1,320 research outputs found
Installation and configuration of an ionospheric scintillation monitoring station based on GNSS SDR receivers in Brazil
No full textThe use of Global Navigation Satellite Systems (GNSSs) is nowadays very popular, and the positioning service that they provide is becoming the basis of several applications. Due to their wide coverage, GNSS signals can be used at no cost as probing signals to retrieve parameters to characterize the atmosphere, such as ionospheric scintillation indexes. GNSS receivers coupled to the specific algorithm are indeed a valid alternative to large and expensive ad hoc equipment such as ionosondes. In particular, Software Defined Radio (SDR) receivers are characterized by a higher level of flexibility and configurability when compared to commercial receivers, which fits for the purposes of ionospheric monitoring and enable the study of advanced and innovative algorithms, both for scientific purposes (ionospheric monitoring, space weather), and for technological development (robust GNSS receivers design). A GNSS-based ionosphere monitoring station, including an SDR-based receiver and a professional receiver, was installed in the CRAAM laboratory at Mackenzie Presbyterian University (São Paulo, Brazil) on May 2017. Details of the installation and the new approaches for the storage, processing, and transfer of GNSS data, including raw Intermediate Frequency (IF) samples, are described, along with preliminary results related to ionospheric events captured during the first months of its operation
Investigation into the Space Weather Event of September 2017 through GNSS Raw Samples Processing
No full textGlobal Navigation Satellite System (GNSS) positioning quality, continuity and reliability can be severely impaired by ionospheric propagation, in particular during strong space weather events. Ionospheric amplitude and phase scintillation cause power fading and random phase fluctuations of the received signal, leading to a reduced performance of the receiver tracking loops. This can translate into significant errors in the final position solution, especially when higher accuracy is concerned. In the period between 4 and 10 September 2017, several space weather events, including two coronal mass ejections, triggered disturbed conditions of the near-Earth space. This interval was considered one of the most flare-productive of now-waning solar cycle. Significant disturbances on GPS L1 signals have been observed and automatically recorded by a network of GNSS monitoring stations based on customized Software Defined Radio data grabbers and receivers. Relevant and highly unique raw samples are being processed to deeply investigate the phenomenon. The analysis of the data collected in different stations, in terms of scintillation indices time-series, shows a connection between the recording in the different locations of the world. In addition, the impact of such a strong event in receiver has been analyzed, focusing on positioning algorithms employing phase measurements to smooth code measurements. Results show a good correlation between the values of the scintillation indices and the positioning error, showing that carrier-smoothing techniques are particularly sensitive to distortion induced by phase scintillation. Such an impact is automatically observed by means of the identification of clusters in the positioning solutions through a machine learning algorithm. The adoption of carrier smoothing hence reveals weaknesses in precise positioning during scintillations events. At the same time, a novel scintillation detection technique based on clustering of the position solution is suggested
Ingrid Ylva och tornet i Bjälbo
No full textThe article discusses the background to the erection of the huge church tower in Bjälbo, Östergötland, Sweden. It also focuses on medieval women as founders of churches. The author maintains that new dendrochronological dating of the tower could mean that founder of this building piece was not one of the male members of the important Bjälbo dynasty, but Ingrid Ylva the mother of Birger Jarl
Installation and configuration of an Ionospheric Scintillation Monitoring Station based on GNSS receivers in Antarctica
No full textGlobal Navigation Satellite Systems (GNSSs), such as the US Global Positioning System (GPS), The
Russian GLONASS or the European Galileo, are space-based navigation systems. GNSSs enable a generic
user located anywhere on the Earth to determine in real time his Position, Velocity and Time (PVT), by
means of a Radio Frequency (RF) electro-magnetic signal, the Signal-In-Space (SIS), transmitted by a
constellation of satellites orbiting around Earth.
