A SEMI-ANALYTICAL METHOD FOR A FLOW OF NON-VISCOUS FLUID AROUND AN AIRFOIL WITH A SHARP TRAILING EDGE

In the present work we propose a method to study a two-dimensional flow of non-viscous fluid around an airfoil with a sharp trailing edge, by the double-layer potential theory. The circulation of velocity vector is modeled by the potential of a point vortex whose center is located inside the boundary contour. The magnitude of the circulation is defined on the basis of the Joukowski-Chaplygin postulate. There are presented some results for a Joukowski rudde, as well as for the airfoil in the form of a pair of interacting circles. It is performed a comparison of the circulation with its theoretical value.

STUDY OF THE SHELL MATTER OF MODERN AND PLEISTOCENE MOLLUSCS OF THE GENUS DIDACNA

One of the ways to study the reactions of marine invertebrates to the external effects of changes in temperature and salinity is the biogeochemical analysis of skeletal parts, which are consistently built up during ontogenesis and record a variety of information about these changes. The most studied shells of mollusks, sea urchin shells and skeletal parts of corals. Information about the chemical composition of modern and fossil mollusk shells is widely used in solving geological and biological problems, including determining the temperature and salinity of ancient marine basins, studying the diagenesis of carbonate sediments, and the biochemical evolution of invertebrates. X-ray diffraction analysis of the shell matter of didacnae belonging to the Cardiidae showed an aragonite composition. The quantitative determination of elements in mollusk shells by microprobe analysis of spot scanning and spectrometric method is carried out. Samples were taken in successive layers of shell growth within the annual ring, and the seasonal dynamics of strontium changes were detected. For Didacna, strontium is the main element-indicator of seasonal and ontogenetic growth, is included in the crystal lattice of aragonite and forms strong compounds in the process of shell formation during the life of these bivalves. The variability of seasonal, ontogenetic, and taxonomic differences in a number of indicator elements in living and Pleistocene bivalves of the genus Didacna was studied.

FEATURES OF THE RADIAL GROWTH OF SHRUBS BETULA NANA AND SALIX LANATA ON VARIOUS LANDSCAPE ELEMENTS IN THE SOUTHERN TUNDRA OF YAMAL

Tundra communities are widespread in the northern part of Russia, in particular on the Yamal Peninsula in the registration of Siberia, where research was carried out. For the study, we used plants of the species Betula nana and Salix lanata, these species are among the most common in the southern tundra of Yamal. Sampling sites were located on various morphological elements of the relief with the identification of patterns in the distribution of natural resources that determine the radial growth of the trunks of Betula nana and Salix lanata. At each site, at least 30 samples of each species were taken to obtain a sufficient sample. The sampling sites were located on different morpholog-ical parts of the relief. In the course of the study, general growth trends are highlighted, as well as absolute values of growth for 5 years. This age corresponds to the minimum age of the selected plants. As a result, data were obtained on the distribution and growth characteristics of Betula nana and Salix lanata shrubs along the relief profile; the most and least favourable areas of the profile for the growth of shrubs were identified. To compare the general trends of radial growth, a faster slowdown in growth was found in Betula nana. In addition, it was found that the species Salix lanata has a stronger effect on mechanical impact (winter road).

BASIC MATHEMATICAL MODELS AND AN APPROXIMATE METHOD OF FILTRATION THEORY

The article defines the basic concepts of filtration theory and provides an overview of the existing mathematical models of inhomogeneous liquids in porous media. The paper considers the Stefan problem. The number of scientific papers devoted to the study of porous structures has recently increased. This is primarily due to the fact that the prob-lems of oil and uranium production have been identified, and the solution of environmental problems is overdue. Therefore, a new device is needed to develop models of liquid filtration. With the advent and development of computer technology, it has become easier to solve problems that require numerical methods for their solution. Understanding the movement of fluids and the mechanism of dissolution of rocks under the action of acids in heterogeneous porous media is of great importance for the extraction and production of oil and the effective management of these processes. The article examines the mathematical model of the theory of isothermal filtration. Possible variants of the solva-bility of the model are shown. The research scheme consists of the output of a mathematical model, the formulation of the problem, one variant of the solution of the problem, the algorithm of the numerical method of solving the problem.

BAIKAL-MONGOLIAN TRANSPORT CORRIDOR: RELATIONSHIP OF PRODUCTION AND POPULATION

The purpose of this study is to identify the spatio-temporal relationship between the population and production of the urbanized territories of the Baikal-Mongolian transport corridor. Cross-cutting methods - statistical, cartograph-ic, comparative-geographical - are used at all stages of the study. The units of measurement taken are the following: in Russia - urban districts and municipal districts, in Mongolia - the capital city and aimags. The main results consist in identifying the main urbanized areas that have formed in places of maximum population concentration: around the capital city of Ulaanbaatar in Mongolia, and in southeastern Siberia around the regional centers of Irkutsk, Ulan-Ude, and Chita. The demographic potential of the Baikal-Mongolian transport corridor is more than half of the population of the corresponding regions, while it reproduces and receives migrants from peripheral territories. Competitive advantages and opportunities of cities and regions are assessed as constituent parts of a single cross-border economic corridor. The increasing role of the main economic centers objectively leads to the growth of the corresponding agglomerations and damages the functioning of other urban settlements. Based on the analysis of the economic com-plex of the studied territory, the branches of industrial specialization are distinguished, the typologies of municipalities of the region are carried out according to the prevalence of the main activity in the industry. The determining factors of the social and economic development of cities are the effects of the economic and geographical location and the accumulated socio-economic potential of the territory in relation to adjacent spaces.

