231. A new approach to universal $F$-inverse monoids in enriched signatureGanna Kudryavtseva, Ajda Lemut Furlani, 2024, original scientific article Abstract: We show that the universal $X$-generated $F$-inverse monoid $F(G)$, where ▫$G$▫ is an $X$-generated group, introduced by Auinger, Szendrei and the first-named author, arises as a quotient inverse monoid of the Margolis-Meakin expansion $M(G, X\cup \overline{G})$ of $G$, with respect to the extended generating set $X\cup \overline{G}$, where $\overline{G}$ is a bijective copy of $G$ which encodes the ▫$m$▫-operation in $F(G)$. The construction relies on a certain dual-closure operator on the semilattice of all finite and connected subgraphs containing the origin of the Cayley graph ${\rm Cay}(G, X\cup {\overline{G}})$ and leads to a new and simpler proof of the universal property of $F(G)$.
Keywords: inverse monoid, F-inverse monoid, Margolis-Meakin expansion, group presentation, Cayley graph of a group, closure operator, dual-closure operator, partial action, partial action product
Published in DiRROS: 21.10.2024; Views: 55; Downloads: 20
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233. Mreža občanske znanosti v SlovenijiMitja Vovk Iskrić, 2024, professional article Abstract: Občanska znanost je koncept znanstvenoraziskovalnega dela, ki spodbuja odprt dialog med znanstveno in širšo skupnostjo, s čimer usmerja tudi družbeni razvoj. V Sloveniji je v zadnjem letu doživela pomemben razvoj, zlasti z vzpostavitvijo specializiranega spletnega portala citizenscience.si in nastankom Mreže občanske znanosti. Tudi Evropska unija je prispevala k napredku in vidnosti občanske znanosti, zlasti s financiranjem projektov. Poleg drugih organizacij, kot so muzeji in društva, ter posameznikov tudi univerze in raziskovalni inštituti prispevajo k razvoju občanske znanosti. Širijo in krepijo raziskovalne dejavnosti z vključevanjem javnosti in hkrati tudi izboljšujejo svoj družbeni položaj ter povečujejo zaupanje v znanost. Hkrati zagotavljajo infrastrukturo, znanje, veščine, etične in pravne okvire ter financiranje. V Sloveniji je vključevanje javnosti v znanost dolgoletna tradicija, ki je potekala pod različnimi imeni, dokler se ni utrdil izraz »občanska znanost« kot najprimernejši prevod. Centralna tehniška knjižnica Univerze v Ljubljani (CTK) že od leta 2017 sodeluje pri promociji in razvoju občanske znanosti v Sloveniji, z organizacijo strokovnih srečanj in pozneje tudi neposredno s podporo projektu občanske znanosti. Sodeluje z drugimi organizacijami pri pripravi dogodkov za spodbujanje sodelovanja med raziskovalci in knjižnicami ter širšo skupnostjo in aktivno deluje v mednarodnih organizacijah. V članku so podrobno predstavljeni vsebina portala citizenscience.si, ki ga je razvila Centralna tehniška knjižnica Univerze v Ljubljani, ter ustanovitev in delovanje Mreže občanske znanosti v Sloveniji.
Keywords: odprta znanost, občanska znanost, spletni portali, sodelovanje, Slovenija
Published in DiRROS: 21.10.2024; Views: 61; Downloads: 31
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234. Laser powder bed fusion parameters optimization for enhanced mechanical properties of EOS Co-Cr dental alloyDalibor Viderščak, Zdravko Schauperl, Biserka Runje, Sanja Šolić, Amir Ćatić, Matjaž Godec, Irena Paulin, Črtomir Donik, 2024, original scientific article Abstract: This research explores how variations in laser powder bed fusion (LPBF) parameters—laser power (P), scanning speed (v), and base plate preheating temperature (ϑp)—affect the mechanical properties of the EOS Co-Cr SP2 dental alloy. A central composite design (CCD) was used to optimize the process parameters. Mechanical testing focused on crucial properties for dental applications, including yield strength (Rp0.2), elongation (ε), toughness (KVa), and flexural strength (Rms). Microstructural analysis was conducted using light and electron microscopy, while XRD identified microstructural phases. Statistical analysis (ANOVA, Scheffé post hoc test, α = 0.05) revealed significant effects of P, v, and ϑp on the mechanical properties. Response surface models (RSMs) were developed, and optimal parameters were determined to achieve maximum toughness and flexural strength. Maximum values were obtained with laser power above 205Wand base plate preheating at 310 ◦C. The mathematical model predicted toughness values with less than 5% deviation from experimental results, indicating high accuracy.
