Results Of Experimental Research Research Articles

About the rational choice of the damper shape for an ultrasonic piezoelectric transducer

The results of the study on the influence of the geometric shape of the damper on its effectiveness and the overall efficiency of the radiation-reception system are presented. One of the possible forms of the damper is considered, where it is shaped like a truncated cone, and its generatrix has an inclination angle relative to the plane of the piezoplate. A criterion for evaluating the efficiency of the damper’s operation is proposed. The study includes the results of computational-theoretical (using the finite element method) and experimental research on the influence of the incline angle of the damper’s generatrix on the signal reflected from its rear part. The inclination angle of the generatrix, at which the minimum of parasitic signals is achieved, is determined. The radiation-reception system is investigated under water loading, and a satisfactory agreement between the theoretical and experimental results is noted.

Modelling of phase transformations occurring in the process of austempered ductile iron manufacturing

The paper presents mathematical models and their implementation in C # language describing the phase transformations occurring in the process of austempered ductile iron (ADI) manufacture. The research includes two main stages: austenitization and isothermal holding at the bainitic range. The influence of free energy of austenite and ferrite on transformations was taken into account. Parameters of models were identified based on inverse analysis and experimental research. As part of the research, verification and validation of the developed models was carried out based on the results of experimental research. The tool developed and implemented enables the analysis of phase transformations occurring during heat treatment with isothermal holding of ductile iron with Ni addition.

Determining infrared radiation intensity characteristics for the exhaust manifold of gas turbine engine ТВ3-117 in МІ-8МSB-B helicopter

The object of this study is the screen-exhaust device in the TV3-117 engine of the Mi-8MSB-B helicopter. To reduce visibility in the thermal range, a system of mixing hot engine exhaust gases with ambient air is used; this technique makes it possible to reduce the infrared radiation of engines. For this purpose, a new sample of screen-exhaust device was designed for testing. A thermal imaging survey of the helicopter was conducted. Three variants of thermal images were acquired: a helicopter without installation of a thermal visibility reduction system, a helicopter with standard exhaust shields installed, and a helicopter with newly developed shield exhaust devices installed. Based on the obtained experimental results, the characteristics of the intensity of infrared radiation were determined for three variants of research in the range of thermal waves of 3–5 μm. The study uses a comprehensive approach to solving the tasks, which includes a statistical analysis of known and promising ways to protect a helicopter from guided missiles with infrared homing heads based on reduced radiation forces and a theoretical method for calculating flow and temperature fields. The advantages of placing the section of the exhaust channel of the designed screen-exhaust device in the horizontal plane for complete shielding of infrared radiation in the lower hemisphere have been experimentally proven. The benefits of directing the flow of exhaust gases from the screen-exhaust device into the space above the helicopter propeller and dividing this flow into four separate flows were shown. The results of experimental research could be used to design new or improve existing screen-exhaust devices by the developers of military aviation

HE EFFECT OF LOADS SUPERPOSITION ON TECHNICAL STRUCTURES, ENVIRONMENT AND LIVING ORGANISMS

The current state of calculation the result of the superposition of loads, or their effects, on a material body is analyzed. The limits of the current calculation methods, based on strength theories, in the case of technical structures are shown. The results of experimental research that refer, in general, to the superposition of two loads of the same nature and without addressing problems of loads of a different nature (mechanical, chemical, electrical, magnetic, radioactive etc.), in the case of technical structures and the environment is analyzed. Starting from the principle of critical energy, which is based on the concepts of the total specific energies’ participation of the loads and of the critical participation, general relations are deduced for these concepts, in the case of the nonlinear behavior of matter, as a function of power. These results are applied to the calculation of the superposition of loads of different nature on a technical structure, the environment and living organisms, taking into account the deterioration of matter. The influence of the loading speed (static, shock ...) is taken into account based on the value of the exponent in the behavior law, which was not possible in the previous calculation methods. From the analysis of the results obtained in the paper, it is found the utility and the high degree of generality of the principle of critical energy and of the concept of the specific energy participation.

