1,721,280 research outputs found
Shape Memory Alloy Actuator for the DORA Deployable Telescope
No full textThe future of spaceborne observations increasingly relies on reducing payload size while maintaining high-performance standards. The miniaturisation of satellites is strongly dependent on advanced deployment technologies for satellite appendages, enabling significant volume reduction and, consequently, lowering the mission costs. As a result, there is significant interest in developing actuators and deployment devices to improve the compactness of deployable structures. Current advancements in the field are focused on passive deployment methods, such as elastic elements and shape control devices, as they offer simpler and more reliable alternatives to conventional electric actuators that can introduce higher complexity, deterioration and failure risks. This work describes the design of a Shape Memory Alloy (SMA) actuator for the deployment mechanism of DORA (Deployable Optics for Remote Sensing Applications), a Cassegrain telescope framed in a mission for Earth observation from low Earth orbit (LEO) for monitoring emissions and diffusion of pollutants. The need to replace previously selected linear electric actuators derives from the possibility of enhancing the mechanism's reliability by simultaneously reducing the required resources, either in terms of mass or power. The proposed design exploits the Shape Memory Effect (SME) of Nitinol wires actuated through the selfheating dissipation. The feasibility design of the intended SMA technology is described, and the wire's characteristics are identified to guarantee deployment and fulfil available size and power constraints. Performed testing activity is presented as well, mandatory to assess the actuator's performance under constant stress conditions and to validate the proposed design by deploying a mockup of the telescope
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
Theoretical models of the spectrophotometric properties of atmosphereless bodies surfaces in the Solar System
No full textIn space missions remote sensing represents one of the most powerful tools for the
observations of planetary objects. It allows to infer physical and chemical properties
both of surfaces and atmospheres by spectroscopic and photometric analysis. However data produced by remote sensing observations need to be interpreted by physical models which describe the interaction between light and observed media.
In this work we have applied the Hapke's solution to the radiative transfer equation to data from the VIMS spectrometer onboard the Cassini spacecraft, orbiting in the Saturn's system. This allowed us to determine the spectrophotometric properties of the major icy moons. In particular the composition of Mimas, Tethys, Dione, Rhea and Enceladus has been investigated. For the two latter moons also photometric properties have been studied. It comes out that the surfaces of these satellites can be modeled with water ice particles (40-70 µm in size) e minimal amounts (generally < 1%) of organic contaminants, like tholins and amorphous carbon. A similar approach has been applied to the study of the Saturn’s rings (A, B, C and Cassini Division), whose spectral characteristics can be obtained with the same paradigm of composition.
At the same time we have applied the Hapke's model to laboratory spectra of pyroxenes powders with well-known composition and physical properties. The aim of this study is to investigate the spectral and photometric output of these minerals to be compared with data from space missions. Moreover it was investigated how geometric and compositional effects can modify spectral signatures (for example the band depth). A further step of this investigation was the application of the Hapke's model to retrieve medium optical constants. The last part of this thesis concerns the development of an IDL routine to simulate light scattering in particulate media with a Montecarlo method. Preliminary results are reported.INAF, IAPS, AS
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
Rosetta Virtis instrument simulation and validation tool
Full text linkThis document provides a detailed description of the SW architecture for the validation of the
VIRTIS command sequences
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