Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2019 number 1

The paper presents a mathematical apparatus based on the requirement of preserving tautochronism in each of the diffraction orders of a harmonic kinoform lens. The apparatus was used as the basis of a method for calculating the lens microstructure.яThe method limits the relative longitudinal chromatism of the lens to a given level and provides the initial parameters necessary for the radial calculation and optimization of the optical system with a harmonic kinoform lens using well-known commercial optical design computer programs

The present study is aimed at solving the problem of in situ thermometry of low-temperature processes of molecular beam epitaxy of indium antimonide. A spectral ellipsometric method for measuring the temperature of InSb epitaxial layers is proposed. The method is based on the temperature dependence of the energy positions of the critical points. The spectra of ellipsometric parameters of the material in the temperature range from 25 to 270^o are measured. The analysis of these spectra shows that the most temperature-sensitive parameters are the spectral positions of the peaks of the ellipsometric parameter Ψ, which are manifested near the critical points E1 and E1 + Δ1. It is found that the dependences of the peak positions on temperature in the above-mentioned temperature range are linear functions with the slope factors of 0.21 and 0.10 nm/^o, respectively. These factors determine the sensitivity of the method and ensure the temperature measurement accuracy within 2-3^o

Diffusion burning of a hydrogen jet is studied by methods of the Hilbert optics. A diagnostic system based on the batch-produced IAB-463M device is implemented, which includes a specially developed Hilbert filtration module coupled with a light source. The influence of local turbulent perturbations (puff or slug) arising in the tube forming the jet on the dynamic structure and flame evolution is revealed. This phenomenon can be used to control the space-time structure of the flame

A procedure of layer-by-layer investigations of characteristics of thick amplitude-phase gratings by the method of laser heterodyne tomography is presented. The parameters of a thick grating nonlinearly written on an additively colored crystal of calcium fluoride (CaF2:Na) are estimated. The main theoretical postulates of laser heterodyne tomography are experimentally validated

The effect of the photoresponse nonlinearity of a holographic material on the achievable diffraction efficiency of holograms has been studied.яIt has been shown that the interaction between the hologram form factor and the photoresponse nonlinearity leads to an increase in diffraction efficiency in comparison with a linear photoresponse. Numerical calculations for the photoresponse nonlinearity corresponding to Reoxan phase holographic material are presented

The direct problem of light scattering for a fiber optic Bragg grating is considered.яThe formulation and solution of the problem based on the transfer matrix method are discussed.яA variant of the method is proposed which reduces to a a universal recurrent algorithm similar to the sweep algorithm and convenient for computing.яThe elements of transfer matrices were calculated with the third local order of accuracy on an uneven computational grid along the coordinate in the approximation of coupled modes using the finite volume method.яThe recurrent algorithm was used in numerical calculations for the direct scattering problem for a Bragg grating with apodization and nonlinear chirp.яNumerical simulations confirmed the significant increase in the accuracy of calculations for solving the scattering problem on the nonuniform grid

The mode composition of a four-layer optical waveguide consisting of an ion exchange channel waveguide in glass coated with a highly refractive nanoscale dielectric film has been studied.яIt has been found that varying the geometric dimensions of the film changes the polarization states of the second and third waveguide modes: the TM0 mode is transformed into the TE1 mode, and the TE1 mode becomes the TM0 mode.яBased on this, a new method of constructing a waveguide polarization converter has been proposed and experimentally confirmed

A new terahertz (THz) imager based on THz-to-IR conversion has been proposed and studied.яThe THz-to-IR converter consists of an ultra-thin resonant THz absorber (meta-absorber) whose backside is coated with an emission layer with an emission coefficient close to unity. The absorption of THz radiation causes heating of the converter, which was recorded with an infrared camera from side of the the emission layer.яThe small thickness of the converter (more than 50 times shorter than the working wavelength of THz radiation) determines its low heat capacity, resulting in an increase in the sensitivity and speed of the visualizer.яOptimization of the optics of the THz visualizer, making cuts in the converter structure to Reduce the blooming and increase the response, and the IR image processing method, which increases the signal-to-noise ratio, provide an increased sensitivity of the THz imager at the level of sensitivity of thermal detectors in the 8-12 $\mu$m IR range

