1,720,964 research outputs found
Dynamic modelling of electrodialysis with bipolar membranes at industrial scale for the sustainable production of chemicals from brines
Full text linkModelling of large scale Electrodialysis with Bipolar Membranes processes using a multi-scale approach with validation at pilot plant scale
Full text linkTesting of Electrodialysis with bipolar membrane at semi-industrial scale for in-situ reactant production
No full textIntroduction. Electrodialysis with bipolar membranes (EDBM) has been gaining attention for the production of chemicals, such as acids and bases, for direct use in situ within circular and integrated processes, thus avoiding transport and handling of highly concentrated and dangerous reagents. Although this process has been explored in recent years at laboratory scale, few studies aimed at the development of pilot scale units. This work aims to fill this gap by scaling up and testing an EDBM unit at semi-industrial scale.
Materials and methods. The pilot unit consists of 50 triplets of 0.32 m2 of active membrane area. The setup includes measurement instruments to monitor flowrates, conductivity, pressure, etc. Tests were performed in batch mode with synthetic solutions at initial concentration of 1.0 mol/L NaCl in the saline channels and 0.05 mol/L HCl and NaOH in the acid and base ones, respectively. The effect of a different initial volumes in the compartments was investigated by comparing performance indicators as current efficiency (CE), specific energy consumption (SEC) and specific productivity (SP).
Results and discussion. Results showed that, when doubling the volume of acid, a SEC of 1.05 kWh/kgNaOH and CE of 95% were reached at 0.5 mol/L of OH-. Moreover, OH- concentration above 1.0 mol/L could also be reached (with corresponding SEC and CE of 1.05 kWh/kgNaOH and 76%, respectively). Indeed, lowering the acid concentration (by increasing the acid tank volume) reduced undesired effect of diffusion towards the saline channel and partial neutralization of acid and base. This work demonstrated the scalability of the EDBM process and highlighted some practical operating conditions to optimize the EDBM performance indicators
Semi-industrial Electrodialysis with bipolar membranes (EDBM) unit for harvesting valuable acid and base from exhausted bitterns
No full textDynamic modelling of electrodialysis with bipolar membranes unit using NARX recurrent neural networks
Full text linkElectrodialysis with bipolar membranes (EDBM) is an innovative and effective process
for the simultaneous production of acid and base solutions from salty streams. It has been
proven to play a key role in several circular economy approaches to valorize waste
industrial brines, but it can also be used for in situ generation of chemicals, especially in
remote areas. The adoption of such technology at industrial scale requires reliable
modelling tools capable of predicting both dynamic and stationary operations as process
conditions vary, such as energy supplied to the system and the target concentration of
chemicals. In this study, nonlinear autoregressive models with exogenous inputs (NARX)
were applied for the first time to EDBM to predict the behaviour of this complex and nonlinear process. Thus, an effective and low computational demanding neural-based
modelling tool was developed. As a preliminary step, the network was trained with three
different datasets, generated by a fully validated model. The best architecture was chosen
to give good performance, testing the network with a new dataset. The NARX network
accurately predicts the different behaviour of EDBM outputs (i.e. voltage and solutions
conductivities) showing low average discrepancies between predicted and true values
(lower than 0.5 %). These results suggest the possibility of using neural network-based
models to effectively optimize and control EDBM process. Next step will focus on the
training and validation of a network obtained with a set of data from a real EDBM plant
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
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
- …
