In the paper, the mixed parametric and self-oscillations in the presence of a nonlinear parametric action and a delay in friction causing self-oscillations have been studied. For this purpose, a model of a frictional self-oscillating system interacting with an energy source of limited power was used. The solution of nonlinear differential equations of motion was constructed using the direct linearization method. The relations of nonstationary and stationary oscillation modes were obtained. By application of the Routh – Hurwitz criteria, the conditions for the stability of stationary oscillations were derived. The calculations were carried out in order to gain information about the dynamics of fluctuations. An analysis of the data showed that the amplitude-frequency dependence changed its behavior under the influence of the delay. The latter also led to the appearance of stability regions on the lower branches of the amplitude curves, and a dependence arose on the steepness of the energy source characteristic.
Supercomputer simulation of several amino acid oligomers using the molecular dynamics method has made it possible for the first time to identify a complex of characteristics of both intrinsic intramolecular local vibrations, or normal modes, and forced vibrations when specifying an alternating electric field in the IR frequency range. Amplitude-time dependences of energy and electric dipole moment were obtained for oligomers of Gly, Ala, Trp, Val amino acids, the Fourier transform of which revealed their frequency spectra. The type of solvent model was shown to significantly affect the position of spectral peaks because of variations in local interactions and system dynamics. The interpretation of the obtained patterns made it possible to propose a non-contradictory model that satisfied the fundamental physical concepts of the intramolecular and intermolecular dynamics of groups of biomolecules. The model allows for intramolecular interactions of normal local vibrations, including those of the Fermi resonance type.
The effect of Ar+ and Cd+ ion implantation and subsequent thermal annealing has been studied on a single-crystal ZnTe (111) using a whole range of spectroscopy methods: ultraviolet photoelectron one (UPS), light absorption one, and Auger electron one (AES). The results showed that bombardment of the surface with Ar+ and Cd+ ions with an energy of E0 = 1 keV until a saturation dose of of Dsat = (6–8)·1016cm−2 was reached resulted in the destruction of the crystal structure of the ion-implanted layers and, as a consequence, in surface metallization. In particular, after implantation with Cd+ ions and subsequent annealing at T = 850 K, the formation of a homogeneous continuous Zn0,5Cd0,5Te film 30–35 Å thick was observed, which indicated the redistribution of components and the formation of a new phase state on the ZnTe surface. The results of the study of Zn0,5Cd0,5Te thin films demonstrate the presence of two clearly defined maxima in the valence electron spectra corresponding to binding energies of −1.4 eV and −5.2 eV.
In the paper, the results of numerical modeling of the formation and propagation of vortex structures generated by a pulsed turbulent buoyant jet have been presented for the Reynolds number Re = 1.5×104, the parameter P = 3.65, and the Grashof number Gr = 3.9×105. A three-dimensional turbulent flow model based on the unsteady Reynolds equations was adopted. The angle between the jet and gravity directions was varied from 0° to 180°. The vortex cloud movement was tracked up to the moment when the maximum velocity value in the cloud became equal to 3.5% of the inlet velocity. For various α values, the power-law relationships describing the propagation of the vortex cloud and a decrease in the maximum velocity value and temperature within the cloud were obtained.
This work has involved the simulation of technological operations of manufacturing a silicon (Si) avalanche photodiode and calculating its output characteristics. As a result, the values of its multiplication factor (from 49.5 to 63.3) and spectral sensitivity (from 15.8 to 19.6 A/W) depending on the shallow trench insulation defect type are presented for a Si avalanche photodiode. It has been shown that the technological defects causing narrowing of the width of the trench towards its bottom have the greatest impact on these parameters. As a result, the multiplication factor decreases to 18%. The dependence of the photodiode gain on the trench’s wall inclination angle was established to be described well by a linear function. It was also demonstrated that the trench narrowing led to an increase in the lateral component of the electric field strength near the groove, which reduced the breakdown voltage, but did not lead to an increase in multiplication.