Determining infrared radiation intensity characteristics for the exhaust manifold of gas turbine engine ТВ3-117 in МІ-8МSB-B helicopter

The object of this study is the screen-exhaust device in the TV3-117 engine of the Mi-8MSB-B helicopter. To reduce visibility in the thermal range, a system of mixing hot engine exhaust gases with ambient air is used; this technique makes it possible to reduce the infrared radiation of engines. For this purpose, a new sample of screen-exhaust device was designed for testing. A thermal imaging survey of the helicopter was conducted. Three variants of thermal images were acquired: a helicopter without installation of a thermal visibility reduction system, a helicopter with standard exhaust shields installed, and a helicopter with newly developed shield exhaust devices installed. Based on the obtained experimental results, the characteristics of the intensity of infrared radiation were determined for three variants of research in the range of thermal waves of 3–5 μm. The study uses a comprehensive approach to solving the tasks, which includes a statistical analysis of known and promising ways to protect a helicopter from guided missiles with infrared homing heads based on reduced radiation forces and a theoretical method for calculating flow and temperature fields. The advantages of placing the section of the exhaust channel of the designed screen-exhaust device in the horizontal plane for complete shielding of infrared radiation in the lower hemisphere have been experimentally proven. The benefits of directing the flow of exhaust gases from the screen-exhaust device into the space above the helicopter propeller and dividing this flow into four separate flows were shown. The results of experimental research could be used to design new or improve existing screen-exhaust devices by the developers of military aviation

Odors Adsorption in Zeolites Including Natural Clinoptilolite: Theoretical and Experimental Studies.

This publication presents the results of combined theoretical and experimental research for the potential use of natural clinoptilolite zeolite (CLI) as an odor-adsorbing material. In this study of adsorption capacity, CLI of various granulation was used and its modifications were made by ion exchange using Sn and Fe metals to check whether the presence of metals as potential active centers does not lead to catalytic processes and may lead to enhanced absorption of odorous substances through their adsorption on the created metallic forms. Additionally, in order to increase the specific surface area, modifications were made in the form of hierarchization in an acidic environment using hydrochloric acid to also create the hydrogen form of zeolite and thus also check how the material behaves as an adsorbent. To compare the effect of CLI as a sorption material, synthetic zeolite MFI was also used-as a sodium form and after the introduction of metals (Sn, Fe). The above materials were subjected to adsorption measurements using odorous substances (including acetaldehyde, dimethylamine, pentanoic acid and octanoic acid). Based on the measurements performed, the most advantageous material that traps odorants is a natural material-clinoptilolite. Depending on the faction, its ability varies for different compounds. In the case of acetaldehyde, an effective material is clinoptilolite with a grain size of up to 2 mm. In the case of carboxylic acids, it is material after hierarchization with a fraction of 3-4 mm. In the case of theoretical calculations, information was obtained to show that metallic centers are more stable above oxygen, which is associated with the skeletal aluminum in clinoptilolite.

Preliminary microstructural research of clay solid bricks taken from historic buildings located in Poland

The article presents the results of the preliminary experimental research and analysis of the structure of samples of clay solid bricks from six historical buildings erected in Poland in the years 1300 to 1910. Images obtained with a scanning electron microscope; parameters characterizing the pore space of the ceramic material, which were obtained using mercury porosimetry; and chemical composition identified using an energy dispersive X-ray spectroscopy, were analyzed. The test results showed that as the age of the brick increases, the homogeneity of its structure decreases, the chemical composition of all samples is quite similar, and in the tested samples, large disproportions in the percentage of pore width in individual ranges can be observed. An indicator P-index useful in comparing the studied structures was proposed, based on the knowledge of the share of the pores’ width within the adopted ranges.

Modeling of Yb:YAG Laser Beam Caustics and Thermal Phenomena in Laser-Arc Hybrid Welding Process with Phase Transformations in the Solid State.

