Traditional grades of aluminum alloys do not always meet the requirements of modern aerospace engineering. Al–Si foundry alloys possess insufficient mechanical strength characteristics and low plasticity due to their structural features (coarse brittle silicon inclusions and intermetallic phases). Therefore they cannot be exposed to pressure treatment. A technique for producing high-strength aluminum alloys, which consists in obtaining ring blanks by means of direct crystallization of melts with application of non-stationary centrifugal force fields and simultaneous introduction of modifiers, is proposed. The microstructure and plasticity of resulting tube-shaped blanks allow them to be exposed to sheeting for subsequent production of pipe workpieces with mechanical strength commensurate with mechanical strength of structural steel. The technique involves hydrothermal synthesis of nanostructured particles of aluminum oxide, which are overheated above the melt temperature prior to introduction into the molten aluminum alloy. This procedure enhances the processes of intercrystalline hardening with minimal fluctuations of internal stresses within the hardened material. The materials have tensile strength of up to 380 MPa (before modification by nanodispersed aluminum oxide it was 210 MPa). The microstructure has showed changes in the acicular dendrite component, which tends to become more dispersed and equiaxial. Eventually this leads to an increase in the mechanical strength by a factor of 1.25–1.32. 

The correlation between structural-phase transformations and physical-chemical properties of surface layers of hard alloy after ion-beam nitriding (temperature range 670–870 K) was established. The distribution of electron work function on hard-alloy plate surface after ion-beam nitriding was investigated. It is shown, that wear resistance of surface layers of hard alloy after ion-beam nitriding under different temperatures is uniform and has the same intensity for the first 450 m. At later stages of testing, the intensity of wear resistance is markedly different due to the modified layer abrasion. It is shown, that hard alloy ВК6 after ion-beam nitriding in the temperature range 750–790 K has enhanced microhardness, corrosion resistance and decreased up to 3 times mass wear during friction without lubricant, which is associated with carbonitrides formation and their strength increasing due to solid-solution hardening. The high values of the electron work function are characteristic for the surface layer of a hard alloy BК6 after ion-beam nitriding under 750–790 K, which is explained by the electron concentration increase. It is suggested, that ion-beam nitriding under this temperature range increases the corrosion resistance. 

The method of mathematical experiment planning was used to determine the factors that exert a determining influence on heat-insulating and weather-resistant properties of flame retardant foaming coatings. The studies were carried out on a model composition consisting of a binder, a carbon source, a flame retardant and a pore-forming agent. Evaluation of the influence of the content and the ratio of the main components of the coating was carried out by a change in its heat-insulating ability and weather resistance. During the exploratory experiments, the formulation of the model composition was chosen with the following content of the main components per 100 g of paint: 30 g of melamine-formaldehyde resin, 10 g of pentaerythritol, 30 g of ammonium polyphosphate, 10 g of titanium dioxide. Experiments on the thermal insulation ability consisted in measuring the time in minutes, during which the temperature of 500 °C was recorded on the back of the metal plate (STB 11.03.02-2010). Weather resistance of the fire retardant coating was determined according to the NPB 98-2004. Using numerous experimental data on the change in the thermal and atmospheric properties of the coating, a mathematical model was constructed to maximize the mathematical expectation, depending on its formulation. This model with the use of the Box – Wilson method allowed to determine the optimal ratio of the base components in the model formulation of the fire-retardant composition to provide the normative heat-insulating and operational properties. It is shown that the basic contribution to obtaining the required heat-insulating effect is made by such basic components of the composition as carbonizing (pentaerythritol) and pore-forming (titanium dioxide) agents. However, the composition with improved properties has the worst physical and mechanical characteristics and does not meet regulatory requirements. It has been found that there is a balance between fire-protective and weather-resistant coating properties. The establishment of these facts will make it possible to approach the regulation of weatherproof and fireproof properties in a directed manner and to create new efficient, economical fire-protective coatings with the required regulatory properties. 

