bluuebunny/crossref_metadata_2025 huggingface dataset:
Driven by Fundamentals or Exploded by Sentiments: Testing for Speculative Bubbles in Emerging Stock Markets
Authors: Shaikh Asra , Kashif Muhammad , Rehman Mobeen Ur , Rehman Shafiq Ur
Published: June 2023

This study investigates the existence of speculative bubbles in diverse nine emerging markets, which may lead to terrible financial disasters. Therefore, a novel approach of Rtadf (Recursive, Right-tailed Augmented Dickey-Fuller) tests, monthly time-series data (January 2000–July 2021), and Monte-Carlo simulation under Gaussian assumptions is used. Our findings imply that massive growth in China, Indonesia, Malaysia, Pakistan, Taiwan, and Thailand is driven by credit or speculative bubbles rather than fundamentals whereas no bubbles are found in South Korea, India, and the Philippines - (as per Generalized Supreme ADF - GSADF test). Furthermore, in each stock market, these bubbles primarily exist prior to any local and global financial crisis.  These findings add to the existing knowledge of the relationship between bubbles and financial crises. Hence, this study suggests the GSADF test could detect an impending financial crisis in any economy, allowing authorities to control or maintain economic and financial stability.
Analysis and investigation on defects - delamination and spalling of metal on rolling surface of rail head under code X 10.1
Authors: Ivanovs Viktors , Gavrilovs Pavels
Published: June 2023

One of the main defects in rail steel is a defect on the rolling surface of the rail head. A sign of the defect appearance is delamination and spalling of the metal on the rolling surface. The development of this type of defect to a length of more than 25 mm and a depth of more than 4 mm requires a decrease of the train speed up to 70 km·h-1, and with a depth of more than 8 mm - to 25 km·h-1. Reducing the speed significantly affects the quality of service and railway performance. As a result, there is a disruption in the accuracy of train traffic, which subsequently leads to material costs for restoring the movement of trains at set speeds. The primary task of the study presented in this article is the collection and analysis of statistical information on the Latvian Railway defective rails in the period from 2011 to 2021. A secondary task is to investigate the causes of the appearance of rail defects under code X 10.1. The research process included: detection of these defects on the Latvian Railway using a modern ultrasonic flaw detector of the “RDM-24” type, determination of the metal hardness (EN 13674-1:2011 standard 350-390 HB) in the rail head and on the rolling surface using a certified modern device “Tinius O Olsen” Firmware Version 1.07, FH - 31 Series as well as the study of the chemical composition of the rail head using the optical emission analyzer PMI - Master PRO and determination of the microstructure of the metal in the rail head. At the final stage, to compare the results obtained in an independent certified laboratory, based on the results of the research to draw conclusions about the causes of this type of defect.
Study of flexural and yield strength of gypsum composite boards
Authors: Irbe Martins , Viba Janis , Cerpinska Marina , Beresnevics Vitalijs , Spade Kristaps
Published: June 2023

The material under study in this paper is a gypsum composite board, which is a sustainable material, and therefore attracts scientists’ attention in the recent years. This material is of a great importance for Latvian economy, since Latvia has gypsum mining sites and has developed a tradition of gypsum manufacturing. The goal of the study was to compare the mechanical properties of gypsum boards from different manufacturers. For comparison of strength one cement board was tested as well. To complete the study a specific experimental setup was developed and is demonstrated in this paper. The results obtained are experimental values, useful for a scientific community because these can be used for CAD modelling in the future. In this paper the experimental results were used to create FEM models in ANSYS program and complete simulation. It was discovered that some gypsum boards have different physical properties in longitudinal and transverse directions, while for other properties do not differ depending on the direction. In this study, the cheapest board had the yield stress of 2.76 MPa in the longitudinal direction, 1.87 MPa in the transverse direction, while the more expensive board was homogeneous, and the physical properties did not change depending on the direction and the average yield stress was 2.19 MPa. The values obtained in the tensile test in other studies of gypsum boards for other manufacturers are even lower - 1.10 MPa in the longitudinal direction and 0.64 MPa in the transverse direction.
Examining regional role of industrial production in transformation of Hungarian economic structure
Authors: Kaposzta Jozsef , Lorinc Balazs
Published: June 2023

