1,720,962 research outputs found
Photovoltaic waste as source of valuable materials: A new recovery mechanical approach
No full textEnd-of-life photovoltaic modules are hazardous waste belonging to the category of waste from electrical and electronic equipment. They contain environmentally hazardous substances, poorly biodegradable materials but also valuable materials. The recovery of these last is the main goal of PV-waste treatments. In order to facilitate the recovery and produce released fractions that are suitable for the recycling of glass, Silicon, Silver, Copper, Lead and Aluminium, the mechanical technics applied in the management of all e-waste without differentiation by type, are the most commonly used. However, a new and appropriate management strategy is required to maximize the recovery efficiency and improve the quality of recovered materials. This paper aims to identify and overcome the critical points in the PV-waste management mechanical processes and provides information on more efficient routes for their treatment. It aims to shed some light on the usefulness of adopting a specific and dedicated approach, to optimize the recovery rate and recovered materials purity level to send to recycling. A new mechanical process of separation and recovery of materials is proposed and compared with a typical conventional e-waste treatment process. The developed process makes improvements in the materials separation step, initial stage conditioning the process, making it more efficient than the conventional one
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
End-of-life of silicon PV panels: A sustainable materials recovery process
No full textIn this paper, the management of end-of-life PV modules based on an advanced eco-sustainable process has been presented and discussed. The thermal removal of the polymeric compounds contained in c-Si PV modules has been investigated to separate and recover Si, Ag, Cu, Al and glass. A two-step thermal process has been employed. In the first step, the rear polymeric layer has been removed without emissions of dangerous fluorinated substances. In the second step, the remaining polymers have been completely removed with low volatile organic compounds (VOCs) emissions. The polymers degradation has been studied at combustion equivalent ratios Φ varying from 0.5 to 2 and at 500 °C. The materials recovery has been evaluated from an environmental point of view and optimized by considering the energy cost, through the identification of the best operating conditions, in terms of temperature, time, atmosphere and gas flow. One hour of heat treatment and a slightly oxidizing atmosphere have been enabled to separate and recover the different materials of the module. The elemental compositions of the PV sample and the residue condensed organic products have been determined. The gaseous degradation products have been characterized by gas chromatographic analysis (GC). © 201
New PV encapsulants: assessment of change in optical and thermal properties and chemical degradation after UV aging
No full textThis work aims to investigate the change in chemical and physical properties of different polymeric materials, potentially usable for photovoltaic modules encapsulation, caused by UV aging. Three classes of polymeric materials have been examined: ethylene-vinyl-acetate (EVA), thermoplastic polyolefins (TPO) and polyolefin elastomers (POE). EVA is currently the most used encapsulant in the photovoltaic field; TPO and POE are new materials, alternative to EVA, which can allow to overcome some of the reliability problems of photovoltaic modules linked to the degradation of EVA properties. Of each of these three material classes, different commercially available encapsulating polymer films, with different chemical formulations, have been examined. Stressful environmental conditions have been simulated in a climatic chamber and the associated changes in optical, thermal and chemical properties of the different encapsulants have been analysed and compared before and after UV aging. The link between the chemical structure, formulation and degradation of the encapsulants with their lifetime under simulated conditions of UV stress has been investigated by the assessment of the changes in thermal stability, optical transmittance, crystallinity, yellowness index and chemical degradation. This study helps to better understand the causes of the module performance reduction due to the degradation of the encapsulant material and is a guide for the selection of encapsulant films with improved characteristics, for the manufacture of more durable PV modules
Silicon photovoltaic modules at end-of-life: Removal of polymeric layers and separation of materials
No full textAn eco-friendly process to recover valuable materials deriving from silicon based photovoltaic panels at end-of-life has been proposed. In particular, in this paper a new two-step process to separate and recover glass, Si and metals has been investigated and discussed. A preliminary mechanical treatment to remove fluorinated polymers allows to exclude dangerous emissions of hydrofluoric acid and fluorinated compounds coming out from conventional heat treatments. A subsequent thermal treatment allows the complete removal of the residual polymers and the separation of valuable materials. The influence of treatment time, temperature and atmosphere, during the polymers degradation has been evaluated and the by-products have been examined. The process efficiency has been assessed by determining the quantity and quality of the recovered materials. The results have shown that the combination of the two mechanical/thermal processes allows energy efficiency and environmental sustainability with respect to conventional recovery treatments. The optimal operating conditions for the thermal treatment have turned out 500 °C for 1 h in oxidizing atmosphere. The quality of the recovered materials has been determined by analysing the residual carbon content after the thermal treatment. The gaseous products of the polymeric degradation have been characterized by gas chromatography-mass spectrometry (GC–MS) 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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