1,721,105 research outputs found
Dosimetry in Space: The shielding effectiveness for the radioprotection of astronauts against 1 GeV protons
No full textThe study of materials suitable for radiation protection of astronauts in space missions is always a topic of fundamental importance. The main aim of any radiation protection program in space is to minimize the crew’s exposure to ionizing radiation. This work concerns the effectiveness of shielding materials against radiation in space conditions, in particular for the Galactic Cosmic Radiation. The study was conducted by developing a simulation tool based on the Geant4 framework. The physics case reported here deals with the interaction of a 1 GeV proton beam (protons represent about 87% of the GCR flux with the energy spectrum peak around 1 GeV) with a target added with boric acid or gadolinium (Gd) to deplete neutron escaping. Charge, mass and energy distributions of secondary particles generated by the interaction are computed on the basis of different interaction models. It is found that the particles escaping the shielding material and reaching an ionization chamber located in the opposite side of the shield are still mainly protons and neutrons. The added boric acid acts as an effective neutron mitigating material. However, the average dose does not change effectively because of the additional production of alpha particles from the reaction 10B(n, α)
Space missions: Comparison of shielding effectiveness among different materials using 1 GeV protons
No full textThe study of materials suitable for radiation protection of astronauts in space missions is always a topic of fundamental importance. This paper shows the results of the comparison of the effectiveness of different materials in cutting down the radiation dose and is intended as a contribution to the search of the most appropriate material for radiation protection against the Solar Particle Events. The physics case deals with the interaction of a 1 GeV proton beam with slabs of different materials having a thickness of 20 g cm - 2 . The study was conducted with a simulation tool based on the well-known simulation package Geant4. We focus in this work only on impinging protons with the energy of 1 GeV, and not on the whole energy spectrum of Solar Particle Events, because the simulated dose can be easily verified under strict experimental conditions thus providing the benefit of the validation of the prediction capabilities of the simulation tool developed. We conclude that the Nomex material, with the inclusion of a percentage of air, is more efficient than aluminum for what it concerns the shielding of the 1 GeV proton component of the Solar Particle Events
LILITA_N21: Updated version of the Monte Carlo fusion–evaporation code
No full textSince the code LILITA was presented in 1981 by Gomez Del Campo and Stockstad (1981)[1] and used to simulate the emission of light particles in the decay of a compound nucleus, relevant improvements have been made. Revisions leading to LILITA_N97 were begun by G. La Rana (Naples), M. Kaplan (CMU, Pittsburgh, PA), J.M. Alexander (Stony Brook, NY) and continued by the Naples Group (Moro et al., 2012) [2]. In this work new key features of the code consisting of the implementation of transmission coefficients based on global parametrization of the optical model potential, a description of the nuclear shape based on the nuclear stratosphere model, the parallelization of the code and a graphical user interface are presented. We expect that the new code version, LILITA_N21, makes it possible a better reproduction of wide data set from literature. In order to illustrate how this could be achieved, the standard statistical model predictions have been compared with those obtained with the new code features. A single set of parameters of the new code simultaneously well reproduces the neutron, proton and α-particle energy spectra, angular distributions, and multiplicities in the fusion–evaporation channel. By way of example, here the calculations are compared with experimental data of the reaction 60Ni+100Mo at the excitation energy of about 280MeV (Charity et al., 2003) [3]. The capability to reduce the execution time by exploiting the code parallelization is also discussed
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
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