Following the economic crisis of 2008, most developed countries, including the European Union member states, have experienced an economic paradigm shift. The rethinking of economic production has led to a shift towards knowledge-intensive, innovative and high-tech industries. As a result, today’s technological innovations are having a markedly more mature and powerful impact on changes in social relations, the labour market and its strategic development. As it has been observed in the technological innovations of recent decades, the industrial sector (manufacturing, energy, IT, automotive) has played a prominent role. At the macroeconomic level, almost all of the strategically comprehensive innovations have been closely linked to the development of this sector. All these visible macroeconomic links have led us to focus our attention on the strengthening of industrial production and its regional disparities, and to explore the regional differentiation in development resulting from FDI. We have chosen the period 2008-2020 as the interval for our analysis, in which we have examined the correlation between the value of industrial production per capita and its changes, as well as the spatial distribution of the value of industrial production. In our study, we sought to answer the question of how spatial inequalities in production change as the value of industrial production increases, and, in a complex model, how the level and unequal spatial distribution of foreign direct investment affect the development of a given economic space in Hungary.
Data correlation of mercury in eggshells and eggshell membranes of wild birds
Authors: Abola Anda , Rimsa Antonija , Strazds Maris , Veilande Rita , Revalde Gita
Published: June 2023

Wild birds are common study subjects as agents of mercury pollution, in particular predominantly fish-eating birds that are at risk for high mercury intake. The Black Stork is one such species in Latvia. Its conservation status is very unfavourable; by the IUCN criteria, it is considered to be critically endangered. Our data encompasses several species of wild birds; however, the bulk of data consists of black stork eggshells. If the target species is endangered, it is highly desirable to reduce the impact caused by the data collection itself. The collection of eggshell remains under nests is one such non-invasive method. Black storks often drop hatched eggshells and the remains of eggs out of their nests. The downside of this method is the fact that one cannot choose a preferable type of artefact to be collected, only what is there. Eggshell remains under nests vary greatly both in size and condition from almost complete eggs to tiny scratches of eggshell. We used an atomic absorption spectrometer with Zeeman correction LUMEX RA-915M paired with its attachment for pyrolytic analysis PYRO-915+ to detect total mercury concentration in our samples. Pyrolytic combustion enables direct measurements without special pre-treatment steps, minimizing sample contamination risk and offering nearly immediate results. To assess our data, we did a statistical analysis using R version 4.2.1. We have previously observed that eggshell membranes contain higher levels of mercury than eggshells themselves. Here we check whether the amount of mercury found in various types of artefacts correlates, using 320 pairs of data for black storks for which both separate measurements were possible. Our data show that the correlation between the two is significant. In addition, we discuss the correlation between eggshells with attached membranes and membranes themselves, as well as between eggshells and eggshells with attached membranes.
Aviation accident - fire modelling using programme pathfinder in Riga airport liability area
Authors: Urbans Mihails , Pundure Jelena , Veiss Rihards
Published: June 2023

The article will explore and collect information about the possible accidents with the Airbus 220-300 aircraft, which is the new and largest aircraft that can be serviced at Riga airport. Previously, such a large plane had not been serviced at Riga Airport, so the article will gather technical information about the characteristics of the Airbus 220-300 compared to previous model planes. As part of the work, passenger evacuation modelling will be carried out with the help of the Pathfinder program, which will be used for emergency simulation. The results of the study may be used to implement further improvements, as well as to ensure more efficient firefighting team work in emergencies in the Riga Airport liability area, as well as other airports serving the Airbus 220-300 aircraft. Reaching the aim will provide an opportunity to look at different variations in the evacuation of people depending on the composition of passengers, behaviour and location of escape exits.
Influence of technological factors on formation process of bimetallic castings
Authors: Aftandiliants Yevhenii , Gnyloskurenko Svyatoslav , Meniailo Helena , Khrychikov Valerii
Published: June 2023

The analysis of the modern state of wear-resistant metallic material production showed that one of the promising directions for improving their quality is the use of bimetallic steel-cast iron castings, which have a complex of properties differentiated over the volume and surface of the products. However, the problem of obtaining a high-quality joint of the steel base and the working cast iron layers is not completely solved at present. So, the research aims to determine the quality criterion of a good diffusion joint and to study the selected technological factor influence on the formation process of bimetallic castings using the developed mathematical model. The paper examines the effect of the steel base temperature at liquid cast iron pouring over it, the temperature of pouring cast iron, as well as the ratio of liquid cast iron mass to the unit surface of the steel base on the contact surface temperature as selected quality criteria, and the structure of the transition diffusion layer of bimetallic castings. It was determined that a high-quality joint is realized when this temperature is larger than the solidus temperature of the cast iron. Moreover, the results of the mathematical model application showed maximum contribution of the liquid cast iron mass/steel unit surface ratio, less effect of the pouring iron temperature and minimum influence of the solidified steel base temperature onto the quality criteria. The metallographic analysis established the diffusion joint formation in the transition steel-cast iron layer consisting of pearlite on the side of the steel base and without the carbide matrix area on the side of the working iron layer. The results obtained are of great importance for the designing bimetallic machine parts worked under intensive wear conditions.
Friction properties of reed stalks
Authors: Vronskis Olafs , Kakitis Aivars
Published: June 2023

