1,721,032 research outputs found
sj-docx-1-smo-10.1177_20503121221146729 – Supplemental material for Obesity and associated factors among high school adolescent students in Bahir Dar town, North West Ethiopia: A cross-sectional study
No full textSupplemental material, sj-docx-1-smo-10.1177_20503121221146729 for Obesity and associated factors among high school adolescent students in Bahir Dar town, North West Ethiopia: A cross-sectional study by Woldeamilak Adamu Hunegnaw, Addisu Gasheneit Ferede, Tiwabwork Tekalign and Abiyot Wolie Asres in SAGE Open Medicine</p
Geoid determination over Ethiopia with emphasis on downward continuation of gravity anomailes
No full textAnalysis of the Accuracy of GMF, NMF, and VMF1 Mapping Functions with GPT 50 a Priori Zenith Constraint in Tropospheric Delay Modelling
Get PDFThis paper compares the accuracy of the different mapping. Global Mapping Function (GMF), Niell Mapping Function (NMF) and Updated Vienna Mapping Function (VMF1), the update of Vienna Mapping Function (VMF) are the mapping functions studied.When modelling the tropospheric delay in Global Positioning System (GPS), the zenith delay is mapped to the slant with numerous mapping functions. The accuracy of the modelled tropospheric delay will be affected by the kind of mapping function used. Fixing the a priori zenith constraint as Global Temperature Pressure Humidity 50 (GPT 50), this paper compares the accuracy of the different mapping. Global Mapping Function (GMF), Niell Mapping
Function (NMF) and Updated Vienna Mapping Function (VMF1), the update of Vienna
Mapping Function (VMF) are the mapping functions studied. All these are used with the
saastamoinen tropospheric delay model which is used in the GPS Analysis Software for the
Massachusetts Institute of Technology software (GAMIT_GLOBK). For the north and east offsets these mapping functions achieved the same accuracy and can therefore be used interchangeably in modelling of the tropospheric delay effect in the planner. However, for the up offsets VMF1 achieved better accuracy compared to GMF and NMF however, being more consistent with GMF than NMF. In the future, if more mapping functions are incorporated in
GAMIT_GLOBK, the accuracy of these new mapping functions should be investigated and use another a priori zenith constraint – meteorological data, which will improve positioning using
Global Navigation Satellite System (GNSS)
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
Absolute geopotential height system for Ethiopia
Get PDFThis study used airborne gravity data, the 2008 Earth Gravity Model (EGM08) and Shuttle
Radar Topographic Mission (SRTM) digital elevation data in a ‘Remove-Compute-Restore’
process to determine absolute vertical reference system for Ethiopia. This gives a
geopotential height at any isolated field point where there is a Global Navigation Satellite
System (GNSS) measurement without reference to a vertical network or a regional datum
point. Previously, height was determined conventionally by connecting the desired field
point physically to a nearby bench mark of a vertical network using co-located
measurements of gravity and spirit levelling. With the use of precise GNSS positioning and a
gravity model this method becomes obsolesce.
The new approach uses the ‘Remove-Restore’ process to eliminate longer to shorter
wavelengths from the measured gravity data using EGM08 and geometrical and condensed
gravity models of the SRTM data. This provides small, smooth and localised residuals so
that the interpolation and integration involved is reliable and the Stokes-like integral can be
legitimately restricted to a spherical cap. A very fast, stable and accurate computational
algorithm has been formulated by combining ‘hedgehog’ and ‘multipoint’ models in order to
make tractable an unavoidably huge computational task required to remove the effects of
about 1.5 billion! SRTM topographic mass elements representing Ethiopia and its immediate
surroundings at 92433 point airborne gravity observations.
