1,721,230 research outputs found
A novel X-ray diffraction approach to assess the crystallinity of regenerated cellulose fibers
No full textPublisher Copyright: © 2022 International Union of Crystallography. All rights reserved.Here, a new accurate approach is presented to quantify the degree of crystallinity of regenerated cellulose textile fibers using wide-angle X-ray scattering. The approach is based on the observation that the contributions to the scattering from crystalline and amorphous domains of the fibers can be separated due to their different degree of orientation with respect to the fiber direction. The method is tested on Ioncell-F fibers, dry jet wet spun with different draw ratios from an ionic liquid solution. The analysis output includes, apart from an accurate estimate of the fiber crystallinity, the degrees of orientation of the cellulose nanocrystals and the cellulose chains in the amorphous domains.Peer reviewe
Modification of Ioncell spinning technology to increase fiber toughness and create a water-repellent surface
No full textThis thesis work presents an eco-friendly way of hydrophobizing the Ioncell fibers and strategies to improve the mechanical properties (especially toughness) of the Ioncell fibers. In the first part of this thesis, hydrophobization of the Ioncell fibers was achieved by incorporating plant-based hydrophobic agents Betulin (BE) and Betulinic acid (BA) into the spun fibers during dry-jet wet spinning. 10 wt% BE and BA incorporated cellulose solution showed excellent spinnabilities, and the mechanical properties of the spun Ioncell fibers. Both BE and BA introduced hydrophobicity (defined by water contact angle >90 degree) into the spun staple fibers, and the hydrophobicity was transferred to the nonwovens and yarns. However, BA showed better compatibility with cellulose than BE, which was evident from the surface morphologies of the fibers and the yarn spinnability of the staple fibers.
To improve the toughness of the Ioncell fibers, the effects of the spinneret aspect ratio (L/D) and the high molecular weight containing pulp on the mechanical properties of spun fibers were investigated in the second part of the thesis. Combining high molecular weight pulp and the spinneret with L/D 2, the highest toughness (83.3 MPa) and tensile strength (61.5 cN/tex) of the Ioncell fibers were achieved. Numeric simulations revealed that the combined effect of the longer molecular cellulose chains and the longer capillary length foster the cellulose chain alignment inside the spinneret capillary resulted in simultaneous improvement of elongation and tensile strength. Furthermore, as a continuation of this research, a wide variety of spinneret geometries was applied to observe the effect of spinneret geometries on fiber toughness. Optimization of spinneret geometrical parameters significantly improved fiber mechanical properties. Interestingly, the fiber toughness was improved up to 93 MPa (12% more than the initial study) using a spinneret with optimized geometries (hole diameter 100 μm, L/D 1 and entrance cone 8°) and high molecular weight pulp. The structural properties such as longer periodicity of the lamellar plane, wider tilt angle, and lower microvoid orientation were presumably attributed to the high toughness of the fibers.
In summary, this thesis work has developed eco-friendly approaches for fiber hydrophobization and improvement of the mechanical properties of the Ioncell fibers – a step forward for building a sustainable textile industry by reducing harmful impacts on the environment
Profiles of alkali concentration and galactoglucomannan degradation in kraft impregnation of Scots pine wood: Experimental observations and modeling
Full text linkA deep understanding of alkali impregnation including the profiles of alkali concentration and hemicellulose degradation is necessary to analyze the optimization of current and innovative processes. In this paper, the impregnation of Scots pine (Pinus sylvestris L.) wood is analyzed and modeled under consideration of deacetylation, reactions of acidic group, and galactoglucomannan (GGM) degradation. The immobile anionic groups activated by the ionization of lignin-derived OH groups are also considered for the assessment of the Donnan effect. Predicted profiles of sodium and hydroxide ions and acetyl group concentrations are compared to experimental results. The balance between impregnation and hemicellulose degradation levels is discussed based on the developed models. Expectedly, higher concentrations and temperatures speed up the impregnation process. Nevertheless, a higher OH-concentration has two benefits for the same impregnation front position – the alkali charge inside the chip is higher and the GGM degradation is lower.Fil: Montagna, Pablo Nicolás. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulosica; ArgentinaFil: Nieminen, Kaarlo. Alto University.; FinlandiaFil: Inalbon, Maria Cristina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulosica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Sixta, Herbert. Alto University; FinlandiaFil: Zanuttini, Miguel Angel Mario. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología Celulosica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin
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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