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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
Innovaatioita Li-ioniakkujen kierrätyksen saralla: uuden sukupolven karakterisointi- ja erotusmenetelmät, sekä näkökulmia teolliseen prosessi-integraatioon
No full textThe exponential growth in the electric vehicle market and the rising demand for sustainable energy storage solutions have resulted in a significant increase in the production rates of lithium-ion batteries (LIBs). Consequently, the demand for critical raw materials needed for LIB manufacturing (e.g., Co, Ni, Cu, graphite, and Li) is projected to increase rapidly in the coming years.
Current industrial-scale recycling technologies, namely pyrometallurgy and hydrometallurgy, face limitations in processing end-of-life LIBs and recovering valuables from their active component mixtures (a.k.a., black mass). To overcome these limitations, this Thesis investigated the potential of froth flotation as a separation process for direct recycling of LIBs, an approach aimed at preserving the structural and chemical integrity of the anode and cathode active minerals (CAMs).
The research comprised multiple campaigns ranging from fundamental understanding of flotation mechanisms to the integration of flotation in industrial processes. Firstly, a novel tomographybased methodology was developed to characterize flotation froths, thus providing insights into the extraction mechanisms of solid particles. A previously overlooked phenomenon was uncovered, where binder-free lithium cobalt oxide (LCO) particles were observed to be hydrophobized by a common oily collector – indicating a lack of collector selectivity. Another campaign focused on flocculation of CAMs, specifically demonstrating the potential for selectively flocculating LCO particles in mixtures with graphite. Building on these insights, a combined approach of selective flocculation and froth flotation was studied, showing promise in improving the selectivity of graphite separation from black mass through a CAM-selective flocculation pretreatment.
Lastly, the integration of LIB recycling into existing industrial slag cleaning processes was studied. It was demonstrated that, in the presence of binder polymers, flotation can effectively separate an industrial black mass into a froth concentrate rich in active minerals and an underflow concentrate comprising current collector metals. Furthermore, the refining of these concentrates was successfully integrated with industrial Ni slag cleaning and Cu slag cleaning processes, revealing synergistic benefits. The integrated processes were found to be chemically self-sustaining, requiring no additional reductants for refining valuable metals Cu, Co, Ni, and Fe, although loss of Li, Al, and Mn to the slag phase was observed.
In summary, this thesis presents a comprehensive investigation into advanced characterization and physical separation techniques for LIB recycling, with perspectives on industrial process integration. The findings contribute to the development of more efficient, cost-effective, and environmentally sustainable recycling methods. The studied methods are expected to address existing concerns associated with the growing demand for critical battery materials.Sähköajoneuvomarkkinoiden eksponentiaalinen kasvu ja kestävien energianvarastointiratkaisujen kasvava kysyntä ovat johtaneet litiumioniakkujen tuotannon merkittävään lisääntymiseen. Tämän seurauksena akkutuotannossa välttämättömien kriittisten raaka-aineiden, kuten Co, Ni, Cu, grafiitti ja Li kysynnän ennustetaan tulevina vuosina kasvavan räjähdysmäisesti.
Jäteakkujen ns. mustan massan käsittelyssä nykyisin hyödynnettävät teolliset kierrätysteknologiat (pyrometallurgia ja hydrometallurgia) ovat osin rajoittuneita ja sisältävät haittavaikutuksia. Tästä syystä tässä väitöstyössä tutkittiin vaahdotusta erotusprosessina akkujen ns. "suorakierrätyksen" mahdollistamiseksi. Suorakierrätyksessä akun anodi ja katodiaktiivimineraalit (KAM) otetaan talteen korkean jalostusasteen tuotteena.
