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#### Author

##### ( see all 255)

- Komrakov, G. P. 3 (%)
- Belikovich, V. V. 2 (%)
- Denisov, G. G. 2 (%)
- Frolov, V. L. 2 (%)
- Ginzburg, N. S. 2 (%)

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- Applied Optics, Optoelectronics, Optical Devices 70 (%)
- Astronomy [x] 70 (%)
- Astrophysics 70 (%)
- Mathematical and Computational Physics 70 (%)
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## Solution of a subsurface radio-imaging inverse problem in the approximation of a strongly refractive medium

### Radiophysics and Quantum Electronics (2007-04-01) 50: 299-307 , April 01, 2007

In the approximation of a strongly refractive medium, we solve the inverse problem of subsurface-radar imaging of buried inhomogeneities using data of multiposition ultra-wideband radio sounding. The fast Fourier transform is used for synthesizing a large aperture with focusing. A mathematical model of the proposed subsurface-imaging system is presented and its accuracy is estimated. The feasibility of the proposed method is confirmed by numerical simulations and model laboratory experiments.

## Field of an electric dipole surrounded by a nonuniform cylindrical plasma sheath

### Radiophysics and Quantum Electronics (2007-05-01) 50: 360-369 , May 01, 2007

We analyze and solve the problem of the field of a dipole surrounded by a cylindrical plasma sheath with a piecewise-linear profile of dielectric permittivity ε including the point at which ε = 0. The predominant influence of the region in which ε = 0 on the formation of the dipole field is shown. The resonant properties of the solution in the case of a small cross-sectional size of the cylindrical sheath are studied.

## Regularization methods in radio interferometry

### Radiophysics and Quantum Electronics (2007-06-01) 50: 413-419 , June 01, 2007

The problem of image retrieval in radio interferometry is a classical example of an ill-posed problem. In this paper, we consider a new approach to the radio-interferometric imaging based on regularization, which is computationally more flexible. A new type of a weighting function suitable for managing the interferometer antenna pattern is obtained. The regularization procedure was implemented in the VLBI-image processing software developed at the Astrospace Center of the Lebedev Physical Institute (ASC LPI). It is shown that the joint use of the developed regularization methods with traditional deconvolution algorithms such as CLEAN and self-calibration improve the quality of images of cosmic radio-emission sources.

## Polarization ring interferometers and their use for studying nonreciprocal optical effects

### Radiophysics and Quantum Electronics (2007-05-01) 50: 402-412 , May 01, 2007

Based on the method of Jones matrices, we consider the optical properties of a polarization ring interferometer and show the possibility of its use for studying various nonreciprocal effects. Using such an interferometer, we measure nonreciprocal magnetooptical linear birefringence in a lithium iodate crystal.

## On a mechanism forming a broadband maximum in the spectrum of background noise at frequencies 2–6 Hz

### Radiophysics and Quantum Electronics (2007-07-01) 50: 555-569 , July 01, 2007

We study the properties of a broadband spectral maximum (BSM) of the background noise at frequencies 2–6 Hz using the data of mid-latitude observations. We find that the parameters of the maximum depend on the local ionosphere properties and that small scales (several tens of km) are absent in the field distribution at the BSM frequencies. We propose a mechanism forming the BSM, which is related to the large gradients of the refractive indices of normal ionospheric-plasma waves at altitudes from 70 to 300 km. The performed simulation of BSM spectra for a plane-stratified model of anisotropic inhomogeneous ionosphere allowed us to explain the main experimentally observed BSM properties.

## Interference scheme with transverse shift of beams for remote precision monitoring of parameters of optical elements

### Radiophysics and Quantum Electronics (2007-07-01) 50: 583-592 , July 01, 2007

In this paper, we present a new interference scheme with transverse shift of beams for remote monitoring of parameters of optical elements. The results of studying the measurement accuracy are given and the main noise sources of the presented scheme are considered. The advantages of this scheme are the high accuracy (the experimentally realized accuracy is higher than λ/3000, where λ is the wavelength of the sounding radiation), high speed allowing us to study nonstationary processes, and selectivity ensuring the study of a given surface by using other optical elements of the scheme.

## Method for synthesis of wideband multimode waveguide elements

### Radiophysics and Quantum Electronics (2007-09-01) 50: 720-725 , September 01, 2007

We propose a modification of the iterative method for synthesis of waveguide mode converters, which allows obtaining various elements of microwave transmission lines with a wide operating frequency band. The efficiency of the synthesis is illustrated by the calculated waveguide components. This method makes it possible to synthesize converters with significantly improved characteristics, e.g., a converter of the TM_{0,1} mode to the rotating TE_{3,1} mode, a converter of the TM_{0,1} to the TE_{1,1} mode, a converter of the TE_{1,1} mode of a smooth waveguide to the HE_{1,1} mode of a corrugated waveguide, and a waveguide 90° bend for the TE_{1,1} mode.

## Diffusion coupling between a barrel-shaped resonant cavity and a coaxial waveguide

### Radiophysics and Quantum Electronics (2007-10-01) 50: 794-802 , October 01, 2007

We consider a resonant cavity in the form of a section of a weakly irregular metal tube coupled with a waveguide of larger cross section. Eigenmodes of such a cavity with frequencies close to the cutoff frequency are described by the inhomogeneous-string equation. The solution of this equation obtained by the variational technique leads to standard formulas for interaction between the cavity and an incident wave.

## BWO spectroscopy of water spin isomers based on desorption from glycerol

### Radiophysics and Quantum Electronics (2007-10-01) 50: 832-836 , October 01, 2007

Violation of the normal spin 3: 1 ortho/para ratio in saturated water vapor above a 0.5% water-glycerol solution was detected using the BWO spectroscopy method. The solution was prepared by pumping the initial solution out at room temperature. The effect is supposed to be due to increased fugacity of ortho water molecules from the solution and the corresponding para enrichment of residual water.

## Radiometer of the 3-mm wave range with a modulator-calibrator

### Radiophysics and Quantum Electronics (2007-10-01) 50: 858-863 , October 01, 2007

We describe a radiometer intended for use in the spectroradiometric complex for remote sensing of the Earth’s atmosphere. The main feature of the radiometer is application of an electrically controlled modulator-calibrator allowing one to perform measurements and thermal calibration in a wide temperature range without using matched loads and means for their connection. The principle of operation and design of the modulator-calibrator are described and the characteristics of the radiometer and its separate units are presented.