461. On the structure of consistent cycles in cubic symmetric graphsKlavdija Kutnar, Dragan Marušič, Štefko Miklavič, Primož Šparl, 2024, original scientific article Keywords: 1/2-consistent cycles, automorphisms, consistent cycles, cubic symmetric graphs, shunt, s-regular graphs
Published in DiRROS: 13.03.2024; Views: 115; Downloads: 56
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462. On the exact region determined by Spearman's rho and Spearman's footruleDamjana Kokol-Bukovšek, Nik Stopar, 2024, original scientific article Abstract: We determine the lower bound for possible values of Spearman’s rho of a bivariate copula given that the value of its Spearman's footrule is known and show that this bound is always attained. We also give an estimate for the exact upper bound and prove that the estimate is exact for some but not all values of Spearman's footrule. Nevertheless, we show that the estimate is quite tight.
Keywords: copula, dependence concepts, supremum and infimum of a set of copulas, measures of concordance, quasi-copula, local bounds
Published in DiRROS: 13.03.2024; Views: 116; Downloads: 65
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463. Minimal surfaces with symmetriesFranc Forstnerič, 2024, original scientific article Abstract: Let $G$ be a finite group acting on a connected open Riemann surface $X$ by holomorphic automorphisms and acting on a Euclidean space ${\mathbb R}^n$ $(n\ge 3)$ by orthogonal transformations. We identify a necessary and sufficient condition for the existence of a $G$-equivariant conformal minimal immersion $F:X\to{\mathbb R}^n$. We show in particular that such a map $F$ always exists if $G$ acts without fixed points on $X$. Furthermore, every finite group $G$ arises in this way for some open Riemann surface $X$ and $n=2|G|$. We obtain an analogous result for minimal surfaces having complete ends with finite total Gaussian curvature, and for discrete infinite groups acting on $X$ properly discontinuously and acting on ${\mathbb R}^n$ by rigid transformations.
Keywords: Riemann surfaces, minimal surfaces, G-equivariant conformal minimal immersion
Published in DiRROS: 13.03.2024; Views: 119; Downloads: 43
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465. Weathering effects on cellulose acetate microplastics from discarded cigarette buttsBranka Mušič, Andrijana Sever Škapin, 2024, published scientific conference contribution (invited lecture) Abstract: Cellulose acetate, commonly used in cigarette filters, poses environmental concerns due to its questionable (bio)degradability and prevalent presence in nature. This study compares the weathering effects on two types of cigarette filters: traditional and newer filters used in heated tobacco devices (HTP). Microplastics were derived from used cigarette parts and then subjected to artificial aging. Analytical techniques (Thermogravimetry-Differential Scanning Calorimetry TG/DSC, Fourier-Transform Infrared Spectroscopic Analysis (FTIR)) and loose bulk density measurements were employed pre- and post-aging cellulose acetate of both types of samples. Despite increasing evidence influencing European Union (EU) directives on tobacco product disposal, there's a lack of systematic analysis on the weathering impact, especially concerning the touted environmental benefits of newer filters. Results indicate decreased particle size in cellulose acetate filters post-aging. Variances were observed in thermal behavior, yet FTIR spectra remained unchanged.
Keywords: cellulose acetate, cigarette filters, microplastics, artificial weathering, polymer degradation
Published in DiRROS: 12.03.2024; Views: 133; Downloads: 147
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466. Green transition in slovenian building and civil engineering industry : 10 years of research on alkali-activated materials and alkali-activated foamsBarbara Horvat, Branka Mušič, 2024, published scientific conference contribution (invited lecture) Abstract: The building and civil engineering industry yearly causes more than 40% of man-made CO2 and consumes raw materials for two-thirds of Mont Everest. To decrease the carbon footprint and consumption of raw materials, alkali-activated materials (AAMs) are researched as an alternative to conventional building and civil engineering products like cements, mortar, and ceramics. Ideally, locally available waste materials are used as ingredients: (i) as precursors that react with alkali and form an aluminosilicate network, and (ii) as fillers that get permanently encapsulated and safely stored in AAMs. The addition of gas bubbles and lightweight fillers transforms AAMs into alkali-activated foams and alkali-activated lightweight materials that have the potential to be used as thermal and acoustic insulation materials. Although AAMs are researched worldwide, this review focuses on the state-of-the-art localised solely to Slovenia, particularly on the materials and curing procedures used, as well as on the scientific contribution of the basic research. Besides, the year 2024 marks 10 years of research on alkali activation of raw and waste inorganic materials in Slovenia.
