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The temperature stability of the laser wavelength is an important characteristic of a laser Doppler anemometer with chromatic channel separation. In this work, experimental studies of the wavelength shift of a semiconductor laser diode by 660 nm as a function of temperature and laser radiation power are carried out. It is established that the temperature drift of the wavelength lies within 0.2 nm/°C. It is shown that the use of semiconductor diodes of this type in laser Doppler anemometers with chromatic channel separation is possible, but requires careful selection of optical filters.

To date, two basic types of algorithms for self-calibration of optical angular encoders have been developed in precision goniometry, differing in regular and irregular localization of the reading heads used in their structure. The analysis of the precision values of such encoders revealed the presence of special features not provided for by the theory, which stimulated the execution of experiments on modeling the expected values of such algorithms. The simulation model of optical angular encoders proposed by the authors of the article based on a two-dimensional data array makes it possible to identify the methodological error of the measurement algorithm used with sufficient accuracy for practice by determining the residual contribution of the distorting function to the final measurement error. In addition, it allows us to identify the characteristic features of calibration curves formed on the basis of methods with uniform or nonuniform localization of the reading heads. The simulation results show that self-calibration methods based on regular localization of the reading heads allow for higher measurement accuracy compared to methods based on the use of irregular localization.

On the base of a physico-mathematical model of ion exchange and field-assisted ion migration in glasses, with the use of a beam propagation method and mode analysis, simulations with subsequent fabrication of photonic integrated circuits in K-8 domestic optical glass operating at a wavelength of 1550 nm, have been performed. The main passive waveguide components, including single-mode waveguide dividers of optical signals, directional couplers, polarization converters, etc., have been fabricated and studied. Multichannel waveguide splitters of optical beams and matrices (512 × 512 pcs) of long-focal plane-convex microlenses for Shack-Hartmann wavefront sensors have been created by the method of field-assisted ion migration in glass substrates.

A method for determining the modulation transfer function (MTF) of infrared (IR) objectives is proposed. With the help of an objective under test, the image of a narrow exit slit of a monochromator used as a radiation source and tuned to a certain wavelength is focused in the form of a long narrow strip onto a cold metal screen with a fine aperture slit. Such a slit aperture, used instead of a pinhole aperture, allowed us to increase the useful signal and employ the exit slit of the monochromator as a radiation source. Behind the screen, instead of a small-area IR detector previously used in similar characterization studies of IR objectives, an apertured 2D IR FPA detector was used. With the help of 320×256 mid-wave IR (MWIR) and long-wave IR (LWIR) focal-plane-array detectors based on epitaxially grown mercury-cadmium-tellurium films, the Line Spread Function and MTF of MWIR and LWIR objectives were measured. The experimental data obtained were compared to the calculated diffraction-limited MTF of the tested objectives.

Analysis of literature data in the field of synthesis and study of the physical and chemical properties of mono-, bi-, tri-, tetracyclic and adamantyl-containing esters of (meth)acrylic acids is systematized and presented in the review. The reactions under consideration involve the synthesis of these compounds by means of esterification of acids with cyclic alcohols, transesterification, as well as the addition of (meth)acrylic acids to unsaturated alicyclic hydrocarbons, etc. The main directions of the practical application of polycycloalkyl-containing (meth)acrylates are indicated. It is stressed that the functionalization of the double bond in norbornene-containing compounds makes it possible to obtain a wide class of functional derivatives with potential chemical activity. The results of studies carried out by the authors of this review on the addition of acrylic acids to the derivatives of cyclo- and polycycloolefins are presented. Studies on the synthesis of the derivatives of acrylic esters of cyclohexene, norbornene, dicyclopentadiene and tetracyclododecene containing hydroxyl, alkoxy, carboxyl, as well as siloxane, isocyanate and other nitrogen-containing groups are considered. It has been shown that these compounds are reactive monomers for obtaining practically valuable polymers used in many industrial areas.