Solid polymer electrolytes (SPE) have received a great attention to the decisive role as an ionic conductor in various electrochemical devices. Significant efforts have been devoted to the high ionic conductivity with better mechanical stability of SPE. The aim of this work is to investigate the relationship between structure, electrical and dielectric properties of the crosslinked ion-conducting polymers based on a mixture of oligomers with similar functional epoxy groups. The effect of lithium perchlorate salt content on structure and properties of the synthesized polymer systems based on aliphatic epoxy oligomer – diglycidylether of ethylene glycol DEG-1 and epoxy-diane resin ED-20, which were cured by polyethylene polyamine, has been studied by means of the Differential Scanning Calorimetry, the Wide Angle X-ray Diffraction and the Broadband Dielectric Spectroscopy. It was found that the glass transition temperature of the synthesized systems increases with increasing amount of the LiClO4 that is connected with formation of coordination complexes between lithium cations and atoms of macromolecular chains. Presence of one single diffraction maximum of the diffuse type, an angular value of which is approximately 19.6, on the wide angle X-ray diffractograms indicates that systems are amorphous and they are characterized by the short-range ordering. The real parts of permittivity and complex electrical conductivity depend on the content of lithium perchlorate salt and temperature of measurements. The maximum level of ionic conductivity and permittivity at elevated temperatures was revealed for the systems with a concentration 30 phr. of the lithium perchlorate salt. 

The problems of measuring hardness of constructions with insufficient rigidity by the dynamic indentation are discussed. The disadvantages of the existing dynamic hardness testers are described, the operation of which consists in impact indentation and determination of the hardness, depending on the restitution coefficient. Finite-element models of the contact of the indenter and the pipes samples with various wall thicknesses and diameters and cantilevered plates of various thicknesses are developed. Indentation diagrams for the investigated samples of pipes and plates in the coordinate plane of force-displacement are obtained. The results of the simulation have good convergence with the experimental data. With the help of the finite element models the separation of local penetration and deflection of construction is made. It is shown the influence of steel construction deflection on the process of indenter impression into the material tested and the change of indentation parameters as restitution coefficient, contact force, penetration depth and time of the active part of the impact. The limits of possible application of dynamic hardness testers have been determined. The ways of the increasing of the hardness measurement accuracy on the base of the data obtained during impact interaction are shown. It is established that the use of dependences between hardness and the time of the active stage of impact, as well as the ratio of the contact force to the depth of penetration at the loading stage, makes it possible to evaluate the hardness for pipes with the wall thickness exceeding 5 mm and cantilevered plates at the distance from the fixed support up to 100 mm. 

The results of studies of drying of thin flat materials by method regular thermal regime are presented. The results of experimental data processing using generalized complex variables are shown. The approximate empirical equation for calculating the heat flow density, the duration of the drying process and the temperature of material at the period of decreasing rate were obtained by processing and analysis of experimental data. The article also indicated kinetics drying calculation with the experimental data of moisture exchange and without the use of criteria heat exchange equations. The equations for determining the rate of heating of the wet material and the rate of decrease in moisture content were obtained by the authors for a group of thin flat materials. The paper demonstrates that the regularization in the drying process takes place not only for temperature and moisture content, but also for thermal flow. An analysis of drying of thin flat materials by the magnitude of the Biot heat exchange criterion in the period of the decreasing drying rate was performed. It was found that in the second drying period, the Biot number is less than 1 and takes the values 0.2–0.5. It is established that the rate of heating of wet material does not depend on the drying regime and the thickness of the material. Analysis of drying curves showed that the rate of moisture content loss is a complex function of the drying regime, initial moisture content, drying speed in the first period, and a number of factors affecting the process. The processing of experimental data on the basis of generalized stable complex variables, which represent the most general regularities of the kinetics of drying, makes it possible to obtain fairly simple and reliable approximate equations for the calculation of heat and moisture exchange in the drying process. The inaccuracy with this method of processing the experiment is within 3–5 %. Validation of the estimated equations and comparison of the numerical values of the heat flows the temperature and duration of the drying process with the experiment were implemented. 

