bluuebunny/crossref_metadata_2025 huggingface dataset:
On mathematical models of artificial neural networks
Authors: Samuilik Inna , Sadyrbaev Felix , Atslega Svetlana
Published: June 2023

Artificial Neural Networks are in focus. The four-dimensional and the five-dimensional systems are considered. The activation function – hyperbolic tangent is used to model the Artificial Neural Networks. By changing one of the parameters in the system, different types of solutions are obtained: periodic solutions and chaotic solutions. The graphs of all solutions, the dynamics of Lyapunov exponents and 2D and 3D projections of attractors are provided using Wolfram Mathematica.
Vehicle slalom passage analysis
Authors: Blatnicky Miroslav , Molnar Denis , Dizo Jan , Ishchuk Vadym
Published: June 2023

The paper is a continuation of the authors’ research dealing with a sensitivity study of the wheel camber variation of the experimental vehicle Alfa Romeo 156. A numerical comparison of the wheel camber change versus vertical axle position has already been performed and published for the vehicle in question. The same methodology was applied to four other selected axle types (for the purpose of comparison with each other), represented by vehicles in which these axles are actually implemented. As a result of the research, the values of the camber and the forces acting on the wheels during the simulated cornering of the vehicle were determined. Subsequently, the influence of the kinematic parameters on the dynamic response of the vehicle was evaluated. The current work of the authors focuses on experimental runs performed on the real vehicle (Alfa Romeo 156). Accordingly, the data from the experimental runs are compared with a numerical simulation of the passage of the modelled vehicle. The aim of this research is to evaluate the magnitude of body roll and body pitch for the vehicle slalom manoeuvre. The results indicate an excellent correlation between the numerical results and the measured values for this manoeuvre. On the basis of these results, it can be concluded that the numerical simulations are predictive, a finding that is crucial for developers pursuing equivalent kinematic parameters. In addition, the predictive nature of the simulation program allows to simulate diverse manoeuvres (e.g. vehicle braking) with variable input parameters, which would be problematic to implement in the case of experimental runs. Reducing the development time and tuning time of a prototype vehicle is one of the key factors to the competitiveness of companies.
Influence of tractor slippage on crop yield
Authors: Damanauskas Vidas , Janulevicius Algirdas
Published: June 2023

The tractor under draft causes slippage of the driving wheels, which negatively affects the soil structure and soil function, influences the plant growth and yield. Tires compress and compact the surface layer, erode the soil, and reduce liveliness of plant roots. Driving of tractors is unavoidable but may be more friendly to the environment. The aim of the research was to establish the dependence of the tire contact area and tractor slip on the plant yield, maintaining a constant draft. The investigative tractor “CASE MX135” was used in this research. The field test was performed by towing another tractor with implements for constant draft load. Several soil plots were compressed track to track separately, changing the tire contact area on each plot. Different tire contact area was achieved by changing the tire pressure and adding double wheels. The correlation of the adjustable contact area and wheel slip and crop yield was developed by comparing to the control plot without soil compression. The results show that enlargement of the tire contact area can reduce the slippage by 19,8% at constant draft and improve the crop yield, by reducing soil damage. It was noticed that the soil plots which were compressed with the lowest tire contact area gave the crop yield by 10% less; in the plots where the soil was compressed with the greatest tire contact area the crop yield increased by 9.5% compared to the control plot without compression of the soil.
Economical linkages of industry ""electricity, gas, steam and air conditioning supply"" in Baltic states and Finland
Authors: Jaunzems Andrejs , Balode Ilze
Published: June 2023

The research is devoted to the industry “Electricity, gas, steam and air conditioning supply” (D35) in the Baltic states and Finland. The goal is to carry out the comparative dynamic analysis of the industry’s D35 domestic and imported product intermediate consumption’s and sales structures’ influence to the value added and final demand creation. The investigation is holistic thanks to the Input-Output approach. In order to estimate the role of the industry D35 in the national economy direct and total backward linkages with respect to the domestic and imported intermediate consumption, direct and total forward linkages are calculated and interpreted (mostly in form of elasticities). The special attention is devoted to the D35 product price change’s influence on the gross value added and final demand of separate industries in order to discover the most sensitive influenced industries. Although there are a lot of publications concerning the industry D35 in the recent time, nevertheless the results of the current research are new. We hope, it will help elaborate management decisions.
Rheological properties of virgin, Recycled and mixed high density polyethylene and wood plastic composites with plywood sanding dust
Authors: Kajaks Janis , Kalnins Karlis , Zalitis Martins , Matvejs Juris
Published: June 2023

