1,720,999 research outputs found
LIBS Collection Optics : comparative analysis of different mirror-based configuration
Full text linkWe have evaluated the efficiency of different reflection based optical systems using numerical simulation. We have realized and started testing the most promising one
Effect of the temporal integration on the accuracy of the measured concentration in LIBS measurements
Full text linkWe have developed a simulation program that allows to calculate the plasma emission spectrum of a coal sample in a LIBS experiment. We used the acquired data to evaluate the effect of temporal integration on the accuracy of measured concentration obtained using the calibration free method
Validazione della tecnica LIBS per l’analisi della composizione di carbone in pezzi edefinizione dei requisiti di un prototipo per misure su impianto
No full textIl documento descrive l’attività relativa allo sviluppo di un sistema LIBS (Laser Induced
Breakdown Spectroscopy) da utilizzare per l’analisi in linea della composizione chimica del
carbone in ingresso ai mulini di macinazione nelle centrali termoelettriche alimentate a
carbone
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
Self-aligning optical particle sizer for the monitoring of particle growth processes in industrial plants
No full textWe describe a diffraction based optical particle sizer to be used on-line in an industrial plant for monitoring the growth process of polystyrene beads in the range (400 μm-4 mm). The instrument has been designed to perform elastic light scattering measurements at very small angles (from 8×10-5 to 8×10-3 rad) and is provided with an active servo system that controls the beam alignment during operations
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
Development of a large depth of field collection optics for on-line LIBS application
No full textIt is common knowledge that LIBS dedicated optical systems usually operate over a quite broad spectral region, typically ranging from 200 nm to 1100 nm. It should also be noticed that in this spectral region, especially at the shortest wavelength, common lenses suffer from great chromatic aberration. Achromatic lenses do exist, but they are expensive and with a limited aperture: for these reasons, the use of mirror based optical systems has become a quite common practice. A typical configuration is the one made of two ellipsoidal mirrors that conjugate the plasma emitting region with the spectrometer slit, which is virtually immune from any kind of aberration. Although suitable for tabletop applications, due to its limited depth of field this system starts failing in application where the distance between the sample and the collection optics may vary from shot to shot, such as in measurements performed on raw minerals transported by conveyor belts.
This problem has been tackled in the past by using optical systems with variable focus or by means of mechanical systems that keep the optics at a fixed distance from the sample. To overcome the difficulties connected to the use of feedback based instrumentation, we investigated the possibility of developing an innovative LIBS setup, with a large depth of field, where moving parts are not required.
To evaluate the collection efficiency of different mirror based configurations we developed a specific ray tracing software. Main boundary conditions imposed to the optical system during simulations were the specifications of the collecting optical fiber (600μm core diameter, 0.22NA) and the distance between the first mirror and the sample (about 1m). According to these conditions, we found that the use of two spherical mirrors with the same curvature radius provide a collection optics free from spherical aberrations. However, due to the off axis configuration of the mirrors, a slight astigmatism still remains. Although this aberration could be compensated by using customized mirrors, an astigmatic system still provides a greater depth of field without a substantial decrease in the collection efficiency.
Tests carried out with an experimental setup show that the collection efficiency of the innovative optical system is in good agreement with the simulations
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
- …
