1,721,261 research outputs found
DEVELOPMENT OF A HEXAGONAL-SHAPED RAPID THERMAL PROCESSOR USING A VERTICAL TUBE
No full textA new RTP system concept is proposed and demonstrated. The system uses a vertical cylindrical quartz tube, while the wafer is placed horizontally. Linear halogen lamps are arranged in a hexagonal shape, and the hexagonal-shaped lamp groups are stacked vertically. Each lamp group is controlled independently, allowing a temperature difference within +/- 1.5-degrees-C to be achieved over a 6-in wafer in steady state. Oxidation under optimal power condition results in a 1.37% standard deviation for an average oxide thickness of 110.4 angstrom. The temperature nonuniformity during the transient has been greatly improved by using dynamic control. The convection loss in the system has been evaluated and its radial dependence is found to be smoother in this chamber than in a conventional rectangular chamber. The ray-tracing simulation in three-dimensional space did result in a better comprehension of the optically complex system. The system efficiency has turned out to be lower than in the case of a conventional rectangular chamber. A large portion of the radiation energy is absorbed by the reflectors. There is a strong side heating to the vertical edge of the wafer. Both are due to multiple horizontal reflections of the rays on the reflectors without hitting the wafer. The temperature profiles calculated from the ray-tracing results show an excellent agreement with experiments and confirm the accuracy of the ray-tracing simulation. The main advantages of this new system concept are its excellent temperature uniformity and the good accessibility of the wafer for technological treatments and in situ measurements
À propos de l'analyse chimique des pigments utilisés dans quelques manuscrits enluminés
No full textDe Reu Martine, Van Hooydonk G., Vandenabeele P., Moens L., Von Bohlen A., Klockenkämper R. À propos de l'analyse chimique des pigments utilisés dans quelques manuscrits enluminés. In: Scriptorium, Tome 53 n°2, 1999. pp. 357-372
Development and evaluation of a simple Raman spectral searching algorithm
No full textRaman spectroscopy has grown to a frequently applied technique in the analysis of art and archaeological objects. The growth in applications is further driven by the development of new, small and compact spectrometers that are well suited for in situ analysis. Different spectral databases have been composed, to allow fast identification of the materials at hand. However, the automated identification of the highly similar spectra of contemporary synthetic organic pigments is not straightforward, as spectral libraries that contain several hundreds of spectra are typically recorded on benchtop spectrometers that have different spectral resolutions and sensitivities and often use different excitation laser wavelengths. Therefore, here a simple automated spectral searching algorithm is proposed that is based on the comparison of a series of Raman band positions, to identify the materials. Thus, many of these interferences can be avoided. In this work, the proposed algorithm is tested on spectra that were recorded by using portable Raman instruments on mock-up samples as well as during the in situ analysis of street art. Graphic abstract: [Figure not available: see fulltext.
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
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