1,721,004 research outputs found
Measurement of the Breathing Mode Oscillations in Hall Thruster Plasmas with a Fast-Diving Triple Langmuir Probe
No full textOn the critical parameters for feasibility and advantage of air-breathing electric propulsion systems
No full textIn recent years, air-breathing electric propulsion emerged as a potential enabling technology for long-duration space missions in Very Low Earth Orbit (VLEO). In this work, we show how the complex relation between mission environment, spacecraft configuration, and propulsive performance can be associated to a single requirement for full air-breathing drag compensation, which becomes less stringent for higher VLEO orbits. The impact of the spacecraft shape and size on the performed analysis is then evaluated and the results compared with conventional electric propulsion solutions with stored propellant, showing how the adoption of air-breathing propulsion becomes more advantageous, from a volume and mass fraction perspective, when the spacecraft scale is reduced
I fiori edibili tra tradizione e innovazione. La valorizzazione di prodotto attraverso lo studio della componente aromatica e del contenuto in flavonoidi
No full textAl giorno d’oggi, il cambiamento delle abitudini alimentari e la ricerca di uno stile di vita più sano e sostenibile hanno incrementato nei consumatori l’interesse verso prodotti alimentari alternativi, ricchi di proprietà salutari, di estetica e a basso impatto ambientale. A livello globale, il consumo di fiori commestibili, benché abbia origini antiche, ha guadagnato recentemente una nuova popolarità tra agricoltori e chef dell’alta ristorazione. Nel prossimo futuro il loro impiego sembra destinato a crescere grazie alle potenzialità espresse come elementi funzionali e alla loro capacità di conferire sapore e aroma a cibi e bevande tradizionali in grado di influenzare significativamente le preferenze del consumatore moderno. Il presente lavoro di ricerca si è posto l’obiettivo di caratterizzare - attraverso la definizione del profilo aromatico e del contenuto in flavonoidi - differenti tipologie di fiori edibili presenti sul mercato con il fine di individuare eventuali sostanze che possano essere utilizzate come marker di prodotto. Un set di campioni provenienti da coltivazione biologica è stato analizzato utilizzando una procedura HS-SPME/GC-MS ed una HPLC-UV-Vis precedentemente sviluppate e ottimizzate. I profili cromatografici ottenuti dall’analisi delle differenti specie di fiori edibili
sono stati successivamente elaborati mediante analisi statistica multivariata. La PLS-DA (Partial Least Squares-Discriminant Analysis) ha consentito la costruzione di modelli di classificazione permettendo di estrarre interessanti informazioni utili a discriminare le diverse classi investigate. Lo studio si propone di ampliare il quadro di strumenti oggettivi, ossia strumentalmente misurabili, da fornire a produttori, utilizzatori e consumatori per valorizzare un prodotto rispetto ad un altro e per offrire opportunità di crescita a filiere emergenti del settore alimentare
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
An unstable 0D model of ionization oscillations in Hall thruster plasmas
Full text linkThe breathing mode is an instability typical of Hall thrusters, which is characterized by oscillations of the discharge current with amplitude of the order of its mean value and frequency in the 5–30 kHz range. The strong link between this instability and the ionization processes is generally recognized. If, on one hand, 1D simulations have shown to be able to reproduce the breathing mode, on the other hand 0D models fell short in recovering self sustained oscillations, making it hard to identify the core physical mechanism governing their formation. In this work an original 0D model is presented and characterized by means of linear stability analysis and direct numerical integration. The electric field is allowed to vary in response to variations of the neutral density, acting on the ionization rate via the electron temperature and the ion dynamics. It is shown that the model is able to reproduce self-sustained oscillations with the typical characteristics of the breathing mode, even when fluctuations of the electron temperature are neglected. The stability of the model is strictly determined by the rigidity with which variations of neutral density reflect into variations of electron mobility
Effects of thermal treatments on durum wheat pasta flavour during production process: A modelling approach to provide added-value to pasta dried at low temperatures
No full textPasta is a key element of the Mediterranean Diet and it has been declared by Unesco intangible cultural heritage of humanity. Despite seems a simple food, only made of semolina and water, pasta is produced following a multi-step process that strongly affect the final product. Drying stage is the one that has the greater influence on its organoleptic/nutritional characteristics. This study aimed to analyse the flavour of pasta to test whether the different drying treatments (High Temperature-Short time or Low Temperature-Long time) have a direct impact on its composition and consequently whether they could influence the end-product quality. The headspace solid-phase microextraction was optimized using an experimental design and 52 samples were analysed by HS-SPME/GC-MS and classified by PLS-DA. The resulting classification model (validated by repeated double cross-validation and permutation tests) allowed correctly predicting more than 80% of samples, confirming that drying may have a significant impact on pasta flavour
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