1,720,996 research outputs found
Reliability assessment of hydraulic cylinders considering service loads and flaw distribution
No full textManufacturing process, service conditions and material properties are all necessary requirements to a good design of tubular mechanical components subjected to fatigue. The most common approach to this design is usually deterministic, where a fixed NDT threshold, related to flaw acceptance limit, is set. However many uncertainties are left aside, i.e. the failure probability related to the fatigue strength under applied loads.
This paper addresses the reliability evaluation of tubular mechanical components carrying some flaws and subjected to cyclic internal pressure variation. The aim is comparing the probability of failure obtained under several assumptions.
A reliability assessment model, based on a random variable approach, has been implemented by using the Monte Carlo method.
The analysis of the results, from a case study based on load spectra measurements of hydraulic cylinders of earth moving machines, has consented to evaluate the most important factors influencing the fatigue life prediction of these components
Fatigue limit assessment on seamless tubes in presence of inhomogeneities: Small crack model vs. full scale testing experiments
No full textThe existence of crack-like flaws cannot be excluded in pressure vessels and piping due to the presence of non-metallic inclusions and surface imperfections. These inhomogeneities reduce the fatigue strength of the pressure vessel. In this work, the detrimental effect of the surface quality on the fatigue strength of cylinder housings is analyzed by means of a fatigue model available in the literature using values obtained by crack propagation tests. The comparison in terms of fatigue limit between model and exper- imental full scale (FS) tests has shown an underestimation of the fatigue strength if the prediction based on DKth,LC values for long cracks is used. This is due to a flattening effect of the DKth,LC values at high stress ratios R under full scale tests that the standard crack propagation tests do not anticipate. Further inves- tigations need to be carried out for more realistic prediction by the mentioned model. In order to obtain an accurate and more realistic fatigue limit, an alternative small scale (SS) fatigue test has been imple- mented. The goal was to reproduce as much as possible the real condition of a full scale (FS) state during the small scale (SS) fatigue limit test; and this has led to a good agreement between the FS and SS fatigue limit tests
L'osservazione nei servizi educativi per la prima infanzia: Paradigmi epistemologici, metodi applicativi e implicazioni educative
Full text linkThis paper aims to highlight importance of observation, understood as a cognitive, metacognitive and methodological process, for the implementation of educational interventions aimed at children from 0 to 6 years. Starting from a semantic reflection around the verb “observe” and its intrinsic connections with the educational activity, the authors analyse its many aspects emphasizing the premises that guide its realization, the methodological characteristics that establish the application paradigms and the tools in which it is substantiated. Finally, observation is proposed as a tool to ensure, within the educational services, respect for the rights of the child and the principle of the participation of childhood in their own educational processes.Il presente contributo intende mettere in evidenza l’importanza dell’osservazione, intesa come processo cognitivo, metacognitivo e metodologico, per l’implementazione di interventi educativi rivolti all’infanzia da 0 a 6 anni. A partire da una riflessione semantica attorno al verbo “osservare” e alle sue intrinseche connessioni con l’attività educativa, le autrici analizzano i suoi numerosi aspetti sottolineando le premesse che ne guidano la realizzazione, le caratteristiche metodologiche che ne stabiliscono i paradigmi applicativi e gli strumenti in cui si sostanzia. Infine, l’osservazione viene proposta come strumento per garantire, all’interno dei servizi educativi, il rispetto dei diritti della bambina e del bambino e del principio della partecipazione dell’infanzia ai propri processi educativi
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
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