Abstract. Bibliometric analysis of publications allows to quantify researchers' interests in this specific topic. This method enables the identification of key authors, who are publishing in this area. It is necessary to define research trends, which have developed in this specific field. It enables to determinate the main research topics, discoveries and correlations in the global knowledge network. The purpose of this work was to identify the trends and research topics in engineering for rural development. The modified method of bibliometric analysis was used, bibliometric analysis of the key word frequency of occurrence and the linkages between the key words. The analysis was performed using bibliometirc post-conference materials of the International Scientific Conference Engineering for Rural Development in Jelgava in the years 2012-2017 downloaded from Web of Science database. The data have been processed and cleaned, then analysed in VOSviewer. This program is used for creating and graphic visualisation of bibliometric maps. VOSviewer utilized the method of "visualization of similarities" VOS. In this work the program was used to create maps of terms in the version of "thermic maps". The main research topics have been presented in the form of associated networks. The last stage was detailed topical analysis and classification into groups according to selected criteria. The provided research enabled an identification of lines of the research. The main research topics in all research period were: energy qualities of plant materials, alternative fuel (biomass, biodiesel, biogas), renewable energy sources, modelling, optimisation and stimulation of processes, mechanisation of plant production and many more. This analysis can be used as a literature review in the selected knowledge area.

Abstract. One of the many advantages in favor of the energy use of biomass is the reduction of greenhouse gas emissions, e.g. carbon dioxide and toxic exhaust components. Depending on the physicochemical and thermal properties, and especially on the calorific value, biomass can be used in heating and electricity. Biomass can be any organic material containing carbon, but without significant physico-chemical changes, which would lead to the formation of specific properties of crude oil or hard coal. The aim of this work was to determine selected properties of hazelnut shells in terms of their suitability for biofuel production. The hazelnut shells of the following varieties were analyzed: Casina, Catalan, Webba Cenny, Berger, Trapezian and Barcelonski. The examined hazelnuts were characterized by slight physicochemical differentiation. The criteria for biomass energy assessment were: calorific value, moisture content, heat of combustion, flash point, volatile content and bulk density. Measurements of selected parameters were made using standardized measuring devices. Among the tested varieties of hazelnut shells, the highest caloric value was characterized by the Casina variety (18.42 MJ . kg -1 ), and the smallest for the Trapezian variety (17.21 MJ . kg -1 ). The highest content of ash was observed for the Catalan variety (1.4 %) and the lowest for Casina (0.89 %). The highest content of volatile parts was noted for Trapezuński (72.3 %) and the smallest for Berger variety (71.73 %). The highest temperature of ignition was distinguished for the variety Webba Cenny (425.07 ºC), and the lowest for the variety Trapezian (368.4 ºC). The moisture content of the tested walnut shells ranged from 5.8 to 6.8 %. The conducted research and the analysis of selected physicochemical properties show that hazelnut shells are suitable for the production of biofuels.

Fruit and vegetable harvest efficiency depends on the mechanization and automation of production. The available literature lacks the results of research on the applicability of pneumatic end effectors among grippers for the robotic harvesting of strawberries. To determine their practical applications, a series of tests was performed. They included the determination of the morphological indicators of the strawberry, fruit suction force, the real stress exerted by fruit suckers and the degree of fruit damage. The fruits’ morphological indicators included the relationships between the weight and geometrical dimensions of the tested fruit, the equivalent diameter, and the sphericity coefficient. The fruit suction force was determined on a stand equipped with a vacuum pump, and control and measurement instruments, as well as a MTS 2 testing machine. The necrosis caused by tissue damage to the fruits by suction cup adhesion was assessed by counting the necrosis surface areas using the LabView programme. The assessment of the necrosis was conducted immediately upon the test’s performance, after 24 and after 72h. The stress values were calculated by referring the values of the suction forces obtained to the surface of the suction cup face. The tests were carried out with three constructions of suction cups and three positions of suction cup faces on the fruits’ surface. The research shows that there is a possibility for using pneumatic suction cups in robotic picking heads. The experiments performed indicate that the types of suction cups constructions, and the zones and directions of the suction cups’ application to the fruit significantly affect the values of the suction forces and stresses affecting the fruit. The surface areas of the necrosis formed depend mainly on the time that elapses between the test and their assessment. The weight of strawberry fruit in the conducted experiment constituted from 13.6% to 23.1% of the average suction force.

Microalgae are a practical source of biological compounds for biodiesel production. This study examined the influence of three different light-emitting diode (LED) systems on the biomass production of green algae Chlorella vulgaris BA0002a. The cultivation was carried out in a photobioreactor illuminated from the bottom with a single side light jacket (PBR I), in a photobioreactor illuminated from the bottom with a double side light jacket (PBR II) and in a photobioreactor illuminated only from the top (PBR III). Research has shown that the intensification of algae cell production and growth depends on the light distribution and exposure time of a single cell to radiation. In the experiment, the highest growth of algae cells was obtained in the photobioreactor with double jacket and lower light panel. The lowest cell growth was observed in the photobioreactor illuminated only from above. For cultures raised in the PBR I and PBR II photobioreactors, increased oxygen production was observed, which was directly related to the increased production of biomass, which in turn was dependent on the increased amount of radiant energy.

One of the aspects of biological activity of vanadium is its influence on carbohydrate metabolism. For more than 30 years, various vanadium complexes have been tested as antidiabetic agents. This study researched organic vanadium complexes with bipyridinium ligands and their influences on metabolic rate, as well as on the antioxidant activity of adipose tissue. The effects of sodium (2,2′-bipyridine) oxidobisperoxovanadate (V) octahydrate (known as the V complex), bis(2,2′-bipyridine) oxidovanadium (IV) sulfate dehydrate (known as the B complex), and bis(4.4′-dimethyl-2,2′-bipyridine) oxidovanadium (IV) sulfate dihydrate (labelled as the BM complex) were assessed. Solutions of the tested complexes were introduced intraperitoneally with a probe to animals fed with either a control diet or a high-fat diet. The BM complex had a significant influence on the increase in ferric reducing antioxidant power, as well as on the concentration of glutathione in the adipose tissue of rats fed with a high-fat diet. The V complex increased the concentration of glutathione in the adipose tissue of rats fed with control fodder, as well as significantly reduced the relative change in rat weight for the high-fat diet. Furthermore, the presence of each tested vanadium complex had an impact of statistically significant increase in basal metabolic rate, regardless of applied diet. Further research on these organic vanadium complexes is necessary to understand the mechanisms responsible for their ability to affect adipose tissue.