1,721,020 research outputs found
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
Fabrication of Boehmite Nanofiber Internally-Reinforced Resorcinol-Formaldehyde Macroporous Monoliths for Heat/Flame Protection
No full textBy
distributing boehmite nanofibers to a resorcinol-formaldehyde
(RF) skeletal phase formed by phase separation in an aqueous sol,
composite macroporous monoliths were produced by performing gelation,
aging, and drying processes at 60 °C. In the nanofiber-reinforced
structure, boehmite nanofiber is arranged in parallel within the RF
skeleton and showed high Young’s modulus against uniaxial compression
for their bulk density. These materials can be expected to be applied
to heat/flame protection materials using their heat insulating properties
and high flame resistance
Marshmallow-like Macroporous Silicone Monoliths as Reflective Standards and High Solar-Reflective Materials
No full textThe growing need to expand outdoor
remote sensing using
drones
and robots and to mitigate the urban heat island effect has led to
an increasing demand for highly reflective materials suitable for
outdoor use. I have successfully developed flexible macroporous silicone
monoliths that exhibit high diffuse reflectance due to Mie scattering
caused by the skeletal structure. The porous silicone materials were
prepared by a two-step acetic acid–triethanolamine catalyzed
surfactant-free sol–gel process using tetra-, tri-, and difunctional
silicon alkoxides as co-precursors. In the optimal sample, the material
exhibited a total reflectance of more than 97.5% in the 400–1100
nm wavelength. This range corresponds to the light detection range
of silicon diodes. The optical property suggests potential applications
for the silicone monoliths as simple optical calibration targets (reflective
standard), providing a viable alternative to conventional materials
such as porous polytetrafluoroethylene or barium sulfate. In addition,
high reflectance of the material surfaces across the solar spectrum
results in a significant reduction of increased surface temperature
when exposed to direct sunlight. With its combination of reflectivity,
water repellency, UV resistance, low thermal conductivity, and mid-infrared
radiation properties, the macroporous silicone monolith offers promising
potential for outdoor thermal management applications
Boehmite Nanofiber-Reinforced Resorcinol-Formaldehyde Macroporous Monoliths for Heat/Flame Protection
No full textBy distributing boehmite nanofibers (BNFs) to a resorcinol-formaldehyde (RF) skeletal phase formed by phase separation in an aqueous sol, composite macroporous monoliths have been produced. The nanofiber reinforced monoliths have a skeleton in which BNF is arranged in parallel within the RF structure, and showed high Young's modulus against uniaxial compression for their bulk density. These materials can be expected to be applied to heat/flame protection materials using heat insulating properties and high flame resistance.<br
Boehmite Nanofiber–Melamine–Formaldehyde Composite Aerogels and Derivatives for Thermal Insulation and Optical Applications
No full textMachinable composite aerogels combining melamine resin
and boehmite
nanofibers were successfully prepared by using a sol–gel reaction
in a mixed solvent of aqueous acetic acid and N,N-dimethylformamide. The composite aerogel exhibits
low thermal conductivity and surface processability, making it a potential
thermal insulating material for electronic substrates. Transparent
γ-alumina aerogels and black alumina–graphite aerogels
with a designed surface topography were also prepared through computer
numerical control (CNC) machining and calcination. These aerogels
with precise surface structures are expected to have applications
in fields such as optical materials
Pseudoboehmite Nanorod–Polymethylsilsesquioxane Monoliths Formed by Colloidal Gelation
No full textThe addition of a trifunctional silicon alkoxide methyltrimethoxysilane (MTMS) to aluminum oxide hydroxide pseudoboehmite nanorod (PBNR) aqueous dispersions resulted in adhesion between the PBNR colloids to form macroporous monoliths. The use of greater amounts of MTMS led to coarsening of the skeleton and strengthening of the skeletal structure, and the monoliths got water resistance. When a dispersion of zirconium oxide nanoparticles and MTMS was used as a starting material, a macroporous monolith was also obtained by the same simple process. The colloidal gelation occurs because the silanol moiety is more likely to react with the colloid surface of ceramic materials than with other silanols derived from MTMS and their oligomer. Due to the development of material chemistry, colloidal dispersions having various shapes and compositions are becoming available as products. Based on this mechanism, it is expected to be feasible to fabricate various porous monoliths with characteristic morphologies and properties depending on the colloid.<br
Boehmite Nanofibers as a Dispersant for Nanotubes in an Aqueous Sol
No full textBy exploiting the dispersibility and rigidity of boehmite nanofibers (BNFs) with a high aspect ratio of 4 nm in diameter and several micrometers in length, multiwall-carbon nanotubes (MWCNTs) were successfully dispersed in aqueous solutions. In these sols, the MWCNTs were dispersed at a ratio of about 5–8% relative to BNFs. Self-standing BNF–nanotube films were also obtained by filtering these dispersions and showing their functionality. These films can be expected to be applied to sensing materials
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
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