Home – Home – Jornals – Avtometriya 2009 number 5

A new algorithm for processing a series of images with a low sampling frequency, aimed at forming high-resolution images, is proposed. The algorithm is based on the use of a linear filter with a limited aperture calculated by the method of optimal linear prediction. Experimental estimates of the quality of high-resolution image reconstruction are given for different values of the filter size, number of initial images, and level of accompanying additive noise.

Some modifications of the algorithm of image construction with a high sampling frequency are proposed. These modifications multiply reduce the computational costs with an almost unchanged quality of the result. Software implementation of the proposed modifications of the algorithm allows the latter to be used in video surveillance systems for real-time formation of high-quality image fragments.

Features of the spontaneous succession in a broad-leaved forest landscape (Polessye province, Belarus) are considered. The regularities of changes of the vegetation (specific structure, vital forms, phytocoenotic structure) and the characteristics of ecotope (on the basis of phytoindicator scales) over the succession gradient were revealed. It was established that the most essential changes of microclimate and soil occur at the stage of formation of the wood ecosystem.

Influence of reservation rate on natural degraded pasture areas at different stages of pasture digression was studied during the years 1994-2004 under the conditions of the right-bank forest-steppe near the Ob river. It was revealed that the isolation of pasture phytocoenoses of a steppe meadow from pasturing causes an increase in the productivity of grass but due to different economic-botanical groups of plants. An increase in the productivity at the initial stage of digression occurs due to overgrowth of legumes and motley grass, while at the final stages mainly due to an increase in the mass of cereals. Removal of pasture load promotes the formation of intermediate communities; in this situation, an increase in their species diversity is to a high extent due to the presence of closely located phytocenoses which are richer from the floristic viewpoint.

Correlations between the structure of phytocenoses representing different stages of the process of forest formation in the Polar Urals mountains and moistening of ecotopes, as well as between the lower layers and forest stand are considered. Current density of trees and undergrowth is not exhaustive of the ecotope capacity, and therefore open woodland can be transformed into closed forest. Perspectives of such a transformation within a certain plot may be assessed by percentage of mesophilic and relatively thermophilous (hypoarctic + boreal) species in the herb-dwarf shrub layer.

The experience of growing field-protective forest belts of different species composition under arid conditions of the Shira steppe of Khakasia is considered. The results of the investigation of species variety, distribution of grass plants over ecological groups, and revelation of the regularities of species composition dynamics, structure and biomass of living grass cover in field-protective forest plantations are reported. The question concerning the influence of development stage of the living grass cover on the forest belts growth is considered.

Specific role of climatic, geographic, lithologic, hydrochemical etc. conditions of soil formation in the differentiation of the soil cover in the Turan-Uyuk depression in Tuva is considered.

Current state of woodland belts in the Altai Territory is anаlyzed; forestry activities aimed at the protection of the existing forests and planting the new ones to improve the ecological situation in steppe Kulunda are planned.

Investigations of the climatic parameters and protective characteristics of forest ecosystems were carried out at a small drainаge area in the upper reach of the Ussuri river (Southern Sikhote Alin') as an example. Anаlysis of the 40 years dynamics of air temperature and the regime of atmospheric precipitation showed that changes of the temperature background and preciрitation redistribution within a year occur: a trend to an increase in the average annual air temperature is observed as a result of warming during the cold and transition periods of a year, the number of years with insufficient wetting during the summer and autumn seasons and with snowy winters increases. The ecological potential of the basin, expressed in the quantitative indices of water-regulative and water protection role of parent forests, is decreased after the experimental felling of main use. With the general increasing negative dynamics of the forest resources of the region, climatic changes may cause an increase in the surface drainage during spring, a decrease in the channel runoff, worsening of watering and water quality of large river basins.

Rare plant species of Central Siberia, included in the regionаl Red Books, are considered from the positions of their population strategies. The analysis of potential possibilities and positions of species populations is given. The functionаl approach to the evaluation of rare plants behavior is proposed.
The functionаl typology of rare plants and specific features of their behavior is recommended to be used for the development of protection modes for rare plants.