This paper focuses on the mathematical and numerical modeling of the electric arc + laser beam welding (HLAW) process using an innovative model of the Yb:YAG laser heat source. Laser energy distribution is measured experimentally using a UFF100 analyzer. The results of experimental research, including the beam profile and energetic characteristics of an electric arc, are used in the model. The laser beam description is based on geostatistical kriging interpolation, whereas the electric arc is modeled using Goldak's distribution. Hybrid heat source models are used in numerical algorithms to analyze physical phenomena occurring in the laser-arc hybrid welding process. Thermal phenomena with fluid flow in the fusion zone (FZ) are described by continuum conservation equations. The kinetics of phase transformations in the solid state are determined using Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) equations. A continuous cooling transformation (CCT) diagram is determined using interpolation functions and experimental research. An experimental dilatometric analysis for the chosen cooling rates is performed to define the start and final temperatures as well as the start and final times of phase transformations. Computer simulations of butt-welding of S355 steel are executed to describe temperature and melted material velocity profiles. The predicted FZ and heat-affected zone (HAZ) are compared to cross-sections of hybrid welded joints, performed using different laser beam focusing. The obtained results confirm the significant influence of the power distribution of the heat source and the laser beam focusing point on the temperature distribution and the characteristic zones of the joint.

Experimental Study of Direct Shear Properties of Anisotropic Reservoir Shale

Understanding the shear mechanical properties of shale reservoirs is of great significance in the study of the formation stability around horizontal shale wells and the propagation and evolution of fractures for shale fracturing. However, the existing direct shear test results are limited due to small sample sizes and low shear rates. Based on previous experimental research results, the mechanical properties of anisotropic reservoir shale in direct shear tests with different experimental conditions were explored in this study. It was found that the shear mode, shear strain rate, and normal stress have a significant impact on the deformation and failure characteristics of shale. The peak shear displacement, peak shear strength, and shear stiffness of shale present an increasing trend of fluctuation, with an increase in the bedding angle. The peak shear strength of shale decreases with an increase in the shear strain rate, and this decrease trend descends with an increase in the shear strain rate. The shape of the shear fracture zone and the shear fracture mode of shale exhibit bedding effect characteristics. The fractal dimension of the shale shear fracture surface morphology shows a trend of fluctuation with the variation in the bedding angle. Further, the shear strain rate was found to play a dominant role in the fractal dimension of the shear fracture surface. The larger shear strain rate strengthens the bedding effect of the roughness for the shear fracture surface morphology. The results of this study provide a theoretical reference for determining the engineering geomechanics characteristics of shale reservoirs.

Results of experimental research of the process of forming reinforced concrete products by the centrifugation method

The method of conducting an experimental study of the process of forming reinforced concrete products is disclosed. The key factors influencing the quality indicators of the product being formed are defined and considered. On the basis of the conducted active, factorial experiment, a regression equation was compiled, graphical dependences of the influence of these factors on the process were obtained, rational parameters of the centrifugation process were determined, which are decisive in the manufacture of reinforced concrete products by the centrifugation method. Based on the results of laboratory experiment data processing, recommendations were developed for optimizing the operating parameters of industrial equipment for forming reinforced concrete products by the centrifugation method. Problem. When forming reinforced concrete products by the centrifugation method, some problems may arise, uneven distribution of the mixture in the mold body and of reinforcement, formation of voids or cracks, insufficient compaction of the mixture. If the parameters of the centrifugation process are not properly controlled, the quality of the products may vary, which may lead to deviations from specifications and standards. Problems with the deformation of the molds after forming the product can lead to damage to the product or difficulties in its removal. Goal. Based on the results of the conducted factorial experiment, recommendations are developed regarding the rational parameters of the process of forming columns of reinforced concrete supports for power transmission lines by the centrifugation method in the conditions of an operating technological line. Methodology. The basis of the research is the method of conducting a planned factorial experiment with further statistical processing of the obtained results using a computer program. Results. Based on the processing of the obtained results of the conducted factorial experiment, the following recommendations are suggested regarding the rational parameters of the process of forming reinforced concrete pillars for power lines by the centrifugation method in the conditions of an operating technological line.

