1,721,009 research outputs found
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
Synthetic Images and Colours of the Dimorphos Asteroid Ejecta Plume as seen from the LICIACube spacecraft
No full textIntroductionThe NASA Double Asteroid Redirection Test (DART) mission will be the first test to check an asteroid deflection by a kinetic impactor. The target of DART mission is Dimorphos the secondary element of the (65803) Didymos binary asteroid system, and the impact is expected in late September - early October, 2022 [1] The DART S/C will carry a 6U cubesat called LICIACube (Light Italian Cubesat for Imaging of Asteroid) [2], provided by the Italian Space Agency, with the aim to collect pictures of the impact"s effects. On board LICIAcube will be hosted 2 camera payloads: LEIA a panchromatic (400-900nm Filter, 2.9x2.9° FOV) Narrow Angle Camera and LUKE a RGB (Bayer color filter, 4.8 x 9.15° FOV). LICIACube will be able to acquire the structure and evolution of the DART impact ejecta plume and will obtain high-resolution images and 2 colours data (B-G, G-R) of the surfaces of both bodies and the plume.In order to check the imaging capability and to optimize the fast scientific phase of LICIACube, the LICIACube team performed simulations of pictures" acquisition. In these simulations, considering the specifications of the 2 optical payloads and the foreseen mission design, we reconstructed synthetic images mainly of the plume. Since the study of the plume and its evolution is one of the main scientific goal of the mission we performed a scattering modelling of the ejecta in order to invert the future photometric data deriving hints on the intimate nature of the dust particles released by the impact.Plume simulated Images and column densityWith the two-fold aim of set the operative parameters for the Payloads and to understand the information retrievable by the images of the evolving plume we started an imaging simulation activities taking into account:LICIAcube mission design [3] (Trajectory, Speed, illumination conditions) Payloads optical characteristics The plume evolution was simplified assuming:Non colliding particles during the plume evolution; A speed distribution in the plume given by eq: Where x is the distance on Dimorphos surface from the DART impact point and the other parameters used, considering as main material of asteroid system the cemented basalt, are reported in table:We considered the most representative 3 size bins for what concerns the ejected mass, the expected total number of particles are reported in table:In Figure 1 is reported the simulated image obtained considering the LICIACube trajectory 50s before the close approach (about 110 s after the DART impact).Figure 1 Plume simulated image relative values for irradianceOnce the simulated column density image was obtained, we added a scattering simulation considering spherical dust particles and using a Mie code well suited for large particles approaching the geometric optics regime [4]. In this way we were able to translate column densities in luminous fluxes measured by the instrument using a methodology described in the next section.Plume colours scattering modellingRGB data of the ejecta plume can be used to derive hints on the physical properties of the ejected particles through scattering modelling of the measured two colours (B-G, G-R) and the phase function versus the phase angle of observation α.Given the intensity of solar light incident on the plume"s single particle Iinc,, considering the incident solar light as unpolarized, the intensity of light scattered by the particle at α, Isca is given by [5]:where S11(α) is the first element of the 4X4 scattering Müller matrix, k=2π/λ is the wave number, and r is the distance between the particle and the observer. In this case: being FSun the solar flux at 1 AU, rh the heliocentric distance of the dust particle, and a its radius.The Mie code provides the complete scattering matrix once the dimension of the particle and its composition in terms of the complex refractive index of the material at the considered wavelength are given as input. We used largely referenced laboratory data on basaltic materials to obtain the optical properties of the dust particles [6]. This composition is used to model the dust particles residing on the asteroid surface [1], [2].Then, in order to find the intensity due to the scattering of a single particle measured by the instrument at phase angle α, we convolved Isca with the photometric response of the instrument. For a generic filter, such measured intensity is where Resp is the photometric response of the instrument extended throughout the bandpass of the filter. This response is a known product of several factors as the entrance pupil of the system, the reflectivity of the optics, the transmission curve of the filter, the quantum efficiency of the detector, and the exposure time.Synthetic colours of the dust particles can therefore being computed being the generic color A-B = -2.5log(IA/IB). We performed sample scattering colour calculations varying the particle size from 0.1 micron to 1 cm.Small particles provide extremely variable colours due to the strong influence of scattering resonances being the incident wavelength comparable with the size of the particles themselves. Colours get stable for a larger interval of phase angle proportionally to the increase of the size. Observations of stable colours in the plume during LICIACube flyby will be indicative of particles larger than 100 micron. At the same time, large basalt particles provide a flatter phase function at intermediate and small phase angles than smaller particles.Combined observations of the plume phase function and colour will therefore effectively constrain the size of the ejected particles providing theoretical inputs to the dynamical models
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Challenges in licia cubesat trajectory design to support DART mission science
No full textIn 2021, the DART spacecraft will be launched by NASA to intercept the binary system Didymos and impact the moonlet (Didymoon), to test the effectiveness of kinetic impactors for the deviation of hazardous asteroids' trajectories. The impact is expected to generate a cloud of particles, whose study could provide valuable data about asteroid's properties and impact models. Observations from ground to characterize ejecta and plume evolution after impact would be possible, but the resulting quality would be significantly lower than a short-range imaging. In this framework, ASI (Italian Space Agency) and NASA started a collaboration to embark on the US DART vehicle the LICIA (Light Italian CubeSat for Imaging Asteroid) 6U CubeSat as a piggyback payload. LICIA is devoted to grasp science data by imaging the ejecta plume just after the impact, while flying by Didymoon. To this end, our analyses underlined that the small vehicle shall be detached from DART several hours before the impact to gain the needed separation from the US spacecraft, and to be on time for impact and ejecta plume imaging, a few minutes after occurrence. Moreover, LICIA scientific goals include imaging the back side of Didymoon, while keeping flying along the binary on its escape leg. The Italian consortium involved in the mission sees ARGOTEC for the platform development, and INAF, Politecnico di Milano and Università di Bologna to cover the mission science, trajectory design and orbit determination tasks, respectively. The paper focuses on the mission analysis and maneuvers design strongly driven by the science return in plume tracking and imaging, under the tight constraints the small platform imposes in terms of agility and control authority. Occurred trade-offs, related to the trajectory design, and navigation and guidance baseline settings to balance the science objectives and the risk mitigation constraints, are discussed in deep. Detailed robustness analysis will show criticalities related to the uncertainties in the flyby trajectory, associated with the cubesat subsystems accuracy. An optimization of correction maneuvers and time windows for Deep Space Networks contacts is finally presented, to show how the deviation of the nominal trajectory can be mitigated to ensure the mission being compliant with the science goals
On-chip micro-incubator with integrated sensors and actuators
No full textDegenerative pathologies are among the greatest long-term risk for astronauts exposed to hazard environment during deep space mission. A breakthrough goal in this area, to improve risk modeling, is to provide biological in-situ analysis of those effects. For this purpose, we developed a scientific payload to study the space environment’s effects on cellular cultures. The system is a micro-incubator based on lab-on-chip technology with integrated thin-film sensors and actuators for the active control of the environmental conditions of the cell culture. In further detail, the micro-incubator is composed of a microfluidic network bonded on a glass substrate on which hydrogenated amorphous silicon sensors and thin-film resistive heaters are fabricated. The device implements a thermally-controlled incubation chamber with a reservoir for the nutrients and a network for the distribution of carbon dioxide through a thin gas-permeable membrane. Carbon dioxide is produced on-chip by the pyrolysis of sodium bicarbonate stored in a separate reservoir with a dedicated thin film heater. The proposed payload represents a viable solution for enabling biological experiments aboard CubeSat satellites
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