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Thermal effects reduction techniques for the SIMBIO-SYS scientific suite of BepiColombo mission
Full text linkThis thesis work investigates techniques of reducing the thermal effects for the SIMBIO-SYS scientific suite of BepiColombo mission. SIMBIO-SYS is an integrated suite of imaging instruments and it has been selected for the European Space Agency BepiColombo mission to Mercury. It includes a stereo imaging system (STC), an high-resolution imager (HRIC) and a visible–near-infrared imaging spectrometer (VIHI). The payload will have to operate in a very harsh environment, mainly from the thermal point of view. For this reason, dedicated state-of-art heat rejection baffles and thermal control devices have to be analyzed and designed. To overcome this issue, a methodological approach has been followed. Starting from the estimation of thermal environment encountered by the payload during mission lead to a deep knowledge of the thermal environment that the instrument will face during the mission phases and provided a framework to the design of the payload baffling system. A mathematical model has been developed and simulations has been carried out to evaluate the incident fluxes on the front end of the payload for all possible hermian seasons during the orbiting of Mercury Planetary Orbiter (MPO) spacecraft around Mercury. The study allowed to identify the most critical orbits from the thermal point of view. Furthermore the mathematical model assess the Sun aspect angle of the optical axes of the three channels (HRIC, VIHI, STC) and identifies the most critical conditions among the various phases of the mission, providing input data for the design of the baffles and constraints for the verification of their geometry. The mathematical model could be applied also to other planetary observational scientific missions and allows to perform sensitivity or uncertainty analysis of incoming solar, albedo and planetary heat fluxes to orbital or attitude parameters. The geometry of the present configuration of SIMBIO-SYS baffles have been verified against direct Sun illumination and dedicated ray-casting algorithms have been implemented to calculate the angular margin to direct entry of solar rays. Thermal analyses of baffles have been afterwards carried out using lumped parameter thermal network method and implemented in ESARAD/ESATAN software. This allows to predict the main heat transfer mechanisms and temperature distribution and to estimate the performance of baffles in terms of heat rejection capability. A study on the appropriate implementation of the HRIC Stavroudis reflective baffle geometry allows to effectively model this type of baffle; furthermore this study led to the definition of a criterion to evaluate the performance of the Stavroudis and to guide the design of the most appropriate test-bed to be used to evaluate its behaviour. The lay-out of a Mercury thermal environment simulator facility has been designed on the basis of the studies carried out. It will consist of a thermal vacuum chamber with heating and cooling sources to simulate the thermal environment that the payload will face on orbit. The design and analysis methods developed had contributed to the definition of efficient baffling system for the three channels of SIMBIO-SYS scientific suite.Il progetto di ricerca di questa tesi di dottorato è finalizzato a indagare possibili tecniche di riduzione degli effetti termici per la strumentazione scientifica SIMBIO-SYS della missione ESA BepiColombo a Mercurio. SIMBIO-SYS è una suite integrata di strumenti ottici costituita da tre canali: High Resolution Imaging Channel (HRIC), STereo Imaging Channel (STC), Visual and Infrared Hyperspectral Imager (VIHI). SIMBIO-SYS dovrà operare nell'ambiente termicamente ostile di Mercurio. E' quindi necessaria la progettazione di dedicati ed efficaci sistemi di reiezione del calore e di controllo termico per lo strumento. Il problema è stato affrontato con un approccio il più possibile metodologico al fine di individuare gli aspetti cruciali del problema progettuale. Inizialmente si è valutato l’ambiente termico che lo strumento incontrerà durante le fasi operative in orbita attorno a Mercurio. A tal fine è stato sviluppato un modello matematico in grado di valutare, per le possibili stagioni di Mercurio, i flussi solare, di albedo e planetario incidenti su una superficie orbitante attorno al pianeta secondo l’orbita e l’assetto nominali previsti per il satellite. Lo studio ha reso possibile identificare le orbite maggiormente critiche dal punto di vista termico. Il modello matematico implementato può essere applicato anche a studi riguardanti altre missioni di osservazione planetaria e consente di effettuare agevolmente studi di sensibilità dei flussi orbitali incidenti ai parametri orbitali o di assetto. Il modello matematico implementato permette inoltre di valutare l'angolo di incidenza solare rispetto agli assi ottici dei tre strumenti e ha consentito di identificare le condizioni maggiormnete critiche alla illuminazione solare diretta fornendo vincoli di progetto per le geometrie dei paraluce (baffle) degli strumenti. Le geometrie dei baffle della attuale configurazione prevista dal progetto sono state verificate all'ingresso diretto di raggi solari in orbita grazie alla implementazione di algoritmi di ray-cating ed è stato fornito un corrispettivo margine angolare per ciascun baffle. Successivamente sono stati sviluppati dei modelli termici, con approccio a parametri concentrati, dei baffle dei tre canali di SIMBIO-SYS utilizzando il software ESARAD/ESATAN, stimando così le potenze termiche scambiate, la distribuzione delle temperature e le prestazioni del sottosistema in termini di capacità di reiezione del calore. E' stato approfondito lo studio del baffle riflettente di tipo Stavroudis del canale ad alta risoluzione ed è stata individuata la geometria ottimale per la modellazione con gli attuali software commerciali disponibili di analisi termica. Questo studio ha condotto inoltre alla individuazione di criteri per la valutazione delle prestazionidel baffle Stavroudis utili a guidare il progetto di un apparato sperimentale per la caratterizzazione delle prestazioni del baffle.L'attività di ricerca è poi proseguita con il dimensionamento a livello di sistema di un apparato sperimentale finalizzato a riprodurre a terra l'ambiente termico incontrato dallo strumento in orbita attorno Mercurio. Esso è concepito per riprodurre all'interno di una camera termo vuoto l'andamento dei flussi solare e infrarosso incidenti sullo strumento e le interfacce radiative e conduttive della strumentazione con il satellite, tenendo conto della orientazione dello strumento durante il moto orbitale rispetto alle sorgenti di radiazione. I modelli matematici sviluppati e le analisi termiche eseguite hanno fornito le specifiche di progetto dell'apparato sperimentale ed utili dati numerici per la definizione del simulatore a livello di sistema. I metodi di analisi e di progetto sviluppati hanno contribuito alla definizione di efficienti sistemi di riduzione degli effetti termici per la strumentazione SIMBIO-SYS
Design and development of a high capacity pressure controlled modular gondola for long duration stratospheric balloon missions
No full textGoing 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
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
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