1,720,982 research outputs found
Tribological effects of mold surface coatings during ejection in micro injection molding
No full textNumerical investigation on the effect of heat transfer coefficient in injection molding
No full textIn injection molding, the heat transfer coefficient (HTC) is a parameter defined as the polymer-mold interface's heat transferring ability. HTC depends on many factors, including polymer properties and processing conditions. Computer-Aided Engineering approaches use a constant preset value of HTC, which might lead to incorrect prediction of simulation results. In this work, a new approach is developed to validate and calibrate HTC using a numerical model. The model is based on Fourier's heat conduction law applied at the interface between the plastic part and the steel mold. Different HTC values on part temperature distribution, fill pressure, and fill time are studied. Moreover, the model is used to validate an injection mold design that could be used for experimental HTC measures using in-mold sensors. The results highlight the effect of HTC on the prediction of crucial injection molding parameters, suggesting the importance of experimental calibration
Modeling of the ultrasound-assisted ejection in micro injection molding
No full textIn this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data
A new approach to the evaluation of ejection friction in micro injection molding
No full textThe ejection phase influences the quality and integrity of micro injection molded parts. The successful design of robust micro mold ejection systems requires studying the tribological interactions at the mold/polymer interface. At the micro-scale, the tooling topography can have a significant impact on the ejection friction. Here we propose a novel approach to the evaluation of ejection friction in micro injection molding. The two main contributors to the ejection force are the normal force due to shrinkage and the static friction coefficient. The former is addressed by developing a procedure for shrinkage characterization at the micro-scale. The latter is studied using experimental measurements of the ejection force in micro injection molding. Comparing the numerical and the experimental results allows identifying the friction coefficient as a function of polymer, process parameters, and mold surface roughness
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
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