1,720,981 research outputs found
Molten metal/die interaction: Die soldering
No full textIn high-pressure die-casting foundry of the aluminium alloys, the interaction between the molten metal and the steel die plays a key role to form surface defects. These are the result of geometric changes on the die surface caused by erosion, soldering and thermal fatigue phenomena. Among all, die soldering is one of the main causes of surface defects in diecastings. This phenomenon leads to the formation of intermetallic phases on the surface of the die, over which the liquid initially solders and then detaches partially and locally, thus leaving defects with different size on the final castings. In this work, the prediction of the increase of the soldered layer has been experimentally and numerically studied by means of a numerical process simulation software. The numerical results have shown a good agreement with the experimental data, thus making the implemented numerical model successfully applicable to industry
Experimental and numerical investigations of oxide-related defects in Al alloy gravity die castings
Full text linkThis research aimed to study the formation and distribution of oxide-related defects in the gravity die casting process of an AlSi7Cu0.5Mg alloy by using experimental and numerical investigations. Metallographic and image analysis techniques were conducted to map the distribution of oxide inclusions inside the casting at the microscopic level. Numerical simulations were used to analyse the filling and solidification stages, and to foresee the turbulence of the melt and the formation of the oxide defects. The results show that most of the defects were correlated with the oxide layers or bubbles entrained inside the liquid metal. The accuracy of the numerical code in simulating the metal fluid-dynamic behaviour and the heat transfer was verified, and the results were in agreement with the experimental findings. The numerical distribution of defects was consistent with the experimental results, proving that the model successfully predicted the formation of oxide-related defects
Advanced Numerical Simulations on the Interaction between Waves and Rubble Mound Breakwaters
No full textTechnical Paper
WordMelodies: supporting the acquisition of literacy skills by children with visual impairment through a mobile app
Full text linkWordMelodies is a mobile app that aims to support inclusive teaching of literacy skills for primary school students. Thus it was designed to be accessible both visually and through screen reader, and it includes over 80 different types of exercises for practicing literacy skills, each with adjustable difficulty levels, in Italian and in English. WordMelodies is freely available for iOS and Android devices. However, it has not been previously evaluated with children having visual impairments. Thus, in this paper, we evaluate the app usability, its perceived ease of use, appreciation and children's autonomy while using it, as well as the characteristics of the end users. To achieve this, we conducted a user study with 11 primary school students with visual impairments, and we analyzed app usage logs collected from 408 users in over one year from the app publication. We show that app usability is high, and most exercises can be completed autonomously. The exercises are also perceived to be easy to perform, and they are appreciated by the participants. Finally, we provide insights on how to address the identified app limitations and propose future research directions
Formation and distribution of entrainment defects in gravity AISi7Cu0.5Mg alloy castings
Full text linkIn this study, the formation of entrainment defects in gravity permanent mould casting process was experimentally and numerically investigated. The distribution of oxide inclusions was mapped at the microscopic scale using metallographic and image analysis techniques. A fluid-dynamic simulation commercial software was used to predict the formation of defects and air entrapment during the casting process. The results showed that the typical casting defects detected throughout the castings were generated by the entrainment of bifilms. Moreover, the good agreement between the numerical results and the experimental findings proved that the numerical models had successfully predicted the entrainment phenomena, especially the formation of oxide inclusions and the entrapment of air bubbles
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
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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