1. Multi-scale and multi-modal imaging study of mantle xenoliths and petrological implicationsMarco Venier, Luca Ziberna, Lucia Mancini, Alexander P. Kao, Federico Bernardini, Giacomo Roncoroni, Sula Milani, Nasrrddine Youbi, Yondon Majigsuren, Angelo De Min, Davide Lenaz, 2024, izvirni znanstveni članek Povzetek: The accurate textural characterization of mantle xenoliths is one of the fundamental steps to understanding the main processes occurring in the upper mantle, such as sub-solidus recrystallization, magmatic crystallization, and metasomatism. Texture, composition, and mineralogy reflect the temperature, pressure, stress conditions, melting, and/or contamination events undergone before and during the entrapment in the host magma. For these reasons, characterizing the three-dimensional (3D) texture of silicate, oxide, sulfide, and glass phases has great importance in the study of mantle xenoliths. We performed a multi-scale and multi-modal 3D textural analysis based on X-ray computed microtomography (µ-CT) data of three mantle xenoliths from different geodynamic settings (i.e., mobile belt zone, pericraton, oceanic hotspot). The samples were selected to represent different, variably complex internal structures composed of grains of different phases, fractures, voids, and fluid inclusions of different sizes. We used an approach structured in increasing steps of spatial and contrast resolution, starting with in-house X-ray µ-CT imaging (spatial resolution from 30 µm down to 6.25 µm) and moving to high-resolution synchrotron X-ray µ-CT at the micrometer scale. We performed a 3D characterization of mantle xenoliths, comparing the results with the analysis of conventional 2D images (thin sections) obtained by optical microscopy and simulating the random sectioning of several thin sections to estimate the probability of correct modal classification. The 3D models allow the extraction of textural information that cannot be quantified solely from thin sections: spinel layering, distribution of silicic glass, and related vesicles. Moreover, high-density volumes identified as sulfides were detected in two xenoliths, showing no relation with the spinel layering in one case and a preferential concentration along fractures in the other. Given the variety of textures and mineral assemblages of mantle xenoliths worldwide, the results are used to suggest experimental and analytical protocols for the characterization of these materials.
Ključne besede: petrology, mantle xenoliths, X-ray microtomography, multi-scale image analysis
Objavljeno v DiRROS: 23.05.2024; Ogledov: 73; Prenosov: 18
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2. A cross-benchmark examination of feature-based algorithm selector generalization in single-objective numerical optimizationGjorgjina Cenikj, Gašper Petelin, Tome Eftimov, 2024, izvirni znanstveni članek Povzetek: The task of selecting the best optimization algorithm for a particular problem is known as algorithm selection (AS). This involves training a model using landscape characteristics to predict algorithm performance, but a key challenge remains: making AS models generalize effectively to new, untrained benchmark suites. This study assesses AS models’ generalizability in single-objective numerical optimization across diverse benchmark suites. Using Exploratory Landscape Analysis (ELA) and transformer-based (TransOpt) features, the research investigates their individual and combined effectiveness in AS across four benchmarks: BBOB, AFFINE, RANDOM, and ZIGZAG. AS models perform differently based on benchmark suite similarities in algorithm performance distributions and single-best solvers. When suites align, these models underperform against a baseline predicting mean algorithm performance; yet, they outperform the baseline when suites differ in performance distributions and solvers. The AS models trained using the ELA landscape features are better than the models trained using the TransOpt features on the BBOB and AFFINE benchmark suites, while the opposite is true for the RANDOM benchmark suite. Ultimately, the study reveals challenges in accurately capturing algorithm performance through problem landscape features (ELA or TransOpt), impacting AS model applicability.
Ključne besede: algorithm selection, multi-target regression, generalization, benchmarking
Objavljeno v DiRROS: 21.05.2024; Ogledov: 77; Prenosov: 222
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3. Invariants of multi-linkoidsBoštjan Gabrovšek, Neslihan Gügümcü, 2023, izvirni znanstveni članek Povzetek: In this paper, we extend the definition of a knotoid to multilinkoids that consist of a finite number of knot and knotoid components. We study invariants of multi-linkoids, such as the Kauffman bracket polynomial, ordered bracket polynomial, the Kauffman skein module, and the $T$-invariant in relation with generalized $\Theta$-graphs.
