838 research outputs found
The statistics of the photometric accuracy based on MASS data and the evaluation of high-altitude wind
The effect of stellar scintillation on the accuracy of photometric
measurements is analyzed. We obtain a convenient form of estimaton of this
effect in the long exposure regime, when the turbulence shift produced by the
wind is much larger than the aperture of the telescope. A simple method is
proposed to determine index introduced by perture of the Kenyon et al.
(2006), directly from the measurements with the Multi Aperture Scintillation
Sensor (MASS) without information on vertical profile of the wind. The
statistics resulting from our campaign of 2005 -- 2007 at Maidanak
observatory is presented. It is shown that these data can be used to estimate
high-altitude winds at pressure level 70 -- 100 mbar. Comparison with the wind
speed retrieved from the NCEP/NCAR global models shows a good agreement. Some
prospects for retrieval of the wind speed profile from the MASS measurements
are outlined.Comment: 11 pages, 9 figures, accepted for publication in Astronomy Letter
Comparison of the scintillation noise above different observatories measured with MASS instruments
Scintillation noise is a major limitation of ground base photometric
precision. An extensive dataset of stellar scintillation collected at 11
astronomical sites world-wide with MASS instruments was used to estimate the
scintillation noise of large telescopes in the case of fast photometry and
traditional long-exposure regime. Statistical distributions of the
corresponding parameters are given. The scintillation noise is mostly
determined by turbulence and wind in the upper atmosphere and comparable at all
sites, with slightly smaller values at Mauna Kea and largest noise at Tolonchar
in Chile. We show that the classical Young's formula under-estimates the
scintillation noise.The temporal variations of the scintillation noise are also
similar at all sites, showing short-term variability at time scales of 1 -- 2
hours and slower variations, including marked seasonal trends (stronger
scintillation and less clear sky during local winter). Some correlation was
found between nearby observatories.Comment: Accepted for publication in Astronomy and Astrophysics, 14 pages, 11
figure
Accurate seeing measurements with MASS and DIMM
Astronomical seeing is quantified by a single parameter, turbulence integral,
in the framework of the Kolmogorov turbulence model. This parameter can be
routinely measured by a Differential Image Motion Monitor, DIMM. A new
instrument, Multi-Aperture Scintillation Sensor (MASS), permits to measure the
seeing in the free atmosphere above ~0.5km and, together with a DIMM, to
estimate the ground-layer seeing. The absolute accuracy of both methods is
studied here using analytical theory, numerical simulation, and experiments. A
modification of the MASS data processing to compensate for partially saturated
scintillation is developed. We find that the DIMM can be severely biased by
optical aberrations (e.g. defocus) and propagation. Seeing measurements with
DIMM and MASS can reach absolute accuracy of ~10% when their biases are
carefully controlled. Pushing this limit to 1% appears unrealistic because the
seeing itself is just a model-dependent parameter of a non-stationary random
process.Comment: 13 pages, 14 figures. Accepted for publication in MNRA
Building extraction from satellite imagery using a digital surface model
In this paper, two approaches to building extraction from satellite imagery and height data obtained from stereo images or LIDAR are compared. The first approach consists of detecting high-rise objects in a digital surface model and then improving recognition accuracy using segmentation of spectral information. The second approach uses the U-Net convolutional neural network, which showed the best results for the extraction of objects from aerospace images on a number of large datasets. Extensive experiments were carried out to evaluate the dependence of the quality of U-Net-based building extraction on the different data types (including high-resolution satellite images and digital surface model data). Building extraction quality of the trained network was also evaluated on satellite images with different spatial resolutions. © 2018 CEUR-WS. All rights reserved
Comprehensive evaluation of combined pharmacotherapy of cardiac pathology considering exogenous and pharmacogenetic factors
The study assessed changes in hemodynamic and biochemical parameters, vascular age and 5-year cardiovascular risk on the background of complex pharmacotherapy in patients with stable angina I-III functional class (FC), hypertension of I-III degree, chronic heart failure (CHF) II-III FC taking into account the influence of exogenous and pharmacogenetic factor
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