1,721,043 research outputs found
Approccio multiscala nell'analisi microstrutturale di leghe di alluminio: dal componente fino agli atomi per comprendere il comportamento di muove leghe = Multi-scale approach in the microstructural analysis of aluminium alloys: from component to atoms to understand the behavior of new alloys
No full textTra le leghe leggere, senza dubbio le più utilizzate sono le leghe di alluminio: un’ampia gamma di composizioni, a partire da leghe per fonderia fino a quelle da deformazione plastica, e da trattamento termico, è a disposizione del progettista, per adattarsi alle varie applicazioni. Nonostante ciò, vi è una continua ricerca di nuove leghe per incrementare ulteriormente la resistenza meccanica ed il campo delle temperature di esercizio, oltre che per soddisfare le esigenze di nuove tecniche di produzione. In parallelo, è necessario conoscere e comprendere al meglio gli effetti microstrutturali, anche secondari, sulle proprietà dei materiali: un adeguato approccio multi-scala è consigliabile per interpretare al meglio le correlazioni tra microstruttura e proprietà di queste nuove o rivisitate leghe. Un esempio di questo approccio applicato ad una lega di alluminio da deformazione plastica e trattamento termico, destinata ad applicazioni ad alta temperatura, è descritto in questa memoria, unitamente ai problemi e soluzioni adottate. Vari aspetti della microstruttura della lega sono stati analizzati per comprenderne al meglio l’evoluzione durante la permanenza alle temperature di esercizio. La microscopia ottica ha fornito le informazioni relative all’aspetto generale della microstruttura e relative macro-caratteristiche. La microscopia elettronica è stata invece utilizzata per analizzare la dimensione dei grani, tessitura e natura delle fasi secondarie di maggiori dimensioni. I risultati di queste prime analisi sono stati utilizzati per la validazione di modelli di comportamento meccanico basati appunto su tessitura e dimensione del grano. Infine per la comprensione del decadimento delle proprietà meccaniche a seguito di prolungato overaging, analisi TEM ad alta risoluzione (HR-TEM) si sono rese necessarie, per poter osservare ed analizzare l’evoluzione delle particelle rafforzanti di dimensioni minori
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
Microstructural changes induced by Er and Zr additions to A356 alloy investigated by thermal analyses and STEM observations
Full text linkThis work is aimed at characterizing the changes induced in the microstructure of an Al-7Si-0.4Mg (A356) alloy when 0.3 wt% Er (alloy E3) and 0.3 wt% Er plusapproximately 0.5 wt% Zr (alloy EZ35) are added. The addition of Er and Zr caused the precipitation of Al3Er and Al3(Er, Zr) precipitates during solution heattreatment, as it was shown by isothermal DSC tests performed at the solution treatment temperature, microhardness measurements on samples subjected to differentsolution treatment time and STEM micrographs. The age hardening response of Er- and Zr-containing A356 is improved, thanks to the formation of further Al3Er andAl3(Er, Zr) precipitates during aging. Er- and Zr-containing precipitates were also identified inside eutectic Si and were identified as Al2Si2Er and Al2Si2(Er, Zr) for E3and EZ35, respectively. Finally, an Er-rich layer was identified at the interface between eutectic Si and Al after thermal treatment, possibly formed by Er atomsdiffusing along the Si twins and accumulating at the eutectic Si interface with the Al matrix.1. IntroductionA356 (Al7Si0.4 Mg) cast alloy is widely used in several industrialfields, especially where high specific mechanical properties and ex-cellent castability are required [1]. Its good mechanical properties de-rive from its significant age hardening response when subjected to aproper heat treatment [2–5]. The precipitation sequence and phaseevolution during aging of Al-Si-Mg cast alloys have been recently de-scribed as those of excess Si Al-Mg-Si wrought alloys [6]:00Al SSSMg/Si coclusters (GP zones)SiSiwhere SSS stands for supersaturated solid solution and GP for Guinier-Preston zone.A recent literature study demonstrated that, in the peak aged con-dition, the main strengthening precipitates in A356 are β′′ needles [6].As aging proceeds, the precipitates evolve, progressively enriching inMg [7], lose coherency with the matrix and coarsen. The natural con-sequence of the last two phenomena is the reduced pinning ability ofthe precipitates for dislocations, which implies the degradation in me-chanical properties typical of overaging.The addition of rare earths and transition metals in the chemicalcomposition of Al-Si-Mg alloys has proven to strengthen the material,thanks to the formation of additional precipitates in intra-dendriticregions [8–11]. In particular, some elements were found to formstrengthening precipitates at temperatures comparable to those usedduring solution heat treatment of Al alloys [12]. In this respect, in thelast years, several researches were focused on the effects of combinedadditions of Er and Zr in pure Al [13–17]. These elements can lead tothe formation of core-shell Al3(Er, Zr) L12precipitates, that are co-herent with the matrix up to a critical size and resistant to coarsening,maximizing the strengthening contribution [13–17]. Despite the posi-tive action of Er and Zr on pure Al, there is still lack of a comprehensivecharacterization of the effects of combined additions of those elementsto commercial Al-Si-Mg alloys.Scope of this work is to study the influence of Er and Zr additions onthe evolution of microstructural constituents, such as strengtheningprecipitates, during thermal treatment of a commercial Al7Si0.4 Mgalloy (A356), by means of Differential Scanning Calorimetry (DSC),microhardness tests and microstructural characterization with ScanningTransmission Electron Microscope (STEM). The development of in-novative Al alloys with improved mechanical properties could havebeneficial effects in many industrial fields, for example in the auto-motive industry, where optimized mechanical properties result inweight saving and, consequently, in reduction of fuel consumption.2. MaterialsandmethodsAl-15 wt% Er and Al-10 wt% Zr master alloys were added to acommercial A356 alloy, which was used as a reference, to obtain thechemical composition reported inTable 1; the chemical composition ofthe studied alloys was selected after preliminary studies performed bysome of the authors and reported in Refs
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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