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For modern information, measuring, and optoelectronic systems based on micro- and nanomechanical sensors of angular velocity and linear acceleration, it is important to ensure their stable functioning in the presence of external factors. The paper presents the results of a study of the effect of a random vibration on the characteristics of micromechanical accelerometers (MMAs) obtained using the LDS V455 vibration bench. The dependence of the spectral density of vibration acceleration on the frequency of one of the samples, intended for acceleration measurements in the range up to ±1.2 g, has a noticeable shift from its predetermined profile. To establish the reasons for this discrepancy, the design of the MMAs’ sensitive element (SE) under the effect of a random vibration is studied. Calculations and simulations are performed in the ANSYS program. The deformations of the MMAs’ SE along the sensitivity axis Z and the capacitance changes due to the acceleration and random vibration along the X, Y, and Z axes, taking into account the crystallographic orientation of the SE’s material (silicon) are determined. The effect of the crystallographic orientation of silicon used to manufacture the MMAs’ SE on the deformation (deflection) of the rotor is considered. The presented results of the theoretical and experimental studies, as well as computer modeling, coincide, which allows us to improve the design of the MMAs’ SE.

One of the necessary requirements in Russia for obtaining subsidies that will compensate investments in a solar power plant (SPP) is to achieve the normative value of the capacity factor (CF). Although the stimulation of solar generation in the Republic of Uzbekistan is unconditional, the task of increasing the CF is also urgent for Uzbekistan. The purpose of the study was to assess the impact on a solar plants CF by the use of two methods for increasing the solar influx on the surface of a SPP solar battery; the use of Sun tracking systems (trackers) and bifacial photovoltaic panels. Calculation of the CF was carried out for several types of photovoltaic panels in the climatic conditions of the Republic of Uzbekistan and the south of Russia by dynamic simulation using the TRNSYS code. Actinometric and climatic data were taken from the NASA POWER satellite observation database; the spatial resolution was 1° × 1° in latitude and longitude. Photovoltaic panels were described by the five-parameter model, whose parameters were determined using the manufacturers’ datasheets. It is shown that the use of vertical axis and tilt axis trackers can increase the CF in comparison with fixed panels by 6.5–6.6%, which is close to the effect of biaxial trackers (up to 7.0% of CF growth). It was found that the use of bifacial panels was most effective together with tilt axis trackers (the increase of CF is up to 4.1%). This effect is less for fixed panels and other types of trackers (up to 3.6%). According to the simulations, the magnitude of surface albedo (without the use of special reflectors) has almost no effect on the usage of bifacial panels.

In microelectromechanical devices and systems (MEMS), capacitive micromechanical accelerometers (MMA) are used in airbag systems, machine vibration monitoring, navigation, seismology, microgravity measurements, etc. The most important structural elements of the sensing element are suspensions, through which the inertial mass is connected to a fixed frame. To ensure reliable operation and stability of sensor parameters, it is necessary to take into account the results of external factors already at the design stage of the sensor structure, especially its sensitive element, and at subsequent stages of the life cycle. In this work, the characteristic structures of suspension elements, which are made of silicon with different crystallographic orientations, are investigated and the results of modeling their most important parameters are presented. The simulation has been performed using the ANSYS program. The natural frequencies of inertial mass oscillations, residual mechanical stresses in the structural elements of silicon sensitive element with different crystallographic orientations have been calculated upon impact (up to 10 000 g). The natural vibration frequency changes and the dynamics of the change in the residual mechanical stress in the suspension elements with a temperature change in the range from +150 to –150 °C for a short time interval of 10 s, which corresponds to thermal shock, investigated. The results of studies of residual mechanical stresses arising upon impact and natural frequencies of inertial mass oscillations have been made it possible to develop recommendations on the choice of the design of suspension elements made of silicon, providing high sensitivity and stability of MMA parameters. It has been established that the use of folded springs with a rectangular or round cross-sectional shape with a suspension element thickness of 40 μm provides the highest temperature stability of the parameters. The results obtained are useful for developing real designs of MMA and other micromechanical devices

