No abstract

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).

Abstract. Biohumus is widely used for various vegetable productions. However, its use is difficult in places such as recreation, sports, golf, and football fields. Humus uneven distribution across the field promotes grass growth at different speeds. The result is not acceptable. Therefore, to develop vermicomposting end product usability work is needed in several directions. One of the directions is to develop the possibility of humus evenly spreading across the field. It can be done developing new or improving the existing technologies, which allow doing it with minimal impact on product quality. Granular vermicompost can be called concentrated fertilizer, because the recycling process reduces the volume of material more than 10 times, due to water removal and material thickening while extruding. It is therefore necessary to examine the humus moisture content and determine the energy needed for drying it. Given that vermicompost is a biologically active material, the drying must be carried out at the lowest possible temperature. It is not recommended to increase the drying temperature above 35 ºC. The aim of this research is to determine the drying rates of vermicompost in different temperatures of the drying agent and avoid overdrying. The drying rate is defined as the variation of the moisture content with respect to the time. The studies showed that the maximum of the drying speed was observed at the beginning of the process and reached 0.86 %·min -1 in the drying temperature 64 ºC. Decreasing of the drying temperature decreases the drying speed to 0.59 %·min -1 .

In practice for material pressing mechanisms are used that provide synchronous motion of components. Gears can satisfy this design specification accurately, but they are more expensive and difficult to manufacture than linkages, and not convenient to transmit the motion between two parallel axis with large center distance. Thus, when a quasi-constant transmission ratio within a wide range of driving link rotation is allowed, four-bar linkages are suitable to replace gears. The possibility of using a four-bar linkage mechanism to ensure opposite rotation of double cranks is analysed. A planar four-bar linkage is characterized by having four revolute joints with parallel axis. The synthesis of four-bar linkages will yield an approximation of transmission ratio between the input and output crank rotation. Crank displacement equations for antiparallelogram and similar forbar linkage mechanisms depending on the sizes of the links are presented. Antiparallelogram mechanism with ratios j = 30 between the center-distance and the crank length provide a transmission ratio u 13 = 1 ± 5 % for driving the crank angle in range 40-140 deg. The Matlab simulation showed quasi-constant transmission ratio u = 1 ± 2 % for the four-bar mechanisms with coupler length not equal with fixed center distance.

It is possible to improve the development of students’ spatial thinking with various information technologies. We can improve students understanding with three dimensional models, created in the CAD program and special processing it in PowerPoint in the program, together with drafting in three planes. Gradually solving tasks in planes and explaining it in three dimensional models, the solution of concrete task is much clearer, because it is possible to look a situation together in planes and 3D models. The students of three faculties were polled that cognize the students’ opinions about teachers teaching methods in descriptive geometry lessons and analyze spatial understanding of students. A possibility to use information technologies to improve a descriptive geometry lectures have been researched in this work. The most important information about working out methodological materials has been generalized in discussion part. The results of research show that lectures with information technologies using improve students’ understanding of solved tasks during the lectures.