1,720,996 research outputs found
Upgraded stability analysis of milling operations by means of advanced modeling of tooling system bending
No full textThe problem of undesired self-excited chatter vibrations in milling is very common. However, only in the last two decades some significant achievements for the theoretical understanding of this intricate phenomenon have been accomplished. Nevertheless, state of the art dynamic models are still not able to completely explain milling dynamics and chatter onset during some conventional milling operations performed by conventional cutting tools. In this research work, a revolutionary model of tooling system dynamics and of the regenerative effect in milling will be presented. The new model introduces a significant correction to the predicted stability borders when the cutter diameter is relatively large in comparison with tooling system overhang and when curved or inclined cutting edges are applied. Accordingly, the new approach may be of great interest for many industrial applications. The model has been successfully validated by performing experimental modal analysis, cutting force coefficient identification and stability lobes diagram determination, through many specific cutting tests. In the considered case study, where the afore mentioned geometrical features of the tooling system were still moderate, a significant shift of the stability borders of about +25% was experimentally observed and correctly predicted by the new approach
Development of a chatter detection methodology for variable spindle speed milling
No full textRegenerative chatter is one of the most detrimental phenomena affecting machining operations both in terms of tool integrity and quality of the machined surface. Most of the developed chatter detection algorithms, being based on the separation of the spindle-related frequencies from the asynchronous frequency components, fails to be effective under non-stationary spindle speed conditions. In order to overtake this limitation, in this research a chatter detection algorithm suitable for a generic spindle speed regime was developed. More specifically, the algorithm is based on the order tracking methodology and allows to perform a process stability assessment through the definition of a suitable chatter indicator, in the spindle angular domain. The developed procedure was then validated performing real milling operations in which the spindle speed variation technique was adopted
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
A Novel Knowledge Formalization Framework to Support Decision-Making in Manufacturing Processes
No full textDespite the recent efforts towards the introduction of advanced digital and automation technologies in the industry, most of the manufacturing processes are still governed and optimized by human expertise. This fundamental contribution is often in the form of explicit and implicit (or tacit) human knowledge, which is extremely difficult to document, structure and transfer to other people. In this scenario, manufacturing companies run the risk of losing this intrinsic asset, held by their personnel, worsening in turn the quality and efficiency of their products and processes. To cope with this knowledge loss problem, a novel approach to knowledge formalization is presented that lays the foundations for the realization of a digital platform equipped with interfacing capabilities as well as AI-based knowledge representation and reasoning tools. The paper focuses on evaluating the current scenario, generalizing the problem in the manufacturing context, identifying the main actors who will interact with the platform and proposing a possible procedure for knowledge formalization
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