The article summarizes investigation results of rheological properties of virgin (vHDPE), recycled (rHDPE) and mixed high density polyethylene (ratios 75/25, 50/50 and 25/75 respectively) and the corresponding composition of wood plastic composites with 50 wt.% of plywood production waste product plywood sanding dust (PSD) and 3 wt.% of coupling agent maleated polyethylene (MAPE). Pure matrices and their mixtures as well as the corresponding WPCs were mixed on two roll mills to maintain equal preparation conditions of the investigated samples. According to our studies we concluded that rheological properties of pure matrices and the corresponding composition of WPCs do not so strongly depend on the composition of composites (character of the fluidity curves and viscosity–shear deformation rate relationships are similar), but are significantly influenced by the parameters of rheological tests (shear stress and shear deformation rate). The most distinctions are observed especially at very high values of deformation rates (up to 5000 1·s-1). The melt flow index (MFI) measurements showed the decrease of MFI values with an increase of the rHDPE content in vHDPE polymer matrix and the corresponding WPCs. The diminution of the values of MFI can reach 2 times. It shows the higher viscosity of recycled HDPE melts which can be related to prior exploitation conditions of recycled polymer. The curves of fluidity indicate the character of typical pseudo-plasticity of all investigated polymer melts because viscosity of the melts not only depends on the temperature, but also decreases with an increase of the shear stress and shear deformation rate. Pseudo-plastic properties of polymer melts confirm also the observed values of the fluidity index (n) which for pseudo-plastic, non-Newtonian liquids always is smaller than one.
Comparison of selected outputs of rail vehicle bogie variant solutions
Authors: Dizo Jan , Blatnicky Miroslav , Ishchuk Vadym , Solcansky Sebastian
Published: June 2023

Rail vehicles are important transport means, which are used for transportation of plenty of passengers as well as tons of goods almost on all continents in the world. Railway transport represents an effective and sufficiently reliable kind of transport, mainly when it comes to electric trains. Increasing transport speeds together with relative strict requirements on safety and costs needed for operation, maintenance and repairing make high demands on operational properties of rail vehicles. They are especially demands on their dynamical properties, at which, a bogie is a key subsystem of a rail vehicle. This presented research is focused on investigation of dynamical properties of a rail vehicle bogie. Specifically, it is a locomotive bogie. It is a prototype two-axle bogie intended to be mounted on a newly designed electric two-bogie locomotive. The main objective of this work is to compare the selected output quantities of three variant solutions of a bogie. These variants differ to each other by values of the weight of bogie components, the weight distribution as well as the pivot pins distance. The article presents a comparison of two output quantities, namely yaw angles of bogies and deformation of springs in bogies. Parameters of a bogie and a locomotive have been provided by a commercial producer of locomotives. Numerical analyses have been performed for specific operational conditions defined by the running speed in a curved track. There have been performed the number of simulation computations for various running speeds and curve radii, at which, the article includes only the particularly chosen data.
On modelling of three dimensional flow in extraction of biologically active substances from plants
Authors: Strautins Uldis , Marinaki Maksims
Published: June 2023

The authors consider the process of extraction from heterogeneous plant material; a novel model offering 3D spatial resolution is proposed and simulation possibilities by applying several modern numerical methods for three dimensional problems are discussed. These types of problems naturally arise when one wishes to mathematically describe the processes of the extraction with solvents such as supercritical carbon dioxide (scCO2). The results of this process meet the demand of the functional foods, nutraceutical, pharmaceutical and cosmetic industries on bioactive compounds. The models used in typical simulations by the industry offer no spatial resolution of the extraction process, however, when novel designs of extractors are developed, the three dimensional flow of the solvent and its interaction with the plant material should be considered. We propose a coupled system of equations consisting of fluid dynamics equations describing the flow of the solvent and reaction-advection-diffusion equations for the solute, plus equations describing the remaining concentration of solute in the biomass. The exchange of the active material between the solid and fluid is modelled by the Langmuir law. The initial distribution of solute in the plant material is not assumed to be homogeneous, nor are the extraction parameters, i.e. heterogeneous mixture of plant materials can be covered by this model. The equations are discretized by using finite volume techniques and currently implemented in Octave/Matlab environment. As a result, the temporal evolution of the three dimensional distribution of the solute is obtained along with the velocity field of the solvent, allowing detailed studies of the extraction process in a virtual design. The model is modular, allowing integrating tailor-made laws to describe various plant materials. The authors present simulation results and analyse the advantages and disadvantages of the proposed methods and approaches.
Analysis of response activity of fire brigades in event of traffic accident with occurrence of hazardous substance near protected area of village
Authors: Ballay Michal , Kapusniak Jaroslav , Kubas Jozef , Macurova Ludmila
Published: June 2023

