Optimization Of Technological Processes Research Articles

In Ukrainian

Blood loss is one of the main causes of death, especially in war and natural disasters. At the beginning of the full-scale Russian-Ukrainian war we established the laboratory and later the industrial production of a powdered topical hemostatic composition based on nanosilica which is intended for providing first pre-medical aid. The composition contains nanosized silica A-300 and sodium alginate as two active ingredients in a mass ratio of 4:1. The aim of the work was to develop the optimal technological process for the production of a hemostatic composition and carry out physico-chemical and medical-biological studies of semi-finished products and the final product. Bulk density measurements, optical microscopy, IR spectroscopy method and microbiological research were used to study the initial materials, intermediate products as well as the final product. The effectiveness of the hemostatic effect of the composition was checked on the model of parenchymal bleeding from the liver of a rat, using the time to stop bleeding (min) as a criterion. As a result of the research, a two-stage method of manufacturing the composition is proposed: at the first stage, certain parts of the initial materials are treated in a ball mill, obtaining the semi-finished product "A-300/sodium alginate"; at the second stage, this semi-finished product is mixed with nanosilica and sodium alginate, obtaining the final product. It is shown that the bulk density serves as a useful technological parameter to control of which helps to produce a structurally homogeneous final product. In the IR spectra of the semi-finished product and the finished product, only the absorption bands of silica and sodium alginate are observed, that is, foreign substances are not formed during technological process. The microbiological purity of the composition meets the pharmacopoeial requirements for drugs of this category. An experimental study of the topical hemostatic effect of the composition revealed its significant advantage compared to the inorganic hemostatic substance kaolin, which acts according to a similar adsorption mechanism.

Numerical Investigation on Flowability of Pulverized Biomass Using the Swelling Bed Model

Numerical investigations on the flowability of pulverized biomass are crucial for agriculture, aiding in optimizing biomass use, crop residue management, soil health improvement, and environmental impact mitigation. Rising interest in biomass and conversion processes necessitates deeper property understanding and technological process optimization. Moisture content is a key parameter influencing biomass quality. In this paper, computer simulations of shear tests depending on the moisture content using the discrete element method were carried out and compared with experimental results. An experimental study and modeling for Jenike’s direct shearing apparatus was carried out. A swelling bed model was proposed to account for the effect of moisture. The swelling bed model assumed an increase in biomass grain vorticity proportional to the moisture content. The model was solved using the discrete element method (DEM). The model considers the effect of moisture on the values of Young’s and Kirchoff’s moduli for biomass grains. The model assumed that moisture is not present in surface form, the total amount of moisture is absorbed into the interior of the material grains, and the volume of a single grain increases linearly with an increase in the volume of the absorbed moisture. The tested materials were pulverized sunflower husks, apple pomace, distiller’s dried grains with solubles (DDGS), meat and bone meal (MBM), and sawdust. Samples with moisture contents of 0%, 10%, 20%, and 30% were tested. The best agreement of the model with the experimental data was observed for the most absorbent materials in which moisture was not present in surface form, such as apple pomace, DDGS, and sawdust. Research data are important for the proper design of biomass storage, transportation equipment, and utilization as feedstock for bioenergy production or soil enrichment.

Experimental Verification of Calculation Formulas for Hydraulic Characteristics of Ash Suspension Removal

Abstract The article presents a comprehensive analysis of the hydraulic characteristics of ash suspensions, in particular the removal of ash from the Dnieper Hydroelectric Station. The importance of this research is justified by the relevance of understanding hydrodynamic processes in suspensions, which is crucial for the efficiency of mineral resource processing. The study focuses on the investigation of the physico-chemical properties of suspensions, which is fundamental for the development and optimization of technological processes. The main goal of the article is to determine the discrepancies between theoretical calculations and experimental data in the context of the hydraulic characteristics of ash suspensions. Focusing on this issue, the research aims to make an important contribution to the accuracy of prediction and calculation of the behavior of suspensions, which has important practical applications. The research methodology includes a series of experiments to measure various hydraulic parameters of the suspension, including suspension density, solid phase weight content, and porosity. The experiments are based on a detailed analysis of ash samples collected from the Dnieper Hydroelectric Station. It is established that theoretical formulas for determining hydraulic characteristics are well confirmed experimentally. The difference is due to the accuracy of measuring the density of the solid phase and errors in measuring weight and volume; it is sufficiently small and does not have a fundamental character.

