1,720,992 research outputs found
Integrità strutturale di un albero di trasmissione per elicotteri sottoposto ad impatto balistico
No full textLa valutazione della vita residua di componenti critici in condizioni di danneggiamento determinate da impatto balistico è di vitale importanza per un elicottero militare, progettato per profili di missione a bassa quota in ambienti ostili. Il requisito balistico qui analizzato prevede la verifica della capacità di un elicottero che abbia subito un danneggiamento alla linea rotore di coda di portare a termine con successo una missione di rientro alla base a potenza ridotta.
In questo lavoro sono state effettuate prove sperimentali di impatto di un proiettile calibro 7.62 NATO su un tubo cilindrico cavo in lega leggera di alluminio rappresentativo di un albero di trasmissione della suddetta linea. Il componente danneggiato da impatto balistico è stato successivamente sottoposto a prove torsionali statiche e di fatica, al fine di valutarne la resistenza residua sotto l’azione di opportuni carichi che simulano le sollecitazioni dovute alle manovre
FATIGUE CRACK PROPAGATION UNDER TORSIONAL SPECTRUM LOAD OF A HELICOPTER TAIL ROTOR SHAFT AFTER BALLISTIC DAMAGE
No full textExperimental tests of impact of a 7.62 NATO projectile perforating a helicopter tail rotor shaft are briefly presented. Subsequently the damaged specimen has been tested with a multiaxial testing machine, in order to evaluate its capability to sustain a recovery mission, simulated by applying a torsional fatigue spectrum. During the test the nucleation and propagation of fatigue cracks have been monitored.
Finite Element analyses have been carried out to simulate both impact and crack propagation for a further analytical automated simulation of these conditions. According to the multiaxial state of stress induced by torque, residual stress field and shape of the damage, mixed mode propagation has been considered, by means of an equivalent SIF. Numerical results are in good agreement with experimental data
BALLISTIC IMPACT ON A TRANSMISSION TAIL ROTOR SHAFT FOR HELICOPTER
No full textFor military rotorcraft, designed for low altitude profile mission in hostile environment, is fundamental to evaluate the damage of high critical components affected by ballistic impact. Actually numerical approach allows to simulate a very complex scenario involving impact phenomena. However, experimental tests still
play a primary role. In this paper an experimental impact test of a 7.62 NATO projectile perforating a helicopter tail rotor shaft is presented. Test equipment includes a dedicated shaft support frame that allows the specimen positioning in order to set the worst operational conditions. Impact velocity, residual velocity and deflection of the projectile have been detected during the test.
Residual stresses have been also measured near the impact zone.
All the experimental activities were compared with numerical simulation of the impact, carried out by an explicit finite element code (ABAQUS/Explicit). The results show a good agreement between numerical and experimental data
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
I punti magici di un fallimento : Remo Bianco a Milano tra anni Cinquanta e primi Sessanta
No full textMostra antologica di Remo Bianco (1922 – 1988), tenutasi a Roma nel 2006-2007
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
Valutazione della capacità di rientro alla base di un elicottero in presenza di danno balistico ad un albero di trasmissione della linea rotore di coda
No full textNella progettazione di un elicottero militare, destinato ad operare a bassa quota e in ambiente ostile, il danneggiamento di componenti critici, conseguente ad impatto balistico, riveste un ruolo primario nella valutazione delle possibilità di sopravvivenza dell’intera macchina. In questo articolo è quindi proposto uno studio sperimentale, suddiviso in diverse fasi, riguardante la verifica della capacità di un elicottero di portare a termine una missione di rientro alla base a potenza ridotta e in presenza di danneggiamento balistico ad un albero di trasmissione della linea rotore di coda. Il lavoro ha richiesto dapprima l’esecuzione, su esemplari del componente in esame, di prove sperimentali di impatto balistico, condotte utilizzando un proiettile calibro 7.62 NATO. Successivamente su ciascun albero danneggiato sono state eseguite prove torsionali statiche ed a fatica, il cui scopo è stato verificare la resistenza residua del componente all’applicazione di opportuni carichi rappresentativi delle sollecitazioni riscontrate durante la missione di rientro
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
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