1,720,985 research outputs found
Valutazione della dose neutronica ambientale a livello del suolo
No full textLo studio e la conoscenza della variabilità della fluenza neutronica di origine cosmica a livello del suolo risulta importante per valutare le misurazioni di dose neutronica ambientale, effettuate sia nell’ambito di molte applicazioni mediche, essenziamente in terapia, sia nelle applicazioni industriali, come nello studio degli effetti delle radiazioni neutroniche sul funzionamento dei più comuni sistemi elettronici. Infatti la sorgente primaria dei neutroni è individuabile nell’interazione tra i raggi cosmici di origine solare ed i vari strati dell’atmosfera e pertanto il campo neutronico non è costante ma dipende fortemente dai cicli di attività solare.
In questo lavoro sono presentati i risultati di due cicli di misurazioni di “dose rate” da neutroni utilizzando un Neutron Dose Rate Meter Alnor 2202 D la cui risposta temporale è acquisita e analizzata tramite l’impiego di una scheda di acquisizione ORTEC MCS-32 controllata in ambiente Windows.
I dati ottenuti sono stati confrontati con valori di precedenti rilevazioni sperimentali e con i dati forniti dall’Osservatorio SVIRCO di Roma, che hanno confermato le fluttuazioni nelle misurazioni su base temporale. E’ stato inoltre possibile definire un fattore correttivo per tenere conto delle fluttuazioni nel flusso di raggi cosmici durante il corso di un ciclo solare, potendosi riscontrare – per il periodo individuato - un valore di correzione k=1,083. Dal confronto tra le misurazioni effettuate ed i dati forniti dalle reti di monitoraggio dei raggi cosmici è possibile ottenere un valore del “dose rate” e del rateo di fluenza neutronici mediati su un ciclo solare che possono essere impiegati come riferimento per qualsiasi misurazione di dose neutronica
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
EVALUATION OF GAMMA-RAY AND NEUTRON FLUXES IN A NEUTRON IRRADIATOR USED FOR RAD-HARD ELECTRONIC COMPONENTS TESTING
No full textAn irradiator with four Am-Be neutron sources (activity 111 GBq each) was used for testing electronic RAD-HARD components developed for space application [1]. For this goal, an essential requirement to be met is the knowledge with sufficient precision of neutron and gamma-ray fluxes in the irradiation channel where the components are put for the test. For this goal, an experimental measurement activity was started to validate also Monte Carlo simulation results, obtained with application of MCNP5 code.
As regards gamma-ray flux, we considered separately two gamma-ray contributions: the first one, at 60 keV energy, associated with the decay of the 241Am, and the second one, at 2.2 MeV, due to the radiative capture of neutrons in the biological shield (water) surrounding the neutron sources. Experimental measurements were realized with TLD700 dosimeters in two different configurations: TLD “naked” to measure the dose of the total gamma irradiation field, and TLD put inside a lead shield to determine (for difference) 60 keV gamma-ray contribution. The dimensions of used dosimeters, very small, allowed an accurate dose behaviour determination. For the TLD calibration, we exposed them to well-know doses values at the 60Co irradiator named IGS3, situated in the Department of the University of Palermo.
As regards the evaluation of the neutron radiation field, experimental measurements were realized both by neutron activation with gold foils (nude and cadmium covered) and with thermoluminescent dosimeters (TLD600 and TLD700). Results have been compared with the ones obtained by a Monte Carlo (MCNP) simulation performed adopting a model of the irradiator previously validated [2].
The comparison between the experimental data and those obtained performing a Monte Carlo simulation allowed the
determination of both neutron (thermal) and gamma field in several points inside the irradiation channel and, in particular, in those positions more used to the realization of irradiation tests.
[1] S.G. Cappello, C. Pace, A. Parlato, S. Rizzo, E.TOMARCHIO: “ Gamma-ray irradiation tests of CMOS sensors used in imaging techniques”, Nuclear Technology & Radiation Protection 29 (2014), pp. S14-S19.
[2] P. Buffa, S. Rizzo, E. TOMARCHIO: “A Monte Carlo-aided design of a modular 241Am-Be neutron irradiator”, Nuclear Technology & Radiation Protection XXVIII, No.3 (2013), pp. 265-272
Le facilities di irraggiamento del DEIM per il testing di componenti rad-hard
No full textIl Dipartimento Energia, Ingegneria dell’Informazione e Modelli Matematici dell’Università degli Studi di Palermo (DEIM), ospita due facility di irraggiamento impiegate per attività di didattica, sperimentale e di ricerca:
• Impianto di irraggiamento Gamma Sicilia 3 (IGS-3); Irradiatore neutronico Am-Be. In questa monografia sono presentate le caratteristiche dei due impianti di irraggiamento insieme alle proprietà di interazione delle radiazioni con la materia, con particolare riferimento agli effetti sui componenti elettronici
Neutron and gamma-ray radiation fields characterisation in a 241Am–Be irradiator in view of its use as research testing tool
No full textA neutron irradiation facility based on four 241Am–Be sources, each one with an activity of 111 GBq, placed in Plexiglas pipes inside a tank filled with water used both as a moderator and a biological shielding, has been realized at the Engineering Department of Palermo University. In view of its use as a testing tool in various research activities, a characterisation of the irradiator has been carried out through the determination of neutron and gamma-ray flux profiles, the evaluation of the thermal to total neutron flux percentage ratio and of the epithermal neutron shaping factor. To this aim, results of a Monte Carlo (MCNP5 code) simulation based on a previously validated source model have been compared with the experimental results obtained from TLD dosimeters and activated gold foils. Experimental values show a good agreement with MCNP5 evaluations, highlighting a gradually decreasing of dose values as a function of the distance from the lying plane of sources. Maximum values of experimental neutron fluxes have been found to be (3.73 ± 0.38) × 104 cm−2 s−1 (thermal) and (2.13 ± 0.25) × 104 cm−2 s−1 (epithermal and fast), with a percentage of 64% of thermal to total neutron flux and epithermal neutron shaping factor equal to −0.16 ± 0.04. Both neutron and gamma fluxes for the most used positions inside the irradiation channel can then be provided and the main parameters for any irradiation plane can be easily established
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
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