1,721,032 research outputs found
FIBRE OPTIC SENSORS FOR THE VALIDATION OF THE NUMERICAL SIMULATION ON THE BREADBOARD OF THE LARES SEPARATION SYSTEM
No full textFibre optic sensor technology is relatively new and in the last ten years its use is becoming common in many fields of engineering. The properties of optical fibre sensors make them very promising for use on space structures. They are immune from electromagnetic interferences, resistant to chemical corrosion, compatible with the space environmental conditions. Fibre Bragg Gratings (FBG) are particularly interesting because they can be multiplexed along the same fibre. Those sensors are basically optical strain gages with many advantages over the conventional ones. In the paper it is proposed the use of those sensors for correlating experimental finite element analysis on the contact point of the separation system with LARES satellite. LARES satellite is spherical and no protruding parts are allowed on its surface. This requirement calls for a special separation system that has four contact points on the satellite surface. To counteract forces acting on the satellite during the launch phase, for the purpose of preventing accidental detachment of the separation system components from the satellite surface, a significant preload force is applied to the satellite through those four contact points. Concern about the admissibility of the consequent contact pressures arose. A direct measurement of the pressures on those contact points seems unfeasible and the purpose of the paper is to investigate the possibility of deriving the local value of the pressure by measuring with FBG sensors the strain on an accessible nearby area
Mathematical prediction of the time evolution of the COVID-19 pandemic in Italy by a Gauss error function and Monte Carlo simulations
Full text linkIn this paper are presented mathematical predictions on the evolution in time of the number of positive cases in Italy of the COVID-19 pandemic based on official data and on the use of a function of the type of a Gauss error function, with four parameters, as a cumulative distribution function. We have analyzed the available data for China and Italy. The evolution in time of the number of cumulative diagnosed positive cases of COVID-19 in China very well approximates a distribution of the type of the error function, that is, the integral of a normal, Gaussian distribution. We have then used such a function to study the potential evolution in time of the number of positive cases in Italy by performing a number of fits of the official data so far available. We then found a statistical prediction for the day in which the peak of the number of daily positive cases in Italy occurs, corresponding to the flex of the fit, that is, to the change in sign of its second derivative (i.e., the change from acceleration to deceleration), as well as of the day in which a substantial attenuation of such number of daily cases is reached. We have also analyzed the predictions of the cumulative number of fatalities in both China and Italy, obtaining consistent results. We have then performed 150 Monte Carlo simulations to have a more robust prediction of the day of the above-mentioned peak and of the day of the substantial decrease in the number of daily positive cases and fatalities. Although official data have been used, those predictions are obtained with a heuristic approach since they are based on a statistical approach and do not take into account either a number of relevant issues (such as number of daily nasopharyngeal swabs, medical, social distancing, virological and epidemiological) or models of contamination diffusion
Analysis of the prediction of the 2021 time-evolution of the Covid-19 pandemic in Italy using a Planck’s distribution
Full text linkIn a previous paper, we studied the time-evolution of the Covid-19 pandemic in Italy during the first wave of 2020 using a number of distribution laws. We concluded that the best distribution law to predict the evolution of the pandemic is a distribution of the type of Planck’s law with three parameters, provided that the basic conditions of the pandemic (such as social distancing, vaccination campaigns and new Covid variants) do not appreciably change the spread of the pandemic. In our 2020 study, we did not use the number of daily positive cases in Italy but the ratio of daily positive cases per number of daily tests, ratio today sometimes referred to as: “positivity rate.” We showed that if basic conditions do not change, the Planck’s distribution with three parameters provides very good predictions of the positivity rate about 1 month in advance. In a second paper, using the Planck’s distribution with three parameters, we predicted, about 1 month in advance, the spread of the pandemic in Italy during the Christmas 2020 holidays. Here we show that indeed in our second paper the spread of the pandemic in Italy, after 1 month, was well predicted using the Planck’s distribution with an error of a few percent only. We then studied the present (October 2021) evolution of the pandemic in Italy, and we showed that the Planck’s distribution, based on the data of July and August, predicted well the evolution of the pandemic. We then show that the peak of the positivity rate was approximately reached during the middle of August. However, the end of the Italian holidays and the start of all the activities including schools, intensive use of public transportation and further distancing measures may change again the trend of the positivity rate of the pandemic
LARES 2 mission in orbit: first laser ranging after the launch
No full textLARES 2 has been launched with the maiden flight of the new Vega-C European launcher on July 13, 2022. The second LAser RElativity Satellite (the first LARES was launched ten years ago) has been put into its orbit, with remarkable precision. The satellite is designed to improve both laser ranging accuracy and the accuracy on the measurement of relativistic frame-dragging effect. Frame dragging has been already measured by the first LARES mission: LARES 2 experiment is expected to improve the accuracy of the previous test of at least one order of magnitude. The improvement in the tests of General Relativity is because of the special orbital configuration, the orbit of LARES 2 is supplementary to the orbit of the LAGEOS satellite (launched by NASA in 1976) while a new retroreflector distribution of the satellite has been adopted to improve the precision of satellite laser ranging measurement. The first laser ranging data were obtained by Matera Space Geodesy Centre just 3 days after the launch, and the satellite is currently tracked by several stations of the International Laser Ranging Service. The data are showing that it is performing on the same level or even better than benchmark targets such as the LAGEOS satellites in spite of LARES 2 having a lower optical cross-section. The data from LARES 2 will be used also for space geodesy and Earth science studies
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
Fracture behaviour of alloys for a new laser ranged satellite
Full text linkA new laser-ranged satellite called LARES 2 (Laser Relativity Satellite 2) has been recently designed for accurate tests of Einsten's theory of General Relativity and space geodesy. Some high density alloys (8.6-9.3 g/dm3) have been studied and characterised for producing the LARES 2 passive satellite. The considered materials were Copper and Nickel based alloys that have been produced and characterised. Aim of this work was to analyse their fracture behaviour that is a requirement for materials to be used for space applications. Fracture tests have been carried out on several specimens and fracture surfaces have been analysed
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
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