Browsing by Author "Ilieva N."

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    AIR QUALITY ASSESSMENT BASED ON LIMITED QUANTITY OF MEASURED DATA
    (2022-01-01) Ilieva N.; Predyov I.; Sokolovski E.
    This study is dedicated to the air quality monitoring regarding the allowed exceedances of PM10 daily average concentration limit. It is directed to air quality assessment in the boundary layer of the atmosphere in cases when a limited quantity of measured data is available. Such cases are typical for small and medium-sized settlements. An appropriate test whether the daily average PM10 concentration is not higher than the limit value 50 μg m−3 for at least 90.4 % of the days in the year has been proposed. It can be applied for analysis of data supplied by mobile automatic monitoring stations or indicative measurements using equivalent methods.
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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.
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    Modelling of ambient air PM2.5 concentration for air quality assessment
    (2015-01-01) Nikolova Y.; Ilieva N.; Sokolovski E.
    During the last decade special attention to the fine particles up to 2,5 μm (PM2.5) is being paid. PM2.5 is treated as a particular pollutant with strong negative impacton human health. In Bulgaria, the levels of PM2.5 are measured only at 9 monitoring stations. Therefore effective air quality monitoring regarding this pollutant can not be expected. In many cases particulate matter with aerodynamic diameter up to 10 μm (PM10) and PM2.5 have common origin. That is why it can be assumed that their concentrations in the air are related. Measured data from two of the monitoring stations ``Kopitoto`` (background) and ``Krasno Selo`` (traffic related) have been investigated. It was established that a strong correlation for ``Krasno Selo`` station exists. Conversely, for ``Kopitoto`` station the correlation is rather weak. A mathematical model has been worked out for calculation of PM2.5 concentration using PM10 concentration data. The model demonstrates good accuracy for urban background and traffic related monitoring stations.
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    Sensors applicability for PM2.5 and PM10 air concentration measurements
    (2018-01-01) Ilieva N.; Nikolova Y.; Predyov I.; Kozarev N.
    Comparisons of Private Stations (PS) measurements with Automatic Monitoring Stations (AMS) included in the National Environmental Monitoring System of the Ministry of Environment and Waters in Bulgaria has been made. The chosen PS (a total of four) are located close to AMS. In order to check whether the PS data are reliable and could be used for air quality monitoring, a statistical analysis of the data from the PS and the AMS was performed. The concentrations measured by two methods are quite different, but a good correlation between them has been established. In order to improve the PS measurement accuracy models for correction of the PM10 and PM2.5 concentrations measured using sensors were derived. They are characterized with good accuracy but are only valid for the warm part of the year. It is necessary to derive another set of coefficients for the cold half of the year. Without correction, the PS measurement error is large and their records may be misleading.