Observations and light curve solutions of a selection of middle-contact W UMa binaries

Photometric observations in Sloan g′and i′ bands of W UMa binaries NSVS 4340949,T-Dra0–00959,GSC 03950–00707,NSVS 4665041,NSVS 4803568,MM Peg,MM Com and NSVS4751449 are presented.The light curve solutions revealed that the components of each target are of G and K spectral types.The binaries of the sample have middle-contact configurations whose fillout factors are within the range 0.2–0.4.The only exception is NSVS 4751449 which is in deeper contact(fillout factor of 0.55).It precisely obeys the relation between mass ratio and fillout factor for deep,low mass ratio overcontact binaries.One of the eclipses of almost all targets(except MM Peg)is an occultation and their photometric mass ratios and solutions could be accepted with confidence.We found that the target components have almost equal temperatures but differ considerably in size and mass.The components of the partially-eclipsed MM Peg have close parameters.Our solutions reveal that NSVS 4340949,T-Dra0–00959,NSVS 4803568 and MM Com are of W subtype while GSC 03950–00707,NSVS 4665041,MM Peg and NSVS 4751449 are of A subtype.This subclassification is well-determined for all totallyeclipsed binaries.The targets confirm the trends in which W-subtype systems have smaller periods and lower temperatures than A subtype binaries.     

Internal Gravity and Infrasound Waves during the Hurricane of May 29, 2017, in Moscow

Izvestiya, Atmospheric and Oceanic Physics - Data on internal gravity and infrasound waves recorded during the passage of both warm and cold fronts throughout Moscow, which are associated with the...     

Correction to: Zeolite containing rocks of kudurs and reasons of geophagy within the territory of Sikhote-Alin Nature Zapovednik,Far East of Russia

This paper establishes a mechanical model of the stress distribution in front of the driving face during coal roadway excavation. Theoretical research shows that the stress state in the plastic zone of the driving face is consistent with the limit equilibrium equation, and the elastic zone is in accordance with the equilibrium equation based on elasticity mechanics. Based on this improved mechanical state solution model, different coal material constitutive hypotheses are used for the analysis. The width of the plastic zone calculated under the brittle-perfectly elastic model can reach 2–5 times the height of the roadway, and the stress concentration coefficient can reach two or more times. 3DEC numerical simulation software was used to simulate the stress distribution of the heading face. The results of the simulation are similar to those of the theoretical analysis. Compared with the elastic-perfectly plastic model, the calculated results of the brittle-perfectly elastic model are more consistent with the numerical simulation results. The heading face coal during roadway excavation shows obvious damage, and the strength characteristics of the coal decrease.     

Climatic and hydrophysical conditions of the development of hypoxia in waters of the northwest shelf of the Black Sea

The data of meteorological and oceanographic observations on the northwest shelf of the Black Sea for 1973–2000 are used to compute the characteristics of the entire area in the presence of hypoxia of waters under the pycnocline in the summer–autumn period and the area of surface waters with a level of salinity lower than 17.5‰ in May. The time of onset of the spring warming of air (stable transition through a temperature of 5°) is determined. A statistically significant positive trend of the air temperature (0.8° per 100 yr) is revealed in Odessa. The process of warming was observed mainly for the winter (1.5° per 100 yr) and spring (0.8° per 100 yr) periods and became especially intense since the beginning of the 1990s. On the basis of the data of correlation analyses, we establish a statistically significant relationship between the large-scale atmospheric processes [the index of North Atlantic Oscillation (NAO) and the wind conditions], the area of surface waters whose salinity is lower than 17.5‰, and the total area with hypoxia in the summer–autumn periods. For positive mean values of the NAO index (in January–March), we most often observe early spring with elevated repetition of the south and west winds with subsequent development of hypoxia in large areas of the northwest shelf. We propose an empirical regression model for the prediction of the total area of summer–autumn hypoxia of waters with predictors: the onset of the spring warming of air and the area of propagation of waters whose salinity is lower than 17.5‰ in May. The maximum error of prediction of the area with hypoxia does not exceed 5.5 ⋅ 10³ km², i.e., less than 2% of the total area of the northwest shelf in the Black Sea (to the north of 45°N).     

The propagation of an acoustic pulse in a near-ground atmospheric waveguide

A wave theory of propagation of an acoustic pulse in a moving stratified atmospheric layer above the ground with a finite impedance of an underlying ground surface is developed. The shapes of acoustic signals in a near-ground atmospheric waveguide, which are formed due to temperature inversion and a vertical shear of the wind velocity, are calculated based on this theory. These signals are compared with those measured during the experiments where vertical profiles of the wind velocity and temperature in an atmospheric boundary layer have been continuously controlled using a sodar, a temperature profile meter, and acoustic anemometers or thermometers mounted on a 56-meter-high mast. The joint action of a near-ground acoustic waveguide, the impedance of the underlying surface, and a vertical layered structure of the boundary atmospheric layer on a signal shape far from the acoustic source are studied.     

The impact of large-scale turbulence on the redistribution of angular momentum in stellar accretion disks

We consider the origin and development of large-scale turbulence in a shear flow in a stellar accretion disk. The ratio of the kinetic energy of vortices originating in the turbulent flow and the total initial kinetic energy of the rotating disk is essentially constant. The large-scale structures that form are able to redistribute the angular momentum without any appreciable heating of the matter.     

The role of winter flaw polynyas in the formation of ice and hydrologic conditions in the Siberian shelf seas in the summer period

This paper analyzes the influence of flaw polynyas of the seas of the Siberian shelf on the formation of ice conditions in summer based on the ten-day data on the areas of flaw polynyas for 1978–2002 obtained by satellite image processing. The results of forecasts of summer ice conditions in the seas of the Siberian shelf are presented. The correspondence between the forecasts and observed data is 94.7% on average. The interrelation of atmospheric and ice processes is shown for the case when winter atmospheric processes determine ice conditions for the following summer and fall.