One of the most important phenomena accompanying numerous processes biomass materials undergo is friction. The identification of the friction processes for plant materials is necessary for the correct design of many technological processes during which they are transported, chopped, or stored. Most research on friction uses the simple Coulomb model. To determine the coefficient of friction, an adjustable tilt plate is used, on which the material under study is placed. The coefficient of static friction was taken as the tangent of the angle of the inclined plate at which the material begins to slide. Friction can be determined by moving biomass against horizontal surfaces of different materials. Common materials for friction pairs with biomass were steel plates, wood, glass and rubber. Common reed (Phragmites australis) is a grass which has spread nearly all over the globe. Considering that the reed stalk is a natural tube, it can be used to make cocktail straws. However, there is a much wider range of uses, such as toy components, room decors etc. Such applications require that the reed stem is not flattened after cutting. Likewise, the end of the stem must be free of sharp edges and smooth. In previous studies, non-destructive cutting of reeds using abrasive discs was evaluated. In order to create a device for non-destructive cutting of reeds, it is necessary to know the coefficient of friction of the reed stalk. This paper analyses friction parameters of reed stalks of different diameters. As a result of the research, the values of friction coefficients for reed against various plastics, metals and rubber were obtained. The coefficient of friction of reeds against hard materials (both metals and plastics) ranges from 0.12 to 0.37. A significant difference depending on the diameter of the reed is not observed. The highest values of the coefficient of friction are between reeds and rubber, from 0.81 (transverse direction) to 1.02 (longitudinal direction).
Analysis of causes and consequences of electric car accidents
Authors: Ballay Michal , Kubas Jozef
Published: June 2023

The vision of a climate-neutral European continent directly relates to road transport, which represents an energy-demanding area. The annual increase in the share of electric cars also contributes to this vision in road traffic. Therefore, it is common that the driver of an electric car causes or is a participant in an accident. These electric powered vehicles require increased attention, especially in matters of the safety of emergency services in the event of accidents. The article is focused on the issue of electric vehicle accidents in terms of their causes and consequences. In this regard, it is important to understand all the risks, which result from accidents involving electric cars. The article is primarily focused on the analysis of the causes and consequences of accidents. For the purposes of risk analysis, the failure mode and effect analysis method is applied. In connection with the wide range of applications of the method in question in various systems and areas, the application of the method in the article is significant and unique. It is based on predefined scenarios of electric car accident events. Its application consists of identification and numerical phases. These are created and calculated on the basis of expert estimates and determine the level of risk of defined scenarios. The degree of risk in the form of a risk number defines the importance of an accident event. The article includes a diagram, which is based on Pareto analysis and points to the susceptibility of defined accident events. The importance of the analysis lies in the discovery of a small number of causes, which significantly influence the defined consequences of accident events.
Innovative engineering modeling technological process of urine collection in dogs
Authors: Deviatko Olena , Kanivets Nataliia , Lokes-Krupka Tereziia , Kravchenko Serhii , Mushtruk Mikhailo
Published: June 2023

The problem statement is revealed as follows. It is recommended to collect urine in the morning, in a sterile vessel; however, the procedure of this biological material collection in animals is rather challenging in implementation and requires certain effort and practical skills. The purpose is revealed as follows. Meanwhile, urine collection in dogs is rather important in a veterinarian’s practice. The test of collected urine allows to check the animal’s state of health and to evaluate the obtained results, which is important for research. The methodology is revealed as follows. The research has been done using factual observation and documentation, systemic and morphological analyses. The mathematical model for the technological process has been compiled based on a set theory. The findings (results). A general model for technological process of urine collection has been developed and a description of the model components provided, which allows to view them as a vector of technical support. Originality (novelty). A distinguishing feature of the offered urine collection technological process model is that based on the aggregate of set elements combining processes, means, objects and phenomena of the model, a device has been developed allowing to select optimal sizes depending on the animal breed. The practical value is revealed as follows. The implementation will allow to obtain a convenient comfortable means for urine collection in dogs of different breeds using vessels of different volume.
Modelling of fam-gate nitrogen balance in pig production - case study of Latvia
Authors: Auzins Alberts , Jansons Imants
Published: June 2023

