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Abstract: Particulate matter (PM10 and PM2.5) is a key contributor to urban air pollution and poses significant health risks, particularly in densely populated areas. While conventional air quality monitoring focuses on particle size and concentration, this study emphasizes the importance of understanding chemical composition and emission sources for effective air pollution management. PM samples were collected between 2019 and 2022 at two locations in the Republic of Slovenia: a traffic-dominated urban site and an industrial area. Annual average PM10 concentrations ranged from 14 to 34 μg/m3, and those of PM2.5 ranged from 9 to 22 μg/m3. In addition to decreasing annual concentrations, a notable reduction in exceedance days was observed between 2019 and 2022, indicating the effectiveness of recent air quality improvement measures. Meteorological data and statistical models were used to assess environmental influences on PM variability. Advanced SEM-EDS analysis revealed substantial seasonal and spatial differences in particle composition, with key elements such as silicon (4.3–28.4%), carbon (13.1–61.7%), and trace amounts of lead and zinc varying across sites and particle types. Mineral dust (Si, Al, Ca, Fe, Mg), originating from soil resuspension, construction, and Saharan dust, was dominant. Combustion-related particles containing C, Pb, Zn, and Fe oxides were associated with vehicle emissions, industrial processes, and biomass burning. Secondary aerosols, such as sulphates and nitrates, showed seasonal trends, with higher concentrations in summer and winter, respectively. The results confirm that PM levels are driven by complex interactions between local emissions, weather conditions, and seasonal dynamics. The study supports targeted policy measures, particularly regarding residential heating and traffic emissions, to improve air quality.
Keywords: air pollution, air quality, PM particles, SEM-EDS, Slovenia
Published in DKUM: 30.05.2025; Views: 0; Downloads: 5
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Abstract: : There has been growing interest and increasing attention in the field of functional clothing textiles, particularly in product and process development, as well as innovations in heat-generating, retaining, and releasing fibers to maintain a healthy body temperature without relying on unsustainable energy sources. This study, for the first time, reports the various physio-mechanical properties of surface-functionalized regenerated cellulose fibers (RCFs) coated with ceramic particles. The coating imparts photothermal conversion-based heat generation and retention properties with the aid of polyelectrolyte binders. In this design, ZrC enables the conversion of light energy into thermal energy, providing heat for the human body. A feasible coating process was employed, utilizing industrially feasible exhaustion methods to deposit the ZrC particles onto the RCF surface in conjunction with two distinctive polymeric binders, specifically polyethyleneimine (PEI) and polydiallyldimethylammonium chloride (polyDADMAC). The morphological characteristics and tensile properties of the coated RCFs were analyzed via scanning electron microscopy (SEM) and single-fiber tensile testing. Heat retention and release behaviors of a bundle of fiber samples were assessed using infrared (IR) imaging and an IR emission lamp setup. The SEM results confirmed the successful coating of the ZrC particles on the surface of the RCF samples, influencing negligible on their physical–mechanical properties. The heat retention of the coated RCFs with ZrC and both binders was higher than that of reference regenerated cellulose fibers (RCFs), demonstrating their effective heat generation, retention, and heat release properties. Based on the highlighted prominent results for the coated RCFs, these findings highlight the suitability of the developed functional clothing textiles for targeted applications in non-extreme thermal conditions, ensuring thermo-physiological comfort by maintaining body temperature within a tolerable thermal range (36.5–37.5 ◦C), in contrast to studies reporting significantly higher temperatures (50–78 ◦C) for extreme thermal conditions.
Keywords: regenerated cellulose fibers, RCFs, ceramic particles, zirconium carbide, ZrC, surface functionalization, heat generation and retention
Published in DKUM: 01.04.2025; Views: 0; Downloads: 136
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Abstract: We propose a novel, demonstrably effective, utmost versatile and computationally highly efficient pseudo-rigid body approach for tracking the barycenter and shape dynamics of soft, i.e. nonlinearly deformable micro-particles dilutely suspended in viscous flow. Pseudo-rigid bodies are characterized by affine deformation and thus represent a first-order extension to the kinematics of rigid bodies. Soft particles in viscous flow are ubiquitous in nature and sciences, prominent examples, among others, are cells, vesicles or bacteria. Typically, soft particles deform severely due to the mechanical loads exerted by the fluid flow. Since the shape dynamics of a soft particle - a terminology that shall here also include its orientation dynamics - also affects its barycenter dynamics, the resulting particle trajectory as a consequence is markedly altered as compared to a rigid particle. Here, we consider soft micro-particles of initially spherical shape that affinely deform into an ellipsoidal shape. These kinematic conditions are commensurate with i) the affine deformation assumption inherent to a pseudo-rigid body and ii) the celebrated Jeffery-Roscoe model for the traction exerted on an ellipsoidal particle due to creeping flow conditions around the particle. Without loss of generality, we here focus on non-linear hyperelastic particles for the sake of demonstration. Our novel numerical approach proves to accurately capture the particular deformation pattern of soft particles in viscous flow, such as for example tank-treading, thereby being completely general regarding the flow conditions at the macro-scale and, as an option, the constitutive behavior of the particle. Moreover, our computational method is highly efficient and allows straightforward integration into established Lagrangian tracking algorithms as employed for the point-particle approach to track rigid particles in dilute viscous flow.
Keywords: soft particles, pseudo-rigid bodies, Barycenter and shape dynamics, Lagrangian particle tracking
Published in DKUM: 19.09.2024; Views: 0; Downloads: 20
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Keywords: lignin particles, pickering emulsions, vegetable oils, UV protection, synergic effect
Published in DKUM: 06.05.2024; Views: 188; Downloads: 23
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Abstract: Cavitation erosion is a problem that presents a challenge for the engineers in different industries, as it erodes the machinery which leads to lower efficiency and higher maintanance costs. An experimental investigation has been conducted to evaluate cavitation and cavitation erosion with and without the presence of solid particles in a Venturi channel. The methodology is based on observing and analysing the evolution of the vapour structures and occurence of cavitation erosion on the sample surface in the Venturi channel. To conduct experiments the cavitation tunnel was used, with the central component being a transparent test section with a Venturi-like channel (constructed from Plexiglass walls and a metal insert) to monitor the process of cavitation. To detect the damage caused by cavitation erosion and abrasion, the most effective solution was found to be an indicator in the form of black acrylic paint thinned with water (at a ratio of 1:2). On the sample surface, a self-adhesive aluminium tape was applied to protect the aluminium base from erosive characteristics from cavitation Furthermore, a comparison between cavitation with and without solid particles was made to determine the effects of solid particles on both cavitation and abrasion of the sample surface. The observation revealed that no matter the solid particles, damage from cavitation erosion appears at the separation point and in proximity to the location of the detached cloud collapse. The spherical glass particles with diameters between 40 µm and 70 µm added an abrasive effect on the sample surface only in the presence of cavitation structures. It was determined, that the intensity of cavitation erosion and abrasion increases when the cavitation number decreases and volumetric flow rate increases. Also, an economic analysis was conducted, to determine which is the more cost beneficial solution between replacement of the metal insert and application of protective coatings over the metal insert.
Keywords: cavitation erosion, solid particles, abrasion, experiment
Published in DKUM: 28.02.2024; Views: 230; Downloads: 33
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