Objectives Development of energy-efficient light-emitting bipolar semiconductor structures.

Method  A method for transforming thermoelectric heat in bipolar semiconductor structures into optical-range electromagnetic radiation, which preserves the cooling effect on thermoelectric transitions, is proposed. Instead of transferring the information impulse electrically from the baseemitter light-emitting transition, the information is transferred directly to the light-absorbing basecollector transition by photons or following multiple re-reflections from mirror metal electrodes.

Results Unlike conventional optocouplers discretely separated in space, the novel optocouplers described in the article are integrated into a single electronic component using the principle of LED radiation. As a result, light-emitting bipolar semiconductor structures will result in the creation of more powerful, faster and better integrated devices.

Conclusion Light-emitting bipolar semiconductor structures will not only increase the reliability of electronic components across a wide range of performance characteristics, but also increase energy efficiency through the use of optical radiation recovery. The future development of light-efficient transistors improves integration and increases processor performance, at the same time as reducing the power consumption of the cooling system and the power supply of the device itself.

Objectives In this research, we aimed to develop a thermoelectric device (TED) for intracavitary hypothermia, to carry out experimental studies into its functional characteristics, as well as to develop treatment procedures using this device.

Method A TED design for intracavitary hypothermia was developed, consisting of two thermoelectric batteries (TEBs) interconnected using an allmetal heat pipeline equipped with an influencing applicator and a liquid heat exchanger. Experimental studies of the device were carried out on a designed bench, which included a climatic chamber, a source of electrical energy and a temperature meter connected to a PC.

Results Temperature changes at the control points of the device were recorded over time. Changes in the time taken to stabilise temperatures of the device tip, heat pipe and heat sink system at different TEB supply currents were investigated. Possible methods for treating some ENT diseases using the developed device are described.

Conclusion It is shown that the temperature of the applicator is stabilised after approximately 4-4.5 minutes without load. At the same time, an increase in the current of the additional TEB from 5 to 12 A at the main TEB current of 23 A reduces the temperature from 237 K to 224 K. In the process of carrying out the procedures, the necessary level of a decrease in the temperature of a biological object can be reached at the supply current of the main and additional TEBs equal to 23 and 12 A, respectively, after 2.5 minutes. The full potential of the TED device will be realised through the developed of methods for treating ENT diseases. 

Objectives Determination of prospects for the use of various refrigerants, as well as the potential for their interchangeability in low-temperature equipment in accordance with the conditions of the Kigali Amendment to the Montreal Protocol on substances that deplete the ozone layer.

Method A computer simulation of heat exchange processes based on generally accepted dependencies was carried out and data for the construction of refrigeration machine elements obtained.

Results R717 and R410A are recommended for use in medium- and low-temperature machines. R32 refrigerant is used in high-temperature refrigeration machines, especially in units with finned copper tubes. The low vapour content of R32 refrigerant prevents steaming of the upper layers of the tube bundle, leading to an increase in the level of the refrigerant in the evaporator and in the working area of the evaporator tube bundle. For R32, it is necessary to conduct additional research to find an alternative refrigerant. The highest values of the heat transfer coefficient are obtained when working on refrigerants R410A and R717.

Conclusion The implemented algorithms can be helpful for obtaining the characteristics of the steam-compressor refrigerator elements across a wide range of boiling and condensing temperatures taking various factors and the percentage composition of the mixed working substance into account. This is a highly important consideration when converting the machines to run on alternative refrigerants. 

 Objectives This work was devoted to the research of thermal processes that occur in the reflex areas of the human body, in particular, in reflexogenic areas of the human foot, under the thermal influence under ambulatory conditions.

Method A model of thermal impact on the reflex areas of the human body was developed on the basis of a semiconductor thermoelectric device. A simplified physical model was studied, which does not consider heat exchange in thermoelectric batteries (TEBs) and elements of TEBs pairing with separate reflex zones.