The two-phase vapordynamic thermosyphon (VDT) is an efficient heat transfer device. Closed vapordynamic evaporative-condensation heat transfer cycle is realized inside it. Vapor pressure acts as a driving force for returning the liquid phase of working fluid to the condenser. The original design of the condenser and the evaporator of the VDT allows to transfer heat flow in horizontal direction to large (10–20 meters) distance. VDT can be used in heat exchangers of heat pumps, heat and cold accumulators of alternative energy sources and secondary energy sources for utilization. This article presents results of the experimental study and shows VDT heat transfer capability depending on the conditions of its work. For this purpose following VDT parameters were determined for different values of heat load and various drops between the thermosyphon evaporator and its condenser: the operating range of heat loads, maximum allowable thermosyphon angle of inclination, dependence of thermal resistance on the transmitted heat flow. The scheme of VDT is described and the methodology of the study is presented. Experimental data allows to conclude that high heat-transfer device working efficiency is achievable with heat loads between 300 and 1500 W and with vertical inclination angles up to 85 degrees. 

A method has been developed to restore the shape of the electrical load duration curve as the main predictive information on the demand for electric energy used in long-term and medium-term optimization studies of power systems. The main feature of the proposed method is the direct use in the algorithm of the basic coefficients characterizing the given form of the expression for energy demand, as well as a number of fixed points on the desired curve that are characteristic of the particular power system under study. The decision on the choice of fixed points is done with the help of retrospective historical statistics on the operation of the power system. The analytical polynomial expressions obtained using this method allow to quickly obtain the shape of the load duration curve and to simplify the procedure for entering the initial forms of curves in optimization programs, as well as to facilitate the process of predicting them for long time periods. The accuracy of the method was verified by comparison with the curves of past years obtained from the detailed hourly electrical load of the power system of the Republic of Belarus. It was found that the error value on the main part of the curve does not exceed ±1 % and slightly increases at its edges (±4–6 %), which is assumed to be sufficient accuracy for long-term energy planning. 

Active jamming of a global navigation system GNSS receiver (GPS, Galileo, GLONASS, BeiDou) is of growing significance for the missions of security, control and monitoring. GNSS facilitates organization of various tasks: transportation, protecting mobile facilities or persons, traffic control, and a lot of others. Organizing generation of effective jamming denying normal navigation represents an important applied problem. Jamming GNSS, even though formally subject to international restrictions, is nevertheless a mandatory military technical component of ensuring the defensive capability of any developed state.

The experience of recent years testifies to fast development of the equipment generating jamming against GNSS, and the technologies of counteracting jamming. Effective employment of jamming against GNSS users made the arms manufacturers seriously tackle the problem of improving jamming immunity of GNSS through modern techniques. Given the certain narrow limits for this characteristic of a system (long distances to satellites, limitations imposed on the power of information signals emitted by them, feeble directivity of their transmitting antennas), the countries possessing GNSS have published a plethora of information related to having achieved a dramatic improvement of their antijamming capacity giving rise to certain doubt in objectivity of the data.

The article presents the results of scientific analysis and modeling of effectiveness of jamming against users of GNSS information with the receivers outfitted with correlative automatic jamming cancellers (AJC). Proof is provided of corrupting effectiveness of jamming cancellation, based on use of essentially parametric properties of the AJCs. 

We suggest the alternative approach based on definition of the moment generating function for the average signal-to-noise ratio (SNR) at the receiver output with the purpose to analyze performance of systems with equal gain combining over Nakagami-n (Rice) and Nakagami-q (Hoyt) fading channels under consideration of land, mobile and satellite telecommunication systems. We derive the exact closed-form mathematical expressions for average symbol error probability and outage probability using the Pade rational approximation to moment generating function of the SNR at the output of the combiner. We investigate the following important receiver performance such as the average SNR at the receiver output, fading, spectral effectiveness at weak input signals. Additionally, we study the rational Pade approximation of the moment generating function applying to the average SNR at the receiver output and evaluate bit error rate and the outage probability. Additionally, we investigate a possibility of modeling a Hoyt fading channel based on presentation Nakagami-m statistical model for evaluation of error performance under the use of equal gain combining technique. 

