243 research outputs found
Anomalous attenuation of extraordinary waves in the ionosphere heating experiments
Multiple scattering of radio waves by artificial random irregularities
HF-induced in the ionosphere F region may cause significant attenuation of both
ordinary and extraordinary waves together with common anomalous absorption of
ordinary waves due to their non-linear conversion into plasma waves. To
demonstrate existence and strength of this effect, direct measurements of
attenuation of both powerful pump wave and weak probing waves of extraordinary
polarization have been carried out during an experimental campaign on September
6, 7 and 9, 1999 at the Sura heating facility. The attenuation magnitude of
extraordinary waves reaches of 1-10 dB over a background attenuation caused by
natural irregularities. It is interpreted in the paper on the base of the
theory of multiple scattering from the artificial random irregularities with
characteristic scale lengths of 0.1-1 km. Simple procedure for determining of
irregularity spectrum parameters from the measured attenuation of extraordinary
waves has been implemented and some conclusions about the artificial
irregularity formation have been obtained.Comment: 17 pages, 9 figure
The Radiation Transfer at a Layer of Magnetized Plasma With Random Irregularities
The problem of radio wave reflection from an optically thick plane monotonous
layer of magnetized plasma is considered at present work. The plasma electron
density irregularities are described by spatial spectrum of an arbitrary form.
The small-angle scattering approximation in the invariant ray coordinates is
suggested for analytical investigation of the radiation transfer equation. The
approximated solution describing spatial-and-angular distribution of radiation
reflected from a plasma layer has been obtained. The obtained solution has been
investigated numerically for the case of the ionospheric radio wave
propagation. Two effects are the consequence of multiple scattering: change of
the reflected signal intensity and anomalous refraction.Comment: 22 pages, 4 figure
Responsible Wastewater Management: Whiting Farm Wastewater System Design and Feasibility Analysis
On the implementation of some methods applied to optimization design problems
It is shown that in optimization problems arising during electronic circuit design constraints often may be represented as a direct product of some sets from different spaces which in general may have different dimensions. Taking into account this form of valid set makes it possible a decomposition of the optimization problem of large dimension. It is also shown that in man-machine decision support systems implemented on parallel computers it is possible to branch the optimization algorithm in order to reduce computing time. The efficiency of the approach is demonstrated by using a modification of gradient and subgradient projection methods for electronic circuit design
Ultrastructure of oocytes and female copulatory organs of Acoela
The ultrastructure of oocytes in four species of Acoela ( Archaphanostoma agile, Otocelis rubropunctata, Symsagittifera japonica, and Amphiscolops sp.) and that of female copulatory organs of S. japonica and Amphiscolops sp. are described for the first time. According to the similarity of the reproductive apparatus structure, the sister relationships between the families Sagittiferidae and Convolutidae are confirmed. The ultrastructure of oocytes and specific features of oogenesis are proposed to be useful in phylogenetics of Acoela
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