1761. The exact region determined by Blomqvist’s beta, Spearman’s footrule and Gini’s gammaDamjana Kokol-Bukovšek, Blaž Mojškerc, 2026, izvirni znanstveni članek Ključne besede: copula, dependence concepts, supremum and infimum of a set of copulas, measures of concordance, quasi-copula, local bounds
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1765. Influence of laser beam shape and post heat-treatment on the microstructure and mechanical properties of nickel-based alloy IN718 manufactured by laser powder bed fusionMatjaž Godec, Narges Mirzabeigi, Črtomir Donik, Danijela Anica Skobir Balantič, Simon Malej, Irena Paulin, Bojan Podgornik, Jonas Grünewald, Tobias Novotny, Florian Bayer, Francisco Ruiz-Zepeda, Katrin Wudy, 2025, izvirni znanstveni članek Povzetek: This study examines the effect of Gaussian and ring-shaped laser beam profiles on the microstructural development and mechanical properties of the PBF-LB/M processed nickel-based alloy Inconel 718 in its as-built and post-heat-treated conditions. Beam shaping was employed to achieve a faster build rate without compromising material properties. One of the objectives was to optimise heat treatment conditions for the beam-shaped profile. The post-heat-treatment process included four different solution annealing temperatures (954 °C, 984 °C, 1034 °C and 1154 °C), followed by two-step ageing, respectively. The microstructure evolution was revealed using scanning electron microscopy (SEM) equipped with energy-dispersive X-ray diffraction (EDS). The mechanical properties in all investigated conditions were evaluated based on tensile tests at room temperature. Using a Gaussian laser beam profile results in a fine-grained microstructure without a strong columnar orientation, while the ring beam profile produces a distinct columnar structure with larger nanodendritic grains and dislocation cells. Both beam profiles exhibit a similar proportion of Laves phase. After post-heat treatment, the Gaussian beam profile generally provides 3-7 % higher mechanical properties. The differences in mechanical properties between horizontal and vertical building directions are greater for ring-shaped laser beam profiles. Heat-treatment temperature above 1034 °C leads to recrystallisation, grain growth and the formation of carbonitrides which reduce mechanical properties. Based on the results, the proposed optimal heat-treatment temperature for both investigated laser beam shapes is 984 °C. At this temperature, tensile strength equalises between horizontal and vertical build directions while yield strength increases, which is beneficial for most applications.
Ključne besede: PBF-LB/M, beam shaping, IN718, heat treatment, mechanical properties
Objavljeno v DiRROS: 07.07.2025; Ogledov: 497; Prenosov: 254
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1768. Nevzdržna svoboda vzporednih svetovIgor Ž. Žagar, 2025, samostojni strokovni sestavek ali poglavje v monografski publikaciji Povzetek: Prispevek je nadaljevanje besedila »Vzhodno od raja« z »drugimi sredstvi«. Če se prvo besedilo ukvarja z retorično optiko nasprotnikov poziva, skuša pričujoče besedilo osvetliti ideološko podstat te optike, vključno z vzroki za rusko-ukrajinsko vojno.
Ključne besede: mednarodni odnosi, geopolitika, etika, vojni konflikti, ZDA, Rusija, Ukrajina
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1769. Normal covers of 2-arc-transitive graphs of prime-power orderMarston D. E. Conder, Primož Potočnik, 2025, izvirni znanstveni članek Povzetek: In a paper by Cai Heng Li in Bull. London Math. Soc. 33 (2001), it was suggested that ‘non-basic’ $2$-arc-transitive graphs of prime-power order that occur as normal covers of smaller $2$-arc-transitive graphs might be rare and difficult to construct. This note describes some of the background to Li’s suggestion, and gives some examples of small valency, and then goes on to show that in fact there are infinitely many examples of valency $d$, for every integer $d \ge 2$. It is also noted that the hypercubes $(Q_n)$ for $n \ge 4$ even, together with a $2$-arc-transitive group $G$ of index $2$ in ${\rm Aut}(Q_n)$, show that the claims of Corollary 1.2 in the above paper by Li are not quite correct.
Ključne besede: graphs, s-arc-transitive, normal cover
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