1. Thin-layer boilover of large-scale diesel pool fires at sub-atmospheric pressureJinlong Zhao, Qingyuan Zhang, Zhenqi Hu, Rongxue Kang, Grunde Jomaas, Rui Yang, 2024, izvirni znanstveni članek Povzetek: As thin-layer burning of fuels on water are often followed by thin-layer boilover fires, particularly during the firefighting process, an experimental and numerical study was undertaken to address key aspects of such fires, especially in plateau areas (i.e., sub-atmospheric pressure). In the thin-layer boilover experiments at sub-atmospheric pressure (69 kPa), diesel was used as the fuel in five circular steel trays (ranging from 0.4 m to 1.2 m in diameter) and a square steel tray (side length of 2.5 m). The burning process, and especially the continuous boilover stage, was presented and the corresponding boilover intensity, time to boilover onset and boilover time interval were measured and analyzed. The results show that the flame height increased sharply at the initial boilover, while this increasing range gradually became weak for the subsequent boilovers. The initial boilover intensity showed a linear dependency on the fuel layer thickness at the time of boilover, and the slope of the boilover intensity line decreased with increasing pan area. Eventually, the effect of pan area on boilover intensity became limit. Moreover, a predictive model for the boilover intensity was established based on dimensionless analysis. The initial boilover onset time under the sub-atmospheric pressure was delayed compared with that under atmospheric pressure. The corresponding predictive correlation (for 69 kPa) with different diameter and fuel thickness was developed based on the one-dimension two-layer conduction model. In the end, the boilover time interval decreased with the boilover times, closing to uninterrupted boilover eventually. This work enriches the thin-layer boilover behavior experimental data at sub-atmospheric pressure and provides guidance for the fuel storage safety.
Ključne besede: thin-layer boilover, boilover intensity, time to boilover onset, boilover time interval, sub-atmospheric fires
Objavljeno v DiRROS: 16.01.2024; Ogledov: 177; Prenosov: 39
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2. Mechanistic study of fast performance decay of PtCu alloy-based catalyst layers for polymer electrolyte fuel cells through electrochemical impedance spectroscopyMaximilian Grandi, Matija Gatalo, Ana Rebeka Kamšek, Gregor Kapun, Kurt Mayer, Francisco Ruiz-Zepeda, Martin Šala, Bernhard Marius, Marjan Bele, Nejc Hodnik, Merit Bodner, Miran Gaberšček, Viktor Hacker, 2023, izvirni znanstveni članek Ključne besede: PEFC, catalyst layer, platinum–copper, degradation, ionomer, electrochemical impedance spectroscopy, membrane electrode assembly
Objavljeno v DiRROS: 23.06.2023; Ogledov: 354; Prenosov: 183
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3. Properties of the fluoroacrylate and methacryloxypropyl-trimethoxysilane applied to a layer of Cu2O on bronze as either single or multi-component coatingsLuka Škrlep, Tadeja Kosec, Matjaž Finšgar, Andrijana Sever Škapin, Erika Švara Fabjan, 2023, izvirni znanstveni članek Povzetek: Various coatings have been developed and explored to protect bronze surfaces against the uncontrolled formation of different corrosion products when exposed to outdoor environments.
In this research, the surfaces of artificially-formed oxidized bronze patinas (OB), consisting of Cu2O, were covered with either a single-component (fluoroacrylate, FA or methacryloxypropyl-trimethoxysilane, MS) or multi-component (a mixture of FA and MS, FA-MS) fluoropolymer coating and investigated. Variations in the concentration of each component in the coating were studied. Electrochemical tests were performed to determine the corrosion protection efficiency, followed by detailed surface analyses of the OBs, both uncoated and covered with single and multi-component coatings. A variety of investigative methods were used, including focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and time-of-flight secondary ion mass spectrometry (ToF-SIMS).
The coating made from a combination of FA and MS resulted in a very high protection efficiency. Despite the increased hydrophilicity of the single MS component, however, it was shown to efficiently protect the oxidized bronze surface. The FA-MS systems showed high hydrophobicity, but no improvement was measured in the efficiency of the corrosion protection when it was compared to the coating that contained 10% MS. According to XPS and ToF-SIMS imaging, the FA component of the FA-MS coating was not present only on the uppermost surface of the coating but throughout the whole coating, which could affect its corrosion protection efficiency.