When transporting dangerous substances, it is essential to comply with all regulations and obligations arising from legal regulations and international agreements regulating the transport of hazardous substances by road transport. The given type of transport is characterized by various risks. In traffic accidents within the transport of dangerous substances in case of leakage of a dangerous substance, its immediate spread into the surroundings occurs, which can cause extensive damage to property, the environment, the lives and health of people, animals and other components of the environment are at risk. The immediate surroundings are immediately exposed to the effects of a dangerous substance, which requires quick and effective intervention and cooperation of rescue services. The supporting part of the contribution is the analysis of the intervention activity of the fire brigades in the traffic accident of a tanker transporting hydrochloric acid in a volume of 22 tons. The authors had at their disposal documentation from the intervention of the accident in question, which was located near the protection zone of natural mineral resources, in the outskirts of the village. The article assesses the coordination of rescue operations with an emphasis on the analysis of the situation in the decision-making of the intervention commander and organizational breakdown of the place of intervention. As part of this assessment, a method focused on ongoing and subsequent activities that are subject to time analysis is applied. The conclusion of the article pays special attention to one of the most dangerous activities during an intervention, namely pumping of the dangerous substance into the replacement tank, as well as the rescue of the crashed tank.
Study of biomass pellet network model for heat and mass transport in porous media through gas channels
Authors: Leja Laura , Strautins Uldis
Published: June 2023

In order to further increase efficiency while reducing harmful emissions, clever control methods have been proposed, e.g. using external electric and magnetic fields. We consider that minimalistic mathematical models are required if heat and mass transfer processes within the granule and the controlling device are low computational power. The authors develop the network model presented in previous publications, further preserving the topology of the network model, consisting of nodes and channels connecting the nodes, with one-dimensional gas dynamics equations governing the gas flow between the nodes. In addition, mass conservation laws are used at the nodes to couple the gas dynamics equations on the various nodes. The resistance to gas flow between the nodes in the two models is described by different parameters – permeability coefficient for the simple network model and channel length and diameter for the alternative model; these can be customized to apply both methods to the main problem. This paper deals with several stages of biomass granule production virtual material design process. At first, a network model describes the biomass granule’s internal structure, and heat, mass transfer, and chemical reaction processes are modeled on the network. Finally, we compare the results of the two models for some representative geometries. The results show good agreement if the network model is a sufficiently good discretization of the one-dimensional pipe network model. The results also depend on the geometry of the model.
Analysis of accident event - agricultural machine and motorcyclist
Authors: Macurova Ludmila , Kohut Pavol , Redl Miroslav , Ballay Michal
Published: June 2023

During the harvest of agricultural crops, the number of tractors, harvesters and other agricultural machines on roads increases. Collision situations of agricultural machines and road vehicles occur most often. In the event of a collision between agricultural machines and more vulnerable road users, the consequences are more serious. For motorcyclists, the collision situation is much more dangerous and there is a greater likelihood of serious injury or death. According to expert evidence and the crash test results show that if, for example, a motorcyclist collides with a tractor at speeds higher than 80 km·h-1, the probability of survival is minimal. The most frequent collision situations are intersections, exits from the side road to the main road, exits from the main road to the side road, confusing turns. The paper deals with the analysis of an accident event of an agricultural machine (self-propelled harvester) and a motorcyclist at a left-hand turn, in the outskirts of the village. The origin is investigated and the course of the accident scene with reference to the resulting specifics from the movement of special agricultural machines on roads. The speed of the vehicles is assessed as part of the analysis before the collision, impact speed with regard to the drivers’ visibility and driving technique are evaluated and the established technical cause of the accident event. At the end, the possibilities of averting an accident on the part of individual road users are described.
Construction industries waste circulation problems in Latvia
Authors: Gusta Sandra , Pavars Mareks , Grabens Kaspars
Published: June 2023

Construction is crucial for the development of a country, it affects both individuals and the whole society’s life, as well as the environment. As construction is so crucial, it must be done as environmentally friendly as possible. During construction processes, a large amount of waste is produced. Incorrect management of this waste degrades our environment. Disposal of construction waste is a very popular way, but it is not a very environmentally friendly way of managing this waste. Interviews and surveys have been conducted in the study to investigate the opinion of construction participants about construction waste in Latvia. The research uses the theoretical research method, survey, interviewing, and data processing methods. Construction waste can be recycled. In construction in Latvia, legal requirements are observed, and construction waste is mostly handed over to processing companies, where a part is sorted. The processing and reuse of construction waste are relatively small. The construction waste sector in Latvia is regulated, but not sufficiently monitored, allowing a grey area to form. Sorting of construction waste at construction sites in Latvia practically does not take place, part of the waste is sorted in landfills. There is not enough research on the possibilities of recycling construction waste. Construction participants are not interested in starting construction waste sorting and recycling with their own initiative. In the procurement of municipalities and state institutions, construction waste sorting should be included as a mandatory requirement.
Enhancing efl profession-based vocabulary acquisition through 3d engineering animation for engineering students
Authors: Chaikovska Olha , Niskhodovska Olena , Spivachuk Valentyna , Kruk Alina
Published: June 2023

