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1.
2.
The paper outlines the most important results of the paraxial complex geometrical optics (CGO) in respect to Gaussian beams
diffraction in the smooth inhomogeneous media and discusses interrelations between CGO and other asymptotic methods, which
reduce the problem of Gaussian beam diffraction to the solution of ordinary differential equations, namely: (i) Babich’s method,
which deals with the abridged parabolic equation and describes diffraction of the Gaussian beams; (ii) complex form of the
dynamic ray tracing method, which generalizes paraxial ray approximation on Gaussian beams and (iii) paraxial WKB approximation
by Pereverzev, which gives the results, quite close to those of Babich’s method. For Gaussian beams all the methods under
consideration lead to the similar ordinary differential equations, which are complex-valued nonlinear Riccati equation and
related system of complex-valued linear equations of paraxial ray approximation. It is pointed out that Babich’s method provides
diffraction substantiation both for the paraxial CGO and for complex-valued dynamic ray tracing method. It is emphasized also
that the latter two methods are conceptually equivalent to each other, operate with the equivalent equations and in fact are
twins, though they differ by names.
The paper illustrates abilities of the paraxial CGO method by two available analytical solutions: Gaussian beam diffraction
in the homogeneous and in the lens-like media, and by the numerical example: Gaussian beam reflection from a plane-layered
medium. 相似文献
3.
We present the second part of the results of our work to investigate the atmospheric parameters and chemical composition of
southern-hemisphere Cepheids obtained by analyzing 24 spectra for eight bright Cepheids and three semiregular bright supergiants
taken with the 1.9-m telescope of the South African Astronomical Observatory. The chemical composition and atmospheric parameters
have been determined for S Cru, AP Pup, AX Cir, S TrA, T Cru, R Mus, S Mus, U Car, V382 Car, HD 75276, and R Pup. 相似文献
4.
The mechanism of brightness outbursts of comets based on selective absorption of solar ultraviolet radiation by hydrogen atoms
in the cometary head is considered. Due to this process, influence of the radiation on parent and daughter molecules in the
near-nucleus region of the cometary head is different. As a result, under certain physical conditions in the cometary coma,
the electronic-temperature increase may cause an outburst in the brightness of the comet. 相似文献
5.
Kiev Polytechnic Institute. Translated from Astrofizika, Vol. 30, No. 1, pp. 208–219, January–February, 1989. 相似文献
6.
L. N. Berdnikov A. Yu. Kniazev V. V. Kravtsov E. N. Pastukhova D. G. Turner 《Astronomy Letters》2009,35(1):39-44
Cepheids, the principal distance indicators, point to the existence of two inner Galactic spiral arms in the immediate solar neighborhood (within 5 kpc). However, the available Cepheids are clearly insufficient for a detailed study of the structure of these arms. Fortunately, southern-sky monitoring (the ASAS project) has led to the discovery of many new variable stars, more than one thousand of which have been identified as possible Cepheids. To improve the classification and to construct reliable light curves for new Cepheids, we have begun their regular photometric observations. Here, we present the first results: 1192 photoelectricBV I c observations were performed for 33 classical Cepheidswith the 76-cm telescope of the South-African Astronomical Observatory (SAAO, the South-African Republic) from December 2006 to January 2008. We provide tables of observations and V light and B-V and V-I c color curves. The new observations together with ASAS-3 data have been used to improve the elements of the light variations. 相似文献
7.
The methods and results of stacking of seismograms of nuclear explosions registered by the world network of seismic stations from 1980 until 1988 are presented. Stacking of seismograms obtained at one seismic station from the sources located in the same place allows us substantially to increase the useful signal/noise ratio. This, in turn, allows more confident correlation of various seismic waves coming to the seismic stations after the first arrivals, particularly, converted and reflected waves from different boundaries inside the Earth. 相似文献
8.
Atmospheric boundary-layer stratification exerts a considerable influence on side-looking radar imagery of the sea surface in the centimeter range. Characteristic cellular structures present on the imagery under conditions of instability in the atmospheric boundary layer do not appear on images recorded under stable atmospheric conditions. The possibility of observation of dry and moist convection in the atmospheric layer above the water surface is examined. 相似文献
9.
L. N. Berdnikov O. V. Vozyakova A. Yu. Kniazev V. V. Kravtsov A. K. Dambis S. V. Zhuiko 《Astronomy Reports》2012,56(4):290-304
We have obtained 26 372 CCD frames in the B, V, and I
c
filters for 81 RR Lyrae stars in 2008–2010, using the 76-cm telescope of the South African Astronomical Observatory and the
40-cm telescope of the Cerro Armazones Observatory, North Catholic University (Chile) using an SBIG ST-10XME CCD camera. For
12 of these RR Lyrae stars, we also obtained 337 brightness measurements in the B and V bands in 2000–2001 using the 60-cm telescope of the High Altitude Mt. Maidanak Observatory (Republic of Uzbekistan). We present
tables of observations, light curves, and improved light-curve elements for all these RR Lyrae stars. The Blazhko effect was
detected for SU Hor. 相似文献
10.
A new method—the circular aperture method—is proposed for determining the physical parameters of gas in the neutral atmospheres of comets. A check has shown that this method is applicable to calculate the hydrodynamic velocity of gas outflow and the lifetime of molecules in the neutral atmosphere of comet 2009/P1 (Garradd). 相似文献