Ključne besede: knotoid, multi-linkoid, spatial graph, Kauffman bracket polynomial, Kauffman bracket skein module, theta-curve, theta-graph
Objavljeno v DiRROS: 15.03.2024; Ogledov: 142; Prenosov: 73
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4. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: agroecology, climate change, in situ conservation, multi-actor engagement, policy
Objavljeno v DiRROS: 11.03.2024; Ogledov: 247; Prenosov: 102
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5. Monitoring the galvanic corrosion of copper–steel coupling in bentonite slurry during the early oxic phase using coupled multielectrode arraysTadeja Kosec, Miha Hren, Klara Prijatelj, Bojan Zajec, Nina Gartner, Andraž Legat, 2023, izvirni znanstveni članek Povzetek: In the case of a two-part container for spent nuclear fuel, consisting of an iron-based inner structure with a copper coating, the potential perforation of copper through minor damage may result in intensive galvanic corrosion between copper and steel. The present work focuses on the corrosion of steel galvanically coupled to copper and exposed to a slightly saline environment under oxic conditions. The electrochemical processes on individual electrodes were monitored by coupled multielectrode arrays (CMEAs). The CMEAs were either in contact with groundwater saturated with bentonite or immersed in groundwater only. Very high galvanic corrosion currents were detected between carbon steel and pure copper in the early oxic phase. Additionally, the use of CMEAs further made it possible to monitor the distribution of cathodic currents around the steel electrode, which behaved anodically. Various microscopy and spectroscopy techniques were applied to identify the modes of corrosion and the type of corrosion products present at the end of the period of exposure.
Ključne besede: copper, steel, bentonite, Aspö groundwater, coupled multi electrode array, electrochemical properties, Raman analysis, corrosion
Objavljeno v DiRROS: 16.11.2023; Ogledov: 463; Prenosov: 78
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7. Monitoring the corrosion of steel in concrete exposed to a marine environmentNina Gartner, Tadeja Kosec, Andraž Legat, 2020, izvirni znanstveni članek Povzetek: Reinforced concrete structures require continuous monitoring and maintenance to prevent corrosion of the carbon steel reinforcement. In this work, concrete columns with carbon and stainless steel reinforcements were exposed to a real marine environment. In order to monitor the corrosion processes, two types of corrosion probes were embedded in these columns at different height levels. The results from the monitoring of the probes were compared to the actual corrosion damage in the different exposure zones. Electrical resistance (ER) probes and coupled multi-electrodes (CMEs) were shown to be promising methods for long-term corrosion monitoring in concrete. Correlations between the different exposure zones and the corrosion processes of the steel in the concrete were found. Macrocell corrosion properties and the distribution of the separated anodic/cathodic places on the steel in chloride-contaminated concrete were addressed as two of the key issues for understanding the corrosion mechanisms in such environments. The specific advantages and limitations of the tested measuring techniques for long-term corrosion monitoring were also indicated. The results of the measurements and the corrosion damage evaluation clearly confirmed that the tested stainless steels (AISI 304 and AISI 304L) in a chloride-contaminated environment behave significantly better than ordinary carbon steel, with corrosion rates from 110% to 9500% lower in the most severe (tidal) exposure conditions.