Työ sisälsi useita tutkimussuuntia, käsitellen esim. vaahdotusmekanismien ymmärtämistä sekä teollista prosessi-integraatiota. Työssä mm. kehitettiin uudenlainen röntgentomografiaan (xRCT) perustuva menetelmä vaahtojakeiden karakterisoimiseksi, jolla kiintoaineiden sijoittumista vaahdon eri kantajafaaseissa (ilma, vesi) kyettiin havainnoimaan. Tämän avulla osoitettiin, että kerosiini (yleisesti käytetty grafiittikerääjä) adsorboituu epäselektiivisesti litiumkobolttioksidi (LCO) partikkelien pintaan. Toisessa hankkeessa tutkittiin KAM-partikkelien flokkulaatiota. Tässä hankkeessa havaittiin, että tietyissä prosessiolosuhteissa LCO on mahdollista flokkuloida selektiivisesti grafiitti–LCO-seoksista. Näiden havaintojen pohjalta tutkittiin yhdistettyä flokkulaatio–vaahdotus-prosessia ja osoitettiin, että vaahdottamalla talteenotetun grafiitin puhtauteen voidaan vaikuttaa positiivisesti LCO-partikkeleja flokkuloimalla.
Lisäksi väitöstyössä tutkittiin akkukierrätyksen integrointia teollisiin kuonankäsittelyprosesseihin. Tässä hankkeessa osoitettiin, että mustasta massasta voidaan ns. sitojapolymeerien läsnä ollessa vaahdottamalla erottaa tehokkaasti aktiivimineraalikonsentraatti sekä Cu–Al-konsentraatti. Näiden konsentraattien jatkojalostus demonstroitiin sekoitettuna nikkeli- ja kuparikuonaan, joiden pyrometallurginen käsittely mahdollisti arvometallien (Co, Ni, Cu, Fe) talteenoton ilman tarvetta lisätylle pelkistimelle. Al, Li ja Mn havaittiin kuitenkin päätyvän sekundäärikuonaan.
Yhteenvetona, tämä väitöstyö esittelee tutkimuksen jäteakkujen karakterisointi- ja erotustekniikoista (xRCT, vaahdotus, flokkulaatio), sekä näkökulmia teolliseen prosessiintegraatioon. Havainnot edistävät kustannustehokkaampien ja kestävämpien kierrätysmenetelmien kehittämistä. Tutkittujen menetelmien pohjalta voidaan tulevaisuudessa vastata kriittisten akkumineraalien kasvavaan kysyntään
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
Adsorption of volatile organic compounds on pore expanded mesoporous materials and MCM-41 silica
No full textThe increasingly stringent environmental regulations worldwide demand the use of efficient methods for air purification. This work is a contribution toward developing efficient adsorbents for volatile organic compounds (VOCs). Three different varieties of ordered mesoporous silicas were evaluated: an ordered MCM-41 mesoporous silica prepared in the presence of a surfactant, a MCM-41 whose pores have been expanded by a post-synthesis hydrothermal treatment in the presence of an organic expander (referred to as MCM-EC), and a pore-expanded hybrid mesoporous silica produced by the selective extraction of its pore expander agent (denominated MCM-EE). With the intention to analyze their performance as adsorbents, the heat of adsorption (-DeltaHa) and adsorption capacity (q) were determined experimentally for five typical VOCs: dichloromethane, chloroform, benzene, toluene and cyclohexane. (Abstract shortened by UMI.
Triamine-grafted pore-expanded mesoporous silica for carbon dioxide adsorption in closed-circuit breathing systems
No full textIn the search for efficient, less energy-intensive alternatives for CO2 capture, and inspired by the scrubbing processes using liquid amine solutions, amine groups have been incorporated onto porous supports. Our research group tailored mesoporous materials type MCM-41 by enlarging their pore size to incorporate a high content of readily available amine groups. In earlier studies, triamine-grafted pore-expanded mesoporous silica (TRI-PE-MCM-41) presented large CO2 removal capacity combined with a fast rate of adsorption. This thesis focused on evaluating TRI-PE-MCM-41 as CO 2 adsorbent by determining a variety of adsorptive properties with the aim of gaining a deep understanding of its behavior and to outline its advantages and limitations.
