1,720,987 research outputs found
Test Devices in Jules Horowitz Material Testing Reactor (JHR): Neutron kinetic design supporting safety analysis of JHR research material testing reactor
No full textJules Horowitz Reactor (JHR) is designed to be the most important European material testing reactor - achieving 100 MW core thermal power. MADISON, ADELINE and MOLFI reflector experimental devices are conceived for material and fuel irradiation tests. Power transient analyses are requested by safety authority for different experiments to be performed in these devices. Issues concerning shutdown power transients need particular verifications for heat removal and temperature control in fissile samples. Proposed innovative calculation model accounts for different nuclear heating processes and related time evolution - spatial impact of radiation transport is evaluated both for neutrons and gamma. Delayed emission related to fission products is then considered through evolution calculations of different fuel compositions. Power transients are then computed for every sample according to envisaged shutdown procedures. Results obtained in this study are aimed at design feedback and reactor management optimization by JHR project team
Implementation of a Novel ERANOS Procedure for the Adjoint Power Evaluation in Coupled Depletion Problems
No full textThe design of nuclear reactor cores heavily relies on the ability to evaluate burnup effects and the resulting changes in material composition at the isotopic level. When considering the design of liquid-metal fast reactors carried out using the ERANOS suite, a novel dedicated procedure to tackle depletion problems, based on the Generalized Perturbation Theory (GPT), was developed and imple- mented in the ERANOS suite. The preliminary results obtained by coupling the Boltzmann/Bateman fields, in both direct and adjoint domains, are presented and briefly discussed in this work, suggesting the possibility of their extension to more realistic applications and practical core design problems
Compact and very high dose-rate plasma focus radiation sources for medical applications
No full textA Dense Plasma Focus (DPF) is a pulsed device able to produce a hot and dense short-lived plasma that could become a fast radiation source for diagnostic applications, external radiotherapy, or intra-operative radiation therapy. The plasma confinement phase, identified as “pinch”, lasts few tens of nanoseconds, during which thermonuclear temperatures and densities could be reached. When the DPF vacuum chamber is filled with gases such as nitrogen, the only significant output are self-collimated charged particle beams (electrons and ions in opposite direction). Using that electron beam, it is possible to devise an ultra-high dose-rate source, with applications for direct irradiation of a tumor bed or for photon conversion after the interaction with a suitable target. The ultra-high dose rate could have potential benefits in mitigating the intrinsic or acquired malignant cell radio-resistance, which can be considered the main obstacle to the long-term survival of a patient, also sparing healthy tissues. This is due as the faster the dose deposition, the more relevant is the radiobiological efficacy (as the tumor cells do not have the time to activate the sub-lethal damage repair mechanisms responsible of the radio-resistance). Due to the novelty of the fast source, the usual models cannot easily describe the biological outcomes, therefore new numerical approaches are needed for predicting the RBE outlined in these regimens.
A parametric investigation through the Monte Carlo Damage Simulation Software (MCDS), coupled with the Monte Carlo N-Particle (MCNP) code, has been performed for supporting the experimental results previously obtained by irradiating melanoma cell lines with the Plasma Focus Device for Medical Applications #3 (PFMA-3) as UHDR source and a conventional XRT as standard of comparison.
The experimental data were benchmarked with MCNP-MCDS, properly fitting the XRT curves. The validation of the MCDS-MCNP coupling was performed by comparing literature data for conventional XRT, with less than 4% of differences. Next, the experimentally evaluated RBE highlighted that for high doses the RBE calculated on the basis of the surviving fraction (RBE(SF)), is the same of the one from double strand break damages (RBE(DSB)), making coherent the application of the Repair Misrepair Fixation theory (RMF) and providing a basis for a reliable comparison between the two devices. The DPF irradiation outcome has been numerically investigated correlating the experimental experiences with a wide range of code parameter variations to find numerical conditions able to reproduce the data. A recipe based on a combination of more than one SF curves to fit the clonogenic assay in UHDR regimen has also been proposed.
The results suggested that the UHDR regimen obtained from the DPF source could change the environmental conditions (e.g., oxygen concentration) while cumulating the dose. This implies that a combination of data and MCDS-MCNP analysis could be applied as a strategy for quantifying biological effects
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
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
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