1,720,956 research outputs found
Influence of various wood modifications on the properties of polyvinyl chloride/wood flour composites
No full textAminosilane, melamine and acetic anhydride treated wood flour were added to polyvinyl chloride (PVC) in order to process improved PVC/wood flour composites. The influence of wood treatment on water absorption and mechanical properties were evaluated. Treatments with amino-alkyl functional oligomeric siloxane and melamine in suitable concentration as well as acetylated wood flour composites showed decreased equilibrium moisture content and reduced speed of water absorption. Tensile strength, elongation at break and unnotched impact strength were considerably improved by the aminosilane treatments. The increase in strength and elongation was mainly influenced by the chemical structure and concentration of the used aminosilanes. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 201
Influence of Particle Concentration and Type on Flow, Thermal, and Mechanical Properties of Wood-Polypropylene Composites
No full textTwo kinds of wood particles with different sizes and properties were compounded with polypropylene (PP) in highly concentrated levels (by 50% and 60% weight concentration). Their flow abilities were estimated by viscosity-shear rheological test and spiral flow mold respectively; the results show that higher concentrations result in poor flow ability. However, to estimate the relation between particle size and flow ability, spiral flow-mold testing results are not consistent with those of the rheological test. The thermal melting, crystallization, and stability of the highly filled wood/PP composites were measured by differential scanning calorimetry (DSC). The results clearly showed that the melting temperature, thermal stability, and crystalline degree of composites decrease when filler contents and size increase. The mechanical properties of these materials were assessed by tensile test machine and testing results also show that the filler concentration and size dramatically affect the mechanical properties, such as E module, tensile strength, and breaking strength of wood-particle-filled PP composites. The weld-line strength of all wood composites with the contents was also tested in the same way. By testing, one found that the usual defect of weld line in injection-molding process had a very significant negative impact on the mechanical properties of wood composites and the relation of wood-particle-filling fraction and size to weld-line strength was also analyzed and clarified.DFG (Deutsche-Forschungsgemeinschaft
Amine treatment of polyvinyl chloride/wood flour composites
No full textEthanolamine and L-arginine treated wood flour were added to polyvinyl chloride (PVC) in order to improve the interphase between PVC and wood. The influence of the treatment on pH-value changes and nitrogen fixation of the wood and mechanical properties of the composite were evaluated. The treatments changed the pH of wood from acidic to basic. The highest nitrogen fixation was measured for monoethanolamine and L-arginine treated wood flour at high concentrations. Tensile strength, elongation at break, and unnotched impact strength were improved by ethanolamine and L-arginine treatments considerably. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011AiF (Arbeitsgemeinschaft industrieller Foschungsungsvereinigungen
Effects of chemical modification of wood particles with glutaraldehyde and 1,3-dimethylol-4,5-dihydroxyethyleneurea on properties of the resulting polypropylene composites
No full textBoth glutaraldehyde (GA) and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) can crosslink the cell wall polymers and dimensionally stabilize wood particles and the treated wood particles are thus expected to enhance the properties of the resulting wood particle/polypropylene composites Compared to the composites filled with untreated particles, treatments of wood particles with both GA and DMDHEU showed a great reduction in water uptake and dimensional swelling of the resulting composites up to 39% and 46%, respectively. Both the flexural and tensile moduli increased due to wood particles treatments with GA and DMDHEU. Treatments of wood particles improved the tensile strength but moderately weakened the flexural strength and Charpy impact strength of the composites. Dynamic mechanical analysis and microscopy suggested an improved interfacial compatibility between wood particles and matrix due to GA and DMDHEU treatments Chemical treatment resulted in smaller particle sizes and altered microscopic fracture appearance after composite production as compared to untreated particles. Morphological changes were attributed to embrittlement of wood particles, which may negatively influence the mechanical properties of the resulting composites. (C) 2010 Elsevier Ltd. All rights reservedGerman Academic Exchange Service (DAAD
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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