Ključne besede: corrosion in concrete, steel reinforcement, long-term exposure, field exposure, electrical resistance (ER) probes, coupled multi-electrodes
Objavljeno v DiRROS: 21.08.2023; Ogledov: 314; Prenosov: 174
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8. Characterization of steel corrosion processes in various blended cements by means of coupled multi-electrode arraysMiha Hren, Tadeja Kosec, Andraž Legat, 2023, izvirni znanstveni članek Povzetek: Supplementary cementitious materials can affect the porosity of concrete, pore solution pH and chloride binding, all of which influence the type and magnitude of corrosion damage. Advanced corrosion monitoring techniques are needed to follow the development of corrosion on steel embedded in concrete across space and over time. In this study, coupled multi-electrode arrays (CMEAs) were used to characterise corrosion processes in OPC and three blended cements. Cyclic wetting with chlorides was undertaken to initiate corrosion. The results showed three distinct types of corrosion: localised corrosion (CEM I), localised corrosion that expanded over time (CEM II), and a combination of localised and general corrosion (CEM III and CEM IV). Cathodic locations were also monitored successfully, and the corrosion behaviour was related to total porosity and pH of the pore solution. MicroCT was used to quantify the volume of corroded material, which agreed well with results calculated from the CMEA measurements.
Ključne besede: blended cements, coupled multi-electrode array, corrosion of steel in concrete, supplementary cementitious materials, open access
Objavljeno v DiRROS: 29.05.2023; Ogledov: 319; Prenosov: 186
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9. In-plane seismic behaviour of ashlar three-leaf stone masonry walls : verifying performance limitsMeta Kržan, Vlatko Bosiljkov, 2021, izvirni znanstveni članek Povzetek: In light of the forthcoming second generation Eurocodes (EC), the results of conducted systematic in-plane cyclic and compressive tests on three-leaf stone masonry walls are discussed following new requirements and provisions. The new proposal for EC8-3 for existing buildings is based on partial factors safety approach, though it considers different uncertainties in defining input parameters for effective seismic performance-based assessment. Prior to its application, massive calibration effort will be needed since there is no standardized method for shear testing of masonry walls. In this paper, the performance limit states damage, resistance, and displacement capacities from conducted test results were evaluated and assessed through comparison with analytical solutions and imposed limit values, as stated in existing codes. The test results provide a much higher deformation capacity than the limits provided in both existing and new proposal of EC8-3 as well as those in the ASCE code provisions. The reason for this lies in the soft, "ductile" mortar for which the presumed resistance according to code provisions should be significantly higher when considering good quality ashlar three-leaf stone masonry.
Ključne besede: historical masonry, multi-leaf stone masonry, mechanical properties, compression tests, in-plane shear tests, failure mechanisms, drift limits, boundary conditions
Objavljeno v DiRROS: 19.05.2023; Ogledov: 374; Prenosov: 183
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10. Attic dust: an archive of historical air contamination of the urban environment and potential hazard to health?Martin Gaberšek, Michael J. Watts, Mateja Gosar, 2022, izvirni znanstveni članek Povzetek: A comprehensive study of attic dust in an urban area is presented. Its entire life cycle, from determining historical emission sources to recognising the processes that take place in attic dust and its potential to impact human health is discussed. Its chemical composition and morphological characteristics of individual solid particles reflect past anthropogenic activities. High levels of Be-Cd-Cu-Sb-Sn-Pb-Te-Zn and occurrence of Cu-Zn shavings are typical for an industrial zone characterised by a foundry and a battery factory. High levels of Co-Fe-Mo-Ni-W-Ba-Cr-Mg-Mn-Nb-Ti and occurrence of various solid Fe-oxides, particularly spherical particles, were identified in another industrial zone, which was dominated by the automotive and metal-processing industries. Emissions from coal combustion affected the distribution of S-Se-Hg-Tl-As-Ag-U. The predominant mineral in attic dust is gypsum, which was presumably formed in situ by the reaction of carbonate dust particles and atmospheric SO2 gas. The high oral bioaccessibility of As-Cd-Cu-Pb-Zn in the gastric phase and high bioaccessibility of As-Cu-Cd-Ni in the gastrointestinal phase were identified. Determined characteristics of attic dust and identified possibilities of prolonged human exposure to it indicate that attic dust should be treated as an excellent proxy for historical air contamination as well as a potentially hazardous material for human health.
Ključne besede: multi-element composition, scanning electron microscopy, oral bioaccessibility, unified BARGE method, urban geochemistry
Objavljeno v DiRROS: 23.06.2022; Ogledov: 613; Prenosov: 228
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