1,720,970 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Performance of NUV-HD Silicon Photomultiplier Technology
No full textIn this paper, we present the full characterization of a new high-density (HD) cell silicon photomultiplier (SiPM) technology for ultraviolet (UV) and blue light detection, named near UV HD SiPM. Thanks to an optimized border region around each cell, we were able to develop devices having a very high detection efficiency and, at the same time, a high dynamic range.
We produced SiPMs with a square cell pitch of 15, 20, 25, and 30 μm featuring a peak efficiency in the violet region ranging from 40% to 55%, according to the cell size. We tested this technology for time-of-flight positron emission tomography. Using two 4×4 mm2 SiPMs with a 25 × 25 μm2 cell pitch coupled to 3×3×5 mm3 LYSO scintillators, we reached for the first time 100-ps full-width at half-maximum coincidence time resolution.
This result was independent of the temperature in a range from 20°C to −20°C. At the same time, thanks to the high dynamic range and low correlated noise, we obtained an energy resolution lower than 9% for 511-keV γ-rays
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
High-Density Silicon Photomultipliers: performance and linearity evaluation for high efficiency and dynamic-range applications
No full textSilicon photomultipliers (SiPM) are photodetectors that have obtained a growing attention in the last years. They have single photon sensitivity, but also a high dynamic range: the output current signal is proportional to the number of detected photons and it is possible to distinguish up to tens of photon per each light pulse. In FBK (Trento, Italy) we developed the so called high-density (HD) SiPMs, with narrow trenches to isolate the cells (i.e. SPADs) and with high fill factor (FF). These detectors feature high photon detection efficiency and high dynamic range. Moreover, the reduction of the cell size reduces the correlated noise (i.e. lower crosstalk between cells and lower afterpulsing probability) and it makes the single-cell response faster, increasing the maximum counting rate. These characteristics can be very important in applications like Light Detection and Ranging (LIDAR), spectroscopy and physics experiments. In this work, we present the structure of high-density SiPMs and their performance. In particular, the photon detection efficiency, the photon number resolving capabilities, the linearity vs. photon flux and the single-photon time resolution, investigating how these parameters change with the cell pitch
Study of the photo-detection efficiency of FBK High-Density silicon photomultipliers
No full textThis work presents a study of the factors contributing to the Photo-Detection Efficiency
of Silicon Photomultipliers (SiPMs): Quantum Efficiency, Triggering Probability and Fill Factor.
Two different SiPM High-Density technologies are tested, NUV-HD, based on n-on-p junction,
and RGB-HD, based on p-on-n junction, developed at FBK, Trento. The quantum efficiency was
measured on photodiodes produced along with the SiPMs. The triggering probability, as a function
of wavelength and bias voltage, was measured on circular Single Photon Avalanche Diodes (SPADs)
with 100% fill factor. Square SPADs, having the same layout of single SiPM cells, were studied to
measure the effective fill factor and compare it to the nominal value. The comparison of the circular
and square SPADs allows to get the transition region size between the effective active area of the
cell and the one defined by the layout
Characterization of Silicon Photomultipliers after proton irradiation up to 1014 neq∕cm2
No full textSilicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications, including large high-energy physics experiments where they often are exposed to high radiation fluences. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after the irradiation with proton or neutron, with different fluence levels.
In this work, samples of different FBK SiPM technologies, made with different manufacturing technologies, were irradiated at the INFN-LNS facility (Italy) with protons reaching fluences up to about 10^14 neq/cm^2 (1 MeV neutron equivalent) and their performances were characterized in detail after about 30-days room temperature annealing. The results show a significant worsening of the primary noise (dark count rate) of the detectors, which increases with the irradiation fluence, whereas the other performance parameters like the micro-cell gain, the correlated noise probability and the photon detection efficiency do not show significant variations up to 10^11 neq/cm^2 at least. The breakdown voltage estimation after irradiation is another important aspect for a SiPM. In this contribution, we show several methods for its estimation and compare the results. We also introduced new methodologies to characterize the performance of the SiPMs when they present a very high level of noise, such as the estimation of the dark count rate based on the measured reverse current, the estimation of variations in the photon detection efficiency through the measurement of the responsivity, and the measurement of the correlated noise and the gain through the average charge in response to a pulsed light signal.
Lastly, we also analyzed the spatial localization of the proton-induced defects inside the device, i.e. the defects that mostly contribute to the increase of the DCR of the device, through the emission microscopy (EMMI) technique. In particular, we analyzed the SiPMs at the single cell level, trying to identify and spatially localize the defects
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