## The features of finite element modeling of a structural element of flexible woven composites

Published in category «Simulation of physical processes»

The features of finite element modeling of both an element itself and its behavior under uniaxial tension have been demonstrated with a structural element of flexible woven composites. The main material partials such as reinforcing fabric and material’s matrix were examined in modeling. The reinforcing fabric is a plain weave. These threads were taken as an elastic material. The matrix of the material was considered as a soft polymer with the possible occurrence of irreversible elastic-plastic deformations. Moreover, the possible occurrence of damages in the structure of the material under high loads was taken into account in modeling. The fields of stresses and strains were built; the zones of material internal damages under uniaxial tension were demonstrated. The risk zones of weave were revealed.

## The semi-markov model for the ‘technological module – storage device’ structure

Published in category «Simulation of physical processes»

The theory of semi-Markov process has been used to design the model of ‘technological module – storage device’ (TM-SD) structure. Stationary characteristics based on obtained equations were determined to find stationary distribution of the Markov embedded chain. Relying upon performed studies the stationary distribution of semi-Markov process was determined. This allowed calculation of the availability ratio of TM-SD structure and the design formula was given. The Markov restoration equations for TM-SD system with taking into account TM and SD failures were solved assuming the exponential behavior of these failures. The obtained expressions describe operating of such a system and allow substitution of TM-SD system with an equivalent element with two factor states. This result significantly simplifies the modeling problem for more complex systems. The legitimacy of using exponential distributions of random variables (error-free periods for TM and SD) was analyzed. The performed simulation modeling disclosed that the hypothesis for an exponential behavior of error-free periods for TM as a whole (and SD as well) can be accepted even in the case that TM (or SD) consists of six nodes.

## Influence of quantity of spray solution on the physical properties of spray-deposited nanocrystalline MgSe thin films

Published in category «Physical materials technology»

Nanocrystalline MgSe thin films have been prepared by varying the quantity of spray solution using the spray pyrolysis technique. The effect of the varying quantity of spray solution on the structural, electrical, morphological and optical properties of MgSe thin films was investigated. The X-ray diffraction studies revealed that the deposited MgSe has a cubic lattice with (111) as the preferred orientation. The optical studies showed that the deposited MgSe exhibited direct optical band gap which varied from 2.45 to 2.75 eV depending on the quantity of spray solution. The electrical resistivity of MgSe decreased with an increase in temperature indicating its semiconducting nature. The electrical resistivity, activation energy and optical band gap energy were found to depend upon the quantity of spray solution. The measurement of thermo-emf with applied temperature gradient across the film confirmed its p-type conductivity.

## Synthesis and luminescence properties OF Ca5(PO4)3Cl:Eu2+ phosphor for solid state lighting

Published in category «Physical materials technology»

A novel method to prepare Eu2+ doped chlorapatite phosphor Ca5(PO4)3Cl useful for solid state lighting has been given in this paper. The phosphor was synthesized by the Pechini (citrate gel) method which turned out to be more efficient than the conventional high temperature solid state reaction. The results of the photoluminescence (PL) investigation revealed that it was possible to efficiently excite the phosphor by a UV-visible light from 220 to 430 nm; the phosphor exhibited a bright blue emission at the wavelength λem = 456 nm for the excitation wavelength λex = 350 nm of near-ultraviolet light. The developed phosphor emits in blue and, hence, could provide one of the three (RGB) primary color components in a phosphor-converted LED-producing white light.

## Sigma-1 receptor as a potential pharmacological target for the treatment of neuropathology

Published in category «Biophysics and medical physics»

Sigma receptors are usually classified as a separate class of intracellular receptors. Among them sigma-1 receptor has received the most study in respect to pharmacology application. This receptor with average or high affinity binds a wide range of chemical compounds of very different structural classes and a variety of therapeutic and pharmacological properties. The sigma-1 receptor is a trans-membrane protein placed in the endoplasmic reticulum (ER), which regulates the function of inositol-3-phosphate receptor, stabilizing the calcium signaling between ER and mitochondria. The receptor in question is involved in the formation of many neurological and psychiatric states. It is assumed that the sigma-1 receptor acts as a sensor of normal calcium operation. The studies over the recent years have shown the role of a disturbance in calcium signaling in the pathogenesis of Alzheimer’s and huntington’s diseases. In particular, changes in calcium homeostasis of the endoplasmic reticulum lead to the break of synaptic connections in the neurons. Thus, sigma-1 receptor holds promise in application as potential therapeutic targets for the treatment of neuropathological diseases.

## Crystal acceleration effect for cold neutrons in the vicinity of the Bragg resonance

Published in category «Nuclear physics»

A new mechanism of neutron acceleration is studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron-crystal interaction potential) for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal-neutron relative velocity. Therefore the neutrons enter into accelerated crystal with one neutron-crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to its homogeneity. So after passage through such a crystal neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.

## Mathematical model of the fluctuation noise based on the wavelet transform

Published in category «Radiophysics»

A new model of white noise on the basis of the wavelet transform has been put forward. This model is more adequate for solving some radiophysical tasks such as the problem of electromagnetic waves reflection from the ionosphere. Moreover, it was shown that in terms of probabilistic description of the random-process trajectories, the wavelet implementation of this random process is more likely (using the probability density functional offered by I.N. Amiantov). The wavelet properties and the famous theorems of mathematical analysis and theory of chances were used to develop our model: the mean value theorem and Lyapunov’s central limit theorem. Our study resulted in a theorem on random-process expansion in terms of wavelet basis. It was also shown that the obtained results were in agreement with those of V.A. Kotelnikov.

## Many-electron correlations in calculations of sodium atom photoabsorption

Published in category «Theoretical physics»

The role of many-electron correlations in photoabsorption processes has been investigated. The results of numerical calculations of photoionization cross sections of sodium atom are presented. The many-body effects such as interchannel correlations resulting in autoionization resonance peaks, as well as effects of atomic core polarization were taken into account in the calculations in terms of RPAE. Polarization corrections were accounted for using both static and dynamic polarization potentials. The influence of correlations on the position and the form of resonance peaks was studied. The obtained results demonstrate necessity of taking into account polarization effects, especially for clarification of autoionization resonance peaks position and the cross-section magnitudes in the low energy range. The best agreement with experimental data was reached with the model of dynamic polarization potential based on Dyson equation.

## Resultes of 17-th Аll-Russian youth conference on semiconductor and nanoctructure physics and semiconductor opto- and nanoelectronics

Published in category «Chronicle»

The paper summarizes the results of the 17th All-Russian Youth Conference on Semiconductor and Nanostructure Physics and Semiconductor Opto- and Nanoelectronics that took place in St. Petersburg on November 23 – 27, 2015. The organizers and the sponsors of the conference have been listed. The reports presented in the 6 sections of the Conference have been reviewed analytically. The participants whose reports were awarded certificates and money prizes by the Conference Program Committee have been mentioned. The list of reports recommended to take part in the ‘UMNIK’ contest (the acronym for the youth science and innovation contest means “a clever person” in Russian) is presented in the nomination “Scientific results which have significant novelty and the prospect of commercialization” and shall be further funded by the Foundation for Assistance to Small Innovative Enterprises in Science and Technology.