1,720,977 research outputs found
Evaluating the material resource efficiency of secondary aluminium production: A Monte Carlo-based decision-support tool
No full textThe contamination of aluminium streams during the different life cycle stages by alloy mixing and/or accumulation of foreign elements, in combination with the limited melt purification options during remelting, represents an important limiting factor in recycling. Consequently, in secondary aluminium production, primary aluminium is used to dilute the concentration of the residual elements, and alloying elements are added to adjust the composition to the target alloy specifications. However, adding elements, for which their refinement in a subsequent recycling step is problematic, results in permanent down-cycling or ‘quality losses’. Hence, it is crucial to more efficiently control the composition of the metal streams prior to remelting. This article focuses on the aluminium cascade recycling chain and presents a Monte Carlo-based decision-support tool aiming to: i) identify all feasible clustering solutions per case based on input/output analysis; ii) quantify their environmental effect, and analyze the trade-offs; iii) consider scrap composition uncertainty/variability. Results reveal that primary resource additions can be minimized by optimizing metal sorting, and thus closing the recycling loop more effectively. Case studies are presented to illustrate the different functions of the tool, including examination of the Pareto front, and evaluation of the ‘recyclability’ of a scrap stream or a sorting solution into different alloy systems
Environmental modelling of aluminium based components manufacturing routes: Additive manufacturing versus machining versus forming
Get PDFAdditive Manufacturing represents, by now, a viable alternative for metal-based components production. Therefore the designer, often, has to select among three options at process design stage: subtractive, mass conserving, and additive approaches. The selection of a given process, besides affecting the manufacturing step impact, influences significantly the impact related to the material production step. If the process enables a part weight reduction (as the Additive Manufacturing approaches do) even the use phase is affected by the manufacturing approach selection. The present research provides a comprehensive environmental manufacturing approaches comparison for components made of aluminum alloys. Additive manufacturing (Selective Laser Sintering), machining, and forming processes are analyzed and compared by means of Life Cycle Assessment techniques. The effect of weight reduction enabled by additive approach is considered. The paper aims at highlighting the strong link between manufacturing approach selection and material use. In this respect, a thorough environmental analysis of the pre-manufacturing step is developed. Moreover, the influence of eco-attributes aluminium variability on the comparative analysis results is studied. The paper, therefore, contributes to the development of a methodology for manufacturing approaches comparison, providing guidelines for green manufacturing approach selection. Results reveal that, for the analyzed case studies, the Additive Manufacturing is a sustainable solution for aluminium components only under a specific scenario: high complexity shapes, significant weight reduction, and application in transportation systems
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
Duurzaam metalenbeheer en smeltloze recyclage van aluminiumlegeringen en magnesiumlegeringen ,,
No full textStarting from existing challenges and limitations in light metal recycling (in particular aluminium and magnesium alloys), this PhD thesis aims to address these and explore new opportunities by sustainable metal management and solid-state recycling (SSR) methods. This PhD also quantifies the potential environmental benefits of the explored strategies and SSR techniques by Life Cycle Assessment (LCA). More specifically:
During pyro-metallurgical recycling of aluminium alloys, the refining/melt purification options of aluminium alloys, restricted by thermodynamic barriers, are very limited compared to other base metals such as steels. As the removal from the melt of most elements is problematic, it is crucial to control their concentration in the scrap streams prior to remelting. Thus, scrap sorting is important to avoid additional (eventually impossible) refining, quality degradation (down-cycling), and dilution of the residual elements with primary aluminium addition. It is therefore described that establishing of well-optimised, harmonised recycling loops is of prime importance from an environmental perspective. Based on these arguments, Chapter 2 addresses this issue by developing a decision support model that aids in the direction of environmental conscious metal clustering. It aims: i) to express and quantify in a LCA framework, dilution and quality losses that occur during open loop recycling, and ii) to determine the optimal material input for the recycling process based on the input/output metal composition. By compositionally closing the recycling loops, it is feasible to minimise primary resource addition (primary aluminium and alloying elements) by maximising the scrap utilisation. A multi-objective optimisation approach (goal programming) is selected as the most appropriate method to prioritise the optimisation goals.
After performing the environmental modelling of the secondary aluminium production as a reference route, Chapter 3 moves on to ‘meltless’ or ‘solid state recycling’ techniques for high grade aluminium production scrap. This approach is studied to achieve a significant material and energy savings by omitting/bypassing the conventional recycling step. Annually more than 40% of liquid aluminium is scrapped during the initial production-fabrication-manufacturing steps. Especially for fine form scrap from material removal processes, their very high surface-to-mass ratio results in significant unrecoverable oxidation losses during remelting. In this context, this work investigates the applicability of Spark Plasma Sintering (SPS) as an alternative SSR technique for aluminium alloy chips (Chapter 3). This allows the direct fabrication of bulk, near-net shape and semi-finished products directly from machining chips. The improved consolidation achieved via SPS is associated with the combined action of plastic deformation and the electric field during SPS processing. Microstructural investigations as well as the mechanical behaviour of the SPS blanks confirm successful solid state chips welding. Furthermore, this work also investigates applications of SPS in scrap consolidation and binding. Chapter 4 examines the use of atomised aluminium powder as a binding material/matrix for the machining chips. Chapter 5 describes the consolidation via SPS of larger scrap types (sheet metal scrap).
After developing a reliable SPS route for SSR of aluminium alloy scrap, Chapter 6 analyses the environmental performance of the SPS route along with major SSR routes for aluminium alloys (recycling via hot extrusion and via screw extrusion). For this reason a LCA study was conducted where the examined SSR routes are compared with their corresponding remelting routes as reference.
Mg alloys confront similar challenges in recycling as aluminium alloys. Taking also into account the wide range of magnesium applications and their higher scrap value compared to aluminium scraps; Chapter 7 focuses on broadening the material palette of SSR via SPS into Mg alloys. In this respect, this work studies the consolidation of machining chips for two Mg systems (i.e., pure Mg and AZ31 Mg alloy). This includes the microstructural evolution in different metal recycling steps (initial ingot, chips, SPSed samples) as well as the mechanical behaviour of the recycled samples versus their parent material. Finally, the conclusions, the contributions to the state of the art as well as proposed future research topics are discussed in Chapter 8.status: Publishe
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
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