Results Diagrams for temperature distribution throughout the foot at different values of heat flow and diagrams of temperature changes over time were obtained. The thermal influence of a TEB brought in thermal contact with the opposite surface of the foot is negligible in this case; this is due to the low thermal conductivity of foot tissues, as well as insignificant thermal flows on its surface (low-power TEBs were used for such procedures).

Conclusion The developed model of a semiconductor thermoelectric device for treating the reflex areas of the human body – in particular, the foot – allows an investigation of thermal processes occurring during the thermal treatment of biologically active points of the human sole. It is established that local temperature impact on a biological object does not result in significant temperature difference over its thickness.

Objectives To analyse the thermophysical processes in the thermoelectric heat transfer intensifier operating as part of a desalination system based on semiconductor thermoelectric converters.

Method A mathematical model for the design of a desalter containing a thermoelectric heat exchanger, which provides for the use of heat flows by natural thermal conductivity due to so-called heat channels, is proposed. The proposed method of using additional heat sinks on the heat-absorbing side of the device and additional heat sources on the fuel side determines the need for a new mathematical model that differs from the known mathematical models describing heat transfer in the heat transfer flowing-type intensifier.

Results The analysis of modelling results shows that a significant contribution to the temperature field of heat conductors is made when considering the heat transfer over the heat channels. The value of the contribution is the greater, the higher the thermal conductivity of the heat channels and the temperature difference between the heat conductors and the surface of the heat channels. In accordance with their purpose, flow-type thermoelectric heat transfer intensifiers (THTIs) for desalination applications must ensure efficient heat transfer from the cooled fluid flow to the heated fluid flow. The results show that, at a given limited length of the heat exchanger, the use of a thermoelectric battery together with heat channels allows equality of temperatures of heat conductors at the output to be achieved.

Conclusion The modelling results show that, under the operating conditions of the thermal battery in intensifier mode, the length of the heat exchanger shall not exceed the value, at which the temperature of the heat conductor at the outlet becomes equal. The system solution provides the required length of the thermal battery, which allows equality of coolant temperatures to be achieved at the exit from the THTI operation mode. Following the logic of the desalter scheme under consideration, it is obvious that the reduction in the length of the heat exchanger, with all other things being equal, gives a reduction in the mass and size of the device as a whole.

 Objectives To develop software methods that can improve the reliability of airfield quasi-Doppler automatic direction finders (ADFs).

Method. Mathematical models and algorithms of software fault recovery of aerodrome quasi-Doppler automatic radio direction finders were developed. It is proposed to change the structure of aerodrome quasi-Doppler automatic radio direction finders.

Results. Methods and algorithms for software improvement of the reliability of airfield quasi-Doppler automatic direction finders are proposed. A novel structural organisation of airfield quasi-Doppler automatic radio direction finders is given. New software methods are proposed for ensuring ADF operability in the event of a failure of the antenna system vibrators, both with the use of phase relations from any two pairs of orthogonally arranged ring antenna vibrators and with the use of the combinatorial method. The proposed organisational ADF scheme allows the average operating time per failure of one direction-finding channel to be increased by 4.4 times.

Conclusion. The developed methods for ensuring ADF operability in the event of a failure of antenna system vibrators enable a simultaneous calculation of the azimuth and angle of position on the radio emission source. The use of the proposed method increases the potential reliability of airfield quasi-Doppler automatic direction finders without any hardware costs, as well as ensuring the adequacy of the calculated instrumental error values of airfield quasi-Doppler automatic direction finders relative to the real ones. 

Objectives Development of a method for selecting the type of accessory function and obtaining its parameters to allow subjective personal influences in automated information processing to be excluded.

Method. Existing methods for constructing membership functions were analysed. The research was based on the methods of fuzzy logic and data analysis.

Results. A method for obtaining the parameters of membership functions of fuzzy sets using real data is suggested. It is proposed to use the data obtained from the object under study to determine the kernel of the fuzzy number, as well as derive theoretical information about the object for the carrier. Triangular, trapezoidal, bell-shaped and Gaussian membership functions are considered. The appearance of the membership function can be defined using the criterion of the relations of the kernel to the carrier of a fuzzy set. The results of calculations for obtaining the membership functions based on data on the power consumption of electric motors of different types are given.