Capabilities of some algorithms of interpolation of quadrature signals currently used for creating parallel-type interface blocks for high-resolution transducers of linear and angular displacements are analyzed

The problem of detection and estimation of spatial coordinates of moving objects by a passive scanning system of vision is solved. Algebraic and algorithmic approaches to determining the spatial coordinates and parameters of object motion are proposed. These approaches differ by taking into account the object velocities in searching for conjugate vectors of directions to the objects. The algorithms developed on the basis of these approaches show that the approach with allowance for motion parameters offers significant advantages of higher accuracy of coordinate estimation and higher probability of detecting all objects

The processing of information signal parameters under conditions of inertialess nonlinear transformation of an input mixture of signals and narrow-band non-Gaussian interference Considered.яThe nonlinear processing of signal parameters is analyzed in the ranges of small and arbitrary detuning between the measured signal parameters and their estimates, as well as at a random signal-to-noise ratio at the gauge input.яTwo variants of optimization of a multichannel discriminator by the criterion of the minimum of the generalized rms error and their corresponding structural schemes were obtained.яThe vector of optimal amplitude characteristics of the nonlinear transformation unit.яIt is shown that the discrimination and fluctuation characteristics of the discriminator are given by the average error signal and its dispersion

Mathematical bases of an integral operator for differentiating 2D images in order to increase their contrast are presented. Images are formed by an optic-electronic device under different background conditions. It is proven that the operator suppresses high-frequency components of images, generated by an applicative background and additive noise of the device. The universal property of the operator is determined, from which the known key differentiation operators are derived: gradient, Roberts, and Laplace operators. The results of contrasting real images by the proposed operator are presented

A specifically planned experiment based on obtaining a required family of estimates of supporting integral curves (approximately described in a given finite system of base functions) is used to solve a problem of active identification of a dynamic object, which corresponds to an a priori unknown differential equation. In view of the fact that experimental data may contain fluctuation and singular interference, a method is developed for optimal unbiased estimation of linear numerical characteristics of the object behavior and approximate analytical solution (differential equation), which is valid for a given set of permitted time values and initial condition. The basic characteristics of the method are substantiated, and the results of the computational experiment are presented

This paper systematizes and generalizes data on the specific features, operation modes, and technical characteristics of world-class ground-based solar telescopes in order to obtain information required to develop and design an automated control systems for the large solar telescope included in the National Heliogeophysical Complex of the Russian Academy of Sciences

The paper deals with the problem of ascertaining the value of air flow velocity necessary to prevent electric current through the motion of ionized air between two asymmetrical electrodes. By means of this experiment, the authors aim to prove the ion basis for the phenomenon of a mechanical force generated by a system of asymmetrical electrodes connected to high voltage. Particle image velocimetry (PIV) is used to precisely map the vector field of the air flow around the electrodes. The calculated and measured values of air flow velocity are compared, and good agreement between them is found.

The possibility of using a combined method of control of an incompressible turbulent boundary layer on the NACA 0012 airfoil is studied experimentally and numerically. The method is based on air blowing and suction through finely perforated walls, which are parts of the airfoil. The study is performed for Reynolds numbers Re_c=0.7 · 10⁶ and angles of attack α =-6 - 60. It is demonstrated that the mechanism responsible for changes in the aerodynamic characteristics of the airfoil is the same for all variants of the control action in the form of air blowing and suction: an increase in pressure due to air blowing on one side of the airfoil and a decrease in pressure due to air suction on the opposite side lead to an increase in the lift force and, finally, to a gain in the lift-to-drag ratio of the airfoil, which reaches three units at α ≈ 0^o. Unfortunately, the efficiency of this method of boundary layer control decreases with increasing α.

A problem of a far field generated by internal gravity waves from an oscillating point source of perturbations that moves in a vertically infinite stratified medium with variable buoyancy. For a simulated quadratic distribution of buoyancy frequencies, analytical solutions of the main boundary-value problem are obtained, expressed through parabolic cylinder functions. Asymptotic solutions constructed in this paper make it possible to describe amplitude-phase characteristics of far fields generated by internal gravity waves in a stratified medium with a variable Brunt- Väiää frequency.