The 150 million pigs reared across EU represent the largest livestock category before that of bovines. In Latvia in 2021 the number of pigs reached 327.0 thousand. The European Green Deal is aimed at transforming EU into an equitable and prosperous society, with a modern, competitive and efficient economy in the use of resources, in which there are no net emissions of greenhouse gases. The EU taxonomy for sustainable activities stipulates that economic activity can qualify as environmentally sustainable only if it substantially contributes to one or more environmental objectives. In case of agriculture, there are limited options how to contribute substantially. One of these options is ensuring sustainable farm-gate nitrogen balance. Moreover, in pig production this option is almost the only real option, especially for landless pig farms. The Platform on Sustainable Finance has proposed several indicators how to measure the farm-gate nitrogen balance, e.g. nitrogen use efficiency (NUE). There is a lack of systematic knowledge about the fam-gate nitrogen balance in Latvia’s pig farming. Therefore, the aim of the study was to model the farm-gate nitrogen balance and examine NUE for both conventional and organic pig production. The input data for modelling were derived from two comparable models of pig production (conventional and organic, 1 000 sows, full production cycle). The criterion of minimum NUE (40%) proposed by the platform was applied to assess the results of the modelling. Results of the study reveal that possibility to meet the minimum NUE of 40% depends on NUE of feed. NUE of feed should be higher than 50% in order to reach the minimum NUE of 40%: at least 58% (conventional production) and 66% (organic production). Thus, ensuring NUE of pig production at least 40% could be challenging for pig farms that purchase feed with unknown NUE or low NUE.
Computer investigation of mineral fertiliser particle movement along centrifugal spreader disc inclined under angle to horizontal plane
Authors: Bulgakov Volodymyr , Rucins Adolfs , Holovach Ivan , Adamchuk Oleg , Aboltins Aivars , Zabolotnyi Hrihorii , Kolomiiets Larysa , Polishchuk Svitlana
Published: June 2023

Spreading of mineral fertilisers on the surface of the soil is the most widely used and effective way to increase the harvest of agricultural crops. The new construction of a centrifugal fertilizer spreading apparatus with the spreading disc the axis of which is inclined to the horizontal plane, developed by the authors, allows for essential increase of the distance of mineral fertiliser particles from leaving the blades of the disc. Nevertheless, the constructive peculiarities of the inclined spreading disc require comprehensive substantiation of the parameters of the disc and feeding mineral fertilisers from the feeder and the tank. The aim of the research is substantiation of the working width of the machine for mineral fertiliser spreading and productivity depending on the constructive and kinematic parameters, as well as the place where the mineral particles will be deposited on the surface of the spreading disc that is inclined at the angle to the horizon based on the performed computer analysis of movement of particles along the surface of the disc of the centrifugal spreader. The present research has been performed using the methods of modeling, theoretical mechanics and higher mathematics, as well as the methods of calculation, using graphs and computer modeling. Based on the mathematical model, previously developed by the authors, for spreading mineral fertiliser particles and the obtained differential equations of the movement of mineral fertiliser particles along the disc of the inclined under an angle to the horizontal plane working body and equations of the absolute movement of the particle leaving the disc of the working body, computer calculations are performed. The graphs of dependence of the absolute speed of mineral fertiliser particles leaving the disc of the working body on the time and the above mentioned parameters have been obtained, on which the distance of the mineral fertiliser particle after leaving the disc blade of the working organ is dependent. The angle speed of the disc and radius of feeding have higher influence on the relative speed of the particle leaving the blade. Rational values of the radius of the fertilizer supply do not exceed 0.5 of the radius of the disk of the fertilizer spreading working body. Changing the angle of the disc within 0°…40° does not influence the dispersion time of the particles and the values of the relative and absolute speed of particles leaving the blade. Rational disc inclination values to the horizontal plane are within 20° … 30°.
Comparative dsc analysis of virgin and nanofiber mats of PA6
Authors: Kanukuntla Sai-Pavan , Sanchaniya Jaymin-Vrajlal , Beresnevics Vitalijs
Published: June 2023

Differential scanning calorimetry (DSC) is a useful technique for analysing the thermal behaviour of materials by measuring the heat transferred through a sample during temperature fluctuations. For polymers, understanding their thermal characteristics is crucial to determine their process capability, mechanical properties, stability at high temperatures, and suitability for specific applications. In this context, the electrospinning process involves heating polymers and subjecting them to high voltage, leading to changes in their thermal properties. Therefore, it is essential to identify these modifications to determine the thermal conductivity, stability, and temperature management of the nanofiber for specific applications. This study focuses on the analysis of polyamide (PA6) nanofibers produced by electrospinning using DSC and compares them to virgin PA6 to identify significant changes in thermal properties. The PA6 nanofibers were prepared by electrospinning PA6 polymer and collecting on a rotating drum at a needle tip of 20 cm to the collector centre distance. For comparison of thermal properties, the same virgin PA6 was used for DSC testing from which nanofibers were produced. The results show that the nanofiber mat’s glass transition temperature increased by 3.2%, while the melting temperature decreased by 0.7%. Furthermore, the delta Cp (change in specific heat capacity) of the nanofiber mat was enhanced by 96%, and its thermal heat capacity and crystallinity increased by 16%. Therefore, this study provides insights into the alterations in the thermal characteristics of the nanofiber mat created by electrospinning.
Improvement of economic mechanism of rational use of forest resources using discrete mathematics method
Authors: Openko Ivan , Tykhenko Ruslan , Tsvyakh Oleg , Shevchenko Oleksandr , Stepchuk Yanina , Rokochinskiy Anatoliy , Volk Pavlo , Zhyla Ivan , Chumachenko Oleksandr , Kryvoviaz Yevheniia , Horodnycha Anastasiia
Published: June 2023

