Objectives. The active digitalization of the Russian economy has resulted in a shortage of IT personnel; this is particularly true of software developers. Thus, the Russian university education is faced with the task of undertaking the large-scale professional training of such specialists. The purpose of the present work was to support the largescale (“massive”) professional training of programmers through the creation and implementation of Digital Teaching Assistant (DTA) computer system, allowing teachers working under stressful conditions to concentrate on functions that require a creative approach, namely, drawing up and discussing nontrivial programming tasks.

Methods. Pedagogical methods for the personification of learning processes were employed. The general approach was based on satisfying the constraints for creating programming task generators. Tasks were generated using methods for generating random programs and data based on probabilistic context-sensitive grammars, along with translation methods using an abstract syntax tree. The declarative representation of the task generator was performed using functional programming methods, allowing the creation of a domain-specific language using combinators. The solutions were checked using automated testing methods.

Results. The developed structure of the proposed DTA system was presented. Considering the automatic generation of programming tasks, classes of practical tasks that reflected the modern specifics of software development were identified along with examples of their generation. A diagram of the programming task generator was provided along with a description of the procedure for automatically checking the solutions of the tasks using a set of program tests generated by the task generator. The presented procedure for comprehensive assessment of a student’s solution included verification of the correctness of the result and plagiarism checks in the case of tasks created manually by the teacher; this also involved validation for compliance with coding style standards, along with metrics for assessing program complexity, etc. The means for recording of statistics of academic achievement of students was characterized along with the interface of interaction between students and teachers.

Conclusions. The experience of introducing a DTA into the learning process of teaching programming in Python confirmed the possibility of personifying the learning process in the form of individual learning paths.

Objectives. Developing the element base of field-programmable gate arrays (FPGA) may significantly affect the design of electronic devices due to the enhanced logical capacity of such chips and the general tendency towards increased subsystem integration. The system-on-a-chip (SoC) concept is aimed at combining receiving, processing, and exchange subsystems onto a single chip, as well as at implementing control, diagnostic, and other auxiliary subsystems. The study aimed at developing a method for soft processor applications, i.e., processors based on configurable logical resources, for implementing control functions in an FPGA-based SoC.

Methods. A digital system design methodology was used.

Results. For soft processors, a unified design route based on selecting architectural parameters qualitatively corresponding to control tasks was considered. In particular, such parameters as instruction set addressness, number of pipeline cycles, and arithmetic logic unit configuration are adjustable at the design stage to allow the optimization of the soft processor in the discrete parameter space. An approach to rapid prototyping of the assembler based on stack-oriented programming language with regular grammar was also considered. The control of digital signal processing hardware as part of an SoC is the promising application area for soft processors. An implementation is considered on the example of an SoC based on Xilinx Virtex-7 FPGA containing several processor cores developed using the proposed methodology.

Conclusions. The considered approaches to soft processor design allow the rapid prototyping of the control processor core for operation as part of an FPGA-based SoC.

Objectives. In order to solve fundamental metrological problems concerning the reproduction and transmission of spectral radiometry units, as well as developing methods and tools for metrological support of modern technologies such as nanophotolithography in the electronics industry, synchrotron radiation can be used. When developing solid-state sources and receivers of radiation, new topical problems arise in connection with the metrological characteristics of light-emitting diodes (LEDs), multi-element array receivers, charge-coupled device (CCD) cameras and telescopes, whose successful solution depends on the properties of a reference source of synchrotron radiation. Therefore, the purpose of the present work is to develop spectral radiometry methods for obtaining metrological channels using an electron storage ring in order to control the characteristics of electronics components, as well as for studying and calibrating radiometers, photometers, and emitters operating in the visible, ultraviolet and infrared regions of the electromagnetic spectrum.

Methods. Methods for transmitting spectroradiometric units on an electron storage ring are based on the classical theory of Julian Schwinger, which describes the electromagnetic radiation of a relativistic electron to calculate the spectral and energetic synchrotron radiation characteristics taking polarization components into account.