DEVELOPMENT OF RECOMMENDATIONS FOR OPTIMIZATION OF TECHNOLOGICAL PROCESSES OF PROCESSING AND USE OF HEAT AND MASS EXCHANGE EQUIPMENT FOR DRYING LEGUMES

The article is devoted to the development of recommendations for the optimization of technological processes of processing and the use of heat and mass exchange equipment for drying legumes. Legumes are an important source of protein and other nutrients in the food and feed industry, and their drying plays a key role in preserving and increasing shelf life. The article includes analysis of technological processes, selection of optimal heat and mass exchange equipment, control of temperature and humidity, reduction of losses of useful substances and implementation of a quality monitoring and control system. Optimizing these processes will help increase production efficiency and improve the quality of dried leguminous herbs, contributing to the development of the industry and meeting the demand for valuable products. In this context, our article is devoted to the development of recommendations for the optimization of technological processes of processing and the use of heat and mass exchange equipment for drying legumes. By combining scientific analysis, practical experience and innovative approaches, we set ourselves the task of developing integrated recommendations that will contribute to increasing the efficiency of the drying process, reducing the loss of useful substances and improving the quality of dried legumes. An important aspect of our article is not only the theoretical base and scientific research, but also a practical approach to solving this problem. We hope that the developed recommendations will find practical application in the agro-industrial sector, contributing to the conservation of resources, increasing the quality and competitiveness of products and contributing to the sustainable development of this important industry.

THERMODYNAMICS OF STEPWISE DISSOCIATION OF GLYCYL-D-PHENYLALANINE IN AQUEOUS SOLUTION

Recently, more and more drugs that are derivatives of oligopeptides have been introduced to the pharmaceutical market. The structural elements of these compounds are amino acids and dipeptides. When stabilizing functional groups are introduced into the peptide structure, as well as through the use of special delivery systems, oligopeptide derivatives can be used as innovative medicines. The calorimetric method was used to determine the heat of interaction of glycyl-D-phenylalanine with solutions of nitric acid and potassium hydroxide at 298.15K and the values of the ionic strength of the solution 0.5, 0.75 and 1.0 in the presence of KNO3. Measurements were carried out on a calorimeter with an isothermal shell and automatic recording of the temperature-time curve. The unit was equipped with a reaction vessel with a volume of 60 cm3. Calibration was performed by current at T = (293.15–308.15) ± 0.01 K and P = 100.5± 0.7 kPa. A thermistor KMT-14 was used as a temperature sensor. The temperature of the calorimetric cell was controlled in a thermostat equipped with a PID controller with an accuracy of 0.002 K. The temperature sensor of the thermostat was a platinum resistance thermometer. The calorimeter was calibrated by current. The volume of the calorimetric liquid is 42.83 ml. The enthalpy of stepwise dissociation of glycyl-D-phenylalanine at zero ionic strength was found by an equation with one individual parameter. Standard thermodynamic characteristics (ΔrH°, ΔrG°, ΔrS°) of acid-base interaction reactions in aqueous solutions of glycyl-D-phenylalanine are calculated. The effect of the background electrolyte concentration on the dissociation heats of glycyl-D-phenylalanine is considered. Knowledge of the thermochemical characteristics of dipeptides is necessary for understanding and subsequent modeling of the process of protein biosynthesis occurring in biological systems. Data on the thermodynamic characteristics of dipeptide solutions are needed in various fields where these compounds are used: pharmacology, medicine, food and cosmetic industries, for the development, justification and optimization of technological processes involving these compounds and their complexes with metals.

Development of automatic control system of drum boiler on the basis of fuzzy controller with pid-controller adaptation

The aim of the study is to reduce energy losses in a drum steam boiler by introducing an automatic control system realized on the basis of fuzzy adaptation of proportional-integral-derivative (PID) controller coefficients using fuzzy term-multiplications. Control algorithms of the main technological parameters of the boiler unit (air quantity, fuel quantity, steam pressure, feed water flow rate), reducing energy costs due to the maintenance of the ratio of fuel and air pressure in accordance with the mode map of the boiler unit (optimal technological process of combustion and steam formation in a steam boiler) are developed. The structural scheme of the object control is offered, in which, besides regulation of values of technological parameters, full compensation of mutual influence of all regulation circuits is made.