This article proposes a balanced approach to the management of forest resources in Ukraine, based on a mathematical model developed using discrete mathematics. The algorithm of our study involved the following stages: 1) delineation of the spectrum of factors that characterize the ecological, economic, social processes of using forestry lands; 2) development of an economic system for the use of forest resources, with the simultaneous scientifically based establishment of interrelationships between the elements of the system; 3) calculation of the matrix of coefficients of pair correlations, which substantiate the relationships between the elements of the economic mechanism of the rational use of forest resources; 4) optimization of the economic graph of the use of forest resources, by distinguishing the key and secondary elements of the system; 5) economic and mathematical modeling of the rational use of forest resources. In order to apply the obtained calculations at the applied level in rational use of forest resources, we proposed appropriate strategic directions for the use of forest resources depending on the degree of impact on the environment. On the basis of the proposed management approaches of rational use of forest resources, we have developed mathematical models that allow to analyse the effectiveness of applying one or another strategy. The adequacy of the developed regression equations is confirmed by the coefficient of determination, Fisher (F) and Durbin-Watson (DW) tests. The developed mathematical models allow tracking the change of modeling indicators depending on the factor criteria and establishing their regularity. The article analyzes the use of forestry land in Ukraine based on two management approaches: an ecocentric approach and a balanced approach. The results show that the ecocentric approach can minimize the ecological situation in the short term but may negatively affect the development of the economy of nature use in Ukraine. The balanced approach, on the other hand, is the most adaptive for sustainable development. To ensure the balanced use of forest resources, the article outlines several conditions, including the regulation of market mechanisms, reduction of the anthropogenic impact, improvement of the ecological situation, and development of state programs. Fulfilling these conditions is mandatory to ensure the maximization of economic benefits from the use of forestry land with the formation of a favourable environment and the promotion of solutions to social problems of the population. The proposed approach can have positive consequences in regions where the level of forest production is low and the use of forest resources is unprofitable.
Study of passive steering of wide span vehicles with power-driven steering method
Authors: Adamchuk Valerii , Bulgakov Volodymyr , Ivanovs Semjons , Rucins Adolfs , Beloev Ivan , Kuvachov Volodymyr , Kaminskii Viktor , Chernysh Oleh
Published: June 2023

One of the defining areas for further research in the world is the development of a set of technological measures for the introduction of resource-saving technologies and technical means, ensuring reduction in the need for material, technical and energy resources. The introduction of track and bridge systems in farming, the basis of which is a wide-span bridge traction vehicle, is really promising in this respect. The development of power-driven agricultural axle traction machines brings forward the necessity of setting and solving the problems of uncontrolled (passive) driving with its own tasks and solution methods. The aim of this research is to investigate uncontrolled passive steering of a bridge vehicle with power steering. The methodological basis of the theoretical research was the system approach, mathematical modelling, the laws of theoretical mechanics, the theory of tractors and vehicles, information technology and the use of PCs. A prototype of a wide span vehicle has been used as the object of experimental investigations. As a result of this research, it was found that the maximum value of asymmetrically applied shear pulling force of the wide span vehicle corresponds to the direction when its line of action passes through the centre of mass. For 1 kN of traction resistance of the bridge machine under study, the lateral slip when it moves along the compacted soil track of a constant tramline for each 1 m of the distance travelled was 0.011…0.015 m. In any deviation from this direction, there is an instantaneous rotational movement (shear) of the wide span vehicle where the total shear force is less than the maximum value. The anisotropy of this process results in a reversal of the hodograph towards a lower coefficient of traction of the wide span vehicle thrusters on the bearing surface of the permanent technological track. The adequacy of the meta-mathematical models of the passive steering of the bridge vehicle with the power method of control allows the solution of problems such as calculation of the minimum turning radius, evaluation of the technological track width, calculation of the maximum traction forces, selection of the rational control scheme under steady driving conditions, calculation and reduction of power on the turn, calculation of the maximum dynamic loads at the moment of active driving and others.
Programming of pedagogical technology for formation of professional competence studying special disciplines in agricultural engineering sciences
Authors: Nikolaenko Stanislav , Bulgakova Oksana , Yasinetska Iryna , Zbaravska Lesya , Dukulis Ilmars , Shynkaruk Nataliia , Rucins Adolfs
Published: June 2023

