1,720,980 research outputs found
Stability of standard dynamic VOC mixtures for atmospheric measures
No full textTraceable and accurate standard of Volatile Organic
Compounds VOC at trace concentration level are necessary
for a framework of quality assurance and quality control of
atmospheric composition measurements. Dynamic preparation
of standard mixtures can fulfill the target accuracy given by
the framework. Short-term concentration stability is one of the
sources of uncertainty of dynamic preparation and depends on
sampling time of the mixture, stability contribution to total
uncertainty must be calculated. A method for the calculation of
the stability contribution is here proposed. The performance of a
preparation device for accurate VOC standard mixtures is here
discussed as an application of the method. Two threshold values
for stability contribution were set to consider the contribution
negligible and relevant respectively. Experimental stability of the
dynamic preparation device was measured. The stability of one
of the five influence quantities resulted to give the total stability
contribution. Stability contribution to total uncertainty resulted
to be negligible below 60 min, while its contribution resulted to
be relevant over 400 min
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
Preparation of standard VOC mixtures for climate monitoring
No full textThe growing need for global volatile organic compounds (VOC) data at trace level for industrial applications, domestic and working health, air quality and climate change is driving research towards the preparation of traceable and accurate standards for the VOC amount of substance fraction in gas phase.The World Meteorological Organization (WMO) has implemented a worldwide VOC monitoring programme, named Global Atmosphere Watch (GAW), which data quality objectives refer to an expanded uncertainty lower than 10% for VOC measurement at amount of substance fractions lower than 100 nmol∙mol−1.Currently, gaseous standard atmospheres are prepared in high pressure gas cylinders, but they do not fulfil GAW requirements of accuracy and stability at ppb level, especially for oxygenated VOCs. Dynamic methods are proposed as an alternative to provide a stable amount of substance fraction of the mixture over time. Diffusion rate, dilution and carrier air flow rates, purity of air, VOC losses due to wall-interactions and leakages were considered as influence quantities of the VOC amount of substance fraction dynamically prepared in gas phase by the diffusion method. The contribution of the VOC losses to standard mixtures uncertainty and their sampling procedure are under study and a solution has not yet been proposed.In this paper, a conservative quantification of VOC losses is proposed, discussed and applied to a case study: a single stage dynamic dilutor with an acetone generation. An uncertainty budget was prepared to calculate target uncertainty for VOC losses due to leakages and VOC–wall interactions on Teflon®, Pyrex® and stainless steel tubing. Teflon® showed negligible interaction effects when the pipe was clean and long term effects were not considered. Uncertainty was not negligible for glass and stainless steel for which more accurate analyses are necessary. A leakage test was developed to assure negligible leakage contribution to uncertainty
Modelling of a standard gas mixtures generator with computational fluid dynamics
Get PDFMonitoring VOC for climate change and for indoor and outdoor air quality at trace level concentrations need reference standard materials at high metrological performance. To improve this performance, the description of phenomena involved in mixtures generation by rigorous models is mandatory. A model to describe diffusion cells of a primary generator was developed and validated with experimental data. A good agreement was found between the uncertainties of measurements and calculations
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
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
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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