On the Development and Adaptation of a Predictive Model of Full-Factor Optimization of The Basic Probiotic Fermented Dairy Product Technological Process

The purpose of building a predictive model for optimization of technological processes probiotic fermented dairy product.

Technological process optimization and measurement of image quality of the electrically bifocal metalens.

This Letter describes the design procedure and process optimization of the electrically bifocal metalens. In our design, horizontal and vertical polarization is manipulated by applying a suitable voltage to a twisted nematic liquid crystal (TN-LC) cell. Each nanostructure is designed to be a rectangular prism, making different polarizations of light experience various phase delays, thus causing bi-focus. We selected lithographical methods to fabricate our metalens because of the minimum physical size, which can be as small as 50 nm, and the maximum aspect ratio, which is as high as 15. Furthermore, to increase the tolerance and make the sidewall vertical and smooth, we coated different characteristics of photoresist sensitivity to the upper and lower layers. After the development, the mushroom-type photoresist makes Ni easier to strip while in the lift-off process, thus increasing the quality of the whole metalens. Our experiment shows that the focal lengths and focusing efficiencies corresponding to the two polarizations are similar to the simulation results. The proposed electrically modulated bifocal metalens can be utilized in different applications and combined with other optical components.

Advantages of multivariate regression analysis over ANOVA

When modeling technological processes nowadays, it is necessary to take into account a large number of factors. Until now, analysis of variance (ANOVA) is often used in educational courses and in practical activities, although the possibility of using regression analysis instead, especially with a large number of factors, has been shown for quite some time. The paper examines in detail, using an example, the advantages of regression analysis over ANOVA in the modeling of technological processes. As an example, modeling of the manufacture of fiberglass bolts taking into account three factors is taken. Models of regression analysis and ANOVA, their statistical characteristics are given. A detailed comparative analysis of their application for modeling and optimization of technological processes was performed. Significant advantages of regression analysis compared to dispersion analysis for modeling technological processes are shown.

STRUCTURE OF THE COMPUTER MODULE OF THE KDAM PROGRAM FOR DETERMINING KINEMATIC AND DYNAMIC PARAMETERS OF THE INPUT LINK

The development of the computer module of the KDAM program for determining the kinematic and dynamic parameters of the input link of the mechanisms of light industry machines allows to determine the coordinates, projections of speeds and accelerations of the center of mass of the crank and the point of attachment of the links of the Asura groups. During the dynamic analysis of the operation of the input link, the projections of the full reaction in the hinge of the input link are determined. The obtained results are used in the program to assess the intensity of technological processes of the light and textile industry when determining the change in the relative tension of the thread in the filling zones on the technological equipment. Lever mechanisms are widely used in light and textile industry machines. The working bodies of the lever mechanisms come into contact with the threads during operation. Depending on the trajectory of the movement, the angle of coverage of the working bodies of the mechanisms of the light and textile industry machines changes. A change in the value of the angle of coverage leads to a change in the tension of the threads. When the coverage angle increases to critical values, the thread may break and the technological equipment may stop. The tension of the thread increases when moving through the refueling zones of the thread feeding system on the technological equipment. This increase is due to the interaction of the thread with the guides and tension devices. The maximum tension value will be in front of the working area. A sharp increase in tension leads to a violation of the normal course of the technological process of thread processing. The development of new schemes of the thread feeding system requires an operational assessment of the value of the tension in front of the working zone. The development of special computer programs for determining the tension in the working area makes it possible to determine the necessary technological parameters. The objective function in the tasks of optimization of technological processes is the minimum necessary tension. The variable parameter in the objective function is the sum of the angles of coverage of the working bodies by the thread. The use of a computer program allows you to determine the tension and change in relative tension in the filling zones of technological machines, which allows you to optimize the shape of the thread supply line even at the stage of designing the technological process. Computer determination of kinematic and dynamic parameters of flat mechanisms allows to determine the parameters used in determining the intensity of technological processes. The study of the influence of the design of the thread tension device on the conditions of its interaction with the thread, taking into account its unevenness in the diameter of the cross section, is important in determining the thread tension. The tension of the thread increases when moving through the refueling zones of the thread feeding system on the technological equipment.