Calculations are made and energy parameters are compared for the actual operation data of three network photovoltaic power plants built in Russia by JSC Solar Systems. As the initial data for the calculations, the daily amounts of solar radiation and ambient temperature taken from the databases of NASA POWER, Meteonorm, and ERA5 have been used. The calculations have been carried out using a TRNSYS simulation environment, a specialized PVSyst engineering software package, and a HOMER Pro software package. In addition, we have used calculations based on a simplified technique including a linearized dependence of the photovoltaic module power on insolation and temperature implemented by means of Microsoft Excel. In all cases, we considered the efficiency of the network inverter depending on the transmitted power and the operating parameters of the module depending on the temperature. The results using each method have shown a good agreement with the actual output of photovoltaic power plants for the considered time periods. The best coincidence was observed for the case of TRNSYS, although the results vary depending on the source of the initial climatic data. Based on a simplified technique, an analysis performed concerning the output sensitivity with respect to the inverter efficiency factor and with respect to the temperature dependence of the power of photovoltaic modules showing that the method taking into account the ambient temperature makes a considerable contribution to the error of the results. The calculation results demonstrate that one could use engineering methods with a linear approximation of the photovoltaic module power depending on insolation and temperature in order to estimate the output of network power plants; however, of great importance is choosing the initial climatic data.

In gliomas, expression of certain marker genes is strongly associated with survival and tumor type and often exceeds histological assessments. Using a human interactome model, we algorithmically reconstructed 7494 new-type molecular pathways that are centered each on an individual protein. Each single-gene expression and gene-centric pathway activation was tested as a survival and tumor grade biomarker in gliomas and their diagnostic subgroups (IDH mutant or wild type, IDH mutant with 1p/19q co-deletion, MGMT promoter methylated or unmethylated), including the three major molecular subtypes of glioblastoma (proneural, mesenchymal, classical). We used three datasets from The Cancer Genome Atlas and the Chinese Glioma Genome Atlas, which in total include 527 glioblastoma and 1097 low grade glioma profiles. We identified 2724 such gene and 2418 pathway survival biomarkers out of total 17,717 genes and 7494 pathways analyzed. We then assessed tumor grade and molecular subtype biomarkers and with the threshold of AUC > 0.7 identified 1322/982 gene biomarkers and 472/537 pathway biomarkers. This suggests roughly two times greater efficacy of the reconstructed pathway approach compared to gene biomarkers. Thus, we conclude that activation levels of algorithmically reconstructed gene-centric pathways are a potent class of new-generation diagnostic and prognostic biomarkers for gliomas.

We consider a system of two hybrid vector equations containing linear difference (defined on a discrete set) and functional differential (defined on a half-axis) parts. To study it, a model system of two vector equations is chosen, one of which is linear difference with aftereffect (LDEA), and the other is a linear functional differential with aftereffect (LFDEA). Two equivalent representations of this system are shown: the first representation in the form of LFDEA, the second — in the form of LDEA. This allows us to study the stability issues of the system under consideration using the well-known results on the stability of LFDEA and LDEA. Using the results of the article [Gusarenko S. A. On the stability of a system of two linear differential equations with delayed argument // Boundary value problems. Interuniversity collection of scientific papers. Perm: PPI, 1989. P. 3–9], two examples are shown when a joint system of four equations will be stable with respect to the right side. In the first example, we use the LFDEA for which sufficient conditions for the sign-definiteness of the elements of the 2 Ч 2 Cauchy matrix function are known (in terms of the LFDEA coefficients). In the second example, LFDEA is given such that LFDEA is a system of linear ordinary differential equations (LODE) of the second order. In both cases, estimates of the components of the Cauchy matrix function are known. An exponential estimate with a negative exponent is given for the components of the Cauchy matrix function of LDEA.

A micromechanical accelerometer (MMA) is used to measure the acceleration based on the change in frequency of the resonator when the acceleration is caused by the displacement of the inertial mass. Its sensitivity can be influenced by factors such as vibration noise and temperature. In this study, using the calculation and modeling in the ANSYS program, the influence of the temperature on the natural oscillation frequency of resonators of various designs has been studied. It is shown that in a number of the studied designs of frequency MMA resonators, the frequency change ∆f0 caused by an increase in temperature is comparable and even exceeds the change in the frequency due to the acceleration effect. It is shown that the known designs of resonators whose operation is based on the oscillations of a beam fixed at both ends do not ensure the stability of oscillations at their natural frequency with a change in temperature. For resonators based on the oscillations of a cantilever beam, the frequency barely changes due to the increase in temperature. The best result from the point of view of the temperature’s stability is obtained for a resonator in the form of a cantilever beam with the beam resonator inside it, for which the frequency change ∆f0 with the temperature increasing up to 70°C was only 4 Hz. The study of the basic MMA construction, consisting of an inertial mass with a resonator made in the form of a cantilever beam with a resonator inside shows that the natural oscillation frequency of this construction is stable when the temperature increases up to 70°C. In this case, the sensitivity is 130 Hz/g and does not depend on temperature.

