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Tecniche di sperimentazione avanzate per lo studio del comportamento anisotropo di materiali ingegneristici
No full textIn questa tesi si parla di tecniche di sperimentazione avanzate per lo studio del
comportamento anisotropo di materiali ingegneristici facendo riferimento a due casi
di studio, entrambi caratterizzati da aspetti anisotropi.
Il primo caso riguarda la descrizione di un metodo innovativo per l’individuazione
della propagazione dello snervamento durante un test di trazione su provini in stato di
deformazione non uniforme: sono stati utilizzati provini ricavati da una lamiera in
acciaio DP600 (GI50/50). Le mappe termiche sono state opportunamente elaborate e
sovrapposte a quelle di deformazione. La validazione è stata condotta applicando il
metodo ad un secondo test e rilevando la tensione di snervamento secondo Swift.
Sebbene il metodo abbia richiesto una correzione per tenere conto dello scambio
termico durante il test, i risultati sono promettenti al punto da invitare il proseguo
dell’attività in tal senso.
Il secondo caso riguarda la caratterizzazione di una sospensione meccanica composita
con comportamento non lineare sottoposta a grandi spostamenti. Si cercano i migliori
coefficienti ortotropi linearizzati del materiale che, utilizzati in un modello FEM,
consentano il miglior adattamento della curva forza-spostamento misurata
sperimentalmente. Il componente analizzato consiste in una membrana perforata di
forma circolare non planare; la sospensione è fissata al suo perimetro esterno e serve
a stabilizzare il moto assiale di un pistone centrale oscillante, collegato al centro della
membrana. Vengono utilizzati tre metodi di caratterizzazione, il primo basato sulle
norme ASTM D3039-08 e D3518-18, mentre gli altri due metodi sono il VFM e sul
FEMU applicati ai risultati ottenuti da prove biassiali su campioni cruciformi. Le tre
curve forza-spostamento risultanti, una per ogni metodo, vengono confrontate con la
curva di riferimento. È emerso che, per riprodurre correttamente il comportamento non
lineare a grandi spostamenti attraverso un'appropriata linearizzazione, i metodi VFM
e FEMU restituiscono un'approssimazione migliore rispetto al metodo ASTM.This paper discusses advanced experimental techniques for the study of the anisotropic
behaviour of engineering materials with reference to two case studies, both
characterised by anisotropic aspects.
The first case concerns the description of an innovative method for the detection of
yield propagation during a tensile test on specimens in a state of non-uniform
deformation: specimens of a DP600 (GI50/50) steel plate were used. The heat maps
were suitably processed and superimposed on the deformation maps. Validation was
conducted by applying the method to a second test and detecting the yield stress
according to Swift. Although the method required a correction to account for heat
transfer during the test, the results are promising enough to invite further work in this
direction.
The second case concerns the characterisation of a composite mechanical suspension
with non-linear behaviour subjected to large displacements. The best linearised
orthotropic coefficients of the material are sought, which, when used in an FEM model,
allow the best fit to the force-displacement curve measured experimentally. The
component analysed consists of a perforated membrane of circular, non-planar shape;
the suspension is fixed to its outer perimeter and serves to stabilise the axial motion of
a central oscillating piston connected to the centre of the membrane. Three
characterisation methods are used, the first based on ASTM D3039-08 and D3518-18,
the other two being VFM and FEMU applied to results obtained from biaxial tests on
cruciform specimens. The three resulting force-displacement curves, one for each
method, are compared with the reference curve. It turned out that in order to correctly
reproduce the non-linear behaviour at large displacements through appropriate
linearisation, the VFM and FEMU methods return a better approximation than the
ASTM method
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
Recent Italian Research In Mathematics Education
No full textIl volume, dedicato alla figura di Francesco Speranza , è costituito in due parti. La prima parte raccoglie quattro ampi contributi, rispettivamente dedicati a: l'evoluzione della ricerca in didattica della matematica e la caratterizzazione del suoi principali indirizzi attuali (Arzarello); la storia del seminario nazionale come ambiente per promuovere e sviluppare ricerche in comune, corredata da una sintesi degli studi realizzati nel suo seno (Malara); la figura di Francesco Speranza come didatta (Malara), la figura di Francesco Speranza come epistemologo (Marchini). La seconda parte è costituita da una selezione di brevi sunti di specifici studi realizzati nel periodo 1996-2000 da ricercatori italiani
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
From research in mathematics education to training of teachers trough Internet
No full textWe present three projects realized in the realm of the National Project S&T (project devoted to the renewal of the Science &Technology teaching and learning). We indicate some iniciatives to promote the teachers interaction through the web and we evidenciate questions arisen and future perspectives
The voices and echoes game» and the interiorization of crucial aspects of the theoretical knowledge in Vygotskian perspective: Ongoing research
No full text
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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