Powder material is a certain set of particles capable of plastically deforming both due to plastic shear of this set of particles, and due to sliding of the same set of contacting particles relative to each other. Making simulation, we proceeded from the fact that the model must have a finite number of features from the number inherent in the original object. At the same time, some of the properties of the object, when transferred to the model, could undergo a number of changes, which, having had insignificant effects on the object under study, could substantially simplify its theoretical-model representation. Using the structural model of diffusion interaction in powder materials, the process of densification and inelastic deformation of powder materials is described under the condition of plasticity using the liquid-dynamic theory of lubrication in a closed volume. Based on this, a theoretical analysis of the mechanism of sintering particles of iron-based powder materials was carried out. The effect of plasticizer introduction at different stages of product manufacturing on the basis of the proposed models of powder metallurgy processes is considered. The results of the scientific publication can be used in experimental studies of diffusion processes in the formation of powder materials and the choice of technological regimes.

Microelectronic products are widely used in aerospace, aviation, military and nuclear engineering. However, they are very sensitive to various ionizing radiations (electrons, protons, heavy charged particles, X-ray and gamma radiation). The common used material for radiation protection is lead. In recent years, bismuth deposition has become an interesting subject for the electrochemical community because of bismuth’s unique electrical, physical and chemical properties. There is a limited number of authors dealing with continuous bismuth films onto metallic substrates by electrodeposition. The conditions of electrochemical deposition of bismuth and the structure of coatings were examined. Electrochemical deposition with the inputted various organic additives and without them was carried out. It is shown that bismuth coatings have a rhombohedral lattice, and thаt adding of a number of organic additives into the electrolyte results changing in a coatings growth texture. The protection efficiency of shields based on bismuth under 1.6–1.8 MeV electron irradiation energy was measured. The electron beam attenuation efficiency was estimated by changing of current-voltage characteristics of semiconductor test structures which were located behind the shields and without them. It has been determined that bismuth shields with 2 g/cm2 reduced thickness and attenuation coefficient of 156 have optimal protection effectiveness and mass dimensional parameters.

The physical and chemical basis of formation of nanostructured state of material are represented and processing methods of nanostructured materials and coatings used in surface engineering are described. The information about the degree of influence of treatment regimes of gas-thermal spraying, electrochemical deposition, microarc oxidation, tribomechanical treatment and frictional cladding by a flexible tool on the processes of formation of structural-phase state and the level of the surface layer properties is given. A new generation of surface engineering technologies on the basis of the research is developed. The formed coating and surface layers maintain stability of structural-phase state under high loads and temperatures and have high wear resistance, thermal resistance and corrosion resistance for a long time. The examples of practical implementation of the developed methods of surface engineering and nanotechnologies for industrial plants are shown. Manufacturing sites are built and the developed technologies of coating application and modification of the surface layers by the activated surface engineering methods are used in more than 50 enterprises of Belarus, Russia, Korea and other countries. The using of developed nanostructured materials and coatings as well as methods and means of surface engineering technologies allows increasing the technical level of the engineering techniques, reducing the cost of production and improving the competitiveness of products.

The question of the choice of two scalar parameters, respectively, the two defining equations of the flow of the particular model of a nonlinear elasticity-plasticity to limit the growth of elastic anisotropy is considered. The elastic properties of the material are described by the generalized Murnaghan law of elasticity. The model is constructed with the assistance of the potentiality principle of defining equations in the stress rate, which lets determine the yield surface deviator cross-section. To simplify the case the material assumed to be perfectly elastic-plastic. The values of the first and second parameters are relative parts of dissipative specific deformation power and projections on the surface of deviator section of yield surface of criterion deviator operator. They are part of the differential equations for determining a specific potential energy of elastic deformation and the Cauchy stress tensor. In the case when the first parameter is independent on the strain rate tensor, the system of equations generates the minimum value of the parameter. This choice makes too large errors in the condition of biaxial state of stress in numerical modeling of Bridgman’s experiments under biaxial compression. The value of the second parameter has to be substantially smaller. The first parameter is chosen while carrying out of this requirement when the first parameter depends on the angle between the normal vector to the surface deviator section and “vector” of strain rate (in basic, epitaxial experiments). The choice of these parameters significantly limits the growth of elastic anisotropy, as it is shown by numerical simulation of biaxial loading. It can be updated by use of additional experimental data of these loadings.

