1,720,985 research outputs found
Identification and characterization of plastics from small appliances and kinetic analysis of their thermally activated pyrolysis
No full textThe first step consisted in a field investigation carried out in Waste Electric and Electronic Equipment (WEEE) treatment plants coupled with a bibliographic product analysis and FT-IR spectroscopy polymers identification. Three main polymers of the thermoplastic fraction of small appliances were identified: in the external cases it was possible to find acrylonitrile- butadiene-styrene (ABS) and high impact polystyrene (HIPS), while polybutadiene terephthalate (PBT) was contained in the printed circuit boards (PCBs). Taking into account this identification, a ternary polymer mixture of ABS-HIPS-PBT was prepared as a representative sample of the thermoplastic fraction contained in WEEE (real WEEE sample). From the thermal characterization (proximate and ultimate analysis, high heating value (HHV) direct measurement and Energy-Dispersive-X-Ray-Fluorescence analysis (ED-XRF)) the only polymer whose properties sensibly differ from the analogous virgin polymer is the one contained in PCBs. A kinetic analysis of pyrolysis occurring on the three components and on their ternary mixture was performed using a thermogravimetry (TG) apparatus in argon atmosphere under non isothermal conditions. Triplicates of TG experiments at four heating rates of 2, 5, 10 and 15 K min-1 were carried out and two different model-free approaches were adopted, namely the Kissinger and Ozawa-Flynn-Wall methods in order to determine the activation energy E (as a single mean value or as a function of the degree of conversion α). The conversion dependencies of both activation energy and pre-exponential factors were determined as well as the reaction model, representing the reaction mechanism. The suitability of the models selected was tested using the Akaike's Information Criteria (AIC) score, being the geometric model R3 the best found for pyrolysis of ABS, HIPS and real WEEE samples, while PBT sample showed an uncertainty between the R3 and the diffusion D2 model. The reaction time values to achieve the maximum pyrolysis rate in the three main components and in the real WEEE sample were also calculated. © 2014 Elsevier Ltd. All rights reserved
Characterization of the residue of a commingled post-consumer plastic waste treatment plant: a thermal, spectroscopic and pyrolysis kinetic study
No full textA plastic packaging residue provided by a central Italy recycling facility was the subject of study of the present paper. The aim is to propose the valorization of plastic film residue (PFR) through a pyrolysis process. The PFR was thermo-chemically characterized through heating value, proximate and ultimate analysis. Fourier transformed infrared measurements have shown that PFR is constituted by 92–95 mass% of polyethylene (PE) film, around 5 mass% of PP, polystyrene (PS) < 1 mass%, PET < 1 mass% and traces of foreign materials. The extremely high percentage (98.7 mass%) of volatile matter and the low content of ash (2.1 mass%), humidity (0.6 mass%) and chlorine (0.1 mass%) make PFR an optimum candidate as load of a pyrolytic reactor. Thermogravimetry (TG) experiments were carried out at five different heating rates (2, 5, 7, 10, 12 K min−1) to determine the kinetic parameters of pyrolysis (activation energy E, pre-exponential factor A and the reaction model). No significant variation of activation energy, calculated by an integral isoconversional method proposed by Vyazovkin, is observed with increasing the degree of conversion. An average value of 264 ± 5 kJ mol−1 was estimated. Then, the Coats–Redfern method and the compensation effect were used to determine the lnA versus α data (being 41.9 the average value within the 0.25 < α < 0.85 range) and the reaction mechanism (R2 contracting cylinder model). Furthermore, the minimum energy required to pyrolyze 1 kg of PFR, about 2.27 MJ, was estimated by differential scanning calorimetry. It corresponds to about 5.5% of the exploitable energy of the input material
Organic matter quality of forest floor as a driver of C and P dynamics in acacia and eucalypt plantations established on a Ferralic Arenosols, Congo
Full text linkBackground: Land-use change and forest management may alter soil organic matter (SOM) and nutrient dynamics, due in part to alterations in litter input and quality. Acacia was introduced in eucalypt plantations established in the Congolese coastal plains to improve soil fertility and tree growth. Eucalypt trees were expected to benefit from N2 fixed by acacia. However, some indicators suggest a perturbation in SOM and P dynamics might affect the sustainability of the system in the medium and long term. In tropical environments, most of the nutrient processes are determined by the high rates of organic matter (OM) mineralization. Therefore, SOM stability might play a crucial role in regulating soil-plant processes. In spite of this, the relationship between SOM quality, C and other nutrient dynamics are not well understood. In the present study, OM quality and P forms in forest floor and soil were investigated to get more insight on the C and P dynamics useful to sustainable management of forest plantations. Methods: Thermal analysis (differential scanning calorimetry (DSC) and thermogravimetry (TGA)) and nuclear magnetic resonance (solid state 13C CPMASS and NMR and 31P-NMR) spectroscopy have been applied to partially decomposed forest floor and soils of pure acacia and eucalypt, and mixed-species acacia-eucalypt stands. Results: Thermal analysis and 13C NMR analysis revealed a more advanced stage of humification in forest floor of acacia-eucalypt stands, suggesting a greater microbial activity in its litter. SOM were related to the OM recalcitrance of the forest floor, indicating this higher microbial activity of the forest floor in this stand might be favouring the incorporation of C into the mineral soil. Conclusions: In relation with the fast mineralization in this environment, highly soluble orthophosphate was the dominant P form in both forest floor and soils. However, the mixed-species forest stands immobilized greater P in organic forms, preventing the P losses by leaching and contributing to sustain the P demand in the medium term. This shows that interactions between plants, microorganisms and soil can sustain the demand of this ecosystem. For this, the forest floor plays a key role in tightening the P cycle, minimizing the P losses
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
Process Intensification: Precipitation of Barium Sulfate Using a Spinning Disc Reactor (SDR)
No full textSoil organic matter quality along rotations in acacia and eucalypt plantations in the Congolese coastal plains
No full textChemical Structure Data File for L. Cafiero's Thesis, "New Synthetic Applications of Trichloromethyl Carbinols in Synthesis."
No full textThis Structure Data File (SDfile) is associated with the thesis: Cafiero, L. "New synthetic applications of trichloromethyl carbinols in synthesis." Ph.D. Thesis, The University of Alabama, 2009. and https://ir.ua.edu/handle/123456789/615 It is distributed by the University of Alabama Libraries. The SDfile is licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). Chemical Structure Data Files can be viewed/processed with most cheminformatics toolkits and stand-alone software packages: See https://en.wikipedia.org/wiki/Cheminformatics_toolkit. Note that this is the archived non-standardized chemical substance data. If you are looking for the standardized data" see the UA Libraries PubChem Data Source: https://pubchem.ncbi.nlm.nih.gov/source/15645. The specific substances associated with this data set are indicated by the local DATSOURCE_REGID identifiers within the SDfile. These identifiers can be used to cross-reference the data within PubChem. We recommend downloading the University of Alabama Libraries chemical structure data from PubChem as PubChem handles the standardization (within the Compound database) of the chemical structures. This archived version and associated data available on GitHub may be useful to understand our workflow. Please see the README on GitHub for important considerations, data reuse notes, and disclaimer: https://github.com/UA-Libraries-Research-Data-Services/UALIB_ChemStructures/blob/master/README.m
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
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