1,720,955 research outputs found
An Innovative Pressing Process by Mechanical Interference Fit for Assembly and Calibration of Fuel Injector
Full text linkIl processo produttivo degli iniettori di combustibile può essere significativamente migliorato con un accurato controllo di posizionamento durante l’assemblaggio per interferenza di componenti sensibili.
Il lavoro di tesi presenta un’innovativa stazione di assemblaggio che combina un cilindro idraulico ed un attuatore piezoelettrico, per raggiungere accuratezze micrometriche nel posizionamento assiale. Il cilindro idraulico esegue grandi corse mente l’attuatore piezoelettrico fornisce l’azione dinamica e l’elevata accuratezza necessaria. La caratterizzazione sperimentale del prototipo di pressa viene presentata, insieme con i fenomeni fisici che ne influenzano le prestazioni. I campioni di prova sono progettati e realizzati per ottenere un’interferenza nota. I sistemi di assemblaggio tradizionali non sono in grado di realizzare accuratezze micrometriche, mentre la nuova stazione di assemblaggio presentata può superare questi limiti grazie all’avanzato algoritmo di controllo sviluppato: quando l’attuatore piezoelettrico è alimentato da un segnale sinusoidale modulato in ampiezza, è possibile raggiungere un’accuratezza di posizionamento di ± 2 μm per forze di inserimento fino a 20 kN.
Le performance ottenute con provini dedicati sono state testate su due casi applicativi reali: un processo di calibrazione a secco di iniettori GDI, nella regione balistica, usando azoto invece di un liquido di test ed il processo di assemblaggio della valvola di controllo a solenoide di un iniettore diesel common rail, che necessita di un’elevata accuratezza geometrica.
Questi studi hanno dimostrato le possibilità del prototipo di stazione di assemblaggio presentato in casi applicativi reali; perciò la pressa può essere inserita in contesti industriali reali, raggiungendo lo scopo della ricerca.The production processes of fuel injectors can be significantly improved by a more accurate positioning control in the assembly of key components by interference fit.
This thesis presents an innovative press-fitting station in the assembly line, that combines a hydraulic cylinder and a piezoelectric actuator to reach micrometric accuracy in axial positioning. The hydraulic cylinder permits a long operational range, while the piezo actuator provides dynamic action and micrometric accuracy. The experimental characterization of the prototype press is presented together with the physical phenomena influencing the overall system performance. The tests are done using cylindrical plugs and sleeves to replicate the insertion of shafts into holes. The test samples are designed and machined to obtain a predefined interference fit. The presented new press-fit station can overcome these limits thanks to the developed advanced control strategy: when the piezo actuator is driven by an amplitude modulated sinusoidal signal, final positioning of ±2 μm is reached insertion forces up to 20 kN.
The remarkable performances obtained using dedicated samples have been then tested for real components in two different use cases: dry calibration process for GDI injector and assembly of a solenoid control valve for state of the art common rail diesel injector.
The first is a cleaner process for calibration of GDI injector in the ballistic region, that uses Nitrogen instead of a liquid working fluid. With this approach a substantially lower error for the injected quantity in the low quantity region can be accomplished. The second application case is an assembly between the pin and the armature of the solenoid control valve of a common rail diesel injector.
These studies have confirmed the possibilities of the press prototype in real application cases; thus, the press can be inserted in real industrial process, achieving the scope of the research
Comparison of contact and non-contact measurement systems for the position feed-back of a press with micrometric accuracy
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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
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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