1,720,986 research outputs found
Interface analysis of additively manufactured pure molybdenum and AISI 304 stainless steel building-plate
No full textIn this study pure molybdenum was produced by laser powder bed fusion on an AISI 304 building-plate. Adhesion issues were found at the interface between the two materials since the very beginning of the production process. Interface analysis was performed in order to investigate possible origins of the failure. The investigation showed that large cracks could propagate and led to separation of the printed part from substrate when the dilution of Mo on AISI 304 platform was approximately in the range 40 ÷ 50. The brittle intermetallic sigma phase was extracted and analysed by XRD on Mo-AISI 304 interface specimens. It is assumed that the sigma phase impaired the interface strength, providing a preferential route for brittle crack propagation
Additive manufacturing for thermal management applications: from experimental results to numerical modeling
Get PDFRecently, Additive Manufacturing (AM) of metal components has opened new frontiers in heat transfer applications, going beyond the capabilities of conventional technologies. Despite the great design freedom offered by AM, when dealing with metals, there are a few issues that should be considered to exploit the great capabilities of this manufacturing technology. In fact, the surface roughness of the components is expected to affect the performance of the devices, which can be remarkably different from the ones simulated with computer codes. This paper presents a critical analysis of the accuracy of the numerical tools to simulate the fluid flow behaviour inside channels obtained via AM, showing the major limitations of the standard approaches to accurately predict the pressure drops in straight and complex channels. Three different copper channels of growing complexity were built via SLM (Selective Laser Melting) and then they were experimentally tested to evaluate the predictive abilities of the numerical model. The results revealed that the surface roughness deeply affects the fluid flow, thus the numerical models need to be calibrated to become reliable design tools. The proposed procedure can be considered the first attempt in this direction and allows for a proper integration of the AM with the numerical simulation tools to boost the design capabilities of SLM technology
Direct ink writing of porous titanium (Ti6Al4V)lattice structures
No full textTi6Al4V components, for biomedical and aerospace sectors, are receiving a great interest especially after the advent of additive manufacturing technologies. The most used techniques are Selective Laser Sintering (SLS), Selective Laser Melting (SLM)and Electron Beam Melting (EBM). In the current research, we developed 3D-printed Ti6Al4V scaffolds by Direct Ink Writing (DIW)technology. Appropriate ink formulations, based on water-titanium powder suspensions, were achieved by controlling the rheological properties of the developed inks. After printing process, and drying, the printed components were sintered at 1400 °C under high vacuum for 3 h. Highly porous titanium scaffolds (with porosity up to 65 vol%)were produced and different geometries were printed. The influence of the porosity on the morphology, compression strength and biocompatibility of the scaffolds was investigated
Interface analysis of additively manufactured pure molybdenum and AISI 304 stainless steel building-plate
No full textIn this study pure molybdenum was produced by laser powder bed fusion on an AISI 304 building-plate. Adhesion issues were found at the interface between the two materials since the very beginning of the production process. Interface analysis was performed in order to investigate possible origins of the failure. The investigation showed that large cracks could propagate and led to separation of the printed part from substrate when the dilution of Mo on AISI 304 platform was approximately in the range 40 ÷ 50. The brittle intermetallic sigma phase was extracted and analysed by XRD on Mo-AISI 304 interface specimens. It is assumed that the sigma phase impaired the interface strength, providing a preferential route for brittle crack propagation
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
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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