Today, a majority of agricultural farms are equipped with a new type of farm machinery, tractors, which require high-quality knowledge, skills and abilities from engineers. Therefore, the ability to describe the objects, mechanisms and working schemes is a priority for future agricultural engineers. Before COVID-19 and the war in Ukraine, most ESP classes were held in specially equipped laboratories, where students could study agricultural machinery and equipment on layouts. Ukrainian educators search for alternative teaching tools to enable effective distance learning of future agricultural engineers. Three-dimensional environments can be very useful to examine agricultural machinery parts. The purpose of this experiment was to test the effectiveness of 3-D engineering animation in improving profession-based vocabulary acquisition. A two-group post-test comparative pedagogical experiment was conducted with the second-year agricultural engineering students (n = 30) during the spring semester of the academic year 2022. A series of online 3-D engineering animations was adapted with the students of the experimental group to reinforce the course content and develop vocabulary skills in participants. The achievement profession-based vocabulary test with experimental and control groups was carried out. The number of participants in each group is equal (n1 = 15, n2 = 15), so the boundary value of Хb at a 5%- level of significance for N = 30 is 4.88. The statistical interpretation of the test results based on the Van der Waerden criterion shows that Xf > Hb, respectively, 8.85 > 4.88. The differences in the results obtained are statistically significant (X = 8.85 at P < 0.05), which allows us to assert the effectiveness of training engaged in the experimental group.
Development of charging infrastructure with regard to differences of regions in environment of Slovakia
Authors: Kubas Jozef , Ballay Michal
Published: June 2023

Nowadays, electric cars are becoming more and more popular in personal transport as well. One of the reasons is, in particular, that the electric car does not create any local emissions and is still considered one of the alternatives for the future in passenger transport. Also, there are often state incentives for the purchase of electric cars in the form of contributions or tax reductions. However, the charging infrastructure itself is an integral part of electromobility. Low coverage rates can be a barrier when customers decide to switch to electric cars and plug-in hybrids. Special representation, which is the supporting part of the cell and requires increased attention, represents the building and development of the charging infrastructure. From the point of view of current standards in real deployment, the contact conductive charging technology is applied. Ensuring compatibility should be a key characteristic of the infrastructure with as many car brands as possible and building a sufficient network of charging stations. Current issues at the international and national level, from the point of view of the infrastructure in question, are directed towards the use, current number and sufficient number of charging stations. The article focuses on the national level and analyzes the development of charging infrastructure in the environment of the Slovak Republic. Attention is mainly paid to high-power public recharges and recharging points. The article compares the coverage of the charging infrastructure in selected regions, while it was determined how the coverage is affected by regional differences from the point of view of their development. Finding answers to key questions is also possible using input indicators such as the number of inhabitants, area and maturity of the region. In addition, the state of the standardized solution is determined, as well as building an interoperable charging infrastructure.
Theoretical determination of absolute speed of mineral fertiliser particles from centrifugal spreading disc
Authors: Bulgakov Volodymyr , Ivanovs Semjons , Holovach Ivan , Adamchuk Oleg , Aboltins Aivars , Ihnatiev Yevhen , Polishchuk Svitlana
Published: June 2023

