1,721,016 research outputs found
Protection of Future Electricity Systems
Full text linkThe electrical energy industry is undergoing dramatic changes: massive deployment of renewables, increasing share of DC networks at transmission and distribution levels, and at the same time, a continuing reduction in conventional synchronous generation, all contribute to a situation where a variety of technical and economic challenges emerge. As the society’s reliance on electrical power continues to increase as a result of international decarbonisation commitments, the need for secure and uninterrupted delivery of electrical energy to all customers has never been greater. Power system protection plays an important enabling role in future decarbonized energy systems. This book includes ten papers covering a wide range of topics related to protection system problems and solutions, such as adaptive protection, protection of HVDC and LVDC systems, unconventional or enhanced protection methods, protection of superconducting transmission cables, and high voltage lightning protection. This volume has been edited by Adam Dyśko, Senior Lecturer at the University of Strathclyde, UK, and Dimitrios Tzelepis, Research Fellow at the University of Strathclyde
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
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
Protection, fault location & control in high voltage multi terminal direct current (HV-MTDC) grids
Full text linkWith an increased penetration of renewable energy sources, balancing the supply and demand is likely to be one of the major challenges in future power systems. Consequently, there is a growing need for meshed interconnections between countries in order to effectively share the available power capacity and thereby increase operational exibility and security of supply. This has been raised as a major issue in Europe but also in Asia and United States of America.;The concept of supergrid has been identifed as a possible solution towards a newback bone transmission system, permitting massive integration of renewable energy sources. High voltage direct current (HVDC) links, utilising voltage-source converters (VSCs),are expected to become the preferred technology for the realisation of such a supergrid. This is due to the fact that such systems offer improvements in terms of system stability, lower cost and operational losses.;A natural extension of the existing point-to-point HVDC transmission technology is a multi-terminal direct-current (MTDC) system which utilises more than two VSC stations, effectively forming a DC grid. Such a configuration can provide further technological and economical advantages and hence accelerate the realisation of a supergrid. However, technical limitations still exist, and it is not yet a straightforward task to construct and operate an MTDC grid, as several outstanding issues need to be solved.;Consequently, it is essential to study, analyse and address potential challenges imposed by MTDC systems in order to enable widespread adoption.;Even though numerous challenges are introduced for the practical implementation of MTDC networks, this thesis deals with the challenges related to the DC-side faults, which is the main issue when considering HVDC technology. DC-side faults in HVDC systems are characterised by large inrush currents caused by the discharge of trapped energy in the system capacitances, escalating over a very short period of time. These include lumped capacitors installed on the DC side of converters, transmission line capacitances, and also the sub-module capacitors contained within modular multi-level converters.;When faults occur in multi-terminal HVDC grids, the DC protection system is expected to minimise the detrimental effects by disconnecting only the faulted section while permitting the remaining healthy part of the grid to continue normal operation. Such requirements introduce the need for transient DC fault characterisation and subsequent development of a discriminative, fast, sensitive and reliable DC protection method.;Therefore, one of the main objectives of this thesis is to provide demonstrable solutions to the key challenges involved in protecting MTDC grids, and hence enabling the realisation of HVDC-based supergrids. Two alternative, novel protection schemes are proposed, designed and assessed with the aid of transient simulation. The key advantages of the proposed schemes consist in enhanced reliability, fast fault detection, superior stability, and high level of selectivity. To further validate the practical feasibility of the schemes, small-scale laboratory prototypes have been developed to test the performance of the schemes under real-time fault conditions.;It should be also highlighted that when a permanent fault occurs in an HVDC transmission system, accurate estimation of its location is of major importance in order to accelerate restoration, reduce the system down-time, minimise repair cost, and hence, increase the overall availability and reliability of HVDC grids. As such, another contribution of this thesis is related to the challenges involved in accurate fault location in HVDC networks, including non-homogeneous transmission media (i.e. the lines which include multiple segments of both underground cables and overhead lines).;Two novel fault location methods have been developed