2025-06-08
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Finite element analysis of nanoindentation pile-up and correction of projected contact area
Kovář, J. ; Fuis, V. ; Čtvrtlík, Radim ; Tomáštík, Jan
This paper deals with the pile-up phenomenon that can occur during nanoindentation. Finite Element (FE) simulation of X5CrNiCuNb16-4 steel nanoindentation with pyramidal Berkovich indenter was done, and stress and strain beneath the indenter leading to pile-up behavior were analyzed in detail. Pile-up also influences the projected contact area, which should be corrected to include the pile-up into the Oliver-Pharr analysis. Accurate calculation of the projected contact area requires knowledge of its boundary. Few methods of boundary approximation were used, including approximation by the triangle and the semi-ellipse. For more precise approximation, the expression for parabolical approximation was derived. These methods were compared with the projected contact area calculated by finite element method. The most precise results were obtained using semi-elliptical and parabolical correction, which can be used for the determination of the projected contact area and its boundary.
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2025-06-08
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2025-06-08
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Asbestos Use - Benefits and Risks
Navrátil, Tomáš ; Hrdlička, Vojtěch ; Lipšová, Hana ; Kotlík, B. ; Zacharov, S. ; Mrázová, K.
Asbestos is a collective term for fibrous silicate minerals with refractory and strength properties that were formerly widely used, especially in the construction industry. However, inhalation of asbestos\nfibers poses a serious health risk, leading to both benign (asbestosis, pleural hyalinosis) and malignant (lung cancer, mesothelioma) diseases. The production of asbestos materials has been\nprohibited in the Czech Republic. Nevertheless, it still poses a risk in reconstruction and mining. There are legislative measures at the EU and Czech levels regulating the management of asbestos\nand asbestos-containing waste to minimize exposure and protect the health of workers and the public. The risk of disease (benign, e.g., asbestosis or pleural hyalinosis, as well as malignant\ncancers, e.g., lung cancer or malignant mesothelioma) persists even after exposure to asbestos dust has ceased.\nThis paper presents an overview of asbestos, its history, the regulations of its application and disposal, and the risks connected with its utilization. However, the main part of the oral presentation\nwill focus on the laboratory tests used to diagnose and characterize diseases associated with asbestos exposure.
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2025-06-08
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Development of Flow-Through Electrochemical Cell RaFEC for Oxidation State Adjustment of Superheavy Elements Homologues
Sochor, J. ; Němec, M. ; Bartl, P. ; Hrdlička, Vojtěch ; Navrátil, Tomáš ; Zach, Václav ; Štursa, Jan ; Omtvedt, J. P. ; John, J.
This paper focuses on the development of a flow-through electrochemical cell called RaFEC for adjusting the oxidation state of short-lived transcatinoid homologs in high yield and short reaction\ntime. In the first development phase, experiments were performed with thallium as nihonium (synthetic element, atomic number 113) homolog, using both long-lived 201 Tl and short-lived Tl\nradioisotopes generated on the U-120M cyclotron. The adjustment of Tl oxidation state in the flow-through cell is followed by the separation of the different oxidation states of thallium \n(Tl +I /Tl +III) by liquid-liquid extraction using Aliquat 336 in a hydrochloric acid environment. The aqueous and organic phases from the extraction were analyzed on a gamma spectrometer.
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2025-06-08
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In-situ Fluorescence Spectroelectrochemistry of Dyes
Beneš, Marek ; Sokolová, Romana ; Swoboda, D. ; Pizzimenti, S. ; Sabatini, F. ; Dostálková, Lucie ; Nycz, J. ; Degano, I.
In-situ spectroelectrochemical techniques are known as efficient methods for determining the intermediates in processes involving charged species. This contribution aims at extending the toolset\nof spectroelectrochemical techniques available beyond the widely exploited combination of cyclic voltammetry or chronoamperometry with UV-Vis, NIR, and IR spectroscopy, by developing\nspecific systems allowing for in-situ fluorescence (FL) spectroelectrochemistry. Three different setups developed for fluorimetric spectroelectrochemistry with different geometries were tested\nusing target fluorescent synthetic dyes such as Eosin Y, belonging to the xanthene derivatives, and a novel derivative of methylene blue, MB, the phenothiazinium dye QMB.
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2025-06-08
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Electrochemical Oxidation and Voltammetric Determination of Triazole Fungicides
Šelešovská, R. ; Matvieiev, O. ; Chýlková, J. ; Sokolová, Romana ; Schwarzová-Pecková, K.
This contribution focuses on the electrochemical behavior of selected triazole fungicides and the development of voltammetric methods for their determination. A boron-doped diamond electrode\n(BDDE) was employed due to its exceptional electrochemical properties, enabling a detailed investigation of the oxidation processes involved. Moreover, the electrochemical oxidation\nmechanisms of these compounds were studied for the first time. A combination of techniques, including, e.g., high-performance liquid chromatography (HPLC) or gas chromatography (GC) with\nmass spectrometry (MS), or spectroelectrochemistry, was employed to identify oxidation products and propose plausible electrochemical oxidation pathways.
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2025-06-08
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2025-06-08
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2025-06-08
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2025-06-08
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Gas Diffusion Electrodes for Efficient Electrocatalytic Reduction of Carbon Dioxide
Vaněčková, Eva ; Hrdlička, Vojtěch ; Dostálková, Lucie ; Pilař, Radim ; Sazama, Petr ; Sádovská, Galina ; Khalilullah, Umar ; Petráková, Vladimíra ; Bouša, M. ; Kolivoška, Viliam
Electrocatalytic processes are of importance for technologies dealing with the utilization of carbon dioxide. Considerable progress in CO2 electrocatalytic reduction was achieved by gas diffusion\nelectrode development, which overcomes limited CO2 mass transport in aqueous medium. The composition of the catalytic layer has a major impact on the efficiency and stability of the\nelectrocatalytic process. In this study, we focus on the effect of the catalytic ink composition (ratio and total amount of silver nanowires, carbon black, and Nafion) on the Faradaic efficiency towards\nCO production at low (-25 mA cm -2 ) and high (-283 mA cm -2 ) current densities applied in the electrocatalytic process.
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