Results. The possibility of developing methods for transmitting spectral radiometric units using synchrotron radiation was evaluated by means of a test setup, which included a monochromator-based comparator, a telescope with a CCD array, a spectroradiometer, a radiometer, a photometer, a goniometer, and an integrating sphere. This allowed the full set of spectroradiometric and photometric characteristics of radiation sources and receivers to be measured: from the most differential distribution of the spectral radiance density of the emitting region to the integral radiation flux. The results were compared with the reference synchrotron radiation source.

Conclusions. Among possible approaches for determining the metrological characteristics of LED emitters, multielement array receivers, CCD cameras, and telescopes, synchrotron radiation seems to be the most promising. This approach allows the small size of the emitting region of synchrotron radiation, the Gaussian distribution of radiance over the emitting region of the synchrotron electron bunch, as well as the wide dynamic range of spectrum tuning due to changes in the energy and number of accelerated electrons, to be taken into account.

Objectives. Terahertz quantum-cascade lasers (THz QCLs) are compact solid-state lasers pumped by electrical injection to generate radiation in the range from 1.2 to 5.4 THz. The THz QCL operating frequency band contains absorption lines for a number of substances that are suitable for biomedical and environmental applications. In order to reduce the size and cost of THz QCLs and simplify the use of THz sources in these applications, it is necessary to increase the operating temperature of lasers.

Methods. To calculate electron transport in THz QCLs, we used a system of balance equations based on wave functions with reduced dipole moments of tunnel-bound states.

Results. As a result of the calculations, an original band design with a period based on three GaAs/Al_0.18Ga_0.82As quantum wells (QWs) and a gain maximum at about 3.3 THz was proposed. Based on the developed design, a THz QCL was fabricated, including the growth of a laser structure by molecular beam epitaxy, postgrowth processing to form strip lasers with a double metal waveguide, as well as an assembly of lasers mounted on a heat sink. The developed THz QCLs was capable of lasing at temperatures of up to 125 K as predicted by the performed calculations. We also studied band designs based on two GaAs/Al_xGa_1–xAs QWs having varying aluminum contents in the barrier layers (x = 0.20, 0.25, and 0.30).

Conclusions. The calculated temperature dependences of the peak gain for two-QW designs with x > 0.2 confirm the possibility of creating THz QCLs operating at temperatures above 200 K. Thus, we have proposed two-QW band designs that outperform existing high-temperature designs in terms of maximum operating temperature.

Objectives. Two-dimensional transition metal dichalcogenides (TMDs) are utilized for various optical applications due to the presence in these materials of a direct band gap corresponding to the visible and near-infrared spectral regions. However, a limited set of existing TMDs makes the region of the used spectral range discrete. The most effective way to solve this problem is to use two-dimensional TMD films based on multicomponent alloys, including three or more different chemical elements (while TMDs consist of two). By varying their morphological composition, one can control the value of the band gap and thus their optical absorption spectrum. However, since the band gap in such structures is highly nonlinear as far as their chemical composition is concerned, it can be challenging to select the required concentration in order to achieve uniform absorption. In this regard, the purpose of this work is to theoretically determine the dependence of the band gap of four-component two-dimensional Mo_xW_1–xS_2ySe_2(1–y) alloys on their morphological composition.

Methods. The calculations were performed within the framework of the density functional theory using the Quantum Espresso software package. Flakes of two-dimensional TMDs alloys were prepared from bulk TMDs crystals by mechanical exfoliation on a Si/SiO₂ substrate. An experimental study of the photoluminescence characteristics was carried out using photoluminescence microscopy-spectroscopy. Results. In this work, the dependence of the band gap on the morphological composition of two-dimensional Mo_xW_1–xS_2ySe_2(1–y) alloys was determined. Upon varying the composition of TMDs alloys, it was found that the band gap changes from 1.43 to 1.83 eV. The obtained theoretical results are in qualitative agreement with the experimental data.

Conclusions. The minimum band gap is observed in alloys close to MoSe₂, while alloys close to WS₂ have the maximum band gap value.

Objectives. A topical task in the design of magnetoelectric (ME) devices based on composite ferromagnetic-piezoelectric heterostructures involves reducing their dimensions to increase their operating frequencies and optimize their integration in modern electronics. The study set out to investigate the influence of in-plane dimensions on the characteristics of ME effects in stripe and periodic nickel-lead zirconate titanate heterostructures manufactured via electrolytic deposition.

