1,721,324 research outputs found
Coal-dust Explosions In A Spherical Bomb
No full textResults of coal dust explosion experiments obtained by means of the Bartknecht-Siwek 20 litre sphere are presented and discussed. Several coal dusts have been tested at ambient conditions. The oxygen mass fraction and the initial pressure have been varied to test their influence. The data collected lead to an extension of the hazard limits for coal dusts with respect to data in the current literature. The maximum explosion overpressure depends linearly on the partial pressure of atmospheric oxygen. The 'optimum' dust concentration depends linearly on the oxygen concentration in the suspending atmosphere. This has led to a useful non-dimensional representation of the results: in the new variables, maximum explosion overpressure data for a coal dust at various values of the initial oxygen partial pressure are correlated by a single curve for all tests in which most of the oxygen is consumed. Differences in the maximum explosion overpressures exhibited by different coals could not be related to chemical parameters due to the prevailing effect of non-adiabatic explosions in this apparatus at such low rates of pressure rise. The maximum rate of pressure rise has been found generally to increase with the standard volatile matter content and with the hydrogen content in the coal
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
Consumo de medicamentos, álcool e fumo na gestação e avaliação dos riscos teratogênicos
No full textMedicações, álcool e fumo podem gerar danos fetais. Este estudo transversal foi realizado entre 2006 e 2007, com 326 puérperas do Hospital Geral de Fortaleza, para avaliar o uso de medicamentos, álcool e fumo na gestação e potencial teratogênico relacionado a diferentes características populacionais. Incluíram-se as puérperas com partos no local da pesquisa e excluíram-se as que não tinham seus filhos internados. Na análise, utilizaram-se os testes Qui-quadrado e t de Student, adotando p < 0,05. O consumo de medicamentos ocorreu em 96,6% (2,8 medicamentos/gestante), e 11,3% automedicaram-se. Solteiras utilizaram mais medicações com alto risco teratogênico (p = 0,037). Foram observados 11 casos de malformação fetal, sendo cinco expostos a elevado risco teratogênico, na gestação. O tabagismo ocorreu em 11,3%, e o etilismo em 16%. Observou-se como fator de risco para exposição a maior risco teratogênico o estado civil solteira. Outras variáveis sociodemográficas e a qualidade do pré-natal não se mostraram relacionadas ao risco teratogênico das exposições
Consumo de medicamentos, álcool e fumo na gestação e avaliação dos riscos teratogênicos
No full textMedicações, álcool e fumo podem gerar danos fetais. Este estudo transversal foi realizado entre 2006 e 2007, com 326 puérperas do Hospital Geral de Fortaleza, para avaliar o uso de medicamentos, álcool e fumo na gestação e potencial teratogênico relacionado a diferentes características populacionais. Incluíram-se as puérperas com partos no local da pesquisa e excluíram-se as que não tinham seus filhos internados. Na análise, utilizaram-se os testes Qui-quadrado e t de Student, adotando p < 0,05. O consumo de medicamentos ocorreu em 96,6% (2,8 medicamentos/gestante), e 11,3% automedicaram-se. Solteiras utilizaram mais medicações com alto risco teratogênico (p = 0,037). Foram observados 11 casos de malformação fetal, sendo cinco expostos a elevado risco teratogênico, na gestação. O tabagismo ocorreu em 11,3%, e o etilismo em 16%. Observou-se como fator de risco para exposição a maior risco teratogênico o estado civil solteira. Outras variáveis sociodemográficas e a qualidade do pré-natal não se mostraram relacionadas ao risco teratogênico das exposições
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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