Ključne besede: bronze, Cu2O layer on bronze, fluoropolymer coating, protection efficiency, surface spectroscopy
Objavljeno v DiRROS: 30.05.2023; Ogledov: 333; Prenosov: 178
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5. Patterns of understory community assembly and plant trait-environment relationships in temperate SE European forestsJanez Kermavnar, Lado Kutnar, 2020, izvirni znanstveni članek Povzetek: We analyzed variation in the functional composition and diversity of understory plant communities across different forest vegetation types in Slovenia. The study area comprises 10 representative forest sites covering broad gradients of environmental conditions (altitude, geology, light availability, soil type and reaction, nutrient availability, soil moisture), stand structural features and community attributes. The mean and variation of the trait values were quantified by community-weighted means and functional dispersion for four key plant functional traits: plant height, seed mass, specific leaf area and leaf dry matter content. At each study site, forest vegetation was surveyed at two different spatial scales (4 and 100 m2 ) in order to infer scale-dependent assembly rules. Patterns of community assembly were tested with a null model approach. We found that both trait means and diversity values responded to conspicuous gradients in environmental conditions and species composition across the studied forests. Our results mainly support the idea of abiotic filtering: more stressful environmental conditions (e.g., high altitude, low soil pH and low nutrient content) were occupied by communities of low functional diversity (trait convergence), which suggests a selective effect for species with traits adapted to such harsh conditions. However, trait convergence was also detected in some more resource-rich forest sites (e.g., low altitude, high soil productivity), most likely due to the presence of competitive understory species with high abundance domination. This could, at least to some extent, indicate the filtering effect of competitive interactions. Overall, we observed weak and inconsistent patterns regarding the impact of spatial scale, suggesting that similar assembly mechanisms are operating at both investigated spatial scales. Our findings contribute to the baseline understanding of the role of both abiotic and biotic constraints in forest community assembly, as evidenced by the non-random patterns in the functional structure of distinct temperate forest understories.
Ključne besede: functional composition, functional diversity, ecological gradients, abiotic filtering, trait convergence, trait divergence, spatial scale, forest ground-layer vegetation, Slovenia
Objavljeno v DiRROS: 26.05.2020; Ogledov: 1895; Prenosov: 1263
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6. Effects of disturbance on understory vegetation across Slovenian forest ecosystemsLado Kutnar, Thomas Andrew Nagel, Janez Kermavnar, 2019, izvirni znanstveni članek Povzetek: The herbaceous understory represents a key component of forest biodiversity across temperate forests of Europe. Here, we quantified changes in the diversity and composition of the forest understory layer in representative Slovenian forest ecosystems between 2004/05 and 2014/15. In total, 60 plots were placed across 10 different managed forest types, ranging from lowland deciduous and mid-altitude mesic mixed forests to mountain conifer forests. This network is part of an international network of sites launched within the ICP Forests Programme aimed to assess the condition of forests in Europe. To examine how disturbance influenced understory dynamics, we estimated the disturbance impacts considering both natural and/or anthropogenic disturbances that cause significant damage to trees and to ground-surface layers, including ground-vegetation layers and upper-soil layers. Species richness across 10 sites (gamma diversity) significantly decreased from 272 to 243 species during the study period, while mean species richness per site did not significantly change. The mean value of site level Shannon diversity indices and evenness significantly increased. The cover of most common plant species increased during the monitoring period. The mean value of disturbance estimates per site increased from 0.8% in 2004/05 (ranging from 0% to 2.5%) to 16.3% in 2014/15 (ranging from 5.0% to 38.8%), which corresponded to a reduction in total vegetation cover, including tree-layer cover. More disturbed sites showed larger temporal changes in species composition compared to less disturbed sites, suggesting that forest disturbances caused understory compositional shifts during the study period. Rather than observing an increase in plant diversity due to disturbance, our results suggest a short-term decrease in species number, likely driven by replacement of more specialized species with common species.
Ključne besede: vegetation dynamics, vascular-plant diversity, understory layer, disturbance, monitoring, temperate forests
Objavljeno v DiRROS: 27.11.2019; Ogledov: 2349; Prenosov: 1433
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