1,720,957 research outputs found
Antimony Mining from PET Bottles and E-Waste Plastic Fractions
Get PDFIn this study antimony concentration was analyzed in 30 plastic items (from polyethylene
terephthalate (PET) bottles and e-waste) directly by X-ray fluorescence spectroscopy (XRF)
spectroscopy. PET samples were digested in a microwave oven with aqua regia. The plastic
components deriving from e-waste followed three parallel routes: 1. microwave digestion using
dierent acids (aqua regia, 18 M H2SO4, 12 M HCl and 6 M HCl); 2. conversion into ash (at 600 C)
and then microwave digestion with aqua regia, and 3. extraction with 12 M HCl at room temperature
for dierent durations (2 h and 24 h). Results showed that antimony extraction yields from PET were
between 57% and 92%. Antimony extraction from e-waste plastics was more challenging: aqua regia
was inecient for poly (acrylonitrile butadiene styrene) (ABS) samples (extraction yield was about
20% only), while on a mixture of ABS and polycarbonate (PC), aqua regia, H2SO4 and HCl exhibited
equivalent performances (~21%). Ashed samples returned yields ranging from 20% to over 50%.
Room temperature extraction on e-waste plastics obtained lower extraction eciencies, yet longer
incubation durations lead to higher yields. In conclusion, the main challenge associated with antimony
mining from plastic waste could be its heterogeneous composition; therefore, the development of
reference analytical procedures is highly needed
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
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
Relevant properties and governing mechanisms for oil recovery and geological carbon dioxide storage applied to jordanian shale
Get PDFMit Blick auf den stetig wachsenden Energiebedarf und der damit im Zusammenhang stehenden
dramatischen Zunahme der CO2-Konzentration in der Atmosphäre steht die Menschheit vor der Aufgabe,
Antworten auf bislang beispiellose Herausforderungen zu finden. Trotz verstärkter Bemühungen, die
sogenannte Energiewende voranzutreiben, geht der Großteil der Vorhersagen davon aus, dass die
Grundlage zur Deckung des globalen Energiebedarfes weiterhin durch fossile Brennstoffe gesichert wird.
Gleichzeitig ist eine deutliche Abnahme der Produktion aus konventionellen Ölreserven zu verzeichnen,
sodass nicht-konventionelle Ressourcen in Zukunft eine größere Rolle übernehmen werden. Auf der
anderen Seite werden die Bemühungen zur Abtrennung und Untertagespeicherung von CO2 als ein
Bestandteil der Dekarbonisierung vorangetrieben. Erfahrungen mit der Injektion von CO2 existieren bereits
seit den 1970er Jahren im Rahmen der sogenannten “CO2-enhanced oil recovery” (CO2-EOR) mit gutem
Erfolg zur Steigerung der Förderraten aus konventionellen Lagerstätten. Daher erscheint es naheliegend,
die beiden Prozesse im Sinne einer zügigen Umsetzung der Energiewende zu kombinieren und in der Folge
auch für nicht-konventionelle Lagerstätten in Betracht zu ziehen. Über die mögliche Anwendung
innovativer Methoden in diesen oft sehr komplexen Gesteinsformationen ist bislang wenig bekannt
geworden. Daher befasst sich die aktuelle Dissertation mit einer Reihe an Phänomenen, die im
Zusammenhang mit der Applikation von komprimiertem CO2 auf Schieferformationen relevant sind.
Entscheidende Systemeigenschaften wurden in dieser Arbeit untersucht mit dem Ziel, Möglichkeiten zur
Kombination einer CO2-gestützten Förderung von Kohlenwasserstoffen mit der Einspeicherung von CO2
in nicht-konventionellen Lagerstätten zu evaluieren. Jordanischer Ölschiefer (Sultani) dient hier als
Beispiel mit einem erheblichen Potenzial aus wirtschaftlicher und umwelttechnischer Sicht. Es werden
umfangreiche und systematische experimentelle Untersuchungen zum grundlegenden Phasen-,
Grenzphasen- und Stofftransportverhalten in komplexen dichten Wasser- und Kohlenwasserstoffhaltigen
Gesteinsformationen in Kontakt mit komprimiertem CO2 vorgestellt.
