Volume 23 (2019): Edition 2 (June 2019)

The objective of the paper was to determine the costs of production and production effectiveness of pellets made of sawdust and characteristics of logistics of raw material carriage and distribution of pellets. The scope of the paper covered the research carried out in the branch of DREWEX company located in Chotelek town (Świętokrzyskie voivodeship, Province of Busko Zdrój). Unit costs of pellets production were: 513.4 PLN∙t⁻¹ for option 1, 423.3 PLN∙t⁻¹ for option 2 and 393.3 PLN∙t⁻¹ for option 3. The most favourable was option 3 when the pellets were produced on the technology line in the 3-shift system day and night. The average distance to seven cities from which sawdust was delivered was 43.6 km and the distance to which production was distributed to ten cities was on average 105.5 km.

The aim of the work was to determine the influence of screw speed and variable amounts of fresh vegetable additives on selected aspects of extrusion-cooking of corn-vegetable blends. Corn grit as a basic component was supplemented with a fresh pulp of beetroot, carrot, leek and onion in amounts of 2.5-10% in the recipe. The extrusion-cooking was carried out using a single-screw extruder in the temperature range 120-145°C and extrudates were formed into directly expanded snacks. Two indicators were measured: the production efficiency (Q) and the specific mechanical energy (SME) consumption. As a result of the findings it was noted that the rotational speed of the extruder’s screw showed a greater impact on both production efficiency and SME as compared to the variable amounts of applied additives. A tendency to increased efficiency and specific mechanical energy consumption was observed along with the increase of screw speed during processing. The highest production efficiency was observed if fresh leek and onion were used as additives and the highest extrusion speed screw was applied. The largest specific energy consumption was noted during the extrusion-cooking of blends containing fresh carrot and onion addition at high screw speed.

Development investment capacity of farms depends on their potential and scale of production, and thus its revenue, which determines the scale of investment purchases. Most specialized farms have growth potential. Farmers take great interest in modernization and investing in new technologies, machinery and agricultural land, as confirmed by market analysis. Literature references offer information regarding the needs and investment opportunities of territorially diversified farms running conventional production, however the aim of the work is to determine the investment possibilities of organic farms with various production branches. The research included 50 farms certified as ecological producers. In order to answer the question which type of business has the greatest development potential, the examined facilities were divided into branch groups.

This paper presents research on the impact of printing speed on the strength of a manufactured object and is the next stage of the author's research on the impact of technological parameters of 3D printing on the strength of printed models. The tested universal specimens were printed using the FDM (Fused Deposition Modeling) method from PLA (polylactic acid, polylactide). The paper presents the maximum breaking force of the samples and the time of printing samples depending on the printing speed, which varied from 20 mm·s⁻¹ to 100 mm·s⁻¹. The research indicates that the strength of samples decreases with increasing speed. In the range of 50-80 mm·s⁻¹, the strength of the specimens remined at a similar level, however, above 80 mm·s⁻¹, it decreased significantly.

The article presents an algorithm for calculating selected energy assessment indexes for grain driers. Particular attention was paid to the conversion of the equations obtained for the operating conditions of the drying process into equations allowing the calculation of indexes for the standard drying conditions. The indexes obtained allow a proper comparison of dryers operating in varied atmospheric conditions, as well as humidity and temperature of the dried material.

Three different types of nozzles (different wear rate) were used in this study. They are classified depending on the severity of their wear to three groups: new, worn and damaged nozzles. Those nozzles were spraying with the same application rate (303 l/ha) on two-year field trials; this was achieved by changing the spraying pressure for each group of nozzles in order to get the same application rate. This practice is usually done by operators of sprayers, who calibrate the sprayers on the same application rate every year without changing the nozzles, so they tend to reduce the spraying pressure in order to compensate the flow rate increase due to the nozzles yearly wear. Two types of plant growth regulators (PGR) agents were used in this study, namely: Moddus and Kelpak, they were applied to wheat plants field to reduce lodging. The results showed that applying PGR in the year 2015 produced an increase in the wheat yield and reduction in the plant height regardless the nozzle type, although there was not any occurrence of wheat lodging. In the year 2016, the new nozzles produced higher values of wheat yield than other two types of nozzles.

Assessment of the colour with the use of many parameters is used with reference to evaluation of the quality changes of products resulting from application of specific technological treatments. The paper investigates the effect of relations between parameters of irradiation of potato bulbs with UVC on selected coefficients of assessment of the colour of fries determined with CIE L*a*b* method. It was statistically significantly proved that UV-C radiation affected brightness of fries, change in colour, recognition of the difference in colour and intensity of the colour reception. Statistical analysis of results was carried out at the assumed level of significance α=0.05.

Conclusions on the analysis of the state of development in the tractor industry are formulated, aspects of the forecasting concept of transformation, general layout solutions and the theory of promising tractor units with new propulsion systems are considered, a general approach to the pre-design substantiation of new generation tractors is presented.

The paper analyzes the development opportunities of solar systems in the Republic of Serbia. Renewable energy sources and their energy potential, such as solar energy, should be considered in order to meet the needs of consumers. Solar energy can be considered the most modern renewable energy whose utility is still developing, and it is not represented as the utilization of hydro energy sources. Researches show that Serbia is a country with a high RES potential and that it has favorable conditions for production of electrical and heat energy from renewable sources. The aim of this paper is to present the possibilities of using solar energy in Serbia. Energy supply from renewable energy sources is a key factor for each country's strategy, because it directly contributes to reducing the negative effect on the environment.

The paper presents the coupled electro-mechanical problem. In the numerical analysis of the issue, piezoelectric solid-to-shell transition elements were applied. They combine three-dimensional or hierarchical shell piezoelectric elements with piezoelectric first order elements. The mentioned first order of the element refers to the field of transversal displacements of an element. The mechanical field of the discussed piezoelectric elements may correspond to: the model of three-dimensional theory of elasticity, hierarchical shell models of higher orders or the first order shell model. The electrical field of the potential may be modelled with hierarchical dielectric first order models or higher in transverse direction or with a three-dimensional theory. Effectiveness of modification of algorithms of classical piezoelectric elements was assessed in this paper. To perform such an assessment, curves of convergence of hp method in model tasks are presented. Curves obtained with the use of classical and modified piezoelectric transition elements were set and compared.