1,720,955 research outputs found
A study of chemical structure in "barkinite" using time-of-flight secondary ion mass spectrometry
No full textThe Late Permian coals from south China are unique in their high content of "barkinite" and elemental hydrogen, and typically produce high yields of tar. "Barkinite" has often been identified as suberinite for a long time, but now many Chinese workers have concluded that "barkinite'" is not suberinite, rather it is a distinct maceral. The term "barkinite" was formally certified and named by the State Bureau of Technical Supervision of the People's Republic of China in 1991, 1995 and 1999; however, it has not been recognized as a scientific term by international coal geologists and ICCP, and TSOP have not recognized the term, either. The petrographic characteristics of "barkinite" and suberinite show that the biggest difference between them is in the cell fillings. Therefore, in the paper, a new in situ microprobe mass chemical analytical method, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was first used to study the chemical structure of cell walls and cell fillings of "barkinite". The results indicate that the chemical structures of cell fillings and cell walls are similar to each other, They are all mostly composed of aliphatic compounds (such as alkane and alkene), and followed by aromatic compounds and alkyl aromatics, in addition to minor amounts of heteroatomic compounds (such as alkoxyl and alkylamine). Based on these, we can deduce that the cell cavities of "barkinite" were mainly filled by original lipid, which were derived from cell secretion of "barkinite" itself, But suberinite is defined only as suberinized cell walls in cork tissue, and cell cavities were usually filled by secondary gelification materials (such as corpocollinite), these characteristics are quite different from those of "barkinite". The chemical characteristics of "barkinite" shown in SIMS spectra coincide with those inferred from its petrographic characteristics. The high content of hydrogen. the high tar yields and the high hydrocarbon generation potential of Late Permian coals from south China are attributed to the high aliphatic content of "barkinite". (C) 2001 Elsevier Science BN. All rights reserved.Energy & FuelsGeosciences, MultidisciplinarySCI(E)EI15ARTICLE11-84
A study of the kinetic parameters of individual macerals from Upper Permian coals in South China via open-system pyrolysis
No full textA unique Upper Permian coal, Leping coal, is widely distributed in South China. The coal samples studied in the paper were collected from two mines in the Shuicheng coalfield of Guizhou Province, southwest China. The geochemical works including coal petrography, maceral content, Rock-Eval pyrolysis, and kinetic modelling of hydrocarbon-generating have been carried out on whole coal and individual macerals. The higher contents of volatile matter, elemental hydrogen, and tar yield, and the high hydrocarbon generation potential of the Leping coals are attributed to their high content of "barkinite", a special liptinite maceral. The hydrocarbon generation potential of "barkinite" (S-2 = 287 mg/g, hydrogen index (HI)= 491 mg/g TOC) is greater than that of vitrinite (S-2 = 180 mg/g, HI = 249 mg/g TOC), and much higher than that of fusinite (S-2 = 24 mg/g, HI = 35 mg/g TOC). At the same experimental conditions, "barkinite" has a higher threshold and a narrower "oil window" than those of vitrinite and fusinite, and consequently, can generate more hydrocarbons in higher coalification temperature and shorter geological duration. Data from the activation energy distributions indicate that "barkinite" has a more homogenous chemical structure than that of vitrinite and fusinite. The above-mentioned characteristics are extremely important for exploring hydrocarbon derived from the Leping coals in South China. (C) 2000 Elsevier Science B.V. All rights reserved.Energy & FuelsGeosciences, MultidisciplinarySCI(E)EI12ARTICLE3-4293-3034
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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