1,720,958 research outputs found
Investigation of materials for use in high-temperature, thin-film heaters and temperature sensors
Full text linkThesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 79-83).by Samara L. Firebaugh.M.S
Miniaturization and integration of photoacoustic detection
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (p. 170-171).Photoacoustic spectroscopy (PAS) is an absorption spectroscopy technique that is currently used for low-level gas detection, biological studies, and catalyst characterization. In PAS, the incident radiation is modulated at an acoustic frequency. In the presence of an absorbing species, the periodic radiation is translated into periodic heat generation, which launches an acoustic signal. PAS is a promising technique for chemical analysis in mesoscale analysis systems because the detection limit scales favorably with miniaturization. This work focuses on the miniaturization of gas-phase photoacoustic detection of propane in a nitrogen or carbon dioxide ambient. This work could be expanded to other chemical species or to spectroscopy with a change of light source. The detection system was modeled with a transmission line analogy, which was verified with a set of experiments. The model includes the effects of acoustic leaks and absorption saturation. These two phenomena degrade the performance of the PA detector and must be controlled to realize the scaling advantages of PA systems. The miniature brass, cells used to verify the model used hearing aid microphones and optical excitation from a mechanically-chopped, 3.39-[mu]m He-Ne laser, transmitted into the cells with an optical fiber. I was able to detect 10 ppm of propane in nitrogen with these cells (a signal level of - 1 Pa/W). This thesis describes the development of two more miniaturized PA systems-- one formed by microfabrication and another in which PA detection is integrated with another miniaturized system. The microfabricated PA detector used the He-Ne laser and a less-sensitive optical microphone. I was able to detect 5% propane in nitrogen with this detector, which had a signal level of about 100 Pa/W. In the integrated system, a PA cell was machined into the mounting chuck of a microfabricated chemical reactor. The detector used a hearing aid microphone and a 3.4 [mu]m infra;red diode that was modulated at the first acoustic resonance of the cell. The integrated system was not as well characterized as the others, but demonstrates the potential for portability and integration of PA detection systems. These systems have shown that PA detection may be inappropriate for systems with large variations in gas concentration because of absorption saturation and changing gas acoustic properties. However, it is a promising technique for the analysis of dilute mixtures in miniature chemical systems and may also be useful in miniaturized multi-phase systems.by Samara Louise Firebaugh.Ph.D
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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