The results of a study on the geometric shape of the damper on the efficiency of the ultrasonic piezoelectric transducer are presented. In particular, a damper in the form of a truncated cone is ...considered, the generatrix of which has an inclination angle α relative to the diameter of the piezoceramic plate. The shape of the damper in the form of a truncated cone is chosen based on the a priori assumption that this helps to increase the path of the wave in the damper material due to numerous reflections in it. A criterion for the efficiency of damper operation is proposed. The optimal (from the point of view of the damper efficiency) value of the angle α was determined theoretically and experimentally. The technology of its production is described. Satisfactory agreement between the results of theoretical and experimental studies was noted.
We present the results of studying the influence of the geometric shape of the damper on its effectiveness and the overall efficiency of the emission–reception system. One of possible shapes for the ...damper is considered where it is a truncated cone with the generatrix tilted relative to the piezoelectric plate plane. A criterion for evaluating the efficiency of the damper operation is proposed. The study includes the results of computational-theoretical (using the finite element method) and experimental research on the influence of the tilt angle of the damper generatrix on the signal reflected from its rear part. The generatrix tilt angle at which the minimum of noise signal is achieved is determined. A study of the emission–reception system under load on the aquatic environment is carried out. A satisfactory agreement between the theoretical and experimental results is noted.
Recent laboratory studies indicated that a photo‐induced heterogeneous reaction of ozone on the surface of aerosol containing humic like substances (HULIS) has the potential to affect the ozone ...budget in biomass burning plumes. To evaluate atmospheric significance of such heterogeneous light induced ozone loss, this process has been taken into account in the simulation of the extreme air pollution episode in the Moscow region during the 2010 mega fire event in western Russia. Results of the numerical experiments performed with the CHIMERE chemistry transport model indicate that photo induced removal of ozone could lead to significant (reaching several tens of percent) episodic decrease of the ozone concentration. The simulations also show that while wildfires provide reactive surface for the considered reaction, they strongly inhibit the photo‐induced heterogeneous ozone loss by attenuating actinic fluxes through the “shielding” aerosol effect. The present results are calling for additional experimental and modelling studies.
Key Points
Photo induced ozone loss on biomass burning aerosol is a significant process
Aerosol is a self‐inhibiting agent of the heterogeneous light induced ozone loss
Uncertainties in reactivity of biomass burning aerosol call for new studies
Well documented adverse health effects of airborne particulate matter (PM) stimulate intensive research aimed at understanding and forecasting its behaviour. Forecasting of PM levels is commonly ...performed with either statistical or deterministic chemistry-transport models (CTM). In this study, we investigate advantages of combining deterministic and statistical approaches for PM10 forecasting over Europe one day ahead. The proposed procedure involves statistical postprocessing of deterministic forecasts by using PM10 monitoring data. A series of experiments is performed using a state-of-the-art CTM (CHIMERE) and statistical models based on linear regressions. It is found that performance of both CTM simulations and "pure" statistical models is inferior to that of the combined models. In particular, the root mean squared error of the deterministic forecasts can be reduced, on the average, by up to 45 percent (specifically, from 12.8 to 6.9I14g/m3 at urban sites in summer) and the coefficient of determination can be almost doubled. Importantly, it is found that the combined models for rural sites in summer and for urban and suburban sites in both summer and winter are representative, on the average, not only for a given monitoring site used for their training, but also of territories of similar type of environment (rural, suburban or urban) within several hundreds of kilometers away.
We consider the results of simulating the smoke aerosol radiative forcing (ARF) at the top and bottom of the atmosphere depending on the photochemical evolution of its organic component, illumination ...conditions, and underlying surface types (water, mixed forest, and snow/ice). At the top of the atmosphere, an increase in the surface albedo and a decrease in the aerosol optical depth can lead to the transformation of the cooling into a heating effect. An increase in absorptance of aerosol particles may cause the ARF to increase at the top of the atmosphere, which is manifested most significantly over snow/ice surfaces; while at the bottom of the atmosphere, ARF decreases. As the solar zenith angle grows, the ARF decreases in absolute value when the smoke plume propagates over weakly reflecting surfaces; however, with growing surface albedo, this dependence becomes nonmonotonic. It is shown that, when the transformations of the optical characteristics of organic aerosol are neglected, the aerosol radiative forcing at the top of the atmosphere can be overestimated or underestimated severalfold (by a few tens of W/m
2
), and this can also cause an error of determining the ARF sign.
The paper presents the results of an analysis of the main pollutants (heavy metals, pesticides, detergents, hydrocarbons) in water, suspended particulate matter, and bottom sediments, as well as the ...hydrophysical fields in the Kerch Strait and adjacent Black Sea water area (2019–2020 ). In all seasons, the concentrations exceeded the maximum permissible values, often significantly, for a number of pollutants, such as hydrocarbons, certain metals, and pesticides. The highest pesticide concentrations were documented in summer, while those of other pollutants peaked in spring. It was observed that the maximum concentrations of most pollutants, as well as dissolved methane and mineral suspended matter, were generally confined to the plume of Sea of Azov waters entering the Black Sea; therefore, their distributions were largely controlled by currents and stratification in the strait.
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