A Couette flow of liquid, described by a modified Vinogradov-Pokrovsky model with a non-monotonic flow curve is simulated. It is shown that the analytical solution of the stationary problem has an infinite set of solutions. The time-dependent problem is numerically simulated in the assumption that the components of the structural tensor take values corresponding to a current change in the velocity field. It is determined that the time it takes for the plate velocity to reach a given value significantly affects the velocity profile and the dependence of tangential stresses on an operating shear rate. It is shown that, as this time decreases, the shear banding of the flow is observed not only for shear rates corresponding to the downward branch of the flow curve, but also in the entire domain of its ambiguity.

The filtration of a graphene suspension through a core sample has been studied experimentally. It has been found that at the oil-water interface in the porous medium of the core sample, a transient multilayer microheterophase structure consisting of planar graphene nanoparticles, hydrocarbon oil molecules and surfactants is formed. It has been found that with an increase in the concentration of graphene nanoparticles, the volume fraction of the displaced oil increases and the volume fraction of water in oil decreases.

This paper presents the results of the numerical calculation of gas filtration in a low-permeability gas formation with a fractured well. It is assumed that finite-conductivity filtering is described by Darcy law. The Peng-Robinson equation was used to take into account the dependence of the PVT properties of the gas on pressure. We studied the effect of fracture conductivity and formation permeability on the distribution of pressure and gas properties in a “fracture-formation” system and on the dynamics of pressure of the well and the gas production rate in the well during well-testing.

The analysis of influence of the sum of effective temperatures (SET) that gypsy moth embryos receive in midsummer-autumn period until overwintering on diapause duration and SET of eclosion, and the assessment of the effect of short-term temperature rising during dormancy period on eclosion duration and diapause strength have been performed. The effect of the midsummer-autumn SET on diapause duration and on the SET of spring eclosion subject to conditions of diapause and following quiescence was found. We showed that short-term rising of temperatures over the development threshold led to proportional decrease of eclosion duration in case the SET of eclosion was lower than 200 degree days. If the SET of eclosion was higher than 200 degree days, the effect of this exposure had either no effect on the eclosion duration, or led to stronger dormancy. The short-term temperature rising led to increased mortality of the embryos which received low midsummer-autumn SET (about 400-450 degree days with threshold about 7 ^оC). The embryos that received high midsummer-autumn SET (about 1300-1500 degree days with threshold about 7 ^оC) showed no increased mortality. Based on these results, we suggest that the populations of south origination have stronger diapause due to the adaptation to the short term casual temperature risings above the embryo development threshold in winter-spring period, that can lead to the untimely eclosion of gypsy moth larvae.

The biotope distribution of Myodes rutilus in the zonal and provincial aspects based on materials collected in the second half of summer for the period from 1954 to 2015 in the plain and mountains of Western Siberia was analyzed. The previously noted preference for plain and mountain forests containing dark coniferous species within the taiga zone of the plain, the Northeast Altai and the Kuznetsk Alatau was confirmed. On the basis of cluster analysis of the matrix of similarity of coefficients of abundance indices the classification of habitats of northern red-backed vole by the degree of optimality of environmental conditions (favorability) for this species was made. The subtypes of habitats characterize an abundance to a lesser extent than types. According to the classification and the structural graph the dependence of abundance is tracked on the zonal-subzonal affiliation of habitats, provincial differences in mountain areas, and also on the vegetation types, altitude zonation in the mountains, the degree of afforestation, the composition of forest-forming species, flooding, swampiness and plowing. The highest correlation between the distribution of the northern red-backed vole and habitats in Western Siberia is traced to warmth and humidity (zoning and subzoning on the plains and altitudinal belts in the mountains). Our research on the distribution of Myodes rutilus clarifies the results of the analysis conducted by previous researchers and gives a more detailed picture of its distribution in habitats.

Population and number dynamics of small mammals in the vicinities of Torey lakes (South-Eastern Transbaikalia, Russia) were characterized between 2008 and 2017. The monitoring was carried out against the backdrop of the complete drying out of these some of the largest lakes in the region. The stability of the fauna of small mammals was revealed over an 80-year period, although the structure of communities rearranged itself significantly as a result of changes in moistening of the territory. Xerophilous species of mammals had an advantage in the period of studies in the dry climate phase. Correlation analysis showed a possible link of population dynamics of some common species of small mammals with precipitation of current and previous years or with the sum of precipitation of some spring (in one case, winter) months.

