1. Pick-up of organic molecules by mixed Ar clusters : a function of gas properties and compositionJernej Ekar, Oksana Plekan, 2026, original scientific article Abstract: Clusters present an intriguing field of research, with their properties bridging the gap between an isolated atom/molecule and a bulk. They can act as a substrate for dopant molecules picked up on the fly and located on or inside the cluster. Our research on Ar clusters reveals that gas pressure and composition are crucial parameters determining the pickup probability for molecules such as adenine, uracil, glycine, and ascorbic acid. For pure Ar expansion, the most intense molecular signals are observed in the stagnation pressure range between 10 and 30 bar. Adding up to 33 mol% of He or O2 at fixed total pressure causes no change in the intensity of dopant and Ar oligomer signals. The addition of N2O or CO2 results in a significant intensity drop, with signals from the molecule and Ar oligomers disappearing above 3 mol% of N2O or CO2. The opposite effects are observed with the Ar-H2 mixture at a pressure of 25 bar. Optimal results are obtained for H2 concentrations between 40 and 50 mol% versus D2 concentrations between 20 and 35 mol%. Substitution of Ar with an Ar-H2 mixture causes signal intensities of dopants and Ar oligomers to increase by more than threefold.
Keywords: gas clusters, argon, hydrogen, doping, pick-up, mass spectrometry, pulsed gas beam
Published in DiRROS: 13.02.2026; Views: 43; Downloads: 19
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2. Strain-controlled superconductivity in epitaxially grown thin films of ▫$1T-TaS_2$▫Yelyzaveta Chernolevska, Anže Mraz, Rok Venturini, Bojan Ambrožič, Tomaž Mertelj, Goran Dražić, Damjan Svetin, Damjan Vengust, Hsin-Chia Ho, Matjaž Spreitzer, Dragan Mihailović, 2025, original scientific article Keywords: transition metal dichalcogenides, thin films, molecular beam epitaxy
Published in DiRROS: 26.11.2025; Views: 825; Downloads: 147
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3. On the direct numerical computation of Hopf bifurcations to assess the dynamic stability of fluid-conveying cantilevered pipesHauke Gravenkamp, Bor Plestenjak, 2026, original scientific article Abstract: In the structural analysis of fluid-conveying pipes, dynamic instabilities can occur at specific values of the flow velocity, depending on the geometry as well as the material parameters of the pipe and the interior fluid. These critical points fall into the broader category of Hopf bifurcations. Typical numerical models of this problem employ a one-dimensional weighted residual method, leading to a velocity-dependent eigenvalue problem. The solutions form eigencurves, and the critical points are characterized by eigenvalues with vanishing real parts. In this paper, we show that critical points can be computed directly as solutions to a single three-parameter eigenvalue problem. In addition, we employ a recently developed method for computing individual eigencurves, based on the concept of exponential residual relaxation. For the discretization of the weak form, we use a finite element method with a particular version of $C^1$-continuous high-order spectral elements, suited for fourth-order differential equations, and we discuss the differences compared to the more commonly used weighted residual method based on the basis functions of a linear Euler-Bernoulli beam. Four numerical examples demonstrate the effectiveness of the implemented algorithms. For verification, we provide a detailed derivation of analytical solutions for special cases.
