1,720,996 research outputs found
Flow properties and arching behavior of biomass particulate solids
No full textThis paper addresses the problem of estimating solid biofuel flowability, with particular reference to arching phenomena in silo discharge. The flowproperties and the tendency to arch formation over openings of three different biomass particulate solids, two cuts of sawdust and a dried ground olive husk, were studied. Shear testing experiments indicated that flow properties of particulate biomass could be measured by shear cells when the particle size is below 2 mmand that, however, particle elasticity or irregular shape could determine uncommon flow behavior. The pipe to arch transition was characterized for the biomass samples and a gypsumpowder in a new tester, in which the critical opening size for arching was characterized as a function of the consolidation stress. This test allowed the ranking of material flowability which compared well with the ranking obtained according to the Jenike classification. A new procedure, derived from the Jenike's classical arch stability analysis, was proposed to evaluate the flow function of the materials from the critical orifice diameter for arching. An optimized procedure was suggested to obtain an estimate of material flow function from arching tests with a limited knowledge of other particulate biomass flow properties
Isoconversional kinetic analysis of olive pomace decomposition under torrefaction operating conditions
No full textKinetic analysis of the olive pomace thermal degradation in the temperature range of interest for torrefaction was performed by using non-isothermal thermogravimetric measurements at different heating rates, ranging from 2 to 40 degrees C/min. A comparison is presented between two selected integral isoconversional methods, i.e., the nonlinear Vyazovkin incremental approach, which is more accurate but time-consuming, and the linear Ozawa-Flynn-Wall (OFW) method, which is less accurate but computationally simpler. Results show that the values of the activation energy by the OFW method are consistent with the ones provided by the Vyazovkin approach. This implies that the OFW method, more user-friendly compared to the Vyazovkin procedure, is suitable for studying the torrefaction kinetics of residual biomass, such as olive pomace. The reliability of the OFW method was further confirmed by the successful application of the derived kinetic data to reproduce (i.e., predict) experimental TG curves not included in the kinetic computations
Characterization of woody biomass flowability
No full textIn this paper a simple method for characterizing the flowability of consolidated samples of woody biomass is presented. The apparatus used consists in a cylindrical bin provided with a circular orifice at the centre of its flat bottom. Biomass samples were consolidated in the bin by applying loads on the material bed surface while the bin
orifice was closed by a plug. After the consolidation phase the loads were removed and the orifice was opened to assess if an arch or a rathole had formed. Critical values of consolidation loads for the formation of a stable arch were determined for different
orifice sizes. These results obtained with two different samples of sawdust were compared in terms of material strength with those of flow functions obtained with a conventional Schulze shear tester
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
Pressurized Steam Conversion of Biomass Residues for Liquid Hydrocarbons Generation
Full text linkBiomass residues are often considered as a resource if conveniently converted in fuel and alternative feedstock for chemical processes, and their conversion into valuable products may occur by different pathways. This work is focused on the thermochemical conversion at moderate temperature and in steam atmosphere, a mild process in comparison to hydrothermal liquefaction, followed by extraction of soluble products in a solvent. Such process has been already applied to various residues and here extended to the case of marc, the residual pomace from wine making, largely produced worldwide. A pressurized batch reactor was used for the quantitative determination of produced solid and liquid fractions, and their qualitative characterization was performed by instrumental analyses. The pressurized steam conversion of marc was effective, providing a yield in liquid fraction, upon extraction in solvent, up to 30% of the raw dried biomass. The use of polar and nonpolar solvent for the extraction of the liquid fraction was inspected. Applied operating conditions, namely residence time in the batch reactor and extraction modality, showed a significant influence on the process performance. In particular, long residence and extraction times and use of nonpolar solvent substantially improved the yield in liquid fraction
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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