1,720,985 research outputs found
Preliminary Measurements of the Xenon Triple Point
No full textEver since the construction and definition of the highly successful International
Temperature Scale of 1990 (ITS-90), one severe deficiency of the scale has been recognized, without a reliable remedy. The problem is the fact that the only then
available high-quality fixed point between the argon triple point and the water triple
point was the mercury triple point, which unfortunately is situated rather closely to
the water triple point, thus having an extremely strong influence on the interpolation
function of SPRTs in the Ar−H2O range. Already before 1990, measurements on possible
fixed points better placed in this temperature range have been investigated, such
as the triple points of krypton and xenon. However, results have been rather elusive,
mainly regarding the rather large melting range of their transition. A turning point
was the 2005 paper from the National Research Council (NRC, Canada), where it
was established that the relatively high content of krypton was the culprit for the large melting range of the xenon transitions published previously. Indeed, measurements on a xenon sample with very low krypton content produced a very high-quality plateau,
of the same level as other ITS-90 fixed points. However, no follow-up measurements
have been reported, and thus neither have comparison measurements been reported.
Shortly, after the appearance of the NRC paper, Istituto Nazionale di Ricerca Metrologica (INRIM, Italy) acquired a batch of the same high-purity xenon as used by NRC
with the aim of preparing a few sealed cells with it and trying to reproduce the NRC
results. However, with the start of the Neon Project (Euromet Project 770), the realization of these intentions had to be postponed until now. Last December, three cells of different design have been filled with this high-quality xenon and preliminary results of the measurements on the triple point are reported
Realization of both the Triple Points of 20Ne and 22Ne in a Multicell
No full textIn an effort to further reduce the uncertainties in the triple point temperatures of 20Ne and 22Ne, already established in previous publications, at INRIM a cell for each of the two high purity isotopes was mounted on the same copper block and their triple points were realized subsequently one after the other, allowing a reduction of the total experimental uncertainty on their temperature difference due to a full correlation of some of the uncertainty components arising from this type of realization. The two meltings remain perfectly distinct and do not interfere with each other, being the temperature difference 0.147 K while the melting ranges are below 0.2 mK. The main difference with respect to single measurements (mounting a single cell at a time), lies in the adiabatic conditions during measurement, which are hardly reproducible when mounting a single cell at a time, leading to one of the dominant uncertainty contributions, 15 μK (single). In the present work, the uncertainty component due to the adiabatic conditions is reduced by using a measurement in sequence (mounting the two cells at a time), 1 μK. Thus, an improved reliability in the experimental realization is obtained as reflected in the experimental contributions to the uncertainty budget
Adjustments to the ICVGT Scale of INRIM
No full textAt the 8th Temperature Symposium the results have been presented for the Interpolating Constant Volume Gas thermometer at INRIM (then IMGC), featuring a cryogenic pressure transducer, with an expanded uncertainty of less then 1.5 mK. However, for its fixed points this scale still relied on a NPL calibration as carried by rhodium-iron thermometer 232324. After the clarification, in 2005, by the Consultative Committee on Thermometry (CCT) of the definition of the equilibrium hydrogen (e-H2) triple point this scale was due to be adjusted for the isotopic content in the e-H2 fixed point cell. Only when this thermometer was re-calibrated in 2010 at INRIM at the three fixed points of the ICVGT was this adjustment performed, being the isotopic composition of the hydrogen cell known. With the start of the Neon Project in 2005, it became clear that a second adjustment would soon be needed, once the CCT will have decided
on the way to deal with the isotopic composition of neon. The paper presents the experimental data of 2010, discusses the stability of the thermometer, and the size of the correction at the hydrogen point and of the likely correction (and its
uncertainty) to be applied to the neon point, the isotopic composition of this cell being known as well
An Accurate Determination of the Triple Point Temperature of Pure 20Ne and 22Ne
No full textThe paper reports on new determinations at INRIM and IRMM of the triple point temperature of pure neon isotopes 20Ne and 22Ne, obtained on samples sealed in cryogenic cells and measured with an uncertainty much lower than that of the previous literature data. The experimental technique is the same used at INRIM and IRMM for recent studies on neon of natural istopic composition, showing an expanded uncertainty of �30 µK for a single cell and 50 µK for the comparison of sample pairs.JRC.D.3 - Knowledge Transfer and Standards for Securit
Triple Point Temperature of Neon Isotopes: Dependence on Nitrogen Impurity and Sealed-Cell Model
No full textThis paper illustrates a study conducted at INRIM, to further check how some quantities influence the value of the triple point temperature of the neon high-purity isotopes 20Ne and 22Ne. The influence of nitrogen as a chemical impurity in neon is critical with regard to the present best total uncertainty achieved in the measurement of these triple
points, but only one determination is available in the literature. Checks are reported, performed on two different samples of 22Ne known to contain a N2 amount of 157·10^–6, using two different models of sealed cells. The model of the cell can, in principle, have some effects on the shape of the melting plateau or on the triple point temperature observed for the sample sealed in it. This can be due to cell thermal parameters, or because the INRIM cell element mod. c contains many copper wires closely packed, which can, in principle, constrain the interface and induce a premelting-like effect. The
reported results on a cell mod. Bter show no evident effect from the cell model and provide a value for the effect of N2 in Ne liquidus point of 8.6(1.9) microK ppm N2^
–1, only slightly different from the literature datum
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
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