Keywords: secondary raw material, alkali-activated material, alkali-activated foams, alkali, circular economy, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 111; Downloads: 105
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468. Influence of ammonium polyphosphates and 2,4,6-triamino-1,3,5-triazine on the mechanical-physical properties of polyurethane and alkali-activated materialsBranka Mušič, Barbara Horvat, 2024, published scientific conference contribution Abstract: In building constructions, the tendency towards an ever-better material directs us to composite materials. In this work, we prepared an organic-organic and organic-inorganic composite material by incorporating fire retardants, ammonium polyphosphates, and 2,4,6-triamino-1,3,5-triazine, into a polyurethane network and an aluminosilicate network (ASN) of alkali-activated material. Polyurethane foams (PUR) are well-known materials that, due to their properties, such as low weight-to-strength ratio, low electrical and thermal conductivity, flexibility, and relatively simple preparation process, are used in various industries, also in the construction industry, e.g., for thermal insulation of windows and doors or fixing and sealing joinery. Opposite, the ASN of alkali-activated metakaolin, successfully paves the way for new applications, such as high-temperature protection. In this paper, these interactive properties of prepared composites are studied using thermal testing and mechanical analysis. It was found that inhibitors significantly increase the fire resistance of PUR systems while they slightly reduce the mechanical properties. Incorporating polymer flame retardant into ASN in building products, such as façade panels , can decrease the mechanical properties but can offer the non-flammable building envelope not get heated from burning surroundings, i.e., not becoming a convection heat source, but rather represent a fire-distinguisher for flammable materials.
Keywords: flame retardants, polyurethane, alkali activated material, metakaolin, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 179; Downloads: 282
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469. Waste rubber incorporated in the alkali-activated metakaolin’s aluminosilicate network enhanced by microwave irradiationBarbara Horvat, Branka Mušič, 2024, published scientific conference contribution Abstract: Building materials represent the possibility of prolonging the life of waste materials. The key is to ensure that the products are suitable for their function. So we activated metakaolin with the alkaline Na-silicate solution in the ratio that ensures the prevention of efflorescence and high mechanical strength (Horvat and Ducman, 2019). As the waste material (to be incorporated in the aluminosilicate network (ASN) of the alkali-activated metakaolin) ground waste rubber from electric cables was used in the preselected mass ratios. Its inclusion in products, like paving stones, can reduce stiffness, improve durability, dampen vibrations, and reduce road noise. The mechanical strengths of test samples with rubber present on the active surface or slightly below were higher compared to samples where rubber was encapsulated throughout the volume. Compressive strength was higher when samples were irradiated with low powers of microwaves while irradiation with higher powers led to the foaming of alkali-activated slurry. The encapsulation quality of the ground rubber was evaluated by SEM while the chemical influence on ASN was determined by EDS, FTIR, and XRD. Slipperiness change on the active surface of pavement stones proved that the addition of the ground rubber enhanced the walking safety of the product.
Keywords: secondary raw material, alkali activated material, waste rubber, metakaolin, encapsulation of organic in inorganic material, microwave irradiation, mechanical strength
Published in DiRROS: 12.03.2024; Views: 237; Downloads: 274
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470. European genetic resources conservation in a rapidly changing world : three existential challenges for the crop, forest and animal domains in the 21st centuryFrançois Lefévre, Danijela Bojkovski, Magda Bou Dagher Kharrat, Michele Bozzano, Eléonore Charvolin-Lemaire, Sipke Joost Hiemstra, Hojka Kraigher, Denis Laloë, Gwendal Restoux, Suzanne Sharrock, Enrico Sturaro, Theo J. L. van Hintum, Marjana Westergren, Nigel Maxted, 2024, original scientific article Abstract: Even though genetic resources represent a fundamental reservoir of options to achieve sustainable development goals in a changing world, they are overlooked in the policy agenda and severely threatened. The conservation of genetic resources relies on complementary in situ and ex situ approaches appropriately designed for each type of organism. Environmental and socioeconomic changes raise new challenges and opportunities for sustainable use and conservation of genetic resources. Aiming at a more integrated and adaptive approach, European scientists and genetic resources managers with long experience in the agricultural crop, animal and forestry domains joined their expertise to address three critical challenges: (1) how to adapt genetic resources conservation strategies to climate change, (2) how to promote in situ conservation strategies and (3) how can genetic resources conservation contribute to and benefit from agroecological systems. We present here 31 evidence-based statements and 88 key recommendations elaborated around these questions for policymakers, conservation actors and the scientific community. We anticipate that stakeholders in other genetic resources domains and biodiversity conservation actors across the globe will have interest in these crosscutting and multi-actor recommendations, which support several biodiversity conservation policies and practices.
Keywords: agroecology, climate change, in situ conservation, multi-actor engagement, policy
Published in DiRROS: 11.03.2024; Views: 154; Downloads: 65
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