Results of the comparative anаlysis of the state of larch plantations in the regions of Krasnoyarsk differing in the levels of air pollution are presented. The features of the structure of crown and the correlation structure of habitus signs and tree states observed in the regions with medium and high level of air pollution are shown. It is concluded that the sensitivity of correlation signs is higher and they are suitable to reveal changes that cannot be diagnosed with the help of the eye survey of tree state.

On the basis of investigation of the features of pollen of 16 coenopopulations of Potentilla bifurca in five provinces of the Altay-Sayan mountain region, two groups of coenopopulations were revealed: western and eastern. Both groups are characterized by the high intrapopulation (44,7-63,9 %) and lower interpopulation (11,4-42,2 %) variability. The observed similarity between the groups of coenopopulations of P. bifurca from different geobotanical provinces is determined by their common origin in the steppe communities of Pliocene-Pleistocene.

Peculiarities of the distribution Coniogramme intermedia within the Russian Far East are marked. The characteristics of location, species diversity and structure of plant groupings in the inhabited placed are presented. Some measures to preserve endangered communities of coniferous and broad leaf forests with the particiрation of Coniogramme intermedia are proposed.

Seasonаl dynamics of Anаbaena flos-aquae (Lyngb.) Breb., including vegetative cells, akinetes and akinete envelopes in bottom sediments and water column in a small Siberian reservoir was studied. It was assumed that even in a rather shallow mixed water reservoir, water bloom with cyanobacteriae starts in the littoral zone and then spreads over the whole water reservoir. Two types of akinetes were observed: in the first half of summer Anаbaenа formed akinetes, which served for vegetative reproduction and germinated in water column soon after differentiation, while in the second half of summer the akinetes served as resting stages, which were deposited to bottom sediments. It was demonstrated that even in the comparatively shallow unstratified reservoir the summer developments of the A. flos-aquae population started in littoral and no rise of akinetes from the sediments of the deeper central station occurred. Thereby, bottom sediments of the profundal parts of reservoirs seem to be a "cemetery" for akinetes of cyanobacteria, which never will germinаte from these sediments. At littoral and open-water stations, abundance and seasonal dynаmics of akinetes in water column and their sinking pattern were very similar. However, seasonаl dynаmics of the abundance of akinetes in sediments in these two reservoir locations differed: whereas the abundance of akinetes in open water increased permanently during the summer, that in the littoral decreased soon after their sedimentation. During winter, the abundance of akinetes in bottom sediments tended to decrease. The reasons of this phenomenon are unknown yet.

The living plankton diatom - Asterionella formosa of Lake Baikal and of the Irkutsk reservoir was studied with the use of light microscopy. The new facts were obtained which provide evidence of the occurrence of multiрle asexual reproduction of Asterionella formosa.

Distribution of phytoecdysteroids in the Caryophyllaceae family is anаlyzed; the largest number of ecdysteroid-containing species was discovered in this family. The species of this family synthesize the wide variety of steroid compounds - the hormones of moult and metamorphosis of insects, many of which are not detected in other plants. The major part of the species of the Caryophyllaceae is characterized by the high levels of phytoecdysteroids. The flowers of the perrenial Silene frivaldszkyanа accumulate up to 7 % of 20-hydroxyecdysone.

Accumulation of phytoecdysteroids in the agropopulations of R. carthamoides (Willd.) Iljin and S. coronata L., as well as their resistivity to phytophagans over the age periods of ontogenesis were investigated for 16 years. As a result of the investigations, the species-specific features of the accumulation of ecdysteroids in vegetative and reproductive organs of plants were determined; interrelations between the distribution of phytoecdysteroids in the structure of plants and the ecological relations with insects were revealed; the factors promoting damage were outlined; the damage caused by pests was evaluated.

The notion of species diversity includes two components: species richness and uniformity. Species diversity is the number of species per unit area (geobotanical description). Uniformity is the distribution of species over their abundance in a community. There is a positive correlation between these indices; however, high species richness is not necessarily accompanied by high uniformity. It is impossible to compare the species richness of the communities formed by the plants of different size (rain tropical forest and meadow steppe). High species diversity is peculiar to the plant communities with a medium level of productivity, medium degree of disturbance and is not connected with their stability.

