1,721,018 research outputs found
Remote sensing and electromagnetic modeling applied to weather and forward scatter radar
Full text linkThis dissertation deals with electromagnetic modelling and data analysis,
related to radar remote sensing and applied to forward scatter and meteorological
polarimetric systems. After an overview of radar fundamentals to
introduce the general terminology and concepts, results are presented at
the end of each chapter.
In this respect, a generalized electromagnetic model is first presented
in order to predict the response of forward scatter radars (FSRs) for airtarget
surveillance applications in both near-field and far-field regions.
The model is discussed for increasing levels of complexity: a simplified
near-field model, a near-field receiver model and a near-field receiver and
transmitter model. FSR results have been evaluated in terms of the effects
of different target electrical sizes and detection distances on the received
signal, as well as the impact of the trajectory of the moving objects and
compared with a customized implementation of a full-wave numerical
tool.
Secondly, a new data processing methodology, based on the statistical
analysis of ground-clutter echoes and aimed at investigating the monitoring
of the weather radar relative calibration, is presented. A preliminary
study for an improvement of the ground-clutter calibration technique is
formulated using as a permanent scatter analysis (PSA) and applied to
real radar scenarios. The weather radar relative calibration has been applied
to a dataset collected by a C-band weather radar in southern Italy
and an evaluation with statistical score indexes has drawn through the
comparison with a deterministic clutter map. The PSA technique has been
proposed using a big metallic roof with a periodic mesh grid structure and
having a hemispherical shape in the near-field of a polarimetric C-band
radar and evaluated also with an ad-hoc numerical implementation of a
full-wave solution.
Finally, a radar-based snowfall intensity retrieval is investigated at centimeter
and millimeter wavelengths (i.e., at X, Ka and W band) using a
high-quality database of collocated ground-based precipitation measurements
and radar multi-frequency observations. Coefficients for the multifrequency
radar snowfall intensity retrieval are empirically derived using
multivariate regression techniques and their interpretation is carried out
by particle scattering simulations with soft-ice spheroids.
For each topic, conclusions are proposed to highlight the goals of the
whole work and pave the way for future studies
Il DNA altamente ripetuto in Vicia faba: caratterizzazione, localizzazione citologica, comportamento durante la differenziazione cellulare
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Localizzazione cromosomica del DNA altamente ripetitivo in relazione alla struttura del nucleo interfasico nelle cellule vegetali
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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
Underrapresentation of nuclear DNA sequences in differentiating root cells of Vicia faba.
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