Background: Kidney injury is a common feature of COVID-19 infection, but serum creatinine (SCr) is not a sensitive or specific marker of kidney injury. We hypothesized that measurement of molecular markers of tubular injury can diagnose COVID-19 associated kidney injury and predict a poor prognosis. Methods: This is a prospective cohort study of 444 consecutive COVID-19 patients in a New York City Emergency Department recruited in March and April, 2020. Urine and blood were collected simultaneously at hospital admission (median time of day 0, IQR 0-2 days) and within 1 day of a positive SARS-CoV-2 test in 70% of patients. Urine NGAL and KIM-1 assays were blinded to clinical data. Primary outcomes included the diagnosis of Acute Kidney Injury (AKI) as defined by AKIN criteria, as well as its duration and severity. Secondary outcomes included death, dialysis, shock, respiratory failure, and length of hospital stay. Kidney biopsies from COVID-19 patients were examined for biomarker gene expression. Results: Elevated urinary NGAL (uNGAL) levels were associated with SCr based AKI (267±301 vs. 96±139 ng/mL, P=1.6x10-10). uNGAL level >150 ng/mL had 80% specificity and 75% sensitivity to diagnose AKIN stage 2 AKI or higher. Higher uNGAL levels were associated with sustained AKI [aOR per SD of uNGAL (95%CI): 2.67 (1.81-4.06), P=1.8x10-6], need for dialysis (aOR: 3.67 (1.89-7.57), P=2.2x10-4), shock (aOR: 1.64 (1.26-2.15), P=2.9x10-4), prolonged length of stay (aHR: 1.22 (1.09-1.36), P=4.8x10-4), and death [aOR=1.62 (1.19-2.24), P=2.5x10-3], independent of baseline SCr and pre-existing co-morbidities. These associations were also preserved after adjusting for proteinuria measured in the same urine sample. NGAL is typically transcribed by distal nephron segments but in COVID-19 kidney biopsies with widespread histopathologic acute tubular injury (ATI), NGAL mRNA expression included proximal tubules. Conclusions: Elevated uNGAL in patients admitted with acute COVID-19 was associated with the development of AKI, increased severity and duration of AKI, the degree of histopathological acute tubular injury, shock, prolonged hospitalization, need for dialysis, and death.

Modern designs of sensitive elements of many MEMS, including micromechanical accelerometers, contain suspension elements, with the help of which the inertial mass is connected to a fixed frame. The simulation was carried out using the ANSYS program, the parameters and characteristics of the sensitive element of a micromechanical accelerometer with suspension elements of various designs made of silicon with different crystallographic orientations were investigated, and the values of their most important parameters were obtained. The natural frequencies of oscillations of the inertial mass, the residual mechanical stress in the structural elements of the sensitive element of the micromechanical accelerometer were calculated. Changes in the natural vibration frequency and residual mechanical stress in the suspension elements were determined when the temperature changed from +150 to –150 ° C in a short time interval (10 s). The change in the residual mechanical stress of the inertial mass of the sensitive element during impact was investigated. The results obtained made it possible to develop recommendations for choosing the design of a sensitive element with silicon suspension elements, which provide high sensitivity and stability of the parameters of a micromechanical accelerometer. The results obtained will be useful in the development of real designs of MEMS sensitive elements with optimal and stable parameters.

There is a wide variety of designs of the suspensions used in capacitive micromechanical accelerometers and other MEMS. In this paper, the most common designs of silicon suspensions of the inertial mass of the sensitive element are investigated. The results of their modeling are presented. The results of modeling the most important parameters of the sensitive element using the ANSYS program are obtained and analyzed. Recommendations have been developed for the choice of the design of silicon suspension elements that provide increased stability of the parameters of the micromechanical accelerometer. The results obtained are in demand in the development of advanced designs for MMA and other MEMS products.

The design of the sensing element (SE) of a ring micromechanical gyroscope is presented. Features of the technological process of its balancing by means of laser punching holes in adjacent segments of the ring are considered. It is established that during its conduction, the energy and duration of the laser pulse must be selected in such a way that silicon drops do not fall on the structural elements of the SE ring.