In einem ersten Schritt wurde Sultani-Schiefer einer Extraktion mit überkritischem CO2 unterzogen. Dabei
wurde der Einfluss unterschiedlicher Betriebsparameter auf die Ausbeute untersucht, die wiederum in
direktem Zusammenhang mit der Löslichkeit unterschiedlicher im Ölschiefer enthaltener Komponenten in
der CO2-Phase steht. Neben der Analyse des Mehrphasenverhaltens, zu dem die Bestimmung von
Gemischdichten, die Löslichkeit von CO2 in Kohlenwasserstoffmischungen und die daraus folgende
volumetrische Ausdehnung der Kohlenwasserstoffphase gehört, bestand ein Schwerpunkt der Arbeit in der
experimentellen Betrachtung von Grenzphaseneigenschaften unter Lagerstättenbedingungen. Als eine
maßgebliche Größe wurde die Grenzflächenspannung in mehrphasigen Multikomponentensystemen
mittels der Methode des hängenden, stehenden bzw. liegenden Tropfens bestimmt. Die Benetzung an den
inneren Porenwänden wird durch den Dreiphasen-Kontaktwinkel beschrieben, der sowohl im System CO2-
Formationswasser-Schiefer als auch in dem System CO2-Kohlenwasserstoff-Formationswasser-Schiefer an
liegenden Tropfen bestimmt wurde. Zur Erklärung der Abhängigkeit der Benetzung von der
Zusammensetzung der wässerigen Phase wurden Messungen des Zeta – Potentials an in wässerigen
Salzlösungen suspendierten Schieferpartikeln unternommen. Die Grenzfläche Feststoff-CO2 war hingegen
Gegenstand von Messungen mittels einer gravimetrischen Methode, mittels derer die Adsorptionskapazität
des Schiefers bestimmt wurde, die einerseits als eine der möglichen Speichermechanismen für CO2 gilt und
andererseits in direkter Beziehung zum Benetzungsverhalten in Anwesenheit von wässerigen Salzlösungen
steht. In Ergänzung zu dem Mehr- und Grenzphasenverhalten wurden Diffusionskoeffizienten von
komprimiertem CO2 im Gestein bestimmt, die letzten Endes über die Zeitskala der im Fokus stehenden
ablaufenden Prozesse entscheidet. Im Ergebnis führen die hohen Wechselwirkungen aller beteiligten
Phasen mit überkritischem CO2 zu bedeutenden Änderungen in den Systemeigenschaften, die die
Mobilisierung der Kohlenwasserstoffe generell fördern, während sich diese auch negativ auf eine GeoSpeicherung von CO2 etwa über die Herabsetzung des kapillaren Eindringdruckes auswirken können. Die
Arbeit liefert einen wertvollen Einblick in Mechanismen, Systemeigenschaften sowie kritische Faktoren,
die für eine erfolgreiche Umsetzung einer CO2-gestützten Ölförderung und der CO2-Speicherung bzw. einer
Kombination beider Prozesse in nicht-konventionellen Gesteinsformationen relevant sindIn light of the ever-growing energy demand and the increasing atmospheric concentrations of carbon
dioxide, the necessity of finding a panacea to these global challenges is unprecedented. In spite of several
attempts to accelerate the energy transition, future outlooks indicate that fossil fuels will remain the
foundation that supports the livelihood and economic prosperity of global societies. Owing to the
declining rates of conventional oil production and the inevitable depletion of conventional reserves, it
is predicted that unconventional resources will play a significant role in reshaping future energy markets,
implying that the climate change dilemma associated with fossil fuels will linger on. On the other hand,
Carbon Capture and Storage (CCS) has emerged as a pathway to decarbonization, whereas enhanced oil
recovery using carbon dioxide (CO2-EOR) has already demonstrated great success in boosting oil
production of existing oil fields since the 1970s. Accordingly, the combination of CCS and CO2-EOR
is proposed as a solution to the energy-climate predicament. This approach is also being currently
considered in shales, however, little is still known about its applicability in these formations.
Accordingly, the current work aims to investigate a series of phenomena that contribute to oil recovery
from shale using supercritical CO2. Additionally, within the context of geological carbon storage (GCS),
several decisive interfacial and phase properties are examined, with the objective of combining the use
of CO2 for oil recovery with its own storage. Jordanian oil shale (Sultani) is used as an example in the
current work for the potential economic and environmental interest on the one hand, and for the acquired
knowledge that can be generalized and transferred to any oil-bearing unconventional reservoir on the
other. The presented work is a comprehensive experimental study on the principal phase, interfacial and
transport properties taking place when complex oil and water-bearing shale formations are contacted
with compressed CO2.
As an initial step in this investigation, Sultani shale is subject to supercritical fluid extraction using CO2
as solvent. The impact of several parameters on the yield, which is related to the solubility of various
compounds in the supercritical phase, is examined. Apart from the phase behavior that also includes
mixture densities, volumetric expansion and gas solubility in hydrocarbons, interfacial properties are
the principal focus of this work. Interfacial tension in binary and multicomponent systems at reservoir
conditions, i.e. at elevated pressures, is measured using the pendant drop and the rising bubble methods,
respectively. The contact angle, a measure of wettability, is determined using the sessile drop in CO2-
brine-shale systems. The captive bubble method is employed to assess the contact angle in the
multicomponent system comprising CO2, brine, oil and shale. Zeta potential is determined for “shale in
water/brine” suspensions to investigate the evolution of the charge at the water/brine-shale interface in
pursuit of explaining the wettability alteration in response to changing the aqueous phase composition.
With respect to the fluid-solid interface, the CO2 adsorption capacity of shale is measured at pressures
and temperatures relevant to gas storage using a gravimetric method, and its relation to the wetting
behavior in presence of brines representative of formation water is elucidated. Complementing the
interfacial properties and the phase behavior, CO2 diffusivity within shale formations is quantified. All
in all, it is found that the strong interactions of supercritical CO2 with all coexisting phases alter the
system properties significantly, mainly in an advantageous way regarding oil recovery. In terms of GCS,
supercritical CO2 is found to alter system properties in both favorable and unfavorable ways, depending
on the gas storage mechanism in question. The findings of the current work give valuable insight into
mechanisms, properties, and critical factors which are necessary for the design and implementation of
successful oil recovery and CO2 storage processe
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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