1,721,094 research outputs found
Renewed ground uplift at Campi Flegrei caldera (Italy): New insight on magmatic processes and forecast
No full textCampi Flegrei caldera, including the extremely
urbanised city of Naples, is the most risky volcanic area
in the World. The last eruption in the area (1538) occurred
at the end of some decades of ground uplift, superimposed
to secular subsidence. During the last four decades, it
experienced a huge uplift phase, reaching about 3.5 m in
1985, when a subsidence phase started. Recent geodetic
data demonstrate that such a subsidence phase has
terminated, and a new uplift episode started in November
2004, with a low but increasing rate leading to about 0.04 m
of uplift till the end of October 2006. A new indicator, based
on the monitoring of maximum horizontal to vertical
displacement ratio with continuous GPS, indicates that
this uplift is likely to be associated with input of magmatic
fluids from a shallow magma chamber. The method is
promising to monitor magma intrusion processes, at this and
other volcanoes. Citation: Troise, C., G. De Natale, F. Pingue,
F. Obrizzo, P. De Martino, U. Tammaro, and E. Boschi (2007),
Renewed ground uplift at Campi Flegrei caldera (Italy): New
insight on magmatic processes and forecast, Geophys. Res. Lett.,
34, L03301, doi:10.1029/2006GL028545
Ionospheric error analysis in GPS measurements
No full textThe results of an experiment aimed at evaluating the effects of the ionosphere on GPS positioning applications are presented in this paper. Specifically, the study, based upon a differential approach, was conducted utilizing GPS measurements acquired by various receivers located at increasing inter-distances. The experimental research was developed on the basis of two groups of baselines: the first group comprises «short» baselines (less than 10 km); the second group is characterized by greater distances (up to 90 km). The obtained results were compared either upon the basis of the geometric characteristics, for six different baseline lengths, using 24 hours of data, or upon temporal variations, by examining two periods of varying intensity in ionospheric activity respectively coinciding with the maximum of the 23 solar cycle and in conditions of low ionospheric activity. The analysis revealed variations in terms of inter-distance as well as different performances primarily owing to temporal modifications in the state of the ionosphere
Ionospheric Error Analysis in GPS Measurements
No full textThe results of an experiment aimed at evaluating the effects of the ionosphere on GPS positioning applications are presented in this paper. Specifically, the study, based upon a differential approach, was conducted utilizing GPS measurements acquired by various receivers located at increasing inter-distances. The experimental research was developed upon the basis of two groups of baselines: the first group is comprised of "short" baselines (less than 10 km); the second group is characterized by greater distances (up to 90 km). The obtained results were compared either upon the basis of the geometric characteristics, for six different baseline lengths, using 24 hours of data, or upon temporal variations, by examining two periods of varying intensity in ionospheric activity respectively coinciding with the maximum of the 23 solar cycle and in conditions of low ionospheric activity. The analysis revealed variations in terms of inter-distance as well as different performances primarily owing to temporal modifications in the state of the ionosphere
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
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