Keywords: LPBF, production parameters, Co-Cr dental alloy, CCD, mechanical properties, ANOVA
Published in DiRROS: 18.10.2024; Views: 125; Downloads: 8122
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236. Enhancing magnesium bioactivity for biomedical applications : effects of laser texturing and sandblasting on surface propertiesMarjetka Conradi, Aleksandra Kocijan, Bojan Podgornik, 2024, original scientific article Abstract: Magnesium and its alloys, valued for their lightweight and durable characteristics, have garnered increasing attention for biomedical applications due to their exceptional biocompatibility and biodegradability. This work introduces a comparison of advanced and basic methods—laser texturing and sandblasting—on magnesium surfaces to enhance bioactivity for biomedical applications. Employing a comprehensive analysis spanning surface morphology, hardness, wettability, tribological performance, and corrosion behavior, this study elucidates the intricate relationship between varied surface treatments and magnesium’s performance. Findings reveal that both laser texturing and sandblasting induce grain refinement. Notably, sandblasting, particularly with a duration of 2 s, demonstrates superior wear resistance and reduced corrosion rates compared to untreated magnesium, thereby emerging as a promising approach for enhancing magnesium bioactivity in biomedical contexts. This investigation contributes to a deeper understanding of the nuanced interactions between diverse surface treatments and their implications for magnesium implants in chloride-rich environments, offering valuable insights for prospective biomedical applications.
Keywords: biomaterial, microstructure, hardness, friction/wear, corrosion
Published in DiRROS: 18.10.2024; Views: 111; Downloads: 12371
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237. Seepage detection using passive temperature measurements by fiber optic DTSYaser Ghafoori, 2024, other scientific articles Abstract: This article is an extended abstract of the doctoral dissertation “Optimization of early seepage detection in embankments using a distributed temperature system based on fiber optic sensing” [1]. Distributed Temperature Sensors (DTS) measure temperature precisely with high spatial resolution, enabling seepage flow detection through the interpretation of temperature measurement. Active DTS measurement which introduces heat into the soil to monitor its dissipation, has been extensively studied for seepage detection. However, the potential of passive measurement, which measures natural soil temperature, for seepage detection demands further exploration. The doctoral research investigated the capability of passive DTS measurements for seepage detection. The findings show that passive DTS detects very small temperature variations as a result of the seepage flow. Additionally, the results offer valuable insights into the coupled hydro-thermal behavior and the influence of seepage on heat transfer. The thesis classified and compared different techniques for temperature data calibration and interpretation. Furthermore, an interpretation approach based on numerical simulation and a fully dynamic calibration technique was developed.
Keywords: optical fiber DTS, soil, emperature, seepage
Published in DiRROS: 16.10.2024; Views: 124; Downloads: 38
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238. Crack size in coating and moisture problems comparing thermally modified and native spruce window frame profiles using hygrothermal simulationGregor Vidmar, Rožle Repič, Boštjan Lesar, Miha Humar, 2024, original scientific article Abstract: Fungal growth and degradation of wood may be caused by damage in the surface coating. The larger the cracks, the greater in principle the possibility of moisture-induced problems. Measuring basic unknown material parameters and employing hygrothermal simulations, the suitability and the maximum acceptable vertical crack size in the surface coating for a given bottom window profile made of thermally modified (TM) spruce(wood) with that made of native spruce were compared for location Ljubljana. Validation with the field test data was the second objective of the respective research. The average calculated maximum moisture content in TM spruce is about 4% (kg/kg) lower than that of native spruce. The 3 mm wide crack in the surface coating of a window frame made of native spruce is of the highest concern, whereas a 9 mm wide crack in the coating of a TM spruce profile is still acceptable. As far as moisture content is concerned in our study the TM spruce window frames were proved to be significantly more suitable for installation than the corresponding frames made of native Norway spruce. It was shown that isopleth, VTT and biohygrothermal models for mould growth do not properly capture the comparison between both materials, mainly because they classify both in the same material class/substrate category and they do not consider the material moisture content.
