11. Optimal approximation of spherical squares by tensor product quadratic Bézier patchesAleš Vavpetič, Emil Žagar, 2023, izvirni znanstveni članek Povzetek: In cited article E. F. Eisele considered the problem of the optimal approximation of symmetric surfaces by biquadratic Bézier patches. Unfortunately, the results therein are incorrect, which is shown in this paper by considering the optimal approximation of spherical squares. A detailed analysis and a numerical algorithm are given, providing the best approximant according to the (simplified) radial error, which differs from the one obtained mentioned article. The sphere is then approximated by the continuous spline of two and six tensor product quadratic Bézier patches. It is further shown that the $G^1$ smooth spline of six patches approximating the sphere exists, but it is not a good approximation. The problem of an approximation of spherical rectangles is also addressed and numerical examples indicate that several optimal approximants might exist in some cases, making the problem extremely difficult to handle. Finally, numerical examples are provided that confirm the theoretical results.
Ključne besede: Bézier patches, spherical squares, optimal approximation, sphere approximation
Objavljeno v DiRROS: 14.03.2024; Ogledov: 87; Prenosov: 46
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15. Scanning electron microscope images of isolates of small cellular particles Phaeodactylum tricornutum grown in media supplemented with Guillard’s (F/2) marine : marine water enrichment solution, BG11 broth and Lennox LB brothApolonija Bedina Zavec, Darja Božič, Matej Hočevar, Aleš Iglič, Marko Jeran, Veronika Kralj-Iglič, Anna Romolo, 2024, objavljeni znanstveni prispevek na konferenci Objavljeno v DiRROS: 08.03.2024; Ogledov: 87; Prenosov: 44
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19. Enhancing ductility of hot-work tool steel through isothermal bainitic transformationAnže Bajželj, Aleš Nagode, Tilen Balaško, Barbara Šetina, Jaka Burja, 2024, objavljeni znanstveni prispevek na konferenci Povzetek: Hot-work tool steels are extensively used in industrial applications that require high resistance to mechanical and chemical degradation at elevated temperatures. To meet these requirements, hot-work tool steels must exhibit good mechanical properties, including high tensile strength, hardness, wear resistance, and tempering resistance, as well as high thermal conductivity and ductility. This study investigates the ductility of the hot-work tool steel HTCS-130, which suffers from low ductility due to the presence of stable molybdenum-tungsten carbides (M6C) on the prior austenite crystal grain boundaries. Increasing austenitisation temperatures or prolonging the dwelling time at temperature can promote intensive migration of grain boundaries, leading to negative effects on the mechanical properties of the steel. To address this issue, isothermal transformation in the bainitic area between 350 and 500 °C was performed. Isothermal transformation at around 350 °C leads to the formation of lower bainite, which has similar hardness to tempered martensite. As the temperature of isothermal transformation increases, the hardness of the material decreases, due to the formation of upper bainite. The hardness analysis was measured using the Vickers method, the impact toughness of the steel samples was measured using a Charpy test with V-notched samples. The microstructure characterization was performed using optical and scanning electron microscopy. The improvement of ductility can be achieved by controlling the isothermal transformation of bainite and adjusting the heat treatment conHot-work tool steels are extensively used in industrial applications that require high resistance to mechanical and chemical degradation at elevated temperatures. To meet these requirements, hot-work tool steels must exhibit good mechanical properties, including high tensile strength, hardness, wear resistance, and tempering resistance, as well as high thermal conductivity and ductility. This study investigates the ductility of the hot-work tool steel HTCS-130, which suffers from low ductility due to the presence of stable molybdenum-tungsten carbides (M6C) on the prior austenite crystal grain boundaries. Increasing austenitisation temperatures or prolonging the dwelling time at temperature can promote intensive migration of grain boundaries, leading to negative effects on the mechanical properties of the steel. To address this issue, isothermal transformation in the bainitic area between 350 and 500 °C was performed. Isothermal transformation at around 350 °C leads to the formation of lower bainite, which has similar hardness to tempered martensite. As the temperature of isothermal transformation increases, the hardness of the material decreases, due to the formation of upper bainite. The hardness analysis was measured using the Vickers method, the impact toughness of the steel samples was measured using a Charpy test with V-notched samples. The microstructure characterization was performed using optical and scanning electron microscopy. The improvement of ductility can be achieved by controlling the isothermal transformation of bainite and adjusting the heat treatment conditions. These findings provide useful insights into the design and optimization of heat treatment processes for hot-work tool steels.ditions. These findings provide useful insights into the design and optimization of heat treatment processes for hot-work tool steels.
Ključne besede: hot-work tool steel, austempering, bainitic transformation, ductility, dilatometry
Objavljeno v DiRROS: 28.02.2024; Ogledov: 130; Prenosov: 60
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20. Small cellular particles from European spruce needle homogenateMarko Jeran, Anna Romolo, Vesna Spasovski, Matej Hočevar, Urban Novak, Roman Štukelj, Vid Šuštar, Matic Kisovec, Apolonija Bedina Zavec, Ksenija Kogej, Aleš Iglič, Polonca Trebše, Veronika Kralj-Iglič, 2023, izvirni znanstveni članek Ključne besede: Picea abies, spruce needles, extracellular particles, extracellular vesicles, small cellular particles, interferometric light microscopy, exosomes, cell-to-cell communication, drug delivery
Objavljeno v DiRROS: 07.02.2024; Ogledov: 153; Prenosov: 100
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