1,720,978 research outputs found
Analysis of Charge Weld Evolution for a Multi-Holes Extrusion Die
No full textExtrusion process presents two types of welding mechanism inside the die: seam and charge weld. The first type is unavoidable in the production of hollow profiles while the second is generated during billet to billet transition. Differently from seam weld, charge weld represent an unacceptable defect that require profile discard. Nevertheless charge weld extent and location on extrudates is not evident, thus requiring scrap definition by means of time-consuming trials or to repetitive tests on each batch. In the present paper an industrial four holes porthole die for hollow profiles production was investigated during billet to billet transition. Extrusion of four billet was performed under strict parameter control. The profiles were microscopically analyzed in order to determine weld evolution: in particular start and end points of weld for each profile were determined
Extrusion Benchmark 2017: Effect of Die Design on Profile Quality and Distortions of Thin C-Shaped Hollow Profiles
No full textThe Extrusion Benchmark 2017 is focused on the evaluation of different die design strategies for the production of two AA6005A thin C-shaped hollow profiles. The process was monitored in term of press load, profiles speed, profiles exit temperature, die temperatures (with specific focus not only on the die but also on the external die ring) and die deflection. Extruded profiles were analyzed in term of geometrical tolerances, microstructure evolution and profile distortions for both air and water quench; the profiles were also be analyzed for retrieving seam welds positions and charge welds extent
Experimental investigation and numerical prediction of the peripheral coarse grain (PCG) evolution during the extrusion of different AA6082 aluminum alloy profiles
No full textPeripheral Coarse Grain (PCG) is an undesirable defect that may occur in the extrusion of medium-strength Al-Mg-Si aluminum alloys. This phenomenon usually degrade extruded profiles in mechanical, crash, corrosion, fracture and surface quality properties thus precluding their applicability in the automotive sector. In this work, an experimental campaign was carried out involving the extrusion of two different AA6082 profiles in a wide range of process parameters. The microstructural analysis of these profiles was conducted in order to investigate the impact of die design and process parameters on PCG occurrence. According to this analysis, it was detected a clear influence of the ram speed and of highly dynamic recrystallized (DRX) zones on the PCG. The modeling for the PCG evaluation was then developed and implemented into the commercial FEM code Qform Extrusion® for the simulation of the extrusion process together with the DRX and the PCG predictions. The numerical results were further compared to the collected experimental data thus proving the reliability of the proposed model
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
La mobilità dei mestieri del libro nello Stato pontificio
No full textIt is by now widely acknowledged that the spreading of printing has been boosted by the travelling printers’ impressive mobility and that nomadism is the distinctive trait of the new book professions. Such migratory flows usually follow the thoroughfares of political, economic and cultural power to seize job opportunities and the profits that could be earned in wider production and trading markets. In the Papal State, Rome is the attraction but there are quite a few examples that go in the opposite direction. This essay tries to explore the distribution of the publishing centres, the professionals’ routes, the size of the companies, the type and range of action of their products in the light of the complex, ever-changing geopolitical coordinates of the Popes’ State.
È acquisizione consolidata che la diffusione della stampa sia stata promossa dal consistente movimento di tipografi itineranti e che il nomadismo sia il tratto caratteristico delle nuove professioni del libro. Il movimento migratorio segue di norma le direttrici dei luoghi del potere politico, economico e culturale per cogliere le opportunità lavorative e i profitti garantiti dai circuiti produttivi e commerciali più ampi. Nello Stato pontificio è Roma il polo di attrazione ma non mancano esempi di segno contrario. Il contributo intende esplorare la
distribuzione dei centri editoriali, gli itinerari dei professionisti, la dimensione delle aziende, la tipologia e il raggio d’azione della loro produzione alla luce delle complesse e mutevoli
coordinate geopolitiche dello Stato dei Pontefici
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
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