The intraspecific relationships between individuals in experimental conditions of two populations of Shikotan vole Myodes sikotanensis from Sakhalin and Shikotan islands were described. We studied the interactions and acoustic activity of voles in groups consisting of 4 males and 2 females. We observed in groups of both populations aggressive and friendly behavior. However, voles from the Shikotan Island were more active and showed more friendly behavior, which is characteristic of the grey voles. Voles from the Sakhalin Island population had mainly aggressive interactions and among them hierarchical relations of domination-subordination were formed which is characteristic of the bank voles. The alarm sound was represented mainly by the squeaks emitted by the voles in the home protection, or in other interactions by the individual experienced discomfort. Acoustic signals do not play an essential role in the formation of relationships in the groups of Shikotan voles.

The results of eddy covariance measurements of carbon dioxide and water fluxes above spruce forest in the middle taiga subzone from April to August in 2013 and 2016 are presented. The ecosystem of spruce forest turned from source to sink of CO2 at average daily air temperatures below zero in late March and early April, in 2016 it was two weeks earlier than in 2013. The maximum net ecosystem exchange (NEE) of CO2 was recorded at the end of June and the beginning of July. In 2016 the average daily NEE of spruce forest decreased at high air temperature and a low amount of precipitation at the beginning of the growing season, and turning from the sink of CO2 to the source was observed in early August. Net exchange of CO2 between spruce and the atmosphere from April to August in 2013 reached -327 g C/m2, and in 2016 -174 g C/m2. Seasonal evapotranspiration of spruce forest in those years was 239-247 mm / m2, and the average value of the water use efficiency (WUE) for photosynthesis in the season was 2.3-3.3 g C/kg H2O. WUE was relatively constant during the growing season as a result of a close relationship between the exchange of CO2 and water, the main processes ensuring the production of organic matter in the spruce forest ecosystem.

Nematode communities were studied in the root-inhabited soil layer under trees introduced in the Polar-Alpine Botanical Garden of Kоla Scientific Centre, RAS in Murmansk region. Nematodes of 48 taxa were found under introduction; bacterial feeders and plant parasites showed the greatest diversity (56 and 21 % of the total number of taxa, respectively). Tendency of genera number decreasing was shown in series “deciduous tree - coniferous tree - natural biocoenosis”; and similar regularity was obtained for plant-parasites. There were found phytoparasitic taxa rare for North-West of Russia. An adaptive mechanism related to delay in egg laying by female and further intra-uterine development of juveniles was found in the populations of Rhabditis producta Schneider, 1866 (bacterial feeding nematodes). This mechanism is very important for offspring survival in unfavorable environmental conditions in the North. The study allows to establish reliable correlation between taxonomic diversity of nematodes and majority of investigated soil properties (pH, ash content, N, P): relative abundance of omnivorous and associated with plants nematodes correlates with content of organic matter, organic carbon, C : N ratio; and relative abundance of plant-parasitic nematodes shows a correlation with vegetation cover.

The features of the long-term fluctuational dynamics of the populations of tuberoid orchids ( Neottianthe cucullata and Dactylorhiza incarnаta ) growing in various phytocoenotic and climatic conditions are presented as the realization of the mechanism of population stability under conditions of a heterogeneous habitat. The work shows ability of populations to take advantage of microsites favorable for their existence, the conditions in which are determined by the temporal dynamics of climatic factors, the abiotic environment and interspecific interactions. It is established that the unidirectional dynamics of the populations of tuberoid orchids, determined by demutative-digressive successions in plant communities under the combined effect of abiotic, biotic and anthropogenic impacts, leads not only to a decrease in abundance and density, but also to the destruction of the spatial distribution and the population life stage structure. The relationship between species abundance and climatic factors is assessed using a correlation coefficient which is significant for adult reproductive plants of forest species ( N . cucullata ) and for juvenile plants of meadow species ( D . incarnаta ).