For Euphorbia genus of Northern Asia as an example, some aspects of the investigation of phylogenetic links of rare and endemic species are considered as the scientific foundation of the conservation of biological diversity. Results of the investigation of specific processes of evolutionаl morphological transformations, ecological and geographic differentiation in different groups of species including rare and endemic taxons are presented.

For the representatives of cereals (Poaceae) characteristic of the flora of the Asiatic part of Russia, a comparative anаlysis of the ecological ranges of plant species confined to the coastal regions and the species for which the major part of the range is situated within the continental regions (interior Asia) was carried out. The anаlysis was carried out according to the ecological phytocoenotic groups: coniferous and mixed forests, broad-leaved forests, meadows, communities of spray zones, rocks and stony rubbly outcrops and talus. The trends in the changes of the whole set of indices of the ecological ranges of species, accompanying the transition from the continental climatic conditions of Interior Asia to the Pacific coast with its monsoon climate were revealed.

Biodiversity patterns of the woodland-steppe ecotone in southeastern Inner Mongolia were investigated. Controlled by climatic factors, the plant species diversity of the woodland-steppe ecotone is medium in comparison to the adjacent woodland zone and steppe zone. From woodland zone, through the woodland-grassland zone and woodland-steppe zone, to the steppe zone, about 2/3 species were replaced at each boundary, only 7 herb species were detected to be distributed in all the four vegetation zones. Landscape classification based on landform, climate and vegetation shows that landform condition is most critical to landscape diversity in the studied area. The most fragmented landform in the woodland zone does not necessarily lead to low plant species diversity. However, similar understory species in different woodland types lead to a continuous woodland vegetation and hence a high species richness. High fragmentation in the woodland-steppe zone and discontinuous distribution of woodlands might be a driving factor for lower species richness in it. Reconstruction of the Holocene climatic changes and vegetation development demonstrates that the highest plant species diversity occurred in the ecotone before 4500 to 2500 ¹⁴C yr B. P. at different sites, while the woodland zone moved much further northwestward. When woodlands retreated from the current ecotone with climatic drying, the fragmentation of woodlands in the current ecotone led to plant species loss.

The diversity of the West-Siberian lichen biota and its distribution within the boundaries of its two components - the West-Siberian plain and the south West-Siberian mountains - were studies. At present, the level of the diversity of West Siberia achieves 1845 species from 325 genera and 95 families, of the West-Siberian plain - 1421 species from 271 genera and 86 families, of the south West-Siberian mountains - 1682 species from 312 genera and 94 families.

Data on nemoral lichens in the Dzherginski state nаtural reserve (Northern Pribaikalia) are reported. The distribution of the lichens of the nemoral element is anаlyzed, a conclusion concerning their most preferable habitats is made. Nemoral lichens prefer dark coniferous forests, exposed slopes and nearby thermal springs in middle elevation.

Measurement results on the mean velocity fields and fields of velocity pulsations in the supersonic flows obtained by means of the PIV measurement set “POLIS” are presented. Experiments were carried out in the supersonic blow-down and stationary wind tunnels at the Mach numbers of 4.85 and 6. The method of flow velocity estimate in the test section of the blow-down wind tunnel was grounded by direct measurements of stagnation pressure in the setup settling chamber. The size of tracer particles introduced into the supersonic flow by a mist generator was determined; data on the structure of pulsating velocity in a track of an oblique-cut gas-dynamic whistle were obtained under the conditions of self-oscillations.

The interaction of disturbances in supersonic boundary layer is considered within the framework of the weakly nonlinear stability theory for the Mach number M = 2 on the solid and porous surfaces. The interrelations in several triplets composed of two- and three-dimensional waves at the frequencies related by the phase synchronization conditions were modelled. It was found that their interactions on the solid surface are much stronger in the asymmetric triplet. It was found that on a porous surface, the linear increments of vortex disturbances increase considerably, the region of dangerous frequencies widens, and the spatial extension of the existence of growing oscillations increases. Nonlinear interactions are, as a rule, much more intense in comparison with the case of an solid surface; they realize in a broad frequency range, which results to a broadband growth of the Tollmien ⎯ Schlichting subharmonic vortex waves. An increase in the surface porosity leads to the intensification of nonlinear processes.