The article deals with the problem of the formation of professional competence of the future engineers in the integration process of special disciplines into the agro-engineering sciences. There has been scientifically substantiated and experimentally verified the efficiency of methodology for the formation of professional competence of the future agro-engineers by integrating special disciplines, based on personal activity, competence, problem-integrative, contextual and system approaches. The psychological and pedagogical conditions for the implementation of the methodology in the process of studying agricultural mechanics, the theory of agricultural machines, machine use in the crop production and animal husbandry, etc. are determined and theoretically substantiated. The purpose of this article is the problem of the formation of sustainable professional competence of the future agricultural engineers in the integration process of natural and general technical disciplines into the special disciplines from the basic training profile. Based on the results of the research, a methodology was built, in which the effectiveness of the formation of professional competence of future agricultural engineers was scientifically substantiated and experimentally verified by integrating fundamental disciplines into special ones. There are determined and theoretically substantiated psychological and pedagogical conditions for the implementation of the developed models in the process of studying these disciplines. There is proved the efficiency of the developed logical models and their impact upon the components of professional competence, which is carried out by applying approaches to the assimilation of the scientific knowledge, the use of integrative learning technologies, as well as increasing the cognitive activity, motivating students to study special disciplines. The developed technologies for the formation of professional competence in the study of special disciplines in agro-engineering sciences can significantly increase the level of professional knowledge of the future engineer of agro-industrial production.
Study of vibrational behaviour of shock absorber in harshness frequency range 20-100 Hz
Authors: Georgiev Zlatin
Published: June 2023

The main task of the shock absorber is to provide good comfort to the vehicle by damping the relative movement between the wheel axle and the body. The damping force in the shock absorber is created by the viscous resistance of the working oil as it passes through the valve systems between the various chambers. At low frequencies (below 1 Hz) and large relative displacements of the shock absorber (over 5 mm), the hysteresis of the gas filled in the shock absorber has a slight damping effect also. The fluid and gas forces are the main components of the total force that acts in the damper during its compression and extension in the frequency range up to 20 Hz. These forces counteract the disturbing forces of road unevenness and reduce the level of vibrations that are transmitted to the body at the mounting points. Road disturbances with a frequency above 20 Hz are characterized by small displacements (amplitudes). Small displacements of the piston rod (less than 1 mm) do not provide the necessary pressure in the chambers to overcome the resistance of the valve springs and actuate the fluid damping. In this frequency range, the compressibility of the working fluid also affects the force in the shock absorber. The work examines the vibrational behaviour of a telescopic shock absorber in the frequency range 20-100 Hz – known as the harshness range in NVH (Noise, Vibration and Harshness) studies. For this purpose, a hydrodynamic test bench is used, which is equipped with a force sensor. The pressures in each chamber of the shock absorber are measured. The pressure in the extension chamber is the indicator of the damping force. The results show that the fluid damping of the shock absorber decreases with the increase of the disturbance frequency. Above 50 Hz, the vibrations passing through the shock absorber are damped only by its rubber mounts. The force transmitted through the shock absorber increases and it is linearly proportional to vibration accelerations.
Justification of parameters affecting increase of hammer crusher productivity
Authors: Revenko Ivan , Khmelovskyi Vasyl , Revenko Yulii , Rebenko Victor , Potapova Svitlana
Published: June 2023

The analysis of the efficiency of the particle sizes of the feed components used in feed rations resulted in proof of the significance of the feed particle size not only while feeding animals with loose dry or wet mixtures but also with feed granules. The study showed that to increase the efficiency of hammer crushers it is relevant to substantiate the parameters of the hammer rotor and the method the raw materials are supplied into the crusher’s working chamber. The experiment involved a stand, which enabled determining the strength of stems while being broken. A sieve classifier was applied to measure the average particle size of the ground products. The rotor speed was monitored electronically and duplicated by a manual tachometer. The average diameter of clover samples was 1.64 mm and correspondingly 3.3 mm of lupine; the length of the samples was 50 and 100 mm. The breaking force on a clover stalk with 13.2% of moisture was 97 N max and 4.4 N min, and correspondingly in the case of a lupine stalk – 22.7 N max and 1.5 N min with 12.3% of moisture. In our case, grinding clover and lupine hay with the minimal energy density Qs, 60 m·s-1 was considered to be the efficient speed of the hammers υм, and the grinding modulus М was within 1.0-1.3 mm. With the different values of the hammer speed and the crusher grinding chamber width of 180 mm, the results of the experimental studies showed that regardless of a supply method and a type of processed raw materials, the output of the ground products was distributed quite unevenly across the width of the working chamber. However, it was found that the peripheral feeding method was significantly more effective than a central one, since the quicker the work was done, the more efficient it became. While at speed υм = 30 m·s-1, the unevenness of the product output under the central supply method was greater than that of the peripheral one only in 8-14%, at speed υм = 75-80 m·s-1 this difference reached 20-32%.
Comparison of linear and nonlinear models for forecasting of food commodity prices in Latvia
Authors: Pavlenko Oksana , Matvejevs Andrejs
Published: June 2023

