1,720,995 research outputs found
Role of grain boundaries and micro-defects on the mechanical response of a crystalline rock at multiscale
No full textThe paper examines the cracks initiation, propagation and coalescence until failure in a crystalline rock under stress states involving rock volumes varying in size, from nano (Berkovich indentation in Continuous Stiffness Measurement mode) to micro (Vickers indentation, scratching) and macro (Rockwell indentation, Rock Impact Hardness Number) scales. The experimental work was performed on a calcitic marble characterized by two different textures (xenoblastic and granoblastic). The grain boundaries microcracks were deeply studied with Focused Ion Beam–Scanning Electron Microscopy technique, innovative approach in Rock Mechanics. The experimental results show that, at the three investigation scales, the microcracks give rise to the rock failure with fractures propagation mechanisms varying with the microstructure. In the granoblastic texture, fracturing is ruled by grain boundaries microcracks, which often appear almost open. Conversely, the fracture behavior of the xenoblastic marble seems dominated by the grains cleavage, even at the macroscale
Titanium carbide films obtained by conversion of sputtered titanium on high carbon steel
No full textOne the most important limitations to the industrial use of hard coatings in severe conditions is associated with their limited adhesion to the substrate. A number of research works have been done in various directions in order to improve the adhesion by post treatments such as laser remelting or thermal treatments. The aim of this work is to evaluate the possibility of using the substrate itself as a carbon source, in order to create very adherent hard titanium carbide coatings by means of a diffusion/precipitation process. A film of pure titanium was prepared by magnetron sputtering on a high carbon content steel substrate. Coated samples were then annealed in vacuum for I h at temperature ranging from 500 to 1100 degrees C. It was observed that the film was totally, partially or not transformed into titanium carbide, depending on heat treatment temperature. The transformation of titanium layer in titanium carbide takes place firstly at the interface between the film and the substrate, then it expands through the whole film thickness, toward the outer surface, by diffusion of carbon coming from the substrate. As a result, complete conversion of the titanium film in titanium carbide is obtained when an annealing temperature of 1100 degrees C is used. A higher adhesion, measured by means of a scratch tester, is found for this coating if compared to the one obtained on samples treated at lower temperatures and to other literature data on coatings having similar thickness and composition. (c) 2005 Elsevier B.V. All rights reserved
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
Indentation size effect of cortical bones submitted to different soft tissue removals
No full textProperties of elasticity, hardness and viscosity are determined for the study of the visco-elastoplastic behavior of bones. The mechanical properties are compared in two upright sections of the bone due to their anisotropy. Besides, influence of hydration treatments leading to structural modifications of collagen and ground substance contents of bones on the mechanical properties is studied on a femoral cortical bovine bone. The treatments applied to the bone are used by forensic anthropologists to remove the soft tissue and modifying the hydration degree coupled to the collagen content. From instrumented indentation experiments, the hardness is characterized by the macrohardness and a hardness length-scale factor stating the hardness-load dependence. The elastic modulus results from the application of the methodology of Oliver and Pharr (1992). The coefficient of viscosity is deduced from a rheological model representing the indenter time-displacement observed under the application of a constant load. As a result, all the mechanical properties are found to be lower in the transverse section in an extent depending on the hydration treatment, i.e. the different values are located between 5% and 25% for the hardness around 0.5. GPa, between 25% and 40% for the elastic modulus around 20. GPa and between 2% and 35% for the coefficient of viscosity around 60. GPa.s. Unexpectedly, the elastic modulus to coefficient of viscosity ratio is found to be independent on the hydration treatment
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
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