1,720,976 research outputs found
On the Measurement of the Lense-Thirring effect using the nodes of the LAGEOS satellites
No full textIn this paper, we provide a detailed description of our recent analysis and determination of the frame-dragging effect obtained using the nodes of the satellites LAGEOS and LAGEOS 2, in reply to the paper "On the reliability of the so-far performed tests for measuring the Lense-Thirring effect with the LAGEOS satellites" by L. Iorio (doi: 10.1016/j.newast.2005.01.001). First, we discuss the impact of the (J)over dot(2n) uncertainties on our measurement and we show that the corresponding error is of the order of 1% of frame-dragging only. We report the result of the orbital simulations and analyses obtained with and without (J)over dot(4) and with a 4 equal to its EIGEN-GRACE02S value plus 12 times its published error, i.e., a (J)ovr dot(4) equal to about 611% of the value adopted in EIGEN-GRACE02S, that is (J)over dot(4) = 6.11 x (-1.41 x 10(-11)) -8.61 x 10(-11). In all these three cases, by also fitting the final combined residuals with a quadratic, we obtain the same value of the measured Lense-Thirring effect. This value differs by only 1% with respect to our recent measurement of the Lense-Thirring effect. Therefore, the error due to the uncertainties in the (J)over dot(2n) in our measurement of the gravitomagnetic effect can at most reach 1%, in complete agreement with our previously published error budget. Our total error budget in the measurement of frame-dragging is about 5% of the Lense-Thirring effect, alternatively even by simply considering the published errors in the (J)over dot(2n) and their recent determinations we get a total error budget of the order of 10%, in complete agreement with our previously published error budget. Furthermore, weexplicitly give the results and plot of a simulation clearly showing that the claim of Iorio's paper that the (J)over dot(2n) uncertainty may contribute to up a 45% error error in our measurement is clearly unsubstantiated. We then present a rigorous proof that any "imprint" or "memory" effect of the Lense-Thirring effect is completely negligible on the even zonal harmonics produced using the GRACE satellites only and used on the orbits of the LAGEOS satellites to measure the frame-dragging effect. In this paper we do not discuss the problem of the correlation of the Earth's even zonal harmonics since it only refers to our previous, 1998, analysis with EGM96 and it will be the subject of a different paper; nevertheless, we stress that in the present analysis with EIGENGRACE02S the total error due to the static Earth gravity field has been calculated by pessimistically summing up the absolute values of the errors due to each Earth's even zonal harmonic uncertainty, i.e., we have not used any covariance matrix to calculate the total error but we have just considered the worst possible contribution of each even zonal harmonic uncertainty to the total error budget. We also present and explain our past work on the technique of measuring the Lense-Thirring effect using the LAGEOS nodes and give its main references. Finally we discuss some other minor points and misunderstandings of the paper by Iorio, including some obvious mistakes contained both in this paper and in some other previous papers of Iorio. In conclusion, the criticisms in Iorio's paper are completely unfounded and misdirected: the uncertainties arising from the possible variations of the (J)over dot(2n) are fully accounted for in the error budget that we have published. (C) 2005 Elsevier B.V. All rights reserve
Measuring the relativistic perigee advance with satellite laser ranging
No full textThe pericentric advance of a test body by a central mass is one of the classical tests of general relativity. Today, this effect is measured with radar ranging by the perihelion shift of Mercury and other planets, in the gravitational field of Sun, with a relative accuracy of the order of 10(-2)-10(-3). In this paper, we explore the possibility of a measurement of the pericentric advance in the I gravitational field of Earth by analysing the laser-ranged data of some orbiting, or proposed, laser-ranged geodetic satellites. Such a measurement of the perigee advance would place limits on hypothetical, very weak, Yukawa-type components of the gravitational interaction, with a finite range of the order of 104 km. Thus, we show that, at the I present level of knowledge of the orbital perturbations, the relative accuracy, achievable with suitably combined orbital elements of LAGEOS and LAGEOS II, is of the order of 10(-3). With the corresponding measured value of (2 + 2gamma - beta)/3, by using eta = 4beta - gamma - 3 from lunar laser ranging, we could get an estimate of the PPN parameters gamma and beta with an accuracy of the order of 10(-2)-10(-3). Nevertheless, these accuracies would be substantially improved in the near future with the new Earth gravity field models by the CRAMP and GRACE missions. The use of the perigee of LARES (LAser RElativity Satellite), with a suitable combination of orbital residuals including also the node and the perigee of LAGEOS II, would also further improve the accuracy of the proposed measurement
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
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
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
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