Vol 24, No 3 (2016)

Instrumental complexes for seismic acoustic and electromagnetic sensing of subsurface soils on the shelf of sea water areas and coastal territories have been designed, produced, and tested under natural conditions. Elements of the cognitive radio network and hydroacoustic stations of the safety system of coastal commercial enterprises are designed and prepared for commercial production. These elements are designed for the infrastructure of distant territories with explored and developed oil and gas deposits.

Nuclear spin dynamics of the ¹²⁹Xe and ¹³¹Xe isotopes in an external magnetic field B₀ is considered. Nuclear spin is pumped by the laser through ⁸⁷Rb, which transfers the electron spin to the ¹²⁹Xe and ¹³¹Xe nuclei in the spin-exchange interaction. The nuclear spin dynamics is controlled with a transverse magnetic field that causes nuclear magnetic resonance in both ¹²⁹Xe and ¹³¹Xe isotopes. Numerical calculations are performed to find conditions at which the transverse component of the nuclear spin in the established motion is of maximum and the slope angle relative to the vector of the constant magnetic field B₀ is 45°. This regime is taken to be optimal for simulation of practical applications. It is also found that the pump of the nuclear spin of xenon is strongly attenuated when the rubidium polarization vector is turned to the plane perpendicular to the external magnetic field vector B₀.

The properties of a single heterojunction between gapless graphenes with identical work functions but different Fermi velocities have been investigated. Reflection and transmission coefficients are obtained for charge carriers passing through this junction. It is shown that total internal reflection (with a critical angle the same as for light incident at an interface between two media) may occur in it.

The effect of the residual gas pressure on the spectral and amplitude characteristics of the output signal from the oscillator with the turbulent electron beam is examined. It is shown that ions resulting from gas ionization in the drift region promote formation of denser and more compact space charge bunches. Denser bunches increase the output signal power and aid in appearance of higher-order components in the spectrum, thus extending the working range to a higher-frequency region. When the device operates in the regime of noiselike signal generation, ions contribute to a decrease in the irregularity of the output power spectrum to about 0.3 dB in the working frequency range up to two octaves.

Solar flares cause sudden disturbances at the Earth’s ionosphere. These effects are detected by the very low frequency (VLF), 3−30-kHz signals which are propagated at the Earth-ionosphere waveguide. The sudden changes on the time-dependent intensity of VLF signals are recorded by Super SID system during February, March, and April, 2013. Then VLF data were compared with the GOES satellite data found in the Space Environment Center online database. The main factors of the variation in VLF signal intensities recorded by the Super SID system are class, duration of the solar flare and the frequency of VLF signals.

The emphasis of this study is on the ejection of single droplets of a certain size under pulsed ultrasound. Droplet ejection from an interface of two immiscible liquids in this mode, which differs from the well-known ultrasonic fountain (where liquid droplets arise spontaneously), has been experimentally implemented and investigated. The spatial and time evolution of the interface deformation and violation of interface integrity, caused by pulsed acoustic radiation pressure, has been recorded with a high-speed video camera. It is shown that, depending on the ultrasound intensity, three characteristic modes of interface response can be distinguished. In the first (low-intensity)mode, the interface undergoes forced oscillations, without violation of its integrity. In the second (intermediate-intensity) mode, which is in the focus of our study, the interface integrity is violated due to the ejection of a single droplet of a certain size; the latter continuously changes its shape when moving in the second liquid. In the third (high-intensity) mode, the predictable ejection of droplets of a predictable size turns into stochastic ejection of multiple droplets with unpredictable sizes. The dependence of the sizes of single droplets on the parameters of focused ultrasound beam have been measured in the second (stable) mode of ultrasound ejection. Based on these measurements, the range of ultrasound parameters providing controlled generation of single droplets of a specified size is estimated. Differences in the dynamics of interface motion and specific features of droplet generation for the liquid/liquid interface in comparison with the liquid/gas interface are indicated. Possible applications of the observed effects are discussed.

A method for experimental estimation of intrinsic and mutual impedances of transducers in a shipborne multielement hydroacoustic array is proposed and investigated. It is shown that consideration of the transducer interactions increases the radiated power and suppresses the lateral field.

A procedure is described for tomographic estimation of parameters of velocity inhomogeneities in a geophysical medium on the basis of the noise data recorded by a system of seismic detectors arranged along the boundary of the region under investigation. Reconstruction of inhomogeneities using this procedure, numerical simulation, and processing of the experimental data are presented.