STUDY OF DEFORMABILITY OF THE LARGE-SPAN ROOF STRUCTURAL SYSTEM IN THE FORM OF AN ASYMMETRICAL SHELL

The scientific article is devoted to a complex study of deformability of saddle-type shell of negative Gaussian curvature of a public object that has been in operation for a long time for further general restoration of the building’s roofing system. The authors have developed a specific algorithm for conducting experimental research, providing additional static load on a shell at the lower point of the gentle axial line of the supporting arches. To smoothly carry out the loading procedure, we mounted containers in barrel form on the roof surface and gradually filled them with water. We carried out an experimental evaluation of the bearing capacity of the shell with the determination of the redistribution of forces along the length of the section in the lower zone of the conventionally outlined arch. The experimental test results revealed that the deformability of the shell surface under short-term loading did not exceed 2.0 mm, and, under long-term loading, it was no more than 4.0 mm. Analysis of the qualitative features of structure deformation shows that the displacement of the roof’s points, located symmetrically to the vertical axis, has the opposite sign to the sign of the displacement of the actual ‘saddle’ point (the case of symmetrical deformation). We conducted a numerical verification of the behaviour of the investigated structure by forming a detailed finite element spatial model of the shell. Comparison of the results of numerical calculation with the results of field tests shows the coincidence of qualitative and quantitative parameters, which, in turn, characterises the developed theoretical model as fully adequate and suitable for analysing the stress-strain state of similar large-span structural systems. Based on the results of comprehensive theoretical and experimental research, we made proposals for the further restoration of the roofing structure with the limitation of the self-weight of the covering to 1 kN/m2. Engineers and scientists can use the research results to reconstruct similar authentic structural systems. Keywords: calculation, restoration, loading, deflection, shell, negative Gaussian curvature.

MATHEMATICAL MODELING OF THE HOLLOW PROFILES FORMING PROCESS

Steel alloys containing manganese and boron are increasingly being used in mechanical engineering, including automotive and agricultural sectors. Products of critical application made from such steels, including hollow ones, have a high level of mechanical properties, surface hardness, and wear resistance. These products are obtained by profiling of previously electrically welded round pipes with a hot sheet stamping or pressure treatment (drawing, cold rolling, stamping). Technological parameters of combined processing methods are determined by the results of experimental research, which, due to the complexity and cost of materials, leads to significant expenses. The application of mathematical modeling can reduce the number of experiments and forecast the quality of finished products. The research focuses on investigating the possibility of obtaining square hollow profiles by means of push-pulling through one stand of a pipe welding unit and defining the requirements for geometric parameters of the billet.

Implication of viruses in the etiology of preeclampsia.

Preeclampsia is one of the most common disorders that poses threat to both mothers and neonates and a major contributor to perinatal morbidity and mortality worldwide. Viral infection during pregnancy is not typically considered to cause preeclampsia; however, syndromic nature of preeclampsia etiology and the immunomodulatory effects of viral infections suggest that microbes could trigger a subset of preeclampsia. Notably, SARS-CoV-2 infection is associated with an increased risk of preeclampsia. Herein, we review the potential role of viral infections in this great obstetrical syndrome. According to in vitro and in vivo experimental studies, viral infections can cause preeclampsia by introducing poor placentation, syncytiotrophoblast stress, and/or maternal systemic inflammation, which are all known to play a critical role in the development of preeclampsia. Moreover, clinical and experimental investigations have suggested a link between several viruses and the onset of preeclampsia via multiple pathways. However, the results of experimental and clinical research are not always consistent. Therefore, future studies should investigate the causal link between viral infections and preeclampsia to elucidate the mechanism behind this relationship and the etiology of preeclampsia itself.

Bплив ранньовесняних строків сівби насіння ромашки лікарської на польову схожість та виживання рослин в умовах правобережного лісостепу України