The article is devoted to the description of techniques for building a base station (BS) of satellite navigation of security robot. An important task for this robotic device is to improve the accuracy of its positioning. In order to solve this problem, a block diagram of the BS has been developed, the structural elements for creating a prototype of the BS have been selected, the reliability calculation and experimental evaluation of positioning parameters are presented.

The task of forecasting the dynamics of changes in the rates of financial instruments is relevant, since its solution would reduce risks and increase the profitability of operations in financial markets. According to the classical concept of the nature of markets, their pricing processes are stochastic and cannot be predicted. In recent years the general trend in scientific research is econo-physics – the science in the convergence of economics and physics that uses the approaches typical for physical phenomena investigation to analyze economic systems. One of these approaches is fractal analysis. It is based on the fractal market hypothesis, which states that the dynamics of changes in prices of financial instruments is subject to power laws and their prediction is possible. The fractal of financial series is expressed in their property to maintain the trend of changes (so called long memory) for a long time. There are modifications of econometric models that take into account the fractal properties of time series. Their use in domestic markets has not been studied enough: there are few examples of successful predictions obtained using such models; there are no works that focus on the comparison of fractal and non-fractal models on sufficiently large arrays of price data, and it does not allow us to say with certainty about the superiority of models that take into account the fractal properties of series. The main idea of the study is to compare the prediction accuracy of econometric models and their fractal extensions using the same data. The purpose of the research is to verify the hypothesis that taking into account the fractal of financial series, while all other things are equal, allows us to obtain better and more accurate forecasts of financial instruments. The following approaches and methods have been used: fractal analysis and econometric models (ARIMA, GARCH), as well as their modifications, taking into account the property of long memory. For the first time, the accuracy of a large number of similar fractal and non-fractal models has been compared with differences in the nuances of fractal parameter estimation on the same data, the problems of determining the boundaries of financial series sections with different fractal properties and selecting a series (initial or transformed) for evaluating the operator of fractional differentiation of the ARFIMA model have been formulated. We have obtained the following results. The hypothesis of the best predictive ability of fractal models is not rejected, since in most cases the forecast accuracy of ARFIMA and ARFIMA-GARCH was higher than the forecast accuracy of ARIMA and GARCH. The hypothesis of a variable fractal structure of financial series has been confirmed, as evidenced by the variable graphs of local fractal dimensions. The hypothesis of the advantage of models with long memory over models with short memory has not been rejected, since the ARIMA model has demonstrated the least accuracy of forecasts. The hypothesis of the alteration of the fractal properties of time series in the transformation has been confirmed, that has been proven with different values of the Hurst exponent and different graphics of local dimensions. We did not manage to confirm the following hypotheses: the use of local fractal indicators instead of global ones to calculate the fractional differentiation parameter increases the accuracy of forecasts; with the growth of the forecast length, its accuracy decreases; sections of series with long memory are better modeled and forecasted. Possible directions for further research have been formulated: to develop a method for determining the boundaries of local areas of financial series with different fractal properties; to formulate recommendations on which series (initial or transformed) should be evaluated by the operator of fractional differentiation of the ARFIMA model; to verify unconfirmed hypotheses with a change in the research methodology; to study various fractal modifications of GARCH models and identification of conditions for their applicability.

The endocrine system plays a key role in the pathogenesis of the non-infectious pathology of dairy cows. However, the role of a number of hormones in pathology is not clear. These hormones include insulin-like growth factors and leptin. The insulin-like growth factor is synthesized predominantly in the liver in response to an increase in the level of somatotropic hormone in the blood. According to its physiological properties, it is close to insulin, structurally similar, has common receptors that trigger the same chain of reactions: stimulates transport of amino acids and glucose in the muscles, increases the sensitivity of cells to insulin, in adipose tissue, transport glucose, oxidation of glucose to carbon dioxide, the inclusion of glucose in lipids. Leptin is synthesized by adipocytes, and its main physiological function is to reduce the synthesis of macroergic compounds and increase energy expenditure. Circulating in the blood, it helps to maintain an optimal level of glucose, which is necessary for the energy needs of the body. The purpose of this study was to investigate the concentration of insulin-like growth factor, leptin, glucose, pyruvate and lactate in the blood of cows under secondary osteodystrophy, ketosis and hepatodistrophy. This will give an opportunity to better understand the pathogenesis and create theoretical preconditions for the development of informative diagnostic tests and effective means of treatment. The experiment was conducted on dairy cows, analogues by age, breed, productivity and physiological state. According to clinical features, urine analysis and values of biochemical parameters of blood of experimental cows were divided into four groups: 1 – clinically healthy cows, 2 – patients with osteodystrophy, 3 – patients with ketosis, 4 – patients with hepatodistrophy. The obtained results of research indicate that the internal non-contagious pathology in dairy cows deficiency of exchange energy is recorded, which induces an increase in the activity of gluconeogenesis and is expressed by lowering the concentration of glucose and increasing the content of pyruvate and lactate. At the same time, a decrease in the level of insulin-like growth factor and leptin was found. The lowest level of insulin-like growth factor and leptin was determined by ketosis. The decrease in the level of tissue hormones in the blood plasma of cows under osteodystrophy was within the statistical error.