Optimal parameters for determining As by the photometric method have been established. Results of arsenic determination in rocks and soils by means of photometry are presented. This method is distinguished by the low detection limit (0.1 g/t) and economic efficiency in comparison with other modern analytical methods (atomic absorption spectrometry, atomic emission spectrometry with inductively coupled plasma, and mass spectrometry with inductively coupled plasma). For rocks and soils containing organic matter, the applicability of the existing methods of acid decomposition and melting was evaluated. The results of As determination by means of photometry were compared with its certified contents in the State Standard Samples of rocks (SGKhM-1, SGKhM-3, SG-3, SZR-2, SKD-1, SGKh-1), and with the data obtained by means of mass spectrometry with inductively coupled plasma on volcanoclastic greywacke. The parameters of As determination by means of photometry were optimized. It is recommended to use the photometric method for mass determination of arsenic in rocks and soils.

Beneficiation of ilmenite ores from the Ha Tinh deposit (Vietnam) is studied by means of electromagnetic, electrostatic separation, and flotation. The dependences of the mass of the obtained magnetic fraction on the current strength and on benefication degree are determined for different numbers of the stages of magnetic separation. The conditions for the change in the concentration of the titanium product depending on the voltage on the electrodes in the process of electrostatic separation are studied. It is shown that separation brings the heavy magnetic fraction apart from the waste rock, while subsequent flotation provides a high efficiency of rutile separation from impurity components. For flotation concentration of the product after separation processes, it is established that process efficiency depends on titanium concentration in the product to be concentrated. As a result of beneficiation, ilmenite concentrate containing more than 50% TiO₂ is obtained, which meets the most stringent requirements of the market. The design of the laboratory facility and the fluorination reactor is described, as well as the materials used to manufacture them. The research methodology is described in detail. During the fluorination of the obtained concentrate with elemental fluorine, the dependences of conversion degree on the time and temperature of fluorination are investigated (S-shaped curves). It is determined that the process is complete (conversion degree is more than 98 %) within 5 min at 700 °C. The features of the fluorination of the obtained concentrate are analyzed on the basis of kinetic equations. The activation energy and preexponential factor in the Yander kinetic equation are determined. It is shown that fluorination kinetics are limited by diffusion processes (supply and removal of reagents) rather than by the rate of the chemical reaction itself.

Thorough investigation of the decomposition of eudialyte concentrate by means of sorption conversion in low-concentration sulphuric acid solutions is carried out. The effect of process conditions on the efficiency of decomposition of acid-soluble minerals from the concentrate and sorption of valuable metals and natural radionuclides from the concentrate by the sorbent is studied. It is shown that the sorption of rare earth elements, manganese, uranium and thorium, which are rather stable against hydrolysis under experimental conditions, is achieved within a broad range of process parameters. The optimal conditions for the sorption of zirconium (hafnium), niobium (tantalum) and titanium by the sorbent differ due to different hydrolytic stability of these elements in low-concentration acid solutions. The choice of optimal process conditions should be determined by economic reasonability because it is impossible to achieve a high recovery of all valuable components at the same time.

Two models of deconvolution of the first-order scattering Raman spectra of semi-coking solid products and initial coals of low metamorphism stage are compared. The results obtained by analyzing the spectra within both models are consistent with each other. It is shown that the I _D/ I _G parameter loses its informational value if additional functions describing the vibrations of C-C bonds with different types of carbon atom hybridization are used. Graphitization degree and the proportion of edge defects in graphite planes may be considered as the main numerical characteristics of imperfection in the carbon frame of low-metamorphised coal and the products of its pyrolysis.

The kinetics and mechanism of hydrogen evolution reaction on Mn₅Si₃ electrode in solutions x M H₂SO₄ + (0.5 - x ) M Na₂SO₄, where x = 0.5, 0.35, 0.20, 0.05, are studied by means of polarization and impedance measurements. It is established on the basis of direct- and alternating-current diagnostic criteria that hydrogen evolution reaction on manganese silicide (Mn₅Si₃) in sulphuric acid electrolyte proceeds via discharge - electrochemical desorption route. Both stages are irreversible, and the transfer coefficients of the stages are not equal. Adsorption of atomic hydrogen is described by the Langmuir isotherm. It is assumed that the hydrogen evolution reaction is complicated by the process of hydrogen absorption by the electrode material, proceeding with kinetic control (within the entire investigated potential range). The effect of a thin oxide film on the kinetics of hydrogen evolution on Mn₅Si₃ is noted at low cathodic polarizations. Keywords: manganese silicide Mn₅Si₃, hydrogen evolution reaction, sulphuric acid electrolyte, impedance