Морфологический анализ и оптимизация технологического процесса продольного раскроя круглых лесоматериалов

Coniferous sawn timber is extensively used in construction. However, the dimensional and qualitative composition of the round timber for lumber production has recently deteriorated significantly. The number of sawn logs with a diameter of 14–20 cm represents barely 50 % of the total supply of raw materials for sawmills. Besides that, large-diameter logs frequently have some signs of decay, which is mostly heartwood rot. Thus, the sawlog must be handled with caution. The problem is to intensify the sawing process, especially when logs have a presence of heartwood rot. This is possible to achieve with the implementation of modern technological sawing processes and specified equipment. A method of morphological research is used to select flowsheet diagrams of sawing and construction solutions for rip cutting equipment. The completeness of the morphological table is determined by the sum of all properties of the concept objects and is evaluated by obtaining effective technological and constructive solutions. According to the morphological method, a procedure of search systematization is developed. The patent search identified the main protective and published application documents concerning programs about ripping machines for round timber. The flowsheet diagrams for rip cutting of round timber and operational schemes for the equipment are adjusted according to the discovered regularities. A new sawing program is proposed in order to improve the efficiency of the equipment. It was licensed under a national patent of the Russian Federation. The evaluation of the possibility of implementing the technological process is made by analyzing the target costs for the production arrangement, the production rate per shift, and the quality of the final products. The proposed method for selecting directions to intensify the rip cutting of round timber gives the possibility to determine the effective technological and technical decisions at a project’s preliminary problem-solving stage. For citation: Toropov A.S., Byzov V.E. Morphological Analysis and Optimization of Technological Process for Rip Cutting of Round Timber. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 2, pp. 132–145. (In Russ.). https://doi.org/10.37482/0536-1036-2023-2-132-145

A study of electrothermomechanical converter for technological purposes with nonlinear changes in the loading and cooling medium

Heavy temperature processes with high-temperature loads require optimisation of technological processes, ensuring high reliability and combining rotating parts of electric machines with actuators to achieve greater efficiency of electromechanical converters. The research aims to provide a theoretical justification and experimental confirmation of the effect of higher harmonics in the air gap under nonlinear changes in the temperature of the medium. The research is based on the basic principles of electrodynamics, heat and mass transfer, mathematical modelling by the finite element method, and experimental verification of multi-physical parameters. Based on the analysis of the differential equation for determining the increase in the surface temperature of a ferromagnetic rotor under conditions of nonlinear temperature changes in the environment surrounding the electromechanical converter, the regularities of the formation of the free and forced components of the instantaneous temperature values of the massive rotor are established. Depending on the mode of interaction between the load-cooling medium and the electromechanical part of the screw units, kinematic diagrams of single-mass and two-mass systems with variable or constant moments of inertia and stiffness were formed. According to the size of the electromagnetic system of the experimental sample, a mathematical model for studying thermal and electromagnetic processes was built. The regularities of the spatial distribution of the temperature of the screw electromechanical unit are determined. The spectra of higher harmonics of voltage and current in the frequency range from 0 to 50 kHz have been experimentally determined, which confirms the presence of the effect of generating higher harmonics when the temperature of the medium surrounding the rotor screw changes. The detected harmonic spectrum affects both the formation of the dynamics of the rotating system and additional thermal power while increasing the overall efficiency of the screw electromechanical converter. The practical value of the obtained results lies in the possibility of predicting the optimal indicators of interrelated electromagnetic and heat exchange processes in screw electromechanical converters for technological purposes

Study of silicon production process in ore-smelting furnace and optimization of technological process

This article presents the results of production experiments to optimize the modes of silicon smelting in an industrial arc furnace. The main factors of the melting process are the size of the fractions of the charge components and the temperature regime of heating. The rate of charge heating in the reaction zone in the temperature range from 950 to 14100C has a special effect on productivity. In this temperature range, the formation of refractory silicon carbide on pieces of quartzite was established, which causes a drop in the magnitude of the electric current in the reaction zone and its freezing. The gornisage, which is formed, displaces the electrodes into the zone of greater charge electrical conductivity - up, which leads to an increase in silicon monoxide emissions through the reduced charge layer. Correction of such a process requires an increase in the temperatures in the reaction zone and the duration of the melt. A method has been developed for calculating the size of quartzite fractions, depending on the power of the furnace and the size of the reaction zone. An example of a simplified calculation is proposed.

