1,720,959 research outputs found
Effect of moisture content levels on the quality of beech wood cut by CO2 laser
No full textThe moisture content of wood influences its machinability and the resulting quality of the machined surface. This study aims to explore the impact of varied moisture content on the final quality of beech wood cut by a CO2 laser (Fagus sylvatica L.). Laser cutting was performed on beech lumbers conditioned at moisture levels of 0%, 8%, 12%, and 18%. The laser-cut specimens were evaluated for surface roughness and waviness by using a stylus surface profilometer at three measuring locations: top, middle, and bottom. The total color difference ΔE was also assessed using a spectrophotometer at the same three locations. The most intriguing findings revealed that surface specimens with higher moisture content are lighter than those with lower moisture content. Specifically, the top areas of specimens with different moisture content exhibited lighter shades than those in the middle and bottom areas. Notably, the surface profile of the specimens remained unaffected by variations in moisture content levels
Catalytic Acetylation of<i>Pinus radiata</i>(D. Don) with Limited Supply of Acetic Anhydride Using Conventional and Microwave Heating
No full textThis study outlines the effect of catalyst (potassium acetate) and microwave heating on the rate and degree of acetylation in radiata pine. Sapwood samples were impregnated with potassium acetate dissolved in two different solvents (water and methanol). Catalyst loaded samples were dried and impregnated with acetic anhydride followed by conventional and microwave heating. The degree of acetylation was evaluated by weight percent gain (WPG) and characterized by Fourier transform infrared spectroscopy using attenuated total reflection (FTIR-ATR). Effect of catalyst loading, reaction temperature, and reaction time on the degree of modification and rate of reaction was investigated. A reaction time of 30 min gave rise to 20.6% weight gain in a catalyzed system while it was only 2.7% in uncatalyzed condition. No significant difference in the WPG and rate of reaction was found when water and methanol were used as solvents. Under catalytic condition 21.6% weight gain was obtained after 10 min of microwave heating. Potassium acetate was found to have no adverse effect on dimensional stability of wood
Acceleration of the chemical modification of wood using microwave heating and catalyst
No full text© 2011 Dr. Anil Kumar SethyWood is a versatile material with many superior properties. However, dimensional instability and biodegradability are the most undesirable properties of wood. There are different methods of improving wood properties and chemical modification is one potential approach. Interest in the chemical modification of wood arises from the need to substitute conventional biocides currently used to protect timber from decay and insect attack while maintaining a substrate that is dimensionally stable. Lower moisture content, preferably 5-6%, is a prerequisite for most of the chemical modification reactions. Economically it is not feasibly to dry the timber to such low moisture content by conventional drying. However, microwave heating was evaluated and found to be effective in reducing the moisture content of radiata pine from 13% to 6% in a microwave cycle of 2 minutes without any drying degrade. The energy consumed to achieve this was 55 kWh/m3.
Acetylation of wood is considered to be one of the most promising ways of enhancing wood properties. However, conventional heating leads to a long reaction time. Reduction in reaction time is an advantage both in terms of economy of the process and properties of the end product. The use of potassium acetate as a catalyst, methanol and water as solvent carriers for this catalyst and microwave heating were investigated to accelerate the acetylation reaction. The properties of the microwave assisted acetylated wood were compared with those of the conventional heated acetylated wood.
Solvents imparted no significant effect on the rate and degree of reaction. Potassium acetate significantly accelerated the reaction. The rate of acetylation was 7.5 times faster in catalysed condition after 30 minutes of reaction. In the catalyzed reaction, an average weight gain of 20.6% was achieved after 30 minutes reaction time, while for the uncatalyzed reaction it was less than 3%. Microwave heating proved to be effective in the acetylation of wood in the presence of potassium acetate. However, a lower catalyst loading is desirable since higher loadings led to charring of samples, particularly where acetylation uses a limited supply of reagent. A weight gain of 21.6% was achieved in 10 minutes of microwave heating using a catalyst compared to 13.4% where no catalyst was employed. The presence of a catalyst provided more uniform acetylation across the sample thickness compared to the uncatalyzed reaction.
The catalyst and mode of heating did not influence the adsorption behaviour of the acetylated sample once the catalyst was leached. Un-leached acetylated samples showed significantly higher EMC values, particularly at higher relative humidities, due to the hygroscopic nature of the catalyst. The mode of heating and catalyst also had no influence on the swelling coefficient, anti-shrink efficiency, modulus of elasticity, modulus of rupture, resilience and decay resistance of the samples. Improvement in the mechanical properties was anticipated with the reduction in reaction time. Although the use of a catalyst and microwave heating reduced the reaction time significantly, no improvement in the strength properties was achieved.
Wood modification with furfuryl alcohol results in a wood polymer composite. Curing by conventional heating is a time consuming process. The dielectric properties of furfuryl alcohol indicate that it can be heated under a microwave field. Microwave curing of furfuryl alcohol caused complete polymerization but the resin yield was 7% lower compared to conventional curing. Oven curing of impregnated samples caused significantly higher weight percent gains compared to microwave curing. A microwaving time of 10 minutes was optimal in terms of weight percent gain and uniformity of colour. Microwave cured samples showed similar anti-shrink efficiency and decay resistance to oven cured samples even at lower weight gains
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
