1,721,563 research outputs found
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
Non-permanent GPS data for regional-scale kinematics: Reliable deformation rate before the 6 April, 2009, earthquake in the l' Aquila area
No full textA GPS-based geodetic study at a regional scale requires the availability of
a dense network that is characterized by 10 km to 30 km spacing, typically
followed in a few continuous GPS stations (CGPSs) and several non-
permanent GPS stations (NPSs). As short observation times do not allow
adequate noise modeling, NPS data need specific processing where the
main differences between NPSs and CGPSs are taken into account:
primarily time-series length and antenna repositioning error. The GPS
data collected in the 1999-2007 time-span from non-permanent
measurement campaigns in the central Apennine area (Italy) that was
recently hit by the Mw 6.3 L'Aquila earthquake (April 6, 2009) are here
further analyzed to compute a reliable strain-rate field at a regional scale.
Moreover, areas characterized by different kinematics are recognized, and
a complete characterization of the regional-scale kinematics is attempted.
These new data can be interpreted as indicators from the viewpoint of
seismic risk assessment
Analyzing virtual reference station for gps surveying: Experiments and applications in a test site of the northern Apennines (Italy)
No full textThe availability of a GPS network of 10-20 km mean size, provides good topographical support for the measurement of ground displacements, even at a local scale such as a landslide. In particular, a series of multitemporal kinematic or rapid-static GPS acquisitions of a landslide allows a good characterization of its displacements if the measurements are referred to a GPS reference network. Nevertheless, a wider network formed by stations located at long distances, for example at several tens of kilometers, characterized by large spacing, can lead to results affected by high noise, degrading the accuracy of final point positions. In order to obtain an adequate GPS reference network, some virtual reference stations (VRSs) can be introduced, even if a network refinement based on VRS cannot reach the same accuracy of a real local network. Some experiments, including measurements on a real landslide, have been performed in order to evaluate the performance of this technique. The results point out that the standard deviation of the obtained solutions is about two or three times larger than those which can be reached using a real local network
Design and submission of rad-tolerant circuits for future front-end electronics at S-LHC
No full textThis work is aimed at defining the architecture of a new digital ASIC, namely Slow Control Architecture (SCA), which will be designed and fabricated in a commercial 130 nm CMOS technology. This chip will be embedded within a high-speed data acquisition optical link (GBT) to control and monitor the front-end electronics proposed for future high-energy physics experiments at the Super-Large Hadron Collider (SLHC), CERN, Geneva. The GBT link provides a transparent transport layer between the SCA and the control electronics in the counting room. It will be provided with rad-hard redundant logic for critical circuits. The project follows a set of designs that were recently developed via a 250 nm CMOS technology for LHC experiments. Since this 250 nm specific technology used to design ASICs for the LHC will no longer be available as it was in the past, requesting an update technology for future experiments must be satisfied in any case. A test chip that implements three different redundant methodologies against single event effects is also described
GPS-based monitoring of land subsidence in the Po Plain (Northern Italy)
No full textWe use regional and local networks of continuously-operating GPS stations (CGPS) distributed in the northern-central part of the Italian peninsula to investigate the subsidence phenomenon of the Po plain sedimentary basin and vertical movements of the surrounding areas. The observations of 146 scientific and commercial stations are analyzed and compared, adopting analytical techniques widely used to study GPS coordinate time series. The use of simple antenna supports in commercial installations, instead of a more rigorous geodetic monument, does not seem to induce significant differences in the noise characteristics and in the amplitudes of annual and semi – annual periodic signals.
The vertical velocity field deduced from 129 sites with observation time spans greater than one year, located in the Central–Northern Italian Peninsula, indicates the presence of two mainly subsidence areas: the Po Plain and the Arno Plain, while the sites located in the Alps and Apennine domains show relatively low uplift.
The areas of the Po Plain monitored by GPS seem to indicate that the subsidence rate is constant or, in some cases, decreasing with respect to the values obtained from the last measurements, performed up to 2006 by means of both SAR and leveling techniques. Only the central part of the eastern Po Plain close to the Apennine border (Modena city area) is characterized by a peak in subsidence consisting in a velocity of about 15 mm/yr
Valutazione di differenti quadripoli e sequenze di misura per tomografie elettriche in contesti industriali e costieri
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