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Observability and estimation of geocentre motion using multi-satellite laser ranging
Get PDFPhD ThesisArtificial satellites orbit about the Earth’s system centre of mass, a point known as the
geocentre that conventionally defines the long-term origin of the terrestrial reference frame
(TRF). In a frame attached to the Earth’s crust, the geocentre exhibits motions on subdaily
to secular time scales due to various geophysical processes. Annual variations induced
by the redistribution of fluid mass in the Earth’s surface layer are most prominent
and can bias ice mass balance and sea level change estimates if neglected. Theoretically,
these annual variations are directly observable by any satellite geodetic technique, but
orbit modelling complications affect the retrieval of geocentre motion from Global Navigation
Satellite Systems (GNSS) and Doppler Orbitography and Radiopositioning Integrated
by Satellite (DORIS) data. This study focuses on Satellite Laser Ranging (SLR),
the only technique proven to yield reliable geocentre motion estimates via translational
approaches.
By means of collinearity diagnosis applied to the determination of geocentre motion
using the network shift approach, it is shown that, subject to certain parameterisation constraints,
the low Earth orbiters (LEOs) Starlette, Ajisai and the Laser Relativity Satellite
(LARES) can beneficially supplement the traditionally employed pair Laser Geodynamics
Satellite (LAGEOS) 1 and 2. In particular, the combination of LAGEOS-1 and 2 with
LARES data can improve the observability of the geocentre coordinates by 25–30% on
average compared to LAGEOS–only solutions due to both the larger number of observations
and the proven higher sensitivity of LARES to geocentre motion. Tests involving
different satellite combinations show that the contribution of Stella is minor owing to its
quasi-polar orbit, whereas observations to the medium Earth orbiters (MEOs) Etalon-1
and 2 are too infrequently acquired to benefit the retrieval of geocentre motion and possibly
other parameters of geophysical interest. An analysis of SLR data spanning two
decades partitioned in weekly batches reveals that geocentre motion estimates derived
from LAGEOS–Starlette–Stella–Ajisai combinations are contaminated by modelling errors
to a larger extent than in LAGEOS–only solutions and, without considerable advances
in orbit modelling, the exploitation of the high sensitivity of Starlette and Ajisai to geocentre
motion appears remote. Compounded by the short tracking history of LARES, a
conclusive assessment of the long-term quality of LAGEOS–LARES solutions is infeasible
at present.
iv
Similar to other geodetic parameters, the geocentre coordinates exhibit temporal correlations
that have been typically neglected in previous studies. The power spectral
densities (PSDs) of weekly derived geocentre coordinates display a power-law behaviour
at long periods and white noise flattening for frequencies above 4 cycles per year (cpy).
When temporal dependencies are appropriately modelled using one of the readily available
maximum likelihood estimation (MLE) software implementations, the uncertainties
of the annual amplitude and phase estimates inflate by an average factor of 1.6 for weekly
time series over 12 years in length. The formal errors of the linear and quadratic trend
estimates amplify by a larger factor of 2.2–2.3. First-order autoregressive noise plus white
noise and power-law noise are the preferred stochastic models in most cases based on
model-selection criteria. As demonstrated through the analysis of independent time series,
for sampling periods longer than one week the first-order autoregressive model becomes
more competitive on its own due to the suppression of white noise at high frequencies,
but the power-law noise model is also occasionally preferred.
Kinematic estimates of geocentre coordinates are highly coherent with network shift
results across the entire frequency range only when station positions are simultaneously
solved for. Additionally, network shift estimates are more coherent with kinematic results
when the scale parameter is omitted from the functional model of the similarity transformation
linking the quasi-instantaneous frames and the secular frame. In addition to
draconitic errors related to solar radiation pressure modelling, long-period tidal aliases
due to mismodelled tidal constituents also contaminate geocentre motion estimates. Independent
geodetic estimates and geophysical model predictions validating the results from
this study agree that the annual geocentre motion signals have amplitudes of 2–3 mm in
the equatorial components and 4–6 mm in the Z component. The maximum geocentre
vector magnitude of about 7 mm is attained in July.partly funded by Newcastle University, the Dinu Patriciu Foundation
and the Romanian–American Foundation
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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