1,720,962 research outputs found
IMPROVEMENTS IN PLASMA RAWMATERIAL RECOVERY BY APPLICATION OF THE SELECTIVE IONIZATION CONCEPT
No full textPlasma Raw Material Recovery refers to the possibility of obtain raw materials as pure elements starting from multiple not refined sources such as wastes, minerals and other sort of low grade materials. The concept has been proposed, for very specific applications and always not in its present and general form, in very different fields ranging from nuclear physics to space science. The process implies the ionization of the source materials and the separation of its constituents by electromagnetic means. Some simplifications in the process are possible in manipulating oxides. In this case it is possible to take advantage of the ionization gap between the oxygen and the other constituent metal to reduce the process required power as in the ”selective ionization” process theorized by NASA in the ’80s. In this paper the energetic feasibility of a direct separation of oxides using Plasma Raw Material Recovery implementing the Selective Ionization concept, hereafter called Enhanced Selective Ionization Method, is evaluated. The general characteristics of the process are described including its physical explanation. The energy required for the oxide dissociation and the separation is calculated separately for each of the main oxides present in the earth crust and hence an assessment of the energy required to separate into pure elements a combination of different oxides is performed along with the indication of the conversion yield
APPLICATION OF THE ENHANCED SELECTIVE IONIZATION METHOD TO SILICON PRODUCTION
No full textPresent productions method of high graded pure silicon for electronics purposes involves usage of large quantities of energy, water and chemicals. The possibility to directly separate silica into its constituents with a single step would provide benefits in terms of energy consumption, logistics and environmental impact. This separation is feasible if performed by electromagnetic means on ionized silica and taking advantage of the ionization gap between oxygen and silicon, a process that can be called Enhanced Selective Ionization. In this paper the energetic feasibility of a direct separation of silica using the Enhanced Selective Ionization Method is evaluated in its energetic requirements and conversion yields. The preliminary configuration of a demonstrator devoted to demonstrate the concept is presented. The main functional parts are presented along with the respective power budget. For each part analytical and numerical allow to calculate a global energy cost per unit of silicon, which is compared with traditional production processes
POWER DISSIPATION IN HEAVY METALS RECOVERY FROM INCINERATOR ASHES
No full textUnder controlled conditions waste-to-energy plants are very useful systems to dispose solid wastes in combination with energy production. For common urban wastes, hence excluding special wastes, the incineration products are fly and heavy ashes where heavy metals are concentrated due to their impossibility to be vaporized. Those metals are usually lost because up to now the common ashes disposal methods have been cement or clay inertization or simple ashes storage in safe places. In order to recover those otherwise lost valuable and useful heavy metals we present the concept of an electromagnetic device able to separate and collect the different atomic species. The proposed device is essentially composed by an atomization stage followed by a separation one. The former atomizes and ionizes ash components allowing the second stage to perform separation of the desired metals by means of an electromagnetic field. Power dissipation represents one of the major issues of such devices due to the high power required to perform species separation. In this paper the major power sources and losses are also identified
THERMAL MODELLING OF LASER ABLATION SIMULATION BY NUMERICAL SOLUTION OF A THREE PHASE STEPHAN PROBLEM
No full textLaser ablation is an important industrial process to remove material from a solid surface by means of a laser beam that heats and evaporates or sublimates the material. One of the most interesting applications of such technique is the laser machining, technique that allow to drill holes and perform other operations on even very hard material in an extremely precise way. Usually this process is performed not continuously but with a pulsed laser, meaning that an extremely high amount of energy is discharged on an extremely small surface, achieving a strong energy density in a small amount of time such that the surrounding material absorbs a very small amount of energy; consequently it does not heat, preserving its properties. This process can be easily modeled as a three phase Stephan problem to which a finite difference solution with the Front Tracking Method is applied. Such methodology has been already used by authors to model electrodes erosion by the establishing of electric arches, with good agreement with literature data. The same methodology is now applied to laser ablation technique taking into account the additional energy contribution mechanisms that could have been previously negligible for an electric arc shock but that are of high relevance in a laser ablation process
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
Waste atomic separation and raw material recovery by application of plasma technology
Full text linkLa possibilità di ottenere materie prime sotto forma di elementi puri a partire da una moltitudine di fonti non raffinate, quali ed esempio rifiuti, minerali e altre forme di materiali grezzi, e teoricamente fattibile usanto tecnologie al plasma. Il concetto è stato proposto in passato, per applicazioni molto specifiche, in campi molto differenti tra loro che vanno dalla fisica nucleare alle scienze spaziali. Il processo implica la ionizzazione del materiale di partenza e la separazione dei suoi elementi costitutivi tramite mezzi elettromagnetici in un unico passaggio, con il vantaggio di accorciare l'intera catena di produzione rispetto ai processi produttivi tradizionali, al prezzo di una grande quantità di energia elettrica. In questo lavoro il problema è analizzato nel caso speciale della produzione di silicio a partire da silice, il cui metodo di produzione tradizionale è composto da diversi passaggi di produzione e richiede l'uso di grandi quantità di energia, acqua e prodotti chimici. Il problema è inizialmente definito in modo da valutare sinergie con tecnologie proposte in passato, ed è proposto in via preliminare il concetto di un impianto dimostratore e dei suoi costituenti. Un modello numerico è quindi sviluppato per analizzare il processo, permettendo di eseguire un dimensionamento più dettagliato. L'approccio proposto è quindi valutato dal punto di vista energetico nella sua globalità, e la sua sostenibilità è confrontata con quella di metodi di produzione tradizionali. I risultati dimostrano la fattibilità dell'approccio, ma purtroppo anche un consumo energetico complessivo più elevato del processo produttivo tradizionale. In ogni caso l'impatto ambientale complessivo risulta limitato alla richiesta di energia elettrica, con nessun prodotto chimico coinvolto nel processo. Aree di ottimizzazione, capaci di portare portare miglioramenti sostanziali nella richiesta di energia, sono identificate.The possibility of obtaining raw materials as pure elements starting from multiple not refined sources, such as wastes, minerals and other sort of low grade materials, is theoretically achievable by using plasma means. The concept has been proposed in the past, for very specific applications, in very different fields ranging from nuclear physics to space science. The process implies the ionization of the source materials and the separation of its constituents by electromagnetic means in a single production step, with the advantage of shortening the overall production chain respect to traditional production processes, at the expenses of a high quantity of electric energy. In this work the problem is analyzed in the special case of silicon production starting from silica, which traditional production method involves many production steps and the usage of large quantities of energy, water and chemicals. The possibility to directly separate silica into its constituents in a single passage would provide benefits in terms of energy consumption, logistics and environmental impact. The problem is initially set to evaluate synergies with previous technologies, and the preliminary set up of a demonstrator plant is proposed with its main constituents. A numerical model is then developed to analyze the process, allowing to perform a more detailed design of the device. The proposed approach is then globally evaluated from the energetic point of view, and its sustainability is compared with traditional production processes. Results show the feasibility of the approach, but also an overall energy consumption unfortunately higher than the traditional production process. Nevertheless the overall environmental impact is limited to the electric energy demand, with no chemicals involved in the process. Areas of optimization are identified, which may lead to substantial improvements in the energy consumption.DIPARTIMENTO DI ENERGIA24BOTTANI, CARLO ENRIC
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