1,720,955 research outputs found
A monte carlo calibration approach for a dual-energy ct system
No full textThis work shows the effectiveness of Monte Carlo methods for calibrating a dual-energy CT (DECT) system on a heterogeneous phantom for radiotherapy. The reference phantom comprising 20 inserts of different materials and densities representing human tissues inserted in a plastic water cylinder has been considered. The reliability of the model, built with the Penelope code, has been verified by comparing the results of the simulations at 80kVp and 140kVp with the experimental data acquired from the CT scans and dosimetry measurements. The effective atomic number from the various materials is also considered a control parameter. Tests for calibration and dose calculation are also based on a homogeneous phantom in PMMA and measurements in air with an ionization chamber. The Monte Carlo simulations coupled with dose evaluations allowed the calibration of the dose deposition effects on the considered tissue models
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
Studio e calibrazione di un sistema per tomografie computerizzate di tipo dual-energy con tecniche Monte Carlo
Get PDFLo sviluppo di nuove tecniche di diagnostica e sempre più moderne strumentazioni medicali nell’ambito della tomografia computerizzata a raggi X ha reso quantomai necessario lo studio dettagliato e la calibrazione di sistemi quali fantocci eterogenei sempre più fedeli alla rappresentazione dei tessuti umani, utilizzando approcci innovativi per la loro modellizzazione numerica.
Nel seguente lavoro, sono messe in evidenza l’efficacia e l’attendibilità delle tecniche Monte Carlo applicate allo studio e la calibrazione di un sistema investito da radiazione ionizzante durante una tomografia computerizzata di tipo “dual-energy”.
Tre modelli vengono costruiti e validati: un fantoccio eterogeneo, costituito da venti inserti cilindrici di materiali di diversa densità e composizione chimica; un fantoccio omogeneo, fatto interamente di PMMA; ed una camera di ionizzazione in aria.
Dopo aver opportunamente impostato i parametri di input, sono state eseguite due simulazioni: una al livello energetico più basso, pari ad 80 kVp ed un’altra ad alta energia, ovvero a 140 kVp.
I risultati numerici ottenuti dalle prove sono stati confrontati con quelli sperimentali, valutando il profilo di dose assorbita e gli spettri energetici.
Questa procedura permette di ottenere maggiori informazioni sulla composizione dei tessuti e di visualizzare dettagli con più precisione.
Preme sottolineare l’importanza dei metodi Monte Carlo applicati ad una tecnica come la tomografia computerizzata di tipo “dual-energy”, in continua evoluzione e che sta assumendo un ruolo fondamentale nella diagnostica per immagini.
La consistenza del modello costruito in questo elaborato suggerisce un ulteriore approfondimento nello studio della tecnologia e dei metodi di supporto ad essa, affinché possa essere possibile fare concreti passi avanti nel miglioramento dello stato dell’arte
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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