Influence of size and orientation of 3D printed fiber on mechanical properties under bending stress

The principle of FFF/FDM (Fused Filament Fabrication/Fused Deposition Modeling) 3D printing technology is the melting and application of a continuous fiber made of thermoplastic material, according to predefined routes on the substrate. A layer is created on which other layers are placed until the object is finished. It is the orientation of these fibers that greatly affects the resulting mechanical properties. Therefore, the printed object behaves orthotropic. The material does not blend perfectly or evenly between the individual fibers, which is why the resulting strength is limited by adhesion. Within the fibers themselves, it is also its dimension that affects the size of the contact surface and therefore the effect of adhesion. This contribution aims to compare the effect of fiber size in a given direction and its rotation in 3-point bending according to the standard ??SN EN ISO 178. The maximum bending load force was obtained and the bending stress and modulus of elasticity were determined. The influence of layer cohesion on the failure of the specimens is compared. One of the other important studied aspects for the effective production is the printing time of each specimen.Web of Scienc

Fungus Aspergillus niger processes exogenous zinc nanoparticles into a biogenic oxalate mineral

Zinc oxide nanoparticles (ZnO NPs) belong to the most widely used nanoparticles in both commercial products and industrial applications. Hence, they are frequently released into the environment. Soil fungi can affect the mobilization of zinc from ZnO NPs in soils, and thus they can heavily influence the mobility and bioavailability of zinc there. Therefore, ubiquitous soil fungus Aspergillus niger was selected as a test organism to evaluate the fungal interaction with ZnO NPs. As anticipated, the A. niger strain significantly affected the stability of particulate forms of ZnO due to the acidification of its environment. The influence of ZnO NPs on fungus was compared to the aqueous Zn cations and to bulk ZnO as well. Bulk ZnO had the least effect on fungal growth, while the response of A. niger to ZnO NPs was comparable with ionic zinc. Our results have shown that soil fungus can efficiently bioaccumulate Zn that was bioextracted from ZnO. Furthermore, it influences Zn bioavailability to plants by ZnO NPs transformation to stable biogenic minerals. Hence, a newly formed biogenic mineral phase of zinc oxalate was identified after the experiment with A. niger strain's extracellular metabolites highlighting the fungal significance in zinc biogeochemistry.Web of Science64art. no. 21

Research of impact of various types of plasticizers on properties of alkaliactivated inorganic polymers

Import 28/11/2008Prezenční223 - Katedra stavebních hmot a hornického stavitelstvíNeuveden

Utilization of sands from production of floated kaolin for manufacture of artificial sandstones

Import 07/02/2010Prezenční223 - Katedra stavebních hmot a hornického stavitelstvívýborn

Effect of intervention programme on changes in selected physical abilities of elementary school pupils

In our paper we focus on the BUBO intervention programme applied on elementary school pupils for the period of 2 years. The intervention programme we have chosen is a part of an extended grant for Physical Education and Sports lessons at the Elementary School in Ružomberok. The focus of the intervention programme is on health-oriented physical education. The experimental group consisted of 49 pupils in the fifth and sixth grades, and included 28 girls and 21 boys. The original total number of the tested pupils was higher, but those who did not undergo the input or output evaluation for health reasons were excluded. The test took place in the school years 2015/2016 and 2016/2017. The programme was conducted in 15-minute time slots during Physical Education lessons three times a week. The principal research method was a one-group pedagogical experiment. The primary method of verifying the mobility ability levels was the Eurofit battery tests. In the results section we established that both tested groups of girls and boys exhibited positive changes after the application of the BUBO intervention programme. Both groups have improved in standing broad jump and sit and reach tests

Subsurface structure and magnetic parameters of Fe-Mo-Cu-B metallic glass

Subsurface properties of 57Fe81Mo9Cu1B9 metallic glass were studied by conversion electron and conversion X-ray Mössbauer spectrometry. They were applied to both surfaces of the ribbons. Deviations in structural surface features are exhibited via different contents of crystalline phases, which were identified as bcc-Fe and magnetite. The presence of small ferromagnetic particles was also suggested from magnetic measurements. An influence of irradiation with 130-keV N+ ions on surface properties of the as-quenched alloy is also discussed