Optimization of Technological Process to Decrease Dimensions of Circuits XOR, Manufectured Based on Field-Effect Heterotransistors

Optimization of Technological Process to Decrease Dimensions of Circuits XOR, Manufectured Based on Field-Effect Heterotransistors

STUDY OF THE ANAEROBIC PROCESS OF INDUSTRIAL WATER PURIFICATION IN COMBINATION WITH SORPTION METHODS

The issues of rational use of natural resources, ecological safety and environmental protection are extremely urgent and require immediate human influence on the optimization of technological processes, reducing the impact on the ecosystem. The implementation of food industry technology is accompanied by the formation of a significant amount of wastewater, into which about a third of processed raw materials go, and the concentration of polluting components in them is 10...100 times higher than in household water. The choice of wastewater treatment methods depends on their composition, prospects for further use, the economic feasibility of applying the methods, and the payback rate of the equipment. Therefore, the modern direction of the development of scientific research and wastewater treatment technology consists in the development of fundamentally new methods of deep wastewater treatment and the study of the possibility of using sorbents of natural and artificial origin.

Определение оптимальных технологических параметров процесса очистки деталей в погружных моечных машинах

Cleaning and washing contaminated surfaces of machine parts is relevant in the repair industry. Improving the efficiency of the process of cleaning metal parts is possible using a combination of submersible, jet and ultrasonic methods. The variety of designs of washing machines and installations using different cleaning methods requires the determination of optimal technological parameters and process modes, as well as the identification of an effective washing solution. For this purpose, an experiment was carried out on the process of cleaning metal parts from the remnants of cutting fluids (coolants) in submersible washing machines using ultrasonic vibrations. Solutions of dimer, labomid, and soda ash were studied to clean metal parts from coolant residues. To intensify the process of washing metal parts, an ultrasonic unit UZDN-A with a constant oscillation frequency was used. The degree of purification of metal parts was estimated by the ratio of the mass of the pollutant removed from its surface to its initial mass, in percent. The obtained mathematical models of the degree of cleaning of metal parts (for grades of structural carbon steels and non-ferrous metals) from coolant made it possible to determine the optimal technological parameters: concentration of cleaning solutions 15 to 20%; working temperature for dimer - 20 to 30°C, for labomid - 70 to 80°C, for soda ash - 80 to 90°C. It has been established that the most energy-efficient and safe cleaning solution is a dimer, and the use of labomid for ultrasonic cleaning is not advisable due to its increased foaming. It was also found that the time of washing (the presence of metal parts in the machine) and the amount of oil on the surface of metal parts do not significantly affect the degree of cleaning.

Design and investigation of 1D photonic crystal based structures for BIPV cell colorization by sol-gel dipping technology

The growth of the building integrated photovoltaic (BIPV) sector is limited by the apparent lack of ways to create the visual impact of the building at acceptable cost efficiency rates in the current PV market. Thus, in this research digital simulations were combined with experimental studies to design and optimize novel 1D photonic crystal structures acceptable to expand and improve the color palette of PV panels. It was proved that the 3-layered system with TiO2/SiO2/TiO2 was both efficient and sufficient for this purpose. Advanced light filtering was implemented experimentally on 5x5 size glass plates with a potentially cheap and simple sol–gel dipping technique with annealing only at 110 °C. The applicability of the proposed technology was validated by manufacturing the PV mini panels that showed 2–3 higher brightness in CIE color space compared to the panels made using commercial solar cells. Experimentally obtained efficiencies were: 18.75% (REF, black), 17.28% (light blue), 17.13% (greenish), 16.52% (yellowish), which is in the range to the commercial colored cells, but could be higher if better cells were used. The technology reliability and scalability were evaluated from analysis of the sensitivity of the 1D photonic crystal parameters to the optical properties of the colored device. The tolerable deviations from the color related numbers are approximately +/- 0.05 for the refractive index spectrum and less than approximately +/- 2% for the thickness. Therefore, the proposed coloring method should be a perspective solution for BIPV, but careful attention should be taken for the technological process optimization.