GEOECOLOGICAL ASSESSMENT OF THE RISK OF BIOLOGICAL CONTAMINATION OF THE REPUBLIC OF BASHKORTOSTAN TERRITORY BY NATURAL AND FOCAL FACTORS

The high significance of the problem of hemorrhagic fever with renal syndrome (HFRS) is associated with the scale of spread, damage to persons of active age, a long period of reduced working capacity and high economic damage. The work presents an assessment of biological contamination by natural - focal viral infection - HFRS in the Re-public of Bashkortostan (RB). The most active foci are associated with linden forests, which prevail in the republic. The work shows the dynamics and features of infection. Analysis of the geoecological state of the territory according to HFRS showed that in the territory of most regions of the republic there are natural-focal infections of HFRS. There is an increase in infection of rodents with the HFRS virus, so in 2016 it was 5.0 %, and in 2019 - 16.2 %. The increase in the incidence of the population has characteristic epidemiological signs for the territory of RB, and the increase in high-risk areas indicates trends in the expansion and activation of foci of infection in them. At the same time, there is an increase in incidence, and infection in 50 % of cases occurs when visiting forests. In the capital of Bashkortostan - the city of Ufa, which is located in the natural zone, the incidence of HFRS is almost 50 % of the entire territory of the republic. In connection with climate changes, the diversity of environmental aspects of natural-focal infection of HFRS should be more widely assessed to counter their spread and measures to reduce this dangerous disease in the RB should be significantly strengthened.

CHANGES IN THE MAMMALIAN COMPLEX (MAMMALIA) ON THE TERRITORY OF THE ROSTOV NATURE RESERVE SINCE THE MID-TWENTIETH CENTURY

The complex of mammals on the territory of the Rostov Nature Reserve located in the arid steppes in the 20th-21st centuries was studied and the reasons for the changes that occurred in it were determined. We used the authors' observations since 1959, data from the staff of the Rostov Nature Reserve and publications on mammals. A total of 46 species of mammals were recorded. Under the influence of human activity steppe ecosystems underwent profound transformations, which led to changes in the number, distribution and importance of many mammals and to the disappearance of some and the penetration of other species here. The creation of the Rostov Nature Reserve has had a positive impact on the restoration of biocenoses. However, their composition differs from that of the mid-twentieth century. In the 21st century steppe ecosystems, including mammals, are affected by increased economic activity and climate change.

THE STUDY OF THE BIOLOGY OF THE ROACH RUTILUS RUTILUS CASPICUS (JAKOWLEV, 1870) IN THE KRAYNOVSKY COAST OF THE CASPIAN SEA

The offshore zone of the western coast of the Caspian Sea is one of the most highly productive. Of the 63 species of fish that live in the Caspian Sea, 34 species are found on the Krainovsky coast, 42 % of which are carp. The most numerous is the roach Rutilus rutilus caspicus (Jakowlev, 1870), which makes up 50–86 % of the number of semi-passerine and river fish. The article presents the results of studies of the peculiarities of the biology of the roach Rutilus rutilus caspicus of the Krainovsky coast of the Caspian Sea. The roach is noted in the catches constantly. Her age in the networks ranges from 2 to 10 years. The share of 3-5-year-olds accounts for 81 %. Females in catches make up 66 %, males - 34 %. The parameters of the Bertalanfi equation are characterized by the following values: L =38.8 cm, K = 0.12, t° = -2.67. The fecundity of the roach on average is 30.2 thousand eggs and tends to increase with increasing length and weight of the fish. As the roach grows, the composition of its food changes significantly. The maximum fed roach length from 10 to 20 cm.

TO STUDY THE BIOECOLOGY OF CASPIAN SHRIMPS

Only two species of shrimps live in the Caspian Sea: Palaemon elegans and P. adspersus (Crustacea, Decapoda: Palaemonidae), which were introduced to the Caspian Sea in 1931-1934 during the introduction of mullets. Data on the biology of these species of shrimps are reflected only in the works by E.N. Kudelina (1950) and M.P. Marochkina (1980). This determines the relevance of research on the current state of the Caspian shrimp population. The material was collected in various areas of the Middle Caspian Sea in the summer-autumn period. Both species live up to five meters deep. P. elegans prefer coastal underwater objects with dense thickets, P. adspersus - open shallow waters with sandy-muddy soil. To the north of Makhachkala, P. elegans predominates, to the south, the number of both species is the same, and to the east, P. adspersus dominates. The characteristics of breeding females are presented, and the dependence of fecundity on the length of egg-bearing females is revealed. The absolute fecundity increased with the increase in the size of the females. Regression equations reflecting the relationship between fecundity and length of egg-bearing females of P. elegans and P. adspersus are calculated, expressed by power equations, respectively: E = 0.044947 · L265356 and E = 2.323 · L17.4, where: E - fecundity, L-length. In October 2017, in May and October 2018, several specimens of the subtropical freshwater shrimp Macrobrachium nipponense were found downstream of the Terek River. Probably, in the near future, the species composition of the Caspian shrimp will be replenished with another species.