## Optical absorption in Ge/Si quantum dots at different population densities of the dots states

Published in category «Condensed matter physics»

The polarization absorption spectra of the Ge/Si quantum dot structures with different doping levels under the photoexcitation of nonequilibrium charge carriers have been investigated. The dependence of the optical absorption coefficient of the holes related to the transitions from the ground state of the quantum dots to the states of continuous spectrum was investigated as a function of dopant concentration. The experimental results were explained using a theoretical calculation of the hole energy spectrum in the framework of the quantum box model.

## The polarization tomography of internal stresses in transparent axisymmetrical structures

Published in category «Condensed matter physics»

An approximate method has been proposed for tomographic reconstruction of the internal stresses distribution in the axisymmetrical phase structures with small stress gradient along a specimen axis. The internal stresses determination procedure in glass optical fiber preforms based on the integrated photoelasticity effect was generalized to the objects mentioned. The complete determination of the stress tensor was carried out in terms of the fictious temperature profile concept.

## Morphology of ferriferous glasses contained different percentage of hematite

Published in category «Condensed matter physics»

The morphology of ferriferous glasses with different iron oxide (III) concentration: 15, 20 and 25% and two types of the magnetic porous glasses have been studied using atomic-force and transmission electron microscopy. The droplet iron bearing phase was detected both on the surface and in the volume of ferriferous glasses. The drops size and their density depended on the iron oxide concentration (Fe2O3).

The regions with different pore sizes and the effect of the partial etching of the iron bearing drops have been observed in porous magnetic matrices.

## The growth of gallium nitride layers with low dislocation density

Published in category «Condensed matter physics»

The growth of ‘thick’ (200 nm) AlN layers on sapphire at 1100–1150°C using STE3N MBE system is shown to be the key step to obtain high quality GaN-based heterostructures. An appropriate sequence of AlGaN transition layers grown on such an AlN both allows to reduce dislocation density in GaN down to (9–10)·108 cm–2 in comparison with GaN layers grown on ‘thin’ (10 nm) low temperature AlN nucleation layer. Maximum electron mobility in 1.5 µm thick GaN silicon doped layer reaches 600–650 сm2/(V·s) at electron concentrations (3–5)·1016 cm–3.

## Mathematical modeling and numerical simulation of aeromechanics of the human lung

Published in category «Simulation of physical processes»

The paper contains a review of basic mathematical models of the human lung. During development, models obtained the possibility to describe more and more correctly an activity of both healthy and pathology sick lung. Main attention is paid to results giving a possibility of numerical simulation of the human lung as a whole.

## Block numerical and analytical methods and new mathematical models in calculation of force interactions of nanoparticles

Published in category «Actual problems of linguistics»

A mathematical model based on degenerate differential equations to describe the strength of interactions of nanoparticles. In combination with the methods and associated (p, q)-related operators extends the use of numerical and analytical methods in field calculations nanoparticles and molecular complexes.

## Flow field numerical investigation in a centrifugal compressor with the vaneless diffuser

Published in category «Simulation of physical processes»

This work is focused on the numerical investigation of the unsteady effects in a stage of a centrifugal compressor with vaneless diffuser. Different turbulence models implemented in NUMECA FINE/TURBO 8.9.1 software package as well as different configurations of computational domain were investigated. Conclusions about applicability of the certain models were made on the basis of the comparison of the results against the experimental data. Satisfactory agreement with experimental data was obtained in the region of high gas flow rates.

## New microscopic models of motorcar traffic

Published in category «Simulation of physical processes»

We propose two new microscopic traffic models. The first one is an extension of the Intelligent Driver Model (IDM) by Martin Treiber and provides the prescribed distance in a steady-state flow. The second model is described by delay-differential equations and takes into account the reaction-time delay of drivers. The stability of new models about the equilibrium is studied analytically. The calibration approach is proposed for both new models.

## Recursive computation of the Cramer – Rao bounds for the Bayesian models with nonlinear measurements and the constant state vector

Published in category «Mathematical physics»

The recursive expression for the Cramer − Rao bounds on the condition that state vector is constant has been presented. Derivation of the main formula is considered. The effectiveness of the proposed recursive method has been illustrated by applying to Вearings-only tracking.

## The application of functional approach to adaptive solving of elliptic problems

Published in category «Mathematical physics»

A modern functional approach to a posteriori error estimation for the energy norm of error is considered. Efficiency of the method is approved by numerical tests for several classical elliptic boundary-value problems

## An estimation of plasma radiation losses in the Globus-M tokamak using silicon SPD photodiodes

Published in category «Experimental technique and devices»

Photodiode SPD diagnostic system development and installation have been made on Globus-M tokamak. The calculation of plasma total radiation losses and the determination of diagnostic possibilities for tokamak plasma were made.

## Upgrade of the charge exchange neutral particle diagnostics in the Globus-M tokamak

Published in category «Experimental technique and devices»

The upgraded neutral particle diagnostics on Globus-M spherical tokamak is described. The results of the experiments on the displacement of the plasma column, acquired with this diagnostics are shown.

## The technique of measuring power structure of a bunch of atoms for Globus-M tokamak injector

Published in category «Experimental technique and devices»

Diagnosis scheme and measuring method for the energy constitution of Tokamak atomic beam injector using Doppler shift of the emission lines Ha for hydrogen and Da for deuterium have been designed and implemented. The experimental emission spectra were presented and the relative concentrations of the components of the beam energy along with components transferable capacities were determined.

## An experimental rate-depth relationship of dye mass-transfer in the aqueous horizontal flat layer

Published in category «Experimental technique and devices»

An investigation of diffusive mass-transfer in the flat horizontal liquid layer is complicated by convective effects. We measured dye mass-transfer speed and found out that effective diffusivity is decreased proportionally to layer thickness. Convective mass-transfer is almost eliminated in 0.5 mm layer.