We consider an abstract hybrid system of functional-differential equations. Both equations are functional-differential with respect to one part of variables and difference with respect to to the other part of variables. To the system of two equations with two unknowns appeared, we apply the W-method of N. V. Azbelev. We examine two models: a system of functional-differential equations and a system of difference equations. We study the spaces of their solutions and obtain the Bohl–Perron-type theorems on the exponential stability.

Two previously obtained, full-size, fully human antibodies that reversibly bind the active form of an enzyme belonging to the subtype EC 3.2.1, which is used for substitutive enzymatic therapy in lysosomal storage diseases, have been characterized by surface plasmon resonance and biolayer interferometry methods. It was shown under normal physiological conditions that the designed antibodies specifically bound with the antigen (KD ~ 10–8 M) and rapidly dissociated at neutral pH in 60% ethylene glycol while leaving the enzymatic activity unchanged. Dan ue to their properties, the developed antibodies can be used in industry as affinity ligand in the isolation of therapeutic substances of the enzyme.

A sensitive element of MEMS capacitive accelerometer with a sandwich construction (X axis) using the variable dielectric displacement method is studied in this article. As a result, there is a change in capacitance in the output measuring circuit. The considered model provides high sensitivity to the effects of acceleration, resistance to temperature changes and low residual mechanical stress in the sensing element. Modeling and calculations are performed using the ANSYS and SOLIDWORKS programs. The magnitude of the displacement of the movable mass along the sensitivity axis (X) is 5 times greater than the displacement of the movable mass along the nonworking axes (Z and Y), and the capacitance changes between the electrodes along the X axis are almost 2500 times greater than the capacitance changes between the electrodes along the nonworking axes (Z and Y). The mechanical stress in the sensitive element is significantly less than the silicon tensile strength of 440 MPa under the acceleration (0-30g). Temperature variations in the range from -40 ° C to + 85 ° C resulted in very insignificant changes in capacitance along the working axis equaled 0.0025 - 0.003pF, which indicates the temperature stability of the sensitive element. The analysis showed that the developed and studied model of the sensitive element’s design provides high MMA sensitivity and the stability of its parameters.

The results of the influence of the diaphragm shape of a piezoresistive pressure sensor on its parameters are determined in this article. Square, rectangular and round diaphragms made of monocrystalline silicon were studied. With the help of the ANSYS program, the simulation was performed, the parameters - deformations and mechanical stresses arising in diaphragms were calculated and which turned out to be different for diaphragms of different shapes. The results are analyzed; recommendations on the choice of diaphragm shape in sensors are given.

Using the finite element modeling in ANSYS, modeling and calculation of the main parameters of the sensitive element of a differential capacitive micromechanical accelerometer were performed. These parameters are the coefficient of elasticity of the suspension, the natural frequency of the sensitive element and relative damping coefficients. The calculation of the stress, which is an integral parameter of the MEMS accelerometer, depends on the sensitive element structure - the coefficient of elasticity of the suspension, the area of the plates, the distance between the plates. An algorithm has been developed for the manufacturing process of the sensitive element; recommendations are given for improving the design.

Aim. To investigate the plasma concentrations of insulin-like growth factor (IGF, somatomedin C), triiodothyronine, thyroxine and insulin in cows during prepartum and postpartum periods. Methods. Enzyme- linked immunosorbent assay, clinical and statistical methods. Results. It was demonstrated that the plasma concentration of IGF, triiodothyronine, thyroxine, and insulin is lower in postpartum cows compared to the interlactation ones. Strong positive correlation dependence (r = 0.7) between the levels of thyroxine and somatomedin C was found on the 2 nd –4 th day after calving. The plasma concentration of all the investigated hormones increased in cows on the 10-14 th day of postpartum period and remained stable until days 30–40. Strong correlation dependence between the levels of somatomedin C and insulin (r = 0.7) was found on the 10- 14 th day of the postpartum period. Conclusions. It was determined that somatomedin C is one of the energetic balance regulators in dairy cows.