and systematically assessed. It is demonstrated that the schemes can reliably identify the faulted segment of the line while consistently maintaining high accuracy of fault location across a wide range of fault scenarios. Further sensitivity analysis demonstrates that the proposed schemes are robust against noisy inputs.;In its concluding section, the thesis also outlines a few possible avenues of further research in this area.With an increased penetration of renewable energy sources, balancing the supply and demand is likely to be one of the major challenges in future power systems. Consequently, there is a growing need for meshed interconnections between countries in order to effectively share the available power capacity and thereby increase operational exibility and security of supply. This has been raised as a major issue in Europe but also in Asia and United States of America.;The concept of supergrid has been identifed as a possible solution towards a newback bone transmission system, permitting massive integration of renewable energy sources. High voltage direct current (HVDC) links, utilising voltage-source converters (VSCs),are expected to become the preferred technology for the realisation of such a supergrid. This is due to the fact that such systems offer improvements in terms of system stability, lower cost and operational losses.;A natural extension of the existing point-to-point HVDC transmission technology is a multi-terminal direct-current (MTDC) system which utilises more than two VSC stations, effectively forming a DC grid. Such a configuration can provide further technological and economical advantages and hence accelerate the realisation of a supergrid. However, technical limitations still exist, and it is not yet a straightforward task to construct and operate an MTDC grid, as several outstanding issues need to be solved.;Consequently, it is essential to study, analyse and address potential challenges imposed by MTDC systems in order to enable widespread adoption.;Even though numerous challenges are introduced for the practical implementation of MTDC networks, this thesis deals with the challenges related to the DC-side faults, which is the main issue when considering HVDC technology. DC-side faults in HVDC systems are characterised by large inrush currents caused by the discharge of trapped energy in the system capacitances, escalating over a very short period of time. These include lumped capacitors installed on the DC side of converters, transmission line capacitances, and also the sub-module capacitors contained within modular multi-level converters.;When faults occur in multi-terminal HVDC grids, the DC protection system is expected to minimise the detrimental effects by disconnecting only the faulted section while permitting the remaining healthy part of the grid to continue normal operation. Such requirements introduce the need for transient DC fault characterisation and subsequent development of a discriminative, fast, sensitive and reliable DC protection method.;Therefore, one of the main objectives of this thesis is to provide demonstrable solutions to the key challenges involved in protecting MTDC grids, and hence enabling the realisation of HVDC-based supergrids. Two alternative, novel protection schemes are proposed, designed and assessed with the aid of transient simulation. The key advantages of the proposed schemes consist in enhanced reliability, fast fault detection, superior stability, and high level of selectivity. To further validate the practical feasibility of the schemes, small-scale laboratory prototypes have been developed to test the performance of the schemes under real-time fault conditions.;It should be also highlighted that when a permanent fault occurs in an HVDC transmission system, accurate estimation of its location is of major importance in order to accelerate restoration, reduce the system down-time, minimise repair cost, and hence, increase the overall availability and reliability of HVDC grids. As such, another contribution of this thesis is related to the challenges involved in accurate fault location in HVDC networks, including non-homogeneous transmission media (i.e. the lines which include multiple segments of both underground cables and overhead lines).;Two novel fault location methods have been developed and systematically assessed. It is demonstrated that the schemes can reliably identify the faulted segment of the line while consistently maintaining high accuracy of fault location across a wide range of fault scenarios. Further sensitivity analysis demonstrates that the proposed schemes are robust against noisy inputs.;In its concluding section, the thesis also outlines a few possible avenues of further research in this area
Roman History of Alexander Mavrocordatos: critical edition
