1,720,962 research outputs found
Non-parametric study of the radioxenon data distribution, measured at the noble gas stations of the International Monitoring System of the CTBTO
No full textThe aim of this work is to apply a non-parametric statistical methodology to the radioxenon activity
concentrations measured at noble gas stations of the International Monitoring System of the
CTBTO, in order to investigate the radioxenon atmospheric background and the radioxenon anomalous
values. The proposed non-parametric statistical methodology does not require any assumption
on the underlying probability distribution of the raw data. The suggested method, based on Recursive
Segmentation and Permutation (RS/P), allows to detect single or multiple mean and/or scale
shifts
A Distribution-Free Approach for Detecting Radioxenon Anomalous Concentrations
No full textThe detection of anomalous radioxenon atmospheric concentrations plays a key role for revealing both underground nuclear explosions and radioactive emissions from nuclear power plants and medical isotope production facilities. For this purpose, the method currently used by the International Data Center of the CTBTO is based on descriptive thresholds. In this work we propose a statistical inference-based method, that allows to distinguish between the typical background of atmospheric radioxenon and anomalous values above background. We used a non-parametric methodology that does not require any assumption on the phenomenon distribution. In such a way we overcome the problem due to the non-normality of the radioxenon data
Parametric study of the radioxenon data distribution, measured at the noble gas stations of the International Monitoring System of the CTBTO
No full textThe aim of this work is to apply a parametric statistical methodology to the radioxenon activity concentrations
measured at noble gas stations of the International Monitoring System of the CTBTO, in
order to investigate the radioxenon atmospheric background and the radioxenon anomalous values.
The proposed parametric statistical methodology is based on the “Statistical Process Control” method
and it consists of using two “Control Charts”. The “Single Observation Control” Chart, sensitive to
large variation of the measured values, could be useful for periodic monitoring of the phenomenon at the noble gas stations; the “Exponentially Weighted Moving Average” Chart, sensitive to small
variations of the measured values, could be used to perform specific studies on the atmospheric
background and on the anomalies of radioxenon activity concentrations
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
Statistical study of the IMS 133Xe data distributions, using both a parametric and a non-parametric method
No full textThe aim of this work is to apply both a parametric and a non-parametric statistical method to the
133Xe activity concentrations measured at noble-gas stations of the IMS of the CTBTO, in order to
investigate the atmospheric background and the anomalous values. The parametric method consists
of two control charts: a single-observation chart sensitive to large variations with respect to the
mean value, and an EWMA chart sensitive to small variations with respect to the mean value. The results show that the control charts could be useful for an NDC carrying out daily monitoring to easily
detect significant variations of the activity concentrations, and to perform more specific analysis
of the anomalous values. The parametric method is expected to be useful to better understand the
false positives. The non-parametric method is based on a Recursive Segmentation and Permutation
(RS/P) algorithm, it does not require any assumption about the underlying probability distribution,
and it associates a significance level to the results. The RS/P method is useful for detecting single
or multiple mean shifts and/or scale shifts, and the results show that it can be useful to highlight
any random oscillations of the phenomenon providing a likely better understanding of anomalous
values
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
Statistical Study of the Atmospheric Background and Anomalous Values of the Radioxenon Activity Concentrations at Some IMS Stations
No full textThe main goal is to perform a detailed statistical analysis of the atmospheric background and of the “Abnormal Concentrations” of radioxenon, measured at some IMS stations. For each IMS station considered, a descriptive statistical analysis of the empirical distribution was performed and two types of “Statistical Process Control Charts” were applied to the measured values. The Shewhart “Control Chart for Individual Measurements”, sensitive to large variations and the “Exponentially Weighted Moving Average (EWMA) Control Chart”, sensitive to small variations, were used to analyze the overall chronology of the observations and to identify and study those values that significantly deviate from the average value. The “Control Charts” method were then compared with the “Inter-Quartile Range” method currently used by the IDC. The results show that the “Control Chart for Individual Measurements” is particularly meaningful for the periodic monitoring of IMS stations in order to identify large variations of radio-xenon activity concentrations, while the “EWMA Control Chart” is more suitable for specific studies on the atmospheric background and on the "anomalies" of radioxenon activity concentrations. The use of “Control Charts” method as a possible complement to the “Inter-Quartile Range” method, could be further investigated
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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