An important place in the effective technology of growing medicinal chamomile (Matricaria recutita L.) is occupied by the early spring sowing period. Therefore, they provide a dense emergence of seeds, as evidenced by many conducted scientific studies in the field of plant breeding. The article presents the results of experimental research on the effect of early spring sowing dates of medicinal chamomile on field seed germination and plant survival. It was established that medicinal chamomile plants depended on weather and climatic conditions, sufficient amount of moisture in the soil, soil crust, which as a result led to variation in the passage of growth and development phases, and therefore, a question arose in the study of agrotechnical techniques aimed at the productivity of medicinal raw materials. The cultivation of tetraploid of medicinal chamomile variety Perlyna Lisostepu and Zloty Lan in the conditions of the Right-Bank Forest-Steppe of Ukraine during the period of research (2018-2023) in the early spring sowing period was studied. It was established that the investigated varieties of medicinal chamomile had the highest field germination of seeds due to the content of productive moisture. The highest field seed germination rates of 74.16% were recorded during the early spring (15-18.04) sowing period of the Perlyna Lisostepu variety, and the Zloty Lan variety was 72.68%, respectively. According to six-year research data, the highest field seed germination of 68.00% on the control variant (1-3.04) according to the sowing dates was noted in the Perlyna Lisostepu variety, and the lowest 67.00% – in the Zloty Lan variety. The maximum rate of plant survival at the end of the growing season was 88.96%, which was obtained in the variant of the early spring (15-18.04) sowing period of the Perlyna Lisostepu variety, the minimum rate was 69.15% in the control (1-3.04) of the Zloty Lan variety. The germination rate on average over six years exceeded the control by 6.14%, and the survival of chamomile plants on average over the years of research exceeded the control option by 1.5%. The difference in factors was insignificant (2-3%)

Passive bandpass filters for modern microwave communication systems

Background. Bandpass filters are an integral part of any radio engineering systems and modern communication systems. Research and development of new passive components is due to growing need for such elements for modernization and creation of new modern communication systems.
 Aim. A brief overview of passive bandpass filters. Their classification according to the type of implementation is given.
 Methods. Results of experimental research and design of different passive bandpass filters are considered.
 Results. Lumped elements filters, microstrip filters, filters on high-temperature superconductor films, filter on dielectric resonators, surface acoustic wave filters, bulk acoustic wave filters are considered. At a qualitative level, the main advantages and disadvantages are considered from point of view of electrical parameters and size indicators. Examples of topological and constructive implementation are given.
 Conclusion. The passive bandpass filters considered in the paper make it possible to implement frequency selection devices at operating frequencies up to 6 GHz and higher, taking into account modern system trends and requirements for devices of this type.

Digital Transformation of Socio-Technological Reality: Problems and Risks

The research is devoted to a discussion of social and humanitarian problems associated with tectonic changes in human life against the backdrop of total digitalization. The author's attention is focused on the uniqueness of the modern situation: never before have innovative technologies had the ability to penetrate so rapidly and deeply into the foundation of modern society, have they become so widespread and accessible to almost all peoples and cultures. At the same time, the undeniable public good and the most serious threats to society that digital reality technologies bring with them are in a very close relationship. This is especially true for artificial intelligence systems. Innovations transform the entire world order, bringing radical changes not only to the material sphere of life, but also to the spiritual and moral state of a person. The research notes that the introduction of information and communication technologies into the life of modern society occurs without reliable support on the results of preliminary experimental research, without taking into account a deep professional and responsible assessment of the social and psychological consequences of their impact on the individual and on society as a whole. As a result, at this stage, society is constantly faced with many negative aspects of the impact of high-tech means. The work examines some of them: a decrease in cognitive and analytical abilities, the devaluation of human labor, the criminalization of cyberspace, the spread of Deepfake technology. Particular attention is paid to the problem associated with the possibility of using information technology as a tool of psychological influence. Information and psychological warfare is implemented on the basis of social networks and artificial intelligence technologies, which provides the enemy with the opportunity to achieve superiority without the use of military force. Information and humanitarian actions in cyberspace, carried out by Western countries in order to destabilize our society, destroy its value foundations, reformat the consciousness, worldview and spiritual and moral qualities of citizens, are becoming increasingly large-scale and aggressive. The work notes that digitalization is gaining momentum, plunging society deeper into new circumstances and requiring decisive action aimed at overcoming the many threats specific to the modern high-tech era.