The compute stage first uses an iterative Fast Fourier Transform (FFT) to predict
residual gravity at aircraft height as a regular grid on to the surface of the ellipsoidal Earth
and then it used a Fourier operation equivalent to Stokes’ integral to transform the localised
gravity disturbance to residual potential. The restore process determines the geopotential
number on or above the Earth’s surface where practitioners need it by restoring the potential
effects of the removed masses. The accuracy of the geopotential number computed from
gravity and topography was evaluated by comparing it with the one derived directly from
EGM08 and precise geodetic levelling. The new model is in a good agreement across 100
km baseline with a standard deviation of 56 10−2 2 −2 × m s and 39 10−2 2 −2 × m s relative to
EGM08 and levelling, respectively ( 10−2 2 −2 m s is approximately equivalent to 1mm of
height). The new method provides an absolute geopotential height of a point on or above the
Earth’s surface in a global sense by interpolating from geopotential models prepared as the
digital grids carried in a chip for use with the GNSS receiver in the field
GNSS related periodic signals in coordinate time-series from Precise Point Positioning
Get PDFpeer reviewedIn Global Navigation Satellite System (GNSS) coordinate time series unrecognised errors and
un-modelled (periodic) effects may bias non-linear motions induced by geophysical signals.
Hence, understanding and mitigating these errors is vital to reducing biases and on revealing
subtle geophysical signals. To assess the nature of periodic signals in coordinate time series
Precise Point Positioning (PPP) solutions for the period 2008 to 2015 are generated. The solu-
tions consider Global Positioning System (GPS), GLObalnaya NAvigatsionnaya Sputnikovaya
Sistema (GLONASS) or combined GPS+GLONASS (GNSS) observations. We assess the pe-
riodic signals of station coordinates computed using the combined International GNSS Service
(IGS) and four of its Analysis Centers (ACs) products. Furthermore, we make use of different
filtering methods to investigate the sources of the periodic signals. A faint fortnightly signal
in our PPP solution based on Jet Propulsion Laboratory (JPL) products and the existence of
an 8-day period for those ACs generating combined GPS+GLONASS products are the main
features in the GPS-only solutions. The existence of the 8-day period in the GPS-only solution
indicates that GPS orbits computed in a combined GNSS solution contain GLONASS-specific
signals. The GLONASS-only solution shows highly elevated powers at the 3rd draconitic harmonic ( ~ 120-day period), at the 8-day period and its harmonics (4 days, 2.67 days) besides the
well-known annual, semi-annual and other draconitic harmonics. We show that the GLONASS
constellation gaps before December 2011 contribute to the power at some of the frequencies.
However, the well known fortnightly signal in GPS-only solutions is not discernible in the
GLONASS-only solution. The combined GNSS solution contains periodic signals from both
systems, with most of the powers being reduced when compared to the single-GNSS solutions.
A 52% reduction for the horizontal components and a 36% reduction for the vertical compo-
nent are achieved for the fortnightly signal from the GNSS solution compared to the GPS-only
solution. Comparing the results of the employed filtering methods reveals that the source of
most of the powers of draconitic and fortnightly signals are satellite-induced with a non-zero
contribution of site-specific errors
Assessment of BLT Tide Gauge Benchmark Monitoring (TIGA) repro2 solutions
Get PDFIn 2013 the International GNSS Service (IGS) Tide Gauge Benchmark Monitoring (TIGA) Working Group (WG) started their reprocessing campaign, which proposes to re-analyze all relevant Global Positioning System (GPS) observations from 1994 to 2013. This re-processed dataset will provide high quality estimates of land motions, enabling regional and global high-precision geophysical/geodetic studies.
Several of the individual TIGA Analysis Centres (TACs) have completed processing the full history of GPS observations recorded by the IGS global network, as well as, many other GPS stations at or close to
tide gauges, which are available from the TIGA data centre at the University of La Rochelle (www.sonel.org). Following the recent improvements in processing models and strategies, this is the first complete
reprocessing attempt by the BLT TIGA Analysis centre to provide homogeneous position time series. We report the quality of the multi-year daily solutions from the consortium of the British Isles continuous GNSS Facility (BIGF) and the University of Luxembourg TIGA Analysis Centres (BLT) based on the Bernese GNSS Software Version 5.2 using a double difference (DD) network processing strategy
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