1,720,963 research outputs found
Formation enthalpies estimation by a semi-empirical approach for chemical considerations in Lead-cooled Fast Reactors
No full text
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
Vaporization behaviour of the Molten Salt Fast Reactor fuel: The LiF-ThF4-UF4 system
Get PDFA selected composition of the initial fuel of the Molten Salt Fast Reactor (MSFR) is assessed by differential scanning calorimetry (DSC) for melting point determination and by Knudsen effusion mass spectrometry (KEMS) for vaporization behaviour. Partial vapour pressures and thermodynamic activities of the MSFR fuel mixture are discussed indicating departures from ideal behaviour, and further interpreted by phase equilibria calculations. The boiling point of the mixture is obtained extrapolating vapour pressure experimental results. New results on the vaporization behaviour of pure uranium tetrafluoride are presented, together with the ionization potentials of UF4 by electron impact
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
Experimental Investigation and modelling of thermo-chemical and thermo-physical properties of fluorides for the molten salt fast reactor
No full textDOTTORATOQuesta tesi di dottorato concerne lo studio di proprietà termo-chimiche e termo-fisiche di sali fluoruri, contribuendo allo sviluppo del reattore veloce a sali fusi (Molten Salt Fast Reactor – MSFR), un reattore nucleare di quarta generazione, in cui il combustibile nucleare (Th, U e/o Pu in forma di fluoruri) si trova disciolto in una matrice di fluoruro di litio, che svolge anche la funzione di fluido refrigerante del circuito primario. Il combustibile liquido, combinato con uno spettro di neutroni non moderato e un design innovativo, conferisce all’MSFR grandi potenzialità in termini di sicurezza e sostenibilità. Per raggiungere e verificare questi obiettivi ambiziosi, le proprietà relative alla sicurezza del combustibile nucleare liquido devono essere studiate approfonditamente. Tuttavia, lo studio di fluoruri allo stato liquido è ostacolato da sfide significative, come ad esempio: la purezza dei campioni (altamente igroscopici e sensibili all’ossigeno); la loro radioattività (che richiede che il lavoro venga svolto in scatole a guanti); l’alta temperatura di fusione dei fluoruri (che rappresenta un’ulteriore fonte di incertezza); la corrosività dei gas rilasciati da questi materiali (che richiede l'incapsulamento dei campioni); e il loro stato liquido. Questa tesi di dottorato, sviluppata nell’ambito del Progetto H2020 SAMOFAR (www.samofar.eu) e nel contesto di una collaborazione tra Politecnico di Milano e Joint Research Centre di Karlsruhe in Germania, descrive procedure e tecniche innovative per affrontare con successo le sfide sopra elencate. I fluoruri di uranio, torio e plutonio sono stati sintetizzati mediante l’utilizzo di fluoruro d’idrogeno sui relativi ossidi. Il trifluoruro di plutonio è stato ottenuto mediante riduzione con idrogeno del rispettivo tetrafluoruro. Diagrammi di fase, calore specifico, pressione di vapore e diffusività termica di diverse miscele di fluoruri sono stati studiati prestando attenzione all'accuratezza e all'incertezza dei risultati. In questo dottorato sono stati raggiunti i seguenti risultati: (1) i sistemi LiF-PuF3 e ThF4-PuF3 sono stati studiati utilizzando campioni incapsulati in crogioli a tenuta con chiusura a vite e misurati mediante calorimetria a scansione differenziale (Differential Scanning Calorimetry - DSC) per la determinazione delle temperature di transizione di fase. I loro diagrammi di fase sono stati determinati con il metodo Calphad; (2) il calore specifico del tetrafluoruro di torio allo stato solido e liquido è stato misurato per la prima volta. I campioni sono stati incapsulati in crogioli sigillati con una tecnica di saldatura laser e misurati con DSC e calorimetria a caduta; (3) le pressioni di vapore parziali di due miscele selezionate come combustibile per l’MSFR sono state misurate esaminando con uno spettrometro di massa i gas uscenti da una cella di Knudsen (Knudsen Effusion Mass Spectrometry - KEMS), e sono stati determinati i loro punti di ebollizione. Sono stati inoltre ottenuti nuovi risultati sulla vaporizzazione del tetrafluoruro di uranio e del trifluoruro di plutonio; (4) è stata esplorata una tecnica innovativa per misurare la diffusività termica di sali fusi mediante Laser Flash (LF), mostrando grandi potenzialità e dando risultati promettenti.This PhD thesis deals with the investigation of thermo-chemical and thermo-physical properties of fluorides, contributing to the development of the Molten Salt Fast Reactor (MSFR), a Generation IV nuclear reactor concept, in which the nuclear fuel (Th, U and/or Pu in form of fluorides) is dissolved in a matrix of lithium fluoride operating at the same time as primary coolant. The liquid fuel, combined with a non-moderated neutron spectrum and an innovative design, confers to the MSFR great potentialities in terms of safety and sustainability.
To meet and verify these ambitious goals, reactor safety-related properties of the liquid fuel must be investigated in depth, but significant challenges concern the investigation of molten fluoride systems, such as: the purity of the end-members (highly hygroscopic and sensitive to oxygen); the radioactivity of the samples (which implies working in glove boxes); the high melting temperatures of fluorides (significant source of uncertainty); the corrosiveness of fluoride vapours (which requires encapsulation of the samples); and the liquid state.
This PhD thesis, developed in the framework of the H2020 SAMOFAR Project (www.samofar.eu) and in the context of a collaboration between Politecnico di Milano and Joint Research Centre of Karlsruhe (Germany), describes innovative procedures and techniques to successfully face the challenges summarized above. Actinide fluorides were synthesised by hydrofluorination of oxides, and PuF3 was subsequently obtained by reduction of PuF4 with hydrogen. Phase equilibria, heat capacity, vapour pressure and thermal diffusivity of different fluoride systems were investigated paying attention to accuracy and uncertainty of the results.
The following results were achieved in this PhD: (1) LiF-PuF3 and ThF4-PuF3 systems were assessed using samples encapsulated in gas tight crucibles with a screw closure and measured by Differential Scanning Calorimetry (DSC) for determination of phase transition temperatures. Their binary phase diagrams were calculated according to Calphad method; (2) heat capacity of solid and liquid ThF4 was measured for the first time. Samples were encapsulated in crucibles sealed by a laser welding technique and measured by DSC and drop calorimetry; (3) partial vapour pressures of two selected MSFR fuel mixtures were assessed by Knudsen Effusion Mass Spectrometry (KEMS), and their boiling points were determined. New results on vaporization behaviour of UF4 and PuF3 were also obtained; (4) an innovative technique to measure thermal diffusivity of molten salts by a Laser Flash (LF) device was explored, showing great potential and giving promising results.DIPARTIMENTO DI ENERGIA31LUZZI, LELIODOSSENA, VINCENZ
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
- …
