1,720,994 research outputs found
Assessment of impact fracture toughness of PP-elastomeric polyolefin blends
No full textThe present investigation is concerned with evaluation of the impact fracture toughness of novel blends based on commercial polypropylene homopolymer (PPH) and elastomeric polyolefin (POEs). At room temperature and high load rate, PPH behaves in a brittle manner while the blends exhibited semi-brittle behavior as judged from the nonlinearity in load deflection curves and fracture surface appearance. The challenge of determining reliable toughness values was faced by applying different approaches available in the literature based on fracture mechanics concepts, including corrected linear elastic fracture mechanics (LEFM), equivalent energy concept, and non-LEFM. The fracture toughness data of the blends appeared to be widely scattered in accord with the samples being in the ductile-brittle transition region. In order to provide a consistent description of the entire range of sample behavior, the statistical weakest link model was also applied to the data.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
Mechanical behaviour of polypropylene modified with an elastomeric polyolefin
No full textEn este trabajo se estudia ampliamente la respuesta mecánica de mezclas novedosas basadas en PP y un 10, 20, y 30% en peso de una poliolefina elastomérica (POEs). La morfología de las mezclas consiste en un patrón continuo de partículas elastoméricas dispersos en la matriz de PP. El módulo elástico resulta el máximo obtenible para una mezcla bifásica. El criterio de Von Mises modificado resulta adecuado para describir los límites de aplicación de las mezclas bajo estados biaxiales. La tenacidad a la fractura a baja temperatura y en condiciones de impacto, determinada aplicando metodologías de la mecánica de fractura, queda representada por una distribución de Weibull. El valor umbral de tenacidad a la fractura del PP se ve notablemente incrementada por la presencia de la POEs, asimismo la modificación incrementa la tendencia a la propagación estable de fisura. Esto es resultado del acrecentamiento de la capacidad inherente de la matriz a deformar por crazing y/o por el desgarramiento dúctil (corte) de los ligamentos entre partículas.In this work the mechanical behavior of novel blends based on PP modified with 10, 20 and 30% weight of an elastomeric polyolefin (POEs) is deeply investigated. Blend’s morphology results a continuous pattern of globular POEs particles dispersed in the PP matrix. Elastic modulus agrees with the maximum value that can be achieved in binary blends. Modified Von Mises Yield Criteria well represents the confidence limits of these blends under biaxial stress states. Low temperature and high impact fracture toughness assessed by the application of different fracture mechanics methodologies are described by a Weibull type distribution model. PP thresholds toughness parameters are notably enlarged by the elastomer modification. The presence of POEs also increases the tendency towards stable crack propagation. Both effects are due to the enhancement of the matrix capability to deform via multiple crazing and to the shear deformation of the PP ligaments between particles.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin
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
Assessment of multiaxial mechanical response of rigid polyurethane foams
Full text linkMultiaxial deformation behavior and failure surface of rigid polyurethane foams were determined using standard experimental facilities. Two Commercial foams of different densities were assayed under uniaxial, biaxial and triaxial stress states. These different stress states were reached in a uniaxial universal testing machine using suitable testing configurations which imply the use of special grips and lateral restricted samples. Actual strains were monitored with a video extensometer. Polyurethane foams exhibited typical isotropic brittle behavior, except under compressive loads where the response turned out to be ductile. A general failure surface in the stress space which accounts for density effects could be successfully generated. All of failure data, determined at the loss of linear elasticity point, collapsed in a single locus defined as the combination of a brittle crushing of closed-cell cellular materials criterion capped by an elastic buckling criterion.Fil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin
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
On the cure kinetics modeling of epoxy-anhydride systems used in glass reinforced pipe production
No full textAiming to determine a suitable model to describe the curing kinetics of a commercial epoxy/anhydride initiated by a quaternary amine system used for the production of glass reinforced pipes, calorimetric and infrared spectroscopic kinetics data were collected. Several phenomenological, isoconversional and mechanistics kinetics models were revisited and tried. In addition, the time-temperature-transformation diagram, which is fundamental for the design of curing cycles, was assessed from calorimetric and gel time experiments. It was found that the Kamal´s model and a mechanistic model comprising an activation reversible step followed by a propagation step (Mauri et al., 1997) were capable to well describe all the experimental data. The kinetics mechanism appeared to be independent of the initiator concentration as suggested by the constancy of the apparent activation energy obtained by the Kissinger´s method. According to the mechanistic model, the activation step resulted independent on initiator concentration while propagation rate accelerated with increasing it. The presence of glass fiber reinforcement did no affect the curing kinetics of the studied reactive system.Fil: Flores, Hugo Alejandro. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Fasce, Laura Alejandra. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Riccardi, Carmen Cristina. Universidad Nacional de Mar del Plata. Facultad de Ingenieria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); Argentin
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