1,720,956 research outputs found
MICRO-CUTTING OF DIFFICULT-TO-CUT-MATERIALS
Full text linkThe objective of this Ph.D. thesis is to study the micro-cutting (micro-milling) of difficult-to-cut materials, devoted to the biomedical applications.
In the first part of this work the interest is aimed to the process and understanding the cutting mechanisms at this scale, in order to choose the most suitable cutting conditions on the basis of the final application.
The actual state-of-the-art in the micro-manufacturing technologies with the target to the micro-milling process was investigated, with the aim of a better understanding of the cutting process and its mechanisms at micro-level.
In particular, up to now, the machinability of difficult-to-cut metals have not been deeply investigated under micro-milling conditions, especially in combination with additive manufacturing (AM) technologies, such as Electron Beam Melting (EBM) and Direct Laser Sintering (DLS), which are more and more used in industry, especially in a biomedical field.
In the second part of this thesis different AM techniques will be studied and their influence on the final material properties especially in relation to the biomedical implants and their function.
Third part of this work consists of the micro-cutting experiments conducted on Ti6Al4V biomedical alloy produced by different AM techniques. Their performances in micro-cutting world are studied and compared especially in the regards of the final applications, thus the most relevant parameters are studied as the quality of the surface finish, burrs formation, microstructural alterations, surface defect, tool state after machining etc
Comparison between EBM and DMLS Ti6Al4V machinability characteristics under dry micro-milling conditions
No full textMicro-drilling and Threading of the Ti6Al4 v Titanium Alloy Produced through Additive Manufacturing
No full textThe paper presents the evaluation of the drillability characteristics of the Ti6Al4 V titanium alloy produced through the Additive Manufacturing (AM) technology called Direct Metal Laser Sintering (DMLS). Holes of 1.6 mm diameter were drilled on a 5-axis high-precision micro-milling machine under dry cutting conditions at varying cutting speed and feed rate. A specific measurement procedure was developed to quantify and compare the most representative geometrical features (diameter and perpendicularity) of the machined holes as well as the quantification of burrs. The influence of the AM material on the geometrical quality of high precision holes is discussed, taking into account the requirements of the following threading operations. Finally, thread milling experiments were carried out to prove the threading feasibility and performances based on the previous drilling experiments. From the results within the tested range of cutting conditions, the lowest values of the cutting speed and feed rate seem to be the best trade-off for achieving the required hole quality
Environmentally clean micromilling of electron beam melted Ti6Al4V
Full text linkThe paper is aimed at evaluating the performances of Minimum Quantity Lubrication (MQL), dry cutting and cryogenic cooling when applied to the micro-milling of Ti6Al4V titanium alloy samples obtained by Additive Manufacturing (AM) using the Electron Beam Melting (EBM) technology. The micro-milling tests were carried out on a high precision 5-axis micro-milling center, at varying cutting speed and feed per tooth. The performances of the different lubrication/cooling strategies were analyzed in terms of surface integrity, namely surface topography, nano-hardness and sub-surface microstructural alterations, in order to prove the impact of clean cutting conditions when applied to micro-machining of a AM titanium alloy of biomedical interest. It is shown that dry cutting assures the same performances of MQL, representing then the most suitable option to decrease the environmental impact of the machining process. (C) 2016 Elsevier Ltd. All rights reserved
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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