On antenna arrays signals resolution
On antenna arrays signals resolution
V.A. Вurоv, О.V. Dmitriev
Three basic problems that arise in signal resolution are examined: what i is the shortest angular distance between signal sources that can be resolved by a discrete array; what is the largest number of resolvable signal sources of unknown power, and what is the nature of optimum processing to resolve signal sources of unknown power that are close to one another? The results cited indicate that the resolution of an antenna array can exceed the Rayleigh limit and Is determined by the output signal/noise ratio, while the number of signals that can be resolved depends on the number of different spatial frequencies in the aperture; of the array. It is shown that in the Gaussian approximation, the optimum - processing algorithm for resolution reduces to weighted processing of estimates of the cross-correlation moments for signals from all elements of the array and makes it possible to ensure resolution near i the potential limit.
Show AbstractSystems of multilayer interference filters at oblique incidence of light
Systems of multilayer interference filters at oblique incidence of light
F.A. Korolev, A.Yu. Klementjeva
The angular properties of narrow - band and band optical filters of various types for the visible, UV, and IR regions of the spectrum are investigated. The basic behavior of the properties at angles from 0 to 60° are indicated with the aid of simple relationships and a matrix procedure. Types of systems with inclination - stable transmission-band contours and minimal variation of the characteristics with angle are designated as effectively performing angled multilayer systems.
Show AbstractAbout the boundary layers, formed on the density jumps
About the boundary layers, formed on the density jumps
E.P. Anisimova, L.V. Poborchaya, A.A. Speranskaya
The results of an observational study of the structure of boundary layers formed on a density discontinuity are discussed, and the velocity profile in the mixing zone at the density discontinuity is calculated. It is shown that the velocity profile in a mixing layer on a density discontinuity can be calculated with Prandtl's formula for the boundary of a free jet if the variation of average velocity with the local Richardson number is taken into account.
Show AbstractTo the method of study of magnetic transformations in amorphous and mictomagnetic materials
To the method of study of magnetic transformations in amorphous and mictomagnetic materials
K.P. Belov, A.N. Goryaga, A.I. Kokorev
It is shown how the differential magnetic susceptibility ($H/σ$)($σ^2$), which is an important parameter for study of the nature of magnetic transfor -mations in amorphous and mictomagnetic materials, can be calculated by using the $|{∂σ }/{∂ H}|$_{H}={const}}$ relation. By way of example, calculated temperature curves of |δσ/σH|$(T)_{H=const}$ are presented for dilute ferrites with spinel structure: Li$_{0,2}$Zn$_{0,6}$Fe$_{2,2}$O$_{4}$ и Mg$_{1,5}$FeTi$_{0,5}$O$_{4}$.
Show AbstractInfluence of suspended sediments on turbulent energy spectra in a three-dimensional channel flow
Influence of suspended sediments on turbulent energy spectra in a three-dimensional channel flow
N.A. Mikhаilоva, О.P. Petrоsyan, V.A. Platоnоv
Experimental studies of kinematic flow characte ristics and turbulent - fluctuation energy spectra on a model estuarine reach are described. They are compared with measurements made on the channel reach of the model. It is shown that feeding additional sediment into the stream changes the nature of the vertical distribution of turbulence intensity: it decreases in the region near the bottom and increases in the subsurface region.
Show AbstractAutodyne detection by reflex klystron with response registration in the reflection circuit
Autodyne detection by reflex klystron with response registration in the reflection circuit
R.V. Lebedev, Yu.A. Pyrogov
It is shown experimentally that detections ensitivity can be raised by 1.5 - 2 orders of magnitude when the response to external microwave radiation is registered in the reflector circuit of the generating klystron as compared to response registration in the resonator or cathode circuit. This is explained by the fact that the reflector - circuit response is as strong as that in the resonator circuit, but the noise current(for shot noise) is 3-4 orders of magnitude lower.
Show AbstractThe correlation between the microwave dielectric constant of TGS and the dimensions of its samples in eight millimetre range
The correlation between the microwave dielectric constant of TGS and the dimensions of its samples in eight millimetre range
M.N. Devjatkоv, G.I.Diakоnоv
Permittivity measurements on triglycine sulfate single crystals at a frequency of 40 GHz as a function of temperature and specimen geometry are reported. In the neighborhood of the phase - transition temperature, the measures indicated the existence of a specific dependence of permittivity on specimen dimensions in the direction perpendicular to the polaraxis. The possible causes of this behavior are discussed.
Show AbstractOn excess emission of dense nitrogen plasma at the temperatures 13000—15000 К
On excess emission of dense nitrogen plasma at the temperatures 13000—15000 К
M. Marenchak, A.P. Ryazin
A method, is proposed for isolating the excess emission of a thermal nitrogen plasma behind a reflected shock wave. The initial pressure of the test gas was 400 Pa in all experiments. The velocity of the incident shock wave was varied from 7.5 to 8.3 km/sec. The probing light source was a discharge in a capillary tube. A reversal effect was observed at a distance of 1.5 mm from the end of the shock tube, simultaneously at several wavelengths in the 0.42-0.52 micron band. The results indicate that an excess component of nonthermal nature is present under certain conditions in the nitrogen - plasma continuum. The values found for the emission - coefficient ratios - excess over thermal to thermal - are of the order of 0.2-0.5 in the temperature range studied.
Show AbstractLimit sensitivity of the absolute dilatometer
Limit sensitivity of the absolute dilatometer
S.I. Vasiliev
The fundamental limits on the sensitivity of the absolute dilatometer are discussed, and it is shown that temperature coefficients of expansion down to around 10$^{-18}$ deg$^{—1}$ can, in principle, be measured by using a capacitive displacement sensor.
Show AbstractOn the connection between the solar activity and total ozone of the atmosphere
On the connection between the solar activity and total ozone of the atmosphere
M.M. Abdel Wahab, A.Kh. Khrguian
Data from the international atmospheric - ozone observing network are used to test for coupling between ozone content and sunspot number. Coupling is observed at latitude 5°N and is absent in other latitude belts.
Show Abstract