Browsing by Author "Metodiev V."

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    ANALYSIS OF MEASURED PM2.5 CONCENTRATIONS AND METHOD FOR DETERMINING THEIR ORIGIN
    (2023-01-01) Ilieva N.; Metodiev V.
    The significance of atmospheric Particulate Matter (PM) size as a determining factor for their source is of utmost importance. The analysis of PM2.5/PM10 ratios serves as a crucial indicator for particle origin. This study utilizes data obtained from measurements of PM2.5 and PM10 concentrations at the “Kamenitsa” automatic measuring station, located in the Kamenitsa district of Plovdiv, Bulgaria. The data covers a period of 6 years. A statistical approach for identifying the source of particulate matter in the air has been investigated and implemented. The findings of the applied method indicate that during winter, the primary source of particles is anthropogenic in nature.
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    Investigation of elastomers ratio influence in the composites for truck tires treads production
    (2022-01-01) Malinova P.; Ilieva N.; Metodiev V.
    An experimental design of model tread compounds for truck tires treads was carried out to test the possibilities for optimizing the ratio between the combination of elastomers (butadiene styrene rubber, isoprene rubber and butadiene rubber) used in their compositions. The experiment was designed using a Scheffe simplex lattice. The target functions, object of the optimization problem, are the main characteristics of the obtained vulcanizates: abrasion, stress at 100 % elongation, stress at 300 % elongation, tensile strength, elongation at break, residual elongation and Shore A hardness. The optimization was performed in the barycentric factor space with limits of variation of all factors from 0 to 1. Since the seven target functions obtain their extreme values at different points, a generalized criterion for optimality is formulated using the desirability function. The composition of the rubber compound at which this function receives its maximum has been established.