Conclusion. The developed method can be used both in decision support systems as well as in automated systems for controlling technological processes. If necessary, the values of the criterion proposed in the article can be revised to take the values included in the set of measured real data into account or to simplify the procedure of automated processing. Further research will use the described method to obtain the terms of linguistic variables. 

Objectives At present, in accordance with the requirements of the guiding documents of the Federal Service for Technical and Export Control (FSTEC) of Russia, as well as international standards in the development and operation of protected automated systems, it is necessary to evaluate the effectiveness (general utility) of information protection systems. The article is devoted to the development of a method for assessing the ergotechnical characteristics of software information security systems for use the assessment of the general utility of such systems. The aim of the work is to develop a methodology for assessing the probabilistic indicator of the timeliness of typical operations for the administration of information security systems.

Method To achieve this goal, user groups were created in order to perform typical administrative operations within the information protection system. The operation time for each group, recorded using the IOGraphV1.0.1 tool, was utilised to calculate the probabilities of timely execution of typical operations by the administrator according to a truncated normal distribution formula.

Results An assessment of a probabilistic indicator was carried out in order to evaluate the timeliness of operations performed by the administrator of the information protection system.

Conclusion The results can be used in a comprehensive assessment of the effectiveness (reliability) of the automated functioning of information security software systems when modelling and analysing the security of special-purpose informatisation facilities.

 Objectives To carry out calculations involved in the design of a microwave mixer with a diplexer with the formation of the antiphase heterodyne signal using a slot resonator.

Method In order to calculate and optimise the characteristics, design and topological parameters of microwave mixers, the results of the design bandpass filter  PF and low-pass filter (LPF) mixers of through-feed type were used. The characteristics of mixers and their structural elements were calculated using the Serenade software package intended for the automated calculation of microwave devices. A distinct feature of designing mixers (with a diplexer) involves the need to optimise the topology of the diplexer before optimising the mixer characteristics.

Results The characteristics of nonlinear distortions show that the maximum power level at the mixer inlet should not exceed -15 – -20 dBm. In order to attenuate the intermodulation distortions of the 3rd order, this level should be higher that 50 dBs. The relatively low level of compression and suppression of harmonic and intermodulation distortions associated with the minimisation of the heterodyne power level at the calculation of characteristics of mixers of the required heterodyne power level (Rh ~ 5-7 dBm) is due to the minimum expenses at the realisation of sources of heterodyne signals. A noticeable improvement in the characteristics of mixers by nonlinear distortions can be achieved by shifting the operating point at the points on the current-voltage characteristic (VAC) diodes by an external voltage source with a simultaneous increase in Ph by several dB (up to Ph = 10 dBm).

Conclusion A mode of increased nonlinear distortion suppression can be practically realised by switching on diodes through resistive-capacitive circuits (auto-shift) or using diodes with an increased potential barrier. The calculation shows that it is possible to realise sufficiently small conversion losses of 6.6-8.0 dB at low levels of Rh ~ 5-7 dBm. 

Objectives This paper sets out to provide a theoretical substantiation of the placement of external fire-prevention water supply sources when designing unique construction objects, for which standard requirements of fire safety cannot be applied. Problematic situations arising during the design of unique construction objects, which relate to the provision of the required level of fireextinguishing substances supply, are described.

Method A model constructed on the basis of graph theory is presented for the preliminary calculation of the location of external fire-fighting water supply sources that takes the equipment of fire-rescue units into account. The utility of developing a universal mathematical model for the preliminary definition of arrangement parameters of sources of external fire-prevention water supply when designing construction objects is substantiated.

Results Examples of preliminary calculation of the number of external fire-fighting water supply sources are given considering the shape of the building perimeter. Additional factors determining the distances from external fire-fighting water supply sources to the projected objects are given.