Analysing real-life data of commodity price dynamics is challenging, there can be non-stationary, non-linear, contain structural breaks. In this paper, we explore whether threshold models are preferable to linear autoregressive models (ARIMA) and whether the logistic smooth transition (LSTAR) model is preferable to the self-exciting threshold autoregressive (SETAR) model for important Latvian food commodity prices. Using historical prices of 16 most popular food products in Latvia over the last 18 years, we assess the goodness of fit of ARIMA (SARIMA), SETAR and LSTAR for each of the most popular commodity prices in Latvia and then compare the out-of-sample forecasts using measures RMSE and MAPE. Although different types of models appear to be most suitable for different commodities, even despite their similarity like fresh pork, chicken and beef, the overarching conclusion is that regime-switching models fit the prices of the majority of products better. ARIMA is the preferred model for some goods for construction of out-of-sample forecasts marginally more often than for the goodness of fit. Nevertheless, threshold models still appear superior in most cases. Additionally, we obtain rather large smoothness coefficients for most LSTAR models, which means that there are no significant reasons to prefer LSTAR to SETAR.
Changes in use of passenger railway transport due to COVID-19 pandemic and expected prospects in Latvia
Authors: Veveris Armands
Published: June 2023

Before the COVID-19 pandemic the development and promotion of public transport, and especially rail transport, was set as one of the significant priorities of transport industry in Latvia. However, COVID-19 and the restrictions related to it have created not only a very deep but also a long-term negative effect on the use of public transport. Taking into consideration that since the beginning of the pandemic significant time has passed, and there has been a significant recovery from it over the last year, the major trends in the use of public transport in Latvia and outside are shown in the article. The paper employs both theoretical and empirical research methods. The official data on the passenger flow from 2018 till 2022 have been analysed in the research. They approve that the COVID-19 pandemic has left lasting effects on the use of public transport, including such effects that are caused by the changes of the population habits. However, the data show that the structure of demand has changed, and in some segments demand is even higher than during the pre-pandemic period. Also, the flow of passengers in different modes of transport has not recovered smoothly, but rail transport is one of the most successful in this regard. The recovery of railway transport has happened faster than of other types of transportation, although about 10% of passengers have not been regained yet. This confirms the perspective of this mode of transport in the future. We can expect to exceed the pre-pandemic passenger flow in Latvia in the coming years, but it is significantly dependent on the implemented state policy - whether it is favourable for passenger rail transport. Experience shows that in countries that take steps to popularize the railway, it recovers much faster.
Treatment quality assessment of sunflower inter-row widths with asymmetric joining of cultivator to tractor
Authors: Bulgakov Volodymyr , Ivanovs Semjons , Adamchuk Valerii , Nadykto Volodymyr , Kyurchev Volodymyr , Yaremenko Vadym , Krasiuk Liudmyla
Published: June 2023

Almost all existing units for mechanical processing of inter-row widths of row crops (corn, sunflower, soybeans, etc.) are symmetrical. In this case, the ratio of the tractor track to the row crop’s inter-row widths is an even integer (k). This article presents the study results of a machine-tractor unit in which the value k equals 3; that is, it is odd. As a result, an asymmetric unit was obtained, in which the cultivator is displaced in the transverse direction relative to the tractor symmetry axis by half the inter-row width, equal to 70 cm. The width fluctuations of sunflower plant protective zone formed by such machine-tractor unit are rather low-frequency. At a speed of 1.9 m·s-1, the main variance spectrum of these oscillations is concentrated in the frequency range 0-0.9 m-1 or 0-0.27 Hz. With an increase in the unit movement speed to 2.4 m·s-1, this diapason narrows to 0-0.6 m-1 (0-0.23 Hz). At the same time, an increase in the movement speed of the studied unit from 1.9 to 2.4 m·s-1 did not lead to a significant change in the mean of the width and variance of the sunflower row protective zone oscillations. The actual difference between the means of this zone (0.6 cm) turned out to be less than LSD05, equal to 0.8 cm. In addition to this, the null hypothesis about the equality of the compared of this parameter fluctuation variances was confirmed. Calculations have established that the possible deviation frequency of the sunflower plant protective zone width actual value of ± 1 cm from the established one can reach 0.007 m-1 or one release per 143 m of the path travelled by the unit at a speed of 1.9 m·s-1. When the machine-tractor unit moves in the sunflower inter-row widths at a speed of 2.4 m·s-1, the value of this indicator is 0.009 m-1 or one release per 111 m of the path. According to the results of experimental studies, real damage (cutting) of sunflower plants for both unit operation modes did not exceed 0.9%. The weed destruction in the inter-row widths of this crop was 98.5%.
Research on gas dynamic flows in poultry house lateral ventilation system using cfd modelling
Authors: Bulgakov Volodymyr , Aboltins Aivars , Trokhaniak Viktor , Beloev Hristo , Trokhaniak Oleksandra , Holovach Ivan , Synyavskiy Oleksandr
Published: June 2023

