http://hdl.handle.net/10563/1000004 Fri, 31 Jul 2026 06:39:46 GMT 2026-07-31T06:39:46Z http://hdl.handle.net/10563/1012847 Effect of cutting conditions on roughness and cutting force when machining a freeform surface with Barrel tools Řezníček, Martin; Hořava, Cyril; Zajíček, Jakub; Ovsík, Martin Barrel tools are relatively new tools that use atypical geometries to achieve shorter production times and improve surface quality. They have been increasingly used in the finishing operations industry, where they are gaining more and more popularity. For their optimal use, it is necessary to know how these tools behave during work in terms of how they load the machined product and what surface qualities they can achieve. For this reason, this study was conducted to compare two tools when machining a free surface. The obtained surface quality and the force load caused by the tool were evaluated. It was found that barrel tool machining results in a heterogeneous surface caused by different cutting speeds along the length of the tool and that the two obtained regions show differences in the obtained roughness. Even though the operation was classified as a finishing process, a difference of up to 30% was identified in the cutting forces acting on the tool and the workpiece. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10563/1012847 2026-01-01T00:00:00Z http://hdl.handle.net/10563/1012839 Physicochemical, rheological, textural, tribological, and sensory insights into the role of citrus fiber in quark cheese spreads with varying fat content Vincová, Anna; Šantová, Kristýna; Jaššo, Miroslav; Lorencová, Eva; Salek, Richardos-Nicolaos The objective of this study was to evaluate the effect of citrus fiber (1% wt/wt) on the physicochemical, rheological, textural, tribological, and sensory properties of quark cheese spreads with different fat content (10%, 15%, and 20% wt/wt). Physicochemical properties, including pH, DM, and water activity, were not affected by citrus fiber addition. Furthermore, rheological and textural analyses showed that citrus fiber increased samples' hardness and viscoelastic moduli, probably by reinforcing the protein-polysaccharide matrix, especially in low-fat variants. Tribological measurements indicated that higher fat improved lubrication, whereas fiber-containing quark cheese spread samples exhibited slightly higher coefficients of friction due to increased structural rigidity. Additionally, color analysis revealed minor shifts toward darker and more yellow tones when citrus fiber was used. Moreover, sensory evaluation confirmed that citrus fiber addition did not affect most of the tested organoleptic attributes, with slight improvement in flavor. The findings indicate that incorporating citrus fiber into quark cheese spreads can improve their functional properties, facilitate fat reduction, and promote the sustainable utilization of byproducts in dairy products. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10563/1012839 2026-01-01T00:00:00Z http://hdl.handle.net/10563/1012840 Production of binderless bricks from Martian regolith simulants Řezníček, Josef; Bednařík, Vratislav; Vinter, Štěpán; Filip, Jaroslav; Kuřitka, Ivo; Šuly, Pavol; Krejčí, Ondřej Building a station on Mars would require a huge amount of building material, and one of the most readily available materials is the ubiquitous regolith, which can be used to make building elements based on the principle of in situ resource utilization. In this paper, we discuss the fabrication of binder-free building elements by cold pressing followed by firing from MGS-1, MGS-1C and MGS-1S simulants in the temperature range of 800–1200 °C. The thermal removal of perchlorates, sulphates and carbonates from simulants is also being investigated. The results show that MGS-1C simulant has the best compressive strength with approximately 113 MPa, followed by MGS-1 with 35.9 MPa, and the worst is MGS-1S with 9.1 MPa. It was also confirmed that the simulants can lower the decomposition temperature of perchlorates by up to 100 °C, as observed for Martian regolith by the Curiosity rover. Finally, it was possible to determine the temperatures at which sulfur dioxide and carbon dioxide begin to be released in the simulants for heating. © 2026 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10563/1012840 2026-01-01T00:00:00Z http://hdl.handle.net/10563/1012844 Graphene field-effect transistor sensor for detection of urea in water: Experimental study and DFT analysis Špaček, Ondřej; Supalová, Linda; Mach, Jindřich; Nezval, David; Šikola, Tomáš; Bartošík, Miroslav Urea sensors are used in medicine for disease monitoring, the automotive industry for emission control, agriculture and food safety for fertilizer and residue analysis, environmental monitoring for water pollution detection, and in industrial processes for production control. This article presents a pioneering experimental study of non-selective urea detection in aqueous solution using graphene doping in a field-effect transistor (FET) configuration. It is demonstrated that water itself p-dopes graphene, while the addition of urea weakens this effect (resulting in reduced p-doping). The response is explained by original density functional theory (DFT) calculations considering the common influence of water and urea. Analyses of charge redistributions and band structures indicate the formation of non-doping urea–water complexes responsible for the observed results. Moreover, the calculations provide deeper insight into the complex urea–water–graphene interactions, which may be utilized in other applications. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10563/1012844 2026-01-01T00:00:00Z