1,721,007 research outputs found
Procedures Conditioning the Absorption/Desorption Behavior of Cold-Cured Epoxy Resins
No full textThe absorption/desorption behavior of a commercial cold-cured bisphenolic epoxy resin, subjected to different treatments prior to exposure to water, was analyzed. The epoxy system has been already used as both matrix and adhesive for the manufacture and application, respectively, of fiber reinforced polymers composites employed for rehabilitation procedures. The effects of different curing, conditioning, and storing conditions on the water absorption/desorption process taking place in the cured resin were evaluated. The different conditioning procedures used to dry the specimens before their exposure to water caused a different extent of physical aging and of curing on each system, influencing the amount and the rate of diffusion of the water molecules inside the specimens. Moreover, if the specimens are subjected to thermohygrometric cycles prior to immersion in water, the rate of diffusion and the amount of water also depends on the presence of water molecules inside the cured resins not easy to remove by any drying treatment. During all the hygrometric treatments
performed, a deaging process took place. The kinetic of this deaging process for the not-fully cured systems depends on the additional crosslinking taking place in the samples. The different procedures used to condition the specimens also affect the
variations in glass transition temperature (Tg) of the cured systems during and after immersion in water. Finally, the different drying procedures employed proved to be not equally appropriate for cold-cured epoxy resins
Natural and Artificial Weathering Effects on Cold-Curing Epoxy Resins
No full textThree cold-cured epoxy resins, specifically designed as structural adhesives for rehabilitation or renewal applications of civil infrastructures and cultural heritage, were submitted to natural and artificial weathering. We evaluated the variations in the thermal and mechanical properties and color changes after an artificial treatment carried out at 70°C and 75% relative humidity and after natural weathering, performed in two areas of South Italy, both located adjacent to the Mediterranean Sea. The variations in properties due to both natural exposure and artificial weathering were qualitatively similar. However, the selected artificial weathering procedure appeared excessively severe compared to the weathering that occurred after outdoor exposure
Effects of humid environment on thermal and mechanical properties of a cold-curing epoxy resin
No full textThe effects of exposure to different humid environments in a commercial cold-cured epoxy adhesive were investigated. Samples were exposed up to one month to 55%, 75% and 100% relative humidity (RH) or immersed in liquid water, at a constant temperature (23 C). Weight changes, thermal and
mechanical properties before and at different stages of the aging, were discussed.
In the examined aging conditions, absorbed water remained below 1% and saturation level was not achieved. Plasticization, reactivation of curing reactions and erasure of physical aging were observed in the specimens subjected to the different humidity regimes, all affecting both the thermal and the mechanical properties of the aged samples: while the Tg was influenced by plasticization mainly at shorter times of exposure and by post-curing at longer treatment times, the mechanical characteristics were less affected by these phenomena. These effects were found more pronounced at humidity levels higher than 75% RH. Doubly hydrogen-bonded water molecules linked to the network also influenced the Tg of the system, while they did not affect noticeably their flexural properties. Finally, the effects of water exposure can be regarded as equivalent to those of a thermal treatment at temperature around the Tg, i.e. both leading to an erasure of the physical aging
Durability prediction of cold-curing epoxy resins subjected to natural and artificial weathering: preliminary results
No full textGoing 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
- …
