1,720,988 research outputs found
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
NMR Investigation of Water Molecular Dynamics in Sulfonated Polysulfone/Layered Double Hydroxide Composite Membranes for Proton Exchange Membrane Fuel Cells
No full textThe development of nanocomposite membranes based on hydrocarbon polymers is emerging as one of the most promising strategies for overcoming the performance, cost, and safety limitations of Nafion, which is the current benchmark in proton exchange membranes for fuel cell applications. Among the various nanocomposite membranes, those based on sulfonated polysulfone (sPSU) and Layered Double Hydroxides (LDHs) hold promise regarding their successful utilization in practical applications due to their interesting electrochemical performance. This study aims to elucidate the effect of LDH introduction on the internal arrangement of water molecules in the hydrophilic clusters of sPSU and on its proton transport properties. Swelling tests, NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation allowed us to demonstrate that LDH platelets act as physical crosslinkers between -SO3H groups of adjacent polymer chains. This increases dimensional stability while simultaneously creating continuous paths for proton conduction. This feature, combined with its impressive water retention capability, allows sPSU to yield a proton conductivity of ca. 4 mS cm−1 at 90 °C and 20% RH
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
Transport Properties in Polymer Nanocomposite Membranes Cataldo Simari
No full textDoctorate school of Science and Technique: Mesophases and Molecular Materials "Bernardino Telesio", Ciclo XXVIII, a.a. 2015--2016The aim of this thesis has been to prepare and characterize innovative composite
membranes for polymer electrolyte fuel cells (PEMFCs) applications. Among the
different energy conversion devices based on polymer electrolytes, PEMFCs, both
hydrogen (DHFC) and direct methanol (DMFC), seems to be one of the most promising
clean energy technologies. As electrochemical devices able to directly convert the
chemical energy of a fuel into electrical energy, PEMFCs offer interesting advantages in
vehicular or portable applications , as the quick start, the high energy conversion
efficiency (~ 50%), the reduced environmental impact for the low CO2 emissions (zero
in the case where the primary fuel is hydrogen) and the flexibility respect to the fuel, in
fact, besides hydrogen (DHFC), they can be fed for example with methanol (DMFC).
However, considerable efforts are still needed to be able to achieve satisfactory
performance in terms of efficiency, durability and cost for mass deployment of such
technology. It is necessary to deal with some problems that concern the electrolyte
membrane, such as the degradation of the materials, the low proton conductivity at low
relative humidity (RH) and poor mechanical properties at temperature higher than 130
°C.
Therefore, the development of high-performance proton conducting polymer electrolyte
membranes is critical for the optimal power density and efficiency a PEMFC can
achieve because membrane ohmic loss is the major cause of overpotential in the
operational current range of the fuel cell. In recent years, increasing interest has been
devoted to the development of high temperature proton conducting polymer
electrolyte fuel cell systems. In fact, most of the shortcomings associated with the lowtemperature
PEMFC technology based on perfluorosulfonic acid (PFSA) membranes
can be solved or avoided by developing alternative membranes with suitable ionic
conductivity and stability up to 150 °C. The increasing the operational temperature
would result in increased performance of the cell because of easier and more efficient
water management, higher reaction rates to the electrodes, improved CO tolerance by
the anode electro-catalysts, faster heat rejection rates and better systems integration. It has been mentioned the possibility to feed PEMFCs systems with other fuel respect to
hydrogen. In particular, direct methanol fuel cells (DMFCs) combine the merits of
polymer electrolyte fuel cells fueled by H2 with the advantages of a liquid fuel, such as
easy handling and high energy density. However, despite these advantages, also regard
this devices there are still technical barriers to overcome for their widespread
commercialization such as methanol crossover from anode to cathode through the
proton exchange membrane.
From the above, it is thus highly important to enhance the proton conductivity of the
electrolyte membrane under low RH in order to accomplish higher PEMFCs
performance. On the other hand, is essential to develop polymer electrolytes with
reduced methanol cross-over for DMFC.
The work presented in this thesis is the result of a Ph.D. project carried out during a
period of about three years from 2012 – 2015, in the Physical Chemistry Soft Matter
Laboratory “Mario Terenzi” (PC_SM Mario Terenzi) at the Department of Chemistry
and Chemical Technologies in the University of Calabria. The thesis was written as part
of the requirements for obtaining the doctor of philosophy degree.
The overall objective of this doctoral thesis was to design, synthesize and evaluate
innovative composite electrolytes with specific properties suitable for PEM fuel cells
that operate at high temperatures (above 100 ° C ) and low RH and/or with low
methanol permeability.
To this purpose, three main classes of materials have been explored as nanoadditives to
create nanocomposite membranes: (i) organo-modified TiO2 nanoparticles, (ii) layered
materials based on clays (anionic and cationic) and graphene oxide and (iii) hybrids
clays-carbon nanotubes. While, as concern the ionomers, perfluorosulfonic acid
(Nafion®) and polyaromatic polymers (sulfonated Polyether Ether Ketone and
Polybenzimidazole) have been evaluated.
In my doctoral porject an attempt was made to conjugate an intense basic research in
order to understand the molecular mechanisms at the basis of ionic conduction in such
complex systems, and the design, synthesis and more comprehensive characterization of
new nanocomposites with opportune requisites. For this purpose an deep study of the
transport properties of the water confined within the electrolyte membranes has been
performed by NMR spectrocopy (diffusometry, relaxometry and 1H spectral analysis) together to a wide physico-chemical, mechanical and electrochemical characterization
in order to achieve a systematic understanding at a fundamental level of the effects of
dimensionality, architecture and organization of these nanofillers on the properties of
the ionomers and to exploit this knowledge for the preparation of high performance
electrolytes.
Some of the electrolytes membranes investigated during my PhD thesis were prepared
and studied in the framework of the PRIN Project: NAMED-PEM “Advanced
nanocomposite membranes and innovative electrocatalysts for durable polymer
electrolyte membrane fuel cells”.
The last part of this thesis concerns a research work arisen from a collaboration with
ITM-CNR of the University of Calabria, on the Ion Exchange Membranes for Reverse
Electrodialysis (RED) process. Here, the NMR techniques were used to study the water
dynamics in anion- and cation- exchange membranes (AEMs and CEMs) in order to
achieved additional important insights about the effect of the electrolyte solution, on
membrane microstructure and its transport and electrical properties.
The results of this research have been published in scientific international Journals and
reported in appendix to the end of the thesis.
During these years I have spent two stages periods abroad:
1) in the “Department of Materials Science and Engineering of the University of
Ioannina, Ioannina (Greece)”, where I worked under the supervision of Prof. D.
Gournis, my research has been focused on the synthesis of novel carbon-based materials
as additives for nanocomposite membranes;
2) in Department of Physics & Astronomy of the Hunter College, New York (USA),
where I worked under the supervision of Prof. S. Greenbaumn, I performed the High
Pressure NMR investigation of water and methanol transport properties in sPEEK-based
nanocomposite electrolytes.
Two scientific papers, based on the results obtained during these stages, have been
recently submitted and also reported in appendixUniversity of Calabri
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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