all-solid-state laser amplifiers for use in master oscillator, power amplifier (MOPA) systems. The second area was the operation of solid-state lasers on low gain transitions. The two areas are related by the fact that the primary aim in each was to maximise the available gain on a given laser transition.Two diode-pumped travelling wave amplifiers are described, both using Nd:YLF as the active medium, and both employed to amplify the output from a modelocked 1047nm Nd:YLF laser. The first amplifier was pumped by a 4W diode, and produced a small signal gain of 34. To suppress gain saturation in the amplifier, the input signal to the amplifier was formed into pulse trains of duration 10µs. The average gain achieved during these pulses was 20, giving rise to an average output power of 5W during the pulse. The amplifier output was subsequently frequency-doubled by a single pass through an LBO crystal. An average conversion efficiency of 57% was obtained, giving an average green power of 2.9W. The green output was subsequently used to pump both an OPO based on LBO, and a Ti:Sapphire laser.The second amplifier had a pump power of 28W. This produced a small-signal gain of 40 at 1047µm, and yielded 6W of amplified modelocked output on a cw basis rather than pulsed as in the first amplifier. The output from this amplifier was used to pump an OPO based on PPLN, and this was able to oscillate at a maximum wavelength of 6.2µm.The work on low gain lasers was addressed at the 1123nm transition in Nd:YAG. This has a cross-section ~15 times lower than at 1064nm. The pump source was a 7W diode-bar, and using this 1.7W of TEM00 output at 1123nm was obtained in a beam with an M2 of 1.1. This output was subsequently used as the pump for a Tm:ZBLAN fibre laser, which produced a maximum of 230mW of 480nm blue light. A second application envisaged for the 1123nm output was to sense atmospheric water vapour by using a differential absorption LIDAR. For this, narrow linewidth operation of the laser was required. To this end, a single-frequency ring laser was constructed, and this produced a maximum power of 180mW, again in a TEM00 mode with M2 = 1.05. The output power was restricted by limitations on available components
An experimental investigation into wing in ground effect over flat and wavy surfaces
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
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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