The transition of the boundary layer from the laminar to the turbulent state on a smooth flat plate at a zero angle of attack is studied in the range of Mach numbers М_∞ = 2−6. It is demonstrated that the results measured at the end of the transition region can be approximated by a simple dependence suitable for applications, which does not require additional measurements, is valid in the range of Mach numbers М_∞ = 2−10, and, with an error lower than 20 %, can be used to estimate the location of the transition region on a flat plate in geometrically similar wind tunnels.

The results of numerical modelling and experimental investigations of high-enthalpy turbulent flows in the neighborhood of 90-degree backward-facing steps at the Mach numbers M_∞ = 2−4 are presented. The experiments were conducted in the hot-shot wind tunnel IT-302M of ITAM SB RAS. The computations were carried out on the basis of the full Favres-averaged Navier ⎯ Stokes equations augmented by the Wilcox turbulence model. The temperature factor influence on the flow structure in the separated zone and temperature distributions was investigated numerically for different Mach numbers. The wall temperature is shown to affect significantly the quantity and sizes of recirculation vortices as well as the temperature distribution in the zone of flow separation and reattachment. The computational results are compared with experimental data on the pressure distribution on the model surface and the wave structure of the flow.

Laminar and turbulent channel flows past a backward-facing step and cross-flow rib were simulated using the commercial FLUENT program package to perform subsequent comparison of FLUENT-simulated data with available experimental results.

The gasdynamic flow structure is studied experimentally and numerically in the zone of jet interaction flowing with considerable underexpansion from two supersonic nozzles located near the spacecraft case. Longitudinal and transversal distributions of the density are obtained by the method of electron beam. They are compared with calculation results for inviscid gas. Generalized dependencies for determination of gas density within the zone of two jets interaction and boundary of this zone are obtained.

An exact analytic solution of the problem of the right circular cylinder in a rarefied molecular gas is constructed in the isothermal approximation. An expression for the velocity of a rarefied molecular gas entrained by the cylinder rotated therein is obtained in the regime of a flow with slip accounting for the second-order correction in terms of the Knudsen number. A generalization of the BGK model of the Boltzmann kinetic equation accounting for the rotational degrees of freedom of gas molecules is used as the governing equation, and the diffuse reflection model is used as a microscopic boundary condition on the cylinder surface. The given approach is shown to enable the consideration of the gas flow dependence on the Prandtl number and the gas temperature.

The known problem of flow transition near a circular cylinder at Re = 40 from a symmetrical form to the Karman vortex street can be considered as the problem of vortex wave development and intensification. Development of three bundles of vortex waves of low intensity is observed in a wake of a cylinder; these bundles are easily visualized as the structures of relative vorticity = Ω(t₁) − Ω(t₀): difference of vorticity Ω at two time moments, t₀ being fixed. In the field of the alternating structure of quadrupoles is characterized by linear parameter l = h/d: the ratio of the width of the central bundle of vortex waves to the distance between the centers of quadrupoles of a "single sign". When l = 0.281 is achieved, which coincides with the value of the same parameter of a stable Karman street, the transition from symmetrical streamlining by viscous incompressible liquid to the vortex street occurs.

The stability to small disturbances of the flow in a pipe of annular cross section is considered in the presence of a spiral magnetic field. The investigated duct configuration consists of two infinite coaxial cylinders between which a weakly electroconductive viscous incompressible fluid is placed, which moves under the axial pressure gradient. The azimuthal magnetic field is created by a current flowing through the central cylinder, and the longitudinal magnetic field is created by an external solenoid. The magnetohydrodynamic approximation is used. It is found that the introduction of the azimuthal magnetic field may lead to a flow destabilization as compared to the case of only the longitudinal magnetic field.

A linear stability problem for a subclass of steady screw flows of a uniform-density inviscid incompressible ideally conducting fluid in the magnetic field is investigated. The necessary and sufficient condition of theoretical (in semi-infinite time intervals) stability as well as the sufficient conditions for the practical (in finite time intervals) instability of the given flows to small screw disturbances are obtained by the direct Lyapunov method. In the case when the theoretical stability criterion is violated, and the sufficient conditions of practical instability are valid, on the contrary, an a priori exponential estimate from below has been derived for the growth of small disturbances under consideration, and the increment of the exponent contained therein is an arbitrary positive constant.