Keywords: pipes, Euler-Bernoulli beam, stability, Hopf bifurcation, multiparameter eigenvalue problem, spectral element method
Published in DiRROS: 20.11.2025; Views: 227; Downloads: 122
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4. Near-surface processes of beam-sensitive materials under low energy electron irradiationIbrahim Hameli, Vasyl Shvalya, Neelakandan Marath Santhosh, Ardita Kurtishaj Hamzaj, Oleg Baranov, Uroš Cvelbar, Janez Zavašnik, 2026, original scientific article Abstract: We investigate the interactions and modifications induced by low-energy electron beam irradiation in beamsensitive materials, with crystalline gold trichloride (AuCl3) as a model system. Employing scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) in an operando setup, we investigated surface and bulk transformations as a function of irradiation time (0–1080 s) and accelerating voltage (1–30 kV). Irreversible structural changes were observed both on the surface and within the bulk of the AuCl3 crystal. Surface analysis revealed the formation and growth of µm-sized vertically oriented carbon nanopillars, with voltage-dependent growth dynamics governed by backscattered (BSE) and secondary electrons (SE). At the same time, the bulk of the AuCl3 decomposed under carbon pillars, forming Au nanoparticles and near-surface voids whose size and spatial distribution correlated with the energy deposition profiles. The observed morphological and chemical alterations pose a significant obstacle to accurate chemical composition analyses by energy-dispersive X-ray spectroscopy (EDS) and suggest a narrow operating window for conducting reliable SEM analysis.
Keywords: beam sensitive materials, electron beam interactions, electron radiation, gold chloride, carbon deposition
Published in DiRROS: 29.09.2025; Views: 364; Downloads: 176
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6. 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, original scientific article Abstract: 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.
Keywords: PBF-LB/M, beam shaping, IN718, heat treatment, mechanical properties
Published in DiRROS: 07.07.2025; Views: 622; Downloads: 314
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7. Composition, microstructure and corrosion resistance of DED-LB additively manufactured Ti–6Al–4V alloy : comparison with wrought alloyIngrid Milošev, Peter Rodič, Barbara Kapun, Denis Sačer, Anish Nair, Davorin Kramar, Andrej Jeromen, Edvard Govekar, 2025, original scientific article Keywords: titanium alloys, directed-energy deposition by laser beam, simulated physiological solution
Published in DiRROS: 03.06.2025; Views: 627; Downloads: 390
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9. Investigations of the thermal parameters of hybrid sol-gel coatings using nondestructive photothermal techniquesŁukasz Chrobak, Dorota Korte, Hanna Budasheva, Mirosław Maliński, Peter Rodič, Ingrid Milošev, Sylwia Janta-Lipińska, 2022, original scientific article Keywords: hybrid sol-gel coatings, non-destructive testing, photothermal radiometry, photothermal beam deflection spectrometry, thermal diffusivity, thermal conductivity
Published in DiRROS: 06.05.2025; Views: 619; Downloads: 340
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10. Experimental investigation on the effect of natural fire exposure on the post-fire behavior of reinforced concrete beams using electric radiant panelBalša Jovanović, Robby Caspeele, Edwin Reynders, Geert Lombaert, Florian Put, Andrea Lucherini, Ruben Van Coile, 2024, original scientific article Abstract: In this study, the effects of natural fire exposure on the post-fire behavior of concrete beams are investigated. The study is based on laboratory tests where three reinforced concrete beams were subjected to fire exposure using an electric radiant panel. This panel enables a precise application of radiative heat exposure closely mimicking natural fire exposure in a safe manner. During the test, the deflections, deformations and temperature changes are measured for all three concrete beams. Additionally, finite element modeling (FEM) is applied to supplement these tests, demonstrating the performance of existing structural fire engineering calculation tools in evaluating the burnout performance of concrete beams. The results of the tests show that the electric radiant panel provide a novel approach for fire simulation which is effective in replicating natural fire conditions, by applying the heat flux as specified in the Eurocode Parametric Fire Curve in a highly controlled manner. The uniformity of the temperature field measured inside the beams and the consistent deformations observed during the heat exposure across all three tests underscores the accuracy of the fire simulation. Furthermore, post-fire assessments reveal that while the exposed beams suffered some reduction in load-bearing capacity, they retained a significant portion of their original strength that was consistent across all three beams. The numerical simulations conducted in this study demonstrate a high level of accuracy in predicting the behavior of the concrete beams during fire exposure. These simulations effectively mirrored the experimental results, validating that they are a valuable tool for assessing concrete structures' performance in fire scenarios.
Keywords: concrete beam, fire testing, numerical modeling, radiant panel
Published in DiRROS: 28.11.2024; Views: 912; Downloads: 393
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