Processes and equipment are classified based on mutual interactions between elements of a technological system. Reliability of each type of the technological system and operated process is different due to varying complexity of the performed operations. The main properties-determining feature of the process is the interaction of the constituent element of the technological process, mainly instrument and machining object. Based on this, technological processes in the interaction zone are divided into four groups: pointed, linear, surface and volumetric. Groups of the technological processes and determination of the reliability of their operations during goods formation is described. Colligation of the technological path with component failure rate is shown. Calculations of the technological path for each group of processes are presented. Intensities and failure rates for the all groups of processes are calculated. Based on the calculations of the object technological path, evaluation of reliability of performed operations for each group of the interactions was obtained. Obtained regularity of the component failure rate during decrease of the technological path allows quantitative comparison of the manufacturing operations reliability during its designing.

The preliminary results of an experimental study of the effect of pressure on the formation of charcoal in the pyrolysis of birch chips are discribed. The experimental investigation was carried out at pressures of 0.1, 0.3, 0.5, 0.7 MPa and at heating rate of the order of 1 °C/min. The initial moisture content of the chips was 14.2 % by weight, and the dimensions – 17×8×6 mm. To investigate the effect of pressure on the pyrolysis process, a laboratory bench was designed and constructed. It was found that increasing the pressure from 0.1 to 0.7 MPa increases the yield of charcoal from 25.1 to 32.4 % by weight (relative to the dry weight of the starting material) and the carbon content from 89.1 % by weight at 0.1 MPa to 96.4 % by weight at 0.7 MPa. The calorific value of charcoal decreases from 34.86 MJ/kg at a pressure of 0.1 MPa to 30.23 MJ/kg at a pressure of 0.7 MPa. This is due to release of oxygen-containing components from the porous coal structure, which have higher calorific value than pure carbon. Reduction of charcoal heat combustion with decrease in the amount of oxygencontaining components confirms conclusion that their calorific value exceeds the calorific value of pure carbon.

The article deals with the results of thermohydrodynamic processes in a spraying chamber with direct gas flow and counter-current flows. The upper gas distribution device in a spraying chamber is shaped as a grid system, while the bottom device represents a branch pipe with a swirler pointing upwards. The chamber features counter-current flow interactions, and the bottom flow is introduced as a swirling jet. The experimental calculations of gas axial flow rates, temperature and thermal conductivity distribution in different chamber sections are provided. The thermal conductivity properties were determined with the normal mode method. The study was performed with ball-shaped sensors made of materials with high thermal conductivity (copper, brass) with centered thermocouples. The upper gas distribution system in the form of two grids (if no bottom gas inlet was involved) was found to build up an axisymmetric thermal conductivity model, and, consequently, the model-specific gas distribution in the spraying chamber. Referring to the study device, a hole (nozzle) near the burner results in asymmetric pattern, irregular gas distribution and generation of low-activity areas. Thermal conductivity values in the chamber central area turn to be higher than at the peripheral areas due to gas jet flow. Besides, heat exchange intensity in the chamber central area decreases significantly upon distance from the chamber floor. An extra bottom inlet of heat medium and creation of counter flows was shown to result in substantial increase in thermal conductivity (1.5–2 times) in the chamber central paraxial area and lower section, thus evidencing the hydrodynamic activation and heat and mass exchange intensification, which benefits to more effective use of chamber capacity and improved drying performance.

A technique for calculation of thermohydraulic and mass-sized parameters of a cooling system based on a dry cooling tower and applied in power units is described. The calculations were performed for the heat load on a tower of 1000 MW. The height of the concrete tower was 180 m. Heat exchange column, made from steel ribbed galvanized pipes with the diameter of 22×1.5 mm and a length of 20 m had standard dimensions: width – 2.4 m, height – 20 m. Determination of the minimum reduced costs for the studied parameters allowed justifying the choice of the best values in the cooling system of the power unit. The minimum reduced costs correspond to 4-row bundle with 2-way traffic pattern chilled water. The optimal parameters of fin match the height of the rib – 7 mm fin step – 3.5 mm, the distance between the finned tubes – 2 mm. The optimal number of columns on a heat exchange cooling tower is 600 pcs., with cooling of the water in a cooling tower at 10 °C. The analysis of changing of mass-sized and cost values has been carried out and the alternative design of the cooling system for the power unit with the capacity of 1200 MW is proposed