Self-Diffusion Coefficients of Components in Liquid Binary Alloys of Noble Metals

An accurate determination of transport coefficients in liquids, such as diffusivity, is crucial for studying fundamental chemical processes, for constructing and verifying model theories of liquid, and for the optimization of technological processes. However, a reliable experimental determination of the diffusivity is a difficult and sometimes nearly impossible task. In this regard, the development of model theories that allow calculating characteristics of atomic transport is of special interest. Here, the concentration dependencies of the self-diffusion coefficients of the components in Cu-Ag, Cu-Au, and Ag-Au liquid alloys at T = 1423 K and T = 1573 K are calculated in the framework of the linear trajectory approximation in conjunction with the square-well model and the semi-analytical representation of the mean spherical approximation. We reveal that peculiarities in the behavior of the obtained dependencies are related to the peculiarities of the phase diagrams of the alloys under consideration. Additionally, we verify our calculation method on Al80-Cu20 and Al80-Au20 liquid alloys. The results obtained are in good agreement with available experimental and molecular-dynamic simulation data. In the cases when the experimental information is not available, the presented results can be considered as predictive to estimate the quantities under consideration approximately.

Ефективність застосування поліоксихлориду алюмінію для очищення питної води

The article presents the results of research of the effectiveness of aluminum-containing coagulants for the purification of water of the Dnipro River.The surface waters of the Dnipro River basin are characterized by a high content of organic compounds of natural origin, the presence of which determines the coloration of the water and significantly affects the course of its purification processes. If the aluminum sulfate reagent is used to purify such water, there is need to increase the dose of the reagent, which can cause an increase in the content of residual aluminum in the purified water. One of the technological solutions for increasing the efficiency of water purification is the replacement of traditional aluminum sulfate with modern highly effective reagents, in particular aluminum polyoxychloride. Based on the results of expe¬rimental studies, there was conducted a comparative analysis of the effectiveness of the use of aluminum sulfate coagulants and aluminum polyoxychlorides with different degrees of basicity. It was established that for the water of the Dnipro River, which is characterized by a high content of organic substances and coloration, the best results were obtained in case of using aluminum polyoxychloride with a degree of basicity of 35—45%. In general, the efficiency of water purification with polyoxychlorides is higher in comparison with aluminum sulfate according to the following quality indicators: coloration — by 10—15%; turbidity — 10%, total iron content — 20—25%; permangana¬te oxidizability — 15—20%. The regression equation whichdescribe the dependence of the above indicators of the quality of purified water on the dosage of reagentswas developed. On the basis of the methods of optimization of technological processes, it was established that the rational dosage of polyoxychlorides for cleaning slightlytur¬bid colored water of the Dnipro River is about 40—50 mg/dm3, and for aluminum sulfate — 90—100 mg/dm3. The application of mathematical modeling and optimization methods in the practical determination of the rational dosage of coagulants for surface water of different quality makes it possi¬ble to effectively adjust the technological process in order toen¬sure the high quality of drinking water in accordance with regulatory requirements.

Influence of the Sintering Method on the Properties of a Multiferroic Ceramic Composite Based on PZT-Type Ferroelectric Material and Ni-Zn Ferrite

This paper presents the research results of multiferroic ceramic composites obtained with three sintering methods, i.e., free sintering FS (pressureless), hot pressing HP, and spark plasma sintering SPS. The multiferroic composite was obtained by combining a ferroelectric material of the PZT-type (90%) and zinc-nickel ferrite (10%). Research has shown that the combination of a magnetic material and ferroelectric materials maintains the multiferroic good ferroelectric and magnetic properties of the composites for all sintering methods. A sample sintered with the HP hot pressing method exhibits the best parameters. In the HP method, the composite sample has high permittivity, equal to 910 (at room temperature) and 7850 (at the phase transition temperature), residual polarization 2.80 µC/cm2, a coercive field of 0.95 kV/mm, and the magnetization of 5.3 and 4.95 Am2/kg at -268 °C and RT, respectively. Optimal technological process conditions are ensured by the HP method, improving the sinterability of the ceramic sinter which obtains high density and proper material compaction. In the case of the SPS method, the sintering conditions do not allow for homogeneous growth of the ferroelectric and magnetic component grains, increasing the formation of internal pores. On the other hand, in the FS method, high temperatures favor excessive grain growth and an increase in the heterogeneity of their size. In obtaining optimal performance parameters of multiferroic composites and maintaining their stability, hot pressing is the most effective of the presented sintering methods.