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Correlations among acoustic measurements of the Boltzmann constant
Get PDFWe review correlated uncertainties among the accurate determinations of the Boltzmann
constant kB that used the techniques of primary acoustic gas thermometry (AGT). We find
correlated uncertainty contributions from four sources: (1) the uncertain chemical and isotopic
compositions of the test gases that lead to an uncertain average molar mass, (2) measurements
of the temperature, (3) measurements of the shape and dimensions of the cavity resonators,
and (4) fitting acoustic resonance frequencies as a function of the pressure. Molar-massdependent
uncertainties are correlated among those measurements that used argon with
isotopic abundances determined using an isotopic standard prepared at the Korea Research
Institute of Standards and Science in 2006. Correlated, cavity-dependent uncertainties result
from using the same cavity for more than one measurement. Small, correlated uncertainties
propagate into all the AGT determinations of kB when acoustic resonance frequencies
are fit for kB using uncertain literature data for the Avogadro constant and for the thermal
conductivity and the higher acoustic virial coefficients of helium or argon
Towards an electromagnetic pressure standard: dielectric permittivity of helium and argon measured with quasi-spherical microwave resonators and cross capacitors
No full textTo develop electrically based pressure standards, we
measured the dielectric permittivity of helium εHe(p,T) and
argon εAr(p,T) using two independent techniques (quasispherical
microwave cavities and cross capacitors). At
7 MPa, the microwave results for helium differ from
NIST’s pressure standards by (18±37)×10−6
Progress towards a primary pressure standard based on the dielectric permittivity of helium
No full textAcoustic Gas Thermometry
No full textWe review the principles, techniques and results from primary acoustic gas thermometry
(AGT). Since the establishment of ITS-90, the International Temperature Scale of 1990,
spherical and quasi-spherical cavity resonators have been used to realize primary AGT in the
temperature range 7K to 552 K. Throughout the sub-range 90K < T < 384 K, at least two
laboratories measured (T − T90). (Here T is the thermodynamic temperature and T90 is the
temperature on ITS-90.) With a minor exception, the resulting values of (T −T90) are mutually
consistent within 3 × 10−6 T . These consistent measurements were obtained using helium and
argon as thermometric gases inside cavities that had radii ranging from 40mm to 90mm and
that had walls made of copper or aluminium or stainless steel. The AGT values of (T − T90)
fall on a smooth curve that is outside ±u(T90), the estimated uncertainty of T90. Thus, the
AGT results imply that ITS-90 has errors that could be reduced in a future temperature scale.
Recently developed techniques imply that low-uncertainty AGT can be realized at
temperatures up to 1350K or higher and also at temperatures in the liquid-helium range
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
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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