Methods. Lead zirconate titanate disks with Ag-electrodes were used for manufacturing the ME heterostructures; Ni was deposited on one Ag-electrode only.

Results. While a reduction in stripe size leads to an increase in the frequency of the resonant ME effect, it is followed by a decrease in ME conversion efficiency. The ME coefficient for the periodic heterostructures is about ~1 V/(Oe·cm). By increasing the angle between the magnetic field H and the Ni-stripe axis from 0° to 90°, a 2.5-fold increase in the optimal field H_m and a 4-fold drop in the maximum amplitude of ME voltage u_max(H_m) was achieved.

Conclusions. In periodic heterostructures, the frequency of the resonant ME effect is determined by the substrate’s size, while ME conversion efficiency depends on the width of the Ni stripes and the distance between them. The observed anisotropy of the ME effects in the investigated heterostructures is explained in terms of demagnetization effects. In the future, the anisotropic ME effect in the periodic heterostructures could be used to develop magnetic field sensors that are sensitive to field orientation.

Objectives. Terahertz time domain spectroscopy (THz-TDS) is currently a promising research method in pharmacology and medicine due to the high sensitivity of terahertz radiation to the chemical composition and molecular structure of organic compounds. However, due to the chirality of many biomolecules, their analysis is performed by THz irradiation with circular dichroism. In particular, circular dichroism of THz radiation allows the study of “soft” vibrational movements of biomolecules with different chiralities. Therefore, when studying such biological materials, accurate control of THz radiation parameters is essential. The paper describes a method for characterizing THz radiation polarization on the example of a black phosphorus source material.

Methods. The analysis of polarization parameters of THz radiation experimentally obtained by THz-TDS and using terahertz polarizers was performed by mathematical modeling of the interaction between THz radiation and a ZnTe crystal as a detector.

Results. Two schemes of terahertz spectroscopy with the ZnTe crystal as the detector were discussed in detail. The polarization parameters were determined using one or two wire-grid THz polarizers. An expression for approximating the dependences of the peak-to-peak amplitude of THz radiation on the rotation angle of the wire-grid THz polarizer for these cases was derived. The impact of the terahertz electric field intensity value on the shape of polarization dependences was considered. The rotation angle of the polarization ellipse of THz radiation emitted by the surface of a bulk-layered black phosphorus crystal illuminated by femtosecond laser pulses was determined.

Conclusions. The amplitude of the THz radiation electric field intensity begins to impact the shape of polarization dependences when its value becomes comparable to or exceeds 40 kV/cm.

Objectives. The development of composite structures in which a strongly anisotropic magnetoelectric (ME) effect is observed is relevant for the creation of sensors that are sensitive to the direction of the magnetic field. Such an ME effect can arise due to the anisotropy of both the magnetic and the piezoelectric layers. In this work, a new anisotropic material named as a magnetostrictive fiber composite (MFC), comprising a set of nickel wires placed closely parallel to each other in one layer and immersed in a polymer matrix, is manufactured and studied. The study aimed to investigate the linear ME effect in a structure comprising of a new magnetic material, MFC, and lead zirconate titanate (PZT-19).

Methods. The magnetostriction for the MFC structure was measured using the strain-gauge method; the ME effect was determined by low-frequency magnetic field modulation.

Results. Structures with nickel wire diameters of 100, 150, and 200 μm were fabricated. The MFC magnetostriction field dependences were determined along with the frequency-, field-, and amplitude dependences of the ME voltage in the case of linear ME effect. Measurements were carried out at various values of the angle between the direction of the magnetic field and the wires. All samples demonstrated strong anisotropy with respect to the direction of the magnetic field. When the magnetic field orientation changes from parallel to perpendicular with respect to the nickel wire axes, the ME voltage decreases from its maximum value to zero.

Conclusions. The largest ME coefficient 1.71 V/(Oe · cm) was obtained for a structure made of MFC with a wire diameter of 150 μm. With increasing wire diameter, the resonance frequency increases from 3.5 to 6.5 kHz. The magnetostriction of the MFC is comparable in magnitude to that of a nickel plate having the same thickness.

