1,720,990 research outputs found
Investigation and comparison of aluminium foams manufactured by different techniques
No full textCellular metals offer a large potential for industrial application. Nevertheless, besides the
costs, there are a lot of technical improvements necessary in order to gain more widespread
use. The reasons for the lack of applications, since now, are multiple and they depend from
the physical properties of foams that are still not good enough and not completely
experienced, and from the insufficient spreading of research results to designers.
To fulfill parts of these requirements, this work investigates in detail three foam production
processes, studies the effect of modifications to standard manufacturing methods, clarifies
the influence of process parameters on the structure of foams, characterises relevant
properties, and finally discusses the difference between powder or melt routes. During
experimentation hundreds of samples were realised to reach these objectives. Moreover
mechanical, physical, and microstructural properties of the produced foams have been
studied using various techniques including compression testing, scanning electron
microscopy, visual inspection, and software measurement tool. The three methods for
manufacturing aluminium foams, applied in this investigation, are named TiH2, SDP and
MGI. Two of them (TiH2 and SDP) start from powdered aluminium as row material, while
MGI starts from melt aluminium. Moreover TiH2 and MGI methods let the production of
closed cells foam while SDP of open cells foam named, more correctly, metal sponge.
The term ‘‘foam’’ was firstly reserved for a dispersion of gas bubbles in a liquid. The
morphology of this type of foams can be preserved by letting the liquid solidify, thus
obtaining what is called a ‘‘solid foam’’. When speaking of ‘‘metallic foams’’ one generally
means a solid foam. The liquid metallic foam is a stage that occurs during the fabrication of
the material. For metallic systems it is possible to define the following classification
according with Babcsan et al. (2003):
•
cellular metals are materials with a high volume fraction of voids made up of an
interconnected network of walls and membranes;
•
porous metals have isolated spherical pores and a porosity level of usually less than
about 70%;
•
metal foams are a soubgroup of cellular metals usually having a polyhedral cells with
closed or open cells (even if there are no membranes across the faces and the voids are
inteconnected, the better definition is metal sponges)
On line verification of CMM metrological performances by measurements reproducibility control
No full textGoing 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
Evaluation of mold roughness influence on injected thin micro-cavities
No full textDue to its ability to produce low-cost and high repeatable micro-polymeric parts, micro-injection molding is emerging as one of the most promising enabling technologies in many different fields. When approaching the micro-scale, different issues related to the process should be addressed, especially as the thickness of the cavities becomes very thin. In particular, the mold roughness affects the surface quality of the micro-components produced, like in macro-molding, but this could also encompass the complete filling of the parts. The main objective of the present paper is to evaluate the roughness influence of the mold on the non-Newtonian fluid flow during the micro-injection process in thin micro-cavities where the mold surface condition could affect the process due to the phenomena neglected in macro- or mesoscale as less important boundary conditions. The part design was properly conceived in order to neglect the effect of dimensions and geometry and to highlight the roughness contribution during the filling phase. The experimentation was performed using cavities with different roughness values and decreasing depths from 200 to 50 ?m, considerably lower than 250 ?m found in literature and manufactured by the micro-electrical discharge machining (?-EDM). The results of the experiments are discussed and show that cavity-surface roughness affects the process as the molding scale is decreased. In particular, in thin cavities, higher surface roughness promotes the filling of component
100 Innovation Stories Abruzzo. Ricerca quali-quantitativa sulle eccellenze industriali e universitarie della Regione Abruzzo
No full textVariations 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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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