1,720,965 research outputs found
Direct Ink Writing of Geopolymers
Get PDFGeopolymers are materials that were studied for the first time in the '70s by J. Davidovits as an alternative to Portland cement. Some aspects about production and some physical proprieties aren't completely understood yet. Recently attention is focused on the realization of geopolymer matrix composites, thanks to the lower fabrication costs compared to the mostly used ceramics composites, for the availability of the raw materials and for their lower environmental impact.
Additive Manufacturing (AM) processes are recent technologies, that starting from early ‘90s begun to gain more and more interest between industrial companies and scientific communities, because they allow fast custom-made production, impossible to obtain with traditional production processes. 3D-printed objects find their application in a wide variety of fields, spacing from military, to aerospace, from automotive, to sports and even to biomedical.
Direct Ink Writing (DIW) is part of direct AM technologies and is based on a layer-by-layer continuous deposition of an extruded filament. This technology was first called “robocasting” by Cesarano in his patent (2001). It is mostly used for the production of porous ceramic structures as tissue repairing lattices and catalyst carriers. Not all materials can be used as ink in DIW, the ideal behavior is that of a Bingham fluid, which can be extruded at low pressure and rapidly recover its viscosity to maintain the shape desired.
Subject of this thesis is the implementation of a geopolymeric slurry in a DIW process for the production of porous structures. To attain this score, a deep rheological optimization was needed, and thanks to the use of rheology agents and different kind of fillers was possible to obtain geopolymeric inks and geopolymeric composite inks with enhanced printability features. Further to this work, it was possible to understand the evolution of compressive strength through the temperature in order to choose the best ratio between performance gained and time of treatment. Density, microstructural, XRD and chemical analysis were involved to clarify how temperature affects the overall samples characteristics.
Finally, the addition of short fibers, especially carbon fibers, gave the possibility to print lattices with enhanced fracture toughness, as observed in SEM micrographs of fracture surfaces, where the strengthening mechanisms (debonding, delamination and pull-out) have been identified
The effect of fillers on the fresh and hardened properties of 3D printed geopolymer lattices
Get PDFThis work analyzed the effect of particle fillers on the rheology of geopolymer-based inks and on the microstructure and mechanical properties of lattices fabricated by Direct Ink Writing and subjected to different curing and firing temperatures. Adding particle fillers effectively improved the printability of the pure geopolymer ink; ground geopolymer filler was the most effective. In particular, it increased the yield strength and storage modulus, speeded up the recovery after extrusion and expanded the working window. The mechanical response of the lattices did not increase with the addition of fillers nor with increased curing temperature and time; curing at 80°C for 1 day was the best compromise between strength and time. The filler influenced the mechanical properties of lattices as a function of the firing temperature. Samples without fillers had a maximum strength of 34 ± 3 MPa after firing at 300°C, whereas those containing sand were damaged by the treatment; samples containing ground geopolymer were the most stable up to 1000°C
Geopolymer based binder for the additive production of manufactured items, its use and process for manufacturing additives
No full text
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