Objectives. Scale formation and corrosion are serious problems for heat and power equipment. These processes, when intense, can completely block the operation of the system, accelerating corrosion and leading to clogging, local overheating, and burnouts and ruptures of boilers and pipes, which in turn can lead to major environmental problems. Therefore, protecting surfaces from scale formation and corrosion is an important task. Promising methods for preventing the development of undesirable consequences include changing the composition of polymer coatings, e.g., by introducing microencapsulated corrosion inhibitors, as well as surface modification approaches, such as hydrophobization of the polymer coating surface. The purpose of the present work is to analyze methods for reducing scale formation and the rate of corrosion processes, as well as to study the efficiency of modification of paints and coatings by introducing microencapsulated corrosion inhibitors.

Methods. The study was based on the use of accelerated corrosion tests.

Results. Existing methods for reducing scale formation and corrosion rate on the surfaces of heat and power equipment were analyzed. The efficiency of modifying protective polymer materials by introducing microcapsules containing an active phosphonate additive was compared with approaches involving the surface modification of such protective materials.

Conclusions. It was determined that the modification of paints and coatings by introducing microencapsulated active additives can significantly reduce the rates of both scale formation and corrosion. By implementing stateof-the-art methods for modifying polymer coatings, a new generation of agents for efficiently preventing scale formation and corrosion processes can be developed for maintaining the high performance of heat-exchange equipment.

Objectives. When used in lighting installations with tubular low-pressure ultraviolet (UV) lamps, electronic ballasts should meet the following basic requirements: low cost, reliable ignition at low temperatures, as well as combining high energy efficiency with reliable lamp operation. As compared with electromagnetic ballasts, electronic ballasts allow the luminous efficiency and power factor of discharge lamps to be increased, reducing the consumption of scarce materials along with the weight of devices. In order to improve their energy efficiency, complete UV lamps are based on low-pressure discharge lamps with pulsed electronic ballasts supplying power at the frequency of 22–50 kHz. Various circuit designs include such basic units as mains filter, rectifier, power factor corrector, smoothing filter, high-frequency converter, ballast, and ignition device. The present study aimed to develop an electronic semiconductor circuit for switching on and powering a discharge lamp of increased energy efficiency using a pulsed electronic ballast.

Methods. Classical methods of mathematical research were applied for determining the flux of the 254-nm mercury resonance line using a structural electronic ballast diagram along with a mathematical description and adaptive model.

Results. Equations for determining the parameters of pulses formed by an envelope having the form of input voltage and current supplied at industrial frequency were formulated for different instants of time. A mathematical description is given for determining pulse duration and lamp current depending on the values of nominal and operating voltage, as well as nominal current. Diagrams for instantaneous voltage values at the high-frequency switch input and generated pulsed current are presented. The parameters of the ‘UV lamp–electronic ballast’ set were calculated using an adaptive model for determining the flux of the 254-nm mercury resonance line according to the condition of lamp power constancy.

Conclusions. Relative values for radiant efficiency of the 254-nm mercury line for UV lamps under study were determined. Theoretical research of electronic ballasts led to the development of a semiconductor switching and power supply circuit for the discharge lamp based on high-frequency rectangular pulses. The parameters of the element base were calculated along with selected basic initial characteristics of the blocking generator.

Objectives. The paper discusses usability as the concept underlying many contemporary design trends and accompanying technological development in various industrial, graphic and digital contexts. A formulation of the concept of usability in digital design contexts is advanced based on the evolution of industrial design.

Methods. Using the historical research method, usability is shown to be characterized by unification of form as applied to the relationship between a person and a design object. This conclusion has been applied to digital design using the analogy method. Basic principles of usability assessment in design are outlined, along with impacts on further development. Requirements for a designed product in terms of usability analysis should be fulfilled taking into account the principles of universality that constitute a basis for a universal design system.

Results. When developing UI/UX design objects, the usability of a digital product is considered in terms of universality based on rational visual image principles of industrial design and taking contemporary requirements in graphic, digital, and website design into account. Examples of industrial and digital design developments carried out by students using the concept of universal design are presented.

Conclusions. The usability of a design object can be shaped by using universal principles applying in both industrial and UI/UX design.