Conclusion A conclusion regarding the adequacy of the proposed model is formulated and directions for future research indicated that allows the applicability of the model to be specified for the calculation of the projected objects, which differ in terms of dimensions given in the plan by above-normative characteristics. 

Objectives The paper proposes a technique that allows the main types of clouds and cloud cover parameters (ceiling, direction and speed of cloud movement) to be determined at minimum cost via observations from the Earth’s surface. The aim is to avoid using meteorological information derived from official sources, which may not always be available for a specific place and time of observation.

Method The method is based on the well-known Ippolitov formula that connects air humidity on the Earth’s surface with the cloud ceiling, whose empirical coefficients depend on the type of the cloud cover. In order to determine this type, a method based on elliptic cloud contour approximation is proposed.

Results Additional classification features were the number of approximating ellipses in the image frame, the proximity of their mutual location, the total area that they occupy in the frame and the area occupied by the largest ellipse. The speed and direction of the clouds are determined through shifting the common key points in image frames obtained over a small fixed time interval. Each point is described by a descriptor calculated using the SURF method from the open image processing library OpenCV.

Conclusion Despite the simplicity of the required software and hardware (web camera, humidity sensor, and OEM – Arduino module), this method provides a definition of these parameters with an error within 20%. Monitoring systems based on this method may be used in private automatic weather stations, such as the Wunderground, for obtaining more information that could improve the accuracy of weather forecasts, as well as for research in meteorology and climatology. 

Objectives Development of compositions filled with binders based on recycled materials for monolithic high-strength concrete.

Method The research methods adopted in the work are based on the theoretical principles and laws of designing and optimizing polydisperse multicomponent systems, the phase and structure formation of clinker minerals, the logic of mathematical calculations, the technological features of the structure formation of composite masses, the theoretical principles of controlling the rheological processes of mixes. All experimental data presented in the work were obtained according to the methods of current regulatory documents (GOST, recommendations, etc.).

Result The paper provides an analysis of the experience of using recycled materials in the form of products of demolition of buildings and structures, the technology for producing secondary raw materials for concrete on their basis. Formulations filled with binders with an activity of 60-71 MPa with finely dispersed mineral fillers from concrete scrap and brick combat with a ratio of 70:30%, respectively, were developed and investigated.

Conclusion The optimal formulations of highly mobile concrete mixtures were designed using local natural and technogenic raw materials with a grade of P5 cone sediment and persistence for more than 8 hours to obtain high-strength classes of compressive strength up to B60-B80 with unique operational properties. 

Objectives This study was aimed at identifying the dependency of the frost resistance of the contact zone of fine-grained concretes (FGCs) obtained from dry building mixtures (DBMs) based on various Portland cements (PCs) with the content of various redispersable polymer powders (RPPs) from 0 to 3%.

Method The research was based on 75 freeze-defrost cycles.

Results Although the average dependency of adhesion with the base on additional porosity after 75 freeze-defrost cycles does not depend on the nature of NMV, adhesion is influenced by the cement type, the type and dosage of RPPs, as well as the nature of additional porosity. Since the content of organised volume of NMV in the form of VV has no effect on changes in adhesion with the concrete base following 75 freeze-defrost cycles, it is impractical to add more than 7% of NMV in the form of MS to the concrete mixture. The feasibility of using sulphate-resistant cement requires more research. The practical RPP dosage should be 1-2%. Some contradictions in conclusions on the volume of the introduced MS (by the strength criterion – at least 6%, by the criterion of frost resistance of the contact zone – no more than 7%) allows us to recommend the dosage of MS in RPP within 6-7% by volume for obtaining additional data on the MS effect on frost resistance.

