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Abstract: Laboratory and field assessments of low-cost sensors (LCS) are essential for ensuring the accuracy of PM2.5 measurements collected by citizens in air quality campaigns. Evaluation of Sensirion SPS30 (LCS SPS30) in controlled laboratory setting showed a coefficient of determination (R2) ranging from 0.81–0.99 and a root mean square error (RMSE) from 0.81–61.72 μg m−3, at average concentration of 21.5 μg m−3. In contrast, co-location assessment at an average concentration of 9 μg m−3 resulted in R2 of 0.5 and a RMSE of 6.82 μg m−3. The results demonstrated that the sensor met micro-environmental monitoring standards (accuracy < 25%) and United States Environmental Protection Agency's performance criteria (RMSE ≤ 7 μg m−3, R2 > 0.7) only at relative humidity (RH) levels below 60%, emphasising its strong sensitivity to RH and the need for RH-dependent data corrections. The observed underestimation or overestimation of PM2.5 readings was primarily attributed to variations in particle composition and concentration. Despite accuracy variations, LCSs can effectively capture spatiotemporal urban air quality patterns and identify pollution hotspots in community monitoring, particularly in low-pollution environments. In a citizen-led PM2.5 monitoring campaign in Maribor, Slovenia, the lowest concentrations were recorded at 15:00 (2.9 μg m−3), while the highest occurred during the morning rush-hour (4.8 μg m−3), likely attributed to the planetary boundary layer’s impact on atmospheric particulate dispersion. Spatial analysis revealed that hotspots clustered near intersections, where vehicle waiting time is the longest.
Keywords: particulate matter, low-cost sensor, Sensirion SPS30, citizen science, calibration
Published in DiRROS: 18.09.2025; Views: 272; Downloads: 183
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Published in DiRROS: 17.09.2025; Views: 343; Downloads: 170
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Abstract: This study investigates heat and mass transfer during energetic melt-coolant interactions, focusing on film boiling around a hot melt particle in subcooled convective flow. The considered conditions, free-flow velocities of a few m/s, melt particle temperatures of several thousand K, particle diameters of several tens of a μm, and liquid subcooling of several tens of a K, align with TREPAM experiments (CEA, France). A two-phase computational fluid dynamics framework, based on the Volume of Fluid method, is used. An improved phase-change model is implemented, combining Chen’s explicit formulation of the phase-change intensity factor with the robustness of the conventional Lee model. The approach reduces sensitivity to empirical parameters and enhances phase-change localisation. Additional constraints on the intensity factor ensure numerical stability under extreme thermal conditions relevant to vapour energetic melt-coolant interactions. Simulations of TREPAM experiments demonstrate improved heat flux predictions and enhanced flow dynamics capture. Analysis of the simulated velocity fields reveal secondary flows in the vapour wake, impacting heat and mass transfer and emphasizing the need to resolve vapor-phase flow conditions. To fully validate proposed modifications to phase-change model further numerical and experimental investigation is required, focusing on vapour film morphology and localized heat transfer intensity.
Keywords: film boiling, extreme thermal conditions, phase-change modelling, computational fluid dynamics, two-phase flow
Published in DiRROS: 16.09.2025; Views: 250; Downloads: 117
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Keywords: varstvo gozdov, morfološke analize
Published in DiRROS: 16.09.2025; Views: 204; Downloads: 0
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Abstract: The demand for rapid, field-deployable detection of hazardous substances has intensified the search for plasmonic sensors with both high sensitivity and fabrication simplicity. Conventional approaches to plasmonic substrates, however, often rely on lithographic precision or complex chemistries limiting scalability and reproducibility. Here, a facile, one-step synthesis of vertically aligned 2D nanosheets composed of intergrown Cu2O/CuO crystallites is presented, fabricated via oxygen plasma discharge on copper substrates. Decorated with a discontinuous Ag nanoparticle layer, the substrates serve as high-performance plasmonic metasurface exhibiting nanomolar sensitivity of explosive molecules, with detection limits as low as 4–5 nm for tetryl and 2–3 nm for HMX under 488 nm excitation. Importantly, the SERS (Surface enhanced Raman scattering) activity expands into a broad spectral range (488, 535, 633 nm), enabled by the formation of plasmonic “hotspots” network within nanoparticle gaps, crevices, that cumulatively boost SERS signal. A pronounced red-shift in the symmetric NO2 stretching mode of tetryl is further demonstrated, attributed to LUMO-mediated charge transfer from the Ag Fermi level—highlighting the need for laser- and substrate-sensitive interpretation of vibrational data. Together, these findings advance the rational design of low-cost, reproducible SERS substrates for trace chemical detection, with potential for integration into autonomous sensing platforms.
Keywords: plasmonic sensors, surface enhanced Raman scattering
Published in DiRROS: 16.09.2025; Views: 354; Downloads: 139
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