1,720,965 research outputs found
Sensitivity to Gamma-Ray Bursts of a Nanosatellite MeV Telescope with a Silicon Tracker
Full text linkWe propose a nanosatellite Compton telescope based on a silicon tracker, both as a fast and low-cost mission for astrophysics in the MeV regime and as a pathfinder for future large-scale Compton orbital observatories. In this paper we assess the sensitivity of such an instrument for the observation of gamma-ray bursts
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
Testing a specific Generalized Brans-Dicke model with the unified Effective Field Theory approach.
Full text linkOne of the most intriguing puzzle of modern Cosmology resides in the late time accelerated expansion of our Universe. Our standard model of Cosmology, the LCDM model, based on the General Relativity theory of gravity, explains this phenomenon in terms of a cosmological constant added into the Einstein equations. Despite the successful agreement of the LCDM model with cosmological data, some issues and internal inconsistencies are still without a satisfactory explanation. This motivates the quest for alternative cosmological model and the necessity of probing gravity at cosmic scales. This Master Thesis is about studying a specific modified gravity model, dubbed as Generalized Brans-Dicke theory, employing the unified language offered by the Effective Field Theory approach to dark energy. Implementing the Generalized Brans-Dicke theory in the EFTCAMB cosmological code, we study the model from a phenomenological point of view. We focus in particular on stability criteria, cosmological perturbations and we perform a Monte Carlo Markov Chain likelihood analysis to estimate parameters using recent cosmological datasets.ope
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
Sensitivity of a Compton nanosatellite for Gamma-Ray Burst observation. Sensitività di un nanosatellite Compton per osservazioni di Gamma-ray Burst
No full textGamma-Ray Bursts (GRB) are of particular interest for multi-messenger astrophysics because they are associated with the production of gravitational waves (GW). The intrinsically unpredictable, short nature of the electromagnetic events make the joint detection of GWs and GRBs still rare.
The solution that we explore is the use of one or more nanosatellites to augment the sky coverage for GRB events. In particular, we focus on a CubeSat nanosatellite with a small detector on board working in the MeV regime, from few keV to few MeV. The nanosatellites could play a key role in confirming and localizing the GRBs in response to alerts sent by detectors working with signals of different type.
To evaluate the CubeSat sensitivity, we simulate the performance of the detector to GRBs with parameters taken from the 3th Fermi GBM catalog. Several assumptions were made in formulating the problem: the presence of an alert coming to the CubeSat, the need of confirming it at 3-sigma significance and localizing it, a fast procedure that could run unassisted. The short hard GRB 090510 and the faint GRB 170817 were studied in more detail to validate the procedure.
I Gamma-ray Bursts (GRB) sono di particolare interesse per l'astrofisica multi-messenger in quanto sono associati alla produzione di onde gravitazionali.
La natura imprevedibile, di breve durata e non localizzata dell'evento rende la misurazione simultanea di GRB e onde gravitazionali ad oggi ancora rara.
La soluzione che consideriamo in questa tesi è l'uso di uno o più nanosatelliti per aumentare la copertura del cielo per osservazioni di GRB. In particolare, il nanosatellite CubeSat che studiamo lavorerà nel regime MeV, cioè ad energie che vanno da pochi keV a pochi MeV.
Il nanosatellite potrebbe avere un ruolo chiave nel confermare e localizzare i GRB a seguito di segnali di allerta forniti da altri strumenti operanti con segnali di vario tipo.
Al fine di valutare la sensitività di CubeSat abbiamo simulato GRBs con parametri tratti dal 3th Fermi GBM Catalog. Diverse assunzioni sono state utilizzate nel formulare il problema: la presenza di un segnale di allerta proveniente da altri strumenti (o generato internamente al nanosatellite), il bisogno di confermare il segnale con un livello di confidenza pari a 3-sigma e di localizzare la sorgente, una procedura veloce e automatizzabile. Il GRB 090510, intenso e hard, e il debole GRB170817 sono stati infine studiati in maggior dettaglio per validare la proceduraope
Sensitivity of a Compton nanosatellite for Gamma-Ray Burst observation. Sensitività di un nanosatellite Compton per osservazioni di Gamma-ray Burst
Full text linkGamma-Ray Bursts (GRB) are of particular interest for multi-messenger astrophysics because they are associated with the production of gravitational waves (GW). The intrinsically unpredictable, short nature of the electromagnetic events make the joint detection of GWs and GRBs still rare.
The solution that we explore is the use of one or more nanosatellites to augment the sky coverage for GRB events. In particular, we focus on a CubeSat nanosatellite with a small detector on board working in the MeV regime, from few keV to few MeV. The nanosatellites could play a key role in confirming and localizing the GRBs in response to alerts sent by detectors working with signals of different type.
To evaluate the CubeSat sensitivity, we simulate the performance of the detector to GRBs with parameters taken from the 3th Fermi GBM catalog. Several assumptions were made in formulating the problem: the presence of an alert coming to the CubeSat, the need of confirming it at 3-sigma significance and localizing it, a fast procedure that could run unassisted. The short hard GRB 090510 and the faint GRB 170817 were studied in more detail to validate the procedure.
I Gamma-ray Bursts (GRB) sono di particolare interesse per l'astrofisica multi-messenger in quanto sono associati alla produzione di onde gravitazionali.
La natura imprevedibile, di breve durata e non localizzata dell'evento rende la misurazione simultanea di GRB e onde gravitazionali ad oggi ancora rara.
La soluzione che consideriamo in questa tesi è l'uso di uno o più nanosatelliti per aumentare la copertura del cielo per osservazioni di GRB. In particolare, il nanosatellite CubeSat che studiamo lavorerà nel regime MeV, cioè ad energie che vanno da pochi keV a pochi MeV.
Il nanosatellite potrebbe avere un ruolo chiave nel confermare e localizzare i GRB a seguito di segnali di allerta forniti da altri strumenti operanti con segnali di vario tipo.
Al fine di valutare la sensitività di CubeSat abbiamo simulato GRBs con parametri tratti dal 3th Fermi GBM Catalog. Diverse assunzioni sono state utilizzate nel formulare il problema: la presenza di un segnale di allerta proveniente da altri strumenti (o generato internamente al nanosatellite), il bisogno di confermare il segnale con un livello di confidenza pari a 3-sigma e di localizzare la sorgente, una procedura veloce e automatizzabile. Il GRB 090510, intenso e hard, e il debole GRB170817 sono stati infine studiati in maggior dettaglio per validare la procedur
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