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Povzetek: Clay-based materials typically require high-temperature processing (>900 ◦C), resulting in high energy consumption. This study explores cold sintering of metakaolin (MK) powders to achieve high mechanical strength at significantly lower processing temperatures. By applying uniaxial pressure of 400 MPa and heating to only 240 ◦ C in the presence of 15 mol/L NaOH solution, successful densification of structurally sound and dense samples with an average density of 2.16 g/cm³ and a biaxial flexural strength of ~35 MPa was achieved. This strength surpasses that of conventionally sintered MK (1470 ◦C) by ~30 %. Densification was found to be governed by synergistic mechanisms involving MK exfoliation, conformal sintering around aggregates, and the precipitation of an amorphous sodium aluminosilicate hydrate phase. Crack formation was avoided through process optimization and verified using X-ray micro-computed tomography. These findings offer new insights into the chemo- mechanical mechanisms of cold sintering and demonstrate its potential as an efficient route for producing structural materials.
Ključne besede: cold sintering, metakaolin, geopolymer, delaminations, exfoliation
Objavljeno v DiRROS: 15.10.2025; Ogledov: 210; Prenosov: 99
Celotno besedilo (7,70 MB)
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Povzetek: Carbon capture plays an important role in the decarbonation of the building sector. One way to capture carbon is through mineral carbonation, in which Ca and Mg compounds react with CO2 to form stable carbonate minerals such as calcite, dolomite, magnesite and/or siderite, permanently sequestering CO2. Various techniques are available to measure the amount of permanently bound CO2 and quantify the carbonation potential. The suitability and accuracy of a particular method are very important, as the accurate determination of CO2 is crucial to correctly assess the sequestration potential of different materials. This study compares the three methods: calcimetric, gravimetric and thermogravimetric analysis used for CO2 determination in different types of ash, slag and natural rock. While the CO2 content in natural rock is stable, the CO2 content in slag and ash can change over time as the contained minerals gradually absorb CO2 (by natural or accelerated carbonation) until they are fully carbonated. To avoid errors in testing the CO2 uptake, as-received samples were first exposed to the full carbonation process and then tested. The comparison of calcimeter, thermogravimetric and gravimetric analysis of ground and sieved samples with a particle size below 125 μm shows that the results usually differ by less than 2 %. Higher deviations could be caused by non-carbonate minerals (especially in slags) that can react with hydrochloric acid during the calcimetric and gravimetric tests and/or decompose in the range where carbonates decompose, contributing to inaccurate CO2 measurements. The measurement uncertainty was calculated for all three quantitative methods to allow a practical comparability.
Ključne besede: CO2 sequestration, ash, slags, natural rocks, TGA, calcimetry, measurement uncertainty
Objavljeno v DiRROS: 15.10.2025; Ogledov: 209; Prenosov: 116
Celotno besedilo (5,06 MB)
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Povzetek: An examination of the Iranian philosopher RezaNegarestani’s development of political theology.Considered within the context of his involvementwith a strand of contemporary philosophicalthinking known as speculative realism, it examinesNegarestani’s use of Islamic referents inCyclonopedia, a multi-layered frame story belongingto the genre of theory fiction, and in more tech-nical-philosophical treatises. Focusing on his deploy-ment of dissenting interpretations of the notions oftaqiyya(concealment, dissimulation) andqiyama(resurrection), the resulting spatiotemporal implica-tions are assessed by putting Negarestani in conver-sation with classical and contemporary Islamic andnon-Muslim thinkers, theologians, and philosophers.
Ključne besede: Iranian philosophy, political theology, contemporary philosophy, Islamic thought, philosophy of religion
Objavljeno v DiRROS: 14.10.2025; Ogledov: 253; Prenosov: 106
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Povzetek: This study aimed to identify the critical ground motion parameters that lead to structural damage and assess their impact on the nonlinear responses of buildings. The analyses are carried out using a calibrated numerical model that was acquired within the ICONS experimental framework that represents reinforced concrete (RC) structures constructed before seismic design regulations were enforced. For the analysis, 30 seismic records were chosen based on magnitude (M), epicentral distance (R), and peak ground acceleration (PGA) for two high seismic activity areas that were observed. Eleven parameters are categorized, traditional metrics, energy-based, spectrum-based, duration-based, and fundamental metrics, and examined based on their main attributes. The results showed a strong relationship between certain seismic properties and the maximum interstory drifts of building as a damage prediction parameter. Peak ground velocity (PGV), specific energy density (SED), and Housner Intensity (HI) were found to be the most important variables in assessing the correlation with possible structural damage. Therefore, the assessment of structural damage based on nonlinear dynamic analysis should primarily incorporate PGV with the possible addition of energy- and spectrum-based metrics as the most reliable ground motion parameters for the selection of earthquake records for time history analysis.
Ključne besede: ground motion record characteristics, nonlinear response, reinforced concrete frame structures, maximum interstory drifts, stavba
Objavljeno v DiRROS: 14.10.2025; Ogledov: 272; Prenosov: 160
Celotno besedilo (3,73 MB)
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Povzetek: Satellite observations of sea surface temperature (SST) are essential for accurate weather forecasting and climate modeling. However, these data often suffer from incomplete coverage due to cloud obstruction and limited satellite swath width, which requires development of dense reconstruction algorithms. The current state of the art struggles to accurately recover high-frequency variability, particularly in SST gradients in ocean fronts, eddies, and filaments, which are crucial for downstream processing and predictive tasks. To address this challenge, we propose a novel two-stage method CRITER (Coarse Reconstruction with ITerative Refinement Network), which consists of two stages. First, it reconstructs low-frequency SST components utilizing a Vision Transformer-based model, leveraging global spatio-temporal correlations in the available observations. Second, a UNet type of network iteratively refines the estimate by recovering high-frequency details. Extensive analysis on datasets from the Mediterranean, Adriatic, and Atlantic seas demonstrates CRITER's superior performance over the current state of the art. Specifically, CRITER achieves up to 44 % lower reconstruction errors of the missing values and over 80 % lower reconstruction errors of the observed values compared to the state of the art.
Ključne besede: deep learning, reconstruction algorithms, satellite measurements
Objavljeno v DiRROS: 14.10.2025; Ogledov: 250; Prenosov: 120
Celotno besedilo (19,22 MB)
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