One of the main technological approaches for ensuring favourable conditions of growth and development of plants is depositing mineral fertilisers. The quality of it influences the soil fertility and harvest of agricultural crops. We have developed a new construction of the spreader working body, the axis of which is at the angle to the horizon. Theoretical and experimental research is conducted on the kinematic parameters of such working body. The aim of the present research is determination of the constructive and kinematic parameters that ensure maximal distance of spreading mineral fertiliser particles from the spreading disc with the angle to the horizontal plane. In the research the methods of modeling, theoretical mechanics and mathematics, as well as calculations and presentations of graphical dependences are used. The present article describes the obtained analitical expressions for determination of the absolute speed of mineral fertiliser particles from the spreader disc with an inclined working body, considering the initial speed of moving the aggregate for spreading mineral fertilisers on the surface. The mineral fertiliser particle absolute speed from the spreading disc of the working body is presented as a vector through its projection on the axis of specially developed system of Cartesian coordinates at a moment of time. Based on the obtained analytical expressions, graphical dependences are presented characterising the studied process. It is proved that at increasing the coefficient of friction of the mineral fertiliser particles from 0.1 to 0.7, the angle of the mineral fertiliser particles leaving the disc increases from 2 to 33 deg at the initial speed of movement of the aggregate 2 m·s-1 and from 2 to 37 deg at the initial speed 4 m·s-1. Therefore, some of the fertiliser particles will leave the disc at the agle bigger than the inclination of the disc to the horizontal plane within 20…30 deg. Changes of the angle speed of the disc rotation do not essentially influence changes of the angle of the fertiliser particles leaving the disc.
Influence of tractor hitch linkage system on plowing unit performance
Authors: Bulgakov Volodymyr , Ivanovs Semjons , Adamchuk Valerii , Nadykto Volodymyr , Zaryshnyak Anatoliy , Yaremenko Vadym , Krasiuk Liudmyla
Published: June 2023

The quality indicators of the ploughing unit largely depend on the joining diagram of the mounted plough with the tractor. Most often, this joining, performed according to a two-point or three-point diagram, is asymmetric. As a result, momentum arises that tries to turn the tractor in a horizontal plane. Depending on the chosen diagram for joining the tractor with a mounted plough, this momentum will be greater or less, and the performance of the ploughing unit will be worse or better. This paper evaluates the dependence of the momentum value on the plough rotation angle and the asymmetry of its joining to the tractor with two-point and three-point diagrams for adjusting the rear hitch linkage system. Calculations have established that the increase in the specified momentum occurs more intensively with a two-point diagram for joining the plough to the tractor. In this regard, its use is advisable only for specific ratios between the plough width and the parameters of the tractor running system. At the same time, with a certain adjustment of the tractor’s rear hitch linkage system according to the three-point diagram, it is possible to achieve such a position when its centre of mass practically coincides with the point of the plough traction resistance application. Ultimately, this ensures the momentum value is reduced to a minimum (almost zero) value. Experimental studies have established, when setting the convergence angle of the lower links of the tractor hitch linkage system according to the three-point diagram at the level of 0.49 rad, the null hypothesis about the equality of the plough operating width variances in comparison with the option of its joining according to the two-point diagram does not deviate. The frequency distributions of the plough rotation angle oscillations (𝛽) are also almost identical. The maxima of the normalized spectral densities of the parameter 𝛽 oscillations fall on the same frequency equal to 0.1 s-1. The oscillation variances of the angle β for both plough joining diagrams are concentrated in the same range of rather low frequencies: 0-1.0 s-1, i.e. 0-0.16 Hz.
Influence of moisture on particle size of plant raw materials after grinding
Authors: Kuzmenko Volodymyr , Bratishko Viacheslav , Subota Sergiy , Kholodiuk Oleksandr
Published: June 2023

Stem plant materials, as a common lignocellulosic raw material, are widely used both in agro-industrial production and in biofuel technologies. One of the main technological operations when using stem plant materials is grinding. The performed studies are dedicated to determining the influence of raw material moisture on the efficiency of grinding plant materials such as wheat straw, rape straw and corn stalks. A hammer grate crusher was used for the research. The diameter of the rotor was 520 mm, the diameter of the sieve holes was 7.25 mm, and the frequency of rotation of the rotor was 1470 rpm. In the upper part of the rotor, four knives are installed on a disk with slots, which preliminarily destroy the raw materials. Raw materials obtained after grinding were analysed using a sieve classifier. Grinding quality was assessed by the weighted average particle size. Experiments were conducted with wheat straw, rape straw and corn stalks with moisture obtained during crop harvesting, as well as additionally dried. Each type of raw material had three levels of moisture, and the repetition of the experiments was threefold. The moisture limits for each crop were individual and ranged from 8 to 30%. When analysing the results of the experiment, mathematical dependencies were obtained that describe the change in the weighted average length of the crushed raw material in the form of linear functions. It was established that when grinding wheat straw, rape straw, and corn stalks with a hammer crusher, an increase in their moisture content within the range of 8-30% leads to an increase in the weighted average length of particles from 1.6 to 2.4 mm, and the coefficient of determination of linear models of the influence of moisture on the change in weighted average length is in the range of 0.68-0.96.
Biogas production from fresh and old sawdust litter with chicken manure
Authors: Dubrovskis Vilis , Dubrovskis Dagnis
Published: June 2023

