1,720,966 research outputs found
Enhancing mechanical properties of particleboards using plasma treated wood particles
No full textThe surface properties of wood particles are one of the key factors for the development of mechanical and physical properties of particleboards. Particles were treated with plasma at atmospheric pressure with ambient air in order to enhance the polarity of wooden surfaces. One-layer particle boards were produced from the plasma-treated particles by using 3, 5, and 8 % urea formaldehyde adhesive (related to the particles). For all adhesive ratios, internal bond strength was increased by approximately 0.1 MPa compared to the respective controls. The modulus of rupture, modulus of elasticity and water related properties were only improved compared to the respective controls at the lowest adhesive content. It is therefore concluded that the plasma treatment can improve the bonding quality and water related properties of particleboards particularly at low adhesive contents.FNR (Fachagentur fur Nachwachsende Rohstoffe) [22005410
Analyzing the UF resin distribution in particleboards by confocal laser scanning microscopy
No full textThe effect of air plasma treatment at atmospheric pressure on thermally modified wood surfaces
No full textThis study tests the hypothesis that thermal modification of wood influences the effectivity of air plasma treatment. Micro-veneers of European beech, Scots pine and Norway spruce were thermally modified at two different temperatures and subsequently plasma-treated for 1 and 3 s. The veneer surfaces were characterized in terms of morphology, wetting behaviour and surface chemistry. No severe changes in the veneer surfaces due to plasma treatment were observed by scanning electron microscopy. Plasma treatment increased surface free energy and wettability by water and urea-formaldehyde adhesive; it was more effective on thermally modified wood than on unmodified wood. X-ray photoelectron spectroscopy revealed a similar distribution of oxygen-containing functional groups on the wood surface after plasma treatment of thermally modified and unmodified beech wood. It is suggested that enhanced wettability through plasma treatment is due to the generation of carboxyl groups within the lignin network, which contribute to the polar part of the surface free energy. The high effectiveness of plasma treatment on thermally modified wood might thus be explained by its high relative proportion of lignin
Enhanced urea-formaldehyde adhesive spreading on plasma treated wood particles
No full textIt is assumed that improved mechanical properties of plasma treated particleboards are caused by enhanced spreading of urea-formaldehyde adhesive on wood particles. Spreading of adhesive drops was therefore microscopically evaluated based on dimensions and shape of the drops. Plasma treated wood surfaces revealed increased adhesive spreading, which resulted in more contiguous and increased adhesive areas; this was indicated by decreased drop circularity. It is concluded that the plasma treatment increases the adhesive coverage of the particles and therefore enhances the mechanical properties
Effect of curing conditions on the water vapor sorption behavior of melamine formaldehyde resin and resin-modified wood
No full textImpregnation modification of wood with melamine formaldehyde resin reduces the adverse effects caused by moisture uptake, but the underlying modes of action are not fully understood. The present study showed that it is crucial to understand the sorption behavior of the pure resin when interpreting the behavior of resin-modified wood. Furthermore, the applied heat-curing conditions had a significant effect on the moisture uptake of resin-modified wood. At the same resin loads, dry curing conditions were more effective in causing a cell wall bulking effect than wet curing conditions. This reduced the water-accessible cell wall pore volume in dry cured wood and counterbalanced the moisture uptake by the resin. Deuterium exchange measurements suggested that the occupancy of cell wall pores reduced the number of simultaneously active sorption sites. However, there was no evidence that a swelling restraint or reduced mechanical relaxation affected the water sorption of resin-modified wood significantly.Peer reviewe
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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