编号 4 (67) (2024)

A theoretical model of electrowetting on a dielectric substrate is proposed taking into account the saturation of the dynamic contact angle from the electric voltage in this article. As an example, forced oscillations of an electrolyte droplet placed between two parallel solid surfaces in an alternating electric field are considered. In the state of mechanical equilibrium, the droplet has the shape of a round cylinder whose symmetry axis is perpendicular to the plates. The velocities of the contact lines on both surfaces depend on the external periodic force of the electric field and the deviation of the contact angle from its equilibrium value. To describe the surface inhomogeneity, it is assumed that the proportionality coefficient is a function of coordinates. This function is individual for each surface. It is shown that this leads to the excitation of additional azimuthal modes, in contrast to the case of homogeneous surfaces. The external alternating electric field is also spatially inhomogeneous, since it is difficult to achieve a uniform field in experiments with finite conductor sizes. It is found that the inhomogeneity of the plates changes the value of the saturation angle. Qualitative agreement with experiments was demonstrated.

Atomic force microscopy (AFM) is based on registration of the interaction of the AFM probe with the sample. A new mathematical model has been developed for the interpretation of experimental data. The relevance of the work is caused by the need to correctly account for the effects that arise in the interaction of bodies at the nanoscale under conditions of large deformations. Standard models (Deryagin-Muller-Toporov (DMT), Johnson-Kendall-Rob­erts (JKR), etc.)  represent a modification of the Hertz model, whose assumptions are not always correct for specific cases. The new model takes into account the curvilinearity of the interface between the probe and the material. Also in the process of model construction the disappearance and appearance of new nonlinear contact surfaces and the corresponding change of surface tension energy were taken into account, which plays an important role in indentation of soft materials (polymers, biological tissues). The results of testing the developed model on experimental data of nanoindentation showed its ability to describe with high accuracy the effects accompanying the contact and the indentation process: a jump-like retraction of the probe into the sample under the influence of surface effects, sticking of the probe at its removal from the sample, and the moment of probe detachment from the sample. A comparison of the obtained model with the results given by the standard DMT and JKR models was carried out. It has demonstrated the greater flexibility of the new model and its ability to describe the experimental data more accurately.

In this work, we study the Soret-driven convection of a two-component liquid in adjacent rectangular cells of a porous medium heated from below, taking into account the influence of random thermal fluctuations of external conditions. Two cases are considered: a spatially regular heat influx and a spatially irregular heat influx. We obtain stochastic equations for the dynamics of oscillation phases. Within the framework of these phase equations, we study the problem of the degree of synchrony of oscillations of convective currents in coupled cells using circular cumulants.

For a mathematical model of an elastomeric material, the researcher must describe its equilibrium curve. This curve can be obtained by very slow stretching or by stress relaxation points at a given deformation. Experimental studies of filled elastomers and the effect of stress relaxation at 100% deformation from the stretching rate were conducted. The aim of the study was to determine how the stretching rate of the material affects the equilibrium state of the nanocomposite. Tests were performed for the specimens of butadiene-nitrile rubber containing 40 parts by weight of black carbon and butadiene-styrene rubber containing 50 parts by weight of black carbon. The specimens were stretched to the strain of 100 % at the rates of 10, 100, 1200 %/min and then aged for 2 hours. The specimens were subjected to tensile-compressive loads up to the strain of 100 % during 200-cycle test, and then were aged at maximum strain for 2 hours. It was found that the tensile rate affects the stress relaxation only at the early stage of aging – up to 15 minutes – after which the stress relaxation curves coincide. In cyclic testing, a decrease in the stress magnitude at the point of maximum strain is very slow and does not coincide with the relaxation curves, but with increasing time of holding one can observe a complete coincidence of the stress and relaxation curves. Such behavior of elastomers is due to their viscoelasticity and the accumulation of damage during stress relaxation at maximum deformation and cyclic testing.

This paper proposes a methodology for comparing the emotional component of the voices of speakers actually experiencing emotions and those trying to reproduce them. The technique assumes the use of as classifiers the ratio of frequencies of local maxima of the spectrum of the of a sound wave.  In this work we studied 4 categories of basic emotions: anger, sadness, fear, joy. To obtain comparative characteristics in each category 30 records with "fake" and " true" emotion were investigated – 240 records in total. A statistical comparative analysis of the classifiers was performed and found a significant differences in the data for the genuine emotion and its imitation.  Also, a model of an artificial neural network, based on which a program was created to recognize the emotional message contained in human voice recordings. On the trained artificial neural network, an experiment was conducted to determine the emotional state of the speaker and the truth or falsity of his emotional message.  Testing of sound files with different emotions showed good results for recognizing both the emotional state of the speaker and the truthfulness or falsity of the speaker's emotional message. 

Nowadays the role of digital educational resources is obvious. Along with the discussion of the advantages of using online platforms for learning programming, important issues are raised concerning the quality of educational content, the need for critical thinking when selecting information sources and the importance of practical application of the acquired knowledge. The need for an integrated approach that combines independent online learning with traditional educational methods is emphasized. The aim of the study is to analyze online resources for teaching programming, taking into account different types of online platforms and their impact on the effectiveness of the educational process. The article considers five types of online resources for acquiring programming skills: online courses and educational platforms, interactive development environments, forums and communities of programmers, open code repositories, platforms for solving algorithmic problems. A comparative analysis of these resources by the criteria of interactivity, content, practical orientation, accessibility, and support was carried out. The study of the influence of different types of Internet resources on IT students with regard to their educational needs was carried out and the scenarios of their use for different target groups were identified. The results of the study show that using a combination of different online resources allows students to significantly accelerate their learning, access up-to-date information, and practice real-world projects.