The CO2-amine chemistry in gas-solid processes was investigated under humid and dry conditions using aminopropyl-grafted pore-expanded MCM-41 silica (MONO-PE-MCM- 41). To draw accurate conclusions regarding CO2 adsorption in the presence of water vapor, an analytical method coupling thermogravimetric analysis (TGA) and mass spectrometry (MS) was developed. The CO2/N molar ratio in dry streams was close to 0.5, consistent with the formation of carbamate and, as the relative humidity in the feed increased, the CO2/N ratio increased up to 0.88, in line with the gradual formation of bicarbonate.
With respect to the effect of moisture on TRI-PE-MCM-41, it was found that its capacity for CO2 in dry streams was enhanced by ca. 17% in streams with 74% relative humidity. In addition, breakthrough curve analysis using a packed-bed column was performed for CO2 mixtures in dry and humid air. The results showed a practically infinite selectivity of TRI-PE-MCM-41 towards CO2 over N2 and O2. While water vapor was also removed by TRI-PE-MCM-41, it did not adsorb competitively with CO 2.
With the aim of predicting the behavior of fixed-bed columns packed with amine-functionalized adsorbents, we developed equilibrium and kinetic models capable of describing CO2 adsorption on TRI-PE-MCM-41 under various operating conditions. A new semi-empirical equilibrium model was developed based on the assumption that adsorption of CO2 occurs via two independent mechanisms: (i) chemical adsorption on the amine functional groups, and (ii) physisorption on the surface of the adsorbent. To investigate the adsorption kinetics of CO2 on TRI-PE-MCM-41, experimental data of CO 2 uptake as a function of time at temperatures between 25 and 70°C were fit to a series of kinetic models, namely Lagergen's pseudo-first and pseudo-second order and Avrami's kinetic models. The best fit was obtained using Avrami's model, as it provided a fractional reaction order (ca. 1.4), which has been associated with the occurrence of multiple adsorption pathways. Using the aforementioned equilibrium and kinetic models, a series of simulations of CO2 adsorption in a column packed with amine-grafted mesoporous silica was carried out to predict breakthrough curves. The simulation results were compared with experimental data produced at various flow rates of a stream of 5% CO2/N2. In all cases, the predicted breakthrough time and the corresponding CO2 uptake were in close agreement with the experimental data.
To further support the potential of TRI-PE-MCM-4l for commercial scale applications, it was necessary to demonstrate its stability throughout intensive cycling. The behavior of the adsorbent was evaluated in batch experiments, via adsorption-desorption cycling using various regeneration conditions. Using a 23 factorial design of experiments, the impact on the performance of the adsorbent of different levels of temperature, pressure and flow rate of purge gas during desorption was determined. It was found that all the investigated parameters have a statistically significant influence on the working adsorption capacity, but only temperature is influential with respect to desorption rate. If vacuum is applied, regeneration can be achieved at a temperature as low as 70°C with only a 13 % penalty in terms of working adsorption capacity. It was also demonstrated that under the proper regeneration conditions, TRI-PE-MCM-4l is stable over 100 adsorption-desorption cycles.
The final chapter of this thesis dealt with the potential application of TRI-PE-MCM-41 as CO2 scrubber in closed-circuit breathing systems, including a first evaluation in a commercial-scale setup. A comparative study between currently used soda lime and TRI-PE-MCM- 4l showed that although the former has a significantly higher CO2 uptake, it was negatively affected by high flow rates, while the former suffered a lower impact, attributed to fast adsorption kinetics. The performance ofTRI-PE-MCM-4l in an anesthesia delivery unit under real operating conditions is presented. Under the current configuration, lower adsorption capacities than those at laboratory-scale testing were measured. Discussion of this low performance and recommendations for future work are included
Triamine-grafted pore-expanded mesoporous silica for carbon dioxide adsorption in closed-circuit breathing systems
No full textIn the search for efficient, less energy-intensive alternatives for CO2 capture, and inspired by the scrubbing processes using liquid amine solutions, amine groups have been incorporated onto porous supports. Our research group tailored mesoporous materials type MCM-41 by enlarging their pore size to incorporate a high content of readily available amine groups. In earlier studies, triamine-grafted pore-expanded mesoporous silica (TRI-PE-MCM-41) presented large CO2 removal capacity combined with a fast rate of adsorption. This thesis focused on evaluating TRI-PE-MCM-41 as CO 2 adsorbent by determining a variety of adsorptive properties with the aim of gaining a deep understanding of its behavior and to outline its advantages and limitations.