Mathematical modeling is a basic tool for design and development of modern telecommunications and radioelectronics systems. It is realized on two fundamentally different levels: schematic circuit and block diagram simulation. At the initial stages of design and development of system (i.e. research scientific work, specification of requirements, initial outlay and technical project) simulation on the block diagram level is applied. Its results define the structure and basic parameters of the quality of created facilities. It has been established, that commonly applied software of block diagram simulation has essential flaws, which are resulted from a scarce mathematical description of signals and links. The research described in the article is aimed at working out the mathematical description of signals, linear links and responses. This description will contribute to creating the enhanced library of mathematical models of signals and linear links, as well as automated procedures of formation, transformation and calculation of time-and-frequency characteristics of signals, links and responses.

We suggest a mathematical description of signals, linear links and responses on the basis of specifically shaped operator fractional-rational function. It embodies and epitomizes all types of signals, linear links and responses used in modeling and provides needed transformation and creation of the enhanced library of mathematical models of signals and linear links. Subsequently, it allows creation of mathematical algorithms of normalization, reactance transformation and multiplication of models of minimum-phase and nonminimum-phase linear links, as well as generalized models of signals, linear links and responses in frequency- and time-domains. These generalized models make a basis of single mathematical algorithms and automated procedures of calculation frequency- and time-characteristics of signals, links and responses. 

The task of filtering random dynamic fields is relevant for a number of applications. To solve it, one can use a statistical approach based on the Kalman filter theory. Because of large dimension of the images, this leads to complicated equations and requires large computational costs, which makes it difficult to solve the problem in real time. Instead of statistical, it is suggested to use a deterministic approach based on the recursive least-squares technique. It is assumed that the field model, its covariance characteristics, as well as the model and characteristics of the measurement results are a priori given. To obtain recursive filter equations the loss function is used, which consists of two parts. The first one is the quadratic residual functional of the solution with weight in the form of an inverse covariance measurement matrix. The second one is a quadratic functional of the difference between the current estimation and its extrapolation to the next time point. As a result, an optimal filtering algorithm is obtained in an explicit form, which can be realized in real time with significantly less computational costs compared to the Kalman filter. An equation for the variance of filtering errors is obtained, that allows estimating the accuracy of the proposed filter and its comparison with the accuracy of the Kalman filter. An example of using the proposed methodology is given. 

The article is based on restoration method for the internal structure of a three-dimensional body using polynomial interflatation based on known tomograms (traces) lying on a system of arbitrary planes, which is a generalization of the method of body restoration with its known tomograms on a system of three groups of parallel planes. A definition of tomograms in the mathematical sense has been provided and the algorithm of transition of tomogram images into the functional dependence has been outlined.

Theorems on interflatation properties and errors of the built operator have been formulated and proved. A test case for the construction of the interflatation operator for the quadratic function has been demonstrated, and the computational experiment involved the development of a number of programs in MathCad. The experiment has provided visualization results for an exact solution and a solution obtained experimentally for the case when the exact function is known. It has been shown that the constructed structure approximates this function exactly, which is not the case of classic interpolation operators.

The suggested method makes it possible to solve the problem of three-dimensional computer tomography for a fundamentally new data collection scheme. For example, it permits the use of the fan scheme for data collection in each of the planes in which the tomograms lie. 

The methods of prediction of location of patient’s soft tissues after the treatment of dentoalveolar anomalies are considered. The base forms of teeth mesh models for modelling patient’s dental systems before and also after the medical treatment and patient’s three-dimensional model from his two photos are used as the input data. The relations are established between the base form of the teeth and three-dimensional model. These relations make it possible to modify the form of teeth with smooth modifications of soft tissues on the patient’s head. The prediction position of soft tissues is based on the position of the skeletal profile. A method for constructing the position of patient’s skeletal profile has been developed. It takes into account individual geometric parameters. The algorithm uses the technique of orthodontists to establish a series of geometric relations between the patient’s teeth. An experimental study was conducted by means of visual and numerical evaluation. The mean square deviation between soft tissues of the patient’s face and the predictable position of soft tissues of the patient’s face hadn’t prevail 10 %.