Uninterrupted Positioning, Navigation, and Timing (PNT) solution is determined by GNSS receivers,
which continuously process the SIS from the satellites in view. GNSS receivers are part of the GNSSs
ground segment. They are a suboptimal implementation of a maximum likelihood estimator of the SIS
propagation time. The PNT solution is indeed based on the computation of the SIS Time Of Arrival (TOA),
according to the satellite and receiver local clocks. This is achieved thanks to the presence of a different
Pseudo Random Noise (PRN) spreading code in the modulated SIS broadcast by each satellite. In the GNSS
receiver, the incoming signal is correlated with a local replica of signal code, obtaining the time difference
information. The time difference is then transformed into a range information by multiplying it by the speed
of light in the vacuum. However, since the receiver clock is not synchronized with the transmitters clock, this
measure suffers of time bias, which is considered as an additional unknown in the navigation solution.
Finally, the user position is determined on an Earth centred reference system with a process denoted
trilateration, by exploiting the range information computed by the receiver and the information contained in
the SIS navigation message, such as satellite ephemeris [Kaplan et al., 2005].Published1-252A. Fisica dell'alta atmosferaN/A or not JC
Ingrid Winterbach: Novelist (Interview)
No full textWinner of the prestigious Hertzog Prize for Literature for Niggie (2002)Ingrid Winterbach is the author of eight novels, three of which have been translated into English and two into Dutch. The translation of her fourth novel, Karolina Ferreira (1993) as The Elusive Moth (2005), and subsequently, Niggie as To Hell with Cronjé (2007) and Die boek van toeval en toeverlaat (2006) as The Book of Happenstance (2008), have brought this author to the attention of a wider South African readership
An upper bound on the rate of strain in the Central Apennines, Italy, from triangulation measurements between 1869 and 1963
No full textItaly is covered by a first-order triangulation network that was established between 1869 and 1908 and re-measured in patches between 1936 and 1963. We analyse the measurements made in the central part of Italy to form an estimate of the rate of strain in the Central Apennines. We conclude that the rate of strain in this region is too small to detect from the repeated triangulation measurements. This result places an upper bound of about 10-7/yr on the strain rate of the Central Apennines, and implies that the maximum rate of extension across the region is no higher than about 3 mm/yr
7. When They Left
No full textFigure 7.1 The author, Ingrid Griffith (right) with her sister Dawn (left) and brother Oliver (center) in December 1968. Their maternal grandmother had taken them to Skevelair’s Photo Studio in Georgetown, Guyana to pose in the church outfits their parents, who had recently migrated to the United States, had sent for Christmas. © Griffith Family Collection. Courtesy of Ingrid Griffith. CC BY 4.0. It was one of the worst days of my life. I was seven years old, my sist..
270 - Ingrid Jane Slette
No full textGlobal climate change is causing more extreme droughts, as well as subtler chronic changes in precipitation patterns. Both chronic and extreme precipitation change can alter ecosystem structure and function, and these alterations may affect how systems respond to future extreme climatic events. Understanding how legacies of various past precipitation changes may alter the effects of future extreme droughts will be important for predicting ecosystem responses to climate change. We investigated how ecological legacies of experimentally-imposed chronic and extreme precipitation changes altered the impact of an extreme drought on an economically-important grassland ecosystem.Top Scholars for University-Wide Graduate Programs
Funktionelle Analyse von potententiell aktivierenden FGFR3 Mutationen
No full textAuthor Ingrid Hartl, MScAbweichender Titel laut Übersetzung der Verfasserin/des VerfassersDissertation Johannes Kepler Universität Linz 2022Arbeit nach Ablauf der Sperre auf den öffentlichen PCs in den Bibliotheken der JKU+Medizin abrufba
Resensies: Vlam in die sneeu. Die liefdesbriewe van André P. Brink en Ingrid Jonker
No full textBook Title: Vlam in die sneeu. Die liefdesbriewe van André P. Brink en Ingrid JonkerBook Author: Francis Galloway (red.)Kaapstad: Umuzi, 2015. 450 pp. ISBN: 978-1-4152-0881-6. Spesiale uitgawe ISBN: 978-1-4152-0893-9
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