## Correlational analysis of broadband signals of ion cyclotron resonance mass-spectrometer

Published in category «Experimental technique and devices»

For expansion of application field of mass-spectrometry analytical methods and for development of new constructions of mass analyzer new effective methods of spectral function modeling of short broadband signals are necessary. In this paper the correlation method of ion signal analysis in mass spectrometer with broadband signal recording is considered, developed algorithms and program principles for faster data analysis with high resolution are presented. The results are compared with Fourier transform results in short ion signal implementations regime, about 1ms.

## A role of nanoparticles in the field electron emission from carbon materials

Published in category «Physical electronics»

A common qualitative model is proposed for explanation of phenomenon of facilitated field-induced electron emission from different types of nano-structured carbonic materials with relatively smooth surface morphology. This model represents a version of two-barrier emission mechanism where intermediary electron states are associated with conductive nano-sized objects at or near the emitter surface. ‘Hot’ electrons injected from emitter bulk have a very large lifetime in such nanoparticles. This feature allows them to travel to the vacuum boundary where they can easily leave the emitter.

## An assessment for biological and ecological risk as a result of using nanomaterials: new approach

Published in category «Biophysics and medical physics»

In clause problems of theoretical representation of questions of biological hazards connected with development of nanotechnologies. The basic prospects with reference to computational toxicology of nanomaterials and nanostructures are stated.

## The static dielectric polarization of shungite carbon structure elements in benzene series of solvents

Published in category «Physics of molecules»

The study of the specific static dielectric polarization of shungite carbon structural elements (‘cups’) was carried out in dilute solutions in benzene series of solvents.

Dipole moments were calculated for the fragments of C60 fullerenes as models of the ‘cups’ (FC) in the temperature range of 25 to 60 о С. The FC dipole moments values obtained were 6.25 – 6.90 D, 5.2 – 5.6 D and 4.5 – 5.1 D in benzene, toluene и ortoxylene correspondingly. These values of dipole moment characterize a polarity of FC associats.

## odeling of hadron production in muon-nuclear interactions at energies of 280 GeV

Published in category «Nuclear physics»

The process of deep inelastic interaction of muons with nuclei at high energies is studied, results of modeling of hadron production in muon-nuclear interactions within the bounds of HARDPING generator are presented. Comparison with experimental data from EMC collaboration is carried out. Fine matching of HARDPING model with experiment is obtained.

## Doubling the variables in equations and sets of ordinary differential equations

Published in category «Mathematics»

The procedure for doubling the variables makes possible to construct an initial flow projector in the extremities field. This procedure contains a simple way of studying the robustness of solution of the initial set, to wit – the Lyapunov function is coincident with the Hamiltonian and as a result the determination of the robustness of the zeroth solution is reduced to that of signs of E (x, y) quadrics and signs of scalar product of E x-gradient by the initial flow of the non-variational set.

## An analysis of strength, buckling and rigidity of composite material water piping

Published in category «Mechanics»

The paper presents results of experimental studies of mechanical properties of glass fiber composite material. On the basis of these results, by using finite-element modeling method, an analysis of strength, stiffness and buckling of the composite material water piping under different operational loads was carried out.

## Characteristics of parameter estimates for random harmonic noised process

Published in category «Radiophysics»

In the paper the variance of parameter estimates for random harmonic noised process with discrete time has been investigated. For the case when noise is represented by mutually independent random variables with equal variance, the linear dependence between the variance of the noise and the variance of parameter estimates was proved. This dependence was described by formulas. For the case of low frequencies the function approximation was suggested.

## An ambiguity problem when analyzing NMR relaxation data

Published in category «Actual problems of linguistics»

A mathematical example being relevant to NMR relaxometry/imaging and showing impossibility to distinguish (within the limits of experimental accuracy) two diametrically opposite approaches to interpretation of small enough deviation from the exponential relaxation curve is considered. As a practical illustration the NMR T2 relaxation data for pure water are given.

## Comparative analysis for refractivity of GNSS decimeter radio waves by radio measurements and by using radiosonde

Published in category «Radiophysics»

The paper presents the results of a study of the radio waves refractivity vertical structure using network of seven ground receivers for GPS and GLONASS located in Kazan. 24-hourly behavior of refractivity at altitudes of 100 m, 4,500 m and 11,500 m was obtained for August 18, 2009. The results are compared with the radiosonde data. It is shown that the correlation coefficient of the results retrieved by radio tomography using measurements of Kazan receivers for GPS and GLONASS and radiosonde data is about 0.9.

## The axisymmetric elastic waves propagation in the wall of an infinite single-layered solid of revolution

Published in category «Radiophysics»

The elastic waves in an infinite axisymmetric single-layered cylindrical pipe have been considered. An approximate analytical solution of dispersion equation for a thin-walled cylindrical pipe and an exact one for a cylindrical pipe with an optional wall thickness were given. The latter solution was obtained using some particular parameter values. The results were interpreted in terms of physics.

## Zeroing of magnetic resonance signals when optically lamps pumping of alkali metal atoms in cells with wall coating

Published in category «Radiophysics»

The paper presents the experimental investigation results of ‘zeroing’ effect of magnetic resonance signals on the upper hyperfine F = I + J level of the ground 2 S1/ 2 state of alkali metal atoms within cells with anti-relaxation wall coating in optical lamp pumping with D2- or (D1 + D2)-emission lines depending on cell temperature. It has been found that, when there are no mutual atomic collisions in the excited 2Р3/2 state, the reason for occurrence of zeroing signals is a feature of magnetic resonance indication by optical cyclic transition of D2-line in the aggregate with a spin exchange in F = I + J state when changing the temperature of the cell. The engineering application of the results of research is given.