Vol 32, No 3 (2022)

Introduction. The level of technological equipment and quality of equipment placement at the technical service enterprises have a significant impact on the size of work areas and the efficiency of travel paths for moving items of agricultural machinery under repair. The purpose of research is to assess the actual equipment level and the quality of equipment placement at the specific work areas of technical service enterprises.
Material and Methods. The quality of the equipment placement at technical service enterprises is determined by comparing the actual and standard values of the coefficient that takes into account the size of work areas and travel paths for moving items of agricultural machinery under repair in particular work areas. There has been proposed a method for determining the level of equipment on the basis of the equipment deterioration and the coefficient of the equipment placement density.
Results. Eighty percent of the work areas do not comply with the basic standards of technological design. The actual value of the equipment placement density coefficient at the work areas under research was 1.1‒42.8. The average value of the coefficient was 12.5 for enterprises with a fleet of less than 25 tractors, 10.2 for enterprises with a fleet of 25 to 50 tractors and 8.6 for enterprises with a fleet of more than 50 tractors. The share of the work areas with high density of equipment placement was 13.3%, with average density 40.0% and with low density 46.7%. The values of the coefficient of equipment placement density at such basic work areas as for bench-working and assembling, forging works, welding, fusing, and etc. in some times differ from the standard values.
Discussion and Conclusion. The conducted research showed that most of work areas of technical service enterprises in the Volga Federal District have a low level of equipment. 

Introduction. Alternative fuels in IC-engines make it possible to reduce the harmful effects of exhaust gases on the environment without the use of expensive cleaning systems, diversify the fuel market, and reduce the consumption of non-renewable energy recourses, while research aimed at studying the use of alternative fuels makes it possible to find optimal options for replacing non-renewable raw materials. 
Materials and Methods. The article deals with the description of the results of the use of rapeseed oil and ethanol in a serial tractor diesel engine of dimension 2F 10.5/12.0 with separate fuel injection directly into the combustion chamber. In the course of experimental studies, the working process was indicated by a piezo quartz pressure sensor installed in the cylinder head, fuel and air consumption were measured, and samples of exhaust gases to study the gas composition and determine the content of toxic components and smokiness were taken.
Results. The exact ethanol and rapeseed oil delivery was determined; the values of the average effective pressure, the average temperature of gases in the cylinder, and active and full heat generation were obtained. It is shown that with an increase in the cyclic ethanol delivery, the proportion of heat from kinetic combustion increases, while the diesel process is characterized by an increase in the proportion of diffusion combustion when the load increases. The analysis of the processes inside the cylinder when the engine runs on ethanol and rapeseed oil in comparison with the traditional diesel process is carried out.
Discussion and Conclusion. The use of rapeseed oil and ethanol can completely replace the traditional fuel of petroleum origin for an operating diesel engine by installing additional fuel equipment and modifying the head of cylinder block through mounting an additional nozzle. In this case, the environmental performance of the diesel engine improves significantly.

Introduction. The problem of determining the optimal mode parameters during the mathematical modeling of chemical and technological processes is the most important. Numerical methods and algorithms for the solution provide the basis for developing software packages to calculate processes and their digital twins. The mathematical model of the chemical-technological process can be described by a system of differential equations, highlighting the phase variables that determine the state of the process, and the control parameters, which can be changed and thereby affect the course of the process. The aim of the work is to develop a numerical algorithm for solving the problem of optimal control of a chemical-technological process in the presence of terminal constraints and the constraints on the control parameter.
Materials and Methods. There was formulated the problem of optimal control in general terms. To solve it, the penalty method and method of artificial immune systems were applied. There was described a method for including constraints in the penalty function and for choosing a sequence of coefficients with which the penalty is taken. To overcome local extrema, a random choice of initial values of control parameters was used.
Results. The article presents a step-by-step numerical algorithm for solving the problem of optimal control of a chemical-technological process with terminal constraints. A computational experiment was carried out for a model example, as a result of which the structure of the optimal process control and the corresponding optimal trajectories of phase variables are determined. It is shown that the calculated solution of the optimal control problem consists with the solution obtained by the needle linearization method.
Discussion and Conclusion. The developed algorithm allows finding a numerical solution to the problem of optimal control of a chemical-technological process with terminal constraints. The solution does not depend on the choice of the initial approximation.

Introduction. Copper foam material has various advantages. It has been proved effective in enhanced boiling heat transfer, but also increases pump power consumption. Grooved copper foam is a solution to achieve good balance between boiling heat transfer characteristics and pump power consumption.
Material and Methods. Grooveless and grooved copper foam in open space was studied. Copper foam specifications comprised the combination of porosities of 70, 80 and 90%, and pore densities of 90 and 110 PPI. The grooved copper foams have two specifications: 11 and 17 grooves. The corresponding rib widths are 2 and 1 mm, with groove depth 2.9 mm and width 0.6 mm. The flow boiling experimental system of copper foam sample includes four parts: a heating water reservoir, pump, a test section, and a data acquisition system. In the test section, liquid water turns into vapor and carries the heat away from a copper block surface.
Results. Grooved copper foam samples presented significantly higher efficiency than grooveless ones. Grooved copper foams can increase the critical heat flux and heat transfer coefficient, compared with grooveless ones. Seventeen-grooved samples showed more excellent performance than 11-grooved ones. Visual observation disclosed that the stratified flow pattern dominated in moderate and high heat flux for grooved copper foam with open space. Covering vapor mass was more effective to be formed above 17-grooved samples, compared with 11-grooved ones.
Discussion and Conclusion. The number of grooves has a significant impact on boiling heat transfer. Grooved copper foam samples present a significantly higher critical heat flux and heat transfer coefficient. Structural parameters such as porosity and pore density, play a relatively secondly role in heat transfer argumentation. Visual observation shows there exists a cyclic alternation of flow patterns: bubbly flow, annular flow and mass vapor formation for grooved samples. 

Introduction. The use of digital technologies will increase the efficiency of animal husbandry. These technologies include optical monitoring of product quality. The aim of the research is to study the dependence of the spectral characteristics and parameters of excitation and luminescence of milk during souring.
Materials and Methods. The milk with a fat content of 3.2% was used for measurements. The acidity was controlled by the titrimetric method. The excitation and luminescence registration spectra were measured on a Fluorat-02-Panorama spectrofluorimeter in the range of 200–500 nm. Spectra parameters were calculated in the PanoramaPro and Microcal Origin programs.
Results. When milk sours, excitation spectra shift downwards, while a qualitative change in characteristics is observed with the range of 350–500 nm, although the photoelectric signal absolute level is almost an order of magnitude less than with a range of 220‒340 nm. The photoluminescence flux when excited by the radiation with wavelength of 262 nm decreases during the souring process. The flux excited by the radiation with wavelength of 385 nm increases especially in the first three days. The flux at wavelength of 442 nm decreases slightly. Statistical parameters and energy of photoluminescence spectra are not informative for the milk souring control. The dependence of the ratio of photoluminescence fluxes excited by the radiation of 385 and 442 nm on acidity is linearly approximated with a determination coefficient of 0.99.
Discussion and Conclusion. The change in the milk luminescent properties can be used as a marker of its souring with acidity control. To create a method for monitoring milk quality indicators during souring, the most informative is the use of excitation wavelengths of 385 and 442 nm with subsequent registration of photoluminescence in the ranges 440–490 and 490–600 nm respectively.