The authors estimated habitats’ ecological conditions and demographic parameters of Pulsatilla patens (L.) Mill s.l. in 10 coenopopulations in Kirov Region. The study states that within the investigated area the species is present in pine communities of green moss and herbaceous types with prevalence of anthropophobic species. Large proportion of anthropotolerant species is typical of communities significantly suppressed by human activity. P. patens s.l. is a hemistenobiotic species whose ecological space amplitude in Kirov Region does not exceed the limits of Tsyganov’s scale ecological range [1983], but soil humidity scale values are approaching the maximum limit and scales of humidity variability - near the minimum. Discomfort index calculated with phytoindication data allows determining the level of favour. We have determined that conditions of mixed herbs - gramineous meadow with bracken coincide with optimum ecological parameters for the species growth. The least favourable conditions for P. patens s.l. development are formed in cowberry-green moss pine forest and herbaceous pine forests where maximum discomfort indices are marked: 1.09 and 1.01, respectively. The coenopopulations studied are of low density and generativity, which demonstrate the decrease tendency on an ecological conditions gradient.

The Fagaria vesca L. seed reproduction in natural populations is characterized by a combination of xenogamy and autogamy. To determine the proportion of xenogamy, a field experiment was conducted. During flowering, inbred line N 08-2 was planted with native wild strawberry populations at two different biotopes. The inbred line is marked with a recessive allele c with a light yellow color of the berry. Plants from native population form berries with only red coloring - a dominant trait. Seeds from the plants of line No. 08-2 were collected after the flowering period. Genetic analysis of these seedlings was carried out on the genetic marker “berries coloring”. In case of autogamy realization, the seedlings had a light yellow color of the berries. If xenogamy was carried out, the plants had red berries. It occurred as a result of insects transfering of pollen with dominant allele C from native plants F. vesca . Significant differences in the ratio of systems of crossing - autogamy and xenogamy among a number of experimental plants after genetic analysis were shown. However, the integral value of xenogamy, realized in the seed progeny, in both natural populations of F. vesca was similar and amounted to 21 %, and the average share of autogamy was 79 %. This ratio of crossing systems for F. vesca population, is optimal for maintaining the heterogeneity of population and realizing life strategy in conditions of natural growth. With xenogamy, a certain proportion of heterozygous heterozygotes is maintained in the population capable of mastering new habitats, while the strategy of explerents is implemented. Autogamy contributes to an increase in the proportion of inbred genotypes - patients. Thus, under the conditions of the environmental heterogeneity of Western Siberia for F. vesca , due to xenogamy, there are conditions for implementing any of the three types of strategies: violents, patients and explerents, depending on the conditions of plant existence.

This work is aimed at assessing the dynamics of the composition of soil water in coniferous forests subjected to air pollution from copper-nickel smelters “Severonickel” in the Murmansk region. Objects of investigations were the most common in boreal zone spruce forests with dwarf shrubs + green mosses and pine forests with dwarf shrubs + lichens. The obtained results showed a significant intra- (below the crowns and between the crowns) and inter-biogeocoenotic (spruce and pine forests) variation in the composition of atmospheric deposition and soil waters in forests under pollution. Atmospheric deposition of pollutants and leaching their compounds from all soil genetic horizons were tens (sulfates) and hundreds (copper, nickel) times higher than in reference sites, and their fluxes below the crowns were usually more intense than between the crowns. Long-term dynamics (from 1993 to 2012) demonstrated reliable trends in reducing concentrations and leaching sulfates and heavy metals from the soil. The molar ratio of basic cations to aluminum (BC/Al) in soil waters from all soil horizons did not drop to the critical level, whereas for mineral nitrogen the lowest critical level (0.2 mg/l) was exceeded in waters from all horizons at all stages of digression. It has been shown that for early detection of exceedances of critical level for mineral nitrogen in soil waters an evaluation of their composition is necessary not only between the crowns but also below them.

The combustion of monodisperse titanium particles with a characteristic size of 38 and 320 m moving in air has been studied. Pyrotechnic samples generating monodisperse particles were burned in a chamber with a nozzle to impart initial velocity to burning particles. Particles were accelerated by the combustion gas flow from the nozzle. The maximum path-averaged particle velocity relative to the ambient air reached 7.9 m/s. Combustion of moving particles was carried out in a quartz tube 2 m long. At the end of the combustion, combustion products - oxide aerosol - were sampled from the tube using a thermophoretic precipitator. The size distribution function of nanometer-sized spherule particles was determined by processing electron micrographs of samples. The velocity and burning time of the burning particles were determined by video recording at a velocity of 300 frame/s. It was found that increasing the speed of motion of agglomerate particles with a diameter of 320 m relative to the gas from 0.9 to 7.9 m/s leads to a decrease in the size of the spherules from 28 to 19 nm and to a decrease in the burning time from 0.45 to 0.26 s.

