Bulletin of the Lebedev Physics Institute最新文献

We present a simple model for calculating the distribution of the currents induced in a superconducting film by a local alternating magnetic field of a measuring coil. The model takes into account both radial and thickness nonuniform current distribution. The spatial distribution of the peak values of the current density in the sample is obtained, and the spectral composition of the response signal is considered depending on the amplitude of the drive current. The model response is compared with the experimental data.

This paper shows that when the velocities of particles in a source are small in comparison with the velocity of light any source generates soft gravitational radiation in which the wavelength is much larger then the dimension of the source. In this case only the polarization of gravitons determines the source and it should not depend on its nature: it may be a string, an accelerated electron, or only the gravitational force acting between the particles in the source. The main harmonic is, of course, quadrupole, the rest are small because of the small velocities of the particles in the source. Their observation would be interesting because it would provide information on the particle velocities in the source.

Potential energy surfaces of a neutral radical and an anion of the CH₂CHO molecule are calculated. The effect of the presence of two alternative electronic configurations of the neutral molecule is analyzed. New data are presented on the dependence of the energies of the ground states of the radical and valence-bound negative ion on the key geometric parameters. The oscillator strengths of the transition between the valence-bound and dipole-bound anion states are determined.

We report the results of simulation of expected angular flux distributions of atmospheric muons after their absorption in an object with a foreign inclusion for a muography study of the Early Saka period monument, the Karkara burial complex.

Using tunneling spectroscopy of break-junctions, we have studied the temperature behavior of the critical current I_c(T) at zero magnetic field for alkali-metal based superconductors: composite K_0.8Fe_1.7(Se_0.73S_0.27)₂ selenides with natural phase separation and polycrystalline samples of CaKFe₄As₄ pnictides. The measured bulk and intergrain I_c(T) dependences are analyzed and compared.

Within the paradigm of intermittent human control, we propose a novel model of dynamical traps to describe the balancing of a dynamical system near its unstable equilibrium. The core of this model is probabilistic, featuring alternating transitions between two behavioral modes of the subject – active and passive phases – in regulating the dynamics of the controlled object. These modes are delineated by action points, which represent the moments when the subject decides to switch between modes. This switching behavior is modeled using an original stochastic differential equation. Within this approach, action points are conceptualized as stepwise transitions in a special variable, (zeta ), which switches between two boundary values: (zeta = 0) and (zeta = 1). The introduced trap function, (Omega (Delta )), quantifies the subject’s perception of the object’s deviation from the unstable equilibrium or a desired state, thereby determining the current priority of the two behavioral modes. Crucially, these transitions— action points—occur before the trap function reaches its extreme values, (Omega (Delta ) = 0) or (Omega (Delta ) = 1), underscoring the probabilistic nature of intermittent human control.

The paper considers a possibility of processing signals from a RICH detector using a neural network when a high-energy particle passes through it at an angle to the sensitive plane. It is shown that only the coordinates of the initiated photomultiplier tubes are required in this case to determine the charge, velocity, and angle of a particle.

Microwave radiation of a gyrotron, during its interaction with powder mixtures, initiates plasma-chemical exothermic processes in air in which components of the initial powder mixture participate. In the experiments performed, use is made of bismuth ferrite (({text{BiFe}}{{{text{O}}}_{3}})) nanopowders with a particle size of 40–50 nm, which are transformed into spheroid microparticles with a size up to 100 μm and a complicated structure and surface morphology. The surface of the synthesized particles has nanoinclusions and dips, due to which the surface area increases (by ~1.5 times). On the surface of the produced particles, two types of inclusions (grains) with an increased iron content and a size up to 3 μm are found against the background of bismuth ferrite, with their shape having the form of quadrangles and hexagons.

The effect is investigated of backscattering of the diffraction grating produced on the mirror surface by gas discharge UV radiation and by counterpropagating waves of a ring laser. Measurements of the dynamics of complex coupling coefficients as the ring laser slowly approaches the lock-in threshold are presented. It is shown that, when the ring laser is near the lock-in threshold, there is a slight decrease in the dissipative component of complex coupling coefficients and a significant increase in their conservative component. The physical model of these effects is discussed.

Use is made of the analytical solution of the wave equation to simulate the light–current characteristics of Fabry–Perot diode lasers designed to operate at high powers. It is shown that at a high output power level, the presence of axial gain nonuniformity does not lead to deviations from the linearity of this characteristic. Only near the lasing threshold, a decrease in efficiency with pump current is found, associated with the transition from a uniform axial gain distribution to a self-consistent nonuniform distribution. It is found that with significant axial nonuniformity of the electron density that depends on the power level, the total optical length of the cavity remains constant.