In Latvia, forest products are widely used for heat production by direct incineration. As it causes air pollution, especially in cities, other technologies are being considered. One of them is anaerobic digestion of biomass or biogas (methane) production. Biofuels and biogas are playing a key role in the decarbonisation of the transport sector and will contribute in the future to a fuel switch in combination with electrification, for example in hybrid cars. In sectors which are difficult to decarbonize, such as heavy-duty vehicles, ships and airplanes, biofuels often represent the only technically and economically viable solution. The European Biogas Association estimates that by 2030 overall annual potential for biogas will be at least 50 billion m3. In Latvia, there is a lot of timber processing and there is a lot of sawdust. They are also used as bedding in poultry farms. Bird droppings could improve their utility for biogas production. This article shows the results about anaerobic digestion of fresh and old sawdust and sawdust litter with chicken manure and slaughterhouse waste. Fresh and old sawdust and sawdust litter with chicken manure and slaughterhouse waste were digested in 6 l digesters at temperature 38 oC in batch mode process. Average specific biogas or methane yield from anaerobic fermentation of fresh sawdust was 0.407 L·g-1DOM or 0.175 L·g-1DOM respectively. Average specific biogas or methane yield from anaerobic fermentation of old sawdust was 0.369 L·g-1DOM or 0.153 L·g-1DOM respectively. Average specific biogas or methane yield from anaerobic fermentation of sawdust litter with chicken manure and slaughterhouse waste was 0.554 L·g-1DOM or 0.335 L·g-1DOM respectively.
Business digitization in Slovakia and its impact on rural development
Authors: Adamickova Izabela , Hallova Marcela , Bielik Peter , Turcekova Natalia
Published: June 2023

In this article, we examined the position of Slovak agriculture and rural businesses using the Digital Economy and Society Index (DESI), which measures a country’s progress towards a digital economy and rural society in comparison to other EU countries. The Digital Economy and Society Index is an online tool for measuring the progress of EU Member States toward a digital economy and society, including rural areas. DESI combines 44 indicators (pillars) and uses a weighted criteria system to rank each country based on its digital performance. As a result, Slovakia lags the EU average in human capital, use of the Internet, and digital public services. Slovakia performs well in fast and ultra-fast broadband Internet coverage, the share of ICT professionals has increased and the number of people who have never used the Internet has decreased. Regional structures and concepts have become increasingly important in recent years, and an active and purposeful policy of integrated rural development is being developed. In strengthening regional functions, account must also be taken of the fact that farms should also be competitive on a supra-regional scale and should also contribute to improving the provision of modern rural infrastructure through their own digitalization.
Development of technological process solutions in modular system of solar electricity and heat supply for greenhouses
Authors: Auce Agris , Horns Indulis Arnis , Ivanovs Semjons , Jermuss Aivars , Grinbergs Ugis , Rucins Adolfs
Published: June 2023

Considering the recent rapid increase of the energy costs for heating commercial greenhouses, solutions for more efficient use of the solar energy are needed. In this study there is investigated application of solar energy for greenhouse heating with a joint equipment, which consists of 8.0 kW solar photovoltaic panels (PV), coupled with a 5.0 kW air-to-water heat pump, 15.0 kW solar collectors (SC), a 10 kWh solar energy accumulator (SEA), and 1600 litre water heat accumulators (WHA). The tests of the joint equipment were made in a 50 m2 experimental greenhouse (EG) in several stages: testing of heat accumulation in the water-based heat tanks, testing of the amount of the solar energy, produced by the photovoltaic panels, used for direct water heating and for the operation of the air-to-water heat pump with and without the solar accumulator; and in the periods with insufficient solar energy directly from the grid. Surplus heat from the system was used to heat the irrigation water or to drive the biomass dryer. The temperatures in various points of the heating system were measured and analysed together with average temperatures and the data about the heat and solar energy. The results of the 2022 study showed that in EG, at the average annual solar intensity of 1227.4 kWh·m-2, 6762.7 kWh of electricity was produced by PV panels, and 12385.2 kWh of heat energy by SC. In the industrial greenhouse (IG), where the total energy consumption during the period, when natural gas was used, was 17.95 m3·m-2 or 163.73 kWh·m-2, causing climate change-promoting gas emissions (GHG) of 30.29 kg CO2·m-2; the experimental greenhouse (EG) emission factor was not detected. We concluded that, without a long–term energy storage system, covering several weeks of heat consumption, the solar energy system should be supplemented with external energy sources to cover the extended periods with insufficient energy supply at the beginning and the end of the vegetation season.
Research on inter-disciplinary links training engineers-designers for agricultural machinery at agricultural universities
Authors: Nikolaenko Stanislav , Bulgakova Oksana , Zbaravska Lesya , Rucins Adolfs , Dukulis Ilmars
Published: June 2023