The CO2-amine chemistry in gas-solid processes was investigated under humid and dry conditions using aminopropyl-grafted pore-expanded MCM-41 silica (MONO-PE-MCM- 41). To draw accurate conclusions regarding CO2 adsorption in the presence of water vapor, an analytical method coupling thermogravimetric analysis (TGA) and mass spectrometry (MS) was developed. The CO2/N molar ratio in dry streams was close to 0.5, consistent with the formation of carbamate and, as the relative humidity in the feed increased, the CO2/N ratio increased up to 0.88, in line with the gradual formation of bicarbonate.
With respect to the effect of moisture on TRI-PE-MCM-41, it was found that its capacity for CO2 in dry streams was enhanced by ca. 17% in streams with 74% relative humidity. In addition, breakthrough curve analysis using a packed-bed column was performed for CO2 mixtures in dry and humid air. The results showed a practically infinite selectivity of TRI-PE-MCM-41 towards CO2 over N2 and O2. While water vapor was also removed by TRI-PE-MCM-41, it did not adsorb competitively with CO 2.
With the aim of predicting the behavior of fixed-bed columns packed with amine-functionalized adsorbents, we developed equilibrium and kinetic models capable of describing CO2 adsorption on TRI-PE-MCM-41 under various operating conditions. A new semi-empirical equilibrium model was developed based on the assumption that adsorption of CO2 occurs via two independent mechanisms: (i) chemical adsorption on the amine functional groups, and (ii) physisorption on the surface of the adsorbent. To investigate the adsorption kinetics of CO2 on TRI-PE-MCM-41, experimental data of CO 2 uptake as a function of time at temperatures between 25 and 70°C were fit to a series of kinetic models, namely Lagergen's pseudo-first and pseudo-second order and Avrami's kinetic models. The best fit was obtained using Avrami's model, as it provided a fractional reaction order (ca. 1.4), which has been associated with the occurrence of multiple adsorption pathways. Using the aforementioned equilibrium and kinetic models, a series of simulations of CO2 adsorption in a column packed with amine-grafted mesoporous silica was carried out to predict breakthrough curves. The simulation results were compared with experimental data produced at various flow rates of a stream of 5% CO2/N2. In all cases, the predicted breakthrough time and the corresponding CO2 uptake were in close agreement with the experimental data.
To further support the potential of TRI-PE-MCM-4l for commercial scale applications, it was necessary to demonstrate its stability throughout intensive cycling. The behavior of the adsorbent was evaluated in batch experiments, via adsorption-desorption cycling using various regeneration conditions. Using a 23 factorial design of experiments, the impact on the performance of the adsorbent of different levels of temperature, pressure and flow rate of purge gas during desorption was determined. It was found that all the investigated parameters have a statistically significant influence on the working adsorption capacity, but only temperature is influential with respect to desorption rate. If vacuum is applied, regeneration can be achieved at a temperature as low as 70°C with only a 13 % penalty in terms of working adsorption capacity. It was also demonstrated that under the proper regeneration conditions, TRI-PE-MCM-4l is stable over 100 adsorption-desorption cycles.
The final chapter of this thesis dealt with the potential application of TRI-PE-MCM-41 as CO2 scrubber in closed-circuit breathing systems, including a first evaluation in a commercial-scale setup. A comparative study between currently used soda lime and TRI-PE-MCM- 4l showed that although the former has a significantly higher CO2 uptake, it was negatively affected by high flow rates, while the former suffered a lower impact, attributed to fast adsorption kinetics. The performance ofTRI-PE-MCM-4l in an anesthesia delivery unit under real operating conditions is presented. Under the current configuration, lower adsorption capacities than those at laboratory-scale testing were measured. Discussion of this low performance and recommendations for future work are included
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
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