959 research outputs found
MicroRadarNet: a Network of Weather Micro Radars for the Estimation of Local High-Resolution Precipitation Pattern and Rainfall Amount
Free Fermionic Heterotic Model Building and Root Systems
We consider an alternative derivation of the GSO Projection in the free
fermionic construction of the weakly coupled heterotic string in terms of root
systems, as well as the interpretation of the GSO Projection in this picture.
We then present an algorithm to systematically and efficiently generate input
sets (i.e. basis vectors) in order to study Landscape statistics with minimal
computational cost. For example, the improvement at order 6 is approximately
10^{-13} over a traditional brute force approach, and improvement increases
with order. We then consider an example of statistics on a relatively simple
class of models.Comment: Standard Latex, 12 page
MicroRadarNet: a Network of Weather Micro Radars for the Estimation of Local High-Resolution Precipitation Pattern and Rainfall Amount
On the polarimetric backscatter by a still or quasi-still wind turbine
Wind turbines negatively affect the performance of weather radars, especially when located in the proximity of a radar site. In March 2019, MeteoSwiss performed a measurement campaign by deploying a mobile X-band radar in Schaffhausen. It proved to be useful for mapping and characterizing
the maximum power returns by three wind turbines observed using standard
scanning strategies. In March 2020, the campaign was repeated using a
more sophisticated scan strategy: ∼ 100 min special
sessions of fixed pointing an antenna towards the nacelle of the closest wind
turbine (WT) located within a range of 7766 m from the radar, interleaved every
2 h by a scanning protocol identical to that of the March 2019 campaign.
Polarimetric radar signatures were derived every 64 ms using 128 radar pulses transmitted every 0.5 ms (pulse repetition frequency (PRF) = 2000 Hz). A thorough overview of the polarimetric signatures of the WT in still or quasi-still conditions has
been obtained based on 30 000 polarimetric measurables acquired
over 32 min on the first day of the campaign (4 March 2020). During
the first 2 min with zero rotor speed, the co-polar correlation
coefficient between the orthogonal polarization states, ρHV, was persistently equal to 1, similarly to the signature of a bright scatterer
observed by a non-rotating antenna. The changes between two consecutive
values of the differential reflectivity and radar reflectivity factor were
either 0 dBz or ±0.5 dBz. Due to the absence of precipitation, one
could assume that the standard deviation of the differential phase shift,
which was as small as 3.0∘, can be entirely attributed to the
variability of the differential backscattering phase shift. There were two
10 min periods during which the rotor moved less than 1 revolution. It
is worth noting that this slow movement could be associated with a change in
the blade pitch angle and the nacelle orientation, which caused extreme
changes in the radar reflectivity factor. For instance, two pairs of 64 ms
consecutive values reached 78.5 dBz, which is the absolute maximum
reached in the whole campaign (4–21 March 2020).</p
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