1,721,028 research outputs found
Investigation of the Influence of Vacuum Venting on Mold Surface Temperature in Micro Injection Molding
No full textThe application of vacuum venting for the evacuation of air from the mould cavity has been introduced in injection molding with the intent to further enhance micro/nano feature replication and definition. The technique is adopted to remove air pockets trapped in the micro-features (which are difficult or impossible to reach using conventional venting technologies), which can create considerable pressure that resist the melt filling flow. Nonetheless, several studies have revealed a negative effect that could possibly arise from the application of vacuum venting. It is proposed that air evacuation removes a mold surface heating effect caused by adiabatic compression of the air ahead of the flow front and subsequent conduction of that heat into the mold surface. Hence, with the increase of the surface-to volume ratio in micro-cavities, air evacuation could have a detrimental effect on the melt fill for polymers that are sensitive to changes of the mold temperature. Although incomplete filling of micro-scale features has often been attributed to poor venting, the limited research examining the application of vacuum venting has produced mixed results.
In this work, the effect of air evacuation on the mold/polymer temperature was experimentally investigated. A novel experimental setup is demonstrated to monitor the mold and polymer temperature during the micro injection molding process using a high speed infrared camera system, Ircam Equus 81k SM, and sapphire window in the mold. A design of experiments (DoE) approach was applied to design and analyze of the experimental campaign. The factor investigated were: the mold temperature (Tm), the injection velocity (Vinj) and the presence of air evacuation (Ea). The choices of the upper and lower levels for the factors derived from a literature review, recommendations of the material supplier and the
technological limits of the available experimental setup. The response variable for this analysis was chosen to be the average temperature of the flow front inside the mold cavity. The results provide empirical evidence about the effect of the air evacuation on the mold/polymer temperature that is more evident at high values of process parameters setting. In fact, as shown in Fig.1, at a Tm of 140°C and Vinj of 800 mm/s, the presence of air evacuation from the mold, imply a decrease on the flow front temperature of 39 °C (-12%) while at a Tm of 80°C and Vinj of 300 mm/s this decrease is about the 4%. In conclusion, the empirical findings in this study provide a new understanding of the effect of cavity air evacuation in microinjection molding process
Effect of different mold coatings on flow resistance in thin-wall injection molding of polystyrene parts
No full text
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
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
- …
