1,720,954 research outputs found
Cold flow defects in zinc die casting: prevention criteria using simulation and experimental investigations
No full textHigh-pressure die casting of zinc alloys is increasingly used in the manufacturing of parts with high aesthetic value. These parts must comply with strict requirements on surface quality, which are generally overlooked in traditional mechanical applications. Cold flow defects, which are a primary concern for surface quality, originate from several different causes that have not yet been fully understood. This report investigates the factors that influence cold flow defects and the choices that can lead to an improvement in surface quality. The research method is based on a case study performed at a die casting company. First, an existing process has been analyzed using simulation to explain the causes of cold flow defects observed in production samples. The temperature at the end of the cavity fill has emerged as a key index for the occurrence of defects, which can be controlled by three primary process parameters: injection velocity, temperature of the cooling medium, and lubricant spraying time. These same factors are then assessed using experimental tests on an existing die, where the number of defects in the selected regions of the casting has been evaluated by image processing. The results suggest that the surface quality can be particularly improved by increasing the flow rate of the molten metal through the gates and avoiding excessive flow turbulence in the wide cavity sections. Consequently, the increase in the gate area has been identified as a specific criterion for the die design. These findings have been validated in the redesign of the die and the selection of the process parameters, which have resulted in a significant reduction in the surface defects
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
Ottimizzazione del processo di pressocolata per componenti ad alta integrità superficiale
No full textLAUREA SPECIALISTICALo scopo del presente lavoro è quello di ottimizzare il processo di pressofusione ad alta integrità per leghe di zinco-alluminio-rame con la finalità di ottenere getti ad alta qualità superficiale. L’ obiettivo è ottenere la prevedibilità degli inestetismi in fase di progettazione così da incrementare la qualità finale ottenibile a lato pressa fino a giungere ad un prodotto per il quale le lavorazioni secondarie siano ridotte al minimo.
Si è sviluppato quindi un modello predittivo per la diagnosi di tali criticità durante il riempimento e la solidificazione, attraverso l’analisi dei percorsi di riempimento e di raffreddamento, tramite l’impiego di simulazione con metodo ad elementi finiti MagmaSoft.
Il percorso ha previsto la definizione dei difetti più ricorrenti, la caratterizzazione della morfologia, dell’ origine e degli effetti sulle lavorazioni successive, l’ individuazione delle variabili di processo che ne causano l’ insorgenza, le dinamiche influenti sulla distribuzione.
I risultati ottenuti si sono rivelati validi per ridurre l’ insorgenza della difettosità sia con interventi dal punto di vista dei parametri tecnologici sia dal punto di vista progettuale.
La ricerca si è avvalsa della collaborazione principale dell’ azienda Bruschi S.p.A e si è basata pertanto su casi pratici. Le conclusioni sono state impiegate per la progettazione di un nuovo stampo attualmente impiegato in produzione.The research objective is to evaluate and optimize the high integrity casting process for zinc-aluminum-copper alloys so as to achieve high surface quality castings. The main aim is to minimize the time dedicated to secondary processes’ and to achieve a near net-shape product by optimizing the predictability of imperfections during the product and die design.
In response, a predictive model for surface flaw diagnosis was developed, which analyzes the filling and cooling paths created with the use of fluidodynamic simulation.
The work provides the definition of the most common faults, the characterization of their morphology, origin and effect on further processing, the identification of process variables that generate their onset and the dynamics influence on their distribution.
The results were proved relevant for reducing the faults both with technological parameter variations as well as from the product and die design point of view.
The research was founded on practical cases thanks to the cooperation of a die casting company. The conclusions were employed for the design of a new mold that is currently in production
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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