There are studied and analysed peculiarities of inter-disciplinary links of the course of theoretical mechanics with general technical and special disciplines when training engineers-designers of agricultural machinery. The topicality of the problem of inter-disciplinary links in education is determined by objective processes in modern education, in particular, in training engineers-designers for agricultural machinery. The purpose of this study is theoretical substantiation of the didactic efficiency of establishing and implementation of inter-disciplinary links between theoretical mechanics, general technical and professional disciplines in order to improve the professional knowledge of the engineers-designers of agricultural machinery. As research methods there are accepted theoretical (comparative analysis of the scientific-methodical and pedagogical literature) and empirical (observation, analysis and generalization of pedagogical learning experience) methods. The comparative analysis of the results of studying theoretical mechanics, the disciplines of natural sciences, general technical and professional cycles, based on statistical processing of the results of the experiment, showed an increase in the level of formation of inter-disciplinary knowledge links and, accordingly, a 17% increase in the level and cognitive activity of future engineers-designers of agricultural machinery. The results of this research allow drawing a conclusion that ensuring integrity, fundamental and professional orientation of education is possible only if inter-disciplinary links are introduced.
Content of professionally oriented training in course of physics for students of agricultural engineering specialties
Authors: Bulgakova Oksana , Zbaravska Lesya , Dukulis Ilmars , Rucins Adolfs
Published: June 2023

The technology of professionally oriented education requires fundamental changes in the organization, content and methods of the educational process. This is, first of all, the transfer of emphasis of theoretical training to theoretical and applied, professionally oriented training. On the scientific and methodological level, the relevance of this investigation is determined by the need to design the process of forming professional competence and to identify didactic conditions that contribute to its efficient implementation. The purpose of this study is the problem of forming professional competence of the future engineers in the process of teaching a physics course. As a result of the investigation the efficiency of the proposed methodology for the formation of professional competence of the future agricultural engineers was scientifically substantiated and experimentally verified. A comparative analysis of the results of the study in the reference and the experimental group showed that the quantitative indicators and qualitative characteristics of the levels of formation of the components of the readiness of the future agricultural engineer to implement professionally oriented training in the experimental groups increased significantly compared to the reference group. In the experimental groups the number of students with a low level of knowledge decreased by 48% and increased with an average of ( 29% and sufficient by 18.5%. The positive dynamics of the level of knowledge revealed as a result of experimental verification gives reason to assert the efficiency of the proposed organizational and pedagogical conditions of this methodology for the implementation of professionally oriented education in the course of physics.
Reinforcement impact on state of cracks in concrete slabs
Authors: Bulgakov Volodymyr , Kutsenko Oleksii , Kutsenko Anastasiya , Aboltins Aivars , Ivanovs Semjons
Published: June 2023

In the present work the stress-strain state of a reinforced concrete slab with a transverse edge crack of constant depth is considered. There is investigated the effect of reinforcement upon the distribution of the fracture mechanics along the crack front. The uniformly or linearly distributed stresses at the slab ends are described as an external load. These loads correspond to pure tension and pure bending of the slab, respectively. For a case when the depth of the crack is less than the depth of the reinforcement rod, an analytical approach for an assessment of the crack state is proposed. As a characteristic of the crack state, the stress intensity factor (SIF) is used. Using the finite-element CalculiX package, the numerical results have been obtained, and adequacy of the analytical solution justified. The calculations have been performed for a wide range of variations in the geometrical parameters of the slab and the crack. For this purpose, a principle of replacing the external load with the pressure on the crack faces, well known in linear fracture mechanics, is generalized for the case of heterogeneous elastic bodies. The results of calculations show that the variation of the SIF value along the crack front is insignificant (up to 5% for practically realizable parameter values). On this basis it is concluded that the crack depth most likely is constant in the early stages of its fatigue development. For shallow cracks the SIF value will decrease near the reinforcing rod. It is interesting to note that for deep cracks the presence of reinforcement can lead to local increasing, not decreasing, of the SIF values. Considering this fact, the results presented in the paper may be useful in the design of reinforced concrete structures. It is especially important to take it into account in an individual design, in particular, in designing agricultural buildings where non-standard reinforced concrete structures are used.
Numerical simulation of polymeric composite nanofiber mat
Authors: Kanukuntla Sai-Pavan , Sanchaniya Jaymin-Vrajlal , Kardani Uchit , Beresnevics Vitalijs
Published: June 2023