Aim. To investigate plasma amino acid composition in dairy cows after ketosis conventional (oral administra- tion of propylene glycol, intravenous injection of glucose and insulin) and proposed treatment (oral administra- tion of propylene glycol, intravenous injection of “Remivital”). Methods. Study was performed on high yield- ing dairy cows with clinical ketosis during their 2 nd to 4 th lactation with milk yield above 8000 L per previous lactation. Content of free amino acids was determined in plasma before and after treatment using amino acid analyzer. Results. Lowering of the level of ketogenic amino acids was revealed after conducted treatment as well as increase in the level of glycogenic and branched amino acids. Signifi cant lowering of the level of meth- ylhistidine gives evidence of decreased catabolism of contractile proteins. Conclusions. Proposed treatment regimen has proven to be superior, since signifi cantly higher level of ornithine and lower level of citrulline were revealed after administration of conventional regimen, which gives evidence of problems in disposal of ammonia and lactate. Moreover, in case of administration of traditional scheme, the concentration of markers of catabolism of contractile proteins was still high, in contrast with such in animals, which were administered proposed regimen, and high concentration of isoleucine contributes to aggravation of ketoacidosis.

Today micromechanical capacitive accelerometers with comb drive constructions are intensively developed. A two axis (X and Z) capacitive accelerometer using vertical overlap comb drives structure has been designed. The capacitance changes between the moveable and fixed electrodes and the main influence factors of the sensor have been calculated. The capacitance changes of the proof mass due to X-axis acceleration and Z axis acceleration are equal to 1.372pF and 7.854pF. Mechanical bending stresses of the proof mass due to X and Z acceleration are equal to 31.959MPa and 26.043MPa. The resonant frequencies of the proof mass at working axis (X) and Z are 1026MHz and 1309MHz. Owing to the temperature from -40°C to 80°C, the deformation of the proof almost never occur. The obtained result is a well-reasoned choice of the design and reasonable parameters of micro comb construction actuators with four folded beams.

This paper focuses on the study of sandwich-type sensitive elements with folded springs of a capacitive micromechanical accelerometer. Larger gaps (up to 20 microns) between the movable and fixed electrodes simplify the manufacturing technology. The optimized design of the sensing element (compared with analogs [1]) ensures high sensitivity. The study reveals that the change in capacitance caused by acceleration along the working axis (Z) is almost 20 times as big as the changes in capacitance along other axes (X and Y). The effect of temperature within the range from -40 °C to + 85 °C on the change of capacitance along the working axis (Z) is small ±0.0025 – 0.003pF. The mechanical stresses that occur in the sensitive element structures at the acceleration of up to 50g do not exceed 2.29MPa, while silicon has a mechanical strength of 440MPa.

To improve the sensitivity of the MEMS comb — drive inclinometer three shapes of the comb-drive: ordinary, triangular and curve were investigated. We used typical folded beam for displacement of rotor part. By calculating the results in ANSYS, the change of capacitance in curve shape comb-drive is more than in the other shapes. And the quality factor of curve shape actuator is higher than in other shape actuator. The curve shape comb-drive is more suitable for getting higher sensitivity for comb-drive MEMS inclinometer.

In the course of the work, the results of estimating the error in the numerical calculation of two-element 3D impeller stages of centrifugal compressors were obtained. Gas dynamic characteristics of 6 computational models of two-element stages of a centrifugal compressor are simulated. Based on available experimental data, models of validation characteristics have been performed. A parametric model has been developed for carrying out multi-criteria and multi-parametric studies.In the course of the work, the results of estimating the error in the numerical calculation of two-element 3D impeller stages of centrifugal compressors were obtained. Gas dynamic characteristics of 6 computational models of two-element stages of a centrifugal compressor are simulated. Based on available experimental data, models of validation characteristics have been performed. A parametric model has been developed for carrying out multi-criteria and multi-parametric studies.

The article considers modeling of modern heat exchange systems which use thermal energy for its beneficial use. The proposed mathematical model makes it possible to investigate systems with utilization of thermal energy. The article presents the results of simulation of heat exchange processes using heat energy recovery for internal combustion engines.