Conclusion The dependency of compressive strength on additional porosity for FGCs without NMV and with NMV in the VV form after hardening during 28 days under normal conditions almost coincides with the known dependency of strength on porosity for cement stone; the maximum divergence of the values ???????? ????0 in the investigated range does not exceed 5%. The dependency of compressive strength on additional porosity for FGCs without NMV and with NMV in the MS form is similar to the known dependency of strength from porosity for cement stone; however, with increasing porosity, there is a slight decrease in the effect of porosity on strength. The dependency of compressive strength after 75 freeze-defrost cycles on additional porosity for FGC without NMV practically coincides with the previously obtained dependency of strength on porosity for cement stone; the maximum divergence of the values ???????? ????0 in the investigated range does not exceed 9%. For FGCs with NMV in the MC form, increasing porosity causes a slight decrease in the porosity effect on strength, and for FGCs with NMV in the VV form, the dependency has a quantitative and qualitative difference. The value of NMV in the VV form recommended for improving the frost resistance of FGCs by the strength criterion is at least 3%, MS – at least 6%. According to the criterion of the frost resistance of the contact zone and the strength of MS, the recommended dosage is 6-7%. It was not possible to disclose the direct impact of the VV volume on the frost resistance of the contact zone. 

 Objectives The creation of clinkerless cements that do not require high-temperature processing and significant natural resources, at the same time as exhibiting good technical parameters, seems to be an important research task. Cements of alkaline instillation, in which alkaline metals play an active role, are capable of interacting with minerals of aluminosilicate nature forming strong and insoluble compounds.

Methods Concrete composites from binding substances activated by alkaline were developed on the basis of Russian and foreign experience of using cinder slag composites in construction.

Results In this work, energy-dispersion microanalysis of the developed clinkerless compositions based on alkaline silicate sodium solutions from silica-containing rocks was carried out.

Conclusion Formulations of clinkerless cements based on high-dispersal powders of different natures mixed by the alkaline solution obtained using the wet technique at temperatures of up to 95 °C and atmospheric pressure are proposed. This technology will expand the use of alkaline cements, thus leading to the development of concrete having desired properties. 

Objectives To study the problem of determining the degree of stress at the apex of a wedge-shaped area in cases where the sides (or one of them) are covered with a thin flexible coating.

Method It is assumed that the coating is not stretchable. On the other side of the wedge-shaped area, the same coating is assumed to be present; it is either fixed, stress-free or in smooth contact with a rigid base. Mathematically, the problem is reduced to the task of determining the roots of characteristic transcendental equations arising from the existence of a nontrivial solution to the system of linear homogeneous equations.

Results Values for the specific characteristics of the radial component of a stress tensor are determined for different combinations of boundary conditions and solution angles. In particular, the angles at which the singular behaviour of stresses occurs are determined. The case is considered when a special boundary condition is given on the edge surface, simulating the overlay. Characteristic equations are obtained to determine the index of the degree dependency of the asymptotic solution in its vicinity for four variants of boundary conditions. In two cases, transcendental equations are obtained, which are solved numerically.

Conclusion Calculations of the first positive roots of the equations depending on the angle of the edge solution and Poisson's ratio are presented. The values of the angles, at which the singular behaviour of stresses occurs, are determined. In the case of a combination of boundary conditions (III – IV), the singular stress behaviour is observed for the angle ???? = ????/8, while in the case of (III – III) this value is equal to ????/4. 

Objectives. In this research, we set out to explore the possibility of increasing the resistance of three-layered panels with a pyramid filler filled with fibrous material to dynamic loads. Although issues associated with dynamic impact, penetration of solid bodies and breaking of solid barriers have always been of interest, particularly in military affairs, they are increasingly attracting the attention of researchers investigating various industrial problems.

Method. A calculation was performed using the finite element method (FEM), which is widely used in various areas including construction. The possibility of calculating the movement of a solid body in fibrous material using the FEM, namely using the LIRA-SAPR software, was considered.

Results. From the constructed models, it can be seen how the striker moves inside the fibrous material. Therefore, using the SC LIRA-SAPR allows the work of the filler to be assessed while a solid body moves inside it. The results of the calculation of striker movement in fibrous material depending on the speed of the body (striker) and the density of the filler (fibre) are shown in figures.

Conclusion. The conducted numerical studies showed that a discrepancy between the calculation results for a three-layered structure under dynamic loads using the FEM and analytical dependencies was about 10%.