THE IMPACT OF SOCIAL COMPARISON ON NEGATIVE PSYCHOLOGY AND IMPULSIVE BUYING BEHAVIOR OF CUSTOMERS IN VIETNAM

Purpose: This study consolidates core theories pertaining to social comparison, particularly upward comparison, impulsive buying behavior and notions associated with social characteristics such as envy, self-esteem, negative mood, depression and self-efficacy. At the same time, provide hypotheses and study models connected to the impact of social comparison on negative psychology and impulsive purchase behavior of customers in Vietnam. Method: Furthermore, this subject employed qualitative research methods such as group discussions and in-depth interviews with experts to reach a consensus on the definition of components, as well as to refine and enhance the measuring scales used to assess these factors. Subsequently, establish a foundation for carrying out initial quantitative investigation in order to finalize the official questionnaire, and subsequently proceed with the official quantitative study. A representative survey was conducted with a sample size of 647 customers who utilize social networks and engage in online shopping on e-commerce platforms. The study was conducted in major cities in Vietnam, including Ho Chi Minh, Hanoi, Da Nang, Hue, Can Tho and Bien Hoa. Result: Experimental research results have indicated that upward social comparison has a negative influence on self-esteem but a favorable impact on envy and negative mood. Simultaneously, increased self-esteem decreases depression and impulsive buying tendencies, whereas feelings of envy and negative mood have a beneficial effect. Conclusion: Additionally, the research findings demonstrate the influence of self-efficacy as a moderator and dedepression as a mediator. These findings provide a foundation for the researcher to suggest managerial recommendations for organizations to enhance client purchasing behavior.

The Impact of Computational Accuracy on the Quality of Direct Drive Control

One of the main aspects of the control system development process for direct drives is the selection of the required computational accuracy while establishing its impact on the quality of the control. Understanding this relationship allows designers to consciously determine the system structure at the early stages of controller development, which enables the optimal usage of hardware resources. This paper analyzes the results of experimental research on the influence of computational accuracy on the quality of control of direct drives. During the carried-out research, several vector controllers with different computational precision were implemented using Field-Programmable Gate Arrays (FPGAs). The experiments were carried out on a dedicated research stand for testing direct drives. Test scenarios included position and trajectory monitoring under various torque loads. To assess the control quality, the measures based on the deviations from the value set by the controller were proposed. In this paper, the results of experiments have been presented in the form of values of the measures in relation to the computational accuracy. The obtained results proved that satisfactory drive operation parameters can be obtained despite the relatively low accuracy of calculations in the control algorithm.

Research on the possibility of manufacturing aerated-foam concrete with a variatropic structure based on aluminum powder and eabassoc foaming agent

This article presents some experimental research results on the composition and properties of aerated-foam concrete with a variable structure using available materials in Vietnam. To obtain concrete products containing anisotropic pores from the central area to the periphery, this study proposed fabricating cubic wooden molds with four perforated mold walls. The diameter of the pores is 1.5 mm and the distance between these pores is 10 mm. The pre-punching of hollow holes in the four mold wall panels is to remove excess gas and liquid phases during the setting and solidification process and form the internal variable structure of the air-foam concrete product. Experimental research results have shown that it is possible to produce anisotropic aerated-foam concrete with an average dry density of about 1459 kg/m3; the average compressive strength at the ages of 7 days, 14 days, and 28 days are 18.2 MPa; 21.2 MPa and 28.7 MPa, respectively. Besides, this study also compares the properties of anisotropic aerated-foam concrete with conventional foam concrete and aerated concrete. The obtained results show that the physical and mechanical properties of aerated-foam concrete with the variable structure are better than conventional foam concrete and aerated concrete with the same density.

Flexural Behavior of a New Precast Insulation Mortar Sandwich Panel

This article introduces the experimental and analytical research results of two precast insulation mortar concrete sandwich panels (PIMSP) and two precast concrete composite panels as one-way slabs under bending load. Obtaining a prefabricated floor slab that can balance thermal insulation and structural performance can reduce material consumption and increase inter-story usage height. As the sandwich material for PIMSP, insulation mortar with a strength of 6 MPa was used. Truss-shaped shear connectors were used for shear force transfer. Then, finite element analysis was used to analyze and study the unidirectional flat plate model. The results showed that the tested PIMSP achieved a complete composite effect in the elastic stage and a semi-composite effect in the plastic stage. The PIMSP crack pattern resembles that of a precast concrete slab when utilized as a one-way slab. The load transfer capacity of truss-shaped shear connectors is relatively small, and it is mainly used as a connection between floors. Experiments have demonstrated that PIMSP panels can serve as a structural substitute for regular concrete floors in residential buildings.