Exact solutions to two problems of solid rotary oscillation in ideal liquid in the presence of gravitation field  have been obtained.

Interaction of sound impulse with porous layer is investigated. The presence of a barrier shielded by the layer and the gap between the porous layer and the barrier is possible. Method of calculation in linear approximation of pressures and tensions in the porous layer, gap, and on the barrier has been proposed. The method serves to interpret data on acoustic waves interaction with porous layer obtained experimentally or with the use of finite-difference methods. Specifics of acoustic wave propagation into the porous layer and further reflection from the barrier has been studied. Comparison of calculation data with experimental data of other authors on impulse propagation through the porous plate submerged in water has been carried out.

Results of measured average expectancy time of n-pentane and n-hexane boiling-up to the boundary of attainable superheating are presented. Experiments have been carried out in glass capillaries with substantially decreasing value of the superheated liquid volume for the preset metastable state (p, T = const). Obtained data fail to prove correlation following from the condition of homogeneity and stationarity of the random process resulting in the superheated liquid boiling-up (J is the frequency of homogenous nucleation, V is the volume of the superheated liquid, is the average life time). Thus, experiments on superheated liquid boiling-up kinetics bound with measurements of average life time in glass capillaries cannot serve a proof of the validity of classical theory of nucleation for superheated liquids since one of the ground conditions ⎯ boiling-up homogeneity ⎯ is not met.

Experimental results on development of crisis phenomena in a falling film of cryogenic liquid at alternating pulse heat release are presented. Experimental data on local temperature evolution along a heat releasing surface are obtained. It is shown that amplitude of heater temperature pulsations depends significantly on the heat flux density and coordinates along the liquid film flow. New experimental data on the critical heat fluxes corresponding to formation of stable dry spots and drying crisis are presented depending on duration of heat release pulses. It is shown that parameters of the forming metastable regular structures and critical drying parameters of the heat-releasing surface are determined by dynamics of the movable boundaries of wetting during self-organization of a system.

An original 3D model was used to numerically examine convective heat-and-mass transfer processes in the melt during the growth of polycrystalline silicon in vertical Bridgman configuration. The flow in the liquid was modelled using the Navier ⎯ Stokes equations in the Boussinesq approximation. The distribution of dissolved impurities was determined by solving the convective diffusion equation. The effects due to non-uniform heating of the lateral wall of the vessel and due to the shape of the crystallization front on the structure of melt flows and on the distribution of dissolved impurities in the liquid are examined.

Experiments and numerical simulation have shown that the two-phase zone of liquid and solid phases concentration, variable over the coordinate, is formed both at alumina heating by laser radiation and at free melt cooling. During heating this zone is formed only at the initial stage of heating. Its width is not large and is lesser than the depth of the heating laser beam penetration due to the effect of intense heat losses through the crystal by thermal radiation and thermal conductivity. Extension of the two-phase zone formed at crystallization is much more under the conditions of free cooling than at melting, and it can cover almost the whole thickness of the melt. Temperature plateau of the brightness (effective) temperature registered at solidification by the pyrometer with the wavelength of 0.65 μm is explained by formation of the extensive two-phase zone. However, this plateau is realized not for all wavelengths. The importance of the melt absorption coefficient influence on probable appearance of temperature plateau is shown. As a result of crystallization with the two-phase zone formation, porous structure consisting of the crystals with small size can be formed. It may cause the diffuse surface reflectivity.

СО₂ lasers with transverse discharge and convective gas cooling find ever-increasing application. One strategy in making such lasers more efficient radiators is increasing the rate of the gas flow through the discharge zone with the help of diametral disk fans-heat exchangers. The application of such fans-heat exchangers, however, entails serious difficulties related to the glow discharge-gas flow interaction. In the present study, we investigate the stability problem for volume discharge in the gas loop of a СО₂ laser with diametral disk fans-heat exchangers.