Computer modeling was carried out for gamma-ray spectra of nuclear materials, which were measured by using a semiconductor high-purity germanium detector ORTEC GEM25P4-70. The standard SRM-969 samples were used as sources of gamma radiation, which are cylindrical tanks of fixed volume, made of aluminum alloy 6061, filled with a dispersed uranium oxide powder (U₃O₈) with different concentrations of ²³⁵U. The products from radioactive decay chains are determined for uranium isotopes ²³⁵U and ²³⁸U, which give the main contribution to the gamma spectrum of uranium oxide (U₃O₈). A technique that makes it possible to compare the results of measurements with model spectra is developed. The correlation of the measured spectra to the model spectra was made by comparing the areas of the total absorption peaks for energies of 185 keV and 1001 keV, which are often used in gamma spectrometry to determine uranium enrichment. The selected parameters of the model and the source of the detector allowed to describe the measured gamma-ray spectra with an accuracy of better than 6 % at the total areas of the absorption peaks in the energy range 150–1100 keV. The developed model makes it possible to obtain the model of gamma spectra of various fissile materials, provided that there are the data available about the isotopic composition, the quantum yield of gamma lines for each isotope, and the activity of fissile material. These model spectra can be used for the development of measurement techniques and software testing in the field of nuclear spectroscopy.

 

Efficiency estimation of a spatial-frequency covariance descriptor of small objects in aerial images is provided. It is based on analysis of computational complexity, storage capacity, Riemann distance values, ROC and DET curves for real video sequences. A criterion of QR-algorithm of choosing of number of steps to compute generalized eigenvalues of covariance matrices is proposed. It is based on analysis of generalized eigenvalues histograms, probability of object correct detection in an aerial image and influence of scale factor and rotation angle of object on Riemann distance value. An estimation of discrimination ability of the spatial-frequency covariance descriptor based on analysis of AUC of ROC-curve is given. A criterion to choose the optimal threshold of object detection based on the Youden’s index and Equal Error Rate is defined. A range of threshold values to make decision of object detection based on the analysis of ROC- and DET-curves for real video sequences is determined. It provides a high probability of object correct detection at given probability of its false detection and optimal ratio between probabilities of type I errors and type II errors.

The spectral and energy characteristics of disk planar dielectric resonator (DR) with high-order whispering gallery modes (WGMs) were investigated in Ka-band. The diameter of the planar DR was several wavelengths in the dielectric material, and its height was much smaller than the wavelength. The dielectric disk was placed by flat bases between two conducting mirrors. Thus, electromagnetic field of the resonator was limited by the height of the planar disk by two conducting surfaces. The resonant properties of such structure were determined by the condition of total internal reflection of the waves from the curved surface of the dielectric disk. A method of effective excitation of WGMs in the planar DR by the coupling slot in the metal mirror was proposed. It is shown that with this excitation method, a regime of supercritical coupling with planar DR is achieved. In this case, the mode spectrum of such a resonator is rarefied relatively. It is established that the Q-factor of a planar DR is mainly determined by the losses in its dielectric material and by the ohmic losses in metallic mirrors, since the radiation losses at a necessary ratio of the wavelength and the diameter of the dielectric disk can be small. For a disk made of teflon with a height of 1 mm, a diameter of 78 mm, located between brass mirrors, the Q-factor of the planar DR can reach 1500 at the high-frequency edge of the Ka-band. The recommendations for increasing of Q-factor of the planar DRs and reducing their dimensions are proposed.

Algorithms to analyze data produced by pressure sensors mounted on hydraulic cylinders of mine linings, which are exploited in lavas of the Starobin potash deposit, are presented. To build algorithms, data mining process has been represented by three general stages. First of them consists of data preprocessing. Based on data specifics, algorithms of removing outliers as well as determining characteristics independent of tunneling machine location and state of bottomhole supports were included in it. The second stage contains algorithms of finding in the preprocessed data of cycles, which were created by descent of mining supports, and phases of cycles that depend on location of the tunneling machine relative to those supports. Algorithms of the third stage were built to compute data characteristics connected with the found cycles and their phases. Besides, modifications of correlation algorithms for aggregated data were developed in order to investigate relationship between the characteristics, including their coupling with behavior of rock pressure. The algorithms are designed for use in automated monitoring systems of rock pressure in lavas of potash mines, including mines of the Joint Stock Company “Belaruskali”. The developed algorithms were programmed. Program realizations were seriously tested on big data supplied by pressure sensors mounted on hydraulic cylinders of bottomhole supports of the Starobin potash deposit. As an example of application of the developed algorithms, it is shown that acceleration of mining process increases the likelihood of rock blows to the supports.