1,720,968 research outputs found
On the Integration and Optimization of Product Design and Process Planning Based on a Genetic Multiobjective Approach
No full textStatic Coefficient of Friction Between Stainless Steel and PMMA Used in Cemented Hip Implants
No full textBackground. Design of cemented hip and knee implants, oriented to improve the longevity of artificial joints, is largely based on
numerical models. The static coefficient of friction between the implant and the bone cement is necessary to characterize the interface
conditions in these models and must be accurately provided. The measurement of this coefficient using a repeatable and reproducible
methodology for materials used in total hip arthroplasty is missing from the literature.
Methods. A micro-topographic surface analysis characterized the surfaces of the specimens used in the experiments. The coefficient of
friction between stainless steel and bone cement in dry and wet conditions using bovine serum was determined using a prototype computerized
sliding friction tester. The effects of surface roughness (polished versus matt) and of contact pressure on the coefficient of
friction have also been investigated.
Findings. The serum influences little the coefficient of friction for the matt steel surface, where the mechanical interactions due to
higher roughness are still the most relevant factor. However, for polished steel surfaces, the restraining effect of proteins plays a very
relevant role in increasing the coefficient of friction.
Interpretation. When the coefficient of friction is used in finite element analysis, it is used for the debonded stem–cement situation. It
can thus be assumed that serum will propagate between the stem and the cement mantle. The authors believe that the use of a static
coefficient of friction of 0.3–0.4, measured in the present study, is appropriate in finite element models
Identification of microtopographic surface features and form error assessment
No full textThis work is concerned with quality inspection of microtopographic surface features, such as those that may be commonly found in semiconductor products, microelectromechanical systems, and other microcomponents. Surface microtopography data are assumed to be available as a height map, acquired through raster scanning over the region of interest, by means of a 3D profilometer or a 3D scanning microscope. An algorithmic procedure is proposed for form error assessment, which comprises several steps: first the feature of interest is localized and identified within the height map; then it is extracted and aligned with a reference (i.e., nominal) geometry modeled by means of a CAD system; finally, form error is evaluated from the volume enclosed between the two aligned geometries. Feature identification is implemented through a modified version of the ring projection transform, adapted to operate on topography height maps; alignment comprises two steps (coarse alignment, consisting in an exhaustive search over discrete angular positions; and fine alignment, done with the iterative closest point technique). The final form error assessment procedure is applied to aligned geometries. The approach is illustrated and validated first through its application to an artificially generated case study, then to a real-life case of industrial relevance. © 2010 Springer-Verlag London
High precision feature detection in laser texturing
No full textThe present work seeks to develop a novel and systematic approach to quantifying the repeatability of textured surfaces, a relevant property for several technological fields. Specifically, aluminum alloy and stainless steel specimens were subject to nanosecond pulsed laser texturing to produce arrays of ablation craters in a typical configuration employed to improve wettability and tribological performance. Feature repeatability was firstly assessed in terms of crater volume and interfacial area, after which an additional parameter was developed based on the Pearson's Correlation Coefficient (PCC). Within the tested laser parameter range, the crater volume exhibited highest repeatability in the high energy dose regime on aluminum alloy specimens, while the crater volume was more repeatable in the low energy dose regime on stainless steel specimens. This difference was attributed to the development of an oxide ring surrounding the craters on stainless steel at high energy dose. This outcome was confirmed through analysis of the point-to-point repeatability, where process repeatability was determined for different portions of the ablation craters
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
AFM, a tool for investigating indentation damage in ZrO2
No full textAtomic force microscopy (AFM) can be a powerful tool to quantitatively describe the fracture process in zirconia. In the study of ceramic materials, AFM is used to produce nanometric-scale information on the indentation fracture and toughening mechanisms acting in zirconia polycrystals samples
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
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