We present the results of a ballistic experiment, in which an intensive capillary wave throws up microdroplets levitated over a heated region of water due to an ascending convective steam–air flow. ...The resistance of this flow to the motion of a droplet is estimated. The flow parameter (the velocity decrease field) is estimated using various theoretical approximations. The maximum size of freely levitated droplets is determined. It is shown that stationary levitation of droplets is impossible in a linearly nonuniform flow.
This paper aims to study the path oscillations of single, spherical water droplets levitated in a wind tunnel to better comprehend the mechanical motion of small raindrops. The observations were ...carried out in the Mainz vertical wind tunnel. The discrete, fast Fourier transform was used to determine the oscillatory frequencies of the droplet paths, and the Hilbert transform was applied to analyze their instantaneous frequency stability. Both transversal and streamwise components of the path oscillations are described with typical frequencies of several tens of Hertz. The studied oscillations elongate the paths, reduce the terminal velocity of the smallest droplets, and make the rain droplet fall in a non-uniform motion even after reaching terminal velocity. The terminal velocity can be considered as physically having been reached if our proposed practical criterion is satisfied. From a fluid mechanics perspective, the paper fills an experimental gap in the studies of the paths oscillations of single, liquid spheres of microscopic sizes at low Bond numbers <1 and relatively low Reynolds numbers ~102.
Oscillatory Motion of a Droplet Cluster Fedorets, Alexander A; Aktaev, Nurken E; Gabyshev, Dmitrii N ...
Journal of physical chemistry. C,
09/2019, Volume:
123, Issue:
38
Journal Article
Peer reviewed
Horizontal oscillations of small droplet clusters (from one to four droplets) levitating over a locally heated water layer in upward vapor–air flow are investigated experimentally. These oscillations ...are caused by a complex dynamic interaction between the droplets and the nonsteady gas flow. The path of the center of the droplet cluster is similar to a random walk in a potential well. The vibrational spectra of clusters’ centers obtained by Fourier analysis showed several frequency peaks between f = 1.61 and 5.96 Hz found in all clusters, which shows that the cluster tends to oscillate as a whole. The possibility of decoupling of the aerodynamic interaction between the gas flow and the droplets and the interaction between individual droplets is discussed.
The forces acting on levitating water microdroplets in the structure of a droplet cluster (A.A. Fedorets, 2004) have been analyzed. It is found that microdroplets in the cluster should undergo ...low-frequency vertical damping oscillations near the equilibrium position. Oscillations occur also when switching on an external electric field, which affects the oscillation frequency and equilibrium position. Microdroplets are shown to lose their stability in the critical range of parameters. The electric fields are calculated in the simplest experimental scheme for simulating the effect of electric field on a droplet cluster.
The results of the experiment on the measurement of the e+e− → π+π− cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the vector ...dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The cross section for the production of a muon pair is measured in the energy range of the experiment.
The paper discusses the issues of individual income tax due to the effective implementation of its fiscal and social functions. An urgent need for resolving problems of the budget and tax systems in ...many countries and stimulating economic growth in the absence of unified methodological approaches necessitates developing new areas of public administration of income tax on individuals. The methodological framework includes public administration theory and the theory of taxation. The study reviews the special features of income taxation of population in Russia and abroad and analyses the contribution of the tax to the government budget. We demonstrate that the social role of income tax on individuals is increasing while its fiscal function is declining. With a view to improving social equity, there is a strong need for the progressive tax system characterized by growing marginal tax rates. The authors propose a mechanism for organizing taxation of individual income based on fundamental mathematical principles and demonstrating the probability of meeting the needs of all parties of the taxation process. Theoretical and practical relevance of the research is that the article justifies the necessity of employing a modified approach to manage income taxation on individuals.
A microscopic-size droplet levitates steadily in a vapor–air flow rising upward over a locally heated thin water layer. A Fourier analysis of the droplet position during a high-speed video recording ...revealed small-amplitude high-frequency droplet oscillations. This study focuses on overcoming the noise hindering extraction of oscillatory modes from spectra. The analysis revealed that some modes are associated with the horizontal droplet motion, while the others are due to the vertical motion. Possible physical reasons for the onset of this oscillatory motion are briefly discussed. Along with a single droplet, small clusters consisting of two or three droplets are considered.
The one-dimensional non-relativistic dust-acoustic soliton is considered in the model of plasma with cold positively charged dust particles, warm ions, and relativistic thermal electrons (taking into ...account trapping of the latter). The influence of an increase in the electron temperature is shown.
The experimental results on the ratios of branching fractions R(D)=B(Bover ¯→Dτ^{-}νover ¯_{τ})/B(Bover ¯→Dℓ^{-}νover ¯_{ℓ}) and R(D^{*})=B(Bover ¯→D^{*}τ^{-}νover ¯_{τ})/B(Bover ¯→D^{*}ℓ^{-}νover ...¯_{ℓ}), where ℓ denotes an electron or a muon, show a long-standing discrepancy with the standard model predictions, and might hint at a violation of lepton flavor universality. We report a new simultaneous measurement of R(D) and R(D^{*}), based on a data sample containing 772×10^{6} BBover ¯ events recorded at the ϒ(4S) resonance with the Belle detector at the KEKB e^{+}e^{-} collider. In this analysis the tag-side B meson is reconstructed in a semileptonic decay mode and the signal-side τ is reconstructed in a purely leptonic decay. The measured values are R(D)=0.307±0.037±0.016 and R(D^{*})=0.283±0.018±0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the standard model predictions within 0.2, 1.1, and 0.8 standard deviations for R(D), R(D^{*}), and their combination, respectively. This work constitutes the most precise measurements of R(D) and R(D^{*}) performed to date as well as the first result for R(D) based on a semileptonic tagging method.
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