Keywords: hygrothermal simulations, mould growth modelling, cracks in surface coating, thermally modified wood, wooden window frame
Published in DiRROS: 16.10.2024; Views: 112; Downloads: 326
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239. The abdominal adiposity index (a body shape index) predicts 10-year all-cause mortality in elderly active non-obese subjectsAlessio Nunnari, Filippo Giorgio Di Girolamo, Kaja Teraž, Nicola Fiotti, Boštjan Šimunič, Filippo Mearelli, Rado Pišot, Gianni Biolo, 2024, original scientific article Abstract: Background/Objectives: A Body Shape Index (ABSI), which accounts for waist circumference relative to mass and height, shows a robust association with mortality risk. The present study evaluates the effectiveness of ABSI as a predictor of 10-year all-cause mortality in physically active, non-obese elderly individuals. Methods: This prospective cohort study included 159 volunteers (94 women, aged 60–80 years), recruited in the frame of the “Physical Activity and Nutrition for Great Ageing” (PANGeA) Cross-border Cooperation Program Slovenia–Italy 2007–2013, and followed for 10 years. Baseline characteristics included anthropometric measurements, bioelectrical impedance analysis, and cardiovascular fitness tests (VO2max). Statistical analyses (Cox regression, Kaplan–Meier survival) were conducted to examine the relationship between ABSI and mortality. Results: During the 10-year follow-up, 10 deaths (6.7%) were recorded. ABSI (adjusted for age, smoking, comorbidities, and therapy) was an independent predictor of mortality (hazard ratio = 4.65, p < 0.001). Higher ABSI scores were linked to reduced VO2max (r = −0.190, p = 0.017) and increased systolic blood pressure (r = 0.262, p = 0.001). An ABSI-based predictive model showed strong discriminatory power (AUROC = 0.91). Conclusions: ABSI is a reliable predictor of 10-year mortality in active, non-obese elderly individuals and may improve risk stratification in clinical practice.
Keywords: ABSI, a body shape index, body shape, fre fat mass, sarcopenia, prognostic index, elderly, mortality
Published in DiRROS: 16.10.2024; Views: 113; Downloads: 255
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240. Influence of the oxidizing technique on the biocompatible and corrosion properties of Ti6Al4V in a physiological environmentMirjam Bajt Leban, Tadeja Kosec, Aleksandra Kocijan, Marjetka Conradi, Ita Junkar, Janez Kovač, 2025, original scientific article Abstract: This work aims to evaluate the corrosion and biocompatibility properties of oxide films generated on Ti6Al4V alloys using both traditional and novel methods. Oxide films were generated by anodization and plasma treatment to achieve a blue surface finish. The oxide films were then characterized and compared to a native film formed on the Ti6Al4V.
Electrochemical tests, incorporating potentiodynamic tests and electrochemical impedance spectroscopy, were employed to define the electrochemical resistance of oxides in an environment simulating biological exposure. In vitro tests were conducted to study ion release and biocompatible properties over a 6-week period of exposure to a 0.9 wt% NaCl solution, at body temperature. Various spectroscopic techniques, including ToF-SIMS, XRD, and Raman analysis, were used to study the structure and chemistry of the oxide films. The sub-surface layer was analysed by microstructural investigation.
The type of oxidation was found to have a key influence on the oxide composition, especially with respect to the depth distribution of the individual alloy elements through the oxide film. The oxidation process determines which of the alloying elements are released into the environment, as a result of the corrosion reactions.
Keywords: oxide film, biocompatibility, surface characterization, ion release, simulated body fluid
Published in DiRROS: 16.10.2024; Views: 120; Downloads: 165
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