1,720,968 research outputs found
3D-printed zeolite 13X-Strontium chloride units as ammonia carriers
Full text linkThe selective catalytic reduction (SCR) system in automobiles using urea solution as a source of NH3 suffers from solid deposit problems in pipelines and poor efficiency during engine startup. Although direct use of high pressure NH3 is restricted due to safety concerns, which can be overcome by using solid sorbents as NH3 carrier. Strontium chloride (SrCl2) is considered the best sorbent due to its high sorption capacity; however, challenges are associated with the processing of stable engineering structures due to extraordinary volume expansion during the NH3 sorption. This study reports the fabrication of a novel structure consisting of a zeolite cage enclosing the SrCl2 pellet (SPZC) through extrusion-based 3D printing (Direct Ink Writing). The printed SPZC structure demonstrated steady sorption of NH3 for 10 consecutive cycles without significant uptake capacity and structural integrity loss. Furthermore, the structure exhibited improved sorption and desorption kinetics than pure SrCl2. The synergistic effect of zeolite as physisorbent and SrCl2 as chemisorbent in the novel composite structure enabled the low-pressure (0.4 bar) NH3 sorption, compared to pure SrCl2, which absorbed NH3 at pressures above 0.4 bar. Regeneration of SPZC composite sorbent under evacuation showed that 87.5% percent of NH3 was desorbed at 20 °C. Thus, the results demonstrate that the rationally designed novel SPZC structure offers safe and efficient storage of NH3 in the SCR system and other applications
Catalytic conversion of carbon dioxide into fuels
No full textHeterogeneous catalysis offers one of the sustainable solutions to the global warming challenge by converting greenhouse gases, particularly carbon dioxide (CO2), into valuable chemicals, notably methane (CH4). The CO2 methanation is a thermodynamically favorable and scalable process, typically carried out using nickel (Ni) based catalysts. However, the intense exothermicity of the methanation reaction poses challenges, including sintering of Ni nanoparticles and carbon deposition, which critically undermine the catalyst's stability. Resilience of the catalyst can be enhanced by tuning the metal-support interaction (MSI) and regulating the dispersion of Ni nanoparticles. The aim of this thesis was to develop stable and robust Ni catalysts by tuning the MSI and dispersion of Ni nanoparticles supported over the hierarchical zeolite 13X (h13X). Preliminary experiments demonstrated that Ni loading, activity, and instability of the catalyst are correlated. Under optimized synthesis conditions, grafting functional groups onto the support resulted in a stronger MSI and preferentially deposited Ni nanolayers, thereby enhancing the activity and stability of the catalyst. The addition of the cobalt cocatalyst strengthened the MSI and stabilized the catalyst's performance, notably during the initial stages of CO2 methanation. The synergistic effect of surface modification and cocatalyst resulted in lower activation energy, higher activity, and increased stability of the catalyst. Additionally, the influence of oxide promoters (La, Ca, Mg, Ce) proved to be dependent on their specific characteristics, with a notable increase in surface basicity, MSI, and catalyst stability. Based on the outcomes of surface modification and traditional catalyst design, a metal-chelation strategy was explored to regulate the size of Ni nanoparticles. The Ni was coordinated to the amine-based ligands, including pyridine, bipyridine, diethylenetriamine, and oleylamine, followed by their impregnation on the support. Remarkable differences were observed in the characteristics of the catalysts depending upon the type of ligand. A broader Ni distribution was observed for the heterocyclic ligand, whereas better textural properties were achieved by the aliphatic amines, which were attributed to the coordination of Ni in the metal-chelate complexes and the strength of interaction with the support. Besides the catalyst’s design, the process parameters, including temperature, pressure, H2/CO2 ratio, gas hourly velocity, and gas composition, showed a profound impact on the CO2 conversion, CH4 selectivity, and stability of the catalysts. overall, this thesis offers insights into regulating the catalyst's MSI, dispersion, distribution, activity, and stability
Catalytic conversion of carbon dioxide into fuels
No full textHeterogeneous catalysis offers one of the sustainable solutions to the global warming challenge by converting greenhouse gases, particularly carbon dioxide (CO2), into valuable chemicals, notably methane (CH4). The CO2 methanation is a thermodynamically favorable and scalable process, typically carried out using nickel (Ni) based catalysts. However, the intense exothermicity of the methanation reaction poses challenges, including sintering of Ni nanoparticles and carbon deposition, which critically undermine the catalyst's stability. Resilience of the catalyst can be enhanced by tuning the metal-support interaction (MSI) and regulating the dispersion of Ni nanoparticles. The aim of this thesis was to develop stable and robust Ni catalysts by tuning the MSI and dispersion of Ni nanoparticles supported over the hierarchical zeolite 13X (h13X). Preliminary experiments demonstrated that Ni loading, activity, and instability of the catalyst are correlated. Under optimized synthesis conditions, grafting functional groups onto the support resulted in a stronger MSI and preferentially deposited Ni nanolayers, thereby enhancing the activity and stability of the catalyst. The addition of the cobalt cocatalyst strengthened the MSI and stabilized the catalyst's performance, notably during the initial stages of CO2 methanation. The synergistic effect of surface modification and cocatalyst resulted in lower activation energy, higher activity, and increased stability of the catalyst. Additionally, the influence of oxide promoters (La, Ca, Mg, Ce) proved to be dependent on their specific characteristics, with a notable increase in surface basicity, MSI, and catalyst stability. Based on the outcomes of surface modification and traditional catalyst design, a metal-chelation strategy was explored to regulate the size of Ni nanoparticles. The Ni was coordinated to the amine-based ligands, including pyridine, bipyridine, diethylenetriamine, and oleylamine, followed by their impregnation on the support. Remarkable differences were observed in the characteristics of the catalysts depending upon the type of ligand. A broader Ni distribution was observed for the heterocyclic ligand, whereas better textural properties were achieved by the aliphatic amines, which were attributed to the coordination of Ni in the metal-chelate complexes and the strength of interaction with the support. Besides the catalyst’s design, the process parameters, including temperature, pressure, H2/CO2 ratio, gas hourly velocity, and gas composition, showed a profound impact on the CO2 conversion, CH4 selectivity, and stability of the catalysts. overall, this thesis offers insights into regulating the catalyst's MSI, dispersion, distribution, activity, and stability
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
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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