1,720,961 research outputs found
The performance of Molybdenum toughened alumina cutting tools in turning a particulate metal matrix composite
No full textIntegrating Meteosat satellite and rain-gauge information to estimate rainfall patterns
No full textThis paper presents the development and the application of techniques for the integration of information coming from Meteosat satellite images and rain-gauge measurements, with the purpose of estimating the rainfall pattern on a certain river basin. The proposed integration techniques are based on the definition of a data coherence problem and on the application of mathematical programming methods. The quality of the estimation procedure is evaluated by using a rainfall/runoff model for the basin which allows the generation of a hydrograph at a given section of the river, on the basis of the above estimated rainfall pattern in the upstream watershed. The comparison of the hydrograph with the observed one allows the parametric tuning of the integration procedure
Wear mechanisms and residual stresses in alumina-based laminated cutting tools
No full textThe outstanding performances of the Al2O3 cutting tools in terms of potential cutting speed can lead to substantial economies in the machining of metallic materials. Nevertheless, their widespread use is limited by some drawbacks such as the tendency to edge chipping and to the propagation of microcracks, which can lead to premature failures. These shortcomings are due to the intrinsic low toughness of the ceramic material, which is in turn related to its characteristics non-metallic bonds. A well-recognised method of increasing the toughness of brittle materials is the introduction of surface compressive stresses, which can be obtained through a suitable lamination geometry of the tools as consequence of the different coefficients of thermal expansion (CTE) of the constituent layers. The performances of an alumina/zirconia laminated cutting tool used for machining steel have been investigated and compared to those of a non-laminated commercial alumina/zirconia cutting tool. The different wear mechanisms are explained on the basis of the different microstructures and chemical compositions. We have shown that residual compressive stresses, measured by Piezo-Spectroscopy, are effective in avoiding the microchipping on the flank zone but cannot avoid larger fractures caused by the residual porosity. (c) 2004 Elsevier B.V. All rights reserved
Ceramic materials wear mechanisms when cutting nickel-based alloys
No full textIn this paper the performances of some commercial ceramic inserts when cutting AISI 310 steel are investigated and compared to those of a traditional carbide based tool. The most important wear mechanism in the ceramic inserts is related to the segmented edges of the chips that abrade a notch at the end of the cut zone. Alumina-zirconia inserts are very sensitive to this kind of wear, whereas tools made of Sialon and alumina with SiC whiskers exhibit slightly better performances despite the concomitant chemical wear mechanisms. (C) 1999 Elsevier Science S.A. All rights reserved
Cutting performance and indentation behaviour of diamond films on co-cemented tungsten carbide
No full textDiamond films were grown by Hot Filament Chemical Vapour Deposition (HFCVD) on differently pretreated ISO-grade K10 cemented carbide (WC-5.8 wt.%Co) cutting inserts. Etching with diluted HNO3 and surface roughening by Murakami's reagent were used as substrate pretreatments. The adhesion of the films was evaluated by indentation tests. In order to obtain a reliable estimation of the adhesion by the slope of the crack radius-indentation load curves, a careful SEM measurement of the crack lengths was performed. Bare and diamond-coated cutting inserts were used for turning tests of Al2O3-reinforced aluminum alloy. The adhesion levels obtained from the indentation curves correlated well the lifetime of diamond-coated cutting inserts used in turning tests performed on metal matrix composite material under severe cutting conditions
The effect of wear on the tetragonal-to-monoclinic transformation and the residual stress distribution in zirconia-toughened alumina cutting tools
No full textZirconia-toughened alumina cutting tools have been examined after machining an AISI 1040 steel. The Raman spectrum of zirconia and the fluorescence spectrum from alumina have been used to determine the extent of the tetragonal-to-monoclinic (t-m) transformation and the residual stresses in and around the worn-out crater, respectively. Although about 15% vol. m-zirconia is present even in a brand new cutting tool, it was shown that the crater region undergoes the t-m transformation up to 40% vol. In both cases, the transformed zone is concentrated near the surface. The residual stresses in alumina are slightly compressive in the new cutting tool and away from the crater region, but they become tensile inside the crater, where the t-m transformation of zirconia has occurred to a larger extent. A stochastic model has been used to predict the stresses and it has been found to reproduce very well the experimental data. Some evidence of the formation of a spinel reaction product in the crater region has been found, likely (Mg, Fe) AlO
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
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