The study of an electrothermal explosion (ETE) of a titanium - soot mixture under quasistatic compression is described. Experimental dependences of thermal and electric parameters of the ETE on the power of electric heating are obtained. It is shown that the heating rate of a reacting mixture significantly affects the ignition temperature and maximum temperature of the ETE. It is determined that, at the stage of pre-explosion heating, the electric resistance of the mixture decreases by 90-95%, and the rate of the temperature rise during a thermal explosion is independent of the heating rate of the mixture. A technique for determining the ignition time and temperature, based on measuring the thermal and electric parameters of the ETE. Liquid-phase and solid-phase interactions in the titanium - soot mixture powders are discussed.

The experimental study of the high-temperature interaction kinetics of a titanium - soot mixture under quasistatic compression in an electrothermal explosion (ETE) is described. Dependences of the heating rate of a sample mixture on temperature are obtained, and the effective values of the energy of ignition activation and thermal explosion are calculated. The formation of the microstructure of intermediate and final interaction products is investigated. It is shown that the formation of a final product occurs according to a shell - core mechanism. The high rate of the solid-phase interaction of titanium and soot is explained by the formation of micropores and microcracks in the intermediate product, which ensure the high rate of surface diffusion of carbon.

The effect of thermocapillary convection on heat transfer in a gas-free combustion wave with a melting reagent is studied analytically and numerically. Convection rate estimates are given. Equations for a burning rate in conductive and convective heat transfer are obtained. Numerical calculations confirm the conclusions of an analytical analysis. Calculated dependences of the burning rate on porosity and phase transition parameters are obtained. The development of instability of a combustion wave propagation in self-oscillating regimes, caused by the action of thermocapically convection, is revealed.

A mixture of SiO₂, C, and Mg powders is mechanically milled in a planetary ball mill during different milling times of 60, 90, 120, and 150 min. The milled powders are then used in a self-propagating high-temperature synthesis (SHS) reaction to produce the Si-SiC composite. The thermal properties of the milled powders are determined by using differential scanning calorimetry and thermogravimetry. The chemical composition and microstructure of both as-synthesized products and as-leached powders are characterized by the x-ray diffraction analysis and scanning electron microscopy, respectively. The results show that an increase in the milling times of the mixture of the reactant powders has a significant effect on the thermal properties, diffusion processes, and SHS reaction mechanisms, as well as on the phase conversion and the final yield of the products.

A mathematical model of synthesis in a mechanically activated 3Ni-Al is constructed in a macroscopic approximation. Different combustion regimes as a function of duration of mechanical activation and the time of the isothermal exposure of the mechanical mixture are determined. Experimental data are used to calculate kinetic constants that characterize the transformation of the substance at the stage of mechanical treatment.

Electromagnetic measurements of the particle velocity are performed in a situation when the detonation wave reaches the interface between a high explosive (HE) powder and a window made of an inert material (Plexiglas). PETN, RDX, and HMX with densities close to the natural bulk density are studied. As it is necessary to measure not only the averaged velocity profile, but also possible fluctuations at scales of the order of the HE grain size, a method of measurements by small sensors with the working arm length approximately 1 mm is developed and tested. In most experiments, profiles with clear chemical spikes are obtained; in some of the measured results, however, the chemical spike cannot be identified on the background of sharp signal oscillations, which may be considered as manifestation of the nonclassical mechanism of wave propagation (explosive combustion in Apin's classification). As compared with the previous study, the present results suggest parallel operation of the shock and convective mechanisms with domination of each mechanism at certain segments of the wave front.

The nonequilibrium radiation arising from the ignition of a 10 % stoichiometric hydrogen-oxygen mixture doped with combustion inhibitors and diluted with argon behind shock waves was studied. The addition of halogen-containing inhibitors led to increased UV radiation around the 220 and 411 nm wavelengths characteristic of the HO₂ radical and H₂O₂ and H₂O molecules, instead of the expected reduction in the super-equilibrium radiation of active radicals in the ignition zone. Therefore, the hypothesis about the inhibition mechanism due to extinguishing by the excited HO₂* radical is not confirmed, and the effect of inhibiting additives is due to the binding of H and O atoms.