307,680 research outputs found
Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses
No full textThis paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples of approximately 220 ?m thick. The space charge measurement technique used in this study is the PEA method. There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kVdc/mm and ac (sinusoidal) electric stress level of 30 kVpk/mm at frequencies of 1 Hz, 10 Hz and 50 Hz ac. In addition, ac space charge under 30 kVrms/mm and 60 kVpk/mm electric stress at 50 Hz was also investigated. The volts off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher. The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge. This paper also gave a brief overview of the data processing methods used to analyse space charge under ac electric stress
Effect of AC Ageing on Space Charge Evolution in XLPE
No full textThis paper reports on space charge dynamics in XLPE samples, which have been pre-stressed under ac electric stress, when subjected to 30kVdc/mm dc electric stress for 24 hours. The samples used for this study were planar XLPE samples of ~ 220 ?m thick aged under 30 kVpk/mm, 30 kVrms/mm and 60 kVpk/mm at 50 Hz ac condition for 24 hours. In addition, the experiments were also extended to samples that were pre-aged under 1 Hz and 10 Hz ac 30 kVpk/mm for 24 hours
Effect of polyethylene interface on space charge formation
No full textThis paper reports the results of an investigation into the space charge formation and decay at different material interfaces. In particular, the influence of the interface between electrode and polymer or polymer and polymer on the space charge dynamics has been studied. Planar samples were subjected to high dc electric stresses for extended periods of time and space charge measurements taken using the pulsed electroacoustic (PEA) technique. It has been found that the types of interface between electrode and polymer play a significant role in determining the charge distribution in the insulation and that the interface between polymer and polymer acts as a potential barrier to electrons whilst allowing positive charge carriers through easily
Scaptomyza andina Wheeler & Takada 1966
No full textandina Wheeler & Takada, 1966: 43. Type locality: Colombia, 11 km E Bogotá, in wasteland on road to Choachi. HT M (USNM). NT Distr.: Colombia, Ecuador.Published as part of Tidon, Rosana & Almeida, Jonathan Mendes De, 2016, FAMILY DROSOPHILIDAE, pp. 719-751 in Zootaxa 4122 (1) on page 737, DOI: 10.11646/zootaxa.4122.1.63, http://zenodo.org/record/26327
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
Praon yomenae Takada 1968
No full textPraon yomenae Takada, 1968 (Figs. 25, 61, 75, 90, 120) Material examined. Uroleucon chondrillae on Chondrilla juncea, HA – Nobaran (35°07′36″N 49°42′33″E, 1774 m), 05.v.2005, 1 J 2 ♀♀.Published as part of Nazari, Yaser, Zamani, Abbas Ali, Masoumi, Seyyed Mohammad, Rakhshani, Ehsan, Petrović-Obradović, Olivera, Tomanović, Snežana, Starý, Petr & Tomanović, Željko, 2012, Diversity and host associations of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) in the farmlands of western Iran, pp. 559-584 in Acta Entomologica Musei Nationalis Pragae 52 (2) on page 568, DOI: 10.5281/zenodo.533264
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
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
Get PDFThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Space Charge in Polyethylene under AC Electric Stress using the Pulsed Electroacoustic Method
No full textThis paper reports on space charge in XLPE planar samples of approximately 220 ?m thick subjected to dc 30 kV/mm and 1 Hz, 10 Hz and 50 Hz ac 30 kVpk/mm conditions for 24 hours. Measurement of space charge was carried out using the pulsed electroacoustic (PEA) technique. In addition, experiments with higher applied electric stress of 60 kVpk/mm at 50 Hz ac condition were also conducted over an ageing period of 24 hours. In order to investigate the effect degassing on space charge distribution of samples under ac stress, both as-received and degassed were used in this study
- …
