1,720,958 research outputs found
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
RECOVERY AND SEPARATION PROCESSES IN THE RECYCLING CHAIN OF POLYAMIDE PLASTIC MATERIALS TO OBTAINECO-SUSTAINABLE RAW MATERIALS
No full textThe rise of fast fashion and the growing accumulation of mixed textile and plastic waste are creating serious environmental and economic challenges. In particular, polyamides, commonly used in technical textiles and plastics, are often blended with other polymers, making recycling difficult. Traditional methods such as mechanical processing or depolymerization often fail when dealing with these complex mixtures, due to degradation, contamination, or the need for extensive purification. This PhD research, carried out in collaboration with Radici InNova s.c.a r.l. (Radici Group), focused on developing and optimizing a solvent-based recycling process to selectively recover polyamide from post-industrial and post-consumer textile and plastic waste.
The process, known as selective dissolution, involves the use of a specific solvent or solvent mixture to dissolve only the target polymer (polyamide) from a complex material. The other components, such as polyurethane or polyester, remain undissolved and are removed by filtration. The dissolved polyamide is then recovered from the solution by changing the solvent conditions (for example, by adding water as an anti-solvent or by evaporating the solvent), allowing the polymer to re-precipitate in a purified form.
Two solvent systems (solvents A and B) were selected for in-depth study based on a literature review and preliminary experimental screening. These solvents were chosen for their ability to dissolve PA while maintaining selectivity over other polymers. Experimental work showed that both solvents were effective, but solvent B allowed better separation, reducing contamination and preserving the possibility to reuse PU. Moreover, by adjusting the composition of the solvent mixture, it was possible to tune the selectivity of the process, either favouring the dissolution of polyamide or the extraction of polyurethane. This tunable selectivity was demonstrated through systematic tests on PA6, PA66, and PU fibers, using controlled solvent B/water ratios and analysing the dissolution temperatures of each sample. The solubility behaviour was mapped in relation to solvent composition, helping to define process windows for each target polymer. Different types of waste were tested.
Various methods were tested to recover PA from the solution, including anti-solvent crystallization, direct evaporation, and spray drying. Anti-solvent precipitation produced a purer polyamide, with limited molecular degradation and mechanical properties comparable to those required for textile applications. Evaporation resulted higher polymer degradation and in a more flexible materials, likely due to the presence of residual low-molecular-weight compounds acting as plasticizers. Spray drying offered rapid solvent removal but posed challenges in terms of polymer degradation and system clogging, especially with PA-rich solutions.
All samples were extensively characterized to assess their chemical integrity and applicability: intrinsic viscosity, end-group analysis (–NH2 and –COOH), infrared spectroscopy, and differential scanning calorimetry (DSC) were used to determine degradation and purity. In selected cases, the recovered PA was also tested for mechanical performance through tensile strength and impact resistance measurements on injection-moulded specimens, without blending with virgin polymer. The results confirmed that the recycled PA showed good performance.
Special attention was given to solvent recovery, which is essential for the environmental and economic sustainability of the process. For the water–solvent A mixture, both simple and multi-stage distillation were tested, showing good efficiency and the possibility of solvent reuse. Both the impurities accumulating in the reboiler and in the distillate were characterized by GC-MS and TOC analyses. Tests were also carried out to evaluate both the direct reuse of the distillation bottom and the complete purification of the glycol through total solvent evaporation. For solvent B, azeotropic distillation using an entrainer was developed to improve separation and reduce losses. Process simulations using AVEVA Pro/II helped design the distillation systems and confirm the experimental results, especially in terms of tray number, reflux ratio, and entrainer recovery. The use of azeotropic distillation proved advantageous over traditional binary separation, both in terms of energy consumption and solvent purity.
Finally, a Life Cycle Assessment (LCA) was conducted to evaluate the environmental performance of the process. Two process options were compared: anti-solvent precipitation and direct evaporation. Both showed much lower impacts than virgin PA production, with the evaporation route performing slightly better in most categories. The potential reuse of polyurethane and the efficient solvent recovery helped improve the overall sustainability. Contribution analysis highlighted the influence of steam consumption and solvent losses, underlining the importance of process optimization for full-scale implementation.
This research shows that selective dissolution is a promising method for recycling nylon-based textiles and plastics. It allows recovery of high-quality PA and offers a feasible path towards more circular and sustainable production. A patent application has been filed, and scale-up activities are currently underway, including pilot plant development studies and additional research on solvent recovery under the RE-POLY.AI project
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Shaping the empty carbon nanocubes: the role of Nitrogen. Insight from X-Ray Raman scattering spectroscopy at the N K-edge
Get PDFCarbon nanomaterials have gained significant attention because of their unique tunable properties, including high surface area, excellent electrical conductivity, and chemical stability. These materials are classified by dimension, including 0D carbon quantum dots, 1D nanofibers, 2D nanosheets, and 3D hierarchical nanostructures such as hollow nanocages. Hollow carbon nanocages exhibit distinct characteristics, such as interior cavities and subnanometer channels, which enhance their structural stability and electrocatalytic efficiency. Furthermore, these structures, particularly when doped with heteroatoms like nitrogen, offer promising applications in energy storage, conversion, and sensing technologies. Nitrogen doping significantly influences the electronic properties, creating additional energy levels and active catalytic sites. Doping also facilitates extreme bending of the graphene planes, which improves electrocatalytic performance by enhancing oxygen reduction reactions and increasing active site density. This paper demonstrates, through both experimental and theoretical methods, that nitrogen atoms preferentially accumulate at the edges of carbon nanocages, inducing curvature in the graphitic structure. This finding provides insight into how heteroatom doping can be leveraged to tune the structural and electrochemical properties of carbon nanomaterials for advanced applications
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