Maintaining a good microclimate in the poultry house is one of the most important factors in poultry breeding. It is the quality of the air parameters that ultimately determines the quality of the yield. Poultry keeping requires a lot of effort and technological solutions. Therefore, the study is aimed to improve the microclimate system in the air environment of the poultry house by incorporating exhaust fans on the rear end wall in a non-traditional way. Computational Fluid Dynamics (CFD) with ANSYS Fluent is a powerful tool for predicting the climate system in the poultry house, as an alternative to experimental studies. CFD modelling of the gas-dynamics and heat-mass exchange processes has led to the conclusion that raising the valves to a height of 210 mm from the slab, and changing the spoiler cut-out by 73 °allows air to be conveyed to the centre of the poultry house. At the same time, the pressure drop of the supply valves is 47.18 Pa, which makes it possible to fully supply the exhaust fan. The air velocity at the inlet of the supply valves is 9.16 m·s-1. The average air speed at 0.7 m above the floor level is 0.71 m·s-1, and the temperature is 14.83 °С. Thus, the research presented can be used to develop new ventilation systems for poultry houses in the future.
Clean energy and hydrogen perspectives in rural regions of Kazakhstan
Authors: Zavadskiy Vladislav , Revalde Gita
Published: June 2023

The paper describes the results of our study about the perspectives of clean hydrogen production in the rural regions of Kazakhstan. A brief introduction to clean hydrogen technology and its connection with renewable energy sources is presented in the article. As an example, the case study on renewable energy sources availability was done for the Akmola region of Kazakhstan. We elaborated the model of clean hydrogen production with numerical results including studying the potential of renewable energy sources and utilizing produced clean energy for hydrogen production using the modern available technologies. Also, a part of using clean hydrogen in the region for the wheat-producing purpose based on the current fuel needs was covered. We believe that our research will stimulate the development of clean hydrogen production in the region. Kazakhstan has great renewable energy potential and could be a promising place for clean hydrogen production in the region as well.
Wellbeing elements in companies located in different settlement types in Hungary
Authors: Grajczjar Istvan , Schottner Krisztina , Harskuti Janos
Published: June 2023

Abstract: This study aims to investigate how applied well-being elements and geographic location of a company/institution influence the workplace satisfaction of different working groups in Hungary. In our research, 108 companies and institutions of different sizes were selected in Budapest and in the countryside, as well as organizations with national scope in Hungary. HR managers and professionals were asked for the help of a self-filling expert questionnaire. The study explores how physical, mental, and emotional support is provided in these different locations, and whether well-being-supportive technologies are utilized. Additionally, the study looks at the availability of self-development opportunities and the impact of location on the differences in real-time workforce monitoring, transparent communication, and the redefinition of HR missions. The provision of appreciation, positive feedback, contact with managers, career planning, mentoring, fringe benefits, and physical and mental health are highlighted in relation to location. Our results show that regarding the applied language of appreciation companies in the countryside are able to stay in the competition with companies located in Budapest (the capital) or the ones with nationwide scope. However, such well-being elements like real-time workforce monitoring, utilizing well-being supportive technologies, physical, mental, and emotional support of new and modern HR strategies are in seriously disadvantaged positions compared to companies located in Budapest or to those with nationwide scope. Independently of all this, we found only at companies in the countryside correlations between the satisfaction level of all three working groups and the implemented well-being dimensions and appreciation languages.
Sustainable consumption and waste management
Authors: Bormane Santa , Sloka Biruta , Skiltere Daina
Published: June 2023

The Just Transition Mechanism, the European Green Deal Investment Plan (EGDIP) and the European industrial strategy highlight the main priorities and lines of action that will affect the course towards sustainable development, its adaptation to the transformation of EU into a new, more sustainable economy – a climate neutral, competitive environment through developing the circular economy. The goal of the study is to assess the public opinion based on an analysis of data on the views of inhabitants of Latvia on pollution, grime or other environmental problems based on the European Union statistics on income and living conditions (EU-SILC). The research methods used to achieve the goal were the analysis of scientific publications and previous research and analysis of views of inhabitants of Latvia on pollution, grime or other environmental problems. For evaluation analysis, time-series analysis and cross-tabulations of evaluation by regions, by territories and by household size were used. For testing the differences of inhabitant evaluations, the chi-square test was used. The results of the analysis show that there are not significant differences in views on pollution, grime or other environmental problems in Latvia’s regions, in territories and by the household size. The results of the study could be useful to industries and situations and can serve as the basis for decision-making for pollution reduction and other researchers’ empirical efforts in this field.