Polymeric composite nanofiber mats have attracted considerable interest due to their unusual features, which include a large surface area, high porosity, and excellent mechanical strength. Numerical simulation is an essential tool for understanding and optimising the behaviour of these nanofiber mats. This research provides a detailed investigation of numerical simulations of polymeric composite nanofiber mats, with particular emphasis on the computational methods used to predict their mechanical characteristics. Tensile testing allows for quick and easy evaluation of the performance of nanofiber composites. To further understand this increase in the mechanical characteristics of polymeric nanofiber composite systems, a finite-element model was built. Using the experimental data of the publicly available authors and an analytical model, the model is evaluated and compared. To compare the numerically and experimentally determined values of the elastic modulus of the nanofiber composite, the Rule of Mixture (ROM) and Tsai-Pagano models were used. Using the experimental data, Representative Volume Elements (RVE) were built, and the elastic modulus was predicted using RVE. In comparison to an additional analytical model, the RVE model that makes use of numerical simulation predicts an elastic modulus that is very nearly identical to the value that is practically observed. In this work, a technique for forecasting the elastic modulus is proposed using a numerical simulation of the nanofiber composite mat.
Synthesis of tillage machines and experimental research on agro technological indicators for tillage quality
Authors: Bulgakov Volodymyr , Ivanovs Semjons , Beloev Hristo , Trokhaniak Oleksandra , Klendii Mykola , Bondarchuk Anatoliy , Rucins Adolfs
Published: June 2023

An important issue in the design of tillage machines is the search for improved machine designs to achieve high levels of productivity and quality of tillage operations, as well as the expansion of technological capabilities. One way of solving the problem of creating new machine designs for soil tillage is to implement progressive methods of searching for new technical solutions in the early stages of design preparation of production. This can be achieved by using morphological analysis, which in the fourth step involves the synthesis of object variants, which, based on the morphological matrix compiled, produces the full number of solutions. The article presents a synthesis of tillage mechanisms and machines using morphological analysis, which has led to improvements in the design of tillage machines. Hierarchical group synthesis using morphological analysis generated workable designs for alternative tillage machine variants. A method of structuring machine design for tillage and a method of their improvement based on the study of the properties of their structure elements, according to the theory of synthesis of hierarchical groups using morphological analysis, are proposed. To determine the agro-technological efficiency of the harrow with helical working tools, we conducted field tests of a rotary tool BDN-1,3 and an experimental sample of a harrow. The article presents the results of comparative tests of the disc harrow BDN-1,3 and the harrow with screw working tools. According to the results of studies, it was found that the density of the cultivated soil with the proposed helical working tools meets agricultural requirements and is 1.21 g·сm-3, which is 4.0% less than the variant with a disc harrow, and 36.3% less, compared to the agricultural background. According to the results of studies, it was found that the density of the cultivated soil with the proposed helical working tools, meets agricultural requirements and is 49.8 kN·m-2, which is 15.2% less compared to the disc harrow tillage, and 43.0% less compared with the background and the standard value. The volumetric crush coefficient of the proposed harrow variant is 51.4% lower than the background and the standard value, which varies between 1...2 N·сm-3 (for a plowed field).
Review of different types of fertilizers for willow plantations
Authors: Vendina Viktorija , Zusevica Austra , Lazdina Dagnija
Published: June 2023

Willow (Salix) family is one of the fastest-growing woody energy crops. It·has been widely used for biomass energy production in short-rotation plantations, carbon storage in longer rotation, and as a phytoremediation plant in Northern Europe. Willows could be cultivated on a wide range of soils, including marginal land, and they are readily propagated by planting un-rooted cuttings. Soil fertilization is necessary for obtaining a higher biomass yield. Different side products of energy production and municipal waste could be used for soil improvement. The aim of this research is to review fertilization practices in short-rotation willow plantations and their impact on the biomass yield. The data from the literature were collected, and different doses of various fertilizers were compared. The response to fertilization is positive if fertilizer contains complex NPK macro elements. The most appropriate dose per hectare varies depending on the soil properties, soil types, willow varieties, weather conditions, water availability, and other factors. Wood ash and peat could be used for soil improvement to solve the main characteristic marginal soils problems in Latvia – low organic content and pH value. Wood ash has high concentrations of calcium (Ca) and magnesium (Mg) and already is widely used as a liming agent in organic farming. Less demanded peat fractions, dewatered wastewater sludge, and biogas fermentation leftover -digestate contain a high amount of organic matter and nitrogen, therefore, could be used as a replacement for previously used fertilizers such as cattle slurry. In addition, wastewater sludge, digestate, and wood ash are also sources of microelements. A mix of all listed products has a high potential to be used as a complex soil amendment.