1,757,915 research outputs found
Sol–gel thermal barrier coatings: Optimization of the manufacturing route and durability under cyclic oxidation
Get PDFA new promising and versatile process based on the sol–gel transformation has been developed to deposit yttria-stabilised thermal barrier coatings. The non-oriented microstructure with randomly structured pore network, resulting from the soft chemical process, is expected to show satisfactory thermo-mechanical behaviour when the TBC is cyclically oxidized. First stage of the research consists of optimizing the processing route to generate homogeneous microstructure and controlled surface roughness. The objective is to reduce, as much as possible, the size and depth of the surface cracks network inherent to the process. Indeed, the durability of the TBC when cyclically oxidized strongly depends on the sharpness of those cracks that concentrate thermo-mechanical stresses and generate detrimental propagation resulting in spallation. Cyclic oxidation tests are performed using a cyclic oxidation rig instrumented with CCD cameras to monitor in a real time basis the mechanism of crack propagation and spallation. The impact of various parameters either directly related to the processing route, e.g. the intimate microstructure of the TBC and the TBC thickness, or to the thermal loading, e.g. the oxidation temperature and the cumulated hot time, on the durability of the TBC is investigate
Beneficial Effect of Pt and of Pre-Oxidation on the Oxidation Behaviour of an NiCoCrAlYTa Bond-Coating for Thermal Barrier Coating Systems
Get PDFThe oxidation behaviour of a thermal barrier coating (TBC) system is a major concern as the growth of the thermally grown oxide (TGO) layer on the bondcoating creates stresses that greatly favour the thermal barrier spallation. To delay the loss of the thermal protection provided, research has focused on the bondcoating composition and microstructure as well as on the parameters required for a suitable pre-oxidation treatment before the deposition of the ceramic top coat. Platinum is known to enhance the oxidation/corrosion resistance of MCrAlY coatings. The effect of Pt on the oxidation behaviour of a NiCoCrAlYTa coating was assessed in this study. In addition, pre-oxidation treatments were conducted to
determine if the oxidation behaviour of the modified NiCoCrAlYTa coating could be further improved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Effect of water vapor on the spallation of thermal barrier coating systems during laboratory cyclic oxidation testing.
Get PDFThe effect of water and water vapor on the lifetime of Ni-based superalloy samples coated with a typical thermal barrier coating system—b-(Ni,Pt)Al bond coat and yttria stabilized zirconia (YSZ) top coat deposited by electron beam physical vapor deposition (EB-PVD) was studied. Samples were thermally cycled to 1,150 C and subjected to a water-drop test in order to elucidate the effect of water vapor on thermal barrier coating (TBC) spallation. It was shown that the addition of water promotes spallation of TBC samples after a given number of cycles at 1,150 C. This threshold was found to be equal to 170 cycles for the present system. Systems based on b-NiAl bond coat or on Pt-rich c/c0 bond coat were also sensitive to the water-drop test. Moreover, it was shown that water vapor in ambient air after minutes or hours at room temperature, promotes also TBC spallation once the critical number of cycles has been reached. This desktop spalling (DTS) can be prevented by locking up the cycled samples in a dry atmosphere box. These results for TBC systems confirm and document Smialek’s theory about DTS and moisture induced delayed spalling (MIDS) being the same phenomenon. Finally, the mechanisms implying hydrogen embrittlement or surface tension modifications are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
595. Kōjō
No full textIwao Seiichi, Iyanaga Teizō, Ishii Susumu, Yoshida Shōichirō, Fujimura Jun'ichirō, Fujimura Michio, Yoshikawa Itsuji, Akiyama Terukazu, Iyanaga Shōkichi, Matsubara Hideichi. 595. Kōjō. In: Dictionnaire historique du Japon, volume 13, 1987. Lettre K (3) p. 70
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