No full textThe aim of the present Ph.D. Dissertation is the critical edition of Alexander Mavrocordatos' (the so called “ἐξ ἀπορρήτων” [=A Secretis]) historical work under the title Ῥωμαϊκά [=Roman History]. In order to reconstruct the original text we used three manuscript copies known till today (Romanian Academy ms 700, Benaki Museum ms 156 and National Library of Greece ms MΠΤ7), which contain the first and the third part of this work. In addition, we also used the Romanian Academy ms 1194, which contains the second part and was considered lost till recently. This manuscript, although included and described in the Romanian Academy Manuscripts Catalogue, vol. 3 (2004), it was not noticed by the researchers, but was spotted lately (June 2019) within the frame of our research for the present Dissertation by its author in the Library of the Romanian Academy. The first part of the Ph.D. is an introductory study aiming to cover various issues that are connected to the life and works of its writer. The first chapter focuses on Mavrocordatos’ life and works, mainly filling the gaps of the existing bibliography or correcting the errors made by various researchers throughout the approximately 300 years that passed since his death. The second comments on the structure of the overall historical composition within which Roman History was included, that is the wider range work under the title: Ἐπιτομαὶ παντοδαπῆς ἱστορίας [=Compendia Historiae Universalis]. In this very chapter we also present (and comment on) the text itself, focusing on those characteristics that are crucial for its identity. The third chapter of the introductory study is an attempt to trace the Roman History’s historical sources (as they will be also mentioned in the corpus fontium of the edited text), both the ones named directly and those referred to indirectly. An account on the way they are used within the text will also be made. The fourth chapter is an approach to other aspects of the work’s nature, such as the political ideology mirrored within it, the form of the language used etc. The introductory part ends with the final (fifth) chapter where we describe the aforementioned manuscript copies containing our text’s three parts, on which we based our edition. In this last chapter we also offer the intra- and extra-textual evidence so as to prove the authorship of the recently spotted manuscript containing the second part (Library of the Romanian Academy ms 1194), which was considered lost till 2019. This very discovery is of utmost importance since it gives us the opportunity to have almost the complete work, although it was difficult to identify as part of the whole because ms 1194 is without author name, title, whereas the beginning of the narration is also missing. The second part of the Dissertation contains the main text, Roman History itself, with apparatus criticus and apparatus fontium. An extent glossary follows, including all the difficult or unusual Ancient Greek words a reader can find in our text. The last part is an Appendix, where there is an index containing all the proverbial phrases that are ornamenting the main historical narration.Θέμα της παρούσας διδακτορικής διατριβής είναι η κριτική έκδοση των Ῥωμαϊκῶν, ενός ανέκδοτου ιστορικού κειμένου του Αλέξανδρου Μαυροκορδάτου, του αποκαλούμενου «ἐξ ἀπορρήτων» (1641-1709). Για τον καταρτισμό του κειμένου λήφθηκαν υπ’ όψιν τα μέχρι πρότινος γνωστά τρία χειρόγραφα (Ρουμανικής Ακαδημίας 700, Μουσείου Μπενάκη 156 και Εθνικής Βιβλιοθήκης της Ελλάδος ΜΠΤ 7), τα οποία περιέχουν τα πρώτο και το τρίτο τμήμα της ρωμαϊκής αυτής ιστορίας, καθώς και το χειρόγραφο της Ρουμανικής Ακαδημίας 1194, το οποίο περιέχει το ενδιάμεσο –αγνώστου μέχρι και τις ημέρες μας τύχης– δεύτερο τμήμα. Το χειρόγραφο αυτό, το οποίο δεν έτυχε της κατάλληλης προσοχής από τους μελετητές –παρά το γεγονός πως ήταν καταλογογραφημένο ήδη από το 2004 στον τρίτο τόμο των χειρογράφων της Ακαδημίας–, εντοπίστηκε εσχάτως (Ιούνιος 2019) από τον γράφοντα. Του κειμένου προτάσσεται μία εκτενής εισαγωγική μελέτη, η οποία επιχειρεί να καλύψει ζητήματα που αφορούν στη ζωή αλλά και το έργο του συγγραφέα. Ειδικότερα, περιλαμβάνονται σε αυτήν α) τα εργοβιογραφικά του συγγραφέα, συμπληρώνοντας τα όποια κενά συναντούμε στη σχετική βιβλιογραφία ή διορθώνοντας τα λάθη τα οποία διατυπώθηκαν κατά καιρούς από διάφορους μελετητές. Επίσης, β) σχολιάζεται η δομή τόσο της ευρύτερης ιστορικής σύνθεσης στην οποία εντάσσονταν τα Ῥωμαϊκά (πρόκειται για το έργο Ἐπιτομαὶ παντοδαπῆς ἱστορίας), καθώς και του ίδιου του έργου, όπως επίσης και τα χαρακτηριστικά εκείνα γνωρίσματα που καθορίζουν την ταυτότητά του. Τμήμα, όμως, της εισαγωγής αποτελεί γ) και μια απόπειρα αναζήτησης των πηγών της συγκεκριμένης ιστορικής μελέτης του Μαυροκορδάτου, τόσο αυτών που αποκαλύπτονται από τον ίδιο όσο και των λανθανουσών, καθώς επίσης και ο τρόπος πραγμάτευσής τους από τον ιστορικό. Μελετάται, επίσης, δ) η φυσιογνωμία του έργου, με την εξέταση διαφόρων πλευρών του, όπως, για παράδειγμα, του ζητήματος της πολιτικής ή της γλώσσας. Η εισαγωγή ολοκληρώνεται ε) με την περιγραφή των χειρογράφων τα οποία διασώζουν το κείμενο και χρησιμοποιήθηκαν κατά τον καταρτισμό της έκδοσης. Στο τελευταίο αυτό κεφάλαιο κατατίθενται και τα στοιχεία εκείνα που αποδεικνύουν την πατρότητα του εσχάτως ευρεθέντος χειρογράφου, ζήτημα ιδιαιτέρως σημαντικό, αν λάβουμε υπ’ όψιν το γεγονός πως το εν λόγω χειρόγραφο είναι ακέφαλο, με αποτέλεσμα να μην δηλώνεται ρητά πουθενά ποιος υπήρξε ο συγγραφέας του κειμένου που αυτό διασώζει. Το κείμενο, τέλος, συνοδεύεται από εκτενές γλωσσάρι, στο οποίο περιλαμβάνονται δύσκολες και ασυνήθιστες λέξεις της αρχαίας ελληνικής γλώσσας που συναντούμε στο κείμενο. Στο παράρτημα –τμήμα ύστατο της έκδοσης– καταγράφονται όλες οι παροιμιακού χαρακτήρα φράσεις οι οποίες διανθίζουν την ιστορική αφήγηση
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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