1,720,979 research outputs found
Non uniform residual stress fields on sintered materials
No full textThe hole-drilling method (HDM) is a convenient and effective method for measuring residual
stresses near the surface of an isotropic linear-elastic material. The measurement procedure is relatively simple,
and has been standardized in ASTM Standard Test Method E837. The HDM is also versatile and can be
performed in laboratory or in situ, on components ranging widely in size and shape. It is often referred to as a
“semidestructive” technique, since the small hole will not, in many cases, significantly impair the structural
integrity of the part being tested.
The basic principle was first introduced by Mathar in 1934. Since that time, many researchers have further
developed the method, culminating in the establishment of a standardized procedure ASTM E837. At least
three established methods are available for estimating non-uniform residual stress fields from relaxed strain data
from the incremental HDM. They are the Power Series, the Integral and the ASTM E837-08 Methods. These
methods rely on finite element calculated calibration data, utilize different approaches for stabilizing and
smoothing the non uniform residual stress field, and do not have the theoretical shortcomings of the two
traditional methods (the Incremental Strain and the Average Strain Methods). Since the strain variations during
drill depends on many factors hardly predictable and checkable a priori, it seems that the best calculation method
should be evaluated for each particular experiment.
This paper compares the Power Series, Integral and ASTM E837-08 methods as procedures for determining
non-uniform residual stress fields using strain relaxation data from the HDM. Specimens made of AISI
Maraging 300 steel by means of Selective Laser Melting are investigated and the residual stress profiles
performed by means of all three stress calculation procedures are also presented and compared
Residual stress on AISI 300 sintered materials
No full textSelective Laser Melting (SLM) is one of the most interesting technologies in the rapid prototyping processes because it allows to build complex 3D geometries. Moreover, full density can be reached and mechanical properties are comparable to those of bulk materials. However, the most important drawback is related to the thermal transient encountered during solidification which generates highly variable residual thermal stresses. Parameters such as laser scanner strategy, laser velocity and power should be optimized also in order to minimize residual stresses that are strictly dependent on the manufacturing process and cannot be completely avoided. Geometry of parts should be optimized in order to keep residual stresses and distortions low. This paper presents a study on residual stress distribution on SLM rectangular plates built by means of a new scanning strategy, implemented by dividing the fused zone in very small square sectors. Residual stresses measurement on SLM samples are performed by means of the hole drilling technique. Specimens made of AISI Maraging 300 steel are investigated and the residual stress profiles are compared with those related to previous measurements on SLM disks coming from the same process parameter
Styrene oxidation to styrene oxide in human erythrocytes is catalyzed by oxyhemoglobin
No full textOxygenated human erythrocytes catalyzed the oxidation of styrene to styrene oxide. This reaction was inhibited by CO but not by superoxide dismutase, catalase and scavengers of hydroxyl radicals. In partially deoxygenated erythrocytes styrene oxidation showed a linear relationship with the molar fraction of oxyhemoglobin. These data indicate that oxyhemoglobin and not free oxygen radicals are involved in styrene oxidation
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
Effetto degli errori di misura delle deformazioni sulle tensioni residue calcolate con il metodo della rosetta forata
No full textVariations 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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