The paper discusses heat transfer and the step response of a low-power induction motor to no-load mode under fan cooled and naturally cooled conditions. In Latvia University of Agriculture (LUA) in the electric drive laboratory the experimental tests were performed on a 1.1 kW totally enclosed fan cooled three phase induction motor with a fan mounted on a shaft for fan cooled conditions and with a fan taken off for naturally cooled conditions. The transient temperatures are measured in nine points of the stator end windings and in two points of the stator frame using thermocouples. Temperature is measured by using K type thermocouples and Pico-Log TC – 08 data logger. The current and voltage are measured by using Simple Logger II L562 two channel data logger. Measurement data are processed and archived using data loggers Pico-Log Recorder, Simple Logger II and Data View software. The experimental test results show that ventilation plays an essential role in the heating process of small power induction motors. Mathematical and virtual models of induction motor windings heating are represented to simulate the heating process of induction motor under no-load mode and different cooling conditions.

This paper investigates the effect of intake runner design on pressure wave propagation and reflection in sparkignited internal combustion (IC) engine. These events are known to leave a noticeable influence on the overall engine performance therefore the aim of this study is to evaluate how changes in intake runner geometry affect pressure oscillations and volume flow rate. Time-dependent computational fluid dynamics (CFD) analysis was carried out to determine how these changes affect the pressure oscillations during a full engine cycle at constant crankshaft speed. Steady state CFD analysis at constant pressure differential was carried out to evaluate the effect on volume flow rate. The simulations were carried out in SolidWorks Flow Simulation environment. Honda CRF450R motorcycle engine was used to define the initial conditions and basic intake runner design. Intake air speed at port entrance cross-section was calculated based on engine parameters and operating speed. The average pressure values with respect to physical time were measured and graphed across the intake port opening cross-section. Six different intake runner designs were compared. It was concluded that the runner taper angle has influence on pressure wave-length but internal geometry (steps, curvature and taper angle) has influence on volume flow rate. It was observed that cylindrical intake runner design produced an increase in pressure wave-length but a cylindrical section of the intake runner with a stepped transition to tapered extension produced a slight increase in pressure wave amplitude.

The aim of the work is to increase the efficiency of cyclone technology by using a separator plate. Cyclone technology is used not only in the processing of various agricultural products, but also in air purification from dust. Air flow trajectories and the movement of dust particles inside the cyclone unit were simulated and analysed using Computational Fluid Dynamics (CFD) and particle study analyses. The separator plate was designed in certain sizes and placed inside the cyclone, thus increasing the efficiency of the cyclone. The angle of position of the separator plate significantly affected the obtained results. The experimental equipment was assembled together to test the simulation results. Wood ash was used to determine the efficiency of the cyclone. Studies have shown that the effect of the separator plate on increasing the efficiency of the experimental equipment is less than that shown in the simulations. Most of the experiments used ash particles that were greater than 20 μm, thus cyclone efficiency was 98.9 ± 0.05%. This confirms the compliance of CFD simulations with the physical model. More detailed research should be carried out in order to use the separator plate effectively for the filtration of very small dust particles.

The development of rural territories in the European Union (EU) plays an essential role, and agricultural development can largely contribute to this process. To project agricultural trends, a number of models have been developed in the EU, while in Latvia the LASAM model was developed in 2016 to generate projections for agricultural sector development in Latvia until 2050. In 2017, LASAM was extended by a module for socio-economic assessment that allows projecting productivity for various types of farming. The research aim is to develop a model for productivity simulation for various specialisation types of farms in order to project their development in Latvia. To achieve the aim, two specific research tasks were set: 1) to develop a model for productivity simulation for various specialisation types of farms in Latvia; 2) to identify the key results of the simulation of productivity for various specialisation types of farms in Latvia. The research found that in the period 2005 – 2016 the value added of agriculture tended to slightly increase in Latvia, whereas an opposite trend was observed for the number of persons employed in agriculture, which tended to decrease in the period of analysis. Both trends determine the agricultural productivity trend as well. A projection of productivity measured as value added per AWU for various farming types in Latvia by means of the LASAM model has revealed that it is different, and the highest level of productivity in 2030 and 2050 is projected for granivores as well as field crop farms.

In educational strategy papers, it is determined that entrepreneurial development should be implemented already in schools. Various methods and approaches can be used for the development. The majority of entrepreneurial competences are developed at the university – subjects devoted to the development of entrepreneurship are included in the study programs. Environment of the university is very friendly to this – not only because of activities devoted to entrepreneurship occurring in the academic environment, plenty seminars and trainings, but also because of the students’ personal maturity and motivation. Scholars actively raise the following questions: how to develop entrepreneurial competences effectively? Which methods are the most applicable? What kind of innovative methods are the most necessary? 104 students, who tried simulation traineeship of entrepreneurial development, were questioned in order to analyse the impact of methods and the change in entrepreneurial competences. The research was carried out in the Faculty of Economics and Management of Aleksandras Stulginskis University. The participants of the research were involved in the business simulation, where they had an opportunity to estimate themselves and improve their backgrounds, abilities and skills. Methods promoting and developing creativity were applied in simulation business enterprises; however, not all methods had worked. The methods of graphic representation were used by the minority and they were not considered to be very effective. The aim of the research was to determine entrepreneurial competences and innovative educational methods theoretically and to test empirically the development of entrepreneurial competences via simulation method.

The tree growth compensation followed by insect damage is important for tree survival. Insect damage by making 3 and 6 holes per each leaf, and clipping one third of a leaf were simulated for one-year old silver birch (Betula pendula Roth) seedlings once, at the beginning of the vegetation season. The height, aboveground and root biomass, root length, stem diameter and leaf area were measured for all damaged and control seedlings. The aim of the study was to examine the effects of different insect-damage simulations on silver birch growth. Our study demonstrated that leaf dry mass decreased in response to leaf perforations and clipping one third of leaf. However, at the end of the experiment, the cumulative dry mass reached the level of the control. We found no statistically significant effect on the aboveground and total biomass of damaged seedlings compared to the control. The leaf clipping decreased the leaf area and stem diameter compared both to the treatment with hole-damaged seedlings and the control. The induced birch growth response showed that tree seedlings were able to compensate their growth up to the control level after the insect damage in eight weeks.

Urban trees, integral to urban environments, demonstrate intricate responses to atmospheric pollutants like particulate matter (PM), tropospheric ozone (O₃), and carbon dioxide (CO₂). Notably, O₃ induces oxidative stress in leaf tissues, while PM, consisting of fine airborne particles, interacts with urban trees through foliar deposition. This interaction is particularly interesting as tree canopies are highly effective filters, capturing and accumulating PM on their surfaces. The present study focused on silver birch, small-leaved lime, and Norway maple seedlings responses to elevated O₃ and CO₂). With and without PM. Maple seedlings exhibited the highest stem height increment, followed by lime and birch. Elevated O₃ and CO₂ without PM led to substantial height increments for lime and maple. Elevated O₃ and CO₂ without PM increased the total polyphenols in lime and maple leaves but decreased the content of total flavonoids in birch and lime leaves. Our findings underscore the adaptability of lime and maple seedlings to elevated O₃ and CO₂, positioning them as promising species for urban environments in the face of changing climates. Birch, while exhibiting biochemical changes, demonstrated less pronounced growth responses. This studyʼs insights into the intricate interactions